JPH11177875A - Electronic camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy-to-use electronic camera with a view finder capable of focusing on a desired object at a desired viewing angle by displaying a distance finding frame at an electronic view finder and arbitrarily setting them by a photographer. SOLUTION: This electronic camera for judging focusing by the contrast of video information mutually among respective picture elements converged by an image pickup element 2 and performing automatic focusing is provided with the view finder 7 for displaying images picked up by the image pickup element and a distance finding frame display means for displaying the distance finding frame 8 for judging focusing at the view finder. At the time of displaying the distance finding frame 8, the automatic focusing is performed based on the video information inside the distance finding frame 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for recording and reproducing video information, and more particularly, to an autofocus system mounted on an electronic camera.

[0002]

2. Description of the Related Art In recent years, an electronic camera which captures an image by an image pickup device using a photoelectric conversion called CCD or MOS instead of a film has appeared in place of a camera which records image information on a normal silver halide film. ing. Many electronic cameras are equipped with a viewfinder, in addition to a normal viewfinder, which is capable of displaying an image captured by an image sensor on a liquid crystal monitor or the like so that an image to be photographed can be confirmed with certainty.

On the other hand, the AF method generally used in such an electronic camera is an automatic focusing detection method based on a so-called hill-climbing method, which extracts a predetermined frequency component from an image signal obtained from an image pickup device (CCD or the like). The focus adjustment is performed by moving an imaging optical system (a lens group or the like) to a position where the output amplitude of the extracted frequency component is maximized. An automatic focus detection method for a TV camera to which this method is applied is described in, for example, NHK Technical Report. Showa 40. Seventeenth
Vol. 86, No. 86 (P21-P37).

A specific example will be described with reference to FIG. The lens position of the photographing optical system is A (the position where the output amplitude corresponds to a)
At the first position, a subject image is formed on an image sensor, photoelectrically converted and amplified to a predetermined size, a predetermined frequency component is extracted by a filter, and the output is detected and peak-held. This hold amplitude value is assumed to be a. Next, as soon as the subject image is photoelectrically converted, the lens position of the photographing optical system moves from A to B, and the subject image is formed on the image sensor in the next field time, photoelectrically converted, and amplified to a predetermined size. After extracting the predetermined frequency component with a filter,
This output is peak-held after detection. This hold amplitude value is assumed to be b. Then, the a-amplitude value is compared with the b-amplitude value, and assuming that the b-amplitude value is large (assumed for explanation), the b-value remains as the sample-and-hold value. As a result, the lens moves to the next C position without changing the traveling direction. Similarly, at the next C position,
In the next field time, a subject image is formed on an image sensor, photoelectrically converted and amplified to a predetermined size, and then a predetermined frequency component is extracted by a filter. The output is detected and peak-held. This hold amplitude value is assumed to be c.
Then, the b amplitude value and the c amplitude value are compared, and assuming that the c amplitude value is large (assumed for explanation), the c value remains as the sample hold value. As a result, the lens proceeds to the next step without changing the traveling direction. In the same manner, the photographing optical system lens is successively moved at one-field time intervals, and the magnitude of the detection value amplitude of the frequency component is compared. This is the method that was adopted.

In the auto-focusing method based on the contrast information of the video information set as described above, the contrast in the central portion is usually detected on the assumption that the central portion of the photographing range is the subject desired by the photographer. . or,
The detection range usually called a distance measurement frame is displayed in the viewfinder, and the photographer puts a desired subject in the distance measurement frame to avoid the problem of defocus.

[0006]

However, in the prior art, when the distance measurement frame is fixed with respect to the photographing range and it is desired to focus on a desired subject at a desired angle of view,
It might not be possible.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems of the prior art, and to determine focus by the contrast of video information between pixels focused on an image sensor. An electronic camera that performs auto-focusing, including a viewfinder that displays an image captured by the image sensor, and a ranging frame display unit that displays a ranging frame for performing focus determination on the viewfinder.
When the distance measurement frame is displayed, autofocusing can be performed based on video information in the distance measurement frame.

[0008] Thus, by displaying the distance measurement frames on the viewfinder and arbitrarily setting them, it becomes possible to focus on a desired subject at a desired angle of view.

[0009]

FIG. 1 is a schematic diagram showing the configuration of an electronic camera according to an embodiment of the present invention. FIG. 2 is a flowchart of the embodiment of the present invention. In the figure, the same parts are denoted by the same reference numerals, and in the figure, 1 is a lens system, 2 is an image sensor such as a CCD, 3
Is a stepping motor for moving and retracting the mechanism on which the image pickup device 2 is mounted with respect to the lens system 1;
2, a signal processing unit for processing the video information taken in from a predetermined signal into a predetermined signal; 5, a processed signal;
Is a control unit for controlling the image display on the viewfinder 7 on the screen, and 6 is an operation unit thereof.

Next, the operation in such a configuration will be described. FIG. 1 is a schematic view showing the configuration of an embodiment of the present invention. This will be described with reference to the flowchart of FIG. 2. In FIG. 1). The captured image signal is converted into a video signal, and an image is displayed on the viewfinder 7 with the already set distance measurement frame superimposed (step 2). Next, the captured video information is A / D-converted by the signal processing unit 4, and the amplitude value of a predetermined frequency component, that is, the contrast detection signal is compared with the previous contrast detection signal to determine the focus, and the lens control accordingly. The data is passed to the control unit 5 (Step 3). According to the lens control data passed to the control unit 5,
The control unit 5 sends a control signal to the stepping motor 3 to change the position of the lens system 1. In the lens extension, if the signal passed to the control unit 5 is an out-of-focus signal, the process proceeds to the next step 5, and if the signal is in focus, the lens returns to the previous lens position. (Step 4). Next, a distance measurement frame is set. If the setting of the ranging frame is changed by the photographer via the operation unit 6, the setting is updated to a new ranging frame setting. If there is no setting change instruction from the photographer, the setting is not updated (step 5). This series of operations is repeated in a loop. When the release operation is performed by the photographer, the focus is locked (step 6), and the photograph is taken (step 8). The above is a series of autofocus operations in the present invention.

[0011]

As described above, according to the configuration and method of the present invention, the distance measurement frames are displayed on the electronic viewfinder, and these are set arbitrarily by the photographer, so that a desired angle of view and a desired angle of view can be obtained. It is possible to focus on the subject,
An electronic camera with a viewfinder that is easy to use can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic external view showing an embodiment of the present invention.

FIG. 2 is a flowchart showing an embodiment of the present invention.

FIG. 3 is a diagram illustrating the principle of autofocus.

[Explanation of symbols]

 1 lens system 2 CCD (imaging device) 3 stepping motor 4 signal processing unit 5 control unit 6 operation unit 7 viewfinder 8 ranging frame

Claims (1)

[Claims] 1. An electronic camera for performing auto-focusing by determining focus based on the contrast of image information between pixels condensed on an image sensor, comprising: a viewfinder for displaying an image captured by the image sensor; And a distance measurement frame display means for displaying a distance measurement frame for performing focus determination on the viewfinder. When the distance measurement frame is displayed, auto focus is performed based on image information in the distance measurement frame. An electronic camera, characterized in that the electronic camera is configured to perform the operation.