Camera Lens Tilt Detection Using Autofocus Position Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Small format factor cameras, such as those in smartphones and tablets, face challenges in maintaining image quality due to lens tilt, which can result in portions of captured images being out of focus, as the optical axis may not be orthogonal to the photosensor plane, leading to dynamic or static tilt issues.
Innovation Solution
The use of autofocus position sensors to derive both the autofocus position and lens tilt, allowing for the application of a tilt correction transform during image processing, and providing optical image stabilization by translating the lens on the X and Y axes to align the image plane with the photosensor, thereby correcting for lens tilt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical lens is moved as a single rigid body along the optical axis to refocus the camera, then the autofocus function is achieved, but lens tilt occurs causing portions of captured images to be out of focus
Solution Approach 1:
The patent uses autofocus position sensors to continuously monitor the lens position and detect tilt conditions. The sensor signals are processed to generate tilt correction signals that are fed back to the actuator system, creating a closed-loop control mechanism that maintains focus accuracy while compensating for tilt during lens movement
Solution Approach 2:
The patent changes the operational parameters by deriving both common mode signals (for focus position) and differential mode signals (for tilt detection) from the same autofocus position sensors. This allows the system to use existing sensor data in multiple ways to simultaneously control focus and compensate for tilt without adding separate measurement devices
2Volume of moving object
If the camera is designed with small form factor for mobile devices, then the device size is reduced, but lens tilt detection and correction capability is compromised
Solution Approach 1:
The patent makes the autofocus position sensors serve dual functions: measuring focus position (common mode signal) and detecting lens tilt (differential mode signal). This multi-functionality eliminates the need for separate tilt sensors, maintaining tilt detection capability while preserving the compact form factor required for mobile devices
Solution Approach 2:
The patent combines the tilt detection function with the existing autofocus positioning system by using the same sensors and signal processing circuitry. The differential mode signal derivation merges tilt measurement capabilities into the focus control infrastructure, reducing component count and maintaining small form factor
3Volume of moving object
If the optical axis is not orthogonal to the photosensor plane, then the camera can be compact, but image quality deteriorates due to lens tilt
Solution Approach 1:
The patent applies tilt correction transforms to image data during the image processing stage, before final image output. This preliminary correction of tilt effects in the digital domain compensates for optical alignment imperfections, allowing the use of compact camera modules with relaxed mechanical tolerance requirements
Data Source
AI summary
Methods and apparatus for detecting and correcting for lens tilt in cameras. The common mode signal may be derived from autofocus position (AP) sensors and used as a measure of the autofocus position of the lens on the Z axis. The differential mode signal may also be derived from the AP sensor signals. The differential mode signal may indicate that the lens is or is not tilted, and if tilted may indicate the direction and magnitude of the tilt. The differential mode signal may be used to apply a tilt correction transform to image data based on the strength and direction of the signal. The differential mode signal may also be used to translate the lens on an axis orthogonal to the Z axis to partially correct for lens tilt to align the image plane with the photosensor.