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 (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 (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 (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 (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: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 (Novel Speckle Velocimeter Using the Double Clipping Cross‐Correlation Method)

Authors:
H. Kitajima
T. Yoshida
N. Nakatsuka
T. Yamashita
Central R&D Lab., Omron Tateisi Electronics Co., Shimokaiinji, Nagaokakyo, Kyoto 617, Japan

A new speckle velocimeter using the cross‐correlation method was developed. Its optical system achieved wide working distance range of ±5mm and small measuring errors for various materials. Furthermore the realtime correlation processor for the clipped signals makes the cross‐correlation method applicable to in‐line measurement in factories.

JLA Vol:2 Iss:1 (Spray Characterization of a NASA MOD‐1 Nozzle)

Authors:
Dennis R. Alexander
Diego F. F. Gutierrez
Center for Electro‐Optics, University of Nebraska‐Lincoln (UNL), Lincoln, Nebraska, U.S.A.

An aerometrics Phase Doppler Particle Analyzer with Frequency Shifting (PDPA/FS) and a Laser Imaging and Video Processing System (LI/VPS) were used to perform a detailed analysis of the spray characteristics of a NASA MOD‐1 air assist nozzle. These results were compared to the results obtained using an earlier version of a Phase Doppler Particle Analyzer (P/DPA). The spray plume was analyzed under two sets of operating conditions. For Case I, a water pressure of 105 psia (723.95 kPa) and a...

JLA Vol:2 Iss:1 (Simultaneous Measurement of Temperature and Size of Droplets in the Micrometer Range)

Authors:
N. Roth
K. Anders
A. Frohn
Institut fu¨r Thermodynamik der Luft‐ und Raumfahrt, Universita¨t Stuttgart, Pfaffenwaldring 31, D‐7000 Stuttgart 80, Federal Republic of Germany

A new optical instrument for simultaneous measurements of temperature and size of periodically generated droplets is described. With this instrument, basic phenomena such as droplet evaporation or combustion can be studied. The droplets, which are produced with a vibrating orifice droplet generator, can be injected into different environments to study, for example, evaporation in a rarefied media or combustion in a hot environment. To determine evaporation o...

JLA Vol:2 Iss:1 (Laser Laparoscopy Contamination)

Authors:
Douglas E. Ott
420 Charter Blvd. Macon, Georgia 31210