KR0130002B1 - Circuit & method for auto-focusing of video camera - Google Patents

Abstract

In the focus circuit, analog/digital converter(ADC1) a luminance signal among input video signals into a digital signal. A focus control circuit(100) samples and a predetermined part of a video signal of a display plane and adds a weight value to the sampled video signal to thereby control a total focus of the display plane. A switch(200) switches focus control circuit(100) during a focus operation. A band pass filter(300) performs a focus operation with respect to a wide frequency band. A RAM temporarily stores a signal from band pass filter(300). A comparator(400) compares a signal from the band pass filter(300) with a signal from the RAM and senses an operation of a focus driving motor according to the comparison result. A delay section(500) delays the signal from comparator(400). An operating switch(SW2) determined whether a focus operation is automatically or manually performed,

Description

Auto focusing circuit and method of video camera

1 is a block diagram of an auto focusing circuit of a conventional video camera.

2 is an auto focusing circuit diagram of a video camera according to the present invention.

3 (a) and 3 (b) are detailed circuit diagrams and input waveform diagrams of the signal separator of FIG.

4 (a) and 4 (b) show a relationship waveform diagram and a monitored video screen schematic gating the signal of the FIG. 2 signal splitter.

5 is a schematic representation of the weighting and addition of a second multiplier and an adder.

6 is a flowchart for performing an auto focusing method of a video camera according to the present invention.

* Explanation of symbols for main parts of the drawings

100: focus adjustment circuit 110: signal separation unit

111 to 113: Signal separator 120: Weight addition unit

121 to 123: multiplier 200: switching unit

300: band pass filter 400: comparator

500: delay unit ADCI: analog digital converter

SW1, SW2: Switch ADDI: Adder

BPF1 to BFPm: Bandpass Filter RAM: RAM

CPU: Central processing unit C1, C2: Auto focusing control signal

The present invention relates to a video camera, and more particularly, by using a fuzzy concept to give the largest weight to the center of the screen and to gradually decrease the weight symmetrically around the screen, thereby increasing focus throughout the screen. It relates to an auto focusing circuit and method of a video camera that fits well.

FIG. 1 is a block diagram of an auto focusing circuit of a conventional video camera, and the infrared detector 20 detects infrared rays reflected after irradiating infrared rays emitted from the infrared generator 10 to a subject.

At this time, the angle θ is changed according to the distance between the subject and the video camera, and the control signal generator 30 calculates the distance of the subject using the size of the angle, and then generates an auto focusing control signal to a focus driving motor that focuses on the subject. Focused.

However, in the auto focusing circuit of the conventional video camera, an infrared generator for generating infrared rays and an infrared detector for detecting infrared rays must be installed in the video camera, and the reference point of the auto focus is fixed to a specific point on the display surface. In this case, the focus is precisely correct, but the focus of the entire screen is poor because the focus of the other points is so disturbed.

The present invention has been made to solve this problem, and an object of the present invention is to use a luminance component of an input video signal so that an additional device is not required, and the fuzzy concept focuses on the most important part and focuses the part. It is an object of the present invention to provide an auto focusing circuit and a method of a video camera that can focus on the entire display surface by symmetrically focusing.

In order to achieve the above object, the present invention provides an analog digital converter for converting a luminance signal into a digital signal among input video signal components, and extracts a specific portion of a video signal on a display surface connected to the analog digital converter. A focus adjusting circuit for focusing the entire display surface by adding a; a switching unit connected to the focus adjusting circuit to be sequentially switched during auto focusing; and a wide frequency band connected to the switching unit from a low frequency band to a high frequency band A band pass filter unit configured to focus on the RAM, a RAM connected to the band pass filter unit to temporarily store a signal from the band pass filter unit, and a RAM connected to the RAM from the band pass filter unit and the RAM. Compare the signals to reduce the operation of the focus drive motor A comparator to be connected to the comparator, a delay unit for delaying a signal input from the comparator, an operation switch for determining whether to focus automatically or manually, and a connection to the operation switch and the comparator and the delay unit. There is an auto focusing circuit of a video camera composed of a central processing unit for controlling the rotation direction of the focus drive motor by detecting the rotation direction of the focus drive motor by comparing the signals before and after the delay of the delay unit. .

