Eccentricity measuring method and device

Abstract

This eccentricity measurement method comprises first to eighth steps. In the first step, an eccentricity measurement device is prepared that is for moving a light image for measurement linearly in relation to an optical unit under inspection and acquiring the image on an observation surface orthogonal to a reference axis defined by the relative movement path of the light image. In the second step, the position of a reference point is specified. In the third step, an optical unit under inspection is positioned. In the fourth step, the light image is projected onto a projection position on the reference axis, and a reflected image that has been reflected by the surface under inspection is formed at an observation position where the distance from the projection position is a set value L. In the fifth step, an image for measurement is acquired. In the sixth step, an image of the reflected image is specified. In the seventh step, the amount of positional deviation of the image of the reflected image is measured. In the eighth step, the amount of eccentricity of the apparent spherical center of the surface under inspection is calculated.

Description

[Technical field]

[0001] The present invention relates to an eccentricity measuring method and an eccentricity measuring device. [Background technology]

[0002] If the required optical performance cannot be obtained in the manufacturing process of an optical unit including multiple lenses, the cause may be decentering of the lens surfaces. For this reason, there is a demand for an eccentricity measurement method and an eccentricity measurement device that can accurately measure the eccentricity of each lens surface in the assembled state of the optical unit. For example, Patent Document 1 describes an eccentricity measuring device capable of measuring the eccentricity of each lens surface in the assembled state of an optical unit. The eccentricity measuring device described in Patent Document 1 uses an autocollimation method. In the autocollimation method, a light image called a "target (image)" is projected onto the apparent center of a sphere of the test surface in the test optical system, and the amount of deflection of the reflected image is measured to measure the eccentricity of each test surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent No. 2621119 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, the objective optical system of an endoscope has a lens with a strong negative power at the front tip, and the positions of the apparent spherical centers of each surface are close to each other. Moreover, endoscopes are large and difficult to fix, making it difficult to measure eccentricity by rotating the test object with high precision, which is commonly done. When attempting to measure such an optical system using the autocollimation method (life-size method) disclosed in Patent Document 1, many reflected images formed on optical surfaces other than the test surface are observed during measurement of the rear test surface. As a result, it becomes impossible to identify the reflected images from the test surface, making measurement difficult. On the other hand, it is also possible to perform eccentricity measurement (unequal magnification method) by setting the IO distance, which is the distance between the projection position of the target image and the formation position of the reflected image in the direction along the reference axis of eccentricity measurement, to a non-zero value. However, there is no known method for measuring eccentricity using a non-unitary magnification method without rotating the test object. For example, the method disclosed in Patent Document 1, which uses an image rotator to measure the test object without rotating it, is a method that is applied to the autocollimation method and cannot be applied to the non-unitary magnification method. Furthermore, the method using an image rotator requires specifying the reference axis of eccentricity each time a reflected image of each test surface is observed, and therefore the measurement takes a long time. In recent years, there has been an increasing need to measure not only the decentering of the lenses in a lens assembly, but also the decentering of the lens frame and the imager assembled to the lens, etc. However, there is no known decentering measurement method that can measure the decentering of the lens frame and the imager assembled to the lens, in addition to the decentering of the lens.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide an eccentricity measuring method and an eccentricity measuring device that can accurately and quickly measure the amount of eccentricity of a test surface without rotating a test optical unit. [Means for solving the problem]

[0006] In order to solve the above problems, a decentering measurement method according to a first aspect includes a first step of preparing an eccentricity measurement device having a measurement imager that holds a test optical unit having a test surface, projects a measurement optical image toward the test optical unit, linearly moves the projected optical image relatively to the test optical unit, and acquires an image of an observation surface perpendicular to a reference axis defined by a relative movement trajectory in air of the projected optical image with respect to the test optical unit, a second step of specifying a position of a reference point in the image acquired by the measurement imager, which corresponds to an intersection of the observation surface and the reference axis, and a third step of arranging the test optical unit on the reference axis. a fourth step of projecting the light image onto a projection position on the reference axis, and forming a reflected image of the light image reflected by the test surface at an observation position which is set so that the distance from the projection position along the reference axis is a set value L; a fifth step of disposing the observation surface at the observation position, capturing an image of the observation surface using the measurement imager, and obtaining a measurement image; a sixth step of identifying an image of the reflected image at the observation position in the measurement image; a seventh step of measuring an amount of positional deviation of the identified reflected image from the reference point; and an eighth step of calculating an amount of eccentricity of the apparent spherical center of the test surface relative to the reference axis based on the amount of positional deviation. Here, "perpendicular" also includes an angle that is not a right angle due to various factors such as errors. In this specification, an angle that is considered to be "perpendicular" is between 89 degrees and 91 degrees. However, in order to improve measurement accuracy, the closer to 90 degrees the angle considered to be "perpendicular" is, the more preferable. For example, the angle considered to be "perpendicular" is more preferably 90 degrees ±30 minutes.

[0007] An eccentricity measuring device according to a second aspect includes a light source unit that forms an optical image for measurement, a holding stage that holds a test optical unit having a test surface, a projection optical system that projects the optical image toward the test optical unit, a moving mechanism that movably holds at least one of the light source unit, the projection optical system, and the holding stage and moves the optical image projected from the projection optical system linearly in air relative to the holding stage, a measurement imager that acquires an image of an observation surface orthogonal to a reference axis at an observation position that is set so that a distance from a projection position of the optical image on the reference axis is a set value L when a relative movement trajectory of the optical image with respect to the holding stage formed by the moving mechanism is taken as a reference axis, and an eccentricity calculation unit that measures an amount of positional deviation from a reference point corresponding to an intersection of the observation surface and the reference axis based on the image at the observation position acquired by the measurement imager, and calculates an amount of eccentricity of an apparent spherical center of the test surface relative to the reference axis based on the amount of positional deviation. Effect of the Invention

[0008] According to the first and second aspects, it is possible to provide an eccentricity measuring method and an eccentricity measuring device that can accurately and quickly measure the amount of eccentricity of a surface to be tested without rotating an optical unit to be tested. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing an example of an eccentricity measuring device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram of a control system in the eccentricity measuring device according to the first embodiment of the present invention. [Diagram 3] FIG. 2 is a cross-sectional view showing an example of a test optical system. [Figure 4] FIG. 1 is a schematic diagram for explaining the principle of eccentricity measurement using a conventional autocollimation method. [Diagram 5] FIG. 1 is a schematic diagram showing an example of a reflected image observed in a conventional autocollimation method. [Figure 6]FIG. 2 is a schematic diagram for explaining the principle of eccentricity measurement in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 7] FIG. 2 is a schematic diagram for explaining the principle of eccentricity measurement in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 8] 3A to 3C are schematic diagrams illustrating the principle of eccentricity measurement when the apparent radius of curvature is infinite, in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 9] FIG. 13 is a schematic diagram illustrating a method for measuring eccentricity when the apparent radius of curvature is infinite using a conventional autocollimation method. [Figure 10] 3A to 3C are schematic diagrams showing examples of indicators used in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 11] FIG. 4 is a schematic diagram showing a first example of a method for discriminating a reflected image in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 12] FIG. 4 is a schematic diagram showing a second example of a method for discriminating a reflected image in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 13] 4 is a flowchart showing an example of an eccentricity measuring method according to the first embodiment of the present invention. [Figure 14] 5 is a flowchart showing an example of a reference point measuring method in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 15] 3A to 3C are schematic diagrams showing a method for measuring an IO distance L in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 16] 3A to 3C are schematic diagrams showing a method for measuring an IO distance L in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 17] FIG. 2 is a schematic diagram for explaining the principle of reference point measurement in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 18] 13 is a graph showing the change in the uncertainty of the reference point measurement depending on the reflection magnification. [Figure 19] FIG. 2 is a schematic diagram showing an example of a reference point obtained in the eccentricity measuring method according to the first embodiment of the present invention. [Figure 20]5 is a schematic diagram showing an example of a display screen after a reference optical element is moved in the decentering measuring method according to the first embodiment of the present invention; FIG. [Figure 21] 4A to 4C are schematic diagrams showing an example of measurement of the amount of deflection of a reflected image in the decentering measuring method according to the first embodiment of the present invention. [Figure 22] FIG. 2 is a cross-sectional view showing an example of a test optical system. [Diagram 23] 10 is a flowchart showing an example of a method for selecting the type of a reflected image in the eccentricity measuring method according to the second embodiment of the present invention. [Figure 24] FIG. 11 is a block diagram of a control system in an eccentricity measuring device according to a third embodiment of the present invention. [Diagram 25] FIG. 11 is a schematic diagram showing the relationship between a coordinate system of a measurement system in an eccentricity measuring device according to a third embodiment of the present invention and a coordinate system of an imager to be measured. [Figure 26] 13A and 13B are schematic diagrams showing examples of images acquired from a test optical unit in a decentering measuring method according to a third embodiment of the present invention. [Figure 27] 13 is a flowchart illustrating an example of an eccentricity measuring method according to a third embodiment of the present invention. [Figure 28] 10 is a schematic diagram showing the relationship between the amount of eccentricity of the spherical center of the test surface and the x-axis components of the tilt eccentricity of the test surface. FIG. [Figure 29] 10 is a schematic diagram showing the relationship between the amount of eccentricity of the spherical center of the test surface and the y-axis components of the tilt eccentricity of the test surface; FIG. [Diagram 30] 13 is a schematic cross-sectional view showing the measurement principle of an eccentricity measuring method according to a third embodiment of the present invention. FIG. [Diagram 31] FIG. 11 is a schematic diagram showing the relationship between an image on a test imager, the coordinate system of a measurement system, and the test imager coordinate system in an eccentricity measuring device according to a third embodiment of the present invention. [Diagram 32] 1 is a schematic diagram showing the relationship between a test imager coordinate system and an xy coordinate system of a measurement system in the orientation displayed on a display unit. [Diagram 33] 1 is a schematic diagram showing the relationship between the amount of eccentricity of the spherical center of a surface to be tested as viewed from a coordinate system of an imager to be tested and the imaging position of a light image IL. [Diagram 34] 13 is a cross-sectional view showing an example of a frame member in an eccentricity measuring device according to a fourth embodiment of the present invention. FIG. [Diagram 35] 10 is a schematic diagram showing an image of a frame member captured by a measurement imager. FIG. [Diagram 36] 10 is a flowchart illustrating an example of an eccentricity measuring method according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding parts are given the same reference numerals, and common explanations will be omitted.

[0011] [First embodiment] An eccentricity measuring device according to a first embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing an example of an eccentricity measuring device according to a first embodiment of the present invention.

[0012] 1 can be used to measure the eccentricity of each optical surface in various optical systems including a plurality of lenses. Here, the optical surface means a surface of an optical element that has an optical action such as refraction or reflection. The shape of the optical surface is not particularly limited, and may be, for example, a spherical surface, an aspherical surface, a flat surface, or the like. The optical system to be measured has a plurality of optical elements, such as lenses and parallel plates, which are arranged on an appropriate holding member based on the surface spacing determined from the design value of the optical system, and are fixed to the holding member. The eccentricity measuring device 50 can measure the eccentricity of each optical surface in an optical unit (test optical unit) in a state in which an optical system to be measured (test optical system) is assembled to a holding member. In measuring the eccentricity of the test optical unit, the eccentricity of a measurement object other than an optical surface may be measured. The type of the optical unit to be tested is not particularly limited. For example, the test optical unit may be a lens unit in which a plurality of optical elements including lenses are assembled in a lens barrel, such as a lens unit for an endoscope, a lens unit for a camera, or a lens unit for a microscope. For example, the optical unit to be tested may be a distal end of an insertion section of an endoscope provided with an objective optical system. In this case, a bending section and a flexible tube section may be connected in this order to the proximal end side of the distal end. In the following, an example will be described in which the optical unit to be tested is the tip portion 40 of the insertion portion of an endoscope. The type of endoscope may be a medical endoscope or an industrial endoscope. The tip portion 40 has a cylindrical outer shape. Inside the tip portion 40, a test optical system 41 and an endoscope imager 42 are fixed. The optical surface at the tip of the test optical system 41 is exposed to an opening formed at the tip of the tip portion 40. The configuration of the test optical system 41 is not particularly limited. For example, the test optical system 41 may be an objective optical system. In the following, unless otherwise specified, the test optical system 41 will be described as an objective optical system. The test optical system 41 is held by a lens frame 40 a disposed inside the tip portion 40 . The endoscope imager 42 photoelectrically converts the optical image on the image plane of the test optical system 41. For example, the endoscope imager 42 may be a CCD or CMOS sensor.

[0013] The eccentricity measuring device 50 has a base 1, a moving stage 2 (moving mechanism), a main body 3, a holding table 4, and a measurement control unit 5 (eccentricity amount calculation unit).

[0014] The base 1 supports the entire eccentricity measuring device 50. The arrangement posture of the base 1 is not particularly limited, but the following description will be given on an example where the base 1 is arranged on a horizontal plane. The moving stage 2 moves the main body 3, which houses a measurement optical system 20 described later, in at least one direction on the base 1. In the example shown in Fig. 1, the moving stage 2 moves the main body 3 at least in one axial direction (the left-right direction in the figure) on a horizontal plane. For example, the moving stage 2 has a guide 2a, an optical system transport unit 2b, and an optical system transport unit drive unit 2c.

[0015] The guide 2a is fixed onto the base 1. The guide 2a guides the optical system transport section 2b so as to be movable in one axial direction on a horizontal plane. The optical system transport unit 2b is guided by the guide 2a and is provided so as to be movable in one axial direction. The optical system transport unit 2b is fixed to the main body unit 3 and can move together with the main body unit 3. The fixed position of the optical system transport unit 2b to the main body unit 3 is not particularly limited as long as the optical system transport unit 2b can move together with the main body unit 3. In the example shown in FIG. 1, the optical system transport unit 2b is fixed to the bottom of the main body unit 3. The optical system transport unit drive unit 2c supplies a driving force for moving the optical system transport unit 2b. For example, the optical system transport unit drive unit 2c may include a motor and a transmission mechanism for transmitting the driving force of the motor to the optical system transport unit 2b. The optical system transport unit drive unit 2c is communicably connected to the measurement control unit 5 described later. The optical system transport unit drive unit 2c drives the optical system transport unit 2b in response to a control signal from the measurement control unit 5.

[0016] In the following description, one axis direction is assumed to be the direction along the z-axis of the x-axis and z-axis which are mutually perpendicular on a horizontal plane. The vertical direction perpendicular to the x-axis and z-axis is the direction along the y-axis. The positive direction of the z-axis (hereinafter, the positive z-axis direction) is the direction along the z-axis from the main body 3 toward the holding base 4 described later, and is the direction from left to right in FIG. 1. The positive direction of the x-axis (hereinafter, the positive x-axis direction) is the direction from right to left along the x-axis when viewed in the positive z-axis direction, and is the direction from the front to the back of the paper in FIG. 1. The positive direction of the y-axis (hereinafter, the positive y-axis direction) is the vertical upward direction, and is the direction from bottom to top in FIG. 1. The directions opposite to the positive direction on each axis are negative directions, and are referred to as the negative z-axis direction, the negative x-axis direction, and the negative y-axis direction, respectively. An xyz coordinate system, which is an orthogonal coordinate system based on the x-axis, y-axis, and z-axis, is fixed to the eccentricity measuring device 50. The xyz coordinate system is a coordinate system of a measurement system in the eccentricity measuring device 50. When only the xy plane is considered, it is called the xy coordinate system. The origin of the xyz coordinate system is arbitrary. Various calculations in eccentricity measurement can be performed, if necessary, using coordinate values ​​of a local coordinate system obtained by translating the xyz coordinate system.

[0017] The main body 3 is a housing supported by the moving stage 2 so as to be movable at least in the positive direction of the z axis and the negative direction of the z axis. A front wall 3a provided at the end of the main body 3 in the positive direction of the z-axis is formed with an opening 3b through which measurement light passes.

[0018] Arranged inside the main body 3 are a measurement optical system 20, a wedge prism 18 (reflection magnification measuring section), an observation imager 44, a measurement imager 17, an adjustment lens driving section 21, and a wedge prism driving section 22 (reflection magnification measuring section). The measurement optical system 20 has a light source 10 (light source section), a beam splitter 11, a collimator lens 12 (light source section), an adjustment lens 13 (light source section), a beam splitter 14, an imaging lens 16 (observation optical system), and an objective lens 15 (projection optical system, observation optical system). The light source 10, the beam splitter 11, the collimating lens 12, the adjusting lens 13, and the objective lens 15 are aligned along the optical axis O of the measurement optical system 20. M The optical axis O of the measurement optical system 20 is M is aligned parallel to the z-axis. In this embodiment, the reference axis O that is the reference for eccentricity measurement is m is defined by the movement locus in air of the optical image formed by the measurement optical system 20. m is an imaginary straight line including the moving range of the light image. When there are no manufacturing errors or assembly errors in the measurement optical system 20 and no bending in the direction of movement of the moving stage 2, the optical axis O M is the reference axis O in the eccentricity measurement of this embodiment. mFor simplicity, in the explanation of the principles related to the measurement optical system 20, the optical axis O is the same as that of the optical axis 1 unless otherwise specified. M and reference axis O m The explanation will be given assuming that the reference axis O of the eccentricity measurement is the same as that of the reference axis O of the eccentricity measurement. m is the optical axis O M The reference axis O in the eccentricity measuring device 50 does not have to be coaxial with the m The method for measuring is described below. The collimator lens 12, the adjusting lens 13, the objective lens 15, and the imaging lens 16 may each be composed of a single lens or multiple lenses.

[0019] The light source 10 generates light for forming an optical image to be projected onto the test optical system 41. The type of the light source is not particularly limited. For example, a semiconductor laser may be used as the light source 10. The wavelength of the light source 10 is not particularly limited as long as it can be imaged by the measurement imager 17 and the observation imager 44 described later. In the example shown in FIG. M The light beam F1 is emitted along the

[0020] The beam splitter 11 is disposed on the optical path of the divergent light beam F1. The beam splitter 11 splits a light beam F7 returning from a projection plane P' toward the light source 10, which will be described later, onto an optical axis O. M It is reflected in the direction that intersects with An observation imager 44 is disposed in the optical path of the light beam F7 reflected by the beam splitter 11.

[0021] The observation imager 44 photoelectrically converts the image formed by the light beam F7 and sends it to the measurement control unit 5 described later. The imaging surface of the observation imager 44 is disposed at a position optically conjugate with a focal plane F' described later. The observation imager 44 can capture an image on the focal plane F'.

[0022] The collimator lens 12 is a condenser lens arranged at a position where its front focal point coincides with the light emitting portion of the light source 10. The collimator lens 12 condenses the divergent light beam F1 and condenses it along the optical axis O. MA parallel beam F2 travels along the

[0023] The adjustment lens 13 is aligned along the optical axis O M In the above, the optical axis O from the collimating lens 12 M The collimator lens 12 is a focusing lens arranged so that the distance therebetween can be changed. The adjustment lens 13 focuses the parallel light beam F2 to form a light beam F3. The light beam F3 is imaged on a focal plane P at the rear focus of the adjustment lens 13. Therefore, on the focal plane P, a light image IP (light image for measurement), which is a real image of the light emitting part of the light source 10, is formed according to the magnification of the optical system formed by the collimator lens 12 and the adjustment lens 13. After passing through the focal plane P, the light beam F3 proceeds as a diverging light beam. Adjustment lens 13 is aligned along the optical axis O M When the focal plane P is translated along

[0024] The light source 10, the collimating lens 12, and the adjusting lens 13 are an example of a light source unit that forms a light image IP for measurement.

[0025] The beam splitter 14 has a beam splitter surface 14a that transmits the light beam F3 traveling in the positive direction of the z axis and reflects the optical axis of the light beam traveling in the negative direction of the z axis in a direction intersecting the z axis. M The axial light beam traveling in the negative direction of the z-axis along the optical axis O M In the direction intersecting with the optical axis O B It is reflected as Optical axis O B An imaging lens 16 facing the beam splitter 14 and a measurement imager 17 facing the beam splitter 14 with the imaging lens 16 in between are arranged above.

[0026] A focal plane F on which the front focal point of the objective lens 15 is located is disposed behind the focal plane P of the adjustment lens 13 . The objective lens 15 collects the light beam F3 and forms a measurement light beam F4. The measurement light beam F4 is emitted toward the test optical system 41 outside the main body 3 through the opening 3b, and forms an image on a projection plane P' (projection position) optically conjugate with the focal plane P. In this manner, the light image IP is projected by the objective lens 15 onto the projection plane P' as a light image IP'.

[0027] The objective lens 15 is an example of a projection optical system that projects the optical image IP toward the optical system 41 to be measured.

[0028] The measurement light beam F4 enters the test optical system 41 from the front side of the test optical system 41, and is refracted or reflected by each optical surface of the test optical system 41. For example, the measurement light beam F4 is refracted by one or more optical surfaces in the test optical system 41, and then reflected forward by the test surface Si, which is one of the optical surfaces. This forms a reflected light beam F5. In this case, the reflected light beam F5 is refracted in sequence by each optical surface in front of the test surface Si through which the measurement light beam F4 has passed, and forms an image on the image plane I. R Form. If the optical system formed by the medium and each optical surface in front of the test surface Si in the test optical system 41 is referred to as the incident side optical system with respect to the test surface Si, the incident side optical system and the test surface Si can be replaced with an apparent surface consisting of a spherical surface having an apparent radius of curvature. The "apparent spherical center" of the test surface Si is a point that is optically conjugate with the spherical center of the test surface Si due to the presence of an incident side optical system related to the test surface Si in the test optical system 41. The apparent spherical center is also called the apparent center of curvature of the test surface Si. Light incident on the "apparent spherical center" of the test surface Si from the front side of the test optical system 41 is refracted by each optical surface of the incident-side optical system, and reaches the spherical center of the test surface Si. The position of the apparent center of the sphere can be calculated from the radius of curvature of each optical surface, the refractive index of each medium, and the distance between each optical surface in the test surface Si and the incident side optical system related to the test surface Si. The "apparent vertex" of the test surface Si is a point that is optically conjugate with the vertex of the test surface Si due to the presence of the incident optical system in the test optical system 41. M is the apex of the test surface Si in the direction along The "apparent radius of curvature" of the test surface Si means the distance from the "apparent surface vertex" of the test surface Si to the "apparent spherical center" of the test surface Si. M When the radius of curvature is on the positive side of the radius, the "apparent radius of curvature" is positive. In the following, when it is necessary to clearly state that an apparent surface having an apparent radius of curvature is being considered instead of the test surface Si, it may be expressed as "apparent test surface si". When the test surface Si is the frontmost optical surface in the test optical system 41, there is no need to consider the apparent surface of the test surface Si, but for simplicity of explanation, the apparent surface of the test surface Si is defined as the test surface Si itself. In this case, the apparent radius of curvature, the apparent spherical center, and the apparent vertex of the test surface Si respectively coincide with the radius of curvature of the test surface Si, the spherical center of the test surface Si, and the vertex of the test surface Si.

