A large field of view optical system small distortion measuring device and method

Abstract

A kind of large field of view optical system small distortion testing device and method, belong to optical system parameter detection field.Grid plate is vertically placed on optical platform, measured large field of view optical system is placed at working distance, large scale area array image detector is placed on the focal plane of measured large field of view optical system, grid plate, measured large field of view optical system optical axis and large scale area array image detector are concentrically arranged, large scale area array image detector is connected with digital-analog converter signal, digital-analog converter is connected with computer equipped with digital image processing software signal.When testing, large scale area array image detector realizes high frequency sampling to imaging information using the characteristics of its multiple pixels, then imaging information is converted into digital image after being converted by digital-analog converter, digital image is preprocessed and edge positioning by digital image processing software, determines actual imaging position and theoretical imaging position, calculates relative distortion value.The application can make the test precision of relative distortion reach below 1%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optical system parameter detection, and particularly relates to a large-view optical system small-distortion measuring device and method. BACKGROUND

[0002] For optical position measurement and acquisition systems such as aerial cameras and remote sensing cameras, large field of view and small distortion are one of the most important optical requirements. In order to accurately reflect the relative position information of the measured object, such cameras not only require a larger imaging range and higher imaging quality, but also must ensure the geometric relative position accuracy of the imaging. Optical distortion is an aberration caused by the inconsistency between the intersection of the chief ray of the imaging of the optical system and the Gaussian image plane and the intersection of the ideal ray and the Gaussian image plane, which does not affect the imaging clarity of the optical system but can seriously affect the geometric position of the imaging, resulting in distortion of the image of the measured object and the true shape of the measured object. In the measurement of the camera, a small distortion error can cause a significant deviation of the geometric position of the measured object. Therefore, the suppression and correction of distortion have always been a difficult problem in the development of high-precision measurement optical systems, and the solution to this problem must measure the distortion of the optical system, so the accurate measurement of the distortion is even more important.

[0003] At present, the methods for measuring the distortion of the optical system can be divided into two categories: precise length measurement method and precise angle measurement method. The precise length measurement method is to place a calibrated grid plate on the object side of the measured optical system, so that the optical axis of the measured optical system is perpendicular to the grid plate and passes through the center thereof, record the image of the grid on the image plane, and measure the distance from each image point in different fields of view to the imaging center by using a precise measurement device, and then calculate the optical system distortion value by the distance length, such as patents CN103994875, US5812260, US5471297 and JP1123726. The precise angle measurement method is to accurately place a calibrated grid plate on the focal plane of the lens, and make the cross center of the grid plate coincide with the optical axis, rotate the precise turntable to make each line on the grid plate reach the measurement position, and use a camera to observe the actual image corresponding to the angle of different lines on the grid plate at the conjugate position on the image side of the grid plate. Although the above two measurement methods are the most popular, they still have some problems in measuring large field of view and small distortion optical systems. For a measurement camera, the field of view angle is generally about 30°, and the relative distortion design value is generally less than 1%, which belongs to a large field of view and small distortion optical system. As shown in FIG. 1, the measured point and the ideal image point of the measurement optical system with 1% relative distortion are basically coincided under the ordinary detector, so it is a technical problem for any distortion measurement method to measure less than 1% relative distortion under the premise of meeting the large field of view. The precision of the relative distortion measured by the currently disclosed methods generally exceeds 1% under the premise of meeting the large field of view, and it is difficult to achieve 1%. Figure 1

[0004] ​In the traditional precision length measurement method, the distortion measurement precision is related to the etching precision of the grid plate, the smaller the distortion to be measured of the system needs to be measured, the smaller the grid unit of the grid plate needs, and the greater the etching difficulty and the higher the etching cost are. In addition, in the aspect of large field of view, for a large field of view optical system, it is also difficult to manufacture a large-diameter grid plate matching. Although the precision length measurement method assisted by a collimator can improve the measurement precision to a certain extent, it cannot meet the requirements of large field of view, and the distortion value of the collimator will also be introduced into the measured distortion value, resulting in measurement error. The precision angle measurement method can meet the measurement precision and field of view requirements of the large field of view small distortion optical system in theory, but the measurement precision and field of view are related to the rotation angle precision and rotation angle range of the turntable, and a high-precision turntable is required to realize the measurement. In addition, the measurement precision is also related to the calibration of the internal orientation elements of the camera to be measured, and the calibration precision will also affect the measurement precision. In the data processing aspect, the precision angle measurement method needs to fit and optimize a large amount of data, and the processing process is very complicated. Therefore, although the precision angle measurement method can meet the requirements of large field of view small distortion optical system precision and field of view, it needs extremely high equipment demand and the data processing process is complex, and the measurement operation is not convenient.

