In what will be Laser Institute of America’s latest offering in a range of vital resources for laser personnel, the ANSI Z136.8 standard arose from the increasing reliance on lasers in labs and other research-designated areas.

“Laser applications in the research setting have been on a steadily increasing pace, in particular with the development of pico- and femtosecond lasers as well as nano laser technology,” explains Ken Barat, chairman of the subcommittee responsible for developing the new standard. “The existing Z136.1 Safe Use of Lasers standard was becoming out of sync with these new laser applications in R&D.”

Highlights of the standard include guidance on a number of topics vital to R&D and testing users says Barat, who is the Laser Safety Officer at Lawrence Berkeley National Laboratory. These include the use of alignment eyewear, use of non-certified lasers, export controls, use of warning signs, inclusion of sample audit forms for labs and program reviews and deletion of some CDRH-based control measures.

“Several engineering controls treated all lasers as if they were commercial products; many homemade, fiber and diode systems no longer neatly fit into that mold,” Barat says. “It also seemed that the development of several application standards would allow for greater safety.”

The lineage of new Z136 standards can be traced back to the annual meeting of the Accredited Standards Committee Z136 on March 6, 2005, according to Barbara Sams, Director of Standards Development at LIA and Executive Director of the Board of Laser Safety. At that session, veteran LIA safety expert Dr. David Sliney proposed the development of new standards for applications that hadn’t been well addressed. Efforts resulting from that session have spun off several new standards.

In the case of the Z136.8 standard, it was crafted to distinguish it from the parent ANSI Z136.1 document by detailing different laser-use locations, as well as noting two additional hazard analysis areas — beam path and beam interaction.

In terms of laser locations, the new standard identifies:

• Unrestricted locations: An area where access is not limited. Example: A hallway in a building containing Class 3B or 4 lasers.
• Restricted locations: An area where access is granted for authorized people and limited for the general public through administrative and engineering control measures. Example: A research laboratory containing Class 3B and/or 4 lasers.
• Controlled locations: An area where the access, occupancy and activities of people within are subject to strict control and supervision. By inference, these are restricted areas with optical radiation hazards at Class 4 with additional control measures specified by the laser operator, the LSO, and the employer management. Example: An R&D area with positive access control and video surveillance.
• Exclusion locations: An area where occupancy by people is possible but is denied by the LSO during operation of the laser system. Example: A free electron laser machine room or beam path.
• Inaccessible locations: An area where occupancy is not possible due to its dimensions. Example: An enclosed beam path on an optical table.

“Laser safety in all research settings I know are an effort between the LSO and researcher,” Barat concludes. “But research settings are more fluid. In industry, once the controls are in place, things are pretty much set for long periods of use. In medical settings, people work off a checklist for each procedure, and the doctor and nurses argue over eyewear use. In R&D a set up can stay the same with just different samples for years or change every few weeks following the path of the results or funding.”

LIA, the recognized industry leader in laser advocacy and safety education since 1968, serves as secretariat of the Z136 series of laser safety standards, administering the process and providing support to the committee. To order the Z136.8 revision ($140 for LIA members, $160 for nonmembers), visit www.lia.org/ANSI or call LIA at 1.800.34.LASER.

About LIA
Laser Institute of America (LIA) is the professional society for laser applications and safety serving the industrial, educational, medical, research and government communities throughout the world since 1968. www.lia.org , 13501 Ingenuity Drive, Ste 128, Orlando, FL 32826, +1.407.380.1553.

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Due to their material properties such as high electrical and thermal conductivity, copper is more and more demanded for industrial applications. The same material properties make laser welding of copper a challenging task. To achieve welds with penetration depths of several millimeters in copper using commercially available laser sources relatively low feed rates of less than 10 m/min are needed. Welds in copper at such low feed rates with 1 µm wavelength lasers often suffer from defective weld seams with melt ejections and pores. Furthermore the absorptivity of pure copper is very low at this wavelength.

The outcome of melt ejections are reflected in holes in the solidified seam surface. These holes are the result of the lack of mass resulting from the ejection of molten material out of the melt pool during the welding process. In most of the cases such holes extend over the complete penetration depth. For industrial applications primarily the cross sectional area of the welds is of interest in order to achieve the highest possible electrical and thermal conductivity. Hence it is of great importance to minimize or even avoid such weld imperfections.

On the one hand the absorptivity of copper strongly increases in the visible wavelength range. On the other hand modulated laser power can reduce melt ejections. A combination of these two approaches is presented in this article. A frequency doubled “green” thin-disk laser at a wavelength of 515 nm with a maximum fundamental mode cw output power of 200 W and a 5 kW thin-disk “IR” laser at the wavelength of 1030 nm were geometrically combined. The focal spot diameters were 25 µm for the green and 100 µm for the IR laser, respectively. The experimental setup is shown in Figure 1.

Figure 1: Experimental Setup.

In order to analyze the influence of the thermal conductivity, a copper alloy CuSn6 (referred to as “bronze”) with a moderate and a pure copper (Cu‑ETP) with very large heat conductivity was examined. The welded samples were analyzed with respect to the number of melt ejections, the penetration depth and quality of the solidified seam surface. The number of melt ejections was counted from the weld seam surface: Each hole located in the melt seam after the solidification was counted as melt ejections. All welds were 80 mm longs bead on plate welds.

