Digital microscope for capturing images of a sample to be microscopically examined with an extended depth of field; comprising: - a stand with an opening for receiving an optical unit, wherein the opening of the stand shows a circular cross section; and - an optical unit comprising: o an objective for gathering light from the sample to be microscopically examined; o an image sensor for converting an image transferred from the objective to the image sensor into an electrical signal; o a microelectromechanical optical system on an optical path from the objective to the image sensor, wherein microelectromechanical optical system is configured for extending a depth of field at the optical path; and o a mounting unit comprising a first portion for removable mounting the mounting unit into the opening of the stand, a second portion for removable mounting an illumination unit onto the mounting unit, and a third portion for removable mounting an additional lens onto the mounting unit into an optical axis of the objective; wherein the first portion of the mounting unit shows a circular cross section that fits into the circular cross section of the opening of the stand; wherein the first portion of the mounting unit is of cylindrical shape; wherein the second portion of the mounting unit is of cylindrical shape; wherein the first portion and the second portion of the mounting unit are arranged coaxially; wherein a diameter of the first portion of the mounting unit is larger than a diameter of the second portion of the mounting unit; and wherein the third portion of the mounting unit is formed as a part of a bayonet mount for receiving a counterpart of the bayonet mount that is formed at the additional lens. - a stand with an opening for receiving an optical unit, wherein the opening of the stand shows a circular cross section; and - an optical unit comprising: o an objective for gathering light from the sample to be microscopically examined; o an image sensor for converting an image transferred from the objective to the image sensor into an electrical signal; o a microelectromechanical optical system on an optical path from the objective to the image sensor, wherein microelectromechanical optical system is configured for extending a depth of field at the optical path; and o a mounting unit comprising a first portion for removable mounting the mounting unit into the opening of the stand, a second portion for removable mounting an illumination unit onto the mounting unit, and a third portion for removable mounting an additional lens onto the mounting unit into an optical axis of the objective; wherein the first portion of the mounting unit shows a circular cross section that fits into the circular cross section of the opening of the stand; wherein the first portion of the mounting unit is of cylindrical shape; wherein the second portion of the mounting unit is of cylindrical shape; wherein the first portion and the second portion of the mounting unit are arranged coaxially; wherein a diameter of the first portion of the mounting unit is larger than a diameter of the second portion of the mounting unit; and wherein the third portion of the mounting unit is formed as a part of a bayonet mount for receiving a counterpart of the bayonet mount that is formed at the additional lens. o an objective for gathering light from the sample to be microscopically examined; o an image sensor for converting an image transferred from the objective to the image sensor into an electrical signal; o a microelectromechanical optical system on an optical path from the objective to the image sensor, wherein microelectromechanical optical system is configured for extending a depth of field at the optical path; and o a mounting unit comprising a first portion for removable mounting the mounting unit into the opening of the stand, a second portion for removable mounting an illumination unit onto the mounting unit, and a third portion for removable mounting an additional lens onto the mounting unit into an optical axis of the objective; wherein the first portion of the mounting unit shows a circular cross section that fits into the circular cross section of the opening of the stand; wherein the first portion of the mounting unit is of cylindrical shape; wherein the second portion of the mounting unit is of cylindrical shape; wherein the first portion and the second portion of the mounting unit are arranged coaxially; wherein a diameter of the first portion of the mounting unit is larger than a diameter of the second portion of the mounting unit; and wherein the third portion of the mounting unit is formed as a part of a bayonet mount for receiving a counterpart of the bayonet mount that is formed at the additional lens.