Disclosure of Invention
Aiming at the problems, the technical problem to be solved by the invention is to provide a testing device and a testing method for head-mounted display equipment, so as to solve the problem of optical performance detection of the head-mounted display equipment.
In order to solve the technical problems, the invention adopts the following technical scheme:
the testing device of the head-mounted display equipment is characterized by comprising a calibration device, a head-mounted display equipment adjusting device, an image receiving system, an image processing system and a guide rail;
the image receiving system consists of a first objective lens and a second objective lens which are identical in structure, a first camera and a second camera which are identical in structure, a first camera displacement platform and a second camera displacement platform and a base which are identical in structure, wherein the first objective lens is fixed on the first camera, the second objective lens is fixed on the second camera, the first camera is arranged on the first camera displacement platform, the second camera is arranged on the second camera displacement platform, the first camera displacement platform and the second camera displacement platform are fixed on the base, the optical axes of the first objective lens and the second objective lens are parallel to each other, the photosurfaces of the photosensitive elements of the first camera and the second camera are respectively overlapped with the image planes of the first objective lens and the second objective lens, the lenses of the first camera and the second camera are respectively aligned with the two display modules of the head-mounted display device, the optical axes of the two display modules of the head-mounted display device and the optical axes of the first camera and the second camera are collinear, the first camera and the second camera are provided with an image acquisition card, and the acquired test images are transmitted to the image processing system for analysis and processing;
the calibration device comprises a bracket and a calibration plate, wherein the bracket is arranged on a fixed guide rail, the guide rail is arranged at the middle position of two cameras, the bracket is arranged in front of a camera lens, and the bracket can stretch and retract to adjust the length along the direction vertical to the ground and can move to a set position along the direction of the guide rail;
the head-mounted display equipment adjusting device consists of a head-mounted display equipment displacement platform and a fixing device, wherein the head-mounted display equipment is arranged on the fixing device, and the fixing device is arranged on the head-mounted display equipment displacement platform;
the image processing system is composed of a computer and is connected with the two cameras through a network cable.
The calibration plate comprises a calibration plate a printed with a grid reference pattern and a calibration plate b printed with an inclined square array reference pattern.
The image processing system comprises an input unit, a display unit, a storage unit and an image processing unit, wherein the image processing unit comprises an image importing module, an offset testing module, a vision testing module, an ROI identification processing module and a testing module, the image importing module is used for receiving input information transmitted by the input unit, generating an image importing instruction according to the input information after identifying the information, controlling the image receiving system to acquire images of head-mounted display equipment and display the acquired images on the display unit, the offset testing module is used for calibrating a testing device and detecting the central offset of the head-mounted display equipment and the included angle of binocular vision axes, the vision testing module is used for detecting the vision FOV of the head-mounted display equipment, the vision identification processing module is used for extracting images of a video image region of interest (ROI), and the testing module is used for measuring the display performance of the head-mounted display equipment according to the determined FOV and the ROI.
The vision testing module comprises a boundary point detection submodule and a vertex detection submodule, wherein the boundary point detection submodule is used for detecting pixels, positions and gray values of boundary lines of the acquired images, and the vertex detection submodule is used for detecting pixels, positions and gray values of vertices of the acquired images.
The ROI identification processing module includes an ROI identification sub-module for identifying an ROI in an acquired image and an ROI processing sub-module for image processing and analysis of the acquired ROI.
