Printing apparatus and determination method

Abstract

To provide a printing device and a determining method which can reduce loads of arithmetic operation of a main control circuit.SOLUTION: A printing device 1 according to the disclosure comprises: a plurality of heads for recording images; a plurality of SoCs 4 (head control circuits), connected to the heads on a one-to-one basis and connected in series to each other, which each control recording of images by the corresponding heads on the basis of manuscript data; a manuscript transmitting part that transmits the manuscript data to the SoC 4 at the most upstream side; and a determining part 34 that determines presence or absence of an abnormality in the recorded image. The plurality of SoCs 4 transmit the manuscript data received by the SoC 4 at the most upstream side to the SoC 4 on the most downstream side in sequence, and generate difference data showing a difference between the manuscript data and read data generated by reading the image. The determining part 34 determines presence or absence of the abnormality on the basis of the difference data.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a printing apparatus and a determination method.

Background Art

[0002] An inkjet recording apparatus, which is a type of printing apparatus, uses ink ejected from an inkjet head to record an image based on original image data on a sheet while conveying the sheet, and discharges the sheet on which the image has been recorded (see Patent Document 1).

[0003] The inkjet recording apparatus described in Patent Document 1 reads an image recorded on a sheet before discharging the sheet, and generates data of a result image. The control unit of the inkjet recording apparatus compares the data of the result image with the original image data. When the difference between the data of the result image and the original image data is large, there is an abnormality (for example, stain) in the recorded image. Therefore, the inkjet recording apparatus records a mark indicating the abnormality on the sheet and then discharges the sheet. Next, the inkjet recording apparatus records (reprints) an image based on the same original image data on a new sheet.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A printing apparatus including a plurality of heads arranged in the width direction (a direction orthogonal to the conveyance direction) of a sheet, a plurality of head control circuits connected to the plurality of heads in a one-to-one correspondence, and a main control circuit can be considered. In such a printing apparatus, since the heads are not reciprocated in the width direction, an image can be recorded on a sheet having a long width in a short time. To determine whether or not there are any abnormalities in the recorded image, the main control circuit compares the original image data with the data of the resulting image. However, the more heads there are, the larger the amount of data in the resulting image, and the larger the amount of data, the greater the computational load on the main control circuit.

[0006] The purpose of this disclosure is to provide a printing apparatus and a determination method that can reduce the computational load of the main control circuit. [Means for solving the problem]

[0007] The printing apparatus according to this disclosure comprises a plurality of heads for recording an image, a plurality of head control circuits connected in one-to-one correspondence to the heads and connected in series with each other, each controlling the recording of an image by the corresponding head based on original data, a document transmission unit that sends the original data to the upstream head control circuit, and a determination unit that determines whether or not there is an abnormality in the recorded image, wherein the plurality of head control circuits sequentially send the original data received by the upstream head control circuit to the downstream head control circuit, generate difference data showing the difference between the original data and read data generated by reading the image, and the determination unit determines whether or not there is an abnormality based on the difference data.

[0008] The determination method relating to this disclosure is a method for determining whether or not there is an abnormality in an image recorded in a printing apparatus comprising: a plurality of heads for recording an image; a plurality of head control circuits connected in one-to-one correspondence to the heads and connected in series with each other, each controlling the recording of an image by the corresponding head based on original data; and a document transmission unit that sends the original data to the upstream head control circuit, characterized in that the upstream head control circuit sends the received original data sequentially to the downstream head control circuit, generates difference data showing the difference between the original data and read data generated by reading the image, determines whether or not there is an abnormality based on the difference data, and the generation of the difference data is performed by the plurality of head control circuits. [Effects of the Invention]

[0009] According to the printing apparatus of this disclosure, multiple head control circuits generate differential data indicating the difference between the original data and the scanned data, so the main control circuit does not need to generate differential data. Therefore, the computational load on the main control circuit can be reduced. According to the determination method of this disclosure, differential data is used to determine whether or not there is an anomaly in the recorded image. The differential data is generated not by the main control circuit, but by multiple head control circuits. Therefore, the computational load on the main control circuit can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic plan view showing the configuration of the printing apparatus according to Embodiment 1. [Figure 2] This is a bottom view of the inkjet print head. [Figure 3] This is a block diagram showing the main control circuit and head unit. [Figure 4] This flowchart shows the steps involved in the printing process executed on the SoC. [Figure 5] This is a block diagram used to explain the detection of image anomalies. [Figure 6] This flowchart shows the steps for sending and receiving data on the SoC. [Figure 7] This flowchart shows the steps for sending and receiving data on the SoC. [Figure 8] This flowchart shows the procedure for the decision-making process performed by the main control circuit. [Figure 9] This is a block diagram showing the main components of the printing apparatus according to Embodiment 2. [Figure 10] This flowchart shows the steps for sending and receiving data on the SoC. [Figure 11] This flowchart shows the procedure for the decision-making process performed by the main control circuit. [Figure 12]It is a block diagram showing the main configuration of the printing apparatus according to Embodiment 3. [Figure 13] It is a block diagram showing the main configuration of the printing apparatus according to Embodiment 4. [Figure 14] It is a schematic diagram for explaining differential data. [Figure 15] It is a schematic diagram for explaining determination data. [Figure 16] It is a schematic diagram for explaining differential data used in the printing apparatus according to Embodiment 5. [Figure 17] It is a block diagram showing the main configuration of the printing apparatus according to Embodiment 6. Embodiments for Carrying out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described. In the following description, up / down, front / rear, and left / right indicated by arrow signs in the drawings are used.

[0012] Embodiment 1. FIG. 1 is a plan view schematically showing the configuration of the printing apparatus according to Embodiment 1. In the figure, 1 is a printing apparatus, and the printing apparatus 1 is, for example, an inkjet recording apparatus. The printing apparatus 1 records an image based on document image data on the paper 21 while conveying the paper 21. The printing apparatus 1 includes a platen 11, two conveyance rollers 12, four head units 13, a control device 14, and a case 15. The platen 11, two conveyance rollers 12, four head units 13, and the control device 14 are housed in the case 15.

[0013] The platen 11 is a support base having an upward-facing surface, and supports the paper 21 being conveyed from below. The paper 21 is sent from a sheet feeder (not shown) provided outside the case 15 to the upper surface of the platen 11 such that both sides face up / down and the width direction faces left / right. The two transport rollers 12 are located on the front and rear sides of the platen 11, with their respective axial directions facing left and right. The paper 21 is subjected to a forward external force from each transport roller 12, which is driven by a motor (not shown), and is transported forward along the upper surface of the platen 11.

