KR960004157B1 - Apparatus and method for automatic focus control of a camcorder - Google Patents

Abstract

The device incorporates an amplifier, which amplifies the video signal generated from the lens. The squeezing is the automatic focal regulation device. The transformation of light input by squeezing into an electric signal, is carried out by solid image pick up element, and generates the video signal. The screen divider(15) divides the block of video signal into frames, is filtered by video signal processor and is processed for displaying on the screen. The A/D convertor(17) converts the analog video signal into digital form. This is given to a low pass filter(16) and then a integrator. The integrator outputs the control signal for moving the lens to the vertex. At this point, the level of the image detection data becomes maximum. The device includes lens motor drive part(12) with applied micro processor(18) for providing variable movement speed of the lens. The device shortens regulation time for automatic focus, avoids microprocessor for lens drive, simplifies circuit composition, and provides high resolution.

Description

Camcorder Auto Focus and Method

1 is a block diagram of a conventional auto focusing apparatus of a camcorder.

2 is a flowchart of an autofocus control method of a conventional camcorder.

3 is a graph showing a conventional auto focusing process.

4 is a block diagram of a camcorder auto focusing apparatus of the present invention.

5 is a flowchart of a camcorder autofocus adjusting method of the present invention.

Figure 6 is a graph showing the auto focus adjustment process of the present invention.

7 is a flowchart of an embodiment of an autofocus adjusting method of the present invention.

* Explanation of symbols for main parts of the drawings

12: lens motor drive unit 13,14: high pass filter

15: fire splitting and digital integrating unit 16: low pass filter

17: A / D converter 18: Micom

The present invention relates to an auto focusing device and a method for automatically adjusting the lens focus in a camcorder. In particular, the present invention relates to a filter and a filter before monitoring the inclination of the auto focus value and crossing the maximum position. The present invention relates to a device and a focus control method by changing the speed of a lens driving motor to prevent over-shoot and to enable high-speed focusing.

In the conventional camcorder, the auto focus adjusting apparatus includes a lens 1 and an aperture 2 for adjusting subject photographing and focusing, and an imaging device 3 for converting the photographed optical signal into an electric signal, as shown in FIG. An amplifier 4 for amplifying the captured image signal, an image signal processor 5 for performing signal processing of the amplified image signal, and a band pass filter 6 for filtering the amplified image signal with different characteristics. (7), a screen division and digital integrator (8) for screen division and digital integration of the filtered video signal, and an A / D converter for converting the filtered signal into a digital signal and supplying it to an integrator (9), the main microcomputer 10 performing device operation control while monitoring the digitally converted video signal level, and the motor driving microcomputer 11 performing auto focus control control under the control of the main microcomputer 10. ), And the motor drive mi The lens motor driver 12 is configured to drive and control the lens 1 under the control of 11 to focus. The focus adjustment operation by the conventional auto focusing apparatus configured as described above is illustrated in FIGS. 1 to 3. Referring to the drawings as follows.

The optical signal of the subject input through the lens 1 is input to the image pickup device 3 by adjusting the amount of light through the aperture 2, where it is converted into an electrical video signal and amplified by the amplifier 4, and then the image signal. It is input to the processing part 5 and the bandpass filter BPF1 (BPF2) (6) (7).

The characteristics of the bandpass filters 6 and 7 have different filtering characteristics as shown in FIG. 3, and at the beginning of the focusing adjustment, the main microcomputer 10 controls the screen splitter and the digital integrator 8 to adjust the bands. The output of the pass filter 6 is accepted.

The screen dividing and digital integrating unit 8 integrates the video signal inputted by the bandpass filter 6 (or the filter 7) in response to the divided screen for focus adjustment. The A / D converter 9 converts this signal into a digital signal and supplies it to the main microcomputer 10 as image detection data for focus adjustment through the integrator 8.

The main microcomputer 10 analyzes the input data to determine whether the subject is changed, and controls the motor driving microcomputer 11 to perform a new focus adjustment when the subject is changed.

Accordingly, the motor driving microcomputer 11 controls the lens motor driver 12 to drive the lens motor in a direction in which the image signal level increases so that the focus of the lens 1 is focused at its peak (maximum value detection position). do.

That is, as shown in FIGS. 2 and 3, in the initial stage of focus adjustment (S1), if the stable data that can be focused is input, the lens motor is fixed through the lens motor driver 12 when the stable data is input. When the input data is increased by step rotation, the direction for moving to the vertex is determined in the same direction as the input data is decreased, and in the opposite direction (S2).

