Auto-focus Technique for Image Capture Devices
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Solution Overview
Problem
Existing image capture devices lack an efficient auto-focus mechanism that can accurately determine and adjust the lens assembly configuration to achieve optimal focus on a scene, particularly for objects like faces, without manual intervention.
Innovation Solution
An image processor in the camera identifies regions of interest, determines the degree of focus using pixel values and luminance variation, and adjusts the lens assembly configuration parameters to achieve optimal focus, specifically by identifying skin pixels and facial regions to prioritize auto-focusing on faces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If manual focusing mechanism is provided, then user can configure lens assembly to obtain desired focus, but device complexity increases and operation becomes less automated
Solution Approach 1:
The image capture device performs auto-focus automatically by analyzing image data and adjusting lens configuration without user intervention. The processor evaluates focus metrics from captured images and autonomously determines optimal lens settings, enabling the device to serve itself in the focusing task.
Solution Approach 2:
The patent replaces manual mechanical focusing operations with an automated electronic control system. The processor uses image data analysis and computational algorithms to determine focus adjustments, substituting the need for manual mechanical manipulation of the lens assembly.
2Measurement precision
If auto-focus determination is performed without region of interest identification, then processing is simpler, but measurement precision of focus quality decreases
Solution Approach 1:
The patent divides the image into multiple regions of interest before performing focus assessment. By segmenting the image and analyzing focus quality in specific regions rather than the entire image, the system achieves more precise focus measurement while managing processing complexity through targeted analysis.
Solution Approach 2:
The system applies different focus assessment criteria to different regions of the image based on their importance. Regions of interest receive specialized focus analysis, allowing the device to prioritize measurement precision in critical areas while maintaining overall system efficiency.
3Reliability
If lens assembly configuration is adjusted frequently for auto-focus, then image quality improves, but loss of time due to continuous adjustment increases
Solution Approach 1:
The system performs focus assessment and adjustment in periodic cycles rather than continuously. The processor captures images, evaluates focus quality, and adjusts lens configuration at discrete intervals, balancing the need for high image quality with the time cost of frequent adjustments.
Solution Approach 2:
The patent implements a feedback mechanism where the processor continuously monitors image focus quality and adjusts lens configuration based on the assessed focus metric. This closed-loop control ensures that adjustments are made only when necessary to improve or maintain image quality, reducing unnecessary adjustments and time loss.
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
The solution enables reliable and adaptive auto-focus capabilities, ensuring clear and sharp images of faces and other objects by dynamically adjusting the lens assembly configuration based on focus analysis, enhancing image capture quality without manual user intervention.
Implementation Method 1
a lens assembly, which receives light rays representing a scene sought to be captured, and converges the light onto the capturing medium
Data Source
AI summary
Multiple sets of pixel values representing a captured image of a scene are received, with each set representing an image captured with a corresponding degree of focus. An image processor may identify a region of interest in the captured image, automatically determine the configuration parameters for a lens assembly to provide a desired degree of focus for the region of interest, and generate signals to configure a lens assembly. In an embodiment, the region of interest is a face, the desired degree of focus of the face is determined by computing a rate of variation of luminance of pixels representing the face, and the desired degree is the degree of the image having the maximum degree of focus.