JPS60103322A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To realize an automatic focusing device high in practicability by switching automatically automatic focusing systems which differ in principle according to whether the output of a focusing detecting circuit is generated or not, and performing focusing operation. CONSTITUTION:Terminals 81 and 83 of an electronic switch 8 are connected and a lens 3 is driven under the control of the 1st automatic focusing part 1 to perform focusing operation; when a switching control circuit 6 detects the stop of the lens 3 after the focusing operation through a detecting circuit 7, the connections of the electronic switch 8 are held if a signal showing that a subject is put in focus is received from a focusing checking circuit 5. When, however, a signal showing that the subject is out of focus is received from the focusing detecting circuit 5, the connections of the electronic switch 8 are switched to between terminals 82 and 83, and the control over the lens 3 is transferred to the 2nd automatic focusing part 2 to perform the focusing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an automatic focusing device suitable for a video camera.

[Background of the invention]

As is well known, conventional autofocus devices have a
) A distance measuring device (hereinafter referred to as a distance measuring system) from a lens to a subject, such as an ultrasonic nose or triangulation by measuring the angle of reflected light of an emitted infrared beam, etc. (11) A method in which the lens position is controlled using an oven loop until the distance indicated by the handheld distance measuring system; (11) The detected height is There is a method (hereinafter referred to as a video method) in which the lens is controlled in a closed loop so that the spectral components are maximized.

Although 11 of these have already been put into practical use, they all have advantages and disadvantages in performance, and their performance cannot be said to be fully satisfactory.

For example, in the ultrasonic radar system, which is known as an example of autofocus with a distance measurement system, there is an out-of-field angle that focuses on objects on the outside of the screen due to the thickness of the ultrasonic beam and side lobes, and there is also a difference in the angle of view of the infrared beam. A method based on triangulation of reflected light is likely to cause malfunctions due to undetected reflected light due to a decrease in the reflectance of the infrared beam, or deviations from the angle of view due to the thinness of the beam. On the other hand, with the video method, it is possible to focus on a subject that has strange components within the frame without worrying about distance or distance, but when shooting a subject with low illumination or low contrast, it is possible to focus on a subject that has strange components within the frame. Difficult to detect and prone to malfunction. In order to compensate for these shortcomings, I cannot think of an autofocus system that combines autofocus with a distance measuring thread and video autofocus.
Because the principles of the two autofocus methods are completely different,
1 no 5. It is difficult for a camera to operate both at the same time and move the lens to focus. It is not enough to simply combine the two methods; instead, the only option is to manually switch between the two methods depending on the subject or the imaging situation. That is, in order to automate this switching, it is difficult and impractical to set the switching in advance according to the situations in which the user is strong or weak.

[Purpose of the invention]

An object of the present invention is to provide a highly practical automatic focusing decoration by automatically switching automatic focusing threads having different principles to perform a focusing operation.

[Summary of the invention]

The present invention utilizes the special characteristics of video cameras. In other words, for most subjects, it is possible to make an absolute evaluation of whether or not the high-frequency components in the video signal obtained from the photographed image are in focus, and if a specific frequency component is not detected. If it is in focus or not detected, it can be determined that it is not in focus.

Therefore, the automatic focusing thread can be switched depending on the presence or absence of the output of such a detection circuit, that is, the focus detection circuit. In other words, when the autofocus operation is finished with one autofocus thread and the lens stops, if there is an output from the focus detection circuit, it means normal focusing operation, and if there is no output, the autofocus operation is stopped. Since the scorching thread is expected to have malfunctioned, it is possible to switch to the other autofocusing system and obtain highly practical autofocus decorations by switching and using autofocusing threads with different principles at the appropriate time. This is what we are trying to do.

