Optical system distortion high-precision automatic measuring device based on node scanning method

Abstract

The utility model discloses an optical system distortion high-precision automatic measuring device based on a node scanning method, and solves the problems of high equipment cost, high environmental requirements and low testing efficiency of the traditional optical system distortion testing equipment and testing method. Starting from the special property of an optical system node (that is, the emergent light of the light passing through an optical image space node is parallel to the incident light, that is, when the optical system takes the image space node as a rotating base point, the position of an imaging image point is kept unchanged); the utility model provides the high-precision automatic measurement device for the distortion of the optical system based on the node scanning method, and the high-precision test of the distortion of the measured optical system is realized by using a low-precision turntable and a microscopic measurement system.

Description

TECHNICAL FIELD

[0001] The utility model relates to optical system distortion's measuring device and method, concretely relates to a kind of optical system distortion high-precision automation measuring device based on node scanning method. BACKGROUND

[0002] With the application field of photoelectric imaging system being more and more extensive, the performance index requirement of photoelectric imaging system is higher and higher, especially in surveying or positioning field, the coordinate position measurement requirement of target area scene or target of photoelectric imaging system is higher, which requires photoelectric imaging system to have smaller distortion characteristics. Figure 1 As shown, optical system distortion will not affect the imaging clarity of optical system to target, but distortion will cause the image formed by optical system to target to deviate from theoretical position, due to the existence of distortion, leading to the imaging of optical system to target to be "barrel-shaped" or "pillow-shaped". The distortion of optical system can be expressed as follows:

[0003]

[0004] Wherein, ΔY ω ' is the absolute distortion of optical system at ω field angle;Y ω ' is the actual image height of optical system at ω field angle;y' ω ' is the theoretical image height of optical system at ω field angle;q' ω ' is the relative distortion of optical system at ω field angle.

[0005] In order to quantitatively calibrate the distortion value of optical system, high-precision distortion measuring equipment is generally needed to measure and calibrate optical system distortion. For optical system with distortion of one thousandth, according to image height 6mm, its maximum absolute distortion is only 6 μm, and in order to measure the absolute distortion of 6 μm, the precision of measuring equipment should be at least 0.6 μm, and currently grating ruler cannot meet the requirement of such high-precision length measurement, generally laser interferometer is needed to cooperate with measurement, and laser interferometer has higher requirement on equipment using environment temperature, vibration and humidity, and it is usually used in professional laboratory, with higher environment requirement, at the same time, the optical path arrangement of laser interferometer is more complex, and the equipment occupies larger space, which is not convenient for generalization.

[0006] As Figure 2As shown, the traditional optical system distortion test principle is to install the measured optical lens on a high-precision single-axis turntable 01, place a parallel light tube 03 provided with a star point differentiation plate 02 in front of the single-axis turntable 01, start the light source 08, and the measured optical system 04 images the star point target of the parallel light tube 03, the position of the star point image on the micro measurement system detector is measured by the micro measurement system 05 installed at the rear end of the measured optical system 04, and is recorded as (x0, y0). i Through rotating the single-axis turntable 01, the measured optical system 04 and the micro measurement system 05 rotate an angle ω i , at this time, the star point target of the parallel light tube 03 is located on the ω field of view of the measured optical system 04, the micro measurement system 05 is moved through the two-dimensional translation table 06, so that the image received by the micro measurement system 05 formed by the measured optical system 04 returns to the (x0, y0) point position of the detector, and the movement amount y i of the micro imaging along the image surface of the measured optical system 04 is recorded by the laser interference length measuring instrument 07 at this time. i Based on the discrete field of view angle ω i and the actual image height y i , the actual focal length f' of the measured optical system 04 can be obtained by least square fitting. i The theoretical image height y max ' of the measured optical system 04 in different fields of view is calculated through the formula y max ' = f' * tan (ω 正 ), and then the difference between the theoretical image height and the actual image height in different fields of view is calculated, that is, the absolute distortion of the measured optical system, and the ratio of the absolute distortion to the theoretical image height is the relative distortion of the measured optical system.

