A lens centering method and device

Abstract

The present invention discloses a lens centering method and device. The lens centering method is applied to a lens centering device, which includes a reticle, an image acquisition device, a focusing device, a centering device, a processing device and a centering adjustment device. The reticle is located on the image plane of the lens, and the image acquisition device is located on the object plane of the lens. The lens centering method includes: obtaining the current object plane reticle image collected by the image acquisition device, where the object plane reticle image includes a marker image; controlling the focusing device to drive the reticle to move to complete the focusing operation; controlling the centering device to drive the lens to move to complete the centering operation according to the distance between the position where the marker image is located and the reference position; calculating the modulation transfer function based on the object plane reticle image, and controlling the centering adjustment device to drive the lens to be adjusted to move to complete the centering adjustment operation according to the calculation result of the modulation transfer function. By adopting the above solution, the effect of adjusting the lens at the imaging end to improve the MTF value of the lens can be achieved.

Description

Technical Field

[0001] Embodiments of the present invention relate to lens technology, and in particular, to a lens centering method and device. Background Art

[0002] At present, the widely used methods for judging the resolution of security fixed-focus lenses include actual shooting, projection, and Modulation Transfer Function (MTF) analysis method. Among them, actual shooting and projection have certain limitations. Basically, one set of devices can only correspond to one or several lenses, and due to the fact that the object distance of security lenses is much larger than the image distance, large venues are required, and manual operation is needed and the quality is judged according to the imaging picture. Although there are the same judgment criteria, there are still differences in everyone's perception of clear and blurred, so there are still quality differences in the lenses tested by these two testing methods, and it is inevitable that personnel inspection will result in defective lenses flowing out.

[0003] The MTF analysis method is a relatively scientific method for analyzing the resolution of lenses at present, and MTF is used for shipment at the request of customers. Therefore, using accurate and stable MTF equipment for lens quality sorting is an important guarantee for the lens shipment quality of the company. Due to high quality and great assembly difficulty, the qualified rate of some types of lenses is low. The resolution of some unqualified products during assembly can be improved by centering. Currently, the lenses that need to be centered are not completely fixed yet, so this end of centering can only be vertically upward. Currently, MTF is detected by the MTF orthographic projection method. At this time, the target board is placed on the object plane above the lens, and an image acquisition device is placed on the image plane below the lens to collect images. Therefore, only the lens close to the object plane can be adjusted, and the lens at the imaging end cannot be adjusted. At the same time, the CMOS / CCD used in the MTF orthographic projection method measurement has a layer of protective glass. The higher the pixel, the thicker the protective glass, and the distance between the lens and the photosensitive surface will be affected by this thickness. When the glass thickness is greater than or close to the back focal length of the lens, the measurement is restricted. Summary of the Invention

[0004] The present invention provides a lens centering method and device to achieve the effect of adjusting the lens at the imaging end.

[0005] In a first aspect, an embodiment of the present invention provides a lens centering method, which is applied to a lens centering device. The lens centering device includes a target board, an image acquisition device, a focusing device, a centering device, a processing device, and a centering device. The target board is located on the image plane of the lens, and the image acquisition device is located on the object plane of the lens; the lens centering method includes:

[0006] Obtain the current object plane target board image collected by the image acquisition device, where the object plane target board image includes a logo image;

[0007] Control the focusing device to drive the reticle to move to complete the focusing operation;

[0008] Control the centering device to drive the lens to move to complete the centering operation according to the distance between the position where the identification image is located and the reference position;

[0009] Calculate the modulation transfer function according to the object surface reticle image, and control the centering device to drive the lens to be adjusted to move to complete the centering operation according to the calculation result of the modulation transfer function.

[0010] In an alternative embodiment of the present invention, the controlling the focusing device to drive the reticle to move to complete the focusing operation includes:

[0011] Determine the first image sharpness of the current object surface reticle image;

[0012] Control the focusing device to drive the reticle to move in the first direction, and control the image acquisition device to acquire the first object surface reticle image after the movement;

[0013] Determine the second image sharpness of the first object surface reticle image;

[0014] Judge whether the second image sharpness is greater than the first image sharpness;

[0015] If so, control the focusing device to drive the reticle to continue to move in the first direction until the second image sharpness reaches the preset sharpness requirement;

[0016] If not, control the focusing device to drive the reticle to move in the opposite direction of the first direction, and control the image acquisition device to acquire the second object surface reticle image after the movement;

[0017] Determine the third image sharpness of the second object surface reticle image;

[0018] Judge whether the third image sharpness is greater than the second image sharpness;

[0019] If so, control the focusing device to drive the reticle to continue to move in the opposite direction of the first direction until the third image sharpness reaches the preset sharpness requirement;

[0020] If not, control the focusing device to drive the reticle to move in the first direction to complete the focusing operation.

[0021] In an alternative embodiment of the present invention, the controlling the centering device to drive the lens to move to complete the centering operation according to the distance between the position where the identification image is located and the reference position includes:

[0022] Obtain the coordinate information of the identification image, where the coordinate information includes first coordinate information and second coordinate information;

[0023] Determine whether the first coordinate information is less than a preset first coordinate information and whether the second coordinate information is less than a preset second coordinate information;

[0024] If so, complete the centering operation;

[0025] If not, control the centering device to drive the lens to move according to the coordinate information and the coordinate information of the reference position until the first coordinate information is less than the preset first coordinate information and the second coordinate information is less than the preset second coordinate information, and complete the centering operation.

[0026] In an alternative embodiment of the present invention, the controlling the centering device to drive the lens to be adjusted to move to complete the centering operation according to the calculation result of the modulation transfer function includes:

[0027] Determine the lens adjustment parameters based on the calculation result of the modulation transfer function, where the lens adjustment parameters include a first adjustment value and a second adjustment value;

[0028] Control the centering device to drive the lens to be adjusted to move in a second direction by the first adjustment value and in a third direction by the second adjustment value based on the lens adjustment parameters; the second direction is orthogonal to the third direction.

