Zoom Lens Feedback and Open-Loop Control for Quiet Zooming
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Solution Overview
Problem
Existing zoom lenses face challenges in controlling drive units for lens movements during zooming and focusing, leading to issues such as power consumption, drive noise, and synchronism loss, particularly when using stepping motors for lens units with different masses.
Innovation Solution
A zoom lens design with a first and fourth lens unit fixed relative to the image plane, and a second and third lens unit moving during zooming and focusing, controlled by feedback and open-loop control mechanisms respectively, using stepping motors for the second lens unit and open-loop control for the third lens unit to reduce power consumption and prevent synchronism loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is used for both lens units during zooming, then positioning precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The control system is segmented into two independent control paths: feedback control for the second lens unit and open-loop control for the third lens unit. This segmentation allows each control path to be optimized independently, reducing overall system complexity while maintaining positioning precision where most needed.
Solution Approach 2:
Different control qualities are applied to different lens units based on their specific requirements. The second lens unit receives high-precision feedback control, while the third lens unit uses simpler open-loop control, optimizing the balance between precision and complexity for each component.
2Measurement precision
If feedback control is used for both lens units during zooming, then positioning precision is improved, but power consumption increases
Solution Approach 1:
The power consumption is segmented by applying feedback control only to the second lens unit where it is most beneficial, while the third lens unit operates with simpler open-loop control, thereby reducing total power consumption while maintaining adequate positioning precision.
Solution Approach 2:
Energy-intensive feedback control is applied locally only where most needed (second lens unit), while other components (third lens unit) use energy-efficient open-loop control, optimizing the overall energy distribution across the system.
3Device complexity
If open-loop control is used for both lens units, then device complexity is reduced, but synchronism loss occurs
Solution Approach 1:
The control system is segmented such that the second lens unit uses feedback control to maintain synchronism, while the third lens unit uses open-loop control, achieving a balance between complexity and reliability through differentiated control strategies.
4Measurement precision
If heavy lens units are controlled with high torque, then positioning accuracy is improved, but drive noise increases
Solution Approach 1:
Feedback control is implemented for the second lens unit to achieve accurate positioning without requiring excessive torque, thereby reducing drive noise while maintaining positioning accuracy through closed-loop error correction.
Data Source
AI summary
An optical apparatus includes an optical system consisting of, in order from an object side to an image side, a first lens unit with negative refractive power, a second lens unit with positive refractive power, a third lens unit with negative refractive power, and a fourth lens unit with positive refractive power, a first drive unit configured to move the second lens unit, a second drive unit configured to move the third lens unit. The first and fourth lens units are fixed relative to an image plane during zooming and focusing, the second lens unit moves toward the object side during zooming, and the third lens unit moves toward the image side during focusing. When the control unit controls the first drive unit by feedback control using the information from the first acquiring unit during zooming, the control unit controls the second drive unit by open loop control.