Optical system distortion measurement device and method based on rotating double prism

Abstract

The present application discloses an optical system distortion measurement device and method based on a rotating double prism, belonging to the technical field of optical system measurement. The present application adopts a two-dimensional linear motion mechanism and a rotating double prism assembly instead of a multi-dimensional turntable to realize field of view change, light beam translation and light beam deflection control, thereby avoiding the motion error of the multi-dimensional turntable; the two-dimensional linear motion mechanism realizes the translation movement of the collimator, and the collimator does not need to change the pitch state, thereby avoiding the safety risks caused by the change of the pitch angle of the collimator; the rotating double prism assembly realizes the deflection control of the parallel light beam, has the advantages of compact structure, small moment of inertia, and can realize large-angle deflection of large-caliber light beams, thereby improving the measurement accuracy and reliability.

Description

Technical Field

[0001] The present application relates to the technical field of optical system measurement, and in particular to an optical system distortion measurement device and method based on a rotating double prism. Background Art

[0002] Optical imaging measurement technology is widely used in modern industry, national defense, surveying and mapping and other fields. With the rapid development of application needs and measurement technology, wider and higher requirements are put forward for the observation field and measurement accuracy of optical imaging systems. Although the distortion of the optical system does not affect the image clarity, it directly affects the geometric position accuracy of the measurement results, and the error increases with the increase of the field of view, causing distortion of the measurement results. Therefore, measures need to be taken to reduce or eliminate the impact of distortion in optical systems with wide field of view and high measurement accuracy. In addition to correcting the distortion as much as possible in the optical design stage, it is particularly important to accurately and reliably measure the distortion of the actual optical system to provide a data basis for subsequent corrections.

[0003] Commonly used distortion measurement methods include length measurement method, angle measurement method, star point method, etc. Among them, the length measurement method is to set a standard grid plate on the object side, shoot the optical system to be measured, and then use a measuring microscope or a length comparison meter to measure the target pattern imaging, and obtain the distortion value by comparison and calculation. The angle measurement method is to install a standard grid plate on the image plane of the lens, fix the optical system to be measured on the rotation center of the precision turntable, observe the grid plate with a telescope on the object side, use the turntable to measure the angle corresponding to each image height, and reversely calculate the actual image height of different fields of view to obtain the lens distortion. The main errors of these two methods include the manufacturing accuracy of the standard grid plate, the angle error of the turntable measurement, the standard error of personnel and the scale error, which restrict the application of distortion measurement of large field of view and high precision optical measurement system. The star point method uses a point light source placed on the focal plane of the collimator, and changes the angle of the output beam of the parallel light source through a multi-dimensional turntable to achieve field of view changes. The center coordinates of the diffusion circle of the star point image of the parallel light source on the image plane of the optical system to be measured are directly measured, and the image height of different fields of view is calculated to obtain the distortion of the optical system to be measured. The main error of the star point method is the motion error of the multi-dimensional turntable, which overcomes the manufacturing error of the test benchmark and the operation error, and is easier to achieve large field of view, high precision, and large-aperture optical system distortion measurement. However, high-performance parallel light sources usually require large weight and volume, especially when the pitch angle changes, there are safety risks. Summary of the invention

[0004] In order to solve the problems of multi-dimensional turntable motion errors and safety risks of changes in the pitch state of parallel light sources in the existing technology of optical system distortion measurement using the star point method, the present application proposes an optical system distortion measurement device and method based on a rotating bi-prism. The present application adopts a two-dimensional linear motion mechanism and a rotating bi-prism assembly instead of a multi-dimensional turntable to achieve field of view change, light beam deflection and light beam translation control, thereby avoiding the multi-dimensional turntable motion errors. At the same time, there is no need to control the pitch angle of the parallel light source, thereby avoiding the safety risks caused by it.

[0005] This application is implemented through the following technical solutions:

[0006] An optical system distortion measurement device based on a rotating double prism, comprising:

[0007] A parallel light source assembly, the parallel light source assembly comprising a two-dimensional linear motion mechanism and a parallel light pipe, the two-dimensional linear motion mechanism is used to drive the parallel light pipe to perform linear motion in a plane perpendicular to the optical axis direction, so that the parallel light beam emitted by the parallel light pipe can be projected into the entrance pupil plane of the optical system under test after passing through the rotating double prism assembly;

[0008] A rotating double prism assembly, the rotating double prism assembly comprising a first prism, a second prism rotating mechanism, a second prism and a second prism rotating mechanism, the first prism rotating mechanism drives the first prism to rotate around the optical axis, the second prism rotating mechanism drives the second prism to rotate around the optical axis, and the light beam angle deflection control is achieved by controlling the rotation angles of the first prism rotating mechanism and the second prism rotating mechanism to achieve the light beam incident field angle required by the optical system under test;

[0009] The optical system under test comprises an entrance pupil plane, an optical lens group and a photoelectric detector, wherein the optical lens group focuses a parallel light beam incident on the entrance pupil plane onto the photoelectric detector to form a star-like diffuse light spot;

[0010] And, a computer device, which is electrically connected to the two-dimensional linear motion mechanism, the first prism rotation mechanism, the second prism rotation mechanism, and the photoelectric detector, respectively, to realize motion calculation and send motion instructions to the two-dimensional linear motion mechanism, the first prism rotation mechanism, and the second prism rotation mechanism, and complete the calculation of the center coordinates of the diffuse spot of the star point image and the distortion value according to the measurement results of the photoelectric detector.

