Head-mounted display and visual acuity inspection method

Abstract

Provided is a head-mounted display in which a space for inspection is minimized and inspection can be performed by a subject alone, so that a burden for visual acuity inspection is small.　A head-mounted display 10 for performing visual acuity inspection comprises: a screen 20 for displaying an index X for visual acuity inspection; a control unit 30 for changing the index X according to the content of the visual acuity inspection; and an answer reception unit 34 for receiving an answer by means of at least one of the movement of the head, the line of sight, and the voice from the subject H.

Description

Head-mounted display and vision testing method

[0001] The present invention relates to a head-mounted display for conducting a visual acuity test and a visual acuity test method.

[0002] Traditionally, vision tests have been conducted using a paper or display with a number of Landolt rings of different sizes, with the test being conducted on each eye at a fixed distance from the paper or display.

[0003] For example, in the index display device and ophthalmic device disclosed in Patent Document 1, the subject can look at an index (such as a Landolt ring) displayed on a display by an examiner (such as a doctor) operating a controller, allowing the subject's visual acuity, etc. to be examined.

[0004] Japanese Patent Application Laid-Open No. 2022-162135

[0005] However, in the conventional devices including the target display device and ophthalmic device disclosed in Patent Document 1, in order to conduct a visual acuity test on a subject, space is required to accommodate the examiner and to maintain a predetermined distance from the target to the subject. In addition, the conventional devices require the examiner to be present and to operate a controller, which creates a problem of a heavy burden on the visual acuity test.

[0006] The present invention has been made in consideration of these problems and demands, and its purpose is to provide a head-mounted display and a vision testing method that require minimal space for testing and that can be performed by the subject alone, thereby reducing the burden on the subject during the vision test.

[0007] According to one aspect of the present invention, there is provided a head-mounted display for conducting a visual acuity test, comprising: a screen for displaying an index for the visual acuity test; a control unit for changing the index according to the content of the visual acuity test; and a response receiving unit for receiving responses from the subject in the form of at least one of head movement, line of sight, and voice.

[0008] Preferably, the answer based on the gaze is obtained by grasping the gaze position on the screen where the subject is looking.

[0009] Preferably, the answer based on the gaze is given based on the direction of movement of the gaze position on the screen that the subject is looking at.

[0010] Preferably, the control unit causes an answer indicator to be displayed on the screen.

[0011] Preferably, the control unit displays the indicator a predetermined number of times to confirm that the subject has a specific visual acuity, and if the subject answers all of the predetermined number of times correctly through the answer receiving unit, it confirms that the subject has a visual acuity that is one level higher, and if the subject answers incorrectly even once of the predetermined number of times, it recognizes the specific visual acuity as the subject's visual acuity reference value.

[0012] Preferably, the control unit determines the actual visual acuity value based on the visual acuity reference value and statistical data of the visual acuity reference value and the actual visual acuity value that has been set in advance.

[0013] Preferably, the control unit blurs the index from a predetermined size.

[0014] Preferably, the device further includes a storage device that stores an individual ID corresponding to the subject and past vision test results corresponding to the individual ID, and the control unit detects trends in vision test results based on the vision test results corresponding to the subject who underwent a vision test, and presents the results of the current vision test and the trends in the vision test results.

[0015] Preferably, the device further comprises an iris authentication unit that authenticates the iris of the pupil to identify the subject.

[0016] Preferably, the control unit performs calibration to improve the accuracy of detecting the gaze position on the screen that the subject is looking at before the visual acuity test.

[0017] Preferably, after the calibration, the control unit performs a test involving detection of the gaze position multiple times, including a visual acuity test.

[0018] According to another aspect of the present invention, there is provided a method for testing visual acuity using a head-mounted display comprising: a screen for displaying indices for a visual acuity test; a control unit for changing the indices in accordance with the content of the visual acuity test; and an answer receiving unit for receiving an answer from the subject by at least one of head movement, line of sight, and voice, wherein the control unit receives an answer from the subject regarding the indices displayed on the screen by at least one of head movement, line of sight, and voice from the subject.

