Image Projection Apparatus Corrects Illumination Angle Distribution
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Solution Overview
Problem
High-definition digital micromirror devices in image projection apparatuses suffer from diffraction effects, leading to uneven color in projected images, especially when using laser light sources, as the smaller pixel pitches act as diffraction gratings, causing different wavelengths to be diffracted at varying angles, which is difficult to mitigate without degrading image quality across the entire screen.
Innovation Solution
An image projection apparatus is designed with a corrector that adjusts the angle distribution of illumination light such that the F-number of light with one wavelength is greater than that of another, ensuring diffracted light with one wavelength is directed farther away from the mirror-reflected light than with another, thereby reducing diffraction effects and achieving uniform color projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pixel pitch of the digital micromirror device is reduced to achieve high definition, then the image quality and resolution are improved, but the diffraction effect increases causing uneven color in the projected image
Solution Approach 1:
The patent applies different F-numbers for different wavelength bands of illumination light. Specifically, the F-number for the first wavelength band (e.g., blue light) is set to be larger than the F-number for the second wavelength band (e.g., red light). This local differentiation in optical parameters compensates for the wavelength-dependent diffraction effects, allowing high-definition imaging while reducing color unevenness caused by diffraction.
Solution Approach 2:
The patent changes the optical parameter (F-number) based on the wavelength of illumination light. By setting different F-numbers for different wavelength bands, the system dynamically adjusts the angle distribution of illumination light to counteract the varying diffraction angles of different wavelengths, thereby reducing the harmful diffraction effect while maintaining high definition.
2Illumination intensity
If a laser light source is used to improve brightness and color saturation, then the illumination efficiency is improved, but the diffraction effect becomes more pronounced due to the coherent nature of laser light
Solution Approach 1:
When using laser light sources, the patent applies wavelength-dependent F-number adjustment to mitigate the coherent diffraction effects. By setting the F-number for each wavelength band (particularly for the laser wavelengths being used), the system controls the angle distribution of the coherent laser light to reduce diffraction-related color unevenness while maintaining the high brightness and color saturation benefits of laser illumination.
3Productivity
If the F-number for all wavelength bands is reduced to improve light gathering ability, then the illumination efficiency is improved, but the diffraction effect increases causing greater color unevenness
Solution Approach 1:
Instead of using a uniform F-number for all wavelengths, the patent implements local optimization by setting different F-numbers for different wavelength bands. The F-number for the first wavelength band is set larger than that for the second wavelength band, creating a tailored angle distribution that maintains adequate light gathering ability while specifically addressing the diffraction characteristics of each wavelength to reduce color unevenness.
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 reduces the influence of diffraction at digital micromirror devices, resulting in high-quality projection images with less color unevenness by optimizing the angle distribution of illumination light, specifically by ensuring the F-number of light with one wavelength is larger than that of another, thus minimizing diffraction-related color discrepancies.
Implementation Method 1
A digital micromirror device has an image display surface composed of a plurality of minute mirrors; it controls the inclination of the individual mirror surfaces on the image display surface, thereby modulates the intensity of illumination light, and thereby forms an image
Implementation Method 2
As digital micromirror devices are given increasingly high definition, they come to have increasingly small pixel pitches, and this makes the influence of diffraction accordingly less negligible. Specifically, the smaller the pixel pitch is, the more a digital micromirror device acts as a diffraction grating, and, since incident light rays having different wavelengths have different diffraction angles
Data Source
AI summary
An image projection apparatus has a corrector that corrects angle distribution of illumination light such that, let, in a comparison in traveling direction between, of diffracted light resulting from light rays with the wavelengths λ1 and λ2 along the illumination optical axis being diffracted on an on-state digital micromirror device, λ1 diffracted light traveling in a direction closest to a traveling direction of the mirror-reflected light and λ2 diffracted light traveling in a direction closest to the traveling direction of the mirror-reflected light, the λ1 diffracted light be diffracted to a position farther away from the mirror-reflected light than the λ2 diffracted light, the angle distribution of the illumination light includes at least an angle distribution that fulfills conditional formula (1): Fλ2<Fλ1, where Fλ1 and Fλ2 represent F-numbers of illumination light with the first and second wavelengths λ1 and λ2, respectively.