Collimating Lens Non-Uniform Illumination for Waveguide Brightness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical systems in electronic devices, such as virtual and augmented reality headsets, often suffer from non-uniform brightness across the field of view due to the components used, leading to unsightly and bulky designs that do not achieve desired optical performance.
Innovation Solution
A display system with a collimating lens having multiple non-parallel lens segments or a freeform curved surface is used to illuminate a spatial light modulator with non-uniform brightness, and a light source with independently driven LEDs to mitigate the non-uniformity introduced by the waveguide, allowing for power-saving modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a waveguide is used to direct image light towards the eye box, then the optical path is extended and compact design is enabled, but non-uniform brightness is introduced across the field of view
Solution Approach 1:
The collimating lens is designed with a specific non-uniform illumination profile before the light enters the waveguide. This preliminary non-uniform illumination is intentionally engineered to counteract and compensate for the non-uniformity that will be introduced by the waveguide's optical path, resulting in uniform brightness at the final output.
Solution Approach 2:
Different regions of the collimating lens are designed with varying optical properties to create a spatially varying illumination profile. The lens applies different local corrections to different parts of the light beam, with each region of the lens contributing to compensating for specific non-uniformities in its corresponding field of view region.
2Ease of manufacture
If the light source illuminates the spatial light modulator uniformly, then the spatial light modulator is easier to manufacture, but non-uniform brightness is imparted to the image light by the waveguide
Solution Approach 1:
The collimating lens pre-shapes the illumination profile to be non-uniform, which compensates for the non-uniformity introduced by the waveguide. This preliminary action ensures that even though the spatial light modulator receives non-uniform illumination, the final image light output is uniform across the field of view.
3Ease of manufacture
If the collimating lens uses a simple geometry, then the lens is easier to manufacture, but it cannot mitigate the non-uniformity introduced by the waveguide
Solution Approach 1:
The collimating lens incorporates freeform curved surfaces with specific geometric profiles that are optimized to create the required non-uniform illumination pattern. These curved surfaces enable complex light manipulation while maintaining a single-integral-piece construction that is manufacturable using modern optical fabrication techniques.
4Illumination intensity
If all LEDs are driven at full power, then maximum brightness is achieved, but power consumption increases
Solution Approach 1:
The LED array is controlled with spatially varying drive signals, where different LEDs or LED regions are driven at different power levels based on the required illumination profile. This local quality control allows the system to achieve the necessary non-uniform illumination pattern while minimizing overall power consumption by not driving all LEDs at full power simultaneously.
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 ensures uniform brightness across the field of view, enhancing the optical performance and reducing power consumption, particularly in applications where virtual objects are confined to peripheral regions.
Implementation Method 1
The collimating lens may include a lens element that has a geometry selected to illuminate the spatial light modulator with a non-uniform brightness across a field of view
Implementation Method 2
The spatial light modulator may modulate the illumination light using image data to produce the image light
Implementation Method 3
A waveguide may direct the image light towards an eye box
Implementation Method 4
The light source may include a light emitting diode (LED) substrate having one or more LEDs
Data Source
AI summary
An electronic device may have a display system with a module that produces image light and a waveguide that directs the image light towards an eye box. The module may include a light source, spatial light modulator, and collimating lens between the lens and modulator. The lens may direct illumination from the light source to the modulator, which modulates the illumination to produce the image light. The lens may have a geometry that illuminates the modulator with a non-uniform illumination pattern to mitigate subsequent brightness non-uniformity introduced by the waveguide. The light source may include one or more LEDs that are independently driven by control circuitry over one or more drive lines to help mitigate the non-uniformity introduced by the waveguide and/or to operate the display in a heads-up display mode.