Vision measurement in VR headsets

Abstract

The headset includes a first display, a second display smaller than the first display and having a lower resolution than the first display, and a dichroic filter positioned to pass visible light from the first display to the eye and reflect visible light from the second display to the eye. The pixel data control circuit is coupled to, in response to the first vision test selection, dim the first display while simultaneously activating the second display to display the vision test pattern. Other aspects are described and claimed.

Description

[Technical field]

[0001] Related Applications This patent application claims the benefit of the earlier filing date of U.S. Provisional Application No. 63 / 325,963, filed March 31, 2022.

[0002] The subject matter of this disclosure relates to techniques for measuring a human user's visual acuity using a virtual reality VR headset worn by the user. [Background technology]

[0003] Visual acuity is one of the most common measurements performed in an eye care professional's (ECP) office. It is proposed that visual acuity testing be performed with a head-mounted VR unit. The user puts on the VR head unit and the ECP operates the software that configures the display inside the VR head unit to display different visual elements whose shape, color or size are selected for the test. The user provides feedback to the ECP about how the user perceived the visual elements. Summary of the Invention [Means for solving the problem]

[0004] One aspect of the present disclosure is a method of measuring visual acuity to at least a 20 / 20 level using an otherwise relatively standard consumer VR headset, modified as described below. Standard consumer VR headsets do not have a display with sufficient full frame pixel resolution to measure visual acuity close to a 20 / 20 level. According to one aspect of the present disclosure, the wearer's central visual acuity may be measured using the following system. The headset includes a first display, a second display smaller than the first display and having a lower pixel count than the first display, and a dichroic filter positioned to pass visible light from the first display to the eye and reflect visible light from the second display to the eye. The pixel data control circuitry is coupled to dim the first display while simultaneously activating the second display to display a visual acuity testing pattern in response to a first visual acuity testing selection.

[0005] The above summary does not include an exhaustive list of all aspects of the present disclosure. The present disclosure is intended to include all systems and methods that may be implemented from any suitable combination of the various aspects summarized above, as well as those systems and methods disclosed in the following detailed description and specifically pointed out in the claims section. Such combinations may have certain advantages not specifically recited in the above summary.

[0006] In the accompanying drawing figures, several aspects of the present disclosure are illustrated by way of example and not by way of limitation, with like reference numerals referring to like elements. It should be noted that references to "an" or "one" aspects in the present disclosure do not necessarily refer to the same aspects, and these references refer to at least one aspect. Also, for the sake of brevity and reduction in the total number of drawings, a given drawing may be used to show features of more than one aspect of the present disclosure, and not all elements of a drawing are required for a given aspect. [Brief description of the drawings]

[0007] [Figure 1]A diagram of a user wearing a VR headset. [Diagram 2] FIG. 1 is a block diagram of an exemplary system for measuring visual acuity using a VR headset with an eye-tracking camera. [Diagram 3] FIG. 3 is a graph of an exemplary transmission spectrum of the first dichroic filter used in the system of FIG. 2. [Figure 4] FIG. 3 is a graph of an exemplary transmission spectrum of a first version of the second dichroic filter used in the first version of the system of FIG. [Diagram 5] FIG. 3 is a graph of an exemplary transmission spectrum of a second version of the second dichroic filter used in the second version of the system of FIG. [Figure 6] 13 is a graph of an exemplary transmission spectrum of another version of the first dichroic filter. [Figure 7] FIG. 1 is a block diagram of an exemplary system for measuring visual acuity using a VR headset without an eye-tracking camera. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Next, some aspects of the present disclosure will be described with reference to the accompanying drawings. Whenever the shape, relative position and other aspects of the described parts are not explicitly specified, it is meant that the scope of the present invention is not limited to only the parts shown, but is for illustrative purposes only. Also, although numerous details are shown, it will be understood that some aspects of the present disclosure can be practiced without these details. In other instances, well-known circuits, structures and techniques are not shown in detail so as not to obscure the understanding of this specification.

[0009] 1 shows a user (wearer) wearing a virtual reality VR headset that has been modified so that the VR headset can be used to perform various ophthalmic tests on the wearer's eyes, including vision testing for 20 / 20 or better vision. The modifications allow for the use of a relatively low-cost solution in the form of an otherwise consumer-grade VR headset.

