JPH1010413A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image pickup device having autofocusing function from being not focused onto an object inside an image plane so as to obtain an object image plane without blur in the case of switching the aspect ratio of photographic picture frame and to obtain an object picture without causing any blurring. SOLUTION: An object image is made incident on a CCD 103 through a focusing lens 102 for performing focusing, and photoelectrically converted to an image signal. By a camera signal processing circuit 105, the signal is subjected to a prescribed signal processing to generate a video signal, and is recorded in a video tape recorder 106. A control microcomputer 112 drives the lens 102 based on an AF evaluation value from an AF evaluation signal processing circuit 111 obtained by sampling the video signal and performs AF control, and also AF control is started again in the case the aspect ratio is changed by an SW unit 113 for switching the aspect ratio.

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 having an automatic focusing function for automatically focusing on a subject.

[0002]

2. Description of the Related Art In an apparatus having an image pickup device such as a video camera, the sharpness of a screen is detected from a video signal of a subject, and the position of a focus lens is controlled so that the sharpness is maximized. Is adopted.

As the evaluation of the sharpness, the intensity of the high-frequency component of the video signal extracted by the band-pass filter or the detection intensity of the blur width of the video signal extracted by the differentiating circuit is generally used. ing. These signals are usually small when the subject is out of focus when the subject is out of focus, and larger when the subject is in focus.
It reaches the maximum value when it is completely in focus.

Therefore, the control of the focus lens is
When the sharpness signal is small, move as soon as possible in the direction of increase, and slowly move as it increases to stop the focus lens accurately at the top of the mountain,
That is, the focus is adjusted.

In general, such an autofocus method is a hill-climbing autofocus (abbreviated as hill-climbing AF).
is called. Since the AF can be realized with a simple system as the camera becomes smaller and lighter, this hill-climbing AF has become mainstream in recent video cameras.

On the other hand, recently, the aspect ratio of the conventional screen has changed to 4: 3 TV (television), and a wide-screen TV having an aspect ratio of 16: 9 has been widely used in homes. This wide-screen TV has a mode in which a conventional 4: 3 screen is expanded 1.33 times in the horizontal direction to 16: 9. Therefore, there has been proposed a video camera which corresponds to the enlargement mode and records the image at a magnification of 1.33 in the vertical direction at the time of shooting. FIG. 4 is a flowchart showing an AF control operation in such a conventional imaging apparatus. This control operation is processed in a microcomputer provided in the main body.

Step 301 indicates the start of the process. First, a wobbling operation is performed in step 302,
By taking in the AF evaluation value while driving the AF lens minutely, it is determined whether the subject is currently focused or out of focus (when the subject is out of focus, it is the front focus or the back focus). Then, in step 303, it is determined whether or not the camera is currently in focus based on the result of the wobbling operation.
If it is determined that the subject is in focus, the AF lens is stopped,
The process proceeds to the restart monitoring routine from step 308.

If it is determined in step 303 that the image is out of focus, the flow advances to step 304 to execute the above-described hill-climbing operation in the direction of the result of the wobbling operation. Then, in step 305, it is determined whether or not the focal point, that is, the vertex of the AF evaluation value, has been exceeded. If not, the hill climbing is continued. Determine if it has been reached.

However, since the subject may change due to panning or the like during the operation of returning to the vertex, if the AF lens arrives at the vertex, the current position is really the vertex, that is, the focal point. Is determined, the process returns to the process from step 302, and the wobbling operation is performed again.

If it is determined in step 303 that the object is in focus, the process proceeds to the restart monitoring routine from step 308 as described above. First, in step 308, AF at the time of focusing is performed.
The level of the evaluation value is stored in the memory. Next Step 30
Reference numeral 9 denotes a restart determination routine, which determines whether the current AF evaluation value level has changed from the level stored in step 308 during focusing. For example, if the amount of change is less than a predetermined percentage with respect to the stored level, it is determined that there is no change in the subject, and “no restart” is determined.

Then, in accordance with the result of the determination in step 309, it is determined in step 310 whether or not the system has been restarted.
In the case of non-restart, in step 311 the AF lens is stopped as it is, and the process returns to step 308 to monitor restart again. In the case of the restart, the process returns to step 302, where the wobbling operation is performed again to determine the moving direction. By repeating such an operation, the AF lens operates so that focusing can be constantly maintained.

[0012]

However, in the above-described conventional imaging apparatus, since the AF control and the aspect ratio switching control are performed independently of each other, the subject in the imaging screen is not focused. There was a problem that sometimes.

