JPS60152173A - Device for reading original picture information - Google Patents

Abstract

PURPOSE:To improve reproducibility of gray graduation at reproducing a picture and to easily obtain black and white binary signals by converting A/D converted signals into pulse width or white and black binary values according to prescribed functional relations. CONSTITUTION:An analog picture signal (a) read by a picture information reader 11 for every one scan is supplied to a peak hold circuit 25 and A/D converter 17. The A/D converter 17 converts the analog picture signal (a) into a digital value based on a shading distortion correction signal (d) from a multiplier 26, and supplies the digital value to a storage device 18. While, a binary counter 20 divides clocks from a pulse oscillator 19 to obtain each divided output and supplies the output to the storate 18, by which an output terminal of the storage 18 outputs time series binary signals possessing pulse width according to digital output values from the A/D converter 17, obtaining impressed characters or reproduced pictures possessing half tone reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to a document image information reading and processing device that reads image signals using a rask scan method, such as in a facsimile machine. The present invention relates to a document image information reading and processing device with improved halftone processing.

(Prior Art) FIG. 1 shows a schematic configuration of a conventionally commonly used document image information reading and processing device, and its operation will be described below.

The original 2 on the original tray 1 is transported by the original feed rolls 3A and 3B.
, 3C one by one and conveyed onto the platen glass 5. The document on the platen glass 5 is illuminated by the fluorescent light 4. The reflected light from the original 2 is transmitted to a light-to-electrical converter 7 (for example, a CCD sensor) by a condenser lens 6.
imaged on top. The optical-to-electrical converter 7 converts image information on the original 2 into electrical signals under the control of the image signal processing circuit 8 . The electrical image signal, which is the read output of the optical-electrical converter 7, is input to an image signal processing circuit 8, converted into a binary signal by an appropriate method, and output.

The original read as described above is stored in the original ejection tray 9 by the original feeding roll 3C driven by the stepping motor 16.

In facsimiles, etc., conventional devices convert the gray gradation (halftone) part of the image information reading analog output, which is obtained by optically reading a document and transmitting it, into a binary signal. (1) A so-called dither processing device that processes and converts the gray gradation part of image information on a two-dimensional plane into a binary signal, and (2) A sum signal obtained by adding a sawtooth wave to an analog image signal. There is known an apparatus that binarizes the signal by comparing it with a predetermined threshold level, that is, converts the analog image signal level into a pulse width to obtain a pseudo halftone signal.

However, dither processing has the disadvantage that good halftones cannot be obtained for various originals.

In the latter case due to sawtooth waves, (1) shading distortion included in the image information (emission intensity decreases at both ends compared to the center of a fluorescent lamp commonly used as a document illumination light source; and Because the amount of light decreases at the periphery of the optical lens, even when reading the same white original, the level of the analog image signal is lower near the start and end of one main scanning period than at the center.) The uniformity of the reproduced image density may deteriorate due to the waveform distortion of the sawtooth wave itself or the superimposition of noise, and the white background may become smeared (2) If the maximum amplitude of the analog image signal changes, There were drawbacks such as deterioration of gray reproducibility and staining of the white background.

Furthermore, since the conventional device described above is capable of transmitting halftones, the quality of the reproduced image deteriorates if the source 1m does not have halftones, for example, only text information. was there. That is, if there are shadings in the characters due to a defect in the manuscript itself, this will be reproduced as is, making it difficult to see on the receiving side.

(Objective) An object of the present invention is to eliminate the drawbacks of the prior art described above, appropriately perform gray gradation processing of original image information, improve the reproducibility of gray gradation in reproduced images, and improve the reproducibility of gray gradation in reproduced images. It is an object of the present invention to provide a small and inexpensive document image information reading and processing device that can easily obtain a binary signal.

