Method of manufacturing member with concave portions, member with concave portions, lens substrate, transmission type screen and rear projection

A method of manufacturing a member with concave portions having a number of concave portions, comprising:

• preparing a base material;
• forming a mask formation film on the base material;
• forming a number of openings in the mask formation film by means of laser processing using a branching filter to obtain a mask, the branching filter having a number of light transmission portions for branching laser light which has been emitted from a laser light source into a plurality of laser beams, the light transmission portions including first light transmission portions arranged in a predetermined region for producing first laser beams and second light transmission portions arranged out of the predetermined region for producing second laser beams;
• and
• etching the base material on which the mask has been formed to form the concave portions in the base material;
• wherein the mask formation film has a plurality of irradiation regions each having a predetermined size, and the laser processing is carried out by performing a laser irradiation treatment with the laser beams branched by the branching filter for each of the plurality of irradiation regions sequentially in a predetermined order to form the openings in the irradiation regions, in which the openings formed by the laser irradiation treatment for each of the irradiation regions including first openings which are formed inside the irradiation region by the first laser beams and second openings which are formed out of the irradiation region by the second laser beams, wherein the first light transmission portions and the second light transmission portions of the branching filter are arranged so that each of the irradiation regions has portions where no opening is formed by the first beams of the laser irradiation treatment for the irradiation region while openings will be formed in the portions of the irradiation region by the second laser beams in one or more of the subsequent laser irradiation treatments, whereby when the laser irradiation treatments have been carried out for all the irradiation regions and then the etching process is completed, a number of concave portions are formed in the base material so that the base material can have an effective area in which the concave portions are formed in a regularly arranged manner and an ineffective area which is positioned out of the effective area and in which concave portions for examination use are formed using some of the openings formed by the second laser beams used in the laser irradiation treatments for the specified irradiation regions.