CN104122078B - Evaluation method for image quality of near-to-eye display optical lens - Google Patents

Abstract

The invention discloses a method for evaluating the image quality of a near-eye display optical lens, which is suitable for rapid detection in commercial production. In this method, the experimenter observes the sample lens with known performance parameters, extracts a set of physical parameters that are more sensitive to the visual experience of the human eye through statistical methods, and quantifies them to obtain the parameters corresponding to the image quality that the human eye can receive. Interval, as the standard of subjective evaluation, a set of near-eye display optical lens image quality evaluation device is used in this method to quickly detect the optical lens to be tested to obtain the quantitative value of the above physical quantity, and compare the obtained results with the objective measurement Values are compared and combined to establish the connection between the subjective and the objective. The established fast inspection system can accurately and quickly evaluate the image quality of the optical system based on the detected lens parameters and the subjective evaluation as the standard. The technical scheme of the invention can quickly and accurately evaluate the imaging quality of the optical lens or its performance, and is very convenient to use.

Description

A method for evaluating the image quality of near-eye display optical lens

technical field

The invention relates to the technical fields of near-eye display, optical lens detection and image quality evaluation, and in particular to a method for evaluating the image quality of an optical lens for near-eye display.

Background technique

In recent years, with the development of micro-display, advanced optics, software and hardware technology, near-eye display products emerge in an endless stream, and its application in entertainment, virtual reality and other fields is also more extensive. The display effect of the device is closely related to the optical lens, so the image quality evaluation of the optical lens is very critical.

Although there have been in-depth researches on the design and application of near-eye display devices, their image quality detection and evaluation methods are relatively lagging behind. Although there are some objective detection or subjective evaluation methods, the former is complicated to operate, cannot be quickly detected, and does not combine the visual experience of the human eye; although subjective evaluation is intuitive and accurate, it requires high evaluation environment and takes subjective experience as the evaluation standard. Neither can be applied to assays in commercial production.

Contents of the invention

In order to solve the above-mentioned shortcomings, the present invention provides a method for evaluating the image quality of an optical lens for near-eye display, which can quickly and accurately evaluate the imaging quality of the optical lens or its performance.

The technical solution adopted in the present invention is: a method for evaluating the image quality of a near-eye display optical lens, comprising:

Measure the optical lens to be evaluated by various objective measuring instruments to obtain objective physical parameter values;

Obtain the physical parameter values corresponding to the different grades of image quality of the optical lens to be evaluated; the physical parameter values corresponding to the different grades of image quality are obtained from subjective evaluation statistics; and from the physical parameter values corresponding to the different grades of image quality Extract the physical parameter value that has the greatest impact on the subjective experience of human vision; quantify the extracted physical parameter value to obtain a parameter interval corresponding to the image quality accepted by the human eye, as a physical parameter value for subjective evaluation;

The near-eye display optical system image quality evaluation device detects the optical lens to be evaluated to obtain the detected physical parameter value;

The evaluation device for image quality of the near-eye display optical system establishes a correspondence between the detected physical parameter value and the objective physical parameter value;

The evaluation device for the image quality of the near-eye display optical system takes the physical parameter value of the subjective evaluation as an input evaluation standard, and according to the detected physical parameter value and the corresponding relationship of the optical lens to be tested, the detected physical parameter value is evaluated. Parameter values are evaluated.

In the method as described above, the evaluation device for the image quality of the near-eye display optical system includes: a micro display screen (1) for displaying a standard test board, an optical lens (2) to be evaluated, and a first CCD for imaging A camera, an image acquisition card (5) for collecting images, a computer (6) for displaying and analyzing and processing images; the first CCD camera includes a lens (3) and a target surface (4);

The near-eye display optical system image quality evaluation device compares and corrects the detected physical parameter value and the objective physical parameter value, and establishes a relationship between the two, specifically including:

The computer compares and corrects the detected physical parameter value with the objective physical parameter value, and repeatedly debugs the algorithm adopted by the computer based on the latter, so that the detected physical parameter value tends to approach the desired physical parameter value. Describe the objective physical parameter values and get the relationship between them.