FIG. 5 shows how the aspect ratio is changed. In FIG. 5, reference numeral 501 denotes an image pickup screen by a CCD or the like, 502 denotes an AF frame, 503 denotes a focused object, and 504 denotes a non-focused object. The in-focus subject 505 is a recording screen in which the aspect ratio of the screen 501 is changed. As shown,
When the imaging screen is enlarged in the vertical direction by switching the aspect ratio, the subject 503 that has been focused so far becomes invisible. Then, when the difference between the evaluation value when the subject 503 in the invisible part is focused and the evaluation value of the unfocused subject 504 in the screen is within a predetermined level, AF is not restarted,
The in-focus subject 504 in the screen cannot be focused.

The present invention has been made in view of the above-described problems, and can prevent a subject in a screen from being in focus when an aspect ratio is switched, and always obtain a subject screen without blur. It is an object of the present invention to provide an imaging device capable of performing such operations.

[0015]

An image pickup apparatus according to the present invention comprises a lens for adjusting a focus, an image pickup device for converting a subject image formed through the lens into a video signal, and a predetermined signal of the video signal. Extraction means for extracting a signal corresponding to the degree of focus from the area, focus adjustment means for performing focus adjustment based on the extracted signal, and change means for changing an aspect ratio of an imaged screen by the video signal When the aspect ratio of the imaging screen is changed by the changing means, the lens is restarted to adjust the focus again.

The aspect ratio changing means enlarges the imaging screen in the vertical direction, and the extracting means reduces the video signal extraction area in the vertical direction.

The aspect ratio changing means enlarges the image pickup screen in the vertical direction by 4/3 times, and the extracting means reduces the video signal extraction area in the vertical direction by 3/4. .

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a basic configuration of an imaging device (video capturing device) according to the present invention.
This shows a case where the present invention is applied to a video integrated camera.

In FIG. 1, reference numeral 101 denotes a subject, 102 denotes a focus (competition) lens (lens group) for performing focus adjustment, and 103 denotes an image pickup device for photoelectrically converting image pickup light (subject image) incident through the lens 102. CCD,
104 is an automatic gain control (AGC) circuit for electrically amplifying the video signal photoelectrically converted by the CCD 103; 114 is a field memory for taking in and storing one screen of video signal processed by the control circuit 104;
Reference numeral 115 denotes an interpolation circuit which reads signals from the field memory 114 at an enlargement ratio corresponding to a control signal from the control microcomputer 112 and generates a signal for interpolating between the read signals. The circuit 115 can implement a so-called electronic zoom.

Reference numeral 105 denotes a standard T after applying processing such as gamma (γ) correction, color separation, and color difference matrix, and adding a synchronization signal.
A camera signal processing circuit 106 for generating a V signal, a video tape recorder (VT) 106 for recording a video signal on a tape
R) and 107 are motors (driving means) for driving the lens 102, and move the lens 102 in parallel with the optical axis.

A driver 108 for outputting driving energy to a lens driving motor 107 in accordance with a driving command for the lens 102 output from the control microcomputer 112;
Reference numeral 109 denotes a driver for controlling the CCD 103 to read out a signal obtained by photoelectric conversion, 110 denotes a gate circuit for sampling only a predetermined extraction area portion from an output signal of the interpolation circuit 115, and 111 denotes a focus degree from the output signal of the gate circuit 110. AF for generating sharpness signal for focus evaluation according to
The evaluation signal (evaluation value) processing circuit includes a so-called band-pass filter (extraction means).

A reference numeral 112 sets a predetermined gate area in the gate circuit 110, and based on an output signal of the processing circuit 111,
The above-mentioned control microcomputer (focus adjustment means) for driving the focus lens 102 to adjust the focus, and 113 is a SW (switch) unit (conversion means) for switching the aspect ratio.

The image pickup apparatus having the above-mentioned structure has a function of enabling the aspect ratio to be changed manually. This will be described with reference to FIG. 201 in FIG. 2 is a CCD
FIG. The control microcomputer 112 controls the interpolation circuit 115 in accordance with the input signal from the aspect ratio switching SW unit 113, and records the image at 1.33 times in the vertical direction as shown in the screen 202. This is a wide-screen TV
When the image is reproduced in the above mode, the screen looks like a screen 203. In the enlargement mode described above, the black portion of the screen disappears, and the aspect ratio of the subject becomes the correct screen 204.

