Abstract: A gas sensor of the type that detects the presence of a specific gas by monitoring the absorption of optical radiation transmitted through a chamber containing a sample of gas under test comprises an optical source for emitting radiation therefrom and a detector sensitive to radiation emitted from the source at opposing ends of a circumferential chamber, having optically reflective surfaces, extending around the periphery of a sensor housing. The optical pathway between the source and detector may include a radial portion, a circumferential portion and an axial portion to allow a compact optical path. The gas sensor includes, within a single housing, electronic circuitry for conditioning the electrical output of the detector to provide an output that is a function of at least one selected gas concentration and which is automatically compensated for at least one of temperature, pressure, humidity, and range normalization.

Abstract: A method and computer system are described for generating compressed image data, and for rendering pixel data using the compressed image data. A plurality of hulls are defined in the image, each hull being defined as a set of polygons in a desired coordinate system. For at least some of said hulls, a portal is defined, each portal being defined as a set of point in the designated coordinate system for that hull. A viewing transform allows the portal to be mapped to another, target hull. A data structure is stored which holds the defined hulls and portals in a manner describing their physical relationship in the image. The data structure can be transmitted via a number of different mediums and represents the compressed image data which can be used to generate pixel data to generate an image at a remote location.