Process Stabilization by Laser Power Modulation

In order to investigate the effect of the formation of melt ejections the laser power was sinusoidally modulated. The laser power was modulated around the deep penetration threshold with an amplitude of 50 % of the average power. The results of these investigations are shown in Figure 2.

Figure 2: Seam Surface (top) and longitudinal cross-section (bottom). Cu-ETP, comparison between cw weld (upper) and modulated weld (lower) at 500 Hz and an average power of 1.7 kW.

Presuming the correct parameters modulation of the power has very distinct advantages: On the one hand there is a reduction of 70 % to 90 % in number of melt ejections. On the other hand a significantly more regular and homogeneous solidified weld seam surface for the modulated welds was achieved as shown in Figure 2.

Increased Process Stability by applying an Additional Green Laser

The output power of 200 W of the green laser is not sufficient to achieve penetration depths of a few millimeters in copper despite the much higher absorptivity at this wavelength. Therefore it is quite straight forward to combine two laser sources for welding copper: A “green” low power laser and a kilowatt infrared laser. On this background the two lasers described above were combined geometrically for the experiments (see Figure 1). For the experiments the green focal spot was set 130 µm in front of the IR with respect to the direction of movement.

Figure 3 shows a comparison of the “IR-only” welding process and the IR-green combined process with the green laser for pure copper. In order to keep the total power constant for the combined process with the 200 W of green laser, the IR laser power was reduced by the power of the green laser. The modulation frequency of the IR laser was set to 500 Hz with an amplitude of ± 750 W.

Figure 3: Melt ejections per weld and penetration depth for Cu-ETP at 6 m/min and a power of 1.7 kW; Left: IR-only; Right: combined process (green and IR).

Due to the combined process the melt ejections could be reduced to not more than one ejection per weld. In addition the penetration depth could also be increased (see blue line Figure 3).

In Figure 4 the solidified seam surface for bronze for the IR-only (top) and the combined process (bottom) is shown. Very homogeneous and regular seam surfaces without any melt ejection could be obtained with the combined process.

Figure 4: Weld seam surfaces for CuSn6 with surface defects; Top: IR cw, bottom: Combined process: Green and IR.

Due to the power modulation the melt flow is influenced in a way that less melt ejections occur. One possible explanation for the improved weld seam quality achieved with the combined process is believed to be a preheating effect. The green laser preheats the material and improves the incoupling of the IR bream.

Conclusion

Weld seams in deep copper welding at low feed rates suffer from many melt ejections and surface inhomogeneities. The presented experimental results clearly show that modulation of the laser power significantly improves the weld quality by considerably reducing the number of melt ejections. Combining the modulated IR laser with an additional green laser allows producing almost ejection-free deep welds and a perfectly homogeneous seam surface.

Acknowledgment

The presented work was funded by the Federal Ministry of Education and Research (BMBF). The CuBriLas-project belongs to the MABRILAS-network. The responsibility for this paper is taken by the authors.

Contact

Andreas Heider, Institut fuer Strahlwerkzeuge (IFSW), University of Stuttgart, Germany

Pfaffenwaldring 43, D-70569 Stuttgart, Germany
Phone ++49-(0)711-685-69730
Fax ++49-(0)711-685-59730
e-mail: andreas.heider@ifsw.uni-stuttgart.de

http://www.ifsw.uni-stuttgart.de

The interaction of light with metallic nanomaterials has led to a new branch of photonics called plasmonics. It has been found that the external electromagnetic waves can excite the collective electron displacements, known as surface plasmons (SP), density waves of electrons propagate along the conductor surface like ripples that spread across the water surface after you throw a stone into a pond. Plasmonic devices offer the potential to transmit optical signals and electric currents through the same thin metallic circuitry, thereby creating the possibilities to combine electronic and photonic components on the same chip. ^{1, 2}This will bring the revolution in high speed carrying of large scale digital data and optical computing.

To date the fabrication of such a plasmonic device is technically challenged since the welding at a nanoscale is required for the permanent integration of individual functional components. Femtosecond laser induced non-thermal melting as a promising method to realize a nanowelding without dramatically changing the shape and crystallinity of nanoparticles. One femtosecond is only 10^-15 second. Nanowelding with ultrashort laser pulses (< 10^-12 sec) is distinct from other fusion nanowelding processes because the interaction between ultrafast laser pulses and materials is a non-thermal phenomenon at surface.³ As the electron-lattice thermal coupling time (typically several picoseconds, 1 ps = 1000 fs) is much longer than the laser pulse width, the electrons do not have enough time to transfer the excitation energy to the lattice. Instead, electrons are excited leading to direct emission. This is accompanied by a reduction in the bond energy between lattice atoms, resulting in “melting” of surface atoms. This melting is non-thermal because it is not due to vigorously thermal vibrations of lattices at an elevated temperature. Furthermore, due to the surface emission the melting is a surface effect. Hence, in this process, melting occurs only on a nanoscale at the surface without damaging the bulk, making it ideal for welding of nanoparticles.

Fig. 1 presents welded Ag nanoparticles with120 fs laser pulses at an intensity of 10¹² W/cm². Four nanoparticles are welded together and form a chain structure. It is obvious that the nanoparticles kept their original shapes and the necks are formed by fusion. This is different from previous laser brazing with a nanosecond laser pulse where Au nanoparticles are totally melted and brazed individual Pt nanoparticles.⁴ Certainly the surface melting is beneficial to keep the original function since the surface plasmonic properties can be dramatically changed by shapes. It is important to point out that the irradiation at a higher energy leads to split nanoparticles into tiny particles. This is consistent with widely reported results that laser bombardment results in the further refinement of nanoparticles. Thus, the key to femtosecond laser induced nanowelding is the proper choice of the energy range. It is expected that the proper energy is dependent on materials.

