Laser Illumination Optical System for Projectors

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Solution Overview

Problem

LED-based projectors face challenges in achieving sufficient brightness due to the limitations imposed by the etendue, which restricts the utilization of light from the light source, making it difficult to increase light quantity without expanding the light-emission area.

Innovation Solution

An illumination optical system incorporating a laser light source, phosphor, and dichroic mirrors to generate and direct fluorescent light, allowing for a high-energy density excitation that converges on the phosphor, thereby reducing the etendue and enhancing brightness while maintaining a long lifetime.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the light-emission area of an LED is increased to increase light quantity, then the light quantity increases, but the etendue increases which limits effective light utilization

Engineering Contradiction:

Improvelight quantityVSAvoidetendue

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent changes the light source from LED to laser, fundamentally altering the parameters of light emission. Laser light sources produce highly directional, coherent light with small etendue, enabling high light quantity without increasing emission area. This parameter change resolves the contradiction by decoupling light quantity from etendue through the use of laser physics principles.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the LED-based illumination system with a laser-based system. This substitution introduces a fundamentally different light generation mechanism that inherently produces low etendue light, thereby resolving the technical contradiction between increasing light quantity and maintaining small etendue for effective projection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If an LED is used as light source, then long lifetime and high reliability are achieved, but insufficient brightness is obtained for projection

Engineering Contradiction:

ImprovelifetimeVSAvoidbrightness

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The patent changes the light source type from LED to laser, which fundamentally alters the illumination intensity parameter. Laser light sources provide high brightness and high energy density while maintaining long operational lifetime, thus resolving the contradiction between reliability and illumination intensity through parameter transformation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes LED with laser as the light source, replacing a broadband incoherent source with a coherent high-intensity source. This substitution maintains the reliability advantage while dramatically improving brightness, enabling effective projection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Duration of action of stationary object

If LED light is used for projection, then long lifetime is achieved, but the light cannot be effectively utilized due to etendue limitation

Engineering Contradiction:

ImprovelifetimeVSAvoidlight utilization efficiency

Core Design Contradiction:

Duration of action of stationary objectVSProductivity

Solution Approach 1:

The patent changes the light source parameters by using laser instead of LED. Laser light has small etendue and high directionality, which fundamentally improves light utilization efficiency for projection while maintaining long lifetime, thus resolving the contradiction between duration of action and productivity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the LED illumination system with a laser illumination system. This substitution creates a low etendue light source that can be effectively utilized in projection applications, resolving the contradiction between long operational duration and light utilization efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 system achieves a smaller etendue, longer lifetime, and higher brightness by utilizing a laser to excite phosphors, resulting in efficient light generation and projection.

Implementation Method 1

a phosphor that generates fluorescent light by means of the excitation light

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 2

a dichroic mirror that is disposed between the laser light source and the light tunnel, and that allows the fluorescent light or the excitation light to pass through, and reflects the remaining excitation or fluorescent light

Methodology Applied

Scientific EffectDichroic reflection: Dichroic Filter

Data Source

PatentUS9022580B2Illumination optical system and projector using the same

Publication Date: 2015.05.05 SHARP KK

AI summary

This invention realizes an illumination optical system with a small etendue that has a longer lifetime and a high degree of brightness. The invention includes: a laser light source that generates excitation light; a phosphor that generates a fluorescent light by means of the excitation light; a light tunnel that projects the excitation light that is incident at one end towards the phosphor from another end, and projects a fluorescent light generated with the phosphor from the one end; and a dichroic mirror that is provided between the laser light source and the light tunnel, and that allows the fluorescent light or the excitation light to pass through, and reflects the remaining excitation or fluorescent light.