Image Reading Device Mirror Array Depth of Field
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Solution Overview
Problem
Conventional image reading devices face challenges in achieving a balance between depth of field and optical path length, with reduction optical systems having deep depth of field but long optical path lengths and unity magnification systems having shallow depth of field and image bleeding issues, while also being costly due to the need for multiple lenses and mirrors.
Innovation Solution
An image reading device with a reading module that uses a mirror array with aspherical concave reflection surfaces and aperture stop portions to adjust image light, employing a telecentric optical system and a reference drawing pattern to connect images imaged in different regions, minimizing chromatic aberration and image blurring, and allowing for a deep depth of field without the need for multiple lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reduction optical system is used, then depth of field is deep, but optical path length becomes very long (200 to 500 mm)
Solution Approach 1:
The optical system is divided into multiple rod lenses arranged in an array, each responsible for imaging a specific region of the document. This segmentation allows the use of shorter optical paths for each individual lens while collectively covering the entire document area, achieving compactness without sacrificing imaging quality.
Solution Approach 2:
The patent transitions from a single-point imaging approach to a multi-point array imaging approach by arranging multiple rod lenses in an array configuration. This dimensional change from one-dimensional to two-dimensional lens arrangement enables parallel imaging of multiple document regions, reducing the required optical path length while maintaining deep depth of field characteristics.
2Length of stationary object
If a unity magnification optical system with rod lenses is used, then optical path length is short and construction is simple, but depth of field is very small causing image bleeding
Solution Approach 1:
Each rod lens in the array is designed with specific local optical characteristics optimized for its particular position and function. The aspherical surfaces of individual lenses are tailored to correct aberrations in their respective imaging regions, allowing the system to achieve adequate depth of field locally while maintaining compact overall dimensions.
3Manufacturing precision
If multiple lenses are used to correct chromatic aberration, then imaging quality improves, but cost increases
Solution Approach 1:
The patent extracts and eliminates unnecessary optical components from the system. By using a telecentric optical system with carefully designed rod lenses, chromatic aberration correction is achieved with fewer lenses than conventional systems, reducing both cost and complexity while maintaining imaging quality.
4Volume of moving object
If multiple mirrors are used in the reduction optical system, then optical path direction is changed to fit limited space, but number of components increases leading to increased cost
Solution Approach 1:
The patent replaces the mechanical mirror-based optical path folding system with a streamlined rod lens array configuration. This substitution eliminates the need for multiple mirrors and their associated mounting mechanisms, reducing component count and complexity while achieving compact carriage integration through the inherent geometry of the rod lens array.
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
The solution provides an image reading device with a deep depth of field that suppresses image blurring and reduces costs by eliminating the need for multiple lenses and mirrors, enabling efficient image capture of documents with varying surfaces and orientations.
Implementation Method 1
a plurality of reflection mirrors whose reflection surfaces are aspherical concave surfaces are coupled together in an array in the main scanning direction
Implementation Method 2
reflection surfaces are aspherical concave surfaces
Implementation Method 3
The aperture stop portions are each arranged in an optical path of image light between a reflection mirror and an imaging region of the sensor, and adjust the amount of image light reflected from the reflection mirror
Implementation Method 4
a plurality of imaging regions for converting the image light imaged by the optical system into an electrical signal
Data Source
AI summary
An image reading device has a reading module including a light source, an optical system having a mirror array where reflection mirrors are coupled together in the main scanning direction and an aperture stop portion, a sensor where imaging regions for converting the image light imaged by the optical system into an electrical signal are arranged, and a housing, and has a reference drawing pattern determining connection positions between the imaging regions. The reference drawing pattern is composed of a plurality of pixel cut lines arranged to correspond to boundary lines between the reflection mirrors. The optical system is fixed on the housing at one point in the main scanning direction, and the pixel cut lines are arranged such that their distances from the boundary lines in the main scanning direction increase the farther away from the fixed position of the optical system in the main scanning direction.