[0011] In some embodiments, the optical system distortion measurement device further includes:

[0012] A test platform, comprising a stage and a lifting mechanism, wherein the test platform is used to place the optical system under test; an installation position line of the entrance pupil plane is arranged on the stage to provide a position reference for the installation of the optical system under test, and the lifting mechanism realizes the height adjustment of the optical axis of the optical system under test.

[0013] In some embodiments, the first prism rotation mechanism and the second prism rotation mechanism both use motors;

[0014] And / or, the first prism and the second prism are a single wedge-shaped mirror or a group of wedge-shaped mirrors;

[0015] And / or, the relative position relationship between the first prism and the second prism is back-to-back, face-to-face or face-to-back.

[0016] In some embodiments, the collimator includes a star point light source and a collimator lens group;

[0017] The star point light source simulates a target, and the collimating lens group realizes parallel emission of light beams.

[0018] On the other hand, the present application also proposes a method for measuring optical system distortion based on a rotating double prism, and the optical system distortion measurement method is implemented based on the above-mentioned optical system distortion measurement device, including:

[0019] Adjust the parallel light source assembly and the rotating biprism assembly to a reference field of view position;

[0020] Installing the optical system to be measured, and ensuring that the entrance pupil plane of the optical system to be measured coincides with the installation reference graticule;

[0021] According to the optical axis height of the outgoing light beam of the parallel light source assembly, adjusting the optical axis height of the optical system under test so that the entrance pupil plane of the optical system under test is concentrically symmetrical with the outgoing light beam;

[0022] Calculate the translation amount of the two-dimensional linear motion mechanism, the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism under each field of view to be measured;

[0023] Control step: sending corresponding motion instructions to the two-dimensional linear motion mechanism, the first prism rotation mechanism and the second prism rotation mechanism respectively according to the order of the fields to be measured, and confirming that the execution is in place according to the feedback position information;

[0024] Measurement and calculation step: calculating the center coordinates of the diffuse light spot of the star point image according to the diffuse light spot of the star point image measured by the photoelectric detector;

[0025] The control step and the measurement and calculation step are repeated until the measurement and calculation of all the fields to be measured are completed, and the distortion value of the full field of view of the optical system to be measured is calculated according to the center coordinates of the diffuse light spot of the star point image of each field to be measured.

[0026] In some embodiments, the calculation process of the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism includes:

[0027] According to a first mapping relationship between the field of view angle of the optical system to be measured and the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism, the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism under each field of view to be measured are calculated; wherein the first mapping relationship is expressed as:

[0028]

[0029] or,

[0030]

[0031] In the formula, θ1 and θ2 represent the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism respectively; θ represents the azimuth of the incident light beam in the spherical coordinate system, which is obtained by converting the field angle of the optical system under test in the rectangular coordinate system; Δθ represents the difference between the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism, which is calculated based on the parameters of the first prism and the second prism and the pitch angle of the incident light beam in the spherical coordinate system, and the pitch angle of the incident light beam in the spherical coordinate system is converted based on the field angle of the optical system under test in the rectangular coordinate system; θ0 represents the deflection angle between the incident light beam introduced into the rotating double prism and the outgoing light beam, which is calculated based on the parameters of the first prism and the second prism and Δθ.

[0032] In some embodiments, the calculation process of the translation amount of the two-dimensional linear motion mechanism includes:

[0033] According to the second mapping relationship between the field of view angle of the optical system to be measured and the translation amount of the two-dimensional linear motion mechanism, the translation amount of the two-dimensional linear motion mechanism under each field of view to be measured is calculated; wherein the second mapping relationship is expressed as:

[0034]

[0035] In the formula, S x , S yThey respectively represent the translation amounts of the two-dimensional linear motion in the X direction and the Y direction; H1, H2, H3, and H4 respectively represent the distances between the left and right surfaces of the first prism, the right surface of the first prism and the left surface of the second prism, the left and right surfaces of the second prism, and the right surface of the second prism and the center of the entrance pupil plane along the axial direction of rotation of the double prism; b1, b2, c1, c3, and c4 all represent intermediate parameters, which are calculated according to the parameters of the first prism and the second prism and Δθ.

[0036] In some embodiments, the calculation formula for the center coordinates of the diffuse spot of the star image is:

[0037]

[0038] In the formula, C x , C y Respectively represent the center coordinates of the diffuse spot of the star image in the X and Y directions; ij , Y ij ,I ij Respectively represent the X coordinate, Y coordinate, and grayscale value of the pixel in the i-th row and j-th column of the photodetector; N x 、N y Respectively represent the number of pixels in the X and Y directions of the photodetector; p x 、p y Respectively represent the size of a single pixel of the photodetector in the X and Y directions;

[0039] The following formula is used to calculate the distortion value of each field of view to be measured:

[0040]

[0041] In the formula, q xi ,q yi Respectively represent the distortion values ​​of the i-th field of view in the X and Y directions; θ xi ,θ yi Respectively represent the viewing angles of the i-th field of view in the X and Y directions; C xi , C yi Respectively represent the coordinate measurement values ​​of the center of the diffuse light spot in the X and Y directions of the i-th field of view; C x0 , C y0 They represent the measured values ​​of the center coordinates of the diffuse light spot in the X and Y directions of the reference field of view respectively; f0 represents the focal length of the optical system under test.

