JP2017085460A - Image forming system and image forming system control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect abnormality in page arrangement due to a reduction in rate of data transfer via a network.SOLUTION: In an image forming system, a first image forming apparatus comprises a first communication part, a first image forming part that forms an image on one side of a sheet on the basis of first image data, a first verification part that calculates a hash value of page arrangement in second image data used by a second image forming apparatus, and a first control part that supplies the first image data to the first image forming part and transmits the second image data to the second image forming apparatus through the communication part; and the second image forming apparatus comprises a second communication part, a second image forming part that forms an image on the other side of the sheet on the basis of the second image data, a second verification part that calculates a hash value of page arrangement in the second image data when the image is formed on the other side of the sheet by the second image forming part, and a second control part that supplies the second image data to the second image forming part. The image forming system compares the hash value calculated by the first verification part with the hash value calculated by the second verification part to determine whether the page arrangement is normal.SELECTED DRAWING: Figure 1

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 technique capable of executing image formation in an appropriate state in an image forming system in which image forming apparatuses are connected in series or in parallel. About.

  As a series tandem image forming system by connecting a plurality of image forming apparatuses in series, a recording sheet on which an image is formed in one area by one image forming apparatus is continuously input to the other image forming apparatus, and the other There is an image forming system that forms an image on another area of the recording paper with the image forming apparatus of FIG.

  According to such an image forming system, two-sided image forming output can be performed at high speed by forming images on both sides of the recording paper with two image forming apparatuses, and there is an advantage that productivity is improved. In addition, two image forming apparatuses can form images using different color toners, or two image forming apparatuses can perform image formation suitable for each of a character area and an image area. It becomes possible to output fine image formation at high speed.

  Note that an image forming system including a plurality of such 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 a main (first image forming apparatus), and the other image forming apparatus is set as a sub (second image forming apparatus). Front and back image data is generated, an image is formed on the front surface of the paper by the main image forming apparatus, and the paper on which the image is formed is transported from the main image forming apparatus to the sub image forming apparatus to form the main image. There is a serial tandem image forming system that forms images on both sides by forming an image on the back side of a sheet with a sub-image forming apparatus that has received back image data from the apparatus.

In FIG. 15, a main first image forming apparatus 100 and a 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, image data for image formation is generated by the image generation unit 108 ((1) in FIG. 15). ). The image data is temporarily stored in the image data storage unit 130 ((2) in FIG. 15), and then the image data for the paper surface is matched with the timing at which the first image forming apparatus 100 forms an image on the paper. The image 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 paper back image data (back image data) is read from the image data storage unit 130 and sent to the communication unit 102 ((4) in FIG. 15). The back 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 necessary, and then imaged in accordance with the timing at which the second image forming apparatus 200 forms an image on a sheet. 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 conveyed toward the outside of the second image forming apparatus 200.

In this description, known processing such as compression / decompression of image data is omitted.
Note that the tandem image forming system holds image data stored in an image data storage unit such as an HDD in each image forming apparatus, thereby enabling re-image formation and subsequent verification of image data. (For example, Patent Document 1).

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

In recent years, as the access speed to storage devices, the communication speed of communication cables, and the read / write speed of memory buses have increased, the image forming speed in image forming systems has been improved, and the productivity of the image forming process has increased. It is coming.
In recent years, the communication speed of network communication units (network controllers) and communication cables has been increased.

For this reason, the processing speed from when image data is transferred from the first image forming apparatus 100 to the second image forming apparatus 200 until the second image forming apparatus 200 can form an image is high. It became possible to satisfy the process speed of the process.
As a result, image data can be transferred in real time, for example, by transmitting image data from the first image forming apparatus 100 to the second image forming apparatus 200 for each page on which an image is formed. Thus, the productivity of the image forming process could be improved.

In order to increase the speed of image formation in a serial tandem image forming system, introduction of 10GBASE-T capable of high-speed transfer at 10 Gbps is being studied 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 designated. However, these upper category LAN cables have mechanical compatibility (connector shape compatibility) with lower category cables.

Therefore, even if 10GBASE-T is introduced in the LAN standard, there is a possibility that a LAN cable for medium and low speeds in the lower category may be used by the user.
However, a lower category LAN cable cannot always guarantee a transfer rate of 10 Gbps. When a connection cannot be established between the first image forming apparatus 100 and the second image forming apparatus 200 at a transfer rate of 10 Gbps, generally, reconnection is attempted by reducing the transfer speed by auto-negotiation.

