JPH02193463A - Digital copying machine - Google Patents

Abstract

PURPOSE:To transmit an image signal without considering which of a one- picture-element binary signal and a one-picture-element multilevel signal a printer itself outputs by outputting both signals in parallel when outputting the image signal to the printer part. CONSTITUTION:Image data after the gamma conversion of a gamma conversion part 40 is separated to a path where each picture element is converted into binary data of 'black' or 'white' and a path where modulation of plural gradations per picture element can be imposed and conversion to multilevel data matching the printer is performed. The data separated into two are sent to the printer part or other output device parts as they are. Consequently, the output device part need not select the binary data and multilevel data distinctively and signals themselves can be made independent in some systems.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention optically reads original image information using a line image sensor such as a CCD, converts it into an electrical signal, and finally records it on a printer, etc. The present invention relates to a digital copying machine that reproduces document image information on a device, and particularly relates to an image signal processing method for a digital copying machine that enables combination with a facsimile and filing device.

[Conventional technology]

Digital copying machines have gone from simply recording black and white to being able to record one pixel in multiple gradations, leading to higher image quality. On the other hand, due to the ease with which digital copying machines can handle data, they are increasingly becoming multifunctional machines, such as being used in combination with facsimile and filing devices, and as output devices for computers.

At this time, reducing the amount of information becomes an important issue for facsimile machines, filing machines, etc., and the transition to single-pixel multi-value systems will be much slower than copying machines. In other words, it has become necessary to allow single-pixel binary signals and single-pixel multi-value signals to coexist within the same system.

[Problem to be solved by the invention]

However, in the past, binary signals and multi-value signals coexisted, and other systems (facsimile, filing devices)
Until now, there has been no system in which both signals coexist.

If we consider the blocks of a reading device (scanner), printer, facsimile, and filing device, image signals are ultimately collected from other blocks to the printer section. Especially when two systems of signals come from the scanner,
If the printer itself could transmit image signals without being aware of which one to output, printer control and hardware could be greatly simplified.

The present invention has been made based on such a background, and an object of the present invention is to clarify a method for connecting image signals when connecting a facsimile, a filing device, etc. as a multifunction device.

[Means to solve the problem]

In order to achieve this object, the present invention provides a digital copying machine that has a basic configuration of a scanner section and a printer section, and can be connected to a facsimile machine and a filing device as a multifunction device, and outputs image signals to the printer section. The present invention is characterized in that it includes a means for outputting a binary signal for one pixel with two values and a multi-value signal outputting means for outputting a multi-value for one pixel.

[Function] In the present invention, when outputting an image signal to the printer section, 1
A pixel binary signal and a single pixel multi-value (greater than binary) signal are output in parallel.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a document reading device constituting a digital copying machine according to an embodiment of the present invention.

In the same figure, a contact glass 1 for placing an original to be read is illuminated by light sources 'la and 2b.
The reflected light from the image surface of the read original is reflected by mirrors 3, 4, 5.
．． 6.7 and the lens 8, the image is formed on the light receiving surface of the CCD image sensor 9.

Further, the light source 2 and the mirror 3 are mounted on a traveling body 11 that moves on the lower surface of the contact glass 1 in parallel to the contact glass l. Main scanning is performed by solid-state scanning of the CCD image sensor 9. The document image is read one-dimensionally by the CCD image sensor 9, and the entire surface of the document is scanned by moving the optical system (sub-scanning).

In this example, the reading density is set to 16 pixels/mm for both main and sub-scanning.
It is possible to read originals up to 1.5 mm. The image signal read at a sampling density of 16 pixels/mm is
As shown in the block diagram of FIG.
It is amplified to a predetermined voltage amplitude by the A/D converter 34, and then converted into digital data of one pixel number level #A (64 gradations in the example) (the number of gradations is 2 to the n power). , treated as an n-bit binary signal). In the example, the A/D converted signal becomes a 6-bit signal, and then
A shading correction unit 35 performs shading correction to correct uneven illuminance of the light source and variations in sensitivity between elements of the CCD sensor 32.

The shading-corrected data is then sent to the filter section, where the frequency characteristics are converted by the spatial filter. At this time, a plurality of filters may be provided depending on the type of document or output mode. In the embodiment, three spatial filters 36, 37, and 38 are provided corresponding to three types of output modes: text image mode, photo image mode, and text/photo mixed mode. Filter ■
36 corresponds to the character image mode and uses high pass filters (H, P, F) to improve resolution. Ideally, the frequency characteristics of H, P, and F should be inverse functions of the input system frequency characteristics that represent the MTF of the input system including the optical system, lens, and sensor, but in reality, consideration must be given to noise components. Although it is necessary, the filter performs MTF correction with a smaller amount of correction than the inverse function. Filter 37 corresponds to the photographic image mode, and uses low pass filters (L, P, F) with emphasis on gradation.

