Abstract: A stepper motor drive which sequentially energizes the windings of a stepper motor (1,2,3,4). The drive includes a binary counter (11) fed by a clock signal and two multipliers (D.A.C.1, D.A.C.2) which are fed by the binary counter (11) and a reference signal. An adjustable feedback network (30) is arranged to combine a fraction of the output of the multipliers (V.sub.1, V.sub.2) with the reference signal so that the output of the multiplier represents unequal steps of a staircase waveform. A switching network (13) under the control of the counter (11) applies to the windings drive signals in accordance with the output of the multipliers.Each winding has its own amplifier (15,17) to control its current, and pairs of antiphase signals from the switching network (13) are combined in the amplifiers to produce symmetrical changes of current in a respective pair of coils (1 and 2 or 3 and 4). The feedback network (30) distorts the otherwise linear outputs from the multipliers (D.A.C.1, D.A.C.

Abstract: A character generator for use in photocomposing comprises a fibre optic faceplate (23) of which the front face is polished and bevelled at its leading and trailing edges. On the rear surface of the faceplate is a mask which has an array of apertures each aperture encompassing a multiplicity of the fibres. Photoemissive diodes or other illuminators (25) are approximately aligned with the holes in the mask and are disposed for connection to terminals 22 on a printed circuit mounting. The generator is intended for use in the constitution of characters by selective illumination of elementary areas. The faceplate is intended to be in close proximity to a film or other radiation sensitive recording medium which is moved relative to the faceplate to build up lines of composition.

Abstract: A method of making an assembly comprising a support plate with an array of lenslets made from optically refractive material mounted thereon, the support plate being substantially optically transparent at least in the regions adjacent the lenses, the method including, in respect of each lenslet, the steps: positioning the lenslet on the plate with a quantity of adhesive therebetween, the adhesive being curable by electromagnetic radiation in a given wavelength range; and, after checking that the lenslet is in a required position relative to the support plate, applying electromagnetic radiation within said wavelength range to the adhesive through the lens and/or the plate to cure the adhesive and fix the lenslet to the plate. The checking step includes observing an image, formed by an optical system including the lenslet, of a reference mark and adjusting the position of the lenslet on the support plate until the observed image is exactly in a predetermined position in an image plane.

Abstract: Optical scanning apparatus comprising a source of light, a rotatable reflecting element having a plurality of reflective facets which are inclined to the axis of rotation, a beam expander for deriving a collimated beam of light from the source, this collimated beam being directed at the reflecting element in a direction parallel to its axis of rotation to impinge upon successive facets thereof as it is rotated. The apparatus also includes a support, which may be a system of rollers, for defining a position for a recording element having a surface that requires scanning, a projection lens for focussing the collimated beam as reflected by the reflecting element onto the surface of the recording element, a motor coupled to rotate the reflecting element, so that each facet in turn causes the focussed beam to scan across the surface in one direction, and a drive for moving the recording element substantially perpendicular to the direction of scanning, past said focussed beam.

Abstract: Photocomposing apparatus comprising a projection system for projecting optical images selected from a character matrix onto a photosensitive recording member by way of a mirror which is rotatable to displace projected images with respect to the recording member. The projection system includes a wide-angle lens for focussing the optical images onto a substantially flat image plane coincident with the recording member, and a zoom lens system arranged to produce a first fixed image which provides, by the action of the rotatable mirror, an object for the wide-angle lens which is selectively positionable in a substantially flat object plane.

Abstract: Photo-composing apparatus comprising a projection system for projecting optical images onto a photo-sensitive recording member by way of a mirror which is rotatable to displace projected images with respect to the recording member, and an element formed by substantially parallel optical fibres between the mirror and the position in which the recording member will be held. The element has first and second major surfaces, the first major surface being concave, and facing the mirror, the second major surface having a radius of curvature substantially greater than that of the first major surface. The optical fibres extending between the first and second major surfaces, and the axis of rotation of the mirror is at the effective centre of curvature of the first major surface.