JPH0472877A - Automatic focus detector - Google Patents

Abstract

PURPOSE:To always obtain good focusing information by comparing features of the whole of a current picked-up image with those of an object stored in a storage means and detecting the present position of the object on the picked-up image and focusing a device on this position. CONSTITUTION:This device consists of an automatic focus detector 1, a camera part 2, and a lens driving part 3, and the automatic focus detector 1 consists of a designating means 4, two feature extracting means 5a and 5b, a storage means 6, a present position detecting means 7, a position display means 8, and a focus detecting part 9. An area including an object 14 is preliminarily designated, and features of the object 14 in the designated area are extracted by feature extracting means 5a and 5b and are stored in the storage means 6. The present position of the object 14 is detected based on stored feature information of the object 14 and features on the present picked-up image extracted by feature extracting means 5a and 5b, and the focus detecting part 9 detects focusing information corresponding to the position of the object 14. Thus, the focus area is moved in accordance with the movement of the object to always obtain the good focusing state.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic focus detection device used in a video camera or the like to detect the focus state of a subject.

2. Description of the Related Art In recent years, automatic focus adjustment devices have become indispensable for video cameras and the like.

Conventionally, a method that has become mainstream is a method of obtaining focus information of a subject from a video signal, as disclosed in Japanese Patent Application No. 63-248198, for example. Such conventional automatic focus adjustment devices use video signals in a limited area (hereinafter referred to as the in-focus area) within the imaging screen to extract focus information, but the setting of this in-focus area is Usually fixed.

Problems to be Solved by the Invention In the conventional automatic focusing device as described above, in order to obtain correct focus information, the camera must be constantly moved so that the subject is in the in-focus area.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an automatic focus detection device that automatically detects the focus state of an object to be imaged, no matter where the object moves on the imaging screen. There is.

Means for Solving the Problems In order to achieve the above object, the present invention provides a designation means for designating a specific subject, a feature extraction means for extracting the features of the designated subject, and a memory for storing the features. current position detecting means for detecting the current position based on the characteristics of the subject stored in the storage means and the features on the current imaging screen extracted by the feature extracting means; The camera is equipped with a position display means for displaying the position on a monitor, and a focus detection section for detecting the focus state at the current position of the subject based on a signal corresponding to the position of the subject obtained by the current position detection means.

Effect of the Invention With the above-described configuration, the present invention specifies a region including the subject in advance, extracts features of the subject within the designated region by the feature extraction means, and stores these features in the storage means. Furthermore, the current position of the subject is detected based on this stored feature information of the subject and the current features on the imaging screen extracted by the feature extracting means, and the focus detection section uses the output to determine the position of the subject. This detects the corresponding focus information. In this way, in the present invention, the focusing area moves following the movement of the subject, so good focus can always be obtained.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows an example of a video camera equipped with an automatic focus detection device according to the present invention.

As shown in FIG. 1, this video camera includes an automatic focus detection device 1, a camera section 2, and a lens drive section 3.

The automatic focus detection device 1 is composed of a specifying means 4, two feature extraction means 5a and 5b, a storage means 6, a current position detection means 7, a position display means 8, and a focus detection section 9.

The camera section 2 includes a photographing lens section 10 and a CCD image sensor (charge coupled imaging device Charg).
eCoupled Imaging Device,
It consists of a CCD (hereinafter referred to as CCD) 11, a camera processing section 12, and a monitor 13.

First, the operation of the camera section 2 will be explained.

The image of the subject 14 is transmitted to the CCD 11 via the photographing lens section 10.
is input. The camera processing section 12 performs various signal processing on the electrical signal (2) obtained from the CCD II and outputs a predetermined video signal C8.

Next, the operation of the automatic focus detection device 1 of the present invention will be explained with reference to FIG. 2 as well.

As shown in FIG. 2, the specifying means 4 includes an input means 15, a range detecting means 16, and a video signal extracting means 17.

