Method, device, computer equipment and medium for evaluating endoscope optical depth of field

Abstract

The present invention discloses an evaluation method, device, computer equipment and medium for the optical depth of field of an endoscope. The evaluation method for the optical depth of field of an endoscope comprises: respectively obtaining image space resolution and local distortion rate at different working distances; calculating object space resolution at different working distances according to the image space resolution and local distortion rate at different working distances, wherein the calculation formula of the object space resolution is object space resolution=image space resolution×distortion rate; wherein the method for obtaining image space resolution at different working distances comprises: adjusting an endoscope body or a star image target so that the endoscope body is perpendicular to the star image target, and an imaging surface of an imaging device of the endoscope body is arranged parallel to the star image target; changing the working distance between the endoscope body and the star image target, and collecting images of the star image target at different working distances; and analyzing the collected images of the star image target at different working distances to obtain modulation transfer function data, namely, image space resolution.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to an evaluation method, device, computer equipment and medium for endoscope optical depth of field. Background Art

[0002] Endoscope is a commonly used medical device, widely used in disease examination and surgical treatment in related departments. Endoscopes currently on the market are divided into rigid endoscopes and flexible endoscopes according to whether their insertion sections are bendable; and they can be divided into optical endoscopes and electronic endoscopes according to the imaging principle.

[0003] The depth of field is the range of front distances closest to and farthest from the distal end of the endoscope, within which objects show acceptable clarity in the captured image. The current depth of field test method generally uses a resolution test card, such as the USAF1951 resolution card or the national standard resolution card, to observe within the nominal range, and watch the image of the resolution test card on the monitor with the naked eye to determine whether it can meet the clarity requirements. However, the results obtained by this method are highly subjective, and different people have different judgment criteria for clarity at the same distance, that is, the final depth of field evaluation results will vary from person to person. Therefore, it is necessary to provide an evaluation method that can quantify the depth of field parameters.

[0004] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0005] The main purpose of the present invention is to provide an evaluation method, device, computer equipment and medium for endoscope optical depth of field, aiming to solve the above-mentioned technical problems in the prior art.

[0006] To achieve the above object, the present invention provides a method for evaluating the optical depth of field of an endoscope, the method comprising:

[0007] Obtain the image resolution and local distortion rate at different working distances respectively;

[0008] According to the image space resolution and local distortion rate at different working distances, the object space resolution at different working distances is calculated, and the calculation formula of the object space resolution is object space resolution = image space resolution × distortion rate;

[0009] Among them, the method for obtaining the image resolution at different working distances includes:

[0010] Adjust the endoscope body or the star icon target so that the endoscope body is perpendicular to the star icon target, and the imaging surface of the imaging device of the endoscope body is arranged parallel to the star icon target;

[0011] Changing the working distance between the endoscope body and the star icon target, and collecting images of the star icon target at different working distances;

[0012] Analyze the images of the star target collected at different working distances to obtain the modulation transfer function data, that is, the image resolution;

[0013] Methods for obtaining local distortion rates at different working distances include:

[0014] Acquire first images of the grid test target at different working distances respectively, wherein the imaging surface of the imaging device on the mounting end of the endoscope body is parallel to the grid test target, and the mounting end of the endoscope body is located at the center of the grid test target;

[0015] Calculating the distortion rate along the first direction for each first image;

[0016] According to the distortion rate, the local distortion rate is calculated and the local distortion rates at different working distances are obtained.

[0017] Preferably, in the method for evaluating the endoscope optical depth of field, calculating the distortion rate along the first direction for each first image comprises:

[0018] According to each first image, pixel coordinate values ​​of each grid intersection point of the first image along a first direction from a central grid point are obtained, wherein the central grid point is a grid intersection point located at the center of the first image;

[0019] According to the pixel coordinate values, the pixel distance and the grid distance between each grid intersection and the central grid point are calculated in units of pixel number and grid number respectively;

[0020] According to the calculated pixel distance and grid distance, a first relational expression between the pixel distance and the grid distance is obtained;

[0021] Calculate the first grid distance of the edge grid point according to the first relational expression and the first pixel distance of the edge grid point in each grid intersection, wherein the edge grid point is the outermost grid intersection on the side opposite to the central grid point along the first direction of each grid intersection;

[0022] Normalizing the pixel distance and the grid distance of each grid intersection according to the first pixel distance and the first grid distance;

[0023] According to the normalized pixel distance and grid distance of each grid intersection, a second relational expression of the normalized pixel distance and grid distance is established;

[0024] Generate a third relational expression between the real grid coordinate value of each grid intersection and the actual size on the imaging device according to the second relational expression and the real size coordinate value of each grid intersection;

[0025] According to the third relationship, the distortion rate of the first image along the first direction is calculated.

[0026] Preferably, in the method for evaluating the endoscope optical depth of field, obtaining the first relationship between the pixel distance and the grid distance based on the calculated pixel distance and grid distance includes:

[0027] According to the calculated pixel distance and grid distance, a first relational expression Ru=f(Rd) of the pixel distance and grid distance is obtained by fitting, wherein the first relational expression is a two-variable multi-time equation;

[0028] Ru is the grid distance between each grid intersection and the central grid point;

[0029] Rd is the pixel distance between each grid intersection and the central grid point;

[0030] Accordingly, calculating the first grid distance of the edge grid points according to the first relational expression and the first pixel distance of the edge grid points at each grid intersection includes:

[0031] Substitute the first pixel distance of the edge grid point into the first relational expression Ru=f(Rd) to calculate the first grid distance Ru1 of the edge grid point.