[0007] The test precision of the traditional optical system distortion test method based on a high-precision turntable and a micro measurement system mainly depends on the angle measurement precision of the high-precision turntable and the translation precision of the micro measurement system (the data is measured by a laser interference length measuring instrument), so that the traditional distortion test device is high in cost, and the test environment needs to be vibration-free, constant temperature and humidity, and the test environment is high in requirement. The translation table needs to be moved to make the star point return to the (x0, y0) point position of the detector after the turntable rotates one field of view, and the test efficiency is very low. The utility model discloses a kind of optical system distortion high-precision automatic measurement devices based on node scanning method.

[0008] To solve the technical problems that the traditional optical system distortion test equipment and test method are expensive, have high requirements on environment and low test efficiency, the utility model provides an optical system distortion high-precision automatic measurement device based on node scanning method.

[0009] The inventive concept of the utility model:

[0010] Based on the special properties of optical system nodes (i.e., the outgoing light rays after passing through the optical image node are parallel to the incident light rays, that is, when the optical system takes its image node as the rotation base point, the position of its imaging point remains unchanged), this invention proposes a high-precision automated measurement device for optical system distortion based on the nodal scanning method. It uses a low-precision turntable and a microscopic measurement system to achieve high-precision testing of the distortion of the optical system under test.

[0011] like Figure 3 As shown, according to the principles of optics, any optical system can be simplified into an equivalent black box system. Any optical system has a pair of points through which the direction of light rays remains unchanged, namely the object node J and the image node J′. The outgoing direction of light rays passing through the image node J′ is the same as the direction of the incident light ray.

[0012] When the optical system is in the same medium, the optical system node is the intersection of the principal plane of the optical system and the optical axis. The propagation direction of the light rays passing through the object-side node J and the image-side node J′ remains unchanged. Figure 3 (Medium-thick dashed line) When an optical system images a target at infinity, the angle between the ray passing through the object-side node J and the optical axis represents the angle of incidence (i.e., the field of view). The outgoing ray is parallel to the incident ray, and the image point is located on the focal plane of the optical system. When the optical system rotates about the image-side node J′ as a reference point, since the spatial position and angle of incidence of the actual incident ray do not change, the outgoing ray still exits from point J′, and the exit angle remains unchanged. The image-side node J′ remains located on the line (or extension line) of the ray exiting from that point. The principle is as follows: Figure 4 As shown.

[0013] Depend on Figure 4 As shown by the image-side node characteristics of the optical system, when an undistorted optical system rotates around its image-side node, the spatial position of the image formed by the optical system on the fixed target moves only along the optical axis direction of the initial position (i.e., from point y1 to point y2), and there is no displacement in the initial image plane perpendicular to the optical axis direction. However, when the optical system has distortion, the image point position will deviate from the initial optical axis, producing a certain amount of absolute distortion in the initial image plane. By measuring the deviation of the image point from the initial optical axis using a microscopic measurement system, the absolute distortion of the optical system under test can be obtained, and then the relative distortion value of the optical system under test can be obtained.

[0014] This invention utilizes this characteristic of the image-side node of an optical system, enabling high-precision and high-efficiency distortion testing of the optical system using a simple combination of equipment.

[0015] To achieve the above objectives and complete the above inventive concept, this utility model adopts the following technical solution:

[0016] The application discloses a high-precision automatic measuring device for optical system distortion based on a node scanning method.

[0017] The first fine adjustment mechanism is installed on the rotary table, and an acting end of the first fine adjustment mechanism is provided with the optical system to be measured.

[0018] The star point light source generating mechanism is arranged on one side of the rotary table and corresponds to the object side of the optical system to be measured, and is used for providing an infinite star point target light for the optical system to be measured.

[0019] The detection mechanism is arranged on the other side of the rotary table and corresponds to the image side of the optical system to be measured, and is used for receiving a star point image formed by the optical system to be measured on the star point target light.

[0020] Further, the second fine adjustment mechanism is further included.

[0021] The detection mechanism is installed on an acting end of the second fine adjustment mechanism, and the second fine adjustment mechanism is used for adjusting the position of the detection mechanism before measurement so that the star point image received by the detection mechanism is located at the center of a target surface of the detection mechanism, and adjusting the position of the detection mechanism during measurement so that the star point image received by the detection mechanism is located at a most clear position.

