Abstract: Multiple pupils (16, 18) are formed in a projection display by employment of a field lens (14) which has at least first and second interleaved Fresnel lens segments. The first set of segments has the equivalent surface of a first lens (34) and the second set of interleaved segments has the equivalent curvature of a second lens (36), with the segments being shaped to produce two exit pupils. More exit pupils, up to four without loss of resolution, can be provided by the interleaving of further lens shapes. A separate lens face (30) controls the other dimension of the exit pupils. The additional lens face may be a Fresnel lens on the opposite side of the same lens element.

Abstract: A stroke expansion technique for use in controlling incremental stroke displays. The technique results in a substantial reduction of the stroke memory required for storage of the stroke sequences of an alphanumeric character set. Logic circuitry is operable to recognize a stroke of the same video state (on or off) in the reverse direction of the immediately preceding stroke to cause a predetermined number of additional strokes identical to the immediately preceding stroke to be generated instead of utilizing the reverse stroke to return the beam to its position immediately previous to execution of the preceding stroke.