A high-precision detection device and method for scanning lens distortion and telecentricity

Abstract

The application discloses a high-precision detection device and method for scanning lens distortion and telecentricity, which comprises a light source assembly, a scanning device, a lens to be detected, a test target, a displacement platform, a photomultiplier, a signal acquisition module and a data processing module. The light source assembly is used to provide scanning light. The scanning device has a movable mirror, which is used to transmit the scanning light to the lens to be detected. The scanning device realizes the scanning action of the scanning light by driving the mirror to rotate around the central axis. The test target is used to receive the converging light spot, and the displacement platform is used to carry the test target. The photomultiplier is used to receive the converging light spot transmitted through the test target and convert the light signal into a pulse signal. The signal acquisition module is used to collect 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 to be detected according to the received pulse signal. The application can conveniently detect the distortion and telecentricity of the lens.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical system performance detection, in particular, to a high-precision detection device and method for scanning lens distortion and telecentricity. BACKGROUND

[0002] With the development of optical technology, optical lenses are increasingly widely used in various industries, and the specifications of various lenses are increasingly diversified. As basic parameters affecting the performance of lenses, distortion and telecentricity play an important role in many lens designs. However, the existing detection methods for distortion and telecentricity usually adopt imaging method, and the camera collects the images of the calibration plate after imaging through the lens, compares the collected images with the actual size to calculate the distortion, and needs to compare the images of calibration plates at different distances to calculate the telecentricity.

[0003] The above method can achieve relatively fast measurement effect for lenses with small field of view and low precision requirements. However, the pixel size of the camera sensor limits the resolution of the obtained image, and the target surface of the camera limits the field of view of the detected lens, so this method cannot meet the detection requirements of large field of view and high precision. In view of this, the present application is dedicated to developing a high-precision lens distortion and telecentricity detection device to effectively solve the problems existing in the prior art. SUMMARY

[0004] Therefore, the first object of the present application 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] In order to achieve the above object, the technical scheme of the present application is as follows:

[0006] A high-precision detection device for scanning lens distortion and telecentricity, comprising a light source assembly, a scanning device, a lens to be tested, 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, which is used to transmit the scanning light to the lens to be tested; 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 tested to form a converging light spot;

[0010] The test target is used to receive the converging light spot, the test target is a light-transmitting material, and the surface has a test pattern;

[0011] The displacement platform is used for carrying the test target and driving the test target to displace along a preset direction.

[0012] The photomultiplier is used for receiving the converging light spot passing through the test target and converting the light signal into a pulse signal.

[0013] The signal acquisition module is used for acquiring the pulse signal and transmitting to the data processing module.

[0014] The data processing module is used for calculating the distortion and telecentricity of the lens to be tested according to the received pulse signal.

[0015] Preferably, a focusing mirror is further arranged between the test target and the photomultiplier.

[0016] Preferably, the light source assembly comprises 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 comprises an oscilloscope or a data acquisition card.

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

[0019] The second object of the present application 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 scheme of the present application is:

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

[0022] Adjusting the displacement platform to make the test target be at the focal point position of the lens to be tested, 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 a reference point, the time of the adjacent rising edge is t n , and the image height Y n of each detection field of view is calculated by the data processing module:

[0024]

[0025] According to the image height Y n , the corresponding distortion is calculated:

[0026]

[0027] Rotating the lens to be tested 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, y n is the theoretical image height, and r is the speed of the rotating mirror, in rpm;

[0029] The focal length f of the lens to be measured is calculated by the following method:

[0030]

[0031] ; Δt is the time interval between adjacent rising edges of the pulse signal at the central position, and d is the pitch of the test pattern.

[0032] A third object of the present application 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] To achieve the above objects, the technical solution of the present application is as follows:

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

[0035] Adjusting the displacement platform to place the test target at the focal point position of the lens to be measured, at which time the pulse width of the pulse signal corresponding to the central field of view is in the narrowest state;

[0036] Moving the displacement platform to move the test target within a preset range from the focal point, so as 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, the time interval between adjacent rising edges is t n , and the image height Y n of each detection field of view is calculated by the data processing module:

[0038]

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

[0040]

[0041] ; the extreme value is 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, y n is the theoretical image height, and r is the speed of the rotating mirror, in rpm;

[0043] The focal length f of the lens to be measured is calculated by the following method:

[0044]

[0045] ; Δt is the time interval between the two adjacent rising edges of the signal at the center position, and d is the pitch of the test pattern.

