Contact Image Sensor Light Guide for Bright Output Correction
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Solution Overview
Problem
Contact image sensors face instability in bright output due to fluctuations in light source intensity caused by environmental temperature and chronological factors, and existing reference data methods, such as using light reflected by a platen roller or white reference tape, are inaccurate or unfeasible, leading to unstable image reading.
Innovation Solution
A contact image sensor design with a light guide system that includes a first exit for illuminating the document and a second exit for direct light to a corrective light receiver, allowing for accurate reference data collection and correction of bright output using a corrector that compares criterion data with reference data from the corrective light receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light reflected by platen roller is used as reference data, then bright output correction can be performed, but reference data cannot be acquired because light receiving element cannot receive light reflected by platen roller while document is positioned
Solution Approach 1:
The light guide is divided into two separate exit parts: a first exit part for emitting light to the document and a second exit part for emitting light to the corrective light receiver. This segmentation allows the reference data acquisition function to be independently implemented without interfering with the document reading function, resolving the conflict between acquiring reference data and positioning the document.
2Measurement precision
If white reference tape is provided on platen glass, then reference data can be acquired, but environmental temperature fluctuation degrades reference data accuracy due to different coefficients of linear expansion
Solution Approach 1:
The light guide acts as an intermediary between the light source and the corrective light receiver. Light travels through the light guide's internal structure (total internal reflection) rather than passing through the platen glass, eliminating the thermal expansion issue. The light guide's enclosed light path isolates the reference data acquisition from environmental temperature fluctuations affecting the platen glass.
3Measurement precision
If light reflected by document is used for correction, then correction can be performed, but document presence and density affect accuracy adversely
Solution Approach 1:
The reference data acquisition path is extracted from the document reading path. The corrective light receiver captures light through the second exit part of the light guide independently of the document, separating the reference measurement function from the document processing function. This eliminates document presence and density from affecting reference data accuracy.
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 stable bright output correction by using direct light reference data, independent of environmental fluctuations and document presence, improving image reading accuracy and reliability.
Implementation Method 1
a light guide in which light emitted from the light source propagates, the light guide having a first exit part for emitting the light to the target to be read and a second exit part
Implementation Method 2
a reading light receiver that generates image data representing an image of the target to be read by photoelectrically converting the light emitted from the first exit part and reflected by the target to be read
Data Source
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AI summary
A light source unit (105) emits light for irradiating a document. A light guide 104 in which light emitted from the light source unit (105) propagates has a first exit part for emitting light to the document and a second exit part (115), which is a different part from the first light part, for emitting light to the outside. A corrective light receiver (106) is disposed in an area receiving direct light of the light emitted from the second exit part (115), and outputs reference data corresponding to the direct light. A controller compares predetermined criterion data with the reference data output from the corrective light receiver (106), and performs processing for correcting a bright output based on a result of the comparison.