Final Report Summary - APACOS (Automated Precision Assembly for Complex Optical Systems)
Executive Summary:
The APACOS project aimed at developing holistic solutions for the automated assembly of laser systems including production equipment, product design and process design. The results include new laser sources and optical designs tailored for automated assembly, as well as industrial micro assembly systems for efficient manual, semi-automated or fully automated assembly. Core components of the assembly solutions are ultra-precise micromanipulator technology, precise dosing systems for adhesives and camera technology for visual location and identification of parts and reference marks. For fully automated industrial automation a micro assembly cell (MicRohCell compact by Rohwedder Micro Assembly GmbH) was mechanically enhanced by an ultra-precise micromanipulator for additional degrees of freedom, a jet-dispensing unit, an actuated target camera for multiple focus levels. A detailed laser safety concept has been developed. The enhanced machine successfully fulfilled the cleanroom requirements defined by the laser manufacturers in the project. For the FISBA Beam Twister module, fully automated alignment strategies of highly sensitive optical components have been developed. For Modulight, a laser manufacturer from Finland, new laser sources for edge emitting lasers in the visible spectrum with increased output power have been developed by the Opto-electronic Research Centre (ORC) at Tampere University of Technology, a leading European research institution in the field of laser sources. Fraunhofer contributed an optical design for a novel multi-single-emitter module in the range of visible red with promising results regarding the coupling efficiency which could be achieved using sophisticated assembly equipment. For Altechna R&D, ORC developed new laser chips with improved efficiency to be applied in the VECSEL technology by Altechna. Also, yield and maximum output power were increased significantly. Altechna aims at a high-power yellow laser based on OPSL technology with perspectives in the markets of health care and life sciences. Modulight pursues the development of a
single-emitter based product platform for visible lasers used for projection and display applications. SmarAct, an SME from Germany, who is provider of precision technology such as multi-axes micromanipulators with nanometer precision was part of the consortium. Products from SmarAct's portfolio can be integrated into highly demanding production solutions. Rohwedder Micro Assembly is a company with long year experience in developing industrial micro assembly systems and was also a partner in the project. The integration of assembly solutions as well as process development was mainly carried out by the Fraunhofer Institute for Production Technology IPT, a leading edge research institute in the field of automated optics assembly. Together, the APACOS consortium achieved on step towards a more standardized and automated assembly of lasers and optical systems considering aspects of product design, production system requirements, and process development. The APACOS project can be considered as a basis for future cooperation between the consortium partners. New business opportunities opened up due to the developments in APACOS. An industrial working group dealing with the assembly of optical systems has been founded during the project's life time. The project results are expected to have a major impact on the European laser industry by strengthening innovative laser manufacturers through more competitive production conditions. Corresponding dissemination and exploitation actions have been defined during project runtime.
Project Context and Objectives:
The motivation of the APACOS project was the improvement of competitiveness of the European laser manufacturing industry by developing standardized production solutions for the automated assembly of optical components for laser systems. A flexible off-the-shelf solution would allow European laser manufacturers, especially SMEs, to focus on the development of leading edge laser technology while being globally competitive from an economical point of view. Improved competitiveness of laser manufacturers would mainly arise from
• shorter time-to-market,
• better scalability of production volume, and
• more constant quality on a high level
of their laser products in a versatile market. The APACOS approach aims for a holistic solution for the laser manufacturing industry addressing interdependencies and challenges of the production system, of the product design, of the optical alignment as well as of the component bonding processes. Key principles of the developments are better flexibility through modularity and more efficiency through re-use applied to an automated production system with highest requirements on precision.
The key for efficient and competitive laser manufacturing in the future is the automation of assembly processes. The main value-adding steps of laser manufacturing will be addressed and optimized including the consideration of their interdependencies. The following paragraphs give an overview of the main technical concepts in APACOS for the production system, the product design (laser sources), and the assembly process design (alignment and bonding).
The developments regarding the production system aim for flexibility while supporting fully automated manipulation and bonding processes. The APACOS approach combines the advantage of conventional positioning systems covering a large work space with the high local precision of micromanipulation and machine vision. Therefore, compact Piezo-driven micromanipulators are mounted to conventional positioning systems adding the necessary degrees of freedom for high precision manipulation. The integrated and versatile assembly system is one major result of the project with high impact potential for the European laser manufacturers.
The control concept aims at combining the robustness of conventional industrial control systems using PLC and the flexibility and potential for re-use of high level programming languages such as C# or Python. One key aspect is the classification of equipment (e.g. actuators, sensors) and processes (e.g. alignment of certain lens types) and the mapping of such a classification to an object-oriented framework allowing the use of programming concepts such as inheritance and polymorphism. A control architecture allowing assembly execution through high-Level programming has been implemented.
The main aspects regarding laser system design which address the challenges of laser manufacturing include
• product design for automated assembly,
• component design for automated assembly, and
• modular product architectures or platforms for a flexible creation of variants.
All of these aspects have been addressed in the APACOS project. Design guidelines for optical components considering handling and manufacturing aspects have been discussed, specified, and disseminated. The objective was to develop and assess standard component geometries for automated handling and bonding. Novel and innovative laser sources with clear market potential have been developed in APACOS. This includes concepts for generic product platforms for large volume markets of semiconductor lasers. The product platform explores the possibilities of standardization and modularization in laser sources to facilitate an automated assembly of different variants on a single assembly system. The basic idea is to achieve high production volumes and increase the efficiency of automated production.
