Near-Eye Display Illumination Balancing for Virtual Image Color Uniformity
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Solution Overview
Problem
Conventional near-eye displays experience color shifts and gradients in virtual images due to wavelength-sensitive performance disparities in optical components, manufacturing variabilities, and environmental factors, leading to undesirable color distributions.
Innovation Solution
An extended light source with multiple cells containing different color light sources is used, along with a partial homogenizer and a spatial light modulator, to adjust and rebalance color distributions by controlling the relative output of individual cells and overlapping light channels at an illumination plane, compensating for color imbalances in virtual images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional image light guides with wavelength-sensitive optical components are used, then virtual images can be displayed, but color shifts and gradients occur in the virtual images
Solution Approach 1:
The light source is divided into multiple independently controllable light emitting elements (LEDs or laser diodes) with different spectral characteristics. Each element can be individually adjusted to compensate for wavelength-sensitive performance disparities in the optical components, thereby correcting color shifts and gradients in the virtual images.
Solution Approach 2:
Different regions of the virtual image are illuminated by light emitting elements with spectrally tailored characteristics. By matching the spectral output of specific light emitting elements to the wavelength-sensitive response of optical components in different regions, local color uniformity is achieved across the entire field of view.
2Adaptability or versatility
If multiple light emitting elements with different spectral characteristics are used, then color distributions can be adjusted, but device complexity increases
Solution Approach 1:
A single light source assembly comprising multiple light emitting elements serves multiple functions: it provides overall illumination for the waveguide while simultaneously enabling independent spectral control to correct color shifts. The controller integrates the functions of multiple separate light sources into one unified system, managing different spectral characteristics through a single control interface.
Solution Approach 2:
The spectral parameters of the light source are dynamically adjusted by independently controlling the intensity and wavelength of individual light emitting elements. This allows the system to adapt to different viewing conditions and compensate for manufacturing variabilities without requiring physical reconfiguration of the optical components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively compensates for color shifts and gradients in virtual images, providing improved color uniformity and contrast by programmatically generating color gradients to match desired distributions, enhancing the viewing experience.
Implementation Method 1
collimated, relatively angularly encoded light beams from an image projector are coupled into an optically transparent planar waveguide by an in-coupling optic such as a diffractive optic
Implementation Method 2
After propagating along the planar waveguide, the angularly encoded light beams can be directed out of the planar waveguide toward a viewer's eye
Implementation Method 3
the angularly encoded light beams can be directed out of the planar waveguide toward a viewer's eye by a similar out-coupling optic
Implementation Method 4
An extended light source with multiple cells containing different color light sources is used, along with a partial homogenizer and a spatial light modulator, to adjust and rebalance color distributions by controlling the relative output of individual cells
Implementation Method 5
A partial homogenizer collects light from different cells within different optical channels and partially overlaps the light from the different optical channels at an illumination plane
Implementation Method 6
A spatial light modulator located at the illumination plane generates real images by selectively modulating the partially overlapping the light at the illumination plane
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A projector (40) for a near-eye display, comprises an extended light source (10) having a plurality of cells (30), wherein each of the plurality of cells (30) includes light sources (32, 34, 36) arranged to vary a relative output of individual cells (30); a partial homogenizer (52) operable to collect light from the plurality of cells (30) within a plurality of optical channels (68a to 68d) and to at least partially overlap the light from the plurality of optical channels (68a to 68d) at an illumination plane (62); a spatial light modulator (44) located at the illumination plane (62), wherein the spatial light modulator (44) is operable to generate real images by selectively modulating the partially overlapping light at the illumination plane (62); an eyepiece optic (46) operable to direct the modulated light from the spatial light modulator (44) toward a pupil (48); and a controller (20) connected to the extended light source (10), wherein the controller is operable to adjust the relative output of one or more of the plurality of cells (30) to alter a distribution of the light over the illumination plane (62) incident to the spatial light modulator (44).