Auto-focus Circuit Architecture for Image Signal Processor
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Solution Overview
Problem
Existing image processing pipelines in electronic devices consume significant resources and bandwidth when performing auto-focusing tasks, affecting user experience and device performance due to the need for CPU execution and increased power consumption.
Innovation Solution
An image signal processor with a separate auto-focus circuit that determines phase shift among focus pixel values to generate signals for adjusting the lens position of the image sensor, allowing continuous processing without impacting other image processing pipelines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If auto-focusing is performed using CPU execution, then processing capability is improved, but power consumption and resource usage increase
Solution Approach 1:
The patent divides the image processing pipeline into separate functional units: a dedicated auto-focus circuit that operates independently from the main image processing pipeline. This segmentation allows the auto-focus function to be handled by specialized hardware rather than consuming CPU resources, thereby reducing power consumption while maintaining processing capability.
Solution Approach 2:
The patent introduces a dedicated auto-focus circuit as an intermediary component between the image sensor and the main image processing pipeline. This intermediary handles focus determination separately, preventing resource contention and reducing the computational burden on the CPU and main processing pipeline.
2Device complexity
If a shared image processing pipeline is used, then device complexity is reduced, but processing speed and responsiveness decrease
Solution Approach 1:
The patent segments the image processing system into independent parallel pipelines: a dedicated auto-focus pipeline and a main image processing pipeline. This segmentation enables simultaneous operation of both functions without mutual interference, improving focus adjustment speed while maintaining manageable device complexity through modular architecture.
Solution Approach 2:
The dedicated auto-focus circuit performs focus determination in advance and independently, generating focus adjustment signals before the main image processing pipeline completes its tasks. This preliminary action ensures rapid focus response without waiting for other processing stages.
3Measurement precision
If CPU resources are allocated for auto-focusing, then processing accuracy is improved, but available resources for other tasks decrease
Solution Approach 1:
The patent introduces a dedicated auto-focus circuit as an intermediary that handles focus determination independently from the main processing pipeline. This intermediary performs precise phase shift calculations and focus metric computations using specialized hardware, achieving high measurement precision while preserving CPU and other system resources for other tasks.
Solution Approach 2:
The auto-focus circuit is self-sufficient, containing all necessary components for focus determination within its dedicated hardware structure. It performs self-service by independently acquiring image data, calculating focus metrics, determining phase shifts, and generating control signals without requiring CPU intervention, thereby maintaining resource availability for other system functions.
Data Source
AI summary
Embodiments relate to image signal processors (ISP) that include one or more auto-focus circuits. Each of the auto-focus circuits may be connected to an image sensor and may be separate from a statistics circuit and other image processing pipelines of the ISP. An image sensor may include one or more focus pixels that are used to generate data for auto-focusing. The auto-focus circuit may extract the focus pixel values and generate a signal to control the lens position of the image sensor. Each image sensor may include a separate auto-focus circuit. When other image processing pipelines of the ISP are processing the image data from one image sensor, the auto-focus circuit for another image sensor may continue to generate focus signals that control the lens position of the other image sensor. The other image sensor may be in standby but may continue to remain in focus.