WO2023202255A1 - Convenient rapid contrast sensitivity test system - Google Patents

Abstract

A convenient rapid contrast sensitivity test system, comprising a test end and a computation end. The test end is connected to the computation end. The test end is used for generating and presenting an optotype to a subject, collecting a "visible-or-not" feedback and physical information of the subject to adjust an optotype generation parameter, and finally obtaining a next optotype parameter by means of a feedback result. The computation end provides requirements such as a hashrate, storage, an algorithm, and parallel computing control required for optotype recommendation. The interaction mode is improved, the test accuracy is guaranteed, a higher test speed is achieved by redesigning the interaction mode, and the test can be completed within one or two minutes. The intervention of medical personnel is not needed, the subject can independently complete interaction, and the result is objective. The system may also be used in cooperation with a mobile device such as a tablet for portable testing, thereby facilitating out-of-hospital test for a doctor.

Description

A convenient and fast contrast sensitivity detection system Technical field

The present invention relates to the field of vision contrast sensitivity detection, and more specifically, to a convenient and fast contrast sensitivity detection system.

Background technique

Visual acuity reflects the ability of the fovea to resolve small objects under high-contrast conditions. However, most of the visual information in life is not high-contrast. Reflecting visual function requires a comprehensive evaluation of contrast sensitivity at different spatial frequencies. Contrast sensitivity is a new method that measures the black-and-white contrast (contrast) on an object surface required when the visual system recognizes the spatial frequencies (cycles/degrees) of objects of different sizes. It is used to evaluate the visual system's ability to resolve objects of different sizes. Methods for quantitative examination of visual function. Contrast sensitivity can not only be used to evaluate a variety of eye diseases, including optic nerve damage, amblyopia, macular disease, retinopathy, glaucoma, etc., but can also be used to evaluate other diseases, such as stroke and other brain diseases, and diabetes and other metabolic diseases. , the visual dysfunction caused by it is evaluated as one of the means of treatment prognosis evaluation.

Contrast is generally evaluated by contrast threshold, which refers to the minimum difference in brightness that can be distinguished between an object and its background. We often use the reciprocal of the contrast threshold, that is, contrast sensitivity (CS), to describe the subject's ability to distinguish contrast. The contrast sensitivity function (CSF) can describe the CS at each spatial frequency. Currently, contrast sensitivity is usually tested clinically using letter/raster charts, and the general testing time takes about an hour. Optimization algorithms based on Bayesian estimation that have appeared in recent years have shortened the detection process to about ten minutes. The long detection time results in low overall detection efficiency, which limits its promotion and application. The biggest bottleneck lies in the cumbersome interaction between the system and the subjects. (1) The keyboard answer method requires the subjects to observe the visual mark and then find the corresponding keys on the keyboard. One answer usually takes more than 10 seconds; (2) The test requires medical care. Personnel assists in completing the guidance, which limits the detection efficiency. At the same time, the existing technology generally requires the use of larger light panels or monitors and other equipment, and patients need to go to the hospital for examination. Therefore, rapid detection methods, relying on portable display devices, and better interaction methods are the basis for the wide application of contrast sensitivity detection.

The prior art discloses a dynamic contrast sensitivity test system and a test method thereof. The test system includes a test computer, a screen, a determiner and a control panel. The screen is used to display dynamic gratings; the determiner is used for the subject to determine the The direction of the raster movement displayed; the control panel is used to adjust the contrast, space, and frequency and movement speed; the test computer is used to run the dynamic contrast sensitivity detection program to display the dynamic grating, receive the direction in which the determiner is pressed and determine whether it is correct or wrong, and receive control information from the control panel; the test computer is set up with dynamic contrast Sensitivity detection program, dynamic contrast sensitivity detection program has dynamic sine grating display function, automatic adjustment function, contrast fast switching function, spatial frequency fast switching function, motion speed fast switching function, automatic test function, automatic test data storage function, test Automatic result output function and automatic drawing function of dynamic contrast sensitivity curve. The interactive method in this solution is time-consuming, and the device is relatively large and cannot be carried portablely.