[0029] In an alternative embodiment of the present invention, the calculation result of the modulation transfer function includes image plane tilt information, field curvature information, and peak information;

[0030] The determining the lens adjustment parameters based on the calculation result of the modulation transfer function includes: determining the tilt angle of the lens to be adjusted based on the image plane tilt information, the field curvature information, and the peak information; determining the lens adjustment parameters based on the tilt angle of the lens to be adjusted.

[0031] In an alternative embodiment of the present invention, before calculating the modulation transfer function according to the object plane reticle image, it further includes:

[0032] Control the focusing device to drive the reticle to move along a preset defocus measurement range;

[0033] After calculating the modulation transfer function according to the object plane reticle image, it further includes:

[0034] Determine whether the reticle meets a preset defocus measurement end rule.

[0035] In an alternative embodiment of the present invention, the controlling the focusing device to drive the reticle to move along a preset defocus measurement range includes:

[0036] Obtain the third coordinate information of the reticle;

[0037] Control the focusing device to drive the reticle to move a preset movement length in the first direction, where the preset movement length = -(preset defocus measurement range / 2) - preset third coordinate information - the third coordinate information;

[0038] Control the focusing device to drive the reticle to move a preset measurement length in the opposite direction of the first direction, and obtain the fourth coordinate information of the reticle after moving the preset measurement length;

[0039] Determining whether the reticle meets the preset defocus measurement end rule includes:

[0040] Determine whether the fourth coordinate information is greater than the sum of the preset third coordinate information and the preset defocus measurement range / 2;

[0041] If so, execute the step of controlling the centering device to drive the lens to be adjusted to move to complete the operation according to the calculation result of the modulation transfer function;

[0042] If not, execute the step of controlling the focusing device to drive the reticle to move a preset measurement length in the opposite direction of the first direction, and obtain the fourth coordinate information of the reticle after moving the preset measurement length.

[0043] In an alternative embodiment of the present invention, the calculation result of the modulation transfer function includes a modulation transfer function value. After calculating the modulation transfer function based on the object plane reticle image, it further includes:

[0044] Determine the lens specification based on the modulation transfer function value and the preset specification determination rule.

[0045] In an alternative embodiment of the present invention, determining the lens specification based on the modulation transfer function value and the preset specification determination rule includes:

[0046] Determine whether the modulation transfer function value is greater than a first preset specification value;

[0047] If the modulation transfer function value is greater than the first preset specification value, determine that the current lens is of the first specification;

[0048] If the modulation transfer function value is less than the first preset specification value, determine whether the modulation transfer function value is greater than a second preset specification value, where the second preset specification value is less than the first preset specification value;

[0049] If the modulation transfer function value is greater than the second preset specification value, determine that the current lens is of the second specification, and the second specification is inferior to the first specification;

[0050] If the modulation transfer function value is less than the second preset specification value, determine whether the modulation transfer function value is greater than a third preset specification value, where the third preset specification value is less than the second preset specification value;

[0051] If the modulation transfer function value is greater than the third preset specification value, determine that the current lens is of a third specification, where the third specification is inferior to the second specification;

[0052] If the modulation transfer function value is less than the third preset specification value, end the centering.

[0053] In an alternative embodiment of the present invention, before the step of controlling the centering device to drive the lens to be adjusted to move to complete the centering operation according to the calculation result of the modulation transfer function, the method further includes:

[0054] Accumulate the centering times;

[0055] Determine whether the centering times are greater than a preset number of times;

[0056] If the centering times are greater than the preset number of times, end the centering;

[0057] If the centering times are less than or equal to the preset number of times, execute the step of controlling the centering device to drive the lens to be adjusted to move to complete the centering operation according to the calculation result of the modulation transfer function.

[0058] In an alternative embodiment of the present invention, the lens centering device further includes a display device; after acquiring the current object plane reticle image collected by the image acquisition device, where the object plane reticle image includes a marking image, the method further includes:

[0059] Control the display device to display the current object plane reticle image on the display screen, where the reference position is the center position of the display screen.

[0060] In a second aspect, an embodiment of the present invention further provides a lens centering device, which includes: a reticle, an image acquisition device, a focusing device, a centering device, a processing device, and a centering device;

[0061] The reticle has a marking image and is located on the image plane of the lens, and the image acquisition device is located on the object plane of the lens;

[0062] The image acquisition device is used to collect an object plane reticle image;

[0063] The focusing device is used to drive the reticle to move so that the reticle is at the focus of the lens;

[0064] The centering device is used to drive the lens to move so that the reticle is on the principal optical axis of the lens;

[0065] The centering device is used to drive the lens to be adjusted to move;

[0066] The processing device is used to execute the lens centering method according to any embodiment of the present invention.

[0067] In the present invention, by placing the reticle on the image plane of the lens and the image acquisition device on the object plane of the lens, the image acquisition device can acquire the reticle image on the object plane. Furthermore, the processing device can calculate the modulation transfer function based on the reticle image on the object plane and control the centering device to drive the lens to be adjusted to move to complete the centering operation according to the calculation result of the modulation transfer function. Compared with the conventional orthographic projection method measurement, the lens can be reversed at this time, so the effect of adjusting the lens at the imaging end to improve the MTF value of the lens can be achieved. Description of the Drawings

[0068] Figure 1 It is a flowchart of a lens centering method provided in Embodiment 1 of the present invention;

[0069] Figure 2 is Figure 1 a flowchart of controlling the focusing device to drive the reticle to move to complete the focusing operation provided in

[0070] Figure 3 is Figure 1 a flowchart of controlling the centering device to drive the lens to move to complete the centering operation according to the distance between the position where the identification image is located and the reference position provided in

[0071] Figure 4 It is a flowchart of a lens centering method provided in Embodiment 2 of the present invention;

[0072] Figure 5 It is a flowchart of a lens centering method provided in Embodiment 3 of the present invention;

[0073] Figure 6 It is a flowchart of a lens centering method provided in Embodiment 4 of the present invention;

[0074] Figure 7 It is a schematic structural diagram of a lens centering device provided in Embodiment 6 of the present invention.

