KR19980066278A - Auto Focus Control Method of Video Camera - Google Patents

Abstract

The present invention relates to a method for controlling autofocus of a video camera, which is intended to accurately track focusing even when a subject changes, or a change in autofocus data due to a change in angle of view when the subject is zoomed.

The present invention as described above comprises a first step of extracting focus data by moving the focus lens by a first predetermined section in the current zoom tracking direction when the subject is zoomed, and extracting a change amount of focus data due to a change in angle of view at this time; A second step of extracting focus data by moving the focus lens by a second predetermined section in the reverse direction of the zoom tracking direction and extracting an amount of change of focus data due to a change in angle of view at this time; A third step of calculating the focus data obtained in the first step and the amount of change thereof; A fourth step of calculating the focus data obtained in the second step and the amount of change thereof; And integrating the two calculated values to determine a focal point tracking direction to perform tracking.

Accordingly, accurate focusing tracking can be performed regardless of the change of the auto focus data and the subject caused by the change in the angle of view when the subject is zoomed.

Description

Auto focus control method of video camera.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to focus control of a camera integrated digital VR (hereinafter, referred to as a video camera), and more particularly, to a change in the angle of view of a subject during zooming in a device such as a video camera employing a digital auto focus method. The present invention relates to an autofocus control method of a video camera which controls to find an accurate focal track regardless of the amount of change in autofocus data.

In general, the high magnification used in a video camera is used to zoom in or out of a subject by using X8 zoom and X10 zoom. However, there is a limit to a zoom device for miniaturizing a lens as well as a high magnification zoom effect in a video camera. .

Therefore, in order to obtain a high magnification zoom effect, the subject is enlarged or reduced by using digital zoom to overcome the limitation caused by the lens.

However, when zooming in such a general video camera, an accurate focus is required in order to reliably reproduce an image of a subject and to capture a momentary image.

As described above, when the subject is enlarged or reduced, the method for reproducing the image of the subject most reliably is to find a track in focus by controlling the focus motor.

However, when zooming in a normal video camera employing a digital autofocus method, the autofocus data size at the right focus position varies depending on the subject and also varies depending on the angle of view, resulting in tracking to an unfocused part. Often it happens.

1 is a block diagram illustrating an auto focus control apparatus of a general video camera.

Referring to FIG. 1, a lens group 100 including a focus lens and a zoom lens that zoom in and out of a subject while receiving and retreating in an optical axis direction and receive an image of the subject; A focus motor 113 supporting the focus lens included in the lens group 100 and rotating left and right; A zoom motor 112 for supporting a zoom lens included in the lens group 100 to enlarge and reduce the magnification of the subject; An aperture 101 for controlling exposure; A zoom motor driver 110 and a focus motor driver 111 for controlling driving of the zoom motor 112 and the focus motor 113 when the subject is captured; An imaging tube (102) having a solid state image pickup device (CCD) for converting an optical signal of a subject through the lens group 100 into a captured image signal according to vertical and horizontal synchronous pulses generated by the timing generator 103; A sampling and gain control unit 104 for sampling, gain-controlling and outputting the video signal picked up from the imaging tube 102; An analog / digital converter 105 for digitizing the captured image signal obtained by the gain adjustment in units of one field; The digitized video signal for one field is encoded and processed by color and luminance signals in NTSC or PAL format, and the subject focus is caused by its focus filtering coefficient according to the separated luminance data. A digital signal processor 106 for changing and outputting focus data for adjustment; The microprocessor 107 controls the zoom motor driver 110 and the focus motor driver 111 to adjust zooming and focus and to control the overall operation of the video camera according to the focus data inputted by the digital signal processor 106. )Wow; A memory 108 for temporarily storing and outputting luminance / color data for one field input from the digital signal processing unit 106 under the control of the microprocessor 107; The digital / analog converter 109 converts one field of the digital video signal stored in the memory 108 into a screen video signal and outputs the same through the output terminal 114.

