Within this paper, we present a novel approach for an optical system for a near infrared (IR) line camera, which exists of
only one monolithical optical element with 3 optical free form surfaces. The optical design was performed with respect
to the following requirements given by the application: wavelength range 0.9 μm to 1.7 μm, field angle 75° x 2°,
horizontal angular resolution 0.5°. Within the design process one of the three optical surfaces is formed biconic, two are
realized as cylindrical surface. The calculated component was realized by means of diamond UP manufacturing. Two of
the optical surfaces were metallized to work as mirrors for the above mentioned spectral range. The realized element has
a size of less than 8 cm3; it was finally characterized.
Typical optical metrology systems for surface and shape characterization are based on a separated camera and
projection unit, yielding to a limitation concerning the miniaturization of the sensor. We present a compact,
highly integrated optical distance sensor applying the inverse confocal principle using a bidirectional OLED
microdisplay (BiMiD). This microdisplay combines light emitting device (AM-OLED microdisplay) and photo
sensitive detectors (photodiode matrix) on one single chip based on OLED-on-CMOS-technology. Comparable to
conventional confocal sensors, the object is shifted through the focal plane (±▴z) and the back reflected/scattered light is collected via an special designed optic and detected by the photo sensitive detector elements. The detected
photocurrent depends on movement (▴z) of the measurement plane. In contrast to conventional confocal sensors,
our inverse confocal sensor detects a minimum of reflected/scattered light if the object is positioned in the focal
plane. We present a novel sensor concept as well as system and optical simulations that demonstrate the principle
of the novel inverse confocal sensor setup.
The objective of this paper is a new accommodating opto-mechanical model of the aging human eye for basic
simulations of presbyopia, especially of the lens. The lens, consisting of cortex and nucleus, of the aging human eye is
mechanically simulated by a FEM model with the program ANSYS. The model results in physiologically correct
parameters, and is used as input for a complete optical eye model, implemented in the software ZEMAX. The optical
performance of the model corresponds fully with clinical data and the model represents the changes in the mechanical
and optical parameters during accommodation and due to the aging process. It is suitable for optical and mechanical
simulation; therefore, for example, different possible treatments for presbyopia can be simulated. Furthermore first
investigations of stray light due to the laser treatment and their impact on visual performance are presented.
We report on multi-channel detection of ultrashort THz pulses by a linear array of 16 photoconductive dipole antennas.
The dipole antennas built on low-temperature grown GaAs are excited by a line focus of fs-pulses. By the parallel
detection of a complete line of ultrashort THz pulses, the measurement speed of THz ultrashort pulse time domain
systems can be accelerated by an order of magnitude. For demonstration, the THz beam profile along the line detector is
determined, and its spectral dependence of the electric field distribution is compared and verified by wave-optical
A THz time domain imaging system is optimized and analyzed with ZEMAX. The requirements to the optical design of
time domain imaging systems in the THz spectral region are deduced. A system is presented, which is diffraction-limited
for wavelengths down to 838 μm and field points up to ±4 mm. In the optical system a 90° off-axis parabolic mirror is
combined with an aspheric plastic lens. The lens was made from ZEONEX E48R®, and it was manufactured by ultraprecision
machining. A resolution test of the system shows that on time domain analysis of the pulse maximum on-axis 1 LP/mm can be resolved with an intensity contrast of 0.22. The resolution of the outermost field point is 0.67 LP/mm with an intensity contrast of 0.23. An outlook of an optimized system for imaging a field of ±10 mm in x- and y-direction
Imaging of styrofoam with the help of ultrashort Terahertz pulses is investigated. With a combination of pulse amplitude
and time delay imaging it is possible to speed up the measurement about two orders of magnitudes.
The applicability of moth-eye structures to THz components is investigated. With the help of RCWA and effective medium theory, optimal structural parameters for one-dimensional and two-dimensional periodical surface-relief gratings are deduced. The required structural parameters are in such order of magnitude that they can be manufactured by ultra-precision machining directly into the surface of the substrate material. Benefiting is that plastic materials, which are preferred materials in THz spectral region, can be accurately manufactured by ultra-precision machining. The application of the moth-eye structures follows directly the primary shaping of the components by conventional manufacturing methods like turning and milling so that no additional materials are necessary. A comparison between several structures fabricated on planar plastic probes is given.
InN, a novel semiconductor material, is used as THz surface emitter. The material is irradiated with fs-laser pulses at 1060 nm and 800 nm and the emitted ultrashort THz pulses are measured by phase sensitive detection. Pulsforms, amplitudes and spectra are compared to the THz emission of p-doped InAs, the standard material for THz surface emission.
