The sensitive detection of delayed luminescence (τ > 100 μs) can be achieved with an optomechanical instrument, the gated autosynchronous luminescence detector (GALD). The device effectively combines an excitation chopper, a detection chopper, and a dichroic mirror into a single element. With dimensions of 12 mm (H), 32 mm (W), and 90 mm (L), it is designed for insertion into the differential interference contrast (DIC) prism slot of a BX51 Olympus microscope. The GALD described here employed a compact high-power UV LED as the excitation source to capture images of Giardia lamblia cysts indirectly labeled with a europium chelate/streptavidin conjugate. Labeled cells were clearly visible in the complete absence of autofluorescence and signal intensity was sufficient to capture high-resolution color images within several seconds. Shorter exposure intervals of 100 ms on a monochrome Andor iXON camera delivered time-gated luminescence images with a signal-to-noise ratio better than 114:1.