Recording method and apparatus

• US 6,529,645 B2
• Filed: 04/29/1999
• Issued: 03/04/2003
• Est. Priority Date: 11/01/1996
• Status: Expired due to Fees

• Current Assignee: Anoto Group AB
• Original Assignee: C Technologies AB (Anoto Group AB)
• Inventors: Nilsson, Jan, Söderlund, Patrik, Fåhraeus, Christer
• Primary Examiner(s): LEE, TOMMY D
• Application Number:
  US09/301,856
• Publication Number:
  US 20020001418A1
• Time in Patent Office: 1,405 Days
• Field of Search: 382/56, 382/173, 382/318, 382/219, 382/314, 382/313, 382/284, 382/174, 358/450, 345/115, 345/117, 345/119, 345/122, 345/123
• US Class Current: 382/313
• CPC Class Codes: G06V 30/142 using hand-held instruments; Constructional details of the instruments
• CPC Class Codes: H04N 1/107 with manual scanning
• CPC Class Codes: H04N 1/1075 Arrangements for facilitating holding of the scanner, e.g. shapes, grips
• CPC Class Codes: H04N 1/195 the array comprising a two-dimensional array or a combination of two-dimensional arrays
• CPC Class Codes: H04N 2201/0414 Scanning an image in a series of overlapping zones

Abstract

In a method for recording a selected sequence of characters with the aid of a pen, the latter is passed over the sequence of characters and a plurality of images, whose contents partially overlap, are recorded simultaneously with the aid of a light-sensitive sensor (8) with a two-dimensional sensor surface. The recorded images are put together, horizontally as well as vertically, into an image. Subsequently, the characters in the composite image are identified and stored in the pen with the aid of a predetermined character code formal. The putting-together, the character identification, and the storing are carried out with the aid of a signal processing unit (20-24). By the method and the pen compensation is obtained for different speeds of movement and different angles of rotation of the pen.

Claims

1. A method for recording a selected sequence of characters with the aid of a portable scanner, comprising the steps of:

passing the portable scanner over a selected character sequence;

imaging the selected character sequence by means of a plurality of images, whereby the content of a second image partly overlaps the content of at least one preceding first image;

for every possible overlap position between the second and first images, an overlap measurement is determined at the pixel level;

for each overlapping pixel position, the grey scale values of the two pixels included are added up if the latter are not white, whereby a pixel position in which none of the pixels are white is designated a plus position;

the greyscale sums for all the plus positions are added up to a grand greyscale sum;

the neighbors of each pixel position are examined and if an overlapping pixel position is not a neighbor of a plus position and consists of a pixel which is white and a pixel position which is not white, the greyscale value of the non-white pixel is subtracted from the grand greyscale sum;

selecting the overlap position which provides the highest grand greyscale sum;

combining the second and first images by means of said overlap position for generating a composite image from said second and first images;

identifying the characters in the composite image; and

storing the identified characters in the portable scanner with the aid of a predetermined character code format.

2. A method according to claim 1, further comprising the step of:

illuminating the characters which are to be recorded with light pulses, when the portable scanner is being passed over them.

3. A method according to claim 1, wherein the portable scanner comprises a pen shape.

4. A method according to claim 1, wherein said non-white pixel value is multiplied by a constant, before being added to the grand greyscale sum.

5. A method according to claim 1, wherein the combining of the recorded images is carried out in real time.

6. A method according to claim 1, wherein the step of identifying the characters comprises dividing the composite image into a plurality of sub-images each comprising a single character.

7. A method according to claim 1, wherein the composite image consists of a plurality of pixels, each being defined by an intensity value, and wherein the step of dividing the composite image into a plurality of sub-images comprises adding up the intensity of the pixels row by row and column by column in the composite image for obtaining a plurality of row sums and column sums as well as identifying local minima among the row sums and column sums obtained for dividing the composite image into sub-images.

8. A method according to claim 1, further comprising the step of, prior to the identification of the characters, rotating the composite image so that the characters in said image form a horizontal row.

9. A method according to claim 1, wherein the portable scanner comprises an indicating device for indicating that the pen is ready to scan the character sequence.

10. A method according to claim 1, wherein the portable scanner comprises a display for showing the identified characters.

11. A method for recording a selected sequence characters with the aid of a portable scanner, comprising the steps of:

passing the portable scanner over a selected character sequence;

imaging the selected character sequence by means of a plurality of images, such that the content of a second image partly overlaps the content of at least one preceding first image;

for each overlapping pixel position, the grey scale values of the two pixels included are added up if the latter are not white, whereby a pixel position in which none of the pixels are white is designated a plus position;

the greyscale sums for all the plus positions are added up to a grand greyscale sum;

the neighbors of each pixel position are examined and if an overlapping pixel position is not a neighbor of a plus position and consists of a pixel which is white and a pixel position which is not white, the greyscale value of the non-white pixel is subtracted from the grand greyscale sum; and

selecting one overlap position which provides the highest grand greyscale sum;

combining the second and first images by means of said overlap position such that a composite image is generated from said second and first images and such that compensation is obtained for different speeds of movement and different angles of rotation of the pen;

determining a pixel intensity value in said composite image for each overlapping pixel, which composite pixel intensity value is based on the intensity values of the pixel in the second and first images;

identifying the characters in the composite image; and

storing the identified characters in the portable scanner with the aid of a predetermined character code format.

12. A method according to claim 11, wherein said composite pixel intensity value is the mean value of the intensity values of the pixel in the second and first images.

13. A method according to claim 11, wherein said non-white pixel value is multiplied by a constant, before being added to the grand greyscale sum.

14. A method according to claim 11, wherein the combining of the recorded images is carried out in real time.

15. A method according to claim 11, wherein the step of identifying the characters comprises dividing the composite image into a plurality of sub-images each comprising a single character.

16. A method according to claim 15, wherein the composite image consists of a plurality of pixels, each being defined by an intensity value, and wherein the step of dividing the composite image into a plurality of sub-images comprises adding up the intensity of the pixels row by row and column by column in the composite image for obtaining a plurality of row sums and column sums as well as identifying local minima among the row sums and column sums obtained for dividing the composite image into sub-images.

17. A method according to claim 15, further comprising the step of, prior to the identification of the characters, rotating the composite image so that the characters in said image form a horizontal row.

18. A method according to claim 11, further comprising the steps of:

examining said second image with respect to possible overlap positions with said first image with the aid of the overlapping content only, vertically, horizontally and rotationally;

determining an overlap position which affords the best correspondence between the contents of said second and first images.