High-precision detection device and method for distortion and telecentricity of scanning lens

Abstract

The invention discloses a high-precision detection device and method for scanning lens distortion and telecentricity. The device comprises a light source assembly, a scanning device, a to-be-detected lens, a test target, a displacement platform, a photomultiplier, a signal acquisition module and a data processing module. Wherein the light source assembly is used for providing scanning light; the scanning device is provided with a movable reflecting mirror, and the reflecting mirror is used for transmitting scanning light to the to-be-detected lens; the scanning device drives the reflecting mirror to rotate around the central shaft so as to realize the scanning action of the scanning light; the test target is used for receiving the converged light spot; the displacement platform is used for bearing the test target; the photomultiplier is used for receiving the converged light spot penetrating through the test target and converting an optical signal into a pulse signal; the signal acquisition module is used for acquiring pulse signals and transmitting the pulse signals to the data processing module; and the data processing module is used for calculating the distortion and telecentricity of the lens to be measured according to the received pulse signal. According to the invention, the distortion and telecentricity of the lens can be conveniently detected.

Description

Technical Field

[0001] The present invention relates to the field of optical system performance detection, and particularly to a high-precision detection device and method for scanning lens distortion and telecentricity. Background Art

[0002] With the development of optical technology, optical lenses are increasingly widely used in various industries, and the specifications of various lenses are becoming more and more diverse. As basic parameters affecting lens performance, distortion and telecentricity play important roles in many lens designs. However, existing detection methods for distortion and telecentricity usually adopt the imaging method. The camera collects the calibration plate after imaging through the lens, compares the collected image with the actual size, and calculates the distortion. For telecentricity, it is necessary to image calibration plates at different distances for comparison.

[0003] For lenses with a small field of view and not demanding high precision, the above method can achieve a relatively fast measurement effect. However, the pixel size of the camera sensor limits the resolution of the acquired image, and the target surface of the camera limits the field of view of the detected lens. This method cannot meet the detection requirements for adapting to a large field of view and high precision. In view of this, the present invention is committed to developing a high-precision lens distortion and telecentricity detection device to effectively solve the problems existing in the prior art. Summary of the Invention

[0004] In view of this, the first object of the present invention is to provide a high-precision detection device for scanning lens distortion and telecentricity, which can conveniently detect the distortion and telecentricity of the lens.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A high-precision detection device for scanning lens distortion and telecentricity includes a light source assembly, a scanning device, a lens to be measured, a test target, a displacement platform, a photomultiplier tube, a signal acquisition module, and a data processing module; wherein,

[0007] The light source assembly is used to provide scanning light;

[0008] The scanning device has a movable mirror, and the mirror is used to transmit the scanning light to the lens to be measured; the scanning device realizes the scanning action of the scanning light by driving the mirror to rotate around the central axis;

[0009] The scanning light passes through the lens to be measured to form a converging light spot;

[0010] The test target is used to receive the converging light spot. The test target is made of a light-transmitting material and has a test pattern on its surface;

[0011] The displacement platform is used to carry the test target and drive the test target to displace along a preset direction;

[0012] The photomultiplier tube is used to receive the converging light spot passing through the test target and convert the optical signal into a pulse signal;

[0013] The signal acquisition module is used to acquire the pulse signal and transmit it to the data processing module;

[0014] The data processing module is used to calculate the distortion and telecentricity of the lens under test according to the received pulse signal.

[0015] Preferably, a focusing lens is further provided between the test target and the photomultiplier tube.

[0016] Preferably, the light source assembly includes a light source body and a beam expander-collimator, and the beam expander-collimator is located between the scanning device and the light source body.

[0017] Preferably, the signal acquisition module includes an oscilloscope or a data acquisition card.

[0018] Preferably, the scanning device uses a rotating mirror or a galvanometer mirror.

[0019] The second object of the present invention is to provide a high-precision detection method for scanning lens distortion, which can conveniently detect the distortion of the lens.

