Method and apparatus of encryption of optical images

• US 4,776,013 A
• Filed: 04/01/1987
• Issued: 10/04/1988
• Est. Priority Date: 04/18/1986
• Status: Expired due to Fees

• Current Assignee: Rotlex Optics Ltd.
• Original Assignee: Rotlex Optics Ltd.
• Inventors: Kafri, Oded, Keren, Eliezer
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US07/032,820
• Time in Patent Office: 552 Days
• Field of Search: 380/54, 380/10, 380/20
• US Class Current: 380/54
• CPC Class Codes: G09C 5/00 Ciphering apparatus or methods not provided for in the preceding groups, e.g. involving the concealment or deformation of graphic data such as designs, written or printed messages
• CPC Class Codes: H04N 1/448 Rendering the image unintelligible, e.g. scrambling
• CPC Class Codes: H04N 1/4493 Subsequently rendering the image intelligible using a co-operating image, mask or the like
• CPC Class Codes: H04N 7/171 Systems operating in the amplitude domain of the television signal

Abstract

A method of encoding an optical image comprises: converting the optical iamge to an image grid comprised of an image matrix of pixels each having at least two possible intensity values; providing a master grid comprised of a master matrix of pixels each having at least two possible intensity values; and transmitting, for each pixel location of the image matrix, a pixel intensity value representing the intensity value of the master matrix at the corresponding location, its complement, or a random intensity value, depending on the intensity value of the pixel in the image matrix at the corresponding location. Also described is an apparatus for carrying out the above encoding method.

Claims

1. A method of encoding an optical image comprising:

converting the optical image to an image grid comprised of an image matrix of pixels each having at least two possible intensity values;

providing a master grid comprised of a master matrix of pixels each having at least two possible intensity values;

and transmitting, for each pixel location of the image matrix, a pixel intensity value representing the intensity value of the master matrix at the corresponding location, its complement, or a random intensity value, depending on the intensity value of the pixel in the image matrix at the corresponding location.

2. The method according to claim 1, wherein the master grid is stored in a memorydevice.

3. The method according to claim 1, wherein the master pixel intensity value is transmitted when the image pixel is of one intensity value, and the complement of the master pixel intensity value is transmitted when the image pixel is of the other intensity value.

4. The method according to claim 1, wherein the master pixel intensity value is transmitted when the image pixel is of one intensity value, and a random intensity value is transmitted when the master pixel is of the other intensity value.

5. The method according to claim 1, wherein a random intensity value is transmitted when the image pixel is of one intensity value, and the complement of the master pixel intensity value is transmitted when the image pixel is of the other intensity value.

6. The method according to claim 1, wherein each pixel has at least three possible intensity values, the master pixel intensity value being transmitted when the image pixel is of one intensity value, a random intensity value being transmitted when the pixel is of the second intensity value, and the complement of the master pixel intensity value being transmitted when the image pixel is of the third intensity value.

7. The method according to claim 1, wherein said optical image is converted to an image matrix of pixels each having more than three pixel intensity values by grouping a plurality of pixels into groups of superpixels having a number of grey levels increasing with the number of pixels in the superpixel.

8. A method of encrypting an optical image, comprising:

transmitting the encoded optical image in accordance with claim 1;

receiving said encoded optical image;

and decoding said encoded optical image by combining each pixel of the received matrix with each pixel of said master matrix.

9. The method according to claim 8, wherein the master grid, during the decoding, is stored in a memory.

10. The method according to claim 8, wherein the master grid, during the decoding, is in the form of a transparency combined with the encoded image matrix.

11. Apparatus for encoding an optical image comprising:

means for converting the optical image to an image grid comprised of an image matrix of pixels each having at least two possible intensity values;

means for storing a master grid comprised of a master matrix of pixels each having at least two possible intensity values;

and means for transmitting, for each pixel location of the image matrix, a pixel intensity value representing the intensity value of the master matrix at the corresponding location, its complement, or a random intensity value, depending on the intensity value of the pixel in the image matrix at the corresponding location.

12. Apparatus according to claim 11, wherein said latter means transmits the master pixel intensity value when the image pixel is of one intensity value, and the complement of the master pixel intensity value when the image pixel is of the other intensity value.

13. Apparatus according to claim 11, wherein said latter means transmits the master pixel intensity value when the image pixel is of one intensity value, and a random intensity value is transmitted when the master pixel is of the other intensity value.

14. Apparatus according to claim 11, wherein said latter means transmits a random intensity value when the image pixel is of one intensity value, and the complement of the master pixel intensity value when the image pixel is of the other intensity value.

15. Apparatus according to claim 11, wherein each pixel has at least three possible intensity values, said latter means transmitting the master pixel intensity value when the image pixel is of one intensity value, a random intensity value when the pixel is of the second intensity value, and the complement of the master pixel intensity value when the image pixel is of the third intensity value.

16. Apparatus according to claim 11, wherein said latter means groups the pixels into groups, each constituting a superpixel, which superpixel has a grey level varying according to the number of pixels in each group, to thereby convert the optical image to an image matrix of superpixels each having more than three intensity values.

17. Apparatus for encrypting an optical image, comprising:

means for transmitting the encoded optical image in accordance with claim 11;

means for receiving said encoded optical image;

and means for decoding said encoded optical image by combining each pixel of the received matrix with each pixel of said master matrix.

18. Apparatus according to claim 17, wherein the master grid, during the decoding, is stored in a memory.

19. Apparatus according to claim 17, wherein the master grid, during the decoding, is in the form of a transparency combined with the encoded image matrix.