KR100378594B1 - Camera Auto-Focusing Method And Apparatus Using Wavelet Transform - Google Patents

Abstract

The present invention relates to a method and apparatus for auto focusing, such as a video camera, comprising: a camera unit (1) converting a captured image into image data and adjusting a camera focus based on a focus driving voltage; A frequency converter (2) for separating the luminance signal from the image data and separating and storing each frequency component through wavelet transform; And a focus control unit 3 which obtains the focus driving voltage through focus control information according to a control mode, and is less susceptible to noise by using a wavelet transformed component, in particular, two high-pass filtering components. It is possible to provide a method and apparatus for adjusting the focus of a camera, and also to reduce unnecessary calculations by calculating the sum of high-frequency components only for the center region under the assumption that the subject is adjusted by the cameraman to come to the center region.

Description

Camera Auto-Focusing Method And Apparatus Using Wavelet Transform}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for automatically adjusting the focus of a photographing apparatus such as a video camera, and more particularly, to an automatic adjustment of the focus on a subject based on an image signal obtained from an image pickup device in a photographing apparatus such as a video camera. The present invention relates to an improved auto focusing control method and apparatus that can achieve high speed.

In general, two types of video camera auto focusing apparatuses are used.

One is an active method, which is provided with an infrared or ultrasonic transmitting and receiving device on one side of the video camera, and analyzes the infrared and ultrasonic waves transmitted and received to measure the distance, and drives the focus lens according to the measured distance. It works by focusing on the means. Conventional techniques of such an active system include those described in Japanese Patent Laid-Open No. 62-67973, Japanese Patent Laid-Open No. 62-286007, Japanese Patent Laid-Open 59-81609, Japanese Patent Laid-Open 59-81631, Japanese Patent Laid-Open 61-191173, and the like.

The other is a passive method, which detects, at every frame, a high frequency signal which is a component proportional to the contrast obtained by the luminance signal passing through the high frequency filter from the image pickup device. By moving the focus lens in the direction of increasing contrast compared to the contrast of the previous frame, the auto focusing function is obtained by stopping the rotational movement of the lens driving motor in the state of the highest contrast. As a conventional technique of such a manual system, Japanese Patent Laid-Open No. 63-20973, Japanese Patent Application Laid-Open No. 62-247314, Republic of Korea Patent Publication 97-11541, Republic of Korea Patent Publication 99-177654, Republic of Korea Patent Publication 97-0031847, Republic of Korea Patent Publication 97-705290. This manual focusing method has various methods depending on a method of detecting high frequency components. For example, television cameras use Discrete Cosine Transform (DCT) processing for automatic focus control. This uses the high frequency component of the frequency-converted DCT coefficients maximized at the focused position based on the image data supplied to the DCT processor. Then, if the position of the focus lens is moved in the direction of focusing step by step, and the value of the high-frequency component of the DCT coefficient of the image data changes from monotonous increase to one-time decrease, the previous position is determined as the maximum position, and the control Perform Such contents are well shown in Japanese Patent Laid-Open Nos. 10-51675 and 6-90396.

On the other hand, in order to focus the subject accurately, it is necessary to increase the correlation between the actual focusing information and the actual focusing state, such as obtaining focusing information based only on the image portion of the subject.

In the conventional camera focus control method using the DCT described above, the control may be terminated without adjusting to the actual focus position due to the increase or decrease of the high frequency component due to some noise or sampling error in the input image.

In addition, since the area that takes DCT is a part of the area and does not cover the entire image, the contour portion containing a large amount of DCT high frequency components may deviate from the area where DCT is taken, that is, the area where focusing information is obtained. In this case, the accuracy of the focusing is reduced or the focusing control is difficult.

An object of the present invention is to solve the problems of the prior art and to provide a method and apparatus for adjusting the camera focus that can be less affected by noise by extracting the high frequency components from the entire image.

Another object of the present invention is a broadcast camera, under the assumption that a cameraman focuses on a subject by focusing on a subject, the high-speed component corresponding to the center region of the photographed image is calculated to reduce unnecessary calculations, thereby increasing focusing speed. To provide a camera focusing method and apparatus that can be accurate.

