Image reproduction system

Abstract: The invention relates to an image reproduction system for reproducing images on a support material. The system is provided with at least one image generator for generating image information concerning images for reproduction, at least one electronic memory in which a number of sets of images can be stored, at least one printing system for printing images stored in the memory on the support material. The system also comprises a control unit. In response to a malfunction in the image generator, the control unit provides the following: the images of complete sets stored in the memory at the time of the malfunction are printed by the printing system the predetermined number of times in the predetermined sequence; and images stored in the memory at the time of the malfunction are not printed if these images belong to incomplete sets stored in the memory and in connection with which at the time of the malfunction image information was still being generated by the image generator.

Description: The invention relates to an image reproduction system for the reproduction of images on a support material, comprising at least one image generator for generating image information regarding images for reproduction, at least one electronic memory in which at least one set of images obtained on the basis of the image information can be stored, each set comprising a number of images which are to be reproduced a predetermined number of times in a selected sequence, at least one printing system for printing images stored in the memory on the said support material, and a control unit for controlling the image generator, the memory and the printing system. A system of this kind is known, inter alia, from US-A-5 075 782. A set of images which is to be reproduced a predetermined number of times in a predetermined sequence is termed a "job" in this specification. The memory operates as a buffer between the image generator and the printing system so that the image generator and the printing system can in principle operate independently of one another. This means that a printing system can continue to operate in the event of a malfunction in the image generator, and vice versa. This possibility is used in the system according to the American patent. If a malfunction occurs in the image generator, the printing system continues to operate until it is ready to print an image not yet stored in the memory. This means that in the system according to the US-A-5 075 782 all the complete images stored in the memory are still printed in the event of a malfunction in the image generator. Even if the malfunction occurs during the printing of a set of images in connection with which the image generator is still generating image information at the time of the malfunction, the images already generated and stored in the memory will still be printed. A disadvantage is that it is completely uncertain whether the rest of the set not yet completely printed will be printed after the malfunction has been remedied by a user even though the job recovery procedure of the apparatus enables him to do so. In practice, the images already printed are frequently simply discarded, particularly if the malfunction is serious and of long duration. The reason for this is that the user is not always prepared to wait until the malfunction has been remedied before the set is printed. If, after the malfunction has been remedied, a user were to have the remaining part of the set printed the selected number of times and in the predetermined sequence, he would also have to check whether the images printed respectively before and after the malfunction are in agreement with the selected number and the predetermined sequence in which the images of the set in question should have been printed. That is also a reason for a user completely to reprint the entire set and discard the part of the set already printed before the malfunction. The result is a considerable waste of support material, usually sheets in practice. The amount of support material discarded can be fairly large, particularly if the memory has a considerable storage capacity, the set is large and/or the number of times that the set is to be printed is considerable. The image reproduction system according to the invention obviates these disadvantages and is characterised in that the control unit in response to a malfunction in the image generator so controls the image reproduction system that: the images of complete sets stored in the memory at the time of the malfunction are printed by the printing system on the support material the selected number of times in the predetermined sequence; and in that images stored in the memory at the time of the malfunction are not printed if said images belong to incomplete sets stored in the memory and in connection with which image information was still being generated by the image generator at the time of the malfunction. A first step in limiting the amount of superfluous prints is proposed in EP-A 0 478 355, considered the closest prior art. According to this publication, when said image generator malfunctions during generating a set of images and said printing system is at that moment printing images of another set, the control unit so controls the image reproduction system that the images of complete sets stored in the memory at the time of the malfunction are printed by the printing system the selected number of times in the predetermined sequence, but the images of the set in connection with which image information was still being generated by the image generator at the time of the malfunction are not