JPS6118271A - Video camera - Google Patents

Abstract

PURPOSE:To attain automatic focusing to an intended object by switching manually the size of an area for automatic focusing. CONSTITUTION:When an object to be focused is positioned at the center of a photodetecting plane, a displacement of a lens 12 is detected, an area setting circuit 20 uses a detection signal to calculate the distance to an object and magnification of image pickup and the automatic focusing operating area is set to set any of the areas 12, 14 depending on the condition of an object for the automatic focusing operating area to set a preset value. In focusing object images B, C to be picked up, when a mode changeover switch 31 sets the manual mode, the area setting switch 30 is activated, area setting information is fed to the area setting circuit 20 so as to set the automatic focusing area with a desired size.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a video camera using an area type solid-state image sensor.

(Prior Art) A video camera is known that performs an automatic focusing operation using a signal from an area-type solid-state image sensor that scans a subject image and converts it into a video signal.

In this type of video camera, the light-receiving surface of the solid-state image sensor is
An automatic focusing area of a predetermined size is set, and signals from this automatic focusing area are used to perform automatic focusing.

However, the lenses used for video cameras usually have 4 to 4 lenses.
It is a 10x zoom lens, and when the subject is photographed at a close distance and wide-angle, the subject image will be present on almost the entire area of the light-receiving surface, and when photographing at a long distance and wide-angle, the subject image will be located on one part of the light-receiving surface. It only exists in the department.

Therefore, if the size of the autofocus area is fixed, malfunctions may occur in the autofocus operation.

In other words, in the case of close-up wide-angle photography, the subject image extends beyond the autofocus area, resulting in insufficient subject information, and in the case of long-distance wide-angle photography, unnecessary information is mixed in, leading to malfunctions. It is the cause.

As a method to solve these problems, a method has been proposed in which the size of the autofocus area is automatically changed based on the center of the light-receiving surface according to the lens condition. No. 58-227965).

Although this method is effective in preventing the above-mentioned malfunctions, it still leaves room for improvement in the following points.

In FIG. 2, reference numeral 10 indicates an effective light-receiving area of the light-receiving surface of the solid-state image sensor. Further, the reference numeral 12 in FIG. 2 (1) and the reference numeral 14 in FIG. 2 (II) are
Both of them show areas for automatic focusing operation that are automatically set in a certain lens state.

Now, among the subject images that you want to autofocus, there are some that exist within the autofocus operation area 12, such as the subject image A in FIG. 2 (I), and the subject image B. There are objects that partially protrude from the autofocus area 12, as in the case of subject C in FIG. There are some things. In the case of a method of automatically changing the size of the autofocus operation area according to the lens condition, it is effective for focusing on subject image A, but it is not possible to focus on subject images B and C.

However, depending on the shooting range and composition intended by the photographer, there may be cases where it is desired to automatically focus on the subject images B and C.

(Objective) The present invention aims to provide a video camera which further improves the technique proposed in Japanese Patent Application No. 58-227965 and also enables automatic focusing on the above-mentioned subjects B and C.

(composition) The present invention will be explained below.

The features of the present invention are as follows.

In other words, the size of the area for autofocusing can be similarly varied with the center of the light-receiving surface of the solid-state image sensor as a reference, and the size of the x IJ area for autofocusing can be changed automatically and manually. I made it possible for him to do so.

When the subject to be focused is located at the center of the light receiving surface, the size of the autofocus area is automatically changed according to the lens condition, and the focus is adjusted to the subject images B and C in Figure 2. When focusing, the above-mentioned size is manually set, and the size of the automatic focusing area is manually set according to the position of the subject image.

FIG. 1 shows a block diagram of an example of a circuit for implementing the present invention.

This circuit has an area setting switch 30 and a mode changeover switch 31. The mode changeover switch 31 is used to select whether to change the size of the automatic focusing area manually or automatically.