[0019] According to the present invention, a head-mounted display is provided that is equipped with a control unit that changes the indicators in accordance with the content of the visual acuity test, and an answer receiving unit that receives answers from the subject using at least one of head movement, line of sight, and voice.This minimizes the space required for the test, and since the control unit changes the indicators, there is no need for an examiner to be present or for the examiner to operate a controller, thereby reducing the burden of the visual acuity test, and furthermore, it is possible to provide a head-mounted display and a visual acuity testing method that do not require the subject to use their hands to answer questions.

[0020] 1 is a diagram illustrating a head-mounted display 10 according to an embodiment. FIG. 1A is a cross-sectional structural view and FIG. 1B is a plan structural view illustrating a display main body 12 according to an embodiment. FIG. 1B is a diagram illustrating a control device 18 according to an embodiment. FIG. 1C is a flowchart illustrating the implementation of a test by a control unit 30 of the control device 18. FIG. 1D is a flowchart illustrating the flow of a visual acuity test. FIG. 1E is a diagram illustrating a state in which an index X is displayed on a screen 20. FIG. 1F is a diagram illustrating a state in which a subject H answers by moving his / her gaze to a position corresponding to the index X. FIG. 1G is a diagram illustrating a state in which a desired test menu or the end of the test is accepted. FIG. 1H is a diagram illustrating an example of an output of all the results of the test. FIG. 1F is a flowchart illustrating the flow of a visual field test. FIG. 1G is a diagram illustrating a state in which an index X' for performing a visual field test is displayed on the screen 20. FIG. 1H is a diagram illustrating a state in which another index X' is displayed at a different position. FIG. 1G is a diagram illustrating a state in which an index X is displayed on the screen 20 according to Modification 7. FIG. 1H is a diagram illustrating a state in which an index X is displayed on the screen 20 according to Modification 7. FIG. 1H is a diagram illustrating a state in which an index X is displayed on the screen 20 according to Modification 9. FIG. 1H is a diagram illustrating a state in which an index X is displayed on the screen 20 according to Modification 9.

[0021] (Configuration of Head Mounted Display 10) As shown in FIG. 1, the head mounted display 10 according to this embodiment generally includes a display main body 12, a housing 14, headphones 16, and a control device 18.

[0022] The display body 12 is a component placed in front of the eyes of the subject H, and as shown in FIG. 2, roughly comprises a screen 20, a lens 22, a light source 24, a hot mirror 26, and a camera 28.

[0023] The screen 20 is a member that displays the indicator X (see FIG. 6) for the visual acuity test, and, if necessary, an explanatory text for the subject H and an image for accepting answers from the subject H.

[0024] The lens 22 is a component placed between the eye Y of the subject H and the screen 20, and has the role of focusing on the screen 20 at a close distance of about 10 centimeters between the eye Y and the screen 20.

[0025] The light source 24 is a component that emits infrared light toward the eye Y, and in this embodiment, six LEDs (light sources 24) are arranged near the lens 22. Of course, the light sources 24 are not limited to LEDs, and other lamps may be used. The number of light sources 24 may also be increased or decreased as needed (at least two are required).

[0026] The hot mirror 26 is a half mirror placed between the screen 20 and the lens 22, and in this embodiment, it transmits light from the screen 20 without reflecting it, and reflects light from the light source 24 (including light reflected within the eye Y).

[0027] The camera 28 receives light that is emitted from the light source 24, reflected within the eye Y, and then reflected by the hot mirror 26. This makes it possible to grasp the positions of the multiple light sources 24 in the image viewed by the camera 28, and the positional relationship of the multiple light sources 24 viewed by the camera 28 changes according to the movement of the eye Y of the subject H. In other words, it is possible to determine which position on the screen 20 the eye Y of the subject H is looking at based on the positional relationship of the multiple light sources 24 viewed by the camera 28.

[0028] Returning to Figure 1, the housing unit 14 is a flexible member that is wrapped around the side of the subject H's head and the back of the head, and both ends are connected to the display main body 12, so that the display main body 12 can be positioned and held in a predetermined position in front of the subject H's eyes.

