JP2004341512A5 - - Google Patents

Claims (10)

  In order from the object side, a positive meniscus lens having a convex surface facing the object side as the first lens, an aperture stop, a meniscus lens having a convex surface facing the image side as the second lens, and the image side as the third lens An imaging optical system comprising: a positive meniscus lens having a convex surface facing to a negative lens as a fourth lens. The imaging optical system according to claim 1, wherein at least one surface of the fourth lens is an aspherical surface and satisfies the following conditional expression.
−2.0 <φm / φp <0
However, [phi] m, the at the maximum ray height position the fourth lens power, .phi.p is the power of the fourth lens in the paraxial. An image forming optical system, wherein the third lens and the fourth lens are made of plastic and satisfy the following conditional expression:
15.0 <ν3-ν4 <40.0
However, .nu.3 the Abbe number of the third lens, .nu.4 is the Abbe number of the fourth lens. 2. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied, where Fno is an open F number of the imaging optical system and P is a pixel interval of the imaging element.
0.40 [1 / μm] <Fno / P [μm] <2.20 [1 / μm] The following conditional expression is satisfied, where TL is a total length of the imaging optical system, and ML is a minimum axial thickness of a plastic lens constituting the imaging optical system. Imaging optical system.
0.02 <ML / TL <0.20 The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
0.1 <r1f / f <2.0
  Here, r1f is the radius of curvature of the first lens on the object side, and f is the focal length of the entire imaging optical system. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
0.5 <f123 / | f4 | <3.0
1.0 <f / | f4 | <5.0
  Here, f123 is a combined focal length of the first lens, the second lens, and the third lens, f4 is a focal length of the fourth lens, and f is a focal length of the entire imaging optical system.
The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
0 <f1 / f234 <3.0
  Here, f1 is a focal length of the first lens, and f234 is a combined focal length of the second lens, the third lens, and the fourth lens. The imaging optical system according to claim 1, comprising four lenses. An electronic apparatus comprising the imaging optical system according to claim 1.