JPH05199445A - Automatic focusing circuit of video camera and method thereof - Google Patents

Abstract

PURPOSE: To focus the whole of display by not only utilizing a fuzzy logic to concentrically focus the most important part but also the periphery. CONSTITUTION: In a focusing circuit 100, a weight adding part 120 is connected to a signal separation part 110, which extracts a specific part of a video signal on a display face, to add a weight value to the extracted signal, and this signal is sent to an adder ADD1. A switching part 200 which is successively switched at the time of automatic focusing is connected, and a band-pass filter 300 is so connected that automatic focusing is performed in a band from a low frequency band to a high frequency band, and an output S9 is stored in a RAM. A comparator 400 compares signals from the filter 300 and the RAM to sense the operation of a focus driving motor, and a delay part 500 is connected to delay the input signal from the comparator 400. A CPU compares signals S11 and S14 before and after the delay in the delay part 500 to sense the rotating direction of the focus driving motor and outputs control signals C1 and C2 to control the focus driving motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera, and more particularly, to a video camera automatic focus adjustment circuit and method that uses a fuzzy logic to achieve good focus on the entire screen.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of a conventional automatic focus adjustment circuit for a video camera. Infrared generator 1
After irradiating the subject with infrared rays emitted from 0, the infrared ray detector 20 senses the reflected infrared rays. At this time, according to the distance between the subject and the video camera, the angle “θ (theta)”
After that, the control signal generator 30 calculates the distance to the subject using the size of the angle, and then applies an automatic focus adjustment control signal to the focus drive motor for focusing to automatically focus. Made of

However, in the conventional automatic focus adjustment circuit for a video camera as described above, an infrared generator for generating infrared rays and an infrared sensor for detecting infrared rays must be installed in the video camera. And since the reference point for focus adjustment is fixed to a specific point on the display surface, it is possible to accurately focus on this point,
There is a problem that the focus on the whole screen is not good because the focus cannot be taken at different points.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve such problems, and an object of the present invention is to utilize a luminance component in an input video signal to
Focusing on the entire display surface by using fuzzy logic to focus on the most important parts and also surrounding the parts without using any additional device. It is an object of the present invention to provide a video camera automatic focus adjustment circuit and method.

[0005]

The features of the present invention for achieving the above object are an analog / digital converter ADC1 for converting a luminance signal Y in an input video signal component into a digital signal, and A focus adjusting circuit 10 connected to the analog / digital converter ADC1 to extract a specific portion of the video signal on the display surface and then add a weight value to focus the entire display surface.
0, and a switching unit 200 connected to the focus adjustment circuit 100 and sequentially switched during automatic focus adjustment,
A bandpass filter 300 connected to the switching unit 200 for performing focus adjustment over a wide frequency band from a low frequency band to a high frequency band, and a bandpass filter unit 300 connected to the bandpass filter unit 300. RAM for temporarily storing the signal from 300,
The band pass filter unit 3 is connected to the RAM.
00 and a signal from the RAM to detect the operation of the focus driving motor, a delay unit 500 connected to the comparator 400 to delay the signal input from the comparator 400, and a focus unit. Mode selection switch SW2 that is switched when automatic or manual selection of
And the mode selection switch SW2, the comparator 400, and the delay unit 500 are connected, and the magnitudes of the signals before and after the delay of the delay unit 500 are compared to detect the rotation direction of the focus driving motor to automatically adjust the focus. And a central processing unit for controlling the rotation direction of the focus drive motor by controlling the control signals C1 and C2.

