Method for determining a printer's signature and the number of dots per inch printed in a document to provide proof that the printer printed a particular document
A method for assigning unique printer resolutions or signatures, i.e., a unique number of dots per inch, to a class, or models of printers or lines of postage meters. The number of dots per inch or resolution may be specified within a image on a document or within a postal indicia and later checked to determine if the image on document or the postal indicia has the correct resolution. The foregoing would be able to detect an image or postal indicia that was scanned into a computer and printed with a printer that did not have the number of dots per inch specified in the image or postal indicia.
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Reference is made to commonly assigned co-pending patent application Ser. No. 10/017,144 filed herewith entitled “A Method For Determining A Printer's Signature To Provide Proof That The Printer Printed A Particular Document” in the names of Donald G. Mackay, Claude Zeller and Robert A. Cordery.
NAMES OF PARTIES TO JOINT RESEARCH AGREEMENTPitney Bowes Inc. and Digimarc Corporation are parties to a written joint research agreement.
FIELD OF THE INVENTIONThe subject invention relates to a method for printing documents, and more particularly, to providing a method for determining the mechanism or printer on which the document was printed.
BACKGROUND OF THE INVENTIONThere are many different types of documents issued by government agencies, corporations and individuals that authorize the holder of such documents to perform authorized tasks or grant rights to the holder of such a document. Examples of such documents are drivers' licenses, passports, entry access badges, identification cards, tickets, gift certificates, coupons, bonds, postal indicia, and the like.
With the advent of computers and refined printers that are available at a relatively low cost, the incidence of forgery of the above types of documents has proliferated. Although there are processes that apply coatings to documents to prevent copying, this does not end the problem of forgery.
Various schemes have been proposed to provide security to issued documents to inhibit forgeries of such documents. One such scheme is to use encryption so that a code can be derived that is based upon the information on the face of the issued document. Unfortunately, because of the limited space normally available in such documents, such a scheme often proves impractical.
The issuance of many types of tickets, such as theater tickets, is currently controlled by means of controlled supplies (e.g., serialized ticket stock, specially printed ticket stock, etc.) and by allowing tickets to be issued only by controlled, authorized issuers (e.g., ticket agents). Controlled supplies are expensive, difficult to control, and prone to theft or counterfeiting. Typically, one stood in line to purchase a ticket at the place the event was being held or purchased the ticket over the phone from an authorized ticket agent who mailed the ticket to the purchaser.
Currently, ticketing companies are giving purchasers the option of printing their electronic tickets at home using ordinary paper, a personal computer printer and an Internet connection. One of the problems in allowing people to print tickets at home is how to ensure that the tickets are not counterfeited. Furthermore, the printing technology used is another major factor, specifically when combined with the type of paper the ticket is printed on.
Unfortunately, if a ticket is printed properly on ordinary paper with an encrypted bar code, the ticket can be photocopied, and the seller of the ticket will be unable to distinguish between the original real ticket and the photocopied ticket.
SUMMARY OF THE INVENTIONThis invention overcomes the disadvantages of the prior art by providing a method that determines whether or not a document was printed by a particular or specified printer. The invention provides a method that is able to determine the printer that produced a document in order to reduce the production of fraudulent documents. This invention utilizes the fact that printers render images that often contain unintended systematic errors that are a product of the design and manufacture of the printer. Even in the best printers, it is impossible to eliminate all possible sources of error. A printed image can be analyzed, and errors detected, thereby providing a ‘fingerprint’ that is used to identify the printer (or product) used to print the image.
This invention provides a method for assigning unique printer resolutions or signatures, i.e., a unique number of dots per inch, to a class or models of printers or lines of postage meters. The number of dots per inch or resolution may be specified within an image on a document or within a postal indicia and later checked to determine if the image or document or the postal indicia has the correct resolution. The foregoing would be able to detect an image or postal indicia that was scanned into a computer and printed with a printer that did not have the number of dots per inch specified in the image or postal indicia.
In much the same way as described above, it is also possible to design ‘errors’ or ‘defects’ into the images appearing on documents, and the mechanism used to print an image to be later used as a way of providing evidence that it was printed with a particular mechanism or printer. This invention makes use of these systematic ‘defects’ to provide forensic evidence of where the image was printed. This invention also makes it difficult to reproduce the images exactly with commercially available printers. In so doing, the value of the image is increased because it not only communicates information that is visible to the observer but it also contains a ‘fingerprint’ that identifies the source of the document and makes the document difficult to copy exactly.
Referring now to the drawings in detail, and more particularly to
Since, cos 10°=M/1
0.9848 inches=M
Thus, 300 dots 15 will be produced in distance M on substrate 14.
