JPH04196685A - Display device for video camera - Google Patents

Abstract

PURPOSE:To recognize a focusing state accurately by superimposing a video image of an object and a distance up to the object when focused by an automatic focus means and displaying the superimposed image onto a view finder. CONSTITUTION:A focus voltage generating circuit 10 extracts a high frequency component in a frame 25 from a video signal (a) of a screen 22 to generate a focus voltage (b) corresponding to the focusing and applies the voltage to a motor control circuit 16 via a switch 15. The motor control circuit 16 decides increase/decrease of the focus voltage to control a motor 17 so as to maximize the focus voltage. Then a position of a front lens 2 on an optical axis moved by the motor 17 is detected by a lens position detection means 6 and a distance display signal generating circuit 18 generates a distance display signal based on a detection signal (d) and a distance display 23 and a distance index 24 up to an object are displayed on a view finder 9. Thus, the focusing state in the automatic focus mode is accurately recognized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display device for a video camera that displays captured images on an electronic viewfinder.

(Prior Art) In recent years, video cameras have been equipped with autofocus devices that automatically focus the zoom lens.
In addition to this autofocus (AF) device, a manually operated focusing mechanism is provided. Generally, a manual focusing mechanism has a distance indicator on a distance ring that can be manually rotated with respect to the lens barrel, and moves the objective lens, the front lens, which is linked to the distance ring, in the optical axis direction. It is configured to perform focusing.

On the other hand, for AFF1a, for example, Japanese Patent Publication No. 63-3231
4 Go Gazette and National Technical Report, Volume 31,
No. 6, December 1985, page 66 (National
Technical Report Vol. 31
No. 5 Dec, 1985)
A TL video system is known. AFF of this method
1a. Extract high-frequency components from the video signal to generate a focal voltage corresponding to the degree of focus, and feed it back to the focus lens so that this focal voltage is maximized, so that the image is the sharpest. is configured to control the focus morph.

In addition, in Japanese Patent Publication No. 63-32314, automatic focusing (
AF) means and manual focusing means, and when the operator selects AF mode, superimposes a black and white image of the field of view with a focusing area and displays it on an electronic viewfinder,
When manual focusing means is selected, a video camera is disclosed that displays only an image of the field of view, and therefore, usability or operability can be improved.

[Problem to be solved by the invention]

However, with the conventional video camera disclosed in Japanese Patent Publication No. 63-32314, when the conditions of each subject are different, such as when there are multiple subjects in front and behind, the operator only needs to see the black and white image displayed on the electronic viewfinder. However, there is a problem in that it is not possible to recognize whether or not the camera is actually in focus.

This tendency is especially strong when the zoom magnification is small (or the depth of field is deep, such as when the aperture is large).
When the operator selects the AF mode, the operator can recognize whether or not the focus is roughly in focus using the distance indicator on the distance ring, but unlike still cameras, the operator can recognize this using the distance indicator on the distance ring. This is not practical in the case of a video camera in which the operator himself continuously takes pictures while looking at the electronic viewfinder.

SUMMARY OF THE INVENTION In view of the above conventional problems, it is an object of the present invention to provide a display device for a video camera that allows an operator to accurately recognize the focusing state in autofocus mode.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a first detection means for detecting the position of a focusing lens when focused by an autofocus means, and a position detected by the first detection means to detect a subject. 2nd to detect distance
a detection means, a generation means for generating a signal for displaying the distance detected by the second detection means, and a view for displaying an image in which the video signal and the signal for displaying the distance generated by the generation means are superimposed. It is characterized by being equipped with a finder.

[For production]

With the above configuration, the distance to the subject and the image of the subject when focused by the autofocus means are superimposed and displayed on the viewfinder, so that the operator can continue while looking at the viewfinder in the autofocus mode. It is possible to accurately recognize the focusing state when taking pictures.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a display device for a video camera according to the present invention, and FIG. 2(a).

(b) is an explanatory diagram showing the display screen of the viewfinder of FIG. 1, respectively.

In FIG. 1, the zoom lens 1a of this embodiment is a lens of a type in which focusing is performed using an objective lens, so-called a front lens 2. As shown in FIG. The zoom lens 1a is roughly composed of a front lens 2, a variator lens 3 for changing the focal length of the zoom lens 1a to change the zoom magnification, an aperture mechanism 4, and an imaging lens called a rear lens 5. The position of the front lens 2 on the optical axis is controlled by a focusing mode 1717 and detected by the lens position detection means 6.

Although not shown, the front lens 2, the variator lens 3, and the rear lens 5 are generally each composed of a plurality of lenses. In addition, a distance ring is provided that can be rotated in conjunction with the movement of the front lens 2, and in manual focus mode, focusing can be performed by moving the front lens 2 by manually operating the distance ring. can. Furthermore, the variator lens 3 is movable along the optical axis in a mode not shown, and zooming is possible.