[0022] Further, the star point light source generating mechanism includes a light source, a band-pass filter, a star point scale plate and a collimator.

[0023] The light source is used for illuminating the star point scale plate.

[0024] The star point scale plate is installed on an object focal plane of the collimator, and emits the star point target light to the optical system to be measured under the illumination of the light source.

[0025] The band-pass filter is arranged between the light source and the star point scale plate, and is used for performing spectral filtering on light emitted by the light source so that a spectral segment of the light is located in a working spectral segment of the optical system to be measured.

[0026] The collimator is arranged between the star point scale plate and the optical system to be measured, and is used for collimating the star point target light to form a parallel light beam and then emitting the parallel light beam to the optical system to be measured.

[0027] Further, the rotary table is a single-shaft rotary table.

[0028] Further, the first fine adjustment mechanism is a two-dimensional fine adjustment mechanism.

[0029] Further, the second fine adjustment mechanism is a three-dimensional adjustment mechanism.

[0030] Further, the detection mechanism is a CCD microscopic measurement mechanism.

[0031] The application discloses a high-precision automatic measurement method for optical system distortion based on a node scanning method.

[0032] Step 1, installing the optical system to be measured on the first fine adjustment mechanism, rotating the rotating table, making the optical system to be measured face the star point light source generating mechanism, starting the star point light source generating mechanism to provide a star point target light for the optical system to be measured, imaging the star point target light by the optical system to be measured, receiving the star point image formed by the optical system to be measured by the detection mechanism, and adjusting the detection mechanism so that the star point image received by the detection mechanism is located at the center of the target surface.

[0033] Step 2, controlling the rotating table to drive the first fine adjustment mechanism and the optical system to be measured to rotate by a preset field of view angle, adjusting the optical system to be measured by the first fine adjustment mechanism, making the image side node of the optical system to be measured coincide with the rotation center of the rotating table, adjusting the position of the detection mechanism along the optical axis direction of the star point target light so that the image received by the detection mechanism is clearest, and measuring the offset image element number N of the image on the target surface of the detection mechanism when the rotating table rotates by the preset field of view angle, wherein the preset field of view angle is within the maximum field of view angle range of the optical system to be measured.

[0034] Step 3, calculating the absolute distortion value Y of the optical system to be measured under the preset field of view angle:

[0035]

[0036] Wherein, S is the image element size, and β is the magnification when the detection mechanism measures the image received.

[0037] Further, in step 2:

[0038] The preset field of view angle is ±0.7ω max , wherein ω max is the maximum field of view angle of the optical system to be measured.

[0039] Further, step 2 is specifically:

[0040] 2.1, controlling the rotating table to drive the first fine adjustment mechanism and the optical system to be measured to rotate by a preset field of view angle ω clockwise, acquiring the offset image element number N of the star point image formed by the optical system to be measured on the target surface of the detection mechanism by the detection mechanism 正 , and the image element size S 正 , calculating the distance of the image deviated from the optical axis when the rotating table rotates clockwise:

[0041]

[0042] After the control turntable is returned to zero, rotate the preset visual field angle ω counterclockwise, and obtain the offset pixel number N of the star point image formed by the to-be-measured optical system on the target surface of the detection mechanism 负 , and the pixel size S 负 , calculate the distance of the star point image deviated from the optical axis when the control turntable rotates counterclockwise:

[0043]

[0044] 2.2, calculate the distance Lx of the image-side node of the to-be-measured optical system and the rotation center of the control turntable in the direction of the optical axis, and the distance Ly of the image-side node of the to-be-measured optical system and the rotation center of the control turntable in the direction perpendicular to the optical axis:

[0045]

[0046] 2.3, adjust the first fine adjustment mechanism to move in the X-axis and Y-axis directions by the distances Lx and Ly respectively, so that the image-side node of the to-be-measured optical system coincides with the rotation center of the control turntable.

[0047] 2.4, adjust the detection mechanism along the direction of the optical axis through the second fine adjustment mechanism, so that the star point image received by the detection mechanism is the clearest, and measure the offset pixel number N and the pixel size S of the image on the target surface of the detection mechanism when the control turntable rotates by the preset visual field angle.

