Imaging optical system for image sensor

1. An imaging optical system for an image sensor, the imaging optical system comprising:

a stop and a first lens sequentially arranged from an object side,

wherein the first lens has aspherical surfaces on both sides and has a positive refractive power, a first surface of the first lens which faces the object side is a convex surface and a second surface of the first lens which faces an image side is a convex surface, and the imaging optical system satisfies the following inequality,

1.0 <C T /E T <1.4,

where C T denotes a thickness of the first lens on a center portion of the first lens, and E T denotes a thickness of the first lens on an edge portion of an effective aperture of the first lens.

2. The imaging optical system of claim 1 , wherein the following inequalities are satisfied:

1.1 <L B /f< 1.5

1.0 <L T /L B <1.4,

where L T represents a distance along an optical axis from a surface of the stop facing the object side to an image surface, f represents an entire focal distance of the focusing optics, and L B represents a distance along the optical axis from the first surface to the image surface.

3. The imaging optical system of claim 1 , wherein the following inequality is satisfied:

0.18≦S≦0.3,

where S denotes a distance of the optical axis from the stop to the first surface of the first lens.

4. The imaging optical system of claim 1 , wherein the following inequality is satisfied:

0.5

<



R

1



f

<

0.9

,

where R 1 denotes a curvature of the first surface of the first lens, and f denotes the entire focal distance of the focusing optics.

5. The imaging optical system of claim 1 , wherein the following inequality is satisfied:

0.35 <C T /f< 0.57,

where C T denotes a thickness of a center portion of the first lens, and f denotes the entire focal distance of the focusing optics.

6. The imaging optical system of claim 1 , wherein the first lens is formed from an infrared absorbing glass.