[0005] In summary, the existing distortion measurement patents and existing technologies have the problems of precision and comprehensiveness in measuring the distortion of the large field of view optical system. That is, some technical solutions can cover a large field of view but have low distortion measurement precision, and some can meet the precision requirements but cannot cover the whole field of view. The measurement camera is different from the general large field of view optical system, and its design requirements not only meet the large field of view but also require the distortion value in the field of view to be small, which belongs to the large field of view small distortion type optical system. Therefore, measuring the distortion in the whole field of view of the measurement camera is essentially measuring the small distortion of the large field of view optical system, and the measurement method needs to cover the large field of view and meet the small distortion precision measurement requirements. Therefore, the present application provides a large field of view optical system small distortion measurement device and method, which can meet the requirements of large field of view and the relative distortion measurement precision can reach below 1%. SUMMARY

[0006] The purpose of the present application is to solve the problems of high cost, large operation difficulty, complex measurement data processing, low precision and inability to meet the requirements of large field of view small distortion precision measurement in the prior art, and to provide a large field of view optical system small distortion measurement device and method.

[0007] The present application is an improvement on the precision length measurement method. In the present application, the calibrated grid plate is placed on the object side of the measured large field optical system, the optical axis of the measured large field optical system is perpendicular to the grid plate and passes through the center of the grid plate, and the image on the image side of the measured large field optical system is recorded by a large-scale area array image detector. The large-scale area array image detector can not only meet the measurement requirements of a large field of view, but also can realize high-frequency imaging information sampling by relying on its own multi-pixel, thereby meeting the requirements of small distortion measurement precision. The grid plate image recorded by the large-scale area array image detector is analyzed to obtain the difference between the actual imaging position and the theoretical imaging position of each grid point, and the distortion distribution of the full field of view of the measured large field optical system is fitted by using the difference, thereby realizing the distortion measurement of the measured large field optical system.

[0008] To achieve the above-mentioned object, the technical scheme adopted by the present application is as follows:

[0009] A small distortion testing device for a large field optical system, comprising a grid plate, a large-scale area array image detector, a digital-to-analog converter and a computer.

[0010] The grid plate is vertically placed on an optical platform, the measured large field optical system is placed at a working distance, and the large-scale area array image detector is placed on the focal plane of the measured large field optical system. The grid plate, the optical axis of the measured large field optical system and the large-scale area array image detector are concentrically arranged. The large-scale area array image detector is signal connected with the digital-to-analog converter, and the digital-to-analog converter is signal connected with the computer provided with digital image processing software.

[0011] Further, a plane flat crystal is attached to the center of the grid plate. When it is needed to make the optical axis of the measured large field optical system concentric with the grid plate, a laser autocollimator is placed on the focal plane of the measured large field optical system, and the measured large field optical system and the grid plate are adjusted by using the laser autocollimator, so that the optical axis of the measured large field optical system passes through the center of the grid plate. When it is needed to make the optical axis of the measured large field optical system concentric with the large-scale area array image detector, the laser autocollimator is moved between the grid plate and the measured large field optical system, the large-scale area array image detector is placed on the focal plane of the measured large field optical system, and the large-scale area array image detector and the measured large field optical system are reversely adjusted by using the laser autocollimator and the plane flat crystal, so that the optical axis of the measured large field optical system passes through the center of the large-scale area array image detector.

