Measurement device, measurement method, and program

Abstract

To provide a measurement device with a small measurement error.SOLUTION: A measurement device (100) for measuring an eccentricity of at least one inspected surface of an inspected optical system (6) with a plurality of inspected lenses which is arrayed in an optical axis direction includes: a light source (1) for applying light; optical systems (4, 5, 8) which guide the light from the light source to the inspected optical system so as to image reflection light reflected by the inspected optical system; a light detection part (9) for acquiring a luminance value of the reflection light; and a calculation part (12) for calculating the luminance value of the reflection light from the inspected surface among the plurality of lens surfaces of the inspected optical system on the basis of information on the time from the application of the light to the acquisition of the luminance value of the reflection light.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a measuring device, a measuring method, and a program.

Background Art

[0002] Conventionally, as a method for measuring the decentration amount of an optical system including a plurality of lenses to be inspected, an autocollimation method is known. In this method, a part of the optical system is driven in the optical axis direction to project an index onto the apparent curvature center position of the lens surface to be inspected, and the reflection image position of the lens surface to be inspected with respect to the reference axis is measured to calculate the decentration amount of the lens surface to be inspected. Patent Document 1 discloses a measuring device that measures the decentration amount of each lens surface by imaging reflection images corresponding to a plurality of lens surfaces of an optical system to be inspected using an image sensor such as a CMOS camera or a CCD camera.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the measuring device disclosed in Patent Document 1, there may be a case where the reflection images from a plurality of lens surfaces of the optical system to be inspected cannot be separated. As a result, the measurement error of the decentration amount of the lens surface may increase.

[0005] Therefore, an object of the present invention is to provide a measuring device with a small measurement error.

Means for Solving the Problems

[0006] A measuring device according to one aspect of the present invention is a measuring device that measures the amount of eccentricity of at least one measured surface of a measured optical system having a plurality of measured lenses arranged in the optical axis direction, the measuring device including: a light source that irradiates light; an optical system that guides the light from the light source to the measured optical system and forms an image of the reflected light reflected by the measured optical system; a light detection unit that acquires a luminance value of the reflected light; and a calculation unit that calculates the luminance value of the reflected light from the measured surface among a plurality of lens surfaces of the measured optical system based on information regarding the time from when the light is irradiated until the luminance value of the reflected light is acquired.

[0007] Other objects and features of the present invention will be described in the following embodiments.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a measuring device with a small measurement error.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] (First Embodiment) First, with reference to FIG. 1, a measuring device (eccentricity measuring device) 100 according to the first embodiment of the present invention will be described. FIG. 1 is a configuration diagram of the measuring device 100. In FIG. 1, an axis extending in the left-right direction is defined as the X-axis, an axis extending in the up-down direction is defined as the Y-axis, and an axis extending in a direction perpendicular to the paper surface is defined as the Z-axis.

[0012] The measuring device 100 measures the eccentricity of at least one measured surface of the measured optical system 6 having a plurality of measured lenses arranged in the optical axis direction. The light source 1 irradiates light. The light emitted by the light source 1 is time-resolved light (light that changes over time), for example, pulsed light. The light emitted from the light source 1 illuminates the indicator chart 2. The light transmitted through the indicator chart 2 passes through the half mirror (beam splitter) 3 and is converted into parallel light by the collimator 4. This light passes through the objective lens (objective optical system) 5 disposed at an arbitrary position and illuminates the measured optical system 6 having a plurality of measured lenses.

[0013] The reflected light reflected by at least two lens surfaces (measured surfaces) among the plurality of measured lenses constituting the measured optical system 6 passes through the objective lens 5 and the collimator 4 and forms an image (reflected image) on the imaging surface chart 7. The reflected image and the imaging surface chart 7 are imaged by the light detection unit 9 via the imaging lens 8. In the present embodiment, the collimator 4, the objective lens 5, and the imaging lens 8 constitute an optical system that guides the light from the light source 1 to the measured optical system 6 and forms an image of the reflected light reflected by the measured optical system 6.

