Projection optical system and projector

A projection optical system that projects, while enlarging, an image displayed on an image display surface and performs zooming by moving a plurality of lens groups arranged along a same optical axis, the projection optical system comprising, from an enlargement side:

• a first lens group having a negative refractive power;
• a second lens group having a negative refractive power and movable during zooming;
• a third lens group having a positive refractive power and movable during zooming;
• and
• a lens group disposed at a most reduction-side position,
• wherein
• the first lens group comprises, from the enlargement side:
• a front group having a negative refractive power;
• and
• a rear group having a positive refractive power and comprising, from the enlargement side, a negative lens element and a positive lens element,
• for zooming from a wide-angle end to a telephoto end, the third lens group moves toward the enlargement side monotonically, and
• conditional formulae (1) and (2) below are fulfilled:
• 0.3<|flf|/L1r<1.4 (1)
• 0.1<L2max/L3max<0.3 (2)
• where
• flf represents a focal length of the front group;
• L1r represents a distance from a vertex of a most enlargement-side surface in the front group to a vertex of a most enlargement-side of the rear group;
• L2max represents a maximum amount of movement of the second lens group;
• and
• L3max represents a maximum amount of movement of the third lens group.