Observation device that controls numerical aperture in accordance with specified observation scope

An observation device for observing an object, the observation device comprising:

• an imaging optical system that forms an image based on light from the object;
• a numerical aperture changing unit that changes a numerical aperture on an emission side of the imaging optical system;
• an imaging device that converts the image of the object into image signals, the image of the object being formed by the imaging optical system;
• an observation scope changing unit that performs an observation scope changing process in which an observation scope is changed to a specified scope by changing an extraction scope, the extraction scope being a scope from which the image signals obtained by the imaging device are extracted;
• a display that displays the image signals from the specified scope obtained through the observation scope changing process;
• and
• a hardware processor that controls the numerical aperture changing unit in accordance with the specified observation scope,
• wherein:
• the image signals are converted through one detection performed by the imaging device,
• the observation scope changing unit adjusts a pixel pitch of the image signals after the observation scope changing process in a pseudo manner such that the display displays the extraction scope for the image signals in a pixel-to-pixel display,
• the hardware processor controls the numerical aperture changing unit based on a numerical aperture in accordance with the pixel pitch, and
• the observation device satisfies a conditional expression of
• 2≤1.22×λ/(NAI1×P)
• where P is a pixel pitch of the imaging device selected in accordance with the specified observation scope, λ is an observation wavelength used by the observation device, and NAI1 is the numerical aperture on the emission side of the imaging optical system.