Imaging Device Time-Division Reading for Autofocus Edge Control
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Solution Overview
Problem
Rolling shutter reading in imaging devices can result in unnatural edges in images, particularly for moving subjects, due to the need to read image signals twice for each vertical line.
Innovation Solution
An imaging device with a control unit that performs time-division reading for rolling shutter systems, where the first reading generates image values by summing first and second pixels of photodiode division pixels, and the second reading separately obtains values for these pixels, with separate exposure periods for each reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reading is performed twice for each vertical line to obtain both image values and phase difference values, then phase difference demodulation accuracy is improved, but unnatural edges occur in images particularly for moving subjects
Solution Approach 1:
The pixel array is divided into first pixel regions and second pixel regions, where first pixels are used for image generation and second pixels are used for phase difference detection. This spatial segmentation allows simultaneous fulfillment of both functions without interference, resolving the contradiction between accurate phase difference measurement and natural image appearance.
Solution Approach 2:
The phase difference detection function is extracted from the image generation process by dedicating specific second pixels solely to phase difference measurement. This extraction allows the phase difference reading to be performed independently without causing the unnatural edge effects that occur when the same pixels are used for both purposes.
2Loss of information
If reading is performed twice for each vertical line, then phase difference information is obtained, but reading time and processing complexity increase
Solution Approach 1:
The reading operations are merged into a single unified reading process that simultaneously retrieves both image values and phase difference values. By combining the reading operations and performing them in parallel rather than sequentially, the total reading time is reduced while still obtaining both types of information.
Solution Approach 2:
The pixel array is designed with multi-functionality, where each pixel type serves its dedicated function but both functions operate within the same imaging system simultaneously. This universal design allows the system to obtain phase difference information without requiring separate reading operations, thereby reducing processing time.
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 prevents unnatural edge shifts in images and maintains accurate phase difference demodulation for autofocus control, enhancing image quality and autofocus performance.
Implementation Method 1
an imaging element including a photodiode division pixel
Data Source
AI summary
An imaging device includes an imaging element including a photodiode division pixel, and a control unit. The control unit performs control such that, as reading corresponding to one frame of an image in a case where rolling shutter reading from the imaging element is performed, first reading that reads an addition value of a first pixel and a second pixel constituting the photodiode division pixel for all pixels as image generation targets, and second reading that can obtain a value of the first pixel and a value of the second pixel for some pixels of pixels as image generation targets are performed in a time division manner, and an exposure period for the first reading and an exposure period for the second reading are separately provided.