Inclined Optical Filter for Projector Color Balance
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Solution Overview
Problem
Projectors using high-pressure discharge lamps for business presentations suffer from greenish tint and reduced brightness due to intense green wavelength band, leading to contrast and color variation issues when used for home applications.
Innovation Solution
An optical filter with different refractive index layers is placed between the light source and optical modulators, inclined at a specific angle to reflect the green spectral component and reduce stray light, thereby correcting color balance and minimizing color variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an optical filter is disposed on the downstream of the projection lens to eliminate spectral components, then the contrast of the projection image can be maintained, but color variation occurs between peripheral and middle portions due to incident-angle dependence
Solution Approach 1:
The optical filter is divided into multiple sections with different inclination angles. The light-irradiation side surface is inclined by a first predetermined angle in a first region and by a second predetermined angle in a second region. This segmentation allows different portions of the light beam to be reflected at appropriate angles, preventing color variation while maintaining contrast.
Solution Approach 2:
Different regions of the optical filter are assigned different local properties (different inclination angles) to optimize performance for different parts of the light beam. This local quality approach ensures that each region of the filter works optimally for the specific incident angles of light beams passing through that region.
2Illumination intensity
If a high-pressure discharge lamp is used to provide sufficient luminance, then brightness is improved, but green spectral intensity becomes too strong causing greenish tint and contrast degradation
Solution Approach 1:
The optical filter selectively extracts and removes the harmful green spectral component from the light beam while allowing other useful spectral components to pass through. This is achieved through the reflective optical filter that reflects the green wavelength band, thereby eliminating the greenish tint while maintaining overall luminance.
Solution Approach 2:
The strong green spectral intensity, which initially causes harm (greenish tint), is converted into a benefit by using it to reflect off the optical filter. The reflected green light is redirected away from the optical path, transforming the harmful excessive green intensity into a controlled element that improves color balance while maintaining luminance efficiency.
3Area of moving object
If the light beam is expanded at a predetermined angle to form enlarged projection image, then projection capability is improved, but incident angle variation causes color variation in peripheral portions
Solution Approach 1:
The solution adds a dimensional element by inclining the optical filter at predetermined angles rather than keeping it parallel to the light beam. This angular dimension allows the filter to compensate for the angular spread of the expanded light beam, ensuring consistent color across the enlarged projection image.
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 prevents contrast degradation and color variation in projection images by eliminating the green spectral component and managing stray light, ensuring consistent image quality across different usage scenarios.
Implementation Method 1
an optical conversion film in which thin layers of different refractive indexes are deposited on a surface of the glass substrate
Implementation Method 2
optical conversion film in which thin layers of different refractive indexes are deposited
Implementation Method 3
an optical filter that reflects a predetermined spectral component of the light beam and transmits the other spectral component
Data Source
AI summary
A projector includes: a light source device, a color-separating optical system for separating a light beam irradiated by the light source device into a plurality of color light components, a plurality of optical modulators for modulating each of the separated color light components in accordance with image information, a color-combining optical device for combining optical images modulated by the plurality of optical modulators and a projection optical device for projecting the combined optical images in an enlarged manner. An optical filter that reflects a predetermined spectral component of the light beam and transmits the other spectral component is disposed in an optical path between the light source device and the optical modulators The optical filter is disposed such that a light-irradiation side surface for irradiating the light beam is inclined by a predetermined angle relative to a plane orthogonal to an optical axis of the light beam.