As described above, the focus control apparatus of the conventional video camera configured as described above includes an image capturing tube 102 in which a video camera is started and an image of a subject has a solid-state image pickup device (CCD) through the lens group 100 and the aperture 101. When inputted to the image capturing tube 102, the image of the input subject is converted into a captured image signal for one field in synchronization with the horizontal and vertical image capturing driving pulses provided by the timing generating section 103.

The captured image signal for one field is provided to the sampling and gain control unit 104.

The sampling and gain control unit 104 samples the input captured image signal in units of one field and adjusts the gain appropriately to provide the analog / digital converter 105.

The analog / digital converter 105 digitizes an input image signal of a subject and provides the digital signal to the digital signal processor 106.

The digital signal processor 106 encodes an image signal of the digitized and input subject into color and luminance data in accordance with an NTSC or PAL format, and stores the image signal in the memory 108. It is changed within a predetermined range by the filtering coefficient set in the signal processing unit 106 and is provided to the microprocessor 107 as auto focus data AFD.

When the microprocessor 107 receives a predetermined range of auto focus data AFD from the digital signal processor 106, the microprocessor 107 moves the focus motor 113 forward and backward in the optical axis direction through the focus motor driver 111. In other words, the autofocus operation is performed while the focus lens of the lens group 100 moves from the near side to the far side, and the zoom motor 112 is moved through the zoom motor driver 110 in wide. A zooming operation is performed to zoom in or out of a subject while moving toward Tele.

Here, the auto focus data AFD output from the digital signal processor 106 is the largest at the position where the subject is most accurately focused, that is, the focal point PF position, as shown in FIG. As the distance from the position, i.e., moves toward the B1 and B2 directions and moves away from the focal point position (PF), the autofocus data AFD becomes smaller.

In addition, the characteristics of the lens included in the lens group 100, as shown in Figure 2, subjects at the same distance according to the zoom position also has a different focus position.

That is, as an example, as shown in FIG. 2, when zooming to capture a subject at a position of 3m, the lens group 100 may be moved through the focus motor 113 along a 3m zoom track A2. Move the focus lens to focus.

A1 in FIG. 2 shows a 1m zoom track when zooming when the subject is at a distance of 1m from the lens, and A3 shows an infinite zoom track when zooming on an infinite subject.

Based on this relationship, in order to accurately find the track in focus when zooming the subject, the microprocessor 107 controls the focus motor control unit 111 and the focus motor 113 as shown in FIG. When the focus lens of the lens 100 is moved from a to b direction, defocus is performed at this time. Therefore, the auto focus data AFD output from the digital signal processor 106 is reduced in the B1 or B2 direction as shown in FIG. 3. Done.

When the auto focus data AFD decreases, the microprocessor 107 reverses the zoom tracking direction.

When the focus lens moves from the b direction to the c direction, and when the focus lens moves from the c direction to the d direction, the auto focus data AFD output from the digital signal processing unit 106 gradually increases since it faces the track direction in focus. Done.

In addition, when the focus lens proceeds from the d direction to the e direction, the autofocus data AFD is clearly increased or decreased since the deviation from the focal point track is the same as the progression from the c direction to the d direction.減) does not appear, and moving from e to f direction reduces the size of auto focus data (AFD), which varies depending on the subject and also depends on the angle of view (zoom). PF) again.

In other words, as shown in FIG. 3, the track of the focal point PF is found using the point where the auto focus data AFD is the largest at the position where focus is best.

In this way, the image data of one field stored in the memory 108 in zooming and focus is converted into a screen image signal through the digital / analog converter 109 and output through the output terminal 114.

However, in the conventional auto focus control method of the video camera, the auto focus data has the characteristics as shown in FIG. 3 described above, but the size of the auto focus data at the focal point position varies depending on the subject, and also changes according to the angle of view. Done.

In other words, since the angle of view changes during zooming, the size of the autofocus data is not constant even in the focused state. If you are capturing a subject where the autofocus data increases during zooming, the autofocus data may grow even if the focus lens is moving away from the focal point track. There was a problem that occurred.