Encoder trigger pulses 20 are produced by a rotary encoder containing a disk with etched lines matched to the printer resolution, coupled to the mechanism transporting the print head (or the substrate to be printed upon). It is necessary to use an encoding device to accurately position individual pixels and build the character ‘A’ by printing dots 21. Encoder 150 described in the description of
The diameter of the roller of encoder 76 of
Another method for analyzing an image to determine the number of dots per inch in the image and to verify that a document was printed on a printer with a unique resolution (a specified number of dots per inch) involves printing a unique pattern of dots that coincides with the printer resolution and measuring the distance between columns of dots and the gaps between them. When the image is printed at a different resolution than the one specified above, the resulting image would not look the same as the image specified above.
IBI data element 12 is contained in space 49. Data element number 12 has been reserved by the United States Postal Service. Space 49 contains information 39.
The above specification describes a new and improved method for increasing the security of a document by being able to detect when an image is copied. It is realized that the above description may indicate to those skilled in the art additional ways in which the principles of this invention may be used without departing from the spirit. Therefore, it is intended that this invention be limited only by the scope of the appended claims.
Claims
1. A method for determining whether an image on a substrate has a specified number of dots per inch, said method includes the steps of:
- specifying that the image on the substrate will be printed with n plus m dots per inch;
- rotating a an ink jet head having n nozzles per inch about a Y axis parallel to a substrate by an angle θ so that the ink jet head will produce an image on the substrate having (n/cos θ) dots per inch;
- storing in the image that the specified image will be printed with (n/cos θ) dots per inch;
- analyzing the image to determine if the image has (n/cos θ) dots per inch;
- comparing the number of dots per inch in the analyzed image with the number of dots per inch stored in the specified image to determine if they have the same number of dots per inch;
- analyzing the image to determine if the image has the specified dots per inch along the X and Y axis; and
- comparing the number of dots per inch along the X and Y axis in the analyzed image with the number of dots per inch along the X and Y axis stored in the image to determine if they have the same number of dots per inch.
2. The method claimed in claim 1, further including the step of:
- encoding the number of dots per inch that is specified to be printed into the image.
3. The method claimed in claim 2, wherein the image is a postal indicia indicium.
4. The method claimed in claim 2, further including the step of:
- encrypting the number of dots per inch indicated in the image.
5. The method claimed in claim 2, wherein the image is a graphic.
6. The method claimed in claim 1, further including the steps of:
- positioning individual dots about the X axis to build an the image.
7. The method claimed in claim 1, further including the steps of:
- specifying the spacing of dots about the X,axis to create an the image.
8. A method for printing an image on a substrate having a surface including a first axis and a second axis with a specified number of dots per inch in at least one of the first and second axes, the substrate moving in the direction of the first axis, said method comprising:
- obtaining data for determining a first specified number of dots per inch that the image on the substrate will be printed with in the direction of the second axis;
- rotating an array number of pixel generating elements per inch about an axis orthogonal to the substrate surface by an angle to produce the image on the substrate having the first specified number of dots per inch in the direction of the second axis, wherein the specified number of dots per inch is larger than the array number;
- storing in the image that the image will be printed with the first specified number of dots per inch in the direction of the second axis;
- analyzing the image to determine a number of dots per inch in the direction of the second axis; and
- comparing the determined number of dots per inch in the direction of the second axis in the analyzed image with the first specified number of dots per inch in the direction of the second axis stored in the image to determine if they have the same number of dots per inch.
9. The method of claim 8, further comprising:
- obtaining data for determining a second specified number of dots per inch that the image on the substrate will be printed with in the direction of the first axis;
- configuring a timing controller for triggering printing of pixels to generate the image with the second specified number of dots per inch in the direction of the first axis; and
- storing in the image that the image will be printed with the second specified number of dots per inch in the direction of the first axis.
10. The method of claim 8, wherein:
- the angle is between approximately 10 and 20 degrees.
11. The method of claim 8, wherein:
- the image is a postal indicium.
12. The method of claim 8, further comprising:
- encrypting the first specified number of dots per inch stored in the image.
13. The method of claim 8, further comprising:
- positioning individual dots about the first axis to build the image.
14. The method of claim 8, further comprising:
- specifying the spacing of dots parallel to the first axis to create the image.
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Type: Grant
Filed: Mar 17, 2005
Date of Patent: Dec 29, 2015
Assignees: Digimarc Corporation (Beaverton, OR), Pitney Bowes Inc. (Stamford, CT)
Inventors: Donald G. Mackay (Roxbury, CT), Claude Zeller (Shelton, CT), Robert A. Cordery (Danbury, CT), Hugh L. Brunk (Portland, OR)
Primary Examiner: Minh T Nguyen
Application Number: 11/084,869
International Classification: B41J 29/393 (20060101); B41J 29/38 (20060101); G07B 17/00 (20060101);