FOCAL POSITION ESTIMATION SYSTEM, FOCAL POSITION ESTIMATION METHOD, FOCAL POSITION ESTIMATION PROGRAM, SEMICONDUCTOR INSPECTION SYSTEM AND BIOLOGICAL OBSERVATION SYSTEM

A focal position estimation system is a system for estimating a focal position when in focus corresponding to an estimation target image, and includes: an estimation target image acquisition unit that acquires an estimation target image; and a focal position estimation unit that outputs a feature quantity of the estimation target image from the estimation target image by using a feature quantity output model and estimates a focal position when in focus corresponding to the estimation target image from the output feature quantity, wherein the feature quantity output model is generated by machine learning from a plurality of learning images associated with focal position information related to a focal position at the time of imaging, and feature quantities of two different learning images are compared with each other according to focal position information associated with the two different learning images, and machine learning is performed based on the comparison result.