JPS6032481A - Focus signal generating device using video signal - Google Patents

Abstract

PURPOSE:To obtain a focus signal in which a signal of a point of high contrast is not particularly emphasized by outputting an averaged signal of high frequency component in any part of a picture. CONSTITUTION:When a video signal is supplied from a video camera 1, the video signal is differentiated by a differentiating circuit 2 and made to an absolute value by an absolute value circuit 3. This absolute value output is supplied to a maximum value holding circuit 5 through the first switching circuit 4. The circuit 5 maintains maximum value of the absolute value, and at the same time, reset to a reference level by a reset signal from a controlling circuit A. Output of the circuit 5 is given to an integrating circuit 7 through the second switching circuit 6, and the circuit 7 adds and integrates output of the circuit 5 in passing period of the circuit 6. The circuit 7 is returned to the reference level by a reset signal from a circuit A. By supplying integrated value of the circuit 7 to a microcomputer C through an A/D converter B, a signal for operation control can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a focus adjustment device that adjusts the focus of an optical system of a video camera or a television camera using a high frequency component of a video signal. The present invention relates to a focus signal generation device that obtains a focus signal that corresponds to the focus state of an optical system.

Conventional Structure and Problems It has been known that the focusing state of an optical system can be controlled by the high frequency component, that is, the degree of definition, in a video signal obtained by a video camera or the like.

In other words, the high-frequency component in the video signal takes advantage of the phenomenon that it reaches its maximum size when the optical system is in focus. The device disclosed in 1965, Vol. 17, No. 1, 86, Pages 21 to 37 [Automatic focus adjustment of television camera using hill-climbing servo system] is well known.

The device disclosed in the above report uses the component with the largest value among the high-frequency components of the video signal forming one screen as the focal signal, and the optical system uses the component with the largest value as the focal signal. It will be automatically controlled to become even larger.

However, in the case of the device disclosed in the above report, the high frequency component of the point with the greatest contrast in the screen becomes the focus signal, so if there is a very bright small point other than the point you want to focus on, This has the problem of forming a focus signal that is erroneously sized.

In other words, since a typical subject is rarely flat with respect to the camera optical system and has irregularities, when trying to focus on a desired point, it is certain that the desired point will be The high frequency component at a point becomes larger as the optical system focuses, but among the high frequency components at points other than the desired point, there are also high frequency components that become smaller.
For example, if the high frequency component of a point other than the desired point to be focused is large, the optical system in the optical reporting device is controlled so that the high frequency component of the point other than the desired point becomes large, and this point is explained above. 5. Needless to say, there is a problem in that if the point has a high frequency component having characteristics opposite to the high frequency component of the desired point, the desired point cannot be brought into focus. be.

In addition, in the above device, one signal having the largest magnitude among the high frequency components is used as the focus signal, so for example, the amount of change in the focus signal due to a change in the optical system is
This has the problem that it can only be extracted as the amount of change in one high frequency component, making it unsuitable for highly accurate adjustment.

OBJECTS OF THE INVENTION An object of the present invention is to provide a focus signal generation device that can improve the problems of conventional devices that generate focus signals from video signals.

Another object of the present invention is to provide a focus signal generating device that generates a focus signal in which only one point of strong contrast signal is not particularly emphasized.

Still another object of the present invention is to provide a focal point that generates a focal signal that is easy to apply digital processing to, for example, as a processing system, in which the absolute amount of the obtained signal is small and the rate of change due to changes in the optical system is large. An object of the present invention is to provide a signal generator.

Structure of the Invention The focus signal generating device according to the present invention includes a differentiating circuit that removes and differentiates a color signal from the video signal in order to extract high frequency components of the video signal, and an absolute value circuit that converts the output of the differentiating circuit into an absolute value. , - a maximum value holding circuit that holds the maximum value among the outputs of the absolute value circuit obtained in a predetermined period of the horizontal video signal, and the output of this maximum value holding circuit is added in a predetermined period of an odd or even field. It is comprised of an integrating circuit that performs integration, and a control circuit that sets a predetermined period of the horizontal video signal and a predetermined period of odd or even fields by being supplied with a horizontal synchronizing signal and a vertical synchronizing signal.

