LED Illumination Control for Scanning System Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing scanner calibration methods fail to account for anomalies in test strips and variations in sensor sensitivity and LED illumination, leading to inconsistent image scanning and suboptimal signal-to-noise characteristics.
Innovation Solution
A method and system for dynamically adjusting the current to the illumination source based on the output of an analog-to-digital converter, using pulse width modulation to modulate the current within a range of 10 mA to 1 A, ensuring optimal light output and compensating for sensor sensitivity and reflectance variations, thereby setting the gain and offset of photosensors effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods using test strips are used, then calibration can be performed, but anomalies in test strips (dust, dirt, hair) cause measurement errors and inconsistent scanning results
Solution Approach 1:
The patent removes the test strip component from the calibration process entirely and replaces it with a digital reference image stored in memory. This extraction eliminates the source of physical contamination (dust, dirt, hair on test strips) while preserving the calibration function through software-based reference comparison.
Solution Approach 2:
The patent uses a digital copy (reference image stored in memory) instead of a physical test strip. The reference image can be a captured image of a standard test target or a pre-stored digital representation, which serves as the calibration reference without being subject to physical degradation or contamination.
2Ease of manufacture
If fixed LED current is used during calibration, then the calibration process is simple, but variations in LED illumination and sensor sensitivity lead to suboptimal signal-to-noise characteristics
Solution Approach 1:
The patent implements dynamic adjustment of LED current during the calibration process. The system measures the actual illumination output and sensor response, then adjusts the LED current to optimize the signal-to-noise ratio for each specific sensor-LED combination, accommodating manufacturing variations without increasing overall system complexity.
Solution Approach 2:
The calibration process incorporates feedback by measuring the actual sensor output in response to LED illumination and using this information to adjust the LED current. The system monitors the signal-to-noise characteristics and adjusts illumination levels to achieve optimal performance for each sensor element.
3Illumination intensity
If LED current is increased to improve illumination output, then brighter scanning is achieved, but sensor saturation occurs leading to loss of image detail
Solution Approach 1:
The patent dynamically changes the LED current parameter during calibration and operation based on measured sensor response. By adjusting the illumination intensity parameter to match each sensor's specific sensitivity characteristics, the system achieves optimal brightness without causing saturation, thereby preserving image detail across the full dynamic range.
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 ensures consistent and accurate image scanning by optimizing light output, improving signal-to-noise ratio, and accommodating a wider range of sensor sensitivities, reducing bit quantization and enhancing manufacturing yield by preventing saturation and underexposure.
Implementation Method 1
The light sources, such as light emitting diodes (LEDs), employed in scanners often vary in their performance due to process variations as well
Implementation Method 2
A scanner comprises a plurality of photosensors, typically in the form of a linear array, that move relative to an image on a sheet of paper. As the linear array of photosensors moves across the image, each photosensor outputs a series of signals related to the intensity of reflected light
Implementation Method 3
A method and system for dynamically adjusting the current to the illumination source based on the output of an analog-to-digital converter, using pulse width modulation to modulate the current within a range of 10 mA to 1 A
Data Source
AI summary
The present application discloses methods and systems for calibrating a scanning system. In one embodiment, the calibration method determines a dark level of at least one pixel, determines a maximum white level for at least one pixel and adjusts the current of an illumination source based upon an output of an analog to digital converter. In another embodiment, the scanning system has a circuit for dynamically adjusting the output of an illumination source. The circuit has a pulse width modulated signal generator for generating a pulse width modulated signal and a driver for receiving the pulse width modulated signal and causing current to the illumination source to be modulated based on the pulse width modulated signal.