SPAD Array Distance Measurement Multiplexer
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Solution Overview
Problem
Conventional optical distance measuring devices require complex electronics for evaluating analog signals from light-sensitive elements, are often incompatible with CMOS technology, and have limitations in dynamic range, signal-to-noise ratio, and manufacturing simplicity.
Innovation Solution
A measuring device using a transmission device emitting time-modulated optical radiation and a reception device with multiple SPADs, where detection signals from pixels are evaluated independently to determine distance, employing simple optics and a multiplexer to selectively forward signals to an evaluation device, optimizing signal-to-noise ratio and reducing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional light-sensitive elements (PIN diodes or APDs) are used to detect optical measurement radiation, then analog detection signals with high bandwidth are obtained, but complicated evaluation electronics are required and CMOS technology compatibility is reduced
Solution Approach 1:
The patent replaces conventional analog light-sensitive elements (PIN diodes or APDs) with a digital detector array consisting of multiple pixels, each containing a photodiode and an integrated evaluation circuit. This substitution eliminates the need for complicated external evaluation electronics while maintaining detection capabilities, as each pixel performs local signal processing independently.
Solution Approach 2:
The detector is divided into multiple pixels arranged in a matrix, where each pixel is an independent functional unit with its own photodiode and evaluation circuitry. This segmentation allows parallel processing of detection signals from different spatial locations, reducing the complexity of centralized evaluation electronics while preserving measurement precision.
2Measurement precision
If a spatially resolving detector with many pixels is used to determine distances to different surface areas, then spatially resolved distance information is obtained, but complicated focusing optics and individual pixel evaluation capability are required
Solution Approach 1:
The detector is segmented into multiple pixels arranged in a matrix, with each pixel independently determining distance information for its corresponding field of view. This segmentation enables spatially resolved measurements without requiring complex focusing optics, as each pixel's independent evaluation circuit processes signals locally.
Solution Approach 2:
Each pixel in the detector array is designed as a universal functional unit capable of independent distance measurement. The evaluation device can selectively evaluate signals from any combination of pixels, providing both spatially resolved measurements and the ability to determine an average distance across multiple pixels, thus serving multiple measurement modes with a single detector design.
3Measurement precision
If the detection surface is matched to the illuminated area to improve signal-to-noise ratio, then measurement accuracy is improved, but the device structure becomes more complex
Solution Approach 1:
The evaluation device dynamically selects and evaluates detection signals from pixels that are actually illuminated by the light spot, rather than using a fixed detection surface configuration. This dynamic adaptation allows the effective detection area to be optimized for each measurement situation, improving signal-to-noise ratio without requiring physical reconfiguration of the detector.
Solution Approach 2:
The system automatically identifies which pixels are illuminated by analyzing the detection signals from all pixels, and then selectively evaluates only those signals. This self-service approach optimizes the signal-to-noise ratio without requiring external intervention or complex mechanical adjustment mechanisms.
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 a simplified design with improved signal-to-noise ratio, increased dynamic range, and reduced chip area, allowing for cost-effective and robust hand-held distance measurement devices that can handle a wide range of distances with enhanced accuracy.
Implementation Method 1
Each of the multiplicity of pixels has at least one SPAD (single photon avalanche diode)
Implementation Method 2
determine a distance between the measuring device and a target object based on an evaluation of detection signals from a number of pixels, in particular a number of pixels which are illuminated at the same time
Data Source
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AI summary
A measuring device (10) for optically measuring the distance to a target object (15) is described. The measuring device (10) comprises a transmitting device (12) for emitting optical measuring radiation (13) towards the target object (15), a receiving device (14) with a detection surface (66) for detecting optical measuring radiation (16) reflected from the target object (15), and an evaluation device (36). The detection surface (66) has a plurality of pixels, each pixel having at least one SPAD (single photon avalanche diode), and each of the plurality of pixels being connected to the evaluation device (36). The measuring device (10) has at least one multiplexer (140) designed to selectively forward detection signals from several pixels (111) to the evaluation device (36).The transmitting and receiving devices are designed such that optical measurement radiation reflected from the target object illuminates a multiple of pixels simultaneously. The evaluation device is designed to determine the distance between the measuring device and the target object based on an evaluation of detection signals from multiple pixels.