[0032] Preferably, in the method for evaluating the optical depth of field of an endoscope, the second relationship between the normalized pixel distance and the grid distance is established based on the normalized pixel distance and the grid distance of each grid intersection, including:

[0033] According to the normalized pixel distance Rd' and grid distance Ru' of each grid intersection, a second relational expression Rd'=f(Ru') of the normalized pixel distance and grid distance is obtained by fitting, wherein the second relational expression is a two-variable multi-time equation;

[0034] Where Rd' is the normalized pixel distance of each grid intersection, Rd'=Rd / Rd1;

[0035] Ru' is the normalized grid distance of each grid intersection, Ru'=Ru / Ru1;

[0036] Preferably, in the method for evaluating the optical depth of field of an endoscope, the step of generating a third relational expression of the real grid coordinate value of each grid intersection and the actual size on the imaging device according to the second relational expression and the real size coordinate value of each grid intersection includes:

[0037] When the actual size of each grid on the grid test target is a×a and the size of a single pixel of the image sensor of the imaging device is b×b, Y is the actual size of each grid intersection on the imaging device, Y=b×Rd=b×Rd'×Rd1; X is the actual grid coordinate value of each grid intersection, X=a×Ru=a×Ru'×Ru1;

[0038] Substituting X and Y into the second relational expression Rd'=f(Ru'), the third relational expression Y=F(X) is obtained.

[0039] Preferably, in the method for evaluating the endoscope optical depth of field, calculating the distortion rate of the first image along the first direction according to the third relationship includes:

[0040] The third relationship Y=F(X) is differentially derived to obtain the distortion rate of the first image along the first direction.

[0041] Preferably, in the method for evaluating the optical depth of field of an endoscope, the step of calculating the local distortion rate according to the distortion rate and obtaining the local distortion rate at different working distances includes:

[0042] Calculate the first pixel when the total field of view is at a preset percentage at different working distances;

[0043] According to the calculated first pixel, solve the normalized grid distance Ru';

[0044] According to the normalized grid distance Ru', the distortion rate is calculated as the local distortion rate at the working distance.

[0045] Preferably, in the method for evaluating the optical depth of field of an endoscope, the first image is a plurality of images, and the plurality of first images include first images at different working distances respectively acquired by grid test targets with different grid spacings;

[0046] Accordingly, the calculating of the local distortion rate according to the distortion rate and obtaining the local distortion rate at different working distances includes:

[0047] According to the distortion rates of the grid test targets with different grid spacings at different working distances, the local distortion rates of the grid test targets with different grid spacings at different working distances are calculated;

[0048] Calculate the average value of the local distortion rate of the grid test targets with different grid spacings at the same working distance;

[0049] The average value of the local distortion rate at the same working distance is taken as the local distortion rate corresponding to the working distance.

[0050] In order to achieve the above object, the present invention further provides an endoscope optical depth of field evaluation device, the endoscope optical depth of field evaluation device comprising:

[0051] An acquisition unit, used for respectively acquiring image resolution and local distortion rate at different working distances;

[0052] An analysis unit, used to calculate the object space resolution at different working distances according to the image space resolution and the local distortion rate at different working distances, wherein the object space resolution is calculated by the formula: object space resolution = image space resolution × distortion rate;

[0053] Wherein, the analysis unit is also used for:

[0054] Adjust the endoscope body or the star icon target so that the endoscope body is perpendicular to the star icon target, and the imaging surface of the imaging device of the endoscope body is arranged parallel to the star icon target;

[0055] Changing the working distance between the endoscope body and the star icon target, and collecting images of the star icon target at different working distances;

[0056] Analyze the images of the star target collected at different working distances to obtain the modulation transfer function data, that is, the image resolution;

[0057] The analysis unit is also used for:

[0058] Acquire first images of the grid test target at different working distances respectively, wherein the imaging surface of the imaging device on the mounting end of the endoscope body is parallel to the grid test target, and the mounting end of the endoscope body is located at the center of the grid test target;

[0059] Calculating the distortion rate along the first direction for each first image;

[0060] According to the distortion rate, the local distortion rate is calculated and the local distortion rates at different working distances are obtained.

[0061] In order to achieve the above object, the present invention further provides a computer device, the computer device comprising:

[0062] at least one processor; and,

[0063] a memory communicatively connected to the at least one processor; wherein,

[0064] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the above-mentioned method for evaluating the endoscope optical depth of field.

[0065] In order to achieve the above-mentioned object, the present invention also provides a computer-readable storage medium storing a computer program, characterized in that when the computer program is executed by a processor, the above-mentioned method for evaluating the optical depth of field of an endoscope is implemented.

[0066] The present invention has at least the following beneficial effects:

[0067] The method for evaluating the optical depth of field of an endoscope provided by the present invention obtains the image space resolution and the local distortion rate at different working distances respectively; according to the image space resolution and the local distortion rate at different working distances, the object space resolution at different working distances is calculated, and the calculation formula of the object space resolution is object space resolution = image space resolution × distortion rate, thereby quantifying the depth of field parameter. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 A schematic diagram of an embodiment of a method for evaluating the optical depth of field of an endoscope provided by the present invention;

[0069] Figure 2 A schematic diagram of an embodiment of a device for testing image resolution provided by the present invention;

[0070] Figure 3 A schematic diagram of an embodiment of a method for testing image resolution provided by the present invention;

[0071] Figure 4 A schematic diagram of an embodiment of a distortion rate testing device provided by the present invention;

[0072] Figure 5 for Figure 4 A schematic diagram of an embodiment of a medium grid test target;

[0073] Figure 6 To adopt Figure 4 A schematic diagram of an image to be analyzed obtained by the test device;

[0074] Figure 7 A schematic diagram of an embodiment of a method for testing distortion rate provided by the present invention;

[0075] Figure 8 A schematic diagram of an embodiment of a method for evaluating the distortion rate of endoscope optical imaging provided by the present invention;

[0076] Fig. 9 A schematic diagram of obtaining the pixel coordinate value of the 0th grid intersection point (center grid point) of the present invention;

[0077] Fig.10 A schematic diagram of obtaining the pixel coordinate value of the first grid intersection point along the horizontal direction from the center grid point in the present invention;

[0078] Fig.11It is a schematic diagram of fitting the second relational equation of the present invention;

[0079] Fig.12 A schematic diagram of an endoscope optical depth of field evaluation device provided by the present invention;

[0080] Fig.13 A schematic diagram of a computer device according to the present invention.

[0081] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0082] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0083] In the embodiments of the present invention, the term "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0084] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0085] In the embodiments of the present invention, the term "plurality" refers to two or more than two, and other quantifiers are similar.

[0086] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0087] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. However, it can be understood by those skilled in the art that in the embodiments of the present invention, many technical details are proposed in order to enable the reader to better understand the present invention. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present invention can also be implemented. The division of the following embodiments is for the convenience of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined and referenced with each other under the premise of no contradiction.

