An optical device includes a diode light source which is preferably in the form of an array of diode elements such as laser diodes or light emitting diodes (LEDs). The light emitted from the diode elements is directed towards a reflector which directs the emitted light through a heat sink member for controlling the temperature of the diode elements. The heat sink member preferably has a plurality of fins for dissipating heat, and the emitted light passes through these fins and away from the optical device. An optical lightguide may be integrated with the optical device to give the user better control over how the emitted light is imaged. The diode elements preferably emit in either the blue or ultraviolet region of the optical spectrum. In one embodiment of the invention, the output from the diode elements has a cross section that is variable in shape, permitting a composite material within a cavity of a tooth to be cured in such a way that microgaps between the tooth and the composite are not formed.