Therefore, in view of the problems of the conventional video camera as described above, the present invention provides an accurate in-focus point track regardless of the change in the autofocus data due to the change in the angle of view of the subject when zooming in the video camera employing the digital autofocus method. It is an object of the present invention to provide an automatic focus control method of a video camera that controls the visit.

Another object of the present invention is to provide an accurate focal point tracking method even when a subject changes while autofocus data changes due to a change in angle of view.

It is still another object of the present invention to provide a method for locating a focused zoom track by excluding an amount of change in autofocus data due to a change in the angle of view during zooming, and extracting data by pure forward / inverse focus.

Another object of the present invention is to prevent the stability of the zoom due to the amount of change in the angle of view generated per unit time as the zoom speed increases.

1 is a block diagram showing an auto focus control apparatus of a general video camera.

FIG. 2 is a view showing characteristics of a lens in the video camera of FIG. 1. FIG.

3 is a graph illustrating characteristics of autofocus data of a digital autofocus method in the video camera of FIG. 1.

4 is an explanatory view showing a tracking state for autofocusing in the conventional zooming according to FIG. 1;

Figure 5 is an embodiment block diagram showing an autofocus control apparatus of the video camera of the present invention.

FIG. 6 is an explanatory view showing a tracking state for autofocus when zooming the present invention according to FIG. 5; FIG.

FIG. 7 is an explanatory diagram illustrating a method of changing an angle of view and an autofocus control method according to a subject during a zooming operation of FIG. 5;

* Explanation of symbols for main parts of drawings>

200: lens group 201: aperture

202: imaging tube 204: analog / digital conversion unit

205: digital signal processing unit 206: microprocessor

207: memory 208: digital / analog converter

209: Aperture motor driving unit 210: Aperture motor

211: focus motor driver 212: focus motor

214: zoom motor 215: digital integrator

The automatic focus control method of a video camera according to an aspect of the present invention for achieving the above object is to adjust the focus of the focus lens by extracting the luminance data obtained by the imaging of the subject when filtering the subject by filtering coefficients A focus control method of a video camera, the method comprising: extracting focus data by moving a focus lens by a first predetermined section in a current zoom tracking direction when zooming the subject, and extracting a change amount of focus data due to a change in angle of view at this time; Steps; A second step of extracting focus data by moving the focus lens by a second predetermined section in a direction opposite to the zoom tracking direction and extracting a change amount of focus data due to a change in an angle of view; A third step of calculating focus data obtained by moving by the first predetermined section and an amount of change thereof; A fourth step of calculating the focus data obtained when the second predetermined section moves and the amount of change thereof; And performing tracking by integrating the two calculated values for one field to determine the focal point tracking direction.

In the automatic focus control method of the video camera according to the present invention, it is preferable that the second predetermined section is 1/2 of the first predetermined section.

In the automatic focus control method of the video camera according to the present invention, it is preferable to sum the focus data obtained in the first predetermined section and the change amount thereof to obtain the resultant value.

In the automatic focus control method of the video camera according to the present invention, it is preferable to sum the focus data obtained in the second predetermined section and the change amount thereof to obtain a result value.

In the automatic focus control method of the video camera according to the present invention, the first predetermined section is divided into 1/2, the focus data is extracted for each divided section, and the amount of change in the angle of view that is changed when the first predetermined section is moved. It is preferable to sum with.

As a result, it can be seen that in a video camera employing a digital autofocus method, an accurate in-focus track can be found regardless of the amount of change in autofocus data caused by a change in the subject or angle of view during zooming. It can be seen that the stability of zooming can be secured regardless of the amount of change in the focus data caused by the angle of view.

Therefore, in the autofocus control method of the video camera of the present invention, there is an advantage that accurate focusing tracking can be found even if the change of the autofocus data due to the change of the angle of view or the subject changes.

And, there may be a plurality of embodiments of the present invention, hereinafter will be described in detail for the preferred embodiment. Through this preferred embodiment, it is possible to better understand the objects, features and advantages of the present invention.

Hereinafter, exemplary embodiments of an automatic focus control method of a video camera according to the present invention will be described in detail with reference to the accompanying drawings.

5 is a block diagram of an embodiment of an automatic focus control apparatus of a video camera of the present invention.

