Global Shutter Imaging Section for High-Speed Focus Detection
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Solution Overview
Problem
In imaging apparatuses using the contrast AF system, the rolling shutter system's varying exposure timing for each line leads to inconsistent focus lens positions, resulting in inaccurate contrast evaluation and reduced focus detection accuracy, while stopping the focus lens during exposure improves accuracy but slows down detection speed.
Innovation Solution
The imaging apparatus employs a global shutter system where exposure for all lines is started and ended simultaneously within a predetermined driving period, using a focus lens driving section to move the focus lens to an in-focus position, and includes a focus detecting section that analyzes image data to determine the in-focus position based on contrast, utilizing a CMOS image sensor and correlated double sampling processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rolling shutter system is used to image during focus lens driving, then focus detection speed is improved, but focus detection accuracy deteriorates due to varying focus lens positions across lines
Solution Approach 1:
The patent applies the dynamics principle by enabling the focus lens to move continuously during the exposure period rather than stopping at fixed positions. The exposure timing is dynamically adjusted for each line so that all lines capture images at the same focus lens position, resolving the contradiction between continuous lens movement and consistent focus position across lines.
Solution Approach 2:
The patent implements preliminary action by pre-calculating and setting the exposure timing for each line before the actual imaging process. The exposure start and end timings are determined in advance based on the focus lens driving speed and position, ensuring that all lines capture images at the intended focus position without requiring real-time adjustment during exposure.
2Measurement precision
If focus lens is stopped during exposure, then focus detection accuracy is improved by maintaining consistent focus lens position, but focus detection speed deteriorates
Solution Approach 1:
The patent applies the dynamics principle by enabling the focus lens to move continuously during the exposure period rather than stopping at fixed positions. The exposure timing is dynamically adjusted for each line so that all lines capture images at the same focus lens position, resolving the contradiction between continuous lens movement and consistent focus position across lines.
3Productivity
If exposure timing varies for each line during focus lens driving, then focus detection speed is improved, but contrast evaluation accuracy deteriorates due to inconsistent focus lens positions
Solution Approach 1:
The patent implements preliminary action by pre-calculating and setting the exposure timing for each line before the actual imaging process. The exposure start and end timings are determined in advance based on the focus lens driving speed and position, ensuring that all lines capture images at the intended focus position without requiring real-time adjustment during exposure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables high-accuracy and high-speed focus detection by ensuring consistent focus lens positions across all lines, improving AF accuracy compared to rolling shutter systems and maintaining faster detection speeds than stopping the focus lens during exposure.
Implementation Method 1
each of the plurality of pixel blocks includes a floating diffusion layer, a plurality of photoelectric conversion sections
Implementation Method 2
a focus detecting section that detects an in-focus position of the focus lens on a basis of contrast of the image data
Data Source
AI summary
An imaging apparatus includes: a focus lens driving section; an imaging section; and a focus detecting section. The focus lens driving section moves a position of a focus lens from one of an image side and an object side to the other over a predetermined driving period. The imaging section generates image data by starting exposure for a plurality of lines simultaneously and then by ending the exposure for the plurality of lines simultaneously within the predetermined driving period. The focus detecting section detects an in-focus position of the focus lens on a basis of contrast of the image data.