Miniaturized MEMS based spectrometers have attracted interest for mobile high volume applications. Performance parameters like resolution, stability and spectral range gain an increased attention for the comparison of different approaches in addition to the classical characteristics such as size and cost. The necessary resolution must be considered with the requirements of the spectral application in mind. For organic material analysis and similar tasks often resolutions around 10 nm have been regarded to be sufficient. Stability - here predominantly relevant is the wavelength scale - is important for the proper operation of the chemometric evaluation in the NIR range where overtone and combination bands have to be evaluated. Resonant scanner devices offer the opportunity to use simple position readout systems and gather accurate position information by tracking many cycles of the resonant movement.
The deflection of the scanning grating device used in this kind of MEMS based spectrometers becomes a limiting factor for extending the spectral range. By using a plain scanner mirror which illuminates a fixed grating and gathers the reflected radiance simultaneously the spectral range can be doubled applying the same MEMS deflection.
Furthermore, the wider spectral range can be supported by using two or more detectors with different spectral characteristics placed behind two or more separated exit slits. These slits could be integrated into the same MEMS chip like the scanner mirror device.
Several optical designs for miniaturized setups have been compared to find an optimized option which requires affordable optical components only. Here especially the two mirrors in the setup are relevant for a suitable spectrometer performance with acceptable effort. Finally a folded Czerny-Turner type setup has been chosen which can be integrated by the “place and bend” assembly.
Next generations of mobile phones will contain spectral analysers. Different concepts and system designs compete in this ultra-high volume market. Especially for the analysis of organic matter, which can be food, human skin or other items, the near infrared range offers substantial advantages, most of all a suitable penetration depth and relevant spectral information. On the other hand the spectrometer has to meet the requirements for the use in a mobile phone, i.e. size and price must drop significantly. The reliable operation, especially for the evaluation of the spectra with chemometric models, requires a very stable wavelength scale of the spectroscopic system. The deviation must not exceed 0.5 nm during operation under any condition and for each device used.
Resonant MEMS devices combine multiple advantages: Ultra compact designs can be realized, MEMS motions allow an operation using a single detector to meet cost issues even with extended InGaAs technology and the position feedback ensures a precise and long term stable wavelength scale. Based on such resonantly actuated MEMS components NIR spectrometers have been designed. Recent research work aims for extreme miniaturization of the optical bench. The presented assembly technology has been optimized for volume production. The outline from the previous published work will be shrunk to 10 x 10 x 5 mm3 with only a slightly reduced resolution. The new design will be optimized for cost efficient production as well.
MEMS technologies have been used successfully to miniaturize optoelectronic systems. Nonetheless alignment issues limit the level of miniaturization for complex optical systems. Especially off-axis optical designs such as used in Czerny-Turner spectrometers or "Schiefspiegler"-cameras offering completely reflective and thus chromatic aberration free optics are difficult to shrink. On the other hand multiple applications request extremely miniaturized and light weight modules for mobile devices, automotive or unmanned aerial vehicles.
A new concept for the efficient realization of complex optical systems has been invented and patented . For the so-called "place and bend assembly" a planar substrate is used which features preprocessed bending lines. Due to the progress in production technologies, 3D printing for small and medium volumes as well as other advanced plastic process technologies for high volumes with supreme accuracy are available. Optical, electronic as well as MEMS components can be placed on such a substrate using standard but precise planar technologies. Then the different parts of the substrate are bent and form the 3D body. Simultaneously the optical path inside is generated. This concept is not limited to rectangular shapes. It may also be possible to realize the "W-configuration" of a Czerny-Turner spectrometer in a very efficient way.
The first proof of concept has been achieved with a camera device realized from a 3D printed substrate. An entrance window, two spherical mirrors, an aperture stop and a detector array have been assembled using planar technology. Afterwards the substrate was folded and fixed. The functional capability has been demonstrated by capturing test images which have been optically evaluated. Challenges for the future development will be named and discussed.
A groundbreaking new approach  for the fabrication of complex photonic systems, especially such with off-axis optics, has been invented based on planar mounting in combination with a novel folding approach.
Up to now volume production of photonic systems has been optimized for on-axis lens based optical systems. Chromatic aberration limits the usage or spectral range of these systems. Applying mirrors instead of lenses may help to suppress chromatic aberrations and wavelength depending absorption. The assembly of reflective optics, often in an off-axis configuration, is a complex process. So far most tools for volume production apply stacking of components in planar technology. Off-axis systems are typically assembled by more or less manually alignment of the components, which is not in favor for mass and low cost production of these systems.