In the method described above, the evaluation device for the image quality of the near-eye display optical system detects the optical lens to be evaluated to obtain the detected physical parameter values, specifically including:

Described micro-display screen (1) shows the standard test plate of manufacture, after described optical lens (2) to be evaluated, exit parallel light, after described first CCD camera takes again, described image acquisition card (5) The collected image is finally displayed on the computer (6); the collected image is processed and analyzed by the software algorithm on the computer (6), to obtain the detected physical parameter value.

In the above method, after quantifying the extracted physical parameter values to obtain the parameter range corresponding to the image quality accepted by the human eye as the physical parameter value for subjective evaluation, the near-eye display optical system image Before the qualitative evaluation device detects the optical lens to be evaluated and obtains the detected physical parameter value, it also includes:

The lens (3) of the first CCD camera, the target surface (4), and the micro-display screen (1) are subjected to calibration processing, so that the obtained physical parameters express only the object to be evaluated. The performance of the optical lens (2).

In the above method, establishing the correspondence between the detected physical parameter value and the objective physical parameter value specifically includes: comparing the detected physical parameter value with the objective physical parameter value and correction, using the latter parameter value as a standard and adjusting the evaluation device for the image quality of the near-eye display optical system to change the detected physical parameter value, so that the detection detected by the evaluation device for the image quality of the near-eye display optical system The value of the physical parameter is close to the value of the objective physical parameter, and the corresponding relationship is established.

In the above method, the performance parameter includes at least one of field angle, distortion, resolution, contrast, MTF value and color saturation.

Compared with the prior art, the present invention has the advantages of: by adopting the above-mentioned technical scheme, it not only combines the subjective experience of the human eye but also establishes a connection with the objective measurement, so the final evaluation result is accurate and reliable, and the most important thing is that it is consistent with the human eye. The results were consistent with the visual perception evaluation. And the technical solution of the present invention can measure one or more physical quantities such as field angle, distortion, resolution, contrast, MTF, color saturation, etc. according to the image formed by the standard test plate displayed by the microdisplay, so as to achieve the effect of rapid detection . Moreover, the technical solution of the present invention has high requirements on the evaluation environment, and with subjective experience as the evaluation standard, it can be applied to the detection in commercial production, and can quickly and accurately evaluate the imaging quality of the optical lens or its performance. It is very convenient to use.

Description of drawings:

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained according to these drawings without any creative effort.

FIG. 1 is a flowchart of a method for evaluating image quality of a near-eye display optical lens provided by an embodiment of the present invention.

FIG. 2 is a schematic diagram of an evaluation device for image quality of a near-eye display optical system provided by an embodiment of the present invention.

FIG. 3 is a test state diagram for measuring on-axis and off-axis characteristics of an optical lens to be evaluated in an embodiment of the present invention.

Fig. 4 is a schematic diagram of the measurement of the MTF value provided by the embodiment of the present invention.

Fig. 5 is a schematic diagram of distortion measurement provided by an embodiment of the present invention.

FIG. 6 is a schematic diagram of the measurement of the viewing angle provided by the embodiment of the present invention.

detailed description:

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

FIG. 1 is a flowchart of a method for evaluating image quality of a near-eye display optical lens provided by an embodiment of the present invention. As shown in Figure 1, the method for evaluating the image quality of the near-eye display optical lens of the present embodiment may specifically include the following steps:

100. Measure the optical lens to be evaluated by various objective measuring instruments to obtain objective physical parameter values;

For example, the performance parameter in this embodiment includes at least one of field angle, distortion, resolution, contrast, modulation transfer function (Modulation Transfer Function; MTF) value, and color saturation. Specifically, measure the optical lens to be evaluated by various objective measuring instruments to obtain various performance parameters, such as the MTF value obtained by a telegraph, and the field of view, distortion and other physical parameters measured by a precision goniometer, each to be evaluated All optical lenses have marked performance parameter values.