[0088] When the distal end (imaging device) of the endoscope observes an object, different resolution requirements need to be met at close and long distances. For example, when the distance is close, it is necessary to see the details clearly, such as when observing the tissue mucosal layer, the requirements are relatively high; while when the distance is far, the requirements are lower and it is sufficient to see clearly.

[0089] Therefore, the object space resolution is defined to evaluate the range of depth of field. Object space resolution represents the actual resolution of the object. Its value is derived from the image space resolution and distortion rate. Image space resolution is the resolution obtained by calculation or automatic analysis of the captured picture. Distortion rate is the magnification from object space to image space.

[0090] More specifically, Figure 1 A schematic diagram of an embodiment of a method for evaluating the optical depth of field of an endoscope is shown. Figure 1 As shown in the figure, object space resolution = image space resolution × distortion rate.

[0091] The image resolution is the MTF (Modulation Transfer Function) at different working distances obtained by changing the working distance. When the MTF is not less than 10%, the image is considered acceptable, so the line pairs when the MTF is not less than 10% are taken as the image resolution at the working distance. For the sake of convenience, when calculating the image resolution, the line pairs of MTF10 are taken as the image resolution at the working distance.

[0092] Distortion changes with the increase of field of view, so the resolution of objects in different fields of view will also be different. However, the trend of the distortion rate of the full field of view changing with the working distance is the same, so a specific field of view can be selected to describe the depth of field. Since in clinical use, the target of interest is usually placed in the center of the field of view, and the distortion rate of the distal end of the endoscope is the largest in the central field of view at the same working distance, in this embodiment, the central field of view is selected to discuss the depth of field of the system. Therefore, when calculating the distortion rate, the calculation point does not exceed a preset percentage of the total field of view. In this embodiment, when calculating the distortion rate, the calculation point does not exceed 20% of the total field of view. For the sake of convenience in explanation, the following calculation of the distortion rate will also be calculated based on the calculation point not exceeding or equal to 20% of the total field of view.

[0093] More specifically, object space resolution MTF OBJ =MTF IMA ×MAG.

[0094] Among them, MTF IMA To obtain the MTF10 corresponding resolution at the center of the image field of view; MAG is the local distortion rate of the endoscope (in this embodiment, the central 20% of the full field of view is selected). By testing the MTF at different working distances IMA And MAG values, and then calculate the corresponding MTF at these working distances OBJ .

[0095] Usually choose MTF OBJ >20lp / mm near end distance and MTF OBJ The distal distance of >1lp / mm is taken as the critical value of the depth of field range. Then the depth of field of the endoscope is from the proximal distance to the distal distance.

[0096] It should be noted that the working distance mentioned in the present invention refers to the distance between the mounting end 11 of the endoscope body 1 and the target to be measured. The mounting end 11 of the endoscope body 1 is the end where the imaging device is mounted.

[0097] The following is a detailed description of the image resolution test and the distortion rate test.

[0098] The present invention also provides a device for testing image resolution. Figure 2 As shown, the image space resolution testing device includes an endoscope body 1 and a star icon target 2.

[0099] Among them, the star icon target 2 can be used as a special target pattern in the performance test or calibration of optical instruments. For example, when testing the imaging quality, resolution, distortion and other parameters of optical systems such as telescopes and camera lenses, the star icon target 2 can be used to more accurately evaluate the focusing and imaging of light in different directions and positions of the optical system, and the performance of the optical system can be judged by analyzing the imaging shape, size, brightness distribution and the like of the star points. The star icon target 2 can be, but is not limited to, a Siemens star icon target 2, etc., and no specific limitation is made here.

[0100] The spacing between the star icon target 2 and the endoscope body 1 is adjustable and can be adjusted as needed. Specifically, the endoscope body 1 and the grid test target 3 are arranged in a lateral spacing and perpendicular to the surface of the star icon target 2, so that the imaging surface of the imaging device is parallel to the star icon target 2.

[0101] The endoscope body 1 has a mounting end 11 close to the star icon target 2, and the mounting end 11 is provided with an imaging device and at least two lighting devices respectively arranged on both sides of the imaging device. Specifically, the light source received by the star icon target 2 can be uniform by adjusting the brightness of the lighting device.

[0102] The present invention also provides a method for testing image space resolution, and the method for testing image space resolution is performed using the above-mentioned image space resolution testing device. Figure 3 A schematic diagram illustrating a method for testing image-space resolution is shown.

[0103] like Figure 3 As shown, at step S1001, the star icon target 2 and the endoscope body 1 are placed on the test platform, and the endoscope body 1 or the star icon target 2 is adjusted so that the endoscope body 1 is perpendicular to the star icon target 2, and the imaging surface of the imaging device of the endoscope body 1 is set parallel to the star icon target 2.

[0104] At step S1002, the working distance between the endoscope body 1 and the star icon target 2 is changed to collect images of the star icon target 2 at different working distances. The adjusted working distance can be determined according to the depth of field standard claimed by the endoscope body 1. For example, if the depth of field standard claimed by the endoscope body 1 is 3-150mm, then the selected working distance can be 1mm, 2mm, 3mm, ..., 130mm, 150mm, etc. The interval of the part with a small working distance can be selected to be smaller. More specifically, the working distance can be selected to be 1mm, 2mm, 3mm, 4mm, 5mm, 7mm, 10mm, 20mm, 50mm, 70mm, 100mm, 130mm, 150mm. It should be noted that the target to be measured here is the star icon target 2.

[0105] At step 1003, the collected images of the star target 2 at different working distances are analyzed to obtain the modulation transfer function data. Specifically, the Imatest software can be used to read and analyze the collected images of the target to be measured at different distances to obtain the modulation transfer function MTF10 data, as shown in Table 1.

[0106] Table 1 MTF10 data obtained at different working distances

[0107]

[0108] The present invention also provides a distortion rate testing device, such as Figure 4 As shown, the image space resolution testing device includes a grid test target 3, an endoscope body 1, a monitor 5 and a processor 4.

