Light-Shielding Mask for Short-Throw Projector Lens Shift
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Solution Overview
Problem
In short throw projectors, the use of an optical shift system to project wide-angled images at a short distance leads to image distortion and the risk of damage from unwanted light irradiation, particularly during lens replacement, causing vignetting and potential damage due to high temperature exposure.
Innovation Solution
A projection system with a first optical system forming an intermediate image and a light-shielding mask positioned at the image forming area, which cuts off unwanted light, reducing image distortion and preventing damage to components by blocking light from areas outside the effective image forming range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If an optical shift system is used to project wide-angled images at a short distance, then the projection distance is shortened and the viewing angle is widened, but image distortion occurs and unwanted light causes damage to components
Solution Approach 1:
The patent extracts and blocks unwanted light rays that fall outside the effective image forming area using a light-shielding mask. This mask is positioned at a specific location in the optical path to intercept stray light before it reaches the projection lens, thereby preventing component damage while maintaining the short throw projection capability
Solution Approach 2:
The light-shielding mask acts as an intermediary element between the light source and the projection lens. It selectively blocks harmful light rays while allowing useful light to pass through, protecting the lens from thermal damage without affecting the intended projection function
2Reliability
If a light-shielding mask is added to block unwanted light, then component damage is prevented, but the device complexity increases
Solution Approach 1:
The light-shielding mask is designed with a specific aperture pattern that matches the effective image forming area. Rather than blocking all light uniformly, it selectively shields only the regions where unwanted light occurs, maintaining optical quality in the useful areas while protecting against damage in the harmful areas
3Ease of repair
If the projection system uses a replacement lens unit, then maintenance is easier, but unwanted light can irradiate the lens unit causing damage during replacement
Solution Approach 1:
The light-shielding mask is pre-installed in the optical path before lens replacement occurs. It continuously blocks unwanted light during the entire operation cycle, including during lens replacement when the lens unit may be temporarily positioned in unsafe locations. This preliminary protective action prevents damage before it can occur
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 image distortion and prevents damage from unwanted light, ensuring the quality of the projected image and minimizing the risk of component damage due to light exposure, while also allowing for a lighter and more cost-effective lens design.
Implementation Method 1
a first optical system (110) that forms an intermediate image
Implementation Method 2
a light-shielding mask (130) that blocks light from areas outside the effective image forming range
Implementation Method 3
a second optical system (120) that projects the intermediate image as an enlarged image
Data Source
AI summary
A projector projects image light generated by an image generation unit, as an enlarged image via a projection system. The incident position of the image light on the projection system is moved by a lens shift mechanism. The projection system forms an intermediate image in the course of the optical path. A light-shielding mask is provided at an image forming position of the intermediate image. A light-shielding area by the light-shielding mask includes an area that does not overlap the intermediate image within a range of an effective image forming area at the image forming position of the intermediate image. For example, the light-shielding area is an area on the side opposite to the side to which the intermediate image is shifted, of the effective image forming area.