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

Abstract

The application discloses a kind of optical system distortion high-precision automation measuring device and method based on node scanning method, solve the problems of traditional optical system distortion test equipment and test method, equipment cost is expensive, the requirement to environment is higher and test efficiency is lower.This application starts from the special nature of optical system node (i.e. the light rays passing through the optical image node, the outgoing light rays are parallel to the incident light rays, i.e. when the optical system takes its image node as the rotation base point, the imaging image point position remains unchanged), proposes an optical system distortion high-precision automation measuring device and method based on node scanning method, uses low-precision rotary table and microscopic measurement system to realize the high-precision test of the measured optical system distortion.

Description

TECHNICAL FIELD

[0001] The present application relates to a measuring device and method for optical system distortion, in particular to a high-precision automatic measuring device and method for optical system distortion based on a node scanning method. BACKGROUND

[0002] With the increasingly wide application of photoelectric imaging systems, the performance index requirements of photoelectric imaging systems are becoming higher and higher, especially in the field of surveying and mapping or positioning and attitude determination, the coordinate position measurement requirements of photoelectric imaging systems for target region scenes or targets are higher, which requires photoelectric imaging systems to have smaller distortion characteristics. Figure 1 As shown in the figure, although optical system distortion does not affect the clarity of the image of the target formed by the optical system, the distortion causes the image of the target formed by the optical system to deviate from the theoretical position, and due to the existence of distortion, the image of the target formed by the optical system is "barrel-shaped" or "pillow-shaped". The distortion of the optical system can be expressed by the following formula:

[0003]

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

[0005] In order to quantitatively calibrate the distortion value of the optical system, a high-precision distortion measuring device is generally needed to measure and calibrate the distortion of the optical system. For an optical system with a distortion of one thousandth, according to an image height of 6mm, the maximum absolute distortion is only 6μm, and in order to measure the absolute distortion of 6μm, the precision of the measuring device should be at least 0.6μm. At present, the grating ruler cannot meet the requirement of such high-precision length measurement, and generally a laser interferometer is needed for cooperation measurement. The laser interferometer has high requirements for the temperature, vibration and humidity of the device using environment, and is usually used in a professional laboratory with high environmental requirements. At the same time, the optical path arrangement of the laser interferometer is relatively complex, and the device occupies a large space, which is not convenient for generalization.

[0006] As Figure 2As shown, the traditional principle of optical system distortion testing involves mounting the optical lens under test on a high-precision single-axis turntable 01. A collimator 03 equipped with a star-point differentiation plate 02 is placed in front of the single-axis turntable 01. The light source 08 is activated, and the optical system under test 04 images the star point target of the collimator 03. A microscopic measurement system 05 mounted at the rear 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, y0). By rotating the single-axis turntable 01, the optical system under test 04 and the microscopic measurement system 05 are rotated by ω. i At this angle, the star target of the collimator 03 is located on the ω field of view of the optical system under test 04. The microscopic measurement system 05 is moved by the two-dimensional translation stage 06 so that the image of the optical system under test 04 received by the microscopic measurement system 05 returns to the (x0, y0) point position of the detector. The amount y of the movement of the interferometric microscopic image along the image plane of the optical system under test 04 is recorded by the laser interferometer 07. i This method is used to measure the actual image height y corresponding to the full field of view ±ω of the optical system under test. Based on discrete field of view ω i And the actual like high y i The actual focal length f′ of the measured optical system 04 can be obtained by fitting using the least squares method. This can be achieved using the formula y i ′=f′×tan(ω i ) Calculate the theoretical image height y of the optical system under test at different fields of view. i Then, calculate the difference between the theoretical image height and the actual image height for different fields of view. This 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] Traditional optical system distortion testing methods based on high-precision turntables and microscopic measurement systems rely heavily on the angular accuracy of the turntable and the translational accuracy of the microscopic measurement system (measured here using a laser interferometer). This results in high costs for traditional distortion testing equipment, and the testing environment requires vibration-free, temperature- and humidity-controlled conditions, placing high demands on the testing environment. Furthermore, traditional distortion testing methods require the translation stage to move to return the star point to the detector's (x0, y0) position after each rotation of the turntable by one field of view, leading to very low testing efficiency. Summary of the Invention

[0008] To address the technical problems of high equipment cost, high environmental requirements, and low testing efficiency in traditional optical system distortion testing equipment and methods, this invention provides a high-precision automated measurement device and method for optical system distortion based on nodal scanning.

