JPH09186835A - Digital copying machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital copying machine sending or receiving image data even without a frame memory. SOLUTION: When 4-lines of read image data MU-IN are fetched by an FIFO 541, image data are transferred to a coding section 542 for each of 4×4 pixel blocks. The coding section 542 compresses the image data into data of a fixed length. Thus, for example, since the data after compression are compressed into a half of the original data, a succeeding clock rate is halved. The data compressed by the coding section 542 are read at once in an FIFO 548 and read in a prescribed timing in synchronism with a clock signal of a scanner and transferred to a driver 546 and sent externally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital copying apparatus capable of transferring image data obtained by reading a document to the outside and receiving image data from the outside to form an image.

[0002]

2. Description of the Related Art Conventionally, in this type of digital copying apparatus, when image data is transferred to the outside, a first method for transferring uncompressed raw data together with a main scanning gate signal and a sub-scanning gate signal has been proposed. A second method is known in which variable-length coding is performed once, such as in a facsimile, and then the packet is transferred as a fixed unit packet. As a specific example, as described in Japanese Patent Laid-Open No. 2-60277, the image data read by the image reading device is once stored in the memory as it is, and then the SCSI (small computer system interface) is used. There is known one that is distributed to a plurality of image creating apparatuses via an interface such as.

[0003]

However, in the above-mentioned first method, it is necessary to perform the transfer by the image clock of the scanner in synchronization with the reading operation of the scanner or the like. Therefore, a low transfer rate method that operates in synchronization with the reading operation of the scanner is desired. In the above-described second method, since variable length data compression is performed on the sending side, it is necessary for the receiving side to have a frame memory for decoding. Therefore, a transfer method of image data that does not require a frame memory for decoding on the receiving side is desired. Further, in a device having an image retention function using a frame memory, it is desired to reduce the cost of the device by sharing a memory for retention and a memory for decoding received image data.

Therefore, the present invention has been made under such a background, and an object thereof is to provide a digital copying apparatus capable of transmitting or receiving image data without a frame memory. It is another object of the present invention to provide a digital copying apparatus which utilizes a frame memory to achieve high speed processing of image data.

[0005]

According to the first aspect of the present invention,
An image reading unit that reads a document and outputs image data corresponding to the document, a data compression unit that compresses the image data output from the image reading unit into data of a predetermined fixed length, and a compression unit that compresses the data. The fixed-length image data is transmitted to the outside in synchronism with the operation of the image reading means, and a transmission means for transmitting a gate signal that controls the timing of the transmission is provided. To achieve.

According to a second aspect of the invention, there is provided a receiving means for receiving the fixed length image data and the gate signal transmitted from the transmitting means of the digital copying apparatus according to the first aspect, and an image received by the receiving means. The object is achieved by including a decoding means for processing the data by using the gate signal and then decoding it, and a printing means for printing the image data decoded by the decoding means.

According to a third aspect of the invention, in the digital copying apparatus according to the second aspect, the image data received by the receiving means is provided with a storage means for storing the image data in a unit printed by the printing means. To achieve the above objectives.

According to a fourth aspect of the present invention, in the digital copying apparatus according to the second aspect, the image data received by the receiving means is controlled to be stored in the storage means while being decoded by the decoding means. The above-mentioned object is achieved by providing the control means for controlling.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the digital copying apparatus of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a sectional view showing a schematic configuration of a digital copying apparatus according to an embodiment of the present invention. In the embodiment of the present invention, as shown in FIG. 1, a contact glass 2 on which an original is placed is provided on an upper surface of an apparatus body 1.
Light source 4 that can move horizontally (movement in the sub-scanning direction)
Are arranged as the traveling body 5. In the lower part between the light sources 4, a mirror 3 for reflecting the light from the document in the horizontal direction is integrally formed with the light source 4. In order to sequentially reflect light from the mirror 3 every 90 degrees, a traveling body including a mirror 6 and a mirror 7 is provided so as to be able to travel according to the movement of the light source 4. A mirror 6 is provided to reflect the light from the mirror 3 downward, and the mirror 7 reflects the light from the mirror 6 in the opposite direction to the light from the mirror 6.
Is provided below the mirror 6. A lens 8 is arranged in the light path of the mirror 7, and a line image sensor (hereinafter referred to as CCD) 9 is arranged at the focus position of the lens 8.