Contents of the invention

The present invention provides a convenient and fast contrast sensitivity detection system, which achieves faster detection speed by improving the interaction method.

In order to solve the above technical problems, the technical solutions of the present invention are as follows:

A convenient and fast contrast sensitivity detection system, including a detection end and a calculation end, and the detection end is connected to the calculation end, wherein:

The detection end includes a display module, a detection control module and a sensor/input module. The display module is used to display the optotype generated by the detection control module. The detection control module contacts the sensor/input module to obtain the physical characteristics of the subject. Information and optotype visible feedback results, based on the optotype parameters and the physical information of the subject obtained by the sensor/input module, the corresponding optotype is generated, and the next optotype parameter is obtained from the computing end based on the optotype visible feedback result, and the cycle continues until the end of the test;

The computing end includes a computing control module, a storage module and a visual mark recommendation module. The computing control module is used to interface with the information of the detection end and allocate and control multi-process tasks. The storage module records all detected results of the subject. As a result, the visual target recommendation module calculates the next detection point that is optimal for the detection progress and the current detection result based on the subject's detection records.

Preferably, the display module is used to display the optotype generated by the detection control module, specifically:

The optotype generated by the detection control module is randomly displayed in the central gaze area of the visual field. The central gaze area of the visual field is defined by the circular area in the center of the display module. The diameter of the circular area is calculated by:

Among them, the width of the screen resolution is automatically obtained by the detection control module of the detection end, and the viewing angle is set in the settings before the test starts. This value is the human central visual field range, ranging from 3 to 7 degrees; the physical width of the screen refers to the display module The lateral distance of the screen; the screen distance is the distance from the screen of the display module to the subject's eyes;

The method for obtaining the random display position of the visual target is through the polar coordinate system P(ρ, θ) relative to the center of the viewing angle range, where ρ is called the polar diameter of point P, and θ is called the polar angle of point P. This polar coordinate system The polar diameter and polar angle obtain random values respectively, thereby obtaining the coordinates (X, Y) randomly displayed on the screen.

Preferably, the optotypes include digital optotypes and raster optotypes. The generation process of the two optotypes is as follows:

For digital optotypes, use 0-9 as the benchmark digital optotype, perform contrast filtering on the benchmark digital optotype to generate digital optotypes with different contrasts, and then adjust the size of the optotype according to the spatial frequency;

For grating optotypes, the grating density is calculated based on the spatial frequency value, the brightness and dark area grayscale values of the grating are calculated based on the contrast, and grating optotypes with different orientations are randomly generated.

Preferably, the size of the visual target changes as the distance between the subject's eyes and the display module changes.

Preferably, the visual target changes as the subject's distance from the display module changes, specifically as follows:

Obtain the distance from the subject's eyes to the display module;

The computing end transmits the spatial frequency and contrast back to the detection control module of the detection end;

The detection control module at the detection end calculates the size of the visual target based on the spatial frequency and contrast returned in real time by the computing end and the distance between the subject's eyes and the display module obtained in real time, and adjusts the visual target and background based on the contrast returned by the computing end. The grayscale difference is pushed to the display module in real time for display. The size of the optotype is calculated as follows:

Among them, the optotype constant is set during the design of the optotype, ranging from 1 to 9; the screen distance is the distance from the subject's eyes to the screen of the display module.

Preferably, the following method is used to obtain the distance from the subject's eyes to the display module:

On small devices, the tof camera/arkit/arcore on the hardware is directly used as the distance measurement to directly obtain the distance from the screen of the display module to the subject's eyes.

