GB1058208A - Transducers - Google Patents

Abstract

1,058,208. Radiation gramophone pick-ups and microphones. A. BERNARD SMITH LABORATORIES Inc. Oct. 3, 1963, No.39055/63. Heading G1A. [Also in Division H4] A stereophonic pick-up comprises an incandescent lamp 1 (Fig. 1) moulded or embedded in a plastics light pipe 3, Fig. 4 (not shown), shaped to channel the light through slots 10 and across two mutually perpendicular vibrating shutter elements 4, Fig. 5 (not shown), of a stylus assembly 5. Each shutter element 4 is formed with a slit 4'. Light from lamp 1 proceeds through the slits 4' and falls upon photo-semi-conductor cells 7. Separate electrical signals are produced by the cells and are amplified. The stylus assembly 5 is secured by a weak spring or grommet 8. Grooves 11 in the light pipe 3 maintain proper alignment of the stylus assembly 5. A hole 17 renders the lamp 1 visible and aids cooling. The lamp 1 is energized by D. C., by rectified A. C. or by use of light chopped at a frequency of 200, 000 c/s. In the latter event the signal is demodulated before amplification, thereby avoiding errors due to thermal noise. Alternatively thermal noise may be eliminated by employing two identical photo-cells in push-pull, one in the dark and the other illuminated by lamp 1. White light, infrared radiation or beta- or gamma-rays may be utilized. Translucent transmitting or reflecting surfaces may be interposed between the light source and the cells to eliminate problems produced by filament vibration. In a second embodiment, Figs. 6, 7 (not shown), a neon tube is utilized and vanes (21) have edges (22) which determine the effective width of the beam impinging on the cells (7). The vanes (21) are not necessarily mutually perpendicular. The vanes (21) are mounted on a cantilever (31). The cells (7) may be silicon type solar cells, photodiodes or photo-transistors. A further embodiment has a vane (36), Fig. 11 (not shown), in the form of a flat V-notch and is secured to or integral with a nylon shaft (31). Photo-transistors (41), (42) are housed in independent light-tight boxes (44), (45) having windows (47). A cylinder (51), Figs. 12, 13 (not shown), has a coaxially mounted lamp (52) with photo-cells (54), (55) on each side. The cylinder (51) is formed with two diametrically opposite slits (57), (58) each having a light cut-off edge (59). The slopes of the slits (57), (58) follow opposite spirals. A gramophone stylus (6) may be secured to the lower edge of the cylinder (51) but is preferably mounted on an arm (61) secured to a shaft (62). The transducers of Figs. 6 to 11 may be modified to provide a stereophonic microphone by arranging the shaft (31) vertical. Fig. 14 (not shown), and connecting struts to mutually perpendicular diaphragms.