DESCRIPTION OF EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of a focus signal generating device according to the present invention. A differentiation circuit removes and differentiates the color signal in order to extract the high frequency component of the luminance signal; 3 is an absolute value circuit that converts the output of the differentiation circuit 2 into an absolute value; 4 controls the transit period of the output of the absolute value circuit 3 a first switch circuit; 5 is a maximum value holding circuit that holds the maximum value of the output signal of the absolute value circuit 3 inputted via the first switch circuit 4; 6 is a transit period of the output of the maximum value holding circuit 5; The second switch circuit that controls the
Maximum value holding circuit 5 inputted via switch circuit 6 of
The integration circuits that add and integrate the outputs of are shown in each figure.

In addition, A is used to extract a synchronizing signal included in the video signal of the video camera 1: a gate signal and a maximum value holding circuit for controlling the operating period of the first and second switch circuits 4.6. 5. Shows a control circuit that outputs a reset signal that returns the operation of the integrating circuit 7 to its initial state. For example, as shown in Figure 17, there is a synchronization circuit that extracts a composite synchronization signal containing a horizontal synchronization signal, a vertical synchronization signal, and a vertical synchronization signal. A signal separation circuit 8, a timing circuit 9 that outputs a predetermined pulse output at a predetermined timing based on the output supplied from the synchronization signal separation circuit 8, and a gate circuit that generates a signal having a predetermined pulse width in accordance with the output of the timing circuit 9. 1o.

Hereinafter, the operation of the focus signal generator according to the present invention having the above-mentioned configuration will be explained with reference to FIG. 2, which shows signal waveforms at each point indicated by lowercase letters in FIG. 1.

Now, the video signals H1, H2, H3, etc. for each scanning period at point a, which is the output end of the video camera 1, are signals as shown in FIG. 2 (a) that do not include color signals. If so, the state of the output terminal of the differentiating circuit 2 to which such a video signal is supplied will be as shown in FIG.

In addition, in the present invention, etc., the high frequency component that serves as a reference for determining the in-focus state based on the video signal is the high frequency component of the brightness signal that indicates the variation in contrast within the screen.
If the video signal of a point contains a color signal, some kind of signal processing is required, but this point can be more easily solved by forming a well-known color signal removal circuit in the differentiating circuit 2. In other words, even if the video signal at point a contains a color signal, the color signal removal circuit can provide the same output as the output of the differentiating circuit 2 as when the video signal as shown in Figure 2A is supplied. There is no need to go into detail about what will happen.

The operation of control circuit A will be briefly described.

The control circuit A has a synchronizing signal dividing circuit 8 to which the video signal shown in FIG. The composite synchronization signal and vertical synchronization signal as shown are outputted to the output terminals, d point and 0 point.

The output of the synchronization signal separation circuit 8 is supplied to the next timing circuit 9, and the timing circuit 9 controls the operation of the gate circuit 10 at a predetermined timing. The first gate signal shown in step 21 is output.

The signals at points f and q are used as the output signals of the control circuit A, but as is clear from FIG. The signal at the point and the output terminal of the timing circuit 9 are generated by dividing the vertical synchronization signal shown in FIG.
It will be used as an output signal.

It goes without saying that the signal shown in FIG. 2 (H) is also used to form the signal shown in FIG. 2 1υ, and even worse, the signal shown in FIG. There is no need to elaborate on the fact that it can be obtained extremely easily if it exists.

Now, among the output signals of the control circuit A as described above, f
Figure 2 is output to points d and d.

It is clear from FIG. 1 that the operation of the first switch circuit 4 and the maximum value holding circuit 5 is controlled by the signal shown in (d). In this case, first, the first switch circuit 4 , by being supplied with the signals shown in FIG. Yes, the maximum value holding circuit 5 is still
The output signal shown in FIG.