It is also possible to select the fastest transfer speed among the low transfer speeds. However, the second image forming apparatus 200 performs image formation by transferring the image data to the image forming unit 250 at a constant speed on the assumption that the image data is transferred at a transfer speed of 10 Gbps.
For this reason, when the transfer rate of image data in the LAN is reduced, an image data transfer error occurs such that the transfer of image data is not in time for image formation in the second image forming apparatus 200 and the image is interrupted in the middle.

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

  In some cases, a user may provide a communication device such as a hub on a LAN that is a transfer path of image data. When the image forming system 1 is incorporated in a general-purpose LAN rather than a dedicated LAN, communication equipment other than the image forming apparatus has unknown communication capability, and thus a transfer rate of 10 Gbps cannot 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, for odd pages P1, P3,..., P11, the first image forming apparatus 100 executes image formation. For the even pages P2, P3,..., P13, the second image forming apparatus 200 performs image formation using the image data sent from the first image forming apparatus 100.

However, as described above, when the medium-to-low speed LAN cable is used in the image forming system 1 that assumes a high-speed LAN, the communication speed decreases, and the data transfer of the P4 image data is not in time. Suppose.
In this case, since the P2 image data remains in the second image forming apparatus 200, the existing P2 image data is sent to the image forming unit 250, and the front side of the P3 sheet is on the back side of the P3 sheet. The image of P2 is repeatedly formed. As a result, a printed matter is produced in which the front and back page arrangements are shifted, such as forming an image of P4 instead of P6 on the back side of a sheet of P5. In addition, the printed matter in a state where the front and back page arrangement is shifted as described above is shown in FIG. 17 in correspondence with FIG. Then, there is a problem that such an image arrangement abnormality cannot be detected by the image forming system 1.

  The present invention relates to an image forming system and an image forming system control capable of detecting a page arrangement abnormality caused by a decrease in the transfer speed of image data via a network in an image forming system that transmits and receives image data via a network. The purpose is to realize the method.

That is, the present invention for solving the above-described problems 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 on image data received from a first image forming apparatus via a network. Here, the validity of the image data is verified for the image formed by the second image forming apparatus. A hash value calculated by inputting image data to a hash function is used as a method for determining the validity of the image data. By characterizing a large amount of image data with a small amount of hash values, it is possible to increase the immediacy of determining the validity of the image data and cope with a high-speed image forming process. By using a small amount of hash values as a comparison target, it is possible to reduce the hardware burden of determining the validity of image data. Specifically, the following (1) to (9) are obtained.

  (1) The present invention is an image forming system that includes at least a first image forming apparatus and a second image forming apparatus that are connected so as to be able to exchange image data via a network and that respectively form images on either side of a sheet. The first image forming apparatus forms an image on one surface of the sheet based on the 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 verification unit that calculates a hash value of a page arrangement of second image data used by the second image forming apparatus for image formation; and the first image forming unit that converts the first image data into the first image forming unit. And a first controller that transmits second image data to the second image forming apparatus via the communication unit, the second image forming apparatus via the network Said A second communication unit that communicates with the image forming apparatus; a second image forming unit that forms an image on the other side of the sheet based on the second image data; and A second verification unit that calculates a hash value of a page arrangement of the second image data when an image is formed on a surface; the first image via the first communication unit, the network, and the second communication unit; A second control unit that supplies the second image data transmitted from the forming apparatus to the second image forming unit, and the hash value calculated by the first verification unit and the second verification unit A determination unit that compares the hash value calculated by the image forming unit and determines whether or not the page arrangement of the image formation on the sheet is normal is provided at any position of the image forming system.

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

  (4) In the above (1) to (3), after the first verification unit continuously inputs the image data for each page into the hash function in the order of the pages on which the second image forming unit forms an image. The hash value calculated from the hash function is output, and the second verification unit transmits image data for each page in the order of pages transmitted from the first image forming apparatus and image-formed by the second image forming unit. Are successively input to the hash function, and then the hash value calculated from the hash function is output.

  (5) In the above (1) to (4), each time the second image forming unit forms an image, the determination unit calculates the hash value calculated by the first verification unit and the second verification. The hash value calculated by the copy unit is compared, and it is determined whether or not the page layout for image formation on the paper is normal.

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

(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 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 connected to the network separately from the first image forming apparatus and the second image forming apparatus. The hash value calculated by the first verification unit 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.

According to the present invention for solving the above-described 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 is sent from the first image forming apparatus via the network. When performing 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 value on the second image forming apparatus side 2 The hash value for the page arrangement of the second image data calculated by the verification unit is compared with the determination unit, and it is determined whether or not the page arrangement for image formation on the paper 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 the page arrangement caused by a decrease in the transfer rate of the image data via the network.
Note that the hash value of the page array of image data has a small data size, and the processing load of the image forming system for comparing and verifying the hash values of the page array is small.