The testing method of the testing device of the head-mounted display equipment is characterized by comprising the following specific steps of:
61 Connecting interfaces of two cameras in the image receiving system with an interface of the switch by using two network wires, and connecting a computer of the image processing system with the switch by using the network wires;
62 The support moves to a set position along the direction of the guide rail, the calibration plate a printed with the grid reference pattern is fixed on the support, and the support is adjusted to enable the center height of the calibration plate a to be consistent with the center height between the two cameras;
63 Adjusting zoom rings of the first camera and the second camera to enable focal lengths of the first camera and the second camera to be equal, enabling the whole image of the calibration plate to be full of a shot picture, adjusting focusing rings of the first camera and the second camera to enable the image of the calibration plate shot by the first camera and the second camera to be clear, and adjusting aperture blades of the first camera and the second camera to enable aperture sizes of the first camera and the second camera to be equal and picture brightness to be moderate;
64 Reading pictures shot by the first camera and the second camera, and obtaining the diagonal line length a of the pictures0 ；
65 Mounting the head-mounted display device to be tested on a fixing device of a head-mounted display device adjusting device, and adjusting the optical axes of two display modules of the head-mounted display device to be collinear with the optical axes of the first camera and the second camera;
66 Detecting the edge position of the picture area of the head-mounted display device to be detected and obtaining the diagonal length a of the picture of the head-mounted display device to be detected, wherein the diagonal length a in the step 64) is defined by the length a0 The focal length f of the first camera and the second camera and the picture size y of the first camera and the second camera are calculated to obtain FOV of the head-mounted display device respectively, wherein FOV=a/a0 *2*arctan(y/2f)。
A method for testing a test device of a head-mounted display device, comprising the steps of:
71 Connecting interfaces of two cameras in the image receiving system with an interface of the switch by using two network wires, and connecting a computer of the image processing system with the switch by using the network wires;
72 The support moves to a set position along the direction of the guide rail, the calibration plate b printed with the inclined square array reference pattern is fixed on the support, and the support is adjusted to enable the center height of the calibration plate b to be consistent with the center height between the two cameras;
73 Adjusting zoom rings of the first camera and the second camera to enable focal lengths of the first camera and the second camera to be equal, enabling the whole image of the calibration plate to be full of a shot picture, adjusting focusing rings of the first camera and the second camera to enable the image of the calibration plate shot by the first camera and the second camera to be clear, and adjusting aperture blades of the first camera and the second camera to enable aperture sizes of the first camera and the second camera to be equal and picture brightness to be moderate;
74 Reading pictures shot by the first camera and the second camera, calculating the modulation transfer function MTF value of at least one region of interest in the pictures, calculating the modulation transfer function MTF value in real time, displaying the value on a display unit, adjusting a focusing ring to find the position with the maximum modulation transfer function, and recording that the modulation transfer function value at the moment is the modulation transfer function value MTF of the test system0 The method comprises the steps of carrying out a first treatment on the surface of the If there are several regions of interest, recording the modulation transfer function MTF of all the regions of interest0 (1)、MTF0 (2)、…、MTF0 (n) is a modulation transfer function value of the test system;
75 Mounting the head-mounted display device to be tested on a fixing device of a head-mounted display device adjusting device, and adjusting the optical axes of two display modules of the head-mounted display device to be collinear with the optical axes of the first camera and the second camera;
76 Generating an inclined square array test chart at the centers of two display modules of the head-mounted display device to be tested through a main board or a control board of the head-mounted display device to be tested, generating virtual images on the object planes of the first objective lens and the second objective lens after passing through an optical system of the head-mounted display device to be tested, and generating images on the photosensitive elements of the first camera and the second camera after passing through the first objective lens and the second objective lens;
77 Reading pictures shot by the first camera and the second camera, calculating the modulation transfer function MTF value of at least one region of interest selected in the step 74) in the pictures, calculating the modulation transfer function MTF value in real time, displaying the value on a display unit, adjusting a focusing ring to find the position with the maximum modulation transfer function, and recording the modulation transfer function value at the moment as the modulation transfer function value MTF of the cascade connection of the head-mounted display device and the test system1 The method comprises the steps of carrying out a first treatment on the surface of the If there are several regions of interest, recording the modulation transfer function MTF of all the regions of interest1 (1)、MTF1 (2)、…、MTF1 (n) is a modulation transfer function value of the test system cascade;
78 Modulation transfer function value MT by test systemF0 MTF cascaded with head-mounted display device and system1 The values may result in a modulation transfer function for the head-mounted display device: MTF (n) =mtf1 (n)/MTF0 (n)。
The testing method of the testing device of the head-mounted display equipment is characterized by comprising the following steps of:
81 Two network wires connect the interfaces of the two cameras in the image receiving system with the switch interface, and the network wires connect the computer of the image processing system with the switch;
82 The support moves to a set position along the direction of the guide rail, the calibration plate a printed with the grid reference pattern is fixed on the support, and the support is adjusted to enable the center height of the calibration plate a to be consistent with the center height between the two cameras;
83 Adjusting zoom rings of the first camera and the second camera to enable focal lengths of the first camera and the second camera to be equal, enabling the whole image of the calibration plate to be full of a shot picture, adjusting focusing rings of the first camera and the second camera to enable the image of the calibration plate shot by the first camera and the second camera to be clear, adjusting aperture blades of the first camera and the second camera, enabling aperture sizes of the first camera and the second camera to be equal, and enabling the picture brightness to be moderate;
84 Reading pictures shot by the first camera and the second camera, calibrating the relative positions of the centers of the first camera and the calibration plate and the relative positions of the centers of the second camera and the calibration plate, and recording calibration data;
85 The head-mounted display device to be tested is arranged on a fixing device of a head-mounted display device adjusting device, and the optical axes of two display modules of the head-mounted display device are aligned with the optical axes of the first camera and the second camera;
86 The method comprises the steps of) generating a cross image at the centers of two display modules of the head-mounted display device to be tested through a main board or a control board of the head-mounted display device to be tested, generating cross virtual images at object planes of a first objective lens and a second objective lens after the cross virtual images pass through an optical system of the head-mounted display device, and generating cross images at light sensitive planes of a first camera and a second camera after the cross virtual images pass through the first objective lens and the second objective lens;
87 Calculating the eccentric displacement amount and the visual axis deviation of the head-mounted display device according to the calibration data and the cross image position data of the head-mounted display device on the first camera and the second camera.