The laser and optics manufacturers face the challenge to implement and test automated alignment processes for optical components. Consequently, one main technological objective was to develop flexible measuring arrangements for passive and active alignment processes and to investigate and optimize alignment algorithms for relevant laser optics. In APACOS process development platforms, prototyping stations, allowing easy-to-use operator access to equipment (such as
micromanipulator, adhesive dosing and curing, …) for analyzing complex optical alignment and bonding processes have been set up. Crucial process steps can be developed without utilizing capacities of a production system. For faster transfer onto the production system, APACOS harmonized the high-level language control interfaces of process prototyping with the interfaces of the production system.
During the APACOS project, Fraunhofer IPT supported SmarAct in setting up a prototyping station for optical assemblies. The main role of IPT were requirements and market analyses, recommendation of equipment, and consulting.
In the course of APACOS project TUT has designed and developed diode lasers for second harmonic generation and miniaturized modules that incorporate laser diode, nonlinear crystal for second harmonic generation and relevant passive optics for beam handling. At 1064 nm TUT has demonstrated 4W single mode laser that outperforms commercially available lasers (currently 2W available) and therefore can be interesting products for Modulight. These sources however require more work within certain application case to study their performance merits, reliably and yield before they can be commercialized. 1180 nm laser sources are not commercially available near to the performance comparable to lasers developed within APACOS. For these lasers Modulight has already found first customer case for which TUT has fabricated batch of the lasers that can be evaluated by to Modulight and Their customer. TUT has agreed with Modulight to make new wafer run that produces next generation chips that are expected to produce even better performance and yield.
As a second strand of developments, TUT has advanced the technology for fabricating SDL gain chips with bottom emission (flip chip). The chips have been delivered to Altechna according to technical Targets specified in the project and integrated in laser prototypes with yellow emission. In parallel TUT has carried out another project funded by TEKES (Finnish Agency for Technology and Innovation) and demonstrated even higher powers for the yellow lab systems than what Altechna has obtained with more compact laser prototypes. This proves the readiness of gain chip technology. The key milestones concerning the commercialization of SDL, is to set up a commercial environment at TUT for manufacturing of gain chips
(currently in progress as part of a pre-commercialization project funded by TEKES). Altechna could then obtain commercial chips for own laser system. As part of the project TUT has transferred not only Chips for test but also know-how concerning thermal management, choice of cavity for efficient nonlinear frequency conversion, choice of nonlinear crystal etc.
Project Results:
In the course of the APACOS project, Fraunhofer IPT setup a prototyping station for the assembly of optical systems. Constraints regarding the assembly of Altechna’s OPSL technology have been considered. In the course of the project, several alternatives of prototyping stations have been designed conceptually. Subsequently, the concepts have been evaluated. The concepts were:
• Prototyping station for manual operation including micro-assembly tools (PC-operated micromanipulator, dosing head and UV-lamp)
• Prototyping station for semi-automated operation including micro-assembly tools as above plus motorized stages moving either the tools or the work pieces
• Prototyping station for fully-automated operation including micro-assembly tools as above plus a full featured gantry system
The technological evaluation resulted in favor of the prototyping station for fullyautomated operation. The purchase of the hardware for such a system was out of the scope of the APACOS project. This led to the decision to setup a low-cost manually operated prototyping station within the project. The parties, Altechna and IPT, agreed to initiate a bi-lateral follow-up project financed by Altechna to enhance the prototyping station to the full-featured version allowing full automation. Since the microassembly tools have been chosen to allow their integration into an automation system, they can be transferred to the new system.
Altechna and IPT identified the core tools of an assembly system for optical components:
• Micromanipulator
• Dispensing unit
• UV-light source
Additional equipment such as cameras needs to be chosen on a process-specific basis and therefore they were not included in this development. Several alternative setups have been designed conceptually and evaluated in order to find the optimal solution for Altechna within the scope of the project. Main requirements criteria for the setup were the following:
• Integration of above mentioned tools
• Sufficient construction space for process-specific setups
• Expenses within project budget
The first concept was the most cost-efficient regarding the initial investment. It includes the main tools and therefore fulfills the main requirement. Using profile construction the required construction space can be realized and adapted in the future. The overall expenses are within the Project budget.
An X-Y-Z-stage is intended to hold the substrate to mount the optical elements. The micromanipulator holds the optical elements. Since the micromanipulator position is not mobile it is required to move the X-Y-Z-stage. In the initial concept, mechanical endstops were designed to allow an operator to manually move the stage between the alignment position under the micromanipulator and the dispensing position under the dispenser. The UV-light source may be operated manually using a hand held device or mounted to where the process requires it to be. Assembly using such a station requires much manual work. It supports the operator in the most critical process steps of precise dispensing and alignment. A drawback of such a system is the need of dispensing lines or patterns as the X-Y-Z stage needs to be moved with reference to the dispenser – a job that can hardly be executed by an operator.
The assembly platform MicRohCell® compact (MRC) by Rohwedder Micro Assembly is a well established industrial assembly solution for micro-systems. The concept of exchangeable process plates makes it a highly flexible system allowing the production of multiple products or variants on a single machine. This key feature makes the machine potentially interesting for the market of micro-optical systems. One goal of the APACOS project was to achieve a more standardized solution for the assembly of micro-optical systems as there is the need for such systems. Prior to the project, the MRC platform consisted of an XYZ-gantry system. Tools have been attached as required by the process. The integration in the machine control (Soft-PLC) has been carried out on an individual basis. The main achievements of the APACOS project are:
• Integration of a micromanipulator including robust communication with machine control
• Integration of an additional rotational axis for more rotational freedom of the attached micromanipulator
• Integration of an additional Z-axis which holds a stereovision system
• Integration of a stereovision system
• Integration of a jet-dispensing system
• Provision of an interface for high-level programming in Python
Additionally, a laser safety concept has been worked out with professionals. This concept has not been realized in the project. It is meant to be applied to upcoming machine orders from laser manufacturers. The standard tools of manipulation, dispensing, and vision have been integrated or enhanced. A mobile control cabinet increases flexibility. The backside was enhanced by a second Z-axis holding a stereo vision system. The original MRC comes with a fixed target camera system. The drawback of such a system is the limited use due to a single focus plane. The height of the focus plane needed to be considered constructing magazine holders and such because features to be detected using image processing needed to be at that specific height of the focus plane.