The novel approach utilizers a planar substrate featuring preprocessed bending lines. A high accuracy tool for planar assembly places the components onto the substrate. Then the sides of the substrate are bent leading to a predefined three dimensional body. The off-axis optical path inside is generated automatically.
This concept is not limited to rectangular shapes but can also be applied to more complex systems, for example the so called “W-configuration” for a Czerny-Turner spectrometer.
First tests of the “bend and place assembly” have been performed successfully on a camera setup to prove the working principle.
An extremely miniaturized scanning grating spectrometer at the size of a sugar cube has been developed at Fraunhofer IPMS. To meet the requirements for the integration into a mobile phone a new system approach has been pursued. The key component within the system is a silicon-based deflectable diffraction grating with an integrated driving mechanism. A first sample of the new spectrometer was built and characterized. It was found to have a spectral range from 950 nm to 1900 nm at a resolution of 10 nm. The results show that the performance of the new MEMS spectrometer is in good agreement with the requirements for mobile phone integration.
Scanning the retinae of the human eyes with a laser beam is an approved diagnosis method in ophthalmology; moreover
the retinal blood vessels form a biometric modality for identifying persons. Medical applied Scanning Laser
Ophthalmoscopes (SLOs) usually contain galvanometric mirror systems to move the laser spot with a defined speed
across the retina. Hence, the load of laser radiation is uniformly distributed and eye safety requirements can be easily
complied. Micro machined mirrors also known as Micro Electro Mechanical Systems (MEMS) are interesting
alternatives for designing retina scanning systems. In particular double-resonant MEMS are well suited for mass
fabrication at low cost. However, their Lissajous-shaped scanning figure requires a particular analysis and specific
measures to meet the requirements for a Class 1 laser device, i.e. eye-safe operation.
The scanning laser spot causes a non-uniform pulsing radiation load hitting the retinal elements within the field of view
(FoV). The relevant laser safety standards define a smallest considerable element for eye-related impacts to be a point
source that is visible with an angle of maximum 1.5 mrad. For non-uniform pulsing expositions onto retinal elements the
standard requires to consider all particular impacts, i.e. single pulses, pulse sequences in certain time intervals and
cumulated laser radiation loads. As it may be expected, a Lissajous scanning figure causes the most critical radiation
loads at its edges and borders. Depending on the applied power the laser has to be switched off here to avoid any retinal
Many applications could benefit from miniaturized systems to scan blood vessels behind the retina in the human eye, so
called „retina scanning“. This reaches from access control to sophisticated security applications and medical devices.
High volume systems for consumer applications require low cost and a user friendly operation. For example this
includes no need for removal of glasses and self-adjustment, in turn guidance of focus and point of attraction by
simultaneous projection for the user.
A new system has been designed based on the well-known resonantly driven 2-d scanner mirror of Fraunhofer IPMS. A
combined NIR and VIS laser system illuminates the eye through an eye piece designed for an operating distance
allowing the use of glasses and granting sufficient field of view. This usability feature was considered to be more
important than highest miniaturization. The modulated VIS laser facilitates the projection of an image directly onto the
retina. The backscattered light from the continuous NIR laser contains the information of the blood vessels and is
detected by a highly sensitive photo diode.
A demonstrational setup has been realized including readout and driving electronics. The laser power was adjusted to an
eye-secure level. Additional security features were integrated. Test measurements revealed promising results. In a first
demonstration application the detection of biometric pattern of the blood vessels was evaluated for issues authentication
There is an increasing need for reliable authentication for a number of applications such as e commerce. Common authentication methods based on ownership (ID card) or knowledge factors (password, PIN) are often prone to manipulations and may therefore be not safe enough. Various inherence factor based methods like fingerprint, retinal pattern or voice identifications are considered more secure. Retina scanning in particular offers both low false rejection rate (FRR) and low false acceptance rate (FAR) with about one in a million. Images of the retina with its characteristic pattern of blood vessels can be made with either a fundus camera or laser scanning methods. The present work describes the optical design of a new compact retina laser scanner which is based on MEMS (Micro Electric Mechanical System) technology. The use of a dual axis micro scanning mirror for laser beam deflection enables a more compact and robust design compared to classical systems. The scanner exhibits a full field of view of 10° which corresponds to an area of 4 mm2 on the retinal surface surrounding the optical disc. The system works in the near infrared and is designed for use under ambient light conditions, which implies a pupil diameter of 1.5 mm. Furthermore it features a long eye relief of 30 mm so that it can be conveniently used by persons wearing glasses. The optical design requirements and the optical performance are discussed in terms of spot diagrams and ray fan plots.
