Abstract: Apparatus and methods are described including a sample carrier (22) configured to carry a portion of a bodily sample, at least a portion of the sample carrier being configured to fluoresce, at least under certain conditions. An optical measurement device (24) performs optical measurements upon the portion of the bodily sample that is housed within the sample carrier (22), and at least partially photobleaches an area within the portion of the sample carrier (22) by causing the area to fluoresce. By detecting that the area within the portion of the sample carrier (22) has been photobleached, an output is generated indicating that at least a portion of the sample carrier (22) is contaminated or that optical measurements cannot be performed on the portion of the sample carrier (22), or the optical measurement device (24) is prevented from performing optical measurements upon a sample portion housed within the given portion of the sample carrier (22).