Another feature of the present invention is, when the automatic or manual focus is selected, when the mode selection switch SW2 to be switched is automatic, the focus drive motor is rotated to set an initial value, and the preparation routine L1. After the routine L1 is performed, the difference between the signals S9 and S10 from the bandpass filter unit 300 and the RAM is compared with the value Δ in the next state when the focus drive motor is moved to detect the focus change caused by the movement of the video camera. If it is determined in step L4 that the value Δ of the next state in which the focus drive motor has moved is small in step L4, the magnitudes of the signals S11 and S14 before and after the delay of the delay unit 500 are compared to perform focus drive. When the rotation direction of the motor is detected and it is determined that the rotation direction of the focus drive motor does not match, the automatic focus adjustment control signals C1 and C2
After resetting the value, the focus drive motor rotation direction detection routine L2 for re-detecting the rotation direction of the focus drive motor, and the value Δ of the next state when the drive motor is moved in step LS4.
Is determined to be large, it is the one that is in focus, so
Bandpass filter unit 3 after temporarily stopping the focus drive motor
00 is switched to a high frequency band, and then a focus state check routine L3 for focusing is provided.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 2 is an automatic focus adjustment circuit diagram of a video camera to which the fuzzy logic of the embodiment is applied. An analog / digital converter A for selecting a luminance signal Y in an input video signal component and converting it into a digital signal
After a specific portion of the video signal on the display surface is extracted at DC1, a weighting value is added to connect a focus adjustment circuit 100 for focusing the entire display surface.

In the focus adjusting circuit 100, the weight value adding section 120 is connected to the signal separating section 110 including the signal separating sections 111 to 113 for extracting a specific portion of the video signal on the display surface, and the signal separating section is connected. A weight value is added to the signal extracted by 110. The weight value adding unit 120 includes multipliers 121 to 123. As shown in FIG. 3A, the signal separators 111 to 113 have an AND gate AND1 that ANDs the horizontal component HP and the vertical component VP of the video signal, and the output of the AND gate AND1 is logical "high". In this case, it is composed of the horizontal component HP which is switched by a logic "high" and the switch SW0 which causes the vertical component VP to extract the display surface. Horizontal component H of video signal
P and the vertical component VP are shown in FIG. 3B. And
The weight value adding unit 120 includes the multipliers 121 to 1
An adder (ADD1) for ANDing each signal of 23 and adding the weighted value of each portion of the display surface is connected.

In addition, the focus adjustment circuit 100 includes a switching unit 200 which is sequentially switched during automatic focus adjustment.
And the switching unit 200 is connected to the bandpass filter unit 300 for autofocusing in a wide frequency band from a low frequency band to a high frequency band. The bandpass filter unit 300 includes two or more handpass filters BPF1 to BPFm.
A RAM is connected to the bandpass filter unit 300 to temporarily store the signal S9 from the bandpass filter unit 300. The RAM is connected to a comparator 400 for comparing the signals from the bandpass filter unit 300 and the RAM to detect the operation of the focus driving motor, and the comparator 400 is connected to a delay unit 500, The signal input from the comparator 400 is delayed.

On the other hand, a central processing unit CPU is connected to the mode selection switch SW2 and the comparator 400 and the delay unit 500 which are switched when the focus is automatically or manually selected, and the signal S11 before and after the delay of the delay unit 500 is connected.
And S14 are compared to detect the rotation direction of the focus drive motor, and the automatic focus adjustment control signals C1 and C2 are output to control the focus drive motor.

FIG. 6 is a flow chart for performing the automatic focus adjustment method for the video camera of the embodiment. When the mode selection switch SW2 becomes automatic, a preparatory routine L1 for rotating the focus driving motor to set an initial value is executed, and then the difference between the signals S9 and S10 from the bandpass filter unit 300 and the RAM and the focus driving motor are performed. Step SL4 of comparing with the next state value Δ that has moved is executed.

When it is determined from the bandpass filter unit 300 and the RAM that the next state value Δ when the focus drive motor has moved is smaller than the difference between the signals S9 and S10, the signals S11 and S14 before and after the delay of the delay unit 500 are detected. Of the automatic focus adjustment control signals C1 and C for detecting the rotation direction of the focus drive motor and adjusting the rotation direction of the focus drive motor.
After resetting the value of 2, the focus drive motor rotation direction detection routine L2 for re-detecting the rotation direction of the focus drive motor is executed. Here, the value Δ is a value that is almost invisible to human eyes in the next state after the focus drive motor is moved.

Then, in step SL4, when the value Δ in the next state where the focus drive motor is moved is large, the focus is achieved. Therefore, after temporarily stopping the focus drive motor, the band pass filter unit 300 is set to a high frequency band. Then, the focus state check routine L3 for focusing is performed. The operation and effect of this embodiment described above will be described below.

