Abstract: An apparatus for varying the path length of a beam of radiation, the apparatus comprising: an element (51) rotatably mounted about an axis, said element comprising two reflective surfaces in fixed relation to one another such that radiation may be reflected between said reflective surfaces and out of the element (51); and driving means (55) for rotatably oscillating said element about said axis.

Abstract: An apparatus for use with an optical scanning or observation system. The apparatus comprises a drawer for receiving, in use, a sample carrier to be scanned or observed. A first clamp member, engages, in use, with one surface of a sample carrier in the drawer. A second clamp member is arranged to engage, in use, with the side of the sample carrier opposite to that of the first clamp member, the second clamp member having an optical window formed therein to enable viewing, in use, of a sample carrier. The first and second clamping members are arranged in use to move the sample carrier out of engagement with the drawer so that the sample carrier is supported solely on the clamping members.