Imaging Reader Illumination Control for Rolling Shutter Energy Reduction
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Solution Overview
Problem
Imaging readers with rolling shutter sensors inefficiently use illumination light, leading to excessive electrical energy consumption, heat generation, and annoyance due to bright illumination, especially in environments with short exposure times and long frames.
Innovation Solution
A control system and method that modulate illumination power in real-time based on exposure time, maintaining maximum power only when exposure time and gain exceed minimum thresholds, and lowering power when they do not, while keeping exposure and gain constant at minimum thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the illuminating light assembly is kept on at maximum power throughout the entire frame time for rolling shutter sensors, then the entire target image can be captured, but electrical energy consumption increases excessively
Solution Approach 1:
The illuminating light assembly operates in periodic pulses synchronized with the rolling shutter exposure periods rather than continuously throughout the entire frame time. Each pulse illuminates only during the active exposure window of rolling shutter pixels, eliminating wasted illumination during non-exposure periods while ensuring complete target capture.
Solution Approach 2:
The illumination duty cycle is dynamically adjusted to match the exposure time-to-frame-time ratio. When exposure time decreases relative to frame time, the illumination is activated only during the exposure window rather than continuously, optimizing energy efficiency while maintaining image capture quality.
2Illumination intensity
If the illuminating light assembly operates continuously at maximum power, then sufficient illumination is provided for image capture, but waste heat generation increases
Solution Approach 1:
The illumination system uses periodic pulsed operation synchronized with rolling shutter exposure windows instead of continuous maximum power operation. This reduces the total duration of high-power illumination while maintaining sufficient light levels during critical exposure periods, thereby reducing waste heat generation.
3Illumination intensity
If the illuminating light assembly is kept on at high intensity throughout the frame time, then the target is well illuminated, but operator annoyance increases
Solution Approach 1:
The illumination is delivered in brief periodic pulses only during rolling shutter exposure windows rather than continuously throughout the frame period. This dramatically reduces the total duration of visible illumination to operators while ensuring adequate target brightness during the brief exposure intervals when the sensor is actively capturing light.
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 reduces electrical energy consumption, minimizes waste heat, and decreases illumination annoyance, extending battery life and improving user comfort without compromising reading performance.
Implementation Method 1
an imaging assembly having a solid-state imager or imaging sensor with an array of photocells or pixels, which correspond to image elements or pixels in an imaging field of view of the sensor
Implementation Method 2
the return light captured by the sensor includes the returning illumination light and any ambient light in the vicinity of the reader
Implementation Method 3
capturing return light scattered and/or reflected from the target being imaged
Data Source
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AI summary
An imaging reader has an illuminating light assembly for illuminating a target with illumination light, and a solid-state image sensor with a rolling shutter for sequentially exposing an array of pixels to capture an image from the illuminated target. Target illumination is controlled by controlling an exposure time and a gain of the sensor, and by controlling an output power of the illumination light. The output power is maintained at a maximum level when the exposure time and/or the gain exceed a minimum threshold, and is lowered when the exposure time and/or the gain does not exceed the minimum threshold, while concomitantly maintaining the exposure time and/or the gain constant at the minimum threshold.