Fig. 1 Welded Ag nanoparticles with 120 femtosecond pulses at an intensity of 10¹² W/cm².

Plasmonic properties of welded Ag nanoparticles have been simulated numerically using a 3D finite element method and a Drude-Lorentz model. ⁵The complex permittivity of silver was obtained from experimental data.  Fig. 2 shows a comparison of the electrical potential distribution between two and four adjacent particles and between welded nanoparticles in air. The diameter of each nanoparticle is 50 nm and the gap is 5 nm for adjacent pairs and -5 nm for welded pairs (corresponding to an overlapping central distance of 5 nm). The results show that welded nanoparticles possess a ring-shaped hot spot in the neck area compared to a central hot-spot in pairs that are together, but not joined. This clearly indicates that the hot-spot area is enhanced in laser welded pairs.  Unlike adjacent dimmers or trimers, which are bonded by a weak van der Waals interaction, welded nanoparticles form strong and permanent joints. These are suitable for use as stable, repeatable Raman probes.

 
Fig. 2 The cross-sectional views of normalized electric field distributed at the surface of the nanostructures in air, top panels: adjacent two and four Ag spheres with a diameter of 50 nm and a central gap of 5 nm; low panels: welded two and four Ag spheres at the same diameter and a overlapped central distance of 5 nm (i.e., the central gap of -5 nm).

References:

¹J. A. Schuller, E. S. Barnard, W. Cai, Y. C. Jun, J. S. White and M. J. Brongersma, Nature Nanomater. 9 (2010) 193

²E. Ozbay, Science 311 (2006) 189

³A. Hu, M. Rybachuk, Q. B. Lu and W. W. Duley, Appl. Phys. Lett. 91 (2007) 131906

⁴F. Mafune, J. Kohno, Y. Takeda, T. Kondow, J. Am. Chem. Soc. 125 (2003) 1686

⁵X. Y. Zhang, A. Hu, T. Zhang, W. Lei, X. J. Xue, Y. Zhou and W. W. Duley, ACS Nano (DOI: 10.1021/nn203336m)

A new standard geared towards lasers employed in research takes a “more realistic” approach to guiding safety officers overseeing such work, in which the use of customized laser devices and fiber optics is common.

American National Standard for Safe Use of Lasers in Research, Development, or Testing, the title of the new ANSI Z136.8 standard, also addresses injury prevention in specific areas where experiments are conducted.

“In the research setting, you’re often dealing with lasers that don’t have all the bells and whistles,” explains Ken Barat, chairman of the subcommittee that developed the new standard. “Z136.8 recognizes that many lasers in the research setting are homemade and may not have all these controls, so I do not have to explain why they are missing to auditors. (Z136.8) allows LSOs to accept those things rather than say you’re out of compliance.”

The ANSI Z136.8 standard — LIA’s latest offering in a range of vital resources for laser personnel — arose from the increasing reliance on lasers in labs and other research-designated areas.

“Laser applications in the research setting have been on a steadily increasing pace, in particular with the development of pico- and femtosecond lasers as well as nano laser technology,” says Barat, Laser Safety Officer at Lawrence Berkeley National Laboratory. “The existing Z136.1 Safe Use of Lasers standard was becoming out of sync with these new laser applications in R&D.”

Other highlights include guidance on export controls, the use of warning signs, inclusion of sample audit forms for labs and program reviews, and deletion of some CDRH-based control measures. Z136.8 further distinguishes itself from the parent ANSI Z136.1 document by:

• Detailing two additional hazard analysis areas — beam path and beam interaction.

• Summarizing proper procedure in unrestricted, restricted, controlled, exclusion and inaccessible locations.

• Allowing the use of alignment eyewear.

“If I have a green laser that I’m trying to align and I put on eyewear that blocks all the green light, I can’t do what I want to do,” Barat says, meaning the user might opt not to wear protection. “(Z136.8) acknowledges that alignment eyewear lets you reduce the intensity of the beam but lets you see it.”

“Laser safety in all research settings I know are an effort between the LSO and researcher,” Barat concludes. “But research settings are more fluid. In industry, once the controls are in place, things are pretty much set for long periods of use. In medical settings, people work off a checklist for each procedure, and the doctor and nurses argue over eyewear use. In R&D a set up can stay the same with just different samples for years or change every few weeks following the path of the results or funding.”

LIA, the recognized industry leader in laser advocacy and safety education since 1968, serves as secretariat of the Z136 series of laser safety standards, administering the process and providing support to the committee. To order the Z136.8 ($140 for LIA members, $160 for nonmembers), visit www.lia.org/ANSI or call LIA at 1.800.34.LASER.

The Laser Institute of America has unveiled an expanded educational track for its second annual Lasers for Manufacturing Event, the highly successful exhibit launched to address a unique and pressing need for the North American industry.

LME 2012 will again provide attendees with vital guidance on how to create effective and efficient laser-based production systems to increase profitability in a broad range of applications, predominantly aerospace, automotive and medical.

