Abstract: A millimetre wave imaging apparatus and method capable of identifying the presence of relatively thin dielectric materials is disclosed. The method involves taking a plurality of millimetre wave images of a scene at different frequencies and analysing the images at different frequencies to look for frequency dependent effects in the scene. Relatively thin dielectric materials can lead to interference effects which can be detected. In one embodiment the imaging apparatus comprises a millimetre wave imager (2) connected to a processor (16) and at least one variable frequency illumination source (22a . . . d, 24a . . . d). The or each illumination source sweeps the illumination frequency across a reasonably wide bandwidth and the imager captures radiation returned from the scene at a number of different illuminating frequencies.

Abstract: A stress or magnetic field sensor comprising a generally elongate magnetically soft amorphous or nanocrystalline electrically resistive element and biasing means for applying to the element a bias magnetic field of which the component directed along the length of the sensor has an amplitude variation pattern along the element. A periodically varying pattern has the effect of reducing the sensitivity of a stress sensor to external ambient fields (FIG. 3 shows that with a sawtooth bias field the sensitive portions a of a sensor move to positions b in the presence of an ambient field, but their number remains the same). A ramped bias field enables the position of the sensitive region of the sensor to be controlled, for measuring local stress, or for mapping an external magnetic field. Control of the regions where the sensor is active may include selective conductive coating of portions of its length.

Abstract: A fuel injector including a combustion air flow conduit, a fuel inlet and, swirlers to mix the air and fuel flowing therethrough, additionally comprising fluidic control diverters including at least one control port, such that flow of control air through said control port allows variation in the degree of flow resistance to which combustion air is subjected. For example, control air flowing through the control port may impart swirl to the combustion air flow from the inlet, thereby subjecting the combustion air flow to increased resistance. Alternatively a fluidic diverter may selectively divert the main flow to either the first or second sub-conduits, each sub-conduit subjecting combustion air to different degrees of flow resistance.