Zoom Lens Stop Control for Brightness Stability
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Solution Overview
Problem
In variable magnification optical systems, such as zoom lenses, changes in magnification often lead to variations in F-Number, causing fluctuations in image brightness, which can result in improper exposure and discomfort for users, while existing control systems increase the load on the control system and complicate data management.
Innovation Solution
A lens unit and camera system with a processor that adjusts the stop's opening amount based on magnification changes, adhering to specific conditional expressions to minimize F-Number variations and maintain consistent image brightness across different zoom settings, while reducing the complexity and load on the control system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the opening amount of the stop is adjusted to maintain constant brightness during magnification change, then image brightness stability is improved, but control system complexity increases
Solution Approach 1:
The patent applies parameter changes by adjusting the opening amount of the stop based on magnification changes. The processor calculates the required opening amount adjustment according to the change in magnification ratio, converting the abstract goal of constant brightness into a concrete parameter adjustment rule. This resolves the contradiction by providing a straightforward parameter-based control method that maintains brightness stability without requiring complex control algorithms.
2Illumination intensity
If the opening amount is frequently adjusted to compensate for F-Number changes, then brightness stability is improved, but control load increases
Solution Approach 1:
The patent implements partial action by adjusting the opening amount only when necessary - specifically when magnification changes occur. Rather than continuously adjusting the stop, the processor calculates and adjusts the opening amount based on the change in magnification ratio. This approach maintains brightness stability while minimizing unnecessary control operations, thereby reducing control load and energy consumption.
Data Source
AI summary
A lens unit includes a variable magnification optical system provided with a stop that adjusts a light amount and a processor that controls an opening amount of the stop based on information on a magnification change of the variable magnification optical system. In a case where a maximum value and a minimum value of an F-Number in the entire variable magnification region of the variable magnification optical system are respectively Fmax and Fmin and an average value of an F-Number at a wide angle end and an F-Number at a telephoto end of the variable magnification optical system is Fave, the processor is configured to control the opening amount within a range satisfying 3 < {(Fmax - Fmin)/Fave} × 100 < 10.