Four new courses addressing the fundamentals of laser additive manufacturing, cutting, drilling and marking have been added, as well as a pair of two-hour tutorials addressing welding and joining and ultrafast laser processes.

Your Source for Answers
LME, being held once again in proximity to thousands of automakers and laser job shops, is geared to be one-stop shopping for those either seeking to refine current laser systems and applications or assessing potential new ways to employ photonics in production. The educational program will emphasize the rudiments of understanding the main types of lasers used for manufacturing, how to justify the investment and even maintaining laser safety.

In addition, the new two-day Laser Welding & Joining Workshop, chaired by Prof. Eckhard Beyer of Fraunhofer IWS, will run concurrently with LME on Oct. 23-24 in Schaumburg, IL. “As many laser manufacturers and system builders are engaged in the workshop, this would be an ideal opportunity to get application-related questions answered and get new ideas on how to use lasers,” Beyer noted. “We are going to unite many people from the laser community who were and are shaping the way the world of lasers is today. This will make it possible to address lasers from basics to high-end applications.”

The Welding & Joining Workshop will feature 18 presentations, spread out to allow ample time for attendees to interact directly with OEMs in the exhibit hall.

“The workshop will start with short courses presented by industrial research experts to give a sound overview of laser basics and current developments. End users with long standing experience will present their solutions to the typical challenges of laser applications.”

Some of those applications will include powertrain welding, remote welding, hybrid welding and “micro” applications, he noted. Such applications are being refined constantly as lasers continue to evolve.

“We still see a big impact of the tremendous rise in beam quality and energy efficiency,” Beyer says. “Here the application fields are expanded in many ways: ultra-low distortions or the realization of new mixed-material joints like copper-aluminum using precisely shaped weld pools. Also, remote-beam applications are now standard; that was a field restricted to expensive high-brightness lasers just a few years ago. Furthermore, laser size reduction is a key development; many lasers are now so small that machine integration is much simpler and can be done in a way not possible before.”

Additional Education Opportunities
Although slated as a tutorial this year, the program on ultrafast lasers could grow into another two-day workshop next year. For the inaugural session, LIA President Prof. Reinhart Poprawe of Fraunhofer ILT says the educational track will feature technical examples, a survey of Technology Readiness Levels (TRL) 1-9 materials and an overview of markets and materials. He says the session will be particularly geared to those involved with optical systems and scanning technologies, as well as users of precision machining applications with accuracy in the range of 10 microns and below.

“The development of ultrafast lasers with pulse durations of some 100 femtoseconds to 10 picoseconds on an industrial scale with powers up to the kilowatt class, has led to a new level of laser processing with ultimate processing quality,” Prof. Poprawe noted. “Starting with physical basics on ultrashort pulse interaction phenomena, the tutorial will give a survey on different applications from electronics, energy topics and tooling technology to large area processing for tribology optimization and surface functionalization.”

The tutorial is particularly suited for engineers and scientists from machine suppliers and end users, Poprawe said. And “manufacturers of ultrafast lasers and optical systems (scanning technologies) will learn about the requirements on system technology with respect to laser parameters and processing parameters.”

LIA is showing once again it is in the forefront of advocating cutting-edge laser technology, as “ultrashort pulsed lasers are heading to the edge of mass industrialization and will undergo similar growth rates like other lasers in the past,” Poprawe asserted.

LME 2012 will again feature the highly popular Laser Technology Showcase, a stage at the front of the exhibit hall that will be used for keynote educational presentations and shorter informational addresses by many companies in attendance. The showcase format helped foster interaction between attendees seeking solutions and a wide array of industry leaders able to lend their expertise in person.

For more information on LIA’s Lasers for Manufacturing Event (LME), visit www.laserevent.org or call 1.800.34.LASER.

Introduction
Optics –seen through the glasses of scientific disciplines – is one of the most widespread topics ranging from basic physics over engineering to medicine. The field of optics therefore is not only basic technology but also enabling technology for a lot of new techniques. To further enhance the innovation level in optics, especially the interdisciplinary research has to be strengthened. To reach this goal, young and motivated scientists are needed that do not hesitate to look beyond their own discipline. Real interdisciplinary innovation needs people that feel at home in more than one community, e.g. in optics engineering and in medicine.

This article shows different results gained in an environment dedicated to strengthen these interdisciplinary skills and shall encourage interested readers to work in different disciplines. The Erlangen Graduate School in Advanced Optical Technologies (SAOT) forms such an environment and brings together researchers of many disciplines in optics. One section of SAOT is especially dedicated to Optics in Medicine and covers a wide range of medical applications. Our lab has a strong contribution and emphasizes the variety by addressing medical photonic topics ranging from diagnostics like a vocal dynamic analyser and a new endoscope for cancer detection to training of human 3D vision in a virtual environment.

