Autofocus Calibration via Inertial Sensor Orientation Data
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Solution Overview
Problem
Low-cost auto-focus camera modules in mobile devices, such as smartphones, are sensitive to external forces like gravity and temperature changes, leading to variations in focal properties that can cause image distortion and affect measurement accuracy, making them unsuitable for measurement applications.
Innovation Solution
Incorporating inertial sensors to measure device orientation and temperature sensors to correct focal properties by adjusting the autofocus mechanism and processing electronic images, using calibration parameters computed from measurements taken in various orientations and temperatures to compensate for these variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-cost autofocus camera modules are used, then device cost is reduced, but focal stability deteriorates due to sensitivity to gravity and temperature
Solution Approach 1:
The system performs preliminary calibration by capturing images at multiple predetermined orientations and temperatures to pre-compute correction parameters. This preliminary action stores compensation data that is later applied during actual operation, allowing the low-cost module to achieve stable focal properties without requiring expensive mechanical stabilization mechanisms.
Solution Approach 2:
The system changes operational parameters by capturing calibration images at different orientations (0°, 90°, 180°, 270°) and temperatures (e.g., 10°C, 25°C, 40°C). These parameter variations are used to compute orientation-dependent and temperature-dependent correction parameters that compensate for environmental effects on focal properties.
2Manufacturing precision
If autofocus mechanism is adjusted to correct focal variations, then image quality is improved, but device complexity increases
Solution Approach 1:
Instead of using complex mechanical stabilization systems to physically maintain focal accuracy, the patent substitutes a computational approach. The system uses image processing and software-based correction algorithms to compensate for focal variations, replacing mechanical complexity with computational simplicity.
Solution Approach 2:
The system captures reference images at predetermined orientations and uses these copies as basis for computing correction parameters. These reference copies are stored and used to generate correction data that compensates for orientation and temperature effects, avoiding the need for real-time complex adjustments.
3Measurement precision
If calibration is performed at multiple orientations and temperatures, then measurement accuracy is improved, but calibration time and resource usage increase
Solution Approach 1:
The comprehensive calibration at multiple orientations and temperatures is performed as a preliminary one-time process during device setup or manufacturing. The correction parameters obtained from this extensive calibration are stored and reused during normal operation, so the time investment is made once rather than repeatedly.
Solution Approach 2:
The system performs calibration at more orientations and temperature points than strictly necessary (e.g., four orientations at 0°, 90°, 180°, 270° and multiple temperature points), creating an excessive amount of calibration data. This excessive action ensures comprehensive coverage of operational conditions and provides robust correction parameters for the entire operating range.
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
Enables accurate image capture and measurement by correcting for focal property changes due to orientation and temperature, improving the reliability of low-cost camera modules for measurement applications.
Implementation Method 1
an inertial sensor outputs a signal indicative of an orientation of the device
Implementation Method 2
a temperature sensor outputs a signal indicative of a temperature of the device
Implementation Method 3
an electronic controller receives an indication from a sensor (which may be the image sensor of the camera itself or an external sensor) of the necessary focus adjustment, and drives a electromechanical element to adjust the focal distance of the camera optics accordingly
Data Source
AI summary
A mobile device includes a camera module, including a lens and an image sensor. An inertial sensor in the mobile device outputs a signal indicative of an orientation of the device. A controller corrects one or more focal properties of the camera module responsively to the orientation indicated by the inertial sensor.