JP6519447B2 - Image forming system and image forming system control method - Google Patents

Description

  The present invention relates to an image forming apparatus, an image forming system, and an image forming system control method, and in particular, a technology capable of appropriately performing image forming in an image forming system in which image forming apparatuses are connected in series or parallel. About.

  By connecting a plurality of image forming apparatuses in series, as a serial tandem image forming system, a recording sheet on which image formation has been performed on a part of the area by one image forming apparatus is continuously input to the other image forming apparatus, There is an image forming system for forming an image on another area of the recording paper in the image forming apparatus of

  According to such an image forming system, high-speed double-sided image forming output can be realized by forming an image on each of the front and back sides of the recording sheet by two image forming apparatuses, and there is an advantage of improving productivity. In addition, image formation is performed using toners of different colors in two image forming apparatuses, or image formation suitable for each of a character area and an image area is performed in two image forming apparatuses. It becomes possible to output fine image formation at high speed.

  An image forming system provided with such a plurality of image forming apparatuses is disclosed in the following patent documents.

JP, 2006-157629, A

  By the way, one of the two image forming apparatuses is set as the main (first image forming apparatus) and the other image forming apparatus is set as the sub (second image forming apparatus), and the main image forming apparatus is used. Image data on the front and back is generated, an image is formed on the sheet surface by the main image forming apparatus, and the sheet on which the image is formed is conveyed from the main image forming apparatus to the sub image forming apparatus to form the main image forming 2. Description of the Related Art There is a serial tandem type image forming system which forms an image on both sides by forming an image on the back side of a sheet by a sub image forming apparatus which has received image data on the back side from the apparatus.

In FIG. 15, the main first image forming apparatus 100 and the sub second image forming apparatus 200 are connected by a local area network (LAN) 10.
In the image forming system 1 of FIG. 15, when job data is input from an external device such as a PC or the scanner unit 106, the image generation unit 108 generates image data for image formation ((1) in FIG. 15). ). This image data is temporarily stored in the image data storage unit 130 ((2) in FIG. 15), and then the image data for the sheet surface is synchronized with the timing when the first image forming apparatus 100 forms the image on the sheet. It is sent to the image forming unit 150 ((3) in FIG. 15). Here, an image corresponding to the image data for the surface of the sheet is formed on the surface of the sheet, and the sheet is conveyed toward the image forming unit 250 of the second image forming apparatus 200.

  Also, the sheet back surface image data (back surface image data) is read from the image data storage unit 130 and sent to the communication unit 102 ((4) in FIG. 15). The back side image data sent to the communication unit 102 is sent to the communication unit 202 of the second image forming apparatus 200 via the LAN 10 ((5) in FIG. 15).

  The image data sent from the first image forming apparatus 100 is temporarily stored in the image data storage unit 230 as needed, and then the image is formed in time with the image forming on the sheet by the second image forming apparatus 200. It is sent to the forming unit 250 ((6) in FIG. 15). Here, an image corresponding to the back surface image data is formed on the back surface of the sheet, and is conveyed toward the outside of the second image forming apparatus 200.

In this description, known processes such as compression and decompression of image data are omitted.
In the image forming system of the tandem system, the image forming apparatus stores the image data stored in the image data storage unit such as the HDD, thereby performing the image formation again and the verification after the image data. And the like are possible (for example, Patent Document 1).

  By the way, in the conventional tandem-type image forming system 1, for example, the image data is transferred from the first image forming apparatus 100 to the second image forming apparatus 200, and the image forming can be performed in the second image forming apparatus 200. In some cases, the processing speed does not satisfy the process speed of the image forming process in the second image forming apparatus 200. Therefore, in the first image forming apparatus 100 and the second image forming apparatus 200, it is necessary to temporarily store the image data in a storage device such as an HDD and then start the image forming process.

In recent years, with the speeding up of access to storage devices, communication cable communication speed, and memory bus read / write speed, the image forming speed in the image forming system is improved, and the productivity of the image forming process increases. It is coming.
Further, in recent years, the communication speed of the communication unit (network controller) of the network and the communication cable has been increased.

Therefore, the processing speed until the image formation is possible in the second image forming apparatus 200 by transferring the image data from the first image forming apparatus 100 to the second image forming apparatus 200 is the image forming in the second image forming apparatus 200. It became possible to meet the process speed of the process.
As a result, it is possible to execute transfer of image data in real time, for example, by transmitting image data from the first image forming apparatus 100 to the second image forming apparatus 200 to perform image formation for each page to be image formed. As a result, the productivity of the image forming process can be improved.

In order to increase the speed of image formation in a serial tandem image forming system, the introduction of 10GBASE-T capable of high-speed transfer of 10 Gbps has been considered as a LAN standard for connecting each image forming apparatus.
In 10GBASE-T, a LAN cable of a higher category such as CAT6a or CAT7 is specified. However, the LAN cables in the upper category also have mechanical compatibility (connector shape compatibility) with the cables in the lower category.

Therefore, even if 10GBASE-T is introduced in the LAN standard, the user may use a LAN cable for medium to low speed in the lower category.
However, the LAN cable of the lower category can not always guarantee a 10 Gbps transfer rate. When a connection can not be established at a transfer rate of 10 Gbps between the first image forming apparatus 100 and the second image forming apparatus 200, generally, the transfer rate is reduced by auto negotiation to try reconnection.

It is also possible to select the fastest transfer rate among the slow transfer rates. However, on the premise that the image data is transferred at a transfer rate of 10 Gbps, the second image forming apparatus 200 transfers the image data to the image forming unit 250 at a constant speed to form an image.
Therefore, when the transfer speed of the image data in the LAN is reduced, the transfer of the image data is not in time for the image formation in the second image forming apparatus 200, and a transfer error of the image data occurs such that the image is interrupted halfway.

  Even when a connection can be established at a transfer rate of 10 Gbps when using the LAN cable of the lower category, communication quality is actually low, image data transfer errors increase, and packet retransmission frequently occurs. As a result, transfer of image data may be delayed, and an image formation error may occur in the second image forming apparatus 200 as described above.

  In addition, there are cases where a communication device such as a hub is provided on the LAN, which is a transfer path of image data, by the user. When the image forming system 1 is incorporated into a general-purpose LAN, not a dedicated one, the communication capability other than the image forming apparatus is unknown, so that the 10 Gbps transfer rate can not be guaranteed.

FIG. 16 schematically shows a state in which images P1 to P12 are formed on the front and back of six sheets by the image forming system 1 shown in FIG.
Here, the first image forming apparatus 100 executes image formation for odd pages of P1, P3,..., P11. For the even pages P2, P3,..., P13, the second image forming apparatus 200 executes image formation using the image data sent from the first image forming apparatus 100.

However, as described above, in the case where a medium-to-low speed LAN cable is used in the image forming system 1 assuming a high-speed LAN, the communication speed is lowered and the data transfer of the image data of P4 is not in time. I suppose.
In this case, since the image data of P2 remains in the second image forming apparatus 200, the image data of existing P2 is sent to the image forming unit 250, and the front surface is the back surface of the sheet of P3. Instead, the image of P2 is repeatedly formed. Then, a printed material with a misaligned page arrangement on the front and back sides is produced, such as sequentially forming an image of P4 instead of P6 on the back surface of the sheet of which the front surface is P5. A printed material in which the page arrangement on the front and back sides is shifted in this way is shown as FIG. 17 in correspondence with FIG. Then, there is a problem that the image forming system 1 can not detect such an abnormality in the image arrangement.

