Illuminator Retardation Element Polarization Control
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Solution Overview
Problem
Projectors using fluorescence light sources suffer from color unevenness due to the non-polarized nature of fluorescence light and the linearly polarized blue light, resulting in intensity distribution discrepancies and undesirable color unevenness in projected images.
Innovation Solution
An illuminator configuration where light components are converted into circularly or elliptically polarized light using a dichroic film and retardation elements, ensuring that both reflected and passed-through components are combined, reducing color unevenness by optimizing the polarization state of the light before it reaches the polarization conversion element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If blue light is used as a light source, then high luminance can be achieved, but color unevenness occurs due to linear polarization
Solution Approach 1:
The patent changes the polarization state parameter of the blue light from linear polarization to circular or elliptical polarization by introducing a retardation element. This parameter change allows the light to interact differently with the polarization separation element, ensuring that both reflected and transmitted components have equal intensity, thereby eliminating color unevenness while maintaining high luminance.
Solution Approach 2:
The patent introduces a retardation element as an intermediary component between the blue light source and the polarization separation element. This intermediary transforms the polarization state of the light, enabling it to produce equal intensity distributions in both reflected and transmitted paths, thus resolving the color unevenness problem.
2Ease of operation
If fluorescence is used, then non-polarized light is obtained, but intensity distribution differs from blue light causing color unevenness
Solution Approach 1:
The patent changes the polarization parameter of the blue light to match the statistical properties of non-polarized fluorescence. By converting linearly polarized blue light into circularly or elliptically polarized light, the intensity distribution becomes uniform across different polarization components, making it equivalent to non-polarized light and eliminating color unevenness.
3Extent of automation
If polarization separation element is used, then polarization control is achieved, but color unevenness occurs due to unequal intensity distribution
Solution Approach 1:
The patent applies preliminary action by transforming the polarization state of the blue light before it reaches the polarization separation element. The retardation element pre-processes the light to create circular or elliptical polarization, ensuring that when the light subsequently interacts with the polarization separation element, both reflected and transmitted paths yield equal intensity distributions, thereby preventing color unevenness.
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 reduces color unevenness in projected images by ensuring that both components of light exiting the polarization conversion element have equal intensity, leading to improved illumination uniformity and high-quality image display.
Implementation Method 1
the first component having passed through the first retardation element is converted into circularly or elliptically polarized light
Implementation Method 2
a dichroic film having polarization separation characteristics for reflecting the first component and transmitting the second component
Implementation Method 3
a light source apparatus using fluorescence
Implementation Method 4
blue light reflected off a phosphor layer
Data Source
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AI summary
An illuminator includes a light source apparatus that outputs first light that belongs to a first wavelength band, an optical element including a dichroic film and a first retardation element, a reflection element, a light dividing element including a plurality of lenses, and a polarization conversion element. A first component of the first light outputted from the light source apparatus passes through the dichroic film and the first retardation element in this order, is reflected off the reflection element, passes through the first retardation element, and is further reflected off the dichroic film. The first component reflected off the dichroic film passes through the light dividing element and is incident on the polarization conversion element. The retardation element is a birefringent waveplate parallel to the dichroic film and polarization ratio can be adujsted by rotating that retardation element.