Abstract: A rotary ring system for use in scale reading apparatus comprises a rotary ring (12), provided with scale marks on its surface and at least one intermediate member (24). The at least one intermediate member (24) is fitted between the rotary ring (12) and the machine part (10) on which the rotary ring is to be mounted. Application of a force to the at least one intermediate member adjusts the effective radius of the rotary ring. The at least one intermediate member may be tangentially compliant.

Abstract: There is disclosed: a measurement scale suitable for use with scale reader for determining displacement; various tracks all for holding the scale and all having a channel into which the scale is magnetically attracted; and a scale tensioner which in use tensions the scale in situ by release of a preload, prior to the scale being secured to a substrate, the tensioner being removable thereafter.

Abstract: There is disclosed: a measurement scale suitable for use with scale reader for determining displacement; various tracks all for holding the scale and all having a channel into which the scale is magnetically attracted; and a scale tensioner which in use tensions the scale in situ by release of a preload, prior to the scale being secured to a substrate, the tensioner being removable thereafter.

Abstract: A length of scale (1) which has a profile consisting of a sequence of troughs (18) and crests (16) is subjected to a process to make the shapes of the crests more regular, thus increasing and making more predictable the signal reflected from the crests on the scale. The process comprises passing a length of scale (1) between upper (20) and lower (22) cylindrical rollers. The lower roller (22) may be driven or the length of scale (1) may be pulled through. Reference marks or identification marks may be added to the scale by appropriately marking the upper roller (20). Alternatively, the marks may be added at an initial embossing step which imparts the troughs and crests profile to the scale or at a separate subsequent step.

Abstract: There is disclosed: a measurement scale suitable for use with scale reader for determining displacement; various tracks all for holding the scale and all having a channel into which the scale is magnetically attracted; and a scale tensioner which in use tensions the scale in situ by release of a preload, prior to the scale being secured to a substrate, the tensioner being removable thereafter.

Abstract: A rotary ring 3 for use in scale reading apparatus has a scale on its outer circumference and is mounted on a rotary shaft 6. To reduce error caused by the rotary ring 3 not sitting concentrically on the rotary shaft 6, the inner circumference 5 of the rotary ring 3 and the outer circumference of the shaft 6 are both tapered. To compensate for eccentricity of the shaft, mounting screws 8 are provided in holes on the rotary ring to adjust the position of the rotary ring until it is concentric with the axis of rotation of the shaft.

Abstract: A scale and scale reader are disclosed for measuring displacement in two directions. One embodiment of the scale shows a chequered pattern forming a matrix of marks for providing a light pattern to a diffraction grating. The diffraction grating has a similar chequered pattern and provides an interference light pattern to a photodetector array. The interference pattern enables the detector to determine movement in each of the two directions.

Abstract: A readhead (18) measures movement in the direction of arrow (20) with respect to a scale (10). The readhead (18) comprises an index grating (12), which interacts with light from the scale (10) to produce fringes in the vicinity of an analyzer grating (14). The resulting light modulations are detected by photodetectors (16). In order to reduce the sensitivity of the apparatus to changes in the ride height (h) of the readhead above the scale, at least two different optical path lengths are provided for light travelling from the scale (10) to the index grating (12), and/or from the index grating (12) to the analyzer (14). Various ways to achieve this are disclosed, e.g. a plate (22) of a refractive medium placed in one optical path, or tilting one of the gratings.

Abstract: An opto-electronic scale reading apparatus includes a reflective scale (410) relative to which a readhead is movable. The readhead includes a light source in the form of the emission end of an optical fiber (300), which directs light via collimating lens (420), beam splitter (310), and deflecting optics (312,314) onto the scale. The light reflected from the scale passes through an index grating (416) to generate a series of spatial fringes in the plane of an analyzer (418). The analyzer comprises a series of elongate light transmitting color filters, extending substantially parallel to the fringes and arranged in a repeating pattern (e.g. red, blue, green, red, blue . . . ); like-colored elements are separated by a distance corresponding to an integer multiple of the fringe pitch. The array (418) encodes the fringes into a plurality of phase-shifted signals, which pass through the beam splitter (310), lens (420) and back along fiber (300).

Abstract: Opto-electronic linear encoding apparatus includes a scale and a readhead movable relative to the scale in a direction of spacing of the scale lines. The readhead is formed of a single semi-conductor substrate, typically made of gallium arsenide. The substrate is divided into two regions, the first region including a light emitting diode having a plurality of elongate electrodes provided on its upper surface and spaced in the direction of spacing of the scale lines. The light emitting diode region, the elongate electrodes and the substrate cooperate to produce a plurality of coplanar elongate light emitting regions between the elongate electrodes which perform the combined functions of a diffused light source and an index grating. The second region is an analyzer having a plurality of elongate photosensitive elements spaced apart in the direction of spacing of the scale lines.

Abstract: A readhead 10 traverses along a scale 12, producing square wave signals in quadrature on lines 24,26. These are counted by an external counter 28 to indicate the position along the scale. The square waves cannot be used to monitor the orientation and stand-off of the readhead 10 relative to the scale 12. To achieve this, therefore, circuitry within the readhead 10 monitors the sinusoidal quadrature signals from which the square waves are produced, and gives a simple go/no-go indication on a LED 62 when these signals have an acceptable amplitude and are in an acceptable quadrature relationship.