It has been shown that it is possible to generate very small lenses by melting 'islands' of photoresist on a glass substrate. We have made lenses with diameters ranging from 5 pm to 750 pn in the form of spheres, cylinders and crossed cylinders and have studied their optical properties. Lenses with numerical apertures between 0.5 and 0.2 may be made close to diffraction limited but those of lower numerical aperture can only be achieved using more complex techniques.

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An instrumental method for the individual, sequential or collective measurement of the physical and chemical properties of liquids is presented. A prototype of the fibre drop analyser (FDA), working at only one wavelength in the infrared, has been constructed and tested. The instrument has been used to measure individually surface tension, viscosity, refractive index and the chemical composition of the test solution. The instrument has the capability of simultaneously measuring all of these quantities in one measurement cycle and this possibility is discussed on the basis of one set of results obtained from the sugar processing industry. The instrument is also potentially capable of measuring electrochemical properties of a liquid and some preliminary results are presented. The laboratory FDA has been used to test a series of samples from a large cane sugar manufacturer's process and these measurements demonstrate that the FDA technology has the potential to be used as a remote optrode industrial process monitor for sucrose manufacture, and possibly in other industrial applications.

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