[0014] The four head units 13 are arranged front to back between the two transport rollers 12. Each head unit 13 is a so-called line-type inkjet head. The head units 13 are columnar in shape, and their axial direction is oriented left to right. The head units 13 are spaced apart from the upper surface of the platen 11 and face the upper surface of the platen 11. The paper 21 passes through the gap between the platen 11 and each head unit 13. The four head units 13 are supplied with ink of different colors from ink tanks (not shown).

[0015] The control device 14 includes a main control circuit 3. The main control circuit 3 is the control center of the printing device 1. The main control circuit 3 may include, for example, an FPGA, but is not limited to this, and may also include an ASIC or the like. The control device 14 further comprises a storage unit 141. The storage unit 141 is configured to be rewritable and includes an EEPROM, FlashROM, hard disk, etc. The storage unit 141 stores a control program. The control program stored in the storage unit 141 is installed into the storage unit 141 from, for example, a recording medium 22 (optical disc, portable flash memory, etc.) or downloaded into the storage unit 141 from a server that can communicate with the printing device 1.

[0016] The control device 14 can communicate with the image processing device 23. The image processing device 23 is a PC, scanner, etc., and transmits the original image data to the control device 14. The original image data represents the entire image to be recorded on the paper 21. The main control circuit 3 controls the operation of each part of the printing device 1 based on the received document image data, according to the control program stored in the memory unit 141. As a result, ink is ejected from each of the four head units 13, and an image is recorded on the paper 21 using the ejected ink. The paper 21 on which the image is recorded is ejected into a tray (not shown) located outside the case 15.

[0017] Figure 2 is a bottom view of the head unit 13. The head unit 13 is equipped with multiple heads 16. Figure 2 illustrates nine heads 16. The nine heads 16 are arranged in a staggered pattern, side by side. Specifically, the nine heads 16 are arranged in two rows, front and back. The heads 16 in each row are arranged linearly from left to right. Four of the nine heads make up the front row, and the remaining five make up the back row. The arrangement of the heads 16 in the front row and the arrangement of the heads 16 in the back row are staggered.

[0018] Each head 16 has multiple nozzles 161 arranged in a staggered pattern on the left and right sides. Each nozzle 161 opens downwards on the underside of the head unit 13. Ink is ejected from the nozzles 161 toward the paper 21, and when it adheres to the paper 21, an image is recorded on the paper 21. Of all the nozzles 161 provided on the head unit 13, the leftmost nozzle 161 faces the left edge of a predetermined size sheet of paper 21, and the rightmost nozzle 161 faces the right edge of a predetermined size sheet of paper 21. Therefore, an image can be recorded on a long sheet of paper 21 in a short time without moving the head 16 back and forth.

[0019] In the following, when distinguishing between the nine heads 16, the leftmost head 16 will be referred to as the first head 16, the head 16 adjacent to the right front of the first head 16 will be referred to as the second head 16, the head 16 adjacent to the right rear of the second head 16 will be referred to as the third head 16, and the head 16 adjacent to the right front of the third head 16 will be referred to as the fourth head 16. Similarly, the five heads 16 to the right of the fourth head 16 will be referred to as the fifth through ninth heads 16, respectively.

[0020] Figure 3 is a block diagram showing the main control circuit 3 and the head unit 13. Figure 3 shows the main control circuit 3 and one of the four head units 13. The following description will focus on the main control circuit 3 and one head unit 13, but the same applies to the other three head units 13.

[0021] The head unit 13 is further equipped with the same number of SoC4 as the number of heads 16. The nine SoC4 are connected to the nine heads 16 in a one-to-one correspondence. Each SoC4 is a head control circuit that controls the recording of images by the head 16 connected to it. Each SoC4 is pre-assigned with unique identification information. In the following, SoC4 connected to the Kth head 16 (where K is a natural number less than or equal to 9) will be referred to as the Kth SoC4. In Figure 3, "SoC(K)" means "the Kth SoC4".

[0022] The nine SoC4s are connected in series with the first to ninth SoC4s arranged in that order. More specifically, each SoC4 has an upstream interface and a downstream interface (not shown), and the downstream interface of the first SoC4 and the upstream interface of the second SoC4 are connected to each other via a communication cable for bidirectional communication. Similarly, the downstream interface of the kth SoC4 and the upstream interface of the k+1th SoC4 are connected to each other (k is a natural number between 2 and 8). The upstream interface of the first SoC4 is connected to an SoC interface (not shown) of the main control circuit 3.

[0023] As a result, the (k-1)th SoC4 is connected upstream of the kth SoC4, and the (k+1)th SoC4 is connected downstream of the kth SoC4. However, the main control circuit 3 is connected upstream of the first SoC4, and nothing is connected downstream of the ninth SoC4.

[0024] The main control circuit 3 comprises a control unit 31 and a document transmission unit 32. The document transmission unit 32 and the first SoC 4 are connected to each other via a communication cable, enabling bidirectional communication. The control unit 31 inputs the document image data received from the image processing device 23 to the document transmission unit 32. The document transmission unit 32 generates document data to be provided to each SoC4 by dividing the input document image data according to a predetermined procedure. The document transmission unit 32 also adds identification information of the SoC4 to which the document data should be provided to the generated document data. Furthermore, the document transmission unit 32 sends nine document data (document data with identification information for the first SoC4, document data with identification information for the second SoC4, ... and document data with identification information for the ninth SoC4) to the first SoC4.

[0025] The nine SoC4s sequentially transmit the document data received by the first SoC4 (i.e., the upstream SoC4) down to the ninth SoC4 (i.e., the downstream SoC4). In other words, for two adjacent SoC4s, the upstream SoC4 is the one that sends the document data, and the downstream SoC4 is the one that receives the document data. In this embodiment, the upstream SoC4 is the SoC4 directly connected to the main control circuit 3.

[0026] Each SoC4 includes a control unit 41 and a storage unit 42. The control unit 41 controls the operation of the SoC4. The control unit 41 may include, for example, a CPU, or it may include logic circuits such as an image processing circuit. The memory unit 42 is a rewritable non-volatile memory such as a FlashROM or EEPROM. The memory unit 42 pre-stores identification information for the SoC4. Hereinafter, the identification information stored in the SoC4's memory unit 42 will be referred to as the SoC4's own identification information, and the document data to which the SoC4's own identification information is attached will be referred to as the SoC4's own document data.

