An apparatus is provided for performing photothermal measurements on a object. The apparatus, which may be provided as a handpiece, houses optical components including a laser, an infrared detector, a dichroic beamsplitter, and focusing and beam directing optics for the delivery of a laser beam to, and the collection of photothermal radiation from, a measured object. Some of the optical components may be provided on an optical bench that is directly attached to a thermally conductive tip portion for the passive heat sinking of internal optical components. The apparatus may further include a sampling optical element and a photodetector for the detection of luminescence, and a camera for obtaining an image of the object during a diagnostic procedure. The apparatus may be employed for the scanning of a tooth to determine an oral health status of the tooth.