  (2) 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 as a tandem image forming system. That is, in the tandem image forming system, the first image forming apparatus executes image formation based on the first image data, and the second image forming apparatus is sent from the first image forming apparatus via the network. When executing image formation based on the 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 hash value of the second image data with the determination unit to determine whether or not the image formation page arrangement on the sheet is normal.

As a result, in a tandem image forming system that transmits and receives image data via a local area network, it is possible to detect an abnormality in the page arrangement caused by a decrease in the transfer speed of the 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 via a local area network, and the sheet on which the image is formed by the first image forming apparatus is the first. This is an in-line tandem image forming system that is transported 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 forms an image on one side of the sheet based on the first image data, and the second image forming apparatus is connected to the first image forming apparatus via the network. A hash value for the second image data calculated by the first verification unit on the first image forming apparatus side when performing image formation on the other side of the sheet based on the second image data sent from Then, the determination unit compares the hash value for the second image data calculated by the second verification unit on the second image forming apparatus side to determine whether the page arrangement of the image formation on the sheet is normal.

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

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

  (6) In the above (1) to (5), when the determination unit determines that the image formation page arrangement is not normal, the first control unit instructs the first image formation unit to stop image formation. The second control unit instructs the second image forming unit to stop image formation, thereby detecting an abnormality in the page arrangement and quickly stopping 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 restart of image formation instructed to be stopped by the first control unit and the second control unit is instructed, 2 The verification unit initializes with the last hash value that is normal, and controls to restart image formation from the image of the page array that was not normal, thereby detecting page layout abnormality and detecting page layout abnormality. 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 the calculated hash value, in an image forming system that transmits and receives image data via a local area network, it is possible to reliably detect abnormal page arrangements caused by a decrease in the transfer rate of image data via the network. It becomes possible to do.

  (9) In the above (1) to (7), the determination unit exists in a state 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. The hash value calculated by the second verification unit 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, so that the first image forming apparatus and the server other than the second image forming apparatus can It is possible to reliably detect abnormal page arrangement.

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.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.
[First embodiment]
[Overall configuration of image forming system]
Here, a specific example when the image forming system 1 of the present embodiment is configured as a serial tandem image forming system will be described in detail with reference to FIGS.

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

With these image forming apparatus 100 and image forming apparatus 200, it is possible to improve the productivity of double-sided image formation by having each image forming apparatus take charge of image formation on one side of a sheet.
Here, the two image forming apparatuses connected along the flow of the paper are referred to as a “series tandem image forming system”. Note that the series tandem image forming system is not limited to the connection of two image forming apparatuses, and may be a connection of three or more. In addition, a paper processing device that performs paper processing on a paper on which an image has been formed may be connected to the subsequent stage of the image forming device 200.

It is assumed that the image forming apparatus 100 and the image forming apparatus 200 are apparatuses having the same configuration. Here, the image forming apparatus 100 is a first image forming apparatus, and the image forming apparatus 200 is a second image forming apparatus.
Further, the image forming apparatus 100 generates image data on the front side of the paper and image data on the back side of the paper, and transmits the image data on the back side of the paper from the image forming apparatus 100 to the image forming apparatus 200 via the network 10. A specific example is a case where the forming apparatus 100 executes image formation using the generated front surface image data, and the image forming apparatus 200 executes image formation using back surface image data received from the image forming apparatus 100 via the network 10. To do.

[Detailed configuration of image forming system]
The image forming apparatus 100 as the first image forming apparatus controls each unit in the image forming apparatus 100 and communicates with other apparatuses, and a control unit 101 as a first control unit that controls the entire system as an image forming system. A communication unit 102 as a first communication unit, an operation display unit 103 that performs an operation input by a user and a status display of the image forming apparatus 100, a non-volatile storage unit 104 that stores various data such as setting values, and a document An image capable of forming an image by performing RIP (Raster Image Processor) processing on PDL (Page Description Language) data input from an external user terminal (external PC) An image generation unit 108 that generates data, and a verification unit 1 as a first verification unit that generates a hash value of a page array and verifies the hash value 0, an image data storage unit 130 for storing image data at the time of image formation, an image processing unit 140 for executing various image processes necessary for image formation, and an image forming command and image data. The image forming unit 150 as a first image forming unit that forms an image in one area (for example, the surface of the sheet), and the sheet on which the image is formed on one side are reversed and conveyed to the subsequent image forming apparatus. And a reversing unit 190.

