System for authenticating an object

1. A system for authenticating an object comprising:

a label with invisible indicia on the object which rotate a polarization of incident light;

a digital camera having a light source, an image sensor, a first linear polarizer having a first orientation, and a second linear polarizer having a second orientation orthogonal to the first orientation;

illuminating the label with light from the light source through the first linear polarizer;

forming an image with the image sensor using reflected light from the label wherein the reflected light passes through the second polarizer prior to reaching the sensor;

wherein the second linear polarizer makes the invisible indicia visible; and

authenticating the object.

2. The system of claim 1 further comprising:

displaying, communicating, or printing the visible indicia.

3. The system of claim 1 wherein the indicia are machine readable or human readable.

4. The system of claim 1 wherein the indicia encode authentication information.

5. The system of claim 4 further comprising:

comparing the authentication information to a predetermined authentication code.

6. The system of claim 5 wherein the comparison is made by a user or a processor in the camera.

7. The system of claim 1 further comprising:

a first transmitter for transmitting the visible indicia to a remote location for authentication; and

a second transmitter transmitting the authentication to the digital camera.

8. The system of claim 7 further comprising:

transmitting a coupon to the digital camera after authentication.

9. The system of claim 8 further comprising:

collecting information related to sale of the object.

10. The system of claim 8 further comprising:

restocking the object based on a sale of the object.

11. The system of claim 8 further comprising:

transmitting the coupon to a cash register on completing a sale of the object.

12. The system of claim 1 further comprising:

a GPS sensor for detecting a geographic location of the digital camera;

a first transmitter for transmitting the visible indicia and the GPS location of the digital camera to a remote location for authentication;

authenticating the object based on the visible indicia and the GPS location;

a second transmitter transmitting the authentication to the digital camera; and

transmitting the authentication to the digital camera.

13. The system of claim 12 further comprising:

transmitting a coupon to the digital camera after authentication.

14. The system of claim 1 wherein the second orientation is 90° with respect to the first orientation;

a first quarter-wave plate is positioned between the first linear polarizer and the label; and

a second quarter wave plate is positioned between the second linear polarizer and the label.

15. The system of claim 14 wherein the invisible indicia change a polarization of incident light.

16. The system of claim 14 wherein the label surrounding the invisible indicia change a polarization of incident light.

17. The system of claim 1 wherein the second orientation is parallel to the first orientation;

a first quarter-wave plate is positioned between the first linear polarizer and the label; and

a second quarter wave plate is positioned between the second linear polarizer and the label.

18. The system of claim 17 wherein the invisible indicia change a polarization of incident light.

19. The system of claim 17 wherein the label surrounding the invisible indicia change a polarization of incident light.

20. The system of claim 1 wherein the second linear polarizer is orthogonal to the first orientation.

21. The system of claim 1 wherein the invisible indicia rotate a polarization of incident light differently from the surrounding label.

22. The system of claim 1 wherein the invisible indicia rotate the incident light greater than 0° and less than 180° and rotate the incident light differently from the surrounding label.

23. The system of claim 1 wherein the invisible indicia rotate a polarization of incident light.

24. The system of claim 1 wherein the label surrounding the invisible indicia rotate a polarization of incident light.

25. A system of authenticating an object comprising:

a light source;

an image sensor;

a first linear polarizer having a first orientation

a second linear polarizer having a second orientation orthogonal to the first orientation;

illuminating a label on the object with light from the light source through the first linear polarizer;

wherein the label has invisible indicia which rotates a polarization of incident light;

forming an image with the image sensor using reflected light from the label wherein the reflected light passes through the second polarizer prior to reaching the sensor;

wherein the second linear polarizer makes the invisible indicia visible; and

authenticating the object.