ADAPTIVE BRIGHTNESS CONTROL OF HEAD MOUNTED DISPLAY

• US 20130113973A1
• Filed: 11/04/2011
• Published: 05/09/2013
• Est. Priority Date: 11/04/2011
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Miao, Xiaoyu
• Granted Patent: US 9,087,471 B2
• Time in Patent Office: Days
• US Class Current: 348/333.01
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 2027/014 comprising information/image processing systems
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2354/00 Aspects of interface with display user
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/003 to produce spatial visual effects

Abstract

A technique for adaptive brightness control of an eyepiece of a head mounted display (“HMD”) includes displaying a computer generated image (“CGI”) to an eye of a user from a viewing region of the eyepiece of the HMD. Image data is captured from an ambient environment surrounding the HMD. A brightness value is calculated for the ambient environment based at least in part upon the image data. A bias power setting is determined based at least in part upon the brightness value. The bias power setting is applied to an illumination source for generating the CGI and a brightness level of the CGI displayed to the eye of the user is controlled with the bias power setting.

Claims

1. A method for adaptive brightness control of an eyepiece of a head mounted display (“

HMD”

), the method comprising;

displaying a computer generated image (“

CGI”

) from a viewing region of the eyepiece of the HMD;

capturing image data from an ambient environment surrounding the HMD;

calculating a brightness value for the ambient environment based at least in part upon the image data;

determining a bias power setting to apply to an illumination source for generating the CGI based at least in part upon the brightness value; and

controlling a brightness level of the CGI with the bias power setting.

2. The method of claim 1, wherein controlling the brightness level of the CGI comprises adjusting the brightness level in real-time in response to changes in the brightness value associated with the ambient environment.

3. The method of claim 1, further comprising:

passing ambient scene light through an ambient scene side and an eye-ward side of the eyepiece in the viewing region to an eye of a user;

determining a control signal for selecting a transparency of a variable transparency layer disposed over the viewing region, wherein the control signal is determined based at least in part upon the brightness value; and

adjusting the transparency of the variable transparency layer based at least in part upon the control signal.

4. The method of claim 3, wherein the variable transparency layer comprises an electro-chromic layer shutter, wherein adjusting the transparency of the variable transparency layer comprises adjusting at least one of a frequency or a duty cycle of the control signal for actuating the electro-chromic layer shutter between two transparency settings.

5. The method of claim 3, wherein the variable transparency layer has more than two transparency settings and the transparency is constant for a given value of the control signal.

6. The method of claim 1, wherein capturing the image data from the ambient environment surrounding the HMD comprises:

capturing the image data with an ambient light sensor mounted forward facing on the HMD.

7. The method of claim 1,

wherein capturing the image data from the ambient environment surrounding the HMD comprises capturing a video image of a forward facing scene, and

wherein calculating the brightness value for the ambient environment comprises calculating the brightness value based at least in part upon the video image.

8. The method of claim 7, wherein the brightness value comprises an auto-exposure value for operating a video camera that captures the video image.

9. The method of claim 1, wherein determining the bias power setting to apply to the illumination source comprises:

indexing into a lookup table using the brightness value to obtain the bias power setting, wherein the lookup tables comprises a calibration curve of default brightness values versus default bias power settings.

10. The method of claim 9, further comprising:

providing a user selectable offset feature to apply a user selectable offset from the default bias power setting for a given default brightness value.

11. The method of claim 10, wherein providing the user selectable offset feature comprises:

providing a graphical user interface for displaying a user selectable offset value within the CGI displayed to the user via the HMD; and

providing a touch interface along an ear arm member of the HMD to receive touch commands.

12. A head mounted display (“

HMD”

) for displaying a computer generated image (“

CGI), the HMD comprising;

a display source for generating the CGI;

an eyepiece having a viewing region, the eyepiece coupled to transport the CGI from the display source and emit the CGI out an eye-ward side of the eyepiece in the viewing region, wherein the viewing region is partially transparent to pass ambient scene light through an ambient scene side and the eye-ward side of the eyepiece in the viewing region;

an ambient light sensor to capture image data from an ambient environment surrounding the HMD; and

a controller coupled to the display source, the ambient light sensor, and a machine-accessible storage medium that provides instructions that, when executed by the controller, cause the controller to perform operations comprising;

calculating a brightness value for the ambient environment based at least in part upon the image data;

determining a bias power setting to apply to the display source based at least in part upon the brightness value; and

controlling a brightness level of the CGI with the bias power setting.