[0010] FIG. 2 is a block diagram of an exemplary system for measuring visual acuity using a VR headset, in particular an exemplary system having an eye-tracking camera 2 (also referred to herein as an eye-tracking headset) aimed at the wearer's eyes. The eye-tracking camera 2 is an imaging device, whose image data may be processed by eye-tracking software (which may be executed by a processor in the VR headset) to measure the wearer's eye movements and track the direction of the wearer's gaze in real time. With the addition of electronic circuitry to process the image data generated by the eye-tracking camera, referred to herein as eye movement interpretation logic, the system allows hands-free feedback from the wearer of the headset during the visual acuity test. This exemplary system is in contrast to the exemplary VR headset shown in FIG. 7 and described further below. The exemplary VR headset of FIG. 7 may also perform visual acuity tests, but without an eye-tracking camera, and therefore with manual or audible feedback from the wearer.

[0011] Integrated within the headset housing of the system of Figure 2 is an illumination source 3, such as one or more near infrared (NIR) light emitting diodes that generate near infrared (NIR) light that illuminates the headset wearer's eyes as shown. This NIR light is reflected from the eye, then travels through lens 8, and then reflects off a first dichroic filter 11 towards an imaging lens 7, which forms an NIR image that is captured by the eye tracking camera 2. The reflected NIR light then passes through a second dichroic filter 12, described below.

[0012] The first dichroic filter 11 is angled with respect to the path taken by visible light, which is emitted from the first display device 4 and passes through the first dichroic filter 11 before hitting the eye. The first display device 4 may be the primary display device of a headset that serves to show virtual reality images to the eye. The first dichroic filter 11 is also angled such that the first dichroic filter 11 may reflect NIR light reflected from the eye towards the second dichroic filter 12. The second dichroic filter 12 is positioned to pass reflected NIR light from the first dichroic filter 11 towards the eye tracking camera 2, but the second dichroic filter 12 is also angled with respect to this path, such that it reflects visible light emitted from the second display device 6 towards the first dichroic filter 11. The second display device 6 may be a microdisplay. More generally, the display surface of the first display device 4 may be at least twice as large as that of the second display device 6, and the first display device 4 has at least twice as many full-frame pixels as the second display device 6. The first display device 4 may have, for example, a full-frame pixel count of 1920×1080 pixels or more, while the second display device 4 may have, for example, a full-frame pixel count of less than 2000 pixels, such as 60×32 dots, or even less than 1000 pixels. As will be explained below, the smaller size and lower pixel count of the second display device 6 allows a low-cost solution for 20 / 20 or better vision tests. Central vision tests using a variation of the typical Snellen test or Random E test (adapted to the distance between the eyes and the second display device 6 in the VR headset) may be performed using the smaller, lower pixel count second display device 6. This feature, in addition to some other ophthalmic tests performed using the VR headset, in particular uses the larger first display device 4 to display patterns for other tests.

[0013] In one embodiment of the present disclosure, the system of FIG. 2 operates on the basis that the first dichroic filter 11, which has a predominant or strong visible spectrum transmission, also exhibits a weak or small amount of reflection (of the visible spectrum). This small visible spectrum reflection may be sufficient to direct the test pattern emitted from the second display device 6 to the wearer's eye. FIG. 3 shows an exemplary transmission spectrum of the first dichroic filter 11. The transmission is not 100% or complete as shown, since there is some relatively small amount of visible band reflection. For example, the visible band reflection may be greater than zero but less than 10 percent across the entire range of visible colors, for example, in the visible spectrum spanning from 380 nm to 700 nm. In another example of the transmission spectrum of FIG. 3, the first dichroic filter 11 exhibits a visible light reflection between 5 percent and 10 percent. With respect to the NIR band, FIG. 3 also shows how the first dichroic filter 11 is nearly non-transmitting in the NIR region, since the NIR is strongly reflected.

[0014] Figure 4 shows an exemplary transmission spectrum of a first version of the second dichroic filter 12 that operates in the first version of the system shown just in Figure 2. In this first version, the second dichroic filter 12 is nearly non-transmitting (or nearly completely reflective) over the entire range of visible colors up to about 700 nm, but exhibits nearly complete transmission in the NIR region.

