Proposed is an ophthalmic lens doublet for indirect ophthalmoscopy. The doublet is cemented into an integral unit from two lens elements, of which is a convex-convex lens element and another is a convex-concave lens element. Both lens elements have external and internal surfaces and may be combined so that the ophthalmic lens doublet has asphericity either on one side or on both sides of the unit. The aspheric surface is characterized by asphericity Z of the following formula (1)
Z=Y.sup.2/{R+[R.sup.2(1+k)Y.sup.2].sup.1/2}(1),
where Z is in one of coordinates in a Cartesian coordinate system, Y is a second coordinate in the Cartesian coordinate system, R and k being variable parameters which are different for each selected values of d, where d is an outer diameter of the ophthalmic lens doublet.

An optical member includes a lens array including lens bodies, and transmissive members. The transmissive members are made of a material having a uniform refractive index, and are disposed at positions nearer an object to be read or at positions farther from the object to be read than the corresponding lens bodies are disposed. The transmissive members have a columnar shape extending along the optical axes of the lens bodies, and allow light incident through one end faces to exit through the other end faces. The optical axes of the lens bodies are deviated from the central axes of the transmissive members corresponding to the respective lens bodies at least in the sub-scanning direction, and an end face of the transmissive member to which an end face of each lens body is opposed is thereby an end face of the corresponding transmissive member.

Proposed is an ophthalmic lens doublet for indirect ophthalmoscopy. The doublet is cemented into an integral unit from two lens elements, of which is a convex-convex lens element and another is a convex-concave lens element. Both lens elements have external and internal surfaces and may be combined so that the ophthalmic lens doublet has asphericity either on one side or on both sides of the unit. The aspheric surface is characterized by asphericity Z of the following formula (1)

Z=Y.sup.2/{R+[R.sup.2(1+k)Y.sup.2].sup.1/2}(1),

where Z is in one of coordinates in a Cartesian coordinate system, Y is a second coordinate in the Cartesian coordinate system, R and k being variable parameters which are different for each selected values of d, where d is an outer diameter of the ophthalmic lens doublet.

A method for improving an OCT image of an object such as the retina of an eye, using optical coherence tomography by an imaging beam path. In order to suppress shadowing effects due to a surgical instrument moved in the imaging beam path, a time series of OCT images is produced. For an OCT image to be corrected, an area of the object lying in the image and shadowed by the instrument is determined. Another earlier OCT image in which the area of the object is not shadowed is searched in the time series. Image information for the area of the object is read from the earlier OCT image. A corrected OCT image is produced by inserting the read-image information into the OCT image to be corrected, wherein in the OCT image to be corrected, the image information replaces the area of the object which is shadowed by the instrument.

A white light interference microscope includes an imaging part taking interference images, a laser light source, a light receiving part receiving reflected light of laser beam from a sample via a confocal optical system and generating a light reception signal corresponding to the light receiving intensity of the reflected light, a focal calculation part calculating a focal position matching a focus of the objective lens with a surface of the sample based on the light reception signal at each height position of the stage or the objective lens, a focus adjustment part adjusting the height position of the stage or the objective lens to match with the focal position, and a first measuring part measuring the surface shape of the sample based on a plurality of interference images taken by the imaging part at a plurality of height positions defined within a height range including the focal position.

A lens unit includes: an imaging optical system; and a lens barrel holding the imaging optical system. The imaging optical system includes, in order from an object side: a first lens having a positive refractive power; a second lens including at least one surface having an aspherical shape; and a third lens having a negative refractive power, at least one surface having an aspherical shape, and an inflection point other than an intersection with an optical axis.

An image pickup apparatus includes an image forming optical system which includes an aperture stop that determines an axial light beam, and one cemented lens, and an image pickup section which is disposed on an image side of the image forming optical system, and which has a surface which is not flat and is curved to be concave toward the image forming optical system, wherein the cemented lens includes in order from an object side, a first lens having a negative refractive power, a second lens, and a third lens having a positive refractive power.

An image pickup apparatus includes an image forming optical system which includes an aperture stop that determines an axial light beam, and one cemented lens, and an image pickup section which is disposed on an image side of the image forming optical system, and which has a surface which is not flat and is curved to be concave toward the image forming optical system, wherein the cemented lens includes in order from an object side, a first lens having a negative refractive power, a second lens, and a third lens having a positive refractive power.

In a propagation optical system to propagate light from an image display element to a light guide element, the propagation optical system includes: a prism having a first surface having negative power to which light emitted from the image display element enters; and a lens group having positive power. The prism and the lens group are arranged between the image display element and the light guide element along an optical axis, and the prism is closer to the image display element than to the light guide element.

In a propagation optical system to propagate light from an image display element to a light guide element, the propagation optical system includes: a prism having a first surface having negative power to which light emitted from the image display element enters; and a lens group having positive power. The prism and the lens group are arranged between the image display element and the light guide element along an optical axis, and the prism is closer to the image display element than to the light guide element.