Patent ID: 7535556

Claim:
An apparatus for optically analyzing samples in a biological sample container, the biological sample container comprising a plurality of samples located at respective sample locations distributed over the biological sample container, each sample location being coincident with, or vertically offset from, a base of the biological sample container, wherein the base is defined by upper and lower surfaces, the apparatus comprising: a container station in which a biological sample container can be arranged; an optical acquisition device comprising a detector and an objective arranged to view a biological sample container arranged in the container station from below, the positions of the detector and objective collectively defining a focal plane for optical acquisition; a focal plane sensor arranged to view a biological sample container arranged in the container station from below and comprising: (i) a polychromatic light source operable to generate polychromatic light over a range of wavelengths; (ii) a focusing arrangement with defined axial chromatism arranged to focus respective wavelengths of the polychromatic light to respective pre-calibrated positions along an axis that extends through where the base of a biological sample container arranged in the container station would be; (iii) a detection unit comprising a spectrometer arranged to spectrally isolate components of said polychromatic light scattered from said optical axis; and (iv) a data processing unit operable to determine the position of at least one of the upper and lower surface of the base from the isolated components of the scattered polychromatic light output by the spectrometer; a positioning apparatus operable to adjust the focal plane of the optical acquisition device relative to the container station; and a controller operable to control the focal plane sensor, optical acquisition device and positioning apparatus to: (i) determine a desired focal plane for each sample location with reference to the determined position of the at least one of the upper and lower surface of the base at that sample location; and (ii) use the optical acquisition device to collect light from each of the sample locations with the focal plane adjusted to its desired setting.