[0020] In order to achieve the above object, the technical solution of the present invention is:

[0021] A high-precision detection method for scanning lens distortion, implemented based on the above high-precision detection device, the method includes:

[0022] Adjust the displacement platform so that the test target is at the focal position of the lens under test, and at this time, the pulse width of the pulse signal corresponding to the central field of view is in the narrowest state;

[0023] Taking the rising edge t0 of the pulse signal corresponding to the central field of view as the reference point, and the adjacent rising edge time as t n , calculate the image height Y of each detection field of view through the data processing module n :

[0024]

[0025] Calculate the corresponding distortion according to the image height Y n :

[0026]

[0027] Rotate the lens under test to detect the distortion of all detection fields of view in different directions;

[0028] In the above formula, n represents the number of rising edges of the pulse signal interval corresponding to the detection field of view and the central field of view, and y n is the theoretical image height, r is the speed of the rotating mirror, and the unit is rpm;

[0029] The calculation method of the focal length f of the lens to be measured is as follows:

[0030]

[0031] ; Δt is the adjacent two rising edge signals at the central position, and d is the pitch of the test pattern.

[0032] The third object of the present invention is to provide a high-precision detection method for the telecentricity of a scanning lens, which can conveniently detect the telecentricity of the lens.

[0033] In order to achieve the above object, the technical solution of the present invention is:

[0034] A high-precision detection method for the telecentricity of a scanning lens, implemented based on the above high-precision detection device, includes:

[0035] Adjust the displacement platform so that the test target is at the focal position of the lens to be measured. At this time, the pulse width of the pulse signal corresponding to the central field of view is in the narrowest state;

[0036] Move the displacement platform to move the test target within a preset range from the focal point to collect the pulse signals corresponding to all detection fields of view at different positions;

[0037] Taking the rising edge t0 of the pulse signal corresponding to the central field of view as the reference point, and the adjacent rising edge time as t n , calculate the image height Y of each detection field of view through the data processing module n :

[0038]

[0039] Calculate the telecentricity of each field of view by comparing the change amount of the image height of each detection field of view after moving a preset distance:

[0040]

[0041] ; Take the extreme value as the telecentricity of the lens;

[0042] In the above formula, n represents the number of rising edges of the pulse signal interval corresponding to the detection field of view and the central field of view, and y n is the theoretical image height, r is the speed of the rotating mirror, and the unit is rpm;

[0043] The calculation method of the focal length f of the lens to be measured is as follows:

[0044]

[0045] ; Δt is the signal between two adjacent rising edges at the center position, and d is the spacing between the test patterns.

[0046] The technical effects of the present invention are mainly reflected in the following aspects:

[0047] The full field of view is sampled by rotating the scanning device and the lens to be tested, meeting the detection requirements for large field of view lenses; the use of photomultiplier tubes instead of cameras as signal receiving devices effectively improves the resolution of acquired signals to meet the high-precision detection requirements of distortion and telecentricity; the full field of view scanning method is simple and can record information on a large number of field of view points at one time, greatly improving the amount of information obtained, and can flexibly select the number of sampled fields of view according to needs, which is more convenient; the displacement platform is used to record the defocus value, which can achieve rapid measurement of telecentricity. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a schematic diagram of a detection device in an embodiment;

[0049] Figure 2 This is a scanning field diagram in the embodiment;

[0050] Figure 3 Schematic diagram of black and white stripes in the embodiment;

[0051] Figure 4 Schematic diagram of pulse signal in the embodiment.

[0052] Figure numerals: 1. light source body; 2. beam expansion collimator; 3. scanning device; 4. lens to be tested; 5. test target; 6. displacement platform; 7. focusing lens; 8. photomultiplier tube. DETAILED DESCRIPTION

[0053] The specific implementation modes of the present invention are further described below in conjunction with the accompanying drawings to make the technical solutions of the present invention easier to understand and grasp.

[0054] Embodiment 1

[0055] Reference Figure 1 This embodiment provides a high-precision detection device for scanning lens distortion and telecentricity, including a light source assembly, a scanning device 3, a lens to be tested 4, a test target 5, a displacement platform 6, a photomultiplier tube 8, a signal acquisition module and a data processing module.

[0056] The light source assembly includes a light source body 1 and a beam expander collimator 2, and the beam expander collimator 2 is located between the scanning device 3 and the light source body 1. The light source assembly can provide stable scanning light; of course, a light source capable of outputting collimated light can also be directly used.

