SPAD Ranging Device Dynamic Bias Voltage Control
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Solution Overview
Problem
The accuracy of distance measurement in ranging devices using single photon avalanche photo diodes (SPADs) is compromised due to fluctuations in electrical characteristics caused by manufacturing variations and environmental conditions, leading to inconsistent cathode voltage decreases and longer measurement times.
Innovation Solution
A ranging device with separate first and second pixels, where the second pixel detects the time of flight (ToF) value and controls the bias voltage of both pixels based on this value, using a control unit to maintain consistent ToF measurements by adjusting anode or cathode voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reverse bias voltage larger than breakdown voltage is applied to SPAD for receiving reflected light pulse signal, then the SPAD can detect the signal, but the cathode voltage decrease becomes inconsistent due to manufacturing variations and environmental conditions, leading to ranging errors
Solution Approach 1:
The patent dynamically adjusts the bias voltage applied to the SPAD based on detected electrical characteristics. By changing the voltage parameter in real-time, the system compensates for manufacturing variations and environmental conditions, ensuring consistent cathode voltage decrease and accurate ranging measurements
Solution Approach 2:
The system measures the actual electrical characteristics of the SPAD (such as cathode voltage decrease) and uses this feedback information to adjust subsequent bias voltage applications. This closed-loop control ensures that despite component variations, the SPAD operates at optimal conditions for accurate distance measurement
2Use of energy by moving object
If the degree of decrease in cathode voltage per unit time is small, then the SPAD can operate with lower bias voltage, but the time until cathode voltage reaches bottom voltage becomes longer, causing distance measurement values to become longer and ranging errors to occur
Solution Approach 1:
The patent employs dynamic bias voltage adjustment rather than fixed voltage levels. The bias voltage is adapted in real-time based on the SPAD's actual response characteristics, allowing the system to optimize between energy consumption and measurement speed for each individual pixel and operating condition
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 approach stabilizes distance measurements by ensuring consistent ToF values, reducing ranging errors and improving accuracy despite variations in SPAD electrical characteristics.
Implementation Method 1
a first photodiode that outputs a voltage signal corresponding to incident light
Implementation Method 2
a single photon avalanche photo diode (SPAD) is used for reception of the Rx pulse signal. In the SPAD, when an Rx pulse signal is received in a state where a reverse bias voltage larger than a breakdown voltage is applied between an anode and a cathode
Implementation Method 3
a first detection unit that detects a time of flight (ToF) value based on light reception time of incident light incident on the second pixel
Data Source
AI summary
Ranging devices that prevent decreases in distance measurement value accuracy are disclosed. In one example, a ranging device includes separate first and second pixels. A first detection unit detects a time of flight (ToF) value based on light reception time of incident light incident on the second pixel, and a control unit controls a bias voltage to be applied to the first pixel and the second pixel on the basis of the ToF value detected by the first detection unit.