[0012] A method for realizing small distortion testing of a large field optical system, the method comprising the following steps:

[0013] Step one: first, place the grid plate vertically on the optical platform, place the measured large field optical system at the working distance, place the large-scale area array image detector on the focal plane of the measured large field optical system, and then start testing after the grid plate, the optical axis of the measured large field optical system and the large-scale area array image detector are concentric;

[0014] Step two: the grid plate is imaged on the large-scale area array image detector, and each grid point of the grid plate corresponds to the field angle (x, y), wherein x is the horizontal direction field angle relative to the vertex of the measured large field optical system, and y is the vertical direction field angle relative to the vertex of the measured large field optical system; the grid point (x, y) is imaged on the large-scale area array image detector by the measured large field optical system, and the imaging information is converted into an analog signal by the large-scale area array image detector;

[0015] Step three: the large-scale area array image detector transmits the analog signal to the digital-analog converter, and the digital-analog converter converts the analog signal into a digital signal;

[0016] Step four: the digital-analog converter transmits the digital signal to the computer, and the digital image is preprocessed and edge positioned by the digital image processing software installed in the computer;

[0017] Step five: the actual position of the grid point after imaging, i.e. the image centroid, is determined by using the digital image processing software, after the actual position after imaging is determined, the relative distance of the actual position after imaging to the center of the large-scale area array image detector in the horizontal and vertical directions is calculated, which is recorded as (x1, y1), and the horizontal and vertical positions of the ideal image point of the point are calculated by x2=ftanx, y2=ftany, which are recorded as (x2, y2), wherein: f is the focal length of the measured large field optical system; finally, the position deviation between the actual image point and the ideal image point is calculated by using the digital image processing software, i.e. the lens distortion variable corresponding to each field angle is expressed by the relative distortion value:

[0018]

[0019]

[0020] Wherein: δ x represents the horizontal direction relative distortion value, and δ y represents the vertical direction relative distortion value.

[0021] Further, the step of centering specifically comprises: after pasting the planar flat crystal at the center of the grid plate, first adjusting the optical axis of the measured large field optical system to be concentric with the grid plate, specifically: placing a laser autocollimator on the focal plane of the measured large field optical system, and adjusting the measured large field optical system and the grid plate by using the laser autocollimator, so that the optical axis of the measured large field optical system passes through the center of the grid plate; then adjusting the optical axis of the measured large field optical system to be concentric with the large-scale area array image detector, specifically: first moving the laser autocollimator to between the grid plate and the measured large field optical system, and then placing the large-scale area array image detector on the focal plane of the measured large field optical system, and adjusting the large-scale area array image detector and the measured large field optical system by using the laser autocollimator and the flat crystal in reverse, so that the optical axis of the measured large field optical system passes through the center of the large-scale area array image detector; after the centering is completed, the laser autocollimator and the flat crystal are removed.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] The large field optical system small distortion measurement device and method provided by the present application is improved on the basis of the traditional precise length measurement method, uses a large-scale area array image detector (which is a purchased part) to replace the detector in the traditional precise length measurement method, and uses a large number of pixels to ensure the measurement accuracy of relative distortion by improving the sampling frequency (the process of collecting imaging information by the large-scale area array image detector is a sampling process, and a large number of pixels means to improve the sampling frequency), so that the measurement accuracy of relative distortion can be less than 1%. Meanwhile, the large-scale area array image detector can also meet the detection requirements of a large field, so that the etching accuracy requirement of the grid plate is not high, the measurement cost and difficulty are greatly reduced compared with the traditional method, and other device errors are not introduced. Compared with the precise angle measurement method, the present application has similar precision, but requires less equipment and has simple data processing and simple experimental process. In summary, the present application can solve the problems of the current distortion measurement methods, such as large influence of human factors, high measurement cost, complicated operation, low precision, and the application requirements of other optical system measurement methods cannot meet the requirements of large field and small distortion. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a comparison diagram of actual image points and ideal image points under a common detector; the grid points of the grid lines in the figure are ideal image points, and the intersection points of the cross lines are actual image points;

[0025] Figure 2 is a schematic diagram of a large field optical system small distortion measurement device of the present application;

[0026] Figure 3 is a flowchart of a large field optical system small distortion measurement method of the present application;

[0027] Figure 4 It is a difference diagram between actual image points and ideal image points measured using the method of the present invention.

