Patent ID: 8854747

Claim:
An optical system comprising: a first lens unit; an aperture stop; and a second lens unit having a positive refractive power, wherein the first lens unit, the aperture stop, and the second lens unit are disposed in that order from an object side to an image side, wherein the first lens unit includes a first lens having a negative refractive power and a second lens having a positive refractive power in that order from the object side to the image side, wherein the second lens unit includes a cemented lens, a fifth lens having a negative refractive power, and a sixth lens having a positive refractive power in that order from the object side to the image side, the cemented lens including a third lens having a positive refractive power and a fourth lens having a negative refractive power, the third lens and the fourth lens being cemented to each other, the fifth lens having a concave surface that faces the object side, the sixth lens having a convex surface that faces the image side, and wherein when a distance from an object-side lens surface vertex of the first lens to the aperture stop is D 1 and a distance from the object-side lens surface vertex of the first lens to an image plane is Dt, the conditional expression 0.10<D 1 /Dt<0.25 is satisfied.