JPH0614245A - Video camera - Google Patents

Abstract

PURPOSE:To suppress a useless hunting, and to shorten a time until a focusing point by controlling a focus adjusting level to a preliminarily decided direction when the level of a focusing signal is lower than a prescribed value. CONSTITUTION:The video signal of an image pickup element 5 is transmitted through an amplifier 6 to a camera process circuit 7. A luminance signal is separated by the circuit 7, the video signal is transmitted through a sharpness signal detecting circuit 8 to a microcomputer(MC) 9. The MC 9 outputs a driving instruction signal to a focus motor driver 10 according to a sharpness signal, drives a focus motor 11, and moves a focus lens 4. Also, the MC 9 detects the positions of variable power lens 2 and 4 by focus encoders 14 and 15. Then, when those lens are at a close range, and when the level of the sharpness signal is lower than the prescribed value, the focus adjusting level is moved to an unlimited direction in a prescribed time. Thus, the hunting of the lens 4 can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera having an automatic focusing function for automatically focusing on a subject in a video camera or the like.

[0002]

2. Description of the Related Art In recent years, video devices such as video cameras and electronic cameras have been remarkably developed, and in order to improve their functions and operability, functions such as automatic focusing (AF) are standard equipment. Has reached the end.

Looking at this type of automatic focus adjustment device, the sharpness (focus signal) of the screen is detected from the video signal obtained by photoelectrically converting the subject image by an image sensor or the like, and the sharpness is detected. A method in which the focus adjustment is performed by controlling the movement of the focus lens (focus adjustment lens) so as to maximize the value is becoming mainstream.

As the evaluation of the sharpness signal (focus signal), generally, the strength of the high frequency component of the video signal extracted by a band pass filter (BPF) or the blur width of the video signal extracted by a differentiating circuit (subject The width of the edge portion of the) detection intensity or the like is used.

This is because when a normal subject image is taken, the level of the high frequency component is small and the blur width is wide when the focus is blurred, and the level of the high frequency component is large and the blur width is small as the focus is adjusted. Then, the maximum value and the minimum value are taken respectively when the focus is completely reached. Therefore, when the sharpness is low, the control of the focusing lens is performed by driving as fast as possible in a direction in which the sharpness becomes high, decelerating as the sharpness becomes higher, and stopping the peak of the sharpness with high accuracy. Controlled. Such a method is generally referred to as a hill-climbing autofocus method (hereinafter, abbreviated as hill-climbing AF).

The adoption of such an automatic focusing device has dramatically improved the operability of conventional video cameras, particularly those for shooting moving images, and has become an essential function in recent years.

In the hill-climbing AF, the focus lens is moved, and the direction in which the focus lens should be moved is detected in order to focus on the basis of the level change of the high frequency component of the subject image. Therefore, in this method, unless the focus lens is moved once, it is unknown whether the focus position is before or after the current position as a reference, and the focus lens may be moved in the wrong direction. .

On the other hand, there is known a method in which the focus lens is slightly moved forward and backward at the current position and the direction in which the focus lens is moved is determined by the level change (Japanese Patent Laid-Open No. 2-140074). According to this method, when the focusing point is deviated due to the moving direction of the focus lens for performing the focusing operation, the movement of the subject after focusing, etc., it is promptly determined whether or not to restart. be able to.

[0009]

However, in the above-mentioned conventional example, when the hill-climbing AF operation is started, especially when the focus lens is near the telephoto end and the focus lens is near the near end, a sharp panning or the like is performed so that an object close to infinity is captured. Looking at it, the image is greatly blurred, and even if the focus lens moves, the sharpness signal does not change, and accurate direction determination cannot be performed. Therefore, the moving direction of the focus lens is reversed, and it takes a long time to reach the focal point.

Further, in the above-mentioned conventional example, during the hill-climbing AF operation, the movement direction of the focus lens is reversed by a slight change in the sharpness signal, especially before a clear difference in the sharpness signal, and the reverse operation is performed. As a result of being repeated many times, there was a problem that it took a long time to reach the focal point.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a video camera in which the time required to reach the focal point is shortened.

[0012]

In order to achieve the above object, the first aspect of the present invention is to detect a focus signal corresponding to the degree of focusing from the video signal and move the focus adjusting lens based on the detected signal. In a video camera that adjusts the focus by
When the level of the focus signal is lower than a predetermined value, control means for controlling the focus adjusting lens to move in a predetermined direction is provided.

In order to achieve the same object, a second aspect of the present invention is to detect a focus signal corresponding to the degree of focusing from the video signal and move the focus adjusting lens based on the detected signal to focus. In a video camera for adjustment, when the level of the focus signal is lower than a predetermined value, when the focus adjustment lens repeats the inversion operation, the focus adjustment lens of the focus adjustment lens is generated based on the level difference of the focus signal during the inversion operation. It is characterized in that a determining means for determining the moving direction is provided.