[0046] The technical effects of the present application mainly embody in the following aspects:

[0047] The scanning device and the rotation of the lens to be tested realize sampling of the full field of view, meet the detection requirements of the large field of view lens, use a photomultiplier tube to replace a camera as a signal receiving device, effectively improve the resolution of the acquired signal, meet the high-precision detection requirements of distortion and telecentricity, the full field of view scanning method is simple, can record a large amount of field point information at one time, greatly improves the amount of information obtained, can flexibly select the number of sampling fields of view according to the requirements, and is more convenient; combined with the displacement platform recording the defocus amount, the telecentricity can be quickly measured. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 It is a schematic view of the detection device in the embodiment;

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

[0050] Figure 3 It is a schematic view of the black and white stripes in the embodiment;

[0051] Figure 4 It is a schematic view of the pulse signal in the embodiment.

[0052] The reference signs: 1, light source body; 2, beam expander collimator; 3, scanning device; 4, lens to be tested; 5, test target; 6, displacement platform; 7, focusing mirror; 8, photomultiplier tube. DETAILED DESCRIPTION

[0053] The specific embodiments of the present application are further described in detail below with reference to the accompanying drawings, so that the technical scheme of the present application is easier to understand and master.

[0054] Embodiment one,

[0055] Referring to Figure 1 , the embodiment provides a high-precision detection device for scanning lens distortion and telecentricity, which comprises 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 comprises 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 adopts a rotating mirror or a vibrating mirror, both of which have a movable mirror for transmitting the scanning light to the lens 4 to be tested; the scanning device 3 realizes the scanning action of the scanning light by driving the mirror to rotate around the central axis. Since the rotating mirror or the vibrating mirror is a prior art instrument, the working principle thereof will not be described herein.

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

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

[0060] The photomultiplier is used to receive the converging light spot transmitted through the test target 5 and convert the light signal into a pulse signal; in addition, a focusing mirror 7 is arranged between the test target 5 and the photomultiplier 8 to increase the intensity of the light signal.

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

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

[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 tested according to the received pulse signal.

[0064] Embodiment two,

[0065] The embodiment provides a high-precision detection method for scanning lens distortion based on the embodiment one, and the method comprises the following steps:

[0066] The displacement platform 6 is adjusted so that the test target 5 is located at the focal point position of the lens 4 to be tested, at this time, the pulse width of the pulse signal corresponding to the central field of view is in the narrowest state;

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

[0068]

[0069] The corresponding distortion is calculated according to the image height Y n :

[0070]

[0071] ​The to-be-tested lens 4 is rotated to detect the distortion of all detection fields of view in different directions. Figure 2 As shown in the figure, the to-be-tested lens 4 is preset with eight rotation directions. Figure 3 The black dot in the figure indicates the sampling point of the rising edge.

[0072] 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.

[0073] The calculation method of the focal length f of the to-be-tested lens is as follows:

[0074]

[0075] ; Δt is the time interval between adjacent rising edges of the pulse signal at the center position, and d is the pitch of the test pattern.

[0076] Similarly, the to-be-tested lens 4 can also be an f-sin(theta) or f-tan(theta) lens, and the calculation formula is different. For the f-sin(theta) lens, the calculation formula of the image height is as follows:

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

[0078] Embodiment Three,

[0079] The embodiment provides a high-precision detection method for the telecentricity of a scanning lens based on the embodiment one, and the method comprises the following steps:

[0080] The displacement platform 6 is adjusted to place the test target 5 at the focal point position of the to-be-tested lens 4, so that the pulse signal corresponding to the central field of view is in the narrowest state;

[0081] The displacement platform 6 is moved to move the test target 5 in a preset range away from or close to the to-be-tested lens 4, so as to collect the pulse signals corresponding to all detection fields of view at different positions;

[0082] The rising edge t0 of the pulse signal corresponding to the central field of view is taken as a reference point, and the time interval between adjacent rising edges is t n , and the image height Y n of each detection field of view is calculated by the data processing module.

[0083]

[0084] The telecentricity of each field of view is calculated 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 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, and only the rising edge pulse width of the pulse signal corresponding to each detection field of view at different positions needs to be recorded. The extreme difference of the position at which the rising edge pulse width of each detection field of view is the smallest can directly give the field curvature of the lens to be measured.

