Polarization Conversion Element with Line-Symmetrical Retardation Layers
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Solution Overview
Problem
The existing polarization conversion elements in projectors suffer from illuminance unevenness and color unevenness due to variations in polarization conversion efficiency caused by the incident angle of light, particularly with retardation films made of overlapping quartz crystal plates, which are costly and complex to manufacture.
Innovation Solution
A polarization conversion element with multiple retardation layers, where the slow axes of at least one retardation layer are line-symmetrical about an axis orthogonal to the slow axes of another retardation layer, ensuring that polarization conversion efficiency variations due to incident angle are canceled out, thereby suppressing illuminance and color unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retardation film made of overlapping quartz crystal plates is used, then polarization conversion function is achieved, but illuminance unevenness and color unevenness occur due to incident angle dependence
Solution Approach 1:
The retardation film is divided into multiple retardation layers (first, second, third, and fourth layers) with different slow axis orientations. Each layer processes a portion of the incident light, and the combined effect cancels out the incident angle dependence, achieving uniform polarization conversion across different incident angles.
Solution Approach 2:
Different regions of the retardation film have different slow axis orientations tailored to compensate for incident angle variations. The first and second retardation layers have slow axes oriented at different angles, and the third and fourth layers similarly have differentiated orientations, creating local optical property variations that collectively eliminate illuminance and color unevenness.
2Device complexity
If a single retardation layer is used, then device complexity is reduced, but polarization conversion efficiency varies with incident angle
Solution Approach 1:
The retardation film is divided into multiple retardation layers (first, second, third, and fourth layers) with different slow axis orientations. Each layer processes a portion of the incident light, and the combined effect cancels out the incident angle dependence, achieving uniform polarization conversion across different incident angles.
Solution Approach 2:
Different regions of the retardation film have different slow axis orientations tailored to compensate for incident angle variations. The first and second retardation layers have slow axes oriented at different angles, and the third and fourth layers similarly have differentiated orientations, creating local optical property variations that collectively eliminate illuminance and color unevenness.
3Illumination intensity
If multiple retardation layers with line-symmetrical slow axis orientations are used, then illuminance and color unevenness are suppressed, but manufacturing complexity increases
Solution Approach 1:
The retardation layers are configured with specific asymmetric slow axis orientations relative to each other. The first and second layers have slow axes at different angles, and the third and fourth layers similarly have differentiated orientations, creating a controlled asymmetric structure that cancels incident angle dependence while maintaining manufacturability.
Solution Approach 2:
The retardation film is divided into multiple retardation layers (first, second, third, and fourth layers) with different slow axis orientations. Each layer processes a portion of the incident light, and the combined effect cancels out the incident angle dependence, achieving uniform polarization conversion across different incident angles.
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 effectively homogenizes the illuminance distribution and suppresses color unevenness in projected images by averaging polarization conversion efficiencies across different retardation layers, regardless of the incident angle, thus improving image quality.
Implementation Method 1
the plurality of polarization separation layers each reflect first polarized light of incident light along the first direction and transmit second polarized light of the incident light along a second direction orthogonal to the first direction
Implementation Method 2
the plurality of reflective layers each reflect, along the second direction, the first polarized light reflected by a corresponding polarization separation layer
Implementation Method 3
the plurality of retardation layers convert the one polarized light incident to the other polarized light, and the direction of a slow axis of at least one retardation layer and the direction of a slow axis of another retardation layer are line-symmetrical
Data Source
AI summary
A polarization conversion element includes: a plurality of polarization separation layers and a plurality of reflective layers alternately disposed along a first direction; and a plurality of retardation layers. The plurality of polarization separation layers reflect first polarized light of incident light along the first direction and transmit second polarized light along a second direction orthogonal to the first direction. The plurality of reflective layers reflect, along the second direction, the first polarized light reflected by a corresponding polarization separation layer. The plurality of retardation layers are provided on an optical path of one polarized light of the first polarized light and the second polarized, and convert the one polarized light to the other polarized light. The direction of a slow axis of one and another retardation layers are line-symmetrical about an axis along a third direction orthogonal to the first and the second directions.