3-Dimensional Analysis of the Vocal Fold Dynamics
The detailed analysis of the human vocal fold dynamics and the resulting acoustic signal allows the prediction of diseases such as laryngitis (inflammation of the larynx). For non-contact and minimal invasive measurement an optical system was developed that allows the analysis of the 3-dimensional vocal dynamics while using a high-speed camera and associated software. The project is attended in collaboration with the University Hospital Erlangen (Department for Phoniatrics and Pedaudiology) and in the framework of the Collaborative DFG supported Research Center FOR894/1. For the measurement of vocal fold dynamics a triangulation based sensor can be used. A system of micro-lens arrays and lenses divide a laser beam in a variety of sub beams and produces a regular point grid that is projected at an angle to the target surface. A high-speed camera collects the image of the point array vertical to the target surface. The topography of the vocal fold leads to a distortion of the recorded point pattern, so that the 3-dimensional surface can be calculated taking into account angles and screen distance. The laser projection unit was designed including an optical simulation software. A prototype was developed and characterized for the measurement of artificial and in-vitro vocal fold studies. In a measuring area of 2 x 2 cm 200 measuring points are generated (figure 1 and 2). A customized software that was developed at the University Hospital of Erlangen is used for the analysis of the point array [1]. For the integration of an endoscope, a miniaturized projection has been realized.

Figure 1: Experimental setup for the proof of concept

Figure 2: Captured camera image: a) larynx, no illumination with multi spot generator, b) larynx, illumination with multi spot generator

Cancer Detection by a Hyperspectral Reflectance and Multispectral Fluorescence Video Endoscope
Cancer is the second upper most killer in the world after cardiovascular related disease [2]. Until now, the respective sensitivity and positive predictive value of standard upper endoscopy for diagnosing Barrett’s Esophagus have been reported to be only 82% and 34% [3]. In our approach we are going to combine reflectance and fluorescence for cancer detection. The overall scope of this project is to develop a prototype of the video endoscopic system that is capable of acquiring multispectral fluorescence and hyperspectral reflectance images over a wide range of wavelengths in the stomach through a standard flexible video endoscope for revealing pre-cancer and cancer and providing a surgical guidance.

In the actual state, we finished the setup for hyperspectral reflectance and the preliminary results on phantoms we developed to simulate optical properties as it is in tissues in vivo. With this system it is possible to select a spectrum with various centre wavelengths between 400 and 630 nm with bandwidths between 20 and 30 nm. For the hyperspectral reflectance measurements eight different wavelengths were used to acquire the reflectance images and the spectra. The following biological tissue-like phantoms with following optical properties were used: μa = 3.7cm^-1 and μs’ = 8.7 cm^-1 for cancerous tissue and μa = 0.3 cm^-1 and μs’ = 6.8 cm^-1 for healthy tissue at a wavelength of 500nm [4]. The first goal for these preliminary results was to get an estimation of the possible accuracy and see how many different wavelength bands we need for optimal differentiation. With a LDA-analysis 90% sensitivity and specificity are reached(figure 3).

Fig. 3: Endoscopy setup

Figure 4: Sensitivity and specificity for increasing number of adjust wavelengths and their standard deviation

Virtual Vision Training
Vision is an important issue for most kind of sports, e.g. ball sports. Catching or throwing a ball requires estimating the trajectory of the ball. The faster athletes are able to accomplish this task the higher their performance resulting in higher precision and lower reaction times. In this project we will evaluate and train the responsible components of vision, i.e. depth and motion.

The final goal is to develop a virtual training system that is able to evaluate and improve the related visual aspects. As for depth estimation a major part is covered by stereo vision, we use a polarized stereo rendering system. When an object is observed with both eyes the two images are fused in the brain. Depth is estimated by disparity, the offset between the twice observed object. This principle is used in passive stereo rendering to simulate depth (figure 5). To provide an interactive control for the virtual environment we developed an automated gesture control via a depth sensor.

As a first step we measure the stereo visual performance. We implemented a vision test using our developed software framework where four objects of the same size are presented to the observer. One of the objects appears closer by having a larger disparity and becomes the front object. During multiple iterations with decreasing disparity differences the observer has to identify the front object (figure 6). Performance is described by (i) the minimum disparity at which the observer is still able to accomplish a correct decision and (ii) the decision time how long it takes for the observer.

Figure 5: Principle for depth simulation via passive stereo rendering. The image is generated by rendering the virtual object for each eye respectively where the viewing ray of the eye hits the screen. Observing this image with 3D glasses simulates the virtual object for the observer.

Figure 6: An observer accomplishing our virtual stereo vision test using our automated gesture control.

Conclusion
The substantial variability of all three listed examples emphasizes the wide range of applications within the field of medical photonic technologies covered by our lab and theErlangenGraduateSchoolin Advanced Optical Technologies (SAOT). We could present essential clinical supports from diagnosis of diseases to training of perceptual functions.

[1]     Luegmair, G.; Kniesburges, S.; Zimmermann, M.; Sutor, A.; Eysholdt, U.; Döllinger, M.: Optical Reconstruction of High-Speed Surface Dynamics in an Uncontrollable Environment. In: IEEE TRANSACTIONS ON MEDICAL IMAGING, VOL. 29, NO. 12, (2010.)

[2]      Jemal, A., R. Siegel, et al. (2006). “Cancer statistics, 2006.” Ca-a Cancer Journal for Clinicians 56(2): 106-130.

[3]      Eloubeidi, M. A. and D. Provenzale (1999). “Does this patient have Barrett’s esophagus? The utility of predicting Barrett’s esophagus at the index endoscopy.” American Journal of Gastroenterology 94(4): 937-943.

[4]     V.V. Tucher, Tissue Optics: Light Scattering Methods and Instruments for Medical Diagnosis, SPIE Society of Photo-Optical Instrumentation Engineering.