Grating spectrometers have been designed in many different configurations. Now potential high volume applications ask for extremely miniaturized and low cost systems. By the use of integrated MEMS (micro electro mechanical systems) scanning grating devices a less expensive single detector can be used in the NIR instead of the array detectors required for fixed grating systems. Meanwhile the design of a hybrid integrated MEMS scanning grating spectrometer has been drawn. The MEMS device was fabricated in the Fraunhofer IPMS own clean room facility. This chip is mounted on a small circuit board together with the detector and then stacked with spacer and mirror substrate. The spectrometer has been realized by stacking several planar substrates by sophisticated mounting technologies. The spectrometer has been designed for the 950nm – 1900nm spectral range and 9nm spectral resolution with organic matter analysis in mind. First applications are considered in the food quality analysis and food processing technology. As example for the use of a spectrometer with this performance the grill process of steak was analyzed. Similar measurement would be possible on dairy products, vegetables or fruit. The idea is a mobile spectrometer for in situ and on site analysis applications in or attached to a host system providing processing, data access and input-output capabilities, disregarding this would be a laptop, tablet, smart phone or embedded platform.
Grating spectrometer, like the well-established Czerny-Turner, are based on an optical design consisting of several components. Typically at least two slits, two mirrors, the grating stage and a detector are required. There has been much work to reduce this effort, setups using only one mirror (Ebert - Fastie) or the replacement of the entrance slit through the use of thin optical fibers as well as integrated electronic detector arrays instead of a moving grating and an exit slit and single detector device have been applied. Reduced effort comes along with performance limitations: Either the optical resolution or throughput is affected or the use of the system is limited to the availability of detectors arrays with reasonable price. Components in micro opto electro mechanical systems (MOEMS-) technology and spectroscopic systems based thereon have been developed to improve this situation. Miniaturized scanning gratings fabricated on bonded silicon on insulator (BSOI-) wafers were used to design grating spectrometer for the near infrared requiring single detectors only. Discrete components offer flexibility but also need for adjustment of two mirrors, grating stage, fiber mount and the detector with its slit and optionally a second slit in the entrance area. Further development leads towards the integration of the slits into the MOEMS chip, thus less effort for adjustment. Flexibility might be reduced as adjustments of the optical design or grating spacing would require a new chip with own set of masks. Nevertheless if extreme miniaturization is desired this approach seems to be promising. Besides this, high volume production might be able for a comparable low price. A new chip was developed offering grating, two slits and a cavity for the detector chip. The optical design was adjusted to a planar arrangement of grating and slits. A detector buried in a chip cavity required a new mounting strategy. Other optical components were optimized and fabricated then the systems was assembled with electronics and software adjusted to the new design including some new features like integrated position sensors. A first test of systems to grant function of all components is presented. Further work will be aimed at improved performance like higher resolution and lower SNR.
Spectrometers and Spectrographs based on scanning grating monochromators are well-established tools for various
applications. As new applications came into focus in the last few years, there is a demand for more sophisticated
and miniaturized systems. The next generation spectroscopic devices should exhibit very small dimensions
and low power consumption, respectively. We have developed a spectroscopic system with a volume of only
(15 × 10 × 14) mm3 and a few milliwatts of power consumption that has the potential to fulfill the demands of
the upcoming applications. Our approach is based on two dierent strategies. First, we apply resonantly driven
MEMS (micro electro mechanical systems). The latest generation of our MEMS scanning grating device has two
integrated optical slits and piezoresistive position detection in addition to the already existing miniaturized 1-d
scanning grating plate and the electrostatic driving mechanism. Our second strategy is to take advantage of the
hybrid integration of optical components by highly sophisticated manufacturing technologies. One objective is
the combination of MEMS technology and a planar mounting approach, which potentially facilitate the mass
production of spectroscopic systems and a signicant reduction of cost per unit. We present the optical system
design as well as the realization of a miniaturized scanning grating spectrometer for the near infrared (NIR)
range between 950 nm and 1900 nm with a spectral resolution of 10 nm. The MEMS devices as well as the
optical components have been manufactured and rst samples of the spectroscopic measurement device have
been mounted by an automated die bonder.
