Imaging Bar Code Reader Adaptive Shutter Mode
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Solution Overview
Problem
Imaging-based bar code readers face challenges in ambient lighting conditions, as traditional rolling shutter mode provides good signal-to-noise ratio but requires long flash duration, while global shutter mode offers short flash duration but is costly and difficult to implement, and neither is adaptable to varying lighting conditions.
Innovation Solution
A 2D sensor array configured to operate in either rolling shutter or pseudo-global shutter mode based on ambient lighting conditions, with an image analysis system determining the mode of operation to ensure decodable images, and an illumination system emitting a pulse during common exposure time in pseudo-global shutter mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional rolling shutter mode is used, then signal-to-noise ratio is improved, but flash duration becomes excessively long
Solution Approach 1:
The patent implements dynamic switching between rolling shutter mode and pseudo-global shutter mode based on ambient lighting conditions. The system adapts its shutter operation dynamically: using rolling shutter in low-light conditions to maximize signal-to-noise ratio, and switching to pseudo-global shutter in bright conditions to enable short flash duration, thus resolving the contradiction between these two parameters.
2Duration of action of moving object
If global shutter mode is used, then flash duration is shortened, but device complexity and cost increase
Solution Approach 1:
The patent employs a pseudo-global shutter implementation that uses software-based exposure timing control rather than complex hardware modifications. This approach achieves short flash duration capability without requiring expensive global shutter hardware, memory buffers, or additional transistors per pixel, thus resolving the contradiction between flash duration and device complexity.
3Ease of manufacture
If rolling shutter mode is used, then ease of manufacture is improved, but adaptability to varying lighting conditions deteriorates
Solution Approach 1:
The system dynamically adapts between rolling shutter and pseudo-global shutter modes based on detected ambient lighting conditions. This dynamic adaptability allows the simple rolling shutter hardware to achieve the versatility of handling both low-light and bright-light scenarios, resolving the contradiction between ease of manufacture and adaptability.
Solution Approach 2:
The patent changes the operational parameters of the shutter system based on lighting conditions. By adjusting exposure timing and mode selection according to ambient light levels, the system maintains ease of manufacture while achieving adaptability to varying lighting environments.
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
Enables efficient imaging of bar codes in varying lighting conditions by adapting the shutter mode to maintain image quality and decoding accuracy, balancing the advantages of both rolling and global shutter modes without the drawbacks of additional complexity or cost.
Implementation Method 1
Light reflected from the target bar code is focused through a system of one or more lens of the imaging system onto the sensor array
Implementation Method 2
An illumination apparatus or system comprising light emitting diodes (LEDs) or other light source directs illumination toward a target object
Implementation Method 3
Light reflected from the target bar code is focused through a system of one or more lens of the imaging system onto the sensor array
Data Source
AI summary
An imaging system for use in an bar code reader for imaging a target bar code. The imaging system includes a 2D sensor array generating a series of image frames and The sensor array can be selectively operated in a rolling shutter mode of operation or a pseudo global shutter mode of operation. The imaging system further includes an imaging lens assembly to focus light from the field of view onto the sensor array and an image analysis system for analyzing the series of image frames generated by the sensor array for image brightness and, based on image brightness, operating the sensor array in a selected one of the rolling shutter mode of operation and the pseudo-global shutter mode of operation.