[0075] Among them, 51 is the reticle; 52 is the image acquisition device; 53 is the focusing device; 54 is the centering device; 55 is the centering device. Detailed Embodiments

[0076] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for ease of description, only the parts related to the present invention rather than all the structures are shown in the drawings.

[0077] Embodiment 1

[0078] Figure 1 FIG. is a flowchart of a lens centering method provided for Embodiment 1 of the present invention. This embodiment is applicable to the situation of manufacturing security fixed-focus lenses. This method can be executed by a lens centering device, which includes a reticle, an image acquisition device, a focusing device, a centering device, a processing device, and a centering adjustment device. The reticle is located on the image plane of the lens, and the image acquisition device is located on the object plane of the lens. The lens centering method specifically includes the following steps:

[0079] S110. Obtain the current object plane reticle image collected by the image acquisition device, where the object plane reticle image includes a marking image.

[0080] Among them, the image acquisition device refers to a device with an acquisition function. The image acquisition device can be composed of multiple cameras. By taking pictures on the object plane of the lens with multiple cameras, an image of the reticle placed on the object plane can be obtained.

[0081] The marking image on the reticle (Chart) is an image that can play a marking role. For example, it can be a cross, a plum blossom shape, etc. In some embodiments, the reticle can be a square plate, and there is a crosshair at the center of the square plate.

[0082] S120. Control the focusing device to drive the reticle to move to complete the focusing operation.

[0083] Among them, the focusing device is a device that can drive the reticle closer to and farther away from the lens. Completing the focusing operation means making the reticle located at the image-side focal point of the lens.

[0084] S130. Control the centering device to drive the lens to move to complete the centering operation according to the distance between the position of the marking image and the reference position.

[0085] Among them, the centering device is a device that can drive the lens to move so that the marking image of the reticle is located on the principal optical axis. The reference position can be a point on the principal optical axis. Taking the reference position as the origin, by controlling the centering device according to the distance between the position of the marking image and the reference position, the centering device can be driven to move the lens so that the marking image is on the principal optical axis.

[0086] S140. Calculate the modulation transfer function based on the object plane reticle image, and control the centering device to drive the lens to be adjusted to move according to the calculation result of the modulation transfer function to complete the centering operation.

[0087] Among them, the modulation transfer function (MTF) is the ratio of the contrast of the output image to the input image. The modulation transfer function is also called the spatial contrast transfer function and the spatial frequency contrast sensitivity function. It is a function of spatial frequency and reflects the ability of an optical system to transfer the modulation of various frequency sinusoidal objects. The modulation transfer function can be used to represent the characteristics of an optical system. The larger the MTF, the better the imaging quality of the system. The calculation result of the modulation transfer function refers to some parameter values obtained when calculating the modulation transfer function, such as the MTF value, the MTF defocus value, the field curvature, etc. The results obtained may be different according to different calculation methods, and no specific limitations are made here.

[0088] The centering device refers to a device that can drive the lens to be adjusted to move. Since the reticle is placed on the image plane at this time, the lens to be adjusted is the lens at the imaging end at this time. Controlling the centering device to drive the lens to be adjusted to move according to the calculation result of the modulation transfer function can make the lens to be adjusted move to a position with a higher MTF value, thereby optimizing the lens performance.

[0089] In the above solution, by making the reticle located on the lens image plane and the image acquisition device located on the object plane of the lens, the image acquisition device can collect the object plane reticle image, and then the processing device can calculate the modulation transfer function based on the object plane reticle image, and control the centering device to drive the lens to be adjusted to move according to the calculation result of the modulation transfer function to complete the centering operation. Compared with the conventional orthographic projection method measurement, the lens can be reversed at this time, so the effect of adjusting the lens at the imaging end of the lens to improve the MTF value of the lens can be achieved.

[0090] Exemplarily, as Figure 2 shown, S120. Control the focusing device to drive the reticle to move to complete the focusing operation, including:

[0091] S121. Determine the first image sharpness of the current object plane reticle image.

[0092] S122. Control the focusing device to drive the reticle to move in the first direction, and control the image acquisition device to collect the first object plane reticle image after movement.

[0093] S123. Determine the second image sharpness of the first object plane reticle image.

[0094] S124. Determine whether the sharpness of the second image is greater than that of the first image.

[0095] If so, return to step S122, control the focusing device to drive the reticle in the first direction, and control the image acquisition device to acquire the first object plane reticle image after movement until the sharpness of the second image reaches the preset sharpness requirement.

[0096] If not, execute step S125.

[0097] S125. Control the focusing device to drive the reticle in the opposite direction of the first direction, and control the image acquisition device to acquire the second object plane reticle image after movement.

[0098] S126. Determine the third image sharpness of the second object plane reticle image.

[0099] S127. Determine whether the third image sharpness is greater than the second image sharpness.

[0100] If so, return to step S125, control the focusing device to drive the reticle to continue moving in the opposite direction of the first direction until the third image sharpness reaches the preset sharpness requirement.

[0101] If not, execute step S128.

[0102] S128. Control the focusing device to drive the reticle in the first direction to complete the focusing operation.

[0103] Among them, the image sharpness of the current object plane reticle image can be calculated through an image sharpness evaluation function. Common image sharpness evaluation functions mainly include evaluation functions based on frequency domain features, evaluation functions based on statistical features, evaluation functions based on spatial domain features, etc. No specific limitation is made on the evaluation function here, as long as the image sharpness of the object plane reticle image can be obtained.

[0104] When the focusing device moves in the first direction until the second image sharpness is less than the first image sharpness, it indicates that the position of the target board for obtaining the second image sharpness is farther from the focus in the first direction than the position of the target board for obtaining the first image sharpness. At this time, the target board moves in the opposite direction of the first direction, indicating that the target board is moving in the direction close to the focus. When the target board moves until the third image sharpness is less than the second image sharpness, it indicates that the position of the target board for obtaining the third image sharpness is farther from the focus in the opposite direction of the first direction than the position of the target board for obtaining the second image sharpness. At this time, control the focusing device to drive the target board to move in the first direction, then the target board will move towards the focus. Therefore, at this time, the target board can move to the focus position and complete the focusing operation. In a specific embodiment, the lens is below the target board. At this time, the first direction is upward and the opposite direction of the first direction is downward.