Therefore, the absolute value output as shown in FIG. 2 (7) at the 0 point is made into a signal as shown in FIG. 6 will be supplied.

The maximum value holding circuit 6 is the gate circuit 1 shown in FIG.
Since the operation is controlled by the output signal of o, the output terminal j is supplied with the signal shown in FIG. While maintaining the maximum value of the signal as shown in FIG. 2F), when a seven-node signal as shown in FIG.

On the other hand, the output signal at point j as shown in Fig. 2G) is
Next, the signal is supplied to the integrating circuit 7 via the second switch circuit 6, and the operation is controlled by the control circuit A at this time as well.

Unlike the previous case, control of the second switch circuit 6 and the integration circuit 7 by the control circuit A is now performed based on the vertical synchronization signal included in the video signal. That is, as mentioned earlier, the vertical synchronizing signal as shown in FIG.
, processed as appropriate via the gate circuit 10 (Fig. 2C), (
By obtaining output signals as shown in f) at points q and h, which are the output terminals of the control circuit A, the second switch circuit 6 and the like are controlled.

As is clear from FIGS. 2(E) and (H), in the present invention, the generation of the signals at points e and h does not have a one-to-one relationship with the generation timing of the vertical synchronization signal. It is constructed with a frequency dividing means so that the frequency is generated in a 2:1 relationship, for example, every odd field.

The signal shown in FIG. 2 serves as a gate signal for setting the operating period of the second switch circuit 6, that is, the period during which an electrical signal can pass, and the signal shown in FIG. This serves as a reset signal for returning the integrated value of the circuit 7 to the reference level. Therefore,
At the output terminal of the second switch circuit 6, only the maximum value of the output of the maximum value holding circuit 5 shown in FIG. 2 (N) is outputted as shown in FIG. Become.

Next, the signal at the above point is supplied to the integrating circuit 7, which integrates the signal as shown in FIG. The signal will be output.

Now, if we consider the meaning of the signal output to this one point, the output signal of this one point is to first convert the video signal from the video camera 1 into the differentiating circuit 2 in any period of the scanning period. The absolute value circuit 3 and the maximum value holding circuit 6 etc. extract the amount of fluctuation of the high frequency component, and then this maximum value is integrated over the activity period of a predetermined field. This can be said to be the set value of the maximum fluctuating high frequency components for each horizontal projection example in any part of . In other words, the high frequency component, which generally increases as the focus state of the optical system progresses, can be said to be an averaged value within an arbitrary portion.

Therefore, it goes without saying that the amount of signal output to this one point changes depending on the state of the optical system, and as a result, it is clear that it can be used as a single focal signal.0 In addition, Since the signal value is an averaged value, within any part, large values among the maximum values of the horizontal period mentioned above are not particularly emphasized; Even if a The value of the signal is used, and although it is true that a large value has a large influence, the in-focus state cannot be judged solely by that large value, and the output signal at the above one point is extremely This can be recognized as a good focus signal.

Although the focus signal obtained as described above does not need to be described in detail, it can be used extremely effectively by being processed by, for example, a configuration as shown by the broken line in FIG.

That is, the focus signal generated by the focus signal generator according to the present invention is supplied to the microcomputer C via, for example, an A/D converter B, and the optical system from the optical system state detection device that is separately supplied to the microcomputer C is supplied. By performing appropriate arithmetic processing along with the information, it becomes possible to easily obtain a signal for controlling the operation of the drive device E that controls the drive of the optical system. The focus signal becomes an extremely effective signal.

Now, FIG. 3 is an electric circuit diagram showing a specific example of the focus signal generating device according to the present invention shown in FIG. 1. Note that circuits with the same figure numbers and points with the same symbols as in FIG. 1 are the same circuits and points as in FIG. 1.

