| 摘要 |
PCT No. PCT/GB80/00169 Sec. 371 Date May 29, 1981 Sec. 102(e) Date May 29, 1981 PCT Filed Oct. 16, 1980 PCT Pub. No. WO81/01195 PCT Pub. Date Apr. 30, 1981.Position sensing apparatus comprises generating means (12) for generating a beam of radiation; rotation means (24) for rotating the beam about a vertical axis to define a horizontal reference plane, the beam having a sectional shape (for example "V" shape or "X" shape) such that a leading edge and a trailing edge are straight and diverge away from the reference plane; two radiation sensors (38, 40) spaced a known vertical distance apart; and means (30, 32, 44, 46) for determining the distances between the leading and trailing edges at the positions along those edges which pass across each sensor. The vertical distance of each sensor from the horizontal reference place and the distance of the sensors from the axis of rotation can then be determined.
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