Patent ID: 6124967
Filing Date: 2000-09-26
Classification: G02B

Abstract:
An apparatus for observing an object comprising:an illuminating optical system for illuminating an object to be observed with visible light;an observing optical system for observing the object positioned within a visual field illuminated by said illuminating optical system;an index projecting optical system for projecting index for focus by luminous flux having wavelength of a visible area, the index projecting optical system having projecting luminous flux at least a part of which is common with a wavelength of illumination luminous flux of said illuminating optical system;a first luminous flux restricting means for cutting an illuminating light of the illuminating optical system;a second luminous flux restricting means for cutting a projecting light of the index projecting optical system;means for controlling said first luminous flux restricting means and said second luminous flux restricting means so that the illuminating light and the projecting light do not overlap with each other on said object, and for controlling the period the illuminating light is off and the projecting light is on such that the projecting light is imperceptible as an after image to a normal human eye; andmeans for restricting luminous flux of index by intermittently projecting index light from said index projecting optical system, each projecting time being set so that no photogene occur in an examiner's eye;means for restricting luminous flux of illumination by intermittently conducting illumination by said illuminating optical system when index projection is not conducted, and by restricting the time for not illuminating to a periodmeans for detecting an image of focus index projected on said object, said means being capable of detecting luminous flux of visible wavelength;wherein relative distance of said object with respect to the focus index is changed based on the results detected by said detecting means.