Polarization Conversion Unit for Laser Illumination Uniformity

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Solution Overview

Problem

Projection devices with laser diodes as light sources face limitations in size reduction and uniformity due to the two-segment beam splitting design, which restricts light source placement options and affects illumination beam uniformity.

Innovation Solution

An illumination system incorporating a laser light source, wavelength conversion module, and polarization conversion unit, where the polarization conversion unit allows the laser beam to be incident on polarized beam splitting sheets in a forward direction, enabling increased light source placement options and concurrent homogenization of laser and wavelength conversion beams, thus improving beam uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a two-segment beam splitting design is adopted to reduce system size, then the projection device size is reduced, but the light source placement options are restricted and beam uniformity deteriorates

Engineering Contradiction:

Improveprojection device sizeVSAvoidlight source placement options

Core Design Contradiction:

Volume of moving objectVSAdaptability or versatility

Solution Approach 1:

The patent inverts the conventional beam splitting approach by using a polarized beam splitting sheet that allows the laser beam to be incident from the front direction rather than from the side. This inversion enables the light source to be placed in multiple positions while maintaining the compact two-segment design, thus resolving the contradiction between size reduction and placement flexibility.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the polarization state parameter of the laser beam through a polarization conversion unit, transforming the beam's polarization characteristics to enable forward incidence on the beam splitting element. This parameter change allows the system to maintain compact size while improving light source placement options and beam uniformity.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If a two-segment beam splitting design is adopted, then the system size is reduced, but the illumination beam uniformity deteriorates due to double speckle formation

Engineering Contradiction:

Improvesystem sizeVSAvoidillumination beam uniformity

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent introduces a polarization conversion unit as an intermediary element between the laser source and the beam splitting system. This intermediary converts the laser beam's polarization state, enabling it to pass through the polarized beam splitting sheet in a forward direction and undergo concurrent homogenization, thereby reducing double speckle formation and improving illumination uniformity while maintaining compact system size.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Volume of moving object

If the laser beam is made to incident on the beam splitting element from one side, then the system can be compact, but the light source placement options are reduced

Engineering Contradiction:

Improvesystem sizeVSAvoidlight source placement flexibility

Core Design Contradiction:

Volume of moving objectVSEase of operation

Solution Approach 1:

The patent inverts the conventional side-incident beam splitting design by implementing front-direction incidence through polarized beam splitting. This allows the light source to be placed flexibly in various positions while maintaining compact system dimensions, thus resolving the contradiction between compactness and placement flexibility.

Inventive Principle:

Principle #13The other way round (Inversion)

4Manufacturing precision

If concurrent homogenization of laser beam and wavelength conversion beam is achieved, then beam uniformity is improved, but the optical system complexity increases

Engineering Contradiction:

Improvebeam uniformityVSAvoidoptical system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges the homogenization functions for both the laser beam and the wavelength conversion beam into a single concurrent homogenization process. By using the polarized beam splitting sheet and polarization conversion unit together, both beams undergo homogenization simultaneously, improving beam uniformity while minimizing the increase in optical system complexity through integrated design.

Inventive Principle:

Principle #5Merging (Combining)

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 a reduction in projection device size while maintaining or improving the uniformity of the illumination beam and image frame, enhancing overall performance.

Implementation Method 1

The wavelength conversion module has a wavelength conversion region, and the wavelength conversion module is deposed on a transmission path of the laser beam. The laser beam is converted into a wavelength conversion beam by the wavelength conversion region

Methodology Applied

Scientific EffectWavelength conversion: Fluorescence

Implementation Method 2

The polarization conversion unit includes a plurality of phase delay sheets, which are correspondingly located on a plurality of surfaces facing the laser light source and located in the plurality of second polarization conversion regions of the polarization conversion unit. The wavelength conversion beam with the first polarization state leaves the polarization conversion unit after passing through the phase delay sheet located in the second polarization conversion region

Methodology Applied

Scientific EffectPhase delay: Birefringence

Implementation Method 3

The polarization conversion unit has a plurality of first polarization conversion regions and a plurality of second polarization conversion regions. The wavelength conversion beam with the second polarization state leaves the polarization conversion unit after passing through a surface of the polarization conversion unit located in the plurality of first polarization conversion regions facing the laser light source

Methodology Applied

Scientific EffectPolarized beam splitting: Polarisation

Data Source

PatentUS11693300B2Illumination system and projection device

Publication Date: 2023.07.04 CORETRONIC CORPORATION

AI summary

An illumination system, including a laser light source, a wavelength conversion module, and a polarization conversion unit, and a projection device are provided. A laser beam of the laser light source is converted to a wavelength conversion beam by a wavelength conversion region of the wavelength conversion module. The polarization conversion unit has multiple first polarization conversion regions and multiple second polarization conversion regions, and includes multiple phase delay sheets correspondingly located on multiple surfaces facing the laser light source and located in the second polarization conversion regions. The wavelength conversion beam with a second polarization state leaves the polarization conversion unit after passing through a surface of the polarization conversion unit in the first polarization conversion regions facing the laser light source. The wavelength conversion beam with a first polarization state leaves the polarization conversion unit after passing through the phase delay sheet in the second polarization conversion region.