Photon Counting Solid-State Imaging Device Pixel Architecture
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Solution Overview
Problem
Current solid-state imaging devices face challenges in increasing the number of pixels while maintaining a small pixel size due to the complexity of digital count-type circuits and variations in photon detection voltage, which affect accurate measurement of weak light.
Innovation Solution
A solid-state imaging device with an avalanche amplification type light receiving element and a resetter that outputs a digital signal indicating photon incidence, using a count value storage to convert digital signals to analog voltages for accurate photon counting, allowing for a high-performance photon count function with a small pixel size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a digital count-type circuit is mounted on a pixel as a counter, then the photon counting function is improved, but the pixel cell size increases and the number of pixels cannot be increased
Solution Approach 1:
The patent extracts the counting function from the pixel-level digital circuit and relocates it to a post-processing stage. Instead of counting photons digitally at each pixel, the system converts photon detection results to analog values and performs counting operations after readout, thereby removing the bulky digital counter from the pixel structure and reducing pixel cell size.
Solution Approach 2:
The patent replaces the digital counting mechanism with an analog-based approach. Instead of using digital circuits to count photons, the system converts photon detection signals to analog voltages and uses analog processing to determine photon counts, substituting mechanical/digital systems with analog field-based processing.
2Measurement precision
If the number of bits is increased to obtain a desired tone level, then the measurement precision is improved, but the number of circuit elements and signal lines increase proportionally, causing the pixel cell size to increase
Solution Approach 1:
The patent changes the parameter representation from digital bits to analog voltage levels. Instead of increasing the number of bits to represent tone levels, the system uses analog voltage amplitudes to encode photon count information, allowing high precision tone levels without increasing digital circuit complexity or signal line count.
3Area of stationary object
If an analog circuit is mounted on a pixel as a counter, then the pixel cell size is reduced, but the amount of electric charges discharged varies due to variations in amplitude and parasitic capacitance, making accurate measurement difficult
Solution Approach 1:
The patent introduces an intermediary conversion stage between photon detection and counting. Instead of directly counting analog charges which vary in amplitude, the system converts photon detection signals to standardized analog voltages through a controlled process, using this intermediate representation to eliminate variations caused by amplitude differences and parasitic capacitance before performing count operations.
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 configuration enables accurate photon counting with reduced error and a smaller pixel size, allowing for a higher number of pixels and improved imaging speed, particularly in detecting weak light.
Implementation Method 1
a light receiving element that is an avalanche amplification type light receiving element and that detects a photon
Data Source
AI summary
A solid-state imaging device includes a detector, a count value storage, and a reader. The detector includes an avalanche amplification type light receiving element that detects a photon, and a resetter that resets an output potential of the light receiving element, and outputs a digital signal that indicates the presence or absence of incidence of a photon on the light receiving element. The count value storage performs counting by converting the digital signal output from the detector to an analog voltage, and stores the result of counting as a count value. The reader outputs an analog signal indicating the count value.