The new vision system is attached to the additional Z-axis on the backside of the MRC. The construction show a kind of L-shape so that the field of view of the camera is close to the manipulator. This construction prevents losing much common workspace between the camera and the rest of the tools attached to the frontside of the MRC.
The camera is attached horizontally while the optical path of the camera view is redirected by a mirror in a 90° angle. This setup saves vertical construction space which is needed in order to prevent collisions.
A second camera (and mirror) is attached to the L-construction so that the system can actually be used as a stereo vision system.
For simplified development of complex tasks involving micromanipulation, image processing, and machine control a high-level programming language has been realized. As a result from the APACOS project it is possible to control all involved devices using the Python scripting language.
In the course of the APACOS project, Fraunhofer setup a process plate for the assembly of the FISBA Beam Twister (FBT). The results are promising and prove the feasibility of automating the demanding subassembly by FISBA. The FBT consists of two beam-shaping optics and a bottom tab to incorporate both components in one module. The first component collimates the irradiated light in fast axis while the second component consists of a beam twisting micro-lens-array. The product is provided from FISBA OPTIK AG and can be utilized e.g. in miniaturized fiber coupling application. A reference diode laser bar is installed to allow for an active alignment process for the sensitive FAC component as well as the beam twisting lens-array.
A breadboard was specially tailored for the assembly of the FBT and it can be exchanged and commissioned in the MRC in a flexible manner. An exchange system provides a supply of air-pressure, electricity and EtherCAT access. All assembly parts are provided on industry standard vacuum release (VR) GelPaks®. The pickup process is realized by a computer vision based part detection. The alignment process is performed with a reference laser (938 nm) which is mounted stationary on the board. Two separate beam paths for FAC respectively FBT assembly are necessary to perform an active alignment based on intensity distributions resulting on the sensor of each camera at either end of the optical path. A beam splitter is utilized to separate both paths behind the assembly on the optical axis.
A mirror in front of the beam splitter diverts 99 % of the output power into a beam dump in order to protect the camera sensors which are otherwise only shaded by neutral density filters (ND filter). ND filter reduce the intensity of all wavelengths equally without change in hue or color rendition. This allows for individual adjustment to avoid oversteer which is crucial for a correct beam analysis. The first beam path passes the beam splitter in one straight line from the reference laser to the camera in the back of the breadboard. The optical components along this optical axis are positioned and tuned to depict the intensity distribution right behind the FAC lens on the camera sensor. This data can be utilized for the active alignment of this first component.
The optical path redirected 90 degrees by the beam splitter is meant to focus the collimated and twisted laser on the camera sensor. By manipulating the cylinder array as a second component in the assembly the resulting intensity distribution is focused and serves as criteria for the active alignment.
The third camera system is equipped with a telecentric macro lens to observe the mounting area in front of the emitter. In order to enable the computer vision to detect the position of FAC and cylinder array during the passive alignment, backlighting has been installed. This illumination technique allows for eased identification of contours as the background appears in bright white, while parts appear dark with clear edges.
Passive alignment is dedicated to ensure a collision free positioning of the FAC lens in front of the laser. Most important hereby is a specified distance in z-axis of the laser reference coordinate system. The passive alignment processes image data, from a side view on FAC and diode laser. Because contours have to be referenced to each other, backlighting has been installed. This illumination technique enhances the contrast of foreground, appearing black or in dark colors, and background, which appears in over steering white.
During active alignment of the FAC the intensity distribution on the camera sensor is analyzed. The characteristic pattern is generated due to the beam shaping in slow and fast axis. Using cylindrical as opposed to spherical lenses this transformation in both axis can be performed with separated lenses which facilitates a manual setup. Thereby the slow axis is influenced solely by two stationary plano-convex lenses located in the center of the optical layout. Plano-convex lenses are used for collimation respectively focusing a beam with the collimated part impinging on the convex side of the lens. In the present setup both lenses are responsible for a clear separation of the emitters. The optical metrology setup for the FBT component is based on the same components as the FAC setup, with the exception of a 90 degree rotation along the optical path.
Another result of the APACOS project is a design of a novel visible red laser module based on multiple single emitters coupled into a fiber. The design has been realized and assembled for demonstration. The results are promising but the performance (mainly coupling efficiency) is not yet fully sufficient for Modulight’s purposes. It is not completely understood if the loss of performance occurred due to lacking assembly experience with this specific module (cooling, assembly order, …) or due to product design.
The optical components have to be aligned actively in order to achieve a high coupling efficiency of the laser system. The process development for automated assembly usually happens in two stages. Firstly, the processes are developed on a manual assembly station (prototyping station) to be transferred onto a production platform. Within the scope of the project the first stage (development of processes on prototyping station) was carried out. Process development was carried out on a prototyping Station.