  The present invention relates to an image forming system for transmitting and receiving image data through a network, and an image forming system capable of detecting an abnormality in page arrangement caused by a reduction in transfer rate of image data through the network, and image forming system control The aim is to realize the method.

That is, the present invention which solves the above-mentioned subject is as follows.
The present invention is a serial tandem image forming system in which a second image forming apparatus forms an image in real time of image data received from a first image forming apparatus via a network. Here, the legitimacy of the image data is verified for the image formed by the second image forming apparatus. As a method of determining the legitimacy of image data, a hash value calculated by inputting image data to a hash function is used. By characterizing a large amount of image data with a small amount of hash value, the immediacy of the determination of the legitimacy of the image data can be enhanced to cope with a high-speed image forming process. By making a small amount of hash values to be compared, it is possible to reduce the hardware burden of determining the legitimacy of image data. In addition, specifically, it becomes like the following (1)-(9).

  (1) The present invention is an image forming system including at least a first image forming apparatus and a second image forming apparatus which are connected to be able to exchange image data via a network and form an image on any side of a sheet. The first image forming apparatus forms an image on one side of a sheet based on first image data and a first communication unit that communicates with the second image forming apparatus via the network. A first image forming unit, a first verifying unit that calculates a hash value of a page arrangement of second image data used by the second image forming apparatus to form an image, and the first image forming unit performs the first image data. And a first control unit that transmits the second image data to the second image forming apparatus via the communication unit, and the second image forming apparatus transmits the second image data via the network. Said A second communication unit for communicating with the image forming apparatus, a second image forming unit for forming an image on the other side of the sheet based on the second image data, and the other of the sheet in the second image forming unit A second verification unit that calculates a hash value of the page arrangement of the second image data when forming an image on a surface; the first image via the first communication unit, the network, and the second communication unit And a second control unit that supplies the second image data transmitted from the forming apparatus to the second image forming unit, and the second verification unit calculates the hash value calculated by the first verification unit and the second verification unit. A determination unit is provided at any position of the image forming system to determine whether the page arrangement of image formation on the sheet is normal or not by comparing the hash value calculated in the copy unit with that of the sheet.

(2) In the above (1), the first image forming apparatus and the second image forming apparatus are connected via a local area network as the network as a tandem type image forming system.
(3) In the above (1), the first image forming apparatus and the second image forming apparatus are connected as a network via a local area network, and an image is formed by the first image forming apparatus. The present invention is a serial tandem image forming system in which the sheet is conveyed to the second image forming apparatus, and an image is formed on each side of the sheet.

  (4) In the above (1) to (3), the first verification unit sequentially inputs image data for each page to the hash function in the order of pages to be image-formed by the second image forming unit. Outputting the hash value calculated from the hash function, and the second verification unit transmits the image data of each page in the order of pages to be formed by the second image forming unit, transmitted from the first image forming apparatus Are sequentially input to the hash function, and then the hash value calculated from the hash function is output.

  (5) In the above (1) to (4), the determination unit determines the second verification and the second verification value calculated by the first verification unit each time the second image forming unit forms an image. The hash value calculated by the copy unit is compared to determine whether the page arrangement of image formation on the sheet is normal.

(6) In the above (1) to (5), when the determination unit determines that the page arrangement for image formation is not normal, the first control unit stops the image formation in the first image forming unit. And the second control unit instructs the second image forming unit to stop the image formation.
(7) In the above (1) to (6), the determination unit determines that the page arrangement for image formation is not normal, and the first control unit and the second control unit issue an instruction to stop the image formation When resumption is instructed, the pre-second verifier controls to initialize with the last hash value that is normal.

(8) In the above (1) to (7), the determination unit is one of the first verification unit and the second verification unit, and the hash value calculated by the first verification unit and the hash value The hash value calculated by the second verification unit is compared.
(9) In the above (1) to (7), the determination unit exists in a state of being separately connected to the network separately from the first image forming apparatus and the second image forming apparatus; (1) The hash value calculated by the verification unit and the hash value calculated by the second verification unit are compared, and the comparison result is supplied to at least the first control unit.

According to the present invention for solving the above-mentioned problems, the following effects can be obtained.
(1) In the image forming system of the present invention, the first image forming apparatus executes image formation based on the first image data, and the second image forming apparatus receives the first image forming apparatus from the first image forming apparatus via the network. When executing image formation based on the two image data, the hash value for the page arrangement of the second image data calculated by the first verification unit on the first image forming apparatus side, and the second image forming apparatus side (2) The determination unit compares the hash value of the page arrangement of the second image data calculated by the verification unit with the hash value to determine whether the page arrangement of image formation on the sheet is normal.

As a result, in an image forming system that transmits and receives image data via a network, it is possible to detect an abnormality in page arrangement caused by a decrease in transfer rate of image data via the network.
The hash value of the page arrangement of the image data is small in data size, and the processing load of the image forming system for comparing and verifying the page arrangement hash value is small.

  (2) In the above (1), the first image forming apparatus and the second image forming apparatus are connected via a local area network as a network as a tandem type image forming system. That is, in the tandem type image forming system, the first image forming apparatus executes image formation based on the first image data, and the second image forming apparatus receives the second image sent from the first image forming apparatus via the network. When performing image formation based on image data, the hash value for the second image data calculated by the first verification unit on the first image forming apparatus side and the second verification unit on the second image forming apparatus side The determination unit compares the calculated second image data with the hash value to determine whether the page arrangement of image formation on the sheet is normal.

As a result, in a tandem-type image forming system that transmits and receives image data via a local area network, it is possible to detect an abnormality in page arrangement caused by a decrease in transfer rate of image data via the network.
(3) In the above (1), the first image forming apparatus and the second image forming apparatus are connected as a network through the local area network, and the sheet on which the image is formed by the first image forming apparatus is the first (2) An image forming system of serial tandem type which is conveyed to an image forming apparatus and forms an image on each side of a sheet, and forms an image by sharing the front and back of the same sheet. That is, in the serial tandem type image forming system, the first image forming apparatus executes image formation on one side of the sheet based on the first image data, and the second image forming apparatus performs the first image forming apparatus via the network. And when performing image formation on the other side of the sheet based on the second image data sent from the printer, the hash value for the second image data calculated by the first verification unit on the first image forming apparatus side and The determination unit compares the hash value of the second image data calculated by the second verification unit on the second image forming apparatus side with the determination unit to determine whether the page arrangement of image formation on the sheet is normal.

As a result, in a serial tandem type image forming system that transmits and receives image data via a local area network, it is possible to detect an abnormality in page arrangement caused by a decrease in transfer rate of image data via the network.
(4) In the above (1) to (3), the first verification unit sequentially inputs the image data of each page to the hash function in the order of pages to be formed by the second image forming unit, The hash value calculated from the function is output, and the second verification unit hashes the image data for each page sequentially in the order of the pages to be formed by the second image forming unit from the first image forming apparatus. After input to the function, the hash value calculated from the hash function is output. That is, a hash value based on the page arrangement of the second image data before being transmitted from the first image forming apparatus to the second image forming apparatus, and an image formed by being transmitted from the first image forming apparatus to the second image forming apparatus The hash value of the page arrangement of the original second image data and the hash value of the page arrangement of the second image data actually formed by comparison with the hash value based on the page arrangement of the second image data And can be compared. As a result, in an image forming system that transmits and receives image data via a local area network, it is possible to detect an abnormality in page arrangement caused by a decrease in transfer rate of image data via the network.