[0015] Figure 5 shows an exemplary transmission spectrum of another version of the second dichroic filter 12 suitable for use in another version of the system of Figure 2. In this other version of the system, the locations of the second display device 6 and the eye-tracking camera 2 are swapped with respect to those shown in Figure 2. Thus, the transmission spectrum of the second version of the second dichroic filter 12 is flipped around about 700 nm with respect to the first version shown in Figure 4. The second version reflects NIR light (from the first dichroic filter 11 towards the eye-tracking camera 2) and passes the full range of visible light (from the second display device 6 to the first dichroic filter 11).

[0016] Still referring to the system of FIG. 2, if the first version of the first dichroic filter 11 shown in FIG. 3 has weak visible band reflection characteristics (relative to its visible band transmission characteristics), the test pattern generated by the second display device 6 may be difficult for the wearer to see. Therefore, it may be necessary to darken the first display device 4 while the second display device 6 is activated to make the test pattern generated by the second display device 6 more visible to the wearer. For this reason, a pixel data control circuit may be added as shown in FIG. 2, which is coupled to darken the first display device 4 while simultaneously activating the second display device 6 to display the visual acuity test pattern. This pixel data control circuit is responsive to the selection of a first visual acuity test, and the image pattern of the first visual acuity test selection may be designed for a visual acuity test of 20 / 20 or greater, which may require the use of the second display device 6. However, when testing visual acuity of 20 / 40, 20 / 60 or less, the first display device 4 may be superior to the second display device 6 in showing a larger pattern. In this case, the pixel data control circuitry may dim the second display device 6 while simultaneously activating the first display device 4 to display a 20 / 40 or below vision test pattern. The term "dimming" as used herein means either turning off the display device and activating a display device with only black pixels in the full frame, or activating a display device that shows a sufficiently dark pixel pattern that does not interfere with the wearer's vision test using another display device (showing a vision test pattern). More generally, there may be a selection between the first display device 4 (e.g., a primary larger high pixel count display device) and the second display device 6 (e.g., a "microdisplay" or a smaller low pixel count display device) according to any one of two or more vision test selections, and the pixel data control circuitry provides the selected display device with the appropriate pixel pattern configured for each test selection.

[0017] As mentioned above, in the system of FIG. 2, the first dichroic filter 11 serves to reflect the vision test pattern displayed by the second display device 6 towards the eye. This visible band reflection may span the entire visible spectrum, but is a weak or slight reflection, as seen in the transmission curve shown in FIG. 3. Thus, the test pattern produced by the second display device 6 may be difficult for the wearer to see due to ghosting effects resulting from the weak reflection characteristics. Because the dichroic filter has two faces, the reflections from each of these faces may be specified or taken into account in the design of the system. If the dichroic filter is thin, e.g., effectively a "thin film," or if it is assumed that the second face is fully anti-reflective AR coated, then advantageously, undesirable, misaligned "ghost" reflections may be hidden from the wearer of the headset.

[0018] To address the ghosting problem, FIG. 6 shows an exemplary transmission spectrum of another version of the first dichroic filter 11 (suitable for use in both versions of the system of FIG. 2). This second version of the dichroic filter 11 allows the image generated by the second display device 6 to be reflected with greater fidelity (than the image achieved using the transmission spectrum shown in FIG. 3). Here, the transmission characteristic of the visible spectrum is not "uniform" over the entire visible range, but varies in such a way that it exhibits notches. In other words, the transmission characteristic has a band-pass characteristic. The transmission characteristic has several passbands that are matched to the individual colors that the first display device 4 respectively emits. The transmission notches are areas where the dichroic filter 11 is strongly reflective (e.g., at least 50%).

[0019] In the example shown in FIG. 6, the first dichroic filter 11 has three passbands that are matched to a first visible color that is a shade of blue, a second visible color that is a shade of green, and a third visible color that is a shade of red. These are a common set of visible band primary colors emitted by the first display device 4 in generating a full color image or a black and white image. The first display device 4 may be implemented as an organic light emitting diode display device having a color filter array or color filter scheme with these three primary colors. Adjusting the transmission characteristics of the first dichroic filter 11 in this way results in a strong transmission (by the first dichroic filter 11) of the image generated by the first display device 4.

