Abstract: An optical product checking system (100) for checking a property and an authenticity of a product (10) emits light from a plurality of light-emitting units (12, 14, 16, 18) toward a surface of the product (10). Respective intensities of light emanating from the surface of the product (10) in response to the emitted light are detected and used to determine the property and the authenticity of the product (10). The optical product checking system can be incorporated into a beverage-preparation system, for example, to determine whether a coffee capsule for a coffee machine is an authentic product of the manufacturer of the coffee machine.