Avalanche Photodiode Bias Switching for Compact Photon Counting
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Solution Overview
Problem
The existing photoelectric conversion apparatuses using avalanche diodes face challenges in reducing circuit area and power consumption due to the need for increased signal lines and counters for independent control of avalanche diodes in photon counting applications.
Innovation Solution
The apparatus incorporates a configuration with two avalanche photodiodes of different light-receiving surface areas, where one is connected to a waveform shaping circuit and a switch, and the other to another waveform shaping circuit and switch, with an inverter circuit controlling the switches, and applies a reverse bias voltage to either diode based on light intensity to optimize photon counting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple avalanche diodes are independently controlled to improve photoelectric conversion gain settings, then the degree of freedom of gain setting is improved, but the circuit area increases due to additional signal lines
Solution Approach 1:
Multiple avalanche diodes share common control signal lines and readout circuits. The patent configures pixels with multiple APDs that can be selectively activated through shared control mechanisms, eliminating the need for completely independent control lines for each diode, thus reducing circuit area while maintaining gain setting flexibility
Solution Approach 2:
The control circuit is designed to universally control multiple avalanche diodes through shared signal lines. The same control infrastructure serves multiple diodes, allowing the system to achieve versatile gain settings without proportionally increasing circuit complexity and area
2Adaptability or versatility
If multiple avalanche diodes are independently controlled to improve photoelectric conversion gain settings, then the degree of freedom of gain setting is improved, but power consumption increases due to increases in the number of signal lines and total count value of counters
Solution Approach 1:
Multiple avalanche diodes share common control signal lines and readout circuits. The patent configures pixels with multiple APDs that can be selectively activated through shared control mechanisms, eliminating the need for completely independent control lines for each diode, thus reducing circuit area while maintaining gain setting flexibility
Solution Approach 2:
The system activates only the necessary number of avalanche diodes based on the required photoelectric conversion gain, rather than keeping all diodes continuously active. This partial activation approach reduces power consumption while maintaining the flexibility to adjust gain settings by selectively enabling appropriate numbers of diodes
3Measurement precision
If avalanche photodiodes are used for single photon level detection, then luminance resolution at single photon level is achieved, but circuit area and power consumption increase due to additional control requirements
Solution Approach 1:
Multiple avalanche diodes share common control signal lines and readout circuits. The patent configures pixels with multiple APDs that can be selectively activated through shared control mechanisms, eliminating the need for completely independent control lines for each diode, thus reducing circuit area while maintaining gain setting flexibility
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 reduces circuit area and power consumption while maintaining high sensitivity and dynamic range in photon counting, allowing for efficient detection of weak light signals.
Implementation Method 1
Using the avalanche multiplication phenomenon generated by an intense electric field induced in a PN junction of a semiconductor, the APD amplifies the amount of signal electric charges excited by photons, several times to around a million times
Implementation Method 2
a technique called photon counting has attracted attention. In photon counting, luminance of incident light, which has conventionally been handled as a continuous value, is counted as a discrete value, i.e., the number of photons
Data Source
AI summary
A photoelectric conversion apparatus includes a plurality of pixels each including a first avalanche photodiode and a second avalanche photodiode having a light-receiving surface area size different from a light-receiving surface area size of the first avalanche photodiode. The first avalanche photodiode is connected between a first waveform shaping circuit and a first switch. The second avalanche photodiode is connected between a second waveform shaping circuit and a second switch. An inverter circuit is connected between a control node of the first switch and a control node of the second switch.