Spatial filter

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

Spatial filter pinhole for high-energy pulsed lasers.

Abstract: Spatial filters are essential components for maintaining high beam quality in high-energy pulsed laser systems. The long-duration (21 ns) high-energy pulses envisioned for future inertial-confinement fusion drive systems, such as the U.S. National Ignition Facility (NIF), are likely to lead to increased plasma generation and closure effects within the pinholes in the spatial filters. The design goal for the pinhole spatial filter for the NIF design is to remove small-angle scatter in the beam to as little as a ±100-μrad divergence. It is uncertain whether this design requirement can be met with a conventional pinhole design. We propose a new pinhole architecture that addresses these issues by incorporating features intended to reduce the rate of plasma generation. Initial experiments with this design have verified its performance improvement relative to a conventional pinhole design.

Fingerprint identification apparatus

Abstract: A coherent optical processor fingerprint identification apparatus in which identification is established by correlating an optical beam pattern representative of the finger to be identified with a prerecorded Fourier transform spatial filter of the fingerprint. Reliability of identification is improved by incorporating a mask in the processor so that the detector receives information primarily indicative of the correlation between certain features of the fingerprint and the spatial filter to the exclusion of other less significant features. Further improvement is achieved by means of dual detector affirmation-negation type signal processing techniques and, in the particular case of holographic filters various multiplexing techniques are also utilized for signal enhancement.

Gaussian Schell-model beams generated with synthetic acousto-optic holograms

Abstract: The recently introduced concept of a synthetic acousto-optic hologram [ J. Appl. Phys.67, 49 ( 1990)] is applied to convert a Gaussian laser beam into a partially coherent anisotropic Gaussian Schell-model (AGSM) beam. Real-time reconfigurability of the coherence properties is achieved by this technique, which features scattering of the laser beam by an electronically synthesized, digitally phase-modulated volume grating that propagates in an acousto-optic Bragg cell. The coherence and intensity distributions of the fields obtained by different types of phase modulation are investigated theoretically. We demonstrate some particularly interesting AGSM sources and fields: a secondary elliptical AGSM source with a circularly symmetric far-field intensity distribution and an AGSM field that retains the eccentricity of its intensity profile in the propagation through any centrosymmetric (paraxial) optical system.

Telecentric Scale Projection System for Real-Time In-Situ Surgical Metrology

Abstract: A system and method for determining endoscopic dimensional measurements including a projector assembly comprising a light source for projecting light through a telecentric lens and into a surgical site, and a mask coupled to the projector assembly. Light projected from the light source projects through the mask. The projected light through the mask may be a collimated pattern which does not significantly change in size as a function of the distance to a projected plane. The projected light patterns may include multiple wavelengths of light for measurements of different features of tissue and may be produced using a laser in conjunction with a light shaping optical diffuser, or using a light emitting diode in conjunction with a light shaping optical diffuser, or using a spatial filter. The projected light patterns may take the form of concentric rings with each ring representing a radius of a given dimension.