[Embodiments of the invention]

A first embodiment of the present invention will be illustrated below with reference to the configuration shown in FIG. 1. In the figure, 1 indicates a first autofocus using one method (for example, autofocus with a distance measurement system), 2 indicates a second autofocus using another method (for example, autofocus using a video method), and 6 indicates A lens, 4 is a camera circuit that outputs an imaging signal from an image formed by the lens 3, and 5 is a camera circuit that determines whether the image signal contains a predetermined frequency spectrum component or not to determine whether the subject is in focus or not. 6 is a switching control circuit; 7 is a focusing operation end detection circuit that detects when the autofocus focusing operation has ended, for example, when the drive signal to the lens 3 is no longer present; It is an electronic switch.

In the same blow drawing, 1st auto focus 1 2nd
The configuration method of Auto Focus 2 is not important for this professional explanation. Similarly, a drive circuit etc. for driving the lens 1 is also not shown. It is important that the control of the focusing operation of the re-lens 6 is controlled by either the first autofocus 1 or the second autofocus 2 by switching between the electronic switch and the second autofocus 8.

The operation of the configuration program 9 in FIG. 1 begins with the switching control circuit 6.
The terminal 81 and the terminal 86 of the electronic switch 8 are connected by the signal, and the lens 3 is driven under the control of the first autofocus 1 to perform a focusing operation. The switching control circuit 6 detects the presence or absence of the output of the focus detection circuit 6 every time it is detected by the output of the focus operation completion detection circuit 7 that the autofocus thread driving the lens has finished focusing on the subject. Based on the determination, switching control of the autofocus system is performed. That is, the switching control circuit 6, which has detected by the focusing operation end detection circuit 7 that the focusing operation of the first autofocus 10 has now ended and the lens 6 has stopped, inputs the captured image signal from the camera circuit 4. The focused point detection circuit 5 detects a specific frequency spectrum component (for example, j ME
(high-frequency components above z) and outputs a signal indicating that the subject is in focus, the electronic switch
If the focus detection circuit 5 outputs a signal indicating that the focus is not in focus without detecting a specific frequency spectrum component, the electronic switch
Between 2 and 83, the control of the switching lens 3 is changed to the second autofocus 2 to perform a focusing operation. Electronic switch 9
If the connection of the switch 8 is continued, the first autofocus 1 will start the focusing operation again due to a change in the subject, and when the signal from the focusing operation end detection circuit 7 is generated, the above-mentioned discrimination operation will be performed again. return. When the connection of the electronic switch 8 is switched, the lens 3 is controlled by the second autofocus to perform a focusing operation. The switching control circuit 6 detects the end of the focusing operation by the focusing operation end detection circuit 7, and simultaneously determines whether or not the focus is achieved based on the output of the focus detection circuit 5. The connection between the terminals 86 is continued, and when the focus is not l/-, the connection of the electronic switches 1 and 2 is switched between the terminals 81 and 83, and the control of the lens 3 is switched to the second terminal.
Switch from autofocus 2 to first autofocus 1. In this way, when focus cannot be obtained with one autofocus method, by switching to another autofocus method and performing the focusing operation, it is possible to configure an autofocus device with fewer malfunctions. The switching operation of the autofocus method described above will be illustrated once again using the state transition diagram shown in FIG. In Figure 2, ←) indicates the control of the first autofocus 1, (b) indicates the control of the second autofocus 2, 0), ni), and (to) indicate the transition loop. There is. Now, when the focusing operation is completed by the first autofocus 10 control 0), if the detection output of the focus detection circuit 5 is in focus, it passes through the loop f → and returns to the control G) of the first autofocus 2. Return and continue the same control. If the focus is not in focus, the process goes through a loop) and moves to control of the second autofocus 2 (b). Control of the second autofocus 2 (if Ron completes the υ focusing operation, the focus detection circuit 5
If the detection output is in focus, it passes through the loop (E) and returns to the second
Return to auto focus 2 control (III middle) and continue the same control. If it is not in focus, follow the loop (to) and return to the first
Move on to autofocus 1 control).