As shown in FIG. 1, the printer unit 11 includes an optical system 23 for focusing the laser light from the laser generator on a predetermined position, and a reflecting mirror 2 for reflecting the output light of the optical system 23.
4, the photosensitive drum 12 to which the beam from the reflecting mirror 24 is exposed, the charging charger 20 that uniformly charges the photosensitive drum 12 before exposure, the developing device 14 that develops the electrostatic latent image by exposure with toner, A registration roller 27 for feeding the transfer sheet to the transfer position at a timing is provided, and a cassette 34 for setting a large number of transfer sheets. Further, the printer unit 11 includes a cassette 35 in which a paper of a size different from that of the cassette 34 is set, a paper feed roller 26 that feeds out only one paper from the cassette 34, and a cassette 35.
A sheet feeding roller 26 that feeds only one sheet from the transfer roller 18, a transfer charger 18 that transfers the toner image on the photoconductor drum 12 to the transfer sheet that is fed from the registration roller 27,
A separation charger 19 that separates the portion of the paper after the transfer is completed from the photoconductor drum 12, a conveyor belt 30 that conveys the separated transfer paper, and a toner image adhered to the transfer paper that is conveyed by the conveyor belt 30 is fixed. Fixer 3
1, a cleaning device 21 for removing the residual toner adhering to the surface of the photosensitive drum 12, and a discharge tray 33 for accommodating the transfer paper from the fixing device 31.

In the printer unit 11 having such a configuration, the laser generator is modulated and driven according to the image information, and the charging charger 20 is preliminarily passed through the optical system 23 and the reflecting mirror 24.
It reaches the photoconductor drum 12 which has been charged by and forms a latent image. This latent image reaches a position facing the developing device 14 according to the rotation of the photosensitive drum 12, and toner development is performed on the latent image. The paper sent from the cassette 34 or the cassette 35 is fed from the registration roller 27 at the timing when the visible image formed by the toner development reaches the transfer position, and is transferred by the transfer charger 18 at the transfer position. The upper toner image sticks to the paper surface. The sheet after the transfer is peeled off from the leading edge of the sheet by the static eliminator charger 29, and is sent onto the conveyor belt 30. The paper on the conveyor belt 30 is
The toner image is carried into the fixing device 31, and heat and pressure are applied thereto, so that the toner image is fixed on the paper surface. The transfer sheet on which the fixing is completed is sent to the discharge tray 33.

FIG. 2 is a block diagram of an image signal processing system of the digital copying apparatus according to the embodiment of the present invention. The image signal processing system includes a video processing unit 51, an image processing unit 52, a printer control unit 53, and a memory / transfer unit 54. The image signal read by the CCD 9 is an amplifier (AMP) of the video processing unit 51.
After being given a proper gain with, A with the A / D converter
The data is D / D converted and is output as 8-bit digital data DATA0 to DATA7 synchronized with the clock clk. To the video processing unit 51, a signal CCDSTN that determines the timing of reading the CCD 9 and a clock clk of 10 MHz are sent from the image processing unit 52.