printed. Since, in the event of a malfunction in the image generator, the complete sets possibly stored in the memory are simply printed the selected number of times in the predetermined sequence, the user will encounter no unnecessary disturbance from the malfunction. If, for example, the printing system is printing another set than the set being processed by the image-generating means when the malfunction occurred, all the complete sets stored in the memory will be printed. However, EP-A 0 478 355 does not disclose the case that a set of images is in both the process of being generated and the process of being printed. The present invention proposes further measures for limiting the amount of support material that is likely to be discarded at a malfunction of the image generator and is therefore characterised in that, when said image generator malfunctions during generating a set of images and said printing system is simultaneously printing images of that same set, said control unit so controls the image reproduction system that said printing system stops printing images of that same set but completes the printing process for those images of that set, for which said printing process has already started. Thus, as little as possible of the set in connection with which the image generator was still generating image signals at the time of the malfunction is printed. This prevents a number of images from being printed and subsequently discarded. However, the printing system will not immediately stop printing, because a sudden interruption of the printing process would necessitate additional measures for preventing contamination of the printing system with unused toner. Therefore, images in connection with which the printing process has already started in the printing system and which belong to the set in connection with which the image generator was still generating image information at the time of the malfunction will still be printed. Fig. 1 shows the general layout of a system according to the invention, Fig. 2 is a diagram showing the construction of a system for processing and intermediate storage of image information for use in the system shown in Fig. 1. Fig. 3 shows a scanning system for use in the system shown in Fig. 1. Fig. 4 shows the construction of a front-end for use in the system shown in Fig.1. Fig. 5 shows the construction of a printing unit for use in the system shown in Fig. 1. Fig. 1 shows the general layout of an image reproduction system according to the invention. This system comprises a first image generator consisting of a scanner 1 for opto-electrical scanning of a document and the delivery of digital image information corresponding thereto, a second image generator consisting of a supply system 2 for inputting digital image signals from an external source, and a printing unit 3 for printing digital image information on a support material. Both the scanner 1 and the supply unit 2 are connected to a system 15 for processing and intermediate storage of image information, said system 15 in turn being connected to the printing unit 3. Scanner 1, supply unit 2, system 15 and printing system 3 are connected to a central control unit 18, which is also connected to an operating unit 19 provided with an operating panel 19A with operating elements and a display screen for use by an operator. Fig. 2 is a diagrammatic illustration of a system 15 for processing and intermediate storage of image information, the rectangles denoting functional modules (both physical components and software modules) and the arrows indicating the data flow from one module to the next. The scanner 1, supply system 2 and printing unit 3 are shown in this Figure in order to illustrate their position with respect to the system 15. Although not shown in the Figure, the various elements of the system 15 are connected to the control unit 18, which co-ordinates their operation. The scanner 1 scans an original document line by line and in so doing delivers digital information in the form of digital signals descriptive of the grey values of raster dots (pixels) of the document. The scanner element (CCD array) and document are moved relatively to one another by means of a motor 9. This can be a servomotor with a feedback circuit for the position of the scanner element. A more detailed description of the scanner will be given hereinafter with reference to Fig. 3. The digital signals from the scanner are fed to a ZOOM module 103 which, if required, provides enlargement or reduction by interpolation. The signals from the ZOOM module 103 are fed via a buffer 104 to a half-tone module 105, which converts the signals then descriptive of grey values into binary signals which specify one of two values for each pixel: zero or one, so that these signals are suitable for controlling a printing unit which can print only white or black image dots. Numerous half-tone processing operations are described in the literature so that no explanation is necessary. It is immaterial to this description which half-tone process is applied provided the resulting signals are of a binary type. The signals from the half-tone module 105 are in turn fed to a multiplexer 106. The supply unit 2 for digital image signals from a local network 16 is connected to another input of multiplexer 106 so that digital signals can be supplied from an external source, such as a workstation. The multiplexer 106 passes one of two data streams (from the scanner or from the network) to a mixing module 108. The latter has a second input to which a return line 120 is connected for returning signals from the memory 111, and this will be discussed