[0020] Here, to achieve also a strong reflection (by the first dichroic filter 11) of the visible image generated by the second display device 6, the second display device 6 may also be implemented as emitting the same primary colors as the first display device 4, or individual colors, but these primary colors are slightly shifted (in wavelength) with respect to the primary colors emitted by the first display device 4. More generally, the color filter array (scheme) of the second display device 4 may have a fourth visible color, a fifth visible color, and a sixth visible color, which are different shades of blue, green, and red, respectively, in the example of FIG. 6. As shown in FIG. 6, these colors are matched with the notch bands of the transmission characteristic of the first dichroic filter 11, resulting in a strong reflection (by the first dichroic filter 11) of the visible band image generated by the second display device 6. Of course, the selection of RGB colors shown in FIG. 6 is only one example. This concept is also applicable to displays emitting in various combinations of primary colors. The dichroic filters may also have polarization dependent transmission and reflection profiles, so the headset may be optimally designed with this profile in mind. Since the first display is the primary display of the headset, the polarization state of the first display is likely not modified, but a polarizer and / or corrugated plate may be placed in the image output path from the second display to optimize the reflection of the second display's output from the first dichroic filter 11.

[0021] The system of FIG. 2 described above has an eye tracking camera 2 that allows hands-free feedback from the wearer during an ophthalmic examination of the wearer's eyes. FIG. 7 is a block diagram of a system for measuring visual acuity, where the VR headset does not have an eye tracking camera 2. Thus, feedback from the wearer (while wearing the VR headset) about what the wearer sees during the ophthalmic examination is provided by the wearer via manual input, such as through a joystick or physical button presses, or via audible input. The headset has a first display device 4, a second display device 6 that is smaller than the first display device 4 and has a lower pixel count than the first display device 4, and a first dichroic filter 11. The first dichroic filter 11 is constructed and arranged to pass visible light (strongly, e.g., with at least 70% transmission) from the first display device 4 towards the eye and to reflect visible light weakly, e.g., with no more than 20% reflection or no more than 5% reflection, from the second display device 6 towards the eye. There may be pixel data control circuitry that is coupled to, in response to a first vision-testing selection, dim the first display device 4 while simultaneously activating the second display device 6 to display the vision-testing pattern, particularly when testing 20 / 20 vision. Many of the other features and processes described above with respect to Figures 3 and 6 apply to the version of the VR headset shown in Figure 7.

[0022] While certain embodiments have been described and illustrated in the accompanying drawings, it is to be understood that such are merely illustrative and not limiting on the broad invention, and that the invention is not limited to the specific constructions and configurations shown and described, since various other modifications may occur to those skilled in the art. Accordingly, the description is to be regarded as illustrative and not restrictive.

Claims

1. 1. A system for measuring visual acuity, comprising: Eye-tracking headset the eye tracking headset comprising: An eye-tracking camera, an illumination source that generates near infrared (NIR) light that illuminates the eyes of a wearer of the headset; A first display device; a first dichroic filter positioned to pass visible light from the first display device to an eye and reflect NIR light reflected from the eye; A second display device; and a second dichroic filter; and the second dichroic filter comprises: i) a first version arranged to pass the reflected NIR light from the first dichroic filter to the eye-tracking camera and to reflect visible light from the second display device to the first dichroic filter; or ii) a second version arranged to reflect the reflected NIR light from the first dichroic filter towards the eye-tracking camera and to pass visible light from the second display device to the first dichroic filter. On the other hand, the system.

2. 10. The system of claim 1, wherein the first dichroic filter has a reflectance of greater than zero but less than 10 percent visible light across the full range of visible colors.

3. The system of claim 2 , wherein the first dichroic filter has a visible light reflection of greater than 5 percent.

4. the first display device comprises a color filter array having a first visible color, a second visible color, and a third visible color, the first dichroic filter having a plurality of passbands matched to each of the first visible color, the second visible color, and the third visible color; 2. The system of claim 1, wherein the second display device comprises a color filter array having a fourth visible color, a fifth visible color, and a sixth visible color, and the first dichroic filter has a plurality of notch bands aligned with each of the fourth visible color, the fifth visible color, and the sixth visible color.