According to this embodiment, the lens group 200 including a focus lens and a zoom lens; A focus ring 200b supporting the focus lens included in the lens group 200 to move forward and backward in the optical axis direction; A focus motor 212 engaged with the focus ring 200b and rotating left and right; A zoom ring 200a for supporting a zoom lens included in the lens group 200 to enlarge and reduce the magnification of the subject; A zoom motor 214 engaged with the zoom ring 200a and rotating left and right; An aperture 201 for controlling exposure; An aperture motor 210 for controlling an opening amount of the aperture 201; An imaging tube (202) having a solid state image pickup device (CCD) for converting an optical signal of a subject through the lens group 200 into a captured image signal for one field; An interrelated sampling and gain control unit 203 for sampling the video signal picked up from the imaging tube 202 and controlling and outputting a gain; An analog / digital converter 204 for digitizing the gain-adjusted captured image signal; By encoding the digitized video signal for one field, color and luminance data are separated by a format of an NTSC or PAL system, and auto focus data is generated for zooming by controlling the reference with the separated luminance data. A digital signal processor 205 for outputting a change amount of auto focus data according to a change in angle of view; A digital integrating unit (215) for integrating and outputting the current autofocus data obtained from the digital signal processing unit (205) and its change amount and the previous autofocus data and the change amount thereof for one field; The focus motor driver 211 is tracked in the focal direction by controlling the focus motor driver 211 based on the integral value obtained by the digital integrator 215, and the zoom motor driver 213 and the aperture motor driver 209 are controlled. A microprocessor 206 for controlling the overall operation of the overall video camera, such as controlling the zoom motor 214 and the aperture motor 210; A memory 207 for storing and outputting luminance / color data, which is separated and processed by the digital signal processor 205 under the control of the microprocessor 206, in units of one field; The digital / analog converter 208 converts the image data stored in the memory 207 into a screen image signal and outputs the same through the output terminal 216.

FIG. 7 is an explanatory diagram illustrating a method of changing an angle of view and an autofocus control method according to a subject during a zooming operation of FIG. 5.

Referring to this, when the subject is zoomed, the autofocus data (x) and (y) are extracted by moving the focus lens of the lens group 200 from the a direction to the c direction by the first predetermined section in the current zoom tracking direction. A first focus data extraction step of extracting a change amount? Of the autofocus data due to the change of angle of view of? The auto focus data y is extracted by moving the focus lens of the lens group 200 from the c direction to the b direction by the second predetermined section in the direction opposite to the zoom tracking direction, and the auto focus data y by the change in the angle of view at this time. A second focus data extracting step of extracting the change amount? A first calculation step of summing up previous autofocus data (x) and (Y) obtained by moving by the first predetermined section and the amount of change (α) thereof; A second calculation step of adding up the current auto focus data y obtained at the time of moving the second predetermined section and the amount of change α thereof; And a tracking step of integrating the current and previous two sum values for one field to determine a focal point tracking direction and perform tracking.

6 is an explanatory diagram showing a tracking state for autofocusing when zooming the present invention according to FIG. 5.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying FIGS. 5 to 7.

First, when a video camera is started and an optical signal of a subject is input to the imaging tube 202 through the lens group 200 and the aperture 201, the imaging tube 202 converts the image of the input subject into a captured image signal by one field unit. And provide it to the correlated sampling and gain control unit 203.

The correlation sampling and gain control unit 203 samples the input captured image signal in units of one field and adjusts the gain appropriately to provide the analog / digital converter 204.

The analog / digital converter 204 digitizes the input image signal of the subject and provides the digital signal to the digital signal processor 205.

The digital signal processor 205 encodes an image signal of the digitized and input subject into color and luminance data according to an NTSC or PAL format, and stores the image signal in the memory 207, wherein the digital signal processor ( In operation 205, the auto focus data required for auto focusing may be changed with reference to the luminance data according to the zooming of the subject.

The auto focus data is provided to the digital integrator 215 which will be described later.