[0028] The names and reference numerals of the components in the above drawings are as follows:

[0029] Grid plate 1, optical lens to be tested 2, large-scale area array image detector 3, digital-to-analog converter 4, computer 5. DETAILED DESCRIPTION

[0030] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] Specific implementation method 1: Figure 2 As shown, this embodiment discloses a small distortion test device for a large field of view optical system, comprising a grid plate 1, a large-scale area array image detector 3, a digital-to-analog converter 4, and a computer 5;

[0032] The grid plate 1 is placed vertically on an optical platform, the large-field optical system 2 to be measured is placed at a working distance, and the large-scale area array image detector 3 is placed on the focal plane of the large-field optical system 2 to be measured. The grid plate 1, the optical axis of the large-field optical system 2 to be measured, and the large-scale area array image detector 3 are concentrically arranged. The large-scale area array image detector 3 is connected to a digital-to-analog converter 4 for signal connection, and the digital-to-analog converter 4 is connected to a computer 5 equipped with digital image processing software for signal connection.

[0033] Furthermore, a flat crystal is attached to the center of the grid plate 1. When it is necessary to make the optical axis of the large-field-of-view optical system 2 to be measured concentric with the grid plate 1, a laser autocollimator is placed on the focal plane of the large-field-of-view optical system 2 to be measured, and the laser autocollimator is used to adjust the large-field-of-view optical system 2 to be measured and the grid plate 1 so that the optical axis of the large-field-of-view optical system 2 to be measured passes through the center of the grid plate 1; when it is necessary to make the optical axis of the large-field-of-view optical system 2 to be measured concentric with the large-scale area array image detector 3, the laser autocollimator is moved between the grid plate 1 and the large-field-of-view optical system 2 to be measured, and the large-scale area array image detector 3 is placed on the focal plane of the large-field-of-view optical system 2 to be measured, and the laser autocollimator and the flat crystal are used to adjust the large-scale area array image detector 3 and the large-field-of-view optical system 2 to be measured in reverse so that the optical axis of the large-field-of-view optical system 2 to be measured passes through the center of the large-scale area array image detector 3.

[0034] The large-field-of-view optical system 2 to be tested is an aerial camera or a remote sensing camera.

[0035] Specific implementation method 2: Figure 2 、Figure 3 The embodiment discloses a method for testing a large field of view optical system with small distortion by using the device in the first embodiment, and the method comprises the following steps:

[0036] Step one: first, place the grid plate 1 vertically on the optical platform, place the measured large field of view optical system 2 at the working distance, place the large-scale area array image detector 3 on the focal plane of the measured large field of view optical system 2, and then start testing after the grid plate 1, the optical axis of the measured large field of view optical system 2 and the large-scale area array image detector 3 are concentric;

[0037] Step two: the grid plate 1 is imaged on the large-scale area array image detector 3, and each grid point of the grid plate 1 corresponds to a field of view angle (x, y), wherein x is the horizontal direction field of view angle relative to the vertex of the measured large field of view optical system 2, and y is the vertical direction field of view angle relative to the vertex of the measured large field of view optical system 2 (calculated by the working distance of the measured large field of view optical system 2 and the distance of the grid point relative to the center of the grid plate 1); the grid point (x, y) is imaged on the large-scale area array image detector 3 by the measured large field of view optical system 2, and the imaging information is converted into an analog signal by the large-scale area array image detector 3;

[0038] Step three: the large-scale area array image detector 3 transmits the analog signal to the digital-to-analog converter 4, and the digital-to-analog converter 4 converts the analog signal into a digital signal;

[0039] Step four: the digital-to-analog converter 4 transmits the digital signal to the computer 5, and the digital image is preprocessed and edge positioned by the digital image processing software installed in the computer 5 (the purpose is to more accurately determine the imaging position);

[0040] Step five: the actual position of the grid point after imaging, i.e. the image centroid, is determined by using the digital image processing software, after the actual position after imaging is determined, the relative distance of the actual position after imaging relative to the center of the large-scale area array image detector 3 in the horizontal and vertical directions is calculated and recorded as (x1, y1), the horizontal and vertical positions of the ideal image point of the point are calculated by the field of view angle corresponding to the grid point and recorded as (x2, y2), wherein: f is the focal length of the measured large field of view optical system 2; finally, the position deviation of the actual image point and the ideal image point is calculated by using the digital image processing software, i.e. the lens distortion variable corresponding to each field of view angle is expressed by the relative distortion value:

[0041]

[0042]

[0043] Wherein: δ x represents the horizontal direction relative distortion value, δy Indicates the relative distortion value in the vertical direction.