hereinafter. The signals from multiplexer 106 and return line 120 can be mixed in accordance with logical functions on a pixel basis, corresponding to mixing two images, in mixing module 108. Examples of such logic functions are: OR, AND, EXOR. The mixing of binary signals in this way is generally known from the literature and requires no further explanation here. The mixing module 108 is connected to a rotation module 109, in which the image defined by the signals from the mixing module 108 can be rotated through an angle of 90°. The signals from rotation module 109 are then compressed in a compression module 110 and stored in a memory 111. Although compression is not strictly necessary, it is advisable, because in this way it is possible to store the data of more documents. The compression method can, for example, be run length coding. The memory 111 is provided with a management system (not shown) to update the addresses where the data of the documents are stored. The memory 111 is constructed with two independent read-out lines, so that the image data of two documents can be read out simultaneously. These read-out lines are each connected to a decompression module 112a, 112b. These are connected to basically identical processing circuits formed by insertion modules 113a, 113b. These modules can combine the image signals with artificial image data corresponding to a blank (white) image and be delivered by a virtual frame module 114a, 114b also connected to insert module 113a, 113b. The purpose of this is to be able to make image data descriptive of a larger image than the image data from the memory 111, e.g. an image which, in the case of the right-hand half, consists of a scanned document, while the left-hand half is blank (white). The insert modules 113a, 113b are connected to a mixer multiplexer 115, in which one of the image signals can be selectively passed or both images signals can be mixed, in the same way as described in connection with mixing module 108. Mixing multiplexer 115 has two outputs. One is the return line 120 already referred to, which enables images stored in the memory to be mixed with newly supplied (scanned) images. The other output is connected via a buffer memory 116 to the printing unit 3, which will be discussed in greater detail hereinafter. Buffers may be provided at various points in the circuit described. Since, however, these are not relevant to the operating principle, they have been omitted from the description. A number of sets of images obtained on the basis of the said image information can be stored in the memory 111. These are images which can be obtained both by means of the scanner and by. means of the network connection 16. Each set comprises a number of images which are required to be reproduced a predetermined number of times in the predetermined sequence. A set of images for reproduction in a predetermined number and in a predetermined sequence is also termed a "job". A set may also consist of just one image. In addition, the predetermined number of times that a set is to be reproduced may be equal to one. As already discussed, an image does not always have to involve the exact reproduction of a document. An image can also be the processed image of a document, part of an image of a document, the image of a number of documents, an image obtained from an external unit, and/or a combination of these images. The scanner 1 is shown in greater detail in Fig. 3. It comprises a tubular lamp 5 and a co-operating reflector 6, by means of which a narrow strip of a document 8 placed on a glass platen 7 is exposed. The scanner also comprises an array 10 of imaging glass fibres (a Selfoc lens array) by means of which the light reflected by the document is projected on a sensor array, e.g. a CCD array 12. The lamp 5, reflector 6, Selfoc lens array 10 and CCD 12 are mounted on a carriage 11 which during scanning is advanced by a servomotor 9 at a uniform speed in the direction of arrow 13 so that the document 8 is scanned line by line by the CCD array 12. The position of the carriage 11 is continually measured by known means and used, inter alia, for the feedback circuit for the servomotor 9. In this way each image dot of the document is converted to an analogue signal corresponding to the grey value of that dot. The analogue signal is then converted to a digital signal for each image dot by an A/D converter 14. The scanner 1 can also be equipped with an automatic or semi-automatic document feed unit (not shown in the drawings). An automatic feed unit (ADF) comprises a tray to receive a stack of documents for copying, a separating mechanism for taking the documents from the stack one by one and a transport mechanism for transporting a taken document to the platen 7. A semi-automatic or manual document feed unit (MDF) comprises a transport mechanism whereby a document inserted by hand is fed to the platen 7. The said feed units are public knowledge so that no further description is necessary. The supply unit 2 for digital image information from an external source, or a "front-end", is shown in Fig. 4. This unit is provided with a network connection unit 220 connected to an external network 16, to which a number of workstations can be connected for example. These workstations can send data files in various generally used formats (page description languages such as PCL, PostScript, etc) via a network 16 for printing. The network technology and the sending of data files over networks is public knowledge and will therefore not be explained here. The connection unit 220 is connected to a job recognition module 222 which is in turn connected