The image of the subject is transmitted to the CCD via this zoom lens 1a.
The signal is photoelectrically converted by an image sensor 7 such as a charge-coupled device (charge-coupled device), and converted into a video signal a by a two-color camera process 8. Next, the focus voltage generation circuit 10 extracts high frequency components from the video signal a, and generates a focus voltage corresponding to the degree of focus.

The focus voltage generation circuit 10 includes a high-pass filter 11 that extracts a high-frequency component from the video signal a converted by the camera process circuit 8, and a high-pass filter 11 that extracts a high-frequency component from the video signal a that has been extracted by the high-pass filter 11. A gate circuit 12 extracts a video signal in a predetermined rectangular or circular area, a detection circuit 13 converts the video signal of the high frequency component in the predetermined area extracted by the gate circuit 12 into an absolute, and the output signal of the detection circuit 13 is It is composed of an integrating circuit 14 that generates a focal voltage by integrating one field.

Here, in the focusing area for the gate circuit 12, a frame is generated by the frame regulating section 20, and then a frame signal generation circuit 19 generates a video signal of the frame.

The output focus voltage of the focus voltage generation circuit 10 is input to the mode control circuit 16 via the switch 15 for the operator to select autofocus mode or manual focus mode, and the motor control circuit 16 is inputted to the mode control circuit 16 when the switch 15 is turned on. In other words, the autofocus motor determines whether the focus voltage is increasing or decreasing, and the motor 17 is controlled so that the focus voltage is maximized, that is, the image is sharpest.

The position of the front lens 2, which is moved by the motor 17, on the optical axis is detected by the lens position detection means 6, and the distance display signal generation circuit 18 generates a distance display signal from this detection signal d.

A video signal a generated by the camera process circuit 8;
The video signal of the focusing frame generated by the frame signal generation circuit 19 and the distance display signal generated by the distance display signal generation circuit 18 are added by an adder 21, and the resulting image is displayed by the viewfinder 9. .

Next, the operation of the above embodiment will be explained. FIG. 2(a) shows a screen 22 displayed by the viewfinder 9, and this screen 22 shows a flower 22a photographed at a relatively short distance by the zoom lens 1a and the camera process circuit 8, and a flower 22a photographed at a relatively medium distance. A tree 22b and a relatively distant mountain 22c are displayed.

In this case, since the flower 22a, which is relatively close, is displayed within the frame 25 at the center of the screen 22, the operator desires to focus on the flower 22a.

In such a photographing state, the focus voltage generation circuit 10 extracts the high frequency component within the frame 25 from the video signal a of the screen 22, generates a focus voltage of an amount corresponding to the degree of focus, and The focus voltage S is applied to the motor control circuit 16 via the switch 15 when the autofocus morph is set.

The motor control circuit 16 determines whether the focus voltage is increased or decreased, and controls the motor 17 so that the focus voltage is maximized, that is, the image is sharpest. This motor 1
The position of the front lens 2 on the optical axis, which is moved by the lens 7, is detected by the lens position detection means 6, and the distance display signal generation circuit 18 generates a distance display signal from this detection signal d, as shown in FIG. 2(a). As shown, a predetermined distance display 23 from close range (1 m) to infinity ((X)) and a distance index 24 to the subject, that is, a flower 22a, are displayed on the viewfinder 9.
will be displayed.

Therefore, according to the above-mentioned embodiment, while looking at the viewfinder 9, the operator continues to see an image of the flower 22a at a relatively short distance, the tree 22b at a relatively medium distance, and the mountain 22c at a relatively long distance. When photographing and focusing on the flower 22a at the center of the screen, the flower 22a within the frame 25 displayed by the viewfinder 9 and the predetermined distance display 2
3 and the distance index 24 to the flower 22a, it can be recognized whether or not the subject is actually in focus.

In the above embodiment, the predetermined distance display 23 and distance index 24 as shown in FIG. 2(a) are displayed on the viewfinder 9, but as shown in FIG. A number 23a representing the distance may be displayed.

FIG. 3 is a block diagram showing a second embodiment of the display device for a video camera according to the present invention, and FIG. 4 is a graph showing the relationship between the zoom magnification and the position of the imaging lens in the display device of FIG. , the same reference numerals are given to the same components and parts as in the first embodiment.

In FIG. 3, the zoom lens 1b of this embodiment is a lens of a type in which focusing is performed by an imaging lens, so-called a rear lens 5. The zoom lens 1b is roughly constituted by a fixed front lens 2, a variator lens 3 for changing its own focal length to change the zoom magnification, and the rear lens 5. The position of the lens is controlled by the focus motor 17 and detected by the lens position detection means 6.

Further, the position of the variator lens 3 on the optical axis is controlled by a zoom motor 28 and detected by a focal length detection means 26. Note that the zoom motor 28 rotates in accordance with the operation of the zoom operation block 29.

Here, in the zoom lens lb that uses the rear lens 5 to perform focusing, as shown in FIG. Therefore, if the distance display 23 from close range (1 m) to infinity (■) is fixed and displayed as shown in FIG. 2(a) of the first embodiment, a problem will occur.

