PURPOSE: To obtain the titled lens system capable of withstanding to a temperature change by constituting an assemblage of the lens from a 2nd lens having a positive power and 1st lens composed of a liquid lens which is interposed to a space between a convex lens made of a plastic material and an another lens.

CONSTITUTION: The 1st lens is formed by interposing the liquid lens E1 having the negative power to the space between the convex lens L1 made of the plastic material and the lens L2. The liquid materials of the lens E1 and a coolant E2 are composed of a liquid or a gel material having the temperature coefficient dn/dT, which denotes the temperature dependency in refractive index and satisfies the formula of -4×10-4<dn/dT<-2.0×10-4. While, the lens L2 is composed of the plastic material or a glass. The 2nd lens is formed by the lens L3 and L4 composed of the plastic material having the positive power. The titled lens capable of compensating the temperature change of the refractive index and having less tendency for moving an imaging plane of the lens, even if the temperature of the lens remarkably changes, is obtd. by constituting the lens system from the 1st and 2nd lens.