[0014] The indicator chart 2 is a small-diameter aperture that forms a transmission portion, for example, a crosshair, and has an asymmetric shape with respect to the Y-axis or Z-axis. A cross dotted line is drawn on the imaging surface chart 7, and the coordinates where the dotted lines intersect are taken as the origin (optical axis). The indicator chart 2 and the imaging surface chart 7 are arranged at equivalent positions with respect to the half mirror 3. Thereby, the reflected image of the indicator chart 2 is formed as an inverted and equal-magnification image at the position of the imaging surface chart 7.

[0015] The objective lens 5 is disposed on the drive stage 10 and is driven in the X-axis direction (optical axis direction) by the drive stage 10. The measured optical system 6 is held by the holding stage 11.

[0016] The light detection unit 9 preferably has a SPAD (Single-Photon Avalanche Diode) that converts a two-dimensional light intensity distribution (light distribution information) into an electrical signal. Since the SPAD has high time resolution, it is possible to discriminate minute time intervals converted from the light quantity distribution information. In this embodiment, other APDs (Avalanche Photo Diodes) may be used instead of the SPAD.

[0017] The light detection unit 9 acquires the light quantity distribution information (luminance value) of the reflected image of the index chart 2 reflected on the detection surface (lens surface) of the optical system 6 to be detected. The computer (control unit) 12 acquires the position coordinates of the reflected image acquired by the light detection unit 9 and calculates the amount of eccentricity of the detection surface. The computer 12 controls the driving of the drive stage 10 and the holding stage 11. When measuring the amount of eccentricity, the drive stage 10 is used to move the objective lens 5 in the optical axis direction (X-axis direction), and the image of the index chart 2 is projected onto the apparent center position of each detection surface of the optical system 6 to be detected.

[0018] In this embodiment, the amount of eccentricity of the detection surface is measured by the autocollimation method using the light from the objective lens 5. However, when the number of lenses constituting the optical system 6 to be detected increases, there may be a detection surface for which it is difficult to measure the amount of eccentricity. Specifically, in a plurality of detection surfaces, the apparent center positions or vertex positions are close to each other, and it may be difficult to discriminate the correspondence between the reflected image and the detection surface. On the other hand, the measuring device 100 of this embodiment can discriminate the correspondence between the reflected image and the detection surface by temporally separating a plurality of reflected images using the light detection unit 9 even for a detection surface for which such measurement is difficult.

[0019] Next, with reference to FIG. 2, the method for measuring the amount of eccentricity in this embodiment will be described. FIG. 2 is a flowchart showing the measuring method in this embodiment.

[0020] First, in step S201, the drive stage 10 of the measuring device 100 is moved in the optical axis direction to move the objective lens 5 to an arbitrary position. Here, the arbitrary position is the position corresponding to the design value of the lens surface (test surface) that is the measurement target of the eccentricity amount among the plurality of lens surfaces constituting the optical system under test 6. In the present embodiment, when the apparent center positions of two lens surfaces (measurement surfaces) in the optical system under test 6 are close to each other, the objective lens 5 is moved to the position of the reflected image of the measurement surface. Note that the movement of the drive stage 10 can be manually performed by the user or automatically performed by the computer 12.

[0021] Subsequently, in step S202, the computer 12 controls the light source 1 to irradiate pulsed light from the light source 1. The pulsed light emitted from the light source 1 passes through the collimator 4 and the objective lens 5 and is guided to the optical system under test 6. Then, the light (reflected light) reflected by the optical system under test 6 passes through the objective lens 5 and the collimator 4 and is imaged by the imaging lens 8.

[0022] Subsequently, in step S203, the computer 12 uses the light detection unit 9 to acquire light quantity distribution information (time information) regarding the reflected image of at least one lens surface (test surface) among the plurality of lenses under test constituting the optical system under test 6. The light quantity distribution information is information indicating the relationship between the time required from when the light source irradiates pulsed light until the light detection unit 9 detects the reflected light (reflected image) and the light quantity (intensity) of the reflected light detected by the light detection unit. Further, the light quantity distribution information is information for measuring the displacement amount from the reference position of the image formed by the reflected light from the test surface. Note that the computer 12 can control the irradiation timing of the light by the light source 1 and the detection timing of the reflected light by the light detection unit 9.