[0027] Figure 4 is a flowchart showing the steps of the printing process performed on the SoC4. The control unit 41 of the SoC4 determines whether or not it has received document data from the main control circuit 3 or the upstream SoC4 (S11). If it has not received the data (NO in S11), it repeats the process in S11. If the original document data is received (YES in S11), the control unit 41 stores all the received original document data in the storage unit 42 (S12).

[0028] Next, the control unit 41 determines whether it has received other document data different from its own by determining whether at least one of the document data stored in the storage unit 42 has identification information different from its own identification information (S13). If the control unit 41 receives other document data that is different from its own document data (YES in S13), it reads the other document data that is different from its own document data from the document data stored in the storage unit 42 and sends it to the downstream SoC 4 (S14). Then, the control unit 41 deletes the other document data that is different from its own document data from the storage unit 42 (S15).

[0029] After processing in S15 is complete, or if no other document data different from its own document data has been received (NO in S13), the control unit 41 moves the process to S16, which will be described later. The control unit 41 may also transfer all received document data to the downstream SoC4. However, as in this embodiment, by sending only the received document data excluding its own document data to the downstream SoC4, the amount of data sent to the downstream SoC4 can be reduced. Therefore, the communication load can be reduced.

[0030] The control unit 41 controls whether or not to eject ink from each nozzle 161 of the print head 16 based on its own document data (S16). As a result, an image is recorded on the paper 21. In other words, the SoC 4 controls the recording of the image by the corresponding print head 16 based on the document data. After the processing in S16 is completed, the control unit 41 terminates the printing process. Even after the printing process is complete, the storage unit 42 retains its original document data.

[0031] Incidentally, abnormalities may occur in the image formed on the paper 21 due to, for example, the deterioration of the print head 16 over time, or the accumulation of dirt on the nozzle 161. Image abnormalities include, for example, missing parts of the image due to ink not being ejected from the nozzle 161, or smudges on the image due to ink adhering to inappropriate locations on the paper 21. Therefore, the printing device 1 detects an abnormality in the image formed on the paper 21.

[0032] As shown in Figure 3, the printing apparatus 1 further comprises a plurality of reading devices 17. The number of reading devices 17 is less than half the number of SoC4, and in this embodiment there are three. In the following, when distinguishing between the three reading devices 17, they will be referred to as the upstream reading device 17, the midstream reading device 17, and the downstream reading device 17. Each reading device 17 is associated with three adjacent SoC4s. The first to third SoC4s are associated with the upstream reading devices 17, the fourth to sixth SoC4s are associated with the midstream reading devices 17, and the seventh to ninth SoC4s are associated with the downstream reading devices 17.

[0033] Each reading device 17 comprises three reading units 171. Each reading unit 171 reads the image recorded on the paper 21 before the paper 21 on which the image is recorded is ejected into the aforementioned tray, and generates reading data indicating the image recorded on the paper 21.

[0034] The three reading units 171 of the upstream reading device 17 are positioned to correspond to the positions of the first to third heads 16 and are connected in series with each other. The upstream reading device 17 is connected to the third SoC4. Although not shown in the diagram, the three reading units 171 of the midstream reading device 17 are connected in series with each other to correspond to the fourth to sixth heads 16. The midstream reading device 17 is connected to the sixth SoC4. Similarly, the three reading units 171 of the downstream reading device 17 correspond to the seventh to ninth heads 16, and the downstream reading device 17 is connected to the ninth SoC4. As described above, the three reading devices 17 are connected in a one-to-one correspondence to three SoC4s, including the furthest downstream SoC4 among the nine SoC4s.

[0035] The three reading devices 17 each have a total of nine reading units 171, and the nine reading units 171 correspond to nine heads 16. Each reading unit 171 reads the image within the range recorded by the corresponding head 16. Since the three reading units 171 are provided in one reading device 17 and the reading device 17 is connected to the SoC4, there is no need to provide a communication cable for sending and receiving read data for each reading unit 171. In other words, the number of communication cables can be reduced from nine to three.

[0036] Hereinafter, the read unit 171 corresponding to the Kth SoC4 will be referred to as the Kth read unit 171. The Kth read unit 171 has a memory (not shown) that pre-stores identification information for the Kth SoC4. The m-th (m=1,4,7) reading unit 171 adds the identification information of the m-th SoC4 to the generated reading data and sends it to the m+1th reading unit 171. The m+1th reading unit 171 adds the identification information of the m+1th SoC4 to the generated reading data and sends it to the m+2nd reading unit 171 along with the reading data received from the m-th reading unit 171. The m+2nd reading unit 171 adds the identification information of the m+2nd SoC4 to the generated reading data and sends it to the m+2nd SoC4 along with all the reading data received from the m+1st reading unit 171.

[0037] The three read data sent by the upstream reading device 17 to the third SoC4 correspond to the three document data stored in the memory units 42 of each of the first to third SoC4. Similarly, the three read data sent by the midstream reading device 17 to the sixth SoC4 correspond to the three document data stored in the memory units 42 of each of the fourth to sixth SoC4. The three read data sent by the downstream reading device 17 to the ninth SoC4 correspond to the three document data stored in the memory units 42 of each of the seventh to ninth SoC4.

[0038] The data read by the (m+2)th SoC4 is sent to the (m+1)th SoC4, as described below, and then to the next (m)th SoC4. Each scanned data entry is the minimum necessary to be compared with the original document data stored in the SoC4, which contains the identification information assigned to that scanned data. Therefore, the amount of data can be reduced, thereby reducing the communication load.

[0039] If there are no abnormalities in the image recorded on the paper 21 by the K head 16, the read data to which the identification information of the K SoC4 is attached is equal to the original data stored by the K SoC4. In other words, if the read data is different from the original data, there is an abnormality in the image. To detect an abnormality in the image, the original data and the read data are compared with each other as described below.

[0040] Figure 5 is a block diagram illustrating the detection of image anomalies. Each SoC4 further comprises a comparison unit 43 and a compression unit 44. The comparison unit 43 generates difference data by comparing the original data and the scanned data with each other. For example, if both the original data and the scanned data are 16-digit numbers represented in binary, the comparison unit 43 performs an exclusive OR operation bit by bit between the value of each bit of the number represented by the scanned data and the value of each bit of the number represented by the original data. In this case, the difference data, which is the result of the operation, is also a 16-digit number represented in binary.