101. Obtain the physical parameter values corresponding to different grades of image quality of the optical lens to be evaluated; and extract the physical parameter value that has the greatest impact on the subjective perception of human vision from the physical parameter values corresponding to different grades of image quality; Quantify the physical parameter values to obtain the parameter range corresponding to the image quality accepted by the human eye, which is used as the physical parameter value for subjective evaluation;

In this embodiment, the physical parameter values corresponding to different levels of image quality are calculated by subjective evaluation; parameter value.

102. The near-eye display optical system image quality evaluation device detects the optical lens to be evaluated to obtain the detected physical parameter value;

The image quality evaluation device of the near-eye display optical system in this embodiment is composed of various optical elements and computers.

103. The near-eye display optical system image quality evaluation device establishes the corresponding relationship between the detected physical parameter value and the objective physical parameter value;

For example, the computer in the evaluation device for the image quality of the near-eye display optical system can establish the corresponding relationship between the detected physical parameter value and the objective physical parameter value.

104. The device for evaluating the image quality of the near-eye display optical system takes the subjectively evaluated physical parameter value as the input evaluation standard, and evaluates the detected physical parameter value according to the detected physical parameter value and the corresponding relationship of the optical lens to be tested.

The evaluation method for the image quality of the near-eye display optical lens in this embodiment, by adopting the above-mentioned technical scheme, not only combines the subjective experience of the human eye but also establishes a connection with the objective measurement, so the final evaluation result is accurate and reliable, and the most important thing is that it is compatible with human The results of the visual perception evaluation of the eye are consistent with the results. And the technical solution of the present invention can measure one or more physical quantities such as field angle, distortion, resolution, contrast, MTF, color saturation, etc. according to the image formed by the standard test plate displayed by the microdisplay, so as to achieve the effect of rapid detection . Moreover, the technical solution of the present invention has high requirements on the evaluation environment, and with subjective experience as the evaluation standard, it can be applied to the detection in commercial production, and can quickly and accurately evaluate the imaging quality of the optical lens or its performance. It is very convenient to use.

FIG. 2 is a schematic diagram of an evaluation device for image quality of a near-eye display optical system provided by an embodiment of the present invention. As shown in Figure 2, the evaluation device of the image quality of the near-eye display optical system of the present embodiment includes: a micro display screen 1 for displaying a standard test board, an optical lens 2 to be evaluated, a first CCD camera for imaging, an acquisition An image acquisition card 5, a computer 6 for displaying and analyzing and processing images; the first CCD camera includes a lens 3 and a target surface 4.

Wherein the micro-display 1 displays the manufactured standard test board, emits parallel light through the optical lens 2 to be evaluated, and after being taken by the first CCD camera, the image collected by the image acquisition card 5 is finally displayed on the computer 6 .

Further optionally, on the basis of the technical solutions of the above-mentioned embodiments, in step 103 of the above-mentioned embodiments, the "apparatus for evaluating the image quality of the near-eye display optical system compares and corrects the detected physical parameter values and the objective physical parameter values, Establishing the relationship between the two", which may specifically include: the computer compares and corrects the detected physical parameter value with the objective physical parameter value, and uses the latter as the basis to repeatedly debug the algorithm adopted by the computer, so that the detected physical parameter value tends to In order to get close to the objective physical parameter values, and get the relationship between the two.

For example, the computer can be installed with software, and the above functions can be realized through the software.

Further optionally, on the basis of the technical solutions of the above-mentioned embodiments, step 102 in the above-mentioned embodiments "the device for evaluating the image quality of the near-eye display optical system detects the optical lens to be evaluated to obtain the detected physical parameter values, specifically including: Micro-display screen 1 displays the manufactured standard test board, passes through the optical lens 2 to be evaluated, and emits parallel light, and then after the first CCD camera picks up, the image acquisition card 5 captures the image and finally displays it on the computer 6; through the computer 6 The software algorithm processes and analyzes the collected images to obtain the detected physical parameter values.