First, the operation of the circuit system will be briefly described, taking as an example a case where a mode in which the size of the area for automatic focusing operation is automatically switched is selected. In a video camera, an area-type solid-state image pickup device 11 scans an image projected onto an effective light receiving area 10 (FIG. 2) by a lens 2 and outputs it in a photoelectric conversion time series. The output signal of this solid-state image sensor 11 is amplified by an amplifier 13 and sent as a video signal to a video processing circuit. The solid-state image sensor 11 is driven by a drive circuit 15 using clock pulses generated from a timing generation circuit 14 and performs self-scanning. At this time, horizontal synchronization clock pulses H9 and vertical synchronization clock pulses V generated from the timing generation circuit 14 are used as horizontal clocks, respectively. counter 16, vertical clock counter 17. is counted. The horizontal clock counter 16, the vertical clock counter 17, and the digital comparators 18 and 19 are preset with preset values corresponding to the automatic focusing operation area from which the signal should be extracted from the area setting circuit 20. By comparing the count values of the clock counter 16 and the vertical clock counter 17 with the precent value, it is detected whether or not the self-scanning of the solid-state image sensor 11 is being performed within the automatic focusing operation area in the horizontal and vertical directions. do. Gate circuit 21
ANDs the output signals of the digital comparators 18 and 19 to generate a pulse when scanning the automatic focusing area, and this pulse is applied to the analog switch 22.

On the other hand, the displacement of the lens 12 is detected by the lens state detection circuit 23, and the area setting circuit 20 calculates the subject distance and imaging magnification based on the output signal of the lens state detection circuit 23, and sets an area for automatic focusing operation. Accordingly, the area for automatic focusing operation is set to one of the areas 12 and 14 (FIG. 2), for example, according to the subject conditions, and the preset value corresponding to the area for automatic focusing operation is set to the horizontal clock counter 16, The vertical clock counter 17 and digital comparators 18 and 19 are preset.

The waveform processing circuit 24 includes a differentiating circuit, a detection circuit, etc., and converts the video signals from the amplifiers 13i- and the like into a form that is easy to process. The output signal of this waveform processing circuit 24 is passed through the analog switch 22 by the output pulse of the gate circuit 21F) when scanning the automatic focusing area.
Only the signal from the autofocus operation area is extracted and integrated by the integrating circuit 25.

The comparison/judgment circuit 26 compares the output signal of the integration circuit 25 with a previous value or a predetermined value and outputs a focus signal or a photometry signal, and the movement amount calculation circuit 27 compares the output signal of the integration circuit 25 with a previous value or a predetermined value. The amount of movement of the lens 12 or the amount of movement of the aperture is calculated. The motor drive circuit 28 drives the motor 29 using the output signal of the movement amount calculation circuit 27 to drive the lens 1.
2 or move the aperture. At this time, if the subject conditions change, the position of the lens 12 also changes, so the above operation changes the area for automatic focusing operation, and proper focusing is performed.

When the manual mode is selected by the mode changeover switch 31, the area setting switch 30 becomes operable. This area setting switch 30 allows area setting information to be sent to the area setting circuit 20 to set an area for automatic focusing operation of a desired size.

(Effects) As described above, according to the present invention, a novel video camera can be provided. With this video camera, the size of the autofocus area can also be changed manually, so even if you want to focus on a subject image located off the center of the light-receiving surface, you can adjust the size to suit that area. It is possible to set an area for automatic focusing operation, and it is possible to perform an automatic focusing operation on the subject intended by the photographer.

Note that the area setting switch may be an on/off switching switch, or may be configured to set a plurality of automatic focusing operation areas in stages. Alternatively, an area setting signal may be generated as a continuous analog signal using an area setting switch, and the size of the area for automatic focusing operation may be continuously changed to set the area to a desired size.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a circuit configuration for implementing the present invention, and FIG. 2 is a diagram for explaining the problems to be solved by the present invention. 12, 14・Area% for automatic focusing operation 〔;Kore sale? Cause

Claims (1)

[Claims] A video camera that performs automatic focusing using a signal from an area-type solid-state image sensor that scans a subject image and converts it into a video signal, comprising: As the region to be extracted, the size of the area for automatic focusing operation set on the light receiving surface of the solid-state image sensor is similarly varied with the center of the light receiving surface as a reference, and the area for the automatic focusing operation is set as a region to be extracted. The area size can be changed automatically and manually.
Video camera.