[0105] Exemplarily, as Figure 3 shown, step S130, controlling the centering device to drive the lens to move to complete the centering operation according to the distance between the position where the identification image is located and the reference position, includes:

[0106] S131, obtaining the coordinate information of the identification image, where the coordinate information includes first coordinate information and second coordinate information.

[0107] S132, judging whether the first coordinate information is less than the preset first coordinate information and whether the second coordinate information is less than the preset second coordinate information.

[0108] If so, complete the centering operation.

[0109] If not, execute step S133.

[0110] S133, controlling the centering device to drive the lens to move according to the coordinate information and the coordinate information of the reference position until the first coordinate information is less than the preset first coordinate information and the second coordinate information is less than the preset second coordinate information, and complete the centering operation.

[0111] Among them, the reference position can be a point on the principal optical axis of the lens. The first coordinate information and the second coordinate information refer to the coordinate information in two different directions in the same coordinate system. When the first coordinate information is less than the preset first coordinate information and the second coordinate information is less than the preset second coordinate information, it indicates that the position of the identification image is close to or located on the principal optical axis, and at this time, it indicates that the centering has been completed. When the first coordinate information is greater than the preset first coordinate information and / or the second coordinate information is greater than the preset second coordinate information, it indicates that the position of the identification image is far from the reference position. At this time, control the movement of the lens according to the difference between the coordinate of the reference position and the first coordinate information and the second coordinate information, so that the lens can move until the identification image is located on the principal optical axis, and at this time, the centering operation can be completed.

[0112] In a specific embodiment, the first coordinate information may be X - coordinate information, the second coordinate information may be Y - coordinate information, the direction of the principal optical axis of the lens is the Z - axis direction, and the reference position also correspondingly has an X - coordinate and a Y - coordinate. Based on the difference between the X - coordinate of the reference position and the first coordinate information and the difference between the Y - coordinate of the reference position and the second coordinate information, the centering device drives the lens to move in the X - direction and in the Y - direction accordingly, so as to complete the centering operation.

[0113] Embodiment Two

[0114] Figure 4 The following is a flowchart of a lens centering method provided in Embodiment Two of the present invention. Embodiment Two of the present invention is optimized based on the foregoing Embodiment One. Optionally, the step of controlling the centering device to drive the lens to be adjusted to move to complete the centering operation according to the calculation result of the modulation transfer function includes: determining lens adjustment parameters based on the calculation result of the modulation transfer function, where the lens adjustment parameters include a first adjustment value and a second adjustment value. Controlling the centering device to drive the lens to be adjusted to move a first adjustment value in a second direction and move a second adjustment value in a third direction based on the lens adjustment parameters; the second direction is orthogonal to the third direction.

[0115] As Figure 4 shown, the method specifically includes:

[0116] S210. Obtain the current object - plane reticle image collected by the image acquisition device, where the object - plane reticle image includes a marking image.

[0117] S220. Control the focusing device to drive the reticle to move to complete the focusing operation.

[0118] S230. Control the centering device to drive the lens to move to complete the centering operation according to the distance between the position where the marking image is located and the reference position.

[0119] S240. Calculate the modulation transfer function according to the object - plane reticle image.

[0120] S250. Determine lens adjustment parameters based on the calculation result of the modulation transfer function, where the lens adjustment parameters include a first adjustment value and a second adjustment value.

[0121] Among them, the lens adjustment parameters refer to the parameter values for adjusting the lens to be adjusted to improve the lens quality. The first adjustment value refers to the difference between the position of the lens in the second direction and the ideal position, and the second adjustment value refers to the difference between the position of the lens in the third direction and the ideal position.

[0122] S260. Control the centering device to drive the lens to be adjusted to move a first adjustment value in a second direction and move a second adjustment value in a third direction based on the lens adjustment parameters; the second direction is orthogonal to the third direction.

[0123] By controlling the centering device to drive the lens to be adjusted to move in the second direction by the first adjustment value and in the third direction by the second adjustment value, the effect of adjusting the lens to be adjusted to improve the lens quality can be achieved. In a specific embodiment, the second direction is the X-axis direction, and the third direction is the Y-axis direction. By making the lens to be adjusted move in the second direction by the first adjustment value and in the third direction by the second adjustment value, centering of the lens to be adjusted can be realized, and the lens quality can be improved.

[0124] Exemplarily, the modulation transfer function calculation results include image plane tilt information, field curvature information, and peak information;

[0125] Determining the lens adjustment parameters based on the modulation transfer function calculation results includes: determining the tilt angle of the lens to be adjusted based on the image plane tilt information, the field curvature information, and the peak information; determining the lens adjustment parameters based on the tilt angle of the lens to be adjusted.

[0126] Among them, field curvature is also called "image field curvature". When there is field curvature in the lens, the intersection points of the entire light beam do not coincide with the ideal image points. Although clear image points can be obtained at each specific point, the entire image plane is a curved surface. In this way, it is impossible to clearly see the entire image plane during microscopy, causing difficulties in observation and photography. Peak information refers to the peak position within the defocus MTF curve.

[0127] Specifically, the imaging quality can be characterized as a function of the image plane tilt T, the field curvature C, and the peak P. The relationship function between the imaging quality and the adjusted lens factor is expressed as:

[0128] F(T, C, P) = f”{f{d(k*cos(θ), k*sin(θ)), t(x, y)}, {h(z), g(z)}, f{(d(x, y), h(z), r(z), t(x, y)}}.

[0129] Among them, in this function, F represents the imaging quality, T represents the image plane tilt, C represents the field curvature, and P represents the peak. d represents the lens eccentricity, t represents the lens tilt, h represents the lens thickness, g represents the lens spacing, r represents the lens surface accuracy, x and y are the direction coordinates decomposed to the image plane perpendicular to the optical axis, z is the direction coordinate along the optical axis, θ is the two-dimensional plane angle coordinate determined by x and y, and k is the absolute value of the eccentricity. In this embodiment, θ is the tilt angle of the lens to be adjusted, and x and y are the first adjustment value and the second adjustment value respectively.