The Fast Axis collimation lens (FAC) and the Slow Axis collimation lens (SAC) need to be actively aligned. In order to position the lens in a suitable position a farfield image needs to be analyzed. Therefore, a farfield imaging system has been setup. One option is to look at a far distance at the remaining divergence of the beam and minimize it.
Potential Impact:
Photonics technologies are key technologies of the 21st century enabling innovative applications in demanding and societal relevant domains. Photonics impacts around 10% of Europe’s economy, generating values worth €58.5billion and providing employment for 290,000 people (Photonics 21 (2011), The Leverage Effect of Photonics Technologies). It has a tremendous leverage for creating products in a broad range of industrial sectors that multiply the value of initial photonic components and technologies.
Markets addressed by APACOS are on the one hand laser applications such as aesthetics and life-sciences (Altechna), projection and displays (Modulight), and high-power fiber-coupling of laser diode bars (FISBA) and on the other production systems for optical assemblies.
Altechna addresses specifically the aesthetics market which recovered from the economic crisis in 2009/ 2010. Worldwide sales numbers are increasing and currently at a total of USD 685 million (2013). The wavelength of 589 nm is applicable for the treatment of port-wine stains (primary application) and Tattoo removal (secondary application). These applications stand for about 20 % of market share which corresponds to USD 141 million.
Within the scope of single-emitter based laser modules, Modulight addresses two laser market segments. First market is the medical field which is a slowly growing market. Increase of quantities is moderate. The second market segment addresses display and projection technologies in the field of cinema applications. Increase of quantities is more drastic. In both areas a price drop per unit is expected to about 66% of the price from 2012. Modulight has business contacts to many companies in the display and projection segment such as Christie, Barco, NEC, and Sony. The market is currently open for new comers because of the novel laser technology – more potential partners for Modulight.
FISBA Beam Twister modules are used for high-brightness fiber coupling for high-power applications. The demand for more modules is high. From FISBA’s customer requests alone, FISBA needs to multiply the current production volume by more than 10.
Rohwedder addresses the diode laser market. Diode lasers have high potential regarding many applications in mass markets such as telecommunication, consumer products such as projection and display, medical and aesthetic applications, and materials processing. But yet, challenging manufacturing circumstances are a major obstacle for diode laser technology. The market trends for the application areas addressed directly by the project are showing a clear upwards trend (LaserFocusWorld 2013). In the field of communications, higher integration levels are required for meeting the demands of communication networks in the future with respect to bandwidths of 100 Gb/s or even 1 Tb/s. The expansion of wireless networks requires optical fiber backbones for mass applications such as video streaming and cloud storage. The communications segment has a total volume of approximately $2.67 billion and a predicted growth of 7 % in 2013. The market of materials processing is dominated by fiber lasers had a strong year in 2012. Most materials processing segments will experience a moderate growth while excimer lasers decrease in market share. The application of diode lasers challenges dominating solutions such as fiber lasers due to higher efficiency and better costeffectiveness. The biggest growth rate can be identified for the entertainment and display application area of about 50 % over the past two years. Projectors will be incorporated in mobile devices and movie theaters for 2D and 3D entertainment with ultra-high brightness values.
With the process prototyping station SmarAct addresses rather small production volumes as well as research and development in micro-optical assembly. The process prototyping station is especially suitable for SME high-technology companies and research and development institutes because of its flexibility.
Dissemination activities include the following:
- Project Website (www.apacos.net)
- Exhibition and talks at Photonics West 2013 and 2014 as well as Laser Fair 2013 and Photonics Europe 2014
- Publications in international peer reviewed journals
- Assembly Workshop at Fraunhofer IPT in 2013 and 2014
- Founding of an industrial working group in June 2014
- Press releases
- Best Paper Award: T. Müller, S. Haag, T. Bastuck, T. Gisler, H. Moser, P. Uusimaa, C. Axt, C. Brecher, “Robust Adhesive Precision Bonding in Automated Assembly Cells,” Presented at IPAS 2014, February 16 – 19, Chamonix, France (2014)
Rohwedder, IPT and SmarAct have worked out a pricing policy for precision actuators and micromanipulators for the use in the enhanced MicRohCell compact. The policy is based on the expected sales numbers of assembly machines (between five and twenty in the first three years after the project). The policy includes discount rates of up to 12.5 % (depending on the ordered amount) for the purchase of precision actuators from SmarAct. IPT worked concepts in order to produce the flexures more efficiently exploiting economies-of-scale. Combining all savings potentials through collaboration of the partners, the costs for the micromanipulator in the MRC can be reduced by more than 20 %.
Rohwedder and IPT worked out a quote for an enhanced MicRohCell compact for series production of the FISBA Beam Twister. In this context, Rohwedder and IPT are clarifying the conditions for the use of Background. The price for licensing active alignment processes from IPT is based on the development efforts divided by the expected licenses to be sold in the first three years after the project.
IPT carried out an analysis regarding high-volume production of the multi-single-emitter module. A list of revision points based on the experience from manual assembly has been documented. Follow-up projectsare between the partners Modulight, IPT and ORC are under discussion.
Modulight will receive a set of 1180 nm DBR lasers for packaging and prospective customer testing. Frequency doubled module design and related know-how will be transferred once full capability is assessed. Altechna and ORC have made a tentative expression of interest for partnership concerning commercial supply of SDL chips and general support for system levels development. ORC has also initiated parallel development projects for SDLs at new wavelengths targeting laser projections and spectroscopic applications.
