Endoscope Objective Optical System Compact Design
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Solution Overview
Problem
Endoscope objective optical systems face challenges in achieving stable focus adjustment and high-resolution image quality due to small depth of focus and sensitivity to manufacturing variations, particularly when reducing pixel pitch and diameter.
Innovation Solution
An endoscope objective optical system configuration with a front group having negative refractive power and a rear group with positive refractive power, including specific lens arrangements and conditional expressions to optimize focus adjustment and image quality, ensuring a bright and wide-angle high-resolution image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the Fno is reduced to make the objective optical system bright, then the brightness is improved, but the depth of focus becomes small
Solution Approach 1:
The patent applies parameter changes by optimizing the Fno value and the ratio of focal lengths (FL1/FL) within specific ranges. By carefully controlling these optical parameters, the system achieves a balance between brightness and depth of focus, resolving the contradiction between making the system bright and maintaining sufficient depth of focus.
2Measurement precision
If the pixel pitch is reduced to increase pixel number, then the image resolution is improved, but the objective optical system requires smaller size and higher brightness which reduces depth of focus
Solution Approach 1:
The patent addresses this contradiction by optimizing multiple parameters simultaneously: reducing the Fno for brightness, controlling the focal length ratio (FL1/FL) within 0.2-0.5, and designing a compact lens arrangement. These parameter changes enable the system to maintain high image resolution while achieving sufficient depth of focus despite the reduced pixel pitch.
3Length of moving object
If the diameter is reduced to make the endoscope compact, then the size is reduced, but the focus adjustment sensitivity increases making stable production difficult
Solution Approach 1:
The patent reduces diameter while controlling focus adjustment sensitivity by optimizing the focal length ratio (FL1/FL) between 0.2 and 0.5, and the Fno value. This parameter optimization allows compact diameter without excessive focus sensitivity, enabling stable production.
Solution Approach 2:
The patent introduces a focus adjustment device that can dynamically adjust the focus position to compensate for manufacturing variations. This dynamic adjustment mechanism allows the system to maintain high image quality despite variations in lens positioning, thereby improving manufacturing stability.
4Illumination intensity
If the Fno is reduced to increase brightness, then the brightness is improved, but the sensitivity of focus adjustment position increases making the system more susceptible to manufacturing variations
Solution Approach 1:
The patent optimizes the Fno value and the focal length ratio (FL1/FL) within specific ranges to achieve a balance between brightness and focus adjustment sensitivity. By controlling these parameters, the system maintains high brightness while reducing excessive sensitivity to focus position variations caused by manufacturing tolerances.
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 enables easy focus adjustment and achieves bright, wide-angle, high-resolution image quality while reducing manufacturing variations and susceptibility to focus shifts, ensuring stable production and improved image quality.
Implementation Method 1
a first lens, which is a single lens having negative refractive power
Implementation Method 2
a second lens, which is a single lens having positive refractive power
Implementation Method 3
a cemented lens formed of a fourth lens having positive refractive power and a fifth lens having negative refractive power
Implementation Method 4
a sixth lens having positive refractive power
Data Source
AI summary
An object of the present invention is to reduce the diameter, to make focus adjustment easy, and to achieve bright, wide-angle, high-resolution image quality.Provided is an endoscope objective optical system including, in this order from the object side, a front group having negative refractive power, an aperture stop, and a positive rear group. The front group includes, in this order from the object side, a first lens, which is a single lens having negative refractive power, and a second lens, which is a single lens having positive refractive power. The rear group includes a third lens, which is a single lens having positive refractive power, a cemented lens formed of a fourth lens having positive refractive power and a fifth lens having negative refractive power, and a sixth lens having positive refractive power. The object-side surface of the first lens is a flat surface, the second lens has as meniscus shape, and the sixth lens is joined to the image-acquisition element, and the endoscope objective optical system satisfies the following conditional expression:4<Fno×F6/F1_5<500 (1)where Fno is the effective F number of the endoscope objective optical system, F6 is the focal length of the sixth lens, and F1_5 is the composite focal length of the first to fifth lenses.