JP2000314834A - Image pickup apparatus and controlling method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make preventable a vignetting caused by the attachment of a wide converter from being recorded, in a video camera or the like having a zoom lens. SOLUTION: The image of image pickup light from a subject is formed by an imaging device 3 through the zoom lens 2, and a video signal is outputted by processing an image pickup signal by a signal processing circuit 4 at this time pickup apparatus. Also, a vignetting caused by the attachment of the wide converter 1 is detected by a vignetting detecting circuit 5, and when the occurrence of the vignetting is recognized during zooming driving to a wide side, zooming operation to the wide side is stopped by a zooming control circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus such as a video camera capable of zoom drive and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, zoom lenses have been widely used in video cameras, and the size of a subject can be changed while keeping focus.
Also, special effects can be obtained.
Recently, the number of users using a commercially available wide converter has been increasing.

[0003]

In an image pickup apparatus using a zoom lens as described above, when a wide converter is mounted and used, unless a dedicated wide converter is used, the vicinity of the wide side of the zoom lens is required. In many cases, the wide converter mounted as described above becomes a shadow on the photographing screen and causes so-called vignetting.

The wide-angle focal length at which vignetting occurs varies depending on the wide converter to be mounted. Conversely, even with the same wide converter, vignetting differs depending on the lens on the main body side.

[0005] In any case, if zooming in the wide direction as it is during photographing, there is a problem that vignetting is recorded as it is.

The present invention has been made in view of the above-mentioned problems, and can suppress the occurrence of vignetting.
It is an object of the present invention to provide an imaging device capable of preventing vignetting from being recorded and a control method thereof.

[0007]

An image pickup apparatus and a control method therefor according to the present invention are configured as follows.

(1) It has a zoom lens, includes zoom control means for controlling the driving of the zoom lens, and vignetting detecting means for detecting vignetting based on a luminance signal from the image pickup device. The zoom drive to the wide side is restricted.

(2) The vignetting detection means determines the occurrence of vignetting from the brightness of an arbitrary portion of the four corners of the screen.

(3) The occurrence of vignetting is detected based on a luminance signal from the image pickup device, and when the occurrence of vignetting is detected, zoom drive to the wide side is restricted.

(4) The vignetting is detected based on the brightness of an arbitrary portion of the four corners of the screen.

[0012]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. Here, a main part of a video camera capable of zoom drive is shown.

In FIG. 1, 1 is a wide converter mounted on a main body, 2 is a zoom lens in a lens of the main body, 3
Denotes an image sensor such as a CCD, and 4 denotes a signal processing circuit for processing an image signal obtained by imaging an object by the image sensor 3 through the wide converter 1 and the zoom lens 2.
The video signal is converted to an SC video signal and output.

Reference numeral 5 denotes a vignetting detection circuit (vignetting detecting means) for detecting vignetting by the wide converter 1 from a luminance signal Y representing the brightness of the subject output from the signal processing circuit 4, and 6 denotes driving of the zoom lens 2. A zoom control circuit (zoom control means) for controlling stops the zoom operation in the wide direction by a signal from the vignetting detection circuit 5.

Reference numeral 7 denotes a drive circuit for a zoom motor 8, which is a zoom switch SW in a tele (TELE) direction to be operated.
1 and zoom switch SW in the wide (WIDE) direction
2 and drives the zoom motor 8 in the direction of the switch, but by a stop signal from the zoom control circuit 6,
The zoom drive in the wide direction is stopped regardless of the zoom switch SW2.

FIG. 2 is a diagram showing a vignetting screen when the wide converter 1 is mounted. When the occurrence of the vignetting is detected, the zoom control circuit 6 limits the wide-angle zoom drive, suppresses the occurrence of the vignetting, and prevents the vignetting from being recorded.

FIGS. 3A and 3B are diagrams showing a vignetting detection method in the vignetting detection circuit 5, wherein FIG. 3A shows an upper left corner, FIG. 3B shows an upper right corner, FIG. 3C shows a lower left corner, and FIG. Is shown.

