| 摘要 |
PURPOSE:To measure the patterns of wafers with a variety of widths by using a liquid crystal having a light transmitting region with a variable width and making the widths of the slit openings substantially continuously change. CONSTITUTION:A slit plate is constituted by a liquid crystal shutter 31 having a plurality of opposite pairs of stripe-shaped transparent electrodes 31a, 31a...31n, 31n arranged on the upper and lower surfaces of the shutter 31. The electrodes 31n are formed in a stripewise configuration with 12mum wide electrodes arranged at predetermined speaces, for example, at 3mum spaces while sandwiching a 3mum thick insulating layer 33. Since those electrodes 31n allow light to pass therethrough when a voltage is applied from a driving circuit, by sequentially increasing the number of electrodese to which the voltage is applied, the widths of the slit openings are accordingly increased. By sequentially stopping the applications of the voltage to the electrodes, the widths of the slit openings are accordingly decreased. The width of the openings in this case, when the arranging width of the electrodes are made, for example, 300mum, can be made continuous within the range of approximately 0mum-300mum. When the weidth of the insulating layer between the electrodes can not be reduced, two laminated liquid crystal shutters 35 and 37 can be used.
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