Preferably, the following method is used to obtain the distance from the subject's eyes to the display module:

Use the principle of similar triangles to measure the distance from the screen of the display module to the human eye on a device with a front camera. The specific steps are:

Obtain the focal length of the front camera or manually determine the focal length of the front camera;

Capture the subject’s face through the front camera;

Perform iris recognition on the obtained facial image of the subject, segment the iris from the image, and calculate the iris diameter;

Using the similar triangle theorem, it can be seen that the relationship between the focal length of the camera, the diameter of the human eye's iris, the diameter of the iris in the image and the screen distance is:

Among them, the iris diameter of the human eye adopts a fixed value of 11.7mm;

It can be seen that the calculation method of screen distance is:

The screen distance is the distance from the subject's eyes to the screen of the display module.

Preferably, the visual target recommendation module is connected to the fast contrast sensitivity open source algorithm, including the qcsf algorithm implemented based on Bayesian estimation and the recommendation algorithm implemented based on deep learning, and calculates the next detection progress based on the subject's detection records. The optimal detection point and the current detection results.

A method of using the above-mentioned rapid contrast sensitivity detection system, including the following steps:

Before the test, the subject adjusts the system default parameters according to the actual situation, including the form of the visual mark, the angle of view, the physical width of the screen and the distance between the screen;

According to the parameters set by the subject, the range in which the visual target appears is calculated;

The subject observes the optotypes on the screen and clicks on the optotypes visible to the naked eye;

If the optotype on the screen is clicked by the subject, the optotype recommendation module of the computer recommends the next optotype, and the appearance principle of this optotype is:

a. The position is uniform and random;

b. Does not overlap with other visual targets on the screen;

c. Located within the viewing angle range;

If the optotype on the screen is not clicked by the subject after the survival time has expired, it will automatically disappear; the computer module recommends the next optotype;

The number of optotypes within the viewing angle range on the above screen always remains the same, and this number can be set by the subject.

Preferably, during the subject's testing process, the subject's cooperation with the test is also evaluated. The evaluation method is specifically:

The display positions of the optotypes are uniformly and randomly distributed, and when the subject cooperates with the test, the click positions are also uniformly distributed. When the number of clicks by the subject is much more than the number of times the optotype is displayed, the click locations of the subjects are unevenly distributed. , then it is assessed that the current subject is not cooperating with the test.

Compared with the existing technology, the beneficial effects of the technical solution of the present invention are:

Compared with previous technologies, the present invention improves the interaction method to ensure detection accuracy. By redesigning the interaction mode, it achieves faster detection speed and can complete the detection in one or two minutes. At the same time, the interaction of the present invention does not require the intervention of medical personnel, and the subjects can complete it independently, and the results are objective. The present invention can also be used with mobile devices such as tablets for portable examination, making it convenient for doctors to conduct examinations outside the hospital.

Description of the drawings

Figure 1 is a schematic diagram of the system module of the present invention.

Figure 2 is a schematic diagram of the digital visual mark of the present invention.

Figure 3 is a schematic diagram of the grating sight mark of the present invention.

Figure 4 is a schematic diagram of the range in which the optotype of the present invention appears.

Figure 5 is a schematic diagram of digital visual targets with different contrast ratios according to the present invention.

Figure 6 is a schematic diagram of the subject observing the optotype on the screen.

Figure 7 is a test contrast sensitivity curve provided by the embodiment.

FIG. 8 is a schematic diagram of the principle of measuring the distance from the screen to the human eye based on the similar triangle principle according to the embodiment.

Detailed ways

The drawings are for illustrative purposes only and should not be construed as limitations of this patent;

In order to better illustrate this embodiment, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product;

It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

The technical solution of the present invention will be further described below with reference to the accompanying drawings and examples.