[0023] Here, with reference to FIG. 3, the light quantity distribution information will be described. FIG. 3 is an example of the light quantity distribution information. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the light quantity (intensity). In FIG. 3, among the optical system 6 to be inspected, the lens surface R1 is taken as the surface to be measured, and the case where the two lens surfaces R1 and R2 in the optical system 6 to be inspected are close to each other is considered. As shown in FIG. 3, in a state where the objective lens 5 is arranged at a specific position (a position corresponding to the design value), the light quantity distribution information includes information (time information) regarding two reflected lights (the first reflected light IR1 and the second reflected light IR2) corresponding to the two lens surfaces R1 and R2 respectively. The first reflected light IR1 has a peak value at time S1, and the second reflected light IR2 has a peak value at time S2. Therefore, the computer 12 can acquire the times S1 and S2 corresponding to each peak value. That is, according to the present embodiment, using the light detection unit 9, the first reflected light IR1 of the lens surface R1 (the surface to be measured) and the second reflected light IR2 of the lens surface R2 that is not the measurement target can be temporally separated.

[0024] Subsequently, in step S204, the computer 12 performs optical path length conversion. That is, the computer 12 uses the times S1, S2 or the time difference (S2 - S1) and the speed of light to acquire the respective optical path lengths or the optical path length difference (information regarding the optical path length) of the lens surfaces R1 and R2. For example, in FIG. 3, the difference between the time S1 when the first reflected light IR1 peaks and the time S2 when the second reflected light IR2 peaks is 60 ps. Therefore, the round-trip optical path length difference between the lens surface R1 and the lens surface R2 is obtained as 18 mm (optical path length difference 9 mm × 2).

[0025] Subsequently, in step S205, the computer 12 specifies the lens surface R1 corresponding to time S1 and the lens surface R2 corresponding to time S2 by using the information regarding the optical path length. Subsequently, in step S206, the computer 12 selects the surface to be inspected (measurement surface) from among the two lens surfaces R1 and R2. That is, the computer 12 specifies the surface to be inspected from among the plurality of lens surfaces of the optical system 6 to be inspected by using the light quantity distribution information. Subsequently, in step S207, the computer 12 calculates the amount of decentration of the surface to be inspected based on the reflected image (reflected image signal) of the selected surface to be inspected.

[0026] As described above, in the present embodiment, the computer (calculation unit) 12 calculates the luminance value of the reflected light from the surface to be inspected among the plurality of lens surfaces of the optical system 6 to be inspected based on the information regarding the time from when the light is irradiated until the luminance value of the reflected light is acquired. Therefore, according to the present embodiment, since the reflected image of the lens surface (surface to be inspected) to be measured and the reflected image of the lens surface that is not the measurement target can be temporally separated by using the light detection unit 9, it is possible to measure only a single reflected image.

[0027] (Second Embodiment) Next, a second embodiment of the present invention will be described. This embodiment relates to a method for measuring the surface interval between two lens surfaces (two surfaces to be inspected) of the optical system 6 to be inspected. The measuring device (surface interval measuring device) of the present embodiment is a measuring device that measures the surface interval between two surfaces to be inspected of an optical system to be inspected having a plurality of lenses to be inspected arranged in the optical axis direction. Note that the configuration of the measuring device (surface interval measuring device) of the present embodiment is the same as that of the measuring device (decentration measuring device) 100 described in the first embodiment with reference to FIG. 1, and thus the description thereof will be omitted.

[0028] With reference to FIG. 4, the method for measuring the surface interval in the present embodiment will be described. FIG. 4 is a flowchart showing the measuring method in the present embodiment. Note that steps S402 to S404 in FIG. 4 are the same as steps S202 to S204 in FIG. 2, respectively, and thus the description thereof will be omitted.

[0029] In step S401, the objective lens 5 is moved to an arbitrary position by moving the drive stage 10 of the measuring device 100 in the optical axis direction. In the present embodiment, in the case of the optical system under test in which the apparent vertex positions of the two lens surfaces are close to each other, the objective lens 5 is moved to the apparent vertex position.