[0130] Determine the adjustment method and adjustment amount of the lens to be adjusted according to the relationship function between the imaging quality and the lens factor to be adjusted, that is, according to the relationship between F(T, C, P) and x, y, z, θ, by confirming the image plane tilt T, field curvature C, and / or peak P as the adjustment target, computer automatic calculation can be used to solve the equation solution that makes F(T, C, P) optimal, that is, solve the values of the target movement positions x, y, z, θ of the lens to be adjusted, that is, by analyzing when the imaging quality is optimal, use software to calculate the values of the target movement positions x, y, z, θ of the lens to be adjusted, and move the lens to be adjusted in a targeted manner according to the calculated target movement positions of the lens to be adjusted, that is, quantitatively adjust the horizontal direction, vertical direction, tilt direction, and circumferential direction of the lens to be adjusted. Through this method, the lens to be adjusted is corrected in a targeted manner, achieving the goal of quickly compensating the imaging quality during the lens production process, compensating for the image plane tilt, field curvature, and the resulting decrease in the imaging quality of the module caused by the tilt of other components and assembly, fixing the lens to be adjusted that meets the requirements after adjustment, and then encapsulating the entire lens to obtain a lens with imaging quality meeting the requirements.

[0131] Embodiment III

[0132] Figure 5 The flowchart of a lens centering method provided by the second embodiment of the present invention is optimized based on the foregoing first embodiment. Optionally, before calculating the modulation transfer function according to the object plane reticle image, it further includes: controlling the focusing device to drive the reticle to move along a preset defocus measurement range. After calculating the modulation transfer function according to the object plane reticle image, it further includes: determining whether the reticle meets the preset defocus measurement end rule.

[0133] As Figure 5 shown, the method specifically includes:

[0134] S310. Obtain the current object plane reticle image collected by the image acquisition device, where the object plane reticle image includes a marking image.

[0135] S320. Control the focusing device to drive the reticle to move to complete the focusing operation.

[0136] S330. Control the centering device to drive the lens to move to complete the centering operation according to the distance between the position where the marking image is located and the reference position.

[0137] S340. Control the focusing device to drive the reticle to move along a preset defocus measurement range.

[0138] Among them, the defocus amount information refers to the defocus curve, that is, the curve formed by the MTF values when the reticle is in the positive defocus range and the negative defocus range of the focus. The preset defocus measurement range is the positive defocus range and the negative defocus range near the focus.

[0139] S350. Calculate the modulation transfer function based on the object plane reticle image.

[0140] S360. Determine whether the reticle meets the preset defocus measurement end rule.

[0141] Among them, by controlling the focusing device to drive the reticle to move along the preset defocus measurement range, when the reticle meets the preset defocus measurement end rule, it means that the reticle has completed the movement along the defocus measurement range. Therefore, the defocus amount information can be calculated when calculating the modulation transfer function based on the object plane reticle image.

[0142] S370. Determine the lens adjustment parameters based on the calculation result of the modulation transfer function. The lens adjustment parameters include a first adjustment value and a second adjustment value.

[0143] S380. Control the centering device to drive the lens to be adjusted to move the first adjustment value along the second direction and move the second adjustment value along the third direction based on the lens adjustment parameters; the second direction is orthogonal to the third direction.

[0144] Exemplarily, controlling the focusing device to drive the reticle to move along the preset defocus measurement range includes:

[0145] Obtain the third coordinate information of the reticle.

[0146] Control the focusing device to drive the reticle to move a preset movement length along the first direction. The preset movement length = -(preset defocus measurement range / 2) - preset third coordinate information - the third coordinate information.

[0147] Control the focusing device to drive the reticle to move a preset measurement length along the opposite direction of the first direction, and obtain the fourth coordinate information of the reticle after moving the preset measurement length.

[0148] Among them, the first direction is one of the positive focus direction and the negative focus direction. The preset third coordinate information is the preset focal point position information. The third coordinate information represents the position information of the reticle when it is at the actual focal point. By making the preset movement length = -(preset defocus measurement range / 2) - preset third coordinate information - the third coordinate information, after the reticle moves along the first direction by the preset movement length, it can move outside the preset defocus measurement range. At this time, then control the focusing device to drive the reticle to move along the opposite direction of the first direction by the preset measurement length. The preset measurement length is the unit length when measuring the defocus information. Thus, the MTF values when the reticle is at different positions within the preset defocus measurement range can be gradually obtained, and then the defocus amount information can be obtained.

[0149] Determining whether the reticle meets the preset defocus measurement end rule includes:

[0150] Determining whether the fourth coordinate information is greater than the sum of the preset third coordinate information and the preset defocus measurement range / 2;

[0151] If so, execute the step of controlling the centering device to drive the lens to be adjusted to move to complete the operation according to the calculation result of the modulation transfer function;

[0152] If not, execute the step of controlling the focusing device to drive the reticle to move along the opposite direction of the first direction by the preset measurement length, and obtaining the fourth coordinate information of the reticle after moving by the preset measurement length.

[0153] Among them, when the fourth coordinate information is greater than the sum of the preset third coordinate information and the preset defocus measurement range / 2, it means that the reticle has moved from outside the preset defocus measurement range on one side of the focal point to outside the preset defocus measurement range on the other side of the focal point, that is, the reticle has gradually moved along the preset defocus measurement range, thus indicating that the defocus measurement has ended.

[0154] Embodiment 4

[0155] Figure 6The figure is a flowchart of a lens centering method provided by the fourth embodiment of the present invention, and the embodiment of the present invention is optimized on the basis of the foregoing first embodiment. Optionally, the modulation transfer function calculation result includes a modulation transfer function value. After calculating the modulation transfer function according to the object plane reticle image, it further includes: determining the lens specification based on the modulation transfer function value and a preset specification determination rule. Optionally, before the step of controlling the centering device to drive the lens to be adjusted to move to complete the centering operation according to the modulation transfer function calculation result, it further includes: accumulating the number of centering times; determining whether the number of centering times is greater than a preset number; if the number of centering times is greater than the preset number, end the centering; if the number of centering times is less than or equal to the preset number, then execute the step of controlling the centering device to drive the lens to be adjusted to move to complete the centering operation according to the modulation transfer function calculation result.

