KR100213888B1 - Auto-focusing control method for video camera - Google Patents

Abstract

The present invention relates to a method for auto focusing of a video camera, which sets an easy filtering coefficient for autofocusing according to various luminance conditions so as to perform autofocusing by selecting a filtering coefficient suitable for input of current luminance data. will be.

As described above, the present invention provides a focusing method of a video camera that adjusts the focus of a focus lens by extracting luminance data resulting from image capturing with a filtering coefficient, and at least two or more conditions due to the brightness conditions. Setting a filtering coefficient to a value; Determining the magnitude of the luminance data currently captured by setting the filtering coefficients; Selecting and setting any one filtering coefficient according to the size of the determined luminance data; And adjusting the focus while moving the focus lens in the optical axis direction with the luminance data obtained due to the set filtering coefficients.

As a result, a wider selection range of focus is obtained at the time of imaging an object according to the luminance condition, and accurate focusing can be performed.

Description

How to adjust auto focus of video camera.

The present invention relates to automatic focusing of a camera-integrated video cassette recorder (hereinafter referred to as a video camera), and more particularly, to easily set filtering coefficients for autofocusing according to various brightness conditions. The present invention relates to an autofocus control method of a video camera that performs autofocus with good filtering coefficients.

In general, in order to most reliably reproduce an image of a subject in a video camera, it is necessary to adjust focus according to the best exposure and luminance conditions.

In this case, in order to adjust the focus according to the brightness condition, the focus motor should be appropriately adjusted in the optical axis direction, and the exposure control should appropriately adjust the opening of the aperture according to the brightness condition through the aperture motor.

As described above, in order to reproduce an image of a subject, autofocus has been performed through a focus motor using a fixed filtering coefficient according to luminance conditions in the autofocus control mode.

However, in general video cameras, since the filtering coefficients according to the luminance conditions are fixed, it is not possible to variously select good data according to the luminance in the autofocus control, and as a result, even in a state where the filtering coefficients are not favorable according to the luminance conditions. Focus control could only be performed.

1 is a block diagram of an automatic focus control apparatus of a conventional video camera.

Referring to FIG. 1, a lens group 100 including a focus lens and a zoom lens that expands and contracts a subject while moving forward and backward in an optical axis direction and receives an image of the subject, and the lens group 100. The focus motor 113 to rotate left and right, the aperture 101 for controlling exposure, the aperture motor 112 for controlling the opening amount of the aperture 101, the aperture motor 112 and the focus motor. The timing generator 103 generates an optical signal of an object that is enlarged and reduced through the aperture motor driver 110 and the focus motor driver 111 that controls the driving of the 113 and the lens group 100. An image pickup tube 102 having a solid state image pickup device (CCD) which operates according to the horizontal and vertical image pickup driving pulses and converts the image image signal into one image field, and samples and gains the image signal picked up from the image pickup tube 102. Sampling and gain control unit to control and output (104), an analog / digital converting section (105) for converting the gain-adjusted captured video signal for one field into a digital signal, and converting the digitized video signal for one field into a format of an NTSC or PAL system. The digital camera processing unit 106 and the digital camera processing unit 106 generated by encoding and outputting color and luminance signals separately and changing the focus data based on its focus filtering coefficient according to the brightness data in the focus control mode. The microprocessor 107 controls the overall operation of the video camera, such as adjusting the focus of the lens group 100 by controlling the driving of the focus motor 113 through the focus motor driver 111 according to the focus data provided by. And a memory 108 for storing luminance / color data for one field processed by the digital camera processor 106 under the control of the microprocessor 107, The digital / analog converter 109 converts the luminance / color data of one field stored in the memory 108 into a screen image signal and outputs the same through the output terminal 114.

2 is an operation signal flow diagram in the auto focus control mode according to FIG. 1.

In such a conventional video camera, when the camcorder first enters the operating state, the optical signal of the subject is input to the image pickup tube 102 having the solid state image pickup device CCD through the lens group 100 and the aperture 101.

The imaging tube 102 is operated by horizontal and vertical imaging driving pulses of the timing generator 103 under the control of the microprocessor 107 which will be described later. The signal is converted into a signal and output to the sampling and gain control unit 104.

The sampling and gain control unit 104 samples the captured image signal input from the imaging tube 102 for one field and adjusts the gain appropriately to provide the analog / digital conversion unit 105.

