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

Abstract

The invention discloses an optical system distortion high-precision automatic measurement device and method based on a node scanning method, and solves the problems that a traditional optical system distortion test device and method are high in equipment manufacturing cost, high in environment requirement and low in test efficiency. Starting from the special property of an optical system node (that is, emergent light of light passing through an optical image space node is parallel to 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 of the optical system is kept unchanged); according to the high-precision automatic measurement device and method for the distortion of the optical system based on the node scanning method, a low-precision turntable and a microscopic measurement system are used for realizing the high-precision test of the distortion of the measured optical system.

Description

Technical Field

[0001] The invention relates to a device and method for measuring optical system distortion, and in particular to a device and method for measuring optical system distortion with high precision and automation based on a node scanning method. Background Art

[0002] As the application fields of optoelectronic imaging systems become more and more extensive, the performance indicators of optoelectronic imaging systems are required to be higher and higher. Especially in the field of surveying and mapping or positioning and attitude determination, the coordinate position measurement of the target area scene or target of the optoelectronic imaging system is required to be higher, which requires the optoelectronic imaging system to have smaller distortion characteristics. Figure 1 As shown, although the optical system distortion will not affect the clarity of the optical system's imaging of the target, the distortion will cause the optical system's image of the target to deviate from the theoretical position. Due to the existence of distortion, the optical system's imaging of the target will be "barrel-shaped" or "pillow-shaped". The distortion of the optical system can be expressed as follows:

[0003]

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

[0005] In order to quantitatively calibrate the distortion value of the optical system, high-precision distortion measurement equipment is generally required to measure and calibrate the distortion of the optical system. For an optical system with a distortion of one thousandth, calculated based on an image height of 6mm, its maximum absolute distortion is only 6μm. In order to measure the absolute distortion of 6μm, the accuracy of the measuring equipment must reach at least 0.6μm. At present, grating rulers can no longer meet the requirements of such high-precision length measurement. Generally, laser interferometer length measuring instruments are required for measurement. However, laser interferometer length measuring instruments have high requirements for the temperature, vibration and humidity of the equipment environment. They usually need to be used in professional laboratories and have high environmental requirements. At the same time, the optical path layout of laser interferometer length measurement equipment is relatively complex, and the equipment occupies a large space, which is not easy to achieve universalization.

[0006] like Figure 2 As shown, the principle of traditional optical system distortion test is to install the optical lens under test on a high-precision single-axis turntable 01, place a collimator 03 equipped with a star point differentiation plate 02 in front of the single-axis turntable 01, start the light source 08, and the optical system under test 04 images the star point target of the collimator 03. The microscopic measurement system 05 installed at the rear end of the optical system under test 04 measures the position of the star point image on the detector of the microscopic measurement system and records it as (x0 ,y 0 ). By rotating the single-axis turntable 01, the optical system 04 to be measured and the microscopic measurement system 05 are rotated ω i At this time, the star point target of the collimator 03 is located on the ω field of view of the optical system 04 to be measured. The microscopic measurement system 05 is moved by the two-dimensional translation stage 06, so that the image of the optical system 04 to be measured received by the microscopic measurement system 05 is returned to the detector (x 0 ,y 0 ) point position, record the movement amount y of the laser interferometer 07 interferometrically measuring the microscopic imaging along the image plane of the measured optical system 04 at this time i , this method is used to measure the actual image height y corresponding to the full field angle range ±ω of the optical system 04 under test. Based on the discrete field angle ω i and the actual image high i , the actual focal length f′ of the optical system 04 under test can be obtained by least square fitting. i ′=f′×tan(ω i ) Calculate the theoretical image height y of the optical system under test 04 at different fields of view i ′, and then calculate the difference between the theoretical image height and the actual image height in different fields of view, which is the absolute distortion of the optical system under test. The ratio of the absolute distortion to the theoretical image height is the relative distortion of the optical system under test.