[0030] In step S405, the computer 12 uses the information regarding the optical path length to obtain an optical path length difference (information regarding the optical path length) based on, for example, the difference (time interval) between time S1 and time S2 in FIG. 3. Then, the computer 12 identifies the two lens surfaces R1 and R2 as the two surfaces under test, and calculates the distance (surface interval) between the lens surfaces R1 and R2.

[0031] In the present embodiment, the computer (calculation unit) 12 obtains distance information of the two surfaces under test of the optical system under test 6 based on the light quantity distribution information (luminance value of the reflected light) acquired by the light detection unit 9, and obtains the surface interval between the two surfaces under test based on the distance information. Therefore, according to the present embodiment, since the reflected images of the two lens surfaces can be separated temporally, it is possible to measure the surface interval between the two lens surfaces.

[0032] (Other Embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiment to a system or device via a network or a storage medium, and causing one or more processors in the computer of the system or device to read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0033] According to each embodiment, even when a plurality of reflected images formed by a plurality of lens surfaces of the optical system under test overlap each other, it is possible to discriminate the correspondence relationship between the reflected image and the surface under test. Therefore, according to each embodiment, it is possible to provide a measuring device, a measuring method, and a program with small measurement errors.

[0034] The disclosure of each embodiment includes the following configurations and methods. (Configuration 1) A measuring device for measuring the eccentricity of at least one measured surface of a measured optical system having a plurality of measured lenses arranged in the optical axis direction, a light source that irradiates light, an optical system that guides the light from the light source to the measured optical system and forms an image of the reflected light reflected by the measured optical system, a light detection unit that acquires the luminance value of the reflected light, and a calculation unit that calculates the luminance value of the reflected light from the measured surface among the plurality of lens surfaces of the measured optical system based on information regarding the time from when the light is irradiated until the luminance value of the reflected light is acquired. The measuring device is characterized by this. (Configuration 2) The measuring device according to Configuration 1, wherein the light is pulsed light. (Configuration 3) The measuring device according to Configuration 1 or 2, wherein the light detection unit has an avalanche diode. (Configuration 4) further having a control unit, The measuring device according to any one of Configurations 1 to 3, wherein the control unit controls the irradiation timing of the light by the light source and the detection timing of the reflected light by the light detection unit. (Configuration 5) The luminance value of the reflected light is information indicating the relationship between the time required from when the light source irradiates the light until the light detection unit detects the reflected light and the amount of light of the reflected light detected by the light detection unit. The measuring device according to any one of Configurations 1 to 4 is characterized by this. (Configuration 6) The measuring device according to Configuration 5, wherein the calculation unit acquires distance information of the measured surface based on the luminance value of the reflected light. (Configuration 7) A measuring device for measuring the distance between two measured surfaces of a measured optical system having a plurality of measured lenses arranged in the optical axis direction, a light source that irradiates light, an optical system that guides the light from the light source to the measured optical system and forms an image of the reflected light reflected by the measured optical system, A light detection unit that acquires the luminance value of the reflected light; A measuring device, comprising: a calculation unit that acquires distance information between two surfaces to be inspected based on the luminance value of the reflected light, and calculates the surface interval between the two surfaces to be inspected based on the distance information. (Configuration 8) The measuring device according to Configuration 7, wherein the light is pulsed light. (Configuration 9) The measuring device according to Configuration 7 or 8, wherein the light detection unit includes an avalanche diode. (Configuration 10) Further comprising a control unit, The measuring device according to any one of Configurations 7 to 9, wherein the control unit controls the irradiation timing of the light by the light source and the detection timing of the reflected light by the light detection unit. (Method 1) A measuring method for measuring the eccentricity of at least one surface to be inspected of a to-be-inspected optical system having a plurality of lenses to be inspected arranged in the optical axis direction, comprising: Irradiating light from a light source; Guiding the light from the light source to the to-be-inspected optical system and imaging the reflected light reflected by the to-be-inspected optical system; Acquiring the luminance value of the reflected light; Calculating the luminance value of the reflected light from the surface to be inspected among the plurality of lens surfaces of the to-be-inspected optical system based on information regarding the time from when the light is irradiated until the luminance value of the reflected light is acquired. (Method 2) A measuring method for measuring the surface interval between two surfaces to be inspected of a to-be-inspected optical system having a plurality of lenses to be inspected arranged in the optical axis direction, comprising: Irradiating light from a light source; Guiding the light from the light source to the to-be-inspected optical system and imaging the reflected light reflected by the to-be-inspected optical system; Acquiring the luminance value of the reflected light; A measurement method characterized by including a step of obtaining distance information of the two surfaces to be inspected based on the luminance value of the reflected light, and calculating the surface interval between the two surfaces to be inspected based on the distance information. (Configuration 11) A program characterized by causing a computer to execute the measurement method described in Method 11 or 12.

