Illuminator Speckle Noise Reduction via Rotating Diffuser

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Solution Overview

Problem

Existing projectors using laser light sources do not sufficiently reduce speckle noise in projection images, as merely irradiating a diffusion plate with combined light does not effectively mitigate this issue.

Innovation Solution

An illuminator configuration that includes a first light source, a second light source, a light combining member, a first diffuser with a rotating substrate, a light collector, and a second diffuser, which temporally changes the state of the combined light spot at the first diffuser's surface, reducing speckle noise by diffusing and parallelizing the light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a diffusion plate is used to reduce speckle noise, then speckle noise reduction is improved, but the noise reduction is insufficient when only simple irradiation is applied

Engineering Contradiction:

Improvespeckle noiseVSAvoidnoise reduction effectiveness

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies the dynamics principle by rotating the diffusion plate at high speed to dynamically change the speckle pattern over time. This rotation transforms the static diffusion process into a dynamic one, where the diffusion plate's orientation continuously varies, causing the speckle noise to fluctuate and average out, thereby achieving superior noise reduction compared to static diffusion plates.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements periodic action through the rotational motion of the diffusion plate. The plate rotates periodically, creating time-varying diffusion effects that modulate the speckle pattern. This periodic variation in diffusion orientation causes the speckle noise to change over time, and when captured by the imaging sensor, the temporal averaging reduces the perceived noise intensity.

Inventive Principle:

Principle #19Periodic action

2Illumination intensity

If laser light sources are used for wide color gamut and high efficiency, then illumination performance is improved, but speckle noise is generated in projection images

Engineering Contradiction:

Improveillumination performanceVSAvoidspeckle noise

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a rotating diffusion plate as an intermediary element between the laser light source and the projection system. This diffusion plate acts as a mediator that scrambles the coherent laser light into incoherent diffused light, thereby eliminating the speckle noise while preserving the illumination benefits. The diffusion plate transforms the harmful coherent light into useful incoherent light for projection.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 described configuration significantly reduces speckle noise in projection images by ensuring the combined light produces a temporally changed speckle pattern, effectively minimizing noise appearance when projected.

Implementation Method 1

a first diffusion surface that diffuses the combined light incident thereon and emits diffused combined light

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

a light collector that is disposed between the light combining member and the first diffuser and collects the combined light at the first diffusion surface of the first diffuser

Methodology Applied

Scientific EffectLight collection: Focusing

Implementation Method 3

a collimator that parallelizes the combined light emitted from the first diffuser

Methodology Applied

Scientific EffectCollimation:

Implementation Method 4

a second diffuser that is disposed between the light collector and the first diffuser and temporally changes the state of a spot of the combined light at the first diffusion surface

Methodology Applied

Scientific EffectTemporal modulation of light spot:

Implementation Method 5

significantly reduces speckle noise in projection images by ensuring the combined light produces a temporally changed speckle pattern

Methodology Applied

Scientific EffectSpeckle noise reduction:

Data Source

PatentUS20250008062A1Illuminator and projector

Publication Date: 2025.01.02 SEIKO EPSON CORP

AI summary

An illuminator includes a first light source that emits first light; a second light source that emits second light; a light combining member that combines the first light and the second light with each other and emits combined light; a first diffuser including a first substrate having a first diffusion surface that diffuses the combined light incident thereon and emits diffused combined light, and a first driver that rotates the first substrate; a light collector that is disposed between the light combining member and the first diffuser and collects the combined light at the first diffusion surface of the first diffuser; a collimator that parallelizes the combined light emitted from the first diffuser; and a second diffuser that is disposed between the light collector and the first diffuser and temporally changes the state of a spot of the combined light at the first diffusion surface.