[0007] The test accuracy of the traditional optical system distortion test method based on a high-precision turntable and a microscopic measurement system mainly depends on the angular measurement accuracy of the high-precision turntable and the translation accuracy of the microscopic measurement system (here, the laser interferometer length meter is used to measure this data), which leads to the high cost of the traditional distortion test device. At the same time, the test environment needs to be vibration-free, constant temperature and humidity, and has high requirements for the test environment. In the traditional distortion test method, after each rotation of the turntable, the translation stage must move to make the star point return to the detector (x 0 ,y 0 ) point position, the test efficiency is very low. Summary of the invention

[0008] In order to solve the technical problems of traditional optical system distortion test equipment and test methods, such as high equipment cost, high environmental requirements and low test efficiency, the present invention provides a high-precision automatic measurement device and method for optical system distortion based on a node scanning method.

[0009] The inventive concept of the present invention:

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

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

[0012] When the optical system is in the same medium, the optical system node is the intersection of the optical system principal plane and the optical axis. The transmission direction of the light passing through the object node J and the image node J' remains unchanged ( Figure 3 When the optical system forms an image of an infinitely distant target, the angle between the light passing through the object node J and the optical axis represents the incident angle of the light (i.e., the field of view angle). The outgoing light is parallel to the incident light, and the image point is located on the focal plane of the optical system. When the optical system rotates with the image node J' as the reference point, the actual spatial position and incident angle of the incident light do not change. Therefore, the outgoing light still emerges from point J', and the emergence angle remains unchanged. The image node J' is still located on the line (or extension line) of the light emerging from this point. The principle is as follows: Figure 4 shown.

[0013] Depend on Figure 4 From the image node characteristics of the optical system shown in the figure, it can be seen that when a distortion-free optical system rotates around its image node, the spatial position of the image of the fixed target by the optical system moves only in the direction of the optical axis along the initial position (i.e., from y 1 Move point to y 2 point), there is no displacement in the initial image plane perpendicular to the optical axis. When the optical system is distorted, the image point position will deviate from the initial optical axis, resulting in a certain amount of absolute distortion in the initial image plane. By using a microscopic measurement system to measure the deviation of the image point from the initial optical axis, the absolute distortion of the measured optical system can be obtained, and then the relative distortion value of the measured optical system can be obtained.

[0014] The present invention utilizes this characteristic of the image node of the optical system and can achieve high-precision and high-efficiency distortion testing of the optical system using a simple device combination.

[0015] In order to achieve the above purpose and complete the above invention concept, the present invention adopts the following technical solutions:

[0016] A high-precision automatic measurement device for optical system distortion based on a node scanning method, which is special in that it includes a first fine-tuning mechanism, a turntable, a star point light source generating mechanism and a detecting mechanism;

[0017] The first fine-tuning mechanism is mounted on a turntable, and the optical system to be measured is arranged at the action end of the first fine-tuning mechanism; the turntable is used to drive the first fine-tuning mechanism and the optical system to be measured to rotate the azimuth angle simultaneously; the first fine-tuning mechanism is used to drive the optical system to be measured to translate on the turntable, so that the image node of the optical system to be measured coincides with the rotation center of the turntable;

[0018] 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 to be tested, and is used to provide infinite star point target light for the optical system to be tested;

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

[0020] Further, it also includes a second fine-tuning mechanism;

[0021] The detection mechanism is installed at the action end of the second fine-tuning mechanism, and the second fine-tuning mechanism is used to adjust 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 its target surface. At the same time, the position of the detection mechanism is adjusted during measurement so that the star point image received by the detection mechanism is in the clearest position.

[0022] Furthermore, the star point light source generating mechanism includes a light source, a bandpass filter, a star point graticule and a collimator;

[0023] The light source is used to illuminate the star point reticle;

[0024] The star point graticule is installed on the object focal plane of the collimator and emits star point target light to the optical system to be measured under the illumination of the light source;

[0025] The bandpass filter is arranged between the light source and the star point graticule, and is used to perform spectral filtering on the light emitted by the light source so that its spectrum is within the working spectrum of the optical system to be measured;

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

[0027] Furthermore, the turntable is a single-axis turntable.

[0028] Furthermore, the first fine-tuning mechanism is a two-dimensional fine-tuning mechanism.

