Microscopes have large amounts of magnification over a very small image plane, so the highest precision target is required.
Imatest provides a variety of chrome on glass test slides in the standard 75mm x 25mm (3″ x 1″) format.
Multi-Size Resolution Test Slides
Depending on what range of working distances, and what sorts of details you need, different slides may work better. Checkerboard provides the most detail about sharpness and distortion. dot pattern provides highly detailed maps of chromatic aberration. The micro-multi slide target provides both of these features. SFRplus is sensitive to vertical framing of the target within the image, but operates an higher speeds and can resist large amounts of defocusing while still detecting properly. eSFR ISO complies with ISO standards and provides wedge patterns for measurement of limiting resolutions which is ideal for measuring systems where sharpening cannot be disabled.
This slide provides a variety of color and tone test targets that can be used across manu different fields of views. Complete spectral transmittance reference data is included for all patches. This can be analyzed with the imatest multicharts module as a general mxn test target.