Image processing apparatus and image processing method

An image processing apparatus comprising:

• an image acquisition unit that acquires a captured image of an object captured through an imaging lens;
• a coordinate transformation unit that performs coordinate transformation for the captured image such that a sagittal resolution in a direction tangent to circumference having a center of an imaging surface as an origin and a tangential resolution in a radial direction perpendicular to the tangential direction are close to each other at a designated spatial frequency;
• and
• a resolution enhancement processing unit that performs a rotationally-symmetric resolution enhancement process for the coordinate-transformed image,
• wherein, in a case in which the higher of the sagittal resolution and the tangential resolution at the designated spatial frequency is 1 in the coordinate-transformed image, the coordinate transformation unit performs the coordinate transformation such that the lower of the sagittal resolution and the tangential resolution is equal to or greater than 0.5, preferably equal to or greater than 0.75.

An image processing method that is performed in an image processing apparatus comprising an image acquisition unit, a coordinate transformation unit, and a resolution enhancement processing unit, the method comprising:

• an image acquisition step of allowing the image acquisition unit to acquire a captured image of an object captured through an imaging lens;
• a coordinate transformation step of allowing the coordinate transformation unit to perform coordinate transformation for the captured image such that a sagittal resolution in a direction tangent to circumference having a center of an imaging surface as an origin and a tangential resolution in a radial direction perpendicular to the tangential direction are close to each other at a designated spatial frequency;
• and
• a resolution enhancement processing step of allowing the resolution enhancement processing unit to perform a rotationally-symmetric resolution enhancement process for the coordinate-transformed image, and
• an inverse transformation step of performing inverse transformation of the coordinate transformation for the image subjected to the resolution enhancement process.