Compact Laser Optical Device with Wavelength Conversion Wheel

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Solution Overview

Problem

Existing image projection apparatuses face challenges in achieving compact and efficient light output due to the complexity of optical paths required for high-resolution image projection, particularly with the use of multiple mirrors and low efficiency of conventional light sources like HID lamps and UHP lamps.

Innovation Solution

A compact optical device utilizing a laser diode for outputting laser light, a polarization separator to transmit and reflect polarized light, a wavelength conversion wheel to generate blue, green, and red lights, and a polarization converter to align and output these colors efficiently, enabling a compact design with high light output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple mirrors are used to divide optical paths for blue, red, and green lights, then the optical device can achieve high-resolution image projection, but the device size increases and compactness is compromised

Engineering Contradiction:
Improveimage resolutionVSAvoidoptical device size
Core Design Contradiction:
Measurement precisionVSVolume of moving object

Solution Approach 1:

The patent combines the optical paths for blue, red, and green lights into a single integrated path using a wavelength conversion wheel with phosphor layers, eliminating the need for separate mirrors for each color channel. This merging of previously separate optical paths achieves the desired image resolution while significantly reducing the overall device size and improving compactness.

Inventive Principle:
Principle #5Merging (Combining)

2Power

If conventional lamps (HID, UHP) are used as light sources, then high power projection is achieved, but the lifespan is short and efficiency is low

Engineering Contradiction:
Improveprojection powerVSAvoidlifespan
Core Design Contradiction:
PowerVSDuration of action of moving object

Solution Approach 1:

The patent replaces conventional thermal arc discharge lamps (HID, UHP) with a laser diode-based light source system. This substitution eliminates the mechanical and thermal limitations of conventional lamps, achieving high projection power with significantly extended lifespan and improved energy efficiency through cold light emission from the laser diode and phosphor conversion.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Power

If conventional lamps are used as light sources, then high power projection is achieved, but energy efficiency is low

Engineering Contradiction:
Improveprojection powerVSAvoidenergy efficiency
Core Design Contradiction:
PowerVSUse of energy by moving object

Solution Approach 1:

The patent replaces inefficient thermal conversion in conventional lamps with the electroluminescence process in laser diodes followed by phosphor wavelength conversion. This substitution dramatically improves energy efficiency by directly converting electrical energy to light energy with minimal thermal loss, while maintaining high projection power output.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

4Measurement precision

If optical paths are divided for different colors, then color accuracy is achieved, but the number of optical components increases and device complexity rises

Engineering Contradiction:
Improvecolor accuracyVSAvoidnumber of optical components
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the separate optical paths for different colors into a single integrated optical path using a wavelength conversion wheel with multiple phosphor layers. This approach maintains color accuracy by sequentially converting laser light to different wavelengths while eliminating the need for multiple mirrors and beam splitters, thereby reducing device complexity and component count.

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 allows for a compact optical device that achieves highly efficient light output by aligning optical paths of blue, green, and red lights, improving reliability and design flexibility while preventing contrast reduction, and enhancing the lifespan of polarization converters.

Implementation Method 1

a laser diode for outputting a laser light having a predetermined wavelength

Methodology Applied
Scientific EffectLaser: Laser

Implementation Method 2

a polarization separator for transmitting a first polarized light of the laser light and reflecting a second polarized light of the laser light

Methodology Applied
Scientific EffectPolarization: Polarisation

Implementation Method 3

a wavelength conversion unit for converting a wavelength of the second polarized light of the laser light reflected by the polarization separator such that the second polarized light of the laser light corresponds to one selected from among a blue light, a green light, and a red light

Methodology Applied
Scientific EffectWavelength conversion: Fluorescence

Implementation Method 4

a polarization converter for converting the light transmitted through the wheel into the first polarized light and outputting the converted first polarized light to the wheel

Methodology Applied
Scientific EffectPolarization conversion: Birefringence

Data Source

PatentEP3149535B1Optical device and image projection apparatus including the same
Publication Date: 2019.10.30 LG ELECTRONICS INC
  • EP3149535B1 patent drawingFigure 1
  • EP3149535B1 patent drawingFigure 2
  • EP3149535B1 patent drawingFigure 3

AI summary

An optical device and an image projection apparatus including the same are disclosed. The optical device includes a laser diode for outputting a laser light having a predetermined wavelength, a polarization separator for transmitting a first polarized light of the laser light and reflecting a second polarized light of the laser light, a wheel including a wavelength conversion unit for converting a wavelength of the second polarized light of the laser light reflected by the polarization separator such that the second polarized light of the laser light corresponds to one selected from among a blue light, a green light, and a red light and a transmission unit for transmitting the other lights, a polarization converter for converting the light transmitted through the wheel into the first polarized light and outputting the converted first polarized light to the wheel, and an optical output unit for outputting the first polarized light from the polarization converter and the light converted in wavelength and reflected by the wheel. Consequently, it is possible to provide a compact optical device that is capable of achieving highly efficient light output.