In the image processing unit 51, black offset correction, shading correction, MTF correction, and electrical scaling in the main scanning direction are performed, and then γ correction and image quality processing such as dithering and error diffusion are performed. Image processing unit 51
Each of the above functions of will be described below. The black offset correction is a correction for subtracting the black level of the dark current of the CCD 9 from the image data. The shading correction eliminates unevenness in the light amount of the light source in the main scanning direction and unevenness due to the difference in sensitivity between the pixels of the CCD 9. Therefore, a white plate having a uniform density is read before the start of document scanning, and the data is stored for each pixel. The correction is performed by dividing the image data during the reading of the document by the stored white plate data for each pixel. MT
The F correction is to correct deterioration of optical frequency characteristics with a two-dimensional spatial filter. The scaling is scaling processing in the main scanning direction that is performed using an interpolation operation by the three-dimensional convolution method. In the image quality processing, after γ conversion, character processing, error diffusion processing, dither processing, etc. are performed according to the mode.

The image data SDT0 to SDT7, which have been subjected to a series of processing in the image processing unit 51, are sent to the printer control unit 53, where the speed is adjusted in accordance with the write clock and then sent to the LD modulation plate. LD
The modulation plate controls the pulse width and the amount of current applied to the semiconductor laser in accordance with the 8-bit 256-gradation image data. The image data after the γ correction in the image processing unit 51 is sent to the memory / transfer unit 54, and after the processing such as compression of the image data, the compressed data is transferred to an external digital copying apparatus. The configuration and operation of this part will be described in detail later. The image processing unit 51 is a CPU of a main control board (not shown).
An address bus and a data bus are shared with the (central processing unit), and communication is performed via this. The main control board controls the motors of the scanner and printer. It also controls various clutches and solenoids.

In such a structure, normally, when an image is read in the original reading mode, the original is set on the contact glass 2 with the image side down and the start button is pressed. As a result, the CPU outputs a scan start signal to the image processing unit 52, and FGATEN indicating the image effective range in the sub-scanning direction becomes ACTIVE. Next, the traveling body 5 starts moving to the left in the figure, and the sub-scanning of the document is performed. The reflected light (reading light) from the document illuminated by the light source 4 passes through the mirror 3, the mirror 6, the mirror 7, and the lens 8 in order, and the CCD 9
To reach. The CCD 9 converts incident light into an electric signal,
The electric signal is amplified by the amplifier of the video processing unit 51, A / D converted by the A / D converter, and sent to the image processing unit 52. Image processing unit 52
The data sent to is subjected to black offset correction, shading correction, MTF correction, electrical scaling in the main scanning direction, and then γ correction and image quality processing such as dithering and error diffusion. After that, the image data processed by the image processing unit 52 is sent to the printer control unit 53. In normal copying, almost simultaneously with the occurrence of FGTEN, the DFGA of the operation start signal of the printer unit 11 is generated.
TEN becomes active (ACTIVE), and writing to the printer is performed. The above is the copy operation in the normal mode.

Next, the memory / transfer unit 5 shown in FIG.
4 will be described in detail with reference to FIG. The memory / transfer unit 54 has a transmission system that compresses the image data from the image processing unit 52 and transfers it to the outside while storing it, and a reception system that receives the image data from the outside, decodes it, and outputs it. Broadly divided. That is, the memory
As shown in FIG. 3, the transmission system of the transfer unit 54 stores 5K × 8 which stores the image data from the image processing unit 52.
FIFO (First-In First-Out) 541 of bit
An encoder 542, a timing controller 543, a data rate converter 544, and an 8K × 8 bit FIFO.
(548) and the driver 546. On the other hand, the receiving system of the memory / transfer unit 54 is the receiver 5
47, a data rate conversion unit 544, an 8K × 8 bit FIFO (545), a decoding unit 549, a timing generation unit 550, and a 5K × 8 bit FIFO (551).
It is composed of DRAM controllers 552 and 12
The frame memory 553 of Mbite is shared by the transmission system and the reception system.

Next, the operation of the transmission system of the memory / transfer unit 54 thus configured will be described with reference to the time chart of FIG. The image data MU-IN from the image processing unit 52 is the sub-scanning gate signal mif.
When the gate, the main scanning gate signal milgate, and the main scanning synchronization signal milsync change as shown in FIG.
It will be sequentially incorporated into 1). When the data of four lines is once stored in the FIFO (541) and the capture of the image data of the fifth line is started, the signal mi-e supplied from the timing control unit 543 to the encoding unit 542.
n becomes active and 4x4 from the FIFO (541)
The image data is captured by the encoding unit 542 and encoded for each pixel block.

