Projection Filter Film Thickness Layout for Blue Shift Control
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Solution Overview
Problem
Current projection systems experience blue shift and uneven color due to non-collimated light beams entering filter elements at large incident angles, causing shifts in transmission bands and color gamut issues.
Innovation Solution
A filter element with a substrate and film having distinct areas of varying thickness, where the peripheral region has a greater average thickness than the central region, maintaining consistent filtering effects across varying incident angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a filter element is used to adjust the spectrum of the light beam, then the color gamut requirements can be met, but if the incident angle is large, the transmission band shifts toward the short wavelength side causing blue shift and uneven color
Solution Approach 1:
The film thickness is made non-uniform with different thicknesses in different areas (first area with smaller thickness, second area with larger thickness). This local variation in thickness compensates for the path length differences caused by large incident angles, maintaining consistent optical path differences across the light beam and preventing blue shift while preserving color gamut requirements.
Solution Approach 2:
The patent changes the physical parameter of film thickness from a uniform value to a spatially varying value. By adjusting the thickness parameter across different regions of the film, the optical path difference is compensated for large incident angles, resolving the contradiction between meeting color gamut requirements and maintaining transmission band position stability.
2Reliability
If the incident angle between the light beam and the filter element is large, then the filtering effect can be achieved, but the transmission band shifts causing blue shift and color coordinates change
Solution Approach 1:
Different regions of the film are designed with different thicknesses to locally compensate for the varying path lengths that light travels at different incident angles. This ensures that the filtering effect remains reliable while maintaining consistent color coordinates across the entire light beam.
Solution Approach 2:
The patent converts the harmful effect of large incident angles (which causes path length variation and blue shift) into a benefit by deliberately designing the film with non-uniform thickness. The thickness variation is specifically engineered to compensate for the angle-induced path differences, turning the potential problem into a solution that maintains both filtering reliability and color accuracy.
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 improves blue shift and color uniformity by ensuring phase differences are maintained, enhancing color performance and adherence to color gamut standards.
Implementation Method 1
the phase difference of the light beam after passing through the first area and the second area of the film is closer
Implementation Method 2
the filter element may still have the similar filtering effect when the incident angle is relatively large
Data Source
AI summary
A filter element and a projection device are provided. The filter element is configured on the transmission path of at least one light beam, and includes a substrate and a film. The film is located on a surface of the substrate, and includes a first area and a second area. The first area includes a center, corresponding to the central axis of the at least one light beam. The distance between the second area and the center of the first area is greater than the distance between any point in the first area and the center. The average thickness of the second area of the film is greater than the average thickness of the first area of the film. The filter element of the disclosure may still have a similar filter effect when the incident angle is relatively large.