[0042] In some embodiments, the calculation process of the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism includes:

[0043] According to a first mapping relationship between the field of view angle of the optical system to be measured and the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism, the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism under each field of view to be measured are calculated; wherein the first mapping relationship is solved by a first-order approximation method, a vector refraction method, and a coordinate transformation method.

[0044] In some embodiments, the optical system distortion measurement method further includes:

[0045] According to the distortion value measurement results of all the fields of view to be measured, a two-dimensional distortion surface of the optical system to be measured is obtained by least square fitting, wherein the two-dimensional distortion surface is a polynomial function relationship between the distortion value and the field of view angle of the optical system to be measured;

[0046] In the subsequent distortion measurement process, the corresponding distortion value is calculated using the polynomial function relationship according to different field of view angles.

[0047] The present application proposes a device and method for measuring distortion of an optical system based on a rotating double prism, which adopts a two-dimensional linear motion mechanism and a rotating double prism assembly instead of a multi-dimensional turntable to realize field of view change, light beam translation and light beam deflection control, thereby avoiding the motion error of the multi-dimensional turntable; the two-dimensional linear motion mechanism realizes the translation movement of the collimator, and the collimator does not need to change the pitch state, thereby avoiding the safety risks caused by the change of the pitch angle of the collimator; the rotating double prism assembly realizes the deflection control of the parallel light beam, which has the advantages of compact structure, small moment of inertia, and can realize large-angle deflection of large-caliber light beams, thereby improving the measurement accuracy and reliability;

[0048] The present application proposes an optical system distortion measurement device and method based on a rotating double prism. The rotation angles of the first prism rotation mechanism and the second prism rotation mechanism are determined by the mapping relationship between the field of view angle of the optical system to be measured and the rotation angles of the first prism rotation mechanism and the second prism rotation mechanism. At the same time, the translation amount of the two-dimensional linear motion mechanism is determined by the mapping relationship between the field of view angle of the optical system to be measured and the translation amount of the two-dimensional linear motion mechanism. Control is performed accordingly, so that the output light beam of the rotating double prism can be projected into the entrance pupil plane of the optical system to be measured, the consistency of the output light beam and the entrance pupil of the optical system to be measured is maintained, and the measurement reliability is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The drawings described herein are used to provide a further understanding of the embodiments of the present application, constitute a part of the present application, and do not constitute a limitation on the embodiments of the present application. In the drawings:

[0050] Figure 1 This is a schematic structural diagram of an optical system distortion measurement device according to an embodiment of the present application;

[0051] Figure 2 This is a flow chart of a method for measuring optical system distortion according to an embodiment of the present application;

[0052] Figure 3 A schematic diagram of the position of the field of view to be measured according to an embodiment of the present application;

[0053] Figure 4 is the rotation angle of the first prism and the second prism under different fields of view in the embodiment of the present application;

[0054] Figure 5 is the translation amount of the two-dimensional linear motion mechanism under different fields of view of the embodiment of the present application;

[0055] Figure 6 Schematic diagram of the relative position relationship of the measuring device under the edge field of view and the central field of view of the embodiment of the present application; wherein (a) is the lower edge field of view; (b) is the central field of view; (c) is the upper edge field of view;

[0056] Figure 7 The theoretical value and measured value of the center coordinates of the diffuse spot of the star image in the full field of view of the optical system under test in the embodiment of the present application;

[0057] Reference numerals and corresponding component names:

[0058] 1-parallel light source assembly, 2-rotating double prism assembly, 3-optical system to be measured, 4-testing platform, 5-computer equipment, 6-two-dimensional linear motion mechanism, 7-parallel light tube, 8-star light source, 9-collimator group, 10-first prism rotation mechanism, 11-first prism, 12-second prism, 13-second prism rotation mechanism, 14-entrance pupil plane, 15-optical lens group, 16-photoelectric detector, 17-stage, 18-lifting mechanism. DETAILED DESCRIPTION

[0059] Hereinafter, the term "include" or "may include" used in various embodiments of the present application indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present application, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items.

[0060] In various embodiments of the present application, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the words listed at the same time. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0061] The expressions (such as "first", "second", etc.) used in the various embodiments of the present application may modify the various constituent elements in the various embodiments, but may not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing one element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of the present application, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0062] It should be noted that if it is described that one component element is “connected” to another component element, the first component element may be directly connected to the second component element, and a third component element may be “connected” between the first component element and the second component element. Conversely, when one component element is “directly connected” to another component element, it can be understood that there is no third component element between the first component element and the second component element.

[0063] The terms used in the various embodiments of the application are only used to describe the purpose of specific embodiments and are not intended to limit the various embodiments of the application. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meanings commonly understood by ordinary technicians in the field of the various embodiments of the application. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in the various embodiments of the application.

