JPH01311675A - Picture signal processor - Google Patents

Abstract

PURPOSE:To obtain a sharp image by outputting a binarized signal ordinarily, and outputting the value as a binary signal when the compared result of first or second comparison means goes to a prescribed value. CONSTITUTION:Preset values W and B at a white side and a black side are provided separately from the binarization level of a binarization circuit 3, and those preset values are compared with a multilevel picture signal 100 at comparators 6 and 7. And the output of the binarization circuit 3 is set at 0(white) compulsorily when the multilevel picture signal 100 is larger than the preset value W, and at 1(black) compulsorily when it is smaller than the preset value B. In such a way, it is possible to obtain the sharp image by applying the enhancement of contrast on the signal of a thinning line, etc., without being affected by the influence of a noise at the white side or the black side.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an image signal processing device installed in a facsimile machine or the like.

(Prior Art) A conventional image signal processing device of this type is configured as shown in FIG. The image signal read by the reading sensor 1 of the reading device is A/D converted by the A/D conversion circuit 2, and is inputted to the binarization circuit 3 as a 4-bit multilevel image signal 100, for example.

The binarization circuit 3 compares the input multilevel image signal with the binarization level, and binarizes it into white (“0”) when it is higher than that level and black (“1”) when it is lower than that level. do.

FIG. 5 shows this binarization operation, where the vertical axis shows the image signal level and the horizontal axis shows time. Since the multilevel image signal 100 has 4 bits of information, it takes values from O to 15.
A larger value represents white. Multilevel image signal 1
When 00 is the binarization level 10 or less, 2 of the binarization circuit 3
The digitized output 200 becomes "1" and a black signal is output.

FIG. 6 shows the reading pixels of the reading sensor 1 and the document 9 in the reading section. When this document 9 is read by the reading sensor 1, the output is the multilevel image signal 1 shown in FIG.
It is 00. At point b, the black line on the document is thin, so sensor 1
The output does not drop all the way down to O, but remains at a level between white and black. Further, in parts a and C, the output read by the sensor does not become completely white or black due to noise and subtle differences in the surface of the original, and a level difference occurs. In the end, in the apparatus shown in FIG. 4, since the point b is higher than the binarization level, the original is erroneously output as white ("O") even though it is black.

Therefore, a conventional image processing apparatus that prevents the above-mentioned erroneous output is shown in FIG. In this apparatus, a multilevel image signal 100 is first input to an ACC circuit (automatic contrast control circuit) 4. This ACC circuit 4 refers to surrounding pixels and is controlled so that the contrast of the pixel of interest is increased. Therefore, when the multilevel image signal 100 is as shown in FIG. 5, the contrast is emphasized by the ACC circuit 4 as shown in FIG. 8, and the signal is output as a signal 300 to the binarization circuit 3. Therefore, in this case, the output signal 200 of the binarization circuit 3 becomes as shown in FIG. The signal at point b is emphasized and becomes higher than the binarization level, and is binarized as black (“'1”). However, this time, there was a small difference in the read level even though the original was white or black, such as point a and point 0, so the ACC circuit 4 emphasized the contrast and erroneously binarized it into black or white. was there.

(Problems to be Solved by the Invention) In the conventional image signal processing device configured to enhance the multilevel image signal in the ACC circuit 4 and then input it to the binarization circuit 3, even though the image is white or black, If there is a small difference in the read level, the contrast is emphasized in the ACC circuit 4, and white is erroneously binarized into black or black into white. However, there was an inconvenience in that the image contained white dot noise. Therefore, the present invention aims to eliminate the above-mentioned drawbacks, and provides an image signal processing device that can obtain a clear image without including noise in the image signal after binarization even if the contrast of the multilevel image signal is emphasized. is intended to provide.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an image signal processing device that binarizes an input signal after emphasizing the contrast of the input signal. a second comparing means for comparing the input signal with a second reference level; and a second comparing means that normally outputs a binary signal, and the comparison result of the first or second comparing means is a predetermined value. The configuration includes a signal output correction means for outputting the predetermined value as a binarized signal when the predetermined value becomes the value.

(Function) In the image signal processing device of the present invention, the first comparison means compares the input signal with the first reference level and outputs the result to the signal output correction means. The second comparing means compares the input signal with a second reference level and outputs the result to the signal output correcting means. The signal output correction means usually outputs a binarized signal, and when the comparison result of the first or second comparison means takes a predetermined value, it outputs this predetermined value as a binarized signal.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings, in which the same parts as those of the conventional example are denoted by the same reference numerals. FIG. 1 is a block diagram showing an embodiment of an image signal processing device of the present invention.