In addition, if there is no focus detection with both autofocus methods, a hunting phenomenon will occur in which the switching operation of both methods continues, so if there is no focus detection with the autofocus method after switching, the switching operation will occur again. It is desirable to use a switching control method in which the same autofocus control is continued without performing the autofocus method, or the switching operation is performed again and the method switching determination operation is stopped immediately after returning to the original autofocus method.

Next, FIG. 6 shows a block diagram showing the second embodiment. Pro 2 in the same figure. 5, 4, 5, 7.8 are blocks having the same functions as the blocks with the same numbers shown in FIG. 1, and 81, 82, and 85 are terminals. 31
32 is the first autofocus based on one autofocus method, and 32 is the second autofocus based on another autofocus method.
36 is a switching control circuit, and 39 is a lens control value change detection circuit. Similarly to Figure 1, the configuration method of autofocus is not important in this professional drawing, so it is excluded. The lens control value change detection circuit 39 detects the lens control value (for example, measured If the distance-based autofocus is the first autofocus 61, the measured value of the distance to the subject is memorized, and if the change in the lens control value is less than a predetermined threshold while the second autofocus 32 is being controlled. ★This is a circuit that outputs a detection signal when this occurs.

Figure 6 Configuration Pro 4. In this operation, the switching control circuit 66 detects the stoppage of the lens 6 by the focusing operation completion detection circuit 7 of one autofocus, and the switching control circuit 66 detects the stoppage of the lens 6 by the focusing operation end detection circuit 7, and the switching control circuit 66 switches the lens 6 in focus due to the lack of output from the focusing detection circuit 5. Continuing the control of the autofocus method that was being controlled, and switching the control to another autofocus method using the key switch 8 if the object is not in focus is the same as the operation of the configuration program diagram in Figure 1. be. That is, in the configuration diagram of FIG. 6, first, the signal from the switching control circuit 66 causes
The lens 5 is controlled by the first autofocus 1 with the 9-inch 8 facing the terminal 81 . Focusing operation end detection circuit 7
The switching control circuit 56 detects that the focus detection circuit 5 has stopped, and when the focus detection circuit 5 indicates that the focus is in focus, the switching control circuit 56 leaves the connection of the Shigeko Sui-Sochi 8 as it is and controls the focus by the first autofocus 31. continue. When the focus detection circuit 5 indicates 7 that the camera is not in focus, the electronic switch 8 is switched to the terminal 821111, and control of the lens 3 is transferred to the second autofocus 32. At the same time, the lens control value change detection circuit 69 detects that the control has been switched from the first autofocus 1 to the second autofocus 2 and stores the lens control value of the first autofocus 31. If focus is detected and the first autofocus 61 is to be subsequently controlled, the above operation is repeated once the focus end detection circuit 7 outputs an output. After detecting that the focus is not in focus based on the output of the focus detection circuit 5 and switching the control of the lens 3, if the focus operation is controlled by the second autofocus 62, the focus operation The switching control circuit 36 detects that the lens 6 has stopped by the end detection circuit 7, and when it detects that the lens 6 is in focus based on the output of the focus detection circuit 5, it connects the terminal 82 side of the electronic switch 8. The second autofocus 32 is maintained and the control of the second autofocus 32 is continued. When it is detected that the camera is not in focus, the connection of the electronic switch 8 is switched to the terminal 811111, and the wholesale control of the lens 3 is returned to the first autofocus 31. The above operation is performed every time the completion of the focusing operation is detected. In addition, compared to the lens tttlJ value of the first autofocus 61 stored at the time when the control is switched to the second autofocus 32, the lens control value of the first autofocus 61 exceeds a predetermined threshold. The switching control circuit 36 switches the output from the lens control value change detection circuit 39 that detects a change in the lens control value change detection circuit 39.
As soon as the control circuit detects the first autofocus 61, the electronic switch 1. Switch to 8 gold and regain control.

