Optical Sensor Pixel Guard Ring for Crosstalk Isolation
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Solution Overview
Problem
Optical sensors with pixels of different spectral properties experience crosstalk, leading to erroneous color data due to photon interference between adjacent pixels, which reduces the accuracy of output data.
Innovation Solution
Incorporating a semiconductor guard ring around each photodetector with a fill factor of less than or equal to 50% to prevent carrier collection by adjacent pixels, combined with a readout circuit that determines ambient light levels by resetting the photodetector voltage and incrementing coarse and fine values based on photon absorption, and using band pass filters and optically reflective coatings to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the photodetector area is increased to improve sensitivity, then the fill factor increases, but crosstalk between adjacent pixels increases
Solution Approach 1:
The pixel structure is segmented into distinct functional zones: an active photodetector region for photon absorption and a semiconductor guard ring region for carrier isolation. This segmentation allows the photodetector to maintain a larger area for improved sensitivity while the guard ring acts as a隔离 barrier to prevent crosstalk, effectively resolving the contradiction between sensitivity and crosstalk reduction
Solution Approach 2:
The semiconductor guard ring serves as an intermediary structure between adjacent photodetectors. It is configured to collect and remove carriers that would otherwise diffuse into neighboring pixels, thereby preventing crosstalk while allowing the photodetector area to be enlarged for better sensitivity. The guard ring acts as a mediator that enables both large photodetector area and effective crosstalk isolation
2Object-generated harmful factors
If the semiconductor guard ring width is increased to reduce crosstalk, then the fill factor decreases, but manufacturing complexity increases
Solution Approach 1:
The invention optimizes the guard ring dimensions by establishing specific parameter ranges: the guard ring width is set to 1-10 micrometers and the photodetector fill factor is maintained at 50-80%. These parameter specifications balance crosstalk reduction effectiveness with manufacturing feasibility, avoiding excessive guard ring widths that would complicate fabrication while still achieving sufficient isolation
Solution Approach 2:
Rather than implementing a full isolation structure around the entire photodetector perimeter, the invention uses a partial guard ring configuration that provides sufficient crosstalk reduction for the specific application requirements. This partial action approach reduces manufacturing complexity compared to complete isolation structures while still achieving the necessary level of crosstalk prevention
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 effectively reduces crosstalk between pixels, improving the accuracy of ambient light sensing while maintaining a high fill factor, thus enhancing the sensitivity and responsivity of the optical sensor without increasing cost or space requirements.
Implementation Method 1
a photodetector configured to absorb at least one photon and collect at least one carrier generated thereby
Data Source
AI summary
An optical sensor includes pixels. Each pixel has a photodetector. A readout circuit performs a process over an exposure time where the photodetector is connected to a reverse bias voltage supply to reset a voltage across the photodetector, and the photodetector is disconnected from the reverse bias voltage supply until that the voltage across the photodetector decreases in response to received ambient light. An ambient light level is then determine an based on a number of times the voltage across the photodetector is reset over the exposure time.