[0029] The headphones 16 are a component for conveying necessary explanations and the like to the subject H by voice as needed during the visual acuity test.

[0030] The control device 18 is a device for controlling the image (including the index X) displayed on the screen 20, the light emission of the light source 24, the operation of the camera 28, and the sound from the headphones 16, and as shown in FIG. 3, it roughly comprises a control unit 30, a memory device 32, and a response receiving unit 34.

[0031] The control device 18, the display body 12, and the headphones 16 exchange signals and information via wired or wireless transmission means (not shown). Although the control device 18, the display body 12, and the headphones 16 are depicted as separate entities in the figure, the control device 18 may be built into the display body 12, etc.

[0032] The control unit 30 is a part that performs the visual acuity test by operating each component included in the head-mounted display 10, and corresponds to, for example, a CPU and a GPU. Note that specific operations performed by the control unit 30 will be described later.

[0033] The storage device 32 is a device that stores, for example, statistical data on a preset visual acuity reference value VP and an actual visual acuity value RP, an individual ID corresponding to the subject H, and past visual acuity test results corresponding to the individual ID, and is realized by, for example, various types of RAM (Random Access Memory), various types of ROM (Read-Only Memory), flash memory, etc. The storage device 32 may also be a storage medium that is used via an interface, such as a Universal Serial Bus (USB) (registered trademark) memory, a Compact Disc (CD), a Digital Versatile Disk (DVD), a memory card, a solid-state drive, an Integrated Circuit (IC) card, an optical card, a mask ROM, an Erasable Programmable Read-Only Memory (EPROM), or an Electronically Erasable Programmable Read-Only Memory (EEPROM).

[0034] The answer receiving unit 34 is a part that receives answers based on the gaze of the subject H. The answer receiving unit 34 can detect the gaze position on the screen 20 that the subject H is looking at and recognize the answer based on the current gaze position (static recognition), or can detect the direction in which the subject H has moved his / her gaze position (movement direction of the gaze position) and recognize the answer (dynamic recognition).

[0035] (Inspection by the Control Unit 30) Next, the inspection by the control unit 30 of the control device 18 will be specifically described with reference to the flowchart shown in FIG.

[0036] First, in order to identify the subject H, iris data of the eye Y of the subject H wearing the head-mounted display 10 is acquired (S1). In this embodiment, the control unit 30 turns on the light source 24 of the display main body 12, receives the iris illuminated by the light from the light source 24 with the camera 28, and performs iris authentication based on the iris data of each subject H stored in the storage device 32. In other words, the control unit 30, the light source 24, the camera 28, and the storage device 32 constitute an iris authentication unit.

[0037] Note that iris authentication may be performed by, for example, lighting up the screen 20 and illuminating the eye Y with light from the screen 20 instead of using light from the light source 24. Alternatively, a separate light source dedicated to iris authentication may be provided.

[0038] If, as a result of iris authentication, the iris data of the subject H is not present in the memory device 32 (if the result in S2 is "No"), the control unit 30 associates an individual ID with the iris data and stores it in the memory device 32, and then proceeds to calibration (S4).

[0039] If, as a result of iris authentication, an individual ID corresponding to the iris data of the subject H is present in the storage device 32 (if the result in S2 is "Yes"), the control unit 30 checks whether a predetermined period (e.g., "24 hours") has passed since the most recent examination of the subject H having that individual ID (S3). If, as a result of the check, the predetermined period has not passed (if the result in S3 is "No"), the control unit 30 skips calibration (S4) and proceeds to examination (S5). Conversely, if the predetermined period has passed (if the result in S3 is "Yes"), the control unit 30 performs calibration (S4) to improve the accuracy of detecting the gaze position on the screen 20 that the subject H is looking at.

[0040] Next, calibration (S4) will be described. As described above, in the head-mounted display 10 according to this embodiment, the answer receiving unit 34 receives an answer from the subject H (for example, an answer indicating the direction in which the Landolt ring, serving as the index X, is missing) in response to a movement of the subject H's line of sight. For this reason, the control unit 30 causes the light source 24 of the head-mounted display 10 to emit light, irradiating the eye Y of the subject H with infrared light, and captures an image of the light reflected by the eye Y with the camera 28, thereby detecting the position at which the subject H is looking.

