| 摘要 |
<p>An optical potentiometer comprises a pair of mutually spaced electrically resistive tracks (40, 42) defining a gap (44) in which a photoconductive amorphous silicon layer (46) is exposed. The optical potentiometer has a light source (36) and a reflector arrangement defined by a reflector body (18) mounted on the lower end of a rotary shaft (16). The reflector body (18) defines a reflective surface (24) lying on an ellipse and a planar mirror (22). The mirror (22) and surface (24) are arranged so that one focal point (F1) of the ellipse lies in the gap (44) between the tracks (40, 42), whilst a virtual focus (Fv) of the other focal point (F2) of the ellipse lies on the axis of rotation (R) of the shaft (16). The light source (36) also lies on the axis of rotation (R) so that light emanating therefrom is concentrated by the reflector arrangement into the gap (44).</p> |
