Projector Polarization Switching for Blue Light Damage Reduction
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Solution Overview
Problem
In single-plate projectors, the high energy density of blue luminous flux can cause light-radiation-induced damage to blue subpixels, leading to degradation of the liquid crystal panel and reduced reliability.
Innovation Solution
A display apparatus with a light source that outputs blue and red light, along with two green lights, uses a polarization separator and retardation film to switch the polarization direction of these lights between subpixels over time, ensuring that blue light is not consistently incident on specific subpixels, thereby reducing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single liquid crystal panel is used to modulate all color luminous fluxes, then the device complexity is reduced, but the blue subpixels are damaged due to high energy density of blue light
Solution Approach 1:
The patent applies periodic action by alternately switching which subpixels receive blue light and which receive red light over time. The liquid crystal panel displays blue light on first subpixels during a first period, then switches to display blue light on second subpixels during a second period, while simultaneously displaying red light on the previously blue-receiving subpixels. This periodic switching distributes the high energy density blue light exposure across different subpixel groups, preventing any single group from accumulating excessive damage while maintaining a single panel configuration.
2Reliability
If blue luminous flux is continuously incident on specific subpixels, then the display quality is maintained, but light-radiation-induced damage occurs to the subpixels
Solution Approach 1:
The patent implements periodic action by periodically switching the assignment of color luminous fluxes to subpixel groups. During a first period, blue light is directed to first subpixels and red light to second subpixels. During a second period, the assignment is reversed: red light to first subpixels and blue light to second subpixels. This periodic switching ensures that no single subpixel group is continuously exposed to high energy density blue light, thereby reducing light-radiation-induced damage and improving subpixel durability while maintaining display quality through temporal multiplexing.
Solution Approach 2:
The patent applies parameter changes by dynamically changing the temporal parameter of light incidence on subpixels. Instead of static assignment, the system varies the time parameter by switching between different assignment configurations at different time periods. This temporal parameter change allows the same physical subpixels to receive different types of light at different times, distributing the harmful blue light exposure and reducing cumulative damage.
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 solution effectively reduces the risk of damage to the liquid crystal panel by alternating the subpixels exposed to blue light, thereby maintaining the reliability and longevity of the projector.
Implementation Method 1
a polarization separator that transmits light polarized in a first polarization direction and reflects light polarized in a second polarization direction different from the first polarization direction
Implementation Method 2
a retardation film provided between the light source apparatus and the polarization separator. In the first period, the optical apparatus converts the first light that exits out of the retardation film into light polarized in the first polarization direction and converts the second light that exits out of the retardation film into light polarized in the second polarization direction
Data Source
AI summary
In a first period, an optical apparatus converts first light that exits out of a retardation film into light polarized in a first polarization direction and converts second light that exits out of the retardation film into light polarized in a second polarization direction, and in a second period, the optical apparatus converts the first light that exits out of the retardation film into light polarized in the second polarization direction and converts the second light that exits out of the retardation film into light polarized in the first polarization direction.