[0156] As Figure 6 shown, the method specifically includes:

[0157] S410. Obtain the current object plane reticle image collected by the image acquisition device, where the object plane reticle image includes a marker image.

[0158] S420. Control the focusing device to drive the reticle to move to complete the focusing operation.

[0159] S430. Control the centering device to drive the lens to move to complete the centering operation according to the distance between the position of the marker image and the reference position.

[0160] S440. Control the focusing device to drive the reticle to move along a preset defocus measurement range.

[0161] S450. Calculate the modulation transfer function according to the object plane reticle image.

[0162] S460. Determine whether the reticle meets the preset defocus measurement end rule.

[0163] S470. Determine the lens adjustment parameters based on the modulation transfer function calculation result, where the lens adjustment parameters include a first adjustment value and a second adjustment value.

[0164] S481. Determine the lens specification based on the modulation transfer function value and a preset specification determination rule.

[0165] Among them, the modulation transfer function value is the MTF value, and the MTF value can represent the quality of the lens. The preset specification determination rule refers to the rule used to classify and determine the lens specification according to the modulation transfer function value. Since the larger the MTF value, the better the lens quality, therefore, the lens specification can be conveniently determined through the modulation transfer function value and the preset specification determination rule, which is convenient for classifying the lenses.

[0166] S491. Cumulative number of centering adjustments.

[0167] Among them, the number of centering adjustments refers to the number of times of adjusting the lens to be adjusted.

[0168] S492. Determine whether the number of centering adjustments is greater than a preset number. If so, end the centering adjustment. If not, execute step S482.

[0169] Among them, when the number of centering adjustments is greater than the preset number, it means that the lens has been centered many times, and the lens may be a defective product and cannot meet the corresponding quality requirements through centering. At this time, end the centering adjustment to avoid affecting the production efficiency due to excessive centering adjustments. If the number of centering adjustments is not greater than the preset number, control the centering device to drive the lens to be adjusted to move the first adjustment value along the second direction and the second adjustment value along the third direction according to the lens adjustment parameters, so as to be able to adjust the lens to be adjusted to improve the lens quality.

[0170] S482. Control the centering device to drive the lens to be adjusted to move the first adjustment value along the second direction and the second adjustment value along the third direction based on the lens adjustment parameters; the second direction is orthogonal to the third direction.

[0171] Exemplarily, the determining the lens specification based on the modulation transfer function value and the preset specification determination rule includes:

[0172] Determine whether the modulation transfer function value is greater than a first preset specification value; if the modulation transfer function value is greater than the first preset specification value, then determine that the current lens is of the first specification.

[0173] If the modulation transfer function value is less than the first preset specification value, then determine whether the modulation transfer function value is greater than a second preset specification value, and the second preset specification value is less than the first preset specification; if the modulation transfer function value is greater than the second preset specification value, then determine that the current lens is of the second specification, and the second specification is inferior to the first specification.

[0174] If the modulation transfer function value is less than the second preset specification value, then determine whether the modulation transfer function value is greater than a third preset specification value, and the third preset specification value is less than the second preset specification value; if the modulation transfer function value is greater than the third preset specification value, then determine that the current lens is of the third specification, and the third specification is inferior to the second specification.

[0175] If the modulation transfer function value is less than the third preset specification value, then end the centering adjustment.

[0176] Among them, when the modulation transfer function value is greater than the first preset specification value, it indicates that the lens has reached the standard of the first specification, so it can be determined that the lens is of the first specification. When the modulation transfer function value is less than the first preset specification value, it indicates that the current lens does not meet the standard of the first specification. At this time, it is determined whether the modulation transfer function value is greater than the second specification standard that is lower than the first specification. If it is greater, it indicates that the current lens is of the second specification. If the modulation transfer function value is also less than the second preset specification value, it indicates that the current lens does not meet the standards of both the first specification and the second specification. At this time, it is determined whether the modulation transfer function value is greater than the third preset specification value. When the modulation transfer function value is greater than the third preset specification value, it indicates that the current lens has reached the standard of the third specification, so it is determined that the current lens is of the third specification. When the modulation transfer function value is less than the third preset specification value, since the third specification is the lowest specification, it indicates that the lens does not meet the standard, and then the centering adjustment ends. By adopting the above solution, it is possible to conveniently obtain the specification of the current lens, which is convenient for classifying the lenses.

[0177] In an optional embodiment of the present invention, the lens centering device further includes a display device; after acquiring the current object plane reticle image collected by the image acquisition device, where the object plane reticle image includes a marking image, it further includes: controlling the display device to display the current object plane reticle image in the display screen, where the reference position is the center position of the display screen.

[0178] Among them, the display device refers to a device that can display a screen and can be a display screen. By displaying the current object plane reticle image in the display screen and the reference position being the center position of the display screen, it is convenient for the user to intuitively obtain the difference between the object plane reticle image and the reference position. In addition, in practical applications, the display device can also display values such as the specification of the lens and the modulation transfer function value.

[0179] Embodiment Five

[0180] Based on the above embodiments, the lens centering method in the embodiments of the present invention will be described below with an actual centering adjustment process.

[0181] First, install the lens and the reticle on the lens centering device. At this time, the reticle is located on the image plane of the lens, and the image acquisition device is located on the object plane of the lens. The focusing device drives the reticle to move to a preset initial position, set the initial value of the centering adjustment times to 1, and then acquire the current object plane reticle image collected by the image acquisition device, and determine the first image sharpness of the current object plane reticle image. If the first image sharpness has reached the preset sharpness, it indicates that the reticle is at the focus at this time, and the centering process is started. If the first image sharpness has not reached the preset sharpness, it indicates that the reticle is not at the focus at this time, start the focusing process and start the centering process after the focusing is completed.

