PTZ Camera Privacy Zone Algorithm Using Angular Coordinates
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Solution Overview
Problem
Existing Pan Tilt Zoom (PTZ) dome cameras fail to effectively maintain privacy zones at higher tilt angles, leading to incomplete masking of objects due to the geometry of camera rotation, resulting in sudden screen blanking and user confusion.
Innovation Solution
An algorithm that translates defined privacy zones from pixel coordinates to absolute angular coordinates, allowing for the continuous masking of objects by converting these coordinates back to pixel coordinates as the camera moves, enabling the creation of a masked area or rectangle that follows the object across different pan, tilt, and zoom operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the privacy zone is defined using fixed pixel coordinates on the screen, then the implementation is simple and straightforward, but the privacy zone fails to track objects properly at higher tilt angles causing screen blanking
Solution Approach 1:
The patent transforms the privacy zone definition from fixed pixel coordinates to dynamic angular coordinates that change with camera orientation. The privacy zone is repositioned and resized based on the current pan and tilt angles, ensuring continuous tracking of the target object. This parameter transformation resolves the contradiction by making the system adaptable to different camera orientations while maintaining implementation feasibility through coordinate transformation algorithms.
2Measurement precision
If the privacy zone is updated in real-time to track moving objects, then the privacy masking remains accurate, but the processing complexity increases significantly
Solution Approach 1:
The patent replaces complex real-time image processing and object tracking algorithms with a simpler coordinate transformation approach. Instead of analyzing video content to track objects, the system uses mathematical transformations based on known camera orientation parameters (pan and tilt angles) to update privacy zone positions. This substitution reduces processing complexity while maintaining positioning accuracy.
3Adaptability or versatility
If the camera operates at higher tilt angles to access different areas, then the surveillance coverage is improved, but the existing privacy zone system fails causing screen blanking and user confusion
Solution Approach 1:
The patent makes the privacy zone dynamic by continuously updating its position and size based on the camera's current orientation angles. The system calculates the transformed coordinates of the privacy zone corners using the current pan and tilt angles, ensuring the privacy zone moves and scales appropriately as the camera tilts. This dynamic adaptation allows the camera to operate at any tilt angle while maintaining reliable privacy masking.
Data Source
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AI summary
The present invention advantageously provides a means by which the privacy zone on a PTZ camera can be maintained so that an object in the camera's sight is always masked or covered. An algorithm which remembers the defined privacy zones as an area in space marked by four rays touching the four corners of the marked zone and having absolute Pan, Tilt angular coordinates is presented. The privacy zone is initially defined by a rectangle on the screen with known pixel co-ordinates which are translated into angular coordinates. Then, when the camera moves and prepares to display a new screen, the privacy zone is superimposed on the object to be masked. Locating the object and displaying its privacy zone is done by translating the absolute angular coordinates of the original privacy zone into pixel coordinates. Additionally, multiple privacy zones can be displayed on one camera screen.