3 is a binarization circuit that converts the multi-value image signal into a black and white binary signal, 4 is an ACC circuit that emphasizes the contrast of the multi-value image signal, and 5 is a white side setting value W for correcting the multi-value image signal. and a register holding the black side setting value B, 6 is the multilevel image signal 10
0 and the set value W; 7 is a comparison circuit that compares the multivalued image signal 100 and the set value B; 8 is 2;
This signal correction circuit corrects the output value of the value converting circuit 3 and includes an AND gate 81, an OR gate 82, and an inverter 83.

Next, the operation of this embodiment will be explained. Multilevel image signal 10
0 is input to the ACC circuit 4 and comparison circuits 6 and 7. If the multivalued image signal 100 is, for example, as shown in FIG. 2, the contrast of this signal 100 is emphasized in the ACC circuit 4, resulting in a multivalued image signal @300 as shown in FIG. . In this case as well, the noise portion a of the multilevel image signal 100,
C is also emphasized, and becomes a and C in the multilevel image signal 300. By the way, set values W and B are supplied from the register 5 to the comparison circuits 6 and 7, respectively, as comparison standards. As a result, the comparator circuit 6 receives multi-value excitation @1 as shown in FIG.
When σO is greater than or equal to the set value W on the white side (A≧B), the output is set to 1, and when the multilevel image signal 100 is less than the set value W, the output is set to O. Further, the comparison circuit 7 receives the multilevel image signal 100.
is less than the set value B on the black side (A≦B), the output is set to 1.
If the multilevel image signal 100 is larger than the setting fiiB, the output is set to O.

Therefore, when the multilevel image signal 100 changes as shown in FIG. After that, it is input to the AND gate 81, and the output 600 is sent to the OR circuit 82 of the signal correction circuit 8.
will be output as is. On the other hand, the output 200 of the binarization circuit 3 is input to the other input of the AND circuit 81. Therefore, when the outputs 500 and 600 of the comparison circuits 6 and 7 are O, the output 200 of the binarization circuit 3 is directly passed to the signal correction circuit 8.
The output will be 400.

However, when the output 500 of the comparison circuit 6 is 1, the output of the AND gate 81 is O, so the output 400 of the signal correction circuit 8 is O (white) regardless of the output of the binarization circuit 3.
become. When the output 600 of the comparison circuit 7 is 1, the output of the OR gate 82 is 1, so the output 4 of the signal correction circuit 8 is
00 becomes 1 (black). In the end, the output 5 of comparator circuits 6 and 7
00 and Boo change as shown in FIG. 2, and when the output 200 of the binarization circuit 3 changes as shown in FIG.
The output 400 of the signal correction circuit 8 changes as shown in FIG. 3, and the influence of noise at points a and C is eliminated, and the black line at point b becomes correctly black and binarized.

According to this embodiment, the binarization level i of the binarization circuit 3. Separately, set values W and B for the white side and black side are provided separately, and these set values and the multi-value image signal 100 are compared in comparison circuits 6 and 7, and it is determined that the multi-value image signal 100 is larger than the set value W. By forcing the output of the binarization circuit 3 to O (white) when the time is smaller than the set value B, and by forcing the output of the binarization circuit 3 to 1 (black) when the value is smaller than the set value B, It is possible to enhance the contrast of signals such as thin lines and create clear images without being affected by side noise.

[Effects of the Invention] As described above, according to the image signal processing device of the present invention, even if the contrast of a multivalued image signal is emphasized, the image signal after binarization does not contain noise, and a clear image can be produced. Obtainable.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram showing an embodiment of the image signal processing device of the present invention, and Fig. 2 shows the multilevel image signal input to the device shown in Fig. 1 and the comparison circuit at that time. Figure 1 shows the comparison results. Third
The figure shows the output of the ACC circuit shown in Fig. 1, the binarized output and the correction output at that time, Fig. 4 is a block diagram showing an example of a conventional image signal processing device, and Fig. 5 shows the output of the ACC circuit shown in Fig. 1. Figure 4 is a diagram showing the multilevel image signal input to the device and the binary output; Figure 6 is a diagram showing the relationship between the pixels of the reading sensor shown in Figure 4 and the document; FIG. 7 is a block diagram showing another example of a conventional image signal processing device, and FIG. 8 is a diagram showing a contrast-enhanced multivalued image signal and its binary output. 3...Binarization circuit 4・-ACC circuit 5...Register 6.7...Comparison circuit 8...Signal correction circuit Agent Patent attorney Noriyuki Ken Yudo Sanno - Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] An image signal processing device that binarizes an input signal after emphasizing the contrast thereof, comprising: a first comparing means for comparing the input signal with a first reference level; and a second comparing means for comparing the input signal with a second reference level. 2 comparing means and usually outputting a binarized signal, and when the comparison result of the first or second comparing means is a predetermined value, outputting this predetermined value as a binarized signal. 1. An image signal processing device comprising: signal output correction means.