APD Sensor Multi-Pixel Counting Accuracy
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Solution Overview
Problem
In ranging systems using avalanche photodiodes, simultaneous input of signals from multiple pixels to a counter leads to inaccurate counting of photon reception times due to pulse width issues, causing errors in distance measurement.
Innovation Solution
An avalanche photodiode sensor with state detection circuits, a logical operation circuit, and a counter that generates a converging signal to enable accurate counting of signals from multiple pixels by controlling the operation of state detection circuits, using a wired NOR circuit and flip-flop circuits to manage signal inputs and reset operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If signals from multiple pixels are simultaneously input to one counter, then device complexity is reduced, but measurement precision deteriorates due to counting errors
Solution Approach 1:
The state detection circuits perform preliminary detection and signal conditioning before signals are input to the counter. By detecting the state of each pixel signal in advance and preparing it for sequential input, the system ensures accurate counting while using only one counter, thus resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
State detection circuits are introduced as intermediary components between the pixels and the counter. These circuits detect the state of pixel signals and control the sequential input to the counter, acting as a mediator that enables accurate measurement with a single counter, thereby resolving the contradiction.
2Ease of manufacture
If signals from multiple pixels are simultaneously input to one counter, then manufacturing cost is reduced, but reliability deteriorates due to counting errors
Solution Approach 1:
The state detection circuits perform preliminary detection and signal conditioning before signals are input to the counter. By detecting the state of each pixel signal in advance and preparing it for sequential input, the system ensures reliable counting while using only one counter, thus resolving the contradiction between manufacturing cost and reliability.
Solution Approach 2:
State detection circuits are introduced as intermediary components between the pixels and the counter. These circuits detect the state of pixel signals and control the sequential input to the counter, acting as a mediator that enables reliable measurement with a single counter, thereby resolving the contradiction.
3Productivity
If state detection circuits operate simultaneously for all pixels, then productivity is improved, but device complexity increases
Solution Approach 1:
The state detection circuits operate periodically rather than simultaneously for all pixels. The fourth signal controls the sequential operation of state detection circuits, with each circuit operating in turn to process pixel signals. This periodic operation maintains productivity while reducing device complexity by avoiding the need for all circuits to operate at once.
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 allows for precise counting of photon reception times across multiple pixels with one counter, reducing errors and enhancing the accuracy of distance measurements in ranging systems.
Implementation Method 1
Each pixel of such a ranging system includes, for example, an APD such as a single photon avalanche diode (SPAD) as a photoelectric converter
Implementation Method 2
The SPAD causes avalanche amplification when one photon is received at a p-n junction in a state (Geiger mode) where a voltage higher than a breakdown voltage is applied
Data Source
AI summary
Provided are an avalanche photodiode (APD) sensor and a ranging system capable of counting, with high accuracy, a value relating to signals from a plurality of pixels with one counter. The APD according to the present disclosure includes a plurality of pixels each including an APD, a plurality of state detection circuits configured to detect states of a plurality of first signals output from the plurality of pixels and generate a plurality of second signals including detection results of the states of the plurality of first signals, a logical operation circuit configured to perform a logical operation on the plurality of second signals or a plurality of third signals that varies in a manner that depends on the plurality of second signals and generate a fourth signal including a result of the logical operation, and a counter configured to count a value relating to the plurality of first signals on the basis of the fourth signal, each of the state detection circuits having an input terminal to which the fourth signal is input, and input of each of the first signals to a corresponding one of the state detection circuits being disabled on the basis of the fourth signal input to the input terminal.