With respect to the upper left corner of FIG.
At the locations (11, 12, 13, 21, 22, 23), when the luminance signal Y is higher than a predetermined threshold level, W is assumed, and when the luminance signal Y is lower than B, as indicated by L1 when vignetting by the wide converter 1 occurs. 11 = B, 12 =
B, 13 = W, 21 = B, 22 = W, and 23 = W.
At this time, since the brightness is equal to or less than the predetermined brightness, the upper left corner is determined to be vignetting.

However, when a black subject is imaged,
There is no distinction between vignetting and the subject, and all are B. In this case, vignetting is not determined.

Similarly, as for the other three corners, L2, L3, L4 as shown in (b), (c) and (d) of FIG.
Is obtained, and it is determined that vignetting occurs.

In this embodiment, if two or more of the four corners are determined to be vignetting, the vignetting detection circuit 5 outputs a detection signal to the zoom control circuit 6. The drive circuit 7 does not perform zooming in the wide direction according to the control signal from the zoom control circuit 6 regardless of the operation of the wide-side zoom switch SW2.

On the other hand, when the zoom switch SW1 on the telephoto side is operated, regardless of the output of the zoom control circuit 6, zooming on the telephoto side is possible. In a general commercial television, the screen is overscanned. Therefore, even if there are vignetting at the four corners of the image signal from the image sensor 3, vignetting does not occur on the television screen if it is slight.

Further, in order to further improve the detection accuracy, it is possible to judge as vignetting based on the fact that the level of the luminance signal Y of the portion designated as B at each of the four corners is within a predetermined range. It is.

FIG. 4 is a diagram showing another method of vignetting detection, and shows a change in vignetting detection at the upper left corner of the screen. That is, during the zoom operation to the wide side, L1 in FIG.
Is changed to L1 ', it is determined that vignetting occurs. If two or more of the four corners are determined to be vignetting, the vignetting detection circuit 5 outputs a detection signal to the zoom control circuit 6 so that the drive circuit 7 does not zoom in the wide direction.

In this case, by returning to the telephoto side by one step after the detection of vignetting, it is possible to take a picture with less vignetting. That is, if the four corners of the screen are equal to or less than the predetermined brightness and are in the predetermined brightness range, the wide-side zoom can be restricted to just before the predetermined brightness.

As described above, this embodiment is characterized in that vignetting is recognized and zooming to the wide side is stopped.
That is, if the vignetting detection circuit 5 recognizes vignetting during the zoom operation to the wide side, the zoom operation to the wide side is stopped any more, thereby preventing the vignetting from being recorded as it is.

FIG. 5 is a flowchart showing the operation of the above-described embodiment. The control processing shown in this flowchart is executed by a CPU (not shown) according to a program stored in advance.

As described above, during the zoom operation to the wide side (S1), vignetting is detected based on the luminance signal (S1).
2) When it is determined that vignetting has occurred (S3), the zoom drive to the wide side is stopped by the output signal of the zoom control circuit 6 (S4).

[0029]

As described above, according to the present invention,
Vignetting can be suppressed and vignetting can be prevented from being recorded.

That is, the occurrence of vignetting due to the mounting of the wide converter is detected on the screen, and the zoom operation toward the wide side is stopped, thereby making it possible to perform photographing by a zoom operation without vignetting.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 shows a vignetting screen.

FIG. 3 is an explanatory diagram showing a vignetting detection method.

FIG. 4 is an explanatory view showing another vignetting detection method.

FIG. 5 is a flowchart showing the operation of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wide converter 2 Zoom lens 3 Image sensor 4 Signal processing circuit 5 Vignetting detection circuit 6 Zoom control circuit 7 Drive circuit 8 Zoom motor SW1 Zoom switch SW2 Zoom switch

Claims (4)

[Claims] A zoom lens; a zoom controller that controls driving of the zoom lens; and a vignetting detector that detects vignetting based on a luminance signal from an image sensor. An imaging apparatus for limiting zoom driving to a side. 2. The image pickup apparatus according to claim 1, wherein the vignetting detecting means determines occurrence of vignetting from the brightness of an arbitrary portion of the four corners of the screen. 3. A control method for an image pickup apparatus, wherein the occurrence of vignetting is detected based on a luminance signal from an image pickup device, and when the occurrence of vignetting is detected, zoom driving to a wide side is restricted. . 4. The method according to claim 3, wherein the occurrence of vignetting is determined from the brightness of an arbitrary portion of the four corners of the screen.