[0048] The beneficial effects of the utility model are as follows:

[0049] 1. The optical system distortion high-precision automatic measurement device based on the node scanning method provided by the utility model utilizes the special properties of the image-side node of the optical system (namely, the characteristics that the transmission direction of the light rays passing through the image-side node of the optical system is unchanged), when the to-be-measured optical system rotates with the image-side node as the center, the star point images formed by the targets provided by the star point light source generating mechanism for different visual fields are all located on the initial optical axis, and the distance of the star point image deviated from the initial optical axis is the absolute distortion value of the to-be-measured optical system under the visual field angle, the advantages of the method are that the absolute distortion value is not affected by the rotation angle precision of the control turntable, and the traditional testing method needs to accurately measure the rotation angle of the control turntable, and then calculate the difference between the actual image height and the theoretical image height to obtain the absolute distortion value. Obviously, the testing method provided by the utility model improves the testing efficiency, and has no special precision requirement for the control turntable, thereby reducing the development cost of the testing equipment.

[0050] 2. The high-precision automated measurement device for optical system distortion based on the nodal scanning method provided by this utility model is unaffected by the measurement accuracy of the CCD microscopic measurement mechanism in terms of absolute distortion. Traditional testing methods require accurate measurement of the image height of star points, followed by calculation of the difference between the actual and theoretical image height to obtain the absolute distortion value. Therefore, compared with traditional testing methods, the testing method provided by this utility model further improves testing efficiency, has no special accuracy requirements for the CCD microscopic measurement mechanism, and further reduces the development cost of testing equipment. Attached Figure Description

[0051] Figure 1 It is a distortion diagram of the optical system;

[0052] Figure 2 This is a schematic diagram of the distortion test principle of a traditional high-precision optical system; (a) is a schematic diagram of the distortion test principle of a traditional high-precision optical system; (b) is a schematic diagram of the test principle when a star point target is incident on the optical system under test at an angle ω.

[0053] Figure 2 The labels in the text:

[0054] 01-Single-axis turntable, 02-Star point differentiation plate, 03-Columnar tube, 04-Optical system under test, 05-Microscopic measurement system, 06-Two-dimensional translation stage, 07-Laser interferometer length gauge, 08-Light source;

[0055] Figure 3 This is a schematic diagram of the optical system nodes; in the diagram, F and F′ are the object-side focus and image-side focus of the optical system, respectively; H and H′ are the object-side principal plane and image-side principal plane of the optical system, respectively; and J and J′ are the object-side node and image-side node of the optical system, respectively.

[0056] Figure 4 This is a schematic diagram of the image point position movement when the optical system rotates around the image-side node; where (a) is a schematic diagram of the image point located at the focal point when the field of view is 0; (b) is a schematic diagram of the image point still located at the original optical axis (thick solid line) when the field of view is ω; and (c) is a schematic diagram of the image point position after rotating around the image-side node by an angle ω and the image point position before rotation.

[0057] Figure 5 This is a schematic diagram of the structure of an embodiment of the high-precision automated measurement device for optical system distortion based on the node scanning method of this utility model;

[0058] Figure 6 This is a schematic diagram of the star point image offset when the image-side node is not at the rotation center in this embodiment of the present invention, wherein (a) is a schematic diagram of the offset ΔX in the X direction; and (b) is a schematic diagram of the offset ΔY in the Y direction.

[0059] Icon labels:

[0060] 1-Light source, 2-Bandpass filter, 3-Star reticle, 4-Columnar tube, 5-Single-axis turntable, 6-Two-dimensional fine-tuning mechanism, 7-Optical system under test, 8-Three-dimensional adjustment mechanism, 9-CCD microscopic measurement mechanism. Detailed Implementation

[0061] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0062] This utility model provides a high-precision automated measurement device for optical system distortion based on the nodal scanning method. This device can achieve high-precision and high-efficiency measurement of the distortion of the optical system under test without special precision requirements for each component.

[0063] like Figure 5 As shown, the measuring device includes a first fine-tuning mechanism, a turntable, a star point light source generating mechanism, a detection mechanism, and a second fine-tuning mechanism.

