Image Sensor Independent Pixel Signal Readout for Autofocus Latency
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Solution Overview
Problem
Existing digital camera autofocus systems experience latency issues, particularly when capturing moving subjects, leading to potential out-of-focus images due to the time gap between exposure for rangefinding and focus lens adjustment.
Innovation Solution
The imaging device independently reads out focus pixel signals from phase-difference pixels and main pixel signals from normal pixels, allowing for simultaneous or sequential processing, with the focus pixel signals being processed prior to or in parallel with the main pixel signals, and temporarily storing main pixel signals in frame memory for later output, enabling faster autofocus adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the digital camera measures distance and drives the lens to adjust focus in sequence, then focusing accuracy is improved, but autofocus latency increases
Solution Approach 1:
The patent implements preliminary action by measuring the distance to the subject and completing focus lens adjustment before the imaging exposure is finalized. The control unit measures distance using focus detection pixels, calculates the required focus adjustment, and drives the focus lens to the correct position during the exposure period or before the imaging signal is fully captured. This ensures the lens is already in focus when the image is captured, eliminating latency without sacrificing accuracy.
Solution Approach 2:
The patent applies dynamics by enabling real-time, continuous autofocus adjustment during the imaging process. Rather than completing focus adjustment after exposure, the system dynamically updates focus based on real-time distance measurements from focus detection pixels. The control unit continuously monitors distance changes and adjusts the focus lens position dynamically during the exposure period, allowing the system to adapt to moving subjects and maintain sharp focus throughout the capture process.
2Measurement precision
If the digital camera uses focus detection pixels to measure distance, then autofocus precision is improved, but the time required for focus adjustment increases
Solution Approach 1:
The patent uses preliminary action by having the control unit calculate the required focus lens adjustment amount based on distance measurements from focus detection pixels before the imaging exposure completes. The system determines the focus adjustment needed during the exposure period and executes the lens movement in advance or concurrently, rather than waiting until after the image is captured. This reduces the perceived focus adjustment time while maintaining precision.
Solution Approach 2:
The patent implements continuity of useful action by performing distance measurement, focus calculation, and lens adjustment continuously during the imaging exposure. The focus detection pixels operate throughout the exposure period, providing continuous distance data that allows the control unit to make real-time focus adjustments. This continuous operation eliminates idle time between measurement and adjustment, maintaining both precision and speed.
Data Source
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AI summary
There is provided an image sensor including: a control unit configured to control pixels in a manner that a readout of a focus pixel signal from a focus detection pixel used for focusing and a readout of a main pixel signal from a pixel used for image generation are conducted independently; and an output unit configured to output the focus pixel signal and the main pixel signal independently from each other.