  The image forming apparatus 200 as the 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 a user and displaying the status of the image forming apparatus 200, a non-volatile storage unit 204 for storing various data such as setting values, and reading image data of an original A scanner unit 206 to generate, an image generation unit 208 to generate image data that can be imaged, a verification unit 210 as a second verification unit that generates a hash value of a page array and verifies the hash value, and image formation An image data storage unit 230 that stores image data and the like, an image processing unit 240 that executes various image processes necessary for image formation, an image formation command, and image data An image forming unit 250 as a second image forming unit that forms an image on the other region (for example, the back side of the sheet) based on the paper, and a reversing unit 290 that reverses and outputs the paper on which the image is formed on both sides. , And is configured.

  Note that the portions indicated as the control units 101 and 201 may be configured separately into a main control unit that performs various controls and an I / O control unit that distributes data. In addition, when the image forming units 150 and 250 are electrophotographic image forming units, as shown in FIG. 2, they are generated on the photosensitive drum by known processes such as charging, exposure, development, transfer, and fixing. An image is formed by transferring the toner image onto 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]
Hereinafter, basic processing for generating and comparing the hash value calculated by the hash function will be described.

[Generation of hash value (1)]
FIG. 3 is a processing procedure explanatory diagram illustrating handling of hash values in the image forming apparatus 100 according to the first embodiment.
In the first embodiment, when the image forming apparatus 100 forms an image on the front surface of the paper based on the front surface image data, and the image forming apparatus 200 forms an image on the back surface of the paper based on the back surface image data, the image forming apparatus 100. To calculate the hash value of the page arrangement of the back image data.

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

  The surface image data for the paper 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 paper is P2, P4, P6, P8, P10,. The first sheet is P1 and P2, the second sheet is P3 and P4, the third sheet is P5 and P6, the fourth sheet is P7 and P8, and the fifth sheet. Are formed as images of P9 and P10, and so on.

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 surface image data based on the back surface image data generated by the image generation unit 108 using the built-in hash function.
First, a predetermined initial value, for example, 0 is set in the hash function at the start of the image forming job. 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 the accumulation of image data input in the order of page arrangement is sequentially input.

  Note that 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 image data is added to the generated image data, and the front image data and the back image data are stored in the image data storage unit 130. Keep it. Further, the image forming apparatus 100 transmits the back surface image data to the image forming apparatus 200 via the network 10 in accordance with the back surface image formation (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 illustrating handling of hash values in the image forming apparatus 200.
The image forming apparatus 200 as the second image forming apparatus receives the back surface image data transmitted from the image forming apparatus 100 via the network 10 via the communication unit 202.

The back side image data for the back side of the paper is P2, P4, P6, P8, P10,... In order from the top as described in FIGS.
The image forming apparatus 200 forms an image on the back side of the paper based on the back side image data transmitted from the image forming apparatus 100.

In parallel with this, the verification unit 210 of the image forming apparatus 200 calculates a hash value based on the page arrangement of the back surface image data based on the back surface image data received from the image forming apparatus 100 using a built-in hash function. .
The verification unit 210 sets the same initial value as the initial value set in the hash function of the image forming apparatus 100, for example, 0 at the start of the image forming job, and converts the back surface image data into the hash function in the order of page arrangement. Input to calculate hash value. In this case, the hash value is generated in accordance with the timing of executing the back side image formation based on the back side image data.

Then, the control unit 201 temporarily stores a hash value calculated from the hash function after inputting image data for each page in the verification unit 210 as necessary, and the image forming apparatus 100 via the communication unit 202 and the network 10. Send to.
That is, when the back side image data P2, P4,..., P10,... Is transmitted from the image forming apparatus 100 to the image forming apparatus 200 without any delay or error, the hash in the image forming apparatus 200 is 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 synchronization 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 synchronization with the image formation timing of the image data P6, the hash value calculated by inputting the image data P6 into the hash function is transmitted to the image forming apparatus 100. Subsequently, in synchronization with the image formation timing of the image data P8, the hash value calculated by inputting the image data P8 into the hash function is transmitted to the image forming apparatus 100. Subsequently, in accordance with the image formation timing of the image data P10, the hash value calculated by inputting the image data P10 into the hash function is transmitted to the image forming apparatus 100.

