Spatial filter

About: Spatial filter is a research topic. Over the lifetime, 6170 publications have been published within this topic receiving 100451 citations.

Achromatic self-referencing interferometer

Abstract: A self-referencing Mach-Zehnder interferometer for accurately measuring laser wavefronts over a broad wavelength range (for example, 600 nm to 900 nm). The apparatus directs a reference portion of an input beam to a reference arm and a measurement portion of the input beam to a measurement arm, recombines the output beams from the reference and measurement arms, and registers the resulting interference pattern ("first" interferogram) at a first detector. Optionally, subportions of the measurement portion are diverted to second and third detectors, which respectively register intensity and interferogram signals which can be processed to reduce the first interferogram's sensitivity to input noise. The reference arm includes a spatial filter producing a high quality spherical beam from the reference portion, a tilted wedge plate compensating for off-axis aberrations in the spatial filter output, and mirror collimating the radiation transmitted through the tilted wedge plate. The apparatus includes a thermally and mechanically stable baseplate which supports all reference arm optics, or at least the spatial filter, tilted wedge plate, and the collimator. The tilted wedge plate is mounted adjustably with respect to the spatial filter and collimator, so that it can be maintained in an orientation in which it does not introduce significant wave front errors into the beam propagating through the reference arm. The apparatus is polarization insensitive and has an equal path length configuration enabling measurement of radiation from broadband as well as closely spaced laser line sources.

Frequency-resolving spatiotemporal wave-front sensor

Abstract: We report on a high-resolution wave-front sensor that measures the complete spatial profile of any frequency component of a laser field containing multiple frequencies. This probe technique was developed to address the necessity of measuring the spatial overlap of the carrier field with each sideband component of the field exiting the output port of a gravitational-wave interferometer. We present the results of an experimental test of the probe, where we were able to construct the spatial profile of a single radio-frequency sideband at the level of -50 dBc.

Anti-aliasing spatial filter system

Abstract: A sensor module for an image capture device including an image sensor and a filter system, the image capture device having a high resolution mode of operation and one or more lower resolution modes of operation; the filter system includes an adjustable spatial filter associated with the optical path of the image capture device having an adjustable optical structure which in response to a first signal causes the adjustable spatial filter to be effective in a high resolution mode of operation and in response to a second signal causes the adjustable spatial filter to be effective in a lower resolution mode of operation.

Random access high-speed confocal microscope

Abstract: Disclosed herein is a confocal imaging system (5) for imaging a specimen. The system comprises a light source (10), a light deflector (20) capable of positioning a beam of light (15) produced by the light source at one of a series of predetermined points on the specimen (30), an addressable spatial filter (60) selectively filtering light from the specimen, and a central processing unit (40) capable of providing selective position control to the light deflector (20) and the addressable spatial filter (60).

Coherent optical processor apparatus with improved fourier transform plane spatial filter

Abstract: A line pattern or fingerprint ridge pattern identification apparatus employs coherent optical processing techniques wherein the line or ridge orientations and spacings in a plurality of preselected finite areas of the fingerprint are inspected by means of a rotating spatial filterdisposed in the Fourier transform plane of the optical processor for cyclically selecting distinct components of the Fourier transform for transmission to the image plane of the processor in which is disposed a plurality of photodetectors each corresponding to a discrete sampled area of the print. The time delays between a reference orientation of the spatial filter and the blocking and unblocking of light transmitted therethrough toward each photodetector are noted. These values are processed to provide proportional representations thereof for storage and for subsequent comparison with similarly obtained signals representative of ridge line orientation and separation of a fingerprint presented for identification.