to a hard disk 223. The job recognition module 222 determines, in respect of each data file supplied, the page description language (PDL) in which it is compiled, and extracts identification data contained therein. Data files sent in network systems always have identification data. These data usually consist of the name of the sender (owner) of the file and the name of the file itself. These data are extracted by the job recognition module 222. The memory disk 223, which is intended for interim storage of a data file supplied, is also connected to a PDL interpreter 224, for converting a data file coded in a page description language into a form suitable for processing by the printing unit 3. This process is generally also termed "rasterising". The PDL interpreter 224 is connected via a buffer 225 to the processing and intermediate storage system 15. The job recognition module 222, hard disk 223 and PDL interpreter 224 are also each connected to the control unit 18. The printing system 3 will now be described with reference to Fig. 5. This system is provided with an endless photoconductive belt 20 advanced at a uniform speed in the direction of arrow 24 by means of drive and guide rollers 21, 22 and 23. By means of the processed image data supplied from system 15, an LED array 15 is driven in such a manner that the photoconductive belt 20 is exposed imagewise line by line after it has been electrostatically charged by a corona system 30. The latent charge image formed by exposure on the belt 20 is developed with toner powder by means of a magnetic brush system 31 to give a toner image which then, in a first transfer zone, is brought into contact under pressure with an endless intermediate medium belt 32 made of or covered with an elastic and heat-resistant material, e.g. silicone rubber. In these conditions the toner image is transferred by adhesion forces from the belt 20 to the belt 32. After this image transfer, any toner powder residues are removed from the photoconductive belt 20 by means of a cleaning device 33, whereupon this belt 20 is ready for fresh use. The intermediate medium belt 32 is trained over drive and guide rollers 34, 35, the said belt 32 being heated to a temperature above the processing temperature of the toner powder, e.g. by means of an infrared radiator disposed inside roller 35. While the belt 32 with the toner image thereon is being advanced, the toner image becomes tacky as a result of the heating. In a second transfer zone between the belt 32 and the pressure roller 36, the tacky toner image is transferred by pressure to, and simultaneously fixed on, a copy sheet supplied from one of the reservoirs 37 or 38. The resulting copy can then be delivered in a tray 39 or be supplied by a deflecting element 40 (in the position indicated by broken lines) to a turn-over device 41 in which the copy sheet is turned over so that it is supplied again to the second transfer zone between the belt 32 and the pressure roller 36 for printing on the other side with a powder image in that transfer zone and then be delivered in the tray 39. Fig. 5 shows only two copy sheet reservoirs 37 and 38 but of course the number of reservoirs can be extended to supply different formats of copy sheets (e.g. A5, A4 and A3, and also other, e.g. American, formats). In addition, it is necessary to be able to offer the various copy sheet formats in different orientations - i.e. longitudinal transit (with the longest peripheral side in the direction of transit) or transverse transit (with the shortest peripheral side in the transit direction), in order to be able to produce copies of one and the same copy sheet format but with the orientation of the image information being selectively in the direction of transit of the copy sheets through the printing system or perpendicularly thereto. The various components of the printing system 3 are controlled by the central processing unit 18 directly or by means of sub-control modules. The system operates as follows: the user places a stack of documents for reproduction in the automatic document feeder of the scanner 1. By means of the operating panel 19A the user can indicate the way in which he wants the documents processed. For example he can indicate the number of copies and the sequence they are to be made in. Required image processing operations can also be input. On the basis of the image information obtained by means of the scanner at least one set of a number of images required to be produced in a predetermined sequence a selected number of times is accordingly made by the system 15. This set of images is stored in the memory (set memory) 111. Images can then be supplied from such a set to the printing unit 3 to enable the said images to be printed on the support material. Similarly, using the operating panel 19A a user can indicate that the image reproduction system is to be used as a printer. One or more data files stored in the supply unit 10 can then be selected, whereupon these data files are read off the hard disk 223, processed by the PDL interpreter 224 and fed via the buffer 225 to the mixing module 108. The information thus supplied to the mixing module 108 can further be processed as discussed in connection with the scanner. Finally, on the basis of the image information obtained from the network, at least one set of images will be stored in the memory 111. The memory 111 enables the printing system 3, on the one hand, and the scanner 1, on the other hand, to be able to operate independently of one another. This means, for example, that the printing system 3 can continue to work in the event of a malfunction in the scanner 