Projection Display Device Light Source Offset for Compact Throw Distance
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Solution Overview
Problem
Conventional projection display devices require a large distance between the projector and the screen to display a large image, which wastes space and increases the size and cost of projectors, and the use of aspherical mirrors to widen the projection light angle results in restricted space and the need for a gigantic projection lens.
Innovation Solution
A projection display device with a light source, cooling unit, imagers for different wavelength bands, and a light guiding optical system where the optical axis of the light source and projection optical system are orthogonal, and the light guiding system protrudes in the opposite direction to the projection optical system, creating space for air stream and reducing the distance between the projector and the screen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the distance between the projector and the screen is increased to display a large image, then the image size is improved, but the space utilization deteriorates and the device complexity increases
Solution Approach 1:
The patent repositions the light source from the optical axis to a location offset toward the projection optical system side, utilizing spatial dimensionality changes to reduce the throw distance while maintaining large image capability. This dimensional repositioning allows the projection light to enter the projected plane from an oblique direction at a wider spread angle, enabling large image display with a compact projector form factor.
2Length of moving object
If the throw distance is reduced to improve space utilization, then the space efficiency is improved, but the projection lens diameter must be increased and focal distance decreased, causing the projection lens to become gigantic
Solution Approach 1:
By offsetting the light source position toward the projection optical system side, the patent creates an oblique projection path that enters the screen from a wider angle. This dimensional change in light path geometry allows reduced throw distance without requiring an oversized projection lens, as the oblique entry angle effectively increases the optical path efficiency.
3Use of energy by moving object
If an aspherical mirror is used to widen the projection light spread angle, then the spread angle is improved, but the space for light traveling is restricted and a gigantic projection lens is still required
Solution Approach 1:
The patent achieves wide spread angle by repositioning the light source toward the projection optical system side, creating an oblique projection path. This dimensional repositioning naturally widens the light spread angle without requiring additional space for light traveling, as the offset position itself generates the wider angle geometry. This eliminates the need for both aspherical mirrors and gigantic projection lenses.
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 reduces the distance between the projector and the screen, minimizing the risk of obstruction and allowing for a more compact and cost-effective projector design while maintaining a wide projection angle without the need for a large lens.
Implementation Method 1
a spread angle of a projection light can be widened by reflecting the projection light from the projection optical system by an aspherical mirror
Implementation Method 2
a suction fan 30 for cooling the light source 11
Data Source
AI summary
An optical system (light guiding optical system) for guiding G-light and R-light to liquid crystal panels is protruded in an opposite direction from projection optical system with regard to an optical axis of a light source. A space is created between an optical engine and a wall surface, and air stream for suction fan is thus secured. A distance (H1) between the optical engine and the wall surface can be reduced to, for example, a thickness of an external housing of the projector. Since a unit comprising the light source and a suction fan is retracted in a direction of the projection optical system than a protruded portion of the light guiding optical system, a distance (H2) from an end edge of the optical engine to a projection light emitting position can be reduced.