[0109] The size of each grid on the grid test target 3 can be of different specifications, for example, Figure 5 As shown, the size of a single small grid on the grid test target 3 is a×a. The size of a single small grid on the grid test target can also be determined based on the distance between the mounting end 11 of the endoscope body 1 and the grid test target. Generally, the larger the distance between the mounting end 11 of the endoscope body 1 and the grid test target, the larger the size of a single small grid on the grid test target can be selected; of course, the larger the distance between the mounting end 11 of the endoscope body 1 and the grid test target, the smaller the size of a single small grid on the grid test target can be selected, but the amount of calculation will increase; when the distance between the mounting end 11 of the endoscope body 1 and the grid test target is smaller, the smaller the size of a single small grid on the grid test target can be selected, so that the number of grids on the image acquired by the endoscope body 1 can be guaranteed.

[0110] The spacing between the grid test target 3 and the endoscope body 1 is adjustable. In this way, when the size of a single small grid on the grid test target is constant, the number of grids of the grid test target 3 captured by the endoscope body 1 can be adjusted by adjusting the spacing between the grid test target 3 and the endoscope body 1.

[0111] In addition, the grid test target 3 can be moved in the up, down, left and right directions relative to the mounting end 11 of the endoscope body 1, so as to adjust the center of the grid test target 3 in the image acquired by the endoscope body 1 to be exactly in the middle of the image, which is convenient for subsequent calculations.

[0112] The endoscope body 1 is arranged with a lateral spacing from the grid test target 3 and is arranged perpendicular to the surface of the grid test target 3. The endoscope body 1 has a mounting end 11 close to the grid test target 3, and the mounting end 11 is provided with an imaging device. When it is necessary to capture the image of the grid test target 3, it can be captured by the imaging device. In addition, the mounting end 11 is also provided with a lighting device, which can cooperate with the imaging device to provide a clearer image to avoid the influence of limited light and affect the image quality. When it is necessary to capture the image of the grid test target 3, the position of the grid test target 3 can be adjusted first so that the central grid point of the grid test target 3 is in the middle of the captured image.

[0113] The monitor 5 is electrically connected to the imaging device. The monitor 5 is used to display the image of the grid test target 3 captured by the imaging device, and is also convenient for the operator to observe. When operating, the operator usually observes the image on the monitor 5 to choose how to adjust the position of the grid test target 3.

[0114] The processor 4 is electrically connected to the endoscope body 1. The processor 4 can obtain and store images taken by the imaging device. Figure 6 More specifically, the processor 4 includes a camera with a built-in camera function, and the camera captures the image captured by the imaging device and stores it; it may also include an external camera, and the image captured by the imaging device is captured by the external camera and sent to the processor 4 for storage. The specific setting can be selected as needed.

[0115] In addition, the processor 4 is also configured to perform analysis and processing based on the captured images and analyze the amount of endoscope optical imaging distortion.

[0116] The present invention also provides a testing method using the above-mentioned distortion rate testing device for testing. Figure 7 A flow chart showing the distortion rate testing method is shown.

[0117] like Figure 7 As shown, in step S101, the grid test target 3 is placed on the optical platform. At this time, the position of the grid test target 3 on the optical platform is adjustable. The grid test target 3 can be moved in the up-down direction, the left-right direction, and can also be moved forward and backward relative to the installation position of the endoscope body 1 to adjust the distance between the grid test target 3 and the endoscope body 1.

[0118] In step S102, the endoscope body 1 is placed on the optical platform, and the imaging surface of the imaging device at the mounting end 11 of the endoscope body 1 is adjusted so that the imaging surface is parallel to the grid test target 3. The step S102 may be preceded by placing the endoscope body 1 on the optical platform before step S101, and the specific method may be selected according to the operating habits. The imaging surface of the imaging device of the endoscope body 1 is parallel to the grid test target 3, so as to avoid the deviation of the captured image and affect the test results. Specifically, the grid test target 3 is placed in front of the imaging surface of the imaging device of the endoscope body 1, and the imaging surface is arranged parallel to the surface of the grid test target 3.

[0119] In step S103, the processor 4 and the monitor 5 are turned on. The image of the grid test target captured by the endoscope body 1 can be observed through the monitor 5, so as to adjust the grid test target to a suitable position.

[0120] In step S104, observe the image on the monitor 5, adjust the grid test target 3, make the mounting end 11 of the endoscope body 1 located at the center of the grid test target, and adjust the distance between the grid test target 3 and the mounting end 11 to the working distance. It can be that the position of the grid test target 3 in the up, down, left, and right directions is adjusted first so that the mounting end 11 of the endoscope body 1 is located at the center of the grid test target, and then the distance between the grid test target 3 and the mounting end 11 is adjusted; it can also be that the distance between the grid test target 3 and the mounting end 11 is adjusted first, and then the position of the grid test target 3 in the up, down, left, and right directions is adjusted so that the mounting end 11 of the endoscope body 1 is located at the center of the grid test target, and there is no limitation here. It should be noted that the working distance between the grid test target 3 and the mounting end 11 can be determined according to actual needs. For example, the working distance may be different in different application scenarios.

[0121] In step S105, the image captured by the imaging device is saved. The image of the grid test target 3 is captured by the imaging device and stored. Specifically, the processor 4 may include a shooting device with a built-in shooting function, and the image captured by the imaging device is shot by the shooting device and stored; or an external shooting device may be provided, and the image captured by the imaging device is shot by the external shooting device and sent to the processor 4 for storage. Figure 6 Schematically shows the first image of the grid test target 3 captured, Figure 6 The central grid point in is located in the middle of the first image.

[0122] It should be noted that the images captured by the imaging device at different working distances can be collected. Specifically, the working distance can be adjusted in step S104, and then step S105 can be executed to save the images captured by the imaging device at different working distances.

[0123] In addition, attention should be paid to the grid spacing of the grid test target 3, in order to avoid the situation where only the middle part of the grid test target 3 can be observed when the endoscope is too close, or too many grid intersections on the image obtained when the endoscope is too far away, resulting in excessive calculation, or insufficient number of grid intersections displayed when the endoscope is too far away. Multiple grid test targets 3 of different sizes can be selected to adapt to different test distances.