Therefore, in this embodiment, the position on the optical axis of the variator lens 3, that is, the focal length, is detected by the focal length detection means 26, and the arithmetic circuit 27 detects this focal length and the lens position based on the information shown in FIG. The distance to the object is compared with the position of the rear lens 5 on the optical axis detected by the detection means 6.

It should be noted that the configurations and operations of other constituent members are the same as in the first embodiment, so their explanations will be omitted.

Therefore, the distance display signal generation circuit 18 generates a distance display signal from this distance, and as shown in FIG. The distance index 24 and Figure 2 (b)
A number 23a representing the distance to the subject is displayed on the viewfinder 9 as shown in FIG.

Similarly, in this embodiment, while looking at the viewfinder 9, the operator continuously captures images of a flower 22a at a relatively close distance, a tree 22b at a relatively medium distance, and a mountain 22c at a relatively long distance. At the same time, when focusing on the flower 22a at the center of the screen, the flower 22a within the frame 25 displayed by the viewfinder 9 and the predetermined distance display 23
It is possible to determine whether or not the subject is actually in focus using the distance index 24 to the subject and the number 23a indicating the distance to the subject.

Additionally, lens position detection means 6 for detecting the distance to the subject
The focal length detection means 26 is manufactured by National Tech.
nical Report Vol. 31 No.
, 5 Dec, 1985, and is commonly used in TTL video type AF devices, and therefore, this embodiment can be configured by simply adding the distance display signal generation circuit 18, resulting in an inexpensive configuration. can do.

Further, the focus motor 17 for controlling the front lens 2 and the rear lens 5 to perform the AF operation may be a pulse signal driven motor such as a step motor. Since the distance can be detected by counting pulses, detection means such as a potentiometer or a rotary encoder are not required, and therefore it can be constructed at low cost.

[Effects of the Invention] As explained above, according to the inventions recited in claims 1 to 6, the distance to the subject and the image of the subject when focused by the autofocus means are displayed in a superimposed manner on the viewfinder. When an operator continuously takes pictures while looking at the viewfinder during autofocus, the focusing state can be accurately recognized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a display device for a video camera according to the present invention, FIG. 2 is an explanatory diagram showing a display screen of the viewfinder of FIG. 1, and FIG. 3 is a block diagram showing an embodiment of a display device for a video camera according to the present invention. A block diagram showing a second embodiment of the display device of
FIG. 4 is a graph showing the relationship between the zoom magnification and the position of the imaging lens in the display device of FIG. 3. la, lb...Zoom lens, 2...
...Objective (front lens) lens, 3...
・Variator lens, 5... Imaging (rear lens) lens, 6... Position detection means, 7...
......Image sensor, 8...Camera process circuit, 9...Viewfinder, 10...Focus voltage generation Circuit, 16...
...Motor control circuit, 17...
- Focus motor, 18... Distance display signal generation circuit, 19... Frame signal generation circuit, 20... Frame control section, 21・・・・・・
... Addition circuit, 27 ... Arithmetic circuit, 2
8...Zoom motor. Figure 1 Figure 2 (a)
(b) Fig. 4 (Wida) (Tele) Zoom magnification (focal length) Fig. 3

Claims (1)

[Scope of Claims] 1. Autofocus means for extracting a high frequency component from a video signal to generate a focus voltage according to the degree of focus, and driving a focusing lens so that the focus voltage is maximized; a first detection means for detecting the position of the focusing lens when focused by the focusing means; a second detection means for detecting the distance to the subject based on the position detected by the first detection means; a generation means for generating a signal for displaying the distance detected by the second detection means; a viewfinder for displaying an image in which the video signal and the signal for displaying the distance generated by the generation means are superimposed; A video camera display device comprising: 2. The display device for a video camera according to claim 1, wherein the focusing lens is an objective lens. 3. Autofocus means for extracting a high frequency component from the video signal to generate a focus voltage according to the degree of focus, and driving a focusing lens so that the focus voltage is maximized; a zoom lens for making the zoom magnification variable; and a third detection means for detecting a focal length according to the position of the zoom lens. and a calculation means for calculating the distance to the subject based on the position and focal length respectively detected by the first and third detection means, and a video signal and a signal for displaying the distance calculated by the calculation means are superimposed. A display device for a video camera, comprising: a viewfinder for displaying a captured image; and a display device for a video camera. 4. The display device for a video camera according to claim 1, wherein the focusing lens is an imaging lens. 5. Claim 1, wherein the autofocus means extracts high frequency components in a predetermined area from the video signal.
and 3. The video camera display device according to any one of 3. 6. The autofocus means includes means for generating a display signal of a frame indicating an area for extracting high frequency components from the video signal, and the viewfinder displays an image in which the video signal and the display signal of this frame are superimposed. A display device for a video camera according to any one of claims 1, 3 and 5.