[0014]

In the video camera of the first aspect of the invention, for example, the position of the focus (focus adjustment) lens is near the telephoto end, and the sharpness signal (focus signal) level is lower than a predetermined value. By forcibly moving the focus lens in the infinity direction for a certain period of time, useless hunting of the focus lens is suppressed, and the time to reach the in-focus point is shortened.

The video camera of the second invention stores the sharpness signal level at that time when the focus lens is inverted, and when the focus lens repeats inversion, the level of the sharpness signal at the inversion point is stored. By looking at the difference and moving the focus lens for a certain period of time in the direction in which the level increases, it becomes easier to find the in-focus point, and the time to reach the in-focus point is shortened.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing the arrangement of a video camera according to the first embodiment of the present invention. In FIG. 1, 1 is a first fixed lens, and 2 is a magnification change (zoom). A lens 3, a second fixed lens 4 and a focus lens 4.

The light passing through each of these lenses 1 to 4 is imaged on the image pickup surface of the image pickup device 5 and converted into an electric signal. This electric signal is amplified by the amplifier 6 and then sent to the camera process circuit 7, where the camera process circuit 7
At, the luminance signal is separated and then sent to the sharpness signal (focus signal) detection circuit 8. The sharpness signal detected by the sharpness signal detection circuit 8 is sent to the microcomputer 9. The microcomputer 9 outputs a drive command signal to the focus motor driver 10 according to the sent sharpness signal. The focus motor 11 is driven by this drive command signal and the focus lens 4 moves.

The microcomputer 9 also outputs a drive command signal to the zoom motor driver 12, and the zoom motor 13 is driven by the drive command signal to move the variable power lens 2.

In addition to the sharpness signal, the microcomputer 9 also receives a focus lens position signal from a focus encoder 14 for monitoring the position of the focus lens 4 and a zoom encoder 1 for monitoring the position of the variable magnification lens 2.
It is possible to capture the variable-magnification-lens position signals from each of the signals 5 and detect the positions of the variable-magnification lens 2 and the focus lens 4 from these signals.

Next, the actual movement of the focus lens 2 in the video camera of this embodiment will be described with reference to FIG. FIG. 2 is a flowchart showing the control procedure performed by the microcomputer 9 in the video camera of this embodiment.

When the hill-climbing AF operation is started, the routine shown in FIG. 2 is executed. In the figure, steps 201 to 20
Reference numeral 3 is a portion for determining a condition for using the control of the present invention. First, in step 201, it is confirmed whether or not the variable power lens 2 is near the telephoto end. If it is near the telephoto end, the process proceeds to step 202, and it is confirmed whether or not the focus lens 4 is near the near end. If it is near the very close end, the routine proceeds to step 203, where it is judged whether or not the level of the sharpness signal is lower than a predetermined value. The determination as to whether this level is high or low is made by providing a threshold level determined from experience in examining the state of the sharpness signal with respect to various charts.

If even one of the judgment conditions in each of the steps 201 to 203 does not apply, normal hill-climbing AF control is performed in steps 206 and 207, and focusing is achieved. In addition, each step 201
If all the determination conditions in steps 203 to 203 are satisfied, the process proceeds to step 204. In step 204, a program for forcibly moving the focus lens 4 in the infinite direction is executed. When you come here, focus lens 4
Is moved in the infinite direction until it is determined in step 205 that a preset time (a fixed period) has elapsed.

Then, if the predetermined period has passed, step 2
The procedure proceeds to 06, and focusing is achieved by the normal hill-climbing AF control. If the focus is achieved in step 207, the process proceeds to step 208 to stop the movement of the focus lens 4, and then the control operation is finished.

FIG. 3 is a diagram showing the relationship between the level change of the sharpness signal and the movement of the focus lens 4.

The horizontal axis of the figure is the position of the focus lens 4, and when the focus lens 4 is near the near end at the telephoto end and the level of the sharpness signal is lower than a predetermined value, the sharpness signal at that time is shown. The change is indicated by a in FIG. At this time, if the conventional hill-climbing AF control is performed, since the sharpness signal does not change, the focus lens 4 repeats hunting as shown in FIG. 3C, and when the sharpness signal changes, the level is changed. This hunting time had lengthened the time until it became in-focus because it headed to the summit of.

In the present invention, in steps 204 and 205 of FIG. 2 described above, the focus lens 4 is forcibly moved in the infinity direction for a certain period of time.
No useless hunting of the focus lens 4 is eliminated as indicated by d.

When the in-focus point is on the near side, the change in the sharpness signal at that time is as shown in b of FIG. 3, and the level of the sharpness signal is determined in step 203 of FIG. 2 described above. Since it does not fall below the threshold level,
Since the normal hill-climbing AF control is performed in step 206, the in-focus state can be obtained without carelessly moving the focus lens 4 in the infinite direction. Further, since the angle of view is widened on the wide side, the level of the sharpness signal is likely to change, and thus it is possible to obtain a focused state without hunting only by the normal hill-climbing AF control.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a block diagram showing the configuration of the video camera according to the second embodiment of the present invention. In the figure, the same parts as those in the first embodiment described above are designated by the same reference numerals and described. 4 is different from FIG. 1 in that a zoom encoder for detecting the position of the variable power lens 2 is not provided.

