Prism Unit Curved Reflective Surface Aberration Correction
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Solution Overview
Problem
Existing illumination optical systems for projectors using digital micromirror devices face challenges in achieving compactness while maintaining high light efficiency and reducing unwanted light, with issues related to air gaps and unclear aberration correction in curved reflective surfaces.
Innovation Solution
A compact illumination optical system incorporating a prism unit with a rotationally asymmetric curved reflective surface, optimized by conditional formulas to correct aberration and separate illumination and projection light effectively, combined with a diaphragm and lens group to regulate and converge light efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a free-form mirror is used in the illumination optical system, then aberration correction is improved, but the configuration becomes disadvantageous for achieving compact projectors due to air medium in optical path
Solution Approach 1:
The patent merges the curved reflective surface with the prism structure, eliminating the air gap between optical elements. The curved surface is formed as an integral part of the prism unit, combining reflection and refraction functions into a single compact component, thereby achieving both aberration correction and compactness without requiring separate air-filled optical paths
Solution Approach 2:
The patent employs a curved reflective surface with specific curvature radius to correct optical aberrations. The curved surface is designed with precise curvature parameters that enable effective aberration correction while maintaining a compact form factor, replacing the need for larger air-filled free-form mirrors
2Adaptability or versatility
If air gaps are introduced between prisms, then design freedom is reduced, but it becomes difficult to optimize the height of the projector
Solution Approach 1:
The patent eliminates air gaps by merging multiple optical functions into a single integrated prism unit. The curved reflective surface and refractive surfaces are combined in one component, removing the need for separate air-filled spaces between prisms, thereby enabling compact height optimization while maintaining design flexibility through the integrated structure
3Volume of moving object
If a compact illumination optical system is designed, then projector size is reduced, but light efficiency deteriorates and unwanted light increases
Solution Approach 1:
The patent uses a curved reflective surface with optimized curvature to efficiently direct and concentrate illumination light onto the image display element. The curved geometry enables effective light focusing and aberration correction within a compact volume, maintaining high light efficiency despite the reduced system size
Solution Approach 2:
The patent optimizes optical parameters including the curvature radius of the reflective surface, refractive indices of prism materials, and geometric angles to maximize light efficiency within a compact configuration. By carefully adjusting these parameters, the system achieves both compactness and high light-use efficiency with minimal unwanted light
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 system achieves high light-use efficiency and compactness, reducing unwanted light and improving contrast, thereby enabling a high-contrast projector with efficient light utilization.
Implementation Method 1
a lens group (LN1) which converges the illumination light L1
Implementation Method 2
a diaphragm (ST) which regulates a beam of the illumination light L1
Implementation Method 3
The curved reflective surface reflects incident illumination light at different reflection angles to direct the illumination light through the third optical surface to the second optical surface
Implementation Method 4
a second optical surface which totally reflects illumination light incoming through the first optical surface
Data Source
AI summary
An illumination optical system includes a lens group, a diaphragm, and a prism unit including first to third prisms and a rotationally-asymmetrical curved reflective surface having a positive power and satisfying the conditional formula: PYa/PZa<PYb/PZb, where Pya, Pyb represent powers of the curved reflective surface at positions of points a, b, respectively within a reference plane formed in the prism unit by rays passing through centers of the lens group and the diaphragm, and PZa, PZb represent powers of the curved reflective surface at positions of points a, b, respectively, within a plane including normal lines of the reference plane and the curved reflective surface, points a and b representing where the principal ray of a beam illuminating the area nearest and farthest, respectively, to the lens group impinges on the curved reflective surface, along an intersection line between an image display surface and the reference plane.