[0057] The scanning device 3 uses a rotating mirror or a galvanometer mirror. Both mirrors have a movable reflecting mirror, which is used to transmit the scanning light to the lens 4 to be measured; the scanning device 3 realizes the scanning action of the scanning light by driving the reflecting mirror to rotate around the central axis. Since the rotating mirror or the galvanometer mirror is an existing instrument, its working principle will not be elaborated in this embodiment.

[0058] The scanning light passes through the lens 4 to be measured to form a converging light spot;

[0059] The test target 5 is installed on the displacement platform 6 and is located at the converging point of the scanning light. The test target 5 is made of a light-transmitting material and has a test pattern on its surface (such as Figure 3 shown), and the converging light spot passes through the test target 5 and is received by the photomultiplier tube 8.

[0060] The photomultiplier tube is used to receive the converging light spot passing through the test target 5 and convert the optical signal into a pulse signal; in addition, a focusing lens 7 is also provided between the test target 5 and the photomultiplier tube 8 to increase the intensity of the optical signal.

[0061] The displacement platform 6 can drive the test target 5 to displace along the preset direction (X-Y).

[0062] The signal acquisition module is used to acquire the pulse signal and transmit it to the data processing module. The signal acquisition module can be a signal acquisition instrument such as an oscilloscope or a data acquisition card.

[0063] The data processing module is carried on a computer and is used to calculate the distortion and telecentricity of the lens 4 to be measured according to the received pulse signal.

[0064] Embodiment 2

[0065] On the basis of Embodiment 1, this embodiment provides a high-precision detection method for scanning the distortion of a lens, and the method includes:

[0066] Adjust the displacement platform 6 so that the test target 5 is at the focal position of the lens 4 to be measured. At this time, the pulse width of the pulse signal corresponding to the central field of view is in the narrowest state;

[0067] Taking the rising edge t0 of the pulse signal corresponding to the central field of view as the reference point, and the adjacent rising edge time is t n , calculate the image height Y of each detection field of view through the data processing module n :

[0068]

[0069] Calculate the corresponding distortion according to the image height Y n :

[0070]

[0071] Rotate the lens 4 to be measured to detect the distortion of all detection fields of view in different directions. As Figure 2 shown, the lens 4 to be measured is preset with 8 rotation directions; Figure 3 The black dots in

[0072] represent the sampling points of the rising edge. In the above formula, n represents the number of rising edges of the pulse signal interval corresponding to the detection field of view and the central field of view, and y n is the theoretical image height, and r is the speed of the rotating mirror.

[0073] The calculation method of the focal length f of the above lens to be measured is:

[0074]

[0075] Δt is to take the adjacent two rising edge signals at the central position, and d is the pitch of the test pattern.

[0076] Similarly, the lens 4 to be measured can also be an f - sin(theta) or f - tan(theta) lens, and the calculation formulas are different. For the f - sin(theta) lens, the calculation formula for the image height is:

[0077] The calculation formula for the image height of the f - tan(theta) lens is:

[0078] Embodiment 3

[0079] Based on Embodiment 1, this embodiment provides a high - precision detection method for the telecentricity of a scanning lens. The method includes:

[0080] Adjust the displacement platform 6 so that the test target 5 is at the focal position of the lens 4 to be measured. At this time, the pulse width of the pulse signal corresponding to the central field of view is in the narrowest state;

[0081] Move the displacement platform 6 to move the test target 5 within a preset range from the focal point (away from or close to the lens 4 to be measured) to collect the pulse signals corresponding to all detection fields of view at different positions;

[0082] Taking the rising edge t0 of the pulse signal corresponding to the central field of view as the reference point, and the adjacent rising edge time as t n , calculate the image height Y of each detection field of view through the data processing module n :

[0083]

[0084] Calculate the telecentricity of each field of view by comparing the change amount of the image height of each detection field of view after moving a preset distance:

[0085]

[0086] ; The extreme value is taken as the telecentricity of the lens;

[0087] In the above formula, n represents the number of rising edges of the pulse signal interval corresponding to the detection field of view and the central field of view, y n is the theoretical image height, and r is the speed of the rotating mirror.

[0088] On this basis, direct measurement of the field curvature can be achieved. Just record the rising edge pulse widths of the pulse signals corresponding to each detection field of view at different positions, and the field curvature of the lens to be measured can be directly obtained from the position extreme value when the rising edge pulse width of each detection field of view is the smallest.