The honor, bestowed at a March 7 ceremony in Washington, D.C., also affirms the decision by the Laser Institute of America to host its fourth annual LAM workshop. LIA, the recognized leader in laser advocacy and safety education since 1968, crafted a program featuring LAM innovations in producing everything from small consumer products to patient-specific medical prostheses to vital aviation components.

Days before receiving the award, keynote speaker Dr. Ingomar Kelbassa of Fraunhofer ILT told a standing-room-only audience at LAM 2012 in Houston, how his firm can make an 80-blade high-pressure compressor BLISK (blade-integrated disk) with high-speed laser metal deposition in under two minutes per blade – 160 minutes total - at near net shape. He compared those results with conventional five-axis milling, which removes 80 percent to 90 percent of material and takes more than 180 hours.

This is the second innovation award longtime LAM workshop sponsor Fraunhofer ILT has won recently. In November, LIA President Dr. Reinhart Poprawe, director of Fraunhofer ILT, was awarded North Rhine-Westphalia’s 2011 Innovation Award. Dr. Poprawe and his team, including Dr. Kelbassa, were recognized for continuing to push the boundaries of manufacture using selective laser melting.

“In a few years’ time, the way spare parts are manufactured for an established supplier of hydraulic components will be radically different,” Dr. Poprawe noted in a recent interview. “Instead of keeping hundreds of variants of spare parts in stock, the manufacturer will simply store the 3D CAD data of all components that have been produced in the past. Then, when an order is received, the appropriate part can be produced on demand using the selective laser melting process and shipped promptly to the customer.”

Corporate member Fraunhofer ILT is sharing its expertise as a partner with LIA corporate member Joining Technologies of Connecticut, in the Joining Technologies Research Center (www.joiningtech.com/jtrc).

The LAM workshop is a vital part of LIA’s suite of renowned conferences, along with the annual International Congress on Applications of Lasers and Electro-Optics (ICALEO^®) and the newer Lasers for Manufacturing Event (LME). LIA’s signature events present the full spectrum of knowledge about laser-based rapid manufacture, from the research driving it to how and when to use it - and employ it profitably. But even outside the realm of high-tech, the technology is gaining notice. Consider:

• The Economist featured the cover story “Print Me a Stradivarius” in February 2010. In that issue, LAM consultant and LAM 2012 keynote speaker Terry Wohlers noted that more than 20 percent of the output of 3D printers is final products; he expects this to rise to 50 percent by 2020.

• A column in the January 30 Wall Street Journal called laser additive manufacturing one of three keys to the new tech boom in the United States, imagining the “ ‘desktop’ printing of entire final products from wheels to even washing machines.”

In short, Kelbassa told LAM 2012 attendees, LAM promises “complexity for free and individualization for free.” In a society growing increasingly concerned for the environmental impact of products, LAM offers a way to substantially reduce part weight, thereby saving aviation fuel costs and minimizing the amount of material required for manufacture.

To learn more about the LIA, its Laser Additive Manufacturing (LAM) workshop, other events and corporate members, visit www.lia.org.

Additive manufacturing is a collection of computer-controlled processes that create parts in a layerwise fashion without part-specific tooling. Applications share the common characteristics of part production with complex geometry in relatively small production runs. Historically, applications were limited to production of prototypes and casting inserts, since part mechanical properties and surface finish were inadequate for actual structural applications. More recently, coupled with post processing, additive manufacturing has been used to produce a variety of production tooling, short-run structural parts, customized bio-engineered parts, mass-customized parts, architectural designs, parts for automotive and aerospace applications, archaeological replicas and artwork [1]. The demand for products and services from additive-manufacturing technology has been strong over its 23-year history (1988-2010). The compound annual growth rate of revenues produced by all products and services over this period is an impressive 25.1% [2].  This article describes an historical context of additive manufacturing technology based largely on US patent literature.

Additive Manufacturing Timeline

The figure displays an early chronological timeline of additive manufacturing. This chronology should not be considered complete; it indicates some but not all of the major time events in this field up to about 2002. Two early roots of additive manufacturing are topography and photosculpture. In the late 1960s, “proto-additive manufacturing” technologies
appeared which ushered in actual additive manufacturing process development in the mid-1980s, concurrent with the advent of low-cost, desktop computing.

As early as 1890, Blanther [3] suggested a layered method for making a mold for topographical relief maps. The method consisted of impressing topographical contour lines on a series of wax plates and cutting these wax plates on these lines. After stacking and smoothing these wax sections, both a positive and negative three-dimensional surface was generated that corresponded to the terrain indicated by the contour lines. After suitable backing of these surfaces, a paper map was then pressed between the positive and negative forms to create a raised relief map.

In 1974, DiMatteo [4] recognized that stacking techniques could be used to produce surfaces that were particularly difficult to fabricate by standard machining operations. In one embodiment, a milling cutter contoured metallic sheets, and these sheets were then joined in layered fashion by adhesion, bolts or tapered rods. In 1979, Professor Nakagawa of Tokyo University used lamination techniques to produce actual tools such as blanking tools [5], press forming tools [6] and injection molding tools [7]. This is a precursor to all “cut-and-stack” additive manufacturing technologies, including laminated object manufacturing.

Photosculpture arose in the 19^th century as an attempt to create exact three-dimensional replicas of any object, including human forms [8]. One somewhat successful realization of this technology was developed by François Willème in Paris in 1860. A subject or object was placed in a circular room and simultaneously photographed by 24 cameras placed equally about the circumference of the room. An artisan then carved a 1/24^th cylindrical portion of the figure using a silhouette of each photograph, and these were later assembled.