  (5) In the above (1) to (4), each time the second image forming unit forms an image, the hash value calculated by the first verification unit and the hash value calculated by the second verification unit are used. By comparing and determining whether the page arrangement of the image formation on the sheet is normal, it is determined whether or not the image formation can be performed with the correct page arrangement in the second image forming unit. As a result, in an image forming system that transmits and receives image data via a local area network, it is possible to detect an abnormality in page arrangement caused by a decrease in transfer rate of image data via the network.

  (6) In the above (1) to (5), when the determining unit determines that the page arrangement for image formation is not normal, the first control unit instructs the first image forming unit to stop the image formation. By instructing the second image forming unit to stop image formation, the second control unit can detect an abnormality in the page arrangement and can promptly stop image formation in which the page arrangement is not normal.

  (7) In the above (1) to (6), when it is determined that the page arrangement is not normal and the first control unit and the second control unit instruct to resume the image formation instructed to stop, 2) The verification unit initializes with the last hash value that is normal, and controls to restart the image formation from the image of the page array that was not normal, thereby detecting an abnormality in the page array and detecting an abnormality in the page array. Image formation can be resumed in a detectable state.

  (8) In the above (1) to (7), the determination unit is either the first verification unit or the second verification unit, and the hash value calculated by the first verification unit and the second verification unit By comparing with the calculated hash value, in the image forming system that transmits and receives image data via the local area network, the page arrangement abnormality caused by the decrease in the transfer speed of the image data via the network is reliably detected. It will be possible to

  (9) In the above (1) to (7), the determination unit exists in a state of being connected to the network separately from the first image forming apparatus and the second image forming apparatus, and is calculated by the first verification unit From the server other than the first image forming apparatus and the second image forming apparatus, the calculated hash value is compared with the hash value calculated by the second verification unit and the comparison result is supplied to at least the first control unit. It becomes possible to detect an anomaly in the page arrangement with certainty.

It is a block diagram which shows the structure of embodiment of this invention. It is a block diagram which shows the structure of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is a flowchart which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is a flowchart which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the process of embodiment of this invention. It is operation | movement explanatory drawing which shows the conventional process. It is operation | movement explanatory drawing which shows the conventional process. It is operation | movement explanatory drawing which shows the conventional process.

Hereinafter, modes for carrying out the present invention (hereinafter, embodiments) will be described in detail with reference to the drawings.
First Embodiment
[Overall Configuration of Image Forming System]
Here, with regard to the image forming system 1 of the present embodiment, a specific example in the case of being configured as an image forming system of serial tandem system will be described in detail based on FIG. 1 and FIG.

  Here, the two image forming apparatuses of the image forming apparatus 100 and the image forming apparatus 200 are mechanically connected along the flow of the sheet to constitute a serial tandem image forming system. In addition, two image forming apparatuses of the image forming apparatus 100 and the image forming apparatus 200 are communicably connected by a network 10 such as a LAN to configure a serial tandem image forming system.

The productivity of double-sided image formation can be improved by having the image forming apparatus 100 and the image forming apparatus 200 take charge of image formation on each side of the sheet in each of the image forming apparatuses.
Here, the two image forming apparatuses connected along the sheet flow will be referred to as “serial tandem image forming system”. The serial tandem image forming system is not limited to the connection of two image forming apparatuses, and may be three or more connections. In addition, a sheet processing apparatus that performs sheet processing on a sheet on which an image is formed may be connected to the rear stage of the image forming apparatus 200.

It is assumed that the image forming apparatus 100 and the image forming apparatus 200 have the same configuration. Here, the image forming apparatus 100 is referred to as a first image forming apparatus, and the image forming apparatus 200 is referred to as a second image forming apparatus.
The image forming apparatus 100 generates image data on the front side of the sheet and image data on the rear side of the sheet, and transmits the image data on the rear side of the sheet to the image forming apparatus 200 from the image forming apparatus 100 via the network 10 The forming apparatus 100 executes image formation using the generated front side image data, and the image forming apparatus 200 executes image formation using the back side image data received from the image forming apparatus 100 via the network 10 as a specific example. Do.

[Detailed Configuration of Image Forming System]
An image forming apparatus 100 as a first image forming apparatus communicates with another apparatus, a control unit 101 as a first control unit that controls each part in the image forming apparatus 100 and controls the entire system as an image forming system. A communication unit 102 as a first communication unit, an operation display unit 103 for performing an operation input by a user and displaying a status of the image forming apparatus 100, a non-volatile storage unit 104 for storing various data such as setting values, An image that can be formed by performing image processing by RIP (Page Description Language) data input from an external user terminal (external PC) and a scanner unit 106 that reads image data and generates image data, and RIP (Raster Image Processor) processing An image generation unit 108 for generating data, and a verification unit 1 as a first verification unit for generating a hash value of a page array and verifying the hash value 0, an image data storage unit 130 for storing image data and the like at the time of image formation, an image processing unit 140 for executing various image processing necessary for image formation, and on paper based on an image formation command and image data Image forming unit 150 as a first image forming unit that forms an image on one of the areas (for example, the surface of the sheet) and the sheet on which the image is formed on one side is inverted and conveyed to a subsequent image forming apparatus And a reversing unit 190.

  Further, the image forming apparatus 200 as a second image forming apparatus includes a control unit 201 as a second control unit that controls each unit in the image forming apparatus 200 and a communication unit as a second communication unit that communicates with other devices. 202, an operation display unit 203 for performing an operation input by the user and displaying a state of the image forming apparatus 200, a non-volatile storage unit 204 for storing various data such as setting values, and the like A scanner unit 206 for generating, an image generating unit 208 for generating image data capable of forming an image, a verification unit 210 as a second verification unit for generating a hash value of a page arrangement and verifying the hash value, Image formation An image data storage unit 230 for storing image data and the like at the time of image processing; an image processing unit 240 for executing various image processing necessary for image formation; Image forming unit 250 as a second image forming unit that forms an image on the other area (for example, the back side of the sheet) of the sheet based on that, and a reversing part 290 that inverts and outputs the sheet on which an image is formed on both sides , Is configured.

  The portions shown as the control units 101 and 201 may be divided into a main control unit that performs various controls and an I / O control unit that distributes data. When the image forming units 150 and 250 are electrophotographic image forming units, as shown in FIG. 2, they are formed on the photosensitive drum by a known process such as charging, exposure, development, transfer, and fixing. An image is formed by transferring a toner image to a sheet.

Further, the reversing units 190 and 290 may be configured separately from the image forming apparatuses 100 and 200 as intermediate units instead of being built in the image forming apparatuses 100 and 200.
[Hash function and hash value]
The basic processes of generation and comparison will be described below for the hash value calculated by the hash function.

[Generation of hash value (1)]
FIG. 3 is a process procedure explanatory view showing handling of a hash value in the image forming apparatus 100 in the first embodiment.
In the first embodiment, when the image forming apparatus 100 forms an image on the front side of the sheet based on front side image data and the image forming apparatus 200 forms the image on the back side of the sheet based on the back side image data, the image forming apparatus 100. The hash value of the page arrangement of the back side image data is calculated.

