Dual-Channel 3D TOF Sensor Layout for SIL-Grade Detection
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Solution Overview
Problem
Existing 3D time-of-flight (TOF) sensors face challenges in ensuring extremely reliable and safe detection of objects and people in a three-dimensional space, particularly in applications requiring high safety integrity levels (SIL) such as SIL-3 or Cat 4, with potential dangerous failures occurring at a probability of less than 1 in 1100 years.
Innovation Solution
A 3D TOF sensor design with a pixel matrix divided into two signal paths (channels A and B) having identical signal transit times, each with independent analog signal outputs, and two optical transmitter groups, along with separate logic for each path to process signal values crosswise, and additional signal processing steps to verify functionality and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single signal path is used in conventional TOF sensors, then the device complexity is low, but the reliability and safety integrity level are insufficient for applications requiring SIL-3 or Cat 4
Solution Approach 1:
The pixel matrix is divided into two separate signal paths (channel A and channel B), each with independent photodetector arrays, signal processing circuits, and readout channels. This segmentation allows independent operation and failure isolation, enabling SIL-3 safety integrity level by ensuring that a failure in one path does not compromise the entire system.
Solution Approach 2:
Different regions of the pixel matrix are assigned to different signal paths with specialized functions. Channel A and Channel B have distinct photodetector arrays optimized for specific detection tasks, allowing each path to be tailored for its intended purpose while maintaining overall system reliability through diversity.
2Measurement precision
If signal paths are routed with different transit times, then the device complexity is low and routing is simple, but the measurement precision and reliability are compromised
Solution Approach 1:
The signal paths are intentionally designed with asymmetric physical routing but compensated to achieve symmetric signal transit times. The asymmetric layout allows practical implementation while the compensation mechanisms (delay lines, path length matching) ensure that both channels experience identical signal propagation delays, maintaining measurement precision.
3Reliability
If only one transmitter group is used, then the device complexity is low, but the reliability and ability to detect dangerous failures are insufficient
Solution Approach 1:
Two transmitter groups are combined in a redundant configuration where both transmitters operate simultaneously or alternately. This merging provides functional redundancy, allowing the system to verify transmitter functionality through cross-comparison and maintain operation even if one transmitter fails, thereby achieving SIL-3 reliability.
Solution Approach 2:
The system implements feedback mechanisms where the receiver monitors the output of each transmitter group and provides status information back to the control logic. This feedback enables real-time verification of transmitter functionality, detection of dangerous failures, and automatic switching or alarm generation to maintain safety integrity.
4Reliability
If crosswise processing of signal values is not implemented, then the device complexity is low, but the ability to verify functionality and ensure safety is reduced
Solution Approach 1:
The signal processing logic is designed to perform multiple functions: normal distance measurement, cross-path verification, dangerous failure detection, and safety status monitoring. This multi-functional logic processes signals from both channels simultaneously, enabling the system to verify functionality and ensure safety without requiring separate dedicated verification circuits.
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 design significantly reduces the likelihood of dangerous failures, ensuring high safety integrity levels by verifying the functionality of both signal paths and transmitter groups, thus enhancing the reliability and safety of object detection.
Implementation Method 1
at least one optical transmitter for emitting electromagnetic radiation, preferably (but not exclusively) in the near infrared range
Implementation Method 2
the energy of the reflected light pulse causes charges—namely photoelectrons—to be released in the photosensitive element
Implementation Method 3
the distance to the objects located in the detection area of the sensor is determined based on the transit time (also referred to as time of flight (tof)) of light pulses
Data Source
AI summary
The invention relates to imaging 3-D time-of-flight sensors that are particularly suitable for the detection of objects and individuals in three-dimensional space. This capability results from the basic principle. In each image point of the sensor, the distance to the object located in the observation space is determined by using the propagation time (time of flight) of light pulses. The sensor therefore supplies a three-dimensional image, which can be analyzed by means of suitable processing algorithms. In specific applications, in particular in the interaction of human and machine, machine and machine, or machine and space, it is necessary that the detection is carried out safely. The level of safety is classified in various standards into safety integrity levels.