[0029] In this embodiment, the objective lens 15 captures the reflected image I R The objective lens 15, for example, collects a reflected light beam F5 traveling from a focal plane F' at the rear focus of the objective lens 15 toward the objective lens 15 within the range of the numerical aperture of the objective lens 15. This forms a light beam F6 traveling toward the beam splitter 14. However, in FIG. 1, for ease of viewing, the reflected image I R In reality, the reflected light beam F5, when passing through the focal plane F', forms a reflected image I R The light is diverged from the position and enters the range of the numerical aperture (NA) of the objective lens 15, whereby it is condensed to form a light beam F6. The light beam F6 is on the optical axis O. M The light beam F6 travels along the line 14a toward the beam splitter 14 and is reflected by the beam splitter surface 14a of the beam splitter 14. The light beam F6 is focused by the imaging lens 16. For example, the focal plane F' of the objective lens 15 is R When the objective lens 15 and the imaging lens 16 are optically conjugate with the image plane I, the image plane I of the imaging lens 16 is formed on the objective lens 15. B2, Reflection I R A real image is formed.

[0030] The objective lens 15 and the imaging lens 16 optically conjugate the focal plane F' of the objective lens 15 with the imaging plane of the measurement imager 17. The objective lens 15 and the imaging lens 16 are an example of an observation optical system observed with the measurement imager 17. The focal plane F' is an object plane in the observation optical system, and has the meaning of an observation plane where an image is acquired by the measurement imager 17. Hereinafter, when it is emphasized that the focal plane F' is the observation plane of the observation optical system, it may be referred to as the observation plane F'. The objective lens 15 and the imaging lens 16 form an image I reflected by the test surface Si on the observation surface F'. R When the reflected image I is aligned with the image plane I, R can be observed by the measurement imager 17. At this time, the observation optical system is such that the imaging surface and the projection position of the measurement imager 17 are optically conjugate with each other. Reflected image I on observation plane F' R Through the observation optical system, the image plane I B Reflection image I formed on R The magnification of the image is determined according to the observation optical system.

[0031] The optical path of the parallel light beam F2 between the collimator lens 12 and the adjustment lens 13 is an example of a parallel optical path that forms a parallel light beam in an optical path different from the optical path of the observation optical system that optically conjugates the measurement imager and the projection position from the light source unit to the projection position.

[0032] In the measurement optical system 20, the optical axis O of the adjustment lens 13 M With the position of the main body 3 in the direction along the optical axis O fixed, the moving stage 2 is used to move the main body 3 along the optical axis O M When the object is moved in the direction along the optical axis O, the optical image IP' and the observation plane F' are aligned along the optical axis O. M The reflected image I moves in unison without changing the distance along the incident optical system and the test surface Si. R Since the light image IP' and the light image IP' are optically conjugate with each other, the optical axis O MThe position of the image plane I in the direction along the optical axis O M is a function of the position of the projection plane P' in the direction along For this reason, the movable stage 2 is an example of a moving mechanism that movably holds the light source unit and the projection optical system included in the measurement optical system 20 without changing their relative positions to each other, and moves the optical image projected from the projection optical system in a straight line relative to the holding table in the air. As a result, the optical axis O of the optical image IP′ with respect to the test optical system 41 M The reflected image I is formed by reflection from the test surface Si according to the position along the R is formed on the optical axis O of the image plane I. M The position along the axis changes. When the light image IP' is at a specific position, the reflected image I R appears on the observation plane F'. Therefore, the optical axis O of the projection plane P' M By appropriately setting the position in the direction along the axis by the moving stage 2, the image plane I and the focal plane F' can be made to coincide with each other.

[0033] In this embodiment, the adjustment lens 13 is aligned along the optical axis O M 1, and by changing the position of the focal plane P of the adjustment lens 13, the distance between the projection plane P' and the observation plane F' can be changed. For example, if the distance converted into the air length from the focal plane F of the objective lens 15 to the focal plane P of the adjustment lens 13 is p, and the distance from the focal plane F' of the objective lens 15 to the projection plane P' is p', then p and p' are calculated by Newton's imaging formula as follows: T That is, pp'=-f T 2 Here, if p'=L, L is calculated by the following formula (1).

[0034]

number

[0035] Image plane I of imaging lens 16 B In the image plane I BA measurement imager 17 is disposed to photoelectrically convert the optical image at the The measurement imager 17 is sensitive to the wavelength of the light beam F6 and captures the reflected image I R There are no particular limitations on the type of photoelectric conversion element as long as it can resolve the image with the necessary resolution. For example, the measurement imager 17 may be a CCD or CMOS sensor. An image signal of an image photoelectrically converted by the measurement imager 17 is sent to the measurement control unit 5, which will be described later. The imaging lens 16 and the measurement imager 17 may be, for example, a digital camera.

[0036] In this embodiment, as described later, the projection plane P', which is the projection position, is determined by aligning the optical axis O from both the apparent spherical center and the design value of the apex of the test surface Si. M The projection plane P' and the image plane I are set at positions shifted along the optical axis O. M Since the light is shifted in the direction along the optical axis O M The image plane I can be observed by setting the distance from the observation plane F' to the projection plane P' as L (where L ≠ 0) in the direction along the optical axis O. M The distance from the observation plane F' to the projection plane P' in the direction along the axis is referred to as the IO distance. The IO distance whose set value is set to L may be referred to as the IO distance L. In this specification, the sign of the set value L of the IO distance is positive in the direction from the decentering measurement device 50 to the test optical system 41. In contrast, for example, in the conventional autocollimation method, the projection plane P' is set at a position that passes through the apparent center of the test surface Si. In this case, the IO distance is zero.

[0037] The wedge prism 18 has a first surface 18a and a second surface 18b that is inclined relative to the first surface 18a by a wedge angle α. The distance between the first surface 18a and the second surface 18b gradually changes along the inclination direction of the second surface 18b. The wedge prism 18 is disposed so as to be movable toward and away from the optical path of the parallel light beam F2 between the collimator lens 12 and the adjustment lens 13. When the wedge prism 18 enters the optical path of the parallel light beam F2, the parallel light beam F2 enters the first surface 18a and exits from the second surface 18b. At this time, due to the refraction effect of the wedge prism 18, the optical path of the parallel light beam F2 is aligned along the optical axis O. M In contrast, the surface is inclined toward the side where the inter-surface distance between the first surface 18a and the second surface 18b increases. As a result, the light image IP' on the projection plane P' is projected along the optical axis O M is shifted in a direction perpendicular to the The direction in which the wedge prism 18 shifts the light image IP' is not particularly limited. For example, the wedge prism 18 may shift the light image IP' in the x-axis direction, the y-axis direction, or a direction different from the x-axis direction and the y-axis direction. The direction in which the wedge prism 18 shifts the light image IP' may be constant or may be changeable. The ray deviation of the wedge prism 18 is preferably about 1 mrad, for example.

[0038] The adjustment lens driving unit 21 drives the adjustment lens 13 along the optical axis O. M The adjustment lens driving unit 21 may include, for example, a motor and a transmission mechanism that transmits the driving force of the motor to the adjustment lens 13 or a holding member of the adjustment lens 13. The adjustment lens driving unit 21 is communicably connected to the measurement control unit 5 described later, and moves the adjustment lens 13 based on a control signal from the measurement control unit 5.

[0039] The wedge prism driver 22 drives the wedge prism 18 along the optical axis O. M 3, and switches between a retracted position where the wedge prism 18 is retracted from the optical path of the parallel light beam F2 and an entrance position where the wedge prism 18 enters the optical path of the parallel light beam F2. The direction in which the wedge prism 18 in the entrance position shifts the optical image IP' is not particularly limited. The configuration of the wedge prism driver 22 is not particularly limited as long as it can switch the position of the wedge prism 18 between the retracted position and the advanced position. For example, the wedge prism driver 22 may be a solenoid that moves the wedge prism 18 or a member that holds the wedge prism 18. For example, the wedge prism driver 22 may include a motor and a transmission mechanism that transmits the driving force of the motor to the wedge prism 18 or the member that holds the wedge prism 18. The wedge prism driver 22 is communicably connected to the measurement controller 5 (described later), and moves the wedge prism 18 based on a control signal from the measurement controller 5.

[0040] The holding stage 4 holds the test optical unit such as the tip portion 40. The holding stage 4 includes a stage main body 4b and a holder 4a provided on the upper end of the stage main body 4b via an adjustment stage. The holder 4a is provided so as to be movable at least in a direction intersecting the z-axis by an adjustment stage. The adjustment stage may be capable of tilt adjustment with respect to the z-axis. The holder 4a detachably holds the test optical unit. For example, when the test optical unit is the tip portion 40 including the test optical system 41, the holder 4a is arranged so as to be aligned with the optical axis O of the test optical system 41 in the design. M Holder 4a can hold tip portion 40 such that the tip of tip portion 40 faces main body portion 3. Holder 4a can hold tip portion 40 such that the tip of tip portion 40 faces main body portion 3. As long as the position of the holding table 4 relative to the main body 3 is fixed during eccentricity measurement, the holding table 4 may be disposed on the base 1 or at a position separated from the base 1. In the example shown in FIG.

[0041] FIG. 2 is a block diagram of a control system in the eccentricity measuring device according to the first embodiment of the present invention. As shown in FIG. 2, the measurement control unit 5 has an overall control unit 101, an arithmetic processing unit 102, an image processing unit 103, a memory unit 104, a transport unit controller 105, a projection position controller 106, a shift amount controller 107, and a display control unit . The overall control unit 101 is communicably connected to the operation unit 24. The overall control unit 101 controls the overall operation of the eccentricity measuring device 50 in response to an operation input from the operation unit 24. The operation unit 24 includes an appropriate input device such as a keyboard, a touch panel, or an operation switch that allows an operator to input operations.

[0042] The overall control unit 101 is electrically connected to the light source 10. The overall control unit 101 performs on / off control of the light source 10 and light amount control based on an operation input from the operation unit 24. The overall control unit 101 is communicably connected to the measurement imager 17 and the observation imager 44. The overall control unit 101 acquires image signals sent by the measurement imager 17 and the observation imager 44. The overall control unit 101 is connected to a calculation processing unit 102, an image processing unit 103, a storage unit 104, a transport unit controller 105, a projection position controller 106, a shift amount controller 107, and a display control unit 108 so as to be able to communicate with each other.

[0043] The calculation processing unit 102 performs calculation processing based on a control signal from the overall control unit 101. The calculation processing performed by the calculation processing unit 102 is not particularly limited as long as it is calculation necessary for measurement in the eccentricity measuring device 50. For example, examples of the calculation processing performed by the calculation processing unit 102 include various calculations based on design values ​​of the test optical system 41 stored in advance in the storage unit 104, and calculation of the amount of eccentricity based on a measurement signal of the amount of runout, which will be described later.

[0044] The image processing unit 103 performs image processing of an image based on an image signal obtained from the measurement imager 17. As an example of the image processing performed by the image processing unit 103, a reflected image I is generated based on the image captured by the measurement imager 17. R Image processing to find the center position of reflected image I R In the case where the imaging device has a magnification measuring section (to be described later), image processing is performed to obtain the dimensions of the magnification measuring section from the image.

[0045] The storage unit 104 stores, for example, data input through the operation unit 24 and the measurement imager 17, data calculated and generated by the calculation processing unit 102 and the image processing unit 103, etc. The storage unit 104 includes one or more appropriate storage media, such as a memory, a hard disk, a removable storage medium, etc.

[0046] The transport unit controller 105 controls the amount and direction of movement of the main body unit 3 by the moving stage 2 based on a control signal from the overall control unit 101 . The transport unit controller 105 is connected to the optical system transport unit drive unit 2c so as to be able to communicate with the optical system transport unit drive unit 2c. By sending a control signal to the optical system transport unit drive unit 2c, the optical system transport unit 2b is driven to move the main body unit 3 in the z-axis direction.

[0047] The projection position controller 106 is connected to the adjustment lens driving unit 21 so as to be able to communicate with the adjustment lens driving unit 21. The projection position controller 106 controls the amount and direction of movement of the adjustment lens 13 by the adjustment lens driving unit 21 based on a control signal from the overall control unit 101. M By moving along the optical axis O, the position where the light image IP' is projected changes M Move along. The control signal sent from the overall control unit 101 to the projection position controller 106 is sent mainly for the purpose of adjusting the IO distance, which will be described later, to a set value. However, the control signal from the overall control unit 101 is not limited to the purpose of setting the IO distance. The overall control unit 101 can send a control signal to the projection position controller 106 to move the optical image IP' to an appropriate position as required for measurement.

[0048] The shift amount controller 107 is communicatively connected to the wedge prism driving unit 22. Based on a control signal from the overall control unit 101, the shift amount controller 107 drives the wedge prism driving unit 22 to selectively switch the position of the wedge prism 18 between the retracted position and the advanced position.

[0049] The display control unit 108 is communicably connected to the display unit 23, which is formed of, for example, a display. The display control unit 108 controls the display of the display unit 23 based on a control signal from the overall control unit 101. The display unit 23 displays various images related to the decentering measurement, such as images acquired by the overall control unit 101 from the measurement imager 17 and the endoscope imager 42, images generated by the image processing unit 103, and images acquired by the overall control unit 101 from the observation imager 44. Furthermore, the display unit 23 displays various information related to the decentering measurement, such as optical design information of the test optical system 41 and numerical information calculated by the arithmetic processing unit 102.

[0050] The details of the control of each part in the measurement control section 5 will be explained in the explanation of the operation of the eccentricity measuring device 50.

[0051] The device configuration of the measurement control unit 5 includes a computer consisting of a CPU, a memory, an input / output interface, an external storage device, etc. An appropriate control program that realizes the control operation of the measurement control unit 5 is loaded and executed in the computer included in the measurement control unit 5. The measurement control unit 5 may include appropriate hardware in addition to the computer.

[0052] Next, an eccentricity measuring method according to this embodiment that can be performed using the eccentricity measuring device 50 will be described together with the operation of the eccentricity measuring device 50. First, a test optical system 41A, which is a specific example of the test optical system 41 to be referred to in the following description, will be described. FIG. 3 is a cross-sectional view showing an example of the optical system to be measured.

[0053] As shown in FIG. 3, the test optical system 41A includes, from the object side to the image side, a first lens L1, a second lens L2, an infrared absorbing filter Fa, an aperture stop S A , the third lens L3, the fourth lens L4, the fifth lens L5, and the cover glass CG A are arranged in this order. I 41A is the image plane of the test optical system 41A. 41AThe imaging surface of the endoscope imager 42 is disposed on the imaging surface.

[0054] The first lens L1 is a negative plano-concave lens with its flat surface facing the object side. The second lens L2 is a positive meniscus lens with a convex surface facing the image side. The infrared absorbing filter Fa is a parallel plate with an infrared cut coating for a YAG laser on the object side and an infrared cut coating for a semiconductor laser (LD) on the image side. Aperture S A is formed on the image-side plane of the infrared absorbing filter Fa. The third lens L3 is a plano-convex positive lens with its flat surface facing the object side. The fourth lens L4 is a biconvex positive lens. The fifth lens L5 is a negative meniscus lens with a convex surface facing the image side. Here, the fourth lens L4 and the fifth lens L5 are a cemented lens in which the image side lens surface of the fourth lens L4 and the object side lens surface of the fifth lens L5 are cemented together. Cover glass CG A is a parallel plate that covers the imaging surface of the endoscopic imager 42 from the object side.

[0055] The following [Table A] shows the numerical data of the design values ​​of the test optical system 41A. In [Table A], the r column is the radius of curvature of each lens surface (mm), the d column is the surface spacing (mm) between each lens surface, the ne column is the refractive index of each lens for the e-line, the V column is the apparent surface apex position (mm), the R column is the apparent radius of curvature (mm), the SC column is the apparent spherical center position (mm), Fno is the F-number, and the aperture is the aperture stop. Appearance The top position V s is the optical axis O from the designed apex position of the first surface M The apparent vertex position V s In the coordinate system expressing the above, the direction from the first surface to the imaging surface is considered positive. In Fig. 3, the radius of curvature and the surface spacing of the surface number s (where s = 1, ..., 14) are r s , ds In the test optical system 41A, the optical surfaces that are the targets of eccentricity measurement by the eccentricity measurement device 50 have surface numbers 1 to 6 and 8 to 14. That is, the test surfaces Si in the test optical system 41A include a maximum of 13 surfaces having surface numbers 1 to 6 and 8 to 14.

[0056] [Table A] Surface number rd ne VR SC 1∞0.2115 1.88815 0.000∞∞ 2 0.6603 0.4242 1.00000 0.112 0.350 0.462 3 -3.0889 0.4871 1.97189 0.382 0.761 1.143 4 -1.9529 0.3281 1.00000 0.460 -2.405 -1.945 5 ∞ 0.4230 1.49557 0.530 0.523 1.054 6 ∞ 0.0000 1.00000 0.579 0.475 1.054 7(Aperture)∞ 0.1872 8 ∞ 0.6251 1.69979 0.606 0.447 1.054 9 -1.1895 0.2131 1.00000 0.652 -0.097 0.555 10 1.4519 0.8357 1.65425 0.678 0.359 1.037 11 -1.0589 0.3277 1.97189 0.784 -0.123 0.662 12 -4.3264 0.1405 1.00000 0.854 -0.305 0.549 13 ∞ 0.8559 1.51825 0.942 -0.443 0.500 14 ∞ 0.0000 1.00000 315.550 -315.050 0.500 Imaging area ∞ Fno 2.95 Half angle of view: 66.2° Image height 0.475mm

[0057] In the objective optical system of an endoscope, such as the test optical system 41A in this example, the first lens L1 has a strong concave power, and therefore has the characteristic that the apparent spherical center of the optical surface on the image side of the first lens L1 tends to be close to each other. Table 1 below shows the apparent spherical center positions (mm) (referred to as "SC (mm)" in Table 1) of each optical surface (surface numbers 1 to 6, 8 to 14, and so on) of the test optical system 41A, sorted in order from the maximum value in the positive direction to the negative direction.

[0058] [Table 1]

[0059] In the "Close Distance" column of [Table 1], the optical axis O M The optical axis O between the two adjacent apparent spherical centers whose positions in the direction along the line are closer to each other. M For example, the apparent center of the third surface is adjacent to the apparent centers of the first and fifth surfaces, but the apparent center of the third surface is closer to the apparent center of the fifth surface than to the apparent center of the first surface. For this reason, the "Closest Distance" column shows 0.089 mm, which is the distance between the apparent centers of the fifth surface and the third surface. As can be seen from [Table 1], the apparent spherical centers of the 5th, 6th, and 8th surfaces are aligned with each other. The apparent spherical center of the 10th surface is adjacent to the apparent spherical centers of the 5th, 6th, and 8th surfaces at an interval of 0.017 mm. The apparent spherical centers of the 11th and 9th surfaces are adjacent to each other at an interval of 0.107 mm. The apparent spherical centers of the 9th and 12th surfaces are adjacent to each other at an interval of 0.006 mm. The apparent spherical center of the 12th surface is adjacent to the apparent spherical centers of the 13th to 14th surfaces at an interval of 0.049 mm. The apparent spherical centers of the 13th and 14th surfaces are aligned with each other. The apparent spherical center of the 2nd surface is adjacent to the apparent spherical centers of the 13th and 14th surfaces at an interval of 0.038 mm. The apparent center of the fourth surface and the apparent center of the second surface are adjacent with a distance of 2.407 mm.

[0060] Fig. 4 is a schematic diagram for explaining the principle of eccentricity measurement by the conventional autocollimation method, and Fig. 5 is a schematic diagram showing an example of a reflected image observed in the conventional autocollimation method. In the conventional autocollimation method, the projection plane P' is set at a position that passes through the apparent spherical center SCi of the test surface Si. However, in Fig. 4, for ease of viewing, the apparent test surface Si is shown by virtual lines instead of the incident optical system and the test surface Si. Since the projection plane P' and the image plane I coincide, the reflected image I can be obtained by setting the IO distance to 0. Ri In this case, the apparent center of the sphere of the optical surface other than the test surface Si is parallel to the optical axis O. M When the objective lens 15 is located near the apparent spherical center SCi of the test surface Si in the direction along the line of the arrows, a reflected image or a blurred image of the reflected image or image of the blurred image of the reflected image or image of the imager 17 for measurement is observed on the observation plane F'. B Since the surface is optically conjugate with the surface Si, images other than the reflected image reflected by the test surface Si are also captured by the measurement imager 17. For this reason, it is not possible to identify which image corresponds to the reflected image reflected by the test surface Si, making it difficult to measure eccentricity.