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

[Comparison verification of hash values]
FIG. 6 is a processing procedure diagram illustrating comparison verification of hash values in the image forming apparatus 100.
That is, the hash value based on the page arrangement of the back 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 are imaged by the image forming apparatus 200. It shows a state in which the hash value calculated by the verification unit 210 is compared 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 and each hash value added to the back surface image data P2, P4, P6, P8, P10. The hash value transmitted from the image forming apparatus 200 to the image forming apparatus 100 is compared with the hash value that is calculated in the image forming apparatus 200 at the timing at which the image forming apparatus 200 forms the back surface image data. The comparison of the hash values is performed at a timing when the hash value is 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, the hash value stored in the image data storage unit 130 and the hash value received from the image forming apparatus 200 are compared by the verification unit 110, and if the comparison results match ( As shown in “Hash value up to P2 = Hash value up to P2” in FIG. 6), the control unit 101 continues execution of image formation.

  If 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 forming timing of the image forming apparatus 200 due to delay, error, packet retransmission, etc., the back side image data once image-formed is updated. Instead, it may be used again for image formation. For example, it is assumed that the back image data P4 is not in time, and the back image data P2 is used again at a timing that should be the back image data P4. In this case, the verification unit 210 calculates the hash value of the page arrangement of the back image data P2 and the back image data P2. In this case, the hash values up to P4 exist in the image forming apparatus 100, which does not match the hash values of P2 and P2 calculated by the image forming apparatus 200 ("Hash values up to P4" in FIG. 6). ≠ P2 · P2 hash value ”), the control unit 101 performs control so as to stop execution of image formation.

[Overall operation of image forming system]
Hereinafter, with reference to the flowchart of FIG. 7 and the operation explanatory diagram of FIG. 8, processing of each unit during the image forming operation will be described.
PDL (Page Description Language) data to be imaged together with an image formation instruction is input from an external user terminal via the communication unit 102 (step S101 in FIG. 7, FIG. 8 (1)). The control unit 101 performs RIP processing on the PDL data in the image generation unit 108 and controls to generate image data that can be formed (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 surface image data for image formation by the image forming 100 and back surface image data for image formation by the image forming apparatus 200. Then, the control unit 101 sends the back image data to the verification unit 110, and the verification unit 110 calculates a hash value based on the page arrangement of the back image (step S104 in FIG. 7, FIG. 3, FIG. 8 (4a)). ). And the control part 101 matches the hash value calculated based on the page arrangement | sequence of back surface image data with the corresponding back surface image data, and memorize | stores it in the image data memory | storage part 130 (step S105 in FIG. 7, FIG. 4). . Here, the hash value may be stored in a form linked to the back surface image data, rather than being stored integrally with the back surface image data.

In parallel with the calculation of the hash value, the control unit 101 transmits the back surface 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 the back side image data received through the network 10 and the communication unit 202 (step S201 in FIG. 7) to the verification unit 210 (FIG. 8 (6a)). A hash value based on the array is calculated (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 surface image data to the image forming apparatus 100 via the communication unit 202 and the network 10 (step S203 in FIG. 7). 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 and FIG. 8 (8)), the control unit 101 verifies the received hash value. (FIG. 8 (9)). The verification unit 110 that has received 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 (step in FIG. 7). S108, S109).

  If there is no delay or error 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. 6).

  As described above, if the hash values compared by the verification unit 110 match (YES in step S109 in FIG. 7), it 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 has received 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 using the back surface image data received from the image forming apparatus 100. (Step S208 in FIG. 7, FIG. 8 (6b)). Then, the control unit 201 performs control so that the sheet on which the image is formed on the back surface by the image forming unit 250 is discharged to the outside of the second image forming apparatus 200 or the discharge unit (step S209 in FIG. 7).

  And the control part 101 and the control part 201 control each part so that the above operation | movement may be repeatedly performed until it reaches the last page of image data (step S114-step S106 in FIG. 7, step S210-step S201). When 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 in FIG. 7).

  On the other hand, if a delay, error, or packet retransmission occurs in the network 10, the hash value stored in the image data storage unit 130 and the hash value received from the image forming apparatus 200 do not match (in FIG. 7). NO in step S109, see “Hash value up to P4 ≠ Hash value of P2 · P2” in FIG. 6).

  If the back side image data P4 is not in time for the back side image data P4, and the image forming apparatus 250 forms a blank image, the verification unit 210 determines that the back side image data P2 and the blank data The hash value (P2 · blank) of the page array (P2 · blank) is calculated. 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), it means that the page arrangement of the back surface image data is not correct in the image forming apparatus 200. The control unit 101 performs control so as to stop execution of image formation.

