US PATENT SUBCLASS 359 / 537
.~.~.~ Directional reflection (e.g., prevent viewing unless critical angle of light is used)

Current as of: June, 1999
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359 /   HD   OPTICS: SYSTEMS (INCLUDING COMMUNICATION) AND ELEMENTS

515  DF  SIGNAL REFLECTOR {11}
534  DF  .~ Including a curved refracting surface {4}
536  DF  .~.~ Minute transparent spheres {4}
537.~.~.~ Directional reflection (e.g., prevent viewing unless critical angle of light is used)

DEFINITION

Classification: 359/537

Directional reflection (e.g., prevent viewing unless critical angle of light is used):

(under subclass 536) Subject matter wherein the reflective structure behind the spheres is arranged to permit viewing of the image behind the spheres, only if the incident light is transmitted to the spheres at the desired critical angle.

(1) Note. The directional reflection of this subclass permits viewing of the image only by those authorized (i.e., knowing the angle).

(2) Note. The image is not changed by the directional reflection but observation is accomplished dependent upon viewing at the proper angle.

(3) Note. A picture that is covered by a substrate containing minute glass spheres to permit viewing of the picture via the reflected light only if the incident light is at a predetermined angle belongs in this subclass.

SEE OR SEARCH CLASS

380, Cryptography,

54, for modifying optical image (e.g., transmissive overlay) by changing its visible appearance.