Optical MEMS (micro electro mechanical systems) have been used to reduce size, weight and costs of any kind of
optical systems very successfully starting in the last decades. Scientists at Fraunhofer IPMS invented a resonant drive for
1-d and 2-d MEMS scanning mirror devices. Besides mirrors also scanning gratings have been realized. Now, rapidly
growing new applications demand for enhanced functions and further miniaturization. This task cannot be solved by
simply putting more functionality into the MEMS chip, for example grating and slit structures, but by three dimensional
hybrid integration of the complete optical system into a stack of several functional substrates. Here we present the optical
system design and realization strategy for a scanning grating spectrometer for the near infrared (NIR) range. First
samples will be mounted from single components by a bonder tool (Finetech Fineplacer Femto) but the option of wafer
assembly will be kept open for future developments. Extremely miniaturized NIR spectrometer could serve a wide
variety of applications for handheld devices from food quality analysis to medical services or materials identification.
A MEMS (micro electro mechanical system) technology has been used to produce scanning grating chips which have a
tiltable plate with grating structures optimized for the 900nm ... 2500nm range as diffractive element. Based on these
chips different spectrometers and a hyper spectral imager have been realized for NIR-spectroscopic applications like
agricultural quality analysis, recycling and process control. Ongoing developments aim at the further reduction of size
and effort. Chip scale or wafer scale packaging technologies could help to shrink the complete spectroscopic system. The
integration of signal processing and evaluation routines opens new applications for a broad range of scientific and nonscientific
In this paper we present an optoelectronic integrated circuit (OEIC) based on monolithic integration of organic lightemitting
diodes (OLEDs) and CMOS technology. By the use of integrated circuits, photodetectors and highly efficient
OLEDs on the same silicon chip, novel OEICs with combined sensors and actuating elements can be realized. The
OLEDs are directly deposited on the CMOS top metal. The metal layer serves as OLED bottom electrode and
determines the bright area. Furthermore, the area below the OLED electrodes can be used for integrated circuits. The
monolithic integration of actuators, sensors and electronics on a common silicon substrate brings significant advantages
in most sensory applications.
The developed OEIC combines three different types of sensors: a reflective sensor, a color sensor and a particle flow
sensor and is configured with an orange (597nm) emitting p-i-n OLED. We describe the architecture of such a
monolithic OEIC and demonstrate a method to determine the velocity of a fluid being conveyed pneumatically in a
transparent capillary. The integrated OLEDs illuminate the capillary with the flowing fluid. The fluid has a random
reflection profile. Depending on the velocity and a random contrast difference, more or less light is reflected back to the
substrate. The integrated photodiodes located at different fixed points detect the reflected light and using crosscorrelation,
the velocity is calculated from the time in which contrast differences move over a fixed distance.
Organic light-emitting diodes (OLEDs) permit the monolithic integration of microelectronic circuits and light-emitting
devices on the same silicon chip. By the use of integrated photodetectors, low-cost CMOS processes and simple
packaging; economically produced optoelectronic integrated circuits (OEICs) with combined sensors and actuating
elements can be realized. The OLEDs are deposited directly on the top metal layer. The metal layer serves as electrode
and defines the bright area. Furthermore, the area below the electrodes can be used for integrated circuits. Due to
efficient emitter with low operating voltage it is possible to renounce high-voltage devices depending on selected CMOS
process. Thus manufacturing cost can be further reduced. Different CMOS metallizations were examined and their
effects on organic light-emitting diodes were analyzed. Red (628nm) and orange (597nm) emitting p-i-n OLEDs with a
radiance of 5W/m2sr at 2.8V and 3.0V and a half angle of ±45° were realized on metal layer with low roughness. Near
infra-red emitters are in development. We will present an optical microsystem. The functionality of combined sensors
and actuating elements as well as advantages and difficulties of the monolithic integration of OLEDs and CMOS will be
discussed. The chip was manufactured in a commercial 1μm CMOS technology. The fabricated microsystem combines
three different types of sensors: a reflective sensor, a colour sensor and a particle flow sensor.