  That is, the control unit 101 gives a paper discharge instruction to the image forming unit 150 and the image forming apparatus 200 (image forming unit 250) (step S110 in FIG. 7). When this sheet discharge instruction is issued from the control unit 101, the image forming unit 150 and the image forming apparatus 250 discharge the sheet existing on the transport path (YES in steps S111 and S204 in FIG. 7, S205). In response to the sheet discharge instruction, the verification unit 210 returns the state of the hash function by one page to the state immediately before the mismatch (step S206 in FIG. 7). When the control unit 101 confirms that the paper has been discharged by various sensors or user operation input, the control unit 101 returns to step S106 and again displays the back side image data whose hash values did not match. The image is transmitted to the image forming apparatus 200 (step S106 in FIG. 7). Thereafter, the processing described above is repeated.

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

[Stopping operation of image forming system]
Hereinafter, with reference to the flowchart of FIG. 9, processing of each unit when image formation is stopped will be described.
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 a series of image data stored in the image data storage unit 130, and the image forming apparatus A stop factor is transmitted to 200 (steps S302 and S401 in FIG. 9).

  If the stop factor is not jam and the hash value stored in the image data storage unit 130 does not match the hash value received from the image forming apparatus 200 (“hash mismatch” in step S303 in FIG. 9). Then, the control unit 101 confirms / generates the final sheet information (step S304 in FIG. 9) and transfers it to the image forming apparatus 200 (steps S305 and 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 so as to stop the operation as the image forming apparatus 100 (step S306 in FIG. 9, step S306). S307, step S308).
The image forming apparatus 200 receives a stop factor from the image forming apparatus 100 by the control unit 201 (step S403 in FIG. 9). If the stop factor is not a jam and the hash value stored in the image data storage unit 130 of the image forming apparatus 100 does not match the hash value calculated by the image forming apparatus 200 (step S402 in FIG. 9). YES), the image forming apparatus 200 waits for the final paper information to be received from the image forming apparatus 100.

  When the final paper information is received from the image forming apparatus 100 (step S403 in FIG. 9), the image forming apparatus 200 waits for the final paper to be passed from the image forming apparatus 100, and the image forming unit 250 When the final sheet passing and discharging are completed, the control unit 101 controls each unit to stop the operation as the image forming apparatus 100 (YES in step S405 in FIG. 9, YES in step S406, step S407).

  That is, 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, the image forming process is stopped and the image forming apparatus is stopped. 100 and the image forming apparatus 200 are out of paper.

  After comparing and verifying 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, 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 a correct state.

  In other words, the hash values are compared and verified to be inconsistent, and after the image forming process is temporarily stopped, the initial value when image formation is resumed is stored in the image data storage unit 130 of the image forming apparatus 100. A comparison is made by comparing the hash value with the hash value calculated in the image forming apparatus 200, and the last hash value that matches is set.

  FIG. 10 shows a 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 for each page. FIG. 10 is a processing procedure diagram illustrating a process of initializing a hash function and restarting the image forming process in the image forming apparatus 200 after the forming process is temporarily stopped.

When performing comparison verification for each page, a verification unit for restarting image formation based on the hash value output by inputting the image data of the previous page of the page that did not match by comparison verification The initial value of the hash function 210 is set.
If the comparison verification is performed for each page, the hash values up to the previous page of the pages that did not match after the comparison verification should have been the same. The last hash value that matches after the comparison verification is set as the initial value. The image formation is restarted by inputting the image data that does not match after comparison verification to the hash function. For example, the hash values calculated by inputting the image data P2 to the hash function are compared and matched. Next, consider a case where the hash values calculated by inputting the image data P4 to the hash function are compared and verified and there is a mismatch. When the image formation is resumed, the hash value output by inputting the image data P2 to the hash function is set as the initial value of the hash function. Image formation is resumed by inputting image data P4 to the hash function.

[Second Embodiment]
In the first embodiment described above, 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. It is. In the second embodiment, the comparison verification for comparing 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 performed for each predetermined page. It is.

As a specific example, a case will be described in which the hash value of the page arrangement of the image data for every fifth sheet is compared and verified.
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 every fifth sheet in the image forming apparatus 200.

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

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

  If the hash value up to the fifteenth 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 fifteen 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) and the hash value stored in the image forming apparatus 100 match, the 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 hash value of the image data for every five sheets is compared with the hash value stored in the main device, and the page arrangement of the image data is compared and verified.
The hash value up to the 25th back image data of the image forming apparatus 200 is compared with the hash value stored in the image data storage unit 130 of the image forming apparatus 100. If the hash value up to the 25th image data and the hash value stored in the main device do not match, the image data of the page up to the 20th image data is normal, but the image data up to 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 way, 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 are sampled and compared, thereby reducing the burden of comparison verification processing. To 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. If they match, the image forming process is continued, and if they do not match, the image forming process is stopped. To do. This process is similar to that already described.