The format of the encoded data at this time is
As shown in FIG. 5, it is 8-byte data obtained by adding dummy 2-byte data to 6-byte data of La, Ld, and φij, and this data is created in the period of 16 clocks of the basic clock of 20 MHz. The output data CMP-OUT of the encoding unit 542 is obtained. In this way, the encoded data is compressed to 1/2 of the original image data, so that the clock rate after this is 10M which is half.
Hz. The encoding of the image data by the encoding unit 542 will be described later.

This encoded data CMP-OUT
Is sent to the DRAM controller 52 and 12 Mbyte
At the same time as being stored in the e frame memory 553, it is sent to the data rate conversion unit 544. Data rate converter 54
4, the signal mi-en from the timing control unit 543 is a FIFO of 8K × 8 bit configuration, as shown in FIG.
It is supplied to the write enable terminal wen of (548),
A clock obtained by dividing the clock clk by 2 is a clock terminal w
ck is supplied to the FIFO (548), and the FIFO (548) receives the compressed data CMP-from the encoding unit 542 according to the clock.
Take in OUT. As shown in FIG.
The read enable terminal ren of (548) has
A gate signal solgate from the ate generation block is supplied, and a clock sclk is supplied to its clock terminal rck.
Is supplied.

Therefore, as shown in FIG. 4, when the reading of the data of the 9th line starts, the gate signal solgate from the solgate generation block becomes active, and the transmission (reading) of data from the FIFO (548) is performed. Done. Read clock scl at this time
k can be freely selected within a limit of 1/2 frequency of the basic clock. The FIFO (548) is composed of two as shown in FIG. 6, and when one FIFO is writing, the other FIFO performs a toggle operation of reading data. Data sent from the FIFO (548) SEND-OUT [7: 0], sol
The signal solgate from the gate generation block and the clock sclk are transmitted to the outside through a differential driver 546 such as RS442 and a balanced line such as a twisted wire.

In the operation of the transmission system of the memory / transfer unit 54 described above, the image data is 1 /
Since the data is compressed and the data after the compression is transferred to the outside as in 2, the data can be transferred in synchronization with the operation of the scanner at a speed lower than the clock rate before the compression. Moreover, since the clock rate can be lowered, there is an advantage that an inexpensive transmission method can be adopted.

Next, the operation of the receiving system of the memory / transfer unit 54 will be described with reference to FIG. First, a case will be described in which image data is received from an external copying apparatus, the image data is decoded without being stored in the frame memory 553, and is printed out. In this case, the data SEND-IN [7: 0] received by the receiver 547 and the signal silg are received.
ate and clock sclk. The data format is the compressed image data in the format of FIG. 5 described above, and is sent at the timing of FIG. In the data speed conversion unit 544, the transmitted data SEN
The D-IN is taken into the FIFO (545). At this time,
As shown in FIG. 7, a signal silgate is connected to the write enable terminal wen of the FIFO (545) and a clock sclk is connected to the clock terminal wck of the FIFO (545) to fetch the data SEND-IN at the timing of the external copying apparatus (opposed machine). . Data is read from the FIFO (545) with a clock having a cycle twice that of the internal clock clk. The read enable signal memgate is the DRAM controller 5 that controls the frame memory 553.
Given from 52.