13. The head mounted display of claim 12, further comprising:

a frame assembly to support the display source, the eyepiece, the ambient light sensor, and the controller for wearing on a head of a user with the viewing region positioned in front of an eye of the user.

14. The head mounted display of claim 13, wherein the ambient light sensor is mounted to the frame assembly with a forward facing orientation.

15. The head mounted display of claim 14,

wherein the ambient light sensor comprises a video camera and the image data comprises a video image of a forward facing scene,

wherein calculating the brightness value for the ambient environment comprises calculating the brightness value based at least in part upon the video image.

16. The head mounted display of claim 15, wherein the brightness value comprises an auto exposure value for operating the video camera.

17. The head mounted display of claim 14, further comprising:

a forward facing camera to capture forward facing scene images; and

a flash;

wherein the forward facing camera, the flash, and the ambient light sensor are all disposed on a single circuit board that is mounted in or on the frame assembly.

18. The head mounted display of claim 13, wherein determining the bias power setting to apply to the display source comprises:

indexing into a lookup table using the brightness value to obtain the bias power setting, wherein the lookup tables comprises a calibration curve of default brightness values versus default bias power settings.

19. The head mounted display of claim 18, further comprising:

a touch interface disposed along a temple region of the frame assembly,

wherein the machine-accessible storage medium further provides instructions that, when executed by the controller, cause the controller to perform further operations, comprising;

providing a user selectable offset feature to apply a user selectable offset from the default bias power setting for a given default brightness value.

20. The head mounted display of claim 12, further comprising a variable transparency layer disposed over the viewing region of the eyepiece, wherein the machine-accessible storage medium further provides instructions that, when executed by the controller, cause the controller to perform further operations, comprising:

determining a control signal for selecting a transparency of the variable transparency layer, wherein the control signal is determined based at least in part upon the brightness value; and

adjusting the transparency of the variable transparency layer based at least in part upon the control signal.

21. The head mounted display of claim 20, wherein the variable transparency layer comprises an electro-chromic layer shutter, wherein adjusting the transparency of the variable transparency layer comprises adjusting at least one of a frequency or a duty cycle of the control signal for actuating the electro-chromic layer shutter between two transparency settings.

22. The head mounted display of claim 20, wherein the variable transparency layer has more than two transparency settings and the transparency is constant for a given value of the control signal.

23. A machine-accessible storage medium that provides instructions that, when executed by a head mounted display, cause the head mounted display to perform operations comprising:

displaying a computer generated image (“

CGI”

) from a viewing region of an eyepiece of the HMD;

capturing image data from an ambient environment surrounding the HMD;

calculating a brightness value for the ambient environment based at least in part upon the image data;

determining a bias power setting to apply to an illumination source for generating the CGI based at least in part upon the brightness value; and

controlling a brightness level of the CGI with the bias power setting.

24. The machine-accessible storage medium of claim 23, further providing instructions that, when executed by the head mounted display, cause the head mounted display to perform further operations, comprising:

determining a control signal for selecting a transparency of a variable transparency layer disposed over the viewing region of the eyepiece, wherein the control signal is determined based at least in part upon the brightness value; and

adjusting the transparency of the variable transparency layer based at least in part upon the control signal.

25. The machine-accessible storage medium of claim 24, wherein the variable transparency layer comprises an electro-chromic layer shutter, wherein adjusting the transparency of the variable transparency layer comprises adjusting at least one of a frequency or a duty cycle of the control signal for actuating the electro-chromic layer shutter between two transparency settings.

26. The machine-accessible storage medium of claim 24, wherein the variable transparency layer has more than two transparency settings and the transparency is constant for a given value of the control signal.

27. The machine-accessible storage medium of claim 24, further providing instructions that, when executed by the head mounted display, cause the head mounted display to perform further operations, comprising:

providing a user selectable offset feature to apply a user selectable offset to the control signal for adjusting the transparency of the variable transparency layer.

28. The machine-accessible storage medium of claim 23,

wherein capturing the image data from the ambient environment surrounding the HMD comprises capturing a video image of a forward facing scene, and

wherein calculating the brightness value for the ambient environment comprises calculating the brightness value based at least in part upon the video image.

29. The machine-accessible storage medium of claim 23, wherein determining the bias power setting to apply to the illumination source comprises:

indexing into a lookup table using the brightness value to obtain the bias power setting, wherein the lookup tables comprises a calibration curve of default brightness values versus default bias power settings.

30. The machine-accessible storage medium of claim 29, further providing instructions that, when executed by the head mounted display, cause the head mounted display to perform further operations, comprising:

providing a user selectable offset feature to apply a user selectable offset from the default bias power setting for a given default brightness value.