High quality image copier with exact reproduction of digitally halftoned images

• US 6,398,328 B1
• Filed: 07/10/1998
• Issued: 06/04/2002
• Est. Priority Date: 07/15/1997
• Status: Expired due to Term

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Stewart, Jr., Charles W.
• Application Number:
  US09/112,824
• Time in Patent Office: 1,425 Days
• Field of Search: 347/19, 347/3, 347/183, 347/188, 400/61, 400/70, 400/76, 400/74, 358/1.2, 358/1.9, 358/1.1, 358/1.124, 358/406, 358/504
• US Class Current: 347/3
• CPC Class Codes: G06F 21/79 in semiconductor storage media, e.g. directly-addressable memories
• CPC Class Codes: G06F 21/86 Secure or tamper-resistant housings
• CPC Class Codes: G06F 2221/2129 Authenticate client device independently of the user
• CPC Class Codes: H04N 1/2112 using still video cameras
• CPC Class Codes: H04N 1/2154 the still video camera incorporating a hardcopy reproducing device, e.g. a printer
• CPC Class Codes: H04N 2101/00 Still video cameras
• CPC Class Codes: H04N 23/00 Cameras or camera modules comprising electronic image sensors; Control thereof
• CPC Class Codes: H04N 5/2628 Alteration of picture size, shape, position or orientation, e.g. zooming, rotation, rolling, perspective, translation

Abstract

The invention relates to a method of generating print data from a printed image produced by a printing device operating at a first dots per inch (dpi) value, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image. The method includes the step of scanning the printed image, at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor so that each dot of the image results in the generation of at least two markers. Data relating to the position and colour value of each marker is generated. The defects in the image are detected and a data value is assigned to such defects. The data is processed and the data value is used to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot. Print data is generated as a result of the processing step, the print data relating to the position and print value of the markers determined as a result of processing the data.

Claims

1. A method of generating print data from a printed image produced by a printing device operating at a first dots per inch (dpi) value, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image, the method comprising the steps of:

scanning the printed image, at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor, which is such that each dot of the image results in the generation of a set of at least two markers;

generating data relating to the position and color value of each marker;

detecting the defects in the image and assigning a data value to such defects;

processing said data and applying the data value assigned to the defects to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot; and

generating print data as a result of the processing step, the print data relating to the position and print value of the markers determined as a result of processing the data.

2. A method as claimed in claim 1, which includes scanning the image at a sampling rate which corresponds to the second dpi value that exceeds the first dpi value by a factor of three, so that each dot of the image results in the generation of a set of three markers.

3. A method as claimed in claim 1, which includes carrying out the scanning step at a point upstream of a printing step earred out by the apparatus.

4. A method as claimed in claim 1, which includes the step of detecting the defects by determining the degree of rotation of the printed image, during the printing step.

5. A method as claimed in claim 1, in which the step of processing the data and applying the data value assigned to the defects includes the steps of:

(a) selecting data relating to an initial group of sets of markers and applying the defect value to the selected data to determine which marker of each selected set is to be recorded as related to the center associated with that set;

(b) determining which marker of each set of at least one further set should be recorded as a center of a corresponding dot by using a relationship existing between the positions of the recorded markers of the initial group of sets;

(c) adding data related to the position of the, or each, marker, recorded as a result of the determination, to the data relating to recorded markers of the initial group of sets of markers; and

(d) repeating steps (b) and (c) until print data for a further, substantially identical image is obtained.

6. A method as claimed in claim 1, which includes the step of printing an image with said apparatus, using said generated print data.

7. An apparatus for generating print data from a printed image, the apparatus comprising:

a printing device that operates at a first dots per inch (dpi) value to generate the printed image, so that the image is composed of a plurality of dots, the image incorporating defects resulting during printing of the image, such as rotation of a print medium and blemishes of the image;

a scanning device positioned downstream of the printing device for scanning the printed image, the scanning device being configured to operate at a sampling rate which corresponds to a second dpi value that exceeds the first dpi value by a predetermined factor, which is such that each dot of the image results in the generation of a set of at least two markers, the scanning device being configured to generate data relating to the position and color value of each marker; and

a processor that is connected to the scanning device and is configured to receive said data from the scanning device, the processor being capable of analysing said data for the defects, applying a data value to the defects, and processing said data together with the data value to determine which of each of the markers generated for a respective dot should be recorded as a center for that dot, and generating print data relating to the position and color value of the markers so determined.

8. An apparatus as claimed in claim 7, in which the printing device is in the form of an inkjet printer.

9. An apparatus as claimed in claim 7, in which the scanning device is configured to operate at a sampling rate which corresponds to the second dpi value that exceeds the first dpi value by a factor of three, so that each dot of the image results in the generation of a set of three markers.

10. An apparatus as claimed in claim 7, in which the scanning device includes a series of staggered charge-coupled device (CCD) arrays to achieve the sampling rate corresponding to the second dpi value.

11. An apparatus as claimed in claim 7, in which the processor is operatively connected with the printing device so that the processor can generate said defect value while the image is printed.

12. An apparatus as claimed in claim 11, in which the processor is operatively connected with the printing device so that the processor can assign said defect value to a degree of rotation of the image while the image is printed.

13. An apparatus as claimed in claim 12, in which the processor is pre-programmed to carry out the following steps:

(a) selecting data relating to an initial group of sets of markers and applying the defect value to the selected data to determine which marker of each selected set is to be recorded as related to the center associated with that set;

(b) determining which marker of each set of at least one further set should be recorded as a center of a corresponding dot by using a relationship existing between the positions of the recorded markers of the initial group of sets;

(c) adding data related to the position of the, or each, marker, recorded as result of the determination, to the data relating to recorded markers of the initial group of sets of markers; and

(d) repeating steps (b) and (c) until print data for a further, substantially identical image is obtained.

14. An apparatus as claimed in claim 13, which includes a memory arrangement that is connected to the processor to store the print data.

15. An apparatus as claimed in claim 13, in which the processor and the memory arrangement are operatively connected to the printing device so that the printing device can print, on demand, said further, substantially identical image.

16. A digital camera which includes an apparatus as claimed in claim 7.

17. A digital camera as claimed in claim 16, in which the processor is defined by a processor unit of a digital camera and the memory arrangement is defined by a memory device of the digital camera.