Light Source Apparatus for Projectors with Polarization Control
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Solution Overview
Problem
Conventional image projection systems face challenges in achieving sufficient luminance and hue accuracy due to insufficient red light emission and mismatched blue light wavelengths, leading to issues with color gamut and luminance saturation in projected images.
Innovation Solution
A light source apparatus comprising a first and second light source with different polarization directions, a polarization rotator, and a wavelength converter, controlled by a controller to adjust light emission based on deterioration and user-set luminance, ensuring balanced light emission to maintain hue and luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only yellow fluorescent body is used to generate red light, then the device complexity is reduced, but the luminance and hue accuracy of red light in projected image deteriorates
Solution Approach 1:
The patent combines multiple light sources (blue LD and red LD) with different polarization directions and merges their outputs through a polarization beam combiner. This merging approach allows the system to achieve sufficient red light luminance by combining red light from both the yellow fluorescent body and the dedicated red LD, while maintaining a relatively compact structure.
Solution Approach 2:
The blue laser diode serves multiple functions: it directly provides blue light for the projected image and simultaneously excites the yellow fluorescent body to generate green and red light. This multi-functionality reduces the need for separate light sources for each color, thereby reducing device complexity while maintaining adequate luminance performance.
2Use of energy by moving object
If blue LD wavelength is optimized for fluorescence conversion efficiency, then energy conversion efficiency is improved, but the blue hue accuracy in projected image deteriorates
Solution Approach 1:
The patent segments the blue light source into two separate blue laser diodes with different wavelengths. One blue LD (first wavelength) is optimized for exciting the yellow fluorescent body with high conversion efficiency, while the other blue LD (second wavelength) is optimized for providing accurate blue hue in the projected image. This segmentation allows each component to be optimized for its specific function without compromise.
Solution Approach 2:
Different parts of the light source system are assigned different local qualities: the first blue LD is designed with characteristics optimized for fluorescence excitation (higher energy wavelength), while the second blue LD is designed with characteristics optimized for display quality (wavelength matching human blue perception). This local quality differentiation resolves the contradiction between conversion efficiency and hue accuracy.
3Duration of action of stationary object
If light emission amount from light sources changes due to deterioration, then the operational duration is extended, but the hue consistency of projected image deteriorates
Solution Approach 1:
The patent incorporates a feedback mechanism where the controller continuously monitors the light emission amounts from the first and second light sources. Based on this feedback information about deterioration, the controller dynamically adjusts the drive currents to compensate for changes in light output, thereby maintaining consistent hue and luminance balance throughout the operational life of the device.
Solution Approach 2:
The system transitions from a static light emission mode to a dynamic adjustment mode. The controller dynamically modifies the drive currents to the first and second light sources based on their respective deterioration rates. This dynamic adjustment allows the system to adapt to aging effects and maintain stable color performance over extended operational durations.
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 enhances image projection by improving hue and luminance consistency, reducing color changes, and increasing the color gamut, resulting in brighter and more accurate projected images.
Implementation Method 1
an optical element configured to transmit one polarized light of the first and second polarized light and to reflect the other polarized light
Implementation Method 2
a wavelength convertor configured to convert the second polarized light from the optical element into wavelength converted light whose wavelength is different from a wavelength of the second polarized light
Data Source
AI summary
A light source apparatus includes light sources emitting first and second polarized light, an optical element transmitting one of the polarized light and reflecting the other, a polarization rotator generating polarization rotated light from the first polarized light, a wavelength convertor converting the second polarized light into wavelength converted light, and a controller. The optical element generates emitted light by combining the wavelength converted light and polarization rotated light. The controller acquires respective deterioration amounts of the light sources, and controls, based on respective changes in light emission amounts from the light sources acquired from the deterioration amounts, the light emission amount from at least one of the light sources for making different respective change amounts of the light emission amounts from the light sources, or changing a ratio between respective light emission amounts from the light sources.