JPS6166480A - Electronic viewfinder - Google Patents

Abstract

PURPOSE:To enable to know that focusing is made exactly by detecting edge of output of a video camera clipping above a level from the edge detection signal and adding to output of the video camera. CONSTITUTION:Video camera output (a) entering a terminal 1 is delayed by a 1H delay circuit 3 of an edge detecting circuit 2 and made to a signal (b), and further delayed by a 1H delay circuit 4 and made to a signal (c). The signal (c) is added to the signal (a) by an adder 5 and made to a signal (d) through a 1/2 attenuator 6, and applied to a subtracter 7. In the subtracter 7, the signal (d) is subtracted from the signal (b), and an edge detection signal (e) is outputted. This edge detection signal (e) is clipped by a base clipping circuit 8 and made to a signal (f), and taken out intermittently every 4 field periods through a gate circuit 9. This output is added to the signal (b) by an adder 10 and supplied to an output terminal 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electronic viewfinder, and more particularly, to an electronic viewfinder for monitoring images captured by a video camera.

2. Description of the Related Art Electronic viewfinders using a small monochrome CR are widely used to monitor captured images in video cameras. However, it is quite difficult to focus on such a video camera, and the first thing that the photographer worries about is whether or not the focus is accurate. In order to eliminate this anxiety, it is necessary to extract a signal indicating when the focus has been accurately achieved, and to notify the photographer in an easy-to-understand manner using this signal.

Problems that the invention aims to solve Conventional video cameras do not have a function that clearly informs the person taking the image that the focus has been accurately achieved, and this has caused the problem that the person taking the image is always anxious. .

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic viewfinder that allows easy confirmation of accurate focusing.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic viewfinder that allows easy confirmation of accurate focusing.

Means for Solving the Problem The edge detection circuit 2 is a means for detecting the edge part of the video camera output, and the base clip circuit 8 is the edge detection circuit 2.
The gate circuit 9 is a means for intermittently taking out the output of the base clip circuit 8, and the #JO calculator 10 is a means for adding the output of the gate circuit 9 and the video camera output.

Detect the edges of the video camera output, clip the amplitude above a certain level from this edge detection signal, extract this clipped signal intermittently, for example at a 4-field period, and combine this extracted signal with the video camera. The output is added and supplied to the CRT.

Embodiment FIG. 1 shows a block system diagram of an embodiment of the electronic viewfinder of the present invention. The signal a input to terminal 1 is the video camera output, and has the waveform shown in FIG. 2 (A), for example (here, for example, only one field period is shown). and the falling edge is steep. Signal a is one day delay circuit 3 of edge detection circuit 2
The signal is delayed by the circuit 4 to become the signal b (FIG. 2 (B)), and further delayed by the delay circuit 4 for one day to become the signal C (FIG. 2 (C)), which is added to the signal a by the adder 5. be done.

The output of the adder 5 is level-attenuated by a 1/2 attenuator 6 to form a signal d ((D) in the same figure), which is subtracted from the signal by a subtracter 7 to produce an edge detection signal e ((D) in the same figure). (E)). The more accurately the signal e is focused (the more spatially high-frequency components it has), the larger its peak-to-peak value becomes, and the waveform shown in the same figure (E) appears continuously in response to the video camera output. is taken out.

This edge detection circuit 2 is a conventionally known circuit, and in this circuit example, vertical edges are detected. By setting the delay amounts of the delay circuits 3 and 4 to appropriate values, edges in a desired direction can be detected.

The signal e is clipped to the clip level (
The signal is clipped by the dotted line in Fig. 2 (E)
(F)) in the same figure, and is supplied to the gate circuit 9. The gate circuit 9 is repeatedly opened and closed by 4-field pulses having a pulse width of 4-field periods, and as a result,
The signal r (actually a signal in which the waveform shown in FIG. 2 (F>) is successive in accordance with the video camera output) is intermittently taken out every four fields.

The outputs of the gate circuit 9 are added together by an adder 10, and are taken out from an output terminal 11 and supplied to, for example, a small CRT. As a result, when the focus is accurately set, the edge portion of the screen flashes at a four-field cycle, allowing the person who is flailing to confirm that the focus is accurately set.

Note that the base clip circuit 8 may have the configuration shown in FIG. 3. The amplitude of the signal e is limited by a clip level in a limiter 12, and is subtracted from the signal @e in a subtracter 13 to obtain a signal ``.

Effects of the Invention The viewfinder according to the present invention includes an edge detection circuit that detects an edge portion of a video camera output, a clip circuit that extracts a portion having an amplitude above a certain level from the output of the edge detection circuit, and an output of the clip circuit that detects an edge portion of the video camera output. A gate circuit that intermittently extracts data at a predetermined period, and a circuit that adds the output of the gate circuit and the output of the video camera and supplies it to the picture tube are installed. The edge part flashes at a predetermined period,
This has the advantage that the photographer can easily confirm that the focus has been accurately achieved.

[Brief explanation of drawings]

1 and 2 are block diagrams and other signal waveform diagrams for explaining the operation of one embodiment of the electronic viewfinder of the present invention, respectively, and FIG. 3 is a circuit diagram of another embodiment of the clip circuit shown in the first diagram. . DESCRIPTION OF SYMBOLS 1... Video camera output input terminal, 2... Edge detection circuit, 8... Base clip circuit, 9... Gate circuit, 10... Adder, 11... Output terminal.

Claims (1)

[Claims] An edge detection circuit that detects an edge portion of a video camera output, a clip circuit that extracts a portion having an amplitude above a certain level from the output of the edge detection circuit, and a gate circuit that extracts the output of the clip circuit intermittently at a predetermined period. and a circuit that adds the output of the gate circuit and the output of the video camera and supplies the sum to a picture tube.