Telecentric Optical Line Sensor Layout for Deep Depth of Field
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Solution Overview
Problem
Existing optical line sensors face challenges in achieving a compact size with a deep depth of field and long working distance, and they are prone to optical axis deviations and performance degradation due to complex optical systems and environmental changes.
Innovation Solution
An optical line sensor design featuring a telecentric optical system with light receiving lenses arranged in a staggered manner along the main scanning direction and light receiving elements in multiple rows, where the width in the sub-scanning direction is smaller than in the main scanning direction, allowing for a compact design and improved depth of field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a telecentric reflection optical system using a mirror optical system is used to achieve a deep depth of field, then the depth of field is improved, but the device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The patent replaces the mirror optical system (mechanical reflection system) with a refractive optical system using lenses. Specifically, it uses a meniscus lens with specific curvature radii and focal length to achieve the telecentric optical system, thereby simplifying the optical path and reducing system complexity while maintaining deep depth of field capability
Solution Approach 2:
The patent specifies precise parameter ranges for the meniscus lens including curvature radii (R1: -50mm to -100mm, R2: 50mm to 100mm), focal length (20mm to 50mm), and thickness (5mm to 15mm) to optimize the balance between depth of field, working distance, and system compactness. These parameter changes enable the refractive system to achieve performance comparable to the reflection system
2Ease of manufacture
If a simple refractive lens system is used to reduce device complexity, then the ease of manufacture is improved, but the working distance and depth of field are insufficient
Solution Approach 1:
The patent achieves deep depth of field and long working distance with a simple meniscus lens design by optimizing specific parameters: curvature radii ratio (|R1/R2| between 0.8 and 1.2), focal length (20-50mm), and thickness (5-15mm). This single lens design eliminates the need for complex multi-element lenses or mirror systems while achieving the required optical performance
Solution Approach 2:
The patent employs an asymmetric meniscus lens design where the curvature radii of the two surfaces have opposite signs (one convex, one concave) and specific magnitude relationships. This asymmetric configuration enables the lens to achieve telecentric optical characteristics and deep depth of field that symmetric lenses cannot provide, while maintaining manufacturing simplicity
3Manufacturing precision
If lenses are spaced apart to prevent crosstalk, then the depth of field is improved, but shading effects cause optical unevenness and reading completeness deteriorates
Solution Approach 1:
The patent converts the harmful shading effect caused by spaced-apart lenses into a beneficial light distribution pattern. By positioning the light source at a specific location (above or below the inspection surface at 30°-60° angle) and using a diffusing plate, the light naturally fills the gaps between lenses while creating a uniform illumination pattern that compensates for the shading, thereby preventing missing pixels and maintaining reading completeness
4Volume of moving object
If a compact design is pursued by reducing lens size, then the device size is reduced, but the working distance and depth of field are compromised
Solution Approach 1:
The patent achieves a compact sensor design with working distance of 20-50mm and depth of field of 10mm or more by optimizing the meniscus lens parameters: focal length (20-50mm), thickness (5-15mm), and curvature radii (R1: -50mm to -100mm, R2: 50mm to 100mm). This compact configuration maintains long working distance and deep depth of field while reducing overall sensor size for easy integration into manufacturing processes
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 sensor achieves a deep depth of field and long working distance while maintaining compactness, reducing manufacturing complexity and cost, and minimizing optical axis deviations.
Implementation Method 1
a new refractive system lens having a long W.D. and a deep depth of field
Implementation Method 2
The plurality of light receiving lenses constitute a telecentric optical system
Data Source
AI summary
A plurality of light receiving lenses are arranged along a main scanning direction. A plurality of light receiving elements are arranged in a line along the main scanning direction, and receive light transmitted through the plurality of light receiving lenses. The plurality of light receiving elements form at least two rows of reading lines. The light receiving lenses constitute a telecentric optical system, and a width W1 in a sub-scanning direction is smaller than a width W2 in the main scanning direction.