The image forming apparatus 100 calculates a hash value based on the page arrangement of the back surface image data among the series of image data generated by the image generation unit 108 using the hash function in the verification unit 110.
The series of image data generated by the image generation unit 108 of the image forming apparatus 100 will be called P1, P2, P3, P4, P5, P6, P7, P8, P9, P10,. .

  The surface image data for the sheet surface is P1, P3, P5, P7, P9, ... in order from the top. On the other hand, the back side image data for the back side of the sheet are P2, P4, P6, P8, P10,. The first sheet is an image of P1 and P2, the second sheet is an image of P3 and P4, the third sheet is an image of P5 and P6, the fourth sheet is an image of P7 and P8, and the fifth sheet Are formed as images of P9 and P10,.

In this case, the verification unit 110 of the image forming apparatus 100 calculates a hash value based on the page arrangement of the back side image data based on the back side image data generated by the image generation unit 108 by the built-in hash function.
First, at the start of an image forming job, a hash function is set to a predetermined initial value, for example, 0. Here, when the image data P2 is input to the hash function, it is a hash value calculated from the image data P2. The hash value when the image data P4 is input to the hash function is a hash value calculated when the image data P2 and the image data P4 are sequentially input. The hash value when the image data P6 is input to the hash function is a hash value calculated when the image data P2, the image data P4, and the image data P6 are sequentially input. The hash value when the image data P8 is input to the hash function is a hash value calculated when the image data P2, the image data P4, the image data P6, and the image data P8 are sequentially input. The hash value when the image data P10 is input to the hash function is a hash value calculated when the image data P2, the image data P4, the image data P6, the image data P8, and the image data P10 are sequentially input. Similarly, the hash value is a hash value calculated when accumulation of image data input in the page arrangement order is sequentially input.

  The image forming apparatus 100 handles the calculated hash value and image data as shown in FIG. As shown in FIG. 4, in the image forming apparatus 100, a hash value corresponding to the back side image data is added to the generated image data, and the front side image data and the back side image data are stored in the image data storage unit 130. Keep it. Further, the image forming apparatus 100 transmits back side image data to the image forming apparatus 200 via the network 10 in accordance with the image formation on the back side (see FIG. 4).

  That is, the image data P2 is input to the hash function, and the calculated hash value is added to the image data P2. Subsequently, the image data P4 is input to the hash function, and the calculated hash value is added to the image data P4. Subsequently, the image data P6 is input to the hash function, and the calculated hash value is added to the image data P6. Subsequently, the image data P8 is input to the hash function, and the calculated hash value is added to the image data P8. Subsequently, the image data P10 is input to the hash function, and the calculated hash value is added to the image data P10. Subsequently, the image data is similarly input to the hash function, and the calculated hash value is added to the input image data.

  Here, the hash value added to the image data P2 is a hash value calculated from the image data P2. The hash value added to the image data P4 is a hash value calculated from the page arrangement of the image data P2 and the image data P4. The hash value added to the image data P6 is a hash value calculated from the page arrangement of the image data P2, the image data P4, and the image data P6. The hash value added to the image data P8 is a hash value calculated from the page arrangement of the image data P2, the image data P4, the image data P6, and the image data P8. The hash value added to the image data P10 is a hash value calculated from the page arrangement of the image data P2, the image data P4, the image data P6, the image data P8, and the image data P10. Similarly, the hash value calculated from the accumulation (page arrangement) of the image data input in the page arrangement order is added to the image data of the page inputted last.

[Generation of hash value (2)]
FIG. 5 is a processing procedure diagram showing handling of the hash value in the image forming apparatus 200.
The image forming apparatus 200 as the second image forming apparatus receives, via the communication unit 202, the back surface image data transmitted from the image forming apparatus 100 via the network 10.

The back side image data for the back side of the sheet are P2, P4, P6, P8, P10,.
The image forming apparatus 200 forms an image on the back side of the sheet based on the back side image data transmitted from the image forming apparatus 100.

At the same time, the verification unit 210 of the image forming apparatus 200 calculates a hash value based on the page arrangement of the back side image data based on the back side image data received from the image forming apparatus 100 by a built-in hash function. .
At the start of the image forming job, the verification unit 210 sets an initial value identical to the initial value set in the hash function of the image forming apparatus 100, for example, 0. Input and calculate the hash value. In this case, the hash value is generated in accordance with the timing of executing the image formation on the back side based on the back side image data.

After the control unit 201 inputs the image data for each page in the verification unit 210, the control unit 201 temporarily stores a hash value calculated from the hash function as necessary, and the image forming apparatus 100 via the communication unit 202 and the network 10. Send to
That is, when the back surface image data P2, P4, ..., P10, ... are transmitted from the image forming apparatus 100 to the image forming apparatus 200 without delay or error, hashing is performed in the image forming apparatus 200 as follows. A value is generated. First, in accordance with the image formation timing of the image data P2, the hash value calculated by inputting the image data P2 into the hash function is transmitted to the image forming apparatus 100. Subsequently, in accordance with the image formation timing of the image data P4, the hash value calculated by inputting the image data P4 into the hash function is transmitted to the image forming apparatus 100. Subsequently, in accordance with the image formation timing of the image data P6, the hash value calculated by inputting the image data P6 to the hash function is transmitted to the image forming apparatus 100. Subsequently, in accordance with the image formation timing of the image data P8, the image data P8 is input to the hash function, and the calculated hash value is transmitted to the image forming apparatus 100. Subsequently, at the image formation timing of the image data P10, the image data P10 is input to the hash function, and the calculated hash value is transmitted to the image forming apparatus 100.

  Here, the hash value calculated after the input of the image data P2 is a hash value calculated from the image data P2. The hash value calculated after the input of the image data P4 is a hash value calculated from the image data P2 and P4. The hash value calculated after the input of the image data P6 is a hash value calculated from the image data P2, P4 and P6. The hash value calculated after the input of the image data P8 is a hash value calculated from the image data P2, P4, P6 and P8. The hash value calculated after the input of the image data P10 is a hash value calculated from the image data P2, P4, P6, P8 and P10. Similarly, the hash value calculated from the accumulation of the image data input in the page arrangement order is temporarily stored.

[Comparison verification of hash value]
FIG. 6 is a process procedure diagram showing comparison verification of hash values in the image forming apparatus 100.
That is, the image forming apparatus 200 uses the image forming apparatus 200 to generate a hash value based on the page arrangement of the back side image data calculated by the verification unit 110 and stored in the image data storage unit 130 and the image data transmitted from the image forming apparatus 100. It shows how to compare with the hash value calculated by the verification unit 210 when forming.

The verification unit 110 in the image forming apparatus 100 compares the hash value stored in the storage unit with the hash value received from the image forming apparatus 200.
That is, the image forming apparatus 100 has been transmitted from the image forming apparatus 100 with the respective hash values stored in the image data storage unit 130 in addition to the back surface image data P2, P4, P6, P8, P10. The image forming apparatus 200 compares it with the hash value calculated in the image forming apparatus 200 at the timing of image formation in the image forming apparatus 200 and transmitted from the image forming apparatus 200 to the image forming apparatus 100. The comparison of the hash values is performed at timing when the hash values are calculated in the image forming apparatus 200 and transmitted from the image forming apparatus 200 to the image forming apparatus 100.