[0124] For example, three grid test targets 3 with different spacings may be selected, including a grid spacing of 1.5 mm × 1.5 mm, a grid spacing of 3 mm × 3 mm, and a grid spacing of 10 mm × 10 mm.

[0125] It is worth noting that the number of grid intersections on the images acquired at different working distances is different, and it is necessary to ensure that there are at least two grid intersections on both sides of the central grid point.

[0126] The present invention also provides a method for evaluating the distortion rate of endoscope optical imaging. Figure 8 A flow chart of a method for evaluating the distortion rate of endoscope optical imaging is shown.

[0127] like Figure 8 As shown, in step S201, first images at different working distances are respectively acquired. The first image is the first image of the grid test target 3 captured by the above-mentioned test method. It should be noted that the center position of the grid test target in the captured first image is in the middle of the first image, and the distance between the grid test target 3 and the mounting end 11 is the working distance. The first image at different working distances may be acquired by using grid test targets 3 with different spacings, or by using grid test targets 3 with the same spacing, which can be determined according to actual conditions. Assume that three grid test targets 3 with different grid spacings are used, and first images at different working distances are acquired respectively.

[0128] At step S202, pixel coordinate values ​​of grid intersections are read sequentially from the central grid point along the first direction to the edge for each first image. For each first image, steps S202 to S212 are used to calculate the MAG values ​​corresponding to different working distances at different grid spacings. The central grid point is the grid intersection located at the center of the first image. The first direction can be horizontal, vertical, or other directions, and the distortion rate in which direction is to be analyzed can be determined as needed. For example, if the distortion rate in the horizontal direction needs to be analyzed, the pixel coordinate values ​​of the grid intersections are sequentially obtained from the central grid point to the edge in the horizontal direction.

[0129] The pixel coordinate values ​​of the grid intersections may be obtained by reading the values ​​through automatic image reading software or manually, and no specific limitation is made here.

[0130] Fig. 9 and Fig.10 The schematic diagram of obtaining the pixel coordinate values ​​of the grid intersection is shown. Fig. 9 The schematic diagram of obtaining the pixel coordinate value of the 0th grid intersection point (center grid point) is shown. Fig.10 A schematic diagram of obtaining the pixel coordinate value of the first grid intersection point along the horizontal direction from the center grid point is shown. Fig. 9 and Fig.10 The lower left corner shows the corresponding pixel coordinate value. For example, the pixel coordinate value of the center grid point is (997,515), and the pixel coordinate value of the first grid intersection point along the horizontal direction from the center grid point is (1065,515). As shown in Table 2, Table 2 shows the original pixel coordinate values ​​of each grid intersection point along the horizontal direction. The grid intersection point with serial number 0 in Table 2 is the center grid point, and the grid intersection point with serial number 1 is the first grid intersection point along the horizontal direction from the center grid point, and so on.

[0131] Table 2 An embodiment of each grid intersection along the horizontal direction

[0132]

[0133] At step S203, the first coordinate transformation is performed to convert the pixel coordinate values ​​so that the pixel coordinates of the central grid point are zero, and the pixel coordinates of other grid intersections are adjusted in sequence. That is, the pixel coordinates of the central grid point are defined as (0,0), and the pixel coordinates of other grids are adjusted in sequence. More specifically, the pixel coordinates of the central grid point of each grid intersection are transformed to zero, and the pixel coordinate values ​​of other grid intersections are adjusted in sequence according to the pixel spacing with the central grid point.

[0134] Taking the pixel coordinate values ​​in Table 1 as an example, the adjusted pixel coordinate values ​​are shown in Table 3. More specifically, in the first coordinate transformation, after the pixel coordinate value of the central grid point is adjusted to (0,0), the coordinates of other grid intersection points are determined according to the pixel distance from the central grid point. For example, the pixel coordinate value of the first grid intersection point in Table 3 is (1065-997, 515-515), the pixel coordinate value of the second grid intersection point is (1137-997, 515-515), ..., and so on.

[0135] Table 3 Pixel coordinate values ​​of each grid intersection after adjustment

[0136]

[0137] At step S204, the pixel distance between each grid intersection and the central grid point is calculated in units of pixel numbers, which is recorded as Rd. The pixel distance between each grid intersection and the central grid point is calculated, that is, the distance between the grid intersection and the central grid point along the first direction. Taking the first direction as the horizontal direction as an example, when calculating the pixel distance between each grid intersection and the central grid point, the vertical coordinate is discarded and only the horizontal coordinate is taken. The pixel distance between the grid intersection and the central grid point is the horizontal coordinate of the grid intersection minus the horizontal coordinate of the central grid point. Table 4 illustrates the pixel distance between each grid intersection and the central grid point after adjusting the pixel coordinate values ​​in Table 3.

[0138] Table 4 Calculation of pixel distance

[0139]

[0140] In step S205, the grid distance Ru between each grid intersection and the central grid point is calculated in units of grid numbers. The grid distance between each grid intersection and the central grid point is the actual number of grids from each grid intersection to the central grid point. Table 5 shows the actual number of grids from each grid intersection in the horizontal direction in Table 2. The 15th grid intersection (sequence number 15 in Table 5) is not a complete integer grid point because it is at the image boundary. Therefore, the actual number of grids at the 15th grid intersection cannot be determined, and may be 14.5, 14.7, 14.8, etc.

[0141] Table 5 Grid distances between each grid intersection and the central grid point

[0142]

[0143] At step S206, the first data fitting is performed to form a first relational expression Ru=f(Rd) between Rd and Ru. The first relational expression between Rd and Ru is formed by data fitting. Specifically, a binary multivariate equation can be used for fitting, and each coefficient can be solved.

[0144] Table 6 Rd and Ru of each grid intersection

[0145]

[0146] Table 6 is an embodiment of the Rd and Ru of each grid intersection point obtained in the horizontal direction. Taking the data in Table 6 as an example, the following first relationship can be obtained by fitting:

[0147] ; (1)

[0148] Among them, the fitting accuracy R of formula (1) 2 >0.9999.