Another aspect of the present invention is to perform a preparation routine for setting an initial value by rotating the focus drive motor when the operation switch is set to auto, and after the preparation routine is performed, the difference between the signals from the band pass filter unit and the RAM is set by the motor. A step of detecting a change in focus according to the movement of the video camera is performed by comparing with the value of the state after the movement. If the value of the state after the movement of the focus motor is small in this step, the signal before and after the delay of the delay unit is determined. If the rotation direction of the focus drive motor is not matched by detecting the rotation direction of the focus drive motor by comparing the sizes, reset the value of the auto focusing control signal, and then perform the focus drive motor rotation direction detection routine to re-examine the rotation direction of the focus drive motor. If the value of the state after the focus drive motor is moved in the step is large, the focus is achieved. Since in the autofocusing method of the video camera made to perform after it has been paused by a focus drive motor, the band-pass filter section focus condition check routine to focus while switching to a high frequency band.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is an auto focusing circuit diagram of a video camera according to the present invention. After extracting a specific portion of a video signal on a display surface of an input video signal component, an analog digital converter ADC1 converts a luminance signal Y into a digital signal. The weight adjusting circuit 100 connects the focus adjustment circuit 100 to add focus to the entire display surface.

The focus adjustment circuit 100 is weighted to the signal separation unit 110 of the respective signal separators 111 to 113 which are connected to the analog digital converter ADC1 and extract a specific portion of the video signal on the display surface. The additional unit 120 is connected to add weights to the signal extracted by the signal separation unit 110, and the weight adding unit 120 is composed of the respective multipliers 121 to 123.

As shown in FIG. 3A, the signal separators 111 to 113 multiply the horizontal component HP and the vertical component VP of the video signal by the AND gate AND1 and the AND gate. When the output of AND1) is logic high, the switch SW0 is switched to logic high to extract the display surface of the horizontal component HP and the vertical component VP.

The weight adding unit 120 connects an adder ADD1 for differently setting the weight of each part of the display surface by performing a logical multiplication on the signals of the multipliers 121 to 123.

In addition, the focus adjustment circuit 100 is connected to the switching unit 200 which is sequentially switched during auto focusing, and the switching unit 200 is a band for auto focusing over a wide frequency band from a low frequency band to a high frequency band The pass filter unit 300 is connected.

The band pass filter unit 300 is composed of respective band pass filters BPF1 to BPFm.

Meanwhile, a RAM is connected to the band pass filter unit 300 to temporarily store the signal S9 from the band pass filter unit 300.

In addition, the RAM (RAM) is connected to the comparator 400 for detecting the operation of the focus driving motor by comparing the signals from the band pass filter unit 300 and RAM (RAM), the comparator 400 The delay unit 500 is connected to delay the signal input from the comparator 400.

On the other hand, the operation switch SW2 for deciding whether to focus automatically or manually, and the comparator 400 and the delay unit 500 are connected to a central processing unit (CPU) to delay the delay unit 500. By comparing the magnitudes of the front and rear signals S11 and S14, the rotation direction of the focus driving motor is sensed to output the auto focusing control signals C1 and C2 to control the focus driving motor.

FIG. 6 is a flowchart for performing an auto focusing method of a video camera according to the present invention. When the operation switch SW2 turns to auto, a preparation routine L1 for rotating the focus drive motor and setting an initial value is performed. The difference between the signals S9 and S10 from the filter unit 300 and the RAM is compared with the value △ after the focus driving motor is moved to determine the change in focus caused by the video camera movement. If it is determined that the value Δ of the state after the focus drive motor is moved is small in the step LS4, the delay unit 500 may detect the signals S11 and S14 before and after the delay. Compares the size of and detects the rotational direction of the focus drive motor and if the rotational direction of the focus drive motor does not match, resets the auto focusing control signals (C1) and (C2) and then re-examines the rotational direction of the focus drive motor. Motor spinner Perform the direction detection routine (L2). In this case, the value Δ is a value after the focus driving motor is moved and is small enough to be hardly detected by the human eye. If the value △ of the state after the focus driving motor is moved is large in the step SL4, the focus is set, and after the pause of the focus driving motor, the band pass filter 300 is switched to a high frequency band. Performs a focus state checking routine L3.

Referring to the operation and effects of the present invention as described above are as follows.

First, the luminance signal Y input is made into a digital signal through the analog digital converter ADC1, and then a specific portion of the video signal is gated using the signal separators 111 to 113.

In the operation of the signal separators 111 to 113, when the horizontal component HP and the vertical component VP of the video signal are logic high at the same time, the switch SW0 is switched to logic high so that S1 = S2, The case cuts off the signal to the rear end.

That is, the relationship of gating the signals of the signal separators 111 to 113 is as shown in FIG. 4 (a). When the display surface of the monitored video signal is represented graphically, as shown in FIG. The signal separators 111 to 113 may sample or extract a portion of the display surface to be focused.

The video signals of the display surface extracted through the signal separators 111 to 113 are applied to the multipliers 121 to 123, and are given a weight for focusing the entire screen.

That is, if the weight of the multiplier 121 is a, the output signal is S5, the weights of the multipliers 122 and 123 are b and c, and the output signals are S6 and S7, respectively. If the signals S5 to S7 having weights a, b, and c added to 123 are added through the adder ADD1, the weight of the center becomes a + b + c as shown in FIG. Symmetrically outward, the weight decreases to b + c and c, respectively.