Next, the actual movement of the focus lens 4 in the video camera of this embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the control procedure performed by the microcomputer 9 in the video camera of this embodiment. When the mountain climbing AF operation is started,
The routine of FIG. 4 is executed. In the figure, first, in step 501, it is determined whether or not the focus lens 4 is inverted. If it is not reversed, the routine proceeds to step 509, which will be described later, to perform normal hill-climbing AF control.

When the reversal of the focus lens 4 is detected, it is determined in step 502 whether the level of the sharpness signal is lower than a predetermined value. If this level is high, the current focus lens position is near the in-focus position, and it is determined that the reversal has occurred due to the change of the subject, and step 508 described later is executed. When the level of the sharpness signal is low, it is determined that the local peak in the middle of the hill-climbing AF control is detected. Then, in step 503, it is determined whether or not the inversion is the first inversion, and if it is the first inversion, the position of the focus lens 4 and the level of the sharpness signal at that time are stored in step 504. Then, step 5 described later
In step 09, the normal hill-climbing AF control is continued.

Further, if the focus lens 4 is inverted at the local peak before reaching the in-focus point, the level of the sharpness signal is lowered, so that it is always inverted again. Therefore, if the second inversion occurs at a low level of the sharpness signal, the process proceeds to step 505. This step 5
In 05, the data at the time of the first inversion previously stored in step 504 is compared with the current data, and it is determined which direction, near or infinity, should be taken to climb the mountain. When the moving direction is determined, the process proceeds to step 506, and the focus lens is moved in the determined direction for a fixed time. As a result, the focus lens 4 can be moved in the true focusing direction beyond the local peak.

Next, the routine proceeds to step 507, where it is judged whether or not a fixed time has passed, and if it has passed, step 508.
After clearing the inversion counter and each stored data in step 509, the process proceeds to step 509, and after normal hill-climbing AF control is performed, it is determined in step 510 whether or not focusing is achieved.
If it is determined that the subject is in true focus, the movement of the focus lens 4 is stopped in step 511, and then this control operation is ended. If it is determined in step 510 that the subject is out of focus, the process returns to step 501.

FIG. 6 is a diagram showing the relationship between the level change of the sharpness signal and the movement of the focus lens 4. The horizontal axis of the figure shows the position of the focus lens 4, and c shows the change of the sharpness signal. Reference characters a and b indicate the movement of the focus lens 4, a is a conventional one, and b is the movement according to the present embodiment. In the figure, "1" and "2" indicate the number of inversions of the focus lens 4, and are represented by the difference ΔEs between the sharpness signal at the position "1" and the sharpness signal at the position "2". The moving direction in step 505 of FIG. 5 is set, and the focus lens 4 is moved in the setting direction. This operation eliminates the useless hunting of the focus lens 4 that has conventionally occurred, and shortens the time until the focus is reached.

[0035]

As described above, according to the video camera of the first invention of the present invention, the variable power lens is near the tele end, the focus lens is near the near end, and the sharpness signal level is predetermined. If the value is lower than the value, by moving the focus lens in the infinity direction for a certain period of time, it is possible to eliminate unnecessary hunting of the focus lens, and the time required to reach the in-focus point is greatly shortened.

Further, according to the video camera of the second aspect of the present invention, when the level of the sharpness signal is lower than a predetermined value and the focus lens causes hunting, the sharpness signal level difference at the time of reversing sharpens the sharpness signal. By moving the focus lens in the direction in which the degree signal increases, a quick focusing operation with less hunting of the focus lens can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a video camera according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure in the video camera.

FIG. 3 is a diagram showing a relationship between a level change of a sharpness signal and a movement of a focus lens in the same video camera and a conventional video camera.

FIG. 4 is a block diagram showing a configuration of a video camera according to a second embodiment of the present invention.

FIG. 5 is a flowchart showing a control procedure in the video camera.

FIG. 6 is a diagram showing the relationship between the level change of the sharpness signal and the movement of the focus lens in the video camera and the conventional video camera.

[Explanation of symbols]

 4 Focus lens (focus adjustment lens) 9 Microcomputer (control means, determination means)

Claims (3)

[Claims] 1. A video camera which detects a focus signal according to a degree of focus in a video signal and moves a focus adjustment lens based on the detection signal to perform focus adjustment, wherein the level of the focus signal is a predetermined value. A video camera provided with a control means for controlling to move the focus adjusting lens in a predetermined direction at a lower time. 2. A determination means for determining whether or not to move the focus adjustment lens in a predetermined direction according to the position of a lens group in the video camera body is provided. The described video camera. 3. A video camera, which detects a focus signal according to the degree of focus from a video signal and moves a focus adjustment lens based on the detection signal to perform focus adjustment, wherein the level of the focus signal is predetermined. When the focus adjusting lens repeats a reversing operation when the value is lower than a value, a determining means is provided for determining a moving direction of the focus adjusting lens based on a level difference of the focus signal during the reversing operation. A video camera.