Optical Multiplexing Circuit for RGB Light Source Monitoring
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Solution Overview
Problem
The existing light combining circuits for RGB light sources face challenges due to non-uniform split ratios of wavelengths, particularly with red, green, and blue light, which complicate monitoring and white balance adjustments in video display devices, requiring complex configurations and large dynamic range photo detectors.
Innovation Solution
A light combining circuit with separate splitting units for red and green-blue light, followed by a main combining unit, allows for independent monitoring of each wavelength using a single photo detector, reducing wavelength dependence and simplifying the configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single splitting unit is used to split all three wavelengths (R, G, B) light, then the configuration is simple, but the split ratio becomes non-uniform across different wavelengths making monitoring difficult
Solution Approach 1:
The patent divides the single splitting function into two separate splitting units: a first splitting unit that splits only red wavelength light, and a second splitting unit that splits combined green and blue wavelength light. This segmentation allows each splitting unit to be optimized for specific wavelength ranges, achieving uniform split ratios across all three colors while maintaining a relatively simple overall configuration.
2Measurement precision
If separate splitting units for R and GB light are used, then uniform split ratio is achieved, but the device complexity increases
Solution Approach 1:
The patent combines green and blue wavelength light processing into a single second splitting unit, while handling red wavelength light separately through a first splitting unit. The split outputs from both units are then combined and monitored together. This merging approach achieves uniform split ratios for all wavelengths while avoiding the need for three completely separate splitting paths, thus controlling device complexity.
Solution Approach 2:
The main light combining unit serves multiple functions: it combines the split red light from the first splitting unit, combines the split green and blue light from the second splitting unit, and outputs the final combined RGB light. This multi-functionality reduces the need for additional separate components, balancing monitoring precision with configuration simplicity.
3Ease of manufacture
If bulk optical components (lenses, dichroic mirrors, half mirrors) are used for light combining and monitoring, then the light combining function is achieved, but the optical system size becomes large
Solution Approach 1:
The patent replaces traditional bulk mechanical optical components (lenses, dichroic mirrors, half mirrors) with an integrated planar lightwave circuit (PLC) system. The PLC implements the splitting and combining functions through planar waveguide structures, significantly reducing the optical system size from a bulky three-dimensional arrangement to a compact planar integration while maintaining the light combining capability.
Solution Approach 2:
The patent embeds multiple functional elements (first splitting unit, second splitting unit, main light combining unit) within a single planar lightwave circuit substrate. The waveguide structures are nested and routed within the planar circuit, allowing complex optical functions to be contained in a compact integrated package rather than requiring separate bulk components.
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 approach significantly reduces the deviation in split ratios between red, green, and blue wavelengths, facilitating easier white balance adjustments and reducing the complexity of the light source configuration, making it more suitable for video display devices.
Implementation Method 1
The PLC includes a flat substrate such as Si that is subjected to patterning such as photolithography and reactive ion etching processing to fabricate an optical waveguide
Implementation Method 2
The first directional coupler 104 couples light λ2 incident from the first input waveguide 101 to the second input waveguide 102, couples light λ1 incident from the second input waveguide 102 to the first input waveguide 101
Implementation Method 3
Combined output light 36 is output from the chip end face
Data Source
AI summary
In a conventional RGB coupler, the split ratio largely depends on the wavelength. The split ratio of R and the split ratios of G and B are non-uniform because R has a wavelength far from those of G and B. Accordingly, a video display device needs to have the monitoring detection value corrected, making it difficult to use the monitoring function. A light combining circuit and a light source of this disclosure include a first splitting unit for splitting R wavelength light and a second splitting unit for splitting G and B combined light. They split monochromatic light of R and combined light of G and B, independently. G and B light from an LD are first combined by a preliminary wave-combining unit before being split. The split lights of each wavelength are combined by a main wave-combining unit, outputting RGB combined light. Each split light from the two splitting units is detected by a single PD.