SCANNING DIGITISER AND/OR PRINTER

Abstract: A scanning digitiser and/or printer which allows reading and printing of two dimensional graphics. The preferred embodiment discloses the adaptation of a dot-matrix printer (12) into a digitiser by replacing the print head with an optical reflective sensor means (26) and allowing the output therefrom to be interrogated by a host computer.

Description: SCANNING DIGITISER AND/OR PRINTER The present invention relates to a scanning digitiser and/or printer and relates particularly, although not exclusively to a scanning digitiser- printer for reading and printing two dimensional graphics. It is an object of the present invention to provide a scanning digitiser-printer which can read into a computer an image contained on a sheet and also have the capability of printing a computer retrieved image. A further object of the invention is to provide a scanning digitiser-printer requiring very little modification to existinq printers. With these objects in view the present invention may provide a scanning digitiser and/or printer device including feed means for an image containing web, optical reflective sensor, means reciprocally mounted to move across, in use, said web, control means for controlling operation of said device and circuit means for providing and receiving signals from a host computer, said signals being partially dependent on the image sensed by said optical reflective sensor means. Preferably said circuit means includes comparator means for comparing the reflective emissivity detected by said optical reflective sensor means with a threshold value. In one preferred embodiment the device is incorporated in a pixel-type or dot-matrix printer whereby for image scanning the print head is replaced by said optical reflective sensor. In a second embodiment the optical reflective sensor is mounted on a support which replaces the ribbon cartridge of the printer. In order that the invention may be better understood and put into practical effect there will now be described with reference to the accompanying drawings a preferred non-limitative practical embodiment of a scanning digitiser-printer according to the present invention. In the drawings :- Fig. 1 is a schematic circuit drawing showing a circuit board used to implement the present invention on a conventional dot-matrix printer; and Fig. 2 is a plan view of a dot-matrix printer having the print head replaced by the optical reflective sensor. In this embodiment the invention will be described with reference to a CP-80 printer with SP-80 chassis and MAIN-VI MDK21HB circuit board made by Shinwa Digital Industry Co., Ltd. This printer is a typical dot-matrix printer which includes a 9 pin square pin dot-matrix print head, 7 x 8 dot character in a 8 x 9 field, 228 ASCII characters with normal and italic fonts, superscript and subscript capability, bi-directional, logic seeking printing mode, bit image graphics, 80 character per second print speed and Centronics- type interface. Printers of this type are common place and familiar to those skilled in the art. The modifications required to the printer are:- (a) Isolation of the SELECT line (Pin 13 of the Centronics port) from all other internal circuitry except the pull up resistor array. (b) Islation of the PAPER EMPTY line (Pin 12 of the Centronics port) from all internal circuitry excepting pull up resistor array and the serial interface expansion socket (or plug) on the mother board. (c) The output of a timer chip (555) is sent to the SELECT line so that now, if the carriage is moving, the SELECT line will change state 640 times per carriage traverse as input to the 555 is fed from a strobe wheel attached to the carriage stepper motor. This strobe wheel gives 1280 pulses per carriage traverse as activation occurs on both the leading and trailing edge of the pulse. The SELECT line (PIN 13) on the Centronics port is now modified to act as the strobe line to tie the scan rate to the host computer. (d) Plugging of the circuit board shown in Fig. 1 into the serial expansion socket (or pluq) . (e) Removal of the print head and existing cable and fittinq of a flexible wire cable with 16 pin pluq to the print head so as it may plug into 11 of the connections on the header mentioned in (f). (11 conductors include 9 print solenoid cables and one or two return lines) . (f) Incorporation of a 16 way eject header to the printer chassis board to allow either the print or scan head to plug in. (g) Modification of the print head mountinq point on the carriage to allow easy changing of print and scan heads. (h) Fitting of a well known Hewlett Packard HEDS- 1000 high resolution optical reflective sensor device into a housing 10 (see Fig. 2) that fits in place of the print head and plugs into 4 of the pins on the 16 way header mentioned in (f) . (i) Swapping around of the nine wires from the print head drivers so as to make things match up with the 16 way header in (f). Fig 2. shows a dot-matrix printer 12 with rotatable printinq platen 14 and ribbon carriage 16. The ribbon carriage 16 is reciprocally movable along bar 18. The housing 10 is secured to ribbon carriage 16 by fasteners 20 with wires 22 from the sensor (not shown) emerging from the housing. The circuit shown in Fig. 1 will now be described. This circuit receives threshold information (grey scale level) from data lines DO to D4 coupled to a host computer (not shown) and latches them into D to A converter 24 via data line D7. The threshold voltage from the D to A converter is balanced across operational amplifier A2 with its output qoinq to the invertinq input of operational amplifier Al. The non- invertinq side of operational amplifier Al is fed with the output voltage from the sensor 26 (i.e. Hewlett Packard HEDS-1000) mounted in the scanning head housing 10. The output from operational amplifier Al is taken into the PAPER EMPTY line via the serial expansion socket (or pluq) and so to the Centronics port. Thus the PAPER EMPTY line is modified to become the output for the scanner. In this regard if the host computer checks and acts on the PAPER EMPTY line, and as this is now isolated, the host computer must be configured to ignore this signal when using as a printer, or a switch must be fitted to allow switching between the cuts on the circuit board. The operation of the scanner will now be described. The host computer will detect a change on the SELECT line and a threshold value is sent down data lines DO to D4, latched by taking data line D7 hiqh then low. A sample is then taken of the output of the PAPER EMPTY line. This sample is compared to the threshold value. If it is hiqher then liqht was received and the signal is interpreted by the host computer to mean plot or store this bit. Sufficient time is available to send different threshold values down and sample the PAPER EMPTY line a number of times. In this way the host computer can test for various grey levels other than black and white if required. When the SELECT line next chanqes state this procedure is repeated and continues until the number of samples taken corresponds to the horizontal screen resolution of the computer if going direct to screen. If going into memory then the limit would be the horizontal resolution, in number of dots, of the printer. This is normally around the 1280 mark for an 8 inch carriage. After each line is sampled an incremental line feed is given to the printer and the process repeats until the number of lines scanned corresponds to the vertical resolution of the computer, or how much memory has been set aside for that purpose. Resolution of the scan head is just under .007", translating to 140 dots per inch or 1120 dots for an 80 column eight inch printer. From the above it is clear that the host computer requires suitable software to control the printer and manipulate the data provided by the printer. Such software can be readily produced by a skilled programmer familiar with the characteristics of the host computer and printer. Although the preferred embodiment has been described with reference to a CP-80 printer having a Centronics interface the inventive concept is not limited to such a printer. It is clear that a skilled computer engineer could make suitable modifications to any printer having individual pixel or dot control. Although the PAPER EMPTY and SELECT lines have been used other suitable lines could be substituted if desired. The use of a Centronics interface is not essential as suitable modifications could be made to other inferfaces e.g. RS-232C or IEEE-4888. The invention is not restricted to the use of interchangeable print head and scanner head as the optical reflective sensor could be integrated into a print head to avoid downtime in changing heads. The simplicity of the invention also allows for the manufacture of a redesigned unit which includes the modifications so that by switch selection the scanning or printing mode could be changed. The optical reflective sensor may also be incorporated into the ribbon cartridge of the printer instead of replacing the print head. In this manner a simple snap-in replacement may be made when changing from printing to scanning. If desired the optical reflective sensor may be a fibre optic device or any similar such device. Although the preferred embodiment has disclosed the use of one optical reflective sensor the incorporation of a plurality of such sensors would reduce the scanning time for an image. The use of a D to A converter is not necessary if black and white recognition is only required. The use of a D to A converter allows the host computer to provide the threshold value and is very flexible for the user. The D to A converter could be replaced by a simple network to provide a constant threshold value. The sensitivity of such a network can be varied by the use of variable impedances. The present invention provides a compact scanning digitiser-printer which can replace facsimile senders/receivers at a substantially reduced cost. The invention can diqitise any printed, photographic or drawn two-dimensional image very simply and quickly. It is believed that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts and that changes may be made in the form, construction and arrangement of the scanning digitiser and/or printer described without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