[0041] If there is no abnormality in the image, ideally the numerical value shown in the scanned data and the numerical value shown in the original data are equal, and the value of each bit in the numerical value shown in the difference data is all "0". On the other hand, if there is an abnormality in the image, the numerical value shown in the scanned data and the numerical value shown in the original data are different, so at least one bit in the numerical value shown in the difference data is "1". However, in reality, even if there are no abnormalities in the image, the values ​​of each bit in the numerical value indicated by the differential data may not all be "0". Therefore, if, for example, a certain number of bits out of the 16 bits have a value of "0", the image is determined to be free of abnormalities.

[0042] The amount of data in the differential data is equal to the amount of data in the original data and the scanned data, respectively, and the amount of data is large. Therefore, the compression unit 44 compresses the differential data. The amount of data in the compressed differential data is less than or equal to the amount of data in the differential data before compression.

[0043] Figures 6 and 7 are flowcharts showing the steps of the send / receive processing performed by SoC4. As shown in Figure 6, the control unit 41 of the SoC4 determines whether or not read data has been sent from the read device 17 or the downstream SoC4 (S21). If no data has been sent (NO in S21), the process in S21 is repeated. If read data is received (YES in S21), the control unit 41 stores all the received read data in the storage unit 42 (S22).

[0044] Next, the control unit 41 determines whether it has received other read data different from its own by determining whether at least one of the read data stored in the storage unit 42 has identification information different from its own identification information (S23). If the control unit 41 receives other read data that is different from its own read data (YES in S23), it reads the other read data that is different from its own read data from the read data stored in the storage unit 42 and sends it to the upstream SoC 4 (S24). Then, the control unit 41 deletes the other read data that is different from its own read data from the storage unit 42 (S25).

[0045] After the processing in S25 is completed, or if no other read data different from its own read data has been received (NO in S23), the control unit 41 moves the processing to S26, which will be described later. The control unit 41 may also transfer all received read data to the upstream SoC4. However, as in this embodiment, by sending only the read data excluding its own read data to the upstream SoC4, the amount of data sent to the upstream SoC4 can be reduced. Therefore, the communication load can be reduced.

[0046] The control unit 41 inputs its own document data and its own scanned data into the comparison unit 43, thereby comparing the two (S26). The comparison unit 43, having received the document data and scanned data, generates difference data, which is the result of the comparison between the two. The control unit 41, which executes the S26 process, reads its own document data from the storage unit 42 and inputs it to the comparison unit 43. In other words, there is no need to send or receive the document data again in order to execute the S26 process. Therefore, the communication load can be reduced.

[0047] After the processing in S26 is completed, the control unit 41 adds its own identification information to the difference data generated by the comparison unit 43, as shown in Figure 7 (S31). Note that the addition of the identification information may be performed by the comparison unit 43. After the processing in S31 is completed, the control unit 41 inputs the differential data to the compression unit 44, thereby compressing the differential data (S32). The compression unit 44 compresses the input differential data. The compression unit 44 may also perform the assignment of identification information. Alternatively, the control unit 41 or the compression unit 44 may assign identification information to the compressed differential data.

[0048] The control unit 41 determines whether it is the downstream SoC4 (S33). In S33, the control unit 41 determines YES if, for example, no SoC4 is connected downstream of it, or if its identification information includes information indicating that it is the downstream SoC4. If it is the downstream SoC4 (YES in S33), the control unit 41 sends the differential data compressed by the compression unit 44 to the upstream SoC4 (S34).

[0049] If it is not the downstream SoC4 (NO in S33), the control unit 41 determines whether or not it has received compressed differential data from the downstream SoC4 (S35). If it has not yet received it (NO in S35), it returns to processing S35.

[0050] If compressed differential data is received from the downstream SoC4 (YES in S35), the control unit 41 sends the received differential data and the differential data compressed by the compression unit 44 together to the upstream SoC4 or main control circuit 3 (S36). Since the differential data is compressed, the amount of data sent and received between each SoC4 or between the SoC4 and the main control circuit 3 can be reduced by executing S34 or S36. Therefore, the communication load can be reduced. After the processing in S34 or S36 is completed, the control unit 41 deletes its own document data and its own scanned data from the storage unit 42 (S37), and terminates the transmission and reception process.

[0051] After the completion of processing in S32, the control unit 41 may send the differential data compressed by the compression unit 44 to the upstream SoC4 or the main control circuit 3 without waiting for the compressed data to be sent from the downstream SoC4. In this case, in processing S36, the differential data received from the downstream SoC4 is sent to the upstream SoC4 or the main control circuit 3. If the answer to S23 is YES, the control unit 41 may execute the process of S24 simultaneously when executing the process of S36. That is, in the process of S36, the control unit 41 sends the differential data received from the downstream SoC4, the differential data compressed by the compression unit 44, and other read data different from its own read data to the upstream SoC4 all together.

[0052] As a result of the transmission and reception processes described above, the main control circuit 3 receives the differential data generated by all SoCs 4, each in a compressed state. Furthermore, if there is no difference between the original data and the scanned data, for example, a 1-bit data indicating that there is no difference between the two may be generated as difference data. In this case, the amount of data sent to the main control circuit 3 can be further reduced. Therefore, the communication load can be reduced.

[0053] As shown in Figure 5, the main control circuit 3 further comprises an extension unit 33 and a determination unit 34. The decompression unit 33 decompresses the compressed differential data. The determination unit 34 determines whether or not there is an abnormality in the image recorded on the paper 21 based on the expanded difference data. If the difference data indicates that the original data and the scanned data are equal, the determination unit 34 generates a determination result indicating that there is no abnormality in the image. If the difference data indicates that there is a difference between the original data and the scanned data, the determination unit 34 generates a determination result indicating that there is an abnormality in the image. The main control circuit 3 receives nine difference data, so the extension unit 33 extends each of the nine difference data, and the determination unit 34 generates nine determination results corresponding to the nine difference data.

[0054] Figure 8 is a flowchart showing the procedure for the determination process executed by the main control circuit 3. The control unit 31 of the main control circuit 3 determines whether or not it has received differential data from the upstream SoC 4 (S41). If it has not received the data (NO in S41), it repeats the process in S41. If differential data is received (YES in S41), the control unit 31 decompresses the differential data by inputting all the received differential data into the decompression unit 33 (S42). Next, the control unit 31 inputs the difference data expanded by the expansion unit 33 to the determination unit 34 to determine whether or not there is an abnormality in the image recorded on the paper 21 (S43).

