Signal beam

About: Signal beam is a research topic. Over the lifetime, 1881 publications have been published within this topic receiving 20717 citations.

Differential focus blade clearance probe

Abstract: An apparatus and a method for ascertaining a gap between a stationary member and a rotating member are disclosed. At least a reference beam and a signal beam, which have different focal lengths or which diverge/converge at different rates, are fixed to the stationary member and proximate to each other. The beams are projected across a gap between the stationary member and the rotating member toward the rotating member. The reference and signal beams are reflected by the translating member when it intersects the reference and signal beam, and the reflected reference and signal pulses are obtained. One or more features of the reflected reference pulse and the reflected signal pulse, such as a rise time of the pulses, a fall time of the pulses, a width of the pulses and a delay between the reflected reference pulse and the reflected signal pulse, among other factors, are obtained. The width of the gap is obtained using at least one of these factors.

Time sequence synthesis quasi-continuous optical fiber laser device

Abstract: The invention provides a time sequence synthesis quasi-continuous optical fiber laser device The device comprises a plurality of identical optical fiber laser device bodies, a laser power supply control pumping monitoring device and a signal beam combiner, wherein the laser power supply control pumping monitoring device is separately connected with the optical fiber laser device bodies, and used for sampling and displaying pumping optical pulse parameters of the optical fiber laser device bodies, and controlling, modulating and triggering corresponding delay for optical fiber laser device bodies without keeping time sequences, so that equal-interval time sequences is kept between the single-way pulse sequences, and time sequence synthesis of laser pulses is achieved; the input end of the signal beam combiner is separately connected with the output ends of the optical fiber laser device bodies, and the output end of the signal beam combiner outputs time sequence synthesized laser By means of the time sequence synthesis quasi-continuous optical fiber laser device, it can be ensured that output long pulse light beams of the optical fiber laser device bodies keep the time sequences on the time, pulse repetition frequency superposition can be achieved after simple beam combination of the signal beam combiner, the average power is effectively improved, and good light beam quality can be kept

Threshold effect for photorefractive light-induced scattering and signal beam amplification in doped LiNbO3 crystals

Abstract: In this article, we have studied experimentally the threshold effect of incident light intensity for the photorefractive light-induced scattering and signal beam amplification in doped LiNbO3 crystals. Our results show that the signal beam can be most effectively amplified for a specific pump light intensity when the threshold effect of incident light intensity for photorefractive light-induced scattering is taken into account in doped LiNbO3 crystals. Doping the LiNbO3 crystal with suitable concentration of Fe and damage-resistant dopants will provide an effective way to control the photorefractive properties of LiNbO3 crystal. We demonstrated the advantage of the fanning-noise-free double-doped photorefractive LiNbO3 crystals for three-dimensional storage. This method to suppress the fanning noise is very simple and convenient to practice.

Spatial coherence methods in undersea image formation and detection

Abstract: Methods for the formation of images in scattering media generally rely upon temporal or spatial methodologies. Holography is a common example of image formation exploiting the mutual coherence between a reference beam and a signal beam. The coherence allows the formation of an interference pattern that carries the signal information on a "spatial carrier". In order for the method to be of use, the medium in which the beams are carried must preserve the coherence or phase spatially across the beams and in relation to the reference beam. In water, the distance over which the phase may be preserved is dependent upon many factors, including turbulence induced refractive index variations, thermal gradient structure, and relative motion. If pathlength differences exceed the temporal coherence length of the beam, interference is not obtained and the method breaks down. Holographic imaging has been demonstrated underwater and coherence measurement techniques have been suggested. Generally, the demands of maintaining a spatially coherent bean at optical frequency is difficult over long range thereby limiting the usefulness of the technique for image formation in turbid media. The authors describe a variation of the spatial interferometric technique that relies upon projected spatial gratings with subsequent detection against a quasi-coherent return signal. The method is advantageous in not requiring temporal coherence between reference and signal beams. Coherency of the spatial beam allow detection of the direction return, while scattered light appears as a noncoherent noise term. The theoretical foundation of the method and initial results for turbid media are developed.