Example 1

This embodiment provides a convenient and fast contrast sensitivity detection system, as shown in Figure 1, including detection terminal and computing terminal, and the detection terminal is connected to the computing terminal, where:

The detection end includes a display module, a detection control module and a sensor/input module. The display module is used to display the optotype generated by the detection control module. The detection control module contacts the sensor/input module to obtain the physical characteristics of the subject. Information and optotype visible feedback results, based on the optotype parameters and the physical information of the subject obtained by the sensor/input module, the corresponding optotype is generated, and the next optotype parameter is obtained from the computing end based on the optotype visible feedback result, and the cycle continues until the end of the test;

The computing end includes a computing control module, a storage module and a visual mark recommendation module. The computing control module is used to interface with the information of the detection end and allocate and control multi-process tasks. The storage module records all detected results of the subject. As a result, the visual target recommendation module calculates the next detection point that is optimal for the detection progress and the current detection result based on the subject's detection records.

The detection end and computing end are connected through common physical connection methods, including but not limited to local machine, LAN/WIFI, Ethernet, mobile network and other connection methods.

Example 2

Based on Embodiment 1, this embodiment continues to provide the following content:

The display module is used to display the visual target generated by the detection control module, specifically:

The optotype generated by the detection control module is randomly displayed in the central gaze area of the visual field. The central gaze area of the visual field is defined by the circular area in the center of the display module. As shown in Figure 4, the diameter calculation method of the circular area is:

Among them, the width of the screen resolution is automatically obtained by the detection control module of the detection end, and the viewing angle is set in the settings before the test starts. This value is the human central visual field range, ranging from 3 to 7 degrees; the physical width of the screen refers to the display module The lateral distance of the screen; the screen distance is the distance from the screen of the display module to the subject's eyes;

The method for obtaining the random display position of the visual target is through the polar coordinate system P(ρ, θ) relative to the center of the viewing angle range, where ρ is called the polar diameter of point P, and θ is called the polar angle of point P. This polar coordinate system The polar diameter and polar angle obtain random values respectively, thereby obtaining the coordinates (X, Y) randomly displayed on the screen.

The optotypes include digital optotypes and raster optotypes. The generation process of the two optotypes is as follows:

For digital optotypes, use 0-9 as the benchmark digital optotype, as shown in Figure 2. Contrast filtering is performed on the benchmark digital optotype to generate digital optotypes with different contrasts, as shown in Figure 5. After adjusting according to the spatial frequency The size of the visual target;

For the grating optotype, the grating density is calculated based on the spatial frequency value, the brightness and dark area grayscale value of the grating are calculated based on the contrast, and grating optotypes with different orientations are randomly generated, as shown in Figure 3.

The size of the optotype changes as the distance between the subject's eyes and the display module changes.

Existing contrast sensitivity testing equipment is generally a larger light panel or display device, and subjects need to go to the hospital for testing. Therefore, the contrast sensitivity rapid testing method relies on portable display equipment and is portable for inspection. It is suitable for more Multiple scenes.

However, compared with traditional testing instruments, when using smaller display devices for testing, the visual distance of the human eye will be reduced, so contrast sensitivity testing needs to be performed closer to the screen. However, when the screen distance is small, Under such circumstances, the swing of the human body will have a great impact on the accuracy of detection. Therefore, the present invention proposes a miniaturized design method for contrast sensitivity detection equipment. This method consists in designing an automatic measurement method for dynamically obtaining the screen distance on a miniaturized device, and a method for adjusting the size of the optotype in real time, thereby eliminating the contrast sensitivity detection error caused by the screen distance and realizing a rapid contrast sensitivity detection system. Miniaturization and portability make it suitable for more scenarios besides hospitals.

Based on the screen size of the device used during detection and the distance between the subject and the screen, this method can be applied to different scenarios. When the distance is far, a device with a larger screen is generally used so that the subject can see the visual mark clearly. .

The visual target changes as the subject's distance from the display module changes, specifically as follows:

Obtain the distance from the subject's eyes to the display module;

The computing end transmits the spatial frequency and contrast back to the detection control module of the detection end;

The detection control module at the detection end calculates the size of the visual target based on the spatial frequency and contrast returned in real time by the computing end and the distance between the subject's eyes and the display module obtained in real time, and adjusts the visual target and background based on the contrast returned by the computing end. The grayscale difference is pushed to the display module in real time for display. The size of the optotype is calculated as follows:

Among them, the optotype constant is set during the design of the optotype, ranging from 1 to 9; the screen distance is the distance from the subject's eyes to the screen of the display module.