  The hash value stored in the image data storage unit 130 of the image forming apparatus 100 is used as an initial value when restarting image formation after the hash value comparison and verification result in mismatch and the image forming process is temporarily stopped. Then, the comparison is performed by comparing the hash values calculated in the image forming apparatus 200, and the last hash value that matches is set.

  When comparison verification is performed for each predetermined page, comparison verification is performed and the last hash value that matches is set as an initial value. If the comparison verification is performed for each predetermined page, the hash values up to the predetermined page before the page that did not match after the comparison verification should have been the same. The last hash value that matches after the comparison verification is set as the initial value. The image formation is resumed by inputting the image data after one page of the image data matched by the comparison verification to the hash function.

  FIG. 12 shows a 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 every five pages. FIG. 10 is a processing procedure diagram illustrating a process of initializing a hash function and restarting the image forming process in the image forming apparatus 200 after the forming process is temporarily stopped.

  For example, the comparison verification is performed every 5 pages. The hash values calculated by inputting the image data P10 into the hash function were compared and verified. Subsequently, the hash values calculated by inputting the image data P20 to the hash function were compared and verified. Subsequently, the hash values calculated by inputting the image data P30 into the hash function were compared and verified. Subsequently, the hash values calculated by inputting the image data P40 into the hash function were compared and verified. Next, let us consider a case where the hash values calculated by inputting the image data P48 into the hash function are compared and verified to be inconsistent. When restarting image formation, the hash value output by inputting the image data P40 into the hash function is set as the initial value of the hash function. Image formation is resumed by inputting the image data P42 to the hash function. Comparison verification is performed every five pages, hash values calculated by inputting the image data P40 into the hash function are compared and matched, and then the hash calculated by inputting the image data P48 into the hash function. When the values are compared and verified to be inconsistent, an abnormality has occurred between the image data P42 and P48. The image data P40 that 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 by inputting image data P42, which may be abnormal, into the hash function.

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

[Third Embodiment]
In the first and second embodiments described above, the image forming apparatus performs comparative verification 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. 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 and the hash value calculated by the image forming apparatus 200.

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

  A series of image data generated by the image generation unit of the image forming apparatus 100 is assumed to be P1, P2, P3, P4, P5, P6, P7, P8, P9, P10,. The surface image data is P1, P3, P5, P7, P9,... In order from the top. The back side image data is 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 surface image data generated by the image generation unit 108.
A predetermined initial value, for example, 0 is set in the hash function at the start of the image forming job. The back side image data is input to the hash function in the order of page arrangement. A hash value calculated from a hash function after inputting image data for each page 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 a series of image data P1, P2, P3, P4, P5, P6, P7, P8, P9, P10,... Generated by the image generation unit in the image data storage unit 130.
Then, the image forming apparatus 100 transfers the 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. In other words, the image forming apparatus 100 forms an image on the surface of the paper based on the surface image data by the image forming unit 150.

  In addition, the image forming apparatus 100 transmits the back surface image data of the series of image data read from the image data storage unit 130 to the image forming apparatus 200 via the communication unit 102 and the network 10. 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 order of page arrangement is added to the image data of the last input page.

  The image forming apparatus 200 receives 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 paper based on the back side image data. The back side image data is 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 surface image data using a hash function.
At the start of the image forming job, the same initial value as that set in the hash function in 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 the hash value calculated from the hash function after inputting the image data for each page is temporarily stored. A hash value calculated from the accumulation of image data input in the order of page arrangement is temporarily stored.

FIG. 14 is a processing procedure diagram illustrating comparison verification of hash values in the image forming apparatus 200. The hash value received from the image forming apparatus 100 is compared with the hash value calculated by the image forming apparatus 200, and a case of mismatch is shown.
If 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 forming timing of the image forming apparatus 200 due to delay, error, packet retransmission, etc., the back side image data once image-formed is updated. Instead, it may be used again for image formation. For example, it is assumed that the back image data P4 is not in time, and the back image data P2 is used again at a timing that should be the back image data P4.

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

  If the back side image data P4 is not in time for the back side image data P4, and the image forming apparatus 250 forms a blank image, the verification unit 210 determines that the back side image data P2 and the blank data The hash value (P2 · blank) of the page array (P2 · blank) is calculated. 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 by the image forming apparatus 200. If they match, the image forming process is continued. To stop.
Further, 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 paper.