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

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

[0031] A high-precision automatic measurement method for optical system distortion based on a node scanning method, using the above-mentioned high-precision automatic measurement device for optical system distortion based on a node scanning method, is special in that it includes the following steps:

[0032] Step 1, the optical system to be tested is mounted on the first fine-tuning mechanism, the turntable is rotated so that the optical system to be tested is facing the star point light source generating mechanism, the star point light source generating mechanism is started to provide star point target light for the optical system to be tested, the optical system to be tested forms an image of the star point target light, the detection mechanism receives the star point image formed by the optical system to be tested, and the detection mechanism is adjusted so that the star point image received by the detection mechanism is located at the center of its target surface;

[0033] Step 2, control the turntable to drive the first fine-tuning mechanism and the optical system to be measured to rotate a preset field of view angle, and then adjust the optical system to be measured by the first fine-tuning mechanism so that the image node of the optical system to be measured coincides with the rotation center of the turntable, and adjust the position of the detection mechanism along the optical axis direction of the star point target light so that the image received is clearest; measure the number N of offset pixels on the target surface of the image received by the turntable when the preset field of view angle is rotated by the detection mechanism, and 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: Calculate the absolute distortion value Y of the optical system under test at the preset field of view angle:

[0035]

[0036] Among them, S is the pixel size, and β is the magnification of the detection mechanism when measuring the image it receives.

[0037] Furthermore, in step 2:

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

[0039] Furthermore, step 2 is specifically as follows:

[0040] 2.1. The control turntable drives the first fine-tuning mechanism and the optical system to be tested to rotate clockwise to a preset field of view angle ω, and obtains the number of offset pixels N of the star point image formed by the optical system to be tested on its target surface through the detection mechanism. 正 , and the pixel size S 正 , calculate the distance that the image deviates from the optical axis when the turntable rotates clockwise:

[0041]

[0042] After the turntable is returned to zero, it rotates counterclockwise to a preset field of view angle ω, and the number of offset pixels N of the star point image formed by the optical system to be tested on its target surface is obtained through the detection mechanism. 负 , and the pixel size S 负 , calculate the distance that the star image deviates from the optical axis when the turntable rotates counterclockwise:

[0043]

[0044] 2.2. Calculate the distance Lx between the image node of the optical system to be tested and the rotation center of the turntable in the direction of the optical axis, and the distance Ly between the image node of the optical system to be tested and the rotation center of the turntable in the direction perpendicular to the optical axis:

[0045]

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

[0047] 2.4. The detection mechanism is adjusted along the optical axis by the second fine-tuning mechanism so that the received star point image is clearest. The number of offset pixels N and the pixel size S of the image on its target surface are measured by the detection mechanism when the turntable rotates at a preset field of view angle.

[0048] Beneficial effects of the present invention:

[0049] 1. The high-precision automatic measurement device and method for optical system distortion based on the node scanning method provided by the present invention utilizes the special properties of the image node of the optical system (i.e., the property that the transmission direction of the light passing through the image node of the optical system remains unchanged). When the optical system to be tested rotates with its image node as the center, the star point images of the targets provided by the star point light source generation mechanism for different fields of view are all located on the initial optical axis. The distance that the star point image deviates from the initial optical axis is the absolute distortion value of the optical system to be tested at the field of view angle. The advantage of this method is that the absolute distortion value is not affected by the accuracy of the turntable rotation angle, while the traditional test method needs to accurately measure the turntable rotation angle, and then calculate the difference between the actual image height and the theoretical image height to obtain the absolute distortion value. Obviously, the test method provided by the present invention improves the test efficiency, has no special accuracy requirements for the turntable, and reduces the development cost of the test equipment.

