On-Chip Spectrometer Pixel Allocation for Uniform Detection
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Solution Overview
Problem
On-chip spectrometers face challenges in providing uniform detection sensitivity across the spectral range due to non-uniform detection efficiency of semiconductor detectors and varying spectral responses of filters, which complicates accurate intensity measurement of impinging light.
Innovation Solution
The design includes an array of sensor pixels on a substrate with a signal processing unit featuring multiple spectral channels, where each pixel comprises a photodetector and an optical filter with a specific transmission curve, and at least one spectral channel has a greater number of pixels than others to ensure uniform detection efficiency across the wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional on-chip spectrometer uses a uniform array of sensor pixels with each pixel having a photodetector and optical filter, then the device structure is simple and manufacturing is easy, but the detection sensitivity is non-uniform across the spectral range
Solution Approach 1:
The patent applies local quality by assigning different numbers of sensor pixels to different spectral channels based on their specific detection requirements. Spectral channels with lower inherent detection efficiency are allocated more pixels, while channels with higher efficiency receive fewer pixels, creating a non-uniform pixel distribution that compensates for intrinsic detection variations across the spectrum.
Solution Approach 2:
The patent changes the parameter of pixel allocation per spectral channel from a uniform value to a variable value. By adjusting the number of pixels assigned to each spectral channel according to its detection efficiency characteristics, the system achieves uniform overall detection sensitivity across all spectral channels despite using identical photodetector and filter components.
2Adaptability or versatility
If the spectrometer uses more spectral channels to cover the entire visible spectrum, then the spectral coverage is complete, but the non-uniform detection efficiency of semiconductor detectors becomes more significant
Solution Approach 1:
The patent addresses spectral coverage versus measurement precision by implementing local quality optimization across the spectral range. Each spectral channel is assigned a specific number of pixels tailored to its wavelength range and detection efficiency characteristics, ensuring that all channels contribute equally to measurement accuracy while maintaining comprehensive spectral coverage from 400 nm to 800 nm.
3Measurement precision
If the on-chip spectrometer cannot alter scan speed across wavelength range to compensate for non-uniform detection efficiency, then the device structure remains simple, but accurate intensity measurement becomes challenging
Solution Approach 1:
The patent changes the operational parameter from scan speed modulation (which would require complex mechanical or electronic control) to pixel allocation configuration. By varying the number of pixels assigned to each spectral channel, the system achieves compensation for non-uniform detection efficiency through a static, simple configuration that does not require dynamic adjustment during operation.
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 enhances the accuracy and fidelity of spectral measurements by ensuring each spectral channel provides approximately the same detection efficiency, compensating for non-uniform detection efficiency and filter responses, thereby improving the performance of on-chip spectrometers.
Implementation Method 1
Each of the sensor pixels comprises a stack of a respective photodetector and a respective optical filter configured to pass light within a respective transmission curve
Implementation Method 2
an array of solid state detectors underlying the array of band pass filters
Data Source
AI summary
An array of sensor pixels is formed on a substrate, and a signal processing unit is connected to the array of sensor pixels. The signal processing unit includes multiple spectral channels that are defined by a respective transmission curve of each optical filter of at least one associated sensor pixel. Each of the sensor pixels includes a stack of a respective photodetector and a respective optical filter. Each spectral channel receives an output signal from one or more sensor pixels including an optical filter having the same transmission curve. At least one spectral channel has a greater number of sensor pixels than another spectral channel among the multiple spectral channels. The different number of pixels for the spectral channels can be employed to compensate for variations of sensor efficiency as a function of wavelength. Adjustment to sensor gain can be minimized through use of different number of pixels for different spectral channels.