[0149] At step S207, the pixel coordinate Rd1 at the edge is substituted into the first relational expression to obtain Ru1. Taking Table 6 as an example, the Ru value of the 15th grid intersection (i.e., the sequence number is 15), i.e., Ru1, is unknown. At this time, Rd1 is known (Rd1 is 921). Then, Rd1 can be substituted into the first relational expression (here, equation (1)) to obtain Ru1. As shown in Table 7, Ru1 can be obtained to be 14.8.

[0150] Table 7 Updated Rd and Ru of each grid intersection

[0151]

[0152] The second coordinate transformation is performed at step S208. According to Rd1 and Ru1, the Rd and Ru of the grid intersections are normalized to obtain Rd' and Ru'. According to the grid distance and pixel distance of the outermost grid intersection, the Rd and Ru of the grid intersections are normalized. It can be understood that the grid distance and pixel distance of the outermost grid intersection are normalized, and the grid distance and pixel distance of the other grid intersections are adjusted in proportion. That is, the grid distance of each grid intersection is multiplied by (1 / Ru1), and the pixel distance of each grid intersection is multiplied by (1 / Rd1). Table 8 shows the Ru' and Rd' after normalization of each grid intersection in Table 7.

[0153] Table 8 Normalized Ru' and Rd' of each grid intersection

[0154]

[0155] At step S209, a second data fitting is performed to form a second relational expression Rd'=f(Ru') between Rd' and Ru'. The second relational expression Rd'=f(Ru') between Rd' and Ru' is formed by data fitting. Specifically, a binary multivariate equation can be used for fitting and each coefficient can be solved.

[0156] Fig.11 is the second relational expression formed by fitting the data in Table 8. Taking the data in Table 8 as an example, the second relational expression after fitting is:

[0157] ; (2)

[0158] In formula (2), x represents Ru' and y represents Rd'. The fitting accuracy R of formula (2) is 2 >0.9999.

[0159] At step S210, the third coordinate transformation is performed, and the real size coordinate values ​​of Rd' and Ru' in Rd'=f(Ru') are replaced to obtain Y=F(X), where X represents the real grid coordinate value of each grid intersection, and Y represents the actual size of each grid intersection on the imaging device.

[0160] Where X and Y are the actual size coordinates of Ru and Rd. It can also be understood that dX is the original physical size of the grid test target (for example, in mm), and dY is the actual shooting size of the image taken by the image sensor of the imaging device on its photosensitive surface (for example, in mm). Taking the actual size of each grid in the grid test target as a×a as an example, X is a×Ru, x=Ru'=Ru / Ru1, x=X / (a×Ru1); taking the single pixel size of the image sensor of the imaging device as b×b ​​as an example, Y is b×Rd, y=Rd'=Rd / Rd1, y=Y / (b×Rd1). Substituting x=X / (a×Ru1) and y=Y / (b×Rd1) into the second relationship, we get Y=F(X).

[0161] k y Y = y ∈ [0, 1] and k x Taking X=x∈[0,1] as an example, substituting it into equation (2), we get:

[0162] ; (3)

[0163] Formula (3) can be transformed into formula (4) as follows:

[0164] ; (4).

[0165] In step S211, Y=F(X) is differentially derived to obtain the distortion rate along the first direction. Taking the first direction as the horizontal direction as an example, for the imaging device of the endoscope body 1, for the same dX length, when moving from the center to the edge, the corresponding dX will gradually decrease (that is, the distortion becomes more and more serious), so it is necessary to use the horizontal distortion rate M LR To characterize the distortion rate from the center to the edge in the horizontal direction. When the first direction is other directions, the lateral distortion rate can be referred to, which will not be described in detail here.

[0166] Taking formula (4) as an example, M LR The calculation formula is:

[0167] ; (5)

[0168] Where x is Ru'.

[0169] For example, the actual size of each grid a×a is 3mm×3mm, and the size of a single pixel of the image sensor b×b is 2.8μm×2.8μm. x =1 / (a×Ru1)=1mm / (3*14.8)=0.02252mm, k y =1 / (b×Rd1)=1mm / (2.8*921 / 1000)=0.38778mm.

[0170] K x and k y Substituting into formula (5), we get:

[0171] ; (6)

[0172] The lateral distortion rate M at each grid intersection can be calculated by formula (6): LR , as shown in Table 9.

[0173] Table 9 Transverse distortion rate at each grid intersection

[0174]

[0175] MAG is calculated at step S212. As mentioned above, when calculating the distortion rate, the calculation point does not exceed the preset percentage of the total field of view. Specifically, assuming that the calculation point is the preset percentage of the total field of view, the first pixel of the total field of view at the preset percentage is calculated; based on the calculated first pixel, the normalized grid distance Ru' is solved; and then based on the normalized grid distance Ru', the corresponding distortion rate is calculated as MAG.

[0176] In this embodiment, the calculation point is 20% of the total field of view when calculating the distortion rate. 20% of the total field of view = 921 × 20% pixels = 184 pixels, that is, Rd is 184 pixels. The corresponding x can be obtained as 0.172. Substituting the value of x into formula (6) can solve the M corresponding to 184 pixels. LR It is 0.067.

[0177] It is worth noting that, as mentioned above, the number of grid intersections on the images obtained at different working distances is different, and it is necessary to ensure that there are at least two grid intersections on both sides of the central grid point. Too few grid intersections will result in failure to calculate; too many grid intersections will result in excessive calculation. Therefore, it is necessary to select multiple grid test targets 3 with different grid sizes.

[0178] When there are multiple selected grid test targets 3 and the grid spacings of the multiple grid test targets 3 are different, steps S202 to S212 are used for each first image to calculate the MAG values ​​corresponding to different working distances at different grid spacings, as shown in Tables 10 to 12. Table 10 shows the MAG at different working distances when the actual size of each grid of the grid test target 3 is 10 mm×10 mm. Table 11 shows the MAG at different working distances when the actual size of each grid of the grid test target 3 is 3 mm×3 mm. Table 12 shows the MAG at different working distances when the actual size of each grid of the grid test target 3 is 1.5 mm×1.5 mm.

[0179] More specifically, according to the distortion rate of the grid test target 3 with different grid spacings at different working distances, the local distortion rate of the grid test target 3 with different grid spacings at different working distances is calculated; the average values ​​of the local distortion rates of the grid test targets 3 with different grid spacings at the same working distance are calculated respectively; and the average value of the local distortion rate at the same working distance is used as the corresponding local distortion rate at the working distance.