The analog-to-digital converter 105 digitizes the image signal of the subject to be gain-controlled and inputs the digital signal to the digital camera processor 106.

The digital camera processing unit 106 encodes a digitally inputted image signal to process color and luminance data in an NTSC or PAL format, and stores the processed color and luminance data in a memory unit in field units. In this case, the luminance data is changed within a predetermined range by a filtering coefficient set fixedly to the digital camera processor 106 and provided to the microprocessor 107 as focus data.

When the focus data of a predetermined range is input from the digital camera processor 106, the microprocessor 107 determines whether the focus lens is in the focus adjustment mode and indicates whether the focus lens of the current lens group 100 is moved forward or backward in the optical axis direction. That is, the direction determination mode indicating whether to move the focus lens from the near side to the far side is searched (step S10), and if the direction is determined, the focus of the lens group 100 through the focus motor driver 111 and the focus motor 113. The direction to move the lens is determined (step S11).

As such, when the direction determination is completed, in order to adjust the focal point position where the focus data from the digital camera processing unit 106 becomes the maximum while moving the focus lens from the near side to the far side through the focus motor 113 to focus. The tracking mode is performed (steps S12 and S13).

In this way, while tracking through the focus motor 113, it is searched whether the focus data has not exceeded the maximum value of the forward focus (step S14), and if it has not exceeded the maximum value of the focal point, tracking is performed to exceed the maximum value of the focal point (step S14). , S15).

Then, if the maximum value of the focal point is exceeded, the focus motor 113 is again tracked through the focus motor driver 111 to stop the driving of the focus motor 113 at the maximum value of the focal point, thereby focusing the focus lens of the range group 100. (Step S16, S17).

Meanwhile, luminance and color data of one field stored in the memory 108 are converted into screen image signals through the digital / analog converter 109 through the above process, and the magnetic recording of the VRF is performed through the output terminal 114. Stored on the medium.

However, such an automatic focusing apparatus of a conventional video camera cannot select a variety of good data according to the luminance in the autofocus control due to the fixed filtering coefficient according to the luminance condition. In other words, there is a problem that the focus control is performed even when the filtering coefficient is not good according to the luminance condition because the coefficient is fixed without searching for the current luminance and setting the filtering coefficient.

Accordingly, in view of the problems with the conventional video camera as described above, the present invention sets a filtering coefficient according to various luminance conditions during autofocus control to perform autofocus with the best filtering coefficient for the luminance conditions. Its purpose is to provide an automatic focus control method.

Another object of the present invention is to set at least two or more filtering coefficients arbitrarily in accordance with luminance conditions.

Still another object of the present invention is to set and set a filtering coefficient according to luminance in auto focus control.

1 is a block diagram denying the automatic focusing apparatus of the conventional video camera.

FIG. 2 is a flowchart illustrating an operation signal in the auto focus control mode according to FIG. 1. FIG.

Figure 3 is an embodiment block diagram showing an automatic focusing apparatus of the video camera of the present invention.

Figure 4 is an embodiment signal flow diagram showing the present invention autofocus operation according to FIG.

FIG. 5 is a view illustrating a change in focus data accompanying a change in position of a focus motor according to FIG. 3.

6 is a diagram illustrating the size and width of the focus data according to the filtering coefficient setting of FIG.

* Explanation of symbols for main parts of the drawings

200: lens group 201: aperture

202: imaging tube 203: sampling and gain control unit

204: analog / digital conversion unit 205: digital camera processing unit

206: microprocessor 207: first memory

212: focus motor 215: second memory

The automatic focusing method of a video camera according to an aspect of the present invention for achieving the above object, the video camera for adjusting the focus of the focus lens by extracting the luminance data obtained by the subject image pickup at the time of focus adjustment with a filtering coefficient A focus adjusting method comprising the steps of: setting a filtering coefficient to at least two condition values due to the luminance condition, determining a magnitude of luminance data currently captured by setting the filtering coefficient, and determining the luminance data Selecting and setting any one of the set filtering coefficients according to the size of the sensor, and adjusting focus while moving the focus lens in the optical axis direction with luminance data obtained from the set filtering coefficients. It is done.

In the automatic focusing method of the video camera according to the present invention, the filtering coefficient is preferably set to three condition values.

In the automatic focusing method of the video camera according to the present invention, the filtering coefficient is preferably set to a value when it is dark, when it is light, and between darkness and light.

In the automatic focusing method of the video camera according to the present invention, it is preferable that the filtering coefficient is arbitrarily changed and set.