Due to the adoption of the technical scheme, the invention has the following advantages:
1) Enabling comprehensive detection of imaging characteristics and optical performance of a head mounted display device
2) Reliable detection and high speed
3) And the cost is low.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples.
The invention provides a testing device of a head-mounted display device, which comprises detection of a modulation transfer function, detection of an imaging position, detection of distortion and detection of binocular matching.
The following describes specific embodiments of the present invention by taking test smart glasses as an example.
FIG. 1 is a system overview block diagram of a test apparatus according to one embodiment of the invention, as can be seen in FIG. 1: the system comprises a calibration device, a head-mounted display device adjustment device, an image receiving system, an image processing system, an output system and a guide rail. The calibration device pattern consists of a large-view-field grid reference and a large-view-field inclined square array reference. The image processing system is composed of a computer, and the output system displays the result and data.
Referring to fig. 2, fig. 2 is a block diagram of a head mounted display device adjusting apparatus and an image receiving system. The image receiving system is composed of an image acquisition card, a camera, a displacement platform, a base and the like, the camera can be a CCD camera, a CMOS camera or other digital cameras, the CCD camera is adopted in the embodiment, specifically, the image receiving system is composed of a first objective lens 21 and a second objective lens 22 which are identical in structure, a first CCD camera 23 and a second CCD camera 24 which are identical in structure, a first CCD camera displacement platform 25 and a second CCD camera displacement platform 26 which are identical in structure, and a base 27, and the position relationship is that: the first objective lens is fixed on the first CCD camera, the second objective lens is fixed on the second CCD camera, the first CCD camera is arranged on the first CCD camera displacement platform, the second CCD camera is arranged on the second CCD camera displacement platform, the first CCD camera displacement platform and the second CCD camera displacement platform are fixed on the base, the optical axes of the first objective lens and the second objective lens are parallel to each other, and the photosurfaces of the photosensitive elements of the first CCD camera and the second CCD camera are respectively overlapped with the image planes of the first objective lens and the second objective lens; the first CCD camera displacement platform and the second CCD camera displacement platform with the same structure are composed of XYZR four-axis platforms, and the XYZR four-axis platforms are four-axis precision platforms. The first objective lens and the second objective lens are composed of a lens group formed by a plurality of lenses and a shell structural member. The housing structure comprises a focusing ring, a zooming ring, an aperture blade and scales. The head-mounted display device adjusting device consists of a head-mounted display device displacement platform 28 and a fixing device 29. The head-mounted display device is mounted on the fixing device 29, and the fixing device 29 is mounted on the head-mounted display device displacement platform 28. The head mounted display device displacement stage 28 is constituted by an XYZ three-axis stage, which is a three-axis precision stage. The head-mounted display device adjusting device is used for adjusting the position of the head-mounted display device, during testing, lenses of the first CCD camera and the second CCD camera are respectively aligned to two display modules of the head-mounted display device through adjusting the adjusting device and the CCD camera displacement platform, optical axes of the two display modules of the head-mounted display device and the optical axes of the first CCD camera and the second CCD camera are aligned so that the first CCD camera and the second CCD camera shoot images (namely test images) displayed by pictures of the two display modules of the head-mounted display device, the first CCD camera 23 and the second CCD camera 24 are provided with image acquisition cards, and the acquired test images are uploaded to the image processing system by the image acquisition cards for analysis and processing.
