JLA Vol:2 Iss:1 (The Clinical Status of Low Energy Laser Therapy in 1989)

Authors:
Jeffrey R. Basford
Department of Physical Medicine and Rehabilitation, Mayo Clinic and Foundation, Rochester, MN, U.S.A. 55902

Low energy laser therapy has gained varying acceptance as a treatment for a broad range of soft tissue, musculoskeletal and neurological conditions. A controversial, but surprisingly large body of research with cell cultures suggests that laser irradiation can nondestructively alter cellular processes. Unfortunately, animal and human studies are often contradictory and difficult to evaluate due to differing study designs. As a result, the clinical effectiveness of low energy laser therapy remains debatable. Nevertheless, the findings are intriguing a...

JLA Vol:2 Iss:1 (The Energy Transfer Efficiency in Laser Welding Process)

Authors:
T. H. Kim
Charles E. Albright
Schichan Chiang
Department of Welding Engineering, The Ohio State University, 190 W. 19th Ave., Columbus, Ohio 43210

The process efficiency of laser beam welding was measured as a function of travel speed. Temperature measurements were carried out during the bead‐on‐plate laser welding of mild steel with a focused 2KW CO₂ laser beam at various welding travel speeds. The laser welding process efficiency (power delivered to work/power in the beam) was calculated from the ratio of the heat content of the welded the specimen to the available laser beam energy (power × time). In the deep penetr...

JLA Vol:2 Iss:2 (A Comparison of Methods for Accurate Image Centroid Position Determination with Matrix Sensors)

Authors:
Paul G. Backes
Warren H. Stevenson
School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907

Optical methods for the measurement of position, part dimensions, or alignment are finding increased application in manufacturing operations. Several of these methods utilize analog or digital position sensitive detectors to find the centroid of an illuminated spot on the detector. The objective of this study was to determine the accuracy with which the centroids of a direct laser beam and a circular incoherent image could be determined using a matrix array sensor. Centroids were found using five different analytical methods. The results showed t...

JLA Vol:2 Iss:2 (Binary Phase Gratings for Materials Processing)

Authors:
Paul J. Patt
Array

The feasibility of using a diffractive optical element, a phase grating, as a beam handling device for use in industrial laser material processing is examined. The binary phase grating is an efficient beam splitting device and is useful in many materials processing operations (welding, cutting, soldering, drilling) where a high degree of parallelism could significantly improve process throughput. Overall efficiency of etched quartz binary gratings agrees well with published predictions (nominal 70–90%). Copies of the grating formed in PMMA (acrylic) survived preliminary life tests (more than 1000 9‐J pulses from a commercial multimode N...

JLA Vol:2 Iss:2 (Composition and Microstructure of Laser Beam Welds between Dissimilar Metals)

Authors:
V. P. Kujanpa¨a¨
J. P. Helin
T. J. I. Moisio
Lappeenranta University of Technology, Lappeenranta, Finland

G. J. Bruck
Westinghouse Electric Corp., Research and Development Center, Pittsburgh, Pennsylvania, U.S.A.

An austenitic stainless steel AISI 304 and a low‐carbon steel 1018 were laser welded in the vertical‐up position to form a dissimilar metal joint, by varying the laser beam alignment, gap between the base metals, and filler metal (AISI 309). The welds were inspected visually and by optical microscopy, and composition profiles were measured using electron probe microanalysis. It was found that the ...

JLA Vol:2 Iss:2 (Infrared Optical Fibers for Surgical Applications)

Authors:
R. W. Waynant
M. N. Ediger
M. Fink
Center for Devices and Radiological Health, Food and Drug Administration, 5600 Fishers Lane, Rockville, MD 20857

The basic characteristics of fibers that are appropriate for surgical use in the infrared are reviewed. New fiber materials, such as sapphire, fluorozirconate and chalcogenide glasses, and polycrystalline fibers are discussed as well as their applicability for surgical procedures.

JLA Vol:2 Iss:2 (Laser Induced Photochromic Flow Visualization)

Authors:
Thomas McWaid
Ekkehard Marschall
Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106

The photochromic flow visualization technique has been utilized to study several different liquid flows. The technique utilizes radiachromic dyes that can be dissolved in a number of liquids. The resulting dye‐solvent solutions remain colorless in the absence of ultraviolet radiation; however, the solutions turn dark blue when exposed to ultraviolet light. A nitrogen pulse laser has been constructed for use as source of ultraviolet radiation. When sharply focused, the emitted beam of ultraviolet light produces a very narrow, well define...

JLA Vol:2 Iss:2 (The Segmented Aperture Integrator in Material Processing)

Authors:
Richard L. Pierce
Spawr Optical Research, Inc., P.O. Box 1899, Corona, California, 91718‐1899

A patented segmented mirror[1] transforms light beams into flat top intensity profiles for uniform effects in materials processing and testing.

JLA Vol:2 Iss:2 (The Use of Laser Systems in Podiatric Medicine)

Authors:
Bruce A. Carlson
Assistant Medical Director, Wenske Laser Center

Robert A. Pyrcz
Laser Coordinator, Wenske Laser Center

JLA Vol:2 Iss:3 (A Relationship between Laser Power, Penetration Depth and Welding Speed in the Laser Welding of Steels)

Authors:
L. Mannik
S. K. Brown
Ontario Hydro Research Division, 800 Kipling Ave., Toronto, Ontario M8Z 5S4, Canada

Experimental data have been generated for the bead‐on‐plate keyhole welding of mild steel using the TEM₀₀ beam from a 1.5 kW CO₂ laser and a range of material thickness from 0.64 to 2.6 mm. For each thickness, the maximum welding speed was measured for laser powers from 600 to 1500 W, using the criterion of full penetration along a 5 cm length. Analysis of the data has yielded a simple correlation between laser power (P,kW), penetration depth (d,cm) and welding speed (v,cm/s). When the specific welding energy per unit thic...