Retrofocus Lens Aberration Control via Segmented Units
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Solution Overview
Problem
Conventional retrofocus type photographic optical systems face challenges in balancing refractive powers to correct aberrations such as coma, astigmatism, and spherical aberration, especially when achieving a wide angle of view and long back focus, leading to difficulties in obtaining high-quality images due to increased aberrations.
Innovation Solution
The optical system consists of a first lens unit with negative refractive power and a second lens unit with a biconvex positive lens located closest to the image side, along with a stop and a rear lens unit, satisfying specific conditions for back focus, focal lengths, and refractive powers to minimize aberrations and achieve a high-quality image across the entire image plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lens having a strong positive refractive power is located distant from the aperture stop, then spherical aberration can be corrected, but the amount of various aberrations such as coma and astigmatism occurring in the lens unit may be increased
Solution Approach 1:
The second lens unit is divided into three distinct components: a front lens unit, a stop, and a rear lens unit. This segmentation allows each component to be optimized for specific functions - the front lens unit corrects spherical aberration while the rear lens unit controls coma and astigmatism, resolving the contradiction between correcting different types of aberrations
Solution Approach 2:
Each lens unit is designed with specific refractive power characteristics tailored to its position and function. The front lens unit has optimized refractive power for spherical aberration correction, while the rear lens unit has different optimized refractive power for controlling coma and astigmatism, allowing local optimization of different optical qualities throughout the system
2Adaptability or versatility
If the absolute value of the negative refractive power of the front lens unit becomes large, then the angle of view can be widened, but the amount of various aberrations occurring therein may become large
Solution Approach 1:
The optical system employs an asymmetrical retrofocus configuration where the front lens unit has negative refractive power and the second lens unit has positive refractive power. This asymmetrical arrangement allows the system to achieve a wide angle of view while using the positive refractive power in the second lens unit to counterbalance and correct the aberrations generated by the strong negative refractive power in the front lens unit
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 effectively suppresses coma and astigmatism while correcting spherical aberration, enabling a retrofocus type optical system with a wide angle of view and long back focus to produce high-quality images throughout the image plane.
Implementation Method 1
a first lens unit having a negative refractive power and a second lens unit having a positive refractive power. The second lens unit includes, in order from the object side to the image side, a front lens unit, a stop, and a rear lens unit. The front lens unit includes a biconvex positive lens located closest to the image side
Data Source
AI summary
An optical system includes a first lens unit having a negative refractive power and a second lens unit having a positive refractive power. The second lens unit includes a front lens unit, a stop, and a rear lens unit. The front lens unit includes a biconvex positive lens located closest to the image side. A back focus during focusing on an infinitely-distant object point (BF), a focal length of the entire optical system (f), a focal length of the positive lens of the front lens unit located closest to the image side (fp), a focal length of the front lens unit (f2a), a refractive power of a surface of the rear lens unit located closest to the object side (&phgr;f), and a refractive power of the entire optical system (&phgr;) satisfy the following conditions: 1.0<BF/f<3.0 0.1<fp/f2a<0.5 0.7<|&phgr;f/&phgr;|<1.5.