Patent ID: 7554724

Claim:
A microscope lens barrel comprising: a collecting lens; and a deflecting optical system that deflects observation light emitted from the collecting lens, the deflecting optical system including: one of a deflecting prism having a triangular cross-section surrounded by first, second, and third planes, and three mirrors respectively having the first, second, and third planes, and one of a plane mirror and a deflecting prism each having a fourth plane, wherein: the first plane transmits the observation light incident from the collecting lens along a first optical axis and reflects the observation light incident at an angle from the second plane along a third optical axis, the second plane reflects the light on the first optical axis transmitted through the first plane and makes the reflected light incident on the first plane at the angle along a second optical axis, the third plane reflects the light on the third optical axis reflected by the first plane in a direction of a second plane side along a fourth optical axis, and the fourth plane reflects the light on the fourth optical axis reflected by the third plane in a direction substantially perpendicular to an optical axis of the collecting lens and in a direction from the optical axis of the collecting lens toward a third plane side along a fifth optical axis.