The data read from the FIFO (545) is converted into the original image data by the decoding section 549, as will be described later, and its output terminal fifo-out outputs 4
The lines are output at the same time. This output data is 4
It is input to the FIFOs (551) at the same time. FIFO
The data reading from (551) is performed one by one and sequentially sent to the image processing unit 52, where gradation processing for obtaining an appropriate image quality is performed. At this time, it is conceivable that what kind of gradation processing is to be carried out may be received in a separate command format from the device that is the source of the image data, or may be determined in the receiver device. The data subjected to the gradation processing by the image processing unit 52 is sent to the printer control unit 53 and the image is printed on the paper. In the operation described above, the received image data can be decrypted and printed without being stored in the frame memory 533, so there is no need to have a frame memory for reception. Further, since the operation is performed in perfect synchronization with the transmitter side, a high speed copying machine can be constructed.

Next, a case will be described in which the data output from the data speed conversion unit 544 is temporarily stored in the frame memory 533, then read from the frame memory 533, decoded by the decoding unit 549 and printed out. In this case, the data output from the data speed conversion unit 544 is temporarily stored in the frame memory 533 via the DRAM controller 552. When one page of data is stored in the frame memory 533, the stored data is read out by the control of the DRAM controller 552 and transferred to the decoding unit 549. Decoding section 5
At 49, the transferred data is converted into the original image data, and four lines are simultaneously output from the output terminal fifo-out. This output data contains four F
It is input to the IFO (551) at the same time. FIFO (55
The data reading from 1) is performed one by one and sequentially sent to the image processing unit 52 to be subjected to gradation processing for obtaining an appropriate image quality. The gradation processed data is
The image is sent to the printer control unit 52 and an image is printed on the paper. In the above operation, the data is temporarily stored in the frame memory 533 at the time of reception. Therefore, when the receiving side prints out a plurality of the same originals, the transmitting side does not need to repeatedly transfer the data, and the high speed is achieved. Can be printed out.

As described above, according to the embodiment of the present invention,
A method of switching between a case where the received data is directly transferred to the decoding unit 549 for decoding and a case where the received data is once stored in the frame memory 533 and then decoded by the decoding unit 549 is used. However, the received data is converted into the decoding unit 549.
And the frame memory 533 may be simultaneously transferred. In this way, when copying the same original document a number of times, the first copy can be obtained while receiving the data from the transmitting side, and the data can be read from the frame memory 533 after the second copy. Can be copied. Therefore,
High-speed processing is possible when copying the same manuscript many times.

Next, the internal structure of the encoding unit 542 will be described with reference to FIG. This encoding unit 542
As shown in FIG. 8, a maximum value / minimum value calculation unit 5421,
La / Ld calculation unit 5422, P1 / P2 calculation unit 5423
And a delay buffer 5 including a flip-flop
424 and a code allocation unit 5425. FI
The 4-line image data input from the FO (541) to the encoding unit 542 is input to the maximum value / minimum value calculation unit 5421 and the delay buffer 5424. In the image data input to the maximum / minimum value calculation unit 5421, the maximum value Lmax and the minimum value Lmin are calculated for each 4 × 4 pixel block. The calculated maximum value Lmax and minimum value Lmin are input to the La · Ld calculation unit, and La = (Lmax +
Lmin) / 2, and Ld = (Lmax-Lmin)
/ 2 is calculated. Both of the calculated La and Lb data are stored in the frame memory 553 as coded data, and are also input to the P1 / P2 calculation unit 5423 to generate P1
= La + 1 / 2.Ld, and P2 = La-1 / 2.L
d is calculated. The calculated data P1, P2, L
Each value of a is input to the code allocation unit 5425. Also,
The code assigning unit 5425 has the data Lmax and L described above.
The data of the 4 × 4 pixel block used for obtaining min, La, Ld, P1, and P2 is the delay buffer 54.
It is input from 24 at a predetermined timing. Therefore, the code assigning unit 5425 assigns a 2-bit code φij to each pixel by comparing each value of the data P1, P2, and La with the data of the 4 × 4 pixel block input from the delay buffer 5424. It is stored in the frame memory 553.

