Hologram graphic data tablet apparatus using a vernier

摘要

A hologram graphic tablet apparatus is described which has an improved resolution. The apparatus includes a hologram plate which includes a plurality of mini-holograms having position code data therein. The hologram plate is sequentially illuminated by a reference laser and an array of vernier lasers. The light from the laser that is diffracted by the mini-holograms is detected to form a reconstructed image of the position data, and the detected information is processed to produce a positional code that has a greater number of bits, and hence greater position resolution, than that directly obtained from the mini-hologram, depending on whether the output codes from the detector are the result of irradiation of the mini-hologram by the reference laser or by the vernier laser array.