First, the input luminance signal 5 is converted to analog /
After being converted into a digital signal by the digital converter ADC1, the specific portion of the video signal is gated using the signal separators 111 to 113. The signal separators 111 to
The operation of 113 is the horizontal component HP and the vertical component V of the video signal.
When P and the logic "high" at the same time, the switch SW0
Is switched to logic "high" and becomes "S1 = S2",
In other cases, the signal to the rear end is cut off. That is, the relationship of gating the signals in the signal separators 111 to 113 is as shown in FIG. 4A, and the display surface of the monitored video signal is schematically shown in FIG.
B, and the signal separators 111 to 1
With 13, the portion of the display surface to be focused is sampled, that is, extracted.

Then, the video signals on the display surface extracted through the signal separators 111 to 113 are applied to the multipliers 121 to 123, and then weighted for adjusting the focus on the entire screen. That is, if the weighted value of the multiplier 121 is "a" and the output signal is S5, and the weighted values of the multipliers 122 and 123 are "b" and "c" and the output signals are S6 and S7, respectively. 121 ~
The signals S5 to S7 to which the weights a, b, and c are added in 123
Through the adder ADD1, the weight value at the center becomes "a + b + c" as shown in FIG. 5, and the weight values decrease in order from "b + c" to "c" as it goes outward from the center. .. This means that the central part is considered the most in order to focus, and the part outside the center also participates with a weight value, and by considering the whole screen in a well-balanced manner, It can be seen that the fuzzy logic is applied here because the focus adjustment beyond the range is prevented.

The flowchart of FIG. 6 will be described in detail below. Switch SW to operate the focus automatically or manually
2 is switched to "high" in order to automatically focus, the switch S of the switching unit 200 is switched by the switching unit switching control signal S13 from the central processing unit CPU.
W1 is sequentially switched.

Switch SW1 according to the control signal S13
The switching is performed by sequentially selecting each of the band pass filters BPF1 to BPFm of the band pass filter unit 300 and adjusting the focus from a low frequency band to a high frequency band. That is, the control signal 13 is set to zero which is a logic "low" at the time of driving the initial focus motor (L1S1), and the switch SW1 is switched to the band pass filter BPF1 located at the uppermost position to adjust the focus from the low frequency band. Carry out. Then, the automatic focus adjustment control signal C
1 is set to a logical "high" (L1S2), the focus drive motor is rotated, and the central processing unit CPU is operated in accordance with the case where the operation switch SW2 is switched to "high".
The signal stored in the RAM is output by the RAM control signal S12. Since there is no signal stored in the RAM from the bandpass filter unit 300 in the initial stage, the output signal S10 of the RAM is also set to zero which is the logical "low" state (L1S3).

Then, the bandpass filter section 300.
Is switched by the switch SW1, the signal S10 output from the RAM by the control signal S12 of the central processing unit CPU and the magnitude of the signal S9 from the band pass filter unit 300 are compared by the comparator 400, and the focus is further focused. It was compared with the next state value Δ when the drive motor moved (L
After S4), the output signal of the comparator 400 (S10-S
9) That is, if S11 is smaller than the value Δ in the next state after the focus drive motor has moved, the output signal S1 of the comparator 400
1 is delayed by a certain time to output a delayed signal S14, and the central processing unit CPU outputs the signal S1 before and after the delay.
1 and S14 are compared in size (L2S
1).

If the pre-delayed signal S11 is larger than the delayed signal S14 from the above, it means that the focus is deteriorated, so that the initial automatic focus adjustment control signal C1 is obtained.
Is wrong because the control signal C1 is set to logic "low" and C2 is set to logic "high" to rotate the focus drive motor in the opposite direction (L2S3).

On the other hand, when the pre-delayed signal S11 is smaller than the delayed signal S14 in step L2S1, it is in the direction of improving the focus that the initial control signal C1 is set to the logical "high". When the control signal C2 is logic "high" and the logic "low", the focus drive motor is driven as in the current state, the output signal S9 of the bandpass filter unit 300 is stored in the RAM, and the output signal S10 of the RAM is generated. Returning to step LS4, the rotation direction of the focus adjustment motor is sensed again to perform focus adjustment.

