SPAD Control Circuit for Shorter Dead Time in Distance Sensing
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Solution Overview
Problem
Conventional distance measuring systems using Single Photon Avalanche Diode (SPAD) elements face challenges in detecting reflected light at intervals shorter than the dead time of the SPAD, limiting the dynamic range of the system, and requiring a short dead time to enlarge it, which can lead to negative effects like uncontrolled avalanche amplification.
Innovation Solution
A control circuit with a passive and active circuit configuration is employed to supply current to the SPAD element through multiple paths, allowing for the generation of pulse signals that shorten the recovery time and dead time of the SPAD, thereby enhancing the dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a SPAD element is used to receive reflected light, then distance measurement capability is achieved, but detection of reflected light at intervals shorter than dead time becomes difficult
Solution Approach 1:
The patent divides the current supply to the SPAD element into multiple independent paths: a first current path that supplies current during the avalanche amplification period, and a second current path that supplies current during the recovery period. This segmentation allows independent optimization of each phase, enabling faster recovery without compromising avalanche amplification stability.
Solution Approach 2:
The patent dynamically switches between different current supply modes by activating different current paths at different time intervals. The control circuit selectively turns on the first current path during avalanche amplification and the second current path during recovery, adapting the current supply characteristics to the real-time operational state of the SPAD element to minimize dead time.
2Adaptability or versatility
If dead time of SPAD element is shortened to enlarge dynamic range, then uncontrolled avalanche amplification may occur
Solution Approach 1:
The patent prepares the SPAD element for rapid recovery by pre-configuring the second current path to be ready for immediate activation. The control circuit is designed to switch to the second current path as soon as avalanche amplification completes, ensuring the recovery process begins without delay. This preliminary preparation of the recovery mechanism allows short dead time without compromising avalanche control.
Solution Approach 2:
The patent implements periodic switching between the first and second current paths, with the first path active during avalanche amplification and the second path active during recovery. This periodic action pattern ensures that the SPAD element receives appropriate current characteristics at the right times, maintaining reliable avalanche control while enabling frequent measurement cycles for extended dynamic range.
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 solution enables the enlargement of the dynamic range of the distance measuring system by shortening the dead time of the SPAD elements, reducing power consumption, and minimizing erroneous detections.
Implementation Method 1
a light receiving element receives reflected light of light having been emitted from a light source which is reflected from an object to be measured
Implementation Method 2
Single Photon Avalanche Diode (SPAD) element
Data Source
AI summary
The control circuit according to the present disclosure includes a passive circuit (10) and an active circuit (20). The passive circuit (10) is configured to: supply current to a Single Photon Avalanche Diode (SPAD) element (6a) from a supply path (Rp); and output a first pulse signal (P1) according to a signal Generated in the SPAD element (6a). The active circuit (20) is configured to: supply current to the SPAD element (6a) selectively from among a plurality of supply paths; and output a second pulse signal (P2) according to a signal generated in the SPAD element (6a).