Neutral filter, light quantity adjustment apparatus, image pickup apparatus, manfacturing method of neutral filter, and die-cutting forming apparatus neutral filter

摘要

The present invention is to provide an optical filter for enabling a neutral filter for suppressing the quantity of passage light in an optical path to be mass-produced in an accurate position of an optical path opening with correct density characteristics without fluctuations, and the neutral filter is comprised of a filter 14 for suppressing a quantity of transmitted light, a base plate (aperture wheel) 11 attached with the filter to cause the filter to face the optical path, and alignment reference faces respectively formed in the base plate 11 and the filter 14 to define mutual bonding positions, where the filter 14 is formed into a predetermined outside shape by press forming from a transparent or translucent sheet with an light-reducing film formed on its surface, and is coated with the light-reducing film in which are formed two or more density regions having at least one density boundary line, while the outside shape of the filter 14 and the alignment reference faces are concurrently formed in beforehand set distance positions from the density boundary line by the press forming.