PURPOSE: To increase the precision and the stability in an angle of fitting plane by specifying the height of three projecting parts when a bearing surface whereon an optical component is to be fitted is a lateral side part in the drawing direction of a mold.
CONSTITUTION: In the case when a bearing surface for fitting an optical component is a lateral side part in the drawing direction of a mold, the height (the dimension of an undercut) G of three projecting parts 6a to 6c is so formed as the satisfy an expression A×B+ A×(C-D)×(E-F)≥G. In the expression, A denotes the section thickness of a fitting instrument (the part of the bearing surface), B a mold shrinkage factor in setting, C a linear expansion coefficient of a molding material, D a linear expansion coefficient of a mold material, E a melting point of the molding material, and F a temperature at the time of drawing from the mold. When an inclination 6e is imparted to the undercut side of the projecting part 6 in the direction of making it easy to draw the mold, the occurrence of hang-up of the projecting part 6 on the occasion of drawing the mold is prevented. As for the fitting instrument 1, two ribs 5a and 5b are formed on the bearing surface 3 and the projecting parts 6a to 6c are formed dispersely on the two ribs 5a and 5b within a space somewhat narrower than the width of the optical component to be fitted. The optical component, such as a mirror 11, is set and fitted on the projecting parts 6a to 6c.
SHIBATA NORIO
KOMORI TAKASHI