This means that the center is considered to be the largest in order to focus, and the off-center part is weighted to give an overall balance on the screen to prevent excessive focusing on a specific part, and the fuzzy concept is applied here.

On the other hand, when the switch SW2 for operating whether to focus automatically or manually is switched high to focus automatically, switching is performed according to the switching unit switching control signal S13 from the CPU. The switch SW1 of the unit 200 is switched in turn.

Switching of the switch SW1 according to the control signal S13 sequentially selects each of the band pass filters BPF1 to BPFm of the band pass filter 300 to focus from a low frequency band to a high frequency band. To be

That is, the control signal 13 is set to zero, which is a logic low when the initial focus motor is driven (L1S1), and the switch SW1 is switched to the band pass filter BPF1 at the highest position to perform focusing from the low frequency band. .

Then, the auto focusing control signal C1 is set to a logic high signal, that is, 1 (L1S2) to rotate the focus drive motor, and the RAM of the central processing unit CPU when the operation switch SW2 is switched to high. ) The signal stored in the RAM is output according to the control signal S12. Since there is no signal stored in the RAM from the band pass filter unit 300, the RAM output signal S10. ) Is also set to zero, which is also a logic low state (L1S3).

In addition, as the band pass filter unit 300 is switched by the switch SW1, the signal 10 and the band pass filter output from the RAM by the control signal S12 of the central processing unit (CPU). The magnitude of the signal SP from the unit 300 is compared in the comparator 400 and compared with the value? Of the state after the focus driving motor is moved (LS4) to output the signal of the comparator 400. When S10-S9, that is, S11 is smaller than the value? Of the state after the focus driving motor is moved, the output signal S11 of the comparator 400 is delayed for a predetermined time to the delayed signal S14. And outputs the central processing unit (CPU) to compare the magnitudes of the signals S11 and S14 before and after the delay (L2S1).

In addition, since the signal before the delay (S11) is greater than the signal after the delay (S14) means that the focus is bad, since the initial auto focusing control signal (C1) is set to a logic high, the control signal (C1) Low logic low and (C2) to logic high to rotate the focus drive motor in reverse (L2S3).

On the other hand, if the pre-delay signal S11 is less than the delayed signal S14 at step L2S1, the control signal C1 is a direction in which focus is improved because the initial control signal C1 is set to logic high. The logic high low control signal C2 is logic low to drive the focus driving motor as it is, and stores the output signal S9 of the band pass filter unit 300 in the RAM to store the RAM output signal ( S10) and proceeds to the step LS4 to detect the rotational direction of the focusing motor again to perform focusing.

On the other hand, when S10-S9? Is satisfied at step LS4, the focus drive motors are temporarily stored with the focus drive motor control signals C1 and C2 as logic low (L3S1).

Then, the central processing unit (CPU) sends a control signal (S13) to switch the band pass filter of the band pass filter unit 300 to a high frequency band.

When the band pass filter is switched (L3S3), the above routines (L1) and (L2) are repeated to finally check whether the band pass filter is the last one, that is, BPFm (L3S2). To exit.

The reason why m band pass filters are used in the above is to first focus using a signal passing through the band pass filter (BPF1) of the lowest frequency band, and then gradually move to a higher frequency band to focus. The pass filter (BPFm) coincides with the highest portion of the video camera's frequency band, so it can autofocus even the highest frequency that the video camera can take.

On the other hand, when the switch SW1 is switched to the band pass filter BPFm, the difference between the signal S9 from the band pass filter 300 and the RAM output signal S10 and the focus driving motor are again obtained. The magnitude of the value △ after the movement is compared (L3S4), which is to detect a change in focus as the video camera moves, and the value of the state after the focus driving motor moves in the step L3S4. If (△) is determined to be large, the process proceeds to the step L3S1 and performs the next step. If it is determined that the value (△) of the state after the focus driving motor is small, the screen is moved and the central processing unit (CPU) The control signal S13 of the switch SW1 is set to zero, which is a logic low, and the process proceeds to the step L2S1 to repeat the refocusing routine L2 to automatically focus.

As described above, the present invention converts the luminance component of the input video signal into a digital signal, extracts a specific portion of the video signal corresponding to the display surface, and adds weights to make the entire display surface in focus, and a central processing unit (CPU). The switching unit 200 is sequentially switched according to the control signal of the control unit so that each band pass filter BPF1 to BPFm of the band pass filter unit 300 is selected so that the focus is focused from the low frequency band to the high frequency band. do.

The signal of the band pass filter unit 300 is temporarily stored in a RAM, and the comparator 400 compares the signals from the band pass filter unit 300 and the RAM to the movement of the video camera. Detect the operation of the focus driving motor according to the delay and delay the output signal of the comparator 400 to the delay unit 500 to compare the input and output signals of the delay unit 5000 in the central processing unit (CPU) to focus By controlling the rotational direction of the drive motor, it is automatically focused.

