Optical product and method of manufacturing the optical product

A method of manufacturing an optical product comprising, in manufacturing a cross dichroic prism by putting together vertexes forming right angles of a first prism element, a second prism element, a third prism element, and a fourth prism element made of glass that have a shape of a right isosceles triangle right prism and joining respective optical sides adjacent to one another among optical sides orthogonal to one another via dichroic films made of multilayer films, respectively:

• forming a first dichroic film made of a multilayer film on one of optical sides orthogonal to each other of the first prism element or the fourth prism element;
• joining, via the first dichroic film, the optical side of the prism element not provided with the first dichroic film of the first prism element or the fourth prism element and the optical side provided with the dichroic film of the other prism element to form a first prism pair;
• forming a first dichroic film made of a multilayer film on one of optical sides orthogonal to each other of the second prism element or the third prism element;
• joining, via the first dichroic film, the optical side of the prism element not provided with the first dichroic film of the second prism element or the third prism element and the optical side provided with the dichroic film of the other prism element to form a second prism pair;
• leveling optical hypotenuse surfaces of the first prism pair and the second prism pair to form adherable surfaces;
• forming a second dichroic film made of a multilayer film on one of optical hypotenuse surfaces of the first prism element or the second prism element;
• and
• joining the second dichroic film of the prism pair formed in the film forming step and the optical hypotenuse surface of the prism pair not provided with the second dichroic film,
• wherein the cross dichroic film is obtained by using one or more of a first combination of the film forming step of forming the first dichroic film, an uppermost layer of which is made of a silicon oxide layer, and the joining step of joining the silicon layer of the uppermost layer of the first dichroic film and the optical sides of the first prism element and the fourth prism element according to the optical contact method to form the first prism pair, a second combination of the film forming step of forming the first dichroic film, an uppermost layer of which is made of a silicon oxide layer, and the joining step of joining the silicon layer of the uppermost layer of the first dichroic film and the optical sides of the second prism element and the third prism element according to the optical contact method to form the second prism pair, and a third combination of the film forming step of forming the second dichroic film, an uppermost layer of which is made of a silicon oxide layer, and the joining step of joining the silicon oxide layer of the uppermost layer of the second dichroic film and the optical hypotenuse surfaces of the first prism pair and the second prism pair according to the optical contact method.