Illuminator Polarization State Conversion for Compact Projectors
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Solution Overview
Problem
Existing illuminators face challenges in adjusting the ratio between P-polarized and S-polarized light, leading to inefficiencies in light usage and alignment issues with stripe mirrors, which restrict the miniaturization of projector systems.
Innovation Solution
An illuminator design that utilizes a polarization state conversion element, such as a half-wave plate, to adjust the ratio between P-polarized and S-polarized light by altering the positional relationship between the polarization state conversion element and the optical axis, allowing for efficient light combination and alignment without requiring precise positioning of stripe mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If stripe mirrors are used to combine light beams, then light combination is achieved, but precise alignment is required and light is blocked when beam distance is small
Solution Approach 1:
The patent introduces a polarization beam splitter as an intermediary element to combine light beams from multiple laser arrays. This mediator separates and recombines light beams based on polarization states rather than requiring direct physical alignment like stripe mirrors, thereby eliminating the need for precise alignment while maintaining effective light combination.
Solution Approach 2:
The patent replaces the mechanical alignment system of stripe mirrors with an optical system based on polarization beam splitting. Instead of relying on mechanical positioning and physical spacing of mirrors, the system uses polarization optics to achieve light combination, substituting mechanical precision requirements with optical property-based separation and combination.
2Volume of moving object
If the pitch of semiconductor lasers is reduced to miniaturize the illuminator, then the size is reduced, but light beams are blocked by stripe mirrors
Solution Approach 1:
The polarization beam splitter acts as an intermediary that allows light beams from closely spaced laser arrays to be combined without physical blocking. By separating beams based on polarization states rather than spatial separation, the system enables miniaturization (reduced pitch) without the light blocking problems that occur with stripe mirrors.
3Illumination intensity
If the amount of light from laser arrays is increased to improve image brightness, then image brightness increases, but the ratio between P-polarized and S-polarized light cannot be adjusted
Solution Approach 1:
The patent introduces a variable retardation film that can dynamically change its retardation amount, enabling the system to adjust the ratio between P-polarized and S-polarized light. This dynamic element allows the polarization state to be varied while maintaining high light output, providing both brightness and adaptability.
Solution Approach 2:
The patent changes the optical parameter (retardation amount) of the variable retardation film to control the polarization state of combined light. By varying this parameter, the system can adjust the P-polarized to S-polarized light ratio while maintaining high overall light intensity, thus achieving both brightness and polarization control.
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 solution enables flexible adjustment of the light ratio, improving light usage efficiency and allowing for a more compact projector design without the need for precise alignment of stripe mirrors, resulting in enhanced white balance and image quality.
Implementation Method 1
a polarization state conversion element, such as a half-wave plate, to adjust the ratio between P-polarized and S-polarized light by altering the positional relationship between the polarization state conversion element and the optical axis
Implementation Method 2
the polarizing beam splitter transmits P-polarized light emitted from one of the laser arrays and reflects S-polarized light emitted from the other laser array to combine the two light beam fluxes with each other
Data Source
Figure 1
Figure 2
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AI summary
An illuminator (2) includes a first light source unit (20) that outputs first light beams (BL1s), a second light source unit (21) that outputs second light beams (BL2p), a polarization combining element (22) that combines the first and second light beams with each other, a polarization state conversion element (23; 123) on which combined light from the polarization combining element (22) is incident, a polarization separation element (25) that separates the combined light having passed through the polarization state conversion element (23; 123) into first light and second light, and a wavelength conversion element (30)) that converts the first light into third light, and the illuminator (2) outputs the second light and the third light as illumination light. The polarization state conversion element (23; 123) includes a plurality of retardation elements (23a) that are separate from one another and arranged in a first direction (Z). The first and second light source units are so configured that a plurality of first regions (A1) through which the plurality of first light beams (BL1s) pass and a plurality of second regions (A2) through which the plurality of second light beams (BL2p) pass are alternately arranged in the first direction (Z) in the polarization state conversion element (23; 123).