[0041] Specifically, the center of the eyeball is detected, and the optical axis of the eye is detected from the center of the eyeball and the center of the pupil. If the optical axis of the eye can be detected, the movement of the eye Y of the subject H (movement of the line of sight) can be detected.

[0042] However, when detecting the position where subject H is looking, it is difficult to determine the position where the subject H is looking by simply detecting the pupil, because the human eye has a cornea and the line of sight may be slightly misaligned with the optical axis of the eye. Therefore, calibration is performed to detect the line of sight connecting the fovea (the part that recognizes images) of the retina of each subject H's eye and the center of the eyeball.

[0043] After the calibration is completed, the control unit 30 enters the inspection step (S5).

[0044] In the test (S5), only a visual acuity test may be performed, or other eye tests may be performed in addition to the visual acuity test. In this embodiment, a case where a visual acuity test and a visual field test are performed will be described.

[0045] First, a visual acuity test is carried out. The flow of the visual acuity test will be specifically explained using the flowchart shown in FIG.

[0046] In this embodiment, the visual acuity test is performed one eye at a time. The control unit 30 displays an indicator (e.g., a Landolt ring) X three times to confirm that the subject H has a specific visual acuity. If the subject H answers correctly all three times through the answer receiving unit 34, the control unit 30 confirms that the subject H has a visual acuity that is one level higher. If the subject H answers correctly two or less times, the control unit 30 recognizes that the specific visual acuity is the visual acuity reference value VP of the subject H.

[0047] For example, the control unit 30 displays an index X on the screen 20 to confirm that the visual acuity reference value VP is "0.2" (S101: see FIG. 6). A Landolt ring (index X) of a size corresponding to a visual acuity reference value VP of 0.2 is displayed in the center of the screen 20. Additionally, arrows Z, which are answer indicators, are displayed at the top, bottom, left, and right edges of the screen 20. More specifically, the index X is displayed in the center of the screen 20, and an arrow Z pointing right is displayed to the right of the index X, an arrow Z pointing left is displayed to the left of the index X, an arrow Z pointing up is displayed to the top of the index X, and an arrow Z pointing down is displayed to the bottom of the index X. While the arrow Z is displayed in this embodiment, the present invention is not limited to this. Alternatively, the arrow Z pointing up may be replaced with a character indicating a direction, such as "up" or "right." The index X is displayed in a predetermined position (center) on the screen 20, but the position of the notch (gap) of the index X is randomly selected among the top, bottom, left, and right. The answer indicators may include buttons for selecting an answer and other indicators that are not answer options but serve as markers for the subject H to use when moving his or her gaze.

[0048] Furthermore, the control unit 30 displays a pointer P at the position on the screen 20 that the subject H is currently looking at (hereinafter also referred to as the "point of view of the subject H"). When the subject H moves his / her line of sight, the control unit 30 detects this and moves the display position of the pointer P in accordance with the movement of the line of sight.

[0049] When an index X is displayed during a visual acuity test, the subject H is required to respond by moving his or her gaze to a position corresponding to the index X (for example, in the case of a Landolt ring, the "arrow Z in the direction of the missing part") (eye tracking), as shown in FIG.

[0050] If the line of sight (pointer P) is positioned at the correct position within a predetermined time after the indicator X is displayed, the answer receiving unit 34 recognizes the answer to the indicator X as the "correct answer."

[0051] Conversely, if the line of sight (pointer P) is not positioned on any of the arrows Z within a predetermined time after the indicator X is displayed, or if the line of sight (pointer P) is positioned in an incorrect position, the answer receiving unit 34 determines that the answer to the indicator X is "incorrect." In this way, the control unit 30 determines whether the received answer is correct or not.

[0052] In this embodiment, it is determined that the subject H recognizes the index X by detecting that the gaze of the subject H is positioned at the correct arrow Z, but the gaze does not necessarily have to be moved to the position of the arrow Z, and it may be determined that the subject H recognizes the index X by detecting that the gaze has moved within a predetermined distance from the arrow Z. Furthermore, regardless of the position of the arrow Z, it may be determined that the subject H recognizes the index X when it is detected that the gaze has moved in the correct direction with the index X as the center.