[0055] After the processing in S43 is completed, the control unit 31 determines whether or not at least one of the nine determination results generated by the determination unit 34 indicates that there is an abnormality in the image (S44). If all nine judgment results indicate that there are no abnormalities in the image (NO in S44), the control unit 31 terminates the judgment process because there are no abnormalities in the image formed on the paper 21. If at least one judgment result indicates that there is an abnormality in the image (YES in S44), then there is an abnormality in at least a portion of the image formed on the paper 21. Therefore, the control unit 31 causes the display unit (not shown) of the printing device 1 to display text or symbols to inform the user that there is an abnormality in the image (S45), and terminates the judgment process.

[0056] When a user is notified of an image abnormality, they visually inspect the image formed on the paper 21 and decide whether the image abnormality is acceptable. If the image abnormality is acceptable, the user continues to use the printer 1. If the image abnormality is unacceptable, the user discontinues use of the printer 1 and makes arrangements for maintenance.

[0057] Note that the printing device 1 is not limited to a configuration that displays an abnormality in the image. For example, the printing device 1 may record an additional image on the paper 21 with an abnormal image to indicate that there is an abnormality in the image. Alternatively, the printing device 1 may record an image based on the same original image data on a new paper 21 (i.e., reprint). In the case of reprinting, nine original data files are resent from the original transmission unit 32 to the upstream SoC 4. As a result, the printing process shown in Figure 4 and the transmission / reception processes shown in Figures 6 and 7 are executed again at the SoC 4.

[0058] It is desirable to store the difference data, which indicates a discrepancy between the original data and the scanned data, in a storage device (not shown) provided by the printing device 1. In this case, a maintenance worker for the printing device 1 can identify the head 16 that caused the malfunction based on the identification information attached to the stored difference data.

[0059] With the printing apparatus 1 described above, the nine SoCs 4 generate differential data showing the difference between the original data and the scanned data, so the main control circuit 3 does not need to generate differential data. Therefore, the computational load on the main control circuit 3 can be reduced. Furthermore, since the amount of data transmitted and received can be reduced, noise generated during data transmission and reception can be reduced. As mentioned above, when generating differential data, the original data already stored in the memory unit 42 of each SoC4 is used, so there is no need to send or receive the original data again in order to generate differential data. This means that the configuration of the printing device 1 is different from one in which the generation of differential data by the main control circuit 3 is replaced by a simple distributed processing by the nine SoC4.

[0060] In this embodiment, three SoC4s correspond to each of the three reading devices 17, but the embodiment is not limited to this. The number of reading devices 17 can be N (where N is a natural number) and the number of SoC4s can be M (where M is a natural number such that M ≥ 2N). Furthermore, as long as at least two SoC4s correspond to each reading device 17, the number of SoC4s corresponding to each reading device 17 may be the same or different. However, since the read data is sent upstream, a reading device 17 must always be connected to the downstream SoC4, and at least one SoC4 that is not connected to a reading device 17 must be connected upstream of the SoC4 to which the reading device 17 is connected.

[0061] The number of reading units 171 in the reading device 17 is equal to, but not limited to, the number of SoC4s corresponding to the reading device 17. For example, the reading device 17 may have one reading unit 171, and the data generated by the reading unit 171 reading the image recorded on the paper 21 may be divided into a number of reading data equal to the number of corresponding SoC4s.

[0062] In this embodiment, the read data and differential data are sent upstream, but are not limited to this. The read data and differential data may also be sent downstream. In this case, the downstream SoC4 and the main control circuit 3 are directly connected, and differential data is sent from the downstream SoC4 to the main control circuit 3. Furthermore, a read device 17 is always connected to the upstream SoC4, and at least one SoC4 that is not connected to the read device 17 must be connected downstream of the SoC4 to which the read device 17 is connected.

[0063] Next, the printing apparatus 1 and determination method according to Embodiments 2 to 5 will be described. In the following, the differences from Embodiment 1 will be explained, and other components identical to those in Embodiment 1 will be denoted by the same reference numerals, and their descriptions will be omitted.

[0064] Embodiment 2. Figure 9 is a block diagram showing the main components of the printing apparatus 1 according to Embodiment 2. In Embodiment 1, as shown in Figure 5, the main control circuit 3 includes an extension unit 33 and a determination unit 34, and each SoC 4 includes a compression unit 44. In this embodiment, as shown in Figure 9, the main control circuit 3 does not include an extension unit 33 and a determination unit 34, and each SoC 4 is equipped with a determination unit 45 instead of a compression unit 44.

[0065] Each determination unit 45 receives differential data from the comparison unit 43 of the SoC4 equipped with the determination unit 45, determines whether or not there is an abnormality in the image recorded on the paper 21 based on the received differential data, and generates a determination result. The determination unit 45 generates a determination result indicating that there is no abnormality in the image when it receives difference data indicating that the original data and the scanned data are equal. On the other hand, when it receives difference data indicating that there is a difference between the original data and the scanned data, the determination unit 45 generates a determination result indicating that there is an abnormality. The determination result is, for example, a 1-bit data indicating the presence or absence of an abnormality, and the amount of data in the determination result is less than or equal to the amount of data in the difference data.

[0066] Figure 10 is a flowchart showing the steps for sending and receiving data on the SoC4. The control unit 41 of the SoC4 first performs the same processing as shown in S21 to S26 in Figure 6. After the completion of processing S26, as shown in Figure 10, the control unit 41 inputs the difference data generated by the comparison unit 43 to the determination unit 45 to determine whether or not there is an abnormality in the portion of the image recorded on the paper 21 that was recorded by the head 16 corresponding to itself (S51). Next, the control unit 41 adds its own identification information to the determination result generated by the determination unit 45 (S52). After the processing in S52 is completed, the control unit 41 determines whether or not it is the downstream SoC4 (S53). The processing in S53 is the same as the processing in S33 shown in Figure 7.