1 is a configuration diagram of the camera focus automatic adjustment device according to the invention,

2 is a flowchart illustrating a method for automatically adjusting a camera focus according to the present invention.

* Brief description of the main parts of the drawing

1: photographing apparatus 15: image signal processing unit

2 frequency conversion unit 24 wavelet conversion processor

3: Focus Control Unit 31: Manual Control Panel

33: A / D converter 34: D / A converter

An apparatus for automatically adjusting the focus of a preferred video camera according to the present invention comprises: a camera unit (1) for converting a captured image into image data and adjusting the camera focus based on a focus driving voltage; A frequency converter (2) for separating the luminance signal from the image data and separating and storing each frequency component through wavelet transform; And a focus control unit 3 for obtaining the focus driving voltage through focus control information according to a control mode.

In addition, the method for automatically adjusting the focus of the video camera according to the present invention comprises the steps of: converting the captured image into image data; Separating the luminance signal from the image data, separating the luminance signal into frequency components through wavelet transform, and storing the converted data; A predetermined range of aggregation frames is set in advance in the center region of the captured image, and the internal components of the aggregation frame are added to absolute values of components that have passed the high frequency filter stored in the frequency converter 2 a predetermined number of times, and the high frequency component sum is added. Obtaining a; Determining a control mode according to the cameraman's operation to obtain focus control information based on the cameraman's manipulation amount in the manual control mode, and in the case of the automatic control mode, obtaining focus control information of the camera based on the change of the sum of the high frequency components; And converting the focus control information into a focus control voltage for adjusting the camera lens.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, referring to FIG. 1, an auto focusing apparatus of a video camera according to an exemplary embodiment of the present invention is illustrated, and an image capturing apparatus 1, a frequency converter 2, and a focus controller 3 are respectively illustrated as dotted blocks. In the conventional focusing apparatus, the frequency converter 2 includes a DCT processor, a high pass filter, an intermediate value processor, and the like according to the high frequency component extraction method. However, in the present invention, the wavelet transform processor 24 includes the frequency converter 2. Is provided.

Since wavelet transform can display an image in two regions of space and frequency, it is more efficient to display spatial characteristics such as edges of the image and frequency characteristics of an image where energy is concentrated in a low frequency region. There are features that can be. In addition, due to the hierarchical structure of wavelet transform, there is an advantage that there is no block artifact that is seriously exhibited at low bit rate of the conventional DCT-based compression method. . The present invention is not related to the wavelet transform, and since the wavelet transform is well known to those skilled in the art, detailed description thereof will be omitted herein.

The imaging section 1 according to the present invention includes a lens 11, an imaging device 12 such as a CCD, a lens driver 13 for imaging an image of a subject whose focus is adjusted on the imaging surface of the imaging device 12, and an imaging device. And an image pickup processor 14 for outputting the video data from the image 12, a video signal processor 15, and a view finder (not shown).

The camera unit 1 may be a general home or broadcast video camera, or may be a general camera. As a preferred embodiment of the present invention, it is preferable that the imaging processor 14 is a video camera configured to output moving image data, particularly a video broadcasting video camera such as a high quality television camera. The video data and the synchronization signal output from the imaging processor 14 are transmitted to the video signal processor 15 and the frequency converter 2, respectively.

The image signal processor 15 according to the present invention includes a luminance signal (Y) processor 15a, a color signal (C) processor 15b, and an encoder 15c. The luminance signal processor 15a is connected to the luminance signal. The signal processing for the color signal is provided to the encoder 15c, respectively, and the encoder 15c encodes and outputs the signal in accordance with NTSC, PAL, HDTV (high definition television) system, and the like. do.

The frequency converter 2 according to the present invention includes a luminance / color signal separator 21, an A / D converter 22, an input image field buffer 23, a discrete wavelet transform (DWT) processor 24, and a wavelet transform image. It consists of a storage buffer 25. In the luminance / color signal separator 21, the luminance signal Y and the color signal C are separated from the input signal, and the separated luminance signal is provided to the A / D converter 22. The A / D converter 22 converts the luminance signal into digital image data, which is stored in the input image field buffer 23 for each frame or field unit screen, and is transmitted to the wavelet conversion processor 24. . The wavelet transform processor 24 separates image data stored in the buffer 23 into respective frequency components through wavelet transform. The image data processed by the wavelet transform processor 24 is stored in the wavelet transformed converted image storage buffer 25 and transferred to the control processor 35 through an adder 37 to be described later.

