Abstract: A laser irradiation apparatus irradiates an irradiation object with a laser beam. The apparatus comprises scanning pattern formation sections that change at least either of an emitting direction and a shift amount (size) of a laser beam periodically so that a position irradiated with a laser beam moves periodically along a predetermined scanning pattern on a predetermined plane. And the apparatus comprises an irradiation control section that stops irradiation of a laser beam directed to an excessive irradiation prevention area set in some area in the scanning pattern or makes an intensity of the laser beam lower in comparison with an intensity of a laser beam directed to an area other than the excessive irradiation prevention area.

Abstract: Provided is a surface treatment method of a metallic material having a protective layer formed thereon. A surface of the protective layer is scanned while irradiating the surface and the surface is scanned while moving an irradiation spot along the surface, in a state in which a side layer of the protective layer along the metallic material remains covering the metallic material, and a side layer of the protective layer opposite to the metallic material side is removed by irradiation with the laser beam.

Abstract: Disclosed is a way of providing a surface processing method for concrete in which vitrifying is suppressed even when high-speed processing is performed. In a surface processing method of concrete, a surface of the concrete is irradiated with a laser beam so that a beam spot is scanned along a predetermined scanning pattern and the scanning pattern moves along the surface at a predetermined feed speed. When the beam spot repeatedly passes through a predetermined portion in the scanning pattern, an overlap ratio, which is a ratio of overlapping of a passage path of the beam spot over a passage path of the beam spot in an immediately preceding irradiation, is 90% or less.

Abstract: Disclosed is a laser irradiation state diagnosing method which allows accurately diagnosing a laser irradiation state. When irradiating a laser beam so that an irradiation spot scans the surface of the irradiation object, acoustic information in vicinity of the irradiation spot is acquired. And based on characteristics of the acoustic information, such as an intensity of a component of a specific frequency band or a frequency band distribution, a state of peeling of the adhered substances existing on the surface of the irradiation object is determined.