[0064] The first fine-tuning mechanism is mounted on the turntable, and its working end is used to mount the optical system under test 7. The turntable can drive the first fine-tuning mechanism and the optical system under test 7 to rotate simultaneously in azimuth angle, realizing the measurement of the distortion of the optical system under test 7 at different field angles. The first fine-tuning mechanism can drive the optical system under test 7 to translate on the turntable so that the image-side node of the optical system under test 7 coincides with the rotation center of the turntable. This turntable is a single-axis turntable 5. The first fine-tuning mechanism is a two-dimensional fine-tuning mechanism 6, which includes two adjustment translation stages. The two adjustment translation stages can perform two-dimensional translation adjustments on the optical system under test 7 mounted on them in a plane parallel to the single-axis turntable surface, ultimately making the image-side node of the optical system under test 7 located at the rotation center of the single-axis turntable.

[0065] The star point light source generating mechanism is arranged on one side of the turntable and corresponds to the object side of the optical system 7 to be measured, so as to provide the optical system 7 to be measured with star point target light of different spectral bands at infinity; the star point light source generating mechanism comprises a light source 1, a band-pass filter 2, a star point reticle 3 and a collimator 4; the light source 1 is used to illuminate the star point reticle 3; the star point reticle 3 is installed on the object focal plane of the collimator 4 and emits star point target light to the optical system 7 to be measured under the illumination of the light source 1; the band-pass filter 2 is arranged between the light source 1 and the star point reticle 3 and is used to perform spectral filtering on the light emitted by the light source 1 so that the spectral band is within the working spectral band of the optical system 7 to be measured; the collimator 4 is arranged between the star point reticle 3 and the optical system 7 to be measured and is used to form a parallel light beam after collimation of the star point target light and then emit the parallel light beam to the optical system 7 to be measured. The band-pass filter 2 can be provided with multiple specifications of band-pass filters, so that different spectral band band-pass filters can be selected according to the test requirement.

[0066] The detection mechanism is arranged on the other side of the turntable and corresponds to the image side of the optical system 7 to be measured, so as to receive the image of the star point target light formed by the optical system 7 to be measured; the detection mechanism is a CCD micro-measuring mechanism 9. The CCD micro-measuring mechanism 9 is used to receive the star point image formed by the optical system 7 to be measured and calculate the off-target amount of the star point image formed by the optical system 7 to be measured from the initial position at different fields of view, so as to calculate the absolute distortion value of the optical system 7 to be measured at the current field of view angle through the size of the photosensitive pixel and the magnification of the micro system. The CCD micro-measuring mechanism 9 is composed of a microscope objective and a CCD detector and is used to amplify and measure the star point image formed by the optical system 7 to be measured.

[0067] The detection mechanism is installed on the acting end of the second fine adjustment mechanism, the second fine adjustment mechanism is used to adjust the position of the detection mechanism, so that the star point image formed by the optical system 7 to be measured received by the detection mechanism is located at the center of the target surface, and at the same time, the star point image received by the CCD micro-measuring mechanism 9 is adjusted to be at the clearest position during the distortion measurement. The second fine adjustment mechanism is a three-dimensional adjustment mechanism 8 and provides three-dimensional adjustment for the CCD micro-measuring mechanism 9, which are horizontal left-right adjustment, horizontal front-back adjustment and height adjustment, so that the star point image of the optical system 7 to be measured measured by the CCD micro-measuring mechanism 9 is located at the center of the target surface of the CCD micro-measuring mechanism 9.

[0068] The light emitted by the light source 1 passes through the band-pass filter 2 installed behind it, and the filtered light illuminates the star point reticle 3 installed on the focal plane of the collimator 4. The star point target light emitted by the star point reticle 3 forms a parallel light beam after collimation by the collimator 4, and then enters the entrance pupil of the optical system 7 to be measured. The optical system 7 to be measured is installed on the two-dimensional fine adjustment mechanism 6, which is used to adjust the image-side node of the optical system 7 to be measured to coincide with the center of rotation of the single-axis turntable 5. The two-dimensional fine adjustment mechanism 6 is installed on the single-axis turntable 5, which is used to provide azimuthal rotation for the optical system 7 to be measured. The CCD micro-measuring mechanism 9 is installed immediately behind the optical system 7 to be measured, and is used to receive the star point image formed by the optical system 7 to be measured. The CCD micro-measuring mechanism 9 is installed on the three-dimensional adjustment system 8, which is used to adjust the position of the CCD micro-measuring mechanism 9 so that the star point image received by the CCD micro-measuring mechanism 9 is located at the center of the target surface of the CCD micro-measuring mechanism 9.

