Four-Lens Image-Taking System with Cemented Negative-Positive Pair
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Solution Overview
Problem
Existing image-taking lens systems for solid state imaging devices face challenges in miniaturization while maintaining performance, as reducing the size of the lens system can lead to uneven light distribution and increased manufacturing errors, and increasing the size to correct these issues is not feasible.
Innovation Solution
A compact image-taking lens system is designed using four lenses in three groups, with a first lens having positive power, a cemented second and third lens with negative and positive power respectively, and a fourth meniscus lens with a concave surface facing the image surface, satisfying specific conditional expressions to minimize performance degradation and achieve compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the image-taking lens system is reduced, then the compactness is improved, but the exit pupil position becomes closer to the image surface causing uneven light distribution and performance degradation
Solution Approach 1:
The second lens (negative power) and third lens (positive power) are merged into a single cemented lens unit. This integration reduces the number of separate components and assembly steps, allowing for better control of the exit pupil position while maintaining compact overall dimensions. The cemented structure ensures precise relative positioning between the negative and positive power elements, improving light distribution uniformity without requiring larger system dimensions.
2Adaptability or versatility
If four separate lenses are used, then the design flexibility is improved, but the manufacture error increases due to assembly work
Solution Approach 1:
The second and third lenses are cemented together as a single unit, eliminating the need for separate alignment and assembly of these two elements. This reduces accumulation of manufacturing errors that would occur with four separate lenses while maintaining the optical benefits of having both negative and positive power elements in the system. The cemented structure provides fixed relative positioning, preventing assembly-induced performance variations.
3Manufacturing precision
If the exit pupil position is set far from the image surface, then the light collecting performance is improved, but the lens system size increases
Solution Approach 1:
The invention optimizes specific parameter ranges to achieve the desired balance. Conditional expression (1) controls the focal length ratio to manage exit pupil positioning, while conditional expressions (2) and (3) control the focal lengths and curvatures of individual lenses to maintain compact dimensions. By precisely controlling these optical parameters, the system achieves adequate light collecting performance with a minimized overall size.
Solution Approach 2:
The fourth lens is designed with a meniscus shape (curved surfaces with different radii), which helps in controlling the exit pupil position and light distribution. The specific curvature configuration of the meniscus lens allows for compact system design while maintaining proper exit pupil positioning for uniform light collection across the image surface.
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 effectively reduces the size of the lens system while minimizing performance degradation due to manufacturing errors and maintaining balanced optical performance, including aberration control and exit pupil positioning.
Implementation Method 1
a cemented lens of a second lens having a negative power and a third lens having a positive power
Data Source
AI summary
An aperture stop, a first lens having a positive power, a second lens having a negative power, a third lens having a positive power, and a fourth lens whose concave face is directed toward the image surface side and having a meniscus shape are disposed in order from the object side. The second and third lenses are cemented to each other. Further, focal length "f" of the entire system and total focal length "f23" of the second and third lenses satisfy the following conditional expression. <?in-line-formulae description="In-line Formulae" end="lead"?>|f/f23|<0.4<?in-line-formulae description="In-line Formulae" end="tail"?>