Dr. Gerhard A. Holst Profile

Dr. Gerhard A. Holst

Head of Science and Research at PCO AG

SPIE Involvement:

Author

Area of Expertise:

Camera Technology , Luminescence Lifetime Imaging , Fluoescence Lifetime Imaging , scientific CMOS technology

Publications (18)

Proceedings Article | 4 March 2019 Presentation

Functional in vivo imaging using fluorescence lifetime light sheet microscopy (Conference Presentation)

Simon Ameer-Beg, Claire Mitchell, Simon Poland, Robert Knight, Guoqing Wang, Gerhard Holst

Proceedings Volume 10882, 108820J (2019) https://doi.org/10.1117/12.2509727

KEYWORDS: Microscopy, Luminescence, In vivo imaging, Fluorescence lifetime imaging, Cameras, Biological research, Statistical analysis, Microscopes, Phase shifts, Modulation

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Proceedings Article | 28 January 2019 Paper

A sine-modulated high-intensity UV-LED light source for pressure-sensitive paint applications using fluorescence lifetime imaging technique

Boleslaw Stasicki, Ulrich Henne, Krzysztof Ludwikowski, Mizue Munekata, Daisuke Yorita, Gerhard Holst

Proceedings Volume 11051, 110510C (2019) https://doi.org/10.1117/12.2524599

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Proceedings Article | 2 March 2015 Paper

Frequency-domain fluorescence lifetime imaging system (pco.flim) based on a in-pixel dual tap control CMOS image sensor

Robert Franke, Gerhard Holst

Proceedings Volume 9328, 93281K (2015) https://doi.org/10.1117/12.2087589

KEYWORDS: Luminescence, Modulation, Imaging systems, Cameras, Image sensors, Phase shift keying, Fluorescence lifetime imaging, CMOS sensors, Endoscopes, Optical filters

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The luminescence lifetime as a beneficial analytical parameter is known for many years and is well described by a large variety of publications. Many instruments including 2D measuring systems with cameras have been developed and applied in the past years. However, since the current instrumentation to perform either time- or frequency-domain lifetime measurements is rather complex, new developments in CMOS image sensor technology have achieved to create new