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

[Fourth embodiment]
In the first and second embodiments described above, the image forming apparatus performs comparative verification 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. 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 and 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 is used. As a determination unit, hash value comparison verification is performed. If 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 that transmits and receives back surface image data via the network 10, an abnormality in the page arrangement caused by a decrease in the transfer speed of the back surface image data via the network 10 is detected. It is possible to stop image formation in an abnormal state. Since the hash value of the page arrangement of the back image data has a small data size and is a comparison for each image data of a plurality of pages, the processing burden on the external PC or server for comparing and verifying the hash values of the page arrangement is not Extremely small.

[Fifth Embodiment]
In the first to fourth embodiments described above, the serial tandem image forming system 1 is assumed. However, even in a parallel tandem image forming system that transmits image data from the image forming apparatus 100 to the image forming apparatus 200 via the network 10, it is possible to perform similar verification of hash values. In this case, the calculation of the hash value is not limited to the back surface image data, and the hash value is calculated by the first image forming apparatus and the second image forming apparatus for any predetermined image that is to be formed by the second image forming apparatus. The hash value may be compared and verified at any position.

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

[Sixth Embodiment]
In the above specific example, 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, the case where the same back side image data is read again or the case where blank image data is read is shown. It is not limited. For example, even when noise is mixed in the network 10 or the like and a part or all of the back side image data is garbled, it is detected as a mismatch of the page arrangement by comparing the hash values of the above embodiments. be able to. That is, as an image forming system, it is possible to realize image formation with correct contents (correct page arrangement).

DESCRIPTION OF SYMBOLS 10 Network 100 Image formation apparatus 101 Control part 110 Verification part 150 Image formation part 200 Image formation apparatus 201 Control part 210 Verification part 250 Image formation part

Claims (10)

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 able to exchange image data via a network and each form an image on one side of a sheet,
The first image forming apparatus includes:
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 the sheet based on the first image data;
A first verification unit that calculates a hash value of a page arrangement of second image data used by the second image forming apparatus for image formation;
A first control unit for supplying the first image data to the first image forming unit and transmitting the second image data to the second image forming apparatus via the communication unit;
Configured with
The second image forming apparatus includes:
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 for supplying the second image data transmitted from the first image forming apparatus to the second image forming unit via the first communication unit, the network, and the second communication unit;
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 or not a page arrangement of image formation on the paper is normal Configured at any position of the image forming system,
An image forming system. The first image forming apparatus and the second image forming apparatus are connected as a tandem image forming system via a local area network as the network.
The image forming system according to claim 1. The first image forming apparatus and the second image forming apparatus are connected via a local area network as the network,
A serial tandem type image forming system in which the paper on which an image is formed by the first image forming apparatus is conveyed to the second image forming apparatus and an image is formed on each surface of the paper;
The image forming system according to claim 1. The first verification unit continuously inputs image data for each page in the order of pages on which images are to be formed by the second image forming unit, and then outputs a hash value calculated from the hash function.
The second verification unit continuously inputs the image data for each page in the order of the pages transmitted from the first image forming apparatus and forms an image in the second image forming unit, and then the hash function. Output the hash value calculated from
The image forming system according to claim 1, wherein the image forming system is an image forming system. 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 an image is formed by the second image forming unit, 5. The image forming system according to claim 1, wherein whether or not a page arrangement of image formation on a sheet is normal is determined. When the determination unit determines that the image formation page arrangement is not normal, the first control unit instructs the first image formation unit to stop image formation, and the second control unit displays the second image. Instruct the forming unit to stop image formation,
The image forming system according to claim 1, wherein the image forming system is an image forming system. When the determination unit determines that the page layout of image formation is not normal, and when the first control unit and the second control unit are instructed to resume image formation,
The second verification unit initializes with the last hash value that is normal,
The image forming system according to claim 1, wherein the image forming system is an image forming system. The determination unit is either the first verification unit or 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. ,
The image forming system according to claim 1, wherein the image forming system is an image forming system. The determination unit
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 and the hash value calculated by the second verification unit;
Supplying a comparison result to at least the first control unit;
The image forming system according to claim 1, wherein the image forming system is an image forming system. 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 to each other through a network so as to be able to exchange image data and form images on either side of a sheet. A method,
The first image forming apparatus includes:
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 the sheet based on the first image data;
A first verification unit that calculates a hash value of a page arrangement of second image data used by the second image forming apparatus for image formation;
A first control unit for supplying the first image data to the first image forming unit and transmitting the second image data to the second image forming apparatus via the communication unit;
Configured with
The second image forming apparatus includes:
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 for supplying the second image data transmitted from the first image forming apparatus to the second image forming unit via the first communication unit, the network, and the second communication unit;
Configured with
Comparing the hash value calculated by the first verification unit with the hash value calculated by the second verification unit to determine whether or not a page arrangement of image formation on the paper is normal;
An image forming system control method.