[0182] After the centering process ends, obtain the third coordinate information of the reticle; control the focusing device to drive the reticle to move a preset movement length in the first direction, where the preset movement length = -(preset defocus measurement range / 2) - preset third coordinate information - the third coordinate information; then control the focusing device to drive the reticle to move a preset measurement length in the opposite direction of the first direction, and obtain the fourth coordinate information of the reticle after moving the preset measurement length. At this time, the reticle will gradually move along the preset defocus measurement range. Then calculate the modulation transfer function based on the object plane reticle image. Since the reticle gradually moves along the preset defocus measurement range, defocus amount information, that is, defocus MTF and peak values, can be calculated when calculating the modulation transfer function. Through different algorithms, information such as modulation transfer function values, field curvature, and image plane deviation can also be obtained when calculating the modulation transfer function value. Then determine whether the fourth coordinate information is greater than the sum of the preset third coordinate information and the preset defocus measurement range / 2. If not, the reticle continues to move a preset measurement length in the opposite direction of the first direction. If so, it means that the reticle has moved from outside the preset defocus measurement range on one side of the focus to outside the preset defocus measurement range on the other side of the focus, that is, the reticle has gradually moved along the preset defocus measurement range, indicating that the defocus measurement has ended.

[0183] Then, based on the lens tilt angle in the calculation result of the modulation transfer function, determine whether the direction coordinate of the vertical optical axis decomposed onto the image plane is less than the preset coordinate value and determine the lens adjustment parameters. The lens adjustment parameters include a first adjustment value and a second adjustment value. If the direction coordinate of the vertical optical axis decomposed onto the image plane is greater than the preset coordinate value, accumulate the centering times, and then determine whether the centering times are greater than the preset times; if the centering times are greater than the preset times, end the centering; if the centering times are less than or equal to the preset times, then execute the step of controlling the centering device to drive the lens to be adjusted to move the first adjustment value in the second direction and move the second adjustment value in the third direction; the second direction is orthogonal to the third direction, and then start from obtaining the current object plane reticle image collected by the image acquisition device again and determining the first image sharpness of the current object plane reticle image, and execute the second centering process.

[0184] If the direction coordinate of the vertical optical axis decomposed onto the image plane is less than the preset coordinate value, the lens specification is determined based on the modulation transfer function value and the preset specification determination rule. That is, first, it is determined whether the modulation transfer function value is greater than the first preset specification value; if the modulation transfer function value is greater than the first preset specification value, the current lens is determined to be of the first specification; if the modulation transfer function value is less than the first preset specification value, it is determined whether the modulation transfer function value is greater than the second preset specification value, and the second preset specification value is less than the first preset specification value; if the modulation transfer function value is greater than the second preset specification value, the current lens is determined to be of the second specification, and the second specification is inferior to the first specification; if the modulation transfer function value is less than the second preset specification value, it is determined whether the modulation transfer function value is greater than the third preset specification value, and the third preset specification value is less than the second preset specification value; if the modulation transfer function value is greater than the third preset specification value, the current lens is determined to be of the third specification, and the third specification is inferior to the second specification; if the modulation transfer function value is less than the third preset specification value, the centering adjustment ends.

[0185] Embodiment Six

[0186] Figure 7 The structural schematic diagram of a lens centering adjustment device provided by Embodiment Six of the present invention is shown as Figure 7 shown. The lens centering adjustment device includes: a reticle 51, an image acquisition device 52, a focusing device 53, a centering device 54, a processing device (not shown in the figure), and a centering adjustment device 55;

[0187] The reticle 51 has a marked image and is located on the image plane of the lens, and the image acquisition device 52 is located on the object plane of the lens.

[0188] The image acquisition device 52 is used to acquire the image of the reticle 51 on the object plane.

[0189] The focusing device 53 is used to drive the reticle 51 to move so that the reticle 51 is at the focus of the lens.

[0190] The centering device 54 is used to drive the lens to move so that the reticle 51 is on the principal optical axis of the lens.

[0191] The centering adjustment device 55 is used to drive the lens to be adjusted to move.

[0192] The processing device is used to execute the lens centering adjustment method described in any embodiment of the present invention.

[0193] In the above solution, by positioning the reticle 51 at the image plane of the lens and the image acquisition device 52 at the object plane of the lens, the image acquisition device 52 can capture the image of the reticle 51 on the object plane. Furthermore, the processing device can calculate the modulation transfer function based on the image of the reticle 51 on the object plane, and control the centering device 55 to drive the lens to be adjusted to move to complete the centering operation according to the calculation result of the modulation transfer function. Compared with the conventional orthographic projection method measurement, the lens can be reversed at this time, so the effect of adjusting the lens at the imaging end of the lens to improve the MTF value of the lens can be achieved.

[0194] Optionally, the lens centering device further includes a display device (not shown in the figure), and the display device is used to display the current image of the reticle 51 on the display screen. In practical applications, the display device can also display values such as the specifications of the lens and the modulation transfer function value. In a specific embodiment, the display device is a display screen, and the lens centering device has a housing (not shown in the figure), and the display screen is arranged on the housing.

