CCD Sensor Integration Time Compensation for Variable Speed Scanning
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Solution Overview
Problem
Scanning systems using cheap CCD sensors face challenges in maintaining consistent image intensity due to variation in integration time, leading to variations in scan speed and image intensity across scanlines, limiting their ability to support variable speed scanning.
Innovation Solution
Implementing digital processing techniques to apply a multiplicative compensation factor to sensed intensity values, adjusting them to match a reference nominal integration time, allowing for variable speed scanning while maintaining consistent image intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If variable speed scanning is implemented, then scanning flexibility and productivity are improved, but image intensity consistency deteriorates due to integration time variation
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the integration time of the CCD sensor to match the variable scan speed. When scan speed varies, the integration time is proportionally adjusted to maintain constant light accumulation, thereby preserving image intensity consistency across scanlines while enabling flexible scanning speeds.
Solution Approach 2:
The patent implements feedback control by monitoring the actual scan speed and using this information to adjust the integration time accordingly. The system measures the scan speed variation and feeds this information back to the sensor control to modify the integration time, ensuring that image intensity remains consistent despite speed variations.
2Manufacturing precision
If integration time is kept constant, then image intensity consistency is maintained, but scanning speed must remain fixed limiting flexibility
Solution Approach 1:
The patent resolves this contradiction by making the integration time a dynamic parameter that changes with scan speed. Instead of keeping integration time constant, the system adjusts it proportionally to the scan speed variations, allowing both image intensity consistency and scanning speed flexibility to coexist.
Solution Approach 2:
The patent applies dynamics by transitioning from a static integration time to a dynamic one that adapts to changing scan conditions. The integration time becomes a variable parameter that automatically adjusts based on the actual scan speed, enabling the system to maintain image quality while adapting to different scanning requirements.
3Ease of manufacture
If cheapest CCD sensors are used, then device cost is reduced, but control over integration time is lost
Solution Approach 1:
The patent introduces an intermediary control mechanism that mediates between the limited capabilities of cheap CCD sensors and the requirement for variable integration time. By using the start-of-scanline pulse timing as an intermediary parameter, the system indirectly controls the effective integration time without requiring expensive dedicated control circuitry.
Solution Approach 2:
The patent makes the existing start-of-scanline pulse generation circuit perform a dual function: it continues to initiate scanline reading while simultaneously controlling the integration time duration. This multi-functionality eliminates the need for separate integration time control circuitry, maintaining device simplicity while achieving the required functionality.
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 scanning systems with cheap CCD sensors to support variable speed scanning by compensating for integration time variations, ensuring consistent image intensity across scanlines, thereby improving image quality and flexibility.
Implementation Method 1
For CIS and CCD linear image sensors, the magnitude of the sensed image signal is determined by the incident light intensity and the integration time. The integration time is the time for which the CIS/CCD sensor elements are allowed to accumulate light.
Data Source
AI summary
A method of compensating for image intensity variation in a scanline of a scanned image caused by variation in sensor integration time in a non-shuttered CCD image sensor comprising the steps of (a) determining for the scanline a multiplicative compensation factor, Kc (b) multiplying the sensed intensity of light received by sensor elements present in the CCD image sensor for the scanline by Kc to produce a compensated intensity value for the scanline and (c) employing the compensated intensity value in an image processing pipeline to produce the scanned image.