[0061] In the example shown in FIG. 4, the projection plane P' and the image plane I coincide with each other, so the light image IP' and the reflected image I formed by reflection from the apparent test surface si are Ri The apparent center of the sphere S C Optical axis O passes through i M When the IO distance is set to 0, the optical image IP' and the observation plane F' coincide with each other. M When the object is moved in the direction along the optical axis O, the optical image IP' and the observation surface F' are integrated. M When the light image IP' is at a specific position, the reflected image I Ri can be observed. Reflected image I for light image IP' RiIf the lateral magnification is called the reflection magnification, then the reflection magnification will be ±1 when the IO distance is 0. Here, a reflection magnification of -1 corresponds to the case where the projection plane P' is aligned with the apparent spherical center SCi (see FIG. 4), and a reflection magnification of +1 corresponds to the case where the projection plane P' is aligned with the apparent surface vertex Vi. Optical axis O M When there is decentering of the spherical center of the test surface Si and the incident optical system, the apparent spherical center SCi, which is a point conjugate with the spherical center of the test surface Si, is also on the optical axis O. M The apparent spherical center SCi is eccentric with respect to the optical axis O M From the optical axis O M If the image is decentered by δ in the direction perpendicular to the axis, the reflected image I Ri is the optical axis O M In this case, the optical axis O on the imaging surface of the measurement imager 17 is M Position and reflected image I Ri If the position of the apparent spherical center SCi can be specified, the eccentricity δ of the apparent spherical center SCi can be obtained by dividing the distance by 2. However, in the test optical system 41, the optical axis O M When there are a plurality of optical surfaces whose apparent spherical centers SCi are close to each other in the direction along the axis of the optical axis, for example, as shown in FIG. 5, a reflected image I reflected by the different optical surfaces is displayed on the display screen 23a of the display unit 23. Ra , I Rb , I Rc are the apparent centers of the spheres S C The observation is made at a position according to the amount of eccentricity of i. However, in the autocollimation method, the reflection magnification of the optical surface is −1 or 1, so it is difficult to identify the image reflected by the test surface Si from the image on the display screen 23a using the difference in reflection magnification as a clue.

[0062] 6 and 7 are schematic diagrams for explaining the principle of eccentricity measurement in the eccentricity measuring method according to the first embodiment of the present invention. 6 and 7 and FIGS. 8 and 9 described later, similarly to FIG. 4, instead of the incident-side optical system and the test surface Si, an apparent test surface si corresponding to the test surface Si is shown by virtual lines.

[0063] In the decentering measurement method of the present embodiment, the state of the decentering measurement device 50 is set so that the I-O distance is L (L ≠ 0) by positioning the adjustment lens 13, and the main body 3 is moved using the moving stage 2 to move the optical axis O M The position of the projection plane P' is moved in the direction along the optical axis O. As a result, the optical image IP' and the observation plane F' are aligned integrally along the optical axis O. M Move in the direction along the axis. 6 shows a state in which a reflected image is observed with the IO distance L set to a positive value. That is, when the light image IP' is on the right side of the observation plane F', L is positive. FIG. 6 shows an example in which the projection plane P' is disposed between the apparent spherical center SCi and the apparent surface vertex Vi. The position of the projection plane P' (not shown) is such that the reflected image I R is positioned at a position where The reflection magnification β of the apparent test surface si is expressed by the following formula (2) based on calculation using the imaging formula for the apparent test surface si.

[0064]

number

[0065] Here, R is the apparent radius of curvature of the test surface Si. As shown in formula (2), when L is not 0, the reflection magnification β takes a positive or negative value, regardless of the magnitude or positive or negative value of L. For example, when R>0, The compound of formula (2) issue but + If β is positive and , Multiple issue but - If β is negative. If R<0, The compound of formula (2) issue but - If β is positive and , Multiple issue but + If β is a negative value. In the example shown in FIG. 6 (R<0), β is a negative value. In this specification, a reflection image I with a positive reflection magnification β is Riis called a "regular reflection image." Similarly, a reflection image I Ri is called a "negative reflex image." The light image IP' is aligned along the optical axis O M When the light image IP′ is moved in a direction perpendicular to the incident light β, the specularly reflected image moves in the same direction as the light image IP′ according to the magnitude of β. The light image IP' is aligned along the optical axis O M When the light image IP′ is moved in a direction perpendicular to the light image IP′, the negative reflection image moves in the opposite direction to the light image IP′ according to the magnitude of β.

[0066] The apparent spherical center SCi is the optical axis O M In the direction perpendicular to the optical axis O M When the reflected image I Ri is the optical axis O on the observation plane F'. M In this case, the optical axis O on the imaging surface of the measurement imager 17 is M Position of and reflected image I Ri The optical axis O calculated based on the position of M The amount of eccentricity δ of the apparent spherical center SCi can be calculated using the amount of deflection (=(1-β)δ) in the direction perpendicular to the target surface si and the reflection magnification β of the apparent test surface si calculated from the design value of the test optical system 41.

[0067] FIG. 7 shows an example in which the projection plane P' is placed near the apparent surface vertex Vi. 7 shows a state in which a reflected image is observed with the IO distance L set to a positive value. That is, when the light image IP' is on the right side of the observation plane F', L is positive. The position of the projection plane P' (not shown) is such that the reflected image I R is positioned at a position where The reflection magnification β of the apparent test surface si is expressed by the above formula (2). In the example shown in FIG. 7 (R<0), β is a positive value. Therefore, the reflection image I Ri is a specular reflection image.

[0068] The apparent spherical center SCi is the optical axis O M In the direction perpendicular to the optical axis O M When the reflected image IRi is the optical axis O on the observation plane F'. M The deflection amount is (1-β)δ. Therefore, the amount of eccentricity δ of the apparent spherical center SCi of the test surface Si can be calculated in the same manner as in the example shown in FIG.

[0069] Next, a method of measuring eccentricity when the apparent radius of curvature of the test surface Si is infinite will be described. Fig. 8 is a schematic diagram for explaining the principle of eccentricity measurement when the apparent radius of curvature is infinite in the eccentricity measuring method according to the first embodiment of the present invention. Fig. 9 is a schematic diagram for explaining the eccentricity measuring method when the apparent radius of curvature is infinite by the conventional autocollimation method.

[0070] In the test optical system 41, the apparent radius of curvature R of the test surface Si is i may become infinite. For example, if the first surface, which is the frontmost surface in the test optical system 41, is a flat surface, the apparent radius of curvature R1 becomes infinite. For example, if the first surface and the second surface adjacent to the rear side of the first surface in the test optical system 41 are flat surfaces, the apparent radii of curvature R1 and R2 become infinite. In particular, in the objective lens of an endoscope, the first surface is often a flat surface. As shown in FIG. 8, according to the decentering measurement method of the present embodiment, a light image IP′ is projected to a position L / 2 away from the apparent vertex of the test surface Si, thereby forming a reflected image I Ri As a result, a specular reflection image with a reflection magnification β of 1 can be formed. Therefore, eccentricity measurement can be performed in the same manner as in the case of using the specular reflection image described above. In addition, for a surface with an apparent radius of curvature of infinity, the apparent center of the sphere is the optical axis O. M If the test surface Si or the incident optical system is decentered, the amount of apparent decentering of the spherical center cannot be defined as the shift amount. M The amount of deflection of the reflected image with respect to the optical axis O is treated as the amount of eccentricity δ of the apparent spherical center. Since the reflection magnification β is 1, if the equations (12) and (13) described later are applied as they are, the denominator becomes 0 and the shift amount of the apparent spherical center diverges. MFor the test surface Si located at infinity along the line, the denominators of the equations (12) and (13) described below are set to 1 to define the shift amount of the apparent sphere center. The coefficient a of the linear combination of the equations (14) and (15) described below is ij For (i=1,…,N, j=1,…,N), calculations are also performed according to the definition. The eccentricity measuring method of this embodiment is preferable in that it can be measured in the same manner whether the apparent radius of curvature of the test surface Si is infinite or not.

[0071] In contrast, as shown in Fig. 9, in the conventional autocollimation method, in order to observe the reflected image of an apparent test surface si with an infinite apparent radius of curvature R, it is necessary to project a parallel light beam Fp and form an image from the reflected light beam Fr in an observation optical system. In other words, it is necessary to change the projection optical system and the observation optical system depending on whether the apparent radius of curvature R is infinite or not. This makes the measurement device complicated, and there is a possibility that measurement errors will increase as the projection optical system and the observation optical system are changed.

[0072] In this manner, once the eccentricity δ of the apparent spherical centers SCi of all test surfaces Si has been calculated, the eccentricity of the spherical centers of each test surface Si is calculated using a matrix that associates the eccentricity δ of the apparent spherical centers SCi of each test surface Si with the eccentricity of the actual spherical centers of the test surfaces Si, and each calculated eccentricity δ, as described below.

[0073] As described above, in the decentering measurement method of the present embodiment, the optical axis O of the projection plane P' is M The position in the direction along the line is shifted from both the apparent spherical center SCi and the apparent surface vertex Vi of the test surface Si, and the reflected image I Ri Form. In this case, the IO distance L is set to a non-zero value, and the reflected image I is projected onto the observation plane F'. Ri If the position of the projection plane P' is appropriately determined so that the reflected image I Ri is formed, and a reflected image I Ri can be observed. In this case, the reflection magnification β of the apparent test surface si takes a value other than ±1 depending on the position of the projection surface P', and the reflected image I Ri becomes a positive or negative reflected image. In Table A above, when attention is paid to the design values ​​of the surface numbers whose apparent centers are close to each other, it can be seen that even though the apparent centers are close to each other, the apparent radii of curvature are different from each other. Therefore, multiple reflection images I Ri are observed, the reflection magnifications of the apparent test surface si that form each are different, so the reflected image I reflected by the test surface Si Ri may be able to identify.

[0074] An eccentricity measurement method that uses a reflected image obtained with an IO distance of 0, such as the conventional autocollimation method, has a reflection magnification of 1, and is therefore sometimes referred to as the 1x magnification method. In contrast, an eccentricity measurement method that uses a reflected image by setting an IO distance that is not 0, such as the eccentricity measurement method of this embodiment, is sometimes referred to as the unequal magnification method.

[0075] Next, an example of a method for distinguishing a reflected image in the eccentricity measuring method of this embodiment will be described. Fig. 10 is a schematic diagram showing an example of an index used in the eccentricity measuring method according to the first embodiment of the present invention. Fig. 11 is a schematic diagram showing a first example of a method for discriminating reflected images in the eccentricity measuring method according to the first embodiment of the present invention.

[0076] In the first example discrimination method, an index having a pattern that allows magnification measurement, rather than a point image, is projected as the light image IP'. The light image IP' shown in FIG. 10 is a first horizontal line portion b Px1 , first vertical line section b Py1 , second horizontal line part b Px2 , second vertical line section b Py2 , and the third vertical line section b Py3 has. First horizontal line b Px1 and the first vertical line b Py1 The optical axis O M The first horizontal line segment b is a line segment of equal length that bisects the first horizontal line segment b. Px1 The first vertical line portion b extends in the x-axis direction.Py1 The first horizontal line portion b extends in the y-axis direction. Px1 and the first vertical line b Py1 Intersection point b PO is the optical axis O M Represents the position of. Second horizontal line b Px2 is the first horizontal line part b Px1 from the negative y-axis direction w Py The first horizontal line part b is separated by Px1 The second horizontal line segment b is a line segment that extends parallel to the Px2 The first vertical line b Py1 From the x-axis, the positive and negative directions are Px The length of the Second vertical line b Py2 The second horizontal line part b Px2 A first horizontal line portion b extends in the y-axis positive direction from the end of the first horizontal line portion b in the x-axis positive direction. Px1 The second vertical line segment b intersects with Py2 and the first vertical line bPy1 The distance between Px It is. Third vertical line section b Py3 The second horizontal line part b Px2 A first horizontal line portion b extends from the end in the negative x-axis direction in the positive y-axis direction. Px1 The third vertical line segment b intersects with Py3 and the first vertical line bPy1 The distance between Px It is.

[0077] In the unequal magnification method using such an optical image IP', the main body 3 is moved along the optical axis O by using the moving stage 2 so that the image plane I coincides with the focal plane F'. M Move the lens in the direction along the optical axis O M When the position of the projection plane P' is moved in the direction along the line, for example, as shown in FIG. 11, the image I of the reflected image is displayed on the display screen 23a. Rk , I Rm , I Rn The top, bottom, left and right of the display screen 23a coincide with the top, bottom, left and right of the observation surface F' as viewed from the positive direction of the z axis (the same applies to the display screens 23a in the other drawings below). Since each image displayed on the display screen 23a is similar in shape to the pattern of the light image IP', it is an image formed by reflecting the measurement light beam, and when the position of the projection plane P' is determined to observe the reflected image of the test surface Si of the observation target, the reflected images of other optical surfaces are also formed near the observation plane F', and are therefore reflected on the observation plane F'. M Since the positions of the images in the direction along the axis of the display 23 differ slightly, each image may appear blurred on the display screen 23a. For example, image I Rm , I Rn The reflected image is an inverted image of the light image IP', so the image I Rm , I Rn The reflected image represented by is a negative reflected image. Image I Rk The reflected image represented by is an upright image of the light image IP', so the image I Rk The reflected image represented by is a specular reflected image. For example, image I Rm is the first horizontal line portion b of the light image IP' Px1 , first vertical line section b Py1 , second horizontal line part b Px2 , second vertical line section b Py2 , and the third vertical line section b Py3 Corresponding to the first horizontal line portion b Rx1 , first vertical line section b Ry1 , second horizontal line part b Rx2 , second vertical line section b Ry2 , and the third vertical line section b Ry3 has. Image I Rm When the length of each part is converted into an actual dimension on the observation plane F', it changes from the dimension of the corresponding part in the light image IP' according to the reflection magnification. For example, image I Rm The reflection magnification of the reflected image corresponding to is β m In the case of the first vertical line part b Ry1 and the second vertical line b Ry2 Distance from Rx W Px of |β m Similarly, the first horizontal line part b Rx1 and the second horizontal line part b Rx2 Distance from Ry W Py of |β m|double.

[0078] For example, image I Rm From w Rx , w Ry By measuring either of these and converting it to the actual dimensions on the observation plane F', the lateral magnification for the light image IP' is calculated as -w Rx / w Px (=-w Ry / w Py ) This lateral magnification is calculated as Rm The reflected image I corresponding to the reflected image formed on the test surface Si is Ri In the case of , the reflected image I Ri The reflection magnification is β. In the eccentricity measuring device 50, the image sent from the measuring imager 17 is processed by the image processing unit 103 to obtain the Rx , w Ry and the lateral magnification is calculated by the calculation processing unit 102. Image I Rk、 I Rn The lateral magnification of each reflected image corresponding to the optical image IP' is calculated in the same manner. The overall control unit 101 calculates the reflection magnification of the apparent test surface si corresponding to each test surface Si of the test optical system 41 when the IO distance is L, and stores the calculated reflection magnification in the storage unit 104. The overall control unit 101 determines that an image having a lateral magnification closest to the reflection magnification of the apparent test surface si corresponding to the test surface Si of the measurement target is a reflected image I reflected by the test surface Si. Ri Identify it as such.

[0079] According to the first example discrimination method, the method includes measuring the lateral magnification of the observation image relative to the light image represented by the observation image formed by reflection of the light image based on an image of the observation surface acquired by a measurement imager, which is the measurement image, and identifying as the reflected image the observation image for which the measured lateral magnification is closest to the design value of the reflection magnification of the apparent surface of the test surface. Image I Rk , I Rm , I Rn The reflected image corresponding to is an example of an observed image formed by reflection of the light image IP'. In particular, according to the first example discrimination method, the optical image has a magnification measurement portion that expands and contracts according to the reflection magnification of the apparent surface, and measuring the lateral magnification includes measuring the dimensions of the magnification measurement portion in the observation image in the measurement image. First horizontal line portion b in the light image IP' Px1 , first vertical line section b Py1 , second horizontal line part b Px2 , second vertical line section b Py2 , and the third vertical line section b Py3 is an example of a magnification measuring unit.

[0080] The discrimination method of the first example can be performed automatically by the measurement control unit 5 of the eccentricity measuring device 50. However, for example, the lateral magnification may be measured by an operator by image measurement on the display screen 23a, so that the operator can determine the lateral magnification.

[0081] Next, the second example of the discrimination method will be described. FIG. 12 is a schematic diagram showing a second example of a method for discriminating a reflected image in the eccentricity measuring method according to the first embodiment of the present invention. In the discrimination method of the second example, the light image IP' is not particularly limited. It may be an index similar to that of the first example, or may be a point image. FIG. 12 shows a schematic image corresponding to the case where the light image IP' is a point image. In the second example of the discrimination method, when a plurality of reflected images are observed on the display screen 23a, the light image IP' is aligned with the optical axis O. M Then, the reflected image I is measured by comparing the measurement image obtained before the measurement and the image obtained after the measurement. Ri Identify. In the eccentricity measuring device 50, the light image IP' is moved by moving the wedge prism 18 to the insertion position. For example, Fig. 12 shows an example in which the light image IP' is moved in the negative direction of the x-axis (the direction from left to right in Fig. 12). In FIG. 12, an image I indicated by a two-dot chain line is displayed on the display screen 23a. Rd , I Re , I Rf is the measurement image. When the wedge prism 18 is moved to the insertion position, image IRd , I Re , I Rf For example, the object moves to the position shown by the solid line. This image is acquired by the measurement imager 17 and used as an image for identifying the reflected image. However, the outline arrow in FIG. 12 is added for explanatory purposes and does not appear in the actual image.

[0082] When comparing the measurement image and the reflection identification image, image I Rd , I Re is moving in the same direction as the light image IP'. Rd , I Re It can be seen that image I is a regular reflection image. Rd , I Re The amount of movement of each of the lenses differs depending on the lateral magnification of the apparent test surface si that forms the corresponding reflected image. Image I Rf is moving in the opposite direction to the light image IP'. Rf It can be seen that the image is a negative reflection image. The lateral magnification of the apparent test surface si corresponding to the test surface Si of the measurement target can be calculated in advance from the design data of the test optical system 41, as in the discrimination method of the first example. Re is reflected by the test surface Si and becomes a reflected image I Ri This determination may be made visually by a measurer, or may be made automatically by the measurement control unit 5 of the eccentricity measuring device 50.

[0083] Here, the amount of shift of the optical image IP' by the wedge prism 18 and the reflected image I Ri The relationship between the displacements will be explained. Optical axis O M Reflection image on a plane perpendicular to Ri The displacement D is expressed by the following equation (3).

[0084]

number

[0085] where f p is the focal length of the adjustment lens 13, f k is the focal length of the imaging lens 16, θ is the ray deflection angle of the wedge prism 18, p is the distance between the focal plane P of the adjustment lens 13 and the focal plane F of the objective lens 15 (see FIG. 1), and β is the reflected image I Ri is the reflection magnification of the apparent test surface si that forms By solving equation (3) for β and eliminating p using equation (1) above, we obtain equation (4) below.

[0086]

number

[0087] For this purpose, the displacement D of each reflected image is measured, the corresponding reflection magnification β is calculated from equation (4), and the reflected image closest to the design value of the reflection magnification β on the apparent test surface si calculated in advance is called the reflected image I Ri This determination can be performed automatically by the measurement control unit 5 of the eccentricity measuring device 50.

[0088] The discrimination method of the second example, like the first example, comprises measuring the lateral magnification of the observation image relative to the light image represented by the observation image formed by reflection of the light image based on an image of the observation surface acquired by a measurement imager, which is the measurement image, and identifying as the reflected image the observation image for which the lateral magnification has been measured to be closest to the design value of the reflection magnification of the apparent surface of the test surface. Image I Rd , I Re , I Rf is an example of an observation image formed by reflection of a light image IP'. In particular, the second example discrimination method includes obtaining a measurement image with the light image positioned on a reference axis, shifting the light image in a direction perpendicular to the reference axis to obtain an image for identifying a reflected image, comparing the measurement image with the image for identifying a reflected image to measure the displacement in the observation plane of the observation image corresponding to the amount of shift of the light image, and measuring the lateral magnification from the amount of shift and the displacement.

[0089] The eccentricity measuring device 50 of this embodiment can execute the discrimination method of the first example described above by control of the measurement control unit 5, so the measurement control unit 5 is an example of a reflection magnification measuring unit that measures the lateral magnification of an observation image relative to the light image represented by the observation image formed by reflection of the light image, based on the image at the observation position acquired by the measurement imager. The eccentricity measuring device 50 of this embodiment has a wedge prism 18, a wedge prism driving section 22, and a measurement control section 5, and can execute the discrimination method of the second example described above by controlling the measurement control section 5. Therefore, the wedge prism 18, the wedge prism drive unit 22, and the measurement control unit 5 are examples of a reflection magnification measurement unit. In particular, the wedge prism drive unit 22 and the measurement control unit 5 are examples of a reflection magnification measurement control unit that, by inserting a wedge prism into the parallel optical path, moves the optical image at the projection position, causes the measurement imager to acquire an image at the observation position, and measures the lateral magnification represented by the observation image based on the image at the observation position.

[0090] In this embodiment, as a method for distinguishing the reflected image, a method of projecting an index to check the direction and size of the reflected image as in the first example, and a method of inserting and removing a wedge prism as in the second example can be used. Either method can be used without changing the position and attitude of each optical element in the measurement optical system 20 of the eccentricity measurement device 50. For example, the wedge prism 18 is inserted into the parallel optical path only when measuring the reflection magnification when distinguishing the reflected image. When performing eccentricity measurement, the wedge prism 18 is located outside the optical path of the measurement optical system 20, so it does not affect the optical path of the measurement optical system 20 during eccentricity measurement. Furthermore, when the wedge prism 18 moves, it does not affect the position and attitude of each optical element in the measurement optical system 20. The same applies to the first example. Therefore, in this embodiment, the reflection magnification can be measured without changing the position and orientation of each optical element in the measurement optical system 20. In contrast, for example, in a method for measuring the reflection magnification, the adjustment lens 13 is disposed in the measurement optics 20 so as to be aligned with the optical axis O. M It is also possible to shift the optical image IP' laterally by shifting it in a direction perpendicular to the axis of the optical axis. In this case, however, it is difficult to completely return the adjustment lens 13 to its original position during decentering measurement, and the position of the reference point on the observation plane F' changes. This causes an error in decentering measurement.

