Camera Lens Assembly Alignment Using MTF Slant-Edge Analysis
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Solution Overview
Problem
Existing methods for aligning camera lens assemblies are inefficient and time-consuming, as they rely on fixed Standard Deviation ranges and do not account for lens rotation, often failing to achieve the required minimum and maximum focus range accurately.
Innovation Solution
The method involves using Modulation Transfer Function (MTF) to estimate contrast variations in slant edges of captured images, automatically detecting slant edges without manual interpretation, and adjusting the lens assembly to achieve maximum MTF values, thereby aligning it efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fixed Standard Deviation range is used for lens alignment, then alignment process is simplified, but alignment accuracy and focus range requirement are not met
Solution Approach 1:
The patent changes the alignment parameter from fixed Standard Deviation range to dynamic MTF (Modulation Transfer Function) values. By calculating MTF at different lens positions and selecting the position with maximum MTF, the system achieves both operational simplicity and high alignment accuracy, resolving the contradiction between ease of operation and measurement precision.
2Measurement precision
If multiple test charts at minimum and maximum working distances are used, then comprehensive alignment is achieved, but processing time increases
Solution Approach 1:
The patent extracts the essential alignment information from multiple test charts by using a single test chart at one working distance. The MTF calculation captures the critical contrast variation data needed for alignment, eliminating the need to process multiple charts at different distances while maintaining comprehensive alignment coverage.
Solution Approach 2:
The system performs preliminary MTF calculation and analysis on a single test chart image to determine the optimal lens position. This preliminary action provides sufficient alignment information, avoiding the need for subsequent adjustments based on additional test charts, thus reducing processing time while maintaining alignment accuracy.
3Ease of operation
If lens rotation is not considered in alignment, then alignment process is simpler, but minimum and maximum working distance requirements are not achieved
Solution Approach 1:
The patent implements feedback by calculating MTF values at different lens positions and using this information to adjust the lens assembly. The MTF calculation inherently accounts for lens rotation effects on image contrast, providing feedback that guides the lens to the optimal position that satisfies both simplicity and precision requirements.
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 allows for precise alignment of the lens assembly to achieve the desired focus range, reducing processing time and ensuring accurate minimum and maximum working distances without manual intervention.
Implementation Method 1
estimating, by the image processor, contrast variations in the at least one slant edge spread over the at least one region of the at least one image frame using Modulation Transfer Function (MTF), wherein the contrast variations in the at least one slant edge identify a black and white transition in the at least one image frame
Data Source
AI summary
Embodiments of the present disclosure provide a method for aligning a lens assembly of a camera. The method is performed by an image processor of the camera. The method includes obtaining at least one image frame being captured by the camera. The method includes determining at least one slant edge spread over at least one region of at least one image frame by analyzing each image frame. The method includes estimating contrast variations in the at least one slant edge spread over the at least one region of the at least one image frame using Modulation Transfer Function (MTF). The method includes aligning the lens assembly of the camera in accordance with the estimated contrast variations in the at least one slant edge spread over the at least one region of the at least one image frame.