[0053] Due to the structure of the human eye, there are cases where the accuracy of detecting the gaze position is low. In such cases, even if the subject H is viewing the arrow Z, the detected gaze position may not be on the arrow Z. Even in such cases, if a configuration is used that detects that the gaze has moved within a predetermined distance from the arrow Z or that detects that the gaze has moved in the correct direction around the index X, it will not be determined that the subject H is unable to correctly recognize the index X even though he or she is viewing the arrow Z, and the test can be carried out without any problems.

[0054] 5, the control unit 30 repeats this process three times and checks the number of times the answer has been determined to be "correct" (S102). If the answer is not "correct" all three times (if the result in S102 is "No"), the control unit 30 determines that particular visual acuity (i.e., "0.2") as the visual acuity reference value VP for the subject H (S103). That is, after the display of the index X, the acceptance of the answer, and the determination of correctness are repeated three times, it is determined whether to display an index with a higher visual acuity or to display the visual acuity result.

[0055] If all three tests are "correct" (if the result in S102 is "Yes"), the control unit 30 performs three new tests with a visual acuity one level higher (for example, "0.4") than the specific visual acuity (i.e., "0.2") (S104). The three new tests are essentially the same as the above-described tests, except that the size of the index X is different.

[0056] The control unit 30 performs three new tests and checks the number of times the test was recognized as "correct" (S105). If the test was not "correct" all three times (if the result in S105 is "No"), the control unit 30 recognizes the specific visual acuity (i.e., "0.4") as the visual acuity reference value VP of the subject H (S106).

[0057] If all three tests are "correct" (if the result in S105 is "Yes"), the control unit 30 conducts three new tests with a visual acuity one level higher than the specific visual acuity (i.e., "0.4") (for example, "0.6") (S104).

[0058] In this way, the control unit 30 certifies the visual acuity reference value VP of the subject H. Furthermore, the control unit 30 determines the actual visual acuity value RP based on this visual acuity reference value VP and the "statistical data of the visual acuity reference value and the actual visual acuity value" that is set in advance and stored in the storage device 32, and records the test date, visual acuity reference value VP, and actual visual acuity value RP in association with the individual ID corresponding to the subject H.

[0059] The actual visual acuity value RP is a "visual acuity" value currently widely used in eye clinics, eyeglass retailers, etc. When there is a discrepancy between the visual acuity reference value VP tested using the head-mounted display 10 according to this embodiment and the actual visual acuity value RP, "statistical data of visual acuity reference value and actual visual acuity value" is obtained by accumulating a large number of specific correspondences, such as, for example, that the subject H, whose visual acuity reference value VP is "0.1," has an actual visual acuity value RP of "0.2," and by making it possible to calculate the actual visual acuity value RP corresponding to the visual acuity reference value VP. Of course, the statistical data may also be a relational expression that can calculate the actual visual acuity value RP from the visual acuity reference value VP.

[0060] Once the vision test for one eye is completed, the vision test for the other eye is performed in the same manner.

[0061] 4, after the first test (visual acuity test) is completed, the control unit 30 checks whether an additional test is necessary (S6). The test menu is predetermined, and if the need for an additional test is clear (if the result in S6 is "Yes"), the additional test is automatically conducted (S7).

[0062] Alternatively, when the examination menu has not been decided or when the subject H is deciding the order of multiple examinations, the control unit 30 displays the examination menu on the screen 20, as shown in Fig. 8. The subject H can take the desired examinations in succession by moving the pointer P to the desired examination from the examination menu using line of sight movement.

[0063] If the subject H does not wish to undergo additional testing, he or she moves the pointer P to "Test End" by moving his or her line of sight. This ends the test (if the result in S6 is "No"). When the test is finished, the control unit 30 stores all test results in the storage device 32, linking them to individual IDs.

