Patent ID: 7344246

Claim:
An observation apparatus, comprising: a variable lens system for changing an observation magnification for observing an eye to be observed, which is an observation object; and an imaging lens for imaging a light flux passing through the variable lens system, the variable lens system and the imaging lens being disposed on one or more observation optical paths between an objective lens opposed to the eye to be observed and eyepieces, an observation optical path which is for relaying a reflection light flux on the eye to be observed as a parallel light flux to the variable lens system, being formed between the objective lens and the variable lens system in the observation optical paths, an observation optical path, which is for relaying the reflection light flux obtained through the variable lens system as a parallel light flux to the imaging lens, being formed between the variable lens system and the imaging lens in the observation optical paths, wherein an astigmatism canceling optical element for canceling power of astigmatism that occurs when a predetermined optical member is placed between the eye to be observed and the objective lens, is provided on the observation optical paths, wherein the astigmatism canceling optical element comprises a variable cross cylinder lens composed of a pair of concave cylinder lens and a convex cylinder lens, which are provided to be relatively rotatable about an observation optical axis of the observation optical path, wherein the predetermined optical member placed between the eye to be observed and the objective lens includes a prism fit in contact with a cornea of the eye to be observed, wherein the observation apparatus further comprises: apex angle input means for inputting an apex angle of the prism; fitting angle input means for inputting a fitting angle of the prism to the cornea; drive means for independently rotating right and left respectively the variable cross cylinder lenses; and control means for independently controlling rotation of the right and left variable cross cylinder lenses by the drive means based on the apex angle inputted by the apex angle input means and the fitting angle inputted by the fitting angle input means.