Further optionally, on the basis of the technical solutions of the above-mentioned embodiments, in step 101 "the extracted physical parameter values are quantified to obtain the parameter range corresponding to the image quality accepted by the human eye as the physical parameter value of the subjective evaluation "Afterwards, step 102" the evaluation device of the image quality of the near-eye display optical system detects the optical lens to be evaluated to obtain the detected physical parameter value "Before, the evaluation method of the present embodiment may also include: the lens 3 of the first CCD camera and The target surface 4 and the micro-display screen 1 are calibrated so that the obtained physical parameters express only the performance of the optical lens 2 to be evaluated. The standard lens is used in the calibration process, the processing precision of the standard lens is high, the error is small, and it is in good agreement with the parameter requirements of the design.

Further optionally, on the basis of the technical solutions of the above-mentioned embodiments, in step 103 of the above-mentioned embodiments, the "apparatus for evaluating the image quality of the near-eye display optical system establishes the correspondence between the detected physical parameter values and the objective physical parameter values "Specifically, it may include: the evaluation device for the image quality of the near-eye display optical system compares and corrects the detected physical parameter values with the objective physical parameter values, and uses the latter parameter value as a standard and basis to debug the image quality evaluation device for the near-eye display optical system By changing the detected physical parameter value, the detected physical parameter value detected by the near-eye display optical system image quality evaluation device is close to the objective physical parameter value, and a corresponding relationship is established.

The computer in the evaluation device for the image quality of the near-eye display optical system of the above-mentioned embodiment will have the standard of subjective evaluation, through the detection of the optical system to be tested by the device, a set of parameter values that can express its performance can be obtained, and then the computer will treat it according to the evaluation standard. Quickly and accurately evaluate the image quality of the measuring optical system.

Further optionally, in the evaluation device for the image quality of the near-eye display optical system in the above embodiment, the micro display screen 1 is installed on the optical lens 2 to be evaluated, and the optical lens 2 to be evaluated is placed on a two-dimensional prism fixed platform, The lens 3 of the first CCD camera is placed at the exit pupil of the optical lens 2 to be evaluated, and the light is imaged on the target surface 4 of the first CCD camera.

Further optionally, in the evaluation device for the image quality of the near-eye display optical system in the above-mentioned embodiment, the computer 6 is equipped with algorithmic software for displaying and processing and analyzing the image, and the image can be analyzed by the processing and analyzing software to obtain multiple expressions of the optical lens at one time. a physical parameter value. The computer 6 will store the standard of subjective evaluation, through the near-eye display optical system image quality evaluation device to detect the optical system to be tested, a set of parameter values that can express its performance can be obtained, and then the computer can obtain the image quality of the optical system to be tested according to the evaluation standard Make fast and accurate evaluations.

Further optionally, in the evaluation device for the image quality of the near-eye display optical system in the above embodiment, the micro-display screen 1, the optical lens 2 to be evaluated, and the lens 3 of the first CCD camera are supported on the guide rail by a bracket, and the first The bracket of the lens 3 of the CCD camera is connected with a three-dimensional translation stage or a corner stage, which can be moved forward, backward, left, and right by manual or stepping motor control to achieve good measurement results.

Further optionally, in the image quality evaluation device of the near-eye display optical system in the above embodiment, the micro-display 1 can be replaced by a light source irradiating a mask plate engraved with a test standard plate pattern.

