Birdbath Optical Element External Exit Pupil Near-Eye Display
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Near-eye display devices face inefficiencies in light coupling due to internal exit pupils, leading to increased power consumption and reduced image quality, as light must pass through additional optics, weakening its optical power.
Innovation Solution
The implementation of a birdbath optical element immersed in a high index glass region within the projection light engine, which collimates and reflects image light to an external exit pupil, allowing for more efficient coupling of image light into a near-eye display device, reducing the need for additional optics and enhancing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If light is coupled at an internal exit pupil, then the projection light engine can be compact, but light coupling efficiency decreases and power consumption increases
Solution Approach 1:
The patent extracts the exit pupil from the internal optics and positions it externally, allowing the waveguide to directly couple with the light source without additional recapture optics. This extraction of the exit pupil function resolves the contradiction by enabling efficient light coupling while maintaining a compact overall device structure through the external positioning of the optical interface.
Solution Approach 2:
The patent introduces a window or lens as an intermediary element that facilitates direct optical coupling between the projection light engine and the waveguide at the external exit pupil. This intermediary enables efficient light transfer while keeping the device architecture simple, resolving the contradiction between coupling efficiency and device complexity.
2Illumination intensity
If additional optics are used to recapture image data, then internal exit pupil can be maintained, but optical power of image light is weakened
Solution Approach 1:
By extracting the exit pupil from the internal optical path and positioning it externally, the patent eliminates the need for additional recapture optics. This maintains the full optical power of the image light from the source directly to the waveguide, resolving the contradiction between illumination intensity and device complexity.
Solution Approach 2:
Instead of bringing the waveguide to the internal exit pupil (conventional approach), the patent inverts the approach by bringing the exit pupil externally to the waveguide. This inversion eliminates the need for additional optics to recapture light, preserving optical power while reducing the number of optical elements.
3Productivity
If exit pupil is positioned externally, then light coupling efficiency improves, but projection light engine structure changes
Solution Approach 1:
The patent extracts the exit pupil function from the internal projection light engine structure and positions it externally where the waveguide can directly access it. This extraction improves light coupling efficiency while the overall device remains compact, as the external exit pupil eliminates the need for complex internal recapture optics.
Solution Approach 2:
The patent uses a window or lens as an intermediary element that enables the external exit pupil configuration. This intermediary facilitates direct optical coupling between the light source and waveguide, improving productivity through efficient light coupling while maintaining a relatively simple projection light engine structure.
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
This solution significantly improves the efficiency of light coupling and image quality by positioning the exit pupil externally, reducing power consumption and enhancing the display's ability to provide high-quality images with reduced illumination requirements.
Implementation Method 1
The birdbath optical element collimates and reflects the image light through the high index glass region to an external exit pupil
Implementation Method 2
A birdbath optical element having a reflective surface is immersed in the high index glass region and positioned by the support structure for optically coupling image light from the image source. The birdbath optical element collimates and reflects the image light through the high index glass region
Implementation Method 3
A high index glass region is supported by the support structure. The birdbath optical element collimates and reflects the image light through the high index glass region
Implementation Method 4
an input grating of a waveguide of the near-eye display optically couples at least the image light of the exit pupil into the waveguide
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
Technology is described for a projection optical system which optically couples image light from an image source to a near-eye display (NED) of a wearable near-eye display device. The projection optical system and the image source make up a projection light engine. Light from the image source is directed to a birdbath reflective optical element which is immersed in high index glass. The image light is reflected and collimated by the birdbath element and travels outside a housing of the projection light engine forming an external exit pupil, meaning the exit pupil is external to the projection light engine. A waveguide optically couples the image light of the external exit pupil. An example of a waveguide which can be used is a surface relief grating waveguide.