Referring to fig. 3, fig. 3 is a block diagram of an image processing system of the testing device. The image processing system is composed of a computer and comprises an input unit, a display unit, a storage unit and an image processing unit. The user displays the picture and acquires the test image through the operation device, and inputs the test image into the processing unit. The display unit is used for displaying the test process, the test image and the processing calculation result. The storage unit is used for storing data generated in the testing process and images of the head-mounted display device acquired by the CCD camera.
The image processing unit comprises an image importing module, an offset testing module, a vision testing module, an ROI (region of interest ) identifying and processing module and a testing module. The image importing module is used for receiving the input information transmitted by the input unit, generating an image importing instruction according to the input information after identifying the information, controlling the image receiving system to acquire the image of the head-mounted display device and displaying the acquired image on the display unit. The offset test module is used for calibrating the center offset of the test device and detecting the included angle of the binocular visual axis of the head-mounted display equipment. The vision field testing module is used for detecting the size of a vision Field (FOV) of the head-mounted display device and comprises a boundary point detection sub-module and a vertex detection sub-module. The boundary point detection submodule is used for detecting the pixels, the positions and the gray values of the boundary lines of the acquired image, the vertex detection submodule is used for detecting the pixels, the positions and the gray values of the vertices of the acquired image, and the functions of the boundary point detection submodule and the vertex detection submodule are shown in fig. 3.
The ROI identification processing module is used for extracting an image of a region of interest (ROI) of a video image, and comprises an ROI identification sub-module and an ROI processing sub-module. The ROI recognition submodule is used for recognizing the ROI in the acquired image, and the ROI processing submodule is used for carrying out image processing and analysis on the acquired ROI.
The test module is to measure an optical performance of the head mounted display device based on the determined FOV and ROI. Such as Modulation Transfer Function (MTF), etc.
FIG. 4 is a flow chart of an offset test module calibration test apparatus, comprising the steps of: and (3) calibrating image acquisition, translation, visual axis error calculation and image correction. The method specifically comprises the following steps: 1) The calibration plate is arranged on the guide rail and is opposite to the front 1m of the outer area of the CCD camera lens, preferably is arranged at the position 3-5m of the front of the CCD camera lens, and is illuminated by a light source, and the focusing rings of the first objective lens and the second objective lens are adjusted to enable the acquired images to be clear; 2) Displaying a cross image with the length and width of 200 pixels at the center of an image obtained by a CCD camera, and judging whether the coordinate difference value between the center of the cross image and the center of a calibration pattern is within a preset maximum deviation receiving range or not; 3) If the judging result is within the maximum deviation receiving range, recording a central coordinate difference value, and if the judging result is not within the maximum deviation receiving range, readjusting the first objective lens and the second objective lens, and repeating the step 2); 4) The center coordinate difference value is compared with a center coordinate difference value preset by the image processing unit, and the difference value after the comparison is the system test visual axis error of the CCD camera.
Fig. 5 is a flowchart of the offset test module detecting the center offset and the binocular viewing axis angle of the head mounted display device. The method comprises the following steps: 1) fixing the head-mounted display device on a fixing device 29 of a head-mounted display device adjusting device, setting a display picture of the head-mounted display device system into a cross pattern, focusing to a clear position, 2) placing a grid calibration plate at a position which is just opposite to a position which is 1m away from the CCD camera, wherein the grid calibration plate is preferably placed at a position which is 3-5m away from the CCD camera, 3) calculating the coordinate position of the cross on the grid through the pixel position, and 4) obtaining the eccentric offset of the head-mounted display device through the coordinate position calculation of the cross on the grid.