On the other hand, in step LS4, "S10-S"
When 9 ≧ Δ ”is satisfied, the focus drive motor control signals C1 and C2 are set to logic“ low ”to temporarily stop the drive of the focus drive motor (L3S1), and the bandpass filter of the bandpass filter unit 300 is turned on. A control signal S13 is sent from the central processing unit CPU so as to switch to a higher frequency band, and when the bandpass filter is switched (L3S3), the above routines L1 and L2 are repeated until the bandpass filter is finally switched. Check for the highest frequency band, ie, "BPFm" (L3S
2) If the bandpass filter is BPFm, the automatic focus adjustment process is temporarily terminated.

The reason why "m" bandpass filters are used is that the bandpass filter BP of the lowest frequency band is first used.
After focusing automatically using a signal that passes through F1,
The bandpass filter BPFm matches the highest part of the frequency band of the video camera, so that the highest frequency that can be taken by the video camera is reached. Even autofocus can be adjusted.

On the other hand, when the switch SW1 is switched by the bandpass filter BPFm, the difference between the signal S9 from the bandpass filter unit 300 and the output signal S10 from the RAM and the next value Δ when the focus drive motor moves are large. Are compared (L3S4). This is to detect a focus change due to movement of the video camera. If it is determined from step L3S4 that the next state value Δ when the focus drive motor has moved is large, the process proceeds to step L3S1 to perform the next step, and the next state value when the focus drive motor has moved is small. If it is determined that the focus is changed along with the movement of the video camera, the central processing unit C
PU switch SW1 and control signal S13 are logic "low"
Is set to zero, and the step L2S1 is performed.
Then, the focus adjustment routine L2 is repeatedly performed to automatically adjust the focus.

As described above, in this embodiment, after converting the luminance component in the input video signal into a digital signal, a specific portion of the video signal corresponding to the display surface is extracted,
A weight value is added to bring the entire display surface into focus, and the switching unit 200 is sequentially switched by a control signal from the central processing unit CPU, so that each of the bandpass filters BPF1 to BPF1 to BPF1 of the bandpass filter unit 300.
The BPFm is selected so that it is focused from the low frequency band to the high frequency band. Then, the signal of the bandpass filter unit 300 is temporarily stored in the RAM, and the comparator 400 stores the bandpass filter unit 300 and RA.
The signal from M is compared, the operation of the focus drive motor due to the movement of the video camera is sensed, the output signal of the comparator 400 is delayed from the delay unit 500, and the central processing unit CPU
The input and output signals of the delay unit 500 from the above are compared, and the rotation direction of the focus drive motor is controlled to perform automatic focus adjustment.

[0025]

As described above, since the present invention utilizes the luminance component in the input video signal, another additional device such as an infrared generator or infrared detector is not required,
Moreover, since the central processing unit, RAM, etc. can be realized inside the existing microcomputer, there is no need for a separate integrated circuit, which has the effect of cost reduction. There is an effect that the entire display can be adjusted without a focus.

[Brief description of drawings]

FIG. 1 is a block diagram of an automatic focus adjustment circuit of a conventional video camera.

FIG. 2 is an automatic focus adjustment circuit diagram of the video camera of the present embodiment.

3A is a detailed circuit diagram of the signal separator of FIG. 2. FIG.

FIG. 3B is an input waveform diagram of the signal separator of FIG. 2.

4A is a related waveform diagram for gating the signals of the signal separator of FIG.

FIG. 4B is a monitored video screen schematic diagram of the signal separator of FIG. 2.

5 is a schematic representation of weighting and addition by the multiplier and adder of FIG.

FIG. 6 is a flow chart for performing the automatic focus adjustment method for the video camera of the present embodiment.