FIG. 3 is a flowchart showing the AF control operation. The control operations in this flowchart are processed in the control microcomputer 112, and the same operations as those in FIG. 4 are denoted by the same reference numerals.

Step 301 indicates the start of the process. First, by the wobbling operation in step 302,
By taking in the AF evaluation value while driving the focus lens 102 minutely, it is determined whether the camera is in focus or out of focus (when it is out of focus, it is the front focus or the back focus).

In step 303, it is determined whether or not the camera is in focus at the moment based on the result of the wobbling operation.
02 is stopped, and the process proceeds to the restart monitoring routine from step 308.

If it is determined in step 303 that the subject is out of focus, the flow advances to step 304 to execute the above-described hill-climbing operation in the direction of the result determined by the wobbling operation. Then, in step 305, it is determined whether or not the focal point, that is, the vertex of the AF evaluation value has been exceeded.
If it has exceeded, the focus lens 102 is returned to the vertex in step 306, and it is determined in step 307 whether or not the vertex has been reached.

However, the subject may change due to panning or the like during the operation of returning to the vertex. Therefore, if the focus lens 102 reaches the vertex, the current position is really the vertex, that is, the focus point. In order to determine whether there is, return to the processing from step 302,
The wobbling operation is performed again.

If it is determined in step 303 that focusing has been achieved, the process proceeds to the restart monitoring routine from step 308 as described above. First, in step 308, AF at the time of focusing is performed.
The level of the evaluation value is stored in the memory. Next Step 30
Reference numeral 9 denotes a restart determination routine, which determines whether the current AF evaluation value level has changed from the level stored in step 308 during focusing. For example, when the stored level changes by a predetermined percentage or more, it is determined that there is a subject change due to panning or the like, and "restart" is determined. Judge.

Then, according to the result of the determination in step 309, it is determined whether or not the restart has been performed in step 310. In the case of non-restart, it is determined in step 401 whether or not the aspect ratio has been changed. Step 3
At 11, the focus lens 102 is stopped as it is,
Returning to step 308, restart monitoring is performed again. If it is determined in step 310 that the camera has been restarted or that the aspect ratio has been changed in step 401, the process returns to step 302, where the wobbling operation is performed again to determine the moving direction.

As described above, even if it is determined in step 310 that "no restart" is performed, when the aspect ratio is changed, the camera is forcibly restarted. You will not be left out of focus. By repeating the above-described operation, the focus lens 102 operates so as to constantly maintain the focus.

By performing the AF control with the algorithm shown in FIG. 3, the AF is restarted in accordance with the change in the aspect ratio. It is possible to prevent the subject in the screen from being in focus, and it is possible to always realize AF control without blurring.

[0033]

As described above, according to the present invention, A
The F control and the change of the aspect ratio are linked to restart the AF with the change of the aspect ratio. It is possible to prevent the in-focus object from being out of focus, and it is possible to always obtain a subject image without blur.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an imaging device according to the present invention.

FIG. 2 is an explanatory diagram showing how an aspect ratio is changed in the apparatus of FIG. 1;

FIG. 3 is a flowchart showing an AF control operation in the apparatus shown in FIG. 1;

FIG. 4 is a flowchart showing an AF control operation in a conventional device.

FIG. 5 is an explanatory diagram showing how an aspect ratio is changed in a conventional device.

[Explanation of symbols]

 Reference Signs List 101 subject 102 focus lens 103 CCD (imaging element) 105 camera signal processing circuit 107 motor (drive means) 111 AF evaluation signal processing circuit 112 control microcomputer (focus adjustment means) 113 SW unit (conversion means)

Claims (3)

[Claims] 1. A lens for performing focus adjustment, an image sensor for converting a subject image formed through the lens into a video signal, and extracting a signal corresponding to a degree of focus from a predetermined area of the video signal. Extracting means, focus adjusting means for adjusting the focus based on the extracted signal, and changing means for changing the aspect ratio of the imaged screen by the video signal, wherein the aspect ratio of the imaged screen is changed by the changing means. An image pickup apparatus, wherein the lens is restarted and the focus is readjusted when the operation is performed. 2. The image pickup apparatus according to claim 1, wherein the aspect ratio changing means enlarges the imaging screen in the vertical direction, and the extracting means reduces the image signal extraction area in the vertical direction. 3. An apparatus according to claim 2, wherein said aspect ratio changing means enlarges the image pickup screen in a vertical direction by 4/3 times, and said extracting means reduces an image signal extraction area in a vertical direction by 3/4. The imaging device according to 1.