Endoscope apparatus

1. An endoscope apparatus having a function of switching between a 2-D observation for a planar view and a 3-D observation for a stereoscopic view, comprising:

an image Processor which carries out processing of reducing a distortion of an image pickup optical system for an image pickup signal achieved by an image pickup element of the endoscope apparatus at the time of the 3-D observation, wherein

the image Processor carries out image processing that satisfies the following conditional expression (1):

0.1 <B/A <0.8, as well as A< 0  (1)

where,

A denotes a distortion at the maximum image height at the time of the 2-D observation, and

B denotes a distortion at the maximum image height at the time of the 3-D observation.

2. The endoscope apparatus according to claim 1 , wherein the following conditional expression (2) is satisfied:

0.6< D/C≤ 1 as well as 100 degrees< C   (2)

where,

C denotes the maximum angle of view at the time of the 2-D observation, and

D denotes the maximum angle of view at the time of the 3-D observation.

3. The endoscope apparatus according to claim 2 , wherein the image Processor reduces the distortion according to the following conditional expression (3):

Y=E×X 3 +F×X 2 +G×X+H   (3)

where,

for the maximum value of X, 0.4<Y<0.8,

X denotes an image height before image processing,

Y denotes (the image height before image processing)/(an image height after image processing), and

E, F, G, and H denote coefficients.

4. The endoscope apparatus according to claim 1 , wherein the following conditional expression (4) is satisfied:

−0.7< B<− 0.1  (4)

where,

B denotes the distortion of the maximum image height at the time of the 3-D observation.