[0064] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with examples and drawings. The illustrative implementation scheme of the present application and its description are only used to explain the present application and are not intended to limit the present application.

[0065] Embodiment 1:

[0066] In view of the problems such as the motion error of the multi-dimensional turntable of the star point method and the safety risk when the pitch state of the parallel light source changes in the optical system distortion measurement, this embodiment proposes an optical system distortion measurement device based on a rotating double prism. The optical system distortion measurement device proposed in this embodiment uses a two-dimensional linear motion mechanism and a rotating double prism assembly instead of a multi-dimensional turntable to realize the control of field of view change, light beam deflection and light beam translation, thereby avoiding the motion error of the multi-dimensional turntable. Among them, the two-dimensional linear motion mechanism is used to realize the translational motion of the collimator, that is, the collimator does not need to change the pitch state, thereby avoiding the safety risk introduced by the change of the pitch angle of the collimator; the rotating double prism assembly is used to realize the deflection control of the parallel light beam, which has the advantages of compact structure, small moment of inertia, and can realize large-angle deflection of large-caliber light beams, thereby improving the measurement accuracy and reliability.

[0067] like Figure 1 As shown, the optical system distortion measurement device proposed in this embodiment includes:

[0068] A parallel light source assembly 1 includes a two-dimensional linear motion mechanism 6 and a parallel light tube 7. The parallel light tube 7 includes a star-point light source 8 and a collimator lens group 9. The star-point light source 8 simulates a target, and the collimator lens group 9 realizes parallel emission of the light beam. The two-dimensional linear motion mechanism 6 drives the parallel light tube 7 to perform linear motion in a plane (i.e., an XY plane) perpendicular to the optical axis direction (i.e., the Z axis), so that the light beam can be projected into the entrance pupil plane 14 of the optical system 3 to be measured after passing through the rotating double prism assembly 2.

[0069] A rotating double prism assembly 2, the rotating double prism assembly 2 comprises a first prism 11, a first prism rotating mechanism 10, a second prism 12, and a second prism rotating mechanism 13. The first prism rotating mechanism 10 drives the first prism 11 to rotate around the optical axis, and the second prism rotating mechanism 13 drives the second prism 12 to rotate around the optical axis. The rotating double prism assembly 2 realizes the light beam angle deflection by controlling the rotation angle of the first prism rotating mechanism 10 and the second prism rotating mechanism 13, so as to achieve the light beam incident field angle required by the measured optical system 3. Optionally, the first prism rotating mechanism 10 and the second prism rotating mechanism 13 can adopt but not limited to motors. Optionally, the first prism 11 and the second prism 12 can be a single wedge mirror or a wedge mirror group. Optionally, the relative position relationship between the first prism 11 and the second prism 12 can be a combination of back-to-back, face-to-face or face-to-back.

[0070] The optical system 3 under test comprises an entrance pupil surface 14, an optical lens assembly 15 and a photodetector 16, wherein the optical lens assembly 15 focuses the parallel light beam incident into the entrance pupil surface 14 onto the photodetector 16 to form a star-shaped diffuse light spot.

[0071] And, a computer device 5, which is electrically connected to the two-dimensional linear motion mechanism 6, the first prism rotation mechanism 10, the second prism rotation mechanism 13, and the photoelectric detector 16, respectively, can realize: setting the field of view angle of the optical system 3 under test, calculating the translational motion and the rotational motion, sending motion instructions, receiving position information, calculating the center coordinates of the diffuse spot of the star image and the distortion value, and other control and calculation tasks.

[0072] Furthermore, the optical system distortion measurement device provided in this embodiment further includes:

[0073] The test platform 4 includes a stage 17 and a lifting mechanism 18, which are used to place the optical system 3 under test. The stage 17 is provided with installation position lines of the entrance pupil surface 14 to provide a position reference for the installation of the optical system under test. The lifting mechanism 18 realizes the height adjustment of the optical axis of the optical system under test.

[0074] Optionally, the computer device 5 may also be electrically connected to the lifting mechanism 18 to send motion instructions to the lifting mechanism to achieve height adjustment of the optical axis of the optical system under test.

[0075] Based on the above optical system distortion measurement device, this embodiment also proposes an optical system distortion measurement method based on a rotating double prism, such as Figure 2 As shown, the optical system distortion measurement method proposed in this embodiment specifically includes the following steps:

[0076] Step 100, adjust the parallel light source assembly 1 and the rotating double prism assembly 2 to the reference field of view position. The so-called reference field of view means that the optical axis of the output light beam of the rotating double prism assembly 2 is in a horizontal state, and the reference field of view is usually selected from the central field of view of the optical system to be measured.

[0077] Step 200, installing the optical system 3 under test (i.e. installing the optical system 3 under test on the test platform 4), and ensuring that the entrance pupil plane 14 of the optical system 3 under test coincides with the installation reference graticule (i.e. the entrance pupil plane 14 coincides with the entrance pupil plane installation position graticule of the test platform 4).

[0078] Step 300, according to the optical axis height of the outgoing light beam, adjust the optical axis height of the optical system 3 under test (which can be achieved by adjusting the height of the lifting mechanism 18 of the test platform 4), so that the entrance pupil plane 14 of the optical system 3 under test is concentrically symmetrical with the light beam.

