Photon Sensing Circuit With Quenching Pulses for High Illuminance
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Solution Overview
Problem
Sensing devices struggle to accurately detect photons in high-illuminance environments due to prolonged recharging times, leading to reduced accuracy in distance measurement.
Innovation Solution
A sensing device with a photodetector and a quenching mechanism, including transistors and inverters, that generates controlled pulses to manage photon detection and reset operations, allowing for accurate photon detection even in high-illumination conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the sensing device operates in high-illuminance environment, then the detection speed increases, but the recharging time is prolonged and detection accuracy drops
Solution Approach 1:
The patent implements dynamic control of the photodetector's operating voltage through a control circuit that adjusts the bias voltage based on ambient light conditions. In high-illuminance environments, the control circuit reduces the bias voltage to prevent saturation and prolong recharging time, while in low-illuminance environments, it increases the bias voltage to enhance detection sensitivity. This dynamic voltage adjustment resolves the contradiction between detection speed and recharging time by adapting the operating parameters to environmental conditions.
Solution Approach 2:
The patent changes the operating parameters (voltage and current) of the photodetector based on illumination conditions. The control circuit monitors ambient light levels and adjusts the bias voltage and gain parameters accordingly. By varying these parameters dynamically, the system maintains optimal detection accuracy across different illuminance levels while managing recharging time effectively.
2Reliability
If the voltage across SPAD terminals is lowered to stop avalanche phenomenon, then the quenching is achieved, but the recharging time increases in high-illuminance environments
Solution Approach 1:
The control circuit performs preliminary action by pre-charging the photodetector to an optimal bias voltage before photon detection events occur. This pre-positioning of the voltage ensures that when a photon is detected and quenching is required, the voltage can be rapidly reduced to stop the avalanche phenomenon, and then quickly restored to the pre-charged level, minimizing recharging time while maintaining reliable quenching control.
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
The device ensures consistent and accurate photon detection by controlling pulse width and timing, enabling precise distance measurement regardless of environmental illuminance levels.
Implementation Method 1
Avalanche photodiodes (APDs) are well-known light-receiving elements used for the sensing device. A single photon entering the photodiode then causes an avalanche phenomenon.
Implementation Method 2
A voltage equal to or higher than a breakdown voltage is applied across terminals of the APD placed in a Geiger mode. A single photon entering the photodiode then causes an avalanche phenomenon. The ADP that multiplies a single photon by the avalanche phenomenon is called a single-photon avalanche diode (SPAD).
Data Source
AI summary
Sensing devices configured to detect photons with high accuracy regardless of environmental illuminance are disclosed. In one example, a sensing device includes a photodetector and a load element connected between the photodetector and a first reference potential. A first transistor is configured to be turned on according to a voltage of a node between the photodetector and the load element. A second transistor is configured to turn on according to either a current of the first transistor or a voltage of a second signal line. A third transistor of an opposite conductivity type to the first and second transistors is configured to turn on according to the voltage of the second signal line. A first inverter is connected between a node between the first transistor and the third transistor and a fourth signal line.