GB516626A - Improvements relating to stroboscopes - Google Patents

Abstract

516,626. Stroboscopic apparatus. LIST, H. July. 1. 1938, No. 19501. Convention date, July 12, 1937. [Class 97 (i)] The shutter of a stroboscopic apparatus is rotatable at a continuously variable speed and has apertures arranged in separate groups each disposed in a ring around its axis of rotation and each group having a different number of apertures; and the viewing aperture is adjustable into register with any desired group. In the form shown, the shutter disc has four groups of apertures a, b, c, d consisting respectively of 1, 2, 4 and 8 slits, which may be made narrower in successive groups in accordance with the number of slits and their relative linear speed when rotating. The slits may have parallel edges, or may taper in a direction either away from or towards the centre of the disc. The shutter is trunnioned at 3 in a housing 1 having an aperture 7 on the object side, and a viewing eyepiece 10 which may be slid along an aperture 9 into register with any group of slits ; and rotation is imparted to it as by a radiallyadjustable friction wheel 5, which may be held against the disc by magnetic attraction, and may be driven by a spring or electric motor. Instead of a slotted disc, a glass disc may be used, .backed with opaque material 12 in which the slits are made ; or the shutter may comprise a disc provided with slits and a frictionally-driven disc mounted on the same shaft, provision being made in this case for reflecting rays from the object first between the discs then 'through the slits of the first disc to the eyepiece. In modifications, the shutter takes the form of a rotatable drum or core. Arcuate scales, one for each group of slits, are provided on the housing 1 round the axis 3, over which scales moves a pointer coupled to the means for adjusting the speed of rotation of the shutter.