First, when the photographer determines the subject to be photographed, he inputs the instruction signal OP into the input means 15 while looking at the screen of the monitor 13, and selects a specific area (hereinafter referred to as the designated area) on the imaging screen that includes the subject 14. ). This specified area is set as a rectangle, the center of which coincides with the center of the subject, and the dimensions of this rectangle include at least one or more features that can distinguish the subject (for example, eyes in the case of humans). It is set as follows. Area detection means 16
recognizes the specified area input via the input means 15 and outputs a specific signal H specifying this specified area. The specific signal H is expressed as a binary signal, and is, for example, a signal that is set to be "1" in a period corresponding to the designated area and "O"' outside the designated area.Video signal The extraction means 17 extracts only the video signal (E) within the specified area indicated by the specific signal H and outputs it.

The feature extraction means 5a differentiates the video signal E, and compares the differential output with a preset threshold value to form a binary signal (the output is designated as E'''(0)).

The storage means 6 stores a binary signal E''(0) representing the feature of the subject obtained from the feature extraction signal 5a.

Thereafter, the feature extraction means 5b differentiates the video signal Y output from the camera processing section 12, compares the differential output with a preset threshold value, and forms a binary signal (the output is E"(t ).

The current position detection means 7 detects the feature E" (t) of the entire current imaged screen obtained by the feature extraction means 5b and the feature E" (0) of the subject 14 stored in the storage means 6.
) and a correlation between the two, the current position of the subject 14 on the image capture screen is detected, and a signal C corresponding to this position (C is usually expressed in the form of a specific area on the image capture screen) is detected. and corresponds to the focus area above)
Output.

The position display means 8 detects the object 14 by the signal G.
Displays the in-focus area on the monitor.

The focus detection section 9 uses the video signal Y output by the camera processing section 12 and the signal G obtained by the current position detection means 7 to generate a signal F indicating the lens drive direction to achieve focusing at the current position of the subject.

and a signal F indicating the driving speed.

The lens driving section 3 receives the signals FD and F.

A focusing lens part (not shown) provided in the photographing lens 10 is driven at a predetermined speed until the subject 14 is brought into proper focus, and a good image in which the subject to be photographed is always in focus can be obtained.

Effects of the Invention As is clear from the above embodiments, according to the present invention, no matter how the current position of the subject moves within the screen,
You can always get good focus information, and the effect is very large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video camera including an automatic focus detection device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a specifying means which is a component of the present invention. ■...Automatic focus detection device, 2...Camera unit, 3...Lens drive unit, 4...Specification means, 5a, 5b... ...Feature extraction means, 6...
... Storage means, 7... Current position detection means,
8...Position display means, 9...Focus detection section, 10...Photographing lens section, 11...
CCD, 12...Camera process section, 13...
...Monitor, 14...Subject, 15...
...Input means, 16... Area detection means, 1
7...Video signal extraction means.

Claims (3)

[Claims] (1) A specifying means for specifying a specific subject present on a monitor screen installed in a video camera, a feature extracting means for extracting features of the subject specified by the specifying means, and extraction by the feature extracting means. a current position of the subject on the image capture screen is detected from the features of the subject stored by the memory means and the features of the entire current image capture screen extracted by the feature extractor; a position detecting means; a position display means for displaying the position on the imaging screen detected by the current position detecting means on the monitor screen; and an image corresponding to the current position of the subject detected by the current position detecting means. An automatic focus detection device comprising: a focus detection section that detects a focus state of a subject from a signal. (2) The designation means includes an input means for inputting an area including the subject on the imaging screen, an area detection means for detecting and outputting an area on the imaging screen of the subject input by the input means, and an area detecting means for detecting the area on the imaging screen, and 2. The automatic focus detection apparatus according to claim 1, further comprising video signal extraction means for extracting a video signal of the area detected by the means. (3) The area specified by the input means is set to be a rectangle, the center of the rectangle coincides with the center of the subject, and the dimensions of the rectangle are such that at least one feature that can distinguish the subject is included within the rectangle. The automatic focus detection device according to claim (2), characterized in that the automatic focus detection device is configured as follows.