Optical Guide With Polarization Splitter For Eye Box Expansion
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Solution Overview
Problem
Existing optical guides face challenges in reducing the size of the injection zone while maintaining a given eye box size and ensuring uniform luminance, with current solutions being complex and costly.
Innovation Solution
Incorporating a delay plate and a polarization splitter between the optical guide element and the extraction device, allowing each ray of the collimated light beam to separate into two parts, with the polarization splitter sandwiched between the guide elements and the extraction device, reducing the injection zone size and improving mechanical strength and manufacturing simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the guide element is reduced to decrease the size of the injection device, then the dimensions of the lens-based optical system are reduced, but the size of the eye box is reduced
Solution Approach 1:
The light beam is segmented into two separate light imprints by the polarization splitter. Each ray of the collimated light beam is divided into two parts: one transmitted directly to form a first light imprint, and the other reflected to form a second light imprint after crossing the delay plate. This segmentation allows the eye box to be effectively doubled in size without increasing the injection zone dimensions.
Solution Approach 2:
A polarization splitter and delay plate are introduced as intermediary elements between the guide element and the extraction device. The polarization splitter separates the light beam into two polarization components, and the delay plate introduces a path difference, creating two distinct light imprints that expand the effective eye box area without requiring a larger injection device.
2Area of stationary object
If a polarization splitter and delay plate are used to increase the eye box size, then the injection zone size is reduced, but the device complexity increases
Solution Approach 1:
The polarization splitter and delay plate are combined into a single integrated assembly that is sandwiched between the guide elements and the extraction device. This merging of components simplifies the overall structure and reduces the number of separate elements that would otherwise need to be aligned and maintained independently.
Solution Approach 2:
The polarization splitter operates in the polarization dimension of light, separating the beam into two orthogonal polarization states. This adds a new dimension to the optical path manipulation, allowing eye box expansion without requiring additional spatial dimensions or larger physical components in the traditional sense.
3Ease of manufacture
If the polarization splitter is placed between the guide element and extraction device, then the manufacturing is simplified by avoiding two laminations, but the mechanical strength must be maintained
Solution Approach 1:
The polarization splitter and delay plate are merged into a single assembly that is sandwiched between the guide elements. This eliminates the need for two separate lamination processes, simplifying manufacturing while maintaining structural integrity through the sandwich construction that distributes mechanical loads across multiple interfaces.
Solution Approach 2:
The sandwich structure provides localized reinforcement at the extraction zone where the polarization splitter is positioned. This allows the guide element to have optimized thickness elsewhere for light guidance, while maintaining sufficient mechanical strength at the extraction interface through the layered sandwich construction.
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 doubles the eye box size, reduces the injection zone size, and enhances the mechanical strength and manufacturing simplicity of the optical guide, while maintaining uniform luminance and see-through effectiveness.
Implementation Method 1
each ray of said collimated light beam striking the polarization splitter a first time separates into two parts, a first part being transmitted to the extraction device and a second part being reflected by the polarization splitter
Implementation Method 2
an optical guide comprising an injection zone intended to inject a light signal into the optical guide and an extraction zone intended to supply the light signal after transport by the optical guide. The guide zone in which the light signal is transported by internal reflections
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An optical guide comprises at least one guiding element (4.1, 4.2) suitable for allowing, by total internal reflection, an image taking the form of a collimated light beam to be conveyed from an injection zone to an extraction zone in which a device (2.14) for extracting the image is mounted. The optical guide comprises a retarder plate (4.3) and a polarizing beamsplitter (4.4), the polarizing beamsplitter (4.4) being placed between the guiding element (4.1) and the extracting device (2.14). The optical guide is such that each ray of said collimated light beam, when it first strikes the polarizing beamsplitter (4.4), is separated into two parts, a first part being transmitted to the extracting device (2.14) in order to define a first luminous imprint and a second part being reflected by the polarizing beamsplitter (4.4), said second part continuing to be guided by the guiding element and, thus, passing two times through the retarder plate (4.3) before striking the polarizing beamsplitter (4.4) in order to define a second luminous imprint.