  Here, in the image forming apparatus 100, if the verification unit 110 compares the hash value stored in the image data storage unit 130 with the hash value received from the image forming apparatus 200 and the comparison result matches ( Refer to “Hash value up to P2 = Hash value up to P2” in FIG. 6), the control unit 101 continues the execution of image formation.

  When the back side image data transmitted from the image forming apparatus 100 to the image forming apparatus 200 is not in time for the image formation timing of the image forming apparatus 200 due to a delay, an error, packet retransmission, etc., the back side image data once image formed is updated. May be used again for image formation. For example, it is assumed that the back side image data P4 is not in time, and the back side image data P2 is used again at the timing which should originally be the back side image data P4. In this case, the verification unit 210 calculates the hash value of the page arrangement of the back surface image data P2 and the back surface image data P2. In this case, the image forming apparatus 100 has a hash value up to P4, which is not identical to the hash value of P2 · P2 calculated by the image forming apparatus 200 (the hash value up to “P4 in FIG. Control unit 101 controls to stop the execution of image formation (refer to “H2 value of P2 · P2”).

[Overall operation of the image forming system]
Hereinafter, processing of each unit at the time of the image forming operation will be described with reference to the flowchart of FIG. 7 and the operation explanatory view of FIG.
From an external user terminal, PDL (Page Description Language) data to be subjected to image formation is input through the communication unit 102 together with an instruction for image formation (step S101 in FIG. 7, FIG. 8 (1)). The control unit 101 controls the image generation unit 108 to RIP the PDL data to generate image data capable of forming an image (step S102 in FIG. 7). Then, the control unit 101 stores the generated image data in the image data storage unit 130 (step S103 in FIG. 7, FIG. 8 (2)).

  Here, the control unit 101 divides the image data stored in the image data storage unit 130 into front side image data on which an image is formed by the image formation 100 and back side image data on which an image is formed by the image forming apparatus 200. Then, the control unit 101 sends back side image data to the verification unit 110, and the verification unit 110 calculates a hash value based on the page arrangement of the back side image (step S104 in FIG. 7, FIG. 3, FIG. 8 (4a)). ). Then, the control unit 101 associates the hash value calculated based on the page arrangement of the back side image data with the corresponding back side image data and stores the hash value in the image data storage unit 130 (step S105 in FIG. 7, FIG. 4). . Here, the hash value is not stored integrally with the back side image data, but may be stored in a form linked to the back side image data.

Further, in parallel with the above calculation of the hash value, the control unit 101 transmits the back side image data to the image forming apparatus 200 via the communication unit 102 and the network 10 (step S106 in FIG. 7, FIG. 4, FIG. 8 (4b), FIG. 8 (5).
The control unit 201 sends back side image data received (step S201 in FIG. 7) via the network 10 and the communication unit 202 to the verification unit 210 (FIG. 8 (6a)), and the verification unit 210 generates a page of the back side image data. Hash values are calculated based on the array (step S202 in FIG. 7, FIG. 5).

The control unit 201 transmits the hash value calculated by the verification unit 210 based on the page arrangement of the received back side image data to the image forming apparatus 100 via the communication unit 202 and the network 10 (step S203 in FIG. 7). , FIG. 6, FIG. 8 (7), FIG. 8 (8).
When the control unit 101 receives the hash value calculated by the network 10 and the image forming apparatus 200 via the communication unit 102 (step S107 in FIG. 7, 8 (8) in FIG. 7), the received hash value is To (Figure 9 (9)). The verification unit 110 that receives the hash value from the image forming apparatus 200 compares the hash value received from the image forming apparatus 200 with the hash value stored in the image data storage unit 130 (steps in FIG. 7). S108, S109).

  If no delay or error occurs in the network 10, the hash value stored in the image data storage unit 130 matches the hash value received from the image forming apparatus 200 (YES in step S109 in FIG. 7). Refer to “Hash value up to P2 = Hash value up to P2” in FIG.

  As described above, if the hash values compared by the verification unit 110 match (YES in step S109 in FIG. 7), this means that the page arrangement is correct. The image forming unit 150 is controlled to form an image (step S112 in FIG. 7, FIG. 8 (3)). Then, the sheet on which the image is formed on the surface by the image forming unit 150 is conveyed toward the second image forming apparatus 200 (step S113 in FIG. 7).

  In the image forming apparatus 200 that receives the sheet from the image forming apparatus 100 (step S207 in FIG. 7), the control unit 201 controls the image forming unit 250 to form an image with the back surface image data received from the image forming apparatus 100. (Step S208 in FIG. 7, FIG. 8 (6 b)). Then, the control unit 201 controls the sheet on which the image is formed on the back surface by the image forming unit 250 to be discharged to the outside of the second image forming apparatus 200 or the discharge unit (step S209 in FIG. 7).

  Then, the control unit 101 and the control unit 201 control each unit to repeatedly execute the above operation until the final page of the image data (steps S114 to S106 and steps S210 to S201 in FIG. 7). If the control unit 101 confirms that the image formation has been completed up to the final page (YES in step S114 in FIG. 7), the control unit 101 gives an instruction to complete the image formation to the control unit 201 (step S115 in FIG. 7). End (the end in FIG. 7).

  On the other hand, if delay, error or packet retransmission occurs in the network 10, the hash value stored in the image data storage unit 130 will not match the hash value received from the image forming apparatus 200 (FIG. 7). (NO in step S109 of step S109) and "Hash value until P4 ハ ッ シ ュ P2 · P2 hash value" in FIG.

  If the back surface image data P4 is not in time at the timing to be the back surface image data P4 and the image forming apparatus 250 forms a blank image, the verification unit 210 determines that the back surface image data P2 is blank data. Calculate the hash value (P2 · blank) of the page array (P2 · blank). Also in this case, the verification unit 110 detects a mismatch of hash values.

  Thus, if the hash values compared by the verification unit 110 do not match (NO in step S109 in FIG. 7), this means that the page arrangement of the back surface image data in the image forming apparatus 200 is incorrect. The control unit 101 controls to stop the execution of image formation.

  That is, the control unit 101 gives a sheet discharge instruction to the image forming unit 150 and the image forming apparatus 200 (image forming unit 250) (step S110 in FIG. 7). When the sheet discharge instruction is issued from the control unit 101, the image forming unit 150 and the image forming apparatus 250 discharge the sheet present in the conveyance path (YES in steps S111 and S204 in FIG. 7, S205). Also, in response to the paper discharge instruction, the verification unit 210 returns the state of the hash function by one page to bring it into a state immediately before the mismatch (step S206 in FIG. 7). Then, when it is confirmed by the control unit 101 by various sensors and user's operation input that the sheet has been discharged, the control unit 101 returns to step S106, and the back side image data for which the hash value has not been matched earlier is restored again. It is transmitted to the image forming apparatus 200 (step S106 in FIG. 7). After this, the processing already described is repeated.

  As a result, in the image forming system 1 that transmits and receives back side image data via the network 10, an abnormality in the page arrangement caused by a decrease in transfer speed of the back side image data via the network 10 is detected, and an image in an abnormal state It becomes possible to stop the formation. The hash value of the page arrangement of the back side image data is small in data size, and the processing load of the image forming system 1 for comparing and verifying the hash value of the page arrangement is extremely small.