[0064] An example output of all test results is shown in Figure 9. All test results include not only the current result, but also past results and their dates (progression of visual acuity test results) linked to the same individual ID. The "progression of visual acuity test results" may also be displayed using a bar graph, line graph, or the like. Furthermore, it may also include suggestions such as "Your right eye's vision is deteriorating. We recommend wearing glasses or contact lenses. You may also have glaucoma, so we recommend you undergo a detailed examination," or referrals to "nearby medical institutions."

[0065] Next, a "visual field test" will be described as an example of an additional test (a test involving detection of the gaze position of the subject H) using the flowchart shown in Fig. 10. Note that the "test involving detection of the gaze position of the subject H" may also include a test in which some kind of answer is given based on detection of the gaze position of the subject H.

[0066] In this embodiment, the visual field test is performed one eye at a time. The control unit 30 displays an index X (a black circle in this embodiment) in the center of the screen 20 (S201: see FIG. 11). After confirming that the eye Y of the subject H is looking at this index X (the subject H's viewpoint is near the index X), the control unit 30 displays an index X' for performing the visual field test (S202: see FIG. 12).

[0067] When the index X' comes into the subject's field of view, the subject H should look at the index X' within a predetermined time. If the subject's viewpoint moves to the vicinity of the index X' within the predetermined time, it is determined that "the index X' is in the field of view" ("Yes" in S203). If the subject's viewpoint does not move to the vicinity of the index X' within the predetermined time after the index X' is displayed, the control unit 30 determines that "the index X' did not come into the field of view" ("No" in S203).

[0068] When a predetermined time has elapsed since the display of the index X', the control unit 30 erases the index X' and returns to displaying only the index X' (S204: FIG. 11). Thereafter, the control unit 30 displays another index X' at a different position from the previous index X' for a predetermined time (S202: see FIG. 13). As with the previous index X', the control unit 30 determines whether this index X' has entered the field of view by determining whether the subject H's gaze has moved within the predetermined time (S203).

[0069] In this way, the indicator X' is displayed in the required positions in order, and the positions that have entered the visual field of the subject H / the positions that have not are confirmed to give the overall result of the visual field test for the eye Y of the subject H.

[0070] Once the visual field test for one eye is completed, the visual field test for the other eye is performed in the same manner.

[0071] (Features of the head-mounted display 10 according to the present embodiment) The head-mounted display 10 according to the present embodiment is equipped with a control unit 30 that changes the index X according to the content of the visual acuity test, and an answer receiving unit 34 that receives answers from the subject H by moving their line of sight, thereby minimizing the space required for the test, and because the control unit 30 changes the index X, there is no need for an examiner to be present or for the examiner to operate a controller, which reduces the burden on the visual acuity test, and furthermore, there is no need for the subject H to use their hands to respond. In particular, when using a head-mounted display 10 for VR, the subject H cannot see what is in front of them, making it difficult to operate, and it may be a burden for them to get used to operating it if they have difficulty using their hands, for example.

[0072] Furthermore, since the subject H can respond by moving his or her gaze, the burden of learning how to operate the device can be reduced compared to using a controller or the like. Furthermore, although the arrow Z is displayed in the above-described embodiment, the subject H can respond by detecting the direction in which the pointer P moves as the subject H moves his or her gaze, so there is no need to display an answer button or the like. By having the subject respond by detecting the direction in which the pointer P moves, the answer can be accepted even in cases where the calibration accuracy is poor and it is not possible to pinpoint that the subject is looking at the arrow Z. Note that if the arrow Z or the like is not displayed and the answer is accepted only based on the direction of the gaze relative to the index X, the answer can be accepted with high accuracy even if the detection accuracy of the gaze position is poor, as long as the direction is not incorrect.

[0073] (Variation 1) In the above-described embodiment, the answer accepting unit 34 accepts answers from the subject H by moving his or her gaze during the visual acuity test. However, instead, the answer accepting unit 34 may accept answers from the subject H by voice, such as "right" or "up." In this case, the answer accepting unit 34 includes a microphone and a voice recognition function for capturing voice. Furthermore, the answer may be accepted by shaking the head (head) or tilting the head in the direction of the answer (answer by head movement). In this case, a gyro sensor incorporated in the head-mounted display 10 detects the tilt and direction of the head and determines the answer of the subject H. Furthermore, answers are not limited to answers by gaze, voice, or head movement, but may be any two or more of these. If multiple answer accepting means are provided, answers can be accepted even when it is difficult to accept one answer.