[0091] In the decentering measurement method of this embodiment, a non-zero set value L is used as the IO distance, so the reflection magnification of the test surface Si has various values ​​other than ±1. This makes it easy to determine from which optical surface the reflected image is reflected. The set value L is set so as not to be too large or too small relative to the apparent radius of curvature of the surface Si to be measured in the optical system 41 to be measured. In the test optical system 41A shown in FIG. 3, as shown in [Table A], the magnitude (absolute value) of the apparent radius of curvature R of most of the optical surfaces is smaller than 0.5 mm. Table 2 below shows the design values ​​of the projection position (mm) of the optical image IP' onto each test surface Si (listed as "projection position (mm)" in Table 2) and the reflection magnification β when the set value L is set to 0.447 mm. Here, the coordinate system of the position is the same as the coordinate system of the apparent spherical center position in Table 1. Each projection position is the projection position when the main body 3 is moved by the moving stage 2 with the IO distance fixed to the set value L. For this reason, the position of the adjustment lens 13 in the measurement optical system 20 is fixed. An example of a value that is neither too large nor too small compared to the apparent radius of curvature of the test surface Si is the median of the apparent radius of curvature of each optical surface of the test optical system 41A, except for those optical surfaces whose apparent radius of curvature is infinite. 0.447 mm is approximately equal to the median value of the apparent radius of curvature in the test optical system 41A.

[0092] [Table 2]

[0093] The projection positions in Table 2 are sorted in order from the maximum value in the positive direction to the negative direction and are shown in Table 3 below. In the "Type of Reflected Image" in Table 3, "Positive" indicates a positive reflected image and "Negative" indicates a negative reflected image. The "Close Distance" column indicates the distance between the optical axis O and the M The optical axis O between the two adjacent reflected images is the closest to each other. M The distance along the line is shown.

[0094] [Table 3]

[0095] From [Table 3], we can see that even if the reflected images are close to each other, they can be distinguished by taking advantage of the difference in reflection magnification. For example, the proximity distance between the specularly reflected image formed on the first surface and the specularly reflected image formed on the second surface is extremely close at 0.003 mm, but the reflection magnifications β are completely different, at 1.000 and 2.901, respectively. For example, as shown in [Table 1], the apparent spherical center distance between the 9th surface and the 12th surface is extremely close at 0.006 mm, so that the conventional autocollimation method cannot distinguish between the respective reflected images. However, as shown in [Table 3], in a measurement with L set to 0.447 mm, the specular reflected image formed at the 11th surface, which is closest to the specular reflected image formed at the 9th surface, is 0.123 mm away. For example, if the depth of field of the observation optical system is about 0.03 mm, no reflected image other than the specular reflected image formed at the 9th surface, including the specular reflected image formed at the 12th surface, will be reflected on the display screen 23a. In this case, an image of a single reflected image will be observed on the display screen 23a.

[0096] The range of the IO distance L can be set with a certain degree of freedom. However, depending on the size of the IO distance L, the reflected image I Ri The optical axis O of the light image IP' MThe position in the direction along the line and the reflection magnification β change. Depending on the magnitude of the error in the value of the IO distance L, the measurement error of the amount of eccentricity of the apparent spherical center of the test surface Si may become large, or the task of identifying the reflected image may be hindered. For example, there is a manufacturing error in the measurement optical system 20, and there is also a movement error in the adjustment lens driving unit 21. For this reason, the IO distance of the eccentricity measuring device 50 adjusted by moving the adjustment lens 13 may deviate from the set value L calculated from the formula (1). In this embodiment, a reference optical element is used to measure the displacement D of the specular reflection image on the test surface. P and the displacement of the negative reflection D N By actually measuring and, the IO distance L can be measured as follows: This makes it possible to measure the value of the IO distance L set by moving the adjustment lens 13. The reference optical element may be any suitable optical element having a test surface with a known radius of curvature that is not infinite. The radius of curvature of the reference optical element is preferably 50% to 200% of the set value L.

[0097] Displacement of the specular reflection image D P and the displacement of the negative reflection D N Both are expressed by equation (3). In the measurement of the positive reflection image and the negative reflection image, f k , f p , θ, and p are the same. Therefore, the reflection magnification β of the test surface that forms the specular reflection image is P The reflection magnification β of the test surface forming the negative reflection image is N Then, the following equation (5) holds.

[0098]

number

[0099] Here, let C be the right-hand side of equation (5). From equation (2), we obtain {L±√(L 2 +R 2 )} / R is β P , the other is β N So, by substituting this into equation (5), we get βP , β N Eliminating this and solving for L gives us the following equation (a), regardless of whether R is positive or negative. In formula (a), R is the radius of curvature of the test surface of the reference optical element used in the measurement.

[0100]

number

[0101] Displacement D using a reference optical element with a known radius of curvature of the test surface P , D N is actually measured and substituted into equations (a) and (b), the value of the IO distance that is actually set can be obtained in the eccentricity measuring device 50. Hereinafter, the measured value of L obtained from equation (a) based on the measured value of variable C may be referred to as the measured value Lm in order to distinguish it from the set value L of the IO distance. The variable C is the ratio of the positive reflectance to the negative reflectance of the reference surface, as shown in equation (5). P , D N The variable C can be measured using any quantity proportional to the positive and negative reflectance of the reference surface. For example, when an index having a magnification measuring portion as shown in FIG. 10 is used as the light image IP', D P Instead, the reflection magnification w of the specular reflection image calculated by the magnification measurement unit Rx / w Px (=w Ry / w Py ) and D N Instead, the reflection magnification -w in the negative reflection image calculated from the magnification measurement unit Rx / w Px (=-w Ry / w Py ) may also be used.

[0102] The measurement of the IO distance can be performed as necessary. For example, the IO distance may be measured when the set value L of the IO distance is changed. For example, the IO distance may be measured when the optical elements included in the measurement optical system 20, such as the adjustment lens 13, the objective lens 15, and the imaging lens 16, are adjusted or replaced. For example, the IO distance may be measured before starting the decentering measurement of the test optical system 41A. In this embodiment, the reference optical element is also used for measuring a reference point, which will be described later, so a detailed method for measuring the IO distance will be described together with a method for measuring a reference point, which will be described later.

[0103] Displacement of the specular reflection image D P and the displacement of the negative reflection D N The measurement value Lm calculated from formula (a) based on the actual measurement values ​​of reflects the manufacturing error of the optical elements of the measurement optical system 20 and the movement error of the adjustment lens 13. For this reason, the measurement value Lm is closer to the actual value than the set value L of the IO distance calculated from formula (1) based on the design values ​​of the optical elements of the measurement optical system 20. By using the measured value Lm obtained by this measurement for eccentricity measurement, the workability and accuracy of the eccentricity measurement can be improved. That is, if the set IO distance value is known accurately, the optical axis O M Therefore, the reflected image in the direction along the line can be more easily seen. When the measurement value Lm of the set IO distance is obtained, the reflection magnification β of the apparent test surface si can be calculated more accurately by substituting the measurement value Lm for L in formula (2). This improves the measurement accuracy of the eccentricity δ of the apparent spherical center of the test surface Si.

[0104] Next, the eccentricity measuring method of this embodiment will be described in detail. FIG. 13 is a flowchart showing an example of the eccentricity measuring method according to the first embodiment of the present invention.

[0105] The eccentricity measuring method of the present embodiment executes steps S1 to S9 based on the flow shown in FIG. In step S1, measurement conditions for decentering measurement are set based on the design data of the test optical system 41A. Examples of the design data include the number of test surfaces Si to be measured for decentering, the radius of curvature r of each test surface Si, the surface interval d, the refractive index ne, and other design values ​​described in [Table A]. The design data is stored in the memory unit 104 of the measurement control unit 5. The design data may include various data that can be calculated using the design values. In this case, the overall control unit 101 of the measurement control unit 5 sends the stored design values ​​to the calculation processing unit 102 and causes the calculation processing unit 102 to calculate values ​​necessary for eccentricity measurement. The calculated values ​​are stored in the memory unit 104. Values ​​calculated using design values ​​include, for example, the position of the apparent vertex V, the apparent radius of curvature R, and the position of the apparent spherical center SC in [Table A]. However, the design data may be calculated in advance by another computer or the like and stored in the storage unit 104. In this case, the calculation process by the measurement control unit 5 can be omitted.

[0106] Examples of the measurement conditions to be set include the set value L of the IO distance, selection of the objective lens 15, selection of the reference optical element, selection of the type of reflected image for each test surface Si used in the decentering measurement, etc. However, the type of reflected image only needs to be selected before the measurement of the test surface Si of the measurement target is performed, and does not have to be selected in this step.

[0107] The set value L may be selected by the measurer, or may be selected by the measurement control unit 5 based on the apparent radius of curvature Ri of each test surface Si. For example, the set value L is selected to be 0.447 mm. After the set value L is selected, the measurement control unit 5 may cause the arithmetic processing unit 102 to calculate values ​​that can be calculated using the set value L and design data, among the values ​​used in the eccentricity measurement. For example, the arithmetic processing unit 102 may calculate the projection position of the optical image IP' and the reflection magnification β for each test surface Si, as shown in [Table 2], and store the calculation results in the storage unit 104.

[0108] After the set value L of the IO distance is selected, the operator selects the objective lens 15 . In the eccentricity measuring device 50, since there is a mechanical restriction on the moving range of the adjustment lens 13, a lens with a focal length that allows the IO distance to be set to the set value L within the moving range of the adjustment lens 13 is selected as the objective lens 15. At that time, a lens is selected that does not interfere with the eccentricity measurement in terms of working distance, observation magnification, numerical aperture, etc. For example, when the value of L is 0.447 mm, a lens having a focal length, NA, and working distance of 3.6 mm, 0.3, and 18 mm, respectively, may be selected as the objective lens 15. In this case, the optical image IP formed by the adjustment lens 13 is p=-3.6 2 It is necessary to position the adjustment lens 13 so that it is at the position / (0.447)=-29 (mm).

[0109] In this embodiment, the reference optical element is used particularly for measuring the IO distance (hereinafter referred to as IO distance measurement) and for measuring a reference point (X0, Y0) on the measurement imager 17 (hereinafter referred to as reference point measurement).

[0110] The reference optical element is an optical element of any type having a reference surface made of a sphere with a known radius of curvature. The reference surface is convex when the set value L of the IO distance is positive, and concave when it is negative. It is preferable that the reference surface has a tolerance of the radius of curvature of 1 μm or less and is polished with high precision. Since the reference optical element only needs to have one reference surface, the reference optical element may be, for example, a single lens. When the reference surface is a convex surface, a biconvex lens, a meniscus lens, a plano-convex lens, a hemispherical lens, a ball lens, or the like may be used. When the reference surface is a concave surface, a biconcave lens, a meniscus lens, a plano-concave lens, or the like may be used. Since the reference surface is used as a reflecting surface, the material is not particularly limited as long as it has good surface accuracy and a reflectance that allows a reflected image to be observed. For example, the material of the reference optical element may be a material that does not transmit light, such as metal or ceramic.

[0111] It is more preferable that the radius of curvature of the reference surface of the reference optical element is close to the set value L of the IO distance. As will be described later, the closer the radius of curvature of the test surface is to the IO distance L, the more the measurement accuracy of the reference point is improved. However, preparing a reference optical element having the same radius of curvature as the set value L of the IO distance suitable for various optical systems 41A to be measured requires a lot of time and cost. For this reason, it is possible to prepare several types of reference optical elements with different radii of curvature of the reference surface and select one close to the set value L.

[0112] In the following, an example will be described in which a highly precisely polished ball lens with a diameter of 0.900 mm is used as the reference optical element. The radius of curvature of this ball lens is 0.450 mm, which is close to the set IO distance L.

[0113] The reference optical element may have a plurality of lenses, and the reference surface may be located behind the first surface. In this case, a lens surface whose apparent radius of curvature is close to the IO distance L is used as the reference surface. For example, when it is known that the test surface of the test optical system 41 has an apparent radius of curvature close to the IO distance L and is formed with high accuracy, the test optical system 41 itself may be used as the reference optical element. In this case, after step S3 described later is completed, the decentering measurement of the test optical system 41 can be performed immediately without replacing the reference optical element with the test optical system 41, and therefore the measurement can be performed efficiently.

[0114] A method for selecting a reflected image in the eccentricity measuring method of this embodiment will be described. In the decentering measurement of this embodiment, it is sufficient that either a positive reflection image or a negative reflection image can be observed for each test surface Si. When the type of reflected image is selected, the projection position of the light image IP' for forming the reflected image for each test surface Si and the reflection magnification of the reflected image are determined. The type of reflected image formed during measurement of each test surface Si can be appropriately selected from the viewpoint of, for example, improving measurement operability, reducing measurement errors, etc. For example, the type of reflected image may be selected from the viewpoint of setting a projection position or reflection magnification suitable for measurement. The selection of the type of reflected image is a preparatory operation for determining the projection positions for forming the reflected image on each test surface Si and for determining the movement positions of the main body part 3 corresponding to each projection position.

[0115] When the measurement conditions necessary for eccentricity measurement are set, step S1 in FIG. 13 ends. As shown in FIG. 13, after step S1 is completed, step S2 is executed. In step S2, the eccentricity measuring device 50 is set. The setting may include, for example, replacing or attaching the objective lens 15 suitable for observing the image of the test optical system 41A, and adjusting the optical axis O of the adjustment lens 13. M The position of the adjustment lens 13 is determined by aligning the focal plane F' of the objective lens 15 with the optical axis O' between the focal plane F' and the projection plane P'. M The distance p' in the direction along the axis is set to coincide with the absolute value of the IO distance L determined in step S1. After the setting is completed, step S3 is executed.

[0116] Steps S1 and S2 are an example of a first step of preparing an eccentricity measuring device having a measurement imager that holds a test optical unit having a test surface, projects a measurement optical image toward the test optical unit, moves the projected optical image linearly relative to the test optical unit, and obtains an image of an observation surface perpendicular to a reference axis defined by a relative movement trajectory in air of the projected optical image with respect to the test optical unit. The optical image IP is an example of the measurement optical image, and the optical image IP' is an example of the projected optical image. The image plane I of the measurement imager 17 B and the focal plane F' are conjugate.

[0117] In step S3, a reference point for eccentricity measurement is measured. In this step, an example in which the IO distance is also measured will be described. The optical axis O of the measurement optical system 20 Mhas been described as an ideal axis of the measurement optical system 20 when there is no decentering error in each optical system of the measurement optical system 20. However, if there is an error in decentering in each optical system of the measurement optical system 20, the optical image IP' will not coincide with the optical axis O of the decentering measurement device 50. M The image plane I B The center position of the measurement imager 17 that photoelectrically converts the light image at is the optical axis O on the focal plane F' (observation plane F'). M In terms of design, it is ideal for the image plane I to be conjugate with the intersection of the two. However, if there is an error in the decentering of each optical system of the measurement optical system 20, B The center position of the measurement imager 17 that photoelectrically converts the light image at is located on the focal plane F' (observation plane F') along the optical axis O. M It is the conjugate of the point shifted to the side from the intersection of For example, every time the eccentricity measuring device 50 is set, there is a possibility that the eccentricity errors of the objective lens 15 and the adjustment lens 13 may change. Therefore, every time the eccentricity measuring device 50 is set, the optical image IP′ and the image plane I B The conjugate point of the center of the measurement imager 17 that photoelectrically converts the light image at is the optical axis O. M The position in the plane perpendicular to the surface may change. In addition, the direction of movement of the moving stage 2 along the z-axis is the same as the optical axis O in the design. M However, due to assembly errors between the measurement optical system 20 and the moving stage 2 and manufacturing errors of the moving stage 2, the orientation may not be exactly the same, and there may be a slight deviation. That is, the optical axis O in the eccentricity measuring device 50 M and a reference axis O defined by the movement locus of the light image IP'. m and may not be coaxial, and the reference axis O m The position on the measurement imager 17 corresponding to the position of may not be the center position on the measurement imager 17. In this embodiment, the reference axis O of the reflected image m The amount of deflection is calculated from the image captured by the measurement imager 17. m The position of the reference point on the measurement imager 17 corresponding to the position of must be known accurately. Furthermore, as described above, the position of the reflected image and the reflection magnification change when the value of the IO distance L changes. By actually measuring the set IO distance L and reflecting it in the calculation of the amount of deflection, the measurement accuracy of the amount of deflection can be improved. In this embodiment, the actual measured value of the IO distance L is also used to calculate the position of the reference point.

[0118] Fig. 14 is a flowchart showing an example of a reference point measuring method in the eccentricity measuring method according to the first embodiment of the present invention. Figs. 15 and 16 are schematic diagrams showing a measuring method of the IO distance L in the eccentricity measuring method according to the first embodiment of the present invention. In step S3, steps S11 to S19 are executed according to the flow shown in Fig. 14. Steps S12 to S16 are steps relating to IO distance measurement. Step S17 is a step relating to reference point measurement.

[0119] 1, a reference optical element 43 is placed in place of the test optical system 41A within a range in which the optical image IP' can be moved by the movement of the moving stage 2. The reference optical element 43 is held on the holding table 4 by a holder 4a. The reference optical element 43 shown in FIG. 1 is held by a holder 4a of the holding table 4, but the reference optical element 43 may be held by a member other than the holding table 4 as long as its position relative to the base 1 is fixed during measurement.

[0120] For example, a ball lens with a diameter of 0.900 mm can be used as the reference optical element 43. Since the set IO distance L is a positive value of 0.447 mm, the first surface, which is a convex spherical surface on the front side of the reference optical element 43, is set as the test surface 43a in this measurement. The radius of curvature of the test surface 43a is 0.450 mm. The spherical center of the test surface 43a is, for example, the optical axis O M Preferably near the optical axis O M It is more preferable that the holding position of the reference optical element 43 in the direction along the z-axis is within a range where each projection position at which a specular reflection image and a negative reflection image by the test surface 43a are observed overlaps with a projection position used for measuring the test optical system 41A. Table 4 below shows the projection positions of the light image IP' for forming the positive reflection image and the negative reflection image, the reflection magnifications β, and the value of (1-β) when the IO distance L is 0.447 mm. Here, the projection positions are those when the IO distance is fixed at 0.447 mm and the main body 3 is moved using the moving stage 2. Therefore, the position of the adjustment lens 13 in the measurement optical system 20 is fixed. The coordinate system of the projection position has the apex of the first surface of the reference optical element 43 as the origin, and the direction from the eccentricity measurement device 50 toward the reference optical element 43 is positive (same below).

[0121] [Table 4]

[0122] As shown in Table 4, the reflection magnification is 2.403 mm for the positive reflection image and −0.416 mm for the negative reflection image. M The (1-β) which represents the sensitivity to deflection in the direction perpendicular to the reflectance is -1.403 for the positive reflection image and 1.416 for the negative reflection image. In this way, by selecting the radius of curvature of the test surface 43a to be a value close to the IO distance L, the magnitude of the sensitivity to deflection of the reflected image (|1-β|) becomes approximately equal.

[0123] In step S12, the specular reflection image formed on the test surface 43a is observed. First, with the light source 10 turned on, the moving stage 2 is driven in the direction along the z-axis to move the optical image IP' onto the test surface 43a. Whether the optical image IP' is projected onto the test surface 43a may be confirmed visually, but it is more preferable to prepare a mechanism in the eccentricity measuring device 50 for more convenient confirmation. In this embodiment, as shown in Fig. 1, an observation imager 44 is disposed for observing an image at a position optically conjugate with the projection surface P'. The observation imager 44 allows the light image IP' and the image around the light image IP' to be observed in a wide field of view. Therefore, it is possible to check whether the light image IP' is projected onto the test surface 43a by using the image captured by the observation imager 44.

[0124] Thereafter, in order to observe the specular reflection image, the moving stage 2 is driven along the z-axis to move the main body 3 by 0.131 mm toward the reference optical element 43 . If the value of the IO distance L on the eccentricity measuring device 50 set in step S2 matches the setting value of the IO distance L determined in step S1, a specular reflection image is formed on the observation plane F'. In this case, an image is formed on the imaging plane of the measurement imager 17 conjugate with the observation plane F' through the observation optical system, so that the measurer can observe the specular reflection image on the display screen 23a of the display unit 23. However, if the IO distance L on the eccentricity measuring device 50 deviates from the set value, the reflected image cannot be observed. In this case, the main body 3 to which the measurement optical system 20 is fixed is moved appropriately along the z-axis to find the regular reflected image formed on the test surface 43a.

[0125] Figure 15 shows a regular reflection image I RP (See solid line) is observed. Center O of the display screen 23a B is expressed as, for example, (Xc, Yc) in an XY coordinate system fixed to the measurement imager 17. Here, the X-axis and the Y-axis are parallel to the x-axis and y-axis of the eccentricity measuring device 50, respectively. The overall control unit 101 processes the image sent from the measurement imager 17 by the image processing unit 103 to obtain a specular reflection image I RP Center of P Position coordinates (X P ,Y P ) is calculated. This completes step S12.

[0126] After this, step S13 is executed. In step S13, the optical image IP' is aligned along the optical axis O M Shift in the direction perpendicular to the normal reflection image I RP Displacement D P Measure. The operator performs an operation input to insert the wedge prism 18 into the optical path of the collimated beam F2 via the operation unit 24. When the overall control unit 101 of the measurement control unit 5 detects the operation input, it sends a control signal to the shift amount controller 107 to drive the wedge prism driving unit 22. As a result, the wedge prism 18 advances into the optical path of the collimated beam F2. As a result, for example, the light image IP' is shifted in the direction along the x-axis. RP is the regular reflection image I shown by the dashed line in Figure 15. RP The overall control unit 101 shifts the specular reflection image I RP 'The Center of P ' position coordinates (X P ',Y P ') is calculated. The overall control unit 101 P (X P ,Y P ) and O P '(X P ',Y P ') is sent to the arithmetic processing unit 102, and the arithmetic processing unit 102 outputs the regular reflection image I RP Displacement of 'D P The calculated value is stored in the storage unit 104. This completes step S13.

[0127] After this, step S14 is executed. In step S14, the negative reflection image formed on the test surface 43a is observed. As in step S12, the main body 3 is moved to a position where the light image IP' is projected onto the test surface 43a, and then the main body 3 is moved 0.766 mm toward the reference optical element 43 to observe the negative reflection image. If the reflected image cannot be observed, similarly to step S52, the main body 3 is moved appropriately along the z-axis from the destination to find a negative reflected image formed on the test surface 43a.