Claims (5)

[Claims] 1. An analog / digital converter ADC1 for converting a luminance signal Y in an input video signal component into a digital signal, and connected to the analog / digital converter ADC1.
After extracting a specific part of the video signal on the display surface,
A focus adjustment circuit 100 for adding a weighted value to adjust the focus of the entire display surface, a switching unit 200 connected to the focus adjustment circuit 100 and sequentially switched at the time of automatic focus adjustment, and the switching unit 200. A band pass filter 300 connected to the band pass filter unit 300 for performing focus adjustment over a wide frequency band from a low frequency band to a high frequency band, and a signal from the band pass filter unit 300 connected to the band pass filter unit 300. A RAM for temporary storage, and the band pass filter unit 3 connected to the RAM.
00 and a signal comparing the signals from the RAM to detect the operation of the focus driving motor, a delay unit 500 connected to the comparator 400 to delay the signal input from the comparator 400, Of the mode selector switch SW2 that is switched during automatic or manual selection of the signal, is connected to the mode selector switch SW2, the comparator 400 and the delay unit 500, and compares the signal magnitudes before and after the delay of the delay unit 500. And a central processing unit that senses the rotation direction of the focus drive motor and controls the automatic focus adjustment control signals C1 and C2 to control the rotation direction of the focus drive motor. circuit. 2. The focus adjustment circuit 100 is connected to the analog / digital converter ADC1 to extract a specific portion of a video signal on a display surface.
0, connected to the signal separation unit 110, and connected to the signal separation unit 1
10 is connected to the weight value adding unit 120 for adding a weight value to the signal extracted by 10, and the signals of the weight value adding unit 120 are logically combined to combine each of the signals on the display surface. 2. The automatic focus adjustment circuit for a video camera according to claim 1, further comprising an adder ADD1 for creating a weight value. 3. A preparatory routine L1 for rotating a focus drive motor to set an initial value when the mode selection switch SW2 to be switched is set automatically when the focus is automatically or manually selected, and after the preparatory routine L1 is performed, Step L of comparing the difference between the signals S9 and S10 from the bandpass filter unit 300 and the RAM with the value Δ of the next state when the focus drive motor is moved to detect a focus change due to movement of the video camera.
4 and the value Δ in the next state in which the focus drive motor has moved in step L4 is determined to be small, the magnitudes of the signals S11 and S14 before and after the delay of the delay unit 500 are compared and the focus drive motor When the rotation direction is sensed and it is determined that the rotation direction of the focus drive motor does not match, the automatic focus adjustment control signals C1 and C
After resetting the two values, the focus drive motor rotation direction detection routine L2 for re-detecting the rotation direction of the focus drive motor, and the value Δ in the next state after the drive motor has moved in step LS4 is determined to be large. And a focus state check routine L3 for focusing after switching the bandpass filter unit 300 to a high frequency band after the focus drive motor is temporarily stopped. How to automatically adjust the camera's focus. 4. The focus driving motor rotation direction detection routine L2 includes a step L2S1 for comparing the magnitudes of the signals S11 and S14 before and after the delay of the delay unit 500, and a delay of the signal S14 delayed in the step L2S1. If it is determined that it is smaller than the previous signal S11, it means that the rotation direction of the focus drive motor is wrong, so that the automatic focus adjustment control signals C1 and C2 are reset and the rotation direction of the focus drive motor is changed to step L2S2. After performing the above step L2S2, the bandpass filter unit 3
Step L2S of storing signal S9 from 00 in RAM
4. The automatic focus adjusting method for a video camera according to claim 3, further comprising: 5. The focus state check routine L3 includes a step L3S1 for temporarily stopping the focus drive motor by setting the automatic focus adjustment control signals C1, C2 to zero, and after performing the step L3S1, a bandpass filter unit 3
00 for checking whether the frequency of 00 is in the highest frequency band, and the band pass filter unit 300 from step L3S2.
If the frequency of is not the highest frequency band, step L3 of switching the switching unit 200 to the highest frequency band.
S3, and the band pass filter unit 200 from step L3S2.
If it is determined that the frequency is the highest frequency band, step L3S4 that compares the difference between the signals S9 and S10 from the bandpass filter section 200 and the RAM with the next state value Δ when the focus drive motor has moved, After performing the step L3S4, if the next state value Δ when the focus drive motor is moved is small, it means that the video camera is moved and the focus is changed. The automatic focus adjustment method for a video camera according to claim 3, further comprising a step L3S5 for initialization.