A diffraction bifocal lens or lens system, comprising two profiled surfaces or interfaces or a linear combination thereof, wherein one profile provides for the bifocality of the lens and the other profile compensates for chromatic aberration. These lenses or lens systems exhibit two focal points, one which exhibits positive chromatic aberration and the other which exhibits negative chromatic aberration.
The invention has for its object to reduce the overall length of a single lens using a diffractive optical element, and provides a diffractive optical element applicable to an optical system for cameras such as silver salt cameras, and electronic cameras, in which both surfaces of the single lens are constructed of diffractive surfaces, are plane surfaces or have curvature, and comprise diffractive surfaces having, in order from a subject side thereof, positive power and positive power, positive power and negative power, and negative power and positive power.
Disclosed is a diffractive optical element which is made of at least two materials of different dispersions and which includes at least two diffraction gratings being accumulated one upon another, wherein each diffraction grating is formed on a curved surface of a substrate, and wherein a diffraction grating, of the at least two diffraction gratings, in which a curvature radius of the curved surface and a curvature radius of a grating surface in a portion where a grating pitch is largest, have different signs, is one of the at least two diffraction gratings which has a smallest grating thickness.
An optical system is provided for a FLIR mounted in a cylindrical turret ch has five folding mirrors, two doubling as scanning mirrors, numerous lenses with aspherical surfaces and different refractive indices, and a rotatable head mirror. Some of the lenses and mirrors being mounted on remote controlled electrically powered focusing or scanning means.
An objective lens for condensing a light beam, has at least one of annular grooves and ridges producing a phase difference. Each of the annular groove and ridge is formed concentrically on at least one of an incident surface which said light beam is introduced, and an emission surface which said light beam is emitted.
According to the invention the ophthalmic lens further comprises a refractive part comprising at least one surface, which is configured to compensate a passing wavefront at least partly for at least one type of monochromatic aberration introduced by at least one of the optical parts of the eye. Said diffractive part is capable of compensating a passing wavefront at least partly for chromatic aberration introduced by at least one of the optical parts of the eye. Furthermore said refractive and diffractive parts together contribute to a required power of the lens.
