JPS58213563A - Circuit for digitizing video signal - Google Patents

Abstract

PURPOSE:To output a digital signal which represents the variation of brightness, by discriminating an analog video signal at a fixed reference level after overlapping a signal of a fixed cycle having a steeply inclined part thereon to encode the analog signal. CONSTITUTION:When video signal, whose brightness is continuously changed, is given to an input terminal 1, triangular wave signal having a fixed cycle is outputted from a triangular wave signal generating circuit 6. Therefore, signal which is formed by overlapping the triangular wave signal upon the video signal is given to the (+) side input terminal of a comparator 2. The comparator 2 performs the discrimination of the level of a reference voltage V0 and a printer 5 performs the printing in accordance with the output of the comparator 2. In the printed content, a condition in which the width of the printed part (hatched part) gradually becomes narrower and the video signal continuously becomes brighter, is shown. In this way, even when analog video signal is simply converted into digital signal of two gradations by level discrimination, the video signal can be printed artificially as if it is of multi-gradation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal digitization circuit, and more particularly to a video signal digitization circuit that converts a video signal into a two-tone digital signal.

FIG. 1 is a diagram showing a conventional video signal digitization circuit. In the figure, an analog video signal is applied to an input terminal 1. This video signal is applied to the + side input terminal of the comparator 2. One side input terminal of this comparator 2 has the divided voltage output of voltage dividing resistors 3 and 4 that divides the voltage of the power supply +B.
0 is given. The comparator 2 uses this divided voltage output vO as a reference voltage to discriminate the level of the video signal. That is,
If the level of the video signal is lower than the reference voltage vO, the output of the comparator 2 becomes a low level, and conversely, if the level of the video signal is higher than the reference voltage 2o, the output of the comparator 2 becomes a high level. The output of the comparator 2 is given to the printer 5 and printed.

FIG. 2 is a waveform diagram for explaining the operation of FIG. 1 and a diagram showing the contents printed by the printer 5. In operation, when a video signal as shown in FIG. 2 is applied to the + side input terminal of the comparator 2, the comparator 2 discriminates the level of the video signal based on the reference voltage 0 applied to its one side input terminal. Therefore, as shown in Fig. 2, the output of the comparator 2 becomes a low level when the level of the video signal is lower than the reference voltage VO, and conversely becomes a high level when it is higher than the reference voltage VO. Become. In printer 5, the second
As shown in the figure, when the output of the comparator 2 is at a low level, printing is performed, and when it is at a high level, no printing is performed.

As mentioned above, in conventional video signal digitization circuits, digitization is performed simply depending on whether the level of the video signal is higher or lower than the reference voltage ○, so the brightness is continuous as shown in Figure 2. If a video signal that changes to the original video signal is input, the content printed by the printer 5 will be considerably different from the image represented by the original video signal.

Therefore, the main object of the present invention is to convert an analog video signal into a digital signal that can represent continuous brightness changes when converting an analog video signal into a two-tone digital signal. The purpose of this invention is to provide an integrated circuit.

In summary, the present invention is such that a constant periodic signal having a steep slope is superimposed on an analog video signal, and then the superimposed signal is discriminated at a constant reference level and binarized.

FIG. 3 is a block diagram showing one embodiment of the present invention.

In construction, this embodiment is the same as that in FIG. 1 except for the following points, and corresponding parts are given the same reference numerals and their explanations will be omitted. The feature of this embodiment is that the triangular wave signal from the triangular wave signal generating circuit 6 is superimposed on the analog video signal applied to the input terminal 1 and is applied to the + side input terminal of the invasive comparator 2. That is, the analog video signal applied to the input terminal 1 is applied to the + side input terminal of the comparator 2 via the input resistor 7.

Further, the output of the triangular wave signal generation circuit 6 that generates a triangular wave signal of a constant period is connected to the + of the comparator 2 via an input resistor 8.
given to the side input end.

FIG. 4 is a waveform diagram for explaining the operation of FIG. 3 and a diagram showing the contents printed by the printer 5.

In operation, assume that a video signal whose brightness changes continuously is applied to the input terminal 1, as shown in FIG. At this time, the triangular wave signal generating circuit 6 outputs a triangular wave signal having a constant period, as shown in FIG. Therefore, the + side input terminal of the comparator 2 is given a signal in which the video signal and the triangular wave signal are superimposed, as shown in FIG. Comparator 2 performs level discrimination using reference voltage VO as in the case of FIG. Therefore, the output will be as shown in FIG. In response to the output of the comparator 2, the printer 5 performs printing as shown in FIG.

The printed content shown in Figure 4 is clearly compared with the printed content shown in Figure 2, as the width of the printed area (hatched area) gradually decreases and the video signal becomes continuously brighter. The situation will be shown. In this way, in the embodiment shown in FIG. 3, even when an analog video signal is converted into a two-tone digital signal by simply level discrimination, it is converted into a digital signal with pseudo-multiple gradations. Can be printed.

In the embodiment shown in FIG. 3, a triangular wave signal is used as the signal to be superimposed on the analog video signal, but a sine wave signal or a trapezoidal wave may be used instead.

That is, any waveform signal may be used as long as it has a constant period and has a steep slope with respect to the video signal.

As described above, according to the present invention, a constant periodic signal having a steep slope is superimposed on an analog video signal and then digitized by level discrimination. Even when a video signal is digitized, it is possible to output a digital signal that can pseudo-represent changes in brightness. Therefore, it is very effective when making a hard copy of the video signal using a simple printer, for example.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional video signal digitization circuit. FIG. 2 is a waveform diagram for explaining the operation of FIG. 1 and a diagram showing the contents printed by the printer 5. FIG. 3 is a block diagram showing one embodiment of the present invention. Figure 4 is the third
FIG. 2 is a diagram showing a waveform diagram for explaining the operation of the diagram and the content printed by the printer 5. FIG. In the figure, 1 is an input terminal, 2 is a comparator, 5 is a printer, and 6 is a triangular wave signal generation circuit. Agent Shin Kuzuno - (1 other person) Ryo 1 Figure 18 Kabuto Z Kasumi

Claims (2)

[Claims] (1) means for inputting an analog video signal; means for generating a constant periodic signal having a steep slope with respect to the analog video signal; means for superimposing a signal from the signal generating means on the analog video signal; and a video m-signal digitizing circuit comprising means for discriminating and binarizing the output of the superimposing means at a certain reference level. (2) The video signal digitizing circuit according to claim 1, wherein the signal generating means includes means for generating a triangular wave signal.