Compact Wide-Angle Optical System with Cemented Lens Aberration Control
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Solution Overview
Problem
Optical systems for image pickup apparatuses face challenges in achieving a small size and wide angle of view while minimizing aberrations such as astigmatism, distortion, and coma, particularly when trying to reduce the total length and effective diameter of the front lens.
Innovation Solution
The optical system consists of a front lens unit with negative refractive power and a rear lens unit with positive refractive power, including specific lens configurations and cemented lenses, with conditional expressions defining the relationships between lens distances and focal lengths to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the total length of the optical system and effective diameter of the front lens are reduced while widening the angle of view, then the refractive power of the negative lens and positive lens must be increased, but this leads to increased incident angle and output angle of off-axial rays, thereby increasing astigmatism
Solution Approach 1:
The front lens unit is divided into multiple lens elements (negative lens and positive lens) with specific arrangements. The negative lens has a meniscus shape with the convex surface facing the object, and the positive lens is positioned behind it. This segmentation allows each lens element to contribute differently to light refraction, enabling compact design while controlling astigmatism through coordinated action of multiple elements.
Solution Approach 2:
The patent applies different surface curvatures and refractive powers to different regions of the lens system. The negative lens has a meniscus shape with specific curvature distribution, and the positive lens has tailored surface properties. This local optimization of optical properties allows the system to maintain small size while correcting off-axial ray deviations and reducing astigmatism in specific field regions.
2Shape
If a front lens unit with negative refractive power and rear lens unit with positive refractive power are disposed asymmetrically to achieve wide angle of view, then the angle of view is widened, but various aberrations including coma, distortion, and lateral chromatic aberration increase due to asymmetry
Solution Approach 1:
The patent deliberately employs asymmetric lens arrangement with the negative lens positioned in front of the positive lens in the front lens unit, and the aperture stop positioned between the front and rear lens units. This controlled asymmetry enables wide angle of view while the specific configuration of lens elements and their relative positions work together to correct the inherent aberrations caused by asymmetric design.
Solution Approach 2:
The patent converts the harmful effect of asymmetric lens arrangement (which causes aberrations) into a beneficial configuration. By carefully designing the meniscus shape of the negative lens and positioning the positive lens with specific refractive power, the system transforms the asymmetric structure into an advantage that achieves both wide angle of view and acceptable aberration control through the coordinated refraction of light by multiple elements.
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 allows for a compact optical system with a wide angle of view and reduced aberrations, achieving high optical performance across the entire field of view.
Implementation Method 1
an optical system includes a front lens unit having a negative refractive power, an aperture stop, and a rear lens unit having a positive refractive power, which are disposed in order from an object side to an image side
Data Source
AI summary
An optical system includes, in order from object side to image side, a negative front lens unit, an aperture stop, and a positive rear lens unit. The front lens unit consists of, in order from object side to image side, a negative first lens having a concave surface on image side, a negative second lens with a concave surface on image side, and a positive third lens. The rear lens unit consists of, in order from object side to image side, a positive fourth lens, and a cemented lens formed by cementing a positive lens and a negative lens together. Here, a distance on optical axis from a lens surface on object side of the first lens to a lens surface on image side of the third lens, a focal length of the third lens, and a focal length of the optical system are set to appropriate values.