The calibration device comprises a bracket, a calibration plate a printed with a grid reference pattern and a calibration plate b printed with an inclined square array reference pattern. The pattern of the calibration plate a is shown in fig. 6a, and the pattern of the calibration plate b is shown in fig. 6 b. The calibration plate a and the calibration plate b can be fixedly assembled on the bracket when in use, and can be freely detached and replaced. The calibration plate b consists of 33 inclined square and stepped square patterns. The support is arranged on the guide rail, the guide rail is arranged at the middle position of the two cameras, the center of the guide rail is aligned with the middle position between the two CCD cameras, the support is arranged in front of the CCD camera lens and is positioned outside the CCD camera by 1m, the support can stretch and retract to adjust the length along the direction vertical to the ground, and the support can move to a set position along the direction of the guide rail. The dimensions of the calibration plate a and the calibration plate b are 110 x 187 cm, and the structure of the lighting device is shown in fig. 6 c. The illumination device serves as a light source for illuminating the calibration plate.
Fig. 7 is a flowchart of a method for detecting FOV by the view detection module, and a specific embodiment of a method for detecting FOV of a head mounted display device by using the head mounted display device testing apparatus described above, including the following steps:
1) The base of the image receiving system is placed on a plane with the height of about 1.5m in the horizontal position, so that the base is convenient for an operator to operate;
2) Connecting interfaces of two CCD cameras in the image receiving system with an interface of a switch by using two network wires, and connecting a computer of the image processing system with the switch by using the network wires;
3) The support moves to a set position along the direction of the guide rail, the support is placed outside the guide rail 1m in front of the CCD cameras, the support is preferably placed at a position 3-5m away from the front of the CCD cameras, the calibration plate a is fixed on the support, the central height of the calibration plate a is consistent with the central height between the two CCD cameras, and a light source is placed to illuminate the calibration plate a as shown in figure 6 c;
4) Adjusting zoom rings of the first CCD camera and the second CCD camera to enable focal lengths of the first CCD camera and the second CCD camera to be equal, enabling the whole image of the calibration plate to be full of a shot picture, adjusting focusing rings of the first CCD camera and the second CCD camera to enable the image of the calibration plate shot by the first CCD camera and the second CCD camera to be clear, and adjusting aperture blades of the first CCD camera and the second CCD camera to enable aperture sizes of the first CCD camera and the second CCD camera to be equal and picture brightness to be moderate;
5) Reading pictures shot by the first CCD camera and the second CCD camera, and obtaining the diagonal line length a of the pictures0 ；
6) Mounting the head-mounted display device to be tested on a fixing device 29 of a head-mounted display device adjusting device, and adjusting optical axes of two display modules of the head-mounted display device and optical axes of a first CCD camera and a second CCD camera to be tested are collinear;
7) Detecting the edge position of the picture area of the head-mounted display device to be detected and obtaining the diagonal length a of the picture of the head-mounted display device to be detected, wherein the diagonal length a in the step 5) is obtained by the length a0 The focal length f of the first CCD camera and the focal length f of the second CCD camera and the picture width dimension y of the first CCD camera and the second CCD camera are respectively calculated to obtain the FOV of the head-mounted display device:
FOV=a/a0 *2*arctan(y/2f) 。
an embodiment of the method for detecting the eccentric position and the off-axis size of the head-mounted display device by using the head-mounted display device testing device comprises the following steps:
1) The base of the image receiving system is placed on a plane with the height of about 1.5m in the horizontal position, so that the base is convenient for an operator to operate;
2) Connecting interfaces of two CCD cameras in the image receiving system with an interface of a switch by using two network wires, and connecting a computer of the image processing system with the switch by using the network wires;
3) The support moves to a set position along the direction of the guide rail, the support is placed on the guide rail at a position which is 1m away from the centers of the two cameras, the support is preferably placed at a position which is 3-5m away from the front of the CCD cameras, the calibration plate a is fixed on the support, and the center height of the calibration plate a is consistent with the center height between the two CCD cameras. Placing a light source to illuminate the calibration plate a as shown in fig. 6 c;
4) And adjusting zoom rings of the first CCD camera and the second CCD camera to make the focal lengths of the first CCD camera and the second CCD camera equal, and enabling the whole image of the calibration plate to be full of the shot picture. And adjusting focusing rings of the first CCD camera and the second CCD camera to enable the images of the calibration plate shot by the first CCD camera and the second CCD camera to be clear. The aperture blades of the first CCD camera and the second CCD camera are adjusted, the aperture sizes of the aperture blades are equal, and the picture brightness is moderate;
5) Reading pictures shot by the first CCD camera and the second CCD camera, calibrating the relative positions of the centers of the first CCD camera and the calibration plate and the relative positions of the centers of the second CCD camera and the calibration plate, and recording calibration data;
6) Mounting the head-mounted display device to be tested on a fixing device 29 of a head-mounted display device adjusting device, and adjusting optical axes of two display modules of the head-mounted display device and optical axes of a first CCD camera and a second CCD camera to be tested are collinear;
7) Generating a cross image at the centers of two display modules of the head-mounted display device to be tested through a main board or a control board of the head-mounted display device to be tested, generating cross virtual images at object planes of a first objective lens and a second objective lens after passing through an optical system of the head-mounted display device, and generating cross images on light sensitive planes of a first CCD camera and a second CCD camera after passing through the first objective lens and the second objective lens respectively;
8) And calculating the eccentric displacement and the visual axis deviation of the head-mounted display device according to the calibration data and the cross image position data of the head-mounted display device in the first CCD camera and the second CCD camera.
