Imaging Lens with Fixed Positive First Group for Compact Close Focus
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Solution Overview
Problem
Conventional floating focus type lens systems for digital cameras face challenges in achieving a compact configuration with a wide angle of view and small F-number while maintaining focusing speed and preventing aberrations, as they often result in large lens diameters and heavy focusing groups, making it difficult to focus on objects at close distances without increasing the lens system size.
Innovation Solution
The proposed imaging lens configuration includes a positive first lens group fixed during focusing, with a second and third lens group moving along the optical axis to change the distance between them, while the first lens group consists of negative lenses to prevent diameter increase, and the third lens group is a single lens to minimize refractive power and diameter, satisfying specific conditional expressions for focal lengths and refractive powers to achieve a wide angle of view and small F-number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional floating focus type lens systems are used with negative first lens group and large diameter focusing groups, then focusing on close objects is achieved, but the lens barrel diameter becomes large and focusing speed decreases due to heavy weight
Solution Approach 1:
The patent inverts the conventional configuration by placing a positive lens group first instead of a negative lens group. This inversion allows the use of smaller diameter lenses while maintaining focusing capability on close objects, thereby reducing the overall lens barrel diameter and weight of focusing groups.
Solution Approach 2:
The patent changes the refractive power parameter of the first lens group from negative to positive. This parameter change fundamentally alters the optical path and allows for compact lens design with smaller focusing groups, improving both size and focusing speed while maintaining close-focus capability.
2Ease of operation
If conventional floating focus type lens systems are used with large diameter focusing groups, then focusing on close objects is achieved, but the weight of focusing groups becomes heavy and focusing speed decreases
Solution Approach 1:
The patent inverts the conventional configuration by placing a positive lens group first instead of a negative lens group. This inversion allows the use of smaller diameter lenses while maintaining focusing capability on close objects, thereby reducing the overall lens barrel diameter and weight of focusing groups.
Solution Approach 2:
The patent changes the refractive power parameter of the first lens group from negative to positive. This parameter change fundamentally alters the optical path and allows for compact lens design with smaller focusing groups, improving both size and focusing speed while maintaining close-focus capability.
3Length of stationary object
If lens system total length is kept constant while focusing on close objects, then compact configuration is maintained, but aberrations occur in wide angle of view and small F-number systems
Solution Approach 1:
The patent segments the lens system into multiple lens groups with specific refractive power distributions. The positive first lens group combined with subsequent negative and positive lens groups creates a segmented structure that maintains compact total length while effectively correcting aberrations across the field of view.
Solution Approach 2:
The patent changes the refractive power parameter of the first lens group from negative to positive. This parameter change fundamentally alters the optical path and allows for compact lens design with smaller focusing groups, improving both size and focusing speed while maintaining close-focus capability.
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 focusing on objects at close distances without increasing the lens system size, suppressing aberrations and maintaining excellent performance by ensuring the diameter of focusing groups remains small, achieving a wide angle of view and a small F-number with improved focusing speed and optical performance.
Implementation Method 1
a first lens group having positive refractive power, a second lens group having positive refractive power
Implementation Method 2
Focusing on an object at close distance from a state of having focused on an object at infinity is performed by moving the second lens group and the third lens group in such a manner that a distance in the direction of an optical axis between the second lens group and the third lens group changes
Data Source
AI summary
An imaging lens includes, consecutively in order from the most object-side, a positive first lens group, a positive second lens group and a third lens group. Focusing on an object at close distance from a state of having focused on an object at infinity is performed by moving the second lens group and the third lens group in such a manner that a distance between the second lens group and the third lens group changes while the first lens group is fixed. The first lens group includes, consecutively in order from the most object-side, a negative first lens and a negative second lens.