Variable Reflectivity Notch Filter for Automotive Laser Projection
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Solution Overview
Problem
Laser-based projection systems in automotive applications face performance issues due to temperature variations, which cause center wavelengths to shift, leading to compromised image quality and visibility, as existing reflective coatings become too reflective and obscure the view.
Innovation Solution
A variable reflectivity notch filter is implemented, with different reflectivities and wider reflective peaks for temperature-sensitive laser sources, allowing for improved light reflection across a wide temperature range without increasing overall reflectivity, ensuring bright, color-balanced images without obstructing the viewer's field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reflective coatings are used in laser projection systems, then the system can achieve adequate performance within a narrow temperature range, but performance is compromised at temperature extremes due to wavelength shifts
Solution Approach 1:
The patent applies a variable reflectivity notch filter that dynamically adapts its reflective properties based on temperature conditions. The filter's reflectivity is adjusted to compensate for wavelength shifts caused by temperature variations, allowing the system to maintain optimal performance across a wide temperature range rather than being fixed for a narrow range only
Solution Approach 2:
The invention changes the reflectivity parameter of the optical filter in response to temperature changes. By modifying the reflectivity characteristic of the notch filter based on temperature conditions, the system compensates for laser wavelength drift and maintains stable projection performance across extreme temperatures
2Illumination intensity
If the projection surface is made more reflective to improve image brightness, then image quality improves, but visibility through the projection surface deteriorates
Solution Approach 1:
The patent applies different reflectivity characteristics to different portions of the projection surface. The variable reflectivity notch filter creates localized reflective regions that enhance image brightness while maintaining transparency in other areas, allowing users to see through the projection surface without sacrificing image quality
Solution Approach 2:
Instead of making the entire projection surface highly reflective, the invention uses partial reflection through the notch filter design. The filter provides just enough reflectivity to enhance the laser projection while allowing sufficient light transmission to maintain visibility, avoiding the excessive reflectivity that would obstruct the view
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 maintains image quality and visibility across a wide temperature range by adjusting reflectivity to accommodate wavelength shifts, ensuring vivid and color-balanced projections without impairing the user's ability to see through the projection surface.
Implementation Method 1
A variable reflectivity notch filter is implemented, with different reflectivities and wider reflective peaks for temperature-sensitive laser sources, allowing for improved light reflection across a wide temperature range
Data Source
AI summary
A variable reflectivity notch filter (100), suitable for use with a laser image projection source (1001) is provided. The variable reflectivity notch filter (100) defines a transmission curve (101) having a plurality of reflective peaks (102,103,104) each centered about a predetermined wavelength (105,106,107), which can correspond to output wavelengths from laser sources. Reflective peaks (204) corresponding to wavelengths that change with temperature are configured with wider widths (223) and lesser reflectivities (210) than are other reflective peaks (202,203). To provide enhanced color balance, lasers (821) corresponding to these reflective peaks (204) can be driven at higher output power. Variable reflectivity notch filters (100) are suitable for use in head-up displays as well as other applications.