[Stop Operation of Image Forming System]
The process of each unit when image formation is stopped will be described below with reference to the flowchart of FIG.
The image forming apparatus 100 compares the hash value stored in the image data storage unit 130 with the hash value received from the image forming apparatus 200, and stops the image forming process if they do not match.

  Here, when a stop factor of the image forming process occurs (step S301 in FIG. 9), the image forming apparatus 100 stops reading out a series of image data stored in the image data storage unit 130, and the image forming apparatus The cause for stopping is transmitted to 200 (steps S302 and S401 in FIG. 9).

  If the cause of the stop is not jamming, but the comparison between the hash value stored in the image data storage unit 130 and the hash value received from the image forming apparatus 200 does not match ("Hash not match" in step S303 in FIG. 9) The control unit 101 confirms and generates final sheet information (step S304 in FIG. 9), and transfers the final sheet information to the image forming apparatus 200 (step S305 and step S403 in FIG. 9).

Further, in the image forming apparatus 100, when the final sheet in the image forming unit 150 is discharged, the control unit 101 controls each unit to stop the operation as the image forming apparatus 100 (step S306 in FIG. 9, step S307, step S308).
The image forming apparatus 200 receives the stopping cause from the image forming apparatus 100 by the control unit 201 (step S403 in FIG. 9). If the stop cause is not jamming, and if the hash value stored in the image data storage unit 130 of the image forming apparatus 100 does not match the hash value calculated in the image forming apparatus 200 (step S402 in FIG. 9). (YES), the image forming apparatus 200 waits for reception of final sheet information from the image forming apparatus 100.

  When the final sheet information is received from the image forming apparatus 100 (step S403 in FIG. 9), the image forming apparatus 200 waits for the final sheet to be passed from the image forming apparatus 100, and the image forming section 250 When the final sheet has been fed and discharged, the control unit 101 controls each unit to stop the operation of the image forming apparatus 100 (YES in step S405, YES in step S406, and step S407 in FIG. 9).

  That is, if the hash value stored in the image data storage unit 130 of the image forming apparatus 100 is not compared with the hash value calculated in the image forming apparatus 200, the image forming process is stopped and the image forming apparatus is stopped. In the image forming apparatus 100 and the image forming apparatus 200, there is no sheet.

  After the comparison between the hash value stored in the image data storage unit 130 of the image forming apparatus 100 and the hash value calculated in the image forming apparatus 200 is not verified and the image forming process is temporarily stopped, When resuming image formation, the image forming apparatus 200 needs to return the hash function provided in the verification unit 210 to the correct state.

  That is, after the image forming process is temporarily stopped after comparing and verifying the hash values, the image forming process is temporarily stopped, and is stored in the image data storage unit 130 of the image forming apparatus 100 as an initial value when image formation is resumed. Comparison verification is performed to compare the hash value with the hash value calculated in the image forming apparatus 200, and the last hash value that matches is set.

  In FIG. 10, comparison verification for comparing the hash value stored in the image data storage unit 130 of the image forming apparatus 100 with the hash value calculated in the image forming apparatus 200 is performed for each page, resulting in a mismatch. FIG. 13 is a processing procedure diagram illustrating processing of initializing a hash function and restarting an image forming process in the image forming apparatus 200 after the forming process is temporarily stopped.

In the case where comparison verification is performed for each page, the verification unit for resuming the image formation to resume the hash value output by inputting the image data of the previous page of the page which is not matched after comparison verification Make it the initial value of the hash function of 210.
If comparison verification is performed for each page, the hash values up to one page before the page that has become unmatched after comparison verification should match. Set the last hash value that matched as the initial value by comparing and verifying. Image formation is resumed by inputting image data that has not been compared after comparison and verification to the hash function. For example, the hash value calculated by inputting the image data P2 into the hash function is compared and verified to match. Subsequently, it is assumed that the image data P4 is input to the hash function, the calculated hash values are compared and verified, and there is a mismatch. When image formation is resumed, the image data P2 is input to the hash function and the output hash value is set as the initial value of the hash function. Image formation is resumed by inputting the image data P4 into the hash function.

Second Embodiment
In the first embodiment described above, the comparison verification is performed for each page by comparing the hash value stored in the image data storage unit 130 of the image forming apparatus 100 with the hash value calculated in the image forming apparatus 200. It is. In the second embodiment, the comparison and verification for comparing the hash value stored in the image data storage unit 130 of the image forming apparatus 100 with the hash value calculated in the image forming apparatus 200 is performed for each predetermined page. It is.

As a specific example, the case of comparing and verifying the hash value of the page arrangement of the image data of every fifth image will be described.
FIG. 11 is a processing procedure diagram showing a procedure for comparing and verifying the hash value of the page arrangement of the image data for each fifth sheet in the image forming apparatus 200.

The hash values up to the fifth back surface image data (P10) of the image forming apparatus 200 and the corresponding hash values of the fifth back surface image data (P10) stored in the image data storage unit 130 of the image forming apparatus 100 are used. Compare.
If the hash value up to the fifth back side image data (P10) matches the hash value stored in the image forming apparatus 100, pages P2, P4, P6, P8 and P10 up to the fifth back side image data It can be said that the image data is normal.

  If the hash value up to the 10th back side image data (P20) matches the hash value stored in the image forming apparatus 100, pages P2, P4, P6, P8 and P10 up to 10 back side image data, and It can be said that the image data of P12, P14, P16, P18 and P20 are normal.

  If the hash value up to the 15th back side image data (P30) matches the hash value stored in the image forming apparatus 100, pages P2, P4, P6, P8 and P10 up to 15 back side image data, and It can be said that the image data of P12, P14, P16, P18 and P20, and P22, P24, P26, P28 and P30 are normal.

  If the hash value up to the 20th back side image data (P40) matches the hash value stored in the image forming apparatus 100, pages P2, P4, P6, P8 and P10 up to 20 back side image data, and It can be said that the image data of P12, P14, P16, P18 and P20, and P22, P24, P26, P28 and P30, and P32, P34, P36, P38 and P40 are normal.

Similarly, the page arrangement of image data is compared and verified by comparing the hash value of image data of every five sheets with the hash value stored in the main apparatus.
The hash values up to the 25th back surface image data of the image forming apparatus 200 are compared with the hash values stored in the image data storage unit 130 of the image forming apparatus 100. If the hash value of the 25th image data and the hash value stored in the main apparatus do not match, the image data of the page up to the 20th image data is normal, but the 25th image data thereafter It can be said that any of the image data of the pages P42, P44, P46, P48 and P50 is abnormal.

In this manner, the burden of processing for comparison and verification is reduced by sampling and comparing the hash value stored in the image data storage unit 130 of the image forming apparatus 100 with the hash value calculated in the image forming apparatus 200. Do.
The image forming apparatus 100 compares the hash value stored in the storage unit with the hash value received from the image forming apparatus 200 and continues the image forming process if they match, and stops the image forming process if they do not match. Do. This process is similar to that already described.

  The hash values stored in the image data storage unit 130 of the image forming apparatus 100 are used as initial values for resuming image formation after the image formation process is temporarily stopped after comparing and verifying the hash values. Then, comparison verification is performed to compare the hash values calculated in the image forming apparatus 200, and the last matched hash value is set.

  In the case where comparison verification is performed for each predetermined page, comparison verification is performed and the last hash value that matches is made the initial value. If comparison verification is performed for each predetermined page, the hash values up to the predetermined page before the page which is not matched after comparison verification should match. Makes the initial value the last hash value matched by comparison verification. Image formation is resumed by inputting image data of one page after the image data that has been matched as a result of comparison and verification into the hash function.

