from June 17 to June 20, 2008 in Frankfurt/Germany
Joint Booth of the Fraunhofer Gesellschaft
Hall 3 Stand D53
The Fraunhofer IPMS carries out customer specific developments in fields of microelectronic and micro systems technology in Dresden, serving as a business partner that supports the transition of innovative ideas into new products. The Fraunhofer IPMS develops and fabricates modern CMOS technology products in its own clean room facilities, up to small pilot series production. With modern equipment and about 240 scientists, the range of projects and expertise covers sensor and actuator systems, microscanner, spatial light modulators, lifetronics and organic materials and systems. At the OPTATEC 2008 in Frankfurt the Fraunhofer IPMS presents:
1. MEMS Adaptive Optic Demonstrator for optical wavefront control and imaging enhancement
Adaptive Optics (AO) is mainly used for the compensation of spatially and timely varying wavefront disturbances within an optical system for an enhancement in optical imaging through inhomogeneous or turbulent media. Originally evolved from astronomy to compensate for atmospheric turbulences, AO techniques also can be used for aberration correction of the human eye in ophthalmology, for imaging through biological tissue in optical microscopy or for any kind of object recognition in machine vision. Furthermore, there are applications in laser beam shaping as well as in ultra-fast laser pulse modulation. The key component is formed by the actual wavefront controlling device. For that purpose MEMS (Micro-Electro-Mechanical-System) micro mirror arrays possess several attractive features. Due to their integrated fabrication capability they can support large pixel numbers providing an exceptional high spatial resolution for an improved reproduction especially of higher order phase aberrations. They also benefit from a step function display capability, fast mechanical response times, low power consumption, broad spectral bandwidth from IR down to DUV and polarization insensitivity. Compared to previous macroscale systems micro mirrors also offer the potential of a substantial cost decrease as well as a significant device miniaturization just facilitating completely new opportunities for a broader commercial exploitation. The Fraunhofer IPMS therefore has developed a complete MEMS Phase Former Kit. The key component is a high-resolution MEMS micro mirror array of 240 x 200 piston-type mirror elements with 40 µm pixel size providing 400 nm stroke at 8 bit resolution suitable for a 2π phase modulation in the visible. Full user programmability and control is established by a comfortable driver software for Windows XP® PCs supporting both a Graphical User Interface as well as an open ActiveX® programming interface for open-loop and closed-loop operation. High-speed data communication is accomplished by an IEEE1394a FireWire interface together with an electronic driving board allowing for maximum frame rates of up to 500 Hz. In order to visualize the potential for optical imaging enhancement a complete AO demonstrator system has been implemented. It basically comprises a projection system, where objects of different complexity are imaged through adaptive optics onto a CCD camera. Phase errors of different severness are introduced by rotating phase plates. Using a Shack-Hartmann sensor and the Fraunhofer IPMS MEMS micro mirror for wavefront sensing and correction respectively, the obtainable imaging improvement can be assessed by means of the recorded CCD picture, which is also projected onto a large screen. For a more quantitative anlaysis also some wavefront data without and with correction are made available.
Addressed business fields are optical system developers and manufacturers in the following areas:
- Machine Vision (in-situ process control through turbulent media)
- Optical Microscopy
- Laser Pulse Shaping
- Laser Beam Shaping
- Diffractive Optics (especially optical tweezers)
2. Tilt compensated laser projection unit integrated into a mobile phone
Fraunhofer IPMS shows a miniaturized monochrome laser projector which optical part fits into a mobile phone. The system is based on its own two dimensional micro scanning mirror. The system contains an ultra compact projection head and a separate laser and signal processing unit. It allows the projection of arbitrary images and video sequences with a geometrical resolution of 640 x 480 pixels, 256 brightness levels per pixel and elementary color, and 50 hertz frame rate. The projection modules developed by Fraunhofer IPMS overcome limitations of conventional projection systems – like rather large components for light deflection and high power light sources that consume lots of electrical power and radiate most of it thermally – by deploying the micro scanning mirror as key element for image generation and lasers as light sources. The patented micro scanning mirror of Fraunhofer IPMS is an ideal base for the development of compact projection heads. It distinguishes itself by high mechanical robustness and ease of both electrical control and optical coupling of the laser beam. Independent from the projector technology one major difficulty has to be solved: Movement of a handheld device will affect the image quality. Every object has six degrees of freedom, three translatory and three rotatory. Position changes are comparably slow and the human eye is used to follow moving objects and images. More difficult is the compensation of rotatory movement that occurs from shiver with a frequency to smear image pixels to lines. This has to be compensated electronically, which is shown in the demonstrator by adding an Inertial Measurement Unit to the system and electronically compensating rotatory movements. Additionally the movement can be used actively to control software functions of the handheld device.