Now, when a video signal from the video camera 1 is supplied onto the lead wire SoO having point a, this video signal is differentiated by the capacitor 301 and the resistors 302 and 303 in the Ushizu differentiating circuit 2, and then by the transistor 304, and is output via a capacitor 305 onto a lead wire 306 having a point b as a signal as shown in FIG. 2(b). At this time, it is assumed that the high-frequency components included in the video signal in the conventional device and the present invention described above are signal components that do not include color signals, as described above. In the device according to the present invention, a color signal removal circuit is constructed, for example, by an inductor indicated by X and a capacitor C.

The signal on the lead wire 306 is input to the differential amplifier 3o of the next absolute value circuit 3, and the differential amplifier 307 outputs the signals on the previous lead wire 306 in an antiphase relationship to its output terminals 308 and 309, respectively. The output of the 0 differential amplifier 307 which outputs a signal with the above-mentioned negative phase relationship is connected to the pair of transistors 310 and 311.
．． The signal is supplied to an amplification stage consisting of a pair of diodes 312 and 313 that amplifies only one direction of the signal, and is converted into an absolute value. An absolute value output as shown in is output.

On the other hand, the video signal on the lead wire 300 is also supplied to the synchronization signal separation circuit 8 of the control circuit A, and the operation of this control circuit A will be briefly described below.
Ox resistance 315. Capacitor 316. Resistance 31, 31
8.319, 320° is amplified by transistor 321 and output on lead 322, then capacitor 323° resistor 324. Diode 325. resistance 326,
327° power supply 32B, FET329. The reference level is clamped to a predetermined level by the resistor 330 and output as a signal to the lead wire 331'2.

The signal on this lead wire 331 is transmitted through the resistors 332 and 333.
, s34,) to the transistor 335''; the video signal amount is removed from the video signal, and as a result, a composite sync signal that is a mixture of the horizontal sync signal and the vertical sync signal is output to the lead wire 336. Become.

The composite synchronization signal on lead 336 is on the one hand.

Resistance 337. Capacitor 338. ) Transistor 339° Capacitor 340. The horizontal synchronizing signal is removed by the resistor 341 and output as a vertical synchronizing signal as shown in FIG.
Resistance 343. ) It is amplified by a transistor 344 and a resistor 345, and is taken out on a lead wire 346 having a point d as an amplified composite synchronizing signal as shown in FIG. 2(d).

The output signal on the leads 342, 346 will then be supplied to the timing circuit 9.

The vertical synchronization signal of the lead wire 342J- is NAN.
The signal is supplied to F, F, and 348 via a D gate 347, where it is frequency-divided and output onto a lead line 349 as a field signal corresponding to either an odd or even field. The field signal on this lead 349 is connected to a monostable multivibrator circuit 350.
A pulse output having a predetermined time width T1 is output onto a lead wire 351 having a point h as shown in FIG. 2 cfJ.

On the other hand, the output signal on lead wire 346 is
2 to the monostable multipipe lake 363, and is output on the lead wire 354 as a pulse output having a predetermined time width.

The pulse output on the leads 5351 and 354 described above is supplied to the gate circuit 10 as an output signal of the timing circuit 9. That is, the gate circuit 1o receives a pulse output from the lead wire 351 that determines a predetermined time T1 from the output point of the field signal that is output for each odd or even field, and also outputs a composite synchronization signal from the lead wire 354. A pulse output determining a predetermined time from a point in time will be provided.

The gate circuit 10 has two monostable multivibrators 3'56 and 356 which are supplied with the pulse outputs of the lead wires 351 and 354, respectively, and which start operating in response to the fall of these pulse outputs. Pulse outputs having predetermined time widths T2 and T3 as shown in FIG. It goes without saying that the relationship between T2 and T3 is T2)T3.

Pulse output 1d on these leads 357.358,
The signal is then supplied to the next NAND circuit 359, and as is clear from the relationships in FIG. A low level pulse output as shown in FIG. 2 will be output on the lead wire 360.

The output signal on the lead wire 360 is inverted by passing through another NAND circuit 361 and supplied to a monostable multivibrator 362, which responds to the fall of the previous inverted signal at 9. Figure 2 (G) is placed on the lead wire 363 having 9 points.
A pulse signal set at a predetermined period as shown in FIG.

