PTZ Camera Auto Focus Using Distance Table Lookup
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Solution Overview
Problem
Existing automatic focusing methods for PTZ cameras are slow due to repeated adjustments of the focus motor and reliance on clarity evaluation and blind hill climbing search algorithms, which hinder fast focusing capabilities.
Innovation Solution
An automatic focusing method that calculates the current target object distance from the PTZ camera's lens to a monitored plane using a pre-established spatial object distance parameter, searching a preset relation table to determine the focus motor position based on object distance and magnification, and driving the focus motor to the determined position for rapid focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the prior art automatic focusing method using repeated focus motor adjustments and blind hill climbing search algorithm is used, then the focus can be obtained, but the focusing speed is slow and fast focusing cannot be achieved
Solution Approach 1:
The patent pre-calculates and stores the correspondence between object distances and focus motor positions in a relation table before actual focusing operations. When focusing is needed, the system directly queries the pre-prepared relation table to obtain the focus position corresponding to the current object distance, eliminating the need for repeated trial adjustments and clarity evaluations during actual focusing, thus achieving fast focusing
Solution Approach 2:
The patent creates a virtual model (relation table) that copies and stores the mapping relationship between object distances and focus positions obtained through preliminary measurements. This virtual model allows the system to quickly determine focus positions through table lookup without physically adjusting the focus motor multiple times, significantly reducing focusing time
2Measurement precision
If the PTZ camera adjusts focus motor position multiple times with clarity evaluation at each position, then accurate focus can be achieved, but the device complexity and operation complexity increase
Solution Approach 1:
The patent performs preliminary focusing measurements to establish the relation table containing object distance-focus position correspondences before actual use. During actual focusing operations, the system only needs to query the pre-established relation table based on object distance, avoiding repeated focus motor adjustments and clarity evaluations, thus simplifying the control process while maintaining focus accuracy
Solution Approach 2:
The patent replaces the mechanical trial-and-error focusing process (repeated focus motor adjustments with clarity evaluation) with an information-based approach (object distance measurement and relation table lookup). This substitution eliminates the need for iterative mechanical adjustments, reducing both device complexity and operational complexity while maintaining focusing accuracy
3Measurement precision
If the PTZ camera uses blind hill climbing search algorithm to find the position with largest clarity value, then focus can be achieved, but the productivity and response speed decrease
Solution Approach 1:
The patent pre-establishes the relation table containing the mapping between object distances and optimal focus positions through preliminary measurements. During actual focusing, the system directly queries this pre-prepared relation table using the measured object distance, obtaining the optimal focus position immediately without performing blind hill climbing search or repeated clarity evaluations, thus dramatically improving focusing efficiency and response speed while maintaining focus clarity
Solution Approach 2:
The patent creates a virtual copy (relation table) of the optimal focus position information for different object distances. Instead of performing time-consuming blind hill climbing searches each time, the system directly retrieves the pre-copied focus position information from the relation table based on object distance, significantly improving productivity while ensuring focus clarity
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 method enables fast focusing by quickly determining the focus motor position using a preset relation table, improving the speed of obtaining a clear image for PTZ cameras, even at arbitrary angles.
Implementation Method 1
The focus refers to a point where parallel light beams converge after refracted by a lens
Data Source
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AI summary
Embodiments of the present application provide an automatic focusing method and a PTZ camera. The method is applicable to the PTZ camera and comprises: calculating a current target object distance from a lens of the PTZ camera to a monitored target monitoring plane based on a pre-established spatial object distance parameter; wherein, the spatial object distance parameter contains a spatial plane equation of a reference monitoring plane; the reference monitoring plane is an equivalent plane of the target monitoring plane; searching in a preset relation table based on the current target object distance, a current magnification of the PTZ camera, determining a position information corresponding to a focus motor of the PTZ camera, the preset relation table including the relationship of the object distance, the magnification and the position information of the focus motor, and driving the focus motor to a position corresponding to the determined position information. Embodiments of the present application are applied to realize fast automatic focusing of the PTZ camera.