Strobe Illumination Control for Barcode Scanning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing digital image capture systems in video mode face inefficiencies due to incorrect initial exposure times, leading to wasted frames and time-consuming auto-exposure methods in imaging devices, particularly in demanding environments like barcode scanners.
Innovation Solution
A digital image capture and processing system employing a variable stroboscopically-pulsed LED-based illumination subsystem, synchronized with image exposure periods, and an optical band-pass filter to reduce dynamic range and improve exposure estimation, allowing for real-time adjustment of illumination energy levels based on image brightness analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the imager runs in video mode with a predetermined exposure time, then continuous image capture is enabled, but subsequent frames are wasted when the exposure time is incorrect
Solution Approach 1:
The system performs preliminary action by capturing a first test image at the initial exposure time before final image capture, analyzes its brightness, and adjusts the exposure time based on the analysis results. This preliminary exposure time adjustment prevents wasting subsequent video frames during auto-exposure, thereby improving image capture efficiency while minimizing time loss.
2Reliability
If the LED illumination array provides continuous illumination, then the imaging area is consistently lit, but energy is wasted when images are already adequately exposed
Solution Approach 1:
The system implements periodic action by controlling the LED illumination array to provide illumination only during specific image capture periods rather than continuously. The controller activates LEDs during the first test image capture and subsequent image captures based on exposure requirements, turning them off during intervals. This maintains reliable illumination when needed while significantly reducing overall energy consumption.
3Measurement precision
If a narrow-band optical filter is used to reduce dynamic range, then exposure estimation accuracy is improved, but the device complexity increases
Solution Approach 1:
The system uses a narrow-band optical filter as an intermediary element positioned between the LED illumination array and the imaging area. This filter allows only specific wavelengths to pass through, reducing the dynamic range of light reaching the sensor and thereby improving exposure estimation accuracy. While it does increase device complexity through additional optical components, the filter integrates into the existing optical path without requiring fundamental system redesign.
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 enhances responsiveness and quality of image capture by ensuring optimal exposure and illumination, reducing frame wastage and improving the accuracy of code symbol reading in continuous video image capture.
Implementation Method 1
An LED-based illumination subsystem, with an LED illumination array, for producing a field of narrow-band illumination within the FOV
Implementation Method 2
an optical band-pass filter to reduce dynamic range and improve exposure estimation
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An adaptive strobe illumination control process for use in a digital image capture and processing system. In general, the process involves: (i) illuminating an object in the field of view (FOV) with several different pulses of strobe (i.e. stroboscopic) illumination over a pair of consecutive video image frames; (ii) detecting digital images of the illuminated object over these consecutive image frames; and (iii) decode processing the digital images in an effort to read a code symbol graphically encoded therein. In a first illustrative embodiment, upon failure to read a code symbol graphically encoded in one of the first and second images, these digital images are analyzed in real-time, and based on the results of this real-time image analysis, the exposure time (i.e. photonic integration time interval) is automatically adjusted during subsequent image frames (i.e. image acquisition cycles) according to the principles of the present disclosure. In a second illustrative embodiment, upon failure to read a code symbol graphically encoded in one of the first and second images, these digital images are analyzed in real-time, and based on the results of this real-time image analysis, the energy level of the strobe illumination is automatically adjusted during subsequent image frames (i.e. image acquisition cycles) according to the principles of the present disclosure.