[0079] Step 400 , setting a list of fields to be measured, and calculating the translation amount of the two-dimensional linear motion mechanism 6 , the rotation angle of the first prism rotation mechanism 10 , and the rotation angle of the second prism rotation mechanism 13 in each field measurement state.

[0080] Step 500 , according to the sequence of the fields to be measured, corresponding motion instructions are sent to the two-dimensional linear motion mechanism 6 , the first prism rotation mechanism 10 , and the second prism rotation mechanism 13 , respectively, and the execution is confirmed according to the feedback position information.

[0081] Step 600 , calculating the center coordinates of the star point image diffuse light spot according to the star point image diffuse light spot of the photoelectric detector 16 .

[0082] Step 700, repeating steps 500 to 600 until all the fields to be measured are measured and calculated, and the distortion value of the full field of view of the optical system 3 to be measured is calculated according to the center coordinates of the diffuse light spots of the star point images of each field to be measured.

[0083] In this embodiment, the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism are determined by the mapping relationship between the field of view angle of the optical system under test and the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism. At the same time, the translation amount of the two-dimensional linear motion mechanism is determined by the mapping relationship between the field of view angle of the optical system under test and the translation amount of the two-dimensional linear motion mechanism, and control is performed accordingly, so that the output light beam of the rotating double prism can be projected into the entrance pupil plane of the optical system under test, the consistency of the output light beam and the entrance pupil of the optical system under test is maintained, and the measurement reliability is guaranteed.

[0084] Furthermore, the field of view angle of the optical system under test in the rectangular coordinate system is set to (θ x ,θ y ), the rotation angle of the first prism rotation mechanism is set to θ1, and the rotation angle of the second prism rotation mechanism is set to θ2. The mapping relationship between the field of view angle and the rotation angles of the first prism rotation mechanism and the second prism rotation mechanism can be obtained through the following process, that is, the rotation angles of the first prism rotation mechanism and the second prism rotation mechanism can be determined according to the field of view angle:

[0085] First, the field of view angle in the rectangular coordinate system is converted into the azimuth and elevation angles of the incident light beam in the spherical coordinate system, expressed as:

[0086]

[0087] Where θ represents the azimuth angle of the incident light beam, and Φ represents the elevation angle of the incident light beam.

[0088] The difference between the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism is expressed as:

[0089]

[0090] Wherein, Δθ represents the difference between the rotation angles of the first prism rotation mechanism and the second prism rotation mechanism; β2 represents the wedge angle of the second prism; n2 represents the refractive index of the second prism; a1 and a2 both represent intermediate parameters, and their calculation formulas are:

[0091]

[0092] Wherein, β1 represents the wedge angle of the first prism; n1 represents the refractive index of the first prism; when the difference between the rotation angles of the first prism rotation mechanism and the second prism rotation mechanism is Δθ, the deflection angle between the incident light beam and the outgoing light beam introduced into the rotating double prism is θ0, and the deflection angle is expressed as:

[0093] θ0=Angle{a1+a3 sinβ2 cosΔθ+j*a3 sinβ2 sinΔθ} (5)

[0094] Wherein, Angle{·} represents the complex angle solving function; a3 represents the intermediate parameter, and its calculation formula is:

[0095]

[0096] Then, two sets of solutions for the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism are obtained, which are expressed as:

[0097]

[0098] or,

[0099]

[0100] Then, during operation, the rotation angles of the first prism rotation mechanism and the second prism rotation mechanism can be determined according to the mapping relationship shown in formula (7) or formula (8), and one of the solutions can be selected as the motion instruction.

[0101] It should be noted that the direct solution process of the above formula (1) to formula (8) is only an exemplary description, and does not limit the solution method of the mapping relationship between the field angle of the optical system under test and the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism. That is, in other optional implementations, the mapping relationship between the field angle of the optical system under test and the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism (i.e., formula (7) or formula (8)) can also be solved by using the first-order approximation method, the vector refraction method, the coordinate transformation method, etc.

[0102] Furthermore, the field of view angle (θ x ,θ y ) and the translation of the two-dimensional linear motion mechanism (Sx ,S y ), that is, determining the translation amount of the two-dimensional linear motion mechanism according to the field of view angle:

[0103] First, according to the mapping relationship between the field of view angle of the optical system under test and the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism (as shown in the above formula (7) or formula (8)), the rotation angle θ1 of the first prism rotation mechanism and the rotation angle θ2 of the second prism rotation mechanism are obtained.

[0104] Then, taking the center of the entrance pupil plane as the origin, the translation amount (S x ,S y ), the specific calculation formula is as follows:

[0105]

[0106] Wherein, H1, H2, H3, and H4 represent the distances between the left and right surfaces of the first prism, the right surface of the first prism and the left surface of the second prism, the left and right surfaces of the second prism, and the right surface of the second prism and the center of the entrance pupil plane along the axial direction of the double prism rotation; b1, b2, c1, c3, and c4 all represent intermediate parameters, and their calculation formulas are:

[0107]

[0108] c1=a1 sinβ2 cosΔθ+a2 cosβ2+a3 (12)

[0109] c3=a2a3 sinβ2 cosβ2 (13)

[0110] c4=a1sinβ2 cosΔθ+a2 cosβ2+a3 sin 2 β2 (14)

[0111] During operation, the translation amount of the two-dimensional linear motion mechanism can be determined according to the mapping relationship shown in formula (9), and sent to the two-dimensional linear motion mechanism as a motion instruction.