[0050] 2. The high-precision automatic measurement device and method for optical system distortion based on the node scanning method provided by the present invention has an absolute distortion that is not affected by the measurement accuracy of the CCD microscopic measurement mechanism, while the traditional test method requires the accurate measurement of the image height of the star point image, and then calculates the difference between the actual image height and the theoretical image height to obtain the absolute distortion value. Therefore, compared with the traditional test method, the test method provided by the present invention further improves the test efficiency, has no special accuracy requirements for the CCD microscopic measurement mechanism, and further reduces the development cost of the test equipment. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0052] Figure 2 : is a principle diagram of distortion test of a traditional high-precision optical system; wherein, (a) is a principle diagram of distortion test of a traditional high-precision optical system; (b) is a principle diagram of test when a star point target is incident on the optical system to be tested at an angle of ω;

[0053] Figure 2 The labels in:

[0054] 01-single-axis turntable, 02-star point differentiation plate, 03-collimator, 04-optical system to be measured, 05-microscope measurement system, 06-two-dimensional translation stage, 07-laser interferometer length meter, 08-light source;

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

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

[0057] Figure 5 It is a structural schematic diagram of an embodiment of a high-precision automatic measurement device for optical system distortion based on a node scanning method of the present invention;

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

[0059] Figure Number:

[0060] 1-light source, 2-bandpass filter, 3-star point graticule, 4-collimator, 5-single-axis turntable, 6-two-dimensional fine-tuning mechanism, 7-optical system to be measured, 8-three-dimensional adjustment mechanism, 9-CCD microscopic measurement mechanism. DETAILED DESCRIPTION

[0061] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] An embodiment of the present invention provides a high-precision automatic measurement device for optical system distortion based on a node scanning method. The device has no special accuracy requirements for each component and can achieve high-precision and high-efficiency measurement of the distortion of the optical system under test.

[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 detecting mechanism and a second fine-tuning mechanism.

[0064] The first fine-tuning mechanism is installed on the turntable, and the action end of the first fine-tuning mechanism is used to install the optical system to be measured 7; the turntable can drive the first fine-tuning mechanism and the optical system to be measured 7 to rotate in azimuth angle at the same time, so as to measure the distortion of different field angles of the optical system to be measured 7; the first fine-tuning mechanism can drive the optical system to be measured 7 to translate on the turntable, so that the image node of the optical system to be measured 7 coincides with the rotation center of the turntable; the turntable is a single-axis turntable 5. The first fine-tuning mechanism is a two-dimensional fine-tuning mechanism 6, that is, it includes two adjustment translation stages, and the two adjustment translation stages can perform two-dimensional translation adjustment on the optical system to be measured 7 installed thereon in a plane parallel to the table surface of the single-axis turntable, so that the image node of the optical system to be measured 7 is 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 tested, so as to provide the optical system 7 with infinitely far star point target light of different spectrum bands; the star point light source generating mechanism comprises a light source 1, a bandpass filter 2, a star point graticule 3 and a collimator 4; the light source 1 is used to illuminate the star point graticule 3; the star point graticule 3 is installed on the object focal plane of the collimator 4, and emits the star point target light to the optical system 7 to be tested under the irradiation of the light source 1; the bandpass filter 2 is arranged between the light source 1 and the star point graticule 3, and is used to perform spectral filtering on the light emitted by the light source 1 so that its spectrum band is within the working spectrum band of the optical system 7 to be tested; the collimator 4 is arranged between the star point graticule 3 and the optical system 7 to be tested, and is used to collimate the star point target light to form a parallel light beam to be emitted to the optical system 7 to be tested. Among them, the bandpass filter 2 can be provided with bandpass filters of various specifications, so that bandpass filters of different spectrum bands can be selected according to the test needs.

[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 tested, so as to receive the image formed by the optical system 7 to be tested of the star point target light; the detection mechanism is a CCD microscopic measurement mechanism 9. The CCD microscopic measurement mechanism 9 is used to receive the star point image formed by the optical system 7 to be tested, and calculate the off-target amount of the star point image formed by the optical system 7 to be tested at different fields of view, which deviates from the initial position, and calculates the absolute distortion value of the optical system 7 to be tested at the current field of view angle through the photosensitive pixel size and the magnification of the microscope system. The CCD microscopic measurement mechanism 9 is composed of a microscope objective lens and a CCD detector, and is used to magnify and measure the star point image formed by the optical system 7 to be tested.

