Industry frequently demands fast and robust measurement techniques for the inline inspection of the full shape
of objects in the micro range. We present a method for complete 360 degree measurement of the shape of
a micro cup using digital holographic microscopy and show first results of sequential 360 degree measurement
using different illumination and observation directions.
We propose a new application of broad band lasers for digital holography. The aim is to capture the shape of
objects by a single hologram using multiple wavelengths. Our approach is to separate the reference wave spectrally
by a grating while the object wave remains unaffected. This leads to many lamellar holograms in one hologram.
As consequence different restrictions like aperture and wavelength dependency of the reconstruction algorithm
have to be taken into account. In experiments we have successfully demonstrate that lamellar holograms can be
generated, reconstructed and that all necessary steps for shape measurement are accomplishable.
We present a new approach for single shot multi wavelengths contouring using the broad spectrum of a fs-laser. The
spectral distribution of a fs-laser contains a multitude of discrete frequencies which principally can be separated and
simultaneously used for gathering holograms with different wavelengths. In order to investigate the characteristics of this
approach, we have built up a setup using a tuneable dye-laser. Several wavelengths of the dye laser have been spatially
distributed for the reference wave on the hologram target. Holograms at different wavelengths are recorded and
superimposed numerically afterwards to guarantee resemblance to the fs-laser setup. In this paper we describe the
theoretical background, derive an algorithm for noise-reduced reconstruction and show corresponding experimental
Recently, we proposed a new approach of a noncollinear correlation technique for ultrashort-pulsed coherent optical
signals which was referred to as Bessel-autocorrelator (BAC). The BAC-principle combines the advantages of Bessellike
nondiffracting beams like stable propagation, angular robustness and self-reconstruction with the principle of
temporal autocorrelation. In comparison to other phase-sensitive measuring techniques, autocorrelation is most straightforward
and time-effective because of non-iterative data processing. The analysis of nonlinearly converted fringe
patterns of pulsed Bessel-like beams reveals their temporal signature from details of fringe envelopes. By splitting the
beams with axicon arrays into multiple sub-beams, transversal resolution is approximated. Here we report on adaptive
implementations of BACs with improved phase resolution realized by phase-only liquid-crystal-on-silicon spatial light
modulators (LCoS-SLMs). Programming microaxicon phase functions in gray value maps enables for a flexible variation
of phase and geometry. Experiments on the diagnostics of few-cycle pulses emitted by a mode-locked Ti:sapphire laser
oscillator at wavelengths around 800 nm with 2D-BAC and angular tuned BAC were performed. All-optical phase shift
BAC and fringe free BAC approaches are discussed.
The considerable potential of advanced thin-film microoptics for tailoring light fields of pulsed high-power lasers even at
extreme parameters like ultrashort pulse durations, broad spectral bandwidths or vacuum ultraviolet wavelengths is
demonstrated. A comprehensive review of the state of the art and the most relevant aspects of this branch of modern
optics is given. In particular, applications of structured dielectric, metallic and compound layers and programmable
liquid-crystal devices for control and diagnostics of ultrashort pulses in space and time are discussed. Recent theoretical
and experimental results of wavefront sensing, pulse diagnostics, multichannel materials processing and information
encoding into the phase maps of arrayed pulsed beams of nondiffracting propagation characteristics are presented here.
Fringe-resolved noncollinear autocorrelation extracts information about the pulse duration of ultrashort optical signals
from analyzing the intensity envelope of fringes. By detecting nonlinear autocorrelation functions after frequency
conversion, even an evaluation of temporal asymmetry and frequency chirp are enabled. Here we report on a modified
approach based on replacing crossed plane waves by Bessel-like beams. In comparison to the conventional method,
appropriate mathematical transforms have to be applied. The method is simple and single-shot capable and takes
advantage of specific advantages of pseudo-nondiffracting beams. First proof-of-principle experiments with few-femtosecond
pulse durations were performed and compared to simulations. In multishot operation regime, the
implementation of phase-shifting procedures by spatial light modulators promises considerable improvements of the time
resolution analogous to the known principle of phase-shift interferometry.
Recently developed Shack-Hartmann sensors with axicon beam shapers show an enhanced robustness compared to
setups with spherical microlenses. With ultraflat axicon arrays, further improvements were obtained. Very extended,
fringeless nondiffracting beams or "needle beams" with self-reconstructing properties can be produced. Specific
advantages of thin-film structures like low dispersion and reflective operation can be implemented. Here we report on
first systematic studies of angular tolerance and displacement sensitivity of different types of refractive, reflective and
diffractive Shack-Hartmann devices. A quantitative description of the functionality is given on the basis of higher order
spatial statistical moments. This method enables for identifying optimum parameter ranges to determine wavefront
curvatures under extreme conditions.