In addition, the frequency characteristics of P and F do not reduce resolution as much as possible, and moreover, the frequency characteristics of halftone dot originals (133 lines/inch to 175 lines/inch)
Select a frequency characteristic that will prevent moiré from occurring in the output image for lines/inch-sized halftone dots). Filter ■3
8 corresponds to the text/photo mixed mode, and selects a filter that exhibits intermediate characteristics between filter ■36 and filter ■37.0For example, H has a smaller correction amount than filter ■36.
For example, it passes frequencies higher than oP, F, or filter 37, or slightly suppresses only the portion of P, F, or noise components close to the Nyquist frequency. Alternatively, the filter 38 may pass the shading-corrected data as is without passing it through the spatial filter.

The selector 39 selects one of the plurality of data obtained by passing through a plurality of spatial filters in parallel in this manner (depending on the device, there may be only one filter or no filter and no selector is necessary). The selection conditions of the selector 39 are such that the operator selects the output mode on the operation panel, or the reading device itself determines the appropriate mode from the document information.
Alternatively, it is determined depending on the destination to which the image data will be output (for example, a laser printer, a facsimile transmitter, a file device such as a disk, etc.).

The data selected by the selector 39 is then scaled in the embodiment. This is magnification change by interpolation calculation only in the main scanning direction.

The method of changing magnification in this type of device is as follows: (1) Changing the magnification in the main scanning direction by changing the reduction ratio of the optical system including the lens, and changing the reading density in the sub-scanning direction by changing the moving speed of the optical system. (2) Scaling in the main scanning direction, using data at the same magnification, and calculating data at sampling points during scaling by interpolation; and (1) scaling in the sub scanning direction. and (3) variable magnification by performing two-dimensional interpolation for main and sub-scanning simultaneously using data at the same magnification. In the example, (2) is used.

The scaled data is then subjected to γ conversion in the γ conversion unit 40. γ conversion is a conversion of output density characteristics, and corresponds to the operation of changing the copy density in a copying machine, facsimile, etc. Digital copying machines, facsimile machines, etc. sometimes convert the density by changing the darkness value during binarization, but in this embodiment, the image data itself is converted to the density selected by the operator or the device itself using a conversion table. Perform the corresponding conversion.

After γ conversion, the image data is either "black" or "black" per pixel.
A bus that converts to binary data of "white" and multi-value data (
In this embodiment, the bus is divided into two buses which are converted into 4-bit coded data (4-bit coded data) in accordance with a printer device capable of PWM modulation of 10 values per pixel. The data divided into two parts is sent as is to the printer section or other output device section.

In the case of the embodiment, at this time, one of the multivalued data and the binary data is selected and outputted so that the multivalued data and the binary data are not sent out at the same time. This is to eliminate the need to distinguish and select between binary data and multi-value data in the output device section, and although the signal lines are independent from each other in terms of hardware, the signals themselves can only be connected to one or the other. It is. Depending on the system, the signals themselves may or may not be independent.

Next, a laser printer device constituting the digital copying machine of the present invention will be briefly described.

Figure 3 shows a structural diagram.

The manuscript reading/listening device and the laser printer may have an integral structure, or may have separate structures and are only electrically connected.

A laser printer is equipped with a laser writing system, an image reproduction system, a paper feeding system, and the like. The laser writing system is a laser output crab unit 12. Imaging lens 13. It is equipped with a mirror 14. Inside the laser output unit 12, there is provided a polygonal mirror (polygon mirror) that is rotated at a constant high speed by a laser diode as a laser light source and a motor. Laser light output from the laser writing system is irradiated onto a photosensitive drum 15 provided in the image reproduction system. Around the photosensitive drum 15, a charger 16. eraser 1
Developing unit 18° Transfer charger 191 Separation charger 20. Separation claw 21. It is equipped with a cleaning unit 22 and the like. Note that a main scanning synchronization signal (MS
A beam sensor (not shown) that generates YNC) is arranged.

The process of image reproduction will be briefly explained. Photosensitive drum 15
The surface of the battery is uniformly charged to a high potential by the charger 16. When that surface is irradiated with laser light, the potential of the irradiated portion decreases. Since the laser light is controlled on/off depending on whether the recorded pixel is black or white, a potential distribution corresponding to the recorded image, that is, an electrostatic latent image, is formed on the surface of the photoreceptor by irradiation with the laser light. When the portion on which the electrostatic latent image is formed passes through the developing unit 18, toner adheres to the portion according to the process of the potential, and a toner image that visualizes the electrostatic latent image is formed. A recording sheet is fed into the area where the toner image is formed at a predetermined timing and overlaps with the toner image. This toner image is transferred to a recording sheet by a transfer charger 19,
It is separated from the photosensitive drum 15 by a separation charger 20 .