[0074] (Variant 2) In addition, in the above-described embodiment, a portable head-mounted display 10 attached to the head of the subject H was used, but instead, other types of head-mounted displays may be used, such as a stationary head-mounted display that is used while the subject H is lying on his or her back.

[0075] (Variation 3) Furthermore, in the above-described embodiment, if subject H answers correctly three times in the visual acuity test, it is confirmed that he / she has one level of visual acuity that is one level higher, and if he / she answers correctly two times or less, that visual acuity is recognized as the visual acuity reference value VP of subject H. However, instead of this, in a test for a relatively high level of visual acuity, if he / she answers correctly two or more times, it may be confirmed that he / she has one level of visual acuity that is one level higher, and if he / she answers correctly one time or less, that visual acuity may be recognized as the visual acuity reference value VP of subject H. Furthermore, the number of times the test is conducted is not limited to "three times," and it may be conducted a predetermined number of times.

[0076] (Variation 4) Furthermore, although examples of visual acuity tests and visual field tests have been given as types of tests, cognitive function tests and dry eye tests may also be used. Regarding the relationship between visual function and cognitive function, the Japan Geriatrics Society proposed the concept of "eye frailty" in 2014.

[0077] (Modification 5) In the above-described embodiment, the pointer P is displayed at the position where the subject H looks. However, the position where the subject H looks does not have to be displayed with the pointer P.

[0078] (Variation 6) In the above-described embodiment, a Landolt ring was used as the index X. However, other index Xs, such as an "U" character consisting of two parallel lines and a line connecting one end of these lines, or English letters, can also be used. For example, an index known as an "E chart" can also be used. The E chart is a table in which multiple "E"s of different sizes are arranged with different opening directions. Therefore, when using an E chart, the letter "E" is displayed on the display instead of the Landolt ring. A "Snellen chart" can also be used. The Snellen chart consists of 11 rows of various sized letters of the alphabet. In this case, letters of the alphabet are displayed on the display. Furthermore, pictures of birds, fish, etc., can be used instead for children. In this case, the pictures are displayed while changing their size, and the answer is selected.

[0079] (Variation 7) In the above-described embodiment, arrows Z are arranged up, down, left, and right around the index X, but instead of arrows, letters such as "up" and "down" may be displayed as shown in Fig. 14. Alternatively, as shown in Fig. 15, without displaying arrows or letters, the subject may be instructed to move their gaze in an open direction of the Landolt ring (index X) or the like before the start of the test, and whether or not the subject H can see the object may be determined based on the subject H's response.

[0080] Alternatively, arrows pointing in different directions or letters such as "up" and "down" may be displayed side by side, and the subject H may answer by gazing at the arrows, etc. Furthermore, instead of indicators indicating directions, "marks" such as dots, triangles, etc. may be displayed.

[0081] (Variation 8) In the above-described embodiment, the next test is selected from the test menu using eye movement, but this is not limited to this. The test menu may be created in advance, and the order of the tests may be determined in advance.

[0082] (Variation 9) In the above-described embodiment, the Landolt ring, which is the index X, is displayed as is on the screen 20. However, instead of this, blurring may be added to the Landolt ring, which is the index X. Specifically, when displaying a Landolt ring smaller than a Landolt ring corresponding to a predetermined visual acuity such as 1.0 or 0.8, a certain width may be blurred (blurred display) as shown in Fig. 16. In other words, when measuring visual acuity better than the Landolt ring corresponding to the predetermined visual acuity such as 1.0 or 0.8, the width of the blurred display of the Landolt ring may be increased rather than making the Landolt ring smaller.

[0083] For example, the gap width W when blur is added to a Landolt ring for measuring 0.8 visual acuity is expressed as the blur diameter, and the Landolt ring for measuring 0.8 visual acuity is displayed so that the gap width W is the blur diameter (blur diameter = gap width W), while the Landolt ring corresponding to better visual acuity such as 1.0 is displayed with blur added so that the blur diameter is twice this gap width W (blur diameter = 2 × gap width W), as shown in Figure 17.

