Patent ID: 7499154

Claim:
A readhead for a diagnostic instrument for illuminating a sample carrier and receiving light from the sample carrier, the readhead comprising: a housing adapted to be incorporated in the diagnostic instrument and including an illumination chamber for receiving a sample carrier; an array of reflectance light sources mounted within the housing in a fixed position relative to the illumination chamber, and including a first light-emitting diode for emitting substantially monochromatic light of a first wavelength and a second light-emitting diode for emitting substantially monochromatic light of a second wavelength substantially different from the first wavelength; a light guide mounted in the housing to receive light from each of the light-emitting diodes, for conveying, when only one of the light-emitting diodes is illuminated, substantially all of the light from the one light-emitting diode to the illumination chamber so that the illumination chamber is illuminated substantially uniformly; a light detector coupled to receive light from the illumination chamber; a fluorescence excitation light source positioned in the housing and positioned to direct excitation light of a predetermined wavelength to the illumination chamber; and a light filter positioned between the illumination chamber and the light detector and adapted to prevent passage therethrough of the excitation light from the fluorescence excitation light source but allow passage of emissive light from a sample carrier in the illumination chamber having a wavelength different from the predetermined wavelength of the excitation light.