[0128] Figure 16 shows negative reflection image I RN (See solid line) is observed. The overall control unit 101 performs the same process as in step S12 to obtain the negative reflection image IRN Center of N Position coordinates (X N ,Y N ) is calculated. This completes step S14.

[0129] After this, step S15 is executed. In step S15, similarly to step S13, the optical image IP' is aligned along the optical axis O M Shift the negative reflection image I RN Displacement D N Measure. The overall control unit 101 controls the negative reflection image I RN 'The Center of N ' position coordinates (X N ',Y N ') is calculated in step S54. N (X N ,Y N ) and O N '(X N ',Y N ') is sent to the arithmetic processing unit 102, and the arithmetic processing unit 102 outputs the negative reflection image I RN Displacement of 'D N The calculated value is stored in the storage unit 104. This completes step S15.

[0130] After this, step S16 is executed. In step S16, the displacement D P , D N and the radius of curvature R of the test surface 43 a of the reference optical element 43, the IO distance L is calculated. The overall control unit 101 detects the displacement D P , D N and the radius of curvature R are sent to the calculation processing unit 102, which calculates the IO distance L. The calculation processing unit 102 calculates the value of the IO distance L based on the above-mentioned formulas (a) and (b). This determines the measurement value Lm of the IO distance L. The value of Lm is sent to the overall control unit 101 and stored in the memory unit 104. In the following, the description will be made on the assumption that the value of the IO distance L measured in this manner is 0.510 mm. This completes step S16 and the IO distance measurement.

[0131] In the above steps S11 to S16, the regular reflection image is observed, and the displacement D P After measuring, the negative reflection image is observed and the displacement D N As explained in the example of measuring the displacement D N After measuring, the specular reflection image is observed and the displacement D P That is, steps S12 and S13 may be performed after steps S14 and S15.

[0132] After that, step S17 is executed. In step S17, a reference point is calculated based on the measurement value of the IO distance L calculated in step S56. The reference point in this specification is a point that should be the origin in measuring the amount of deflection of the reflected image. The amount of deflection of the reflected image is calculated from the image on the measuring imager 17. B However, since there are manufacturing and assembly errors in the eccentricity measuring device 50 and the measurement optical system 20, it is preferable that the reference point coincide with the center O. B In many cases, the deviation from the reference point is unacceptable for eccentricity measurement. If the holding table 4 has a rotation holding mechanism that can rotate the test object around the reference axis of measurement with high precision, the rotation center of the reflected image can be used as the reference point. However, for example, a test object such as the tip of an endoscope is long with a bending section and a flexible tube section connected to the rear end of the tip, and in order to rotate the tip, the bending section and the flexible tube section must also be rotated together with the tip, making it difficult to provide a rotation holding mechanism for a test object such as the tip of an endoscope. In this embodiment, the movement locus of the optical image IP′ is set to the reference axis O for eccentricity measurement. m In this case, the reference point is the intersection of an observation plane F', which is the object plane of the observation optical system optically conjugate with the imaging plane of the measurement imager 17, and the movement locus of the optical image IP'.

[0133] Before describing a specific example of step S17, the principle of reference point measurement in this embodiment will be described. Fig. 17 is a schematic diagram for explaining the principle of reference point measurement in the eccentricity measuring method according to the first embodiment of the present invention, and Fig. 18 is a graph showing the change in the uncertainty of the reference point measurement depending on the reflection magnification.

[0134] FIG. 17 shows the spherical center C of the test surface 43a when measuring the positive reflection image and the negative reflection image using the test surface 43a of the reference optical element 43. ref , the light image IP', and the regular reflection image I RP and negative reflection image I RN For simplicity, the positional relationship between the spherical center C of the test surface 43a is shown. ref It is assumed that the eccentricity δ occurs only in the direction along the x-axis.

[0135] A light image IP' is projected onto a point zp in the direction along the z axis ((IP') in FIG. 17). zp ) and the image plane I is a distance L away from point zp on the negative z-axis direction. P Regular reflection image I RP Similarly, a light image IP' is projected onto the point zn (see FIG. 17 for (IP') zn ) and the image plane I is a distance L away from point zn on the negative z-axis direction. N Negative reflection image I RN The optical image IP' by the eccentricity measuring device 50 is a straight line O passing through the points zp and zn. L Moving upward. Regular reflection image I RP Image plane I P Straight line O on L The deflection amount from (1-β P )δ. Negative reflection I RN Image plane I N Straight line O on L The deflection amount from (1-β N )δ, where β P , β N are the reflection magnifications of the positive reflection image and the negative reflection image, respectively. The observation plane F' in the observation optical system is the image plane IP , I N If we move it so that it coincides with the image plane I P , I N Each reflected image at is reflected by the image plane I B The observation plane F' moves together with the measurement optical system 20 and the optical image IP', so that the observation plane F' and the straight line O L The reference point X0, which is the intersection point with the z-axis, is at the same position on the observation plane F' regardless of the position of the light image IP' in the direction along the z-axis. Therefore, the observation plane F' is the image plane I P When the specular reflection image I is matched to RP Position X on the observation plane F' P And the observation plane F' is the image plane I N Negative reflection image I when matched to RN Position X on the observation plane F' N and have the relationship with the reference point X0 expressed by the following expressions (6) and (7).

[0136]

number

[0137] By eliminating δ from equations (6) and (7) and solving for X0, we obtain the following equation (c).

[0138]

number

[0139] Similarly, for the reference point Y0 in the direction along the y-axis, the following formula (d) is obtained.

[0140]

number

[0141] Above, (X P ,Y P ), (X N ,Y N ), (X0, Y0) have been described as positions on the observation plane F', but (XP ,Y P ), (X N ,Y N ), (X0, Y0) is the image plane I of the observation optical system B Since there is a one-to-one relationship with the position coordinates above, image plane I B This can be measured from the location information above.

[0142] Here, conditions for improving the measurement accuracy of the reference point (X0, Y0) will be described. Equations (c) and (d) are expressed as the image plane I P Specular reflection image in I RP and image surface I N Negative reflection image in I RN Measurement of location information with (X P ,Y P ), (X N ,Y N ), it includes the uncertainty u associated with the measurement error. From the uncertainty propagation side, the combined standard uncertainty u c is expressed by the following equation (8).

[0143]

number

[0144] In equation (8), u 2 Let f be the expression in the braces that is the coefficient of β P >0, β P β N =-1, and β P =β, f is expressed as a function of β in the range of β>0, as shown in the following equation (9). P -β N ) 2 is (β N -β P ) 2 Since the value of f does not change even if β is set to 0, equation (9) also holds true for β<0.

[0145]

number

[0146] Curve 200 shown in Fig. 18 is a graph of f (where β ≠ 0). In Fig. 21, the horizontal axis is β and the vertical axis is f. Combined standard uncertainty due to measurement errors, u c To minimize f, it is necessary to select β that provides the minimum value of curve 200. If f is differentiated with respect to β to obtain the minimum value of curve 200, it is found that f has a minimum value of 0.5 when β = 1 ± √2. When β = -1 ± √2, f has a maximum value of 1.5. When β = ±1, f is 1. As β approaches ±∞, f approaches 1 asymptotically. Therefore, the reference point measurement is β P =1+√2, β N By performing the test under the condition of =1-√2, the u c It can be seen that the value is approximately 1 / √2 to 1 / √3 times smaller. By substituting β, which gives the minimum value of f, into equation (2), we obtain the relationship L=R. In other words, it is understood that the uncertainty of the reference point caused by the measurement error can be minimized by making the value of the IO distance L equal to the curvature radius R of the reference optical element 43. In this case, 1-β P =-√2, 1-β N =√2, so the magnitude of the sensitivity of the positive reflection image and the magnitude of the sensitivity of the negative reflection image with respect to the amount of eccentricity δ of the test surface 43a become equal to each other. Therefore, in order to measure the reference point with high accuracy, it is preferable to use a reference optical element 43 having the same radius of curvature as the set IO distance L. Alternatively, it is more preferable that the radius of curvature of the reference optical element 43 is 50% or more and 200% or less of the set value L.

[0147] Returning to the explanation of the specific example of step S17. FIG. 19 is a schematic diagram showing an example of a reference point obtained in the eccentricity measuring method according to the first embodiment of the present invention. Table 5 below shows the projection position of the light image IP', the reflection magnifications β of the positive reflection image and negative reflection image, and the calculated value of (1-β) when the measured value Lm of the IO distance L is 0.510 mm.

[0148] [Table 5]

[0149] As shown in [Table 5], the projection position is 0.140 mm for the positive reflection image and 0.820 mm for the negative reflection image. The magnification β of the reflected image is 2.645 for the positive reflection image and -0.378 for the negative reflection image. (1-β) is -1.645 for the positive reflection image and 1.378 for the negative reflection image. First, the specular reflection image is observed in the same manner as in step S12, except that the driving amount of the moving stage 2 after the optical image IP' is aligned with the test surface 43a is set to 0.140 mm based on [Table 5]. The operator adjusts the driving amount of the moving stage 2 as necessary to find the specular reflection image. FIG. 19 shows the specular reflection image I displayed on the display screen 23a. RP is shown by a solid line. In the same manner as in step S12, the regular reflection image I RP Position coordinates (X P ,Y P ) is calculated. After this, similarly to step S14, the negative reflection image I RN However, the driving amount of the moving stage 2 after the optical image IP' is aligned with the test surface 43a is set to 0.820 mm based on [Table 5]. The operator adjusts the driving amount of the moving stage 2 as necessary to find the negative reflection image. FIG. 19 shows the negative reflection image I displayed on the display screen 23a. RN is indicated by a dashed line. In the same manner as in step S14, the negative reflection image I RN Position coordinates (X N ,Y N ) is calculated.

[0150] After this, β is calculated based on the measured IO distance Lm. P , β N and the position coordinate (X P ,Y P ), (X N ,Y N) into equations (c) and (d) to calculate the coordinates (X0, Y0) of the reference point. This calculation is performed by the arithmetic processing unit 102 based on a control signal from the overall control unit 101. The calculated (X0, Y0) is stored in the storage unit 104. For (X0, Y0), a more accurate β P , β N The reference optical element 43 is a straight line O L Even if the object is eccentric with respect to the object, (X0, Y0) will be calculated as an accurate value. This completes step S17. In step S17, an example has been described in which the specular reflection image is observed and then the negative reflection image is observed. However, the specular reflection image may be observed after the negative reflection image.

[0151] After step S17, step S18 is executed. In step S18, it is determined whether or not to end the measurement. In step S17, the reference point measurement is performed by measuring the line O L If there is an error in the measurement of the radius of curvature R of the test surface 43a and the measurement value Lm of the IO distance, the error in the reflection magnification changes, which causes an error in the measurement of the reference point. In order to further reduce the influence of measurement errors of R and Lm, the reference point can be measured in a state where there is no eccentricity of the test surface 43a, thereby enabling more accurate IO distance measurement and reference point measurement. For example, the magnitude of the decentering amount of the reference optical element 43 can be determined based on the amount of deflection of the reflected image from a reference point, as shown in FIG. The measurer determines whether to end the measurement based on the amount of deflection of the reflected image, etc. This determination may be made automatically by the measurement control unit 5, which calculates the amount of deflection and bases it on a predetermined allowable value. When ending the measurement, the overall control unit 101 causes the calculation processing unit 102 to calculate the movement position of the main body unit 3 for forming a reflection image selected for each test surface Si, and the reflection magnification of the selected reflection image, based on the measurement value Lm of the IO distance L calculated in the last executed step S16, and stores each calculation result in the memory unit 104. This completes step S3 in FIG. If it is determined not to end the measurement, step S19 is executed.

[0152] In step S19, the regular reflection image I RP or negative reflection I RN The position of the reference optical element 43 in the direction perpendicular to the z-axis is adjusted so that the center of the reference optical element 43 moves to the reference point (X0, Y0) measured in step S17. FIG. 20 is a schematic diagram showing an example of a display screen after the reference optical element is moved in the decentering measuring method according to the first embodiment of the present invention. The position adjustment in this step is performed to adjust the straight line O L The eccentricity δ of the test surface 43a is adjusted to be 0. ref Line O L This is equivalent to positioning it above. Specular reflection image I RP and negative reflection image I RN There is no particular limitation on which of the above images is observed to adjust the position. For example, the reflected image observed at the end of step S17 may be used. In this case, since there is no need to re-drive the moving stage 2, the measurement can be performed quickly. 20 shows superimposed reflected images observed at the positions of the respective reflected images after adjusting the position of the reference optical element 43. When one reflected image is aligned with the reference point (X0, Y0), the other reflected image is also positioned at the reference point (X0, Y0). This completes step S19.

[0153] After step S19, steps S12 to S17 are executed. As a result, in a state in which decentering of the test surface 43a is suppressed, even if a slight error remains in the IO distance L measured in step S16, the reference point can be measured with high accuracy. After step S19, by re-measuring the IO distance L in steps S12 to S17, it is possible to measure the IO distance L with high accuracy assuming that the objective lens 15 has aberrations such as distortion. However, if the aberrations such as distortion of the objective lens 15 can be ignored, it is not always necessary to re-measure the IO distance L.

[0154] After step S3 is completed, unless the setting of the measurement optical system 20 is changed, the reference point (X0, Y0) finally calculated in step S17 can be used as the origin for measuring the amount of deflection of the reflected image. m However, based on actual measurements using the reference optical element 43, a straight line O L This is equivalent to what is prescribed by Therefore, in this embodiment, it is not necessary to rotate the test object to obtain the deflection center of the reflected image and determine the origin of the decentering measurement. As a result, even if the test object cannot be rotated and held, the decentering measurement can be performed quickly and with high accuracy.

[0155] Step S3 is an example of a second step of identifying the position of a reference point corresponding to the intersection of the observation plane and the reference axis in the image acquired by the measurement imager.

[0156] As shown in FIG. 13, after step S3, step S4 is executed. In step S4, the optical unit to be tested, which includes the optical system to be tested, is held on the holding table. 1, instead of the reference optical element 43, the tip portion 40 including the test optical system 41A is held by the holder 4a of the holding table 4. At this time, the tip portion 40 is aligned so that the designed optical axis of the test optical system 41A coincides with the reference axis O obtained in step S3. mHowever, it is more preferable that the optical axis of the optical system 41A to be measured is coaxial with the reference axis O. m In this case, the reference axis O m Since the amount of decentering of each test surface Si from the test optical system 41A only shifts as a whole, the relative amount of decentering of each test surface Si in the test optical system 41A can be measured accurately.

[0157] Step S4 is an example of the third step of arranging the test optical unit on the reference axis. In the above description, the test optical unit is disposed on the reference axis by holding the tip portion 40 including the test optical system 41A in the holder 4a of the holding table 4 instead of the reference optical element 43. However, the eccentricity measuring device 50 may be configured so that it is possible to omit the switching between the reference optical element 43 and the tip portion 40 including the test optical system 41A. For example, the holding stage 4 can simultaneously hold the reference optical element 43 and the test optical system 41A, for example, separated in the x-axis direction. Furthermore, the moving stage 2 can also move the main body 3 parallelly in the x-axis direction. In this case, the above-mentioned step S3 is executed in a state where the main body 3 is moved to a position facing the reference optical element 43. Thereafter, in step S4, the main body 3 is moved parallelly in the x-axis direction using the moving stage 2 to a position where the optical image IP' can be projected toward the test optical system 41A. In this way, it is not necessary to switch the reference optical element 43 and the tip portion 40 in step S4, and the next step S5 can be performed quickly.

[0158] After the holding of the tip portion 40 is completed, step S5 is executed. In step S5, a counter j is set to 1 for identifying the test surfaces Si of the measurement targets in the order of measurement. The counter j and the surface number of each test surface Si are associated by the overall control unit 101 before this step is executed. The overall control unit 101 assigns numbers from 1 to N to each test surface Si in the order of measurement, where N is the number of test surfaces Si to be measured. This association may be performed after the selection of the type of reflected image is completed in step S1. The order of measuring the test surfaces Si is not particularly limited. For example, the order of measuring the test surfaces Si may be the order of the surface numbers of the test surfaces Si, or the order of proximity to the objective lens 15. For example, the order of measuring the test surfaces Si may be the order in which the projection positions for measuring the test surfaces Si are arranged from the closest to the objective lens 15 to the furthest from the objective lens 15.

[0159] After step S5, step S6 is performed. FIG. 21 is a schematic diagram showing an example of measurement of the amount of deflection of a reflected image in the decentering measuring method according to the first embodiment of the present invention.

[0160] In step S6, the deflection amount (d xj , d yj ) is measured. The overall control unit 101 reads out the position of the light image IP' at which the selected reflected image can be observed on the test surface Si corresponding to the counter j from the storage unit 104, and sends it to the transport unit controller 105. The transport unit controller 105 drives the moving stage 2 to move the main body unit 3.

[0161] Thereafter, the measurer looks at the display screen 23a and determines whether or not a reflected image of the test surface Si corresponding to the counter j has been observed. If the reflected image is not observed or is blurred, the operation unit 24 is operated to finely adjust the position of the moving stage 2, and a proper reflected image is observed. When multiple reflected images are observed, the reflectance image is discriminated by an appropriate discrimination method by the measurer or the measurement control unit 5. For example, any of the above-mentioned reflected image discrimination methods may be implemented. In this way, the appropriate reflected image is identified. When there are a plurality of reflected images, for example, the measurer may be allowed to select a reflected image for which the amount of deflection is to be calculated in advance through a GUI (Graphical User Interface) in the operation unit 24. Alternatively, after the measurement control unit 5 calculates the amounts of deflection of a plurality of reflected images, the measurer may be allowed to select an appropriate amount of deflection of a reflected image through an operation input. Figure 21 shows the reflection image I corresponding to j. Rj 2 shows the display screen 23a on which the

[0162] After this, the measurer operates the operation unit 24 to input the reflected image I Rj Position coordinates (X j ,Y j ) and the deflection amount from the reference point (d' xj , d' yj ) is calculated by performing an operation input. The overall control unit 101 outputs the reflected image I Rj Center of R Calculate the position coordinates of the center O R From the position coordinates of and the reference point (X0, Y0), the calculation processing unit 102 calculates the image plane I B The actual value of the deflection amount from the reference point of the reflected image (d' xj ,d' yj ) where the subscripts x and y are the image plane I B The subscript j indicates the value of counter j (hereinafter the same). Furthermore, the calculation processing unit 102 calculates the reflected image I Rj Reference axis O in the observation plane F' m The amount of deflection from (d xj ,d yj ) and the eccentricity of the apparent spherical center of the test surface Si (δ xj , δ yj ) and calculate.

[0163]

number

[0164] where f T is the focal length of the objective lens 15, f k is the focal length of the imaging lens 16, β j is the reflected image I reflected from the apparent test surface si corresponding to j Rj The reflection magnification β jis obtained by substituting the measured value Lm of the IO distance L into L in equation (2) at the end of step S3. Calculated deflection amount d xj , d yj and the eccentricity δ of the apparent spherical center of the test surface Si xj , δ yj is stored in the storage unit 104. This completes step S6.

[0165] Step S6 is an example of steps including a fourth step of projecting the light image to a projection position on the reference axis and forming a reflected image of the light image reflected by the test surface at an observation position that is set so that the distance from the projection position along the reference axis is a set value L; a fifth step of capturing an image of the observation surface at the observation position using a measurement imager to obtain a measurement image; a sixth step of identifying an image of the reflected image at the observation position in the measurement image; a seventh step of measuring the amount of positional deviation of the identified reflected image from a reference point; and an eighth step of calculating the amount of eccentricity of the apparent spherical center of the test surface relative to the reference axis based on the amount of positional deviation.

[0166] After step S6, step S7 is executed. In step S7, the counter j is updated.

[0167] After step S7, step S8 is executed. In step S8, it is determined whether the value of the counter j is greater than the number N of the test surfaces Si. When this is executed by the measurement control unit 5, the overall control unit 101 compares the value of N stored in the memory unit 104 with the value of j. If j is greater than N, step S9 is executed. If j is not greater than N, step S6 is executed.

[0168] In step S9, the eccentricity δ of the apparent spherical center of each test surface Si measured up to this step is j (j=1,…,N), the eccentricity ε of each test surface Si i Calculate (i=1,…,N). In the following description, the subscript j of a variable indicates the order from the front side when the test surfaces Si are arranged in order from the front side of the test optical system 41A, that is, from the side closest to the objective lens 15. The nth test surface Si from the front n The apparent eccentricity of the spherical center δ xn is the number of test surfaces Si from the first to the nth. j Each eccentricity ε for (j=1,…,n) xj Similarly, the surface to be inspected, Si n The apparent eccentricity of the spherical center δ yn is the surface area Si j Each eccentricity ε for (j=1,…,n) yn However, the eccentricity of each apparent spherical center (δ xj , δ yj ) is the reference axis O m represents the shift amount relative to the eccentricity ε xj , ε yj is the reference axis O m This represents the amount of tilt eccentricity of the test surface Si relative to the j The tilt eccentricity of the test surface Si j The shift amount of the sphere center is measured on the test surface Si j Radius of curvature R j It can be found by dividing by. For this reason, each test surface Si j The eccentricity of each apparent spherical center δ xj , δ yj is expressed by the following equations (14) and (15) using a matrix of linear combination coefficients. ij (i=1, . . . , N, j=1, . . . , N) are calculated in advance based on the design data of the test optical system 41A and stored in the storage unit 104. If this matrix is ​​referred to as a decentering matrix, the test optical system 41A is an axially symmetric optical system, and therefore the decentering matrix of formula (14) and the decentering matrix of formula (15) are equal to each other.

[0169]

number

[0170] The overall control unit 101 causes the calculation processing unit 102 to calculate each eccentricity ε xj , ε yj As a result, the eccentricity ε xj , ε yj are required, respectively. Each eccentricity ε xj , ε yj is stored in the storage unit 104 and is displayed on the display unit 23 as necessary.

