KR20000042950A - Auto focus control apparatus and method for comcorder - Google Patents

Abstract

PURPOSE: An auto focus control apparatus is provided to execute precise auto focusing operations by performing auto focusing operations with the use of luminance distribution data having the characteristics indicating minimum values. CONSTITUTION: A focus lens moves forwards and backwards along an optical axis to focus on an object. A focus motor(14) moves the focus lens forwards and backwards in the optical axis direction according to a predetermined control. A signal processor has a logic unit constituted with an auto focus data generator and a luminance distribution data generator(306) to carry out the auto focus and produces auto focus data and luminance distribution data from a photographing video signal of the object photographed and inputted from a camera for the auto focusing.

Description

Camcorder autofocus control device and method

The present invention relates to a camcorder, and more particularly, to an auto focus control apparatus and method of a camcorder.

In general, a camcorder is a portable photographing apparatus which not only has a function of a general video camera for photographing a subject but also has a function as a video recorder for recording a photographed subject.

The camcorder as described above typically implements an auto focusing function for automatically correcting a pint with a subject.

FIG. 1 illustrates an example of a device configuration of a camera system in a camcorder. Referring to FIG. 1, the lens unit 10 includes a zoom lens, a focus lens, and the like. The zoom lens is a lens that is moved back and forth in the optical axis direction by the zoom motor 12 to enlarge and reduce the magnification of the subject, and the focus lens is moved back and forth in the optical axis direction by the focus motor 14 so that the subject is in focus. to be. Each of the zoom motor 12 and the focus motor 14 is driven by the zoom motor driver 16 and the focus motor driver 18 controlled by the microcomputer 30. The aperture 20 located at the rear of the lens unit 10 is opened and closed by an aperture meter driven by the aperture control unit 32 to adjust the amount of incident light. The aperture control unit 32 is controlled by the microcomputer 30 to drive the aperture meter, and further includes a hall sensor to sense the opening / closing degree of the aperture 20 and the detected value of the microcomputer 30. Will print The CCD (Charge Coupled Device) 22 converts and outputs the optical signal of the subject that has passed through the lens unit 10 and the aperture 20 into an electrical signal (imaging image signal), and correlated double sampling / auto gain (CDS / AGC). The control unit 24 correlates double-sampled the captured image signal and adjusts the gain to output the CDS output to the aperture control unit 32 and outputs the gain-controlled output to the analog to digital converter (ADC) 26. The ADC 26 converts and outputs a captured image signal of one field, which is gain-adjusted by the CDS / AGC 24, into a digital signal. The digital signal processor (hereinafter referred to as "DSP") 28 includes an image signal processor for image processing and a logic unit for auto focusing, and the image signal processor is digitally converted. One field video signal is processed as NTSC (National Television System Committe) or PAL (Phase Alternation by Line) video signal (Y, C) and output to the VCR system.

The microcomputer 30 generally controls operations related to auto focusing of the video camera based on a control program stored in the internal memory. The microcomputer 30 is a focus lens in the lens unit 10 at a peak point at which the auto focus (hereinafter referred to as “AF”) data output from the integrator of the DSP 28 is the largest for auto focusing. Is controlled to stop the autofocusing operation. That is, the microcomputer 30 controls to stop when the position of the focus lens corresponds to the peak point P of the AF data as shown in FIG.

As described above, the bandpass filtered AF data shows a maximum value in a focused state in most cases, but when a part of the subject is saturated, that is, the luminance of a part of the subject is very large compared to the surroundings. If there is a portion, the distribution of AF data values according to the position of the focus lens has a data distribution in the form of a center portion not a peak as shown in FIG.

Therefore, as in the prior art, when performing an autofocusing operation to stop the position of the focus lens at the peak point P of the AF data, there is a problem that autofocusing is not performed properly.

As described above, in the conventional camcorder, the autofocusing operation of stopping the position of the focus lens at the peak point of the AF data does not accurately set the position of the focus lens due to the unbalanced distribution of the AF data when a part of the subject is saturated. There was a problem.

Accordingly, it is an object of the present invention to provide an apparatus and method for autofocus control of a camcorder for accurately setting the position of a focus lens even when a part of a subject is saturated.

1 is a block diagram of a conventional camcorder;

FIG. 2 is a diagram illustrating an autofocus data distribution according to a position of a focus lens in a case of a general subject and an autofocus data distribution in accordance with a position of a focus lens in a case of a shaded subject;

3 is a detailed block diagram of a logic unit for autofocusing in a signal processing unit according to an embodiment of the present invention;

4 is a detailed block diagram illustrating the luminance distribution data generation unit of FIG. 3;

5 is a diagram illustrating luminance distribution data for each position of a focus lens and autofocusing data distribution according to the position of the focus lens in the case of a saturated subject;

6 is a process flowchart for autofocusing control according to an embodiment of the present invention;

According to an aspect of the present invention, an autofocus control apparatus for a camcorder includes a focus lens that is moved back and forth in the optical axis direction to focus a subject, and a focus that moves the focus lens back and forth in the optical axis direction according to a predetermined control. Autofocus (AF) data and luminance for autofocusing from the captured image signal of the subject captured and input from the camera unit having a motor and a logic unit for autofocusing comprising an autofocus data generator and a luminance distribution data generator A signal processor for generating and outputting distribution (HISTO) data; and when the luminance level of the captured image signal exceeds a preset reference value, the current subject is judged as a saturation subject, and the luminance distribution data value is minimized. To control the focus lens to be located It is characterized by including a microcomputer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Many specific details are set forth in the following description and in the accompanying drawings to provide a more general understanding of the invention. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. And a detailed description of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

3 is a detailed block diagram illustrating a logic unit for autofocusing in a camcorder signal processing unit according to an exemplary embodiment of the present invention. Referring to FIG. 3, the logic unit 300 for autofocusing in the DSP includes a band pass filter 302, an integrator 304, and the like that sets a band width for autofocusing. The band pass filter 302 performs band pass filtering on the luminance signal of the digitally converted captured image signal to a predetermined bandwidth, and the integrator 304 integrates the AF data generated by integrating the signal passed through the band pass filter to the microcomputer 308. Output The luminance distribution (HISTO) data generating unit 306 is a newly provided block according to an embodiment of the present invention. The luminance signal is divided by size and the luminance signal counted by counting the distribution of the luminance signal size. Output the distribution (HISTO) data.

FIG. 4 illustrates a detailed block configuration of the luminance distribution data generator 306. Referring to FIG. 4, the operation of the luminance distribution data generator 306 will be described in detail. 306 includes a luminance signal size determining unit 400 and a pixel number calculating unit 402. The luminance signal size determining unit 400 determines the luminance signal size of each input pixel, that is, the amount of light of each pixel. The calculating unit 402 adds each pixel determined by the luminance signal size determining unit 400 for each luminance signal and outputs the luminance distribution data.

5 illustrates a distribution diagram corresponding to the position of the focus lens of the luminance distribution data output from the luminance distribution data generator 306. The distribution chart of the luminance distribution data shows the lowest value at the portion where the focus lens is focused as shown in FIG. 5A when a part of the subject is saturated.

Therefore, when a part of the subject is saturated according to the characteristics of the luminance distribution data as described above, the microcomputer 308 may reduce the autofocusing error by performing autofocusing using the luminance distribution data instead of using the AF data. .

FIG. 6 illustrates a processing flow in the microcomputer 308 for performing autofocusing by using luminance distribution data input from a signal processor when a part of a subject is saturated according to an exemplary embodiment of the present invention. Hereinafter, an embodiment of the present invention will be described in detail with reference to the flowchart of FIG. 6. In particular, in the embodiment of the present invention, a case in which the luminance signal of the CCD pixel picked up from the subject is displayed with 10 bits, that is, 0 to 1024 levels will be described as an example.

First, the microcomputer 308 receives AF data and luminance distribution (HISTO) data together from the logic unit 300 for autofocusing to the signal processing unit in step 600 to perform an autofocusing operation. The microcomputer 308 proceeds to step 602 to calculate the number of pixels whose magnitude of the luminance signal is between 128 and 1024 levels in the CCD pixels of the photographed subject to determine whether the number of the pixels exceeds a preset reference value K. FIG. Examine whether or not. The reference value is a preset value for determining whether a part of a subject is saturated, and means the number of pixels whose magnitude is between 128 and 1024 levels. In this case, if the number of pixels whose luminance signal is between 128 and 1024 levels in the CCD pixels of the subject does not exceed the reference value in operation 602, the microcomputer 308 saturates the subject in operation 604. It is determined as a general subject having no part, and autofocusing operation is performed using AF data among the data input from the signal processor as in the normal case. That is, the microcomputer 308 moves to the focus lens in step 606, and in step 608, a peak at which the value of the AF data becomes the maximum value among the distributions of the AF data shown in FIG. It is checked whether the focus lens is located at the point P. If the position of the focus lens is not located at the peak point P corresponding to the maximum value of the AF data, the microcomputer 308 repeats steps 606 to 608, and the position of the focus lens is AF data. Control to be located at the maximum value point of. On the other hand, if the position of the focus lens is located at the point corresponding to the maximum value of the AF data in step 608, the microcomputer 308 proceeds to step 610 to stop driving the focus motor 14 so that the focus lens is Control not to move anymore.

On the contrary, if the number of pixels whose luminance signal is between 128 and 1024 levels in the CCD pixels of the subject exceeds the reference value in step 602, the microcomputer 308 sets a portion of the subject in step 612. It is determined that the operation is performed, and accordingly, an autofocusing operation is performed using the luminance distribution data among the data input from the signal processor. That is, the microcomputer 308 moves to the focus lens in operation 614, and in operation 616, the value of the luminance distribution data becomes the minimum value among the distribution diagrams of the luminance distribution data shown in FIG. 5A. It is checked whether the focus lens is located at the point M. If the position of the focus lens is not located at the point M corresponding to the minimum value of the luminance distribution data, the microcomputer 308 performs steps 614 to 616 again, and the position of the focus lens is the luminance distribution data. Control to be located at the minimum value point (M) of. On the contrary, when the position of the focus lens is located at the point M corresponding to the minimum value of the luminance distribution data in step 616, the microcomputer 308 proceeds to step 618 to stop driving the focus motor 14. Controls that the focus lens no longer moves.

Therefore, when a part of the subject is saturated, the autofocusing operation is performed using luminance distribution data having a characteristic indicating a minimum value at the point where the focus lens is focused, thereby auto-focusing conventional AF data by part of the subject. Accurate autofocusing can be performed even if it is not available for operation.

As described above, according to the present invention, when a part of the subject is saturated, a part of the subject is saturated by performing an autofocusing operation using luminance distribution data having a characteristic indicating a minimum value at the point where the focus lens is focused. Even if the AF data of the data cannot be used for the autofocusing operation, there is an advantage of performing an accurate autofocusing operation.

Claims (6)

In the autofocus control device of a camcorder, A focus lens which is moved back and forth in the optical axis direction to focus the subject, A focus motor for moving the focus lens back and forth in the optical axis direction according to a predetermined control; Autofocus (AF) data and luminance distribution (HISTO) for autofocusing from the captured image signal of the subject captured and input from the camera unit having a logic unit for autofocusing comprising an autofocus data generator and a luminance distribution data generator A signal processor for generating and outputting data; When the magnitude of the luminance signal of the captured image signal exceeds a preset reference value, the subject currently being captured is regarded as a saturated subject, and the focus lens is positioned at a point where the value of the luminance distribution data is minimized. Autofocus control device for a camcorder, characterized in that consisting of a microcomputer to control. The method of claim 1, wherein the luminance distribution data generation unit, A luminance signal magnitude determining unit for classifying all pixels of the captured image signal according to the magnitude of the luminance signal represented by each pixel; And a pixel number calculating unit for outputting the luminance distribution data as a result of summing pixels having the same luminance signal size. The method of claim 1, wherein the autofocus data generator, A bandpass filter for bandpass filtering the luminance signal of the captured image signal to a predetermined bandwidth; And an integrator for integrating the bandpass filtered luminance signal to output the autofocus data. The method of claim 1, wherein the microcomputer When the magnitude of the luminance signal of the captured image signal does not exceed a preset reference value, the subject currently being captured is regarded as a general subject, and the focus lens is positioned at the point where the value of the autofocus data is maximized. An autofocus control device for a camcorder. In the autofocusing method of an autofocus control apparatus of a camcorder comprising a focus lens, a focus motor, a signal processor, and a microcomputer, Receiving luminance distribution data and autofocus data input from the signal processor; Inspecting whether or not the magnitude of the luminance signal of the captured image signal of the subject imaged and input from the camera unit exceeds a preset reference value; If the magnitude of the luminance signal of the captured image signal exceeds the reference value as a result of the inspection, the subject is currently photographed as a saturated subject, and the focus lens is positioned at a point where the value of the luminance distribution data is minimized. Autofocus control method of the camcorder, characterized in that consisting of a process of controlling. The method of claim 5, If the magnitude of the luminance signal of the captured image signal does not exceed the reference value, determining that the subject being captured is a general subject and controlling the focus lens to be positioned at the point where the value of the autofocus data is maximized. Autofocus control method of the camcorder characterized in that it further comprises.