Abstract:
An improved mirror scan control for driving a movable mirror (14) in an interferometer with a constant scan velocity comprises a closed loop servo control which provides constant velocity mirror scan in response to a phase comparison of a signal derived from the beat frequency of a two frequency laser beam (16) passing through the interferometer and a selected frequency reference signal, wherein the difference in frequencies or beat frequency of the two frequency laser beam is stabilized at a specified difference in frequencies. The mirror scan control employs a phase lock control loop which locks the frequency of the referenced signal with the frequency of the signal derived from the laser beam to provide precise mirror velocity control.
Abstract:
Fiber optic probe assembly is provided. The probe comprises a first optical system and a second optical system, a delivery light guide comprising one or more than one delivery optical fiber for transmitting excitation radiation from a radiation source disposed at a proximal end of the light guide to the first optical system. The first optical system comprising one or more than one first optical element for forming a substantially collimated illumination beam from the excitation radiation. An optically opaque tubular sleeve is fitted over the first optical system to optically isolate the first optical system and the delivery light guide from the second optical system. The second optical system comprising one or more than one second optical element for gathering optical radiation scattered from a sample and forming the optical radiation into a collection beam. A collection light guide comprising one or more than one collection optical fiber receives the collection beam and transmits the collection beam to an analyzer. The first and second optical systems are disposed within a housing so that an emission cone of the first optical system and an acceptance cone of the second optical system substantially overlap. A spectroscopic measurement system comprising the optic fiber probe is also provided.
Abstract:
Low aberration relay systems modified to perform as spatial filters in reflectometer, spectrophotometer, ellipsometer, polarimeter and the like systems.
Abstract:
The present invention provides methods and compositions for attenuating expression of a target gene in vivo. In general, the method includes administering RNAi constructs (such as small-interfering RNAs (i.e., siRNAs) that are targeted to particular mRNA sequences, or nucleic acid material that can produce siRNAs in a cell), in an amount sufficient to attenuate expression of a target gene by an RNA interference mechanism, e.g., in a sequence-dependent, PKR-independent manner. In particular, the subject method can be used to alter the growth, survival or differentiation of cells for therapeutic and cosmetic purposes.
Abstract:
A Littrow-type spectrometer or monochromator using a folded light path to provide a compact optical instrument is disclosed. Light enters the instrument through an inlet aperture on a planar mirror. The aperture is located at the focus of a parabolic collimetor mirror. Collimated light reflected by the parabolic miror is reflected back to the planar mirror, which is positioned at an angle to the collimated light. The light reflected from the planar mirror is directed at a planar grating that produces diffracted light having all the wavelengths input into the system, including light of a selected wavelength, back towards the planar mirror. Light having the selected wavelength is thus caused to fall on the parabolic mirror. The parabolic mirror then focuses the selected wavelength of light ont a light exit aperture that is juxtaposed to the inlet light aperture. The planar grating can be rotatably mounted to scan the input light spectrum.
Abstract:
An electron microscope (10) is adapted to enable spectroscopic analysis of a sample (16). A parabolic mirror (18) has a central aperture (20) through which the electron beam can pass. The mirror (18) focuses laser illumination from a transverse optical path (24) onto the sample, and collects Raman and/or other scattered light, passing it back to an optical system (30). The mirror (18) is retractable (within the vacuum of the electron microscope) by a sliding arm assembly (22). An adjustable kinematic mount (44) defines the inserted position of the parabolic mirror (18). A second parabolic mirror (104) is provided to direct the scattered or generated light towards an optical analyser. The parabolic mirrors are positioned in an aberration cancelling orientation and such that they compensate for inaccuracies in the position of the sliding arm assembly (22).