Compact Observation Optical System Design
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Solution Overview
Problem
Conventional observation optical systems, like the Kepler type, sacrifice miniaturization and weight savings to achieve a wider apparent field of view, resulting in a bulky and heavy design.
Innovation Solution
A compact and lightweight observation optical system is achieved by incorporating an objective optical system, an inversion optical system that inverts the image, and an eyepiece optical system positioned close to the pupil, with specific focal length and refractive index ratios that satisfy conditional expressions to ensure miniaturization and weight savings while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the number of lenses is reduced in the observation optical system, then the device complexity and weight are reduced, but the apparent field of view becomes narrower and image quality deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the focal length ratio (f/F') between the objective optical system and eyepiece optical system within 1.05 to 1.30, and setting the inversion optical system's optical path length L within specific ranges (2.5mm ≤ L < 5.0mm or 5.0mm ≤ L < 7.5mm). These parameter optimizations enable a compact design with fewer lenses while maintaining an adequate apparent field of view of at least 30 degrees and correcting optical aberrations effectively.
2Productivity
If the focal length of the objective optical system is increased to achieve higher magnification, then the magnification power increases, but the overall system length increases
Solution Approach 1:
The patent achieves high magnification (40x or higher) in a compact form by optimizing the focal length ratio f/F' between the objective and eyepiece systems, and by precisely controlling the inversion optical system's optical path length L. This allows the objective optical system to have a longer focal length for high magnification while the overall system remains compact due to the optimized inversion system path length.
Solution Approach 2:
The patent employs an inversion optical system (such as a Porro prism or roof prism) that folds the optical path, effectively changing the linear dimensional relationship between the objective and eyepiece systems. This allows the light to travel a longer effective optical path for high magnification while the physical length of the device remains compact.
3Reliability
If the inversion optical system is positioned far from the objective optical system to reduce aberrations, then aberration correction improves, but the device length increases
Solution Approach 1:
The patent optimizes the distance between the objective optical system and inversion optical system by controlling the inversion system's optical path length L within specific ranges. This parameter optimization enables effective aberration correction while maintaining a compact overall device length, resolving the contradiction between aberration correction quality and system compactness.
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 allows for a compact and lightweight design that maintains high magnification and corrects aberrations, making it suitable for medical and working loupes without compromising image quality or increasing weight.
Implementation Method 1
an inversion optical system provided in the objective optical system or immediately posterior to the objective optical system to invert an inverted image to an erected image
Data Source
AI summary
An observation optical system 10 is provided with an objective optical system LO, an inversion optical system PR provided in the objective optical system LO or immediately posterior to the objective optical system LO to invert an inverted image to an erected image, and an eyepiece optical system LE arranged so as to be the closest to a pupil EP to observe the erected image, the observation optical system satisfying following conditional expressions 1.6<f×N/L<2.5 . . . (1) and |D/H|<3 . . . (2) Herein, a value f represents a focal length of the objective optical system LO, a value N represents a refractive index on a d-line of the inversion optical system PR, a value L represents an optical path length of the inversion optical system PR, a value D represents a maximum height from an optical axis AX in an incident light ray on the object side of the inversion optical system PR, and a value H represents an exit pupil radius.