Projection Display Aperture Stop for Flare Reduction
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Solution Overview
Problem
Conventional projection display apparatuses using reflective image display elements suffer from image deterioration due to flare caused by air gaps, limiting the improvement of resolution and image quality.
Innovation Solution
A projection display apparatus with a prism unit having an air gap tilted at a predetermined angle and a noncircular aperture stop in the projection optical system, where the aperture stop has a segment-shaped shade portion to block the flare component, satisfying specific conditional formulae to optimize the air gap angle and shading ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an air gap is provided for totally reflecting illumination light and directing it to the image display element, then illumination light can be effectively directed, but flare is generated in transmitted image light causing image deterioration
Solution Approach 1:
The patent extracts the harmful flare component from the transmitted image light by introducing a stopper that selectively blocks the flare while allowing the useful image light to pass through. The stopper is positioned to intercept the flare generated at the air gap interface, separating the harmful effect from the useful function.
Solution Approach 2:
The stopper acts as an intermediary element between the air gap and the projection optical system. It mediates the interaction by blocking the flare component generated at the air gap while maintaining the transmission of image light, thus resolving the conflict between the air gap's useful function and its harmful effect.
2Object-affected harmful factors
If conventional aperture stops are used to block interfering light, then contrast can be improved, but flare caused by air gap is not addressed and image quality remains limited
Solution Approach 1:
The patent applies local quality by creating a non-circular aperture stop with a specific shape that is optimized for blocking flare from the air gap. The stopper has a particular geometry (with parameters defined in the patent) that targets the flare component specifically, rather than using a conventional circular aperture that cannot effectively address the air gap flare problem.
3Manufacturing precision
If resolution is improved, then image quality enhances, but flare from air gap increases and degrades the projected image
Solution Approach 1:
The patent converts the harmful flare generated by the air gap into a beneficial effect by using the flare's directional characteristics to guide the design of the stopper. The flare, which would normally degrade image quality, is instead exploited to define the optimal shape and position of the stopper, which then blocks flare from other sources and improves overall image quality.
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 effectively blocks the flare component, enhancing image quality and achieving a bright, high-resolution projection display by eliminating flare while maintaining brightness.
Implementation Method 1
an air gap provided for totally reflecting illumination light and directing the illumination light to an image display element
Implementation Method 2
a reflective image display element which converts illumination light into image light by reflection on an image display surface
Data Source
AI summary
A projection display apparatus includes a reflective image display element having an image display surface including micromirrors, a prism unit bending an optical path of illumination light and transmitting image light, and a projection optical system. The prism unit has an air gap tilted with respect to a principal ray of the image light emitted from the center of the image display surface, and the image light passes through the air gap. The projection optical system includes an aperture stop with a noncircular aperture so shaped that part of a circular aperture in a peripheral portion thereof is cut off in a shape of a segment to serve as a shade portion, and image light corresponding to an end portion at a side where an incidence angle with respect to the air gap is large in an F-number beam is blocked by the shade portion satisfying predetermined conditions.