The separated recording sheets are conveyed by a conveyor belt 23, thermally fixed by a fixing roller 24 having a built-in heater, and then discharged to a paper discharge tray 25.

In the embodiment, there are two paper feeding systems. The one paper feeding system is equipped with a paper feeding cassette 26, and the other paper feeding system is equipped with a paper feeding cassette 27. The recording sheets in the paper feed cassette 26 are fed by paper feed rollers 28 . Recording sheets in the paper feed cassette 27 are fed by paper feed rollers 29 . The fed recording sheet stops once in contact with the registration rollers 30, and then moves onto the photoreceptor drum 1 at a timing synchronized with the progress of the recording process.
Sent to 5. Although not shown, each paper feed system includes
It is equipped with a size sensor that detects the sheet size of the cassette.

Here, we return to the explanation of the image signal after γ conversion.

Of the two passes mentioned above, the binarization pass will be explained first.

The present invention has two binarization methods, and one is selected depending on the mode.

One method is normal binarization, which compares the data after γ conversion and the dark value, and when the data is greater than or equal to the dark value, it is set to, for example, "1" (1 is black). When it is small, it is determined as "0" (0 is white), and the binarization circuit 47 binarizes it. As for the darkness value, the selector 46 selects either a fixed threshold value 44 or an organized dither threshold value 45 depending on the mode. For example, the fixed threshold value 44 is predetermined for text mode, the dither threshold value 45 for photo mode, and the fixed threshold value 44 or dither threshold value 45 for text/photo mixed mode.

In addition, between T-transformation and binarization, a pass is provided in which image data processing for preventing moiré, which is conventionally known as an error dispersion method (error dispersion unit 43), is executed and a pass is not executed. Select.

A plurality of combinations of these dark values and data processing methods can be considered for each mode.

In other words, since the optimal settings for each mode may change depending on the purpose of use of the machine and the type of document, convenience for the user can be achieved by responding to this.

One way to deal with this is to change the combination by operating dip switches or special keys on the operation panel (service keys for setting various functions, program mode, etc.). The settings and changes of this combination are not normally performed by an operator, but are performed by a service person or the like at the time of machine installation or delivery, or during the process according to the user's wishes. Of course, it may be operated by a user or an operator. In the example, the combinations shown in Table 1 were selected using a dip switch.

Table 1 Due to the combination of data processing methods shown in Table 1 and the difference in frequency characteristics of filter processing in each mode, two
A valued image can be obtained.

Next, multi-value data processing in accordance with multi-value writing will be explained. Laser printers used to be completely binary printers, meaning that each pixel could be either all white or all black.
Previously, only 1" or 0 could be reproduced, but recently several methods have been proposed to express multiple gradations for one pixel.

One of these is PWM, which provides gradation for one pixel by controlling the pulse width of a pulse signal for driving a laser diode.

In the embodiment, PWM is used to perform multi-value writing for one pixel.

The T-transformed data in FIG. 1 is sent to the PWM encoding section 42, apart from the aforementioned binarization pass, and is encoded there. Encoding does not mean generating the pulse itself to drive the laser diode, but converting it into numerical data corresponding to the desired pulse width. The printer unit sets the drive pulse to the required pulse width.

As for the image data, as described above, the binary signal DA2 and the multi-value encoded DAM are sent in parallel to the printer section. However, as mentioned above, although the signal lines are parallel, the signals themselves do not coexist at the same time. When one of them is valid, the other is invalid, and the output of the signal line is fixed at either high impedance, "1" or "0" level. This allows the printer to wire-OR or logically OR the both signals.
By simply performing R, you can receive and receive image signals without being aware of whether they are binary or multivalued. For example, if the multi-level coding is set to 3 bits, the invalid signal is fixed to "0", rl 11J is all black, ro OOJ is all white, and the code is set with intermediate tones between them, the With the circuit configuration as shown in Figure 6, the binary signal DA2 and the multi-value code signal DA are
M can be synthesized. The binary signals that enter the printer section include not only the signal DA2 from the scanner, but also facsimile reception signals, signals from filing devices, etc., and it is necessary to combine the binary signals with these signals in the printer section.

After all the binary signals are combined, the binary signal and the multi-value signal are combined.

Next, a method of performing error dispersion during binarization and a method of switching paths to be executed and not to be executed will be explained.