(Overview) In order to achieve the above object, the present invention provides an analog-digital converter that converts an output signal of an image information reading device that converts optical image information into an analog electrical signal into a digital signal, and The present invention includes a digital-pulse width converter that converts the output digital signal of the digital converter into a pulse width according to a predetermined functional relationship, and a means for generating a black and white binary signal according to the predetermined functional relationship. It has characteristics.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram of one embodiment of the present invention, and FIG. 3 is a timing chart for explaining its operation.

A time-series analog image signal a read every scan by a known appropriate image information reading device 11 is supplied to a peak hold circuit 25 and an analog-to-digital converter 17.

The peak hold circuit 25 has the analog confidence @a (
The signal b) in FIG. 3 is supplied with the signal a) in FIG. 3, holds the image signal voltage value (peak voltage) that covers the whitest part of the document, and outputs it. Shading distortion inverse signal generator 2
7, the distortion correction signal (third
Signal C) in the figure is output.

The peak voltage of the analog image signal a is multiplied by the distortion correction signal C in a multiplier 26 to become a shading distortion correction signal d of the analog image signal.

The analog-digital converter 17 converts the analog image signal a into a digital value using the shading distortion correction signal d as a reference.

For example, in order to do this, (1) First, multiply the shading distortion correction signal d and the analog image signal a to generate an analog image signal (signal ad in FIG. 3) in which the shading distortion has been corrected, and ( 2) Convert this into a digital value (signal e in Figure 3)
).

Furthermore, as another method of analog-to-digital conversion, those skilled in the art will easily understand that the shading distortion correction signal itself, which is obtained by inverting the shading distortion correction signal d, may be used as the conversion reference level. .

Of course, by improving the illumination source or focusing optics,
If the shading distortion can be sufficiently reduced, shading distortion correction becomes unnecessary, so the analog-digital converter 17 can simply convert the analog image signal a into a digital value using a normal method.

The digitally converted image signal e is supplied to the storage device 18 as a read address. As a result, within the memory device 18, a memory cell corresponding to the digital image signal value at that time is selected.

On the other hand, the pulse oscillator 19 is connected to the clock input terminal of the binary counter 20. Each frequency-divided output signal of the binary counter 20 (for example, 1/2.1/4.1/8
and 1716 frequency division output) are provided to the memory device 18 as another read address of the memory device @18.

That is, as described above, the address of the memory cell selected according to the digital image signal output value at that time is cyclically selected according to the count output value of the binary counter 20.

Therefore, as is clear, the binary counter 20
It is desirable that the digital image signal output e from the analog-to-digital converter 17 is held constant until the output reaches the maximum value from the minimum value.

To this end, in FIG. 2, a latch circuit is provided between the analog-to-digital converter 17 and the memory device M18, and the output of the analog-to-digital converter 17 is It may be temporarily recorded. FIG. 3 shows the latch timing in the above case.

Note that in this specification, the read address supplied from the binary counter 20 is referred to as a circular address signal.

An example of the memory map of the storage device 18 is shown in Table 1. In this example, a 3-bit counter is used as the binary counter 20, and the image signal is also digitized in 8 stages of 3 bits.

As can be clearly seen from this table, the memory cell groups corresponding to each digital image signal (in Table 1, each memory area in one horizontal column) receive H-level signals at a rate proportional to the digital value. (shown as 1″ in the table) and L
A level signal (indicated by 0' in the table) is stored in advance.

Accordingly, depending on the digital output value of the analog-to-digital converter 17, a particular memory cell in the storage device 18 is first selected, while the stored contents of the selected memory cell are read out by said circular address signal. .

In this way, a time-series binary signal (signal g in FIG. 3) having a pulse width corresponding to the digital value is output to the output terminal of the storage device 18.

Table 1 Note that in this case, the conversion function between the output of the pulse width and the input of the digital image signal is not limited to a linear relationship, but also various relationships (for example, sine wave shape, logarithmic function shape, (exponential, etc.) are possible. And which one or more of these conversion functions should be adopted?
The shape and density of the dots forming the reproduced image can be determined depending on what is desired.

