439,558 research outputs found
Microlenses immersed in nematic liquid crystal with electrically controllable focal length
A microlens immersed in a nematic liquid crystal cell has been constructed with avariable focal length which can be controlled by applying an analogue voltage to thenematic liquid crystal. The focal length is -910 ± 30 ? m with no electric field appliedand with an applied field the focal length can be varied from 380 ± 50 to 560 ± 20 ? malthough at present the lens performance is limited by aberrations. A microlens immersed in a nematic liquid crystal cell has been constructed with avariable focal length which can be controlled by applying an analogue voltage to thenematic liquid crystal. The focal length is -910 ± 30 ? m with no electric field appliedand with an applied field the focal length can be varied from 380 ± 50 to 560 ± 20 ? malthough at present the lens performance is limited by aberrations. 12 May 199
Torque-operated gradient-index axicon
We describe a gradient-index axicon based on twisting of crystals. We
demonstrate that the focal length of the axicon can be efficiently operated by
the torsion moment. The working analytical relations describing the focal
length of the axicon and its dependence on different geometrical parameters as
well as the torsion moment has been derived.Comment: 13 pages, 5 figure
Design of a variable-focal-length optical system
Requirements to place an entire optical system with a variable focal length ranging from 20 to 200 cm within a overall length somewhat less than 100 cm placed severe restrictions on the design of a zoom lens suitable for use on a comet explorer. The requirements of a wavelength range of 0.4 to 1.0 microns produced even greater limitations on the possibilities for a design that included a catadioptric (using mirrors and glass) front and followed by a zooming refractive portion. Capabilities available commercial zoom lenses as well as patents of optical systems are reviewed. Preliminary designs of the refractive optics zoom lens and the catadioptric system are presented and evaluated. Of the two, the latter probably has the best chance of success, so long as the shortest focal lengths are not really needed
Spectral slicing X-ray telescope with variable magnification
A telescope for viewing high frequency radiation (soft X-ray, extreme ultraviolet) is described. This telescope has a long focal length with a selection of magnifications despite a short housing. Light enters the telescope and is reflected by the telescope's primary optical system to one of several secondary mirrors at different locations on a movable frame. The secondary mirrors have varying degrees of magnification and select narrow spectral slices of the incident radiation. Thus, both the magnification and effective focal length field of view and wavelength can be altered by repositioning the moving frame. Configurations for spaceborne applications are discussed
A magnetic lens for cold atoms controlled by a rf field
We report on a new type of magnetic lens that focuses atomic clouds using a
static inhomogeneous magnetic field in combination with a radio-frequency
field. The experimental study is performed with a cloud of cold cesium atoms.
The rf field adiabatically deforms the magnetic potential of a coil and
therefore changes its focusing properties. The focal length can be tuned
precisely by changing the rf frequency value. Depending on the rf antenna
position relative to the DC magnetic profile, the focal length of the atomic
lens can be either decreased or increased by the rf field
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