[0044] Furthermore, the step 1 of centering is specifically as follows: after attaching a flat crystal to the center of the grid plate 1 (its function is to reflect the laser emitted by the laser autocollimator for the laser autocollimator to align), first adjust the optical axis of the large field of view optical system 2 to be measured to be concentric with the grid plate 1, specifically: place the laser autocollimator on the focal plane of the large field of view optical system 2 to be measured, and use the laser autocollimator to adjust the large field of view optical system 2 to be measured and the grid plate 1 so that the optical axis of the large field of view optical system 2 to be measured passes through the center of the grid plate 1; then adjust the large field of view optical system 2 to be measured The optical axis is concentric with the large-scale area array image detector 3. Specifically, the laser autocollimator is first moved between the grid plate 1 and the large-field-of-view optical system 2 to be measured, and then the large-scale area array image detector 3 is placed on the focal plane of the large-field-of-view optical system 2 to be measured. The laser autocollimator and the flat crystal are used to reversely adjust the large-scale area array image detector 3 and the large-field-of-view optical system 2 to be measured, so that the optical axis of the large-field-of-view optical system 2 to be measured passes through the center of the large-scale area array image detector 3. After the centering is completed, the laser autocollimator and the flat crystal are removed.

[0045] The present invention utilizes a large-scale area array image detector 3 to improve the accuracy of the actual image height measurement position by increasing the sampling frequency. In terms of detector selection, the total number of pixels of the detector can be first determined when one pixel corresponds to one image point according to the accuracy requirements. For example, the number of row pixels corresponding to 1% is at least 100. Then, according to the sampling theorem, more than 20 pixels are made to correspond to one image point, and the number of row pixels is at least 20,000. This ensures that there are enough sampling points to provide to the digital image processing software for image fitting, so as to ensure the measurement accuracy of the actual image height position, thereby realizing measurement of a large field of view and small distortion.

[0046] Therefore, the present invention solves the technical challenge of measuring minute distortion in large-field optical systems, boasting a compact size, low cost, simple data processing, fast calculation speed, and high accuracy. It overcomes the difficulties of traditional precision length measurement methods, such as the difficulty in grid plate fabrication and low measurement accuracy, as well as the accuracy and error introduced. It also overcomes the influence of the turntable on precision in precision angle measurement methods. While maintaining the same accuracy, the present invention requires significantly less measurement cost and space than precision angle measurement methods.

[0047] Figure 4 The processed grid plate image shows the difference between the actual grid point imaging position (i.e., the intersection of the cross lines) and the ideal imaging position (i.e., the grid points of the grid lines). Because the sampling accuracy is sufficient, the measurement of relative distortion values ​​below 1% can be achieved while meeting the large field of view.

[0048] It will be obvious to a person skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments and can be implemented in other forms without departing from the spirit or essential characteristics of the application. The embodiments are considered in all respects to be illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalents of the claims are therefore intended to be embraced therein. No reference signs in the claims should be considered as limiting the scope of the claims to the features to which the reference signs are attached.

[0049] Furthermore, it should be understood that although the description is made on the basis of the embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A device for testing small distortion of a large field of view optical system, characterized by: It includes a grid plate (1), a large-scale array image detector (3), a digital-to-analog converter (4) and a computer (5); The grid plate (1) is placed vertically on an optical platform, the large-field optical system (2) to be measured is placed at a working distance, the large-scale array image detector (3) is placed on the focal plane of the large-field optical system (2) to be measured, the grid plate (1), the optical axis of the large-field optical system (2) to be measured and the large-scale array image detector (3) are concentrically arranged, the large-scale array image detector (3) is connected to the digital-to-analog converter (4) for signal connection, and the digital-to-analog converter (4) is connected to the computer (5) equipped with digital image processing software for signal connection.