1. Alternatively, the scanner 1 can continue to work if there is a malfunction in the printing system 3. In addition, it is possible for the printing system 3 to continue to operate in the event of a malfunction in the network connection 2 and vice versa. The term "malfunction" in connection with the scanner, for example, may mean that the documents successively scanned jam in the automatic document feeder. Other types of malfunction are feasible, e.g. a malfunction in the drive of the carriage 11. The control unit 18 is so arranged that in response to a malfunction in the scanner 1 it so controls the image reproduction system that only the images of complete sets stored in the memory 111 at the time of the malfunction are printed by the printing system 3 the selected number of times in the predetermined sequence. This means that a user will encounter the minimum disturbance from the malfunction in the scanner. Assuming that there is at least one complete set with images stored in the memory and being printed at the time of the malfunction, the printing unit will completely print this at least one set. In other words, the at least one complete job stored in the memory 111 is completely processed. Any other complete job stored in the memory will also be printed. The printing system will stop after these complete jobs have been processed. The incomplete set stored in the memory at the time of the malfunction, and in respect of which image information was still being generated at the time of the malfunction, is not printed. Moreover, an incomplete set stored in the memory and the image information of which is still being generated by the supply system 2, is printed in the event of scanner malfunction - obviously, this set can be completed in the usual way. The advantage is that no support material, particularly sheets, will be discarded. If the incomplete job stored in the memory and in connection with which the scanner malfunction occurred is actually printed, there is a considerable risk that the user will discard these prints. The user frequently chooses completely to re-scan and print in one operation in its entirety the set of documents in connection with which the malfunction occurred during scanning, even though the apparatus is provided with an error recovery procedure enabling him to resume the job stopped by the malfunction at the malfunction point. In practice, restarting the entire job is often preferred over checking whether the resumption was without errors. Another situation arises if there is no single complete set stored in the memory. In that case, there is only an incomplete set of images stored in the memory and at the time of the malfunction they are printed by the printing system and documents thereof are still being scanned by the scanner. At the time that the malfunction occurs, however, no further images of the incomplete set are supplied from the memory to the printing system 3. This means that the printing system stops printing as quickly as possible. The advantage of this in turn is that if a user chooses to re-scan the complete set, only a minimum quantity of images already printed has to be discarded. If, however, the printing system were not stopped, the images of the incomplete set stored in the memory would still all be printed, i.e. all the images completely scanned until the time of the malfunction. If a malfunction occurs in the supply system 2, the control unit controls the image reproduction system in response to said malfunction as described in connection with the malfunction in the scanner. This means that the images of complete sets stored in the memory at the time of the malfunction in the supply system 2 are printed by the printing system the predetermined number of times in the predetermined sequence and images which are stored in the memory at the time of the malfunction in the supply system 2 are not printed if these images belong to incomplete sets stored in the memory and in connection with which image information was still being generated at the time of the malfunction by the supply system 2. Since these conditions are completely similar to the description in relation to a malfunction in the scanner, no further explanation will be given here. In the event of one or more jobs still being printed in the event of a malfunction in the scanner 1, it may occur that the malfunction is so quickly remedied by the operator that the end of jobs still being processed is not reached. In that case, there would be no point in stopping the machine when the said end of the jobs still to be finished is reached. Consequently, after the malfunction in the scanner has been remedied, the machine will continue to accept new jobs. The job in which the scanner malfunction occurred can at the choice of the operator either be resumed at the point of the malfunction, or be cancelled. In the later case the images of the incomplete set of images belonging to that job will be erased from the memory 111, after which the machine is immediately ready for scanning in new jobs and for storing the images thereof in the memory. It was stated above that in the case in question the printing system is stopped as quickly as possible in the event of a malfunction in the scanner 1 or supply system 2. This means that the printing system does print images whose printing process in the printing system has already started. If this were not the case, the powder image formed by exposure and development on the belt 20 would not be transferred to the belt 32. There would then be considerable toner powder on the belt 20 and this would have to be removed from the belt 20 by means