List of Websites:
http://www.apacos.net/
Coordinator contact: Fraunhofer Institute for Production Technology IPT, Sebastian Haag (Group Manager Assembly of Optical Systems and Automation), sebastian.haag@ipt.fraunhofer.de +49 241 8904 - 253
The APACOS project aimed at developing holistic solutions for the automated assembly of laser systems including production equipment, product design and process design. The results include new laser sources and optical designs tailored for automated assembly, as well as industrial micro assembly systems for efficient manual, semi-automated or fully automated assembly. Core components of the assembly solutions are ultra-precise micromanipulator technology, precise dosing systems for adhesives and camera technology for visual location and identification of parts and reference marks. For fully automated industrial automation a micro assembly cell (MicRohCell compact by Rohwedder Micro Assembly GmbH) was mechanically enhanced by an ultra-precise micromanipulator for additional degrees of freedom, a jet-dispensing unit, an actuated target camera for multiple focus levels. A detailed laser safety concept has been developed. The enhanced machine successfully fulfilled the cleanroom requirements defined by the laser manufacturers in the project. For the FISBA Beam Twister module, fully automated alignment strategies of highly sensitive optical components have been developed. For Modulight, a laser manufacturer from Finland, new laser sources for edge emitting lasers in the visible spectrum with increased output power have been developed by the Opto-electronic Research Centre (ORC) at Tampere University of Technology, a leading European research institution in the field of laser sources. Fraunhofer contributed an optical design for a novel multi-single-emitter module in the range of visible red with promising results regarding the coupling efficiency which could be achieved using sophisticated assembly equipment. For Altechna R&D, ORC developed new laser chips with improved efficiency to be applied in the VECSEL technology by Altechna. Also, yield and maximum output power were increased significantly. Altechna aims at a high-power yellow laser based on OPSL technology with perspectives in the markets of health care and life sciences. Modulight pursues the development of a
single-emitter based product platform for visible lasers used for projection and display applications. SmarAct, an SME from Germany, who is provider of precision technology such as multi-axes micromanipulators with nanometer precision was part of the consortium. Products from SmarAct's portfolio can be integrated into highly demanding production solutions. Rohwedder Micro Assembly is a company with long year experience in developing industrial micro assembly systems and was also a partner in the project. The integration of assembly solutions as well as process development was mainly carried out by the Fraunhofer Institute for Production Technology IPT, a leading edge research institute in the field of automated optics assembly. Together, the APACOS consortium achieved on step towards a more standardized and automated assembly of lasers and optical systems considering aspects of product design, production system requirements, and process development. The APACOS project can be considered as a basis for future cooperation between the consortium partners. New business opportunities opened up due to the developments in APACOS. An industrial working group dealing with the assembly of optical systems has been founded during the project's life time. The project results are expected to have a major impact on the European laser industry by strengthening innovative laser manufacturers through more competitive production conditions. Corresponding dissemination and exploitation actions have been defined during project runtime.
Project Context and Objectives:
The motivation of the APACOS project was the improvement of competitiveness of the European laser manufacturing industry by developing standardized production solutions for the automated assembly of optical components for laser systems. A flexible off-the-shelf solution would allow European laser manufacturers, especially SMEs, to focus on the development of leading edge laser technology while being globally competitive from an economical point of view. Improved competitiveness of laser manufacturers would mainly arise from
• shorter time-to-market,
• better scalability of production volume, and
• more constant quality on a high level
of their laser products in a versatile market. The APACOS approach aims for a holistic solution for the laser manufacturing industry addressing interdependencies and challenges of the production system, of the product design, of the optical alignment as well as of the component bonding processes. Key principles of the developments are better flexibility through modularity and more efficiency through re-use applied to an automated production system with highest requirements on precision.
The key for efficient and competitive laser manufacturing in the future is the automation of assembly processes. The main value-adding steps of laser manufacturing will be addressed and optimized including the consideration of their interdependencies. The following paragraphs give an overview of the main technical concepts in APACOS for the production system, the product design (laser sources), and the assembly process design (alignment and bonding).
The developments regarding the production system aim for flexibility while supporting fully automated manipulation and bonding processes. The APACOS approach combines the advantage of conventional positioning systems covering a large work space with the high local precision of micromanipulation and machine vision. Therefore, compact Piezo-driven micromanipulators are mounted to conventional positioning systems adding the necessary degrees of freedom for high precision manipulation. The integrated and versatile assembly system is one major result of the project with high impact potential for the European laser manufacturers.
The control concept aims at combining the robustness of conventional industrial control systems using PLC and the flexibility and potential for re-use of high level programming languages such as C# or Python. One key aspect is the classification of equipment (e.g. actuators, sensors) and processes (e.g. alignment of certain lens types) and the mapping of such a classification to an object-oriented framework allowing the use of programming concepts such as inheritance and polymorphism. A control architecture allowing assembly execution through high-Level programming has been implemented.
The main aspects regarding laser system design which address the challenges of laser manufacturing include
• product design for automated assembly,
• component design for automated assembly, and
• modular product architectures or platforms for a flexible creation of variants.
All of these aspects have been addressed in the APACOS project. Design guidelines for optical components considering handling and manufacturing aspects have been discussed, specified, and disseminated. The objective was to develop and assess standard component geometries for automated handling and bonding. Novel and innovative laser sources with clear market potential have been developed in APACOS. This includes concepts for generic product platforms for large volume markets of semiconductor lasers. The product platform explores the possibilities of standardization and modularization in laser sources to facilitate an automated assembly of different variants on a single assembly system. The basic idea is to achieve high production volumes and increase the efficiency of automated production.