[0171] As can be seen from equations (12) and (13), the apparent eccentricity of the spherical center (δ xj , δ yj ) is the reflection magnification β j Therefore, the reflection magnification β j The error of each eccentricity ε xj , ε yj This affects the error. In this embodiment, the reflection magnification β j Since a value calculated based on the measurement value Lm of the IO distance L is used as , it is possible to perform measurement while correcting the setting error of the IO distance L in the eccentricity measuring device 50. Therefore, it is possible to measure the eccentricity of the test surface Si with higher accuracy than in a calculation using the set value of the IO distance L.

[0172] Step S9 is an example of a ninth step of calculating the amount of eccentricity of each of the test surfaces with respect to the reference axis based on the calculated value of the amount of eccentricity of the apparent spherical center after step S6 has been executed for the N test surfaces Si.

[0173] The overall control unit 101 in this embodiment is an example of an eccentricity calculation unit that measures the amount of positional deviation from a reference point corresponding to the intersection of the observation surface and the reference axis based on an image at the observation position acquired by a measurement imager, and calculates the amount of eccentricity of the apparent spherical center of the test surface relative to the reference axis based on the amount of positional deviation.

[0174] As described above, the eccentricity measuring device 50 of this embodiment can execute the eccentricity measuring method of this embodiment.

[0175] In this embodiment, the optical image IP′ is moved linearly relative to the test optical system 41A, and a reference axis O defined by the movement locus of the optical image IP′ in air is m In step S3, the coordinates of the reference point on the measurement imager 17 are measured, so that the reflected image I R Therefore, the amount of deviation from the reference point can be measured accurately without rotating the optical system 41A to be measured. In particular, according to this embodiment, even though the method does not rotate the test optical system 41A, decentering measurement can be performed more quickly and easily than with a method that uses an image rotator. Furthermore, in this embodiment, the IO distance is set to a value other than 0 by the unequal magnification method, and the optical axis O is M A reflected image I appears at a distance IO along the line. R Therefore, even if multiple reflected images appear on the image, the reflected image of the measurement target can be easily distinguished based on the difference in reflection magnification. In the above explanation of the unequal magnification method, the optical axis O is M A reflected image I appears at a distance IO along the line. R For convenience, it is described that the light image IP' and the observation plane F' are observed on the reference axis O m and move integrally along the optical axis O M and reference axis O m The angle between the optical image IP' and the reference axis O is designed to be, for example, 1 degree or less. m A reflected image I appears at a distance IO in the direction R This is no different from what we are observing.

[0176] In this embodiment, after a target IO distance L is set in the eccentricity measurement device 50, the IO distance L is measured using a reference optical element 43 having a known radius of curvature, and the reference point for eccentricity measurement can be obtained based on the measured value Lm of the IO distance L. Therefore, the amount of eccentricity can be obtained with higher accuracy. In this embodiment, the measurement value Lm of the IO distance L is calculated based on the magnification error β i In addition, the amount of eccentricity can be calculated with higher accuracy.

[0177] As described above, according to the decentering measuring method and apparatus of the present embodiment, the amount of decentering of the test surface can be measured with high accuracy without rotating the test optical unit. In particular, in this embodiment, since L≠0, decentering can be measured quickly and with high accuracy even if the positions of the apparent spherical centers of the optical surfaces of the optical unit to be measured are close to each other.

[0178] [Second embodiment] Next, an eccentricity measuring device and an eccentricity measuring method according to a second embodiment of the present invention will be described. As shown in Fig. 1, an eccentricity measuring apparatus 50A according to the second embodiment has a measurement control unit 5A instead of the measurement control unit 5 of the eccentricity measuring apparatus 50 according to the first embodiment. As shown in Fig. 2, the measurement control unit 5A has an overall control unit 101A instead of the overall control unit 101 of the measurement control unit 5 in the first embodiment. The following description will focus on the differences from the first embodiment.

[0179] The test optical unit of the eccentricity measuring device 50A can be the same optical unit as that of the first embodiment. However, in the following, in order to make it easier to understand the characteristic action of this embodiment, an example having a test optical system 41B instead of the test optical system 41A will be described. First, the configuration of the test optical system 41B will be described. Fig. 22 is a cross-sectional view showing an example of an optical system to be tested, in which (a) is a cross-sectional view of the lens in a far point observation state, and (b) is a cross-sectional view of the lens in a near point observation state.

[0180] As shown in FIG. 22B, the test optical system 41B in this embodiment includes, in order from the object side, a front group G having a negative refractive power. o and the intermediate group G with positive refractive power. f and the rear group G with positive refractive power. t And, it has. Front group Go is composed of a negative meniscus lens L11 with a convex surface facing the object side, a biconcave negative lens L12, and a biconvex positive lens L13. The negative lens L12 and the positive lens L13 are cemented together.

[0181] intermediate group G f is the filter F B1 and aperture S B and a plano-convex positive lens L14 having a flat surface facing the object side.

[0182] rear group G t includes a plano-concave negative lens L15 with a flat surface facing the object side, a biconvex positive lens L16, a biconvex positive lens L17, a negative meniscus lens L18 with a convex surface facing the image side, a biconvex positive lens L19, a biconcave negative lens L20, and a cover glass F. B2 And the cover glass CG B The plano-concave negative lens L15 and the biconvex positive lens L16 are cemented together. The biconvex positive lens L17 and the negative meniscus lens L18 are cemented together. The biconvex positive lens L19 and the biconcave negative lens L20 are cemented together.

[0183] I 41B is the image plane of the test optical system 41B. 41B The imaging surface of the endoscope imager 42 is disposed on the imaging surface.

[0184] The following [Table B] shows the numerical data of the design values ​​of the test optical system 41B. In [Table B], the columns r, d, and ne are defined in the same way as in [Table A]. The column νd is the Abbe number of each lens. In (a) of FIG. 22, the radius of curvature and the surface spacing of the surface number s (where s=1, ..., 22) are respectively expressed as r s , d s The first and second surfaces are aspheric, but the aspheric surface data is omitted.

[0185] [Table B] Surface number rd ne νd 1 2.9142 0.4000 1.81078 40.86 2 1.0606 0.8400 1.00000 - 3 -18.3770 0.5000 2.01169 28.27 4 2.6340 1.2000 1.85504 23.76 5 -8.5320 Variable 1.00000 - 6 ∞ 0.3000 1.523 65.13 7 ∞ 0.0300 1.00000 - 8(Aperture)∞ 0.1100 1.00000 - 9 ∞ 0.3500 1.65425 58.55 10 -35.6450 Variable 1.00000 - 11 ∞ 0.4000 2.01169 28.27 12 9.9720 0.7800 1.80642 34.97 13 -3.3750 0.0800 1.00000 - 14 24.6880 0.9000 1.73234 54.68 15 -2.7820 0.5300 1.93429 18.90 16 -5.6250 1.2453 1.00000 - 17 3.3750 1.3000 1.73234 54.68 18 -3.3750 0.3500 2.01169 28.27 19 8.0420 0.8560 1.00000 - 20 ∞ 0.5000 1.51825 64.14 21 ∞ 0.4000 1.50700 63.26 22∞0.0000 1.00000 - Imaging area ∞ Various data Surface spacing Far point object Near point object (Object distance 60mm) (Object distance 31mm) d5 0.2100 0.6800 d10 0.7200 0.2500

[0186] In the following description, in the test optical system 41B, test surfaces Si that are targets of eccentricity measurement by the eccentricity measurement device 50A are assumed to be 20 surfaces with surface numbers 1 to 7 and 9 to 21, excluding surfaces 8 and 22. Test surfaces Si are assigned test surface numbers from 1 to 20 in the order of their surface numbers. In the following [Table 6], the apparent vertex position V of each test surface Si is represented by the test surface number j (j = 1, ..., 20). j (mm), apparent radius of curvature R j (mm), apparent center position SC j The calculated value (mm) is shown. Apparent apex position V j The definition and coordinate system are the same as in Table A above. However, the fifth and tenth surfaces are set to 0.6800 mm and 0.2500 mm, respectively, corresponding to the object distance of 31 mm, which is the near point object.

[0187] [Table 6]

[0188] The decentering measurement method of this embodiment relates to a method for selecting the type of reflected image in the unequal magnification method. In this embodiment, the reference axis O of the projection position for forming the reflected image used in the measurement is m The distribution range in the direction along is selected to be minimum. The operation when such a selection is made will be described in comparison with a comparative example using the same magnification method. The following [Table 7] shows the correspondence between the test surface numbers and the projection positions when measuring the eccentricity of the test optical system 41B by the unit magnification method. Note that the test surface numbers are sorted so that the corresponding projection positions are from the far side to the closer side with respect to the objective lens 15. In the life-size method, the projection position is also the observation position where the reflected image is observed.

[0189] [Table 7]

[0190] As shown in [Table 7], in the 1x magnification method, when measuring all of the reflected images from the test surface Si, it is necessary to move the projection position of the light image by 42.201 mm from the position of -1.690 mm corresponding to test surface number 13 (14th surface) to the position of 40.511 mm corresponding to test surface number 16 (17th surface).

[0191] Since the optical system transport section 2b of the moving stage 2 can only move within the range of accuracy of the straightness, pitching, yawing, etc. of the guide 2a, the movement trajectory of the optical image IP' in the air is not completely straight. If the straightness of the movement trajectory of the optical image IP' in the air decreases while the moving stage 2 is moving the main body 3 by 42.201 mm, this will result in an error in the position coordinates of the reference point for eccentricity measurement, which will become a factor in an error in the amount of eccentricity of the test surface Si.

[0192] In contrast, when eccentricity measurement is performed by the unequal magnification method with the IO distance L set to 1 mm, all the projection positions corresponding to the types of reflected images are listed as shown in the following [Table 8]. Here, as in [Table 7], the projection positions corresponding to the test surface numbers are sorted from the farthest to the closest with respect to the objective lens 15. In [Table 8], the sorting order is displayed in descending order from 40 to 1.

[0193] [Table 8]

[0194] As shown in [Table 8], in the case of the test optical system 41B, when the IO distance L is set to 1 mm, the projection positions are distributed in a range of 42.280 mm, from a position of -1.262 mm corresponding to test surface number 13 (surface number 14) which forms a negative reflection image, to a position of 41.018 mm corresponding to test surface number 16 (surface number 17) which forms a negative reflection image. In the unequal magnification method, it is sufficient to measure either a positive reflection image or a negative reflection image for each test surface Si. Therefore, by selecting the type of reflection image for each test surface Si, the distribution range of the projection positions required for measurement can be narrowed. Table 9 below shows an example of selecting the type of reflection image.

[0195] [Table 9]

[0196] According to the selection example in [Table 9], the projection positions are distributed in a range of 2.218 mm, from a position of 0.417 mm corresponding to test surface number 1 (first surface) which forms a specular reflection image to a position of 2.634 mm corresponding to test surface number 16 (seventeenth surface) which forms a specular reflection image. Therefore, the distribution range of the projection positions is remarkably short, about 5% of the distribution range of the projection positions in the 1:1 magnification method. The accuracy of the straightness of the guiding mechanism of the guide 2a of the moving stage 2 decreases as the distance along the guide 2a increases. Therefore, the shorter the moving distance of the optical system transport unit 2b, the more the straightness of the movement trajectory of the optical image IP' in the air improves. In this embodiment, the distribution range of the projection positions is minimized, so that the accuracy of the decentering measurement can be improved.

[0197] For example, when the guide 2a is used in a local range, the tilt attitude per unit length can be considered to change monotonically due to the error of the guide 2a. In this case, the movement trajectory of the optical image IP' in the air caused by the driving of the moving stage 2 changes as a quadratic curve. If the moving distance is Z, the straightness of the movement trajectory is αZ 2 It can be estimated to be about / 8, where α is the amount of change in the tilt attitude per unit length. If the accuracy required for eccentricity measurement is assumed to be 20 nm, and half of that, 10 nm, is allowed for the straightness of the movement path, then αZ 2 / 8≦10nm must be satisfied. For example, if the tilt posture of the guide 2a can be considered to change monotonically per 1 mm per second, then α = 1 (seconds / mm) = 4.85 × 10 -6 (rad / mm), so if Z≦4.1 (mm) or less, sufficient eccentricity measurement accuracy can be obtained. From this point of view as well, it can be seen that when the distribution range of the projection positions that defines the amount of movement of the optical image IP' is 2.218 mm, the decentering can be measured with high accuracy.

[0198] Next, an example of the eccentricity measuring method according to this embodiment will be described in detail. 13, the eccentricity measuring method of the present embodiment has step S21 instead of step S1. The following will mainly describe the points that are different from the first embodiment. Step S21 is the same as step S1 except for the method of selecting the type of the reflected image. However, as in the first embodiment, the type of the reflected image only needs to be selected before the measurement of the test surface Si of the measurement target, and does not have to be selected in this step.

[0199] FIG. 23 is a flowchart showing an example of a method for selecting the type of a reflected image in the eccentricity measuring method according to the second embodiment of the present invention. The method of selecting a reflected image in step S21 involves executing steps S31 to S43 based on the flow shown in FIG.

[0200] In step S31, each projection position for obtaining a negative reflection image and a specular reflection image on each test surface Si of the test optical system 41B is calculated, and each projection position is associated with a test surface number. For example, in the eccentricity measuring device 50A, the overall control unit 101A of the measurement control unit 5A associates the surface number of the test surface Si to be measured with a test surface number as shown in [Table 6]. Furthermore, the overall control unit 101A causes the calculation processing unit 102 to calculate the projection positions for forming a specular reflection image and a negative reflection image by reflection from each test surface Si. In the case of the test optical system 41B, there is no test surface Si whose apparent radius of curvature is infinite, so a specular reflection image and a negative reflection image are obtained for each test surface Si. When the apparent radius of curvature becomes infinite, there is no projection position that forms a negative reflection image, so a dummy maximum value is given as the projection position so that a negative reflection image is not selected. In this way, when the number of test surfaces Si to be measured is M (in the example of [Table 6], M=20), 2M projection positions are obtained. The calculation results are associated with the test surface numbers and the types of reflected images and stored in the storage unit 104. This concludes step S31.

[0201] After step S31 ends, step S32 is executed. In step S32, the projection positions are sorted in ascending order of proximity to the projection optical system, and sequential numbers from 1 to 2M are assigned to each test surface number. For example, the overall control unit 101 sorts based on the magnitude relationship of the projection positions stored in the storage unit 104, assigns sequential numbers from 1 to 2M to the test surface numbers sorted in ascending order of the projection positions, and stores them in the storage unit 104. Thereby, a table as shown in [Table 8] is generated in the storage unit 104. Here, M is the number of test surfaces Si to be measured. This concludes step S32.

[0202] After step S32 ends, step S33 is executed. In step S33, the distribution range D(a, b) is initialized to the maximum value. Here, a and b are counters indicating the sequence numbers giving the lower limit value and the upper limit value of the distribution range, respectively. That is, a and b are integers satisfying a < b, 1 ≤ a ≤ M + 1, and M ≤ b ≤ 2M.

[0203] After step S33 ends, step S34 is executed. In step S34, the overall control unit 101A initializes the counter a to 1. After step S34 ends, step S35 is executed. In step S35, the overall control unit 101A initializes the counter m to 1. After step S35 ends, step S36 is executed. In step S36, the overall control unit 101A substitutes a+(M - 1)+m - 1 into the counter b.

[0204] After step S36 ends, step S37 is executed. In step S37, the overall control unit 101A refers to the table in the storage unit 104 and determines whether all of the test surface numbers from 1 to M are included in the sequence numbers from a to b. If all of test surface numbers 1 to M are included, step S38 is executed. If all of the test surface numbers 1 to M are not included, step S39 is executed.

[0205] In step S38, the overall control unit 101A assigns to the distribution range D(a,b) the length obtained by subtracting the projection position corresponding to the arrangement sequence number a from the projection position corresponding to the arrangement sequence number b into the distribution range D(a,b). The value of the distribution range D(a,b) is stored in the storage unit 104 in the storage location corresponding to (a,b). After step S38 is completed, step S39 is executed.

[0206] In step S39, overall control unit 101A updates counter m.

[0207] After step S39 is completed, step S40 is executed. In step S40, overall control unit 101A determines whether b is less than 2M. If b is less than 2M, step S36 is executed. If b is not less than 2M, the loop on counter m is exited and step S41 is executed.

[0208] In step S41, overall control unit 101A updates counter a.

[0209] After step S41 is completed, step S42 is executed. In step S42, general control unit 101A determines whether a is less than M+2. If a is less than M+2, step S35 is executed. If a is not less than M+2, the loop on counter a is exited and step S43 is executed.

[0210] In step S43, the overall control unit 101A selects the projection positions of test surface numbers 1 to M included in a to b when D(a, b) is the minimum value. For example, as shown in [Table 9], the projection positions and types of reflected images are selected from sequence numbers 2 to 16. Different types of reflected images for the same test surface number have different projection positions, so the selection of reflected images for the same test surface number is synonymous with the selection of projection positions. Here, when the same test surface number is included from a to b, either a specular reflection image or a negative reflection image may be selected from the viewpoint of minimizing the distribution range of the projection positions. For example, in the example of [Table 8], test surface numbers 2, 4, and 12, which are between sequence numbers 2 and 24, are examples of test surfaces Si for which either a specular reflection image or a negative reflection image may be selected. The overall control unit 101A selects one type of reflected image corresponding to the test surface number based on a predetermined rule. For example, to select the type of reflected image shown in [Table 9], a rule may be set to select the reflected image with the smaller projection position. In this case, the number of test surfaces Si with projection positions close to the minimum value increases, so that the number of test surfaces Si that are less susceptible to the effect of movement errors of the moving stage 2 increases overall.

[0211] When step S43 is completed, the selection of the reflected image is completed.

[0212] As described above, the eccentricity measuring device and the eccentricity measuring method using the same of the present embodiment are similar to those of the first embodiment except for the method of selecting the type of reflected image. Therefore, similar to the first embodiment, the amount of eccentricity of the test surface can be measured with high accuracy without rotating the test optical unit. In particular, according to this embodiment, the distribution range of the projection positions is minimized by selecting the type of reflected image, so that the accuracy of eccentricity measurement can be further improved.

[0213] [Third embodiment] Next, an eccentricity measuring device and an eccentricity measuring method according to a third embodiment of the present invention will be described. An eccentricity measuring apparatus 50B according to this embodiment shown in FIG. 1 includes a measurement control section 5B and a front wall 3aB instead of the measurement control section 5 and the front wall 3a of the eccentricity measuring apparatus 50 according to the first embodiment. The following description will focus on the differences from the first embodiment.

[0214] The eccentricity measuring device 50B has an endoscopic imager 42 (test imager) like the eccentricity measuring device 50. However, the eccentricity measuring device 50B differs from the eccentricity measuring device 50 in that the eccentricity amount of the imaging surface 42a of the endoscopic imager 42 can be calculated using an image acquired from the endoscopic imager 42. The endoscopic imager 42 in this embodiment is the target of eccentricity measurement. The endoscopic imager 42 in this embodiment is an example of a test imager in which an imaging surface 42a is arranged on the image plane of a test optical system 41 at a tip portion 40 which is a test optical unit.

[0215] FIG. 24 is a block diagram of a control system in the eccentricity measuring device according to the third embodiment of the present invention. As shown in FIG. 24, the measurement control unit 5B includes an overall control unit 101B (test imager image acquisition unit) and an arithmetic processing unit 102B (test imager eccentricity calculation unit) instead of the overall control unit 101 and arithmetic processing unit 102 of the measurement control unit 5, respectively. The overall control unit 101B is communicably connected to the endoscopic imager 42. The overall control unit 101B can acquire images captured by the endoscopic imager 42 and send them to the image processing unit 103, the display control unit 108, and the arithmetic processing unit 102B.

[0216] The calculation processing unit 102B calculates the reference axis O based on the image sent from the endoscope imager 42. m The amount of rotation of the endoscopic imager 42 around the target can be calculated. Furthermore, the arithmetic processing unit 102B calculates the reference axis O based on the information on the amount of eccentricity of each test surface Si of the test optical system measured in the same manner as in the first embodiment. m The shift amount of the imaging plane of the endoscopic imager 42 relative to the target position can be calculated. An example of the calculation in the calculation processor 102B will be explained in the description of the eccentricity measuring method described later.

[0217] The front wall 3aB shown in FIG. 1 differs from the front wall 3a in that a reference mark is provided in a range that can be observed by the endoscope imager 42 through the test optical system included in the tip portion 40. FIG. 25 is a schematic diagram showing the relationship between the coordinate system of the measurement system in the eccentricity measuring device according to the third embodiment of the present invention and the coordinate system of the imager to be measured. FIG. 25 shows a schematic diagram of the reference marks 47 formed on the front wall 3aB. In the example shown in FIG. 25, the reference marks 47 are provided at four locations surrounding the opening 3b in the front wall 3aB. The positional relationship between the reference marks 47 and the z-axis of the eccentricity measuring device 50B is stored in advance in the measurement control unit 5B. In the use of the reference marks 47 to calculate the amount of rotation of the endoscope imager 42, m Straightness error of the z-axis and the reference axis O m The parallelism error between the reference axis O and the reference axis O is very small and has almost no effect on the measurement accuracy. m can be regarded as an axis line perpendicular to the xy plane in the xyz coordinate system of the measurement system and parallel to the z axis. In FIG. 25, for ease of understanding, the x and y axes of the coordinate system of the measurement system are m The positive z-axis direction is the reference axis O. m The negative direction of the z-axis is from left to right in the figure, and the negative direction of the z-axis is from right to left in the figure. The position of the reference mark 47 is the reference axis O m In a plane perpendicular to the reference axis O m The following description will be given on the assumption that the positional relationship between the

[0218] The reference mark 47 is configured by detecting the reference axis O using the image of the endoscope imager 42. m There is no particular limitation as long as the amount of rotation of the front wall 3aB around the reference mark 47 can be detected. For example, the reference mark 47 may be an image drawn on the front wall 3aB, or a structure on the front wall 3aB. In the case of a structure, the reference mark 47 may be, for example, a groove engraved in the front wall 3aB, or a protrusion protruding from the front wall 3aB. For example, the reference mark 47 may be composed of a bolt, a nut, a nameplate, or the like attached to the front wall 3aB. 25, the reference mark 47 is a cross drawn on the front wall 3aB. The horizontal line of the cross extends in the x-axis direction, and the vertical line of the cross extends in the y-axis direction. Among the reference marks 47, the reference mark 47a located at the upper left as viewed from the negative z-axis direction and the reference mark 47b located at the upper right as viewed from the negative z-axis direction are located on the same line parallel to the x-axis. 47a and the intersection point O of the cross at reference mark 47b 47b The line segment X connecting ab is parallel to the x-axis.

