Geiger Mode Avalanche Photodiode Sensor for Distance Measurement
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Solution Overview
Problem
Optoelectronic distance sensors face challenges in achieving high accuracy and cost-effectiveness due to the need for complex high-voltage control and amplification in avalanche photodiodes, especially when measuring small light signals with noise interference, and the Geiger mode operation limits proportional signal output.
Innovation Solution
Operating a large number of avalanche photodiode elements in Geiger mode to achieve linear amplification through averaging, reducing the need for high-voltage components and complex electronics, and using a two-frequency or multi-phase method to generate an intermediate frequency signal for distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If avalanche photodiodes are operated in Geiger mode to detect low light signals, then detection sensitivity is improved, but the ability to output proportional signals is lost
Solution Approach 1:
The sensor is divided into multiple avalanche photodiode elements (e.g., 4 elements) that operate independently in Geiger mode. Each element provides binary detection (signal present/absent), and the combination of these segmented detectors restores proportional response through statistical averaging while maintaining single-photon sensitivity.
Solution Approach 2:
Multiple copies of the avalanche photodiode detector are used instead of a single detector. The proportional signal is reconstructed by counting the number of active detectors among the copies, transforming the loss of proportional output in individual Geiger-mode detectors into a recoverable statistical property.
2Power
If conventional avalanche photodiodes are used with high-voltage control to achieve amplification, then signal amplification is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The high-voltage control circuitry and complex amplification electronics are extracted and removed from the system. The avalanche photodiodes are operated in Geiger mode with simplified low-voltage control, and the amplification function is replaced by the inherent gain of the Geiger mode operation combined with digital counting.
Solution Approach 2:
The patent replaces expensive, complex high-voltage controlled avalanche photodiodes with simpler, lower-cost Geiger-mode operated detectors that require minimal external control circuitry. The cost reduction is achieved by eliminating complex high-voltage power supplies and control electronics.
3Measurement precision
If high amplification is applied to detect small light signals, then detection capability is improved, but noise interference increases
Solution Approach 1:
The patent replaces continuous analog amplification with discrete digital counting of photon events. By counting the number of avalanche photodiode elements that detect photons in a given time window, the system achieves detection capability without the noise amplification problems of analog systems, as digital counting is inherently more resistant to noise.
Solution Approach 2:
The detection system is segmented into multiple independent avalanche photodiode elements, each operating in Geiger mode. This segmentation allows the system to distinguish true photon signals from noise by statistical analysis of the distribution of detected events across the segmented detectors, improving signal-to-noise ratio.
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 results in a cost-effective, robust, and stable distance measurement system with reduced temperature dependence and lower production costs, capable of handling shiny surfaces and ambient noise, while maintaining high accuracy with fewer components and simpler electronics.
Implementation Method 1
The incident light triggers a controlled avalanche (avalanche effect). As a result, the charge carriers generated by incident photons are multiplied and a photocurrent is produced which is proportional to the light reception intensity
Implementation Method 2
Avalanche photodiodes (APD, Avalanche Photo Diode) are conventionally used in some optoelectronic distance sensors. The incident light triggers a controlled avalanche
Implementation Method 3
Optoelectronic distance sensors based on the time-of-flight principle determine the distance to an object based on the transit time of a light signal, which corresponds to the distance via the speed of light
Implementation Method 4
a short light pulse is emitted and the time until reception of a remission or reflection of the light pulse is measured
Implementation Method 5
in a phase method, the transmitted light is amplitude-modulated and a phase shift between the transmitted and received light is determined, the phase shift also being a measure of the light propagation time
Implementation Method 6
Optoelectronic distance sensors based on the time-of-flight principle determine the distance to an object based on the transit time of a light signal
Data Source
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Figure 5~6
AI summary
An optoelectronic sensor (10) for measuring the distance of objects in a monitoring area (22) is specified according to a time-of-flight method, wherein the sensor (10) comprises a light transmitter (18) with a transmit light modulation unit (16) for emitting transmit light (209) modulated with a first signal, a light receiver (26) with a receive sensitivity modulation unit (28) for receiving light (24) from the monitoring area (22) with a receive sensitivity modulated with a second signal, such that the light receiver (26) acts as a mixer and outputs an evaluation signal mixed from the first and the second signals, and an evaluation unit (34) for determining the time of flight from the evaluation signal.The light receiver (26) has a plurality of avalanche photodiode elements, each of which is biased with a voltage above a breakdown voltage and is thus operated in a Geiger mode, the second signal modulates the receiver sensitivity by modulating the bias voltage, and the evaluation signal is a common signal of the avalanche photodiode elements.