Range Image Sensor Pixel Design for Spatial Resolution
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Solution Overview
Problem
Conventional range image sensors face challenges in achieving accurate spatial resolution due to large pixel size and increased parasitic capacity, and suffer from switching noise that affects distance calculation accuracy.
Innovation Solution
A range image sensor design with a semiconductor substrate featuring one-dimensional or two-dimensionally arranged pixels, each with a photosensitive region, accumulation regions, and transfer electrodes, utilizing a capacitor and switches to control charge integration and cancel background light components, while reducing switching noise through optimized switching patterns and phase differences in modulating signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple capacitors are provided within one pixel to cancel background light charges, then background light rejection is improved, but pixel size increases and spatial resolution deteriorates
Solution Approach 1:
The patent merges the functions of multiple capacitors into a single capacitor by using one capacitor to store charges from both first and second accumulation regions. This combining approach maintains the background light rejection capability while reducing pixel size and improving spatial resolution.
Solution Approach 2:
The single capacitor in the patent serves multiple functions: it stores charges from the first accumulation region, stores charges from the second accumulation region, and enables background light cancellation through differential measurement. This multi-functionality eliminates the need for separate capacitors for each accumulation region.
2Reliability
If multiple capacitors and switches are provided within one pixel to cancel background light, then background light rejection is improved, but the number of circuit elements increases and parasitic capacity increases
Solution Approach 1:
The patent reduces the number of circuit elements by merging multiple capacitors into one capacitor and using a minimal set of switches (first and second switches) to control charge transfer from both accumulation regions. This merging significantly reduces parasitic capacity while maintaining background light rejection functionality.
3Adaptability or versatility
If more switching circuits are added to control charge distribution, then charge control flexibility is improved, but switching noise increases and distance calculation accuracy deteriorates
Solution Approach 1:
The patent extracts and eliminates unnecessary switching circuits from the pixel structure, retaining only the essential first and second switches needed for charge transfer. By removing redundant switching elements, the patent reduces switching noise while maintaining sufficient charge control flexibility through the remaining switches and the capacitor's charge storage capability.
4Reliability
If pixel size is increased to accommodate more capacitors, then background light cancellation capability is improved, but spatial resolution deteriorates
Solution Approach 1:
The patent combines the charge storage function of multiple capacitors into a single capacitor, dramatically reducing the area required for background light cancellation circuitry. This allows the pixel size to be reduced, thereby improving spatial resolution while maintaining the background light cancellation capability through the single capacitor's differential charge storage.
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 design enhances spatial resolution, improves signal-noise ratio, and enables accurate distance calculation by integrating charges in specific periods and canceling background light components, resulting in a more accurate range image.
Implementation Method 1
each of the pixels is provided with a photosensitive region, first and second accumulation regions adjacent to the photosensitive region
Data Source
AI summary
Since the accumulation regions fd1, fd2 are connected only to a single capacitor C1, a pixel can be decreased in size to improve spatial resolution. And, charges transferred into the accumulation regions fd1, fd2 are temporarily accumulated, thereby improving a signal-noise ratio. The driving circuit DRV conducts dummy switching so that the number of switching of the first switch Φ1 is equal to the number of switching of the second switch Φ2 after termination of the reset period within one cycle, thus making it possible to cancel offset and obtain a more accurate range image.