[0089] Of course, the above are only typical examples of the present invention. In addition, the present invention can also have many other specific implementation manners. Any technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention.

Claims

1. A high-precision detection device for scanning lens distortion and telecentricity, characterized in that including a light source assembly, a scanning device (3), a lens under test (4), a test target (5), a displacement platform (6), a photomultiplier tube (8), a signal acquisition module, and a data processing module; wherein, the light source assembly is used to provide scanning light; the scanning device (3) has a movable mirror, and the mirror is used to transmit the scanning light to the lens under test (4); the scanning device (3) realizes the scanning action of the scanning light by driving the mirror to rotate around the central axis; the scanning light passes through the lens under test (4) to form a converging light spot; the test target (5) is used to receive the converging light spot, the test target (5) is made of a light-transmitting material, and the surface has test patterns with a preset pitch; the displacement platform (6) is used to carry the test target (5) and drive the test target (5) to displace in a preset direction; the photomultiplier tube (8) is used to receive the converging light spot passing through the test target (5) and convert the optical signal into a pulse signal; the signal acquisition module is used to acquire the pulse signal and transmit it to the data processing module; the data processing module is used to calculate the distortion and telecentricity of the lens under test (4) according to the received pulse signal.

2. The high-precision detection device for scanning lens distortion and telecentricity according to claim 1, characterized in that, A focusing lens (7) is further provided between the test target (5) and the photomultiplier tube (8).

3. The high-precision detection device for scanning lens distortion and telecentricity according to claim 1, characterized in that, The light source assembly includes a light source body (1) and a beam expander and collimator (2), and the beam expander and collimator (2) is located between the scanning device (3) and the light source body (1).

4. The high-precision detection device for scanning lens distortion and telecentricity according to claim 1, characterized in that, The signal acquisition module includes an oscilloscope or a data acquisition card.

5. The high-precision detection device for scanning lens distortion and telecentricity according to claim 1, characterized in that, The scanning device (3) uses a rotating mirror or a vibrating mirror.

6. A high-precision detection method for scanning lens distortion, implemented based on the high-precision detection device according to any one of claims 1-5, characterized in that, The method includes: Adjusting the displacement platform (6) so that the test target (5) is at the focal position of the lens under test (4), and at this time, the pulse width of the pulse signal corresponding to the central field of view is in the narrowest state; Taking the rising edge t0 of the pulse signal corresponding to the central field of view as the reference point, the time between adjacent rising edges is t n , and the image height Y of each detection field of view is calculated by the data processing module n : According to the image height Y n Calculate the corresponding distortion: Rotating the lens under test (4) to detect the distortion of all detection fields of view in different directions; In the above formula, n represents the number of rising edges of the pulse signal interval corresponding to the detection field of view and the central field of view, and y n is the theoretical image height, and r is the speed of the rotating mirror, with the unit of rpm; The calculation method for the focal length f of the lens (4) to be measured is as follows: Δt is the adjacent two rising-edge signals at the center position, and d is the pitch of the test pattern.

7. A high-precision detection method for the telecentricity of a scanning lens, implemented based on the high-precision detection device according to any one of claims 1-5, characterized in that including: Adjusting the displacement platform so that the test target is at the focal position of the lens under test, and at this time, the pulse width of the pulse signal corresponding to the central field of view is in the narrowest state; Moving the displacement platform (6) to move the test target (5) within a preset range from the focus to collect the pulse signals corresponding to all detection fields of view at different positions; Taking the rising edge t0 of the pulse signal corresponding to the central field of view as the reference point, and the adjacent rising edge time as tn, calculate the image height Y of each detection field of view through the data processing module n : Calculating the telecentricity of each field of view by comparing the change amount of the image height of each detection field of view after moving a preset distance: Taking the extreme value as the telecentricity of the lens; In the above formula, n represents the number of rising edges of the pulse signal interval corresponding to the detection field of view and the central field of view, and y n is the theoretical image height, r is the speed of the rotating mirror, and the unit is rpm; The calculation method of the focal length f of the lens under test (4) is: Δt is to take the adjacent two rising edge signals at the central position, and d is the pitch of the test pattern.

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