[0067] If the result in S53 is YES, the control unit 41 sends the determination result to the upstream SoC4 (S54). If the result in S53 is NO, the control unit 41 determines whether or not it has received a judgment result from the downstream SoC4 (S55). If it has not yet received the result (NO in S55), the process returns to S55. If the control unit 41 receives a determination result from the downstream SoC4 (YES in S55), it sends the received determination result and the determination result generated by the determination unit 45 together to the upstream SoC4 or main control circuit 3 (S56). Since each judgment result has a small amount of data, the amount of data transmitted and received between each SoC4 or between the SoC4 and the main control circuit 3 can be reduced by executing S54 or S56. Therefore, the communication load can be reduced.

[0068] After the completion of processing in S54 or S56, the control unit 41 deletes its own document data and its own scanned data from the storage unit 42 (S57), and terminates the transmission and reception process. As described above, the transmission and reception process in this embodiment is similar to the transmission and reception process in Embodiment 1 (see Figures 6, 7, and 10), and the main difference between the two is whether the differential data is sent upstream or the determination result is sent upstream.

[0069] As a result of the transmission and reception process shown in Figure 10, nine judgment results are sent from the upstream SoC4 to the main control circuit 3. Figure 11 is a flowchart showing the procedure for the determination process executed by the main control circuit 3. The control unit 31 of the main control circuit 3 determines whether or not it has received a judgment result from the upstream SoC 4 (S61). If it has not received a result (NO in S61), it repeats the process in S61.

[0070] If a judgment result is received (YES in S61), the control unit 31 determines whether at least one of the nine received judgment results indicates that there is an abnormality in the image (S62). If all nine judgment results indicate that there is no abnormality in the image (NO in S62), the control unit 31 terminates the judgment process because there is no abnormality in the image formed on the paper 21. If at least one judgment result indicates that there is an abnormality in the image (YES in S62), the control unit 31 notifies the user that there is an abnormality in the image (S63) in the same manner as the process in S45 shown in Figure 8, and terminates the judgment process.

[0071] The determination process shown in Figure 11 corresponds to the determination process shown in Figure 8, but as can be seen by comparing Figure 8 and Figure 11, the determination process in this embodiment is simpler. Therefore, the computational load on the main control circuit 3 is small. It is desirable to store the judgment result indicating an abnormality in the image in, for example, a storage device (not shown) provided by the printing device 1. In this case, a worker maintaining the printing device 1 can identify the head 16 that caused the abnormality based on the identification information attached to the stored judgment result.

[0072] With the printing apparatus 1 described above, the computational load of the main control circuit 3 can be further reduced compared to the case of Embodiment 1. In addition, since the amount of data transmitted and received can be further reduced, the noise generated in conjunction with the transmission and reception of data can be further reduced. In this embodiment, the read data and the judgment result are sent upstream, but are not limited to this, and may also be sent downstream. In this case, similar to the case where differential data is sent upstream, the downstream SoC4 and the main control circuit 3 are directly connected, and the judgment result is sent from the downstream SoC4 to the main control circuit 3.

[0073] Embodiment 3. Figure 12 is a block diagram showing the main components of the printing apparatus 1 according to Embodiment 3. The hardware configuration of the printing apparatus 1 according to this embodiment is substantially the same as the hardware configuration of the printing apparatus 1 according to Embodiment 1 or Embodiment 2. However, the printing apparatus 1 of this embodiment is equipped with nine reading devices 18 instead of three reading devices 17, and nine SoC4s and nine reading devices 18 are connected in a one-to-one correspondence. Therefore, the number of communication cables for sending and receiving read data is nine.

[0074] Each reading device 18 reads the image recorded on the paper 21 within the range where the head 16 connected to the corresponding SoC4 records the image, and generates reading data indicating the read image. The nine reading devices 18 correspond to the nine reading units 171 in Embodiment 1, but it is not necessary to add SoC4 identification information to the read data generated by each reading device 18. Therefore, the computational load on the reading devices 18 can be reduced.

[0075] The control unit 41 of each SoC4 executes either the send / receive processing shown in Figures 6 and 7, or the send / receive processing shown in Figures 6 and 10, but does not need to execute the processes S23 to S25 shown in Figure 6. If the control unit 41 determines in the S21 process that read data has been sent from the read device 18, it only needs to execute the S26 process after the S22 process. As a result, the computational load on the SoC4 can be reduced, and the communication load between each SoC4 or between the SoC4 and the main control circuit 3 can also be reduced.

[0076] Embodiment 4. Figure 13 is a block diagram showing the main components of the printing apparatus 1 according to Embodiment 4. The hardware configuration of the printing apparatus 1 according to this embodiment is substantially the same as that of the printing apparatus 1 according to Embodiment 1. However, in this embodiment, the main control circuit 3 further comprises a data generation unit 35.

[0077] The control unit 31 of the main control circuit 3 also inputs the document image data input to the document transmission unit 32 to the data generation unit 35. Based on the input document image data, the data generation unit 35 generates data for correcting the difference data, and divides the generated data into nine judgment data in the same procedure as the division of the document image data in the document transmission unit 32. The nine judgment data correspond to the nine document data generated by the document transmission unit 32. The data generation unit 35 assigns the same identification information to the generated judgment data as the identification information assigned to the document data corresponding to that judgment data.

[0078] The control unit 31 inputs nine determination data with identification information to the determination unit 34. The determination unit 34 corrects each difference data expanded by the expansion unit 33 using determination data having the same identification information as the identification information attached to that difference data, and determines whether or not there is an abnormality in the image recorded on the paper 21 based on the corrected difference data.

[0079] Figure 14 is a schematic diagram illustrating the difference data. Figure 14A is a schematic diagram showing an example of an image recorded on paper 21. Virtual regions 211 and 213 of paper 21 each contain important parts of the image to be recorded on paper 21. Virtual region 212 of paper 21 contains unimportant parts of the image to be recorded on paper 21. Region 211 is separated from regions 212 and 213, while regions 212 and 213 are adjacent to each other.

[0080] The important parts of an image are those where imperfections such as blemishes or defects are unacceptable (for example, highly visible elements like logos, or two-dimensional codes like barcodes). The important parts that are not images are those where imperfections such as blemishes or defects are acceptable (for example, numbers representing serial numbers, which are less noticeable, or which can still be read by humans even with some imperfections or defects).

[0081] The image recorded on paper 21 includes a stain 214 extending both inside and outside region 211, and a stain 215 extending both inside and outside region 212. The stain 214 is small, but a portion of it is located inside region 211 (an area where staining is unacceptable). The stain 215 is large, but it is located outside regions 211 and 213 respectively (an area where staining is acceptable).