Configuration program 1 shown in FIG. 6 described above. The switching operation of the second autofocus method will be explained once again with reference to the state transition diagram shown in FIG. In FIG. 4, 0) controls the first autofocus 61, and (b) controls the second autofocus 32.
(/i, ni), (e) and (g) indicate the transition loops, respectively. If the focusing operation is now completed by the control (a) of the first autofocus 31, and the detection output of the focus detection circuit 5 indicates that the focus is in focus, the control of the first autofocus will be performed again through the loop (c). G) Continue the same control. If the focus is not in focus, the process goes through a loop) and moves to second autofocus control (b). 2nd auto focus 6
2 control (when the focusing operation is completed, if the detection output of the focus detection circuit 5 is in focus, it passes through the loop (e) and returns to the control of the second autofocus 32 (b). If the camera is not in focus, it passes through the loop and goes to the first autofocus 310 air control 0). Regarding the same loop, control of the second autofocus 62 (b)
If a detection signal from the lens control value change detection circuit 59 connected to the first autofocus 31 is generated in the state shown in FIG.

In addition, similar to the configuration shown in Figure 1, if the focus detection is not available in the double-edged autofocus, the switching operation will continue, so the autofocus method after switching as described above will If there is no focus detection, that is, if focus detection cannot be obtained with the double-edged type, - Stop the old switching operation in the switched method only once and continue the operation in the switched method. , OFF #) It is desirable to carry out a switching operation to the changed bale and then stop the switching operation once when the focused detection of the blood bale is detected. Or in this example, the first
It is also possible to always return to the control of the autofocus 31 and not perform the switching operation immediately after the return.

2nd auto focus 62 by configuring on stage
Since the object is observed by the first autofocus 31 even during the operation, it is possible to perform even better autofocus operation, and it is possible to immediately respond to changes in the situation of the object.
Autofocus with good tracking performance and fewer malfunctions can be achieved.

Next, the sixth embodiment is shown in the configuration diagram of FIG. 3.4, 5.7-. 8 is a program having the same function as the program having the same number in the constituent blocks of FIG. 81, 82 and 83 are terminals. 511 is a distance detection circuit that calculates and outputs the distance from the lens 6 to the subject (for example, using a radar method or a triangulation method); 512 is a lens position detection circuit that detects the position of the lens 3; and 513 is a comparison circuit. , 514 is lens 6
56 is a switching control circuit, and 59 is a lens control value change detection circuit. In the same figure, a distance measuring system that calculates distance using a distance measuring circuit 511, a lens position detection circuit 512, a comparison circuit 513, connections between terminals 81 and 85 of frost, small sui, and sochi 8, a driving circuit 514, and a lens 6. Configures autofocus with In other words, a distance measuring circuit 51 that measures and outputs the distance to the target object.
A lens that detects the output of lens 1 and the subject distance indicated by lens 3.
If the lens position detected by the lens position detection circuit 512 is on the main side of the distance-measured subject position, the lens 6 is moved through the drive circuit 514.
By generating the output signal of the comparator circuit 516 to move the bubbles toward infinity and conversely toward infinity, the lens 1 is moved until the distance measurement output and the lens position detection output become equal to one another. Shifts the layer to 1 and performs an automatic focusing operation.