[0069] The specific working principle is as follows:

[0070] The light source 1, the band-pass filter 2, the star point reticle 3, and the collimator 4 generate an infinite point light source within the working spectral range of the optical system 7 to be measured. The optical system 7 to be measured is directly opposite the collimator 4 and simulates imaging of the star point of the collimator 4. The CCD micro-measuring mechanism 9 detects and receives the star point image on the focal plane of the optical system 7 to be measured. By measuring the distance between the star point image under different field angles of the optical system 7 to be measured and the initial star point image position, the absolute distortion of the optical system 7 to be measured can be calculated. The specific measurement steps are as follows:

[0071] Step 1, install the optical system 7 to be measured on the first fine adjustment mechanism, which is installed on the single-axis turntable 5. Rotate the single-axis turntable 5 so that the optical system 7 to be measured is directly opposite the collimator 4. Install the band-pass filter 2 of the appropriate spectral range, turn on the light source 1 to illuminate the star point reticle 3, and make the optical system 7 to be measured image the star point target light simulated by the collimator 4. The detection mechanism detects and receives the star point image on the focal plane of the optical system 7 to be measured. Adjust the CCD micro-measuring mechanism 9 through the three-dimensional adjustment mechanism 8 so that the star point image received by the CCD micro-measuring mechanism 9 is located at the center of the target surface.

[0072] Step 2, at this time, the three adjustment degrees of freedom of the three-dimensional adjustment mechanism 8 are zeroed, the single-axis turntable 5 drives the two-dimensional fine adjustment mechanism 6 and the optical system to be measured 7 to rotate by a preset field of view angle, and then the two-dimensional fine adjustment mechanism 6 is adjusted to make the image side node of the optical system to be measured 7 coincide with the rotation center of the single-axis turntable 5, the position of the CCD microscopic measurement mechanism 9 is adjusted along the optical axis direction to make the star point image received by the CCD microscopic measurement mechanism 9 clearer, the CCD microscopic measurement mechanism 9 measures the offset pixel number N and the offset pixel size S of the star point image received by the single-axis turntable 5 on the target surface of the CCD microscopic measurement mechanism 9 when the single-axis turntable 5 rotates by the preset field of view angle, and the preset field of view angle is within the maximum field of view angle range of the optical system to be measured 7; the preset field of view angle is ±0.7ω max , wherein ω max is the maximum field of view angle of the optical system to be measured 7. As shown in Figure 6 , specifically comprising:

[0073] 2.1, control the single-axis turntable 5 to drive the two-dimensional fine adjustment mechanism 6 and the optical system to be measured 7 to rotate clockwise by a preset field of view angle ω, and obtain the offset pixel number N 正 and the pixel size S 正 of the star point image formed by the optical system to be measured 7 on the target surface of the CCD microscopic measurement mechanism 9, and calculate the distance of the image deviating from the optical axis when the single-axis turntable 5 rotates clockwise:

[0074]

[0075] After the single-axis turntable 5 is controlled to return to zero, the single-axis turntable 5 is controlled to rotate counterclockwise by the preset field of view angle ω, and the offset pixel number N 负 and the pixel size S 负 of the star point image formed by the optical system to be measured 7 on the target surface of the CCD microscopic measurement mechanism 9 are obtained, and the distance of the star point image deviating from the optical axis when the single-axis turntable 5 rotates counterclockwise is calculated:

[0076]

[0077] In this step, the clockwise rotation and the counterclockwise rotation have no sequence.