[0112] Furthermore, this embodiment may use, but is not limited to, a centroid algorithm to calculate the center coordinates (C x ,C y ), which is calculated as follows:

[0113]

[0114] Where, X ij , Y ij ,I ijRespectively represent the X coordinate, Y coordinate, and grayscale value of the pixel in the i-th row and j-th column of the photodetector; N x 、N y Respectively represent the number of pixels in the X and Y directions of the photodetector; p x 、p y They represent the size of a single pixel of the photodetector in the X and Y directions respectively.

[0115] Then, according to the measured value of the center coordinate of the diffuse spot of the star image and its theoretical value, the corresponding distortion value is calculated. According to the list of fields to be measured, all distortion measurements and diffuse spot center coordinate calculations are completed, among which the distortion measurement results of the X and Y directions of the i-th field of view (q xi ,q yi ), expressed as:

[0116]

[0117] In the formula, θ xi ,θ yi Respectively represent the viewing angles of the i-th field of view in the X and Y directions; C xi , C yi Respectively represent the coordinate measurement values ​​of the center of the diffuse light spot in the X and Y directions of the i-th field of view; C x0 , C y0 They represent the measured values ​​of the center coordinates of the diffuse light spot in the X and Y directions of the reference field of view respectively; f0 represents the focal length of the optical system under test.

[0118] Furthermore, the optical system distortion measurement method proposed in this embodiment can also calculate the distortion result Q(θ x ,θ y ), which is calculated as follows:

[0119] Q(θ x ,θ y )=(Q x (θ x ,θ y 0,Q y (θ x ,θ y )) (17)

[0120] In the formula, Q x (θ x ,θ y ), Q y (θ x ,θ y ) represent the field of view angle (θ x ,θ y ) The distortion values ​​in the X and Y directions are calculated as follows:

[0121]

[0122] Where N is the maximum order of the polynomial; t and s are the powers of the X-direction field of view angle and the Y-direction field of view angle, respectively; a ts , b ts They represent the coefficients of the X-direction distortion polynomial and the Y-direction distortion polynomial corresponding to the product of the X-direction field of view angle t-th power and the Y-direction field of view angle s-th power, respectively. The coefficients can be obtained by the least squares algorithm, as shown in formula (19):

[0123]

[0124] In subsequent work, the corresponding distortion value can be calculated according to different field of view angles in combination with formula (18).

[0125] Embodiment 2:

[0126] This embodiment takes the optical system to be measured with the field of view range of -14° to +14° in both the X and Y directions as an example to further illustrate the device and method proposed in the above embodiment. In this embodiment, the field of view to be measured is divided equally, and a 7×7 field of view table is selected for measurement. Figure 3 A schematic diagram of the positional relationship of the fields to be measured is given, and the serial number in the figure represents the i-th field to be measured.

[0127] In the measuring optical path, along the direction of the rotation axis of the double prism, the distance H1 between the left surface and the right surface of the first prism is 50 mm, the distance H2 between the right surface of the first prism and the left surface of the second prism is 80 mm, the distance H3 between the left surface and the right surface of the second prism is 50 mm, and the distance H4 between the right surface of the second prism and the center of the entrance pupil plane of the measured optical system is 150 mm; the wedge angle β1 of the first prism is 20°, the refractive index n1 is 1.5, the wedge angle β2 of the second prism is 20°, and the refractive index n2 is 1.5; the focal length f0 of the measured optical system is 50 mm, the pixel size of the photodetector is 3.76 μm×3.76 μm, and the resolution is 14192×10640.

[0128] Based on equations (1) to (8) and the above parameters, we get Figure 4 The rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism corresponding to the field to be measured are shown, and the sequence number in the figure represents the i-th field to be measured.

[0129] Based on equations (9) to (14) and the above parameters, we get Figure 5 The translation amount of the two-dimensional linear motion mechanism corresponding to the field of view to be measured is shown in the figure, and the serial number in the figure represents the i-th field of view to be measured.

[0130] Figure 6 A schematic diagram of the relative position relationship between the edge field of view and the center field of view measuring device is shown. It can be seen from the figure that the translation of the collimator and the rotation of the first prism and the second prism match the field of view angle of the incident light beam, the pupil position, and the imaging position on the photodetector of the optical system under test.

[0131] The center coordinates of the diffuse spot of the star image are calculated using formula (15): Figure 7 The theoretical and measured values ​​of the center coordinates of the diffuse spot of the star image in the full measurement field of view of the optical system under test are given. It can be seen from the figure that the optical system under test has obvious barrel distortion. The serial number in the figure represents the i-th field of view to be tested.

