Showing papers on "Bessel beam published in 1994"

Holographic nondiverging hollow beam.

Abstract: A simple holographic technique is used to generate a nondiverging hollow beam, which is similar to a ${\mathit{J}}_{1}$ Bessel beam. The hollow beam is obtained from a Gaussian beam with a high conversion efficiency (greater than 50%). We describe briefly the merit of this hollow beam, which has potential applications in particle collimation.

Laser scanning optical system using axicon.

Abstract: A laser scanning optical system is so arranged to comprise an optical converting unit, an optical scanning unit, and an optical converging unit. Here, the optical converting unit is composed of two axicon prisms which are arranged such that apexes thereof are opposed forward or backward to each other at a predetermined distance and optical axes thereof are coincident with each other and which are made of respective materials having a same refractive index and shaped with a same apical angle. By this, the laser beam incident into the optical converting unit becomes a cylindrical ray bundle having an annular cross-sectional intensity perpendicular to the optical axis. Therefore, the cylindrical ray bundle is changed in the traveling direction by the optical scanning unit to be scanned and is then converged by the optical converging unit to become a Bessel beam having a high energy utilization factor, a high resolution and a long focal depth.

Laser scan optical system and laser scan optical apparatus

Abstract: PURPOSE:To obtain an optical system and an optical apparatus executing optical scan in a short time. CONSTITUTION:A sample 15 is irradiated with a laser light 2 emitted from a laser 1 and passed through a plane mirror 3, a beam expander 4, an axicon pair 6, a beam reducer 9, a dichroic mirror 11a, an X-Y scanner 12, a focus lens 13 and an objective lens 14. A fluorescence 16 emitted from the rear side of the sample 15 is detected by a PMT 19a through a condenser lens 17 and a barrier filter 18. A fluorescence 16a emitted from the surface side of the sample 15 travels on the optical path of the laser light 2 reversely and detected by a PMT 30a through the dichroic mirror 11a. The axicon pair 6 comprises two axicon prisms 7a, 7b and the laser light passes through the axicon pair 6 to produce a cylindrical luminous flux 8 which then passes through the objective lens 14 to produce a Bessel beam.

Fabrication of Weighted Conical Transducer for Generation of Quasi-Nondiffracting Beam.

Abstract: The use of conical transducers with weighted velocity distribution has been proposed by the authors as a simple and practical approach for generating Bessel-type quasi-nondiffracting beams. In this paper we present the fabrication of a weighted conical transducer employing a dielectric layer of varying thickness. The dielectric layer is used for applying a radially diminishing voltage to the piezoelectric material, which will create the desired weighting on the vibration amplitude. It is shown from the experiments that the weighted conical transducer has the capability of generating a narrow-beam ultrasound over a long range along the central axis.

Bessel beam generating element

Abstract: PURPOSE:To effectively utilize a Bessel beam without deterioration in characteristics such as depth of focus and the possibility that the intensity varies with the propagation direction by composing the element of an optical fiber, and forming its one end part into a light incidence terminal in a conical shape having a vertical angle within a specific range and the other end part into a flat light projection terminal. CONSTITUTION:The Bessel beam generating element 2 consists of the optical fiber 4, and its one end part is formed into the light incidence terminal 4a in a conical shape having a vertical angle within a range of 90-170 deg. and the other end part is formed into the flat light projection terminal 4b. Thus, the one end part of the optical fiber 4 is formed into the conic light incidence terminal 4a and then when laser light S is made incident on the light incidence terminal 4a, the part function as an axicon prism, so that the Bessel beam J0 is generated in the optical fiber 4. This Bessel beam J0 is confined to the core 14 of the optical fiber 4, propagated while characteristics are maintained, and projected from the light projection terminal 4b.

Double bessel generating method and device therefor

Abstract: PURPOSE:To restrain subsidiary maximum while keeping a small spot diameter and a large depth characteristic by superposing Bessel beams having subsidiary maximum in different positions in amplitude so as to interfere with each other. CONSTITUTION:A laser beam L as a parallel light irradiates a concentric double ring opening 1, and the laser beam outgoing from the double ring opening 1 becomes two ring-like lights and pass through a lens 2, and they are superposed on the focal plane on the image side of the lens 2. The two ring-like lights become Bessel beams having mutually different diameters and distributions, and they interfere with each other to form a double Bessel beam due to being coherent. In this case, the parameter (6) is the ratio of diameters of two rings, and namely the parameter (f) is equal to the ratio of systems of two Bessel beams. This device is constituted so that the ratio (epsilon) of the two Bessel beams satisfy the relation; 0.3<=(epsilon)0.7.