Light Sensor With Pixel Diffraction Gratings For Spectral Analysis
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Solution Overview
Problem
Existing light sensors are limited in their ability to perform spectral analysis over a large number of narrow wavelength ranges, as they typically use multilayer interferential filters or plasmonic filters, which are either difficult to manufacture or lack sufficient spectral selectivity.
Innovation Solution
A light sensor design featuring a semiconductor substrate with multiple pixels, each equipped with a photoconversion zone and an optical diffraction grating of varying pitches, where the diffraction gratings are positioned above the photoconversion zone and configured to deflect specific wavelengths, allowing for precise analysis of light distribution across multiple wavelength ranges by comparing the output signals from pixels with different grating pitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multilayer interferential filters are used for spectral analysis, then spectral selectivity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent changes the key parameter from filter layer composition to diffraction grating pitch. By varying the pitch of diffraction gratings across different pixels, the system achieves spectral selectivity through geometric parameter variation rather than complex multilayer filter fabrication, thereby simplifying manufacturing while maintaining measurement precision
Solution Approach 2:
Each pixel is equipped with diffraction gratings having a specific local pitch value tailored to its spectral analysis requirements. This local differentiation of grating pitch enables each pixel to selectively respond to specific wavelength ranges, achieving spectral selectivity without requiring complex global filter structures
2Measurement precision
If more wavelength ranges are analyzed, then spectral resolution is improved, but device complexity increases
Solution Approach 1:
The sensor is segmented into multiple pixels, each dedicated to analyzing a specific wavelength range. By dividing the spectral analysis task across numerous pixels with different grating pitches, the system achieves high spectral resolution without requiring a single complex filtering system, thereby managing device complexity through functional segmentation
Solution Approach 2:
The diffraction grating structure serves multiple functions: it diffracts light, separates wavelengths, and when combined with the photoconversion zone, enables spectral detection. This multi-functionality of the grating structure allows the system to analyze multiple wavelength ranges without proportionally increasing device complexity
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
Enables accurate analysis of light over numerous narrow wavelength ranges, improving spectral resolution and selectivity, while being easier to manufacture compared to multilayer interferential filters and maintaining higher spectral selectivity compared to plasmonic filters.
Implementation Method 1
optical diffraction gratings, wherein each optical diffraction grating is positioned on the side of the back face of the substrate, at a location over and facing the photoconversion zone of a corresponding pixel
Implementation Method 2
the optical diffraction gratings of at least two of said pixels having different pitches
Implementation Method 3
each pixel comprises: a photoconversion zone extending in the substrate, between a front face and a back face of the substrate
Data Source
AI summary
A light sensor includes a semiconductor substrate supporting a number of pixels. Each pixel includes a photoconversion zone extending in the substrate between a front face and a back face of the substrate. An optical diffraction grating is arranged over the back face of the substrate at a position facing the photoconversion zone of the pixel. For at least two different pixels of the light sensor, the optical diffraction gratings have different pitches. Additionally, the optical grating of each pixel is surrounded by an opaque wall configured to absorb at operating wavelengths of the sensor.