PTZ Camera Privacy Zone Coordinate Conversion
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Solution Overview
Problem
Current video security systems lack an effective method to convert privacy zone points from a still planar video image to corresponding pan/tilt/zoom coordinates in digital IP dome cameras, which are necessary for defining and masking private areas within the camera's field of view.
Innovation Solution
A method and system that utilize equations for distance along great circles of a sphere, where the sphere is defined by the pan-tilt axes of a PTZ camera with a radius equal to the focal length, to convert planar coordinates of privacy zone corners to corresponding pan/tilt coordinates, allowing for accurate positioning of privacy zones on the camera's field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If privacy zone corners are defined by moving the pan-tilt motor in analog dome cameras, then the privacy zone coordinates can be obtained, but this method cannot be applied to digital IP dome cameras which use compressed digital data streams
Solution Approach 1:
The patent replaces the mechanical pan-tilt motor positioning method with a mathematical coordinate conversion system. Instead of physically moving the camera to define privacy zones, the invention uses spherical coordinate geometry to convert planar image coordinates to PTZ motor coordinates, enabling digital IP dome cameras to define privacy zones on compressed video streams without mechanical movement.
Solution Approach 2:
The patent introduces spherical coordinates as an intermediary system between planar image coordinates and PTZ motor coordinates. The spherical coordinate system serves as a mathematical bridge that enables conversion between the two coordinate systems using great circle distance equations, facilitating the adaptation of privacy zone definition to digital IP camera systems.
2Ease of operation
If privacy zone corners are marked on a still video image, then visual definition is simplified, but converting these planar coordinates to PTZ coordinates requires an adequate conversion method which currently does not exist
Solution Approach 1:
The patent applies spherical geometry to solve the coordinate conversion problem. By modeling the camera's field of view as a sphere and using great circle distance equations, the invention accurately converts planar coordinates from still images to spherical PTZ coordinates, maintaining measurement precision while enabling easy visual definition of privacy zones on video images.
3Reliability
If the privacy zone algorithm draws coverage areas on received live video before compression, then privacy protection is achieved, but the camera must have accurate PTZ coordinates for each privacy zone corner which cannot be obtained from still images without conversion
Solution Approach 1:
The patent performs preliminary coordinate conversion by converting planar coordinates from still images to PTZ coordinates before the privacy zone algorithm processes live video. This preliminary action provides the camera with accurate PTZ coordinates needed for reliable privacy zone masking, while the conversion system maintains manageable complexity through mathematical formulations.
Data Source
AI summary
A method and system for converting privacy zone corner points in a still image to PTZ coordinates using the equations for distance along the great circles of a sphere, where the sphere is defined along the pan-tilt axes of a PTZ camera with radius equal to the focal length of the image. The method includes receiving planar coordinate data defining a plurality of privacy zone corner points, the planar coordinate data taken from a still image, converting each privacy zone corner point to corresponding spherical coordinates, converting each of the corresponding spherical coordinates to corresponding PTZ coordinates, and storing the corresponding PTZ coordinates in a storage device. The stored PTZ coordinates may then be transmitted to a computer monitor. The motor of the PTZ camera moves the camera according to the PTZ coordinates until the privacy zone corner points appear at the substantial center of the monitor screen.