[0195] Note that the above is only the preferred embodiment of the present invention and the applied technical principle. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A lens centering method, applied to a lens centering device, the lens centering device including a target board, an image acquisition device, a focusing device, a centering device, a processing device and a centering device, characterized in that, The reticle is located on the image plane of the lens, and the image acquisition device is located on the object plane of the lens; The method for aligning the lens includes: Obtaining the current object plane reticle image collected by the image acquisition device, where the object plane reticle image includes an identification image; Controlling the focusing device to drive the reticle to move to complete the focusing operation; Controlling the centering device to drive the lens to move to complete the centering operation according to the distance between the position where the identification image is located and the reference position; Calculating the modulation transfer function according to the object plane reticle image, and controlling the alignment device to drive the lens to be adjusted to move to complete the alignment operation according to the calculation result of the modulation transfer function; The controlling the focusing device to drive the reticle to move to complete the focusing operation includes: Determining the first image sharpness of the current object plane reticle image; Controlling the focusing device to drive the reticle to move in the first direction, and controlling the image acquisition device to collect the first object plane reticle image after movement; Determining the second image sharpness of the first object plane reticle image; Judging whether the second image sharpness is greater than the first image sharpness; If so, controlling the focusing device to drive the reticle to continue moving in the first direction until the second image sharpness reaches the preset sharpness requirement; If not, controlling the focusing device to drive the reticle to move in the opposite direction of the first direction, and controlling the image acquisition device to collect the second object plane reticle image after movement; Determining the third image sharpness of the second object plane reticle image; Judging whether the third image sharpness is greater than the second image sharpness; If so, controlling the focusing device to drive the reticle to continue moving in the opposite direction of the first direction until the third image sharpness reaches the preset sharpness requirement; If not, controlling the focusing device to drive the reticle to move in the first direction to complete the focusing operation; The controlling the centering device to drive the lens to move to complete the centering operation according to the distance between the position where the identification image is located and the reference position includes: Obtaining the coordinate information of the identification image, where the coordinate information includes first coordinate information and second coordinate information; Judging whether the first coordinate information is less than the preset first coordinate information and whether the second coordinate information is less than the preset second coordinate information; If so, completing the centering operation; If not, controlling the centering device to drive the lens to move according to the coordinate information and the coordinate information of the reference position until the first coordinate information is less than the preset first coordinate information and the second coordinate information is less than the preset second coordinate information to complete the centering operation; The controlling the alignment device to drive the lens to be adjusted to move to complete the alignment operation according to the calculation result of the modulation transfer function includes: Determining the lens adjustment parameters based on the calculation result of the modulation transfer function, where the lens adjustment parameters include a first adjustment value and a second adjustment value; Based on the lens adjustment parameters, controlling the alignment device to drive the lens to be adjusted to move in the second direction by the first adjustment value and in the third direction by the second adjustment value; the second direction is orthogonal to the third direction.

2. The lens centering method according to claim 1, wherein The calculation result of the modulation transfer function includes image plane tilt information, field curvature information, and peak information; Determining the lens adjustment parameters based on the calculation result of the modulation transfer function includes: Determining the tilt angle of the lens to be adjusted based on the image plane tilt information, the field curvature information, and the peak information; Determining the lens adjustment parameters based on the tilt angle of the lens to be adjusted.

3. The lens centering method according to claim 2, wherein Before calculating the modulation transfer function according to the object plane reticle image, it further includes: Controlling the focusing device to drive the reticle to move along a preset defocus measurement range; After calculating the modulation transfer function according to the object plane reticle image, it further includes: Determining whether the reticle meets the preset defocus measurement end rule.

4. The lens centering method according to claim 3, characterized in that, The controlling the focusing device to drive the reticle to move along a preset defocus measurement range includes: Obtaining the third coordinate information of the reticle; Controlling the focusing device to drive the reticle to move a preset movement length along a first direction, where the preset movement length = -(preset defocus measurement range / 2) - preset third coordinate information - the third coordinate information; Controlling the focusing device to drive the reticle to move a preset measurement length along the opposite direction of the first direction, and obtaining the fourth coordinate information of the reticle after moving the preset measurement length; The determining whether the reticle meets the preset defocus measurement end rule includes: Determining whether the fourth coordinate information is greater than the sum of the preset third coordinate information and the preset defocus measurement range / 2; If so, performing the step of controlling the centering device to drive the lens to be adjusted to move to complete the operation according to the calculation result of the modulation transfer function; If not, performing the step of controlling the focusing device to drive the reticle to move a preset measurement length along the opposite direction of the first direction, and obtaining the fourth coordinate information of the reticle after moving the preset measurement length.

5. The lens centering method according to claim 1 or 2, characterized in that, The calculation result of the modulation transfer function includes the modulation transfer function value. After calculating the modulation transfer function according to the object plane reticle image, it further includes: Determining the lens specification based on the modulation transfer function value and the preset specification determination rule.

6. The lens centering method according to claim 5, characterized in that, The determining the lens specification based on the modulation transfer function value and the preset specification determination rule includes: Determining whether the modulation transfer function value is greater than a first preset specification value; If the modulation transfer function value is greater than the first preset specification value, determining that the current lens is of the first specification; If the modulation transfer function value is less than the first preset specification value, determining whether the modulation transfer function value is greater than a second preset specification value, where the second preset specification value is less than the first preset specification value; If the modulation transfer function value is greater than the second preset specification value, determining that the current lens is of the second specification, and the second specification is inferior to the first specification; If the modulation transfer function value is less than the second preset specification value, determining whether the modulation transfer function value is greater than a third preset specification value, where the third preset specification value is less than the second preset specification value; If the modulation transfer function value is greater than the third preset specification value, determining that the current lens is of the third specification, and the third specification is inferior to the second specification; If the modulation transfer function value is less than the third preset specification value, ending the centering.

7. The lens centering method according to claim 1, wherein Before the step of controlling the centering device to drive the lens to be adjusted to move to complete the centering operation according to the calculation result of the modulation transfer function, it further includes: Cumulative centering adjustment times; Determine whether the centering adjustment times are greater than a preset number of times; If the centering adjustment times are greater than the preset number of times, end the centering adjustment; If the centering adjustment times are less than or equal to the preset number of times, then perform the step of controlling the centering adjustment device to drive the lens to be adjusted to move to complete the centering adjustment operation according to the calculation result of the modulation transfer function.

8. The lens centering method according to claim 1, wherein The lens centering adjustment device further includes a display device; after obtaining the current object plane reticle image collected by the image acquisition device, the object plane reticle image includes an identification image, and further includes: Control the display device to display the current object plane reticle image in the display screen, wherein the reference position is the center position of the display screen.

9. A lens centering device, characterized in that, Including a reticle, an image acquisition device, a focusing device, a centering device, a processing device and a centering adjustment device; The reticle has an identification image and is located on the lens image plane, and the image acquisition device is located on the lens object plane; The image acquisition device is used to collect the object plane reticle image; The focusing device is used to drive the reticle to move so that the reticle is at the lens focus; The centering device is used to drive the lens to move so that the reticle is on the principal optical axis of the lens; The centering adjustment device is used to drive the lens to be adjusted to move; The processing device is used to execute the lens centering adjustment method according to any one of claims 1-8.

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