Further optionally, in the evaluation device for the image quality of the near-eye display optical system in the above embodiment, when measuring the on-axis characteristics of the optical lens 2 to be evaluated, all devices need to be on the same guide rail line; if the off-axis characteristics are measured, It is necessary to use the translation table 9 or the turntable 9 to place the optical lens 2 to be evaluated at the center of the turntable, place the second CCD camera 10 at the exit pupil distance of the optical lens 2 to be evaluated, and adjust the axis of the second CCD camera 10 and The angle between the 2 axes of the optical lens to be evaluated can be up to the angle θ.

FIG. 3 is a test state diagram for measuring on-axis and off-axis characteristics of an optical lens to be evaluated in an embodiment of the present invention. As shown in FIG. 3 , when measuring the on-axis characteristics of the optical lens 2 to be evaluated, all devices must be on the same guide rail line; to measure its off-axis characteristics, a translation stage or a turntable 9 needs to be used. The optical lens 2 to be evaluated is placed at the center of the turntable 9, the second CCD camera 10 is placed at the exit pupil distance, and the detection can be realized by adjusting the angle between the axis of the camera and the axis of the optical lens 2 to be evaluated to an angle θ.

Since the standard test board displayed by the micro-display screen 1 for displaying the standard test board in this embodiment includes a pattern capable of measuring multiple parameters, and the process of measuring different parameters does not interfere with each other, so the device can be used at the same time. Multiple parameters are detected to obtain parameter results, which shortens the detection time and achieves the purpose of rapid evaluation.

The measurement principles of the various physical parameter values are briefly described below.

For the measurement of MTF value, Fig. 4 is the measurement schematic diagram of the MTF value that the embodiment of the present invention provides, as shown in Fig. 4 left and right two figures, the contrast of black and white fringe can change to some extent before and after imaging, the fringe change situation of different frequency is different The same, and the gray value of the gray scale image is proportional to the light intensity value. By analyzing the distribution of gray values, according to Calculate the contrast ratio of black and white stripes before and after imaging to get the MTF value at this frequency v, where M' _img represents the contrast of the fringe image, and M _obj represents the contrast of the object. After obtaining the MTF value at certain frequencies, you can analyze the performance of contrast and resolution. For example, when the frequency is 10lp/mm, you can see the performance of contrast; when the frequency is 30lp/mm, it is the performance of resolution. Of course, the larger the MTF value, the better the contrast or resolution performance.

For the measurement of the distortion, FIG. 5 is a schematic diagram of the measurement of the distortion provided by the embodiment of the present invention. As shown in Figure 5, the image before distortion is a square image in the middle, and as shown in Figure 5, the image after distortion is a pincushion image on the outside. ΔL and L are obtained through algorithm analysis, where ΔL represents the amount of distortion, and L represents the size before distortion, which can be calculated according to the formula Find the magnitude of the distortion.

For the measurement of the viewing angle, FIG. 6 is a schematic diagram of the measurement of the viewing angle provided by the embodiment of the present invention. As shown in Figure 6, use the first CCD camera to observe the grid plate as shown in the figure, and then according to the formula Where f is the focal length of the lens of the first CCD camera, h is the height of imaging on the s target surface of the first CCD camera, and the size of the angle of view θ is calculated.

For the measurement of color reproduction, the measurement of color reproduction requires the use of 24-color standard color comparison cards. The principle is that each color has a corresponding RGB value. The RGB value of each color of the color comparison card changes before and after imaging. . The degree of color reproduction can be quantified according to the specific algorithm of the degree of restoration. The smaller the deviation of the RGB value before and after imaging, the better the color reproduction of the optical system.

According to the specific algorithm and principle when measuring each parameter, the parameter size of the optical system can be detected. However, since the imaging quality is also affected by the micro-display screen, the lens and the target surface of the first CCD camera, etc., they still need to be calibrated. A standard lens is required for calibration to measure the influence of other devices on each parameter. Since each device is independent, they can be treated as a cascaded system.

After obtaining the parameters of the lens to be tested, compare them with the standard values measured by the standard measuring instrument. By repeatedly debugging the algorithm of the computer software of the quick inspection device, try to make the measured value obtained by the quick inspection system close to the standard value or be a certain value. Functional relationship.

