Avalanche Photodiode Array Sensitivity Control
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Solution Overview
Problem
Avalanche photodiodes in Geiger mode suffer from high sensitivity issues due to interference from extraneous light and dark noise, leading to measurement errors and reduced operational time, as they cannot distinguish between measurement and interference events, necessitating statistical processing and large arrays of SPADs to compensate.
Innovation Solution
A light receiver with groups of avalanche photodiodes distributed in a pattern, where sensitivity is dynamically adjusted through time sequencing, allowing for activation and deactivation between linear and Geiger modes, reducing dead time and improving signal-to-noise ratio by alternating sensitivity of groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If avalanche photodiodes are operated in Geiger mode with high sensitivity, then detection sensitivity is improved, but measurement precision deteriorates due to interference from extraneous light and dark noise
Solution Approach 1:
The array of avalanche photodiodes is divided into multiple groups that can be independently controlled. By segmenting the detection array, the system can activate only specific groups during different time intervals, reducing the impact of dark noise and extraneous light on the overall measurement while maintaining high detection sensitivity for useful signals.
Solution Approach 2:
The patent implements periodic activation and deactivation of different photodiode groups in a time-sequenced manner. This periodic action allows the system to alternate between high-sensitivity detection phases and low-sensitivity recovery phases, effectively managing the trade-off between detection sensitivity and interference rejection by resetting dark noise accumulation periodically.
2Productivity
If avalanche photodiodes remain continuously active in Geiger mode, then detection capability is maintained, but operational duration is reduced due to dead time after each avalanche event
Solution Approach 1:
The system performs preliminary deactivation of photodiode groups before they enter dead time periods. By proactively switching off groups after detection events, the system prevents the accumulation of extended dead time effects and prepares the groups for renewed high-sensitivity operation, thereby extending the effective operational duration of the detection system.
Solution Approach 2:
The patent dynamically adjusts the operational state of different photodiode groups based on their individual detection history and current sensitivity requirements. This dynamic control allows the system to optimize the balance between maintaining continuous detection capability and managing the operational duration limitations imposed by dead time effects.
3Power
If all avalanche photodiodes are activated simultaneously, then signal detection is maximized, but signal-to-noise ratio deteriorates due to increased dark triggers
Solution Approach 1:
The system employs periodic activation of photodiode groups rather than continuous simultaneous activation. This periodic operation reduces the total accumulation of dark triggers across the array while maintaining sufficient signal detection strength by ensuring that at least some groups are actively detecting at any given time, thereby improving the signal-to-noise ratio.
Solution Approach 2:
By segmenting the photodiode array into independently controllable groups, the system can activate only the necessary subsets for current detection needs. This segmentation reduces the total number of simultaneously active detectors, thereby reducing dark trigger events while maintaining adequate signal detection capability through coordinated group activation.
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 enhances flexibility and adaptability for time-of-flight measurements, reduces dark triggers, and improves signal-to-noise ratio, enabling more accurate and efficient distance measurements by minimizing measurement errors and power consumption.
Implementation Method 1
In an avalanche photodiode (APD), the incident light triggers a controlled avalanche effect. The charge carriers generated by incident photons are thus multiplied and a photocurrent is produced
Implementation Method 2
The charge carriers generated by incident photons are thus multiplied
Data Source
AI summary
A light receiver (22) is provided having a plurality of avalanche photodiode elements (24) that can each be biased above a breakdown voltage by a bias voltage and can thus be operated in a Geiger mode, wherein the avalanche photodiode elements (24) form a plurality of groups, and having a control unit (30) to change the sensitivity of the avalanche photodiode elements (24) of a respective group. In this respect, the control unit (30) is configured to respectively change the sensitivity of the avalanche photodiode elements (24) of a group at at least one point in time assigned to the group, with different points in time being assigned to the groups.