The laser and optics manufacturers face the challenge to implement and test automated alignment processes for optical components. Consequently, one main technological objective was to develop flexible measuring arrangements for passive and active alignment processes and to investigate and optimize alignment algorithms for relevant laser optics. In APACOS process development platforms, prototyping stations, allowing easy-to-use operator access to equipment (such as
micromanipulator, adhesive dosing and curing, …) for analyzing complex optical alignment and bonding processes have been set up. Crucial process steps can be developed without utilizing capacities of a production system. For faster transfer onto the production system, APACOS harmonized the high-level language control interfaces of process prototyping with the interfaces of the production system.
During the APACOS project, Fraunhofer IPT supported SmarAct in setting up a prototyping station for optical assemblies. The main role of IPT were requirements and market analyses, recommendation of equipment, and consulting.
In the course of APACOS project TUT has designed and developed diode lasers for second harmonic generation and miniaturized modules that incorporate laser diode, nonlinear crystal for second harmonic generation and relevant passive optics for beam handling. At 1064 nm TUT has demonstrated 4W single mode laser that outperforms commercially available lasers (currently 2W available) and therefore can be interesting products for Modulight. These sources however require more work within certain application case to study their performance merits, reliably and yield before they can be commercialized. 1180 nm laser sources are not commercially available near to the performance comparable to lasers developed within APACOS. For these lasers Modulight has already found first customer case for which TUT has fabricated batch of the lasers that can be evaluated by to Modulight and Their customer. TUT has agreed with Modulight to make new wafer run that produces next generation chips that are expected to produce even better performance and yield.
As a second strand of developments, TUT has advanced the technology for fabricating SDL gain chips with bottom emission (flip chip). The chips have been delivered to Altechna according to technical Targets specified in the project and integrated in laser prototypes with yellow emission. In parallel TUT has carried out another project funded by TEKES (Finnish Agency for Technology and Innovation) and demonstrated even higher powers for the yellow lab systems than what Altechna has obtained with more compact laser prototypes. This proves the readiness of gain chip technology. The key milestones concerning the commercialization of SDL, is to set up a commercial environment at TUT for manufacturing of gain chips
(currently in progress as part of a pre-commercialization project funded by TEKES). Altechna could then obtain commercial chips for own laser system. As part of the project TUT has transferred not only Chips for test but also know-how concerning thermal management, choice of cavity for efficient nonlinear frequency conversion, choice of nonlinear crystal etc.
Project Results:
In the course of the APACOS project, Fraunhofer IPT setup a prototyping station for the assembly of optical systems. Constraints regarding the assembly of Altechna’s OPSL technology have been considered. In the course of the project, several alternatives of prototyping stations have been designed conceptually. Subsequently, the concepts have been evaluated. The concepts were:
• Prototyping station for manual operation including micro-assembly tools (PC-operated micromanipulator, dosing head and UV-lamp)
• Prototyping station for semi-automated operation including micro-assembly tools as above plus motorized stages moving either the tools or the work pieces
• Prototyping station for fully-automated operation including micro-assembly tools as above plus a full featured gantry system
The technological evaluation resulted in favor of the prototyping station for fullyautomated operation. The purchase of the hardware for such a system was out of the scope of the APACOS project. This led to the decision to setup a low-cost manually operated prototyping station within the project. The parties, Altechna and IPT, agreed to initiate a bi-lateral follow-up project financed by Altechna to enhance the prototyping station to the full-featured version allowing full automation. Since the microassembly tools have been chosen to allow their integration into an automation system, they can be transferred to the new system.
Altechna and IPT identified the core tools of an assembly system for optical components:
• Micromanipulator
• Dispensing unit
• UV-light source
Additional equipment such as cameras needs to be chosen on a process-specific basis and therefore they were not included in this development. Several alternative setups have been designed conceptually and evaluated in order to find the optimal solution for Altechna within the scope of the project. Main requirements criteria for the setup were the following:
• Integration of above mentioned tools
• Sufficient construction space for process-specific setups
• Expenses within project budget
The first concept was the most cost-efficient regarding the initial investment. It includes the main tools and therefore fulfills the main requirement. Using profile construction the required construction space can be realized and adapted in the future. The overall expenses are within the Project budget.
An X-Y-Z-stage is intended to hold the substrate to mount the optical elements. The micromanipulator holds the optical elements. Since the micromanipulator position is not mobile it is required to move the X-Y-Z-stage. In the initial concept, mechanical endstops were designed to allow an operator to manually move the stage between the alignment position under the micromanipulator and the dispensing position under the dispenser. The UV-light source may be operated manually using a hand held device or mounted to where the process requires it to be. Assembly using such a station requires much manual work. It supports the operator in the most critical process steps of precise dispensing and alignment. A drawback of such a system is the need of dispensing lines or patterns as the X-Y-Z stage needs to be moved with reference to the dispenser – a job that can hardly be executed by an operator.
The assembly platform MicRohCell® compact (MRC) by Rohwedder Micro Assembly is a well established industrial assembly solution for micro-systems. The concept of exchangeable process plates makes it a highly flexible system allowing the production of multiple products or variants on a single machine. This key feature makes the machine potentially interesting for the market of micro-optical systems. One goal of the APACOS project was to achieve a more standardized solution for the assembly of micro-optical systems as there is the need for such systems. Prior to the project, the MRC platform consisted of an XYZ-gantry system. Tools have been attached as required by the process. The integration in the machine control (Soft-PLC) has been carried out on an individual basis. The main achievements of the APACOS project are:
• Integration of a micromanipulator including robust communication with machine control
• Integration of an additional rotational axis for more rotational freedom of the attached micromanipulator
• Integration of an additional Z-axis which holds a stereovision system
• Integration of a stereovision system
• Integration of a jet-dispensing system
• Provision of an interface for high-level programming in Python
Additionally, a laser safety concept has been worked out with professionals. This concept has not been realized in the project. It is meant to be applied to upcoming machine orders from laser manufacturers. The standard tools of manipulation, dispensing, and vision have been integrated or enhanced. A mobile control cabinet increases flexibility. The backside was enhanced by a second Z-axis holding a stereo vision system. The original MRC comes with a fixed target camera system. The drawback of such a system is the limited use due to a single focus plane. The height of the focus plane needed to be considered constructing magazine holders and such because features to be detected using image processing needed to be at that specific height of the focus plane.
