Gradient-Index Rod Lens Array for Equal-Magnification Imaging
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Solution Overview
Problem
Conventional rod lens arrays in contact image sensors (CIS) struggle to achieve high accuracy in image magnification and measurement, particularly in applications requiring precision within 0.1 mm, leading to issues like color bleeding and distortion in printing and inspection devices.
Innovation Solution
A rod lens array with gradient index lenses arranged in the main scanning direction, ensuring parallel optical axes and specific parameters such as ΔW, ΔX, and St, along with a refractive index distribution and aperture angle, to form an erect equal-magnification image, enhancing measurement accuracy to 0.1 mm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional rod lens arrays are used in contact image sensors, then the optical system is compact and easy to install, but the measurement accuracy cannot achieve 0.1 mm precision
Solution Approach 1:
The patent applies parameter changes by optimizing the refractive index distribution parameter g within the range 0.05 < g ≤ 0.45, and controlling the rod lens array parameters including aperture angle γ (10° ≤ γ ≤ 30°), inter-lens distance s (0.5 mm ≤ s ≤ 2.0 mm), and rod lens diameter φ (1.0 mm ≤ φ ≤ 3.0 mm). These parameter optimizations enable the rod lens array to achieve equal magnification with 0.1 mm measurement accuracy while maintaining the compact optical system structure.
2Manufacturing precision
If conventional rod lens arrays are used, then the device structure is simple, but distortion aberration occurs and equal magnification cannot be achieved
Solution Approach 1:
The patent achieves equal magnification by optimizing the refractive index distribution parameter g (0.05 < g ≤ 0.45) and controlling the aperture angle γ (10° ≤ γ ≤ 30°). This eliminates distortion aberration while maintaining the simple rod lens array structure without requiring complex additional optical components.
3Measurement precision
If the rod lens array parameters are not optimized, then the device is compact, but measurement accuracy within 0.1 mm cannot be achieved
Solution Approach 1:
The patent achieves 0.1 mm measurement accuracy by optimizing the refractive index distribution parameter g (0.05 < g ≤ 0.45) and controlling the aperture angle γ (10° ≤ γ ≤ 30°), inter-lens distance s (0.5 mm ≤ s ≤ 2.0 mm), and rod lens diameter φ (1.0 mm ≤ φ ≤ 3.0 mm). These optimized parameters enable high precision measurement while keeping the optical system compact.
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 improves the equal magnification and measurement accuracy of the rod lens array, enabling precise image formation and inspection with reduced aberrations, suitable for high-precision applications like image dimension measuring devices.
Implementation Method 1
A rod lens is a cylindrical lens having an axisymmetric refractive index distribution in which a refractive index decreases from a center toward a peripheral portion
Data Source
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Figure 3~4B
AI summary
A rod lens array in which a plurality of gradient index rod lenses 12 are arranged in a main scanning direction such that optical axes thereof are substantially parallel satisfies 0.01 [mm] ≤ ΔW ≤ 0.1 [mm] when a substantially erect equal-magnification image of an object surface OS is formed on an image surface IS (Note that ΔW is an absolute value of a difference between a length Wob of the object in the main scanning direction and a length Wim of the image in the main scanning direction).