Dynamic Calibration for Image Capture Device Focus Accuracy
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Solution Overview
Problem
Image capture devices face calibration errors due to limitations in production line processes and device aging, leading to focus speed issues and lens wobble, which are not adequately compensated by existing methods.
Innovation Solution
A dynamic calibration method that collects data during device operation to estimate and update calibration parameters, compensating for errors caused by production line, gravity, and thermal effects, improving auto-focus speed and reducing lens wobble.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If production line process calibration is used to set DAC codes for infinity and macro distances, then calibration parameters can be determined and stored, but calibration errors occur due to limitations in the production line process and device aging
Solution Approach 1:
The system performs preliminary calibration actions during production line processing to establish initial DAC codes for infinity and macro distances. These preliminary calibration values are stored and serve as the basis for subsequent operational calibration, allowing the device to function immediately after manufacturing while enabling future dynamic adjustments to correct any initial calibration errors.
Solution Approach 2:
The system continuously monitors actual focus performance during device operation and uses this feedback to detect calibration errors. By comparing expected focus positions (based on stored calibration parameters) with actual focus outcomes, the system identifies deviations caused by production limitations or device aging, and dynamically adjusts DAC codes to compensate for these errors.
2Reliability
If calibration parameters are adjusted to compensate for SAG and thermal effects, then focus accuracy improves under those conditions, but other calibration errors remain uncorrected
Solution Approach 1:
The system implements a universal calibration correction mechanism that handles multiple types of calibration errors through a single dynamic adjustment process. Rather than having separate compensation mechanisms for SAG, thermal effects, and other errors, the system uses a unified approach that can address various error sources simultaneously by dynamically adjusting DAC codes based on actual focus performance monitoring.
Solution Approach 2:
The system dynamically changes calibration parameters (DAC codes) during device operation based on detected focus errors. By continuously adjusting these parameters in response to actual performance data, the system can adapt to different error conditions including SAG, thermal effects, and other calibration issues, thereby improving both reliability and adaptability.
3Measurement precision
If the camera module hunts for focus when calibration errors are not compensated, then it can eventually find focus, but focus speed decreases and lens wobble increases
Solution Approach 1:
The system performs preliminary focus positioning using stored calibration parameters before initiating the focus hunt. By pre-positioning the lens close to the expected focus point based on previously calibrated DAC codes, the system significantly reduces the search range and time required to achieve actual focus, thereby improving focus speed while maintaining accuracy.
Solution Approach 2:
The system uses real-time feedback from focus detection to immediately adjust lens position and prevent excessive hunting. By continuously monitoring focus quality and making corrective adjustments, the system minimizes lens wobble and reduces the time spent searching for focus, thereby improving both focus speed and stability.
Data Source
AI summary
A method for dynamically calibrating an image capture device comprises: a) determining a distance (DCRT, DEST) to an object within a scene; b) determining a first lens actuator setting (DACINIT) for the determined distance; c) determining a second lens actuator setting (DACFOCUS) providing maximum sharpness for the object in a captured image of the scene; and d) storing the determined distance (DCRT, DEST) and the first and second lens actuator settings. These steps are repeated at a second determined distance separated from the first determined distance. A calibration correction (ERRNEARPLP, ERRFARPLP) for stored calibrated lens actuator settings (DACNEARPLP, DACFARPLP) is determined as a function of at least: respective differences between the second lens actuator setting (DACFOCUS) and the first lens actuator setting (DACINIT) for each of the first and second determined distances; and the stored calibrated lens actuator settings are adjusted according to the determined calibration corrections.