Multipass Scanner for Near-Eye Display Scanning Range
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Solution Overview
Problem
Constructing a scanning display with a tiltable reflector that achieves a large scanning range is challenging due to the need for compromises in flexure stiffness and scan rate, as thin, flexible hinges cannot support a larger reflector for desired beam size and image quality.
Innovation Solution
The implementation of a multipass coupler that directs a light beam to impinge multiple times on a tiltable reflector, multiplying the scanning range without increasing the maximum tilting angle, using a combination of lenses and polarization elements to achieve enhanced angular scanning capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a larger reflector is used to achieve a wider scanning range, then the scanning range is improved, but the flexure stiffness and scan rate deteriorate due to the inability of thin, flexible hinges to support a larger reflector
Solution Approach 1:
The scanning function is segmented into multiple passes instead of requiring a single large deflection. The light beam scans the same physical reflector multiple times, with each pass covering a portion of the total scanning range. This allows the reflector to remain small and rigid while achieving an expanded effective scanning range through repeated use.
Solution Approach 2:
The optical path is folded back on itself, with the light beam returning to the same reflector after an intermediate reflection. This nested path allows the system to achieve double the scanning range (or more with additional passes) without requiring a larger reflector, maintaining both compact size and high scan rates.
2Area of stationary object
If a larger reflector is used to achieve a wider scanning range, then the scanning range is improved, but the device complexity increases due to additional optical elements required
Solution Approach 1:
The same physical reflector serves multiple functions: it is used repeatedly for multiple scanning passes, and a single intermediate optical element (such as a polarization beam splitter or curved mirror) performs the task of redirecting the beam back to the reflector. This multi-use approach expands scanning range without proportionally increasing device complexity.
Solution Approach 2:
A polarization beam splitter or curved mirror acts as an intermediary element that redirects the light beam back to the original reflector without requiring additional large scanning components. This intermediary enables the multipass configuration with minimal added complexity.
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 approach allows for a wider scanning range without compromising other parameters, such as flexure stiffness and scan rate, enabling improved image quality and user comfort in near-eye displays.
Implementation Method 1
a tiltable reflector (106) for reflecting the light beam (102) provided by the light source (104)
Implementation Method 2
receives the light beam (102) reflected from the tiltable reflector (106) for a first time (131) at twice the angle of tilt of the tiltable reflector (106), and redirects the light beam (102) back to the tiltable reflector (106) for a second reflection
Implementation Method 3
A reflective polarizer (208) is disposed on the convex surface and a quarter-wave plate (211) is disposed between the reflective polarizer (208) and the tiltable reflector (106)
Data Source
Figure 1~3
Figure 4A~4B
Figure 5A~5B
AI summary
A multipass scanner usable e.g. in a near-eye display is disclosed. The multipass scanner scans a light beam angularly, forming an image in angular domain. The multipass scanner includes a light source, a tiltable reflector, and a multipass coupler that couples light emitted by the light source to the tiltable reflector, receives the reflected light and couples it back to the tiltable reflector to double the scanning angle. Then, the multipass coupler couples the light reflected at least twice from the tiltable reflector to an exit pupil of the scanner. A pupil-replicating waveguide disposed at the exit pupil of the scanner extends the image in angular domain. Multiple reflections of the light beam from the tiltable reflector enable one to increase the angular scanning range and associated field of view of the display without having to increase the angular scanning range of the tiltable reflector.