[0009] The inventive concept of this invention:

[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 and method for optical system distortion based on the node 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 to achieve 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, the present invention 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 optical system to be measured on the target surface of the detection mechanism 负 , and the pixel size S 负 , calculate the distance of the star point image deviating from the optical axis when the control turntable rotates counterclockwise:

[0043]

[0044] 2.2, calculate the distance Lx of the image node of the optical system to be measured and the rotation center of the control turntable in the direction of the optical axis, and the distance Ly of the image node of the optical system to be measured 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 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 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 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 the preset visual field angle.

[0048] Advantages of the present application:

[0049] 1. The optical system distortion high-precision automatic measurement device and method based on the node scanning method provided by the present application utilize the special properties of the image node of the optical system (i.e. the characteristics of the light rays passing through the image node of the optical system, the transmission direction is unchanged), when the optical system to be measured rotates with the image node as the center, the star point image formed by the target provided by the star point light source generating mechanism in different visual fields is located on the initial optical axis, and the distance of the star point image deviating from the initial optical axis is the absolute distortion value of the optical system to be measured under the visual field angle. The advantages of the method are that the absolute distortion value is not affected by the rotation angle accuracy 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 present application 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 application provides the high-precision automatic measuring device and method for optical system distortion based on the node scanning method, and the absolute distortion is not affected by the measuring precision of the CCD microscopic measuring mechanism, and the traditional test method needs to accurately measure 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 efficiency of the test method is further improved, the CCD microscopic measuring mechanism has no special precision requirement, and the development cost of the test equipment is further reduced. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0053] Figure 2 the reference numerals in the figure are:

[0054] 01 - single-axis turntable, 02 - star point differentiation plate, 03 - collimator, 04 - optical system to be measured, 05 - microscopic measuring system, 06 - two-dimensional translation table, 07 - laser interference length measuring instrument, 08 - light source;

[0055] Figure 3 is the node principle diagram of the optical system; in the figure, F and F' are the object side focal point and the image side focal point of the optical system respectively, H and H' are the object side principal plane and the image side principal plane of the optical system respectively, and J and J' are the object side node and the image side node of the optical system respectively;

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

[0057] Figure 5 is the structural schematic diagram in the embodiment of the high-precision automatic measuring device for optical system distortion based on the node scanning method of the application;

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

[0059] the reference numerals in the figure are:

[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 the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] This invention 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 requiring special precision 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 adjustment 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°, and 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 formula , 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 of the application 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 the height of ±6mm, the 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 of 5μm, the pixel offset corresponding to the image height of ±3mm 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%. 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 automatic measuring device for optical system distortion based on node scanning method, characterized in that: The first fine adjustment mechanism, a turntable, a star point light source generating mechanism, a detection mechanism and the second fine adjustment mechanism are included. The first fine adjustment mechanism is installed on the turntable, and an action end of the first fine adjustment mechanism is provided with the optical system to be measured (7); the turntable is used to drive the first fine adjustment mechanism and the optical system to be measured (7) to rotate simultaneously in the azimuth angle; the first fine adjustment mechanism is used to drive the optical system to be measured (7) to translate on the turntable, so that the image side 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 to be measured (7), and is used to provide the optical system to be measured (7) with the star point target light at infinity. 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 (7), and is used to receive the star point image formed by the optical system to be measured (7) on the star point target light. The detection mechanism is installed on the action end of the second fine adjustment mechanism, and the second fine adjustment 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 the target surface of the detection mechanism, and 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 at the sharpest position. The second fine adjustment mechanism is a three-dimensional adjustment mechanism (8). The detection mechanism is a CCD microscopic measurement mechanism (9).

