JPH0317432B2 - - Google Patents

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 small black and white CRTs 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 to be Solved by the Invention Conventional video cameras do not have a function that clearly informs the photographer that the focus has been accurately achieved, and this causes the problem of constant anxiety for the photographer. Ta.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic viewfinder that makes it easy to know whether focusing has been achieved accurately.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic viewfinder that makes it easy to know whether focusing has been achieved accurately.

Means for solving the problem The edge detection circuit 2 is a means for detecting the edge part of the video camera output, the base clip circuit 8 is a means for clipping the output of the edge detection circuit 2, and the gate circuit 9 is a means for clipping the output of the edge detection circuit 2. The adder 10 is a means for intermittently taking out the output of the gate circuit 9 and the output of the video camera.

Function: Detects the edge of the video camera output, clips the amplitude above a certain level from this edge detection signal, and extracts this clipped signal intermittently, for example, at a 4-field period, and combines this extracted signal with the video camera output. are 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 that enters terminal 1 is the output of a video camera, and has the waveform shown in FIG. 2A (for example, only one field period is shown here). is steep. signal a
is delayed by the 1H delay circuit 3 of the edge detection circuit 2 to become the signal b (FIG. 2B), further delayed by the 1H delay circuit 4 to become the signal c (FIG. 2C), and then sent to the adder 5. and is added to signal a.

The output of the adder 5 is attenuated in level by a 1/2 attenuator 6 to produce a signal d (D in the same figure), which is subtracted from the signal b in a subtracter 7 to produce an edge detection signal e (E in the same figure).
It is said that 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 Figure E is continuously extracted according to the video camera output. be done.

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 by the base clip circuit 8 at a clip level (broken line in E in FIG. 2) to become a signal f (F in the same figure), which 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 f (actually, a waveform as shown in FIG. 2 F) is continuously generated in response to the video camera output. (signals) are taken out intermittently every four fields.

The output of gate circuit 9 is added to signal b in adder 10, taken out from output terminal 11, and supplied to, for example, a small CRT. As a result, when the focus is accurate, the edge portion of the screen flashes at a four-field cycle, allowing the photographer to confirm that the focus is accurate.

Note that the base clip circuit 8 may have the configuration shown in FIG. A limiter 12 limits the amplitude of the signal e by a clip level, and a subtracter 13 subtracts it from the signal e to obtain a signal f.

Effects of the Invention The view finder according to the present invention includes an edge detection circuit that detects an edge portion of a video camera output;
A clip circuit extracts a portion having an amplitude above a certain level from the output of the edge detection circuit, a gate circuit extracts the output of the clip circuit intermittently at a predetermined period, and adds the output of the gate circuit and the video camera output. Since the camera is equipped with a circuit to supply the picture tube, when the focus is accurately achieved, the edge part of the image on the viewfinder flashes at a predetermined period, making it easy for the photographer to know that the focus has been accurately achieved. It has features such as being able to be confirmed.

[Brief explanation of the drawing]

1 and 2 are block diagrams and 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 FIG. 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] 1 An edge detection circuit that detects the edge portion of the video camera output, a clip circuit that extracts a portion with an amplitude above a certain level from the output of the edge detection circuit, and a gate that extracts the output of the clip circuit intermittently at a predetermined period. An electronic viewfinder comprising: a circuit; and a circuit for adding the output of the gate circuit and the output of the video camera and supplying the sum to a picture tube.