[0180] In this embodiment, three grid test targets 3 with different grid sizes are selected; MAGs at different working distances are obtained respectively through the three grid test targets 3 with different grid sizes. Then, the average value of MAG at each working distance is calculated as the MAG value at the working distance, as shown in Table 13.

[0181] Table 10 MAG when the actual size of each grid is 10mm×10mm

[0182]

[0183] Table 11 MAG when the actual size of each grid is 3mm×3mm

[0184]

[0185] Table 12 MAG when the actual size of each grid is 1.5mm×1.5mm

[0186]

[0187] Table 13 Average values ​​of MAG for different actual mesh sizes at the same working distance

[0188]

[0189] More specifically, the MAG values ​​of multiple grid test targets 3 with different grid sizes at different working distances may be obtained, and then the MAG values ​​of all the grid test targets 3 at each working distance may be averaged.

[0190] Table 14 MTF at different working distances OBJ Calculation example

[0191]

[0192] Table 14 shows the MTF at different working distances. OBJ As mentioned above, the object space resolution MTF OBJ =MTF IMA ×MAG. Therefore, the MTF at different working distances can be calculated according to Table 1 and Table 13. OBJ , as shown in Table 14.

[0193] Usually choose MTF OBJ >20lp / mm near end distance and MTF OBJ The distal distance of >1lp / mm is taken as the critical value of the depth of field range. Then the depth of field of the endoscope is from the proximal distance to the distal distance. Table 14 shows the MTF at different distances OBJ All meet the requirements of the near end distance or the far end distance. For example, the depth of field standard claimed by the endoscope body 1 is 3-150mm, and the MTF corresponding to the working distance of 150mm OBJ The MTF is 1.3lp / mm, which meets the requirements of the far end distance (>1lp / mm). The working distance is 3mm. OBJ The 32.0lp / mm meets the near-end distance requirement (>20lp / mm).

[0194] The present invention also provides an evaluation device for endoscope optical depth of field, such as Fig.12 As shown, the evaluation device for the endoscope optical depth of field includes an acquisition unit 310 and an analysis unit 320 .

[0195] The acquisition unit 310 is used to respectively acquire the image resolution and the local distortion rate at different working distances;

[0196] The analysis unit 320 is used to calculate the object space resolution at different working distances according to the image space resolution and the local distortion rate at different working distances, wherein the object space resolution is calculated by the formula: object space resolution = image space resolution × distortion rate;

[0197] The analysis unit 320 is further used to adjust the endoscope body or the star icon target so that the endoscope body is perpendicular to the star icon target, and the imaging surface of the imaging device of the endoscope body is arranged parallel to the star icon target; change the working distance between the endoscope body and the star icon target, and collect images of the star icon target at different working distances; analyze the collected images of the star icon target at different working distances, and obtain modulation transfer function data, that is, image resolution;

[0198] The analysis unit 320 is also used to: respectively obtain first images of the grid test target at different working distances, wherein the imaging surface of the imaging device on the mounting end of the endoscope body is parallel to the grid test target, and the mounting end of the endoscope body is located at the center of the grid test target; calculate the distortion rate along the first direction for each first image; and calculate the local distortion rate based on the distortion rate and obtain the local distortion rate at different working distances.

[0199] In order to achieve the above object, the present invention also provides a computer device, such as Fig.13 As shown, the computer device includes at least one processor 401; and a memory 402 communicatively connected to the at least one processor 401; wherein the memory 402 stores instructions executable by the at least one processor 401, and the instructions are executed by the at least one processor 401 so that the at least one processor 401 can execute the above-mentioned method for evaluating the endoscopic optical depth of field.

[0200] The memory 402 and the processor 401 are connected in a bus manner, and the bus may include any number of interconnected buses and bridges, and the bus connects various circuits of one or more processors 401 and the memory 402 together. The bus can also connect various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and are therefore not further described herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be one element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices on a transmission medium. The data processed by the processor 401 is transmitted on a wireless medium via an antenna, and further, the antenna also receives data and transmits the data to the processor 401.

[0201] The processor 401 is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interfaces, voltage regulation, power management and other control functions. The memory 402 can be used to store data used by the processor 401 when performing operations.

[0202] In order to achieve the above object, the present invention provides a computer-readable storage medium storing a computer program, wherein the computer program implements the above-mentioned method for evaluating the optical depth of field of an endoscope when executed by a processor.

[0203] That is, those skilled in the art can understand that all or part of the steps in the above-mentioned implementation method can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions to enable a device (which can be a single-chip microcomputer, chip, etc.) or a processor to execute all or part of the steps of the method described in each implementation of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0204] Obviously, the embodiments described above are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, ordinary technicians in this field can make other different forms of changes or modifications without creative work, which should fall within the scope of protection of the present invention.

Claims

1. A method for evaluating the optical depth of field of an endoscope, characterized in that: include: Obtain the image resolution and local distortion rate at different working distances respectively; According to the image resolution and local distortion rate at different working distances, the object resolution at different working distances is calculated. The object resolution is calculated as follows: object resolution = image resolution × distortion rate. OBJ >20lp / mm near end distance and MTF OBJ The distal distance of >1lp / mm was used as the cutoff value of the depth of field range; Among them, the method for obtaining the image resolution at different working distances includes: Adjust the endoscope body or the star icon target so that the endoscope body is perpendicular to the star icon target, and the imaging surface of the imaging device of the endoscope body is arranged parallel to the star icon target; Changing the working distance between the endoscope body and the star icon target, and collecting images of the star icon target at different working distances; Analyze the images of the star target collected at different working distances to obtain the modulation transfer function data, that is, the image resolution; Methods for obtaining local distortion rates at different working distances include: Acquire first images of the grid test target at different working distances respectively, wherein the imaging surface of the imaging device on the mounting end of the endoscope body is parallel to the grid test target, and the mounting end of the endoscope body is located at the center of the grid test target; Calculating the distortion rate along the first direction for each first image; According to the distortion rate, the local distortion rate is calculated and the local distortion rates at different working distances are obtained.