  In FIG. 12, the comparison and verification for comparing the hash value stored in the image data storage unit 130 of the image forming apparatus 100 with the hash value calculated in the image forming apparatus 200 is performed for every five pages, FIG. 13 is a processing procedure diagram illustrating processing of initializing a hash function and restarting an image forming process in the image forming apparatus 200 after the forming process is temporarily stopped.

  For example, comparison verification is performed every five pages. The image data P10 is input to the hash function, and the calculated hash value is compared and verified to match. Subsequently, the image data P20 is input to the hash function, and the calculated hash values are compared and verified to match. Subsequently, the image data P30 is input to the hash function, and the calculated hash values are compared and verified to match. Subsequently, the image data P40 is input to the hash function, and the calculated hash values are compared and verified to match. Subsequently, the image data P48 is input to the hash function, the calculated hash values are compared and verified, and it is considered that they do not match. When resuming image formation, the image data P40 is input to the hash function and the output hash value is set as the initial value of the hash function. Image formation is resumed by inputting the image data P42 to the hash function. The comparison verification is performed for every 5 pages, and the image data P40 is input to the hash function, the calculated hash value is compared and verified, and matches are made. Subsequently, the image data P48 is input to the hash function and calculated hash When the values are compared and verified and they do not match, it means that an abnormality has occurred between the image data P42 and P48. The image data P40 for which the image data is confirmed to be normal is input to the hash function, and the output hash value is set as the initial value. Image formation is resumed from the input of image data P42 which may be abnormal image data to the hash function.

  As a result, in the image forming system 1 that transmits and receives back side image data via the network 10, an abnormality in the page arrangement caused by a decrease in transfer speed of the back side image data via the network 10 is detected, and an image in an abnormal state It becomes possible to stop the formation. Since the hash value of the page arrangement of the back side image data is small in data size and is a comparison for each image data of a plurality of pages, the processing load of the image forming system 1 for comparing and verifying the page arrangement hash value is It is also extremely small.

Third Embodiment
In the first and second embodiments described above, the image forming apparatus is compared with the hash value stored in the image data storage unit 130 of the image forming apparatus 100 and the hash value calculated in the image forming apparatus 200. 100 is the case. In the third embodiment, the image forming apparatus 200 compares and verifies the hash value received from the image forming apparatus 100 with the hash value calculated by the image forming apparatus 200.

FIG. 13 is a processing procedure diagram showing the handling of hash values in the image forming apparatus 100 according to the third embodiment.
The image forming apparatus 100 calculates a hash value based on the back surface image data among the series of image data generated by the image generation unit using a hash function.

  A series of image data generated by the image generation unit of the image forming apparatus 100 are sequentially referred to as P1, P2, P3, P4, P5, P6, P7, P7, P8, P9, P10,. The surface image data are P1, P3, P5, P7, P9, ... in order from the top. The back side image data are P2, P4, P6, P8, P10, ... in order from the top.

In the image forming apparatus 100, the verification unit 110 calculates a hash value by a hash function based on the page arrangement of the back side image data generated by the image generation unit 108.
At the start of the image forming job, the hash function is set to a predetermined initial value, for example, 0. The back side image data is input to the hash function in the order of page arrangement. After the image data for each page is input, a hash value calculated from the hash function is added to the input image data. The hash value added to the image data P2 is a hash value calculated from the image data P2. The hash value added to the image data P4 is a hash value calculated from the image data P2 and P4. The hash value added to the image data P6 is a hash value calculated from the image data P2, P4 and P6. The hash value added to the image data P8 is a hash value calculated from the image data P2, P4, P6 and P8. The hash value added to the image data P10 is a hash value calculated from the image data P2, P4, P6, P8 and P10. Similarly, the hash value calculated from the accumulation of the image data input in the page arrangement order is added to the image data of the page input last.

The image forming apparatus 100 stores, in the image data storage unit 130, a series of image data P1, P2, P3, P4, P5, P6, P7, P8, P9, P10,.
Then, the image forming apparatus 100 transfers surface image data of the series of image data read from the image data storage unit 130 to the image forming unit 150 via the image processing unit 140. That is, the image forming apparatus 100 causes the image forming unit 150 to form an image on the surface of the sheet based on the surface image data.

  Further, the image forming apparatus 100 transmits back side image data to the image forming apparatus 200 via the communication unit 102 and the network 10 among the series of image data read out from the image data storage unit 130. In the back side image data P2, P4, P6, P8, and P10, a hash value calculated from the accumulation of the image data input in the page arrangement order is added to the image data of the page input last.

  The image forming apparatus 200 receives the image data transmitted from the image forming apparatus 100 via the network 10 by the communication unit 202. The image forming apparatus 200 forms an image on the back side of the sheet based on the back side image data. The back side image data are P2, P4, P6, P8, P10, ... in order from the top.

In the image forming apparatus 200, the verification unit 210 calculates a hash value based on the page arrangement of the back side image data by the hash function.
At the start of the image forming job, the same initial value as the initial value set in the hash function by the image forming apparatus 100, for example, 0 is set. The back side image data is input to the hash function in the order of page arrangement, and after inputting the image data for each page, the hash value calculated from the hash function is temporarily stored. A hash value calculated from the accumulation of image data input in the page arrangement order is temporarily stored.

FIG. 14 is a process procedure diagram showing comparison verification of hash values in the image forming apparatus 200. The case where the hash value received from the image forming apparatus 100 and the hash value calculated in the image forming apparatus 200 are compared with each other is shown.
When the back side image data transmitted from the image forming apparatus 100 to the image forming apparatus 200 is not in time for the image formation timing of the image forming apparatus 200 due to a delay, an error, packet retransmission, etc., the back side image data once image formed is updated. May be used again for image formation. For example, it is assumed that the back side image data P4 is not in time, and the back side image data P2 is used again at the timing which should originally be the back side image data P4.

  In this case, the verification unit 210 calculates a hash value (P2 · P2) of the back surface image data P2 and the page arrangement (for P2 twice) of the back surface image data P2. In this case, the hash value of P2 transmitted from the image forming apparatus 100 does not match. This is shown as “hash value of P2 to P2 hash value of P2 · P2 in FIG.

  If the back surface image data P4 is not in time at the timing to be the back surface image data P4 and the image forming apparatus 250 forms a blank image, the verification unit 210 determines that the back surface image data P2 is blank data. Calculate the hash value (P2 · blank) of the page array (P2 · blank). Also in this case, the hash value of P2 transmitted from the image forming apparatus 100 does not match.

That is, the image forming apparatus 200 compares the hash value received from the image forming apparatus 100 with the hash value calculated in the image forming apparatus 200, and continues the image forming process if they match, and the image forming process if they do not match. Stop.
In addition, the image forming apparatus 200 compares the hash value received from the image forming apparatus 100 by the communication unit 202 with the hash value calculated by the image forming apparatus 200. Based on this, an image is formed on the back side of the sheet.

  Also in the case of the third embodiment, in the image forming system 1 that transmits and receives back side image data via the network 10, an abnormality in the page arrangement caused by a decrease in transfer speed of the back side image data via the network 10 is detected. It becomes possible to stop image formation in an abnormal state. Since the hash value of the page arrangement of the back side image data is small in data size and is a comparison for each image data of a plurality of pages, the processing load of the image forming system 1 for comparing and verifying the page arrangement hash value is Very small.

