Lens-barrel device and microscope system

A microscope system comprising:

• a microscope body;
• an objective;
• an eyepiece;
• an imaging device;
• and
• a lens-barrel device that is attachable to the microscope body,
• wherein the lens-barrel device includes:
• an eyepiece sleeve that the eyepiece is attachable to;
• an imaging lens that a light flux from the microscope body is made incident on, the lens-barrel device having been attached to the microscope body;
• a relay optical system that relays a primary image to an object plane of the eyepiece attached to the eyepiece sleeve, and forms a secondary image, the primary image having been formed by the imaging lens;
• a first reflection optical system that reflects and bends the light flux from the imaging lens in a first horizontal direction;
• a second reflection optical system that is disposed on a first horizontal plane where the first reflection optical system is disposed, the second reflection optical system reflecting and bending the light flux that has passed through the first reflection optical system, in a vertically upward direction;
• a third reflection optical system that is disposed on a second horizontal plane that is different from the first horizontal plane, the third reflection optical system reflecting and bending the light flux that has passed through the second reflection optical system, in a second horizontal direction;
• an additional optical system that transmits the light flux for forming an image that is different from the secondary image, on the object plane of the eyepiece;
• and
• an optical element that is disposed on the second horizontal plane, and guides the light flux from the additional optical system to a light path to the object plane of the eyepiece.