Contact Image Scanner LED Timing Control for Color Registration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Contact-type image scanners suffer from color misregistration due to time lags resulting from sequential turn-on operations of red, green, and blue LEDs during scanning, leading to scanning position errors and unsatisfactory color registration.
Innovation Solution
A method and apparatus for a contact-type image scanner that controls the on durations and sequences of red, green, and blue LEDs, where the second light source is turned on immediately after the first light source is turned off or after a delaying time, and all three are simultaneously turned on for shorter durations, optimizing the illumination energy and reducing scanning position errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the red, green, and blue LEDs are sequentially turned on during scanning, then each color can be illuminated separately, but color misregistration occurs due to time lags between color readings
Solution Approach 1:
The patent applies periodic action by using multiple start pulses (first, second, and third start pulses) to sequentially control the illumination of different color LEDs (red, green, blue) in a periodic cycle. Each start pulse triggers a specific color LED to illuminate, creating a time-multiplexed illumination sequence that systematically addresses color registration through controlled periodic operation
Solution Approach 2:
The patent changes the timing parameters of LED illumination by adjusting the on-durations (Tr, Tg, Tb) and inter-pulse intervals based on scanning speed. The control unit dynamically modifies these temporal parameters to compensate for scanning-induced color misregistration, transforming the timing characteristics of the illumination sequence to maintain color alignment accuracy
2Productivity
If the scanning speed is increased to improve productivity, then more images can be scanned per unit time, but color misregistration worsens due to larger scanning position errors
Solution Approach 1:
The patent implements dynamics by making the LED illumination timing adaptive to scanning speed variations. The control unit adjusts the start pulse intervals and LED on-durations dynamically based on the actual scanning speed, transforming a static illumination sequence into a dynamic system that automatically compensates for speed-induced color misregistration
Solution Approach 2:
The patent employs feedback by using the scanning position information to adjust the timing of subsequent LED illumination sequences. The control unit monitors scanning progress and modifies the start pulse timing accordingly, creating a closed-loop system that corrects color misregistration in real-time based on actual scanning performance
3Illumination intensity
If the on duration of each LED is extended to improve illumination quality, then color brightness improves, but the time lag between colors increases causing worse color misregistration
Solution Approach 1:
The patent optimizes the LED on-durations (Tr, Tg, Tb) as adjustable parameters that balance illumination quality and timing precision. By carefully selecting and adjusting these duration parameters, the system achieves sufficient color brightness while minimizing the cumulative time lag between different color readings, thereby reducing color misregistration
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 minimizes color misregistration by reducing the overall time interval and enhancing scanning quality, ensuring uniform illumination and accurate data acquisition across the RGB color space, converting RGB to YCbCr for improved image processing.
Implementation Method 1
an illumination unit including a first light source, a second light source and a third light source for respectively emitting red, green and blue light beams on an original surface
Implementation Method 2
the photo-sensing unit for receiving the light beams reflected from the original surface
Implementation Method 3
a photo-sensing unit for receiving the light beams reflected from the original surface and outputting an image message
Data Source
AI summary
A contact-type image scanner includes an illumination unit, a control unit and a photo-sensing unit. The illumination unit includes a first, a second and a third light source for respectively emitting different color light beams on an original surface. The control unit is in communication with the illumination unit for controlling on durations of the light sources. In response to a first start pulse and a second start pulse, the first light source and the second light source are turned on for a first on duration and a second on duration respectively, wherein the second light source is turned on immediately after the first light source is turned off or after the first light source is turned off for a delaying time. In response to a third start pulse, the first, second and third light sources are simultaneously turned on for a first minor on duration, a second minor on duration and a third minor on duration, respectively. The photo-sensing unit obtains a first image data value during the first on duration, obtains a second image data value during a second on duration and obtains a third image data during the first, second and third minor on durations.