The new vision system is attached to the additional Z-axis on the backside of the MRC. The construction show a kind of L-shape so that the field of view of the camera is close to the manipulator. This construction prevents losing much common workspace between the camera and the rest of the tools attached to the frontside of the MRC.
The camera is attached horizontally while the optical path of the camera view is redirected by a mirror in a 90° angle. This setup saves vertical construction space which is needed in order to prevent collisions.
A second camera (and mirror) is attached to the L-construction so that the system can actually be used as a stereo vision system.
For simplified development of complex tasks involving micromanipulation, image processing, and machine control a high-level programming language has been realized. As a result from the APACOS project it is possible to control all involved devices using the Python scripting language.
In the course of the APACOS project, Fraunhofer setup a process plate for the assembly of the FISBA Beam Twister (FBT). The results are promising and prove the feasibility of automating the demanding subassembly by FISBA. The FBT consists of two beam-shaping optics and a bottom tab to incorporate both components in one module. The first component collimates the irradiated light in fast axis while the second component consists of a beam twisting micro-lens-array. The product is provided from FISBA OPTIK AG and can be utilized e.g. in miniaturized fiber coupling application. A reference diode laser bar is installed to allow for an active alignment process for the sensitive FAC component as well as the beam twisting lens-array.
A breadboard was specially tailored for the assembly of the FBT and it can be exchanged and commissioned in the MRC in a flexible manner. An exchange system provides a supply of air-pressure, electricity and EtherCAT access. All assembly parts are provided on industry standard vacuum release (VR) GelPaks®. The pickup process is realized by a computer vision based part detection. The alignment process is performed with a reference laser (938 nm) which is mounted stationary on the board. Two separate beam paths for FAC respectively FBT assembly are necessary to perform an active alignment based on intensity distributions resulting on the sensor of each camera at either end of the optical path. A beam splitter is utilized to separate both paths behind the assembly on the optical axis.
A mirror in front of the beam splitter diverts 99 % of the output power into a beam dump in order to protect the camera sensors which are otherwise only shaded by neutral density filters (ND filter). ND filter reduce the intensity of all wavelengths equally without change in hue or color rendition. This allows for individual adjustment to avoid oversteer which is crucial for a correct beam analysis. The first beam path passes the beam splitter in one straight line from the reference laser to the camera in the back of the breadboard. The optical components along this optical axis are positioned and tuned to depict the intensity distribution right behind the FAC lens on the camera sensor. This data can be utilized for the active alignment of this first component.
The optical path redirected 90 degrees by the beam splitter is meant to focus the collimated and twisted laser on the camera sensor. By manipulating the cylinder array as a second component in the assembly the resulting intensity distribution is focused and serves as criteria for the active alignment.
The third camera system is equipped with a telecentric macro lens to observe the mounting area in front of the emitter. In order to enable the computer vision to detect the position of FAC and cylinder array during the passive alignment, backlighting has been installed. This illumination technique allows for eased identification of contours as the background appears in bright white, while parts appear dark with clear edges.
Passive alignment is dedicated to ensure a collision free positioning of the FAC lens in front of the laser. Most important hereby is a specified distance in z-axis of the laser reference coordinate system. The passive alignment processes image data, from a side view on FAC and diode laser. Because contours have to be referenced to each other, backlighting has been installed. This illumination technique enhances the contrast of foreground, appearing black or in dark colors, and background, which appears in over steering white.
During active alignment of the FAC the intensity distribution on the camera sensor is analyzed. The characteristic pattern is generated due to the beam shaping in slow and fast axis. Using cylindrical as opposed to spherical lenses this transformation in both axis can be performed with separated lenses which facilitates a manual setup. Thereby the slow axis is influenced solely by two stationary plano-convex lenses located in the center of the optical layout. Plano-convex lenses are used for collimation respectively focusing a beam with the collimated part impinging on the convex side of the lens. In the present setup both lenses are responsible for a clear separation of the emitters. The optical metrology setup for the FBT component is based on the same components as the FAC setup, with the exception of a 90 degree rotation along the optical path.
Another result of the APACOS project is a design of a novel visible red laser module based on multiple single emitters coupled into a fiber. The design has been realized and assembled for demonstration. The results are promising but the performance (mainly coupling efficiency) is not yet fully sufficient for Modulight’s purposes. It is not completely understood if the loss of performance occurred due to lacking assembly experience with this specific module (cooling, assembly order, …) or due to product design.
The optical components have to be aligned actively in order to achieve a high coupling efficiency of the laser system. The process development for automated assembly usually happens in two stages. Firstly, the processes are developed on a manual assembly station (prototyping station) to be transferred onto a production platform. Within the scope of the project the first stage (development of processes on prototyping station) was carried out. Process development was carried out on a prototyping Station.
The Fast Axis collimation lens (FAC) and the Slow Axis collimation lens (SAC) need to be actively aligned. In order to position the lens in a suitable position a farfield image needs to be analyzed. Therefore, a farfield imaging system has been setup. One option is to look at a far distance at the remaining divergence of the beam and minimize it.