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

[0068] The light emitted by the light source 1 is spectrally filtered by the bandpass filter 2 installed behind it, and the filtered light illuminates the star point dividing plate 3 installed on the focal plane of the collimator 4. The star point target light emitted by the star point dividing plate 3 is collimated by the collimator 4 to form a parallel light beam and incident on 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-tuning mechanism 6. The two-dimensional fine-tuning structure 6 is used to adjust the image node of the optical system 7 to be measured to coincide with the rotation center of the single-axis turntable 5. The two-dimensional fine-tuning mechanism 6 is installed It is mounted on a single-axis turntable 5, which is used to provide azimuth angle rotation for the optical system 7 to be measured. The CCD microscopic measurement mechanism 9 is installed just 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 microscopic measurement mechanism 9 is installed on a three-dimensional adjustment system 8, and the three-dimensional adjustment system 8 is used to adjust the position of the CCD microscopic measurement mechanism 9 so that the star point image formed by the optical system 7 to be measured received by the CCD microscopic measurement mechanism 9 is located at the center of the target surface of the CCD microscopic measurement mechanism 9.

[0069] The specific working principle is as follows:

[0070] The light source 1, the bandpass filter 2, the star point graticule 3 and the collimator 4 generate an infinite point light source within the working spectrum of the optical system 7 to be tested. The optical system 7 to be tested faces the collimator 4 and forms a star point image simulated by the collimator 4. The CCD microscopic measurement mechanism 9 detects and receives the star point image on the focal plane of the optical system 7 to be tested. By measuring the distance of the star point image of the optical system 7 to be tested under different field angles from the initial star point image position, the absolute distortion of the optical system 7 to be tested can be calculated. The specific measurement steps are as follows:

[0071] Step 1, the optical system to be tested 7 is installed on the first fine-tuning mechanism, the first fine-tuning mechanism is installed on the single-axis turntable 5, the single-axis turntable 5 is rotated to make the optical system to be tested 7 face the collimator 4, the bandpass filter 2 of the appropriate spectrum is installed, the light source 1 is turned on to illuminate the star point graticule 3, so that the optical system to be tested 7 images the infinite 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 to be tested 7, and the CCD microscopic measurement mechanism 9 is adjusted by the three-dimensional adjustment mechanism 8 so that the star point image received by the CCD microscopic measurement mechanism 9 is located at the center of its target surface;

[0072] Step 2: At this time, the three adjustment degrees of freedom of the three-dimensional adjustment mechanism 8 are cleared, and the single-axis turntable 5 is controlled to drive the two-dimensional fine-tuning mechanism 6 and the optical system to be measured 7 to rotate to a preset field of view angle. The optical system to be measured 7 is adjusted by the two-dimensional fine-tuning mechanism 6 so that the image node of the optical system to be measured 7 coincides 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 received star point image clearer. The CCD microscopic measurement mechanism 9 measures the number of offset pixels N and the size of the offset pixel S of the star point image received by the single-axis turntable 5 on its target surface when the preset field of view angle is rotated. 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 , where ω max is the maximum field angle of the optical system 7 to be tested. Figure 6 As shown, specifically including:

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

[0074]

[0075] After the single-axis turntable 5 is returned to zero, it rotates counterclockwise to a preset field of view angle ω, and the number of offset pixels N of the star point image formed by the optical system 7 to be measured on its target surface is obtained through the CCD micro-measurement mechanism 9. 负 , and the pixel size S 负 , calculate the distance that the star image deviates from the optical axis when the single-axis turntable 5 rotates counterclockwise:

[0076]

[0077] In this step, there is no order of priority for clockwise rotation and counterclockwise rotation.

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

[0079]

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

[0081]

[0082] Similarly, it can also be calculated that the star point image will produce a displacement △Y in the positive direction of the Y axis.

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

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

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

[0086] 2.4. The CCD microscopic measurement mechanism 9 is adjusted along the optical axis direction by the three-dimensional adjustment mechanism 8 to make the image received clearer. The CCD microscopic measurement mechanism 9 measures the offset pixel number N and pixel size S of the star point image on its target surface when the single-axis turntable 5 rotates at a preset field of view angle.

