In a novel hyperspectral imaging concept based on confocal chromatic microscopy, a pinhole array (matrix of pinholes) has to be scanned across an intermediate image plane to capture the full object plane. In this paper a two-axis stepping microdrive is presented for the pinhole array (6×7.5×0.2 mm3 of glass, weight 20 mg), featuring a 10 μm step size and a 200 μm displacement range in each direction. With the two-axis stepwise actuation of the pinhole array, the imaged area of the object plane is increased from 7% (fixed pinhole array) up to 89% with actuated array. The two-axis positioning is implemented with a three-axis inchworm motion driven by electrostatic forces. A combination of horizontal and vertical electrostatic actuators are arranged to achieve a precise in-plane actuation of the pinhole array. The microdrive is fabricated with established MEMS technologies and features a size about 1 cm2 with 1 mm thickness. The microdrive is capable to position the pinhole array over the displacement range. The array size enables a 1:1 optical imaging on an 8 mm diagonal size CCD. The presented stepping microdrive outperforms existing microsystem solutions with a combination of high payload, large step size, displacement range, and the large optical aperture. Furthermore, the device concept enables the positioning of milligram weights with a highly integrated microsystem.
In this paper we present chromatic confocal distance sensors for the parallelized evaluation at several lateral positions.
The multi-point measurements are performed using either one- or two-dimensional detector arrays. The first sensor combines
the concepts of confocal matrix sensing and snapshot hyperspectral imaging to image a two-dimensional array of
laterally separated points with one single shot. In contrast to chromatic confocal matrix sensors which use an RGB detector
our system works independently from the spectral reflectivity of the surface under test and requires no object-specific
calibration. Our discussion of this sensor principle is supported by experimental results. The second sensor is a multipoint line sensor aimed at high speed applications with frame rates of several thousand frames per second. To reach this evaluation speed a one-dimensional detector is employed. We use spectral multiplexing to transfer the information from different measurement points through a single fiber and evaluate the spectral distribution with a conventional spectrometer. The working principle of the second sensor type is demonstrated for the example of a three-point sensor.
Compared to conventional optics like singlet lenses or even microscope objectives advanced optical designs help to
develop properties specifically useful for efficient optical tweezers. We present an optical setup providing a customized
intensity distribution optimized with respect to large trapping forces. The optical design concept combines a refractive
double axicon with a reflective parabolic focusing mirror. The axicon arrangement creates an annular field distribution
and thus clears space for additional integrated observation optics in the center of the system. Finally the beam is focused
to the desired intensity distribution by a parabolic ring mirror. The compact realization of the system potentially opens
new fields of applications for optical tweezers such as in production industries and micro-nano assembly.
The highly sensitive photoluminescence (PL) response of group III-Nitrides (III-N) nanowire heterostructures (NWHs) to hydrogen (H2) and oxygen (O2) allows for the realization of reliable gas detectors. For industrial real time gas monitoring applications, e.g. in the field of aerospace, a large scale laboratory setup was miniaturized by integrating electro-optical components and the NWHs within a robust micro optical system. As a result of the all optical addressing and read out the detection periphery can be completely isolated from the investigated environment which significantly increases the detection sensitivity. The optical design and fabrication techniques as well as an experimental investigation of the system performance are the main topics discussed in this paper.
Dispersion causes the focal lengths of refractive and diffractive optical elements to vary with wavelength. In our contribution
we show how it can be used for chromatic encoding and decoding of optical signals. We specifically discuss how
these concepts can be applied for the implementation of systems with applications in the growing fields of hyperspectral
imaging and chromatic distance coding. Refractive systems as well as hybrid combinations of diffractive and refractive
elements are used to create specific chromatic aberrations of the sensors. Our design approach enables the tailoring of the
sensor properties to the measurement problem and assists designers in finding optimized solutions for industrial applications.
The focus of our research is on parallelized imaging systems that cover extended objects. In comparison to point
sensors, such systems promise reduced image acquisition times and an increased overall performance. Concepts for
three-dimensional profilometry with chromatic confocal sensor systems as well as spectrally resolved imaging of object
scenes are discussed.
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