One specific example mode of the method for detecting the optical modulation transfer function of the head-mounted display device by using the head-mounted display device testing apparatus described above includes the following steps:
1) The base of the image receiving system is placed on a plane with the height of about 1.5m in the horizontal position, so that the base is convenient for an operator to operate;
2) Connecting interfaces of two CCD cameras in the image receiving system with an interface of a switch by using two network wires, and connecting a computer of the image processing system with the switch by using the network wires;
3) The support moves to a set position along the direction of the guide rail, the support is placed on the guide rail at a position which is 1m away from the centers of the two cameras, the support is preferably placed at a position which is 3-5m away from the front of the CCD camera, the calibration plate b is fixed on the support, and the support is adjusted to enable the center height of the calibration plate b to be consistent with the center height between the two cameras. Placing a light source to illuminate the calibration plate b as shown in fig. 6 c;
4) Adjusting zoom rings of the first CCD camera and the second CCD camera to enable focal lengths of the first CCD camera and the second CCD camera to be equal, enabling the whole image of the calibration plate to be full of a shot picture, adjusting focusing rings of the first CCD camera and the second CCD camera to enable the image of the calibration plate shot by the first CCD camera and the second CCD camera to be clear, and adjusting aperture blades of the first CCD camera and the second CCD camera to enable aperture sizes of the first CCD camera and the second CCD camera to be equal and picture brightness to be moderate;
5) Reading pictures shot by the first CCD camera and the second CCD camera, calculating the modulation transfer function MTF value of at least one region of interest in the pictures, calculating the modulation transfer function MTF in real time, displaying the value on a display unit, adjusting a focusing ring to find the position with the maximum modulation transfer function, and recording that the modulation transfer function value at the moment is the modulation transfer function value MTF of the test system0 . If there are several regions of interest, recording the modulation transfer function MTF of all the regions of interest0 (1)、MTF0 (2)、…、MTF0 (n) is a modulation transfer function value of the test system;
6) Mounting the head-mounted display device to be tested on a fixing device 29 of a head-mounted display device adjusting device, and adjusting optical axes of two display modules of the head-mounted display device and optical axes of a first CCD camera and a second CCD camera to be tested are collinear;
7) Generating an oblique square array test chart at the centers of two display modules of the head-mounted display device to be tested through a main board or a control board of the head-mounted display device to be tested, wherein the oblique square array test chart is shown in fig. 6b, virtual images are generated on object planes of a first objective lens and a second objective lens after the virtual images pass through an optical system of the head-mounted display device to be tested, and images are generated on light sensitive planes of a first CCD camera and a second CCD camera respectively after the virtual images pass through the first objective lens and the second objective lens;
8) Reading pictures shot by the first CCD camera and the second CCD camera, calculating the modulation transfer function MTF value of at least one region of interest selected in the step 5) in the pictures, calculating the modulation transfer function in real time, displaying the values on a display unit, and adjusting a focusing ring to find the modulation transfer functionThe maximum position records that the modulation transfer function value at the moment is the modulation transfer function value MTF of the cascade connection of the head-mounted display device and the test system1 . If there are several regions of interest, recording the modulation transfer function MTF of all the regions of interest1 (1)、MTF1 (2)、…、MTF1 (n) modulation transfer function values for a cascade of head mounted display devices and test systems;
9) Modulation of transfer function value MTF by test system0 MTF cascaded with head-mounted display device and system1 The value may be the modulation transfer function MTF (n) =mtf of the head-mounted display device1 (n)/MTF0 (n)。
The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention.