Method for authenticating an object

A method of authenticating an object comprising:

• providing a light source;
• providing an image sensor;
• providing a first linear polarizer having a first orientation
• providing a second linear polarizer having a second 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 rotate 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.

A method of authenticating an object comprising:

• illuminating a label on the object with light having a first linear polarization;
• wherein the label has invisible indicia which rotate the first polarization of incident light to a second polarization;
• passing the light from the label through a linear polarizer which passes light having the second linear polarization and makes the invisible indicia visible;
• forming an image of the visible indicia;
• and
• authenticating the object.