As a result, when shooting an object in a dark place, a bright place, or a place where the brightness is normal, the auto focus basic function can be enhanced by selecting the best filtering coefficient for focusing according to the brightness condition. It can be seen that it performs.

Therefore, there is an advantage in that the selection range of the focus is widened at the time of imaging the object according to the luminance condition, and the accurate focus is achieved.

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, with reference to the accompanying drawings will be described in detail a preferred embodiment of the video camera automatic focusing method according to the present invention.

3 is a block diagram of an embodiment of an automatic focusing apparatus of a video camera of the present invention.

According to the present embodiment, a lens group 200 including a focus lens and a zoom lens, a focus ring 200b for supporting the focus lens included in the lens group 200 and moving back and forth in the optical axis direction, and its focus A focus motor 212 engaged with the ring 200b to rotate 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, and a zoom ring 200a thereof. The zoom motor 214 to rotate left and right, the aperture 201 for controlling exposure, the aperture motor 210 for controlling the opening amount of the aperture 201, and the subject through the lens group 200. An image pickup tube 202 having a solid state image pickup device (CCD) for converting an optical signal into a captured image signal, a sampling and gain control unit 203 for sampling, gain controlling and outputting the image signal picked up from the image pickup tube 202; Digitalizing the gain-adjusted captured image signal for one field An analog / digital conversion unit 205, a digital camera processing unit 205 for encoding the digitized video signal for one field and separating and outputting the color signal and luminance signal in NTSC or PAL format, and auto focus control Set the filtering coefficient according to the luminance condition at the time and store it in the second memory 215 and then receive the Hall of the aperture 201 to determine the current luminance data size and according to the result of the determination A microprocessor 206 for selecting the filtering coefficients stored in the memory 215 and setting them in the digital camera processing unit 205 to receive the focus data therefrom and to control the overall operation of the video camera, and to control the microprocessor 206. The aperture motor control unit 209, the focus motor control unit 211, the zoom motor control unit 213 for controlling the driving of the aperture motor 210, the focus motor 212 and the zoom motor 214 according to the On-screen character generator 216 for generating on-screen characters for various functions of the video camera under the control of the microprocessor 206 and displaying them on the LCD screen, and 1 obtained by the digital camera processor 205. A first memory 207 for storing and outputting color and luminance data for a field, and a digital for converting data for one field stored in the first memory 207 into a screen image signal and outputting it through an output terminal 217. / Analog converter 208.

4 is an embodiment of an autofocus control method of a video camera of the present invention in which a filtering coefficient is set according to a luminance condition during autofocus control, and then the focus is adjusted with the set filtering coefficient according to the luminance data size obtained by imaging. The signal flow is also shown.

Hereinafter, with reference to the accompanying Figures 3 to 6 will be described a preferred embodiment according to the present invention through the following.

First, when the video camera enters the operating state, the microprocessor 206 uses the aperture motor control unit 209, the focus motor control unit 211, the zoom motor control unit 213, and the aperture motor 210, the focus motor 212, and the like. The zoom motor 214 is controlled to adjust the zoom lens and the focus lens of the aperture 201 and the lens group 200.

In such a state, when the optical signal of the subject is focused to some extent by the zoom lens and the focus lens, and is input to the image capturing tube 202 having the solid state image sensor (CCD) through the aperture 201, the image capturing tube 202 is connected to the input object. The optical signal is converted into a captured image signal for one field and provided to the sampling and gain control unit 203.

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

The analog / digital converter 204 digitizes an image signal of a subject input by adjusting the gain and provides the digital signal to the digital camera processor 205.

The digital camera processing unit 205 encodes an image signal of the digitized subject, separates the color signal and luminance data of an NTSC or PAL system format into a first memory 207, and then stores it in the first memory 207. In the auto focus control, first, the filtering coefficient according to the luminance condition is set and stored in the second memory 215.

As such, when the filtering coefficient is set according to the luminance condition, the microprocessor 206 retrieves the luminance data through the signal flow as shown in FIG. 4 to adjust the focus (step S100).

The luminance data is determined by receiving a Hall value HA of the diaphragm 201.

The hole value HA varies somewhat depending on the model. Therefore, when the hole value HA is smaller than 80H, the luminance is bright, and when the hole value HA is larger than A0H, the luminance is dark.

And when the hall value HA is between 80H and A0H, the luminance represents a condition in the normal case. Where H is the hexacode.

