Multi-Mode Photodiode Sensor for Distance and Intensity Measurement
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Solution Overview
Problem
Current optoelectronic sensors face challenges in achieving high resolution and dynamic range for distance measurement, particularly with SPAD detectors which are unsuitable for image sensing and require complex systems when combined with image sensors, and existing methods struggle with triangulation and time-of-flight measurements due to limitations in sensitivity and interference handling.
Innovation Solution
An optoelectronic sensor with photodiode elements that can operate in multiple modes (SPAD, APD, and linear PD) via adjustable bias voltage, allowing for high sensitivity, fine-grained analog information, and robust distance measurement across large ranges, combining time-of-flight and triangulation methods for accurate object detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SPAD detectors are used for time-of-flight measurements, then sensitivity is improved with amplification factors up to 10^8, but the detectors cannot provide brightness images and are unsuitable for triangulation
Solution Approach 1:
The patent applies dynamics by enabling photodiode elements to dynamically switch between different operating modes (SPAD, APD, linear PD) based on measurement requirements. The control unit adjusts the bias voltage in real-time to transition detectors between Geiger mode for time-of-flight and linear mode for triangulation, making the system adaptable to different measurement tasks rather than being fixed in one mode
Solution Approach 2:
The patent implements multi-functionality by designing a single photodiode array that can perform multiple functions: time-of-flight measurement in SPAD mode, triangulation in linear PD mode, and intermediate measurements in APD mode. This universal detector replaces the need for separate specialized detectors, allowing one system to handle both distance measurement methods effectively
2Device complexity
If a single SPAD receiver array is used for both time-of-flight and triangulation, then device complexity is reduced, but triangulation requires deactivating pixels which reduces measurement capability
Solution Approach 1:
The system dynamically adjusts the operating mode of each photodiode element based on the current measurement task. During triangulation, pixels are switched to linear PD mode instead of being deactivated, enabling continuous analog intensity measurement. The control unit manages mode switching to optimize measurement capability while maintaining a single receiver array structure
Solution Approach 2:
The patent changes the operating parameter (bias voltage) of the photodiode elements to transition between SPAD and linear PD modes. By adjusting the bias voltage below breakdown voltage during triangulation, the pixels operate in linear region providing analog intensity information, while above breakdown voltage they provide single-photon sensitivity for time-of-flight, thus optimizing measurement precision for each task
3Loss of information
If photodiode elements are operated in linear PD mode for triangulation, then analog intensity information is available, but sensitivity is reduced compared to SPAD mode
Solution Approach 1:
The system dynamically selects the appropriate operating mode based on the measurement task and environmental conditions. For triangulation where analog intensity information is needed, pixels switch to linear PD mode. For time-of-flight or low-light conditions requiring maximum sensitivity, they switch to SPAD mode. This dynamic adaptation ensures optimal performance for each specific measurement scenario
Solution Approach 2:
The bias voltage parameter is changed to control the operating region of the photodiode. In linear PD mode, bias voltage is kept below breakdown voltage to maintain linear response and analog intensity information. In SPAD mode, bias voltage exceeds breakdown voltage to enable single-photon detection through avalanche multiplication, thus trading off between information type and sensitivity through parameter control
4Loss of information
If multiple detectors and receiving optics are combined for SPAD and image sensing, then measurement information is improved, but system complexity, size, and adjustment requirements increase
Solution Approach 1:
The patent implements a universal photodiode array that serves multiple measurement functions through software-controlled mode switching rather than requiring separate physical detector systems. The same receiver optics and photodiode elements are used for both time-of-flight and triangulation, eliminating the need for additional detectors and reducing system complexity while maintaining comprehensive measurement information
Solution Approach 2:
The patent merges the functions of separate SPAD detectors and image sensors into a single integrated photodiode array system. By combining the detection capabilities in one unified structure with a single receiving optics system, the patent reduces the overall system complexity, alignment requirements, and physical size while still providing both time-of-flight and triangulation measurement information
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 sensor achieves high sensitivity with amplification factors up to 10^8 in SPAD mode, enables fine-grained analog information in linear PD mode, and reliable distance measurement over a wide dynamic range, enhancing robustness and performance with a single system that maintains a common field of view and reduces complexity and adjustment requirements.
Implementation Method 1
When a bias voltage above the breakdown voltage is applied, and then a single charge carrier released by a single photon is sufficient to trigger an uncontrolled avalanche
Implementation Method 2
a single charge carrier released by a single photon is sufficient to trigger an uncontrolled avalanche, which, due to the high field strength, recruits all available charge carriers
Implementation Method 3
Time-of-flight methods measure the transit time of a light signal, which corresponds to the distance being sought via the speed of light
Implementation Method 4
In triangulation, the light source and receiver are positioned side-by-side at a baseline distance. Depending on the distance of the object reflecting the emitted light, the received light is registered at a different position on a spatially resolved receiver
Data Source
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AI summary
An optoelectronic sensor (10) for detecting an object (10) in a monitoring area (18) is specified, comprising a light transmitter (12) for emitting a light signal (16), a light receiver (26) for receiving received light (22) from the monitoring area (18), a plurality of photodiode elements (26a) for generating respective received signals, and a control and evaluation unit (28) which is designed to change a bias voltage on the photodiode elements (26a) and to evaluate the received signals in order to determine the distance to the object (20) using a time-of-flight method and to obtain further measurement information from the intensity of the received signals.The control and evaluation unit (28) is further configured to change the bias voltage such that at least one of the photodiode elements (26a) is selectively operated either in a SPAD mode with a bias voltage above a breakdown voltage and thus in a Geiger mode, in an APD mode with a bias voltage below the breakdown voltage with controlled avalanche breakdown, or in a linear PD mode with low or no bias voltage.