Autofocus Calibration for Miniaturized Camera Modules
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Solution Overview
Problem
Existing digital image capture devices face challenges in accurately calibrating autofocus systems for miniaturized focus systems like voice-coil and MEMS, especially when used in non-horizontal orientations, due to varying actuator characteristics and non-linearities, leading to poor autofocus performance and increased focus times.
Innovation Solution
A method for dynamically adjusting autofocus operations based on device orientation, using batch characterization and statistical data to determine device-specific DAC settings for focus points of interest, allowing for accurate calibration without the need for precise calibration at each orientation, and storing these settings in a one-time programmable memory for efficient mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate image and autofocus sensors are used, then autofocus measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses the image sensor to capture images at multiple focus positions and creates a virtual autofocus measurement system through software processing. Instead of requiring a separate autofocus sensor, the system copies the imaging function to perform contrast detection on successive images, thereby achieving autofocus capability without additional hardware.
Solution Approach 2:
The image sensor serves dual purposes: it performs the primary imaging function and simultaneously enables autofocus measurement through contrast detection on sequential images. This multi-functionality eliminates the need for dedicated autofocus sensors in single-function digital cameras.
2Device complexity
If fixed number of lens positions or points of interest are used, then device complexity is reduced, but autofocus performance at non-horizontal orientations deteriorates
Solution Approach 1:
The patent dynamically determines the number and positions of points of interest based on the device's current orientation. Instead of using a fixed set of lens positions, the system adapts the autofocus parameters in real-time according to orientation data from sensors, ensuring optimal focus performance across all orientations while maintaining manageable system complexity.
Solution Approach 2:
The system changes the autofocus parameters (number of points of interest, lens positions) based on orientation conditions. By modifying these parameters dynamically according to the device orientation, the system maintains high autofocus reliability without requiring a completely different fixed configuration for each orientation.
3Manufacturing precision
If pre-defined points of interest are used, then manufacturing precision requirements are reduced, but autofocus accuracy at non-horizontal orientations deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where orientation information from sensors is continuously fed back to adjust the autofocus parameters. This feedback loop allows the system to compensate for orientation variations and maintain accurate focus measurement without requiring extremely precise manufacturing tolerances for fixed points of interest.
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 enables accurate and efficient autofocus calibration across multiple orientations, reducing focus times and eliminating focus hunting, while being cost-effective and practical for mass production of miniaturized camera modules.
Implementation Method 1
miniaturized focus systems such as voice-coil and MEMS focus systems
Implementation Method 2
miniaturized focus systems such as voice-coil and MEMS focus systems
Data Source
AI summary
A method for calibrating an image capture device comprises mounting at least one sample device from a batch for movement through a plurality of orientations relative to a horizontal plane. For a given orientation, the sample device is focused at a sequence of positions, each position being at a respective focus distance from the device. A lens actuator setting is recorded for the sample device at each position. This is repeated at a plurality of distinct orientations of the sample device. Respective relationships are determined between lens actuator settings at any given position for distinct orientations from the plurality of distinct orientations and actuator settings at a selected orientation of the plurality of distinct orientations. Lens actuator settings for the image capture device to be calibrated are recorded at least at two points of interest (POI), each a specified focus distance from the device with the image capture device positioned at the selected orientation. The image capture device is calibrated for the plurality of distinct orientations based on the determined relationships and the recorded lens actuator settings.