[0087] After the image node of the optical system 7 to be measured is adjusted to coincide with the rotation center of the single-axis turntable 5, the CCD micro-measurement mechanism 9 is readjusted to the center of the target surface by the three-dimensional adjustment mechanism 8, and the position coordinates of the star point on the CCD target surface are recorded as A(x 0 ,y 0), the single-axis turntable 5 is rotated at equal intervals within the field of view of the optical system 7 to be measured, and the rotation angle of the single-axis turntable 5 is recorded as ω, and the corresponding coordinate position of the star point image collected by the CCD micro-measurement mechanism 9 on its target surface is recorded as A(x i ,y i ), where i ranges from 0, 1, 2, 3, ... n. When i = 0, ω = 0°, and when i = n, ω max is the maximum field angle of the optical system 7 to be measured. The distortion data collection of the optical system 7 to be measured is automatically completed by setting the software, and the rotation angle of the series turntable and the star point coordinate position collected by the CCD microscopic measurement mechanism 9 are obtained.

[0088] according to The different fields of view of the optical system to be tested can be calculated point by point i The absolute distortion value of the system at angle Δy i (n i is the number of offset pixels of the star image under different field of view angles).

[0089] Step 3: Calculate the absolute distortion value Y of the optical system 7 under test at a preset field of view angle:

[0090]

[0091] Among them, β is the magnification of the detection mechanism when measuring the image it receives.

[0092] Based on the measurement device and method provided above, the final distortion data of the optical system 7 to be measured only uses the number of offset pixels, pixel size and magnification of the microscope objective of the star point image on the target surface of the CCD microscope measurement mechanism 9, while the number of offset pixels and pixel size are known quantities, and the magnification of the microscope objective can be accurately calibrated. Therefore, the quantities used by the optical system distortion measurement device of the present invention when finally measuring the distortion of the optical system are all known quantities, making the measurement device particularly convenient to use.

[0093] For an optical system with an image height of ±6mm and a relative distortion of 5%, the absolute distortion is ±0.3mm, and the nominal magnification of the microscope objective is 10 times. The nominal image height of the CCD microscopic measurement mechanism is ±3mm, and the magnification of the microscope objective can be accurately calibrated. According to the CCD pixel size of 5μm, the pixel offset corresponding to the ±3mm image height is ±600 pixels. Here, the star point image is not subdivided, that is, the accuracy of the star point image centroid reading is 1 pixel (5μm). Combined with the magnification of the microscope objective, it can be calculated that the absolute distortion measurement accuracy of the device is 0.5μm, and the relative distortion measurement accuracy is 0.017%. The relative distortion measurement accuracy of the traditional high-precision distortion test equipment using a high-precision turntable and a laser interferometer length meter is only 0.02%. Therefore, it can be said that the measurement device provided in this embodiment utilizes the special properties of the image node of the optical system, and can use simple testing equipment to complete the distortion measurement of the optical system under test with high precision.

[0094] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A high-precision automatic measurement device for optical system distortion based on a node scanning method, characterized in that: It includes a first fine-tuning mechanism, a turntable, a star point light source generating mechanism and a detecting mechanism; The first fine-tuning mechanism is mounted on a turntable, and an optical system to be measured (7) is arranged at an action end of the first fine-tuning mechanism; the turntable is used to drive the first fine-tuning mechanism and the optical system to be measured (7) to rotate in azimuth angle at the same time; the first fine-tuning mechanism is used to drive the optical system to be measured (7) to translate on the turntable, so that the image node of the optical system to be measured (7) coincides with the rotation center of the turntable; 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, and is used to provide infinitely distant star point target light for the optical system (7) to be measured; 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, and is used to receive the star point image formed by the optical system (7) to be measured for the star point target light.

2. The high-precision automatic measurement device for optical system distortion based on the node scanning method according to claim 1 is characterized in that: Also included is a second fine adjustment mechanism; The detection mechanism is installed at the action end of the second fine-tuning mechanism, and the second fine-tuning mechanism is used to adjust 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 its target surface. At the same time, the position of the detection mechanism is adjusted during measurement so that the star point image received by the detection mechanism is in the clearest position.

