1. An inspection apparatus for an object sample positioned on a support, the inspection apparatus comprising: a light source that illuminates the object sample on which a pattern is formed; a detector configured to detect light reflected from the object sample illuminated by the light source, the detector obtains a plurality of sample images by shooting the object sample under a plurality of shooting conditions for the object sample, each of the plurality of sample images corresponding to a respective shooting condition and in each sample image a position on a surface of the object sample is associated with a brightness value; and a processing device configured to perform an inspection of the object sample based on a correlation between a reference brightness value of each of a plurality of reference images obtained by the detector and at least one of a dimension value of a surface in a height direction or an in-plane direction of a reference sample, wherein the processing device is configured to perform the inspection by (1) for each sample image determining a respective product of a brightness value of the sample image and a weighted parameter corresponding to the respective shooting condition of the sample image, (2) determining a sum of the respective products, and (3) comparing the sum to a threshold, each of the weighted parameters being based on a determined reference brightness value for the reference sample observed under the respective shooting condition associated with the weighted parameter.