Imaging Sensor Tilt Coordinate Correction for Depth of Field
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Solution Overview
Problem
Network cameras face challenges in maintaining a deep depth of field in scenes like long houses or corridors, leading to image distortion and positional shifts when tilting the imaging plane, affecting privacy masking, image analysis, and compression areas.
Innovation Solution
A control apparatus and method that includes a CPU with zoom, focus, tilt, pan head, and coordinate management units, which performs coordinate correction processing to adjust the focal plane and maintain intended positional relationships of masking, analysis, and compression areas when the image sensor is tilted, using expressions to calculate new coordinates and apply corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the imaging plane is tilted to adjust the focal plane for deep depth of field scenes, then the depth of field coverage is improved, but image distortion and positional shifts occur
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between tilt angles and coordinate shifts. Before actual imaging, the system creates a correction map that maps original coordinates to corrected coordinates based on the tilt angle. When tilting occurs, the system simply looks up and applies the pre-computed correction, preventing distortion rather than correcting it afterward.
Solution Approach 2:
The patent replaces mechanical/optical correction mechanisms with a computational approach. Instead of using complex optical elements or mechanical adjustments to correct distortion, the system uses software-based coordinate transformation. The CPU performs mathematical calculations to map distorted coordinates back to their correct positions, substituting computational processing for physical correction mechanisms.
2Manufacturing precision
If the imaging plane is tilted to achieve deep depth of field, then the focus range is improved, but the positional relationship between image areas and coordinate system shifts
Solution Approach 1:
The patent implements feedback by continuously monitoring the tilt angle and using this information to dynamically adjust coordinate mappings. The system measures the actual tilt angle, retrieves the corresponding correction parameters, and applies the appropriate coordinate transformation. This closed-loop approach ensures that coordinate positions remain accurate despite changes in tilt angle, maintaining measurement precision across different focal plane configurations.
3Area of stationary object
If the imaging plane is tilted for deep depth of field coverage, then the scene coverage is improved, but privacy masking and image analysis functions are affected due to coordinate shifts
Solution Approach 1:
The patent applies preliminary action by pre-defining privacy masking areas and image analysis regions in the corrected coordinate system. Before tilting the imaging plane, the system calculates where these functional areas should be positioned in the distorted image. This allows privacy masking and image analysis to maintain their intended functionality even when the image is distorted by tilting, as the correction ensures these areas remain accurately positioned.
Data Source
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Figure 3A~3C
AI summary
A control apparatus (101) includes an angle control unit (101-3) configured to change an angle between an imaging plane of an image sensor (102-4) and a plane orthogonal to an optical axis of an imaging lens, an acquisition unit (101-7) configured to acquire positional information of a specific area of an image, and a management unit (101-7) configured to change the positional information based on the angle.