When direction determination is completed, move to the vertex (S3), and if data having a small level is passed after the vertex is input, the driving direction of the lens motor is inverted and input from the band pass filter (BPF2) (7). Select the video signal to store the position where the maximum value is detected while moving the lens 1 until the output of the bandpass filter 7 passes the vertex and falls below a certain level (S4). Then, the lens 1 is returned (S5), and a certain step is moved to the front / rear position of the vertex position (S6).

However, such a conventional camcorder auto focusing apparatus and method need to spend a lot of time for the control of the lens driving motor, which requires a separate dedicated microcomputer, which complicates the circuit configuration and passes back to the peak for focusing. Since a series of operations are repeated, the image change caused by the overshoot appears, which causes a visual burden and causes a long focusing time.

The present invention tracks and monitors the slowness of the detection data by driving the lens motor during focusing, and determines the inclination, and changes the filter before reaching the peak while controlling the lens motor driving speed variably according to the inclination to fine focus. The purpose of the present invention is to provide a method and method for automatically focusing and controlling an overshoot image, and to provide a simple circuit configuration. The configuration will be described below.

Referring to FIG. 4, the automatic focusing apparatus of the present invention includes a lens 1 and an aperture 2 for adjusting subject photographing and focusing, an imaging device 3 for converting photographed optical signals into electrical signals, The amplifier 4 of the photographed video signal, the video signal processor 5 for performing signal processing of the amplified video signal, and the high pass filter 13 and 14 for filtering the amplified video signal with different characteristics. ), A screen division and digital integrator 15 for screen division and digital integration of the filtered video signal, a low pass filter 16 for low-pass filtering the filtered signal, and a low pass filtered video signal. An A / D converter 17 for converting a digital signal into an integrating unit, a microcomputer 18 that monitors the digital video signal level and performs lens motor driving control to a vertex, and the microcomputer 18 controls the microcomputer 18. Receives and drives the lens 1 to control the focus Lens consists of a motor driving unit 12 to fit.

On the other hand, the microcomputer 18 has an internal timer and outputs a pulse having a duty ratio of 50% from the output stage P1 to the motor driver 12 according to the timer value, and this output outputs an external pulse to a counter circle. Source) feeds back to the terminal P2 that can generate interrupts for the desired number of pulses.

Referring to FIG. 5, the auto focus adjusting method according to the apparatus of the present invention configured as described above determines the inclination while moving the lens driving motor to the vertex of the detected image signal level, and vertex according to the determined inclination. The first step of variably controlling the moving speed to the first and the set value to detect whether the inclination near the vertex is reached before passing the slope and the vertex is sharply filtered for the fine focus at the time point is reduced below the set value A second process of searching for a vertex by selecting a detection image signal and changing the lens driving motor to 1 stem / feed, and checking the vertex by micro reciprocating the front and back points of the vertex found in the process, and monitoring whether the vertex is changed. It consists of a third process.

The automatic focusing method and the focusing operation in the apparatus according to the present invention made as described above will be described in detail with reference to FIGS. 6 and 7.

First, in FIG. 4, the optical signal of the subject input through the lens 1 is input to the image pickup device 3 by adjusting the amount of light through the aperture 2, where it is converted into an electric image signal and the amplifier 4 After being amplified by the video signal processor 5 and the high pass filter (HPF1) (HPF2) (13) (14).

The high pass filters 13 and 14 have different filtering characteristics as shown in FIG. 6. In the initial stage of focusing, a high pass filter 13 having a wide bandwidth filtering characteristic is used to roughly detect peaks. In addition, in the vicinity of the vertex, a high pass filter 14 having a sharp filtering characteristic is selected for more precise fine focus, which is performed by the screen division and the digital integrating unit 15 under the control of the microcomputer 18.

The screen dividing and integrating unit 15 integrates the image signal input from the high pass filter 13 (or the filter 14) in correspondence with the screen divided for the focus adjustment.

That is, the output of the selected filter is filtered by the low pass filter 16, digitally converted by the A / D converter 17, and the digital signal is integrated to supply the microcomputer 18 with data corresponding to the detected video signal level. As shown in FIGS. 6 and 7, the microcomputer 18 checks whether the input data is input as stable data capable of focus adjustment (S1). If the stable data is input, the microcomputer 18 controls the lens motor driver 12 to control the lens. While the motor is rotated by the predetermined step forward / reverse, it is judged whether the data input / decreased at that time (S2).

When the input data increases, the moving direction of the lens 1 is determined in the same direction, and in the opposite direction when the input data increases. When the movement direction is determined, the lens 1 is moved in steps through the lens motor driver 12 (S3).