Well, 1 big mouth 1. The operation shown in the diagram is based on the switching control circuit 5.
Reference numeral 6 denotes an electronic switch. Terminals 81+a3fi4+ of switch 8 are connected to perform an autofocus operation using a distance measuring circuit 511. When the stoppage of the lens 3 is detected by the focusing operation completion detection circuit 7, the switching control circuit 56 continues the connection state of the 1b slave switch 8 when the focus is detected by the output of the focusing detection circuit 5, and automatically switches the distance control. Continue focusing, and then focus
To do this, switch the connection of the terminal 82 and 83 to the terminals 82 and 83. In the case of switching, the switching control circuit 56 starts moving the lens 8, judges that the output of the focus detection circuit 5 indicates that the subject is in focus, and stops the lens 8. As described above, even if a malfunction occurs in the focusing operation by the distance measuring system, it is possible to correct the automatic focusing operation to a normal automatic focusing operation using the output of the focus detection circuit 5. In addition, electronic switch, Vchi8
When the terminals 82 and 85 are connected, the lens 6 is moved between the close range and the infinity end, but if the subject detected by the focus detection circuit 5 is not between the close range and the infinity end, the electronic switch Switch to the connection between terminals 81 and 83 to return to autofocus operation in the distance measuring system. In this case, if the lens 3 stops simply by returning to autofocus using the distance measurement system, the switching control circuit 8 may make a focus judgment again and switch the electronic switch and V switch 8, so immediately after switching It is desirable to take measures to prevent malfunctions, such as ignoring focus judgment during playback. In addition, when performing automatic focusing operation only by the output of the focus detection circuit 5, the movement of the lens 6 fk
h is determined by the switching control circuit 56 based on the output from the lens position detection circuit 512 (the signal path is not shown in FIG. 5). It is desirable to first move the lens 5 in the direction of infinity. Also, terminal 8
2 to terminal 81, the lens control value change detection circuit 59
The change in the output of the focus detection circuit 5 is performed when the switching control circuit 56 detects the output of the focus detection circuit 5.
Of course, the moon may be used to detect the in-focus point, but it may also be used to return to autofocus operation using the distance measuring system.

By performing switching control as in the third embodiment shown above, autofocus with fewer malfunctions can be configured. In addition,
In the above description, the configuration of the focus detection circuit 5 has been particularly shown, and the operation of the embodiment has been explained by simply describing the circuit as a circuit for detecting the presence or absence of a predetermined frequency spectrum component. Next, one embodiment of the focus detection circuit 5 is shown in the configuration diagram of FIG. 6, and its operation will be explained below. In FIG. 6, 6(N, 602, 603).

604 is a terminal, and an image signal is inputted to the terminal 601 from the camera circuit 4. 61 is a filter circuit that extracts only specific frequency spectral components; 62 is a gate circuit that passes signals from a specific area, for example, the center of the screen; 65 is a detection circuit; and 64 is a filter circuit for image signals. Since the output usually does not include noise, etc., a threshold circuit is used to detect the presence or absence of the output of the detection circuit 63, and an appropriate threshold value is set to prevent the detection of stiffness. The operation of the configuration flow shown in FIG. 6 will be explained with reference to the waveform conceptual diagram shown in FIG. The waveform shown in FIG. 7(a) is an image signal inputted to the terminal 601 in FIG. 6, and the waveform after passing through the filter circuit 61 and outputted to the terminal 602 is shown in FIG. 7(b). In the same waveform diagram, (e),
(II) , (The filter output part shown in Fig. At the same time, since the target object is often located in the center of the screen, only a specific area is allowed to pass through.

The signal waveform of the gate circuit 62 and the output waveform of the terminal 60 are shown in FIGS. 7(c) and 7(d).

As shown in FIG. 7(d), filter output unrelated to blurring cannot be removed, and by passing tl through a detection circuit 66 and a threshold circuit 64, the presence or absence of a frequency spectrum component is detected.

In the configuration shown in FIG. 6, it is not appropriate to change the order of the filter circuit 61 and the gate circuit 62. That is, when I9 is changed, the output of the gate circuit 62 becomes as shown in FIG. 7(e), and the output of the filter circuit 61 becomes
This is because outputs (forces, (wa), ψ), and (yo) that are almost unrelated to blurring are generated as shown in Figure (f).