The focus control unit 3 according to the present invention is shown in FIG. 1 by a dashed line “3”, a manual operation unit 31 having a focus knob, an iris knob, a zoom knob, etc., a manual / automatic switching switch ( 32), A / D converter 33, D / A converter 34, control processor 35, bit switch 36, adder 37, and the like.

The manual operation unit 31 generates a focus driving voltage corresponding to the amount of operation when the cameraman who is an operator operates the focus knob, and supplies it to the manual / auto switching switch 32, and an operation state signal indicating whether or not the focus knob is in operation. (OP) is supplied to the control processor 35. In the manual focus adjustment mode, the changeover switch 32 outputs the focus driving voltage from the manual operation unit 31 to the lens driver 13, and in the auto focus control mode, the control processor 35 generates The focal drive data is converted into analog voltage by the D / A converter 34 and output.

The A / D converter 33 obtains, from the lens driver 13, analog signals relating to the arrival position information of the focus lens, the magnification information of the zoom lens, and the iris information, and converts them into digital data and supplies them to the control processor 35. Here, the focus control of the lens driver 13 obtains the current position information of the focus lens as an analog signal, and uses the data obtained by A / D conversion as the correct focus lens position information of the auto focus control.

The control processor 35 may have a general configuration including a control operation unit such as a CPU and a storage unit such as a ROM or a RAM, and a bit switch 36 is connected. The control processor 35 stores the maximum value of the high frequency component to be described later in the RAM, and is initially initialized to a very small value. As will be described later, the bit switch 36 is used to allow the cameraman to move the camera so that the subject is at the center of the screen, and then set a fixed size aggregation frame at the center of the screen.

The adder 37 performs absolute value addition on the components of the window frame for the aggregation among the components (hh components) that have passed the high frequency filter a proper number of times among the data stored in the wavelet transform image storage buffer 25. Preferably, the number of passes through the high frequency filter is two times.

Hereinafter, a camera auto focusing method using wavelet transform and a specific operation thereof will be described.

2, a flowchart of an auto focus adjusting method according to the present invention is shown. The program for executing such a flowchart is stored in advance in the ROM inside the control processor 35. If a hard disk, floppy disk, MO disk, or CD-ROM drive or the like is added and installed, the program or various parameters can be stored in advance in a storage medium which can be read / written or read-only.

First, in step 200, it is determined whether manual manipulation of the focus knob has ended. This determination is performed by measuring by the timer that the operation state signal Op is turned on, then turned off, and then the off state has not changed for a predetermined time. If it is determined that the manual operation has been completed, the flow advances to step 201 to switch the focus switch voltage from the D / A converter 34 to the lens driver 13 instead of the focus control voltage from the manual operation unit 31. 32).

In step 202, the number of repetitions k is zero, the direction variable D is zero, the maximum focus control voltage value V _f.max and the maximum value S sum of the high frequency components S _Yhh.max are very small. Initialize to a value.

In step 203, the digital device acquires a digital image by the photographing apparatus 1, transfers it to the frequency converter 2, and calculates the absolute sum _SYhh of the high frequency component at the current position by Equation 1. .

Where M is the row size of the center area and N is the column size of the center area.

In step 204, it is checked whether the current repetition number k is zero, if "k" is 0, the process proceeds to step 206, and if "k" is not 0, in step 205, S _Yhh and Compare the magnitudes of S _{Yhh, max} . If S _Yhh is greater than S _{Yhh, max} , go to step 206.

In step 206, the current focus control voltage V _f and the high frequency component sum S _Yhh are stored in V _f.max and S _{Yhh, max} , respectively.

In step 207, it is again examined whether "k" is 0, and if k = 0, S _Yhh is _stored in S _{Yhh, prev} and V _f is stored in V _{f, prev} as in step 209, and " Increase k "by one.