5. 5. The system of claim 4, wherein the first visible color and the fourth visible color are shades of blue, the second visible color and the fifth visible color are shades of green, and the third visible color and the sixth visible color are shades of red.

6. The system of claim 1 , wherein the second dichroic filter is the first version and not the second version.

7. The system of claim 1 , wherein the second dichroic filter is the second version and not the first version.

8. 2. The system of claim 1, wherein a display surface of the first display device is at least twice as large as a display surface of the second display device, and the first display device has at least twice the full frame pixel resolution of the second display device.

9. Pixel Data Control Circuit 2. The system of claim 1, further comprising: the pixel data control circuitry is coupled to, in response to a first vision test selection, dim the first display device while simultaneously activating the second display device to display a vision test pattern.

10. 10. The system of claim 9, wherein the first vision test selection is for testing 20 / 20 or better vision.

11. 11. The system of claim 10, wherein the pixel data control circuitry, in response to a second vision test selection, dims the second display device while simultaneously activating the first display device to display a pattern for testing 20 / 40 or below vision.

12. 11. The system of claim 10, wherein the pixel data control circuitry, in response to a second vision test selection, dims the second display device while simultaneously activating the first display device to display a pattern for testing 20 / 60 or below vision.

13. 10. The system of claim 9, wherein the pixel data control circuitry, in response to a second vision test selection, darkens the second display device while simultaneously activating the first display device to display a vision test pattern.

14. The eye-tracking headset is a virtual reality headset, and the system comprises: Eye movement interpretation logic circuit 13. The system of claim 1, further comprising: the eye movement interpretation logic processes image data generated by the eye tracking camera to detect hands-free feedback from a wearer of the eye tracking headset during a vision test.

15. The system of claim 1 , wherein the second display device has a full frame pixel resolution of less than 1000 pixels.

16. 1. A system for measuring visual acuity, comprising: a headset comprising a first display, a second display smaller than the first display and having a lower full frame pixel resolution than the first display, and a dichroic filter positioned to pass visible light from the first display to an eye and to reflect visible light from the second display to the eye; a pixel data control circuit coupled to dim the first display device while simultaneously activating the second display device to display a vision testing pattern in response to a first vision testing selection; A system comprising:

17. 17. The system of claim 16, wherein a display surface of the first display device is at least twice as large as a display surface of the second display device, and the first display device has at least twice the full frame pixel resolution of the second display device.

18. 17. The system of claim 16, wherein the dichroic filter has a reflectance of greater than zero but less than 10 percent visible light across the visible spectrum extending from 380 to 700 nanometers.

19. 20. The system of claim 18, wherein the dichroic filter has a visible light reflection of greater than 5 percent.

20. the first display device comprises a color filter array having a first visible color, a second visible color, and a third visible color, the dichroic filter having a plurality of passbands matched to each of the first visible color, the second visible color, and the third visible color; 17. The system of claim 16, wherein the second display comprises a color filter array having a fourth visible color, a fifth visible color, and a sixth visible color, and the dichroic filter has a plurality of notch bands aligned with each of the fourth visible color, the fifth visible color, and the sixth visible color.

21. 21. The system of claim 20, wherein the first visible color and the fourth visible color are shades of blue, the second visible color and the fifth visible color are shades of green, and the third visible color and the sixth visible color are shades of red.

22. A method for testing visual acuity using a system according to any one of claims 1 to 21, said method comprising the steps of: providing a first vision test selection that dims the first display while simultaneously activating the second display to display a vision test pattern; A method comprising:

23. 23. The method of claim 22, wherein the first vision test selection is for testing 20 / 20 or better vision.

24. providing a second vision test selection that dims the second display while simultaneously activating the first display to display a 20 / 40 or below vision test pattern; 24. The method of claim 23, further comprising:

25. providing a second vision test selection that dims the second display while simultaneously activating the first display to display a 20 / 60 or below vision test pattern; 24. The method of claim 23, further comprising:

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