Generation of InAs-surface-emitted terahertz radiation by application of an ultrashort pulse 1064 nm parabolic fiber amplifier source is reported for the first time. The fiber amplifier delivers 100 fs pulses at a repetition rate of 75 MHz and an average power of maximum 12 W. This new excitation laser for surface-emitters generates high brightness broadband THz radiation ranging from 100 GHz to over 2.5 THz. THz detection is demonstrated based on two-photon absorption at low-temperature-grown GaAs dipole receivers.
New projection concepts based on OLED (organic light-emitting diode)-microdisplays will be presented. Up to now mostly all projection systems are based on reflective and/or transmissive microdisplays like digital micromirror devices (DMDs), nematic liquid crystals displays (LCDs) or liquid crystal on silicon displays (LCOS). But the size of necessary light source and illumination optics is a strong limitation for the miniaturization of the projection system itself or for system integration. Here we propose to use a high-brightness OLED-microdisplay as active element for image or pattern generation, giving the possibility to realize compact projection or imaging units. Optical parameters of the microdisplays are determined to get input data for optical system design. Based on these experimental results specially adapted optical systems are designed. First prototypes and realized projection systems for applications in optical 3Dshape detection are presented.
A new illumination concept for fringe projection will be presented. Up to now fringe projection systems were based on reflective and/or transmissive microdisplays like digital micromirror devices (DMDs), nematic liquid crystals displays (LCDs) or liquid crystal on silicon displays (LCOS). But the size of the light source and of the illumination optic is a strong limitation for the miniaturization of the sensor system itself or for the integration in other illumination setups. Here we propose to use a high-brightness OLED-display (organic light-emitting diode) as active element for fringe pattern generation, giving the possibility to realize compact projection units.
This paper describes a new method for detecting structural brain differences based on the analysis of deformation fields. Deformations are obtained by an intensity-based nonlinear registration routine which transforms one brain onto another one. We present a general multivariate statistical approach to analyze deformation fields in different subjects. This multivariate general linear model provides the implementation of most forms of experimental designs. We apply our method to the brains of 85 schizophrenic patients and 75 healthy volunteers to examine, whether low frequency deformations are sufficiently sensitive to detect regional deviations in the brains of both groups. We demonstrate the application of the multivariate general linear model to a subtractive (modeling group differences) and a parametric design (testing a linear relationship between one variable and the deformation field).
We present an evaluation technique of two dimensional (2D) nuclear magnetic resonance (NMR) chemical shift images (CSI) to analyze spatial differences of metabolite distributions and/or concentrations between groups of probands. Thus, chemical shift imaging is not only used as localization technique for NMR-spectroscopy, but the information of the complete spectroscopic image is used for the evaluation process. 31P CSI of the human brain were acquired with a Philips Gyroscan ACSII whole-body scanner at 1.5 T. CSI for different phosphorus metabolites were generated, all representing the same anatomical location. For each metabolite the CSI of two groups of subjects were compared with each other using the general linear model implemented in the widely distributed SPM96 software package. With this approach, even covariates or confounding variables like age or medication can be considered. As an example for the application of this technique, variations in the distribution of the 31P metabolite phosphocreatin between unmedicated schizophrenic patients and healthy controls were visualized. To our knowledge, this is the first approach to analyze spatial variations in metabolite concentrations between groups of subjects on the basis of chemical shift images. The presented technique opens a new perspective in the evaluation of 2D NMR spectroscopic data.
Phosphorus-31 magnetic resonance spectroscopy (31P-MRS) has gained much interest in schizophrenia research in the last years since it allows the non-invasive measurement of high- energy phosphates and phospholipids in vivo. We investigated hemispherical differences of the concentrations of different phosphorus compounds in the frontal lobes. For this purpose, well defined volumes in the dorsolateral prefrontal cortex of 32 healthy controls and 51 schizophrenic patients were examined. Schizophrenic patients showed significant lateralization effects of phosphodiesters (PDE) and the intracellular pH-value. Differences in the lateralization of 31P-MRS parameters between patients and healthy volunteers were only detected for the pH-value. While healthy controls exhibit lower pH-values in the left frontal lobe (6.96), in schizophrenic patients we found lower pH-values in the right (6.89). Detailed examinations showed that this effect is mainly based on the subgroup of schizophrenics who received atypical neuroleptic medication.