Negative Lead Lens Optical System for Peripheral Illumination
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Solution Overview
Problem
Conventional fixed focal wide angle lenses experience a reduction in light quantity in the peripheral part of the field of view due to a short distance between the exit pupil and the sensor, leading to reduced aperture efficiency and imaging performance.
Innovation Solution
An optical system comprising a first lens with negative refractive power, a second lens with negative refractive power, a third lens with positive refractive power, and a fourth lens with positive refractive power, arranged in a specific configuration to extend the distance between the exit pupil and the imaging plane, ensuring sufficient light quantity and high imaging performance across the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a fixed focal wide angle lens with four lenses is used, then the lens achieves downsizing and weight reduction with satisfactory imaging in the near-infrared region, but the distance between exit pupil and sensor surface is short causing reduced aperture efficiency and light quantity in peripheral parts
Solution Approach 1:
The patent changes the optical parameters of the lens system by introducing a negative lead lens at the object side, which modifies the exit pupil position and extends the distance to the sensor surface. This parameter change allows peripheral light rays to enter more perpendicularly, improving aperture efficiency and light quantity without increasing overall lens size
Solution Approach 2:
The patent segments the lens system into five distinct lens components with specific refractive power assignments. The negative lead lens is separated from the other positive lenses, allowing independent optimization of each component's function. This segmentation enables the negative lens to specifically address the exit pupil position issue while positive lenses maintain imaging performance
2Illumination intensity
If the distance between exit pupil and sensor surface is extended, then aperture efficiency and light quantity in peripheral parts are improved, but lens complexity and manufacturing difficulty increase
Solution Approach 1:
The patent achieves the extended exit pupil distance through controlled parameter changes in lens refractive powers and spacing. By setting specific focal length relationships (f1/f < -2.0 and f4/f < 5.0), the design extends the exit pupil position while maintaining a compact overall structure, avoiding excessive complexity
Solution Approach 2:
The patent merges the functions of multiple lenses into a coordinated five-element system where the negative lead lens and four positive lenses work together. This merging allows the system to achieve extended exit pupil distance and improved peripheral illumination while maintaining manageable complexity through functional integration
3Manufacturing precision
If a wide angle lens is designed to receive reflected light uniformly across the entire field of view, then imaging performance is improved, but lens size and weight increase
Solution Approach 1:
The patent uses parameter changes in lens refractive powers and spacing to achieve uniform light reception across the field of view. The negative lead lens combined with four positive lenses creates an optical path that directs both central and peripheral light rays to the sensor surface effectively, maintaining high imaging performance without requiring a larger, heavier lens system
Solution Approach 2:
The patent applies local quality by giving each lens component a specific refractive power characteristic tailored to its position in the optical system. The negative lead lens addresses peripheral ray control, while the four positive lenses handle different stages of image formation. This localized optimization allows uniform field-of-view coverage without increasing overall lens weight
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 prevents reduction in light quantity in the peripheral part of the field of view while maintaining high imaging performance and achieving a wide angle, all while being cost-effective and compact.
Implementation Method 1
a first lens L1 having negative refractive power, a second lens L2 having negative refractive power, a third lens L3 having positive refractive power, and a fourth lens L4 having positive refractive power, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 being disposed in this order from an object side
Data Source
AI summary
Provided is an optical system and an imaging apparatus provided with the optical system. The optical system includes: a first lens having negative refractive power; a second lens having negative refractive power; a third lens having positive refractive power; and a fourth lens having positive refractive power, the first lens, the second lens, the third lens, and the fourth lens being disposed in this order from an object side. The optical system satisfies a predetermined condition relating to the focal length of the optical system and the distance on the optical axis between an exit pupil and an imaging plane in the optical system.