Imaging Device Focus Control Using Variable Shift Amounts
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Solution Overview
Problem
Existing phase difference AF methods in imaging devices perform redundant operations regardless of the subject's blurring state, leading to inefficient focus control, as the shift amount L is constant regardless of the subject's condition.
Innovation Solution
An imaging device with a sensor comprising first and second phase difference detecting pixels, a defocus amount calculating unit that adjusts the upper limit of signal shift based on the F value, focal distance, and focus lens position, and a focus control unit that optimizes focus state control by calculating the defocus amount from shifted signal groups when their correlation is maximum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant shift amount L is used in phase difference AF calculation, then the calculation is simple, but redundant operations are performed reducing efficiency
Solution Approach 1:
The patent applies dynamics by making the shift amount L variable rather than constant. The shift amount is dynamically adjusted based on the detection result from the contrast AF, which indicates the blurring state of the subject. When the subject is significantly blurred, a larger shift amount is used, and when slightly blurred, a smaller shift amount is used. This dynamic adjustment optimizes the phase difference AF calculation efficiency without sacrificing accuracy.
Solution Approach 2:
The patent changes the parameter L (shift amount) based on the subject's blurring state detected by contrast AF. By varying this critical parameter according to actual conditions rather than keeping it fixed, the system achieves optimal balance between calculation simplicity and processing efficiency for different focusing scenarios.
2Adaptability or versatility
If the shift amount L is increased to cover significantly blurred subjects, then all subjects can be focused, but unnecessary operations are performed on slightly blurred subjects
Solution Approach 1:
The patent uses partial action by adjusting the shift amount L to match the actual blurring state. Instead of always using a large shift amount that covers all cases (excessive action), the system uses a smaller, appropriate shift amount when the subject is only slightly blurred, based on contrast AF detection. This eliminates unnecessary calculations while maintaining the ability to handle significantly blurred subjects when needed.
3Productivity
If the shift amount L is decreased for slightly blurred subjects, then calculation efficiency improves, but focus precision may be reduced
Solution Approach 1:
The patent implements feedback by using the contrast AF detection result to determine the appropriate shift amount L before performing phase difference AF calculation. The contrast AF provides information about the subject's blurring state, which feeds back into the phase difference AF process to optimize the shift amount. This feedback mechanism ensures that the shift amount is appropriate for the actual subject condition, maintaining precision while improving efficiency.
Data Source
AI summary
An imaging device, includes: a sensor including first phase difference detecting pixels arranged in a row direction and second phase difference detecting pixels arranged in the row direction; a defocus amount calculating unit which calculates a correlated amount of a first output signal group and a second output signal group while shifting the first output signal group and the second output signal group in the row direction by an arbitrary amount to calculate a defocus amount from a first shift amount of the first output signal group and the second output signal group when the correlated amount is at a maximum. The defocus amount calculating unit changes an upper limit of a shift amount of the first output signal group and the second output signal group in accordance with at least one of an F value, a focal distance, and a position of a focus lens.