AUTOFOCUS CAMERA SYSTEM AND CONTROL METHOD THEREOF

• US 20140125859A1
• Filed: 10/13/2011
• Published: 05/08/2014
• Est. Priority Date: 05/23/2011
• Status: Active Grant

• Current Assignee: HDC Corporation
• Original Assignee: HDC Corporation
• Inventors: Jung, Sung Ho
• Granted Patent: US 9,055,199 B2
• Time in Patent Office: Days
• US Class Current: 348/347
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming
• CPC Class Codes: H04N 25/615 involving a transfer function modelling the optical system, e.g. optical transfer function [OTF], phase transfer function [PhTF] or modulation transfer function [MTF]
• CPC Class Codes: H04N 7/18 Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast
• CPC Class Codes: H04N 7/183 for receiving images from a single remote source

Abstract

Disclosed is an autofocus camera system and a control method thereof. A CCTV camera system which includes a main processor installed in a CCTV, a memory unit connected with the main processor, an input unit, a CCD camera, a video processing unit, a focus lens, and a zoom lens is provided. The CCTV camera system is designed to input and output control instructions through RS-485 communication and is controlled by a focus motor driver and a zoom motor driver which are connected to the main processor in which a focus motor and a zoom motor are comprised of stepping motors.

Claims

1. wherein autofocus camera system is composed of main processor within the CCTV, memory unit connected to the main processor, input unit that provide user interface connected to the main processor, output unit that shows the content that had been processed in the main processor, CCD camera that take photograph of the subject, video processing unit that converts analog signal that have been taken from the CCD camera to digital signal to be sent to the main processor, zoom and focus lens that have been prepared in order to carry out the focus function while taking picture of the object wherein the images are zoomed in or zoomed out;

main processor that had been mentioned above is connected to RS-485 transceiver which is built to receive or give out control command through RS-485 communication;

above mentioned focus and zoom lens are controlled by independently placed motors in each one that are connected to the main processor that are made from stepper motors;

image that had been filmed by CCD does not go through video processing unit but goes to BNC connector and shown to the user to CVBS by analog signal;

digital signal that had been converted in the image processing center will be stored in the memory unit to be used as location information with the autofocus;

focus motor drivers that are divided into several units according to the size of the lens move to focus points that are divided into units where it carries out the auto focusing function as one of the characteristics of the autofocus camera system;

2. wherein it pertains to claim 1 which states that the main processor is connected to the MTF calculation unit and focus error detection unit. Focus error detection unit refers to the value of MTF for lenses which are calculated by MTF calculation unit in order to detect the focus related errors and modify the errors as one of the characteristics of the autofocus camera system;

3. wherein it pertains to claim 1 which states that input unit is provided with focus initialization button to be used when focus function error occur form the main processor for initialization as one of the characteristics of the autofocus camera system;

4. wherein it pertains to claim 1 which states that autofocus camera system and the control method thereof is provided wherein return to the starting point stage where the coordinates of the focus motor returns or maintained to the home position when power is energized or the system is rebooted;

calculation stage is when image displacement occurs by the request of the user or through the zoom function, main processor that got the image from the CCD camera from the displaced location calculates the average value of the luminance which are from the various points in the recorded images;

movement by unit stage is where focus motor driver controls the movement of focus motor in order to move the focus lens into the nearby unit of the average luminance and contrast that had been calculated by referencing the Look Up Table henceforth known as LUT (Look UP Table) which is stored in the memory unit;

control stage is when the focus motors are rotated each in clockwise and counter clockwise direction to get each image in the moved number of steps by basing it on the unit;

adjustment stage where contrast ratio is calculated from each image;

focus stage wherein main processor compares two contrast ratios after the adjusting stage and winding the focus motor that had been rotated according to the set number of times of the steps towards where contrast is greater to adjust the focus; and

focus completion stage where average value of luminance and contrast ratio is calculated to store it to the memory unit after the focus has been set as one of the characteristics of the autofocus camera system and the control thereof;

5. wherein it pertains to claim 4 which states that focus stage is where focus motors are rotated clockwise and counter clockwise direction to get the images in the moved number of steps by basing it on the unit;

adjusting stage where contrast ratio is calculated from the images;

focus motor is rotated in clockwise direction to basic number of steps and winded in clockwise direction again until the point where change in luminance does not happen and set the focus starting from that point as one of the characteristics of the autofocus camera system and the control thereof;

6. wherein it pertains to claim 4 which states that contrast level which moved clockwise is greater than the contrast level that had been moved counterclockwise after the comparison from the comparative stage, focus motor is rotated in counterclockwise direction to basic number of steps and winded in clockwise direction again until the point where change in luminance does not happen and set the focus starting from that point as one of the characteristics of the autofocus camera system and the control thereof.