GB905682A - Electroluminescent device - Google Patents

Abstract

905,682. Piezo-electric elements. SYLVANIA ELECTRIC PRODUCTS Inc. Dec. 18, 1959 [Dec. 31, 1958], No. 43170/59. Addition to 900,995. Class 40 (8). [Also in Group XL (a)] The electroluminescent device of the parent Specification is modified by the provision of a second pair of contacts 18 and 20 on opposite sides of the piezo-electric strip 10, of a polarized sintered mixture of lead titanate and lead zirconate, and spaced from the electroluminescent layer 24. First voltage pulses are applied between the contacts 12 and 14, each pulse producing a first elastic wave and an accompanying first electric field which travel along the strip 10, and second voltage pulses are applied between the contacts 18 and 20, each pulse producing a second elastic wave and an accompanying second electric field, a moving spot of light being generated in the layer 24 at a point corresponding to the point of intersection of the first and second waves. Under some conditions of operation several spots of light can be produced. The ends of the strip 10 are coated with a material, such as lead, to provide terminations 30 and 32 for absorbing, substantially without reflection, elastic waves from the strip 10 as described in the parent Specification. Means are provided to vary the amplitude of the first and second pulses, whereby the light from the spot is modulated, and means are provided to vary the relative timing between successive first pulses and corresponding successive second pulses to shift the point of intersection of the waves. The first and second voltage pulses can be of sawtooth form generated under the control of trigger pulses from a common source, to provide spike-like pulses in the electroluminescent layer 24, the recurrence frequency of the first pulses being varied by a voltage of sawtooth form and the second pulses being of fixed recurrence frequency.