Polarization Conversion Element for Image Display Depolarization
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Solution Overview
Problem
There is a need for technology capable of displaying high-quality images, as existing image display apparatuses face challenges in achieving uniform depolarization of image light, leading to color unevenness and luminance drops.
Innovation Solution
An image display apparatus comprising a light emission unit and a polarization conversion element that converts the polarization state of image light to an unpolarized state, with non-uniform conversion properties across the incident surface, effectively depolarizing the image light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polarization conversion unit with uniform depolarization properties is used, then the structure is simple, but color unevenness and luminance drops occur in the displayed image
Solution Approach 1:
The polarization conversion element is designed with non-uniform depolarization properties across different regions of the incident surface. Specifically, the phase difference introduced by the element varies continuously from the center toward the edges, with larger phase differences at the edges and smaller phase differences at the center. This local variation in depolarization characteristics compensates for the non-uniform illumination distribution and optical path differences across the projection lens aperture, thereby eliminating color unevenness and luminance drops while maintaining a relatively simple single-element structure.
2Manufacturing precision
If a polarization conversion element with non-uniform conversion properties is used, then image quality is improved, but the device complexity increases
Solution Approach 1:
The polarization conversion element achieves non-uniform depolarization by varying the physical parameters of the element across its surface. This is accomplished through techniques such as varying the thickness of a waveplate, using materials with spatially varying birefringence, or applying gradient-index optics. These parameter changes create the desired continuous phase difference variation without requiring complex multi-element assemblies, thus improving image quality while keeping the overall device structure relatively simple.
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 enables the display of high-quality images by sufficiently depolarizing image light, reducing color unevenness and luminance drops, and improving overall image quality.
Implementation Method 1
a polarization conversion element that has an incident surface, converts a polarization state of the image light that enters the incident surface, emits the converted light as image light in an unpolarized state
Implementation Method 2
The polarization conversion element may be configured such that a birefringence with respect to the image light is non-uniform in the incident surface
Data Source
AI summary
An image display apparatus according to an embodiment of the present technology includes: a light emission unit; and a polarization conversion element. The light emission unit emits image light. The polarization conversion element has an incident surface, converts a polarization state of the image light that enters the incident surface, emits the converted light as image light in an unpolarized state, and is configured such that conversion properties of the polarization state are non-uniform in the incident surface. As a result, it is possible to sufficiently depolarize the image light and display a high-quality image. In addition, it is possible to reduce uneven polarization and speckles.