Imaging Apparatus Focusing Position Calculation
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Solution Overview
Problem
Existing imaging apparatuses face challenges in achieving high precision auto-focus, especially when the vicinity of the maximal point of the evaluated value curve has a steep mountain shape due to the influence of wide-angle lenses and varying brightness, leading to increased errors in focusing position calculation.
Innovation Solution
An imaging apparatus and method that calculates the sharpness in the vicinity of the maximal point of the evaluated value curve using at least three evaluated values and position information, selecting between a second or higher degree function and a first degree function for focusing position calculation based on sharpness and noise levels to improve precision and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a second or higher degree function is used to calculate the focusing position, then the measurement precision of the focusing position is improved, but the device complexity increases
Solution Approach 1:
The patent changes the parameter of curve fitting degree from fixed to variable. It selects between first degree (linear) and second or higher degree (quadratic or cubic) functions based on the sharpness value and noise level of the evaluated value curve, optimizing the balance between precision and complexity for different imaging conditions
Solution Approach 2:
The patent introduces dynamic selection of calculation methods based on real-time curve characteristics. The system dynamically adjusts the focusing position calculation approach by evaluating sharpness and noise metrics, switching between simple linear interpolation and more complex curve fitting methods as needed
2Productivity
If a small sampling number of evaluated values is used, then the AF speed is improved, but the measurement precision of the focusing position deteriorates
Solution Approach 1:
The patent changes the parameter of curve fitting degree to compensate for small sampling numbers. By using second or higher degree functions that can accurately represent steep mountain shapes with fewer points, the system maintains high precision even when sampling frequency is reduced to increase AF speed
Solution Approach 2:
The patent combines multiple evaluation metrics (sharpness calculation, noise level assessment) with curve fitting methods to create a composite evaluation system. This composite approach enables accurate focusing position determination with minimal sampling points by leveraging the complementary information from different metrics
3Measurement precision
If the sharpness calculation is performed using at least three evaluated values, then the measurement precision of the focusing position is improved, but the loss of time increases
Solution Approach 1:
The patent applies partial action by using exactly three evaluated values for sharpness calculation when needed, rather than processing all available data points. This selective approach provides sufficient precision for determining the maximal point while minimizing calculation time and data processing burden
Data Source
AI summary
Provided is an imaging apparatus capable of performing AF with a high precision regardless of an object while realizing increase in AF speed. When there is an AF instruction, photographing is performed while a focus lens is moved. AF evaluated values are calculated at every position of the focus lens by a contrast AF processing unit. The contrast AF processing unit calculates a sharpness in the vicinity of the maximal point of an evaluated value curve from three AF evaluated values, including the maximum value among calculated AF evaluated values and AF evaluated values calculated at positions in front and rear of a focus lens position corresponding to the maximum value, and position information of the focus lens corresponding thereto, and calculates a focusing position by a calculation method selected from among plural kinds of methods according to the sharpness.