[0082] Figure 14B is a schematic diagram showing an example of difference data for the image shown in Figure 14A. The bit values ​​corresponding to stains 214 and 215 are "1", indicating that there is a difference between the original data and the scanned data. The bit values ​​other than those corresponding to stains 214 and 215 are "0", indicating that there is no difference between the original data and the scanned data. In the example shown in Figure 14A, a portion of the stain 214 is located within an unacceptable range, so it is determined that there is an abnormality in the image recorded on the paper 21. However, if stain 214 is not present, then stain 215 is within an acceptable range, and therefore it is undesirable to determine that there is an abnormality in the image recorded on paper 21.

[0083] Figure 15 is a schematic diagram illustrating the data used for judgment. Figure 15A is a schematic diagram showing an example of data used for judgment. The values ​​of all bits corresponding to the inside of areas 211 and 213 of paper 21 (areas where smudges cannot be tolerated) are "1", indicating that the difference between the original data and the scanned data is not ignored. The values ​​of all bits corresponding to the outside of areas 211 and 213 (areas where smudges can be tolerated; the areas hatched in Figure 15A) are "0", indicating that the difference between the original data and the scanned data is ignored.

[0084] The determination unit 34 corrects the difference data using the determination data by performing a bitwise logical AND operation between the value of each bit of the difference data and the value of each bit of the determination data. Figure 15B is a schematic diagram showing an example of corrected difference data. As can be seen in the figure, the bit value corresponding to the portion of the stain 214 located inside area 211 is "1", and the values ​​of the other bits are "0". Therefore, it is determined that there is an abnormality in the image recorded on paper 21. If the stain 214 is not present, it is determined that there is no abnormality in the image recorded on paper 21.

[0085] With the printing device 1 described above, it is possible to determine whether or not there is an abnormality based solely on a significant difference between the original data and the scanned data. Since the judgment data is generated based on the original image data each time the original image data is input, the actual state of the image recorded on paper 21 can be reflected in the corrected difference data. The procedures and conditions for generating judgment data from original image data are pre-programmed into the data generation unit 35. Alternatively, the user may select appropriate procedures and conditions from a set of pre-programmed procedures and conditions provided to the printing device 1, and these may be provided to the data generation unit 35.

[0086] Embodiment 5. The hardware configuration of the printing apparatus 1 according to this embodiment is substantially the same as the hardware configuration of the printing apparatus 1 according to Embodiment 1. The determination unit 34 is pre-defined with conditions for correcting each difference data expanded by the expansion unit 33.

[0087] Figure 16 is a schematic diagram illustrating the differential data used in the printing apparatus 1 according to Embodiment 5. Figure 16A is a schematic diagram showing an example of the difference data before correction. Minor defects and blemishes in the image are not noticeable and can be tolerated. For example, if the value of the first bit is "1" and the values ​​of the two second bits adjacent to the first bit are "0", the difference in the location corresponding to the first bit is based on a minor anomaly and should be ignored. Therefore, the determination unit 34 replaces the value of the first bit with "0".

[0088] Furthermore, if, for example, the value of the third bit is "1", and at least one of the two fourth bits located to the left and right of the third bit is also "1", then the difference in the location corresponding to the third bit is based on a significant anomaly. Therefore, the determination unit 34 leaves the value of the third bit as "1". Figure 16B is a schematic diagram showing an example of corrected difference data. In the differential data shown in Figure 16B, the information indicating the presence of minor anomalies that was included in the differential data shown in Figure 16A has been ignored.

[0089] With the printing apparatus 1 described above, if there is a difference between the original data and the scanned data that satisfies the given conditions, the determination unit 34 ignores the difference and determines whether or not there is an abnormality. Therefore, it is possible to determine whether or not there is an abnormality based only on a significant difference between the original data and the scanned data. Since this condition is given, there is no need to generate new data to determine whether or not the difference is significant. In other words, the computational load can be reduced.

[0090] In this embodiment, a given condition is used in which the bits to the left and right of a bit with a bit value of "1" each have a bit value of "0", but the embodiment is not limited to this. For example, the area of ​​the range where the bit value of "1" is continuous may be smaller than a predetermined value, or the location corresponding to the bit value of "1" may be located at the periphery of the paper 21.

[0091] Alternatively, the user may select an appropriate condition from several conditions pre-provided to the printing device 1, and the selected condition may be provided to the determination unit 34. In this embodiment, the difference data is corrected in the determination unit 34, but it is not limited to this, and the comparison unit 43 of each SoC4 may correct the difference data generated by comparing the original data and the scanned data as described above. Furthermore, the comparison unit 43 or determination unit 45 of each SoC4 in the printing apparatus 1 according to Embodiment 2 may correct the difference data as described above.

[0092] Embodiment 6. Figure 17 is a block diagram showing the main components of the printing apparatus 1 according to Embodiment 6. The hardware configuration of the printing apparatus 1 according to this embodiment is substantially the same as that of the printing apparatus 1 according to Embodiment 2. However, in this embodiment, the main control circuit 3 further comprises a data generation unit 35.

[0093] The data generation unit 35 generates nine judgment data in the same manner as the data generation unit 35 in Embodiment 4. The data generation unit 35 also sends the nine judgment data to the upstream SoC4 in the same manner as when the document transmission unit 32 sends the nine document data to the upstream SoC4. The nine SoC4s, in the same way as with the original document data, sequentially send the judgment data received by the upstream SoC4 down to the downstream SoC4. The judgment data is sent downstream after the original document data has been sent downstream. Alternatively, the original document data and the judgment data may be sent downstream simultaneously.

[0094] The determination data is stored in the memory unit 42 of the SoC4. The control unit 41 of the SoC4 inputs the determination data, to which its own identification information has been added, to the determination unit 45. The determination unit 45 uses the input determination data to correct the differential data as described in Embodiment 4. Alternatively, judgment data may be input from the storage unit 42 to the comparison unit 43, and the comparison unit 43 may correct the difference data generated by comparing the original data and the scanned data using the judgment data. For a single difference data, both correction using the determination data described in Embodiments 4 and 6, and correction using the given conditions described in Embodiment 5 may be applied.

