Optical Time-of-Flight Sensor Freezing Circuit for Channel Misjudgment
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Solution Overview
Problem
Conventional time-of-flight distance detection devices using single-photon avalanche diodes (SPAD) face performance issues due to misjudgments and double counting of photons when their arrival time is close to channel switching, affecting distance estimation accuracy.
Innovation Solution
An optical time-of-flight sensor with a sensor array and a first channel sampling circuit, comprising a freezing circuit and a counting circuit, which generates a freezing signal and a channel event signal to prevent double counting by keeping the freezing signal state until the photon pulse signal's falling edge, ensuring accurate photon counting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional channel sampling is used without freezing signal, then the device complexity is low, but measurement precision deteriorates due to channel misjudgment when photon arrival time is close to channel switching
Solution Approach 1:
The freezing signal is generated in advance based on the photon pulse signal before channel switching occurs. When a rising edge of the photon pulse signal is detected, the freezing signal is activated to lock the channel selection signal at its current state, preventing any subsequent channel switching during the photon detection window. This preliminary action ensures that the channel assignment is determined before the potential misjudgment window, thereby improving measurement precision without requiring complex real-time intervention circuits.
2Reliability
If channel switching occurs during photon detection window, then the productivity of photon counting is high, but reliability deteriorates due to double counting or misjudgment of photon arrival channel
Solution Approach 1:
The freezing signal acts as an intermediary between the photon pulse signal and the channel selection signal. When activated, it mediates the interaction by holding the channel selection signal constant, preventing channel switching during the photon detection window. This intermediary mechanism ensures that each photon is counted in the correct channel without losing counting efficiency, as the freezing signal only activates when needed (at rising edges of photon pulses) and releases automatically at falling edges, allowing continuous high-rate photon counting across multiple channels.
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 solution significantly improves the accuracy of distance estimation by avoiding channel misjudgments and double counting, enhancing the reliability of time-of-flight measurements.
Implementation Method 1
a conventional time-of-flight distance detection device may adopt single-photon avalanche diode (SPAD) units to sense and sample the reflected photons
Data Source
AI summary
An optical time-of-flight sensor includes a sensor array and a channel sampling circuit. The channel sampling circuit is arranged for receiving a photon pulse signal, generated from a senor unit of the sensor array, receiving a first channel selection signal to generate a first freezing signal, generating a first channel event signal to a first counting circuit in response to the first freezing signal and the photon pulse signal, and receiving the first channel event signal to generate and count a pulse number of the photon pulse signal received by the first channel; when a rising edge of the photon pulse signal occurs, the first freezing signal is kept at a previous state until a falling edge of the photon pulse signal occurs.