[0089] Of course, the above is only a typical example of the present application, and in addition to this, the present application can have other various specific implementation manners, and any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of the present application.

Claims

1. A high-precision detection method for scanning lens distortion, characterized in that, This method is implemented based on a high-precision detection device for scanning lens distortion and telecentricity, the device comprising: The light source assembly, scanning device (3), lens under test (4), test target (5), displacement platform (6), photomultiplier tube (8), signal acquisition module, and data processing module; among which, The light source assembly is used to provide scanning light; The scanning device (3) has a movable reflector, which is used to transmit the scanning light to the lens (4) under test; the scanning device (3) realizes the scanning action of the scanning light by driving the reflector to rotate around the central axis; The scanning light beam 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 has test patterns with a preset spacing on its surface. The displacement platform (6) is used to support the test target (5) and drive the test target (5) to move along a preset direction; The photomultiplier tube (8) is used to receive the focused light spot transmitted through the test target (5) and convert the light 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) based on the received pulse signal; The method includes: Adjust the displacement platform (6) so that the test target (5) is at the focal position of the lens (4) to be tested. At this time, the pulse width of the pulse signal corresponding to the central field of view is at its narrowest. Taking the rising edge t0 of the pulse signal corresponding to the center field of view as the reference point, the time interval between adjacent rising edges is t. n The image height Y of each detection field of view is calculated through the data processing module. n : ; According to like high Y n Calculate the corresponding distortion: ; Rotate the lens under test (4) to detect the distortion of all test fields 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. It is the theoretical image height, and r is the rotation speed of the mirror, in rpm; The method for calculating the focal length f of the lens (4) under test is as follows: ; To obtain the two adjacent rising edge signals at the center position, d is the spacing of the test pattern.

2. A high-precision method for detecting the telecentricity of a scanning lens, characterized in that, This method is implemented based on a high-precision detection device for scanning lens distortion and telecentricity, the device comprising: The light source assembly, scanning device (3), lens under test (4), test target (5), displacement platform (6), photomultiplier tube (8), signal acquisition module, and data processing module; among which, The light source assembly is used to provide scanning light; The scanning device (3) has a movable reflector, which is used to transmit the scanning light to the lens (4) under test; the scanning device (3) realizes the scanning action of the scanning light by driving the reflector to rotate around the central axis; The scanning light beam 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 has test patterns with a preset spacing on its surface. The displacement platform (6) is used to support the test target (5) and drive the test target (5) to move along a preset direction; The photomultiplier tube (8) is used to receive the focused light spot transmitted through the test target (5) and convert the light 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) based on the received pulse signal; The method includes: including: Adjust the displacement platform to position the test target at the focal point of the lens under test. At this point, the pulse width of the pulse signal corresponding to the central field of view is at its narrowest. The moving displacement platform (6) moves the test target (5) within a preset range from the focal point in order to collect pulse signals corresponding to all detection fields at different positions; Using the rising edge t0 of the pulse signal corresponding to the central field of view as the reference point, and the time interval between adjacent rising edges as tn, the image height Y of each detection field of view is calculated by the data processing module. n : ; The telecentricity of each field of view is calculated by comparing the change in image height after moving a preset distance. The extreme value is 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 r is the rotation speed of the mirror, in rpm; The method for calculating the focal length f of the lens under test (4) is as follows: ; To obtain the two adjacent rising edge signals at the center position, d is the spacing of the test pattern.

3. The high-precision detection method for the telecentricity of a scanning lens as described in claim 2, characterized in that, A focusing lens (7) is also provided between the test target (5) and the photomultiplier tube (8).

4. The high-precision detection method for the telecentricity of a scanning lens as described in claim 2, characterized in that, The light source assembly includes a light source body (1) and a beam expander collimator (2), with the beam expander collimator (2) located between the scanning device (3) and the light source body (1).

5. A high-precision detection method for the telecentricity of a scanning lens as described in claim 2, characterized in that, The signal acquisition module includes an oscilloscope or a data acquisition card.

6. The high-precision detection method for the telecentricity of a scanning lens as described in claim 2, characterized in that, The scanning device (3) uses a rotating mirror or a galvanometer.

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