Optical Scanner Light Intensity Compensation
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Solution Overview
Problem
Optical scanners face challenges in maintaining consistent light intensity due to variations in temperature and aging of light sources, leading to reduced image quality, as existing feedback systems struggle to accurately compensate for these changes.
Innovation Solution
A device with a specific configuration of photo sensors, where a subset of sensors measures light intensity from the light source independently of the object, allowing for continuous measurement and compensation of light source variations, thereby maintaining consistent image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LEDs are used as illumination source in contact image sensor, then power efficiency is improved, but light intensity varies with temperature and aging leading to reduced image quality
Solution Approach 1:
The patent implements a feedback system where photo sensors continuously monitor the light intensity emitted by the LED array, and a control unit adjusts the current to the LEDs based on this feedback to maintain constant illumination intensity despite temperature changes and aging effects
Solution Approach 2:
The patent replaces traditional mechanical or optical aperture control mechanisms with an electronic feedback control system that uses photo sensors and controlled current adjustment to regulate light intensity, enabling more precise and stable illumination control
2Reliability
If feedback system is added to control LED current, then light intensity stability is improved, but device complexity increases
Solution Approach 1:
The patent combines the feedback control functionality with the existing LED driver circuitry and photo sensor array, integrating the control unit into the scanner's existing architecture rather than adding completely separate systems, thereby reducing overall complexity
Solution Approach 2:
The photo sensors serve dual functions: they detect reflected light from the document for imaging purposes and simultaneously monitor the LED light output for feedback control, eliminating the need for separate dedicated sensors and reducing system complexity
3Reliability
If AGC function is added to correct illumination density, then image quality is improved, but processing time increases and continuous black signals may be falsely corrected to white signals
Solution Approach 1:
The patent extracts the illumination intensity measurement function from the document imaging process by using dedicated photo sensors that monitor only the LED output, separating the feedback control path from the document analysis path to avoid false corrections of black signals
Solution Approach 2:
The feedback control system continuously adjusts LED intensity in real-time before the scanning process begins, pre-compensating for illumination variations rather than correcting them during post-processing, thereby reducing processing time and avoiding false corrections
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 solution enables improved color intensity and uniformity in scanned images by compensating for light source variations, reducing the need for additional corrections and allowing for faster scanner startup, while being cost-effective for implementation in both new and existing scanners.
Implementation Method 1
a plurality of photo sensors (101) with a plurality of first photo sensors and, as a portion of said array, at least one second photo sensor, where the first photo sensors are arranged to detect light incident on the photo sensors, emitted from a light source (103) and reflected from an object subject to optical scanning
Implementation Method 2
The illumination in a contact image sensor may be provided by light-emitting diodes (LEDs) which are very precise components and may therefore be suitable for use in scanners
Data Source
Figure 1
Figure 2a~2b
Figure 2c
AI summary
Disclosed is a device for optical scanning, comprising: a plurality of photo sensors, where the photo sensors are arranged to detect light incident on the photo sensors, emitted from a light source and reflected from an object subject to optical scanning; wherein the amount of light received at at least one of the photo sensors is to a larger extent light transmitted from the light source; and to a smaller extent light reflected from the object.