2. The method for evaluating the endoscope optical depth of field according to claim 1, characterized in that: The step of calculating the distortion rate along the first direction for each first image includes: According to each first image, pixel coordinate values ​​of each grid intersection point of the first image along a first direction from a central grid point are obtained, wherein the central grid point is a grid intersection point located at the center of the first image; According to the pixel coordinate values, the pixel distance and the grid distance between each grid intersection and the central grid point are calculated in units of pixel number and grid number respectively; According to the calculated pixel distance and grid distance, a first relational expression between the pixel distance and the grid distance is obtained; Calculate the first grid distance of the edge grid point according to the first relational expression and the first pixel distance of the edge grid point in each grid intersection, wherein the edge grid point is the outermost grid intersection on the side opposite to the central grid point along the first direction of each grid intersection; Normalizing the pixel distance and the grid distance of each grid intersection according to the first pixel distance and the first grid distance; According to the normalized pixel distance and grid distance of each grid intersection, a second relational expression of the normalized pixel distance and grid distance is established; Generate a third relational expression between the real grid coordinate value of each grid intersection and the actual size on the imaging device according to the second relational expression and the real size coordinate value of each grid intersection; According to the third relationship, the distortion rate of the first image along the first direction is calculated.

3. The method for evaluating the endoscope optical depth of field according to claim 2, characterized in that: The first relationship between the pixel distance and the grid distance is obtained according to the calculated pixel distance and grid distance, including: According to the calculated pixel distance and grid distance, a first relational expression Ru=f(Rd) of the pixel distance and grid distance is obtained by fitting, wherein the first relational expression is a two-variable multi-time equation; Ru is the grid distance between each grid intersection and the central grid point; Rd is the pixel distance between each grid intersection and the central grid point; The calculating the first grid distance of the edge grid point according to the first relational expression and the first pixel distance of the edge grid point at each grid intersection includes: Substitute the first pixel distance of the edge grid point into the first relational expression Ru=f(Rd) to calculate the first grid distance Ru1 of the edge grid point.

4. The method for evaluating the endoscope optical depth of field according to claim 3, characterized in that: The step of establishing a second relational expression of normalized pixel distance and grid distance according to the normalized pixel distance and grid distance of each grid intersection includes: According to the normalized pixel distance Rd' and grid distance Ru' of each grid intersection, a second relational expression Rd'=f(Ru') of the normalized pixel distance and grid distance is obtained by fitting, wherein the second relational expression is a two-variable multi-time equation; Where Rd' is the normalized pixel distance of each grid intersection, Rd'=Rd / Rd1; Ru' is the normalized grid distance of each grid intersection, Ru'=Ru / Ru1; Rd1 is the pixel coordinate value of the outermost grid point.

5. The method for evaluating the endoscope optical depth of field according to claim 2, wherein: The step of generating a third relational expression of the real grid coordinate value of each grid intersection and the actual size on the imaging device according to the second relational expression and the real size coordinate value of each grid intersection includes: When the actual size of each grid on the grid test target is a×a and the size of a single pixel of the image sensor of the imaging device is b×b, Y is the actual size of each grid intersection on the imaging device, Y=b×Rd=b×Rd'×Rd1; X is the actual grid coordinate value of each grid intersection, X=a×Ru=a×Ru'×Ru1; Substituting X and Y into the second relational expression Rd'=f(Ru'), the third relational expression Y=F(X) is obtained.

6. The method for evaluating the endoscope optical depth of field according to claim 2, wherein: Calculating the distortion rate of the first image along the first direction according to the third relationship includes: The third relationship Y=F(X) is differentially derived to obtain the distortion rate of the first image along the first direction.

7. The method for evaluating the endoscope optical depth of field according to claim 2, wherein: The calculating the local distortion rate according to the distortion rate and obtaining the local distortion rate at different working distances includes: Calculate the first pixel when the total field of view is at a preset percentage at different working distances; According to the calculated first pixel, solve the normalized grid distance Ru'; According to the normalized grid distance Ru', the distortion rate is calculated as the local distortion rate at the working distance.

8. The method for evaluating the endoscope optical depth of field according to claim 1, wherein: The first images are multiple, and the multiple first images are multiple images at different working distances respectively acquired by using a grid test target with different grid spacings; The calculating the local distortion rate according to the distortion rate and obtaining the local distortion rate at different working distances includes: According to the distortion rates of the grid test targets with different grid spacings at different working distances, the local distortion rates of the grid test targets with different grid spacings at different working distances are calculated; Calculate the average value of the local distortion rate of the grid test targets with different grid spacings at the same working distance; The average value of the local distortion rate at the same working distance is taken as the local distortion rate corresponding to the working distance.

9. An evaluation device for endoscope optical depth of field, characterized in that: include: An acquisition unit, used for respectively acquiring image resolution and local distortion rate at different working distances; The analysis unit is used to calculate the object space resolution at different working distances according to the image space resolution and the local distortion rate at different working distances. The object space resolution is calculated as follows: object space resolution = image space resolution × distortion rate. The object space resolution MTF OBJ >20lp / mm near end distance and MTF OBJ The distal distance of >1lp / mm was used as the cutoff value of the depth of field range; Wherein, the analysis unit is also used for: Adjust the endoscope body or the star icon target so that the endoscope body is perpendicular to the star icon target, and the imaging surface of the imaging device of the endoscope body is arranged parallel to the star icon target; Changing the working distance between the endoscope body and the star icon target, and collecting images of the star icon target at different working distances; Analyze the images of the star target collected at different working distances to obtain the modulation transfer function data, that is, the image resolution; The analysis unit is also used for: Acquire first images of the grid test target at different working distances respectively, wherein the imaging surface of the imaging device on the mounting end of the endoscope body is parallel to the grid test target, and the mounting end of the endoscope body is located at the center of the grid test target; Calculating the distortion rate along the first direction for each first image; According to the distortion rate, the local distortion rate is calculated and the local distortion rates at different working distances are obtained.

10. A computer device, characterized in that: include: at least one processor; as well as, a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method for evaluating the endoscope optical depth of field as described in any one of claims 1 to 8.

11. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for evaluating the endoscope optical depth of field according to any one of claims 1 to 8 is implemented.

Images