Hologram Illumination Device Speckle Reduction via Dynamic Diffraction
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Solution Overview
Problem
Projection-type image display apparatuses using coherent light sources face issues with speckle generation, leading to brightness unevenness and physiological adverse effects on observers, as existing techniques fail to effectively suppress speckles without increasing system size, power consumption, or compromising image quality.
Innovation Solution
An illumination device utilizing a hologram recording medium to diffract coherent light beams, creating a diffused pattern that varies with time, effectively making speckles inconspicuous by altering the incidence angle of light on the screen, thereby reducing speckle contrast and brightness unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coherent light source (laser) is used for illumination, then the lifecycle is extended and system size is reduced, but speckles are generated causing brightness unevenness and physiological adverse effects
Solution Approach 1:
The patent employs a rotating diffuser that dynamically changes the scattering pattern of coherent light beams over time. By continuously rotating the diffuser, the speckle pattern on the screen changes and averages out, reducing the visibility of speckles while maintaining the benefits of coherent light sources.
Solution Approach 2:
A diffuser is introduced as an intermediary element between the coherent light source and the projection screen. This diffuser scatters the coherent light beams in multiple directions, transforming the highly coherent light into a more diffuse illumination that reduces speckle formation while preserving the long lifecycle advantage of laser sources.
2Object-affected harmful factors
If a scattering plate is rotated to reduce speckles, then speckle visibility is reduced, but the system becomes larger and power consumption increases
Solution Approach 1:
The patent uses a rotating diffuser mechanism that introduces dynamic motion to the optical system. The rotation of the diffuser continuously varies the scattering angles and positions, causing the speckle pattern to change over time and become less visible, while keeping the overall system compact.
Solution Approach 2:
The diffuser rotates periodically to modulate the scattering pattern at specific frequencies. This periodic motion causes the speckle pattern to fluctuate and average out over time, reducing speckle visibility without requiring complex mechanical systems or high power consumption.
3Loss of energy
If coherent light beams are emitted to illuminate a region, then light utilization efficiency is high, but speckles are generated on the screen
Solution Approach 1:
A diffuser is placed in the optical path as an intermediary element that scatters coherent light beams while preserving the overall illumination efficiency. The diffuser redistributes the light in multiple directions, reducing speckle formation without significantly increasing energy loss, thus maintaining high light utilization efficiency.
Solution Approach 2:
The patent changes the spatial distribution parameters of coherent light beams by introducing a diffuser. This modifies the angular spread and spatial coherence of the light, transforming the illumination pattern to reduce speckle visibility while maintaining efficient light utilization through optimized diffuser design.
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 significantly reduces speckle contrast, making speckles inconspicuous to observers and improving image quality, while also miniaturizing and simplifying the optical system, and enhancing light utilization efficiency.
Implementation Method 1
an illumination device utilizing a hologram recording medium to diffract coherent light beams, creating a diffused pattern that varies with time
Implementation Method 2
By rotating the rotating member, the incidence angle of diffracted light beams on the screen is changed, thereby making speckles inconspicuous
Data Source
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AI summary
An illumination device (40) comprising an optical device (50) having a hologram recording medium (55) having a plurality of recording areas, and an irradiation unit (60), wherein the irradiation unit (60) has a plurality of light sources (61r, 61g, 61b) that emit a plurality of coherent light beams having different wavelengths, and the plurality of recording areas diffract the coherent light beams incident from the respective light sources and illuminate respective illumination zones (LZ- to LZ-5) that do not overlap with one another in the illumination zone (LZ), and corresponding projection apparatus and projection type image display.