# US 10,121,419 B2 · Head mounted display device with rapid gamma correction between display panels > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,121,419 B2 - Document ID: US10121419B2 - Status: Granted - Kind: B2 - Application number: 15/349,087 - Filed: 2016-11-11 - Published: 2017-05-18 - Granted: 2018-11-06 - Earliest claimed: 2015-11-13 - Assignees: Google Inc. - Applicants: Google Inc. - Inventors: Zhibin Zhang - Web page: https://patentgrep.com/patent/US10121419B2 ## CPC - G09G 3/3426: {the different display panel areas being distributed in two dimensions, e.g. matrix} - G02B 27/017: {Head mounted} - G09G 3/003: {to produce spatial visual effects} - G09G 5/14: Display of multiple viewports - G02B 2027/0118: {comprising devices for improving the contrast of the display / brillance control visibility} - G09G 2320/0233: Improving the luminance or brightness uniformity across the screen - G09G 2320/0276: for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction - G09G 2320/029: by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel - G09G 2320/041: Temperature compensation - G09G 2320/043: Preventing or counteracting the effects of ageing - G09G 2320/045: Compensation of drifts in the characteristics of light emitting or modulating elements - G09G 2320/06: Adjustment of display parameters - G09G 2320/0626: for control of overall brightness - G09G 2320/0673: for control of gamma adjustment, e.g. selecting another gamma curve - G09G 2320/0693: Calibration of display systems - G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A head mounted display (HMD) device periodically measures a gamma characteristic of each of a plurality of display panels, then adjusts the characteristic of one of the panels to closely match the other. For example, the HMD device can periodically apply a set of currents to selected pixels at each display panel and measure the resulting sets of voltages at the selected pixels. The set of voltages for each display panel indicates the gamma characteristic of the corresponding panel. The HMD device can apply the sets of voltages to a filter to generate a gamma figure of merit (FOM) for each display panel, and adjust a bias (e.g., a backlight bias or a bias of a light emitting diode (LED)) of one or more of the display panels, so that each display panel exhibits similar gamma characteristics. ## Claims ### Claim 1 In a head mounted display (HMD) device comprising first and second display panels, a method comprising: identifying a first gamma characteristic of the first display panel by applying a set of currents to a first pixel of the first display panel causing the first pixel to generate a corresponding set of voltages; identifying a second gamma characteristic of the second display panel by applying the set of currents to a second pixel of the second display panel causing the second pixel to generate a corresponding set of voltages; identifying any difference between the first and second gamma characteristics; when a difference is identified, identifying an adjustment to the second gamma characteristic, based on the difference, so that the first and second gamma characteristics substantially match; and adjusting the second gamma characteristic of the second display panel based on the adjustment. ### Claim 2 (depends on 1) The method of claim 1, wherein identifying the first gamma characteristic further comprises: identifying the first gamma characteristic by applying the set of voltages to a filter. ### Claim 3 (depends on 2) The method of claim 2, wherein identifying the first gamma characteristic further comprises: generating a gamma figure of merit (FOM) for each of the first display panel and the second display panel after and based on applying the set of voltages to the filter. ### Claim 4 (depends on 1) The method of claim 1, wherein adjusting the second gamma characteristic comprises: adjusting the second gamma characteristic based on a stored nominal gamma value for the second display panel. ### Claim 5 (depends on 1) The method of claim 1, wherein adjusting the second gamma characteristic comprises: adjusting a bias of the second display panel based on the first gamma characteristic. ### Claim 6 (depends on 5) The method of claim 5, wherein adjusting the bias comprises adjusting a bias of a backlight of the second display panel. ### Claim 7 (depends on 5) The method of claim 5, wherein adjusting the bias comprises adjusting a bias of a light emitting diode of the second display panel. ### Claim 8 (depends on 1) The method of claim 1, wherein identifying the first gamma characteristic comprises identifying the first gamma characteristic in response to an indication of a first synchronization period of the first display panel. ### Claim 9 (depends on 8) The method of claim 8, wherein identifying the first gamma characteristic comprises completing identification of the first gamma characteristic during the first synchronization period. ### Claim 10 (depends on 1) The method of claim 1, wherein identifying the first gamma characteristic comprises identifying the first gamma characteristic at a first time and adjusting the second gamma characteristic comprises adjusting the second gamma characteristic in response to identifying the first gamma characteristic, and further comprising: identifying a third gamma characteristic of the first display panel at a second time after the first time, the third gamma characteristic different from the first gamma characteristic; and in response to identifying the third gamma characteristic, adjusting the second gamma characteristic of the second display panel based on the third gamma characteristic. ### Claim 11 (depends on 10) The method of claim 10, wherein: the first time corresponds to a first synchronization period of the first display panel and the second time corresponds to a second synchronization period of the first display panel. ### Claim 12 A method, comprising: periodically measuring a first gamma characteristic of a first display panel of a head mounted display (HMD) device by applying a set of currents to a pixel of the first display panel causing the pixel to generate a corresponding set of voltages; periodically measuring a second gamma characteristic of a second display panel of the HIVID device by applying the set of currents to a pixel of the second display panel causing the pixel to generate a corresponding set of voltages; identifying an adjustment to the second gamma characteristic, based on a difference between the first and second gamma characteristics, so that the first and second gamma characteristics substantially match; and periodically adjusting a bias applied to at least one pixel of the second display panel of the HMD device based on the identified adjustment, the second display panel different from the first display panel. ### Claim 13 A head mounted display (HMD) device, comprising: a first display panel having a first pixel; a second display panel having a second pixel; and a gamma correction module comprising: a sensor configured to identify a first gamma characteristic of the first display panel and a second gamma characteristic of the second display panel by applying a set of currents to the first pixel and the second pixel to generate respective sets of voltages; and a control module configured to: identify any difference between the first and second gamma characteristics based on the sets of voltages; when a difference is identified, identify an adjustment to the second gamma characteristic, based on the difference, so that the first and second gamma characteristics substantially match; and adjust the second gamma characteristic of the second display panel based on the identified adjustment. ### Claim 14 (depends on 13) The HMD device of claim 13, wherein identifying the first gamma characteristic further comprises: identifying the first gamma characteristic by applying the set of voltages to a filter. ### Claim 15 (depends on 13) The HMD device of claim 13, wherein adjusting the second gamma characteristic comprises: adjusting the second gamma characteristic based on the first gamma characteristic and a stored nominal gamma value. ### Claim 16 (depends on 13) The HIVID device of claim 13, wherein adjusting the second gamma characteristic comprises: adjusting a bias of the second display panel based on the first gamma characteristic. ### Claim 17 (depends on 13) The HIVID device of claim 13, wherein: the first and second display panels are operated to present stereoscopic virtual reality imagery. ### Claim 18 (depends on 13) The HIVID device of claim 13, wherein: the first and second display panels are operated to present stereoscopic augmented reality imagery.