2. The high-precision automatic measurement device for optical system distortion based on nodal scanning method according to claim 1, characterized in that: The star point light source generating mechanism includes 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 the star point target light to the optical system to be measured (7) 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 segment is located within the working spectral segment of the optical system to be measured (7). The collimator (4) is arranged between the star point reticle (3) and the optical system to be measured (7) and is used to collimate the star point target light to form a parallel light beam and emit it to the optical system to be measured (7).

3. The optical system distortion high-precision automatic measurement device based on node scanning method according to claim 2, characterized in that: The turntable is a single-axis turntable (5).

4. The optical system distortion high-precision automatic measurement device based on node scanning method according to claim 3, characterized in that: The first fine adjustment mechanism is a two-dimensional fine adjustment mechanism (6).

5. A high-precision automatic measurement method of optical system distortion based on the node scanning method, using the high-precision automatic measurement device of optical system distortion based on the node scanning method according to any one of claims 1-4, characterized in that, The following steps are included: Step 1, install the optical system to be measured (7) on the first fine adjustment mechanism, rotate the turntable, so that the optical system to be measured (7) faces the star point light source generating mechanism, start the star point light source generating mechanism to provide the optical system to be measured (7) with the star point target light, the optical system to be measured (7) images the star point target light, the detection mechanism receives the star point image formed by the optical system to be measured (7), and adjusts the detection mechanism, so that the star point image received by the detection mechanism is located at the center of the target surface of the detection mechanism. Step 2, the turntable drives the first fine adjustment mechanism and the optical system (7) to rotate a preset field of view angle, and then the first fine adjustment mechanism adjusts the optical system (7) to make the image side node of the optical system (7) coincide with the rotation center of the turntable, and the position of the detection mechanism is adjusted along the optical axis direction of the star point target light to make the received image clearest; the detection mechanism measures the offset image element number N of the received image on the target surface of the turntable when the turntable rotates 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 (7); Step 3, the absolute distortion value Y of the optical system (7) under the preset field of view angle is calculated: Wherein, S is the image element size, and β is the magnification of the detection mechanism when measuring the received image.

6. The method according to claim 5, wherein, In step 2: The preset field of view angle is ±0.7ω max , wherein ω max is the maximum field of view angle of the optical system (7) to be measured.

7. The method according to claim 6, wherein, Step 2 is specifically: 2.1, control the turntable to drive the first fine adjustment mechanism and the optical system (7) to rotate clockwise by a preset field angle ω, and obtain the offset pixel number N of the star point image formed by the optical system (7) on the target surface through the detection mechanism 正 , and the pixel size S 正 , calculate the distance of the image deviating from the optical axis when the turntable rotates clockwise: After the control turntable is returned to zero, rotate the preset field of view angle ω counterclockwise, and obtain the offset pixel number N of the star point image formed by the optical system (7) on the target surface through the detection mechanism 负 , and the pixel size S 负 , calculate the distance of the star point image from the optical axis when the control turntable rotates counterclockwise: 2.2, the distance Lx between the image side node of the optical system (7) and the rotation center of the turntable in the optical axis direction and the distance Ly between the image side node of the optical system (7) and the rotation center of the turntable in the direction perpendicular to the optical axis are calculated: 2.3, the first fine adjustment mechanism is adjusted to move Lx and Ly distances in the X-axis and Y-axis directions respectively, so that the image side node of the optical system (7) coincides with the rotation center of the turntable; 2.4, the detection mechanism is adjusted along the optical axis direction by the second fine adjustment mechanism to make the received star point image clearest, and the detection mechanism measures the image element size S and the offset image element number N of the image on the target surface of the turntable when the turntable rotates the preset field of view angle.

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