Abstract: A method includes a plurality of scanners, each scanner directing a corresponding laser beam to different positions on a powder bed, an isotropic position sensitive detector arranged to detect electromagnetic radiation arising from interaction of the laser beams with the powder bed and a movable optical component for moving a field of view of the isotropic position sensitive detector to different positions on the powder bed. The method includes positioning the movable optical component and/or a first or second scanner of the plurality of scanners such that a first or second point irradiated by a first or second laser beam of the first or second scanner within the field of view of the isotropic position sensitive detector and recording a first or second position of an image on the isotropic position sensitive detector generated during irradiation of the first or second point by the first or second laser beam.

Abstract: An auto-focus system suitable for a spectroscopy system uses the same illumination beam as the exciting light for spectroscopy. This is focused to a spot or line focus on the sample. An image of the spot or line focus is directed to a detector via one or more pupils located eccentrically of the optical axis, so that the focus condition is indicated by displacement of the image on the detector. The spot or line focus on the sample provides contrast in the image to enable auto-focusing without the need to observe contrast over an area of the sample. A method of scanning the surface of a sample is also described, in which a topographical map of the sample is built in a pre-scan with an objective lens having a long working distance. This enables selection of an objective with a shorter working distance for a subsequent scan.

Abstract: An auto-focus system suitable for a spectroscopy system uses the same illumination beam as the exciting light for spectroscopy. This is focused to a spot or line focus on the sample. An image of the spot or line focus is directed to a detector via one or more pupils located eccentrically of the optical axis, so that the focus condition is indicated by displacement of the image on the detector. The spot or line focus on the sample provides contrast in the image to enable auto-focusing without the need to observe contrast over an area of the sample. A method of scanning the surface of a sample is also described, in which a topographical map of the sample is built in a pre-scan with an objective lens having a long working distance. This enables selection of an objective with a shorter working distance for a subsequent scan.

Abstract: This invention relates to the manufacture of composite propellants containing rubbery binders and particulate non-binder ingredients. The process consists of curing a mixture of a functionally-terminated hydro-carbon prepolymer and a cross-linking agent to form a viscoelastic first binder composition, mixing the binder with non-binder ingredients to form a plastic propellant, and rubberising at least a part of the plastic propellant by adding to it a further quantity of the cross-linking agent, provided the propellant is formed into a propellant charge while still in a plastic state. The further quantity of the cross-linking agent may be mixed in with the plastic propellant prior to forming, or applied to the surface of the plastic propellant after having been formed into a charge.In a preferred embodiment of the invention, the prepolymer consists of an hydroxy-terminated polybutadiene having a molecular weight of about 3000 and a functionally of about 2.