Light Guide Illumination System for Projector Uniformity

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Solution Overview

Problem

Existing illumination optical systems in projectors suffer from uneven screen illuminance due to inefficient capture of diffused light, which can be mitigated but at the cost of reduced absolute illuminance when increasing the diffusion angle of diffusing plates.

Innovation Solution

An illumination optical system that includes a light guide with a dichroic layer intersecting its center axis at 45 degrees, a diffusing member, and a configuration that directs blue light through the light guide while reflecting green and red light, enhancing the capture and utilization efficiency of diffused laser light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the diffusion angle of the diffusing plate is increased to prevent illuminance unevenness, then illuminance uniformity is improved, but absolute illuminance is reduced due to light loss

Engineering Contradiction:

Improveilluminance uniformityVSAvoidabsolute illuminance

Core Design Contradiction:

Stability of the object's compositionVSIllumination intensity

Solution Approach 1:

The patent introduces a light guide that extends the optical path in a new spatial dimension, allowing diffused light to be captured and directed through total internal reflection. This dimensional extension enables the system to maintain both uniformity (through diffusion) and absolute illuminance (through efficient light guidance), resolving the trade-off between these two parameters.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The light guide acts as an intermediary between the diffusing plate and the output, capturing light that would otherwise be lost and redirecting it through total internal reflection. This intermediary component enables the system to preserve absolute illuminance while maintaining the uniformity benefits of diffusion.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If a reflector is used to convert incoherent light into parallel light, then light utilization efficiency is improved, but projected image unevenness in screen illuminance occurs

Engineering Contradiction:

Improvelight utilization efficiencyVSAvoidscreen illuminance uniformity

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent segments the light guidance function into multiple components: a diffusing plate for uniformity and a light guide for efficient transmission. This segmentation allows each component to optimize its specific function without compromising the other, resolving the contradiction between efficiency and uniformity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the traditional reflector-based mechanical light redirection system with an optical fiber-based light guide that uses total internal reflection. This substitution enables more precise and uniform light distribution while maintaining high efficiency, eliminating the illuminance unevenness caused by conventional reflectors.

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

This configuration increases the efficiency of light utilization and reduces illuminance unevenness by effectively guiding and diffusing laser light within the projector, improving the overall brightness and uniformity of the projected image.

Implementation Method 1

a dichroic layer provided inside the light guide, the dichroic layer being arranged so as to intersect a center axis of the light guide at about 45 degree to transmit the blue light while reflecting the green light and the red light

Methodology Applied

Scientific EffectDichroic reflection: Dichroic Filter

Implementation Method 2

a fluorescence plate comprising a green fluorescence region and a light transmission region, wherein the green fluorescence region is excited by the blue light to emit green light

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 3

laser light is diffused by a diffusing member provided in the light guide and resulting diffused laser light can be captured reliably and more efficiently by the light guide

Methodology Applied

Scientific EffectLight diffusion: Scattering

Implementation Method 4

a light guide comprising a dichroic layer therein... guide the red light, the blue light and the green light to the light guide

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS8777422B2Illumination optical system including light guide on which blue light is incident at one end surface and green and red light are incident on a side surface, and projector including the same

Publication Date: 2014.07.15 CASIO COMPUTER CO LTD

AI summary

An illumination optical system includes: a light source device including: a red light-emitting device that emits red light; a blue light-emitting device that emits blue light; and a fluorescence plate comprising a green fluorescence region and a light transmission region, wherein the green fluorescence region is excited by the blue light to emit green light, and the light transmission region transmits the blue light; a light guide including a dichroic layer therein, wherein the dichroic layer is arranged to intersect a center axis of the light guide at about 45 degree to transmit the blue light while reflecting the green light and the blue light; a mirror group and a lens group. The blue light transmitted through the light transmission region is incident on an end surface of the light guide, and the red light and the green light are incident on a side surface of the light guide.