JPS6312617Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic viewfinder for a video camera.

In a video camera that captures a subject and obtains a television image, an optical viewfinder that obtains a purely optical viewfinder image is used as a viewfinder device for checking the field of view of the imaging unit and adjusting and checking the focus of the imaging optical system. and electronic finders, which mainly obtain finder images electronically. The former, that is, the optical finder, employs a so-called single-lens reflex system, for example, and guides the light beam from the imaging optical system of the imaging section to the finder optical system to form a finder image, while the latter, that is, the electronic finder, uses the video output of the imaging section. The image is displayed on a small picture tube for the viewfinder.

Electronic viewfinders directly use the video output from the imaging unit to form a viewfinder image, so they have the advantage that the captured image can be viewed as is on the viewfinder, and there is little room for parallax to occur in time or space. In addition, since the viewfinder is configured independently of the optical system of the imaging section,
There is also the advantage that the function of the viewfinder is not affected at all even if the imaging optical system is replaced, and a common viewfinder can be used for any imaging optical system.
Detachable types that are constructed separately from the video camera body and are attached to the video camera body from the outside are widely used.

FIG. 1 shows an example of the basic configuration of this type of electronic finder. In Fig. 1, the finer cylinder 1
A viewfinder picture tube 2 on which an image based on a video signal from an imaging section (not shown) is displayed is disposed inside the picture tube 2, and an optical system for enlarging the image on the picture tube display screen 2a is arranged in front of the picture tube 2. A magnifying glass 3 is provided. That is, picture tube 2
The viewfinder image displayed is magnified by a magnifying glass 3 and guided to the eye E of the viewfinder viewer.

By the way, in such an electronic finder, the optical system used for the magnifying glass 3 is a relatively simple lens such as a single lens or a laminated lens of about two lenses for achromatization (removal of chromatic aberration). When adopted, if the focal length is shortened in order to increase the magnification, pincushion distortion appears in the magnifying glass 3, for example. In other words, for example, when an object with a grid pattern as shown in FIG. 2 is imaged, the screen of the picture tube 2 will display a grid pattern similar to that shown in FIG. becomes a distorted image as shown in Figure 3. While the magnitude of distortion is generally proportional to the cube of the angle of incidence, shortening the focal length of the magnifying glass 3 means increasing the angle of incidence of the magnifying glass 3, which significantly increases the distortion. In general, distortion is ±
It is said that the distortion becomes noticeable to the observer when it exceeds 5%, that is, the range of +5% to -5% (+ distortion is called pincushion-shaped distortion, and - distortion is called barrel-shaped distortion).

Furthermore, with the magnifying glass 3 having such a simple lens configuration of one or two lenses, distortion of the viewfinder image cannot be optically removed and the distortion increases, so it is necessary to shorten the focal length of the magnifying glass 3. I couldn't do it. As a result, the distance between the viewfinder picture tube 2 and the magnifying glass 3 inevitably becomes long, making it impossible to make the viewfinder compact, and since the viewfinder magnification is inversely proportional to the focal length of the magnifier 3, it is necessary to increase the viewfinder magnification. I had a problem that I couldn't do it.

On the other hand, if the configuration of the magnifying glass 3 is made complicated in order to reduce the distortion of the viewfinder image, the magnifying glass 3 will no longer be compact and the configuration will not be simple, resulting in the problem that the magnifying glass 3 will become larger and the cost will increase. arise.

By the way, the deflection distortion caused by the cathode ray tube and the distortion aberration caused by the lens system, which occur when the image on the display screen of the cathode ray tube is enlarged and projected using a lens system, can be corrected by the correction circuit of the X-axis and Y-axis deflection amplifiers of the cathode ray tube. A lens distortion aberration correction circuit configured to perform electrical correction is disclosed in Japanese Patent Publication No. 55-13036.

However, this lens distortion aberration correction circuit only discloses a technique for simply correcting the lens distortion aberration that becomes a problem when an image on a display surface is projected through a lens system as described above, and the present invention is directed to a video camera. The problems unique to camera electronic viewfinders have yet to be solved.

That is, even if the lens distortion aberration could be corrected by the correction circuit, as will be explained in detail later, the frame of the viewfinder that limits the range of the displayed image cannot be corrected at all. The video camera's electronic viewfinder allows you to adjust the focus of the imaging optical system.
It is essential to have a function that contributes to confirmation as well as a function that contributes to confirmation of the imaging field of the imaging unit. Therefore, in the above-mentioned conventional lens distortion aberration correction circuit, there is a risk that a part of the imaging field of the imaging unit will be lost, and even if it is configured so that it will not be lost,
This makes it extremely difficult for the viewfinder observer to confirm the imaging field of view, and the imaging unit cannot sufficiently perform its function of confirming the imaging field of view.

