Illumination Mirror Positioning for DMD Uniformity
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Solution Overview
Problem
Existing image displaying apparatuses using reflective image displaying elements like DMDs face issues with light interference and irregular illuminance due to the placement of folding mirrors, leading to reduced image quality and increased costs with Total Internal Reflection (TIR) prisms, which also result in a heavier and less efficient system.
Innovation Solution
An image displaying apparatus with a light source, light condenser, light mixing element, and a reflective image displaying element, featuring a mirror for illumination positioned nearest the reflective image displaying element, with a reflection surface aligned to avoid interference with the projection lens system, ensuring uniform illuminance and improved image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a folding mirror is arranged at the exit end side of the lens barrel to reflect light to the DMD, then the optical path can be configured, but physical interference with the lens barrel occurs and extensive notching is required, causing light loss and irregular illuminance
Solution Approach 1:
The folding mirror is repositioned from the exit end side to the entrance end side of the lens barrel, changing the spatial dimension of arrangement. This dimensional shift allows the mirror to be placed where it does not interfere with the lens barrel, eliminating the need for extensive notching and preventing light loss while maintaining the optical path configuration capability
2Ease of manufacture
If a folding mirror is arranged at the exit end side of the lens barrel, then the optical path can be configured, but the aperture of the projection lens must be decreased, reducing projection speed and design freedom
Solution Approach 1:
By relocating the folding mirror to the entrance end side of the lens barrel instead of the exit end side, the spatial arrangement is optimized. This allows the projection lens to maintain its original aperture size without being constrained by the mirror placement, thereby preserving projection speed and design freedom while still achieving the required optical path configuration
3Measurement precision
If a TIR prism is used to fold the optical path, then the reflection surface can be positioned near the center of the DMD, but high precision polishing and integration are required, increasing cost
Solution Approach 1:
Instead of using a complex TIR prism that requires high-precision polishing and integration, the patent employs a simpler folding mirror system that achieves the same optical path folding function. This substitution with a less complex component reduces manufacturing precision requirements and lowers cost while still positioning the reflection surface appropriately near the center of the DMD
4Measurement precision
If a TIR prism is used to fold the optical path, then the reflection surface can be positioned near the center of the DMD, but light loss occurs at multiple surfaces, reducing efficiency
Solution Approach 1:
The patent replaces the TIR prism with a folding mirror arrangement that achieves the same optical path folding without the multiple surface reflections inherent in prism geometry. This eliminates light loss at entrance and exit surfaces of prisms, maintaining reflection surface positioning near the DMD center while significantly improving light efficiency
5Measurement precision
If a TIR prism is used to fold the optical path, then the reflection surface can be positioned near the center of the DMD, but the mass of the prism is greater than a mirror, inhibiting lightweight design
Solution Approach 1:
The patent substitutes the heavy TIR prism with a lightweight folding mirror system that performs the same optical path folding function. This replacement dramatically reduces the mass of the optical component while maintaining the ability to position the reflection surface near the center of the DMD, enabling lightweight image displaying apparatus 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
This configuration enhances the uniformity of illuminance on the reflective image displaying element and the projected image, reducing light loss and maintaining efficiency while avoiding physical interference, thus improving the overall quality and efficiency of the image displaying system.
Implementation Method 1
a light condenser for condensing light emitted from the light source to form a condensed light image at a predetermined position
Implementation Method 2
a mirror for illumination positioned nearest the reflective image displaying element, with a reflection surface aligned to avoid interference with the projection lens system
Data Source
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AI summary
Disclosed is an image displaying apparatus (100, 101) including a light source (1), a light condenser (2) for condensing light emitted from the light source (1) to form a condensed light image at a predetermined position, a light mixing element (13) having an entrance end near the condensed light image, a reflective image displaying element (7) having plural micro-mirrors (7-1 - 7-k) arranged two-dimensionally and configured to change an inclination angle of an individual micro-mirror (7-1 - 7-k) between an on-state and an off-state so that emission of reflected light turns on or off, an illumination optical system (8) including a condenser lens (3) and a mirror (4-5) for illumination arranged between an exit end of the light mixing element (13) and the reflective image displaying element (4), and a projection optical system (10) for projecting, onto a surface (101) to be projected, reflected light from a micro-mirror (7-1 - 7-k) being at an on-state among plural micro-mirrors (7-1 - 7-k) constituting the reflective image displaying element (7), wherein the mirror (7-1 - 7-k) for illumination is arranged at a position nearest the reflective image displaying element (7) on an optical path from the light mixing element (13) to the reflective image displaying element (7) and a reflection surface of this mirror (4-5) for illumination is positioned at a side of the reflective image displaying element (7) with respect to a projection lens system (10) constituting a part of the projection optical system (8).