[0095] With the printing apparatus 1 described above, just like in the case of the printing apparatus 1 according to Embodiment 4, it is possible to determine whether or not there is an abnormality based solely on a significant difference between the original data and the scanned data. In the determination method for determining whether or not there are abnormalities in an image recorded by the printing device 1 of Embodiments 1 to 6, it is not limited whether or not the printing device 1 is equipped with a device that generates read data (e.g., read devices 17, 18). The SoC 4 may generate the differential data in hardware or in software. The determination of whether or not there are abnormalities based on the differential data may be performed by the SoC 4, the main control circuit 3, or any other circuit. Therefore, the design flexibility of the printing device 1 is improved.

[0096] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is intended to include, but not in the sense described above, the equivalents of the claims and all modifications within the claims. The constituent elements (technical features) disclosed in each embodiment are combinable with each other, and new technical features can be formed by these combinations. Furthermore, the independent and dependent claims described in the claims can be combined with each other in all combinations, regardless of the form of reference.

[0097] Furthermore, while the claims are written in a format that includes claims referencing two or more other claims (multi-claim format), they are not limited to this. They may also be written in a format that includes multi-claims referencing at least one multi-claim (multi-multi-claim format). [Explanation of symbols]

[0098] 1 Printing device 16 heads 17,18 Reading devices 3. Main control circuit 32 Manuscript Transmission Section 34 Judgment section 35 Data Generation Unit 4. SoC (Head Control Module) 45 Judgment section

Claims

1. Multiple heads for recording images, Multiple head control circuits are connected to the head in a one-to-one correspondence and are connected in series with each other, each controlling the recording of the corresponding head based on the original data. A document transmission unit that sends the document data to the head control circuit at the uppermost level, A determination unit that determines whether or not there are abnormalities in the recorded image. In a printing apparatus equipped with, Multiple head control circuits, The upstream head control circuit sequentially sends the document data received by the upstream head control circuit to the downstream head control circuit. Difference data is generated showing the difference between the original document data and the read data generated by reading the image. The printing apparatus is characterized in that the determination unit determines whether or not there is an abnormality based on the difference data.

2. The reading device further comprises reading the aforementioned image and generating the aforementioned reading data, Each head control circuit is pre-assigned unique identification information. The aforementioned document transmission unit, By dividing the original image data representing the entire image to be recorded, multiple original data files are generated. Multiple original document data, each assigned the aforementioned identification information, are sent to the head control circuit at the very top. Each head control circuit is: When the document data to which identification information different from its own is assigned is received, the document data is sent to the downstream head control circuit, The document data to which the aforementioned identification information is attached is stored, Based on the stored original document data, the recording of the corresponding image by the head is controlled. The printing apparatus according to claim 1, characterized in that it generates difference data showing the difference between the stored original data and the read data generated by the reading device.

3. The number of the aforementioned reading devices is N (where N is a natural number), The number of head control circuits is M (where M is a natural number ≥ 2N), The N reading devices are connected in a one-to-one correspondence to the N head control circuits, including the downstream head control circuit. Upstream of the head control circuit to which the reading device is connected, at least one head control circuit to which the reading device is not connected is connected, Each reading device reads the image, generates a plurality of the read data, assigns the identification information to each, and sends them to the head control circuit connected to it. Each head control circuit is: When the read data to which identification information different from its own is assigned is received, the read data is sent to the upstream head control circuit. The printing apparatus according to claim 2, characterized in that it generates differential data showing the difference between the stored original data and the read data to which its own identification information has been added.

4. Multiple reading devices are connected in a one-to-one correspondence to multiple head control circuits. Each reading device sends the reading data generated by reading the image to the head control circuit connected to it. The printing apparatus according to claim 2, characterized in that each head control circuit generates difference data indicating the difference between the stored document data and the read data received from the reading device.

5. The main control circuit further comprises the document transmission unit and the determination unit, Each head control circuit, excluding the upstream head control circuit, The generated difference data is then sent to the upstream head control circuit after its own identification information is added to it. When the differential data is received from the downstream head control circuit, the received differential data is sent to the upstream head control circuit. The upstream head control circuit is, The generated difference data is sent to the main control circuit after being assigned its own identification information. The difference data received from the downstream head control circuit is sent to the main control circuit. The printing apparatus according to claim 3 or 4, characterized in that the determination unit determines whether or not there is an abnormality based on the difference data received by the main control circuit from the head control circuit at the uppermost level.

6. Each head control circuit compresses the differential data it generates and then sends it to the upstream head control circuit or the main control circuit. The main control circuit expands the received difference data, The printing apparatus according to claim 5, characterized in that the determination unit determines whether or not there is an abnormality based on the difference data extended by the main control circuit.

7. The main control circuit further comprises the document transmission unit described above, Each head control circuit has the determination unit, Each determination unit determines whether or not there is an abnormality based on the differential data generated by the head control circuit having the determination unit. Each head control circuit, excluding the upstream head control circuit, The determination result obtained by the determination unit itself is sent to the upstream head control circuit after being associated with its own identification information. When a determination result is received from the downstream head control circuit, the received determination result is sent to the upstream head control circuit. The upstream head control circuit is, The determination result obtained by the determination unit, which it possesses, is sent to the main control circuit after being associated with its own identification information. The printing apparatus according to claim 3 or 4, characterized in that it sends the determination result received from the downstream head control circuit to the main control circuit.

8. The system further comprises a data generation unit that generates determination data based on the original document data, which includes information on areas where the difference between the original document data and the read data should be ignored. The difference data includes information about the locations where there are differences between the original data and the scanned data. The printing apparatus according to claim 1, characterized in that the determination unit determines whether or not there is an abnormality by ignoring the difference when the location with the difference is included in the location indicated by the determination data.

9. The difference data includes information about the locations where there are differences between the original data and the scanned data. The printing apparatus according to claim 1, characterized in that the determination unit determines whether or not there is an abnormality by ignoring the difference when the location with the difference satisfies a given condition.

10. Multiple heads for recording images, Multiple head control circuits are connected to the head in a one-to-one correspondence and are connected in series with each other, each controlling the recording of the corresponding head based on the original data. A document transmission unit that sends the document data to the head control circuit at the uppermost level, A method for determining whether or not there is an abnormality in an image recorded by a printing device equipped with the following: The upstream head control circuit sequentially sends the document data received by the upstream head control circuit to the downstream head control circuit. Difference data is generated showing the difference between the original document data and the read data generated by reading the image. Based on the differential data, determine whether or not the aforementioned abnormality exists. A determination method characterized in that the generation of the differential data is performed by a plurality of head control circuits.

Images