[0078] 2.2, calculate the distance Lx of the image side node of the optical system to be measured 7 and the rotation center of the single-axis turntable 5 in the optical axis direction and the distance Ly of the image side node of the optical system to be measured 7 and the rotation center of the single-axis turntable 5 in the direction perpendicular to the optical axis:

[0079]

[0080] When the image of the to-be-tested optical system 7 is not at the center of rotation of the single-axis turntable 5, as the single-axis turntable 5 rotates, the star image formed by the to-be-tested optical system 7 received by the CCD micro-measuring mechanism 9 will produce a certain amount of displacement in the X direction, which can be calculated by the number of moving image elements of the star image on the target surface of the CCD micro-measuring mechanism 9 and the magnification of the micro-objective lens. According to the geometric imaging principle, when the image of the to-be-tested optical system 7 is located at the right side of the single-axis turntable 5 (i.e. the direction of the CCD micro-measuring mechanism 9), when the single-axis turntable 5 drives the to-be-tested optical system 7 to rotate, the image of the to-be-tested optical system 7 formed by the collimator 4 will produce a displacement ΔX in the positive direction of the X axis, and the distance ΔX of the star image deviating from the X axis can be calculated by the number N of moving image elements of the star image on the target surface of the CCD micro-measuring mechanism 9, the image element size S and the magnification β of the micro-objective lens, and the calculation formula is as follows:

[0081]

[0082] Similarly, the displacement ΔY of the star image in the positive direction of the Y axis can also be calculated.

[0083] According to the triangular relationship, the adjustment distances Lx and Ly of the to-be-tested optical system image node and the single-axis turntable 5 can be calculated.

[0084] 2.3, adjust the two-dimensional fine adjustment mechanism 6 to move in the X axis and Y axis directions by distances Lx and Ly respectively, so that the image node of the to-be-tested optical system 7 coincides with the center of rotation of the single-axis turntable 5.

[0085] If the moving direction of the star image is the same as the rotating direction of the single-axis turntable 5, it means that the image node of the to-be-tested optical system 7 is at the left side of the center of rotation of the single-axis turntable 5, and if the moving direction of the star image is opposite to the rotating direction of the single-axis turntable 5, it means that the image node of the to-be-tested optical system 7 is at the right side of the center of rotation of the single-axis turntable 5 (the direction of the CCD micro-measuring mechanism). Thus, through simple testing and debugging, the image node of the to-be-tested optical system 7 can be adjusted to the center of rotation of the single-axis turntable 5.

[0086] 2.4, adjust the CCD micro-measuring mechanism 9 along the optical axis direction by the three-dimensional adjustment mechanism 8, so that the image received by the CCD micro-measuring mechanism 9 is clearer, and measure the number N of offset image elements and the image element size S of the star image on the target surface of the CCD micro-measuring mechanism 9 when the single-axis turntable 5 rotates by a preset field angle.

[0087] After the to-be-measured optical system 7 image node is adjusted to coincide with the single-axis turntable 5 rotation center, the CCD micro-measuring mechanism 9 is re-adjusted to the star point image on the target surface center through the three-dimensional adjusting mechanism 8, and the star point position coordinates of the CCD target surface at this time are recorded as A(x0, y0); the single-axis turntable 5 is rotated at equal intervals in the field angle range of the to-be-measured optical system 7, the rotation angle of the single-axis turntable 5 is recorded as ω, and the corresponding star point image position coordinates collected by the CCD micro-measuring mechanism 9 are recorded as A(x i ,y i ), wherein the value range of i is 0, 1, 2, 3... n, when i = 0, ω = 0°, when i = n, ω max is the maximum field angle of the to-be-measured optical system 7. The distortion data collection of the to-be-measured optical system 7 is automatically completed by setting the software, and a series of turntable rotation angles and star point coordinates collected by the CCD micro-measuring mechanism 9 are obtained.

[0088] According to , the absolute distortion value Δy i of the to-be-measured optical system 7 under different field angles ω i (n i is the offset pixel number of the star point image under different field angles) can be calculated point by point.

[0089] Step 3, calculating the absolute distortion value Y of the to-be-measured optical system 7 under a preset field angle:

[0090]

[0091] Wherein, β is the magnification of the detection mechanism when measuring the received image.