[0132] According to the discrete measurement results, this embodiment uses a cubic polynomial to fit the two-dimensional distortion surface of the measured optical system (that is, the polynomial function relationship or mapping relationship between the distortion value and the field of view angle of the measured optical system), and obtains the following results:

[0133]

[0134] A two-dimensional distortion surface is obtained. In the subsequent distortion measurement process, the corresponding distortion value can be directly calculated using the above formula according to the field of view angle of the optical system under test.

[0135] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0136] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0137] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0138] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0139] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only the specific implementation method of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An optical system distortion measurement device based on a rotating double prism, characterized in that: include: A parallel light source assembly (1), the parallel light source assembly (1) comprising a two-dimensional linear motion mechanism (6) and a parallel light pipe (7), the two-dimensional linear motion mechanism (6) being used to drive the parallel light pipe (7) to perform linear motion in a plane perpendicular to the optical axis direction, so that the parallel light beam emitted by the parallel light pipe (7) can be incident on an entrance pupil plane (14) of a measured optical system (3) after passing through a rotating double prism assembly (2); A rotating double prism assembly (2), the rotating double prism assembly (2) comprising a first prism (11), a second prism rotating mechanism (10), a second prism (12) and a second prism rotating mechanism (13), the first prism rotating mechanism (10) driving the first prism (11) to rotate about the optical axis, the second prism rotating mechanism (13) driving the second prism (12) to rotate about the optical axis, and the light beam angle deflection control is achieved by controlling the rotation angles of the first prism rotating mechanism (10) and the second prism rotating mechanism (13), so as to achieve the light beam incident field angle required by the optical system (3) under test; An optical system (3) to be measured, the optical system (3) to be measured comprising an entrance pupil surface (14), an optical lens group (15) and a photodetector (16), the optical lens group (15) focusing a parallel light beam incident on the entrance pupil surface (14) onto the photodetector (16) to form a star-shaped diffuse light spot; and a computer device (5), wherein the computer device (5) is electrically connected to the two-dimensional linear motion mechanism (6), the first prism rotation mechanism (10), the second prism rotation mechanism (13), and the photoelectric detector (16) respectively, realizes motion calculation and sends motion instructions to the two-dimensional linear motion mechanism (6), the first prism rotation mechanism (10), and the second prism rotation mechanism (13), and completes the calculation of the center coordinates of the diffuse light spot of the star point image and the calculation of the distortion value according to the measurement results of the photoelectric detector; The computer device (5) determines the rotation angle of the first prism rotation mechanism (10) and the rotation angle of the second prism rotation mechanism (13) through a first mapping relationship between the field of view angle of the optical system (3) under test and the rotation angle of the first prism rotation mechanism (10) and the rotation angle of the second prism rotation mechanism (13); and at the same time, determines the translation amount of the two-dimensional linear motion mechanism (6) through a second mapping relationship between the field of view angle of the optical system (3) under test and the translation amount of the two-dimensional linear motion mechanism (6), and controls accordingly, so that the output light beam of the rotating double prism can be incident on the entrance pupil plane of the optical system (3) under test, and the consistency of the output light beam with the entrance pupil of the optical system (3) under test is maintained.

2. The optical system distortion measurement device based on a rotating biprism according to claim 1, characterized in that: Also includes: A test platform (4), the test platform (4) comprising a stage (17) and a lifting mechanism (18), the test platform (4) being used to place the optical system (3) under test; the stage (17) being provided with installation position markings of the entrance pupil surface (14) to provide a position reference for the installation of the optical system under test, and the lifting mechanism (18) realizing optical axis height adjustment of the optical system (3) under test.

3. The optical system distortion measurement device based on a rotating biprism according to claim 1, characterized in that: The first prism rotating mechanism (10) and the second prism rotating mechanism (13) both use motors; And / or, the first prism (11) and the second prism (12) are a single wedge-shaped mirror or a group of wedge-shaped mirrors; And / or, the relative position relationship between the first prism (11) and the second prism (12) is back-to-back, face-to-face or face-to-back.

4. The optical system distortion measurement device based on a rotating biprism according to any one of claims 1 to 3, characterized in that: The collimator (7) comprises a star point light source (8) and a collimator lens group (9); The star point light source (8) simulates a target, and the collimating lens group (9) enables the light beam to be emitted in parallel.

5. A method for measuring optical system distortion based on a rotating biprism, characterized in that: The optical system distortion measurement method is implemented based on the optical system distortion measurement device according to any one of claims 1 to 4, comprising: Adjusting the parallel light source assembly (1) and the rotating biprism assembly (2) to a reference field of view position; Installing the optical system (3) to be measured, and ensuring that the entrance pupil plane of the optical system (3) to be measured coincides with the installation reference scribed line; According to the optical axis height of the outgoing light beam of the parallel light source assembly (1), the optical axis height of the optical system (3) to be measured is adjusted so that the entrance pupil plane (14) of the optical system (3) to be measured is concentrically symmetrical with the outgoing light beam; Calculating and obtaining the translation amount of the two-dimensional linear motion mechanism (6), the rotation angle of the first prism rotation mechanism (10), and the rotation angle of the second prism rotation mechanism (13) in each field of view to be measured; Control step: sending corresponding motion instructions to the two-dimensional linear motion mechanism (6), the first prism rotation mechanism (10) and the second prism rotation mechanism (13) respectively according to the sequence of the fields to be measured, and confirming that the execution is in place according to the feedback position information; Measurement and calculation steps: calculating the center coordinates of the diffuse light spot of the star point image according to the diffuse light spot of the star point image measured by the photoelectric detector (16); The control step and the measurement and calculation step are repeated until the measurement and calculation of all the fields to be measured are completed, and the distortion value of the full field of view of the optical system (3) to be measured is calculated based on the center coordinates of the diffuse light spots of the star point images of each field to be measured.