Although the filter circuit 61 in the configuration of FIG. 6 was not specifically explained, it may be an LC filter such as 4J:bL, a comb filter, or a dovetail filter to pass a specific frequency component. Needless to say. Furthermore, when a filter with predetermined characteristics is configured by combining several filters, a filter that removes the low-frequency components of the image signal is inserted before the gate circuit 62, and another filter is inserted in the place of the gate circuit 62. It goes without saying that the focus detection circuit may be configured as It goes without saying that the detection means does not need to be a signal-based detection means. For example, in this embodiment, a photodetecting element (for example, a CCDCD array) is arranged on the focal plane of the lens, and the detection output is used to detect whether or not the captured image has a specific spatial frequency component. It is possible to provide exactly the same IQI characteristics as the focus detection circuit described above.This detection method extracts the output of the photodetector element continuously, treats it as if it were a video signal, and detects the frequency spectrum components. Of course, by arranging the photodetecting elements in a circular manner, in the same direction as the video camera's scanning direction, or in any other direction, it is possible to create a more diverse array of structures than when using video signals. It goes without saying that a focus detection circuit is configured for the subject.

Note that the focused point detection circuit 5 detects a specific frequency spectrum component (for example, 1.2 ME (near z), but it may detect a frequency component above a certain level, or it may detect a position such that the high frequency component is maximum). In other words, as the lens moves, the amount of high-frequency components forms a mountain, but even if the method detects the lens position where the change in the slope (change in the amount of high-frequency components) changes from large to small or nothing, Needless to say, it's a good thing.

In addition, although it has been explained that the output of the focus detection circuit 5 is detected at the same time as the output of the focus operation end detection circuit 7 and the switching judgment is made immediately, the detection period of the output of the focus detection circuit 5 is set for a certain period of time. Needless to say, it is okay.

Similarly, when moving from one autofocus method to another autofocus method, for example, a judgment period is provided for detecting a change in the lens control value change detection circuits 57, 57, and the detection output shows the same output again during the judgment period. Needless to say, it can be concluded that there is no change.

〔Effect of the invention〕

As described above in detail with reference to FIGS. 1 to 7, the autofocus device according to the present invention enables excellent autofocusing operation without malfunction. In the above embodiments, two independent autofocus systems are switched. However, these autofocus systems do not necessarily have to be two, but the components or design values of one focusing thread can be switched. In particular, it is clear that the focusing devices may operate as if they were two focusing devices, which is also within the scope of the present invention. For example, an automatic focusing device that uses the principle of ultrasonic radar can switch the output power and radiation angle of ultrasonic waves, or detect an automatic focusing device that emits infrared rays and measures distance from the angle of reflection. This includes switching the width of the reflection angle.

[Brief Description of the Drawings] Figures 1, 3, and 5 show the first part of the autofocus device according to the present invention. Second. Figure 4, Figure 2, and Figure 4 are respectively similar to Figure 1.
State transition diagram for explaining the operation of the second embodiment, No. 6
The figure shows a configuration diagram showing one embodiment of the focus detection circuit.
FIG. 7 is a conceptual diagram of a waveform concept for explaining the embodiment of FIG. 6. 19.・First autofocus, 2...Second autofocus, 3...Lens, 4...Camera circuit, 5...Focus detection circuit, 6...Switching control circuit, 7... - Focusing operation end detection circuit, 37... Lens control value change detection circuit, 8... Electronic switch, Sochi, 61... Filter, 62... Gate circuit. Representative Patent Attorney Akio Takahashi No. 1 Mata No. 2 Hi No. 3 Fig. 9 Fig. 4 S Illustration No. 6 Fig. 7

Claims (1)

[Claims] 1. first and second automatic focusing threads, and the first or second
a first detecting means for detecting the degree of alignment between a first photographing lens controlled by an automatic focusing system and a video signal obtained by scanning a photographic subject image of the first photographing lens; , a second detection means for detecting that the first photographing lens has stopped; and a focusing operation by one of the two automatic focusing systems is completed; Each time the second detection means detects that the photographic lens has stopped, it is determined whether the output of the first detection means is null or not, and if no output is output, a cutting signal is applied to the other automatic focusing thread. An automatic focusing device characterized in that it includes a first control means for changing the focus.