An astigmatism generator such as may be used in the pickup of an optical disk player which produces substantially no other aberrations yet which can be manufactured at a low cost. The astigmatism generator is fabricated from a plate (21) having four plane surfaces, including a first surface (22) through which light is introduced,a second surface (23) parallel to the first surface and through which the light exits, and a third surface (24) by which light transmitted thorough the first surface is reflected toward the second surface. The third surface is arranged at an oblique angle (α) to the first and second surfaces and is selected such that almost all coma is eliminated from the light passing through the second surface.