[0084] Increasing the blur diameter in this way increases the line width of the Landolt ring and, conversely, decreases the gap. Statistical data can be used to determine the level of visual acuity of subject H who is able to visually identify the direction of the gap in the Landolt ring when the blur diameter is twice the gap width W.

[0085] For example, many subjects whose visual acuity is known in advance are asked to view a Landolt ring or the like with a blur diameter twice the gap width W, and experimental data is collected, and from this data, the reference visual acuity is determined based on the visual acuity of the subjects who can view the Landolt ring. If a relational expression is obtained from such statistical data, the reference visual acuity can also be determined from this relational expression.

[0086] Similarly, the reference visual acuity can be determined when the blur diameter is 2.5 or 3 times the gap width W, and for tests of visual acuity better than 0.8, visual acuity can be measured using a Landolt ring with blur added.

[0087] In this way, by using a blurred Landolt ring, there is no need to display a Landolt ring that is smaller than a certain size, so visual acuity can be measured even when using a VR head-mounted display that has low resolution and cannot display a small Landolt ring, in other words, where a small Landolt ring would appear distorted if displayed.

[0088] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0089] 10...head mounted display, 12...display main body, 14...casing part, 16...headphones, 18...control device 20...screen, 22...lens, 24...light source, 26...hot mirror, 28...camera, 30...control part, 32...storage device, 34...answer receiving part H...subject, X...index, Y...(subject H's) eye, VP...visual acuity reference value, RP...actual visual acuity value, Z...arrow, P...pointer, W...gap width

Claims

1. A head-mounted display for performing visual acuity tests, comprising: a screen that displays an index for the visual acuity test; a control unit that changes the index according to the content of the visual acuity test; and a response receiving unit that receives responses from the subject in the form of at least one of head movement, line of sight, and voice.

2. The head mounted display according to claim 1, wherein the answer based on the gaze is obtained by grasping the gaze position on the screen where the subject is looking.

3. The head mounted display according to claim 1, wherein the answer based on the gaze is based on the moving direction of the gaze position on the screen that the subject is looking at.

4. The head mounted display according to claim 1, wherein the control unit causes an answer indicator to be displayed on the screen.

5. The control unit displays the indicator a predetermined number of times to confirm that the subject has a specific visual acuity, and if the subject answers all of the predetermined number of questions correctly through the answer receiving unit, confirms that the subject has a higher visual acuity, and if the subject answers incorrectly even once among the predetermined number of answers, recognizes the specific visual acuity as the subject's visual acuity reference value.

6. A head-mounted display as described in claim 5, wherein the control unit determines the actual visual acuity value based on the visual acuity reference value and statistical data between the predetermined visual acuity reference value and the actual visual acuity value.

7. The head mounted display according to claim 1, wherein the control unit adds blur to the indicator from a predetermined size.

8. A head mounted display as described in claim 1, further comprising a storage device that stores an individual ID corresponding to the subject and past vision test results corresponding to the individual ID, wherein the control unit detects a trend in vision test results based on the vision test results corresponding to the subject who underwent a vision test, and presents the results of the current vision test and the trend in the vision test results.

9. The head mounted display according to claim 1, further comprising an iris authentication unit that identifies the subject by authenticating the iris of the subject's eye.

10. The head-mounted display according to claim 1, wherein the control unit performs calibration to improve the detection accuracy of the line-of-sight position on the screen that the subject is looking at before performing the vision test.

11. The head-mounted display according to claim 10, wherein the control unit performs an inspection involving detection of the line-of-sight position a plurality of times including a vision test after the calibration is performed.

12. Using a head-mounted display comprising a screen that displays an indicator for a vision test, a control unit that changes the indicator according to the content of the vision test, and a response reception unit that receives a response by at least one of head movement, line of sight, and voice from the subject, a vision test method in which the control unit receives a response from the subject regarding the indicator displayed on the screen by at least one of head movement, line of sight, and voice from the subject.

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