Head-worn See-through Display Optical Configuration
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Solution Overview
Problem
Existing head-worn see-through computer displays face challenges in providing a compact, lightweight, and high-quality image while maintaining a clear view of the environment, with issues related to image quality, weight, and contrast.
Innovation Solution
The described optical configurations for head-worn see-through computer displays incorporate a reflective display, a field lens, a reflective polarizer, and a light source, with overlapping illumination and imaging optical paths to reduce size and weight. A flat reflective polarizer is used to redirect illumination light and act as an analyzer, enhancing contrast and reducing scattered light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If traditional optical systems are used in head-worn see-through displays, then image quality can be maintained, but the device becomes bulky and heavy
Solution Approach 1:
The patent merges the illumination optical path and imaging optical path into a single overlapping configuration. The reflective display serves dual purposes: reflecting illumination light toward the user while also serving as the image source. The polarizer is integrated directly onto the reflective display surface, combining polarization function with the display substrate. This merging reduces the number of separate optical components, thereby reducing overall device weight and complexity.
Solution Approach 2:
The reflective display performs multiple functions simultaneously: it acts as the image source, the illumination reflector, and the polarizer substrate. The overlapping optical paths allow a single optical element to serve multiple purposes in the system, reducing the total component count and weight while maintaining image quality.
2Illumination intensity
If a flat reflective polarizer is used at high incident angles, then scattered light increases and contrast decreases
Solution Approach 1:
The patent changes the incident angle parameter of the illumination light to be less than 45 degrees relative to the normal of the reflective display surface. This parameter modification reduces the scattering of light by the flat reflective polarizer while maintaining sufficient illumination intensity, thereby improving image contrast without generating excessive scattered light.
3Volume of moving object
If the optical paths are overlapped to reduce size, then the display becomes more compact, but alignment precision becomes more difficult to maintain
Solution Approach 1:
By merging the illumination and imaging optical paths through the reflective display and integrating the polarizer directly onto the display surface, the patent reduces the number of separate alignment interfaces. This integration simplifies the assembly process and reduces cumulative alignment errors, making it easier to maintain optical alignment precision in a compact configuration.
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 configuration achieves a compact and lightweight display assembly with high image quality and contrast, allowing for a clear and unobstructed view of the environment while providing an effective digital overlay.
Implementation Method 1
a reflective polarizer and a light source. The optical layout of the illumination optical path and the imaging optical path are overlapped to reduce the overall size of the optics package
Implementation Method 2
a flat reflective polarizer is used both to redirect polarized illumination light toward a reflective image source and to act as the analyzer polarizer on the image light
Implementation Method 3
a field lens, a reflective polarizer and a light source
Implementation Method 4
the lower optics comprising a beam splitter, a quarter wave film and a rotationally curved partial mirror
Data Source
AI summary
An optical system for a head-worn computer includes an upper optical module adapted to convert illumination into image light by illuminating a reflective display through a field lens, wherein the image light is transmitted back through the field lens, then through a partially reflective partially transmissive surface and into a lower optic module adapted to present the image light to an eye of a user wearing the head-worn computer and the upper optical module being positioned within a housing for the head-worn computer and having a height of less than 24 mm, as measured from the reflective display to the bottom edge of the rotationally curved partial mirror.