Auto Focus Search Range Segmentation for Faster Camera Focusing
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Solution Overview
Problem
Conventional digital cameras with contrast-type auto focus systems require a long time for focusing operations due to the need for drive scanning from the shortest distance to infinity, which increases the number of stepper motor switching steps, leading to inefficient focusing times.
Innovation Solution
An image pickup apparatus with the ability to arbitrarily set and select different auto focus search ranges, allowing for a desired search range to be chosen for auto focus operations, thereby reducing the time required for focusing by limiting the lens movement range to the necessary area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If drive scanning is performed in the AF search range from the shortest distance to infinity, then the focusing point can be obtained, but the time required for the focusing operation increases
Solution Approach 1:
The patent divides the entire AF search range from shortest distance to infinity into multiple sub-ranges (first AF search range and second AF search range). The focus detection is performed sequentially in these segmented ranges rather than scanning the entire range at once, thereby reducing the time required for focusing operation while maintaining the ability to detect the focusing point accurately.
Solution Approach 2:
The patent performs preliminary focus detection in a limited first AF search range before expanding to the full search range. By conducting initial focus detection in a smaller, predefined range, the system can quickly determine if focus is achievable within that range, avoiding unnecessary scanning of the entire infinity range and thus reducing overall focusing time.
2Loss of time
If the focus lens is moved within a limited movement range corresponding to the selected photograph mode, then the time required for auto focus operation is shortened, but the ability to focus on objects outside this range is lost
Solution Approach 1:
The patent dynamically adjusts the AF search range based on the selected photograph mode. When macro photograph mode is selected, the system uses a first AF search range optimized for close-up subjects. When normal photograph mode is selected, it uses a second AF search range optimized for distant subjects. This dynamic adaptation allows the system to maintain versatility across different photography scenarios while minimizing focusing time for each specific mode.
Solution Approach 2:
The patent changes the parameters of the AF search range (distance boundaries, search limits) according to the selected photograph mode. By modifying the search range parameters to match the expected subject distance for each mode, the system achieves both time efficiency and adaptability - the focusing operation is quick because the search range is appropriately limited, yet versatile because the range can be changed based on photography needs.
3Measurement precision
If the number of switching steps of the stepper motor is increased, then the focusing point can be detected with higher precision, but the focusing operation time increases
Solution Approach 1:
The patent applies partial action by performing focus detection only within a limited first AF search range initially, rather than scanning the entire possible range. This partial scanning approach achieves sufficient focusing precision for the selected photograph mode without requiring the full number of stepper motor switching steps that would be needed to scan the complete range from shortest distance to infinity, thereby improving focusing speed while maintaining adequate precision.
Data Source
AI summary
An image pickup apparatus comprises a setting unit which arbitrarily sets different auto focus search ranges, a selection unit which selects a desired auto focus search range from said different auto focus search ranges arbitrarily set by the setting unit, and an auto focus control unit which performs an auto focus operation based on the desired auto focus search range selected by the selection unit.