Document Feeder Mirror Positioning for Dust Reduction
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Solution Overview
Problem
Conventional back surface reading parts in document feeders are prone to dust streaks in read images due to dust adhering to the reflective surface of the first mirror, which is positioned close to the document reading position.
Innovation Solution
Positioning the first mirror farther away from the document reading position than other reflecting mirrors in the optical axis direction, or opposite to the document reading position with respect to the optical path, and arranging it to intersect with other optical paths to maximize distance within a limited volume, while ensuring the first mirror is in contact with a protrusion or the inner wall surface to prevent dust accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the first mirror is positioned close to the document reading position to secure sufficient optical path length, then the optical path length is improved, but dust streaks in read images increase due to dust adhering to the mirror surface
Solution Approach 1:
The patent positions the first mirror farther away from the document reading position in the optical axis direction, utilizing the third dimension (depth along the optical axis) to resolve the contradiction. By redistributing mirror positions along the optical axis rather than keeping them close to the document, the patent achieves both sufficient optical path length and reduced dust adhesion, as the first mirror is positioned opposite to the document reading position with respect to the optical path connecting the last reflecting mirror and the photoelectric transducer
2Object-affected harmful factors
If the first mirror is positioned farther away from the document reading position to reduce dust influence, then dust streaks are reduced, but the optical path length may be insufficient within limited volume
Solution Approach 1:
The patent utilizes the optical axis direction (third dimension) to position mirrors at optimized distances from the document reading position. By arranging the first mirror opposite to the document reading position with respect to the optical path connecting the last reflecting mirror and the photoelectric transducer, the patent maximizes the distance of the first mirror from the document while still achieving sufficient optical path length through the multi-mirror reflection system
Solution Approach 2:
The patent employs multiple reflecting mirrors arranged in sequence within the limited volume of the document feeder. The optical path is folded back and forth through the housing using these nested mirror arrangements, allowing the light to travel a sufficient optical path length while keeping the physical footprint compact and maintaining appropriate distances from the document reading position
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 configuration reduces the influence of dust on the first mirror, minimizing dust streaks in read images and efficiently securing an optical path length within the limited volume of the document feeder.
Implementation Method 1
reads an image by reflecting light reflected at a document reading position of the document and directing the light to be incident on the photoelectric transducer with the plurality of reflecting mirrors
Implementation Method 2
read the light incident on the CCD through the lens
Implementation Method 3
a CCD (photoelectric transducer) as an image reading means
Data Source
AI summary
An image reader used as a back surface reading unit includes LEDs, a first mirror, a second mirror, a third mirror, a lens, and a CCD inside a housing. The first mirror, which first reflects light reflected from the document, is positioned farther away from the document reading position than other reflecting mirrors (i.e. the second mirror and the third mirror) in an optical axis direction of the optical path connecting the document reading position and the first mirror.