That is, when the vertex search flag is not determined and set as shown in FIG. 7, when the current input data is small by comparing the magnitude of the current input data and the previous input data provided from the high pass filter (HPF1) 13 Next, the lens driving motor is inverted to be driven, and when the current input data is large, the tilt is calculated while driving the lens driving motor in the current driving direction.

The slope is obtained by dividing the difference between the current data and the previous data by the motor driving speed, and comparing the slope with a preset value (x) that is set in advance to detect whether the near point is reached before passing the peak. When the comparison result exceeds the set value x, the lens driving motor is driven at high speed until the set value x is near, and the drive speed decreases as the set value x approaches.

When the detected slope is less than or equal to the set value (x), the output of the high pass filter (HPF2) 14 is selected at that point, and the driving speed is changed by changing the speed of the lens driving motor to 1 step / feed. At this time, after the vertex search flag is set, the threshold value Threshold Value (TH.V) (the lower limit of the decrease when gradually decreasing past the vertex) is calculated and returned from the current input data.

As a result, the vertex flag is set, so the vertex position counter is increased by +1 and the magnitude of the current input data and the previous input data are compared.

As a result of this comparison, if the current input data is smaller than the previous input data, the difference value (dif) (dif = dprevious data-current data) is calculated because the result of the slow tracking (S4) tracking result is exceeded in FIG. The value dif is compared with the reference value TH.V.

The result of the comparison is returned if the difference value (dif) is equal to or less than the reference value (TH.V). If the reference value (TH.V) is exceeded, the driving direction of the lens driving motor is reversed from this point (S5). After shifting the position of the lens 1 by the value, stop the lens 1 at the vertex position to complete the focus control, set the vertex check mode, and monitor the presence / absence of the vertex variation due to the subject variation (S6). Cope with restart.

As described above, the present invention outputs a pulse from a microcomputer to drive a motor, and feeds the pulse back to an interrupt port to control motor driving, thereby simplifying circuit configuration and reducing manufacturing costs. By approaching the vertex at high speed and performing fine focus before passing the vertex, the amount of overshoot can be restrained as much as possible, thus eliminating image changes during focusing, thereby preventing visual impairment or burden, and providing fast focusing. Through this, the performance of the device can be improved.

Claims (5)

A high pass filter 13 and 14 for filtering the amplified image signals photographed by the subject with different characteristics, and a screen splitting and digital integrating unit for selecting and filtering the image signals and performing digital integration. 15), a low pass filter 16 for low pass filtering the selected signal, an A / D converter 17 for converting the filtered video signal into a digital signal and supplying it to an integrator, and monitoring the digital video signal level. Autofocus of a camcorder consisting of a microcomputer 18 that performs lens motor driving control to a vertex and a lens motor driving unit 12 that drives and controls a lens 1 under the control of the microcomputer 18. Regulator. A first process of driving the lens driving motor to determine the inclination while moving to the vertex of the detected image signal level, and variably controlling the moving speed to the vertex according to the determined inclination; and before passing the inclination and the vertex Compare the set value to detect whether the vertex is reached near the vertex, select the sharply filtered detection image signal for fine focus at the point of decreasing below the set value, and change the lens driving motor to 1 step / feed. And a second step of searching, and a third step of checking the vertex and monitoring whether the vertex changes by reciprocating the front and rear points of the vertex found in the process. The method of claim 2, wherein the first process compares the magnitude of the current input data and the previous input data of the detected image signal, and reverses the driving direction of the lens driving motor if the current input data > the previous input data. If the previous input data, the process of calculating the slope by dividing the difference between the current input data and the previous input data by the moving speed, and comparing the set value set to detect whether the calculated slope reached near the vertex before passing the vertex. And if the slope calculated as a result of the comparison is greater than or equal to the set value, driving the moving speed to the vertex at a high speed until the set value is reached, and decelerating and moving as the set value is approached. How to adjust the auto focus of the camcorder. The method of claim 2, wherein the second process selects a filter output video signal having a sharp filtering characteristic near a vertex as detection data when the slope calculated in the first process is equal to or less than a predetermined set value and sets the speed of the lens driving motor. Calculating the reference value of the vertex search from the current input data after changing to one step / feed, and comparing the calculated reference value with the difference between the current input data and the previous input data until the difference value becomes equal to or greater than the reference value. Automatic focus adjustment method of the camcorder consisting of the process of increasing the vertex position counter value while repeating the process. 3. The method of claim 2, wherein the third process comprises: comparing input data values near the vertex with a reference value of the vertex search based on the vertices found in the second process; and when the difference is greater than or equal to the reference value, driving the lens. A method of adjusting the auto focus of a camcorder comprising reversing the driving direction of a motor, shifting a lens by a vertex position counter value, and setting a vertex check mode.