Fourth Embodiment
In the first and second embodiments described above, the image forming apparatus is compared with the hash value stored in the image data storage unit 130 of the image forming apparatus 100 and the hash value calculated in the image forming apparatus 200. 100 is the case. In the third embodiment, the image forming apparatus 200 compares and verifies the hash value received from the image forming apparatus 100 with the hash value calculated by the image forming apparatus 200. On the other hand, in the fourth embodiment, an external PC, a server, or the like that receives the hash value calculated by the first image forming apparatus and the hash value calculated by the second image forming apparatus via the network 10 As a determination unit, comparison verification of hash values is performed. Then, when a mismatch is detected, an image formation stop instruction is given to the image forming apparatus 100 and the image forming apparatus 200.

  Also in the case of the fourth embodiment, in the image forming system 1 for transmitting and receiving back side image data via the network 10, an abnormality in page arrangement caused by a reduction in transfer speed of the back side image data via the network 10 is detected. It becomes possible to stop image formation in an abnormal state. Since the hash value of the page arrangement of the back side image data is small in data size and is a comparison for each image data of a plurality of pages, the processing load of the external PC or server for comparing and verifying the page arrangement hash value is Very small.

Fifth Embodiment
In the first to fourth embodiments described above, the image forming system 1 of the serial tandem system is assumed. However, even in a parallel tandem image forming system in which image data is transmitted from the image forming apparatus 100 to the image forming apparatus 200 via the network 10, similar comparison and verification of hash values can be performed. In this case, the calculation of the hash value is not limited to the back side image data, and the hash value is calculated by the first image forming apparatus and the second image forming apparatus for any predetermined image to be formed by the second image forming apparatus. You can compare and verify the hash value at any position.

  Also in this case, it is possible to detect an abnormality in the page arrangement caused by a decrease in transfer rate of image data via the network 10, and to stop image formation in an abnormal state. Since the hash value of the page arrangement of the image data is small in data size and is comparison for each image data of a plurality of pages, the processing load of the external PC or server for comparing and verifying the hash value of the page arrangement is extremely high. It becomes smaller.

Sixth Embodiment
The above specific example shows the case where the same back side image data is read again or the case where blank image data is read out as an example in which the correct back side image data does not exist at the image formation timing of the back side image data. It is not limited. For example, even if noise is mixed in the network 10 or the like, and some or all of the back image data is garbled, the page alignment mismatch is detected by comparing the hash values in the above embodiments. be able to. That is, as an image forming system, it is possible to realize image formation of the correct content (correct page arrangement).

10 Network 100 Image Forming Apparatus 101 Control Unit 110 Verification Unit 150 Image Forming Unit 200 Image Forming Apparatus 201 Control Unit 210 Verification Unit 250 Image Forming Unit

Claims (10)

An image forming system comprising at least a first image forming apparatus and a second image forming apparatus which are connected so as to be capable of transmitting and receiving image data via a network and which form an image on any side of a sheet,
The first image forming apparatus is
A first communication unit that communicates with the second image forming apparatus via the network;
A first image forming unit that forms an image on one side of a sheet based on the first image data;
A first verification unit that calculates a hash value of the page arrangement of the second image data that the second image forming apparatus uses for image formation;
A first control unit that supplies the first image data to the first image forming unit and transmits second image data to the second image forming apparatus via the first communication unit;
Is configured with
The second image forming apparatus is
A second communication unit that communicates with the first image forming apparatus via the network;
A second image forming unit that forms an image on the other side of the sheet based on the second image data;
A second verification unit that calculates a hash value of a page arrangement of the second image data when the second image forming unit forms an image on the other side of the sheet;
A second control unit that supplies the second image data transmitted from the first image forming apparatus via the first communication unit, the network, and the second communication unit to the second image forming unit;
Is configured with
A determination unit that compares the hash value calculated by the first verification unit with the hash value calculated by the second verification unit, and determines whether the page arrangement of image formation on the sheet is normal or not Configured in any position of the imaging system,
An image forming system characterized by The first image forming apparatus and the second image forming apparatus are connected via a local area network as the network as a tandem type image forming system.
The image forming system according to claim 1, The first image forming apparatus and the second image forming apparatus are connected as a network via a local area network,
The image forming system is a serial tandem system in which the sheet on which an image is formed by the first image forming apparatus is conveyed to the second image forming apparatus, and the image is formed on each side of the sheet.
The image forming system according to claim 1, The first verification unit outputs the hash value calculated from the hash function after continuously inputting the image data of each page to the hash function in the order of pages to be image-formed by the second image forming unit.
The second verification unit sequentially transmits image data for each page to the hash function in the order of pages to be formed by the second image forming unit after being transmitted from the first image forming apparatus, and then the hash function is generated. Output the hash value calculated from
An image forming system according to any one of claims 1 to 3, characterized in that. The determination unit compares the hash value calculated by the first verification unit with the hash value calculated by the second verification unit each time the second image forming unit forms an image. The image forming system according to any one of claims 1 to 4, wherein it is determined whether or not the page arrangement for image formation on a sheet is normal. When the determination unit determines that the page arrangement for image formation is not normal, the first control unit instructs the first image formation unit to stop image formation, and the second control unit controls the second image. Instruct the forming unit to stop image formation,
An image forming system according to any one of claims 1 to 5, characterized in that. When the determination unit determines that the page arrangement of the image formation is not normal and the first control unit and the second control unit instruct to resume the image formation instructed to stop.
The second verifier initializes with the last hash value that is normal,
The image forming system according to any one of claims 1 to 6, characterized in that: The determination unit is one of the first verification unit and the second verification unit, and compares the hash value calculated by the first verification unit with the hash value calculated by the second verification unit. ,
An image forming system according to any one of claims 1 to 7, characterized in that. The determination unit is
The first image forming apparatus and the second image forming apparatus are separately connected to the network.
Comparing the hash value calculated by the first verification unit with the hash value calculated by the second verification unit;
Supplying a comparison result to at least the first control unit,
An image forming system according to any one of claims 1 to 7, characterized in that. Image forming system control for controlling an image forming system including at least a first image forming apparatus and a second image forming apparatus which are connected so as to be capable of transmitting and receiving image data via a network and which form an image on any side of a sheet Method,
The first image forming apparatus is
A first communication unit that communicates with the second image forming apparatus via the network;
A first image forming unit that forms an image on one side of a sheet based on the first image data;
A first verification unit that calculates a hash value of the page arrangement of the second image data that the second image forming apparatus uses for image formation;
A first control unit that supplies the first image data to the first image forming unit and transmits second image data to the second image forming apparatus via the first communication unit;
Is configured with
The second image forming apparatus is
A second communication unit that communicates with the first image forming apparatus via the network;
A second image forming unit that forms an image on the other side of the sheet based on the second image data;
A second verification unit that calculates a hash value of a page arrangement of the second image data when the second image forming unit forms an image on the other side of the sheet;
A second control unit that supplies the second image data transmitted from the first image forming apparatus via the first communication unit, the network, and the second communication unit to the second image forming unit;
Is configured with
The hash value calculated by the first verification unit is compared with the hash value calculated by the second verification unit to determine whether the page arrangement of image formation on the sheet is normal or not.
And controlling the image forming system.