Dual Photodetector Scan Module for Accurate Working Distance Determination
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Solution Overview
Problem
Existing technologies fail to accurately and rapidly determine the working distance of a target, such as a bar code symbol, leading to erroneous adjustments in reading parameters, which affects the performance of electro-optical readers like laser scanners and imaging readers.
Innovation Solution
A dual-photodetector system is employed in the scan module, where a first photodetector generates a first analog signal and a second photodetector, positioned in close proximity, generates a second analog signal. The ratio of these signals is processed to determine the working distance, allowing for real-time adjustments of reading parameters like scan angle, gain, and laser power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single photodetector is used to detect return light, then the device complexity is low, but the measurement precision of working distance is insufficient
Solution Approach 1:
The single photodetector is segmented into multiple photodetectors (first photodetector and second photodetector), each detecting light from different spatial regions. This segmentation enables the system to measure working distance more accurately by comparing signals from multiple detectors while maintaining relatively simple device architecture.
2Reliability
If reading parameters are adjusted based on estimated working distance, then the adaptability is improved, but the reliability of reading performance deteriorates due to erroneous distance determination
Solution Approach 1:
The system implements feedback by using the ratio of signals from multiple photodetectors to determine working distance, which then feeds back to automatically adjust reading parameters. This closed-loop feedback mechanism ensures reliable reading performance while maintaining adaptability to different working distances.
3Measurement precision
If the scan angle is made narrow for far zone reading, then the measurement precision at far distance is improved, but the productivity decreases due to slower scanning speed
Solution Approach 1:
The scan angle is made dynamic rather than fixed. The system automatically adjusts the scan angle based on the determined working distance: using narrow scan angles for far zone targets to maintain precision, and wider scan angles for near zone targets to improve scanning speed and productivity.
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 method provides accurate and rapid determination of the working distance, enabling dynamic and precise adjustments of reading parameters, thereby enhancing the performance of electro-optical readers across varying distances.
Implementation Method 1
a photodetector for detecting return light reflected and/or scattered from the symbol through the window, and for converting the detected return light into an analog electrical information signal
Data Source
AI summary
First and second photodetectors having first and second collection areas receive return laser light that is reflected and scattered from a target, and generate first and second analog electrical output signals having first and second magnitudes. The second collection area is in close proximity to the first collection area. The first output signal is processed to obtain information related to the target. The first and the second output signals are processed, preferably by determining a ratio of the second magnitude to the first magnitude. A working distance to the target is determined based on the determined ratio. One or more reading parameters by which the target is electro-optically read are adjusted based on the determined working distance.