| 摘要 |
The moulded convexities (12) face the light source in horizontal rows, each comprising adjoining refracting cells (Cm,n) whose reverse sides (11) form a continuous flat surface. The convex faces constitute parabolic cylinders each derived from a parabolic generant (G), in a horizontal plane, which is set asymmetrically w.r.t. the cell's median vertical plane, its axle (A) making an angle (b) with the lamp's emission axis (DG). The position chosen ensures all cell sides have the same shape, adjoining convexities in the same row intersecting the straight lines (14). Light from the point source is redirected in traversing each cell, emerging closely parallel to the intended axis of emission. The need for correction increasing towards the plate edges, the degree of convexity and/or the angle (a) the face makes with the vertical, are greater for cells near the edges. Opt., the convexity may exhibit elliptical or hyperbolic curvature, or curvature in both horizontal and vertical section. The plate is interposed between the source and a clear front-glass. Opt., the plain reverse side functions as the front-glass.
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