Claims: The claims defining the invention are as follows:- 1. A scanning digitiser and/or printer device including feed means for an image containing web, optical reflective sensor means reciprocally mounted to move across, in use, said web, control means for controlling operation of said device and circuit means for providing and receiving signals from a host computer, said signals being partially dependent on the image sensed by said optical reflective sensor means. 2. The device of claim 1, wherein said circuit means includes first comparator means for comparing the reflective emissivity detected by said optical reflective sensor means with a threshold value. 3. The device of claim 2, wherein said threshold value is provided by grey scale level indicator means within said circuit means. 4. The.device of claim 2, wherein said threshold value is provided by said host computer. 5. The device of claim 4, wherein said circuit means includes a D to A converter, the inputs of said D to A converter adapted to be coupled to data lines from said host computer with the output of said D to A converter coupled to an input of said first comparator means to provide said threshold value. 6. The device of claim 5, wherein the output of said D to A converter is coupled to said first comparator means via a second comparator means. 7. The device of any one of claims 2 to 6, wherein the output of said first comparator means is adpated to be interrogated by said host computer. 8. The device of claim 7, wherein said device includes an input/output connector for allowing a cable connection of said host computer to said device. 9. The device of claim 7 when appended to claim 5, wherein said device further includes an input/output connector for allowing a cable connection of said host computer to said device, said connector including pins for inputs from said host computer for said D to A converter and said output from said first comparator means. 10. The device of any preceding claim, wherein said device is a printer, said optical reflective sensor means replacing the printing head of said printer when image recognition is required. 11. The device of claim 10, wherein said optical reflective sensor means is adapted to be interchanged with said printing head. 12. The device of any one of claims 1 to 9, wherein said device is a printer, said optical reflective sensor means being mounted on a support which replaces the ribbon cartridge of said printer. 13. A method of converting a dot-matrix printer having the capability of incremental line feeds into a scanning digitiser, said method including the steps of inserting an optical reflective sensor means on the printing carriage of said printer, connecting the output of said optical reflective sensor means to one input of a comparator means, coupling the other input of said comparator means to a grey scale level indicator means and coupling the output of said comparator means to a pin of the input/output interface connector of said comparator means for interrogation by an external computer. 14. A scanning digitiser and/or printer device substantially as hereinbefore described with reference to the accompanying drawings. 15. A method of converting a dot-matrix printer into a scanning digitiser substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: WRIGHT WARWICK LINDSAY JAMES, WRIGHT, WARWICK, LINDSAY, JAMES
Applicants: WRIGHT WARWICK LINDSAY JAMES, WRIGHT, WARWICK, LINDSAY, JAMES
Application year: 1985
Main classification: H04N1
IPC codes: H04N1