Systems and methods for optical alignment of display modules in a head-mounted device
A display device may include first and second display modules that provide image light to first and second waveguides. The waveguides may direct the image light to first and second eye boxes. Each display module may include optics mounted to a housing and mechanical alignment structures that mechanically adjust the position of an optical axis of the optics. The alignment structures may rotate the entire housing, may mechanically translate the optics, may adjust the position of a spatial light modulator within the module, and/or control circuitry may change a subset of pixels used by the modulator to compensate for optical misalignment between the first and second eye boxes. The device may include optical misalignment sensors that detect the optical misalignment. The control circuitry may compensate for the optical misalignment as detected by the optical misalignment sensors.
1 . A display system comprising:
a waveguide;
an input coupler on the waveguide and configured to couple image light into the waveguide;
an output coupler on the waveguide and configured to couple the image light out of the waveguide; and
a display module configured to produce the image light, the display module comprising:
a display module housing,
a display panel within the display module housing,
collimating optics mounted to the display module housing and configured to direct the image light towards the input coupler,
alignment structures configured to adjust a position of the display panel with respect to the collimating optics and to mechanically rotate the display module housing about an axis,
a lens housing, the collimating optics being mounted within the lens housing, and
a set of piezo-driven flexure stages that couples the lens housing to the display module housing, wherein the set of piezo-driven flexure stages is configured to mechanically translate the lens housing along a first axis relative to the display module housing.
2 . The display system of claim 1 , wherein the display module further comprises:
an additional set of piezo-driven flexure stages that couples the lens housing to the display module housing, wherein the additional set of piezo-driven flexure stages is configured to mechanically translate the lens housing along a second axis relative to the display module housing, the second axis being orthogonal to the first axis.
3 . The display system of claim 1 , wherein the display module further comprises:
at least one light source configured to emit illumination light, wherein the display panel is a reflective display panel configured to produce the image light by modulating the illumination using image data.
4 . The display system of claim 1 , wherein the display module further comprises:
at least one light source configured to emit illumination light, wherein the display panel has pixels, wherein the display panel is configured to produce the image light by modulating, using a subset of the pixels, the illumination light using image data, and wherein the display system comprises control circuitry configured to change the subset of pixels that are used by the display panel.
5 . A display system comprising:
a waveguide;
an input coupler on the waveguide and configured to couple image light into the waveguide;
an output coupler on the waveguide and configured to couple the image light out of the waveguide;
a display module configured to produce the image light, the display module comprising:
a display module housing,
a display panel within the display module housing,
collimating optics mounted to the display module housing and configured to direct the image light towards the input coupler, wherein the collimating optics have an optical axis, and
alignment structures configured to adjust a position of the display panel with respect to the collimating optics;
an additional waveguide;
an additional input coupler on the additional waveguide and configured to couple additional image light into the additional waveguide;
an additional output coupler on the additional waveguide and configured to couple the additional image light out of the additional waveguide;
an additional display module configured to produce the additional image light;
an optical alignment sensor configured to detect a position of the display module relative to the additional display module; and
control circuitry configured to control the alignment structures to mechanically adjust the position of the optical axis with respect to the waveguide based on the position detected by the optical alignment sensor.
6 . The display system of claim 5 , wherein the optical alignment sensor comprises:
at least one image sensor configured to receive a portion of the image light from the waveguide and a portion of the additional image light from the additional waveguide.
7 . The display system of claim 6 , wherein the output coupler is configured to pass the portion of the image light to a first additional output coupler on the waveguide, the first additional output coupler is configured to couple the portion of the image light out of the waveguide and towards the optical alignment sensor, the additional output coupler is configured to pass the portion of the additional image light to a second additional output coupler on the additional waveguide, and the second additional output coupler is configured to couple the portion of the additional image light out of the waveguide and towards the optical alignment sensor.
8 . The display system of claim 7 , wherein the at least one image sensor comprises first and second image sensors, the first image sensor is configured to receive the portion of the image light, and the second image sensor is configured to receive the portion of the additional image light.
9 . The display system of claim 7 , wherein the at least one image sensor comprises a single image sensor, the display system further comprising:
a first mirror;
a second mirror;
a third mirror; and
a partially reflective beam splitter, wherein the first mirror is configured to reflect the portion of the image light towards the second mirror, the second mirror is configured to reflect the portion of the image light towards the partially reflective beam splitter, the third mirror is configured to reflect the portion of the additional image light towards the partially reflective beam splitter, and the partially reflective beam splitter is configured to direct the portion of the image light and the portion of the additional image light towards the single image sensor.
10 . The display system of claim 5 , wherein the optical alignment sensor comprises:
a first light emitter configured to emit first infrared light;
a first set of retro-reflective gratings on the waveguide and configured to diffract the first infrared light;
a second light emitter configured to emit second infrared light;
a second set of retro-reflective gratings on the additional waveguide and configured to diffract the second infrared light;
a first set of photo reflective sensors on the waveguide and configured to generate a first set of voltages based on a reflected version of the first infrared light diffracted by the first set of retro-reflective gratings; and
a second set of photo reflective sensors on the additional waveguide and configured to generate a second set of voltages based on a reflected version of the second infrared light diffracted by the second set of retro-reflective gratings, wherein the control circuitry is configured to control the mechanical alignment structures to mechanically adjust the position of the optical axis with respect to the waveguide based on the first and second sets of voltages.
11 . A display system comprising:
a waveguide;
an input coupler on the waveguide and configured to couple image light into the waveguide;
an output coupler on the waveguide and configured to couple the image light out of the waveguide; and
a display module configured to produce the image light, the display module comprising:
a display module housing,
a display panel within the display module housing,
collimating optics mounted to the display module housing and configured to direct the image light towards the input coupler,
a lens housing, wherein the collimating optics are mounted within the lens housing, and
alignment structures that couple the lens housing to the display module housing, wherein the alignment structures are configured to adjust a position of the display panel with respect to the collimating optics and to mechanically translate a position of the lens housing relative to the display module housing along at least one axis.