Compact Oblique-View Objective Optical System Design
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Solution Overview
Problem
Conventional oblique-view objective optical systems require a large space due to the use of optical path changing elements with long glass paths, leading to increased size and length compared to direct-view systems.
Innovation Solution
The objective optical system comprises a negative front lens group, an aperture stop, and a positive rear lens group, with specific lens configurations and conditional expressions to optimize focal lengths and curvature radii, allowing for downsizing while maintaining optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional oblique-view objective optical system uses an optical path changing element with a long glass path length (such as a prism), then the optical path can be effectively changed to achieve oblique viewing, but the space required in the optical system increases, leading to a longer overall length and larger size
Solution Approach 1:
The patent changes the key parameter from glass path length to air path length by replacing the prism with a view-direction changing element. This parameter change allows the optical path to be redirected without requiring a long glass path, thereby reducing the overall length of the objective optical system while maintaining oblique viewing capability
Solution Approach 2:
The patent extracts the view-direction changing function from the conventional prism structure. By using a separate view-direction changing element with a shorter glass path length, the system removes the need for a long glass path while preserving the essential function of changing the optical path direction for oblique viewing
2Ease of operation
If a conventional oblique-view objective optical system uses a prism with long glass path length, then the optical path changing function is achieved, but the device size increases making it less compact
Solution Approach 1:
The patent changes the critical parameter from glass path length to air path length by replacing the prism with a view-direction changing element. This parameter substitution reduces the volume occupied by glass material while maintaining the optical path changing function, thereby achieving a more compact device size
Solution Approach 2:
The patent extracts the view-direction changing function from the bulky prism structure and implements it with a more compact view-direction changing element. This extraction allows the system to maintain the essential oblique viewing function while significantly reducing the overall device volume
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
This configuration achieves downsizing of the objective optical system in both radial and axial directions, making it more compact and suitable for applications like endoscopes, while maintaining effective optical performance.
Implementation Method 1
a negative first lens L1 disposed closest to the object
Implementation Method 2
a meniscus second lens L2 having a convex surface facing toward the image side
Implementation Method 3
a view-direction changing element P
Data Source
AI summary
There is provided an objective optical system, an image pickup apparatus, and an endoscope that are small in size and easy to assemble. The objective optical system includes, in order from the object side to the image side, a negative front lens group, an aperture stop, and a positive rear lens group. The front lens group includes a negative first lens disposed closest to the object, a meniscus second lens having a convex surface facing toward the image side, and a view-direction changing element. The objective optical system satisfies the following conditional expressions (1) to (4):9<FL2/FL<15 (1)0.3<FL1/FLf<0.64 (2)−95<(r2f+r2r)/(r2f−r2r)<−18 (3)2.8<FLr/FL<4 (4).