Fisheye Zoom Lens System for Full-Size Sensors
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Solution Overview
Problem
Existing fisheye lenses fail to achieve a circular fisheye or diagonal fisheye angle of 180° across various image sensor sizes, leading to insufficient magnification and telescopic phenomena, especially with full-size image sensors.
Innovation Solution
A fisheye zoom lens system comprising a first lens unit with negative refractive power and a second lens unit with positive refractive power, where the lens units' intervals are adjusted to vary magnification, allowing for a single-focus circular fisheye on full-size sensors and diagonal fisheye on APS-C and APS-H sensors, with specific conditional expressions for image height ratios and focal lengths to maintain optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a fisheye lens is designed for full-size image sensors, then circular fisheye coverage is achieved, but the lens becomes too large and complex for smaller sensors like APS-C and APS-H
Solution Approach 1:
The patent designs a fisheye lens that can serve multiple image sensor formats (full-size, APS-C, APS-H) with a single optical system. By carefully selecting focal lengths and adjusting lens unit intervals, the same lens achieves circular fisheye on full-size sensors and diagonal fisheye on smaller sensors, eliminating the need for multiple specialized lenses.
Solution Approach 2:
The patent varies the interval between lens units to change the effective focal length and image coverage. By adjusting this parameter, the lens can adapt its performance characteristics to match different image sensor sizes, transforming from a fixed-design lens to a variable-performance system.
2Productivity
If zooming is implemented in a fisheye lens, then magnification varies, but telescopic phenomena occur and the angle of field of 180° is lost
Solution Approach 1:
The patent implements a zoom mechanism where the interval between the first and second lens units varies to change magnification. This dynamic adjustment allows the lens to provide different fields of view (from wide-angle to telephoto) while maintaining proper optical performance through coordinated movement of multiple lens units.
Solution Approach 2:
The lens is divided into multiple lens units (first lens unit with negative power, second lens unit with positive power) that can move independently. This segmentation allows complex zoom functionality to be achieved through coordinated movement of separate units, maintaining optical performance throughout the zoom range.
3Ease of operation
If the focal length is increased to reduce the angle of field, then telephoto effect is achieved, but the lens length and complexity increase
Solution Approach 1:
The patent uses a retrofocus design where the first lens unit has negative refractive power and the second has positive power. This inverted arrangement (negative element first, then positive) allows telephoto functionality to be achieved with a more compact overall lens length compared to traditional positive-first designs.
Solution Approach 2:
The lens units are arranged concentrically around the optical axis, with multiple elements nested within each other. This nested configuration allows the lens to achieve long effective focal lengths for telephoto capability while keeping the physical lens barrel length relatively short.
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 system achieves a circular fisheye on full-size sensors at the shortest focal length, diagonal fisheye on APS-C and APS-H sensors in intermediate ranges, and maintains a desired image quality by satisfying conditional expressions for image height ratios and focal lengths, ensuring effective zooming without telescopic phenomena.
Implementation Method 1
a first lens unit L1 having a negative refractive power and a second lens unit L2 having a positive refractive power
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
An optical system (1) includes, in order from an object side, a first lens unit (L1) having a negative refractive power and a second lens unit (L2) having a positive refractive power. The optical system satisfies: 1.70≤Yt/Yw≤2.5, Y=2×f×sin(θ/2) (85°≤θ≤90°), and 3.45≤bfw/|f1|≤7, where fw is the shortest focal length, ft is the longest focal length, f is an arbitrary focal length that satisfies fw≤f≤ft, θ is an angle between an optical axis (O) and a principal ray (P) of an off-axis light flux incident upon a lens surface closest to the object, Y is a formed image height of a ray incident at the angle θ, Yw is the largest image height at the shortest focal length, Yt is the largest image height at the longest focal length, f1 is a focal length of the first lens unit, and bfw is a back focus at the shortest focal length.