FIG. 4 is a circuit block diagram for error dispersion and binarization according to the embodiment. The error dispersion method is as shown in Figure 5, where the CCD solid-state scanning is main scanning and the scanner movement direction is sub-scanning, and when these directions are as shown in the figure, the error ER when binarized is shown in the figure. Allocate to the pixel 41'A of the arrow in the middle. Although various weighting methods for distribution can be considered depending on the system, equal distribution is used in this embodiment. That is, 1/4 is distributed to each of the four pixels. There are several ways to allocate pixels, such as not only the allocation as shown in FIG. 5, but also allocating them to the entire surrounding area.There are also several ways of thinking about the error ER. The error is the error of binarization, and after a certain dark value, it becomes "1" or "0".
”, and for example, when 32 is the threshold value for 64 gradations (0 to 63), 0 to 31 will be “0”, and 32 to 63 will be “1”.
”, then decide which level of the 64 gradations corresponds to the binary values “0” and “1”, and set each value to th
Q.

Let it be thl. By setting th□ and thl, E
The meaning of R changes. That is, when the result of binarization of data d is "0", the error ER is ER=d-thO, and when the result of binarization is "1", ER=d-thl. The general idea is that thQ=Q and th1=63, but the settings differ depending on the scanner system or the idea. In the example, tho=o, t
h1=47. In the block diagram of FIG. 4, DATA is image input data, which in FIG. 5 is data on the lower line. This DATA is a transfer lock (pixel clock DCK) and is latched at the next stage and the next stage, and the ER generated from the previous line is distributed at each stage, and the adder 51,
Error is added at 52.53. After the error is added three times, this data is stored in the line memory 61.

Since ER has positive and negative values, this data is signed data. When the scanning of one line ends and the next line starts, the data stored in the line memory 61 is sequentially retrieved. This is the upper line in Figure 5. This data is part 1.
Errors generated from data before a pixel are added only once. At this point, the error has been added to the data four times, and since this data may be outside the range of θ to 63, the limiter 55 returns it to 0 to 63.

In other words, when data is 0, data = 0, data>63
In this case, set the data to 63. Then, binarization is performed using the dark value TH, and from the binarization result, ER=data (binarization “0
) or ER=data 47 (binarized "1") is selected by the selector 57, and this ER is distributed to surrounding pixels by 1'/4.

Here, if the selector 57 selects ER=O, the error will not be dispersed, so it is possible to select whether or not to perform the error dispersion depending on the method of distributing the ER using the selector 57. This is how to switch paths. In addition, 48.49.50,58.
60 is a latch, 54.degree. 56 is an adder, and 59 is a comparator. In this way, various image processes can be performed simultaneously or with common hardware. The next problem is how to select which one out of the many types and combinations in that system.

As mentioned above, as digital copiers are currently using technology to express gradation per pixel in printers, there is a need and demand to utilize this to improve image quality. Although the use of pixel multivalues is progressing, when considering the application of digital copiers to facsimiles and expansion to filing systems, there is still a strong demand for as little information as possible and high image quality. The application range of binary images is still wide. Furthermore, even if we consider only copying machines, there are increasing demands for complex editing, image processing, etc., and the combination of these functions and multivalue becomes extremely complex. To prevent this, it is effective to use software to select binary data during complex editing and processing using the apparatus of the embodiment. Also, depending on the type and content of the document, there are cases where binary values are sufficient, and cases where binary values are better.
There is also a method of switching between binary and multi-value. Among the binary values, there are multiple modes as shown in Table 1, and from these,
The system can be selected in its own way.

Incidentally, the binary signal output means described in the claims includes two
The value converting circuit 47 constitutes this, and the PWM encoding circuit 42 constitutes the multi-value signal output means.

〔Effect of the invention〕

As described above, according to the present invention, in a digital copying machine whose basic configuration is a reading device (scanner) and a recording device (printer), a facsimile, a facsimile,
Connecting image signals when connecting filing devices, etc.
This can be clarified by considering the combination of 1-pixel binary and 1-pixel multi-value.

[Brief explanation of the drawing]

FIG. 1 is a system block diagram of a digital copying machine according to an embodiment of the present invention, FIG. 2 is a schematic diagram of a document reading device constituting the digital copying machine, and FIG. 3 is a schematic diagram of a printer device. FIG. 4 is a block diagram of error dispersion and binarization, FIG. 5 is an explanatory diagram of error dispersion, and FIG. 6 is a combination circuit diagram of a binary signal and a multi-value code signal. 42...PWM encoding circuit, 47... Binarization circuit.

Claims (1)

[Claims] A digital copying machine whose basic configuration is a scanner section and a printer section, and which can be connected to a facsimile machine and a filing device as a multifunction device, outputs a binary signal of 1 pixel binary as an image signal output means to the printer section. means and
1. A digital copying machine characterized by comprising a single pixel multi-value signal output means.