To obtain the distance from the subject's eyes to the display module, the following method is adopted:

On small devices, the tof camera/arkit/arcore on the hardware is directly used as the distance measurement to directly obtain the distance from the screen of the display module to the subject's eyes.

To obtain the distance from the subject's eyes to the display module, the following method is adopted:

Use the principle of similar triangles to measure the distance from the screen of the display module to the human eye on a device with a front camera. The specific steps are:

Obtain the focal length of the front camera or manually determine the focal length of the front camera;

Capture the subject’s face through the front camera;

Perform iris recognition on the obtained facial image of the subject, segment the iris from the image, and calculate the iris diameter;

Using the similar triangle theorem, it can be seen that, as shown in Figure 8, the relationship between the focal length of the camera, the diameter of the human eye's iris, the diameter of the iris in the image and the screen distance is:

Among them, the iris diameter of the human eye adopts a fixed value of 11.7mm;

It can be seen that the calculation method of screen distance is:

The screen distance is the distance from the subject's eyes to the screen of the display module.

Optotypes are also divided into static optotypes and dynamic optotypes. The size of the static optotypes does not change with the change of distance, and the size of the dynamic optotypes changes with the change of distance. When the distance between the subject and the screen is close (less than 0.6m) ) scene is presented to the subject using dynamic optotypes; the subject can use one of the interactive methods of touch, mouse click, and eye tracking to conduct contrast sensitivity detection. When the subject is far away from the screen (greater than 0.6m), a static optotype can be used to present it to the subject; the subject can use an interactive method of mouse clicks. Contrast sensitivity detection using the formula.

The visual target recommendation module is connected to the fast contrast sensitivity open source algorithm, including the qcsf algorithm based on Bayesian estimation and the recommendation algorithm based on deep learning. Based on the test record of the subject, it calculates the next optimal method for the detection progress. Testing points and current test results.

Example 3

This embodiment provides a method for using the rapid contrast sensitivity detection system described in Embodiment 1 and 2, specifically:

Before the subject is re-examined, the system default parameters, including optotype form, viewing angle, screen physical width and screen distance, should be adjusted according to the actual situation;

According to the parameters set by the subject, the range in which the visual target appears is calculated;

The subject observes the optotypes on the screen, as shown in Figure 6, and clicks on the optotypes visible to the naked eye;

If the optotype on the screen is clicked by the subject, the optotype recommendation module of the computer recommends the next optotype, and the appearance principle of this optotype is:

a. The position is uniform and random;

b. Does not overlap with other visual targets on the screen;

c. Located within the viewing angle range;

If the optotype on the screen is not clicked by the subject after the survival time has expired, it will disappear automatically (usually the disappearance time is set to more than 3 seconds to eliminate the interference of human body reaction and movement on the detection. If there are subjects with limited mobility, If necessary, the disappearing time can be increased as appropriate); the computer module recommends the next visual target, which is the same as the above-mentioned visual target appearance principle;

The number of optotypes within the viewing angle range on the above screen always remains the same, and this number can be set by the subject;

The subject keeps clicking until the number of tests is completed, and the test contrast sensitivity curve appears on the screen, as shown in Figure 7. The abscissa is the spatial frequency, the ordinate is the sensitivity (1/contrast), and the curve is the contrast sensitivity curve. By clicking the previous/next button, you can see the changes in the contrast sensitivity curve as the detection process progresses.

There are three direct interaction methods between the subject and the system mentioned above. Different interaction methods are selected according to different application scenarios and actual needs.