The operation as described above is the operation of the control circuit A, and this control circuit A controls the operation of the first switch circuit 4 in the subsequent stage to which the absolute value output on the lead wire 314 described above is supplied. It turns out.

Hereinafter, the operation of the first switch circuit 4 and the like will be explained together with its control operation.

The video signal on the lead wire 300 is differentiated by a differentiating circuit 2. The absolute value output on line 314 obtained by processing by absolute value circuit 3 is then supplied to switch element 364 of first switch circuit 4. This switch element 364 has control poles of diodes 3 to 5. It is connected to a negative potential via a resistor 366 and to a positive potential via a transistor 366 (diode 365, ), so that when such a transistor 366 is made conductive, it becomes conductive and holds the previous absolute value output at its maximum value. This means that it can be supplied to the circuit 5.

By the way, the transistor 3660 control alTh is connected to the point f on the lead wire 360 of the control circuit A via a resistor 367, etc., and therefore conducts by the output signal of the point f as shown in FIG. This results in repeated non-conduction.It goes without saying that the output signal at point f corresponds to the horizontal and vertical synchronizing signals from the operation of the synchronizing signal separation circuit 8, etc. mentioned earlier. Therefore, the transistor 366 is controlled to have a conductive state and a non-conductive state within one horizontal scanning period, and it goes without saying that the switch element 364 also operates in conjunction with the operation of the transistor 366. Become.

As a result, the absolute value output on the lead wire 314 is output on the lead wire 368 having the i point for a predetermined period of the horizontal scanning period as shown in the second diagram, and is supplied to the capacitor 370 via the diode 369. It turns out.

Since the capacitor 370 will be charged by the supplied signal, the voltage value of the signal having the highest voltage level among the supplied signals, such as the second diagram, will be held on the lead wire 371. Become.

On the other hand, this lead wire 371 is connected to a resistor 372. IJ-do wire 34
It is connected to ground through a transistor 373 connected to 6. Therefore, when the signal as shown in FIG. 2(D) on the lead 346 having 61 points becomes a high level, the voltage held on the lead wire 371 is brought to the ground potential.

That is, the voltage signal on the lead wire 371 having point j becomes as shown in FIG.

The voltage signal on the lead wire 371 is then supplied to the second switch circuit 6. The second switch circuit 6 first includes a switch element 374, a resistor 375 .
376 divides the voltage signal on the lead wire 371 as appropriate.

The divided signal is outputted via a resistor 377 onto a lead wire 378 having a point at . The lead wire 378 is connected to ground via a transistor 379 on the one hand.

The control pole of the transistor 379 is connected to the lead wire 363 having the q point. Therefore, when the output signal at the q point is at a high level as shown in FIG. By bypassing the output signal of the lead wire 378 to the ground, the output signal on the lead wire 378 becomes a signal as shown in Figure 2, and is supplied to the next-stage integrating circuit 7 only when the q point is at a low level. .

Integrating circuit 7 operates in response to the supply of the voltage signal described above, and as shown in the figure, diodes 381 .
1- Has a voltage-current conversion circuit consisting of transistors 382 and 383 and a diode 384, and converts a current corresponding to the voltage level of the voltage signal on the lead wire 378 supplied via the second switch circuit 6 to the lead wire 385. It is configured to flow upward.

Therefore, since the voltage signal appearing on the lead wire 378 is converted into a current signal and supplied to the integrating capacitor 386, unlike the previous capacitor 370, all the voltage signals appearing on the lead wire 378 are added together. and will be charged.

The charging voltage of the integrating capacitor 386 appears on the lead wire 386 and is applied via the resistor 387 to the transistor 388 whose control pole is connected to the lead wire 351 having the point h, and is applied to the resistor 390 via the switch element 389. A lead wire 391. is replaced with a terminal voltage and has one point. is output above.

By the way, the transistor 388 to which the lead wire 361 and the control pole are connected becomes conductive when the signal at point h on the lead wire 351 becomes high level as shown in FIG. Therefore, the charge stored in the integrating capacitor 368 is discharged when the transistor 388 is guided.