In 1951, Munz [9] proposed a system that has features of present day stereolithography techniques. He disclosed a system for selectively exposing a transparent photo emulsion in a layerwise fashion where each layer comes from a cross section of a scanned object. Lowering a piston in a cylinder and adding appropriate amounts of photo emulsion and fixing agent created these layers. After exposing and fixing, the resulting solid transparent cylinder contained an image of the object. Subsequently this object could be manually carved or photochemically etched out to create a three-dimensional object.

Early Chronology of Additive Manufacturing Processes based on US Patent Filings

In 1971, Ciraud proposed a powder process that has the features of modern powder-based direct deposition additive manufacturing techniques [10]. This disclosure described a process for the manufacture of objects from a variety of materials that were at least partially able to melt. To produce an object, small particles were applied to a matrix, and a laser, electron beam or plasma beam then heated the particles locally. As a consequence of this heating, the particles adhered to each other to form a continuous layer.  Brown, Breinan and Kear at United Technologies Corporation in 1982 patented a similar powder-based technique for building up material in a near net shape fashion to produce rotors for the aerospace industry [11].

Early Additive Manufacturing Laser-Based Powder Processes of Ciraud [10] and Housholder [12]

In 1979, Housholder [12] presented the earliest description of a powder laser sintering process in a patent. He discussed sequentially depositing planar layers and solidifying a portion of each layer selectively. The solidification can be achieved by using heat and a selected mask or by using a controlled heat scanning process.

Hideo Kodama of Nagoya Municipal Industrial Research Institute was the first to publish an account of a functional photopolymer rapid prototyping system in 1981 [13]. In his method, a solid model was fabricated by building up a part in layers where exposed areas corresponded to a cross-section in the model. He studied three different methods for achieving this using both a mask and an x-y plotter with an optical fiber.

The roots of modern additive manufacturing trace back about 50 years, although preceding topographic and photosculpture methods share much in common with additive manufacturing and are over 100 years old.  The prehistory of additive manufacturing provides a rich backdrop for current and future developments.  One such articulation of the future was a research roadmap exercise for additive manufacturing organized by one of the authors [14].  In addition to technical targets, educational needs and a national testbed center were highlighted.

REFERENCES

[1]        Proceedings of the Solid Freeform Fabrication Symposium, (Mechanical Engineering Department, The University of Texas, Austin, Texas 78712, 1990-2010). Available at http://utwired.engr.utexas.edu/lff/symposium/proceedingsArchive/toc.cfm.

[2]        “Wohlers Report 2011:State of the Industry/Annual Worldwide Progress Report”, T.T. Wohlers, ed., Wohlers Associates, Inc., Fort Collins CO, 2011.

[3]        J.E. Blanther, “Manufacture of Contour Relief Maps ”, US Patent #473,901, 1892.

[4]        P.L. DiMatteo, “Method of Generating and Constructing Three-Dimensional Bodies”,US Patent #3,932,923, 1976.

[5]        T. Nakagawa, et al, “Blanking Tool by Stacked Bainite Steel Plates ”, Press Technique, 1979, pp. 93-101.

[6]        M. Kunieda, T. Nakagawa,“Development of Laminated Drawing Dies by Laser Cutting”, Bull of JSPE ,1984, pp.353-54.

[7]        T. Nakagawa, et al, “Laser Cut Sheet Laminated Forming Dies by Diffusion Bonding”, Proc 25^th MTDR Conf ,1985, pp.505-510.

[8]        M. Bogart, “In Art the End Don’t Always Justify Means ”, Smithsonian, 1979, pp.104-110.

[9]        O.J. Munz, “Photo-Glyph Recording”, US Patent #2,775,758, 1956.

[10]      P.A. Ciraud, “Process and Device for the Manufacture of any Objects Desired from any Meltable Material”, FRG Disclosure Publication 2263777, 1972.

[11]      Clyde O. Brown, Edward M. Breinan, Bernard H. Kear, “Method for Fabricating Articles by Sequential Layer Deposition”, US Patent #4,323,756, 1982.

[12]      R.F. Housholder, “Molding Process”, US Patent #4,247,508, 1981.

[13]      H. Kodama, “Automatic Method for Fabricating a Three-Dimensional Plastic Model with Photo Hardening Polymer”, Rev Sci Instrum, 1981, pp.1770-73.

[14]      “Roadmap for Additive Manufacturing: Identifying the Future of Freeform Processing”, D.L. Bourell, M.C. Leu, D.W. Rosen, eds., Univ. of Texas, 2009, 92 pages. Available for free as on-line download at http://wohlersassociates.com/roadmap2009.pdf.

LIA is the recognized leader in teaching the safe use of lasers in applications ranging from industrial to medical to research. It is the latest in a series of moves by LIA to gives its members and customers the newest training information available in print, online or onsite.

Noticing a significant rise in Canadians signing up for the online Laser Safety Officer Training course (www.lia.org/store/train/LSOONLINE), LIA Education Director Gus Anibarro responded quickly to address their specific requirements.

Among the key differences between U.S. and Canadian regulations, he says, is the Radiation Emitting Devices Act, which emerged from Canada’s Department of Justice in 1985. “It is their version of our Center for Devices and Radiological Health, where our government regulates laser manufacturers,” Anibarro notes. “It regulates laser products that are sold in Canada. REDA applies to manufacturers, distributors, people who lease lasers and those who import lasers, including laser scanners and lasers for demonstration.”