[0219] When measuring the eccentricity of the endoscopic imager 42, it is necessary to measure the horizontal direction of the endoscopic imager 42 of the test optical system 41 together with the horizontal direction in the eccentricity measuring device 50B. However, since the tip portion 40 has a structure that is easily rotated, the horizontal direction of the endoscopic imager 42 is easily misaligned with the horizontal direction of the eccentricity measuring device 50B when the tip portion 40 is held by the holding base 4. For this reason, there is a possibility that the amount of eccentricity of the endoscopic imager 42 cannot be measured appropriately. Therefore, in this embodiment, the rotation error between the x-axis direction indicating the horizontal direction of the coordinate system of the measurement system of eccentricity measuring device 50B and the horizontal axis of the test imager coordinate system in endoscopic imager 42 is measured, and after performing rotational correction of the test imager coordinate system, the amount of eccentricity of endoscopic imager 42 is measured.

[0220] Here, the subject imager coordinate system in the endoscope imager 42 will be described. As shown in FIG. 25, the imager coordinate system under test is I x Axis and I y It is a two-dimensional coordinate system with axes I and x The axis is parallel to the bottom side of the imaging surface 42a in the figure, and I y The axis is parallel to the left side of the imaging surface 42a as viewed from the positive direction of the z axis with the y axis facing up. Hereinafter, the subject imager coordinate system in this embodiment is referred to as I x I y This is sometimes called a coordinate system. In FIG. 25, the x-axis and y-axis translated on the imaging surface 42a are indicated by two-dot chain lines so that it is easy to understand that the endoscope imager 42 is rotating with respect to the coordinate system of the measurement system. 25 illustrates a state in which the x-axis of the coordinate system of the measurement system is rotated by φ with respect to the horizontal direction of the endoscopic imager 42. Here, the positive direction of rotation in the xy plane is the direction in which a right-handed screw advances in the positive direction of the z-axis. In the endoscope imager 42, which is arranged in such a direction that the inverted image through the test optical system 41 can be correctly captured in all directions, x The positive direction of the I axis is the positive x-axis direction. y The positive direction of the axis is the negative direction of the y-axis. I x I y Coordinate values ​​in the coordinate system are expressed in units of pixel pitch P of the endoscopic imager 42. Here, the pixel of the endoscopic imager 42 means the unit of the coordinate value output from the endoscopic imager 42, and may be different from the physical pixel in the endoscopic imager 42. I x I y The origin of the coordinate system is not particularly limited, but for example, the coordinates of the pixel in the lower left corner when viewed from the positive direction of the z axis with the y axis facing up (I xB ,I yB )

[0221] FIG. 26 is a schematic diagram showing an example of an image acquired from a test optical unit in the decentering measuring method according to the third embodiment of the present invention. Fig. 26 shows an example of an image of the front wall 3aB and the reference mark 47 captured by the endoscope imager 42 rotated -φ about the x-axis and displayed on the display screen 23a of the display unit 23. The x-axis and y-axis shown by the two-dot chain lines in Fig. 26 are translated in parallel to the x-axis and y-axis of the coordinate system of the measurement system fixed on the front wall 3aB. On the display screen 23a, the I of the endoscopic imager 42 x An image is obtained in which the x-axis is rotated by +φ relative to the axis.

[0222] Next, the eccentricity measuring method of this embodiment will be described. FIG. 27 is a flowchart showing an example of an eccentricity measuring method according to the third embodiment of the present invention. The eccentricity measuring method of the present embodiment executes steps S51 to S54 based on the flow shown in FIG. In step S51, the amount of decentering ε xj , ε yj (where j=1, ..., N, N is the number of test surfaces Si). Hereinafter, a quantity with a subscript j represents N numerical values, j=1, ..., N, unless otherwise specified. This step is the same as the eccentricity measuring method of the first embodiment. Specifically, steps S1 to S9 shown in Fig. 13 are executed in the same manner. However, step S1 may be executed in the same manner as step S21 in the second embodiment. The design data stored in step S1 of this embodiment includes information on the coordinate system in the endoscope imager 42 and information on a representative point of the endoscope imager 42 whose eccentricity is to be measured. Calculated eccentricity ε xj , ε yj is stored in the storage unit 104.

[0223] Here, the eccentricity ε in the coordinate system of the measurement system xj , ε yj The symbols will be explained. Fig. 28 is a schematic diagram showing the relationship between the amount of eccentricity of the spherical center of the test surface, the tilt eccentricity of the test surface, and each x-axis component. Fig. 29 is a schematic diagram showing the relationship between the amount of eccentricity of the spherical center of the test surface, the tilt eccentricity of the test surface, and each y-axis component. As shown in FIG. 28, the jth test surface Si j Eccentricity ε xj is the reference axis O in the zx plane. m The direction of rotation from the positive direction of the z-axis (positive direction of the z-axis) to the positive direction of the x-axis is positive. As shown in FIG. 29, the jth test surface Si j Eccentricity ε yj is the reference axis O in the yz plane. m The direction of rotation from the positive direction of the z-axis (positive direction of the z-axis) to the positive direction of the y-axis is positive. Eccentricity ε xj , ε yj and the test surface Si j The center of the ball SC j Eccentricity δ xj , δ yj The relationship between and is the test surface Si j Radius of curvature r j Using these, it is expressed by the following equations (16) and (17).

[0224]

number

[0225] When step S51 is completed, step S52 is executed. In step S52, the reference mark 47 is imaged by the endoscope imager 42, which is the imager to be examined, and the horizontal coordinate axis (I x Calculate the amount of rotation φ of the x-axis of the coordinate system of the measurement system relative to the x-axis of the coordinate system of the measurement system. x The amount of rotation about the axis is -φ. The amount of rotation -φ is an example of the amount of rotation of the test imager coordinate system relative to a reference line perpendicular to the reference axis in a plane perpendicular to the reference axis.

[0226] The amount of rotation is measured based on position information of a reference mark 47 in an image captured by an endoscope imager 42 through a test optical system 41 . After the eccentricity measurement is completed, the overall control unit 101B acquires an image of the reference mark 47 captured by the endoscope imager 42. At this time, the image of the optical image IP' is not necessary, but if the optical image IP' is projected onto any of the test surfaces Si, a blurred image I of the optical image IP' is displayed on the display screen 23a. L ' is displayed. For example, it is assumed that the overall control unit 101B acquires an image as shown in FIG. The overall control unit 101B sends the acquired image to the image processing unit 103. The image processing unit 103 executes appropriate image processing such as feature extraction to obtain the Ix I y Intersection point O in the coordinate system 47a Coordinates of (L x ,L y ) and intersection point O 47b Coordinates of (R x ,R y ) and are sent to overall control unit 101B. The overall control unit 101B sends each coordinate value to the calculation processing unit 102B. The calculation processing unit 102B calculates the amount of rotation φ of the x-axis direction of the coordinate system of the measurement system relative to the horizontal direction of the test imager based on the following formula (18). The calculated amount of rotation φ is stored in the memory unit 104.

[0227]

number

[0228] This completes step S52. In the above, an example of using the images of the reference marks 47a and 47b in the method of measuring the amount of rotation has been described, but the present invention is not limited to this example. m Alternatively, the calculation may be performed using an image of another reference mark 47 whose positional relationship with the target object is known.

[0229] After step S52, step S53 is executed. In step S53, the eccentricity ε xj , ε yj The eccentricity ε' corrected so that the horizontal direction of the imager under test coincides with the x-axis direction of the coordinate system of the measurement system. xj , ε' yj Calculate. The overall control unit 101B causes the calculation processing unit 102B to execute a calculation based on the following formula (19) using the amount of rotation φ calculated in step S52.

[0230]

number

[0231] This is the end of step S53. After step S53, step S54 is executed. In step S54, the eccentricity ε' xj , ε' yj The amount of eccentricity of the imager under test is calculated using First, the principle of measuring the eccentricity of the endoscope imager 42 will be described. Fig. 30 is a schematic cross-sectional view showing the measurement principle in the decentering measurement method according to the third embodiment of the present invention. Fig. 31 is a schematic diagram showing the relationship between the image on the test imager, the coordinate system of the measurement system, and the test imager coordinate system in the eccentricity measurement device according to the third embodiment of the present invention. Fig. 32 is a schematic diagram showing the relationship between the test imager coordinate system and the xy coordinate system of the measurement system in the orientation displayed on the display unit.

[0232] In FIG. 30, as an example of the optical system 41 to be tested, an optical system to be tested 41C is arranged. The test optical system 41C includes, from the object side to the image side, seven lenses L21 to L27 and a cover glass CG, where the lenses L26 and L27 are cemented lenses. The test optical system 41C is decentered as shown in FIG. m The amount of eccentricity (tilt eccentricity) from the target has already been calculated in step S51. Since the imaging surface 42a is attached to the cover glass CG so as to be parallel to the cover glass CG, the tilt eccentricity of the imaging surface 42a coincides with the tilt eccentricity of the cover glass CG. However, the position of the endoscopic imager 42 in the direction along the surface of the cover glass CG may vary due to assembly errors. The shift eccentricity of the imaging surface 42a is measured along a reference axis O m The representative point is defined as the amount of deviation of a representative point on the imaging surface 42a from the target position. Any point on the imaging surface 42a can be selected as the representative point. In the following explanation, an example will be explained in which the representative point is the origin of the target imager coordinate system fixed to the imaging surface 42a. However, since at least a part of the optical surfaces of the test optical system 41C is decentered, in the state where the test optical system 41C and the endoscope imager 42 are assembled into an optical unit, the reference axis O m It is difficult to measure the intersection point between the imaging surface 42a and the imaging plane 42b.

[0233] In this step, as shown in FIG. 30, a light image IP' is projected from the eccentricity measuring device 50B to a position optically conjugate with the imaging surface 42a. m The light image I is located above the image pickup surface 42a. L is determined according to the amount of decentering of the test optical system 41C. m The image is formed at a position shifted in a direction perpendicular to point O. C is the center of the imaging surface 42a shown for reference. For example, as shown in FIG. 31, a light image I L is the reference axis O m From point G, which is the intersection point of I x Axial and I y Axial separation. In the following, x I y Light image in coordinate system I L , point G, and representative point O B The position coordinates of (I X ,I Y ), (I Xo ,I Yo ), and (I xB , I yB ) is written as Light Image I L The position coordinates of are expressed in the xy coordinate system of the measurement system as follows: (Z X ,Z Y ) Representative point O as seen from point G B The eccentricity of is expressed as (X G ,Y G ) is written as FIG. 32 shows a light image I in an image displayed on the display screen 23a based on an image signal sent from the endoscope imager 42. L , I x I yThe coordinate system and its relationship to the x-y coordinate system are shown. Here, Z X ,Z Y , X G , and Y G is a quantity in the xy coordinate system and is the actual size.

[0234] (Z X , Z Y ) is the light image IP' along the reference axis O m When the optical axis of the image sensor 42 is positioned at a position optically conjugate with the image sensor 42a on the left, the optical image I L The reference axis O on the imaging surface 42a m This is an example of the deviation from

[0235] Z X , Z Y are expressed by the following equations (20) and (21).

[0236]

number

[0237] Here, N is the number of test surfaces Si when all optical surfaces of the test optical system 41C are the test surfaces Si. j is the j-th test surface Si in the test optical system 41C. j With a unit amount of tilt decentering, such as 1 min, M It can be found by calculating the position on the image plane when the light is incident from above. Thus, the light image I L The position coordinates of I x I y It can be measured in the coordinate system and calculated in the xy coordinate system, and x I y By utilizing the fact that the amount of rotation φ between the coordinate system and the xy coordinate system has been found, the amount of eccentricity of the endoscopic imager 42 can be found as follows.

[0238] Figure 33 shows the relationship between the eccentricity of the spherical center of the test surface as viewed from the test imager coordinate system and the optical image I L1 is a schematic diagram showing the relationship between the imaging position of the Reference axis O m X represents the x-axis and y-axis components of the eccentricity of the endoscopic imager 42 relative to G ,Y G are expressed by the following equations (22) and (23), respectively.

[0239]

number

[0240] Here, P is the pixel pitch P of the endoscopic imager 42. I Xo , I Yo is the I in the x'y' coordinate system, which is obtained by rotating the xy coordinate system by -φ. L The position coordinate of (Z X ',Z Y ') is calculated using the following equations (24) and (25).

[0241]

number

[0242] As shown in Figure 33, the test surface Si j Center of the ball C j The position coordinates of in the xy coordinate system are (r j ε xj ,r j ε yj ) and in the x'y' coordinate system, (r j ε xj ',r j ε yj '). Therefore, Z X ',Z Y ' is the same as in equations (20) and (21). j Using these, the calculations can be done as shown in the following equations (26) and (27). Here, ε xj ', ε yj ' can be calculated using equation (19).

[0243]

number

[0244] In this step, the above calculations are performed as follows. The overall control unit 101B controls the light image I L The image of I is acquired and input to the image processing unit 103. x I y Light image in coordinate system I L Position coordinates of (I X ,I Y ) is calculated. X ,I Y ) is stored in the storage unit 104. The overall control unit 101B sends a control signal to the calculation processing unit 102B to cause it to execute the following calculations. The calculation processing unit 102B calculates ε xj , ε yj After rotation correction, ε xj ', ε yj The calculation processing unit 102B calculates the eccentricity amount ε xj ',ε yj Substituting ' into equations (25) and (26), Z X ',Z Y After that, the calculation processing unit 102 calculates I X , I Y , Z X ',Z Y Substituting ' into equations (24) and (25), I Xo , I Yo Calculate and I Xo , I Yo Substituting into equations (22) and (23), X G , Y G Calculate. In this way, the eccentricity X of the endoscope imager 42 G , Y G is calculated and step S54 is completed. Above, the representative point is O B As explained in the example of (I xB , I yB ) to the coordinates of the representative point, the amount of eccentricity of the endoscope imager 42 with respect to an arbitrary representative point can be obtained. For example, if the representative point is the center O C In the case of (IxB , I yB ) instead of I x I y Center O in the coordinate system C The position coordinates of the

[0245] Step S54 is a step of calculating the amount of deviation (Z X ,Z Y ) based on the amount of eccentricity of the test surface; projecting the optical image at a position optically conjugate with the imaging surface on the reference axis, acquiring an image of the optical image with the test imager, and calculating position coordinates (I X ,I Y ) and the amount of deviation (Z X ,Z Y ) and position coordinates (I X ,I Y ) and the position coordinate (I Xo ,I Yo and calculating the amount of eccentricity of the imaging plane with respect to the reference axis by calculating

[0246] The x'y' coordinate system in FIG. 33 is based on the magnitude of the rotation amount and is arranged such that the tip portion 40 is a reference axis O. m In this way, the tip 40 is actually rotated to correct the rotational position, and then the eccentricity of the test surface Si is measured. L An image of the endoscope imager 42 may be acquired to determine the amount of eccentricity of the endoscope imager 42. However, it takes time to correct the rotational position of the tip portion 40, and since it is difficult to adjust the rotation of the tip portion 40, there is a possibility that a correction error will remain. In contrast to this, in this embodiment, the tip portion 40 is not actually rotated, but instead, rotation correction is performed by calculation, so that the amount of eccentricity of the endoscope imager 42 can be measured more quickly and accurately.

[0247] In this embodiment, the overall control unit 101B of the measurement control unit 5B is an example of a test image acquisition unit that acquires an image from a test imager. The calculation processing unit 102B of the measurement control unit 5B is an example of a test imager eccentricity calculation unit that calculates the position of the optical image on the imaging surface based on the image acquired by the test imager image acquisition unit when the optical image is moved relatively to a position optically conjugate with the imaging surface of the test imager using a moving mechanism, and calculates the relative eccentricity between the test optical system and the test imager based on the calculated position value.

[0248] As described above, the eccentricity measuring device and the eccentricity measuring method using the same of this embodiment are the same as those of the first embodiment, except that the eccentricity measurement device measures the eccentricity of the test imager. Therefore, like the first embodiment, the amount of eccentricity of the test surface can be measured with high accuracy without rotating the test optical unit. In particular, according to this embodiment, the amount of eccentricity of the endoscope imager 42 in a state where it is incorporated into the optical unit to be tested can be accurately measured. Measuring the amount of rotation of the endoscope imager 42 using the reference mark 47 may be used to adjust the horizontal direction of the tip portion 40 to match the horizontal direction of the xy coordinate system.

[0249] [Fourth embodiment] Next, an eccentricity measuring device and an eccentricity measuring method according to a fourth embodiment of the present invention will be described. An eccentricity measuring apparatus 50C according to this embodiment shown in FIG. 1 includes a measurement control section 5C instead of the measurement control section 5 of the eccentricity measuring apparatus 50 according to the first embodiment. The eccentricity measuring device 50C is similar to the eccentricity measuring device 50, except that in addition to measuring the eccentricity of each optical surface of the test optical system 41, it is also capable of measuring the amount of eccentricity of a frame member arranged inside the lens frame 40a. The following description will focus on the differences from the first embodiment.

[0250] As shown in FIG. 2, the measurement control section 5C includes an overall control section 101C and an arithmetic processing section 102C instead of the overall control section 101 and the arithmetic processing section 102 of the measurement control section 5, respectively. Overall control unit 101C and calculation processing unit 102C are similar to overall control unit 101 and calculation processing unit 102, except that they are configured to perform control and calculation related to eccentricity measurement of a frame member, which will be described later. The detailed control and calculation in the overall control unit 101C and the calculation processing unit 102C will be explained in the description of the eccentricity measuring method described later.

[0251] The frame member in this embodiment will be described. Fig. 34 is a cross-sectional view showing an example of a frame member in an eccentricity measuring device according to a fourth embodiment of the present invention. Fig. 35 is a schematic diagram showing an image of the frame member captured by a measurement imager. In Figs. 34 and 35, the dimensional difference between the outer diameter of lens L25 and the inner diameter of opening 45a is exaggerated for ease of viewing.

[0252] As long as the frame members are located in positions that allow observation from the front side of the test optical system 41, the positions and number of the frame members to be arranged on the lens frame 40a are not limited. FIG. 34 shows a frame member 45 protruding from the inside of the lens frame 40a. The frame member 45 is aligned along the reference axis O m 34, a test optical system 41C similar to that of the third embodiment is used as the test optical system 41. The frame member 45 is provided to regulate the position of the outer periphery of the lens L25 that is the fifth lens from the front in the test optical system 41C. The frame member 45 has a plate portion that is thicker than the lens thickness of the lens L25. An opening 45a having an inner diameter larger than the outer diameter of the lens L25 penetrates the plate portion of the frame member 45 in the thickness direction. On the front side of the frame member 45, an edge portion 45b consisting of a plane perpendicular to the central axis of the lens frame 40a is formed around the opening 45a.

[0253] The edge portion 45b is disposed behind the lens L24, which is the fourth lens from the front in the test optical system 41C. The opening 45a is aligned with the optical axis O of the lens L25. L25is positioned so as to be substantially coaxial with the central axis of the lens frame 40a. The opening 45a may be used as an adhesive surface when the lens L25 is adhesively fixed to the lens frame 40a. The opening 45a is used to position the lens L25. 45 Reference axis O m By measuring the amount of decentering with respect to the target optical unit, the relationship between the optical performance of the target optical unit and the assembly error can be evaluated. For example, by comparing the decentering of the opening 45a with the shift decentering of the lens L25 in the test optical system 41C, it is possible to accurately evaluate which of the manufacturing error of the lens L25 itself, the manufacturing error of the lens frame 40a, and the assembly error has a larger contribution to the decentering of the lens L25.

[0254] Next, the principle of the method for measuring the eccentricity of the frame member 45 will be described. The eccentricity of the edge 45b is such that the edge E 45 Any part may be measured, but in the following, the measurement will be performed on the edge E 45 This will be explained using an example of measuring the amount of eccentricity at the center. In measuring the eccentricity of the frame member according to this embodiment, the position of the adjustment lens 13 is fixed, and the main body 3 is moved using the moving stage 2 to move the observation plane F' in the observation optical system to a position conjugate with the edge 45b. This allows the measurement imager 17 to observe the edge 45b. When the observation plane F' is moved to a position optically conjugate with the edge 45b, an image of the edge 45b is displayed on the display screen 23a as shown in Fig. 35. For reference, the position of the lens L25 is shown by a two-dot chain line, but the image of the lens L25 may be blurred. This image is seen through an optical system in front of the edge 45b in the test optical system 41C (hereinafter referred to as the incident optical system with respect to the edge 45b). The incident optical system with respect to the edge 45b is made up of lenses L21, L22, L23, and L24. The image of edge 45b is displayed at a position decentered from the reference point (X0, Y0) depending on the amount of decentering of the entrance optical system with respect to edge 45b and the amount of decentering of edge 45b itself.

[0255] The center O of the opening 45a measured from the reference point (X0, Y0) on the display screen 23a 45 The x-axis and y-axis components of the distance to W x ',W y '. Center O 45 The position coordinates of the edge E of the edge portion 45b are 45 It is sought as the center of W x ',W y ' is expressed by the following equations (28) and (29).

[0256]

number

[0257] Here, m is the magnification of the image of the edge 45b on the observation surface observed through the incident side optical system with respect to the edge 45b. As m, the lateral magnification calculated from the design data of the incident side optical system is used. W x , W y is the reference axis O of the edge 45b. m k is the number of optical surfaces in front of the edge 45b in the test optical system 41C. In the example of FIG. 34, k=8. N j (j=1,...,k) is a coefficient that determines the shift in the image position due to the incident optical system. N j is the coefficient K in the third embodiment. j However, in the calculation, design data of the entrance side optical system is used instead of the optical system to be measured 41C. Equations (28) and (29) are expressed as W x , W y By solving for , we obtain the following equations (30) and (31).