Next, the internal structure of the decoding unit 549 will be described with reference to FIG. The decoding unit 549 is shown in FIG.
As shown in, a Q1 to Q4 calculation unit 5491 and a quantized value assignment unit 5492 are included. Now, when the data La and Ld for one pixel block are read from the frame memory 553 and input to the Q1 to Q4 calculation unit 5491, Q
The 1-Q4 calculator 5491 performs the following calculations. Q1 = La + 3/4 · Ld Q2 = La + 1/4 · Ld Q3 = La-1 / 4 · Ld Q4 = La-3 / 4 · Ld In the quantized value assigning unit 5492, the 2-bit code φij is converted into the quantized value Q1. To Q4, the decoded image data for each pixel block is output. The output decoded image data is supplied to the FIFO (551), and then transferred to the image processing unit 52 by the connection to the “A” side of the contact of the switching unit of the image processing unit 52, and gradation processing is performed. And printed out.

[0028]

According to the first aspect of the invention, the data read by the image reading means is compressed into data of a predetermined fixed length,
Since the data is transmitted in synchronization with the operation of the image reading means, data can be transmitted without having an expensive storage means such as a frame memory, and the side receiving the data also has an expensive storage means. It is possible to realize image output without the need. According to the second aspect of the present invention, since the data compressed with a fixed length can be received and decoded and printed out, it is not necessary for the receiving side to have an expensive storage means such as a frame memory.

According to the third aspect of the present invention, since the data compressed in the fixed length can be temporarily stored in the storage means, when printing a large number of the same document on the receiving side, the data can be transmitted once. A high-speed processing device can be realized. According to a fourth aspect of the invention, the received fixed-length compressed image data is
Since the data is stored in the storage means while being decrypted, the first printed material can be printed in synchronization with the reception when the receiving side prints a large number of the same original document, and the second and subsequent sheets can store data from the storage means. Since it can read out and print, a high-speed processing device can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a digital copying apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of an image signal processing system of the digital copying apparatus.

FIG. 3 is a block diagram of a memory / transfer unit of the digital copying apparatus.

FIG. 4 is a time chart showing signals of respective parts of the memory / transfer unit.

FIG. 5 is a diagram showing a configuration of compressed data compressed by an encoding unit of a memory / transfer unit.

FIG. 6 is a diagram showing a configuration of a data rate conversion unit of a memory / transfer unit during transmission.

FIG. 7 is a diagram showing a configuration at the time of reception of a data rate conversion unit of the memory / transfer unit.

FIG. 8 is a block diagram showing an internal configuration of an encoding unit.

FIG. 9 is a block diagram showing an internal configuration of a decoding unit.

[Explanation of symbols]

 9 CCD 51 Video processing unit 52 Image processing unit 53 Printer control unit 54 Memory / transfer unit 541 FIFO 542 Encoding unit 543 Timing control unit 544 Data rate conversion unit 545 FIFO 546 Driver 547 Receiver 548 FIFO 549 Decoding unit 550 Timing control unit 551 FIFO 552 DRAM controller 553 Frame memory

Claims (4)

[Claims] 1. An image reading unit for reading a document and outputting image data corresponding to the document, and a data compressing unit for compressing the image data output from the image reading unit into data of a predetermined fixed length. Fixed length image data compressed by data compression means
A digital copying apparatus comprising: a transmission unit that transmits to the outside in synchronization with the operation of the image reading unit and that transmits a gate signal that controls the timing of the transmission. 2. A receiving unit for receiving fixed length image data and a gate signal transmitted from the transmitting unit of the digital copying apparatus according to claim 1, and the image data received by the receiving unit for the gate signal. A digital copying apparatus comprising: a decoding unit that processes the image data using the above and then decodes the image data; and a printing unit that prints the image data decoded by the decoding unit. 3. The image data received by the receiving means,
3. The digital copying apparatus according to claim 2, further comprising a storage unit that stores the printing unit in a printing unit. 4. The image data received by the receiving means is
The digital copying apparatus according to claim 2, further comprising a control unit that controls the storage unit to store the data while the decryption unit decrypts the data.