Zoom Lens Focusing Unit Design for Magnification Stability
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Solution Overview
Problem
Conventional zoom lens systems for interchangeable-lens type digital cameras face challenges in achieving a compact focusing lens unit with minimal image magnification changes during focusing, leading to increased motor requirements and larger lens barrel sizes, which cause unease due to high-frequency focusing operations and image distortion.
Innovation Solution
The proposed zoom lens system consists of multiple lens units with specific optical powers and configurations, including negative and positive meniscus lenses, that move along the optical axis to achieve focusing and zooming, maintaining a compact design and minimizing image magnification changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the weight of the focusing lens unit is reduced, then the motor size and lens barrel diameter can be reduced, but the ability to perform high-frequency focusing operations at 30 Hz becomes compromised
Solution Approach 1:
The lens system is divided into multiple lens units (first through fourth lens units) with different optical powers. The focusing operation is assigned to a specific lens unit (the fourth lens unit with negative optical power), separating the focusing function from the entire lens system. This segmentation allows the focusing lens unit to be optimized for light weight while other lens units handle the bulk of the optical power, enabling high-frequency focusing operations with a lightweight actuator.
2Ease of operation
If the focusing lens unit moves along the optical axis during focusing, then focusing from infinity to close-point is achieved, but image magnification changes causing unease to the image taking person
Solution Approach 1:
The fourth lens unit is specifically designed with negative optical power and positioned to move along the optical axis during focusing. This localized design allows the focusing function to be achieved while the movement is constrained to minimize magnification changes. The negative optical power of this specific lens unit compensates for the magnification variations that would otherwise occur during focusing operations.
3Productivity
If a larger motor or actuator is used to move the focusing lens unit at high rate, then high-frequency focusing operations can be performed, but the outer diameter of the lens barrel is increased
Solution Approach 1:
The patent changes the optical parameters of the lens system by assigning negative optical power to the fourth lens unit, which is dedicated to focusing. This parameter change allows the focusing lens unit to have lower mass while still achieving the required focusing performance. The negative optical power configuration reduces the moment of inertia of the focusing lens unit, enabling a smaller, more compact actuator to achieve high-frequency focusing operations without increasing the lens barrel outer diameter.
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 focusing lens unit with suppressed image magnification changes, reducing motor requirements and lens barrel size, while maintaining high-image quality and minimizing image distortion during high-frequency focusing operations.
Implementation Method 1
The fourth lens unit moves to the image side along an optical axis at the time of focusing from an infinity in-focus condition to a close-point in-focus condition
Data Source
AI summary
Provided is a zoom lens system including a compact focusing lens unit and having a suppressed change in image magnification at the time of movement of the focusing lens unit. The zoom lens system of the present invention includes, in order from an object side to an image side, a first lens unit G1 having negative optical power, a second lens unit G2 having positive optical power, a third lens unit G3 having positive optical power, and a fourth lens unit G4 having negative optical power. The fourth lens unit G4 moves to the image side along an optical axis at the time of focusing from an infinity in-focus condition to a close-point in-focus condition.