Telecentric Image Reading Apparatus with Multi-Cell Optics
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Solution Overview
Problem
Conventional image reading apparatuses face challenges in achieving a large depth of field while maintaining a compact size and preventing image distortion, due to issues such as chromatic aberration, mirror alignment errors, and increased complexity with bending mirrors.
Innovation Solution
The apparatus employs a telecentric optics system with a plurality of cells arranged in a zigzag pattern in the main scanning direction and two rows in the sub-scanning direction, using first and second reflective light-gathering optical elements with an aperture at the back focal point of the first element, eliminating bending mirrors and reducing incident angles to minimize distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-eye lens system is used to read the entire image in the main scanning direction, then the depth of field is large (several millimeters), but the optics system becomes large in size
Solution Approach 1:
The patent divides the imaging optics system into multiple cells (first cell, second cell, third cell, fourth cell) arranged in a 2x2 matrix, each cell independently imaging a portion of the document onto corresponding image pickup devices. This segmentation allows the system to achieve large depth of field through telecentric design while reducing the overall optics system size compared to a single large-eye lens system.
2Ease of operation
If bending mirrors are used to change the optical path direction, then the optical path can be redirected, but image distortion occurs due to mirror alignment errors and manufacturing errors
Solution Approach 1:
The patent removes bending mirrors from the optical path entirely. Instead of using mirrors to redirect light, the system employs multiple cells with reflective light-gathering optical elements that directly image the document onto the image pickup devices. This extraction of the problematic bending mirror component eliminates the source of alignment errors and manufacturing errors that cause image distortion.
Solution Approach 2:
Rather than using bending mirrors to change the optical path direction (the conventional approach), the patent inverts the approach by arranging multiple cells in a matrix configuration where each cell's optical axis is perpendicular to the document surface, eliminating the need for optical path bending and thereby eliminating distortion from mirror alignment errors.
3Productivity
If multiple mirrors are arranged in the optical path to scan the entire document, then the document can be scanned, but the moving speed control becomes complex to prevent optical path changes
Solution Approach 1:
The patent employs a movable document table that scans the document in the sub-scanning direction while the multiple cells simultaneously capture images across the main scanning direction. This dynamic scanning approach eliminates the need for multiple moving mirrors and complex speed control mechanisms, as the document itself moves through the stationary multi-cell imaging system.
4Volume of stationary object
If the incident angle of light beams is large, then the optics system can be compact, but distortion increases due to manufacturing and installation errors
Solution Approach 1:
The patent designs each cell with the aperture positioned at the back focal point of the reflective light-gathering optical element, creating a telecentric optics system. This equipotential design ensures that light beams from different object points all converge at the same focal plane regardless of incident angle variations, making the system insensitive to manufacturing and installation errors while maintaining compact dimensions.
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 allows for a high-quality image with a large depth of field, reduced size, and minimized distortion, as the telecentric optics system maintains consistent transfer magnification and reduces the impact of manufacturing and installation errors.
Implementation Method 1
a first reflective light-gathering optical element which reflects and condenses light from the document
Implementation Method 2
reflects and condenses light from the document to form an intermediate image at its back focal point
Implementation Method 3
an aperture which transmits light beams from the back focal point of the first reflective light-gathering optical element to the second reflective light-gathering optical element
Implementation Method 4
a second reflective light-gathering optical element which reflects and condenses light from the aperture to form an image on the image pickup device
Implementation Method 5
reflects and condenses light from the aperture to form an image on the image pickup device
Data Source
AI summary
The object of the present invention is to provide an image reading apparatus having a large depth of field and being compact in size.The image reading apparatus includes a light source, an imaging optics system, an image pickup device unit, a memory, and a processor. The imaging optics system has a plurality of cells each being an independent optics system arranged in a main scanning direction, and arranged in two rows in a sub-scanning direction. In each of the cells, a first reflective light-gathering optical element, a first plane mirror, an aperture, and a second reflective light-gathering optical element are arranged in this order from a document, and the aperture is arranged at the back focal point position of the first reflective light-gathering optical element to form a telecentric optics system at the side of the document.