The digital integrator 215 will be described in more detail later, but integrates the current autofocus data and the previous autofocus data provided by the digital signal processor 205 in units of one field and provides them to the microprocessor 206. Done.

When the autofocus data is changed and input from the digital integrator 215, the microprocessor 207 moves the focus motor 212 in the optical axis direction through the focus motor driver 211, that is, near the focus lens. Zooming in or out of the subject while moving the far side from the camera to the far side while performing the auto focusing operation and moving the zoom motor 214 from wide to tele through the zoom motor driver 213. Will be performed.

Here, the automatic focus control according to the change of angle of view and the subject during the zooming operation according to the present invention will be described with reference to FIG. 7. First, the focus motor driver 211 may operate the focus motor 212 by the microprocessor 206. Control to move the focus lens by a constant pulse in the zoom tracking direction through the focus ring 200b of the lens group 200, that is to say, in the direction a to c in FIG. By moving half the pulse, i.e. from c to b, the direction of the next zoom tracking is determined.

In the above, the auto focus data when moving from a to c direction is the auto focus data (x) when moving from point A to B and the auto focus data (y) when moving from point B to C and the angle of view The change amount α of the autofocus data is added to the change.

In addition, the autofocus data when moving from the c direction to the b direction sums up the autofocus data (y) when moving from the point C to the point B and the amount of change (α) of the autofocus data due to the change in the angle of view. do.

That is, in summary, the autofocus data when moving from the a direction to the c direction becomes x + y + α, and the autofocus data when moving from the c direction to the b direction is y + α.

Here, the difference between the auto focus data when moving from the a direction to the c direction and the auto focus data when moving from the c direction to the b direction is the auto focus data x when moving from the A point to the B point.

If the auto focus data x has a negative value, the auto focus data moved from the c direction to the b direction is larger than the auto focus data moved from the a direction to the b direction. In other words, the current zoom tracking direction is correct.

In addition, when the autofocus data X has a positive value, autofocus data moved in the c direction in the a direction is larger than the autofocus data moved in the c direction to the b direction. In this case, the microprocessor 206 determines that the current zoom tracking direction is wrong and sets the opposite direction as the zoom tracking direction.

As a result, the present invention is stable zoom tracking because only the autofocus data x between the A and B points is involved regardless of the auto focus data according to the angle of view or the change amount of the subject.

In other words, when zooming excludes the change amount α of the autofocus data according to the change of angle of view or the subject in the above-described manner, the autofocus integrated through the digital integrator 215 near the point of focus is obtained. The data is larger than the autofocus data integrated from the less focused position to near the fit position.

In other words, if the point C is the focused position, the autofocus data integrated from the c direction to the b direction is largely displayed. That is, the result of the auto focus data (x) is a negative value.

On the contrary, if the point A is in the focused position, the autofocus data moved from the focused position to the less-fitted position is larger than the autofocused data moved from the less-fitted position to the slightly more-suited position. In other words, the auto focus data integrated from the a direction to the c direction is larger than the auto focus data integrated from the c direction to the b direction. That is, the auto focus data x is shown as a result of being positive.

In the above description, autofocus control according to the angle of view change and the subject during the zooming operation described above will be described in more detail with reference to FIG. 6. First, when the current zoom track direction is A direction, Move it. That is, it moves in the a direction from the beginning.

Then, it moves from a to b by half the position previously moved in the B direction, that is, the position moved in the a direction from the beginning.

Since the current zoom tracking direction is the wrong direction, the auto focus data integrated through the digital integrator 215 by moving from the beginning to a becomes larger than the integrated auto focus data by moving from a to b.

Therefore, the microprocessor 206 controls the focus motor driver 211 and the focus motor 212 by the integral value input through the digital integrator 215 to change the zoom tracking direction in the B direction.

Then, it moves by the position b from position c in the direction B and then moves from position c to position d again in the direction A.

Here, when the focus lens is moved from the b position to the c position, the focus lens passes through the focal point track, and the c position to the d position is moved in the focal point track direction, so that the autofocus data are both similar.

Therefore, the zoom tracking direction may be set in the A direction, and the zoom tracking direction may be set in the B direction.

