Projection Device Using Crossed Dichroic Mirrors to Eliminate Stray Light
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Solution Overview
Problem
Existing projection devices using dichroic prisms suffer from stray light production due to light reflection, leading to reduced image quality and increased size and weight.
Innovation Solution
A projection device employing a configuration of first and second dichroic mirrors that cross each other, combined with self-luminous display devices emitting red, green, and blue light, which superimpose image light without a dichroic prism, thereby preventing stray light and allowing for a compact, high-luminance, and lightweight design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a dichroic prism is used to combine light beams from three self-luminous display devices, then the light beams can be superimposed to form an image, but stray light is generated due to reflection from the top surface, bottom surface, or side surfaces of the prism
Solution Approach 1:
The patent divides the single dichroic prism into multiple separate dichroic mirrors (first dichroic mirror and second dichroic mirror). Each mirror handles specific wavelength combinations, separating the light combination function into discrete segments that reduce unwanted reflections and stray light generation.
Solution Approach 2:
The patent extracts the problematic surfaces (top, bottom, and side surfaces) from the light path by replacing the enclosed prism structure with open mirror arrangements. This removes the surfaces that cause harmful reflections while preserving the essential light combining function.
2Reliability
If a dichroic prism is used to combine light beams, then image projection is achieved, but the device size and weight increase
Solution Approach 1:
The patent segments the monolithic dichroic prism into separate dichroic mirrors, allowing each component to be optimized independently and arranged in a more space-efficient configuration, thereby reducing overall device weight while maintaining projection capability.
Solution Approach 2:
The patent transitions from a three-dimensional enclosed prism structure to a two-dimensional mirror arrangement system. This dimensional change allows for more flexible spatial configuration that reduces material usage and device weight while achieving the same light combination function.
3Reliability
If a dichroic prism is used to combine light beams, then image projection is achieved, but the device occupies more space
Solution Approach 1:
By dividing the dichroic prism into separate mirrors, the patent enables a compact modular arrangement where each mirror can be positioned optimally in space, reducing the overall footprint of the projection device while maintaining full image projection functionality.
Solution Approach 2:
The patent employs a two-dimensional mirror configuration instead of a three-dimensional prism, allowing the light combination system to be flattened and integrated into a more compact device form factor with reduced area occupation.
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 effectively suppresses stray light, enabling high-quality image projection with a small, lightweight, and high-luminance projection device, eliminating the need for a dichroic prism and reducing size and weight.
Implementation Method 1
a first dichroic mirror (40) configured to transmit light of a first wavelength and reflect light of a second wavelength
Implementation Method 2
a second dichroic mirror (50) configured to transmit the light of the first wavelength and reflect light of a third wavelength
Implementation Method 3
a first self-luminous display device (11) including a plurality of first light-emitting elements configured to emit the light of the first wavelength
Data Source
AI summary
A projection device includes a first dichroic mirror configured to transmit light of a first wavelength and reflect light of a second wavelength, a second dichroic mirror configured to transmit the light of the first wavelength and reflect light of a third wavelength, a first self-luminous display device configured to use the light of the first wavelength to emit first image light, a second self-luminous display device configured to use the light of the second wavelength to emit second image light, a third self-luminous display device including a plurality of third light-emitting elements configured to emit the light of the third wavelength, and a projection optical system configured to project, onto a projection target, image light obtained by being combined by the first dichroic mirror and the second dichroic mirror.