Projection Display Prism Sharing for NIR Contrast
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Solution Overview
Problem
Existing projection-type display apparatuses struggle to balance the contrast of images formed by visible light and near-infrared (NIR) light, particularly when using a configuration with two prisms for reflection-type light modulation elements, as optimizing the polarization separation film for three colors is difficult, leading to compromised image quality in either visible or NIR modes.
Innovation Solution
A projection-type display apparatus design where one prism is shared by two reflection-type light modulation elements, with the first polarization-separation unit optimized for green and NIR light, and the second for red and blue light, allowing for balanced image quality between visible and NIR light modes by guiding light paths differently through dichroic mirrors and polarization beam splitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one prism is shared by two reflection-type light modulation elements to reduce device complexity, then the number of prisms is reduced, but it becomes difficult to optimize polarization separation films for multiple colors simultaneously
Solution Approach 1:
The patent divides the polarization separation function into two distinct units: a first polarization-separation unit optimized for green and NIR light, and a second polarization-separation unit optimized for red and blue light. This segmentation allows each unit to be independently optimized for its specific wavelength range, resolving the contradiction between reducing the number of prisms and maintaining optimization precision for multiple colors.
2Reliability
If a configuration with three prisms is used for reflection-type light modulation elements for respective colors, then each color can be modulated independently, but the device complexity increases
Solution Approach 1:
The patent merges the functions of three separate prisms into two prisms by sharing one prism between two reflection-type light modulation elements. Specifically, the first prism handles green and NIR light, while the second prism handles red and blue light. This merging reduces device complexity while maintaining independent color modulation capability through the shared prism design.
3Measurement precision
If polarization separation films are optimized for three colors simultaneously, then all colors can be separated effectively, but the contrast balance between visible and NIR light images deteriorates
Solution Approach 1:
The patent applies local quality by optimizing each polarization-separation unit for specific wavelength ranges: the first unit is optimized for green and NIR light, while the second unit is optimized for red and blue light. This localized optimization ensures that each polarization-separation film is tuned to its specific color range, achieving effective color separation while maintaining proper contrast balance between visible and NIR light images.
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 enables balanced image quality for both visible and NIR light images, preventing a decrease in contrast and allowing simultaneous projection of visible and NIR images, while reducing the complexity of optimizing polarization separation films for multiple colors.
Implementation Method 1
a color separation unit which guides the first color light coming from the light source unit in a direction different from a direction of the second color light and the third color light coming from the light source unit
Implementation Method 2
a first polarization-separation unit which guides the first color light coming from the color separation unit to the first reflection-type light modulation element and guides the first color light coming from the first reflection-type light modulation element to the color combining unit, and a second polarization-separation unit which guides the second color light coming from the color separation unit to the second reflection-type light modulation element
Data Source
AI summary
A projection-type display apparatus includes a light source unit, reflection-type light modulation elements, a color combining unit, a color separation unit, and a filter. The light source unit is capable of emitting first color light, second color light, third color light, and near infrared light. A first polarization separation unit receives the first color light, and a second polarization separation unit receives the second color light and the third color light. The color separation unit guides near infrared light to the first polarization separation unit, and the color combining unit guides the near infrared light from the first polarization separation unit to color combining unit. The projection-type display apparatus can be switched between a first mode in which a first region of the filter unit is inserted into the light path and a second mode in which a second region of the filter unit is inserted to the light path.