Abstract: A rideheight sensing device is described for providing a measure of the separation between the readhead portion and the scale of an encoder. The rideheight sensing device comprises a rideheight sensor that is located at, or is attachable to, the readhead portion of an encoder. The temporary, or permanent, attachment of such a device to the readhead portion of an encoder is also described. In a preferred embodiment, a rotary encoder is described and the rideheight sensing device is used to measure the eccentricity thereof.

Abstract: Interferometry apparatus which comprises a measurement light beam (2a, 2b) and a reference light beam (2c, 2d) which interact with each other to cause a spatial fringe pattern (24). An optical device (12) is provided which interacts with the spatial fringe pattern (24), such that light is spatially separated into different directions (30, 32, 34, 36). The intensity modulation in two or more directions of the spatially separated light is phase shifted. The optical device may comprise, for example, a diffractive device, a refractive device or a diffractive optical element.

Abstract: A measurement scale (20) is movable in plane x relative to a mask (10) and photodetector (30). When a pattern of apertures in the mask (10) are in correlation with a pattern of apertures e.g. a reference mark in the scale (20) then light bands a b and c may propagate to the detector (30). The relative sizes of the patterns is such that the light bands converge at the detector (30). Other embodiments show light divergent and light inversion correlation of incongruent patterns.

Abstract: A calculator for analyzing options and option spreads includes a memory storage having software where the software permits a user to input into the system a type of transaction, a type of option contract, a number of option contracts, a strike price and a premium price. A processor in communication with the memory storage uses the software to calculate a maximum profit, maximum loss and breakeven level based on the type of transaction, type of option contract, number of option contracts, the strike price and the premium price entered by the user. A display is in communication with the memory storage and the processor and presents to the user the maximum profit, maximum loss and breakeven level as well additional information. The calculator also provides error trapping and a help function that includes a glossary of terms.

Abstract: A scale (10) is illuminated by a light source (18). After interaction with an index grating (12), fringes (F) are formed in a Talbot plane and analyzed by an analyzer grating (14). To decrease the sensitivity to changes in the ride height of the index grating above the scale, the light source is restricted to a small but finite size, and positioned so that it subtends a small angle Ø at the analyzer grating (or, if a collimating lens (24) is used, positioned so that it subtends a small angle Ø at the lens). The size of the light source should preferably be smaller than a predetermined value such that the extent of a geometric fringe visibility envelope exceeds the extent of a Talbot fringe visibility envelope.

Abstract: A measurement scale (20) is movable in plane x relative to a mask (10) and photodetector (30). When a pattern of apertures in the mask (10) are in correlation with a pattern of apertures e.g. a reference mark in the scale (20) then light bands a b and c may propagate to the detector (30). The relative sizes of the patterns is such that the light bands converge at the detector (30). Other embodiments show light divergent and light inversion correlation of incongruent patterns.

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: A scale (10) is illuminated by a light source (18). After interaction with an index grating (12), fringes (F) are formed in a Talbot plane and analyzed by an analyzer grating (14). Th decrease the sensitivity to changes in the ride height of the index grating above the scale, the light source is restricted to a small but finite size, and positioned so that it subtends a small angle Ø at the analyzer grating (or, if a collimating lens (24) is used, positioned so that it subtends a small angle Ø at the lens). The size of the light source should preferably be smaller than a predetermined value such that the extent of a geometric fringe visibility envelope exceeds the extent of a Talbot fringe visibility envelope.