(1) When using a tablet for contrast sensitivity testing, you can interact by touching and clicking. The subject can directly interact with the system by touching the visual target visible to the naked eye on the screen with his finger. Interaction;

(2) When using a computer to perform contrast sensitivity testing, the subject interacts directly with the system by clicking the mouse on an optotype visible to the naked eye on the screen;

(3) When using a tablet or computer to conduct contrast sensitivity testing, you can choose to interact through eye tracking. The subject can directly interact with the system by staring at an optotype visible to the naked eye on the screen;

Through the direct interaction between the subject and the system, the present invention only needs to click on the visual target visible to the naked eye during the entire process, without considering the attributes of the visual target in the previous detection process, saving the pause time when the visual target is difficult to identify, and solving the problem This solves the problem that in the past, the optotype display process that required segmentation and grouping could not be detected continuously and quickly. Without the assistance of a doctor, the subject can complete the contrast sensitivity test by himself, thus shortening the detection time and achieving a smooth and efficient detection process.

Example 4

On the basis of Embodiment 3, this embodiment also evaluates the subject's cooperation with the test during the subject's detection process. The evaluation method is specifically as follows:

The display positions of the optotypes are uniformly and randomly distributed, and when the subject cooperates with the test, the click positions are also uniformly distributed. When the number of clicks by the subject is much more than the number of times the optotype is displayed, the click locations of the subjects are unevenly distributed. , then it is assessed that the current subject is not cooperating with the test.

The above operation process is to prevent the impact of the subject's random clicks and failure to cooperate with the test on the results. By recording the user input position and analyzing the distribution of click areas, the subject's cooperation in the test is evaluated.

The same or similar numbers correspond to the same or similar parts;

The terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limitations to this patent;

Obviously, the above-mentioned embodiments of the present invention are only examples to clearly illustrate the present invention, and are not intended to limit the implementation of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. An exhaustive list of all implementations is neither necessary nor possible. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (10)

A convenient and fast contrast sensitivity detection system, which is characterized in that it includes a detection end and a calculation end, and the detection end is connected to the calculation end, wherein: The detection end includes a display module, a detection control module and a sensor/input module. The display module is used to display the optotype generated by the detection control module. The detection control module contacts the sensor/input module to obtain the physical characteristics of the subject. Information and optotype visible feedback results, based on the optotype parameters and the physical information of the subject obtained by the sensor/input module, the corresponding optotype is generated, and the next optotype parameter is obtained from the computing end based on the optotype visible feedback result, and the cycle continues until the end of the test; The computing end includes a computing control module, a storage module and a visual mark recommendation module. The computing control module is used to interface with the information of the detection end and allocate and control multi-process tasks. The storage module records all detected results of the subject. As a result, the visual target recommendation module calculates the next detection point that is optimal for the detection progress and the current detection result based on the subject's detection records. The convenient and fast contrast sensitivity detection system according to claim 1, wherein the display module is used to display the optotype generated by the detection control module, specifically: The optotype generated by the detection control module is randomly displayed in the central gaze area of the visual field. The central gaze area of the visual field is defined by the circular area in the center of the display module. The diameter of the circular area is calculated by:

Among them, the width of the screen resolution is automatically obtained by the detection control module of the detection end, and the viewing angle is set in the settings before the test starts. This value is the human central visual field range, ranging from 3 to 7 degrees; the physical width of the screen refers to the display module The lateral distance of the screen; the screen distance is the distance from the screen of the display module to the subject's eyes; The method for obtaining the random display position of the visual target is through the polar coordinate system P(ρ, θ) relative to the center of the viewing angle range, where ρ is called the polar diameter of point P, and θ is called the polar angle of point P. This polar coordinate system The polar diameter and polar angle obtain random values respectively, thereby obtaining the coordinates (X, Y) randomly displayed on the screen. The convenient and fast contrast sensitivity detection system according to claim 2, characterized in that: The above-mentioned optotypes include digital optotypes and raster optotypes. The generation process of the two types of optotypes is as follows: For digital optotypes, use 0-9 as the benchmark digital optotype, perform contrast filtering on the benchmark digital optotype to generate digital optotypes with different contrasts, and then adjust the size of the optotype according to the spatial frequency; For grating optotypes, the grating density is calculated based on the spatial frequency value, the brightness and dark area grayscale values of the grating are calculated based on the contrast, and grating optotypes with different orientations are randomly generated. The convenient and fast contrast sensitivity detection system according to claim 3, characterized in that the size of the visual target changes as the distance from the subject's eyes to the display module changes. The convenient and fast contrast sensitivity detection system according to claim 4, characterized in that the visual target changes as the distance between the subject and the display module changes, specifically: Obtain the distance from the subject's eyes to the display module; The computing end transmits the spatial frequency and contrast back to the detection control module of the detection end; The detection control module at the detection end calculates the size of the visual target based on the spatial frequency and contrast returned in real time by the computing end and the distance between the subject's eyes and the display module obtained in real time, and adjusts the visual target and background based on the contrast returned by the computing end. The grayscale difference is pushed to the display module in real time for display. The size of the optotype is calculated as follows:
Among them, the optotype constant is set during the design of the optotype, ranging from 1 to 9; the screen distance is the distance from the subject's eyes to the screen of the display module. The convenient and fast contrast sensitivity detection system according to claim 5, characterized in that the following method is used to obtain the distance from the subject's eyes to the display module: On small devices, the tof camera/arkit/arcore on the hardware is directly used as the distance measurement to directly obtain the distance from the screen of the display module to the subject's eyes. The convenient and fast contrast sensitivity detection system according to claim 5, characterized in that the following method is used to obtain the distance from the subject's eyes to the display module: Use the principle of similar triangles to measure the distance from the screen of the display module to the human eye on a device with a front camera. The specific steps are: Obtain the focal length of the front camera or manually determine the focal length of the front camera; Capture the subject’s face through the front camera; Perform iris recognition on the obtained facial image of the subject, segment the iris from the image, and calculate the iris diameter; Using the similar triangle theorem, it can be seen that the relationship between the focal length of the camera, the diameter of the human eye's iris, the diameter of the iris in the image and the screen distance is:
Among them, the iris diameter of the human eye adopts a fixed value of 11.7mm; It can be seen that the calculation method of screen distance is:
The screen distance is the distance from the subject's eyes to the screen of the display module. The convenient fast contrast sensitivity detection system according to claim 6 or 7, characterized in that the optotype recommendation module is connected to a fast contrast sensitivity open source algorithm, including a qcsf algorithm based on Bayesian estimation and a deep learning-based algorithm. The implemented recommendation algorithm calculates the next detection point that is optimal for the detection progress and the current detection results based on the subject's detection records. A method of using the rapid contrast sensitivity detection system according to any one of claims 1 to 8, characterized in that it includes the following steps: Before the test, the subject adjusts the system default parameters according to the actual situation, including the form of the visual mark, the angle of view, the physical width of the screen and the distance between the screen; Calculate the range in which the visual target appears based on the parameters set by the subject; The subject observes the optotypes on the screen and clicks on the optotypes visible to the naked eye; If the optotype on the screen is clicked by the subject, the optotype recommendation module of the computer recommends the next optotype, and the appearance principle of this optotype is: a. The position is uniform and random; b. Does not overlap with other visual targets on the screen; c. Located within the viewing angle range; If the optotype on the screen is not clicked by the subject after the survival time has expired, it will automatically disappear; the computer module recommends the next optotype; The number of optotypes within the viewing angle range on the above screen is always maintained at the same number. This number can be determined by the subject. Set it yourself. The method of using the rapid contrast sensitivity detection system according to claim 9, characterized in that during the subject detection process, the subject's detection cooperation degree is also evaluated, and the evaluation method is specifically: The display positions of the optotypes are uniformly and randomly distributed, and when the subject cooperates with the test, the click positions are also uniformly distributed. When the number of clicks by the subject is much more than the number of times the optotype is displayed, the click locations of the subjects are unevenly distributed. , then it is assessed that the current subject is not cooperating with the test.