[0035] As described above, the preferred embodiments of the present invention have been explained, but the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

Explanation of Reference Numerals

[0036] 1 Light source 4 Collimator (optical system) 5 Objective lens (optical system) 6 Optical system to be inspected 8 Imaging lens (optical system) 9 Light detection unit 12 Computer (calculation unit, control unit)

Claims

1. A measuring device for measuring the eccentricity of at least one measured surface of a measured optical system having a plurality of measured lenses arranged in the optical axis direction, comprising: a light source for irradiating light; an optical system for guiding the light from the light source to the measured optical system and forming an image of the reflected light reflected by the measured optical system; a light detection unit for acquiring the luminance value of the reflected light; a calculation unit for calculating the luminance value of the reflected light from the measured surface among the plurality of lens surfaces of the measured optical system based on information regarding the time from when the light is irradiated until the luminance value of the reflected light is acquired. The measuring device is characterized by having the calculation unit.

2. The measuring device according to claim 1, wherein the light is pulsed light.

3. The measuring device according to claim 1 or 2, wherein the light detection unit includes an avalanche diode.

4. further comprising a control unit, wherein the control unit controls the irradiation timing of the light by the light source and the detection timing of the reflected light by the light detection unit. The measuring device is characterized by having the control unit.

5. The luminance value of the reflected light is information indicating the relationship between the time required from when the light source irradiates the light until the light detection unit detects the reflected light and the amount of light of the reflected light detected by the light detection unit. The measuring device is characterized by having the above-described relationship.

6. The measuring device according to claim 5, wherein the calculation unit acquires distance information of the measured surface based on the luminance value of the reflected light.

7. A measuring device for measuring the distance between two measured surfaces of a measured optical system having a plurality of measured lenses arranged in the optical axis direction, comprising: a light source for irradiating light; an optical system for guiding the light from the light source to the measured optical system and forming an image of the reflected light reflected by the measured optical system; a light detection unit for acquiring the luminance value of the reflected light; a calculation unit for acquiring distance information of the two measured surfaces based on the luminance value of the reflected light and calculating the distance between the two measured surfaces based on the distance information. The measuring device is characterized by having the calculation unit.

8. The measuring device according to claim 7, wherein the light is pulsed light.

9. The measuring device according to claim 7 or 8, wherein the light detection unit includes an avalanche diode.

10. further comprising a control unit, The measuring apparatus according to claim 7 or 8, wherein the control unit controls the irradiation timing of the light by the light source and the detection timing of the reflected light by the light detection unit.

11. A measuring method for measuring the amount of eccentricity of at least one inspection surface of an inspection optical system having a plurality of inspection lenses arranged in the optical axis direction, comprising: irradiating light from a light source; guiding the light from the light source to the inspection optical system and imaging the reflected light reflected by the inspection optical system; acquiring a luminance value of the reflected light; calculating a luminance value of the reflected light from the inspection surface among a plurality of lens surfaces of the inspection optical system based on information regarding the time from when the light is irradiated until the luminance value of the reflected light is acquired.

12. A measuring method for measuring the distance between two inspection surfaces of an inspection optical system having a plurality of inspection lenses arranged in the optical axis direction, comprising: irradiating light from a light source; guiding the light from the light source to the inspection optical system and imaging the reflected light reflected by the inspection optical system; acquiring a luminance value of the reflected light; acquiring distance information of the two inspection surfaces based on the luminance value of the reflected light, and calculating the distance between the two inspection surfaces based on the distance information.

13. A program for causing a computer to execute the measuring method according to claim 11 or 12.

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