of the cleaning device 33 to enable the belt to be prepared for re-use. In such cases the cleaning device 33 would be subjected to unnecessarily heavy stress. In that case it is preferable to transfer the image in question to the belt 32, whereupon belt 32 transfers the toner image to a copy sheet supplied from one of the reservoirs 37 or 38. A suitable criterion for stopping the printing system 3 is that any charge image present on the belt 20 is to be printed. As already stated, a malfunction can also occur in the printing system 3. In response to such a malfunction, the control unit 18 controls the image reproduction system in such manner that the scanner 1 and/or the supply system 2 continue to work until the first of the following conditions is satisfied: all images for reproduction are stored in the memory; or the memory is full. If all the images for reproduction are stored in the memory and if the malfunction in the printing system 3 is then remedied, the said images can still be printed. If the memory is full, printing of the images from the memory can be continued after the malfunction has been remedied. This again gives room in the memory and the control unit will so control the scanner 1 and/or inputting system 2 that their operation can again continue and the memory can again be filled with new images. The invention is in no way limited to the above-described exemplified embodiment. For example, it is possible that the control unit, in response to the remedying of a malfunction in the printing system when the memory is full, will allow only the complete sets of images from the memory to printed. Here too there is of course the possibility that the user will, in the event of a malfunction in the printing system, choose completely to re-scan the set of documents which were scanned at the time that the scanner stopped working because the memory was full. These and other obvious variants are all considered as coming within the scope of the invention.

Claims: An image reproduction system for the reproduction of images on a support material, comprising at least one image generator (1,2) for generating image information regarding images for reproduction, at least one electronic memory (111) in which at least one set of images obtained on the basis of the image information can be stored, each set comprising a number of images which are to be reproduced a selected number of times in a predetermined sequence, at least one printing system (3) for printing images stored in the memory (111) on the said support material, and a control unit (18) for controlling the image generator (1,2), the memory (111) and the printing system (3), wherein, when said image generator (1,2) malfunctions during generating a set of images and said printing system is at that moment printing images of another set, the control unit (18) so controls the image reproduction system that the images of complete sets stored in the memory (111) at the time of the malfunction are printed by the printing system (3) the selected number of times in the predetermined sequence, but the images of the set in connection with which image information was still being generated by the image generator (1,2) at the time of the malfunction are not printed, characterised in that , when said image generator (1,2) malfunctions during generating a set of images and said printing system (3) is simultaneously printing images of that same set, said control unit (18) so controls the image reproduction system that said printing system (3) stops printing images of that same set but completes the printing process for those images of that set, for which said printing process has already started. An image reproduction system according to claim 1, characterised in that the control unit (18) in response to a malfunction in the printing system (3) so controls the image reproduction system that the image generator (1,2) continues to operate until the first of the following conditions is satisfied: all the images for reproduction are stored in the memory (111); or the memory (111) is full. An image reproduction system according to claim 1 or 2, characterised in that the image generator consists of a scanning system (1) for scanning original images and for generating the image information representing the scanned images. An image reproduction system according to claim 1 or 2, characterised in that the image generator consists of a supply system (2) to which image signals can be supplied from an external source for further processing. An image reproduction system according to any one of claims 1 to 3, characterised in that the system is provided with a second image generator consisting of a supply system (2) to which image signals can be supplied from an external source for further processing. An image reproduction system according to claim 5, characterised in that the control unit (18) in response to a malfunction in the first-mentioned image generator (1,2) so controls the image reproduction system that complete and not yet complete sets of images which are stored in the memory (111) on the basis of image information originating from the second image generator (2) are printed by the printing system in the normal manner. An image reproduction system according to any one of the preceding claims, characterised in that the system is also provided with image processing means (15) for processing the said image information.

Inventors: DEEN JUREK NIKOLAJ, VAN VLIEMBERGEN E J W, DEEN, JUREK NIKOLAJ, VAN VLIEMBERGEN, E.J.W.
Applicants: OCE TECH BV, OCE-TECHNOLOGIES B.V.
Application year: 1996
Main classification: H04N1
IPC codes: H04N1, B41J29