As described above, since the present invention uses the luminance component of the input video signal, an additional device such as an infrared generator or an infrared detector is not required. Also, when the central processing unit or the RAM is added to the existing microcomputer, Therefore, there is no need for a separate integrated circuit, thereby reducing the cost, and by applying the fuzzy concept, it is possible to focus the entire display surface instead of focusing on a part.

Claims (5)

The analog digital converter ADC1 converts the luminance signal Y into a digital signal among the input video signal components, and extracts a specific part of the video signal on the display surface by adding weights after being connected to the analog digital converter ADC1. It is connected to the focus adjusting circuit 100 to focus on the entire display surface, the switching unit 200 connected to the focus adjusting circuit 100 and sequentially switched during auto focusing, and the switching unit 200. A band pass filter 300 for focusing over a wide frequency band from a low frequency band to a high frequency band, and connected to the band pass filter 300 to temporarily receive a signal from the band pass filter 300. Operation of a focus driving motor by comparing a RAM to be stored with signals from the band pass filter unit 300 and RAM connected to the RAM A comparator 400 for sensing, a delay unit 500 connected to the comparator 400 for delaying a signal input from the comparator 400, and an operation for determining whether to focus automatically or manually It is connected to the switch SW2, the operation switch SW2, the comparator 400 and the delay unit 500 to detect the rotation direction of the focus driving motor by comparing the magnitudes of the signals before and after the delay of the delay unit 500. And a central processing unit (CPU) for controlling the rotation direction of the focus drive motor by controlling the auto focusing control signals (C1) and (C2). The signal adjusting unit (100) of claim 1, wherein the focus adjustment circuit (100) is connected to the analog digital converter (ADC1) and extracts a specific portion of a video signal on a display surface. The weight adder 120 is connected to the weight adder 120 to add a weight to the signal extracted by the signal separator 110 and the weight adder 120 is connected to each of the signals of the weight adder 120. An auto focusing circuit of a video camera composed of an adder (ADD1) which logically multiplies and sets weights of different parts of a display surface differently. When the operation switch SW2 is set to auto, the preliminary routine L1 for setting the initial value by rotating the focus drive motor is performed. After the preliminary routine L1 is performed, the band pass filter 300 and the RAM are performed. Comparing the difference between the signals S9 and S10 with the value? Of the state after the focus driving motor is moved, and performing a step LS4 of detecting a focus change caused by the movement of the video camera. If it is determined in step LS4 that the value? Of the state after the focus drive motor is moved is small, the magnitudes of the signals S11 and S14 before and after the delay of the delay unit 500 are compared to compare the magnitudes of the focus drive motor. If it is determined that the rotation direction of the focus drive motor is not correct by detecting the rotation direction, the focus drive motor rotation direction detection routine (L2) re-checks the rotation direction of the focus drive motor after resetting the auto focusing control signals (C1) and (C2). In the step LS4). If the value △ of the state after the cursor drive motor is large is the focus, the focus state irradiation routine for focusing while the focus drive motor is paused and then switching the band pass filter unit 300 to a high frequency band L3), the method of auto focusing of the video camera. 4. The method of claim 3, wherein the focus driving motor rotation direction detection routine L2 performs a step L2S1 comparing the magnitudes of the signals S11 and S14 before and after the delay of the delay unit 500, and If the signal S14 delayed in step L2S1 is smaller than the delay signal S11, the direction of rotation of the focus drive motor is wrong. Therefore, the auto focusing signals C1 and C2 are reset and changed to reset the value L2S2. To perform the rotation direction of the focus drive motor, and to perform the step (L2S3) of storing the signal (S9) from the band pass filter unit 300 in the RAM (RAM) after performing the step (L2S2). How to auto focus video cameras. The focus state checking routine L3 performs the step L3S1 of temporarily stopping the focus drive motor by setting the autofocusing control signals C1 and C2 to zero, and performing the step L3S1. After performing step (L3S2), it is determined whether the frequency of the band pass filter unit 300 is the highest frequency band, and in step L3S2, the frequency of the band pass filter unit 300 has the highest frequency. If it is not a band, the step L3S3 of switching the switching unit 200 to a high frequency band is performed, and if it is determined in step L3L2 that the frequency of the band pass filter unit 200 is the highest frequency band, the band pass is again. Performing a step (L3S4) of comparing the difference between the signals S9 and S10 from the filter unit 200 and the RAM with a value? Of the state after the focus driving motor is moved; After the step L3S4, the value of the state after the focus drive motor is moved If (△) is small, the video camera is moved and the focus is changed, so that the step L3S5 of initializing the switching control signal S13 of the switching unit to logic low is performed.