Avalanche Photodiode Sensor Pixel Grouping for Power Reduction
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Solution Overview
Problem
Photon counting type image sensors using avalanche photodiodes in Geiger mode require high voltage for operation, leading to increased power consumption when all pixels are exposed simultaneously, which is inefficient and results in high power consumption.
Innovation Solution
The image sensor is divided into pixel groups, with a control unit that selectively applies either a high voltage or a lower voltage as a reverse bias, allowing only specific groups to operate in Geiger mode, reducing overall power usage by turning off or reducing voltage for other groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all pixels are exposed at the same time using high voltage to generate avalanche phenomenon, then photon counting capability is achieved, but power consumption sharply increases
Solution Approach 1:
The image sensor is divided into multiple pixel groups, and only one pixel group is selected to operate in Geiger mode at a time while other groups operate in linear mode. This segmentation allows the system to maintain photon counting capability in the selected group while reducing overall power consumption by limiting high-voltage operation to a small portion of the sensor array.
2Reliability
If high voltage is applied to all pixels simultaneously, then avalanche phenomenon occurs for photon detection, but energy efficiency deteriorates
Solution Approach 1:
Different operating modes are applied to different regions of the sensor. The selected pixel group operates in Geiger mode with high voltage for accurate photon detection, while other pixel groups operate in linear mode with lower voltage. This local differentiation maintains detection accuracy where needed while improving overall energy efficiency.
Solution Approach 2:
The system periodically switches between different pixel groups operating in Geiger mode. By cycling through multiple groups over time, the sensor maintains photon counting capability across the entire array while ensuring that at any given moment, only a small fraction of pixels consume high power, thereby improving average energy efficiency.
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 significantly reduces power consumption by limiting the number of pixels active at any given time, while maintaining photon counting capability, thus optimizing energy efficiency without compromising image quality.
Implementation Method 1
When an APD is operated in Geiger mode, a large current is produced by the avalanche phenomenon when a single photon enters the APD
Implementation Method 2
a large current is produced by the avalanche phenomenon when a single photon enters the APD
Data Source
AI summary
An image sensor comprises: a plurality of pixels each having an avalanche photodiode; and a control unit that controls, for each of a plurality of pixel groups which are obtained by dividing the plurality of pixels, to supply either of a first voltage and a second voltage as a reverse bias voltage of the avalanche photodiodes, wherein the first voltage is greater than a breakdown voltage of the avalanche photodiodes and the second voltage is smaller than the breakdown voltage.