[0258]

number

[0259] Next, the eccentricity measuring method of this embodiment will be described. The eccentricity measuring method of this embodiment is to measure the eccentricity of the reference axis O of the edge portion 45b that forms the front edge of the opening 45a. m This embodiment is similar to the first embodiment except that the amount of eccentricity with respect to the target is measured. However, to measure the decentering of the edge 45b, it is necessary to measure the amount of decentering of each optical surface of the entrance-side optical system related to the edge 45b as the test surface Si. Since the decentering of the optical surfaces other than the entrance-side optical system in the test optical system 41C is not necessary for the decentering measurement of the edge 45b, they may be excluded from the measurement target of the decentering measurement, or may be the measurement target as in the first embodiment. The eccentricity measurement of the edge portion 45b can be performed continuously or in a dispersed manner at an appropriate timing between after step S4 and after step S9 in FIG. The following description will focus on the steps relating to the measurement of eccentricity of the edge 45b, and will focus on the differences from the first embodiment.

[0260] FIG. 36 is a flowchart showing an example of an eccentricity measuring method according to the fourth embodiment of the present invention. The eccentricity measuring method of the present embodiment executes steps S61 to S63 based on the flow shown in FIG. In step S61, the optical surfaces of the entrance optical system located in front of the edge 45b forming the front edge of the opening 45a of the frame member 45 are used as test surfaces, and the amount of eccentricity ε xj , ε yj Calculate. This step may be performed in the same flow as in the first embodiment shown in FIG. 13, or in the flow shown in FIG. 13, if only the eccentricity of frame member 45 is to be measured, steps S1 to S9 may be performed by replacing N with k. However, in this embodiment, the design data stored in step S1 includes data on the position and shape of the lens frame 40a whose decentering is to be measured, and m and N j The data includes:

[0261] After step S61, step S62 is executed. In step S62, an image of edge 45b is acquired at a position optically conjugate with edge 45b via the incident side optical system, and the apparent position of edge 45b is calculated. The overall control unit 101C sends a control signal to the transport unit controller 105 to drive the optical system transport unit driver 2c so that the focal plane F' of the observation optical system is located at a position optically conjugate with the edge 45b. The optical system transport unit driver 2c moves the optical system transport unit 2b in response to a control signal sent from the transport unit controller 105 based on the control signal from the overall control unit 101C. At this time, the overall control unit 101C may perform control to move the light image IP' to a position where the edge 45b is illuminated by the light image IP' and becomes easy to observe. In this case, the overall control unit 101C sends a control signal to the adjustment lens driving unit 21 via the projection position controller 106 to move the adjustment lens 13. The appropriate movement position of the light image IP' can be calculated in advance based on the design data of the incident side optical system and stored in the storage unit 104. In this case, since the optical image IP′ is only used for illumination purposes, the movement error of the adjustment lens 13 and the error in the movement position of the optical image IP′ associated with the movement error do not affect the measurement accuracy of the eccentricity of the frame member 45. For example, if the amount of light on the edge 45b is insufficient when observing the edge 45b, the amount of light from the light source 10 may be increased. For example, an illumination light source for observing the edge portion 45b may be provided in addition to or instead of the light beam that forms the light image IP'.

[0262] When the focal plane F' is moved to a position optically conjugate with the edge 45b, for example, as shown in FIG. 35, an image of the edge 45b is displayed on the display screen 23a. The overall control unit 101C acquires an image from the measurement imager 17, sends it to the image processing unit 103, and extracts the edge E from the image of the edge 45b. 45 Extract the edge E 45 Center of 45 Position coordinates (X o45 ,Y o45 ) is calculated by the image processing unit 103. o45 ,Y o45) is stored in the storage unit 104. Position coordinates (X o45 ,Y o45 ) represents the apparent position of edge 45b as seen through the incident optical system. This completes step S62.

[0263] Step S62 is an example of a step including a step of calculating the amount of eccentricity for each of the plurality of optical surfaces, at least one of which is in front of the front edge of the opening, as the test surface, placing the imaging surface of the measurement imager at a position optically conjugate with the edge of the opening via the entrance side optical system in front of the edge of the test optical system, obtaining an image of the edge through the entrance side optical system by the measurement imager, and calculating the apparent position of the edge relative to a reference point based on the image of the edge.

[0264] After step S62, step S63 is executed. In step S63, the calculated eccentricity ε xj , ε yj (j=1,…,k) and the apparent position (X o45 ,Y o45 ) based on the reference axis O m The amount of eccentricity of edge 45b relative to the target is calculated. When the overall control unit 101C sends a control signal for calculating the amount of eccentricity of the edge portion 45b to the calculation processing unit 102C, the calculation processing unit 102C performs the following calculation. The calculation processing unit 102C calculates the amount of deviation of the apparent position from the reference point (X0, Y0) as (W x ', W y ')=(X o45 -X0,Y o45 -Y0). Thereafter, the calculation processor 102C performs the calculations of the equations (30) and (31) based on the values ​​stored in the memory unit 104 to obtain the eccentricity amount (W x , W y ) is calculated. x , W y ) is stored in the storage unit 104 and is displayed on the display screen 23a as necessary. This completes step S63.

[0265] Step S63 is an example of a step of calculating the amount of eccentricity of the edge with respect to the reference axis based on the amount of eccentricity and the apparent position calculated in step S62.

[0266] In the above description, it is described that this is executed after step S61, but it may be executed before step S61 as long as it is executed after step S4 in the flow shown in FIG. Step S63 may be executed at any time after steps S61 and S62 and after step S4 in the flow shown in FIG.

[0267] As described above, the eccentricity measuring device and the eccentricity measuring method using the same of the present embodiment are similar to those of the first embodiment, except that the eccentricity measurement is performed on a frame member. Therefore, similar to the first embodiment, the amount of eccentricity of the test surface can be measured with high accuracy without rotating the test optical unit. In particular, according to this embodiment, the decentering of the frame member that holds the test optical system with respect to the reference axis can be accurately measured in a state in which the frame member is assembled in the test optical unit.

[0268] Although the above description has been given of an example in which the lens of the test optical system is located inside the opening of the frame member, the type of the frame member is not limited as long as it has an opening and is provided at a position where an image can be acquired by the measurement imager through the entrance optical system and the observation optical system related to the edge of the opening. For example, the frame member may be a diaphragm in the test optical system.

[0269] In the above embodiments, the reference axis O for measuring eccentricity is m The example was explained using the example where the reference axis O m The extension direction of the reference axis O is not limited to the horizontal direction. m may extend in a direction intersecting the horizontal plane.

[0270] In each of the above embodiments, the moving mechanism is composed of the moving stage 2, and the reference axis O m In the above example, the optical image IP' moves toward the test optical unit held by the holding stage 4 along the reference axis O. However, the moving mechanism moves the optical image IP' toward the test optical unit along the reference axis O. m It is sufficient if the eccentricity measuring device 50 can move relatively along the axis of the optical axis. For example, in the eccentricity measuring device 50, the main body 3 is fixed to the base 1, and instead of the moving stage 2, a linear moving stage that moves the holder 4a, the holding table 4, etc. together with the optical unit to be tested may be provided as a moving mechanism. In this case, the optical image IP' is stationary and the optical unit to be tested moves, so that the movement trajectory of the optical image IP' in the air is defined as a relative movement trajectory with the optical unit to be tested as a reference. Furthermore, as long as a movement accuracy that does not impede decentering measurement can be obtained, both the measurement optical system and the test optical unit may be movably supported by a movement mechanism that moves each of them.

[0271] In the above embodiments, an example has been described in which the optical image IP' is aligned with the apex of the test surface 43a before being moved to the projection position each time the optical image IP' is moved to measure the reference point. However, if the optical image IP' is aligned with the apex of the test surface 43a first when measuring the reference point, it is not necessary to align the optical image IP' with the apex of the test surface 43a when measuring the second reflected image.

[0272] In each of the above embodiments, an example has been described in which, when measuring the reference point, the light image IP' and its surrounding image are observed using the observation imager 44 to align the light image IP' with the apex of the test surface 43a. However, if the light image IP' can be aligned with the apex of the test surface 43a without observation with the observation imager 44, the observation imager 44 and the beam splitter 11 may be omitted.

[0273] In each of the above embodiments, an example has been described in which the set value L of the IO distance is not 0. However, even if L=0, if it is possible to identify a reflected image, a similar decentering measurement may be performed with the set value L set to 0. In this case, by projecting an optical image for measurement and performing the decentering measurement using the movement trajectory of the projected optical image in air as a reference axis, the amount of decentering of the test surface can be measured accurately and quickly without rotating the test optical unit.

[0274] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Addition, omission, substitution, and other modifications of the configuration are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited by the foregoing description, but only by the scope of the appended claims. For example, in the first and second embodiments, eccentricity measurement of the endoscopic imager 42 may be performed similarly to the third embodiment. For example, in the first and second embodiments, the eccentricity measurement of the frame member may be performed similarly to the fourth embodiment. In this case, the aperture stop S in the test optical system 41A may be used as the frame member. A , the aperture stop S in the test optical system 41B B may be included. [Industrial Applicability]

[0275] According to each of the above-described embodiments, it is possible to provide an eccentricity measurement method and an eccentricity measurement device that can accurately and quickly measure the amount of eccentricity of a test surface, without rotating the test optical unit, even if the positions of the apparent spherical centers of the optical surfaces of the test optical unit are close to each other. [Explanation of symbols]

[0276] 2. Moving stage (moving mechanism) 3 Main body 3a, 3aB front wall 4 Holding stand 5, 5A, 5B, 5C Measurement control section (eccentricity calculation section, reflection magnification measurement section, reflection Magnification measurement control unit 10 Light source (light source part) 12 Collimating lens (light source) 13 Adjustment lens (light source part) 15 Objective lens (projection optical system, observation optical system) 16 Imaging lens (observation optical system) 17 Measurement Imager 18 Wedge Prism 20 Measurement optical system 21 Adjustment lens drive unit 22 Wedge prism drive unit (reflection magnification measurement unit) 23a Display screen 24 Control section 40 Tip (test optical unit) 40a Lens frame 41, 41B Test optical system 42 Endoscope Imager (Subject Imager) 43 Reference Optical Element 43a Test surface 45 Frame members 45a opening 45b Edge (front edge of opening) 47, 47a, 47b reference marks 50, 50A, 50B, 50C eccentricity measuring device 101, 101A, 101C Overall control unit 101B Overall control unit (subject imager image acquisition unit) 102B arithmetic processing unit (test imager eccentricity calculation unit) b Px1 First horizontal line (magnification measurement part) b Py1 First vertical line (magnification measurement section) b Px2 Second horizontal line (magnification measurement part) b Py2 Second vertical line (magnification measurement section) b Py3 Third vertical line (magnification measurement section) C ref center of the ball D P , D N Displacement E 45 edge F, P focal plane F' Focal plane (observation plane) F2 parallel beam I, I B , I N , I P Image plane (observation position) IP light image (light image for measurement) I L , IP' optical image I R , I RN , I RP , I Ra , I Rb , I Rc , I Ri reflected image I RN Negative reflection image I RP , I RP’ Specular reflection image L IO distance Lm measurement O m Reference axis O M , O B optical axis P' Projection plane (projection position) SC, SCi apparent center of sphere si Apparent test surface Si, Si j Test surface

Claims

1. a first step of preparing an eccentricity measuring device having a measurement imager that holds a test optical unit having a test surface, projects a measurement light image onto the test optical unit, linearly moves the projected light image relatively to the test optical unit, and obtains an image of an observation surface perpendicular to a reference axis defined by a relative movement locus in air of the projected light image with respect to the test optical unit; a second step of identifying a position of a reference point corresponding to an intersection of the observation plane and the reference axis in an image acquired by the measurement imager; a third step of arranging the test optical unit on the reference axis; a fourth step of projecting the optical image to a projection position on the reference axis and forming a reflected image of the optical image reflected by the test surface at an observation position that is set such that the distance from the projection position along the reference axis is a set value L; a fifth step of placing the observation surface at the observation position, capturing an image of the observation surface using the measurement imager, and acquiring a measurement image; a sixth step of identifying an image of the reflected image at the observation position in the measurement image; a seventh step of measuring a positional deviation of the identified reflected image from the reference point of the image; an eighth step of calculating an amount of eccentricity of an apparent spherical center of the test surface with respect to the reference axis based on the amount of positional deviation; Equipped with Eccentricity measurement method.

2. the test optical unit has a plurality of test surfaces, After the third step is executed, the fourth step, the fifth step, the sixth step, the seventh step, and the eighth step are executed with the set value L of the distance being constant for each of the test surfaces; a ninth step of calculating an amount of eccentricity of each of the test surfaces with respect to the reference axis based on the calculated value of the amount of eccentricity of the apparent spherical center. The method for measuring eccentricity according to claim 1.

3. the test optical unit includes a test optical system having a plurality of optical surfaces constituting the test surface, and a test imager having an imaging surface arranged on an image plane of the test optical system, In the third step, the test optical unit is disposed on the reference axis so that the optical image can be projected from a front side of the test optical system; When the optical image is positioned at a position optically conjugate with the imaging plane on the reference axis, the amount of deviation (Z Ｘ , Z Ｙ ) based on the amount of eccentricity of the test surface; The optical image is projected at a position optically conjugate with the imaging surface on the reference axis, an image of the optical image is acquired by the test imager, and position coordinates (I Ｘ , I Ｙ 11. An eleventh step of measuring The deviation amount (Z Ｘ , Z Ｙ ) and the position coordinates (I Ｘ , I Ｙ ) to obtain the position coordinate (I Ｘｏ , I Ｙｏ a twelfth step of calculating an amount of eccentricity of the imaging surface with respect to the reference axis by calculating Further comprising: The method for measuring eccentricity according to claim 2.

4. the test optical unit includes a test optical system having a plurality of optical surfaces that form the test surface, and a frame member having an opening, In the ninth step, the amount of decentering is calculated by using, as the test surface, each optical surface of the plurality of optical surfaces that is in front of at least a front edge of the opening portion; a tenth step of disposing an imaging surface of the measurement imager at a position optically conjugate with the edge of the opening through an incident-side optical system of the test optical system that is in front of the edge, and acquiring an image of the edge through the incident-side optical system by the measurement imager; an eleventh step of calculating an apparent position of the edge relative to the reference point based on the image of the edge; a twelfth step of calculating an amount of eccentricity of the edge with respect to the reference axis based on the amount of eccentricity calculated in the ninth step and the apparent position measured in the eleventh step; Further comprising: The method for measuring eccentricity according to claim 2.

5. The second step comprises: Placing an optical element having a spherical surface with a known radius of curvature on the reference axis; The optical image is moved on the reference axis, and the positive reflection magnification β by the spherical surface is calculated. Ｐ The image of the specular reflection image formed on the first observation plane is acquired by the measurement imager, and the position of the image of the specular reflection image acquired by the measurement imager is expressed as position coordinates (X Ｐ , Y Ｐ ) and The optical image is moved on the reference axis to obtain a negative reflection magnification β Ｎ The image of the negative reflection image formed on the second observation surface is acquired by the measurement imager, and the position of the image of the negative reflection image acquired by the measurement imager is expressed by position coordinates (X Ｎ , Y Ｎ ) and The position coordinates (X ０ , Y ０ ) as the position coordinates of the reference point; Equipped with The method for measuring eccentricity according to claim 1. [0010]

6. The radius of curvature of the spherical surface is in the range of 50% to 200% of the set value L of the distance. The method for measuring eccentricity according to claim 5.

7. The second step comprises: Placing an optical element having a reflective surface made of a spherical surface or a flat surface with a known radius of curvature on the reference axis; projecting the optical image onto a projection position on the reference axis, and forming a reflected image of the optical image reflected by the test surface at an observation position that is set so that the distance from the projection position along the reference axis is zero; The optical image is moved on the reference axis, and a positive reflection magnification β of the reflecting surface at an observation position where the projection position of the optical image is the same as a position along the reference axis is obtained. Ｐ The image of the specular reflection image formed by the measurement imager is acquired by the measurement imager, and the position of the image of the specular reflection image acquired by the measurement imager is expressed by position coordinates (X Ｐ , Y Ｐ ) and The position coordinates (X Ｐ , Y Ｐ ) as the position coordinates of the reference point; Equipped with In the fourth step, the set value L of the distance is set to 0. The method for measuring eccentricity according to claim 1.

8. The sixth step is measuring a lateral magnification of an observation image formed by reflection of the optical image with respect to the optical image represented by the observation image based on an image of the observation surface acquired by the measurement imager; Identifying the observed image in which the lateral magnification is measured to be closest to a design value of the reflection magnification of the apparent surface of the test surface as the reflected image; Equipped with The method for measuring eccentricity according to claim 1.

9. The fifth step is acquiring the measurement image in a state where the optical image is disposed on the reference axis; Shifting the optical image in a direction perpendicular to the reference axis to obtain an image for identifying a reflected image; Equipped with The sixth step is comparing the measurement image with the reflection image identifying image to measure a displacement of the observation image on the observation plane corresponding to a shift amount of the optical image; measuring the lateral magnification represented by the observation image from the shift amount and the displacement; Equipped with The method for measuring eccentricity according to claim 8.

10. The optical image has a magnification measuring section that expands or contracts according to the reflection magnification of the apparent surface, The sixth step is measuring the lateral magnification by measuring the size of the magnification measuring portion in the observation image in the measurement image; Equipped with The method for measuring eccentricity according to claim 8.

11. After the first step and before calculating the eccentricity amount of the apparent spherical center of the test surface, a ninth step of measuring the set distance to obtain a measured value Lm using an optical element including a reference surface made of a spherical surface with a known radius of curvature; a tenth step of calculating a reflection magnification of the test surface by using the measured value Lm instead of the set value L; Further comprising: The method for measuring eccentricity according to claim 1.

12. The ninth step is locating the optical element on the reference axis; projecting the optical image to a projection position on the reference axis, and capturing an image of the observation surface of the specular reflection image, which is reflected by the reference surface and formed at the observation position with a positive reflection magnification, at an observation position set so that the distance from the projection position along the reference axis is a set value L, using the measurement imager; projecting the optical image to a projection position on the reference axis, and capturing an image of the observation surface of the negative reflection image, which is reflected by the reference surface and formed at the observation position with a negative reflection magnification, at an observation position set such that the distance from the projection position along the reference axis is a set value L, using the measurement imager; Calculating a ratio C of the positive reflection magnification to the negative reflection magnification based on the image of the positive reflection image and the image of the negative reflection image; determining the measured value Lm of the distance based on the following formula (a); Equipped with The method for measuring eccentricity according to claim 11. [0025] Here, R is the radius of curvature of the reference surface.

13. a tenth step of selecting, after the third step and before the fourth step is executed for the first time, the projection positions used for measuring the amount of positional deviation on each of the test surfaces so that a distribution range in a direction along the reference axis is minimized; The method for measuring eccentricity according to claim 2.

14. the eccentricity measuring device is provided with a reference mark, the positional relationship of which with respect to the reference axis is known in advance in a plane perpendicular to the reference axis, in front of the test optical system, a thirteenth step, subsequent to the third step, of imaging the reference mark with the test imager and calculating, from the image of the captured reference mark, an amount of rotation of the test imager coordinate system relative to a reference line perpendicular to the reference axis in a plane perpendicular to the reference axis; a fourteenth step of correcting the amount of eccentricity in the observation coordinate system calculated in the ninth step based on the amount of rotation to an amount of eccentricity based on the test imager coordinate system; Further equipped with the amount of eccentricity corrected in the fourteenth step is used as the amount of eccentricity of the test surface in the tenth step; The method for measuring eccentricity according to claim 3.

15. a light source unit for forming a light image for measurement; a support table for supporting a test optical unit having a test surface; a projection optical system that projects the optical image toward the test optical unit; a moving mechanism that movably holds at least one of the light source unit and the projection optical system and the holding stage, and moves the optical image projected from the projection optical system linearly in air relative to the holding stage; a measurement imager for acquiring an image of an observation plane perpendicular to a reference axis at an observation position set so that a distance from a projection position of the optical image on the reference axis is a set value L when a relative movement locus of the optical image with respect to the holding table formed by the movement mechanism is set as a reference axis; an eccentricity calculation unit that measures an amount of positional deviation from a reference point corresponding to an intersection of the observation surface and the reference axis based on an image at the observation position acquired by the measurement imager, and calculates an amount of eccentricity of an apparent spherical center of the test surface with respect to the reference axis based on the amount of positional deviation; An eccentricity measuring device comprising:

16. a test imager image acquisition unit that acquires an image from a test imager when the test optical unit has, in this order along the reference axis from a front side close to the projection optical system to a rear side far from the projection optical system, a test optical system having a plurality of optical surfaces that constitute the test surface, and a test imager that is disposed on an image plane of the test optical system; a test imager eccentricity calculation unit that calculates a position of the optical image on the imaging surface of the test imager based on an image acquired by the test imager image acquisition unit when the optical image is moved relatively to a position optically conjugate with the imaging surface of the test imager using the moving mechanism, and calculates a relative eccentricity between the test optical system and the test imager based on the calculated value of the position; Further comprising:

16. An eccentricity measuring device according to claim 15.

17. a reflection magnification measuring unit that measures a lateral magnification of an observation image formed by reflection of the light image with respect to the light image represented by the observation image based on an image at the observation position acquired by the measurement imager, 16. An eccentricity measuring device according to claim 15.

18. a parallel optical path is formed between the light source unit and the projection position, the parallel optical path forming a parallel light beam in an optical path different from an optical path of an observation optical system that optically conjugates the measurement imager and the projection position; The reflection magnification measuring unit is a wedge prism inserted in the parallel optical path; a reflection magnification measurement control unit that, by inserting the wedge prism into the parallel optical path, causes the measurement imager to acquire an image at the observation position while moving the optical image at the projection position, and measures the lateral magnification represented by the observation image based on the image at the observation position; having 18. An eccentricity measuring device according to claim 17.

19. a reference mark, the positional relationship of which with respect to the reference axis is known in advance, is further provided in a plane perpendicular to the reference axis within a field range of the test optical system; 17. An eccentricity measuring device according to claim 16.

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