Prism Device Reducing Stray Light in Two-Plate Video Projectors
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Solution Overview
Problem
Conventional video projector apparatuses experience reduced video contrast and brightness due to stray light caused by wavelength shift in dichroic coating layers, which occurs due to differences in incident angles of illuminating and modulated light, and existing solutions either increase the number of optical components or complicate the control mechanism.
Innovation Solution
A prism device with specific geometric configurations, including inclined side faces and a dichroic coating layer, is used to reduce stray light by ensuring that unnecessary transmitted and reflected light is not totally reflected, thereby maintaining video contrast and controlling temperature rise without adding optical components or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dichroic coating layer is used to separate and combine color components, then color separation and combination efficiency is improved, but wavelength shift occurs due to different incident angles of illuminating and modulated light, causing stray light inside the prism device
Solution Approach 1:
The harmful stray light is extracted and removed from the optical system by designing the sixth side face to redirect it outside the prism device, preventing it from causing contrast degradation and temperature rise in the optical modulator element
Solution Approach 2:
Different regions of the prism device are assigned different functions: the dichroic coating layer region handles color separation/combination, while the sixth side face region specifically handles stray light extraction, allowing each region to optimize its local function without interfering with others
2Illumination intensity
If conventional prism designs are used, then color components can be separated and combined, but stray light strikes the optical modulator element and raises its temperature, limiting brightness increase
Solution Approach 1:
The stray light that would normally be harmful and raise temperature is converted into a beneficial outcome by redirecting it outside the device, allowing brightness to be increased without temperature penalties
3Object-generated harmful factors
If the number of optical components is increased to reduce stray light, then stray light reduction is achieved, but device complexity increases
Solution Approach 1:
The prism device is designed to perform multiple functions simultaneously: color separation/combination through the dichroic coating layer and stray light redirection through the sixth side face, eliminating the need for separate stray light management components
Solution Approach 2:
The stray light reduction function is merged into the existing prism structure by adding the sixth side face to the existing dichroic prism, combining color separation and stray light management in a single integrated component
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 prism device effectively reduces stray light and temperature rise, enhancing video contrast and brightness in two-plate video projector apparatuses without increasing the number of optical components or complicating the control mechanism.
Implementation Method 1
a prism device having a dichroic coating layer is used
Implementation Method 2
such that a light beam incident from the first optical modulator element to the first prism element via the first side face, then reflected by the second side face, and then incident from the first prism element to the second prism element via the third and fourth side faces is not totally reflected by the sixth side face
Data Source
AI summary
A first prism has first to third faces. The first face is opposing a first optical modulator. Any two planes among three planes respectively including the first to third faces intersect with each other. A second prism has fourth to sixth faces. The fourth face is provided to be in contact with the third face via a dichroic coating layer and in parallel with the third face. The fifth face is opposing a second optical modulator and in parallel with the second face. The sixth face is in opposite to the first optical modulator with respect to an optical axis of the second optical modulator. The sixth face is formed to be inclined with respect to a reference surface, such that an unnecessary transmitted light and an unnecessary reflected light of the dichroic coating layer are not totally reflected by the sixth face.