Potential Impact:
Photonics technologies are key technologies of the 21st century enabling innovative applications in demanding and societal relevant domains. Photonics impacts around 10% of Europe’s economy, generating values worth €58.5billion and providing employment for 290,000 people (Photonics 21 (2011), The Leverage Effect of Photonics Technologies). It has a tremendous leverage for creating products in a broad range of industrial sectors that multiply the value of initial photonic components and technologies.
Markets addressed by APACOS are on the one hand laser applications such as aesthetics and life-sciences (Altechna), projection and displays (Modulight), and high-power fiber-coupling of laser diode bars (FISBA) and on the other production systems for optical assemblies.
Altechna addresses specifically the aesthetics market which recovered from the economic crisis in 2009/ 2010. Worldwide sales numbers are increasing and currently at a total of USD 685 million (2013). The wavelength of 589 nm is applicable for the treatment of port-wine stains (primary application) and Tattoo removal (secondary application). These applications stand for about 20 % of market share which corresponds to USD 141 million.
Within the scope of single-emitter based laser modules, Modulight addresses two laser market segments. First market is the medical field which is a slowly growing market. Increase of quantities is moderate. The second market segment addresses display and projection technologies in the field of cinema applications. Increase of quantities is more drastic. In both areas a price drop per unit is expected to about 66% of the price from 2012. Modulight has business contacts to many companies in the display and projection segment such as Christie, Barco, NEC, and Sony. The market is currently open for new comers because of the novel laser technology – more potential partners for Modulight.
FISBA Beam Twister modules are used for high-brightness fiber coupling for high-power applications. The demand for more modules is high. From FISBA’s customer requests alone, FISBA needs to multiply the current production volume by more than 10.
Rohwedder addresses the diode laser market. Diode lasers have high potential regarding many applications in mass markets such as telecommunication, consumer products such as projection and display, medical and aesthetic applications, and materials processing. But yet, challenging manufacturing circumstances are a major obstacle for diode laser technology. The market trends for the application areas addressed directly by the project are showing a clear upwards trend (LaserFocusWorld 2013). In the field of communications, higher integration levels are required for meeting the demands of communication networks in the future with respect to bandwidths of 100 Gb/s or even 1 Tb/s. The expansion of wireless networks requires optical fiber backbones for mass applications such as video streaming and cloud storage. The communications segment has a total volume of approximately $2.67 billion and a predicted growth of 7 % in 2013. The market of materials processing is dominated by fiber lasers had a strong year in 2012. Most materials processing segments will experience a moderate growth while excimer lasers decrease in market share. The application of diode lasers challenges dominating solutions such as fiber lasers due to higher efficiency and better costeffectiveness. The biggest growth rate can be identified for the entertainment and display application area of about 50 % over the past two years. Projectors will be incorporated in mobile devices and movie theaters for 2D and 3D entertainment with ultra-high brightness values.
With the process prototyping station SmarAct addresses rather small production volumes as well as research and development in micro-optical assembly. The process prototyping station is especially suitable for SME high-technology companies and research and development institutes because of its flexibility.
Dissemination activities include the following:
- Project Website (www.apacos.net)
- Exhibition and talks at Photonics West 2013 and 2014 as well as Laser Fair 2013 and Photonics Europe 2014
- Publications in international peer reviewed journals
- Assembly Workshop at Fraunhofer IPT in 2013 and 2014
- Founding of an industrial working group in June 2014
- Press releases
- Best Paper Award: T. Müller, S. Haag, T. Bastuck, T. Gisler, H. Moser, P. Uusimaa, C. Axt, C. Brecher, “Robust Adhesive Precision Bonding in Automated Assembly Cells,” Presented at IPAS 2014, February 16 – 19, Chamonix, France (2014)
Rohwedder, IPT and SmarAct have worked out a pricing policy for precision actuators and micromanipulators for the use in the enhanced MicRohCell compact. The policy is based on the expected sales numbers of assembly machines (between five and twenty in the first three years after the project). The policy includes discount rates of up to 12.5 % (depending on the ordered amount) for the purchase of precision actuators from SmarAct. IPT worked concepts in order to produce the flexures more efficiently exploiting economies-of-scale. Combining all savings potentials through collaboration of the partners, the costs for the micromanipulator in the MRC can be reduced by more than 20 %.
Rohwedder and IPT worked out a quote for an enhanced MicRohCell compact for series production of the FISBA Beam Twister. In this context, Rohwedder and IPT are clarifying the conditions for the use of Background. The price for licensing active alignment processes from IPT is based on the development efforts divided by the expected licenses to be sold in the first three years after the project.
IPT carried out an analysis regarding high-volume production of the multi-single-emitter module. A list of revision points based on the experience from manual assembly has been documented. Follow-up projectsare between the partners Modulight, IPT and ORC are under discussion.
Modulight will receive a set of 1180 nm DBR lasers for packaging and prospective customer testing. Frequency doubled module design and related know-how will be transferred once full capability is assessed. Altechna and ORC have made a tentative expression of interest for partnership concerning commercial supply of SDL chips and general support for system levels development. ORC has also initiated parallel development projects for SDLs at new wavelengths targeting laser projections and spectroscopic applications.
List of Websites:
http://www.apacos.net/
Coordinator contact: Fraunhofer Institute for Production Technology IPT, Sebastian Haag (Group Manager Assembly of Optical Systems and Automation), sebastian.haag@ipt.fraunhofer.de +49 241 8904 - 253