A non-contact tool measurement apparatus is used in a machine tool environment. The apparatus includes a transmitter including a first aperture and a laser for generating light that is emitted from the transmitter through the first aperture towards a tool-sensing region. A receiver includes an optical detector and is arranged to receive light from the tool-sensing region. A processor analyses the light detected by the optical detector to enable the measurement of tools in the tool-sensing region. The laser is capable of generating light having a wavelength of less than 590 nm thereby enabling the size of the first aperture to be reduced resulting in a reduction in contaminant ingress. In one embodiment, the laser generates blue light.