In step 210, the direction control variable D is compared to be greater than or equal to zero. If "D" is greater than or equal to zero, go to step 211, and if less than zero go to step 212.

In step 211, the motor of the lens driving unit 13 is moved by one scale in the current travel direction, and then the direction control variable D is changed to "+1". If " D " is less than zero, as in step 212, the motor is moved by one scale in the opposite direction of the current run, and then the direction control variable value D is changed to " -1 ". After completing steps 211 and 212, the process returns to step 203 again.

On the other hand, in step 207, in the direction if which k ≠ 0 is, by comparing the size of the S _{Yhh, prev} and S _Yhh in step (208) S _Yhh is greater than or equal to S _{Yhh, prev,} of focus to be fit The determination then proceeds to step 209. If S _Yhh is smaller than S _{Yhh, prev} , it is determined in the direction where the focus is off, and the flow proceeds to step 213.

In step 213, the current k is " 1 " is compared to " k " if k = 1, and if k ≠ 1, the maximum high pass component sum S _{Yhh, max &lt}; passing the control of the focus voltage (V _{f, max)} to the control processor 35, and finishes the autofocus control.

In step 214, the motor is moved two divisions in the opposite direction, the direction control variable D is changed to -2, k is increased by one, and then back to step 203, the process is repeated.

When the auto focus control is finished, the process returns to step 200 to check whether the manual operation switch is on, and if it is on, continues to perform the auto focus control and if it is off, returns to the manual operation state.

The description so far is not limited to the invention as a preferred embodiment of the invention, and various modifications and / or variations may be made by those skilled in the art without departing from the scope and spirit of the appended claims. For example, the present invention can be implemented in software using a microcomputer, so that the calculation position and area size of the high frequency component sum can be changed as necessary.

As described above, the present invention enables the extraction of high-frequency components of the entire image by using wavelet transform for high-pass filtering the entire image within a predetermined region, and uses a component that performs two high-pass filtering of the wavelet transformed components. By doing so, it is possible to provide a camera focusing method and apparatus that can be less affected by noise. In addition, it is possible to reduce unnecessary calculation by calculating the sum of the high-frequency components only for the center area under the premise that the subject is adjusted to the center area by the cameraman.

Claims (7)