2. The device for testing small distortion of a large field of view optical system according to claim 1, characterized in that: A plane flat crystal is attached to the center of the grid plate (1). When it is necessary to make the optical axis of the large-field optical system (2) to be measured concentric with the grid plate (1), a laser autocollimator is placed on the focal plane of the large-field optical system (2) to be measured, and the laser autocollimator is used to adjust the large-field optical system (2) to be measured and the grid plate (1) so that the optical axis of the large-field optical system (2) to be measured passes through the center of the grid plate (1); when it is necessary to make the optical axis of the large-field optical system (2) to be measured concentric with the large-scale area array image detector (3), the laser autocollimator is moved between the grid plate (1) and the large-field optical system (2), the large-scale area array image detector (3) is placed on the focal plane of the large-field optical system (2) to be measured, and the laser autocollimator and the plane flat crystal are used to reversely adjust the large-scale area array image detector (3) and the large-field optical system (2) to be measured so that the optical axis of the large-field optical system (2) to be measured passes through the center of the large-scale area array image detector (3).

3. A method for implementing small distortion testing of a large field of view optical system using the device of claim 1 or 2, characterized in that: The method comprises the following steps: Step 1: First, place the grid plate (1) vertically on the optical platform, place the large field optical system (2) to be tested at the working distance, place the large-scale area array image detector (3) on the focal plane of the large field optical system (2) to be tested, and start the test after the optical axes of the grid plate (1), the large field optical system (2) to be tested, and the large-scale area array image detector (3) are concentric. Step 2: The grid plate (1) is imaged on the large-scale array image detector (3), and each grid point of the grid plate (1) corresponds to a field of view angle of (x, y), wherein x is the field of view angle in the horizontal direction relative to the vertex of the large-field optical system (2) under test, and y is the field of view angle in the vertical direction relative to the vertex of the large-field optical system (2) under test; the grid points (x, y) are imaged on the large-scale array image detector (3) by the large-field optical system (2) under test, and the imaging information is converted into an analog signal by the large-scale array image detector (3); Step 3: The large-scale array image detector (3) transmits the analog signal to the digital-to-analog converter (4), and the digital-to-analog converter (4) converts the analog signal into a digital signal; Step 4: The digital-to-analog converter (4) transmits the digital signal to the computer (5), and the digital image is pre-processed and edge-located by the digital image processing software installed in the computer (5); Step 5: Use digital image processing software to determine the actual position of the grid point after imaging, that is, the image centroid. After determining the actual position after imaging, the relative distances of the actual imaging position relative to the center of the large-scale array image detector (3) in the horizontal and vertical directions are calculated and recorded as ( , ), the field of view angle corresponding to the grid point is given by The horizontal and vertical positions of the ideal image point of the grid point are calculated and recorded as ( , ),in: is the focal length of the large field of view optical system (2) under test; finally, the position deviation between the actual image point and the ideal image point is calculated using digital image processing software, that is, the lens distortion corresponding to each field of view angle is expressed as a relative distortion value: （1） （2） in: Indicates the relative distortion value in the horizontal direction. Indicates the relative distortion value in the vertical direction.

4. The method for testing small distortion of a large field of view optical system according to claim 3, characterized in that: Step 1 centering is specifically as follows: after attaching a flat crystal to the center of the grid plate (1), first adjust the optical axis of the large field optical system (2) to be measured to be concentric with the grid plate (1), specifically: place a laser autocollimator on the focal plane of the large field optical system (2) to be measured, and use the laser autocollimator to adjust the large field optical system (2) to be measured and the grid plate (1) so that the optical axis of the large field optical system (2) to be measured passes through the center of the grid plate (1); then adjust the optical axis of the large field optical system (2) to be measured to be concentric with the large-scale array image detector (3) Specifically, the laser autocollimator is first moved between the grid plate (1) and the large-field-of-view optical system (2) to be measured, and then the large-scale area array image detector (3) is placed on the focal plane of the large-field-of-view optical system (2) to be measured, and the large-scale area array image detector (3) and the large-field-of-view optical system (2) to be measured are reversely adjusted by using the laser autocollimator and the flat crystal so that the optical axis of the large-field-of-view optical system (2) to be measured passes through the center of the large-scale area array image detector (3); after the centering is completed, the laser autocollimator and the flat crystal are removed.

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