Patent ID: 7397610

Claim:
A zoom lens comprising: three lens units including a first lens unit having negative refractive power, a second lens unit having positive refractive power, and a third lens unit having positive refractive power in this order from an enlargement conjugate side, wherein a magnification change is performed by moving only the second lens unit in an optical axis direction of the zoom lens, focus adjustments of the zoom lens is performed by moving the first lens unit on the optical axis, and the zoom lens is approximately telecentric on reduction conjugate side of the zoom lens, wherein when a focal distance of the second lens unit is referred to as “f v ” and a lateral magnification, a magnification changing ratio, an F-value in an intermediate region at a time of the magnification changing, and a minimum diameter of a circle of confusion of the third lens unit are respectively referred to as “β r ”,“Z”, “F m ”, and “ε”, a following expression is satisfied: 2 F m ·ε−|−f v ·(1 −√Z ) 2 |·β r 2 /√Z >0.