JPS6145661Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image signal binarization circuit that converts an analog image signal obtained by reading and scanning a document or the like in a facsimile machine or the like into a binary tone signal.

In the conventional binarization circuit of this kind, the analog image signal V is converted into the binary signal D by comparing it with a fixed reference level L as shown in FIG. There is a drawback that it is not possible to sufficiently binarize the portion N in which the gradation change in gradation is relatively small.

Therefore, as shown in FIG. 2, the analog image signal V is applied as one input to the comparator circuit 4, and
The image signal V is differentiated by a differentiating circuit 1 and then inverted by an inverting circuit 2 to obtain a signal H, and the image signal V is integrated by an integrating circuit 3 to obtain a signal I. It may be possible to obtain a binary signal output D from the comparator circuit 4 by combining the two signals through the variable resistor 7 and applying the composite signal C as another input to the comparator circuit 4. It will be done.

Here, the reason why the above-mentioned composite signal C is used as the comparison reference signal of the comparator circuit 4 is that the integral waveform of the part M where the gradation change is relatively small and wide in the scanning line direction is used as the comparison reference level, and the gradation change This is to allow the differential waveform of the portion N, which is small and narrow in the scanning line direction, to be comparatively detected using the differential waveform as a comparison reference level. Note that resistors 8 and 9 in the figure are for level adjustment of the image signal V and composite signal C, respectively.

According to the method shown in FIG. 2, the above-mentioned parts M and N
Both can be detected as binary signals, but
The composite signal C for comparison reference has a gradual rise due to the integration circuit, so the gradation is adjusted at the leading edge (period T in Figure 2b) corresponding to the initial stage of each line (1L) of the image signal V. A disadvantage arises in that the narrow portion N' where the change is small cannot be detected as a binary signal.

Therefore, the present invention proposes an image signal binarization circuit that solves these problems using a technically extremely easy method, and the details thereof will be explained below with reference to FIG.

In FIG. 3a, an analog image signal V derived from a facsimile reading scanner or the like is applied as one input to a differential amplifier circuit 11 via a level adjustment resistor 10. On the other hand, the control signal S becomes "high" during the period of each line of the image signal V.
is applied to the differentiating circuit 12, and the output B of this differentiating circuit 12 is applied to the variable resistor 13 and the resistor 1 for level adjustment.
4 is applied as another input to the differential amplifier circuit 11. Therefore, the output of this differential amplifier circuit 11, which is an analog amplifier, is derived as an image signal V' whose leading edge has a gradual rise as shown in FIG. 3b, and this signal V' is used for level adjustment. resistance 1
5 as one input of the comparator circuit 16. Further, as in the case of FIG. The outputs are combined by the resistors 20 and 21 and the variable resistor 22 to form a signal C. This composite signal C is applied as the other input of the comparator circuit 16 through the resistor 23, and the binary signal D is output from the comparator circuit 16. I'm starting to get it.

In this way, in the binarization circuit of the present invention, the analog image signal derived from a facsimile reading scanner etc. is processed so that the change in the leading edge corresponding to the initial stage of each line is gradual. Since the image signal is binarized using the signal obtained by combining the differential inversion output and the integral output of the analog image signal as a comparison reference signal, the gradation change is small at the leading edge of the analog image signal. Moreover, even narrow portions can be binarized sufficiently. Furthermore, when making the change in the leading edge of the image signal gradual, differential outputs of the input image signal and the signal that is "high" for each line of the image signal are differentially amplified. This has the advantage of being extremely easy to implement.

Note that instead of differentiating the signal S that is "high" during each line of the image signal in the differential circuit 12 in FIG. 3 and applying it to the differential amplifier circuit 11, the signal S shown in FIG. As shown, the signal S is inverted by the inverting circuit 25, and the signal S', which is "low" for each line of the image signal, is integrated by the integrating circuit 24, and the signal from the integrating circuit 24 is A similar effect can be obtained even if B' is applied to the differential amplifier circuit 11.

It goes without saying that the control signal S can be easily created from a facsimile synchronization signal or the like.

[Brief explanation of the drawing]

Fig. 1 is a signal waveform diagram for explaining a conventional image signal binarization circuit, Fig. 2 shows a prior art of this kind of binarization circuit, and Fig. 1a is a block diagram showing its schematic configuration. Figure b is a waveform diagram illustrating the operation. FIG. 3 shows an embodiment of the image signal binarization circuit according to the present invention, FIG. 3a is a block diagram showing its schematic configuration, FIG. Different embodiments of the image signal binarization circuit are shown, and FIG. 3A is a block diagram showing the schematic structure thereof, and FIG. 1B is a waveform diagram illustrating its operation. 12, 17... Differential circuit, 11... Differential amplifier circuit, 18, 25... Inverting circuit, 19, 24... Integrating circuit, 16... Comparing circuit.

Claims (1)

[Scope of utility model registration request] A circuit for converting an analog image signal obtained by reading and scanning a document, etc. into a binary signal of density and darkness, and a differential circuit that differentiates a signal that is "high" over a period of one line of the image signal. circuit or an integrating circuit that integrates a signal that becomes "low" over a period of one line, and a differential circuit that takes the image signal as one input and receives the signal from the differentiating circuit or integrating circuit as the other input. an amplifier circuit, a differentiation circuit that differentiates the output of this differential amplifier circuit, an inversion circuit that inverts the signal from this differentiation circuit, an integration circuit that integrates the output of the differential amplifier circuit, and a signal output from this integration circuit. Comparison of a circuit connection that combines the signal and the signal from the inverting circuit, and the output of the differential amplifier circuit as one input, and the combined output signal from the circuit connection as the other input, and outputs a binary signal. An image signal binarization circuit consisting of a circuit.