Position tracking systems and methods for head-mounted display systems with LED droop compensation
Systems and methods for tracking the position of one or more head-mounted display (HMD) system components of an HMD system. The HMD components may carry a plurality of angle sensitive detectors or other types of detectors. The HMD system may be operative to detect corrupted position tracking samples, allowing such samples to be ignored, thereby improving the position tracking process. Control circuitry causes light sources to emit light according a specified pattern, and receives sensor data from the plurality of detectors. Control circuitry may process the sensor data, for example using machine learning or other techniques, to track a position of one or more HMD components.
1 . A head-mounted display system, comprising:
a first head-mounted display system component wearable by a user;
an angle sensitive detector carried by the first head-mounted display system component, in operation, the angle sensitive detector captures sensor data indicative of an angle of arrival of light, wherein the angle sensitive detector comprises a plurality of sensor cells, in operation, each sensor cell outputs sensor cell samples that represent an intensity of light incident on the sensor cell;
a second head-mounted display system component that includes one or more light sources; and
control circuitry operative to:
cause a light source of the one or more light sources to emit light during an illumination period;
receive sensor data from the angle sensitive detector, including sequentially capturing sensor cell samples from the plurality of sensor cells during the illumination period;
process the received sensor data, including applying calibration data to the sensor cell samples to account for non-uniform brightness of the light source of the one or more light sources during the sequential capturing of the sensor cell samples; and
track a position of the first or second head-mounted display system components based at least in part on the processing of the received sensor data.
2 . The head-mounted display system of claim 1 wherein the calibration data represents a characteristic slope of the brightness of the light source of the one or more light sources during the illumination period.
3 . The head-mounted display system of claim 1 wherein, in operation, the control circuitry iteratively determines updated calibration data, and tracks the position of the first or second head-mounted display system components using the updated calibration data.
4 . The head-mounted display system of claim 3 wherein, to determine the updated calibration data, the control circuitry:
disables the light source of the one or more light sources for a calibration period;
sequentially captures sensor cell samples from the plurality of sensor cells during the calibration period;
interpolates the captured sensor cell samples; and
determines the updated calibration data based on the interpolation of the captured sensor cell samples.
5 . The head-mounted display system of claim 1 , further comprising an analog-to-digital converter configured to convert the sensor cell samples into digital data for subsequent processing by the control circuitry.
6 . The head-mounted display system of claim 1 , wherein the plurality of sensor cells are sequentially read by a multiplexer arranged to sample the sensor cells in a predetermined order during the illumination period.
7 . The head-mounted display system of claim 1 , wherein the control circuitry is further configured to determine a correction factor based on a rate of change in brightness of the light source of the one or more light sources during the illumination period, thereby compensating for thermal droop effects.
8 . The head-mounted display system of claim 1 , wherein the control circuitry iteratively updates the calibration data by temporarily disabling the light source of the one or more light sources during a calibration period, capturing baseline sensor cell samples, and recalculating the calibration data based on an interpolation of the captured samples.
9 . A method of calibrating a head-mounted display system component, the head-mounted display system component comprising an angle sensitive detector that, in operation, captures sensor data indicative of an angle of arrival of light emitted from one or more light sources, wherein the angle sensitive detector comprises a plurality of sensor cells, in operation, each sensor cell outputs sensor cell samples that represent an intensity of light incident on the sensor cell, the method comprising:
causing a light source of the one or more light sources to emit light for an illumination period;
receiving sensor data from the angle sensitive detector during the illumination period, including sequentially capturing sensor cell samples from the plurality of sensor cells;
processing the received sensor cell samples to generate calibration data that accounts for non-uniform brightness of the light source of the one or more light sources during the illumination period; and
storing the calibration data in a nontransitory processor-readable storage medium for subsequent use in tracking at least one component of a head-mounted display system.
10 . The method of claim 9 wherein the calibration data represents a characteristic slope of the brightness of the light source of the one or more light sources during the illumination period.
11 . The method of claim 9 wherein processing the received sensor cell samples comprises:
interpolating the captured sensor cell samples; and
determining the calibration data based on the interpolation of the captured sensor cell samples.
12 . The method of claim 9 , further comprising sequentially capturing the sensor cell samples using a multiplexer and converting the captured sensor cell samples to digital signals via an analog-to-digital converter.
13 . The method of claim 9 , wherein processing the received sensor cell samples comprises determining a correction factor that accounts for temporal variations in light intensity due to non-uniform brightness during the illumination period.
14 . The method of claim 9 , further comprising iteratively updating the calibration data by performing the calibration method at periodic calibration intervals during operation of the head-mounted display system component.
15 . The method of claim 9 , wherein the generated calibration data is stored in a nontransitory processor-readable storage medium integrated with the head-mounted display system.
16 . A head-mounted display system for tracking positions of system components, comprising:
a light source configured to emit light during an illumination period;
an angle sensitive detector comprising a plurality of sensor cells configured to sequentially capture sensor cell samples during the illumination period, each sensor cell sample representing an intensity of light incident thereon;
control circuitry configured to:
initiate emission of light from the light source;
receive the sensor cell samples from the angle sensitive detector;
process the received sensor cell samples to determine calibration data that compensates for non-uniform brightness of the light source during the illumination period, the calibration data representing a characteristic slope of brightness variation over time; and
track a position of a head-mounted display system component using the calibration data.
17 . The head-mounted display system of claim 16 , wherein the control circuitry is further configured to sequentially capture the sensor cell samples using a multiplexer coupled to the plurality of sensor cells.
18 . The head-mounted display system of claim 16 , wherein the control circuitry further comprises an analog-to-digital converter configured to convert the sensor cell samples into digital data.
19 . The head-mounted display system of claim 16 , wherein the control circuitry iteratively updates the calibration data by temporarily disabling the light source during a calibration period, capturing baseline sensor cell samples, and interpolating the captured sensor cell samples to generate updated calibration data.
20 . The head-mounted display system of claim 16 , wherein the calibration data is stored in a nontransitory processor-readable storage medium for subsequent use in tracking the position of the head-mounted display system component.