Lens Control Apparatus for Seamless Autofocusing via Speed Segmentation
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Solution Overview
Problem
Conventional focus detection techniques, such as those described in Japanese Patent Laid-Open No. 2018-36509, fail to ensure seamless and smooth autofocusing operations when shifting focus from one object to another, leading to unnatural defocusing changes perceived by the user, as they lack control over lens driving during the autofocusing process.
Innovation Solution
A lens control apparatus and method that independently control the speed of lens driving using acceleration, constant speed, and deceleration control modes, allowing for seamless rack-focusing and comfortable autofocusing operations without relying on focus detection results, by setting appropriate speed control parameters and modes based on defocus amount and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional focus detection techniques are used with only deceleration control when the lens is brought into an in-focus state, then the lens can be focused accurately, but the focus shifting becomes unnatural and uncomfortable for users when the target object changes
Solution Approach 1:
The autofocusing operation is divided into multiple distinct phases: acceleration phase, constant speed phase, and deceleration phase. Each phase has its own control parameters and characteristics, allowing for optimized control at different stages of the focusing process. This segmentation enables the system to provide both accurate focusing and smooth focus transitions by appropriately managing each phase.
Solution Approach 2:
The lens driving speed is made dynamic rather than static. The system automatically adjusts the driving speed according to the current phase of autofocusing operation, transitioning between acceleration, constant speed, and deceleration phases. This dynamic speed control ensures natural and comfortable focus shifting when target objects change, while maintaining precise focusing capability.
2Productivity
If the lens driving speed is increased to improve focusing speed, then productivity increases, but the focus shifting becomes less smooth and comfortable for users
Solution Approach 1:
The lens driving follows a periodic pattern with distinct phases: acceleration period, constant speed period, and deceleration period. This periodic action structure allows the system to achieve high focusing speed during the constant speed phase while ensuring smooth transitions during acceleration and deceleration phases, thereby maintaining both productivity and user comfort.
Solution Approach 2:
The driving parameters (speed, acceleration) are changed according to the current phase of operation. During acceleration phase, speed increases; during constant speed phase, speed is maintained at optimal levels for fast focusing; during deceleration phase, speed is reduced for smooth stopping. These parameter changes enable the system to balance focusing speed with comfort.
Data Source
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AI summary
The present invention realizes seamless rack-focusing for smoothly shifting a focus from one to another and a smooth autofocusing operation which makes a viewer feel comfortable, regardless of a result of focus detection in lens control in a period from the beginning to the end of autofocusing operation. A lens control apparatus includes: focus detection means configured to detect a defocus amount; and control means configured to control a focus lens to move based on the defocus amount, wherein the control means includes three speed control patterns of acceleration control, constant speed control, and deceleration control, and the speed control patterns are changed based on at least two or more parameters.