This pulse signal 9 is latched by a latch circuit 23 by a period 9 latch signal h (FIG. 3) corresponding to the pixel interval on the printer (not shown) side, and is applied to each signal electrode of the printer.

Therefore, printing is not performed when the output signal is 111 II, and printing is performed when the output signal is "0".
When the printer is controlled, 1 as shown in waveform k in Figure 3 is generated.
Printing for the line will be performed.

That is, by using the method described above, gray gradation (halftone) reproduction with a relationship similar to that of halftone dots used in printing technology is performed for image signals such as those shown in a or ad in Fig. 3. Printed characters or reproduced images with high quality can be obtained.

In addition, when outputting a black and white binary signal, the binary
A binary signal generator 28 fixed to the parallel input terminals of the counter 20
A predetermined binary address signal sum is applied from
The counter 20 outputs this value m. A white/black binary signal (1 or 0) is read out from the memory 18 using the address signal m and the digital image signal.

For example, if the value of the binary counter 20 is 010, the memory 18 outputs 0'' in the range of image signal digital values 000 to 010, and outputs 1'' in the range of 011 to 111.

Also, if the value of the binary counter "" is 001,
Memory 18 in the range of image signal digital value OOO~100
O” is output from 101 to 111, and “1” is output from 101 to 111.
is output.

In other words, if you change the setting value of the fixed binary signal generator 28,
You can change the density of the reproduced image.

Further, the signal of the pulse oscillator 19 and the fixed binary address signal m are switched by the serial-parallel selection signal applied to the a terminal of the binary counter 20, and the signal output from the binary counter 20 is changed. .

For example, when an H level signal is applied to the a terminal, the counter 20 outputs a signal representing the count value of the pulse oscillator 19, while when an L level signal is applied to the a terminal, the counter 20 outputs a signal representing the count value of the pulse oscillator 19. A fixed binary signal generator 28 outputs a preset binary signal.

As the binary counter 20, a commercially available model 74LS161.74LS393 (model name), for example, can be used. Furthermore, as the fixed binary signal generator 28,
A well-known dip switch can be used.

The line synchronization pulse generator 21 generates line synchronization pulses shown at 1 in FIG.
4 to the stepping motor 16.

As a result, the stepping motor 16 is activated intermittently.
The recording paper (not shown) is driven one line at a time in the sub-scanning direction.

As described above, when, for example, an H level signal is applied to the a terminal of the binary counter 20, the gray gradation (intermediate) level portion as well as the white and black level portions of the original image are adjusted to their respective levels. It will be played using the corresponding number of dots. On the other hand, when an L level signal is applied to the a terminal, for example, a black and white binary image is reproduced.

As is clear, in FIG. 2, the storage device 1
Although 8 is shown as having multiple output lines, this is not necessary.

However, if a plurality of memory maps with image signal digital values and counter outputs as parameters as shown in Table 1 are provided corresponding to various conversion functions as shown in FIG. 4, the conversion functions can be adjusted as appropriate. The characteristics of the reproduced image can be changed by selecting , and the optimum reproduced image according to the purpose can be obtained.

Furthermore, as detailed below, if the conversion function is switched for each adjacent scanning line, the shape of a group of dots (e.g., equivalent to one halftone dot in halftone dot printing) can be changed to a circular shape. This makes it possible to reproduce more natural midtones.

An example of pulse width conversion for the analog image signal level for this purpose is shown in FIG. In the figure, waveform ad represents an analog image signal, and F1 to F4 represent pulse signals generated corresponding to the analog image signal, respectively.

That is, F1 to F4 correspond to the plurality of conversion functions previously described with respect to FIG. In the first and fourth memory maps, as shown in Fl and F4,
The pulse width for the same analog image signal level is set relatively narrow, and in the second and third memory maps, F
As shown by 2 and F3, the pulse width for the same analog image signal level is set relatively wide.