Accordingly, the microprocessor 206 retrieves the hole value HA through the aperture 201, and reads the filtering coefficients when the hole value HA is bright from the second memory 215. 205, the digital camera processing unit reads the normal filtering coefficient or the dark filtering coefficient from the second memory 215 when the hole value HA is normal or dark. It sets to 205 (step S102, S103).

The digital camera processing unit 205 changes the processed luminance data within a predetermined range by a filtering coefficient of bright, normal or dark when selected and set by the microprocessor 206 as shown in FIG. 5. The auto focus data FD is provided back to the microprocessor 107.

Here, the characteristics of the autofocus data FD according to the filtering coefficient setting are inclined in all sections as shown in FIG. 6A and as shown in FIG. 6A under the same luminance condition. It can be said that it is a good characteristic that the maximum value can be recognized. In FIG. 6B, the maximum value of the auto focus data FD is good, but there is a flat portion without inclination, which makes it difficult to determine the direction.

In addition, in FIG. 6C, the maximum value of the auto focus data FD as well as the direction determination is small, so that the maximum value is not easily recognized.

Accordingly, when setting the filtering coefficient according to the luminance condition, as shown in FIG. 6A, the filtering coefficient which is easy to recognize the maximum value of the direction determination and the auto focus data FD is set and stored in the second memory 215 as described above. Put it.

The filtering coefficient may be changed and stored at an arbitrary value according to the selection of the photographer.

Subsequently, when the microprocessor 206 is changed by the filtering coefficient according to the luminance condition from the digital camera processor 205 and the focus data as shown in FIG. 5 is input, the microprocessor 206 determines that the focus control mode is performed and the current lens group 200 is present. Search for a direction determination mode indicating whether to move the focus lens forward or backward in the optical axis direction, that is, whether to move the focus lens from the near side to the far side (step S104). The direction a to move the focus lens of the lens group 200 through the focus motor 212 is determined (step S105).

As such, when the direction determination is completed, in order to focus the focal point position where the focus data from the digital camera processing unit 205 becomes the maximum while moving the focus lens from the near side to the far side through the focus motor 212 to focus. As shown in FIG. 5, the normal tracking is performed in the b direction (steps S106 and S107).

In this way, while tracking in the b-direction of FIG. 5 through the focus motor 212, it is searched whether the focus data has exceeded the maximum value D of the forward focus (step S108), and has not exceeded the maximum value D of the focal point. If so, tracking is performed in the c direction to exceed the maximum value of the focal point (step S109).

After exceeding the maximum value D of the focal point, the focus motor 212 is reversely tracked through the focus motor control unit 211 to stop the driving of the focus motor 212 at the maximum value D of the focal point and the range group 200. ), The focus lens is accurately focused (steps S110 and S111).

In this way, the luminance and color data of one field stored in the first memory 208 are precisely focused and converted into a screen image signal through the digital / analog converter 209 and the V through the output terminal 217. It is stored in the magnetic recording medium of the seed.

As described above, in the present embodiment, before the video camera is started and the image capturing function is performed, the filtering coefficient for focus adjustment according to the luminance condition is first set and stored in the second memory 215. By adjusting the focus by selecting the best filtering coefficient according to the luminance data of, it can be seen that the auto focus basic function is more faithful.

In addition, while 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.

In the present invention, when the target is photographed in a dark place, a bright place, or a place where the luminance is normal, the focus is adjusted by selecting a filtering coefficient that is best for focusing according to the luminance condition of the current imaging target. As a result, a wider selection range of focus is obtained at the time of photographing the object, thereby achieving an accurate focus.

Claims (4)

A focus adjustment method of a video camera which adjusts the focus of a focus lens by extracting the luminance data filtering coefficients obtained by subject imaging during focus adjustment, wherein the filtering coefficients are set to at least two condition values due to the luminance conditions. Determining, by the controller, determining the size of the luminance data currently captured after setting the filtering coefficient, selecting and setting any one filtering coefficient according to the determined luminance data size, and setting the filtering coefficient. And adjusting the focus while moving the focus lens in the optical axis direction with the luminance data obtained by the method. The method of claim 1, wherein the filtering coefficient is preferably set to three condition values. The method of claim 1 or 2, wherein the filtering coefficient is set to a condition value between dark, light, and dark and light. The method of claim 1, wherein the filtering coefficient is arbitrarily changed and set.

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