Compact Projection Display Using Light-Shielding Plate for OFF Light Management
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Solution Overview
Problem
The existing projection display apparatuses using digital micromirror devices (DMD) face challenges in compactness due to the need to separate and position the DMD and color separating and combining prism to prevent off-light from entering the prism, leading to increased overall configuration size.
Innovation Solution
An image generation unit is designed with three light modulation elements, a color separating and combining prism, a light-shielding plate, and a reflecting surface that absorbs and reflects off-light, allowing for a more compact configuration by directing off-light away from the optical axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the DMD and color separating and combining prism are separated to prevent OFF light from entering the prism, then OFF light is blocked, but the overall configuration size increases
Solution Approach 1:
The patent converts the harmful OFF light into a beneficial element by using it to illuminate a light-shielding plate, which then reflects the OFF light back onto the DMD. This approach blocks the harmful OFF light from entering the color separating and combining prism while maintaining a compact configuration, as the OFF light is reused rather than simply blocked.
Solution Approach 2:
The patent merges the light-shielding plate with the DMD by positioning it on the front surface of the DMD. This integration allows the light-shielding plate to serve dual purposes: blocking OFF light from entering the prism and reflecting OFF light back onto the DMD, thereby preventing harmful light while maintaining compact dimensions.
2Object-affected harmful factors
If the color separating and combining prism height is increased to release OFF light to the upper side, then OFF light is redirected, but the overall configuration size increases
Solution Approach 1:
Instead of increasing prism height to redirect OFF light, the patent converts the harmful OFF light into a useful illumination source for the light-shielding plate. The OFF light illuminates the plate, which then reflects it back onto the DMD, achieving OFF light redirection without increasing prism dimensions.
Solution Approach 2:
The light-shielding plate acts as an intermediary between the OFF light and the DMD. It receives the harmful OFF light, processes it by reflection, and redirects it back onto the DMD, thereby eliminating the need to increase prism height for OFF light management.
3Object-affected harmful factors
If a light-shielding plate is added to absorb OFF light, then OFF light is blocked, but device complexity increases
Solution Approach 1:
The light-shielding plate is merged with the DMD by positioning it directly on the front surface of the DMD. This integration reduces device complexity as the light-shielding plate serves dual functions: blocking OFF light from entering the prism and reflecting OFF light back onto the DMD, thereby eliminating the need for separate components.
Solution Approach 2:
The light-shielding plate is designed to perform multiple functions: it blocks OFF light from entering the color separating and combining prism, reflects OFF light back onto the DMD, and can be integrated with the DMD structure. This multi-functionality reduces the overall device complexity by eliminating the need for separate components for each function.
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 solution enables a more compact projection display apparatus by suppressing the height of the color separating and combining prism, thereby reducing the overall size of the device.
Implementation Method 1
a light-shielding plate that absorbs a part of OFF light generated by the third light modulation element, the OFF light having passed through the third prism, the second prism, and the first prism
Implementation Method 2
a reflecting surface that reflects the OFF light emitted from the first prism in a direction of the light-shielding plate
Implementation Method 3
a color separating and combining prism that guides the light to each of the three light modulation elements and includes a first prism, a second prism, and a third prism arranged in order from a light incident surface of the color separating and combining prism along from a front side to a rear side of an optical axis
Data Source
AI summary
An image generation unit includes: three light modulation elements of a first light modulation element, a second light modulation element, and a third light modulation element, the three light modulation elements each modulating light based on an image signal to generate image light; a color separating and combining prism that guides the light to each of the three light modulation elements and includes a first prism, a second prism, and a third prism arranged in order from a light incident surface of the color separating and combining prism along an optical axis; a light-shielding plate that absorbs a part of OFF light generated by the third light modulation element, the OFF light having passed through the third prism, the second prism, and the first prism; and a reflecting surface that reflects the OFF light emitted from the first prism in a direction of the light-shielding plate.