Therefore, the signal at one point on the lead wire 391 output as the terminal voltage of the resistor 390 becomes as shown in FIG.

The operation of the specific circuit example of one embodiment of the present invention shown in FIG. Needless to say, if the optical system is appropriately controlled, for example, so that the level of such a signal is increased, a focused state of the optical system can be obtained.

Effects of the Invention The focus signal generating device according to the present invention generates, as a focus signal, an output signal which is a collection of the maximum fluctuating high frequency components for each horizontal projection example in a predetermined section of the screen, that is, averages the high frequency components in any part of the screen. Because it is possible to output a signal with a high frequency component that varies greatly within the screen, unlike conventional devices, it does not emphasize the large amount of fluctuation in high-frequency components within the screen.For example, when considering use in an automatic focusing device. , the focus state is not controlled only by the large fluctuation amount of the high frequency component, and the effect that an extremely good focus state can be obtained, that is, the effect that an extremely high precision focus signal can be obtained. have.

Furthermore, in the integration operation in the present invention, the absolute amount of the output level of the focus signal obtained by extracting the maximum value within a predetermined period for each horizontal scanning period and adding and integrating this signal does not become an extremely large value. For example, it also has the effect of making it possible to easily perform processing using digital technology using a microcomputer or the like.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the focus signal generation device according to the present invention, FIG. 2 is a signal waveform diagram at an arbitrary point in FIG. 1, and FIG. 3 is an example of the focus signal generation device according to the present invention. FIG. 2 is an electrical circuit diagram showing an example. 2... Differential circuit, 3... Absolute value circuit, 6
・Mountain...Maximum value holding circuit, 7...Integrator circuit, 8
... Synchronous signal separation circuit, 9 ... Timing circuit, 1o ... Gate circuit, A ... Control circuit.

Claims (1)

[Claims] (1) A differentiation circuit that removes and differentiates a color signal from a video signal from a video camera or the like to extract a high frequency component in a luminance signal of the video signal, an absolute value circuit that converts the output of the differentiation circuit into an absolute value, and the video signal a maximum value holding circuit that holds the output level of the maximum value among the outputs of the absolute value circuit obtained at every predetermined period within one horizontal scanning period; an integrating circuit that performs addition and integration for each predetermined period within a vertical scanning period of a field; an integrating circuit that sets a predetermined period within the horizontal scanning period and a predetermined period within the vertical scanning period; the video camera (2); the control means includes a synchronization signal separation circuit for extracting horizontal and vertical synchronization signals included in the video signal; A control circuit that generates various output signals in accordance with each synchronization signal, and a control circuit that is inserted between the absolute value circuit and the maximum value holding circuit, and one of the output signals of the control circuit that corresponds to the horizontal synchronization signal. a first switch circuit that controls supply of the output signal of the absolute value circuit to the maximum value holding circuit, and an output of the control circuit that is inserted between the maximum value holding circuit and the integrating circuit; One of the signals corresponding to the vertical synchronization signal is supplied to control the supply of the output signal of the maximum value holding circuit to the integrating circuit. (3) The maximum value holding circuit controls the absolute value of the absolute value circuit. 4) The integrating circuit has a current value corresponding to the voltage level of the output signal of the maximum value holding circuit. a voltage-current converter that generates a current;
The integrator (4) synchronization signal separation circuit charged by the current obtained by the voltage-current converter generates a composite synchronization signal that includes both a horizontal synchronization signal and a vertical synchronization signal, and the vertical (5) control circuit , a timing circuit that generates a pulse output having a predetermined time width that can be arbitrarily set by supplying horizontal and vertical synchronization signals extracted by a synchronization signal separation circuit; and a timing circuit that generates a desired gate pulse output by the pulse output of the timing circuit. The output of the synchronizing signal separation circuit and the timing circuit generates a set signal for the maximum value holding circuit and the integrating circuit, and the output of the gate circuit generates the first... Second
Raw equipment.