Camera Autofocus Using Image Analysis and Simple Lens Drive
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Solution Overview
Problem
The high cost and complexity of existing autofocus systems in cameras, which require specialized components like range finders and motors, increase the cost and size of digital cameras.
Innovation Solution
A camera autofocus system that captures a series of images at different lens positions and analyzes them to select the best-focused image, eliminating the need for a range finder and allowing the use of an inexpensive motor, such as a DC motor, to move the lens through a range of motion without seeking a specific position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional autofocus system with range finder and specialized motor is used, then focusing accuracy is improved, but camera cost and size increase
Solution Approach 1:
The patent removes the range finder from the autofocus system, extracting this specialized component while retaining focusing capability through alternative means (capturing multiple images at different lens positions and selecting the best-focused image through digital analysis)
Solution Approach 2:
The image sensor serves multiple functions: it acts as both the primary imaging device and the range finder for autofocus determination. The same sensor that captures the final photograph also captures the series of images used to determine focus distance, eliminating the need for a separate range finder
2Manufacturing precision
If a stepper motor or voice coil motor is used for lens control, then lens positioning precision is improved, but device cost and complexity increase
Solution Approach 1:
The patent uses a simple, inexpensive DC motor instead of a expensive stepper motor or voice coil motor. The system accepts that the motor does not need precise positioning control since it will move through the entire lens position range multiple times, and the correct focus position is identified through digital image analysis rather than precise mechanical positioning
3Speed
If the lens is moved to a pre-identified target position, then focusing speed is improved, but device complexity and cost increase
Solution Approach 1:
The system performs preliminary actions by capturing a series of images at different lens positions before the final photograph is taken. This allows the best-focused image to be identified in advance, and the lens can be moved to that position quickly without requiring complex real-time focusing control during the actual shot
Data Source
AI summary
A camera provides an autofocus function by capturing a series of images when a lens is at different positions, analyzing the images to identify a best-focused image, and outputting the best-focused image. Unselected images can be discarded. The camera can include a FIFO buffer that receives image data from an image sensor as the image sensor captures images. When a photographer activates a shutter button, an analysis system, which may be implemented in software, analyzes the images in the FIFO buffer and selects the best-focused image for output. In alternative embodiments, the movement of the lens and the capture of the images can be before or in response to activation of the shutter button.