Abstract: With a device for measuring the fluorescent light or scattered light emitted by microscopically small particles or cells (12), with a flow-through cuvette (8) through which the luminescent particles or cells (12) are guided, whereby the flow-through cuvette (8) has a transparent window (3), and with a photodetector (2), which records the light emitted by the luminescent particles or cells (12), and with an optical element that guides the light emerging from the window (3) to the photodetector (2), the invention suggests that the optical element is embodied as a cylinder (4, 9) with a cylindrical reflecting surface.

Abstract: With a device for measuring the fluorescent light or scattered light emitted by microscopically small particles or cells (12), with a flow-through cuvette (8) through which the luminescent particles or cells (12) are guided, whereby the flow-through cuvette (8) has a transparent window (3), and with a photodetector (2), which records the light emitted by the luminescent particles or cells (12), and with an optical element that guides the light emerging from the window (3) to the photodetector (2), the invention suggests that the optical element is embodied as a cylinder (4, 9) with a cylindrical reflecting surface.