Projector Optical Combining for Aligned Visible and Infrared Images
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Solution Overview
Problem
The existing projectors that project both visible and infrared images suffer from reduced contrast and increased lens size due to the long back focal length, which affects the image formation plane of both light modulators, leading to suboptimal image quality.
Innovation Solution
A projector system that includes a first light source, a light modulator, a relay optical system, an enlarging optical system, and a light combiner to form and project combined visible and invisible images on a single projection surface, with the invisible image formed at a conjugate position to the projection image, and a positional deviation correction mechanism using an imager and recognizer to maintain image alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the reduction-side image formation plane of the projection lens is located at the image formation surfaces of the visible light modulator and the infrared light modulator, then both visible and infrared images can be formed, but the back focal length becomes long causing decreased contrast and increased lens size
Solution Approach 1:
The patent divides the optical system into separate visible light projection path and infrared light projection path. The visible light modulator and infrared light modulator are positioned at different locations, with the infrared light modulator placed at a position conjugate to the visible light image formation plane. This segmentation allows each modulator to be optimized independently, avoiding the need for a long back focal length while maintaining the capability to project both visible and infrared images.
Solution Approach 2:
The patent introduces a beam combiner as an intermediary optical element that combines the visible light and infrared light paths. The beam combiner allows the infrared light to be superimposed on the visible light image formation plane without requiring the infrared modulator to be positioned at the same location as the visible modulator. This intermediary enables flexible positioning and maintains short back focal length while achieving dual-image projection capability.
2Manufacturing precision
If the reduction-side image formation plane is located at the modulator surfaces, then image formation is achieved, but the projection lens size increases
Solution Approach 1:
The patent segments the image formation process into two independent paths: visible light image formation at the visible modulator surface, and infrared light image formation at a conjugate position. This segmentation allows the use of a compact projection lens with short back focal length, as each path can be optimized separately without requiring the lens to accommodate both modulators at its focal plane, thereby reducing overall lens size while maintaining image formation accuracy.
3Device complexity
If a single projection lens is used for both visible and infrared light, then device complexity is reduced, but image contrast decreases due to long back focal length
Solution Approach 1:
The patent segments the optical paths by introducing a beam combiner that separates the visible and infrared light paths within a single projection lens system. The infrared light modulator is positioned at a conjugate position rather than at the lens focal plane, allowing the use of a compact projection lens with short back focal length. This segmentation approach maintains device simplicity (single projection lens) while improving image contrast by avoiding the long back focal length penalty.
Solution Approach 2:
The patent changes the positional parameter of the infrared light modulator from the traditional focal plane location to a conjugate position relative to the visible light image formation plane. This parameter change allows the projection lens to achieve both visible and infrared image formation with a short back focal length, thereby maintaining high image contrast while using a single projection lens and keeping device complexity low.
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 system enhances image contrast and reduces lens size by aligning and correcting positional deviations, resulting in improved image quality and stability.
Implementation Method 1
a light combiner disposed in an optical path between the enlarging optical system and the light modulator and configured to combine the visible light and the invisible light with each other into combined light
Implementation Method 2
a first relay optical system configured to relay the projection image to a first position
Implementation Method 3
an enlarging optical system configured to form an image at the first position and project the combined light to display the projection image and the invisible image on a single projection surface
Data Source
AI summary
A projector includes a first light source, a light modulator that modulates visible light output from the first light source to form a projection image, a first relay optical system that forms the projection image at a first position, an enlarging optical system, an invisible image generator that forms an invisible image made of invisible light, and a light combiner that is disposed in the optical path between the enlarging optical system and the light modulator and combines the visible light and the invisible light with each other into combined light. The invisible image is formed at a second position conjugate with the position where the projection image is formed. The enlarging optical system forms an image at the first position and projects the combined light to display the projection image and the invisible image on a single projection surface.