Abstract: An imaging lens system consists of: a first lens group; an aperture stop; and a second lens group having positive power. The first lens group includes: a first lens having negative power; a second lens having negative power; and a sub-lens group having positive power. The first lens is a negative meniscus lens having a surface convex toward an object. The second lens is a negative meniscus lens having a surface convex toward the object. The imaging lens system satisfies the following inequalities (1) and (2): 0.35<T2/R2<4.0??(1) 3.0<T4/R4<10.0??(2).

Abstract: An imaging lens system includes, in order from an object side: a first lens group consisting of at least one lens element having negative power; a second lens group having positive power and configured with a single lens element; and a third lens group having power, and the third lens group includes a lens element having positive power and a lens element having negative power. In addition, conditional expressions (1) and (2) shown below are simultaneously satisfied: ?1.2×10?5<dn/dtpi<0, where i?1 (1); ?1.0×10?6<dn/dtmi<1.5×10?5, where i?1 (2), where dn/dtpi is a relative refractive index temperature coefficient, of an i-th lens element having positive power included in an entire system for light in a wavelength range from 580 nm to 640 nm in air in a range from 0° C. to 20° C.

Abstract: An imaging lens system includes, in order from an object side: a first lens group consisting of at least one lens element having negative power; a second lens group having positive power and configured with a single lens element; and a third lens group having power, and the third lens group includes a lens element having positive power and a lens element having negative power. In addition, conditional expressions (1) and (2) shown below are simultaneously satisfied: ?1.2×10?5<dn/dtpi<0, where i?1 (1); ?1.0×10?6<dn/dtmi<1.5×10?5, where i?1 (2), where dn/dtpi is a relative refractive index temperature coefficient, of an i-th lens element having positive power included in an entire system for light in a wavelength range from 580 nm to 640 nm in air in a range from 0° C. to 20° C.

Abstract: A single focal length lens system which, in order from an object side to an image side, includes a first unit, an aperture diaphragm, and a second unit is provided. The second unit includes a cemented lens having positive optical power, and a joint surface of the cemented lens is an aspheric surface. The cemented lens satisfies a condition: |dn/dt1|MAX?2.67×10?5 (|dn/dt1|MAX: A Maximum Value of Absolute Values of Relative Refractive Index temperature coefficients in an atmosphere at 0 to 20° C. with respect to light having a wavelength range of 580 to 640 nm, which is calculated for each of lens elements constituting the cemented lens).

Abstract: A single focal length lens system which, in order from an object side to an image side, includes a first unit, an aperture diaphragm, and a second unit is provided. The second unit includes a cemented lens having positive optical power, and a joint surface of the cemented lens is an aspheric surface. The cemented lens satisfies a condition: |dn/dt1|MAX?2.67×10?5 (|dn/dt1|MAX: A Maximum Value of Absolute Values of Relative Refractive Index temperature coefficients in an atmosphere at 0 to 20° C. with respect to light having a wavelength range of 580 to 640 nm, which is calculated for each of lens elements constituting the cemented lens).

Abstract: A single focal length lens system which, in order from an object side to an image side, includes a first unit, an aperture diaphragm, and a second unit is provided. The second unit includes a cemented lens having positive optical power, and a joint surface of the cemented lens is an aspheric surface. The cemented lens satisfies a condition: |dn/dt1|MAX?2.67×10?5 (|dn/dt1|MAX: a maximum value of absolute values of relative refractive index temperature coefficients in an atmosphere at 0 to 20° C. with respect to light having a wavelength range of 580 to 640 nm, which is calculated for each of lens elements constituting the cemented lens).

Abstract: A single focal length lens system, in order from an object side to an image side, includes a first lens unit having optical power, an aperture diaphragm, and a second lens unit having positive optical power is provided. The first lens unit, in order from the object side to the image side, includes a first sub-lens unit having negative optical power, and a second sub-lens unit having positive optical power. The single focal length lens system satisfies the following condition: |dn/dt|MAX?2.67×10?5 (|dn/dt|MAX: a maximum value of absolute values of relative refractive index temperature coefficients in the atmosphere at 0 to 20° C. with respect to light having a wavelength range of 580 to 640 nm, which is calculated for each lens element constituting the second sub-lens unit).

Abstract: A single focal length lens system, in order from an object side to an image side, includes a first lens unit having optical power, an aperture diaphragm, and a second lens unit having positive optical power is provided. The first lens unit, in order from the object side to the image side, includes a first sub-lens unit having negative optical power, and a second sub-lens unit having positive optical power. The single focal length lens system satisfies the following condition: |dn/dt|MAX?2.67×10?5 (|dn/dt|MAX: a maximum value of absolute values of relative refractive index temperature coefficients in the atmosphere at 0 to 20° C. with respect to light having a wavelength range of 580 to 640 nm, which is calculated for each lens element constituting the second sub-lens unit).

Abstract: A single focal length lens system which, in order from an object side to an image side, includes a first unit, an aperture diaphragm, and a second unit is provided. The second unit includes a cemented lens having positive optical power, and a joint surface of the cemented lens is an aspheric surface. The cemented lens satisfies a condition: |dn/dt1|MAX?2.67×10?5 (|dn/dt1|MAX: a maximum value of absolute values of relative refractive index temperature coefficients in an atmosphere at 0 to 20° C. with respect to light having a wavelength range of 580 to 640 nm, which is calculated for each of lens elements constituting the cemented lens).