Image Reading Device Light Amount Adjustment
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Solution Overview
Problem
Image reading devices face challenges in accurately setting the amounts of red, green, and blue light for monochrome mode, as increasing electric current to light sources by a uniform percentage does not allow for precise adjustments, leading to suboptimal light emission and image quality.
Innovation Solution
The implementation of a light-amount adjusting section that uses pulse width modulation (PWM) to adjust the lighting periods of red, green, and blue light sources based on white and black reference data, allowing for precise calibration of light amounts in both color and monochrome modes, ensuring optimal image reading with good white balance and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the amounts of red, green, and blue light are increased by increasing the electric current supplied to each light source by the same percentage, then the light emission amount increases to reduce the influence of decrease over time, but the settings cannot achieve highly accurate light amounts for monochrome mode reading
Solution Approach 1:
The patent changes the control parameter from electric current amplitude to pulse width (duty cycle) of PWM signals. By varying the pulse width while maintaining constant current amplitude, the system achieves precise control over light emission amounts for each color channel independently, resolving the inability to accurately adjust monochrome mode light amounts that plagued the uniform current increase approach
Solution Approach 2:
The patent introduces dynamic adjustment capability through PWM control, allowing the light emission amounts of red, green, and blue light sources to be independently and flexibly adjusted. This dynamic control enables the system to adaptively optimize light amounts for monochrome mode based on actual reading requirements, rather than relying on static uniform percentage increases
2Productivity
If the red, green, and blue light sources are lighted at the same time in monochrome mode to shorten reading time, then productivity increases, but the photodetector requires increased dynamic range to handle the combined light amounts
Solution Approach 1:
The patent employs periodic pulse width modulation to control the light sources. By using periodic PWM signals with adjustable duty cycles, the system can precisely control the effective light emission duration for each color channel, enabling simultaneous lighting in monochrome mode while maintaining manageable light amounts through temporal control rather than requiring excessive dynamic range
Solution Approach 2:
The patent changes the control approach from adjusting current amplitude to varying pulse width parameters. This allows the system to maintain high productivity through simultaneous lighting while controlling the effective light exposure through duty cycle adjustment, thereby managing the photodetector's dynamic range requirements without sacrificing reading speed
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 enables highly accurate settings for light emission in monochrome mode, improving image quality by ensuring the light amounts reach target values, even when initial settings fall short or are affected by offsets, resulting in enhanced dynamic range and white balance.
Implementation Method 1
an image reading device reads an image of an original document by a photodetector detecting light reflected from the surface of the original document that is illuminated with light emitted by a light source
Implementation Method 2
a photodetector detecting light reflected from the surface of the original document that is illuminated with light emitted by a light source
Implementation Method 3
a light-amount adjusting section that uses pulse width modulation (PWM) to adjust the lighting periods of red, green, and blue light sources
Data Source
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AI summary
An image reading device (10) includes a red light source (21r), a green light source (21g), a blue light source (21b), a white reference plate (50), a light-amount adjusting section (40), a photo-detecting section (27), and a signal processing section (31). The light-amount adjusting section (40) sets lighting periods of the red, green, and blue light sources (21r, 21g, 21b) for reading in a monochrome mode, based on: lighting periods of the red, green, and blue light sources (21r, 21g, 21b) set for reading in a color mode; and a result of detection performed by the photo-detecting section (27) when the white reference plate (50) is illuminated with the red light, the green light, and the blue light respectively emitted by the red, green, and blue light sources (21r, 21g, 21b) for the respective lighting periods set for reading in the color mode.