In this article, we have calculated the thermal field within an edge of a specimen parallelepipedic irradiated by a laser beam transformed by an optical device whicli converts an axisymetrical beam (gaussian) into a gaussian-strip beam. The evolution of temperature at surface of the specimen have been measured during the heat treatement by means of a line scanning infrared camera. We have observed that the agreement between the experimental and theoretical results are satisfactory. We find that the liardened zones obtained by experiment correspond to that predicted by the calculation within the tolerance permitted (~10%). As a result, we can use this method of calculation to select certain parameters to optimize the laser treatement of a specimen ridge.