Then, the above F1 to F4 are stored in 4 of the storage device 18 in FIG.
The configuration is such that the output lines are outputted to the respective output lines of the book, and the output lines are switched by the digital selector 22 for each -scanning line.

According to such a configuration, when the analog image signal levels of corresponding pixel positions on four consecutive scanning lines are equal, the first
A relatively small number of continuous dots are printed on the fourth scanning line, and a relatively large number of continuous dots are printed on the second and third scanning lines in between, so that dots that are nearly circular as a whole are printed. That will happen.

This makes it possible to improve the quality of reproduced images.

In the above, when converting a digital value into a pulse width, as shown in Table 1, the output ``1''' is generated continuously, and the digital value is converted as shown by waveform g in Figure 3. Although we have described the example of generating a single pulse with a pulse width that is a function of value, the invention is not so limited.

In other words, in general, the number of "1"s generated within one conversion period (i.e., within the time from when the binary counter 20 is reset until it counts up) is a function of the digital value. That's fine.

In addition, in the embodiment of FIG. 2, the fixed binary signal generator 2''8
The output of
Although the h1 number output of the pulses outputted from the input signal and the fixed 2 advance signal are selected, the present invention is not limited thereto. That is, the count signal of the pulse oscillator 19 is output from the binary counter 20, the fixed binary signal generator 28 is inputted to the memory 18 without going through the binary counter 20, and the count signal of the binary counter 20 is The output and the output of the fixed binary signal generator 28 may be selectable by suitable switching means.

(Effects) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) Since the conversion between the -C digital value and the pulse width is performed through digital processing, it is possible to speed up the conversion and increase the reading speed.

('2J) A unique memory cell is provided according to the digitized image signal output, and this is addressed by a counter output to read out the data, so setting and changing the conversion function (i.e., image reproduction characteristics) is extremely easy. It's easy.

(3) Since the digital value versus pulse width is converted by digital processing, the conversion function does not change during operation, and image reproducibility is improved.

+41 - A binary (white, black) signal and a pseudo halftone signal can be obtained with a simple configuration. Further, for this reason, when transmitting original information such as text, the quality of the reproduced image is improved.

[Brief explanation of drawings]

FIG. 1 is a side view showing a schematic configuration of a general document image information reading device, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG.
The figure is a timing chart for explaining the operation of Fig. 2, Fig. 4 is a graph showing an example of an analog-to-digital conversion function that can be used in the present invention, and Fig. 5 is a graph showing an example of an analog-to-digital conversion function that can be used in the present invention. There is a timing chart C showing an example of the relationship between analog signals and pulse widths for a group of cases. 11... Image information reading device, 16... Stepping motor, 17... Analog-digital converter, 18...
...Storage device, 19...Pulse oscillator, 20...Binary counter, 21...Line synchronous pulse generator, 22...Digital selector, 23...Latch,
25... Peak bold circuit, 26... Multiplier, 2
7... Shading distortion inverse signal generator 28... Fixed binary signal generator Patent attorney Michito Hiraki and 1 other person

Claims (1)

[Claims] (1) An image information reading device that reads a document using a rask scan method and outputs an electrical analog image signal having a level corresponding to the density of the document image, and an analog device that converts the electrical analog image signal into a digital signal. a digital converter, a plurality of memory cells storing predetermined binary signal sequences for the multi-value digital signal, and a cyclic address signal for cyclically specifying a read address of each of the memory cells. generating means; fixed address signal generating means for addressing the memory cell with a predetermined value; switching means for switching between the circular address signal generating means and the fixed address signal generating means to connect to the memory cell; and each of the memory cells. 1. A document image information reading and processing device comprising means for latching and outputting a read signal from a printer at a dot printing cycle of a printer. ('2J) A patent processing apparatus characterized in that the output of the fixed address signal generating means is connected to the circulating Amires signal means, and selection between the rotating address and the fixed address is performed by the switching means.