6. The method for measuring optical system distortion based on a rotating biprism according to claim 5, characterized in that: The calculation process of the rotation angle of the first prism rotation mechanism (10) and the rotation angle of the second prism rotation mechanism (13) includes: According to a first mapping relationship between the field of view angle of the optical system (3) to be measured and the rotation angle of the first prism rotation mechanism (10) and the rotation angle of the second prism rotation mechanism (13), the rotation angle of the first prism rotation mechanism (10) and the rotation angle of the second prism rotation mechanism (13) under each field of view to be measured are calculated; wherein the first mapping relationship is expressed as: or, In the formula, θ1 and θ2 represent the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism respectively; θ represents the azimuth of the incident light beam in the spherical coordinate system, which is obtained by converting the field angle of the optical system under test in the rectangular coordinate system; Δθ represents the difference between the rotation angle of the first prism rotation mechanism and the rotation angle of the second prism rotation mechanism, which is calculated based on the parameters of the first prism and the second prism and the pitch angle of the incident light beam in the spherical coordinate system, and the pitch angle of the incident light beam in the spherical coordinate system is converted based on the field angle of the optical system under test in the rectangular coordinate system; θ0 represents the deflection angle between the incident light beam introduced into the rotating double prism and the outgoing light beam, which is calculated based on the parameters of the first prism and the second prism and Δθ.

7. The method for measuring optical system distortion based on a rotating biprism according to claim 6, characterized in that: The calculation process of the translation amount of the two-dimensional linear motion mechanism (6) includes: The translation amount of the two-dimensional linear motion mechanism (6) under each field of view to be measured is calculated based on a second mapping relationship between the field of view angle of the optical system (3) to be measured and the translation amount of the two-dimensional linear motion mechanism (6); wherein the second mapping relationship is expressed as: In the formula, S x , S y respectively represent the translation amounts of the two-dimensional linear motion in the X direction and the Y direction; H1, H2, H3, and H4 respectively represent the distances between the left and right surfaces of the first prism, the right surface of the first prism and the left surface of the second prism, the left and right surfaces of the second prism, and the right surface of the second prism and the center of the entrance pupil plane along the axial direction of rotation of the double prism; β1 represents the wedge angle of the first prism; a1, a2, b1, b2, c1, c3, and c4 all represent intermediate parameters, which are calculated according to the parameters of the first prism and the second prism and Δθ.

8. The method for measuring optical system distortion based on a rotating biprism according to claim 5, characterized in that: The calculation formula for the center coordinates of the diffuse spot of the star image is: In the formula, C x , C y Respectively represent the center coordinates of the diffuse spot of the star image in the X and Y directions; ij , Y ij ,I ij Respectively represent the X coordinate, Y coordinate, and grayscale value of the pixel in the i-th row and j-th column of the photodetector; N x 、N y Respectively represent the number of pixels in the X and Y directions of the photodetector; p x 、p y Respectively represent the size of a single pixel of the photodetector in the X and Y directions; The following formula is used to calculate the distortion value of each field of view to be measured: In the formula, q xi ,q yi Respectively represent the distortion values ​​of the i-th field of view in the X and Y directions; θ xi ,θ yi Respectively represent the viewing angles of the i-th field of view in the X and Y directions; C xi , C yi Respectively represent the coordinate measurement values ​​of the center of the diffuse light spot in the X and Y directions of the i-th field of view; C x0 , C y0 They represent the measured values ​​of the center coordinates of the diffuse light spot in the X and Y directions of the reference field of view respectively; f0 represents the focal length of the optical system under test.

9. The method for measuring optical system distortion based on a rotating biprism according to claim 5, characterized in that: The calculation process of the rotation angle of the first prism rotation mechanism (10) and the rotation angle of the second prism rotation mechanism (13) includes: According to a first mapping relationship between the field of view angle of the optical system (3) to be measured and the rotation angle of the first prism rotation mechanism (10) and the rotation angle of the second prism rotation mechanism (13), the rotation angle of the first prism rotation mechanism (10) and the rotation angle of the second prism rotation mechanism (13) under each field of view to be measured are calculated; wherein the first mapping relationship is obtained by solving the first-order approximation method, the vector refraction method and the coordinate conversion method.

10. The method for measuring optical system distortion based on a rotating biprism according to any one of claims 5 to 9, characterized in that: Also includes: According to the distortion value measurement results of all the fields of view to be measured, a two-dimensional distortion surface of the optical system to be measured is obtained by least square fitting, wherein the two-dimensional distortion surface is a polynomial function relationship between the distortion value and the field of view angle of the optical system to be measured; In the subsequent distortion measurement process, the corresponding distortion value is calculated using the polynomial function relationship according to different field of view angles.

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