Reimaging Optical System for Endoscope Image Magnification
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Solution Overview
Problem
Conventional endoscope systems face challenges in providing adequate image magnification and quality for observation by multiple users, with existing reimaging optical systems struggling to form clear images on CCDs with diagonal lengths of 6.5 mm or longer, leading to noise and image deterioration when images are electrically enlarged.
Innovation Solution
A reimaging optical system is designed with specific conditions to ensure improved magnification and image quality, comprising a front unit, stop, and rear unit, with a lens arrangement that includes positive and negative lenses, and an optical low-pass filter located on the image guide side, along with a white light emitting diode as the light source, which enhances image reproduction without the need for color correction filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the transverse magnification of the reimaging optical system is increased to form adequate images on a CCD with a diagonal length of 6.5 mm or longer, then the image quality and observation capability are improved, but the optical system becomes more complex and the focal length increases
Solution Approach 1:
The reimaging optical system is divided into multiple lens groups (first lens group with positive power and second lens group with negative power) rather than using a single complex lens. This segmentation allows each group to contribute differently to the overall magnification while controlling aberrations, achieving high transverse magnification (0.6D×|β|/V ≥ 0.6) without excessive system complexity
Solution Approach 2:
The patent specifies particular parameter ranges for the lens groups, including the focal length ratio (1 < fF/F ≤ 2.5) and power distribution (0.9 < f2P/F ≤ 3), to optimize the balance between magnification capability and system complexity. By carefully controlling these parameters, the system achieves adequate image formation on large CCDs without requiring overly complex optical designs
2Length of moving object
If the focal length of the front unit is decreased to reduce the overall system length, then the portability is improved, but spherical aberrations increase and imaging capability deteriorates
Solution Approach 1:
The front unit is designed with specific local optical properties through the combination of positive and negative lens groups, each with predetermined power ratios. The first lens group (positive power) and second lens group (negative power) are positioned and sized to locally correct spherical aberrations while maintaining short overall focal length (1 < fF/F ≤ 2.5), thus achieving compact size without sacrificing imaging capability
Solution Approach 2:
The optical system uses a composite lens structure combining materials with different refractive indices and dispersion properties in the cemented lens configurations. This allows the system to achieve short focal length while correcting spherical aberrations through the complementary optical properties of different lens materials
3Measurement precision
If electrical enlargement is applied to increase the image size on the display, then the observation capability is improved, but noise and image quality deterioration increase
Solution Approach 1:
Instead of relying on post-capture electrical enlargement that amplifies noise, the optical system performs preliminary optical enlargement through the reimaging optical system with transverse magnification designed to directly form adequately sized images on the CCD sensor. This preliminary optical action ensures the image is sufficiently large at the sensor level without requiring aggressive digital zooming that would amplify noise and deteriorate quality
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 reimaging optical system effectively forms images on a solid-state imaging device with improved magnification and reduced aberrations, allowing for clear observation by multiple users without image quality deterioration, even when images are electrically enlarged, and enhances the portability of the endoscope by eliminating the need for bulky components.
Implementation Method 1
a reimaging optical system adapted to re-form an image by an image guide on a solid-state imaging device
Implementation Method 2
β is the optical transverse magnification of said reimaging optical system
Implementation Method 3
a white light emitting diode as the light source, which enhances image reproduction
Data Source
AI summary
The invention relates to an reimaging optical system that has a sufficiently enhanced magnification and better performance, and an endoscope using the same. The reimaging optical system 3 is adapted to re-form an image by an image guide 6 on a solid-state imaging device 4 having a diagonal length of 6.5 mm or longer, and satisfies the following condition.0.6<(D×|β|)/V (1).Here D is the diameter of the image guide 6, β is the optical transverse magnification of the reimaging optical system 3, and V in mm is the minor axis direction length of an imaging area of the solid-state imaging device 4.