A device for automatically adjusting the focus of a video camera, A camera unit 1 for converting a captured image into image data and adjusting a camera focus based on a focus driving voltage; A frequency converter (2) for separating the luminance signal from the image data and separating and storing each frequency component through wavelet transform; And A focus control unit 3 for obtaining the focus driving voltage through focus control information according to a manual or automatic control mode, When the focus control unit 3 is in the automatic control mode, Of the wavelet-converted image data stored in the frequency converter 2, the absolute value sum of the components of a predetermined range of components within the aggregation frame, which is preset in the central region of the captured image, of the components that have passed the high frequency filter a predetermined number of times. Obtaining a sum of the high frequency components and calculating the focus driving voltage based on the change of the sum of the high frequency components. The method of claim 1, The camera unit 1 is: A lens 11; Imaging elements 12 such as CCDs; A lens driver 13 for forming an image of a subject whose focus is adjusted on the imaging surface of the imaging device 12; An imaging processor 14 for outputting image data from the imaging device 12; And a luminance signal processor 15a for signal processing of the luminance signal among the image data output from the imaging processor 14, a color signal processor 15b for signal processing for color signals, and the signal processor 15a, 15b. An encoder 15 for encoding the processed signal in a predetermined manner and outputting the same; The frequency converter 2 is: A luminance / color signal separation unit 21 for separating luminance signals and color signals from the image data from the camera unit 1; An A / D converter 22 for converting the luminance signal separated by the luminance / color signal separation unit 21 into digital image data; An input image field buffer 23 for storing the digital image data output from the A / D converter 22 for each frame or screen unit; A wavelet transform processor 24 for separating the digital image data stored in the input image field buffer 23 into respective frequency components through wavelet transform; And a converted image field buffer (25) for storing the data converted and output by the wavelet transform processor (24) and outputting the converted data to the focus control unit (3). The method of claim 2, The focus control unit 3 is: It is provided with a focus knob, an iris knob, a zoom knob, etc., and supplies to the control processor 35 an operation state signal Op indicating whether or not the focus knob is being operated, and when the cameraman has operated the focus knob, a considerable focus is applied to the operation amount. A manual operation unit 31 for generating a driving voltage; In the manual control mode, the manual / auto switching switch 32 outputs the focus driving voltage generated by the manual operation unit 31 and the focus driving voltage generated by the control processor 35 to the lens driver 13 in the automatic control mode. ); An A / D converter (33) which obtains an analog signal relating to the arrival position information of the focus lens, the magnification information of the zoom lens, and the iris information from the lens driving unit (13) and converts it into digital data and supplies it to the control processor (35); A D / A converter 34 converting the focus control information calculated by the control processor 35 into a focus driving voltage for driving the camera focus lens and providing the same to the manual / automatic switching switch 32; The operation state signal Op is stored after storing the maximum value of the high frequency component obtained by the adder 37 and comparing it with the data supplied from the A / D converter 33 and obtaining focus control information based on the change amount of the maximum value. A control processor (35) for supplying the focus control information to the D / A converter (34) when the focus knob is not in operation through the controller; A bit switch (36) connected to the control processor (35) and setting the aggregation frame; And And an adder 37 for obtaining the sum of the absolute values of the components inside the counting frame among the components that have passed the high frequency filter stored in the converted image field buffer 25 a predetermined number of times, and providing them to the control processor 35. Camera auto focus. The method of claim 3, wherein And a frequency of passing the high frequency filter twice. In the method of automatically adjusting the focus of the video camera, Converting the captured image into image data; Separating luminance signals from the image data, separating the luminance signals into frequency components through wavelet transform, and storing the frequency signals; A predetermined range of aggregation frames is set in the center region of the captured image, and the absolute value of the components inside the aggregation frame is added by adding the absolute values of the components that have passed the high frequency filter stored in the frequency converter 2 a predetermined number of times. Obtaining a; Determining a control mode according to the cameraman's operation to obtain focus control information based on the cameraman's manipulation amount in the manual control mode, and in the case of the automatic control mode, obtaining focus control information of the camera based on the change of the sum of the high frequency components; And And converting the focus control information into a focus driving voltage for adjusting the camera lens. The method of claim 5, And the frequency of passing the high frequency filter is twice. The method according to claim 5 or 6, Obtaining the focus control information in the automatic control mode, Initializing the control number k and the direction control variable D to 0 and the maximum values V _f.max , S _{Yhh, max of the} focal drive voltage and the high frequency component absolute sum to a predetermined minimum value (203); Determining whether the number of times of control k is zero when calculating the maximum value of the high frequency component absolute sum S _Yhh (204); In step 204, if k ≠ 0 _, the magnitudes of S _Yhh and S _{Yhh, max} are compared (205), and if k = 0, the current focal driving voltage (V _f ) and S _Yhh are respectively V _f.max and S _Yhh. storing (206) as _.max ; Determining whether k = 0 again after updating the maximum value (207); In step 207, if k ≠ 0, the sizes of S _Yhh and S _Yhh.pre are compared (208), and if k = 0, S _Yhh is _stored in S _Yhh.pre and V _f is stored in V _f.pre and k after increasing = k + 1 (209), comparing 210 the direction control variable D with D≥ 0; As a result of the step 210, if D≥0, the motor in the camera unit 1 is rotated once in the current direction and changed to D = D + 1 (211), and if D <0, in the opposite direction to the current direction Rotating the motor once and changing to D = D-1 (212); As a result of step 208, if S _Yhh ≥S _{Yhh, prev} , proceeding to step 209; and if S _Yhh <S _{Yhh, prev} , comparing whether current k is 1 (213); As a result of the step 213, if k = 1, the motor is moved two divisions in the direction opposite to the current direction, the direction control variable D is changed to D = D-2, and k is increased to k + 1 (215). , when k ≠ 1, S _{Yhh, max} up to that step and V _{f, max} at that time are transmitted to the control processor 35, and after changing to the manual operation mode, the auto focus control is terminated (Step 214). Camera auto focus adjustment method, characterized in that performed.