3. The high-precision automatic measurement device for optical system distortion based on the node scanning method according to claim 1 or 2, characterized in that: The star point light source generating mechanism comprises a light source (1), a bandpass filter (2), a star point graticule (3) and a collimator (4); The light source (1) is used to illuminate the star point graticule (3); The star point graticule (3) is mounted 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 bandpass filter (2) is arranged between the light source (1) and the star point dividing plate (3) and is used to perform spectral filtering on the light emitted by the light source (1) so that its spectrum is within the working spectrum of the optical system (7) to be measured; The collimator (4) is arranged between the star point graticule (3) and the optical system to be measured (7), and is used for collimating the star point target light to form a parallel light beam and emit it to the optical system to be measured (7).

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

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

6. The high-precision automatic measurement device for optical system distortion based on the node 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 automatic measurement device for optical system distortion based on the node scanning method according to claim 5, characterized in that: The detection mechanism is a CCD microscopic measurement mechanism (9).

8. A method for high-precision automatic measurement of optical system distortion based on a node scanning method, using the high-precision automatic measurement device for optical system distortion based on a node scanning method according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, installing the optical system to be tested (7) on the first fine-tuning mechanism, rotating the turntable so that the optical system to be tested (7) is facing the star point light source generating mechanism, starting the star point light source generating mechanism to provide star point target light for the optical system to be tested (7), the optical system to be tested (7) images the star point target light, the detection mechanism receives the star point image formed by the optical system to be tested (7), and adjusting the detection mechanism so that the star point image received by the detection mechanism is located at the center of its target surface; Step 2, controlling the turntable to drive the first fine-tuning mechanism and the optical system to be measured (7) to rotate to a preset field of view angle, and then adjusting the optical system to be measured (7) by the first fine-tuning mechanism so that the image node of the optical system to be measured (7) coincides with the rotation center of the turntable, and adjusting the position of the detection mechanism along the optical axis direction of the star point target light so that the image received is the clearest; and measuring the number N of offset pixels on the target surface of the image received by the turntable when the turntable rotates to the preset field of view angle by the detection mechanism, wherein the preset field of view angle is within the maximum field of view angle range of the optical system to be measured (7); Step 3: Calculate the absolute distortion value Y of the optical system (7) under the preset field of view angle: Among them, S is the pixel size, and β is the magnification of the detection mechanism when measuring the image it receives.

9. The high-precision automated measurement method for optical system distortion based on node scanning method according to claim 8, characterized in that: In step 2: The preset viewing angle is ±0.7ω max , where ω max is the maximum viewing angle of the optical system (7) to be measured.

10. The high-precision automated measurement method for optical system distortion based on node scanning method according to claim 9, characterized in that: Step 2 is as follows: 2.

1. The control turntable drives the first fine-tuning mechanism and the optical system to be tested (7) to rotate clockwise at a preset field of view angle ω, and obtains the number of offset pixels N of the star point image formed by the optical system to be tested (7) on its target surface through the detection mechanism. 正 , and the pixel size S 正 , calculate the distance that the image deviates from the optical axis when the turntable rotates clockwise: After the control turntable is reset to zero, it rotates counterclockwise to a preset field of view angle ω, and the number of offset pixels N of the star point image formed by the optical system (7) to be tested on its target surface is obtained through the detection mechanism. 负 , and the pixel size S 负 , calculate the distance that the star image deviates from the optical axis when the turntable rotates counterclockwise: 2.

2. Calculate the distance Lx between the image node of the optical system (7) to be tested and the rotation center of the turntable in the direction of the optical axis and the distance Ly between the image node of the optical system (7) to be tested and the rotation center of the turntable in the direction perpendicular to the optical axis: 2.

3. Adjust the first fine-tuning mechanism to move Lx and Ly distances in the X-axis and Y-axis directions respectively, so that the image node of the optical system (7) to be measured coincides with the rotation center of the turntable; 2.

4. The detection mechanism is adjusted along the optical axis by the second fine-tuning mechanism so that the received star point image is clearest. The number of offset pixels N and the pixel size S of the image on its target surface are measured by the detection mechanism when the turntable rotates at a preset field of view angle.

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