JPS6057778A - Television signal processing circuit - Google Patents

Abstract

PURPOSE:To obtain electrically a sharp picture by changing a band variable low pass filter with an output of a variable voltage generating circuit so as to control the frequency characteristic of a luminance signal or the luminance signal and a chrominance signal. CONSTITUTION:A timing signal from a stop/start signal generator 5 changing a state into the state between sharp and unsharp state changes an output voltage of the variable voltage generating circuit 6. An output of the circuit 6 changes the band of variable low pass filters 7, 8 and 9 through which the luminance signal 2 and color difference signals R-Y3 and B-Y4 of the chrominance signal are passed respectively. Then the frequency band of the filters 7, 8 and 9 is changed from the frequency band required for the picture to become in the sharp state to the frequency band required for the picture to become in a the unsharp state in response to the potential of the timing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to television signal processing that gives special effects to images by electrically processing the television signal to make the image completely clear or blurry. It relates to circuits and is used in television cameras, video tape recorders, etc.

Conventional configuration and its problems To make the image clear or blurry, we obtain a special effect that changes the image from blurred to clear at the start of shooting, and from clear to blurred at the end of shooting. was used for. This achieves the same effect as fade-in and fade-out used in the camera section.

Conventionally, the method of obtaining this special effect was to set the focal length of the lens away from the focal point and then bring it back to the focal point. In other words, the optical system created a state in which it was in focus and out of focus. This method has problems in that it takes time to change the focus from an unfocused state to a focused state, and it is difficult to change the focus continuously. Furthermore, since it uses an optical system, it has the disadvantage that it cannot be used with electrical signals recorded by a video cheap recorder or the like.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a television signal processing circuit capable of producing clear images and blurred images entirely electrically.

Structure of the Invention The television signal processing circuit of the present invention includes a variable voltage generation circuit that gradually changes the output voltage in one direction and the other direction in synchronization with a start timing signal and a stop timing signal, respectively. The present invention is characterized in that the frequency characteristics of the brightness signal or the brightness signal and chroma signal of the television signal are controlled by changing the band of the variable low-pass filter depending on the output voltage of the circuit.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows a block diagram of a television signal processing circuit according to an embodiment of the present invention. In FIG. 1, l is a television camera l ((, 2, 3 and 4 are an output terminal for a luminance signal obtained from the television camera section 1, an output terminal for a color difference signal RY of a chroma signal, and an output terminal for a chroma signal 5 is a start/stop signal generator that outputs stop and start timing signals that vary from clear to unclear and from unclear to clear; 6 is the timing signal; Variable voltage generator with variable output voltage, 7.8 and 9
are the luminance signal and the color difference signals RY and B of the chroma signal.
-YTh is a variable low-pass filter that passes each of the signals, and the band changes depending on the output voltage of the variable voltage generation circuit 6. 1
0 is an encoder signal that inputs variable low-pass filters to 9 and produces all standard color television signals.

The start/stop signal generator 5 shown in FIG. 1 generates all timing signals shown by AIK in FIG. 2, which are used, for example, when starting and ending recording in a video tape recorder. 11 and 13 start recording, 12 and 14
is a timing signal indicating the end of recording, and this timing signal causes the output voltage of the variable voltage generating circuit 6 to change as shown in FIG. 2 fBl. Variable low pass filter 7
．． 8.9, depending on the potential of the timing signal shown in +X2 diagram iBl, the image changes from a clear state to an unclear state, that is, the image changes from the frequency band necessary for the image to become clear. The entire frequency band consists of a low-pass filter.

Therefore, when the output voltage of the variable voltage generation circuit 6 is low, the frequency band of the variable low-pass filters 7 to 9 is narrow, and when the output voltage is high, the frequency band of the variable low-pass filters 7 to 9 is sufficiently wide. Then, at the same time as timing signal 11, the image went from being unclear to gradually becoming clearer and stabilizing at a sufficiently clear point, and then at the same time as timing signal 12, the image gradually changed from being clear to being unclear until it became sufficiently unclear. Suddenly, the image becomes clearer. Since the actual start and end of recording on a video tape recorder is performed a little later than the timing signal shown in Figure 2 IN, the recorded portion varies from a blurry state to a clear state. Ends with part. Therefore, it is possible to give special effects to images, similar to the fade-in and fade-out currently used in television cameras.

The variable low-pass filter 7 can be easily realized by the circuit shown in FIG. In FIG. 3, 2 is a luminance signal input terminal, 15 is an output terminal of a variable voltage generation circuit 6, 16 is an output terminal of a variable low-pass filter 7, 17 is a resistor (resistance value R), 1
8 is a capacitor (capacitance C), and 19 is an FET.

The resistance value of the FET 19 depends on the gate voltage V, so the resistance value 'kFR (expressed in Vl, the input/output transfer function T of the luminance signal is jωC), FR (when Vl is infinite, T =1 ・
...(2) When the FR function is zero, the band is not limited by a low-pass filter having an RC time constant of 1 R + - jωC. Therefore, by varying the gate voltage v of the FET 19, FR(V+) changes, and the entire frequency band of the variable low-pass filter shown in FIG. 3 can be changed.

The same applies to the variable low-pass filter 8.9.

As a result of these efforts, it is possible to obtain clear and blurred images electrically with a simple configuration, which makes it easier to record images on video tape recorders, etc. compared to obtaining the same effect optically. It can also be used to reproduce images, and has the advantage that the transition from a clear image to an unclear image can be freely selected using electrical signals, and switching can be done even in an extremely short period of time.

In the above explanation, the operation is performed at the timing of the start and end of recording of the video tape recorder, but this timing can be set arbitrarily (and the output of the variable voltage generating circuit 6 can also be set as shown in FIG. 2 tBl). It is not necessary to limit the waveforms to those shown.The variable low-pass filters 7, 8, and 9 are filters for passing the luminance signal and the color difference signals R-Y, B-Y, respectively, and have the passbands necessary for clarity. The functions are the same, but the characteristics are different.Also,
Since the color difference signals R-Y and B-Y have narrower frequency bands than the luminance signal, in the embodiment shown in FIG. ? , 8.
9, it is clear that almost the same effect can be obtained even if only the luminance signal is passed through the fully variable low-pass filter 7.

Effects of the Invention According to the television signal processing circuit of the present invention, it is possible to produce clear images and unclear images entirely electrically, and therefore it can also be used for reproducing the entire image recorded on a video tape recorder or the like. In addition, the transition state of the image can be set arbitrarily.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram of each part thereof, and FIG. 3 is a specific circuit diagram of a variable low-pass filter. 5...Start/stop signal generator, 6.°° variable voltage generation circuit, 7-9...Variable low-pass filter Figure 1

Claims (2)

[Claims] (1) A start strip signal generator that generates a start timing signal and a stop timing signal, and an output voltage that gradually changes in one direction in synchronization with the start timing signal and output in synchronization with the stop timing signal. A variable voltage generating circuit that gradually changes the voltage in the other direction, and a variable low-pass filter that controls the frequency characteristics of at least the brightness signal of the television signal according to the output voltage of the variable direct voltage generating circuit. Television signal processing circuit. (2) The television signal processing circuit according to claim 1, wherein the variable low-pass filter also controls the frequency characteristics of the chroma signal of the television signal.