The REDA applies to medical and industrial lasers, which have to be reported to Canada’s Consumer and Clinical Radiation Protection Bureau. “They assess, monitor and assist in the reduction of health and safety risks associated with lasers,” Anibarro points out. Lasers are further covered under the labor code of the Canadian Centre for Occupational Health and Safety.

Even though the REDA covers the whole of Canada, “each province has its own regulations — and some don’t have any,” Anibarro says. Another notable aspect of Canadian laser regulations, he says, is that REDA references the U.S. 21 CFR and International Electrotechnical Commission’s IEC 60825 standards.

In addition to the inclusion of Canada’s regulations, the online LSO course has been made easier to use by being broken into separately accessible topics. “For the customer, it will load faster on their computer system and they’ll be able to navigate through the course a lot quicker,” Anibarro says.

Beyond those improvements, the course will continue to detail:

• Up-to-date information on ANSI Z136 standards for laser use.

• The effects of lasers on the eyes and skin.

• Non-beam issues such as laser-generated airborne contaminants and electrical hazards.

• Laser control measures and personal protective equipment such as laser eyewear.

• Strategies in laser safety program administration, including training requirements for laser personnel, medical surveillance and LSO duties and responsibilities.

The expanded LSO course is one of several recent additions to LIA’s repertoire of laser safety offerings, including the new book for certified medical laser safety officers, titled CMLSOs’ Best Practices in Medical Laser Safety, and the new ANSI Z136.3 standards regulating the use of lasers in hospitals, clinics, ambulatory surgery centers, private medical practices and the home.  Visit the LIA’s online store at www.lia.org/store to learn more.

About LIA

Laser Institute of America (LIA) is the professional society for laser applications and safety serving the industrial, educational, medical, research and government communities throughout the world since 1968. www.lia.org , 13501 Ingenuity Drive, Ste 128, Orlando, FL 32826, +1.407.380.1553

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The honor, bestowed at a March 7 ceremony in Washington, D.C., also affirms the decision by the Laser Institute of America to host its fourth annual LAM workshop. LIA, the recognized leader in laser advocacy and safety education since 1968, crafted a program featuring LAM innovations in producing everything from small consumer products to patient-specific medical prostheses to vital aviation components.

Days before receiving the award, keynote speaker Dr. Ingomar Kelbassa of Fraunhofer ILT told a standing-room-only audience at LAM 2012 in Houston, how his firm can make an 80-blade high-pressure compressor BLISK (blade-integrated disk) with high-speed laser metal deposition in under two minutes per blade – 160 minutes total - at near net shape. He compared those results with conventional five-axis milling, which removes 80 percent to 90 percent of material and takes more than 180 hours.

This is the second innovation award longtime LAM workshop sponsor Fraunhofer ILT has won recently. In November, LIA President Dr. Reinhart Poprawe, director of Fraunhofer ILT, was awarded North Rhine-Westphalia’s 2011 Innovation Award. Dr. Poprawe and his team, including Dr. Kelbassa, were recognized for continuing to push the boundaries of manufacture using selective laser melting.

“In a few years’ time, the way spare parts are manufactured for an established supplier of hydraulic components will be radically different,” Dr. Poprawe noted in a recent interview. “Instead of keeping hundreds of variants of spare parts in stock, the manufacturer will simply store the 3D CAD data of all components that have been produced in the past. Then, when an order is received, the appropriate part can be produced on demand using the selective laser melting process and shipped promptly to the customer.”

Corporate member Fraunhofer ILT is sharing its expertise as a partner with also LIA corporate member Joining Technologies of Connecticut, in the Joining Technologies Research Center (www.joiningtech.com/jtrc).

The LAM workshop is a vital part of LIA’s suite of renowned conferences, along with the annual International Congress on Applications of Lasers and Electro-optics (ICALEO^®) and the newer Lasers for Manufacturing Event (LME). LIA’s signature events present the full spectrum of knowledge about laser-based rapid manufacture, from the research driving it to how and when to use it - and employ it profitably. But even outside the realm of high-tech, the technology is gaining notice. Consider:

• The Economist featured the cover story “Print Me a Stradivarius” in February 2010. In that issue, LAM consultant and LAM 2012 keynote speaker Terry Wohlers noted that more than 20 percent of the output of 3D printers is final products; he expects this to rise to 50 percent by 2020.
• A column in the January 30 Wall Street Journal called laser additive manufacturing one of three keys to the new tech boom in the United States, imagining the “ ‘desktop’ printing of entire final products from wheels to even washing machines.”

In short, Kelbassa told LAM 2012 attendees, LAM promises “complexity for free and individualization for free.” In a society growing increasingly concerned for the environmental impact of products, LAM offers a way to substantially reduce part weight, thereby saving aviation fuel costs and minimizing the amount of material required for manufacture.

To learn more about the LIA, its Laser Additive Manufacturing (LAM) workshop, other events and corporate members, visit www.lia.org.

About LIA
Laser Institute of America (LIA) is the professional society for laser applications and safety serving the industrial, educational, medical, research and government communities throughout the world since 1968. www.lia.org, 13501 Ingenuity Drive, Ste 128, Orlando, FL 32826, +1.407.380.1553

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