3. MEMS Spatial Light Modulator Demonstrator
MEMS Spatial Light Modulators (SLMs) are used to arbitrarily modulate the entire cross section of an incident beam of light simultaneously. Usually, MEMS thin film technology is used to fabricate an array of micromirrors on top of a CMOS backplane. Each mirror can be addressed and moved individually to control either intensity or phase of one pixel. SLMs are used in a range of applications from video projectors to Adaptive Optics (astronomy, ophthalmology) and mask writers in the semiconductor industry. Contrary to the digitally addressed SLMs in projectors that use time multiplexing to generate grey levels, the SLMs developed by Fraunhofer IPMS are addressed with analogue voltages that enable the chip to directly generate analogue intensities. Micronic Laser Systems ABs mask writers exploit this feature to shift the generated patterns with accuracies far smaller than the system's pixel resolution. The mirrors of the Fraunhofer IPMS device are specified for monochromatic light between 248 nm up to 520 nm, enabling not only the use of the DUV excimer wavelengths, but also the less aggressive (and less costly) near UV light sources. One example where the mirrors could be used is pattern generation for High Definition Interconnect (HDI) for Laser Direct Imaging (LDI) of printed circuit boards, but also other areas that require a combination of both highest resolution and throughput. The SLM is capable of patterning 1 million pixels at a framerate of 2 kHz (that is, 2 Gpixel/s). The demonstrator setup visualizes the function of the SLM. A green LED generates a light beam, lenses and mirrors guide the light onto the SLM, where it is modulated. The reflected beam is then filtered and projected into a camera. The live image of this camera shows the pattern programmed in the SLM.
4. Scanning Photon Microscope
The laser scanning microscopy is a well-established visualising method for different fields of application. The objects being detected are raster scanned by a focusing laser beam and the light diffused from the samples surface is collected by a suitable mounted detector. However, systems which are currently available on the market, are very voluminous and cost-intensive. That is why the possibilities for applications are limited. The Fraunhofer IPMS presents an alternative with its »Scanning Photon Microscope«. It works on a similar principle but uses a two-dimensional resonant microscanning mirror developed at the Fraunhofer IPMS for the deflection of light. Various possibilities for miniaturization of the system result from the minimal dimension of the mirror (4 x 3 mm²). The presented demonstrator with a dimension of 4 x 10 x 20 cm collects pictures of 1000 x 1000 pixels with a resolution of 10 µm per pixel. Therefore the image area is 1 x 1 cm. By changing the optical design it is possible to increase the performance parameters. Very interesting for future applications is the possibility to choose the wave length of the radiated light and therefore to activate processes like fluorescence and to evaluate them wave length specific. Non-destructive testing, e. g. to detect microcracks, or the biotechnology are potential fields of application. Measurements are possible both in the illuminated area and in the dark field.
5. OLED-on-CMOS-Integration for sensor applications
Besides the standard substrate glass, Organic Light Emitting Diodes (OLEDs) are suited for the integration on different application-specific materials, like silicon wafers. Due to the combination of OLEDs with CMOS technology (OLED-on-CMOS) advantages concerning light-brightness, efficiency, low operating voltage and spectral characteristics can be achieved. In comparison with traditional adoptions in small and medium-sized displays this offers a great variety of completely new applications regarding the possibilities of the integration of different sensor-devices (e. g. photo detectors) into the CMOS-circuit-technology. Advantages refer mainly to the supplement of efficient and stable light-emitting devices on the CMOS-chip, using the OLED-on-CMOS-technology, as well as the CMOS-based activation and signal processing. Doing so, the light-emitter can be placed above the CMOS-electronics without claiming useful space on the chip. This combination allows the production and application of highly developed devices: OLED-microdisplays (based on CMOS-technology) with integrated image-receiver or optoelectronic sensors with an integrated light source. Since a while the Fraunhofer IPMS offers developments in this field and is able to present different technology-demonstrators. During the OPTATEC 2008 the Fraunhofer IPMS will present a reflex-light barrier sensor, which includes the required light source on the CMOS-sensor chip. Due to the achieved reduction of the expenditure regarding the construction and circuit technology numerous applications of those devices are enabled. Applications vary from light barriers over opto-couplers and optical sensors for chemistry, medicine or the life science to optical communications.