Patent ID: 6923545

Claim:
A method for manufacturing a color combining optical system, the color combining optical system having: a color combining optical element that has four reflection surfaces arranged roughly in X-shape to form an incident angle of approximately forty-five degrees seen in a direction orthogonal to an optical axis of a plurality of incident light beams, the four reflection surfaces including one pair of reflection surfaces along one extending direction of the roughly X-shape and the other pair of reflection surfaces along the other extending direction of the roughly X-shape, the one pair of reflection surfaces reflecting a light beam of wavelength different from a light beam reflected by the other pair of reflection surfaces; and a fixing plate that is bonded on a side of the color combining optical element intersecting the reflection surfaces arranged roughly in X-shape, the method comprising: a reference position adjusting step where a position of an intersecting line of the one pair of reflection surfaces and the other pair of reflection surfaces is adjusted relative to a reference position set on the fixing plate; a rotary position adjusting step where a rotary position of the reflection surfaces is adjusted relative to the fixing plate around the intersecting line of which position is adjusted; a tilt adjusting step where a tilt of the reflection surfaces is adjusted relative to a bonding surface of the fixing plate; and a bonding step where the color combining optical element is bonded to the fixing plate after these adjusting steps are completed.