Projection optical system

Abstract

A projection optical system satisfies a conditional formula: 0.01<{(tan θf1−tan θf2)−(tan θn1−tan θn2)}·(β2/β1)<0.20 where the direction of a normal to and the direction of a long side of the screen of the screen surface are referred to as a 'z-direction' and an 'x-direction', respectively, the x-z plane component of the angle of incidence with respect to the screen surface is referred to as an “incident angle θ” and when, among rays that pass through the center of an aperture and that are incident on the ends of the upper and lower sides of the screen of the screen surface, the incident angle θ of rays whose incident angle θ is larger is referred to as “θf” and the incident angle θ of rays whose incident angle θ is smaller is referred to as “θn”, θn and θf2 respectively represent, when the absolute value of a projection magnification is the highest or lowest during focus adjustment, the incident angle θf, θn1 and θn2 respectively represent, when the absolute value of the projection magnification is the highest or lowest during focus adjustment, the incident angle θn, and β1 and β2 respectively represent the maximum and minimum values of the projection magnification during focus adjustment (except that β1 and β2 respectively represent, if the projection magnification is negative, a value of the projection magnification when the absolute value thereof is the highest or lowest).