The present invention was developed in view of these circumstances, and even when using a high-magnification magnifying glass with an inexpensive and simple configuration, the captured image and the range of the captured image caused by the distortion of the magnifying glass can be reduced. To provide an electronic viewfinder for a video camera in which there is no distortion in a limiting frame, or even if there is, the distortion can be reduced or eliminated to an unnoticeable degree, and as a result, compactness can be realized rationally. The purpose is

That is, in order to achieve the above-mentioned object, the present invention includes a picture tube, a magnifying glass for enlarging the displayed image of the picture tube, and a video signal obtained by an imaging section to be applied to the picture tube for display. In the electronic viewfinder for a video camera, the display circuit is provided with a distortion generating circuit that electrically generates distortion that substantially cancels out the effect of distortion generated by the magnifying glass, and The shape of the frame that limits the range of the displayed image is shaped in advance to have a distortion that almost cancels out the distortion generated by the magnifying glass, and the frame is arranged on the display surface side of the picture tube. This is a characteristic feature.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 4, the picture tube 2 for viewfinder
A synchronizing signal D and a video signal V are supplied from an image pickup section (not shown) to a display circuit 4 for displaying video. The imaging section is composed of an imaging tube or a solid-state imaging device, its control circuit, and the like. The synchronizing signal D given from this imaging section is input to the deflection circuit 41 in the display circuit 4 and converted into sweep signals for horizontal and vertical deflection. By the way, this deflection circuit 41 includes a pincushion distortion correction circuit which is made up of a distortion generating circuit that generates distortion that can almost cancel out the pincushion distortion generated by the magnifying glass 3, that is, a barrel-shaped distortion that is almost opposite to the pincushion distortion. 42 is attached. This pincushion distortion correction circuit 42 may be substantially the same as that used to correct pincushion distortion that occurs in conventional wide-angle picture tubes,
For the vertical direction, a parabolic wave (so-called parabolic wave) proportional to the vertical deflection angle and synchronized with horizontal scanning is generated and superimposed on the vertical deflection sweep wave generated by the deflection circuit 41, and for the horizontal direction, the wave is generated by the deflection circuit 4.
The horizontal deflection sweep wave generated in step 1 is amplitude-modulated with a parabolic wave synchronized with vertical scanning. Further, the video signal V given from the imaging section is amplified by a video amplification circuit 43 in the display circuit 4 and applied to the picture tube 2 as a brightness modulation signal.

In such a configuration, the image displayed on the viewfinder picture tube 2 is not the original photographed image as shown in FIG. This is an image with type distortion added. Therefore, by observing this through the magnifying glass 3 having pincushion distortion, an image without distortion or with inconspicuous distortion as shown in FIG. 5 can be observed.

In this way, even if the magnifying glass 3 causes distortion exceeding ±5%, it can be electrically corrected so that the distortion is zero or sufficiently small in the viewfinder image.

Further, if a frame 5 (see FIG. 4) that limits the range of the displayed image is provided on the front side of the display surface 2a of the picture tube 2, and this frame 5 is rectangular as shown in FIG. The magnified image by the magnifying glass 3 is distorted into a pincushion shape as shown in FIG. 5 due to the distortion of the magnifying glass 3. Therefore, in such a case, the shape of the frame 5 is made in advance to have a barrel-shaped distortion that almost cancels out the distortion caused by the magnifying glass 3, as shown in FIG. 7, so that the shape shown in FIG. Like frame 5
A viewfinder image with little or no noticeable distortion can be observed through the magnifying glass 3.

In this way, since the distortion caused by the magnifying glass 3 can be effectively corrected, the lenses 1 to 2 can be used as the magnifying glass 3.
Using a simple lens configuration of about 1 lens, with a short focal length and high magnification, there is no distortion problem, making it easy to simplify and downsize the device.
Moreover, it can be realized at low cost.

Note that the present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be made without changing the gist.

For example, in the above embodiment, a case where pincushion-shaped distortion occurs due to a magnifying glass is explained, but if barrel-shaped distortion occurs due to a magnifying glass, the pincushion-shaped distortion can be electrically corrected to correct it. It is sufficient to use a distortion generating circuit that generates the distortion. The distortion generation circuit in this case can also be configured in a similar way to the pincushion distortion correction circuit described above. Also,
The distortion generating circuit such as the pincushion distortion correction circuit may have any configuration as long as it has the same function.

As detailed above, according to the present invention, even if a high-magnification magnifying glass with an inexpensive and simple configuration is used, the captured image and the frame that limits the range of the captured image due to the distortion of the magnifying glass can be removed. An extremely lightweight and compact video camera electronic viewfinder that eliminates distortion or reduces or eliminates distortion to an unnoticeable degree, and eliminates the need for a complex, bulky, and heavy magnifying glass. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view schematically showing the structure of an electronic viewfinder, FIGS. 2 and 3 are diagrams for explaining the occurrence of distortion caused by a magnifying glass, and FIG. 4 is a diagram showing one example of the present invention. A schematic block diagram showing the configuration of an embodiment,
FIG. 5 is a diagram for explaining the effect of the same embodiment, and FIGS. 6 to 8 are diagrams for explaining the case where measures against distortion are further applied to the frame that limits the display image plane in the same embodiment. be. 2... Picture tube for viewfinder, 3... Magnifying glass, 4... Display circuit, 41... Deflection circuit, 42...
...pincushion correction circuit, 43...video amplification circuit, 5...
…frame.

Claims (1)

[Scope of utility model registration request] An electronic viewfinder for a video camera comprising a picture tube, a magnifying glass for enlarging a displayed image of the picture tube, and a display circuit for applying a video signal obtained by an imaging section to the picture tube for display, A distortion generating circuit is attached to the display circuit to electrically generate distortion that substantially cancels out the effect of distortion generated by the magnifying glass, and on the other hand, the shape of the frame that limits the range of the display image is The shape has a distortion that almost cancels out the distortion caused by the mirror,
An electronic viewfinder for a video camera, characterized in that the frame is disposed on the display surface side of the picture tube.