Image Sensor Pixel Circuit with Separate Electron and Hole Collection Electrodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Film-based image sensors face limitations in effectively collecting and processing both electrons and holes from incident photons, leading to suboptimal signal-to-noise ratio and dynamic range in image sensing.
Innovation Solution
The design includes an array of pixel circuits on a semiconductor substrate with separate electron-collecting and hole-collecting electrodes, coupled with charge stores and circuitry to apply potentials and output signals, enabling the collection and differential output of electrons and holes for enhanced dynamic range and signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate electron-collecting and hole-collecting electrodes are implemented, then signal-to-noise ratio and dynamic range are improved, but device complexity increases
Solution Approach 1:
The pixel circuit is segmented into separate electron-collecting and hole-collecting electrodes, allowing independent collection and processing of electrons and holes. This segmentation enables differential signaling that improves signal-to-noise ratio while distributing the complexity across specialized sub-circuits rather than a single complex unit.
Solution Approach 2:
The electron collection circuit and hole collection circuit are merged into a unified pixel circuit architecture that processes both charge carriers simultaneously. This merging allows for correlated double sampling and differential output that enhances measurement precision while sharing common circuit resources.
2Measurement precision
If both electrons and holes are collected simultaneously, then dynamic range is enhanced, but circuit complexity increases
Solution Approach 1:
The pixel circuit employs dynamic control of electron and hole collection through timed gating signals. The circuit can dynamically switch between collecting electrons, collecting holes, or performing correlated double sampling operations, enabling enhanced dynamic range through adaptive charge carrier management.
Solution Approach 2:
The circuit performs preliminary collection of charge carriers in dedicated time periods before final readout. Electrons and holes are collected in separate integration periods, and correlated double sampling is performed in advance to subtract offset charges, thereby extending dynamic range before the final measurement stage.
3Productivity
If separate charge stores for electrons and holes are used, then signal processing capability is improved, but area of pixel circuit increases
Solution Approach 1:
The charge storage nodes are designed with multi-functionality, serving both as temporary collection points for charge carriers and as part of the differential readout circuitry. The same circuit elements participate in multiple operations including charge collection, storage, transfer, and differential signaling, thereby improving signal processing without proportional area increase.
Solution Approach 2:
The pixel circuit employs a nested architecture where charge storage functions are integrated within the readout circuit structure. The differential pair transistors nest the charge-to-voltage conversion function within the differential amplification stage, allowing compact arrangement that improves signal processing capability while minimizing pixel area.
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 signal-to-noise ratio and dynamic range of image sensors by allowing simultaneous collection and processing of both charge carriers, improving the intensity sensing of incident light.
Implementation Method 1
a photosensitive medium configured to convert incident photons into pairs of electrons and holes
Data Source
AI summary
Imaging apparatus (100, 200, 300) includes a photosensitive medium (302) configured to convert incident photons into pairs of electrons and holes. An array of pixel circuits (304) is formed on a semiconductor substrate (305). Each pixel circuit defines a respective pixel and includes an electron-collecting electrode (306, 502) in contact with the photosensitive medium at a first location in the pixel and a hole-collecting electrode (308, 504) in contact with the photosensitive medium at a second location in the pixel. Circuitry (800, 1000) is coupled to apply a positive potential to and collect the electrons from the electron-collecting electrode and to apply a negative potential to and collect the holes from the hole-collecting electrode and to output a signal indicative of an intensity of the incident photons responsively to the collected electrons and holes.