According to the above embodiment, the connection between the subjective evaluation and the objective measurement is established through the quick inspection system. Therefore, the quick detection system can detect the value of each parameter, and then evaluate according to the evaluation standard.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (5)

1. A method for evaluating the image quality of a near-eye display optical lens, characterized in that it comprises: Measure the optical lens to be evaluated by various objective measuring instruments to obtain objective physical parameter values; Obtain the physical parameter values corresponding to the different grades of image quality of the optical lens to be evaluated; the physical parameter values corresponding to the different grades of image quality are obtained from subjective evaluation statistics; and from the physical parameter values corresponding to the different grades of image quality Extract the physical parameter value that has the greatest impact on the subjective experience of human vision; quantify the extracted physical parameter value to obtain a parameter interval corresponding to the image quality accepted by the human eye, as a physical parameter value for subjective evaluation; The near-eye display optical system image quality evaluation device detects the optical lens to be evaluated to obtain the detected physical parameter value; The evaluation device for image quality of the near-eye display optical system establishes a correspondence between the detected physical parameter value and the objective physical parameter value; The evaluation device for the image quality of the near-eye display optical system takes the physical parameter value of the subjective evaluation as an input evaluation standard, and according to the detected physical parameter value and the corresponding relationship of the optical lens to be tested, the detected physical parameter value is evaluated. Parameter values are evaluated; The evaluation device for the image quality of the near-eye display optical system includes: a micro display screen (1) for displaying a standard test board, an optical lens (2) to be evaluated, a first CCD camera for imaging, an image acquisition device for collecting images Card (5), computer (6) for displaying and analyzing and processing image; Described first CCD camera comprises lens (3) and target surface (4); The near-eye display optical system image quality evaluation device compares and corrects the detected physical parameter value and the objective physical parameter value, and establishes a relationship between the two, specifically including: The computer compares and corrects the detected physical parameter value with the objective physical parameter value, and repeatedly debugs the algorithm adopted by the computer based on the latter, so that the detected physical parameter value tends to approach the desired physical parameter value. Describe the objective physical parameter values and get the relationship between them. 2. The method according to claim 1, wherein the evaluation device for the image quality of the near-eye display optical system detects the optical lens to be evaluated to obtain the detected physical parameter value, specifically comprising: Described micro-display screen (1) shows the standard test plate of manufacture, after described optical lens (2) to be evaluated, exit parallel light, after described first CCD camera takes again, described image acquisition card (5) The collected image is finally displayed on the computer (6); the collected image is processed and analyzed by the software algorithm on the computer (6), to obtain the detected physical parameter value. 3. The method according to claim 1, characterized in that, after quantifying the extracted physical parameter value to obtain a parameter interval corresponding to the image quality accepted by the human eye, as the physical parameter value of subjective evaluation Before the evaluation device for the image quality of the near-eye display optical system detects the optical lens to be evaluated to obtain the detected physical parameter value, the method also includes: The lens (3) of the first CCD camera, the target surface (4), and the micro-display screen (1) are subjected to calibration processing, so that the obtained physical parameters express only the object to be evaluated. The performance of the optical lens (2). 4. The method according to claim 1, wherein establishing the correspondence between the detected physical parameter value and the objective physical parameter value specifically comprises: combining the detected physical parameter value with the objective physical parameter value The above objective physical parameter values are compared and corrected, and the latter parameter value is used as a standard and based on debugging the evaluation device of the image quality of the near-eye display optical system to change the detected physical parameter value, so that the image quality of the near-eye display optical system The value of the detected physical parameter detected by the evaluation device is close to the value of the objective physical parameter, and the corresponding relationship is established. 5. The method according to any one of claims 1-4, wherein the detected physical parameter values include at least one of field angle, distortion, resolution, contrast, MTF value and color saturation.