[0092] Based on the above provided measuring device and method, finally, the distortion data of the to-be-measured optical system 7 only uses the offset pixel number of the star point image on the target surface of the CCD micro-measuring mechanism 9, the pixel size and the magnification of the microscope objective, the offset pixel number and the pixel size are known quantities, and the magnification of the microscope objective can be accurately calibrated, so that the optical system distortion measuring device finally uses the known quantities when measuring the optical system distortion, so that the measuring device is particularly convenient to use.

[0093] For an optical system like height ± 6mm, relative distortion is 5%, the absolute distortion is ± 0.3mm, the nominal magnification of the microscope objective is 10 times, then the nominal image height of the CCD microscopic measuring mechanism is ± 3mm, the magnification of the microscope objective can be accurately calibrated, according to the CCD pixel size is 5μm, the pixel offset corresponding to the ± 3mm image height is ± 600 pixels, the star point image is not subdivided here, that is, the star point image centroid interpretation accuracy is 1 pixel (5μm), combined with the magnification of the microscope objective, the absolute distortion measurement accuracy of the device is 0.5μm, and the relative distortion measurement accuracy is 0.017%. And the relative distortion measurement accuracy of the traditional high-precision distortion test equipment using high-precision rotary table and laser interference length measuring instrument is only 0.02%. Therefore, it can be said that the measuring device provided in the embodiment uses the special properties of the optical system image node, and high-precision distortion measurement of the measured optical system can be completed using simple test equipment.

[0094] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A high-precision automated measurement device for optical system distortion based on nodal scanning method, characterized in that: It includes a first fine-tuning mechanism, a turntable, a star point light source generation mechanism, and a detection mechanism; The first fine-tuning mechanism is mounted on the turntable, and the working end of the first fine-tuning mechanism is set with the optical system under test (7); the turntable is used to drive the first fine-tuning mechanism and the optical system under test (7) to rotate simultaneously in azimuth angle; the first fine-tuning mechanism is used to drive the optical system under test (7) to translate on the turntable so that the image node of the optical system under test (7) coincides with the rotation center of the turntable; The star point light source generating mechanism is located on one side of the turntable and corresponds to the object side of the optical system under test (7), and is used to provide the target light of the star point at infinity to the optical system under test (7); The detection mechanism is located on the other side of the turntable and corresponds to the image side of the optical system under test (7), and is used to receive the star image formed by the star target light of the optical system under test (7).

2. The high-precision automated measurement device for optical system distortion based on the nodal scanning method according to claim 1, characterized in that: It also includes a second fine-tuning mechanism; The detection mechanism is installed at the working end of the second fine-tuning mechanism. The second fine-tuning mechanism is used to adjust the position of the detection mechanism before measurement so that the star image received by the detection mechanism is located at the center of its target surface. At the same time, the position of the detection mechanism is adjusted during measurement so that the star image received by the detection mechanism is in the clearest position.

3. The high-precision automated measurement device for optical system distortion based on the nodal scanning method according to claim 1 or 2, characterized in that: The star point light source generating mechanism includes a light source (1), a bandpass filter (2), a star point reticle (3), and a collimator (4); The light source (1) is used to illuminate the star reticle (3); The star reticle (3) is installed on the object-side focal plane of the collimator (4) and emits star target light to the optical system under test (7) under the illumination of the light source (1); The bandpass filter (2) is disposed between the light source (1) and the star reticle (3) to perform spectral filtering on the light emitted from the light source (1) so that its spectral band is within the working spectral band of the optical system under test (7); The collimator (4) is positioned between the star reticle (3) and the optical system under test (7) to collimate the star target light and form a parallel beam that is emitted to the optical system under test (7).

4. The high-precision automated measurement device for optical system distortion based on the nodal scanning method according to claim 3, characterized in that: The turntable is a single-axis turntable (5).

5. The high-precision automated measurement device for optical system distortion based on the nodal scanning method according to claim 4, characterized in that: The first fine-tuning mechanism is a two-dimensional fine-tuning mechanism (6).

6. The high-precision automated measurement device for optical system distortion based on the nodal scanning method according to claim 2, characterized in that: The second fine-tuning mechanism is a three-dimensional adjustment mechanism (8).

7. The high-precision automated measurement device for optical system distortion based on the nodal scanning method according to claim 5, characterized in that: The detection mechanism is a CCD micro-measuring mechanism (9).

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