Polarization Separation Element for Projection Light Source
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Solution Overview
Problem
Conventional light source devices for projection display apparatuses suffer from low light utilization efficiency due to the dichroic mirror's partial reflection and transmission of polarized light, leading to wasted light and decreased brightness.
Innovation Solution
A light source device comprising a light source unit emitting linearly polarized light, a polarization separation element that transmits one polarization direction and reflects the other, a phosphor for wavelength conversion, and a phase conversion element to enhance light utilization by combining the converted light, improving the light source's efficiency and brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a dichroic mirror is used for polarization separation, then the light source can generate white illumination light, but the light utilization factor decreases due to partial reflection and transmission of polarized light
Solution Approach 1:
The invention segments the blue laser beam into two separate optical paths based on polarization direction. The P-polarized light component is transmitted through the dichroic mirror to excite the phosphor, while the S-polarized light component is reflected to a phase conversion element that converts it to P-polarized light, which is then transmitted through the dichroic mirror. This segmentation allows both polarization components to be utilized effectively, resolving the contradiction between achieving white illumination and maintaining high light utilization efficiency.
Solution Approach 2:
The invention changes the polarization state parameter of the S-polarized light component by using a phase conversion element (such as a quarter-wave plate or half-wave plate) to convert S-polarized light into P-polarized light. This parameter change enables the previously lost S-polarized light to be transmitted through the dichroic mirror and contribute to the illumination light, thereby improving the light utilization factor while maintaining the desired brightness.
2Adaptability or versatility
If the dichroic mirror spectral characteristic shifts due to incident angle changes, then light utilization factor may further decrease
Solution Approach 1:
The invention segments the blue laser beam into two separate optical paths based on polarization direction. The P-polarized light component is transmitted through the dichroic mirror to excite the phosphor, while the S-polarized light component is reflected to a phase conversion element that converts it to P-polarized light, which is then transmitted through the dichroic mirror. This segmentation allows both polarization components to be utilized effectively, resolving the contradiction between achieving white illumination and maintaining high light utilization efficiency.
Solution Approach 2:
The invention changes the polarization state parameter of the S-polarized light component by using a phase conversion element (such as a quarter-wave plate or half-wave plate) to convert S-polarized light into P-polarized light. This parameter change enables the previously lost S-polarized light to be transmitted through the dichroic mirror and contribute to the illumination light, thereby improving the light utilization factor while maintaining the desired brightness.
3Illumination intensity
If a wavelength selective type polarization beam splitter and dichroic mirror are used in combination, then color synthesis can be achieved, but propagation loss increases due to more components
Solution Approach 1:
The invention extracts and utilizes the S-polarized light component that would otherwise be lost in the conventional dichroic mirror configuration. By directing this component to a phase conversion element and converting it to P-polarized light, the system recovers what would have been wasted light, reducing propagation loss while maintaining the color synthesis capability through the phosphor conversion process.
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 significantly improves light utilization efficiency and outputs brighter illumination light by effectively utilizing both polarized components of the blue laser beam, enhancing the overall brightness of the projection display apparatus.
Implementation Method 1
The polarization separation element has a polarization transmission wavelength region including the first wavelength range, transmits the light in the first polarization direction and reflects the light in the second polarization direction in the polarization transmission wavelength region
Implementation Method 2
The phosphor converts the received first light into third light in a wavelength range on a longer wavelength side than the polarization transmission wavelength region and emits the third light to the polarization separation element
Implementation Method 3
The phase conversion element phase-converts the received second light into fourth light that is the light in the first polarization direction in the first wavelength range and emits the fourth light to the polarization separation element
Data Source
AI summary
A light source device includes: a light source unit emitting first light in a first polarization direction and second light in a second polarization direction; a polarization separation element receiving the first light and the second light; a phosphor receiving the first light transmitted through the polarization separation element; and a phase conversion element receiving the second light reflected by the polarization separation element. The polarization separation element reflects visible light having a longer wavelength than a polarization transmission wavelength region. The phosphor converts the received first light into third light having a longer wavelength than the polarization transmission wavelength region. The phase conversion element phase-converts the received second light into fourth light in the first polarization direction. The polarization separation element combines illumination light with the third light reflected by the polarization separation element and the fourth light transmitted through the polarization separation element.