Camera Focus Control Mode Switching for Zoom Speed
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Solution Overview
Problem
Existing camera systems face challenges in maintaining focus accuracy during variable proportion zooming, especially when zooming speed is high, as they rely on contrast-based auto focusing which may not be effective and can lose focus due to limitations in focus lens group movement.
Innovation Solution
A camera system with a focus lens and zoom lens drive mechanism that switches between a first control mode for wobbling operations and a second control mode using a tracking table to maintain focus, based on the rate of change in focal length, ensuring focus is maintained regardless of zooming speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contrast-based auto focusing is used during variable proportion zooming, then focus accuracy can be maintained at low zooming speeds, but focus accuracy deteriorates at high zooming speeds due to limitations in focus lens group movement
Solution Approach 1:
The patent implements dynamic switching between two control modes based on the current zooming speed. When zooming speed is low, the system uses contrast-based auto focusing (first control mode). When zooming speed exceeds a threshold, it switches to tracking table-based control (second control mode). This dynamic adaptation resolves the contradiction by selecting the appropriate control method for each operating condition, maintaining focus accuracy across all zooming speeds.
Solution Approach 2:
The patent changes the control parameter from contrast-based feedback to pre-calculated tracking table data when zooming speed increases. The tracking table stores predetermined focus lens positions corresponding to various zoom positions and object distances. By switching parameters based on zooming speed, the system overcomes the limitation of contrast-based focusing at high speeds while maintaining accuracy.
2Reliability
If focus lens group movement is limited by driving mechanism constraints, then contrast-based auto focusing can work at low speeds, but it becomes impossible to maintain focus during quick variable proportion zooming
Solution Approach 1:
The patent pre-calculates and stores tracking tables that contain the relationship between zoom positions, object distances, and required focus lens positions. These tracking tables are prepared in advance for various shooting conditions. During quick zooming, the system simply retrieves and executes the pre-calculated focus positions from the tracking table, eliminating the need for real-time contrast-based adjustment and overcoming driving mechanism speed limitations.
Solution Approach 2:
The patent replaces the mechanical feedback-based contrast focusing system with a computational control system using tracking tables. Instead of relying on the physical movement capabilities of the focus lens group to respond to contrast changes, the system uses pre-computed positional data to directly control focus, substituting mechanical feedback with informational guidance.
3Device complexity
If a single control method is used for all zooming speeds, then the system structure remains simple, but focus accuracy cannot be maintained across different zooming speed conditions
Solution Approach 1:
The patent segments the control system into two distinct control modes: contrast-based auto focusing for low-speed zooming and tracking table-based control for high-speed zooming. Each segment handles specific operating conditions optimally. The control portion determines which mode to use based on zooming speed, creating a segmented control architecture that maintains focus accuracy across all conditions while keeping each individual control method relatively simple.
Data Source
AI summary
A camera system that can maintain a good focus state regardless of the speed of zooming during variable proportion zooming is provided. The camera system has a control portion that, based on information on the speed of the change in the focal length, determines whether to control a focus lens drive portion in either a first control mode or a second control mode. If it determines that control is to be performed in the first control mode, then the control portion controls the focus lens drive portion so that it drives a focus lens in the direction that brings a predetermined captured object into focus based on estimated values for auto focusing that have been calculated from the image data at various positions by controlling the focus lens drive portion so that the captured object distance is moved forward and backward in the optical axis direction. If the control portion determines that control is to be performed in the second control mode, then the control portion controls the focus lens drive portion based on a tracking table.