| 摘要 |
1,223,807. Optical position detector. INTERNATIONAL BUSINESS MACHNIES CORP. 11 June, 1969 [12 July, 1968], No. 29488/69. Heading H4D. [Also in Division H1] Specification describes an arrangement for determining the orthogonal co-ordinate position of a light pen 24, Fig. 1, over a display means 9. Said arrangement comprises a pulsed laser source 1 providing two beams of laser pulses 2 and 3 at slightly different pulse repetition periods. The parallel beams are diverged by cylindrical lenses 6 and 16 to cause each light path to travel as a circular wave front. The pulses intercept the circular edges 8 of a plate of photochromic glass 9, whereby the circular wave fronts are converted into straight wave fronts 10, 20 and 18, 21 travelling through the glass such that the locus of a cross over (coincidence) point 20, 21 of two orthogonal wave fronts, is line 23. Because of the slight difference in the periods of two light pulses, the locus of the next cross-over point, 10, 18 will be slightly displaced from, but parallel to, locus 23. The whole of display area 11 will thus eventually be raster scanned. The laser light is infra red and the light pen comprises, Fig. 4, a light guide 61 shining a beam of ultra-violet on area 11. This causes the photochromic glass to locally scatter the infra-red wave fronts. The increased scattered infra-red, caused by the passage of a wave front cross-over point, causes non-linear detectors 62, 63 to emit a pulse, which by its timing with respect to known reference times, gives the orthogonal co-ordinates of the pen. The plate 9 may alternately be a simple glass sheet with a light scattering ground surface. The ultra-violet illumination may then be dispensed with. |
