GB230152A - Improvements in cinematograph projection - Google Patents

Abstract

230,152. Taylor, A., and Taylor, H. D. Nov. 29, 1923. Kinematograph apparatus.-In a continuousfeed projector, the gate has a height not exceeding one picture pitch, and compensation for the movement of the film F is effected by reflection from an outwardly reflecting drum M of at least 48 flat mirrors ranged evenly and cylindrically. The rotation of the drum is so synchronized with the travel of the film that the angle of reflection with the perpendiculars to the mirrors changes at half the rate of the angular movement of the pictures as subtended at the back principal point of the lens F. In such an apparatus, the lens described in Specification 210,705 is preferably utilized so that the virtual stop or the image of the electric arc is situated at such a distance in front of the lens as to fall upon the mirrors of the rotating drum. The optical principles involved in the production of good definition in the image projected by the above arrangement of apparatus are discussed at length in the Specification. The mirrors are preferably of tapered form across the width of the drum, Fig. 5, the mean width in the direction of movement being about one-sixth of the focal length of the projector lens. Each mirror is supported upon two independent rocking frames l and a stud s on the drum, and held in contact with studs s, s<2> on the frames l and the stud s by spring clips 6 as shown. The frames l or each provided underneath with two rounded edged knife edges k riding in grooves in the drum at right-angles to the radius of the drum through the centre of each mirror. The other ends of the frames rest on points of adjusting screws a. A spring p keeps the frames l bearing on the grooves. Each mirror is thus supported on three points and is adjustable by means of a single screw a. When an internally reflecting drum, Fig. 10, is used the projector lens L is situated so that the optical axis is at an angle of about 30‹ to the perpendicular to a mirror centrally opposed to it, and the image is projected on to a screen by means of an inclined mirror R. Specifications 178,474 and 184,258 also are referred to.