That is, the dotted line in FIG. 6 is the case where the zoom tracking direction is set in the B direction, and the solid line is the case where the zoom tracking direction is set in the A direction.

In this case, for the sake of convenience, the focus lens is moved from the d position to the e position in the A direction by the e position, and the focus lens is moved from the e position to the f position in the B direction.

Similarly, since the current zoom track direction is out of the focal point track, the autofocus data integrated through the digital integrator 215 moves the focus lens from the e position to the f position by moving the focus lens from the d position to the e position. Through unit 215, it becomes larger than the integrated auto focus data.

Therefore, the zoom tracking direction is changed to the B direction to move from the f position to the g position and again to the A direction to move the focus lens from the g position to the h position.

By repeating the above operation to find the focusing track during zooming, the focus lens of the lens group 200 is accurately adjusted through the focus motor driver 211 and the focus motor 212.

Here, it is to be noted that a control method for determining whether the current is in the direction of focusing or the direction of focus is excluded, except for the change of the auto focus data due to the change of the angle of view or the subject in the change of the auto focus data.

As such, when zooming and focusing are performed and luminance / color data of one field is stored in the above-described memory 205, the image data of one field is converted into a screen image signal through the digital / analog converter 208. It is output through the output terminal 216 and is recorded on the recording medium of the VLC of the rear stage.

As described above, in the present embodiment, since the focusing is performed by finding the correct focal point even when the video camera changes the autofocus data due to the change of the angle of view when zooming or the subject changes, the autofocus data according to the existing view angle change or the subject is tracked. It can be seen that the image is prevented from being judged to be correct in the out of focus state by the change.

In addition, although specific embodiments of the present invention have been described and illustrated above, it is obvious that the present invention may be variously modified and implemented by those skilled in the art.

Such modified embodiments should not be individually understood from the technical spirit or the prospect of the present invention, and such modified embodiments should fall within the appended claims of the present invention.

Zoom speed in video cameras is getting faster. The faster the zoom speed, the greater the amount of change in autofocus data caused by the angle of view per unit time (1 Vsync). The larger the amount of change in the angle of view, the more likely the defocus amount is in the prior art. That is, the stability of the zoom is poor.

The present invention has the effect of ensuring the stability of zooming by providing a control method that operates regardless of the change in autofocus data due to the amount of change in angle of view during zooming.

Claims (9)

In the focus control method of a video camera that adjusts the focus of the focus lens by extracting the luminance data resulting from the image pickup during zooming of the subject with a filtering coefficient, A first step of extracting focus data by moving the focus lens by a first predetermined section in the current zoom tracking direction when zooming the subject and extracting a change amount of focus data due to a change in angle of view at this time; A second step of extracting focus data by moving the focus lens by a second predetermined section in the reverse direction of the zoom tracking direction and extracting an amount of change of focus data due to a change in angle of view at this time; A third step of calculating the focus data obtained in the first step and the amount of change thereof; A fourth step of calculating the focus data obtained in the second step and the amount of change thereof; And And performing tracking by determining a focal point tracking direction using the two calculated values. The method of claim 1, wherein the second predetermined section is 1/2 of the first predetermined section. The method of claim 1, wherein the calculating step adds the amount of change in the focus data obtained by the first predetermined section and the focus data due to the change in the angle of view. The method of claim 1, wherein the calculating step adds the amount of change in the focus data obtained by the second predetermined section and the focus data due to the change in the angle of view. 4. The video camera according to claim 3, wherein the first predetermined section is divided into one half and the focus data is extracted for each divided section, and the video camera is added to the change amount of the focus data changed when the first predetermined section is moved. Auto focus control method. The method of claim 1, wherein the focal point tracking direction is determined as a result of focus data obtained by integrating two calculation values. The method of claim 6, wherein the integration of the focus data is performed in units of one field. The method of claim 1, wherein any one of the first predetermined section and the second predetermined section is set as a zoom tracking section. 10. The method of claim 8, wherein if the focus data of the 1/2 division point of the first predetermined section has a negative value, the second predetermined section is set as the zoom tracking section. Focus control method.