An apparatus (10) for measuring temperature using luminescence thermometry, comprising: a photon emitter (42) for providing photons (3) of at least a first frequency; photoluminescent material (30) that produces photons (5) of at least a second frequency in response to the incidence of photons (3) of the first frequency; one or more photon receivers (44); and an optically dispersive element (50) for directing photons (5) of at least a second frequency produced by the photoluminescent material (30) into the photon receiver(s).