The identity or credit card checking system uses a card with a portion of hologram plate incorporated in it. A typical design uses a rectangular card (1) with rectangular panels (2) for the indicia and a square member (5) for the hologram. The card is inserted in a viewer which uses a helium-neon gas laser as a source of coherent light. A metal film reflecting strip is placed behind the hologram image so that two beams of reflected light are produced which form a phase contrast image on the screen. The identity card main indicia can be seen to conform, or otherwise, with the subsidiary indicia on the hologram square.
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