Phase difference observation apparatus and cell treatment apparatus

A phase difference observation apparatus, comprising:

• a light source;
• an illumination guide that guides illumination light from the light source to an observation target object in a cell culture vessel;
• an optical imager that forms an optical image of the observation target object on an image sensor;
• and
• a central processing unit,
• wherein the optical imager comprises:
• a phase plate, and
• an imaging lens,
• wherein the illumination guide comprises:
• a spatial modulator that changes an intensity distribution of the illumination light,
• wherein the central processing unit:
• stores intensity distribution correction information associating a position of the optical imager with respect to the cell culture vessel and an intensity distribution of the illumination light that is included in a phase plate image, formed upon a phase plate imaging lens being inserted between the imaging lens and the image sensor, at the position of the optical imager with respect to the cell culture vessel,
• acquires position information of the optical imager, and
• changes an intensity distribution of illumination light in the spatial modulator on a basis of the position information of the optical imager and the intensity distribution correction information to include an illumination light image in the phase plate image with an optical conjugation of the spatial modulator and the phase plate.