Projection Optical System Unit Short Throw Efficiency
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Solution Overview
Problem
Existing projection optical systems struggle to achieve a balance between reducing size and increasing efficiency while maintaining a very short projection distance, as reducing the F-number compromises image contrast and increasing micromirror inclination angles decreases transmittance.
Innovation Solution
Optimizing the projection optical system by setting the maximum micromirror inclination angle to 15 degrees or more and the entrance pupil distance to a range of 3 to 7 times the maximum distance from the optical axis to the image display surface, while using a non-telecentric optical system with a refractive and reflective optical system configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the F-number is reduced to increase brightness and efficiency, then the projection distance becomes shorter, but the image contrast deteriorates
Solution Approach 1:
The patent optimizes the micromirror inclination angle parameter to be 15 degrees or more, which changes the optical path and allows for better separation of reflected light from the cover glass. This parameter change enables the system to maintain high brightness with reduced F-number while preserving image contrast through improved light separation geometry.
2Reliability
If the micromirror inclination angle is increased to improve light separation, then the projection distance decreases, but the transmittance of the cover glass decreases
Solution Approach 1:
The patent identifies and optimizes the micromirror inclination angle parameter to a specific range (15 degrees or more) that achieves the optimal balance between light separation capability and cover glass transmittance. This parameter optimization ensures sufficient contrast while minimizing energy loss through the cover glass.
3Volume of moving object
If the entrance pupil distance is reduced to decrease system size, then the projection apparatus becomes more compact, but the efficiency and image quality are compromised
Solution Approach 1:
The patent optimizes the entrance pupil distance parameter to be within 3 to 7 times the maximum distance from the optical axis to the image display surface. This parameter optimization allows the system to achieve a compact form factor while maintaining high efficiency and image quality through the combined refractive and reflective optical configuration.
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 allows for a smaller, high-efficiency projection optical apparatus that maintains image quality and efficiency even at very short projection distances.
Implementation Method 1
a projection optical system unit (1) including an image forming portion (LV) and a plurality of mirrors (22, 23). The plurality of mirrors (22, 23) reflects light from the image forming portion (LV)...
Implementation Method 2
the projection optical system (25) includes, in order from the image forming portion (LV) side toward the screen (SC) side, the refractive optical system (21)...
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
A projection optical system (25) satisfies θ1 ≥ 15 (deg) and 3 < EP/Ym < 7. 01 is a maximum inclination angle of the reflective surface of each of the micromirrors (100) with respect to the line normal to the image display surface; EP is an entrance pupil distance of the projection optical system (25); and Ym is a maximum distance in a plane (C) from an optical axis to a point on the image display surface, the plane being a plane in which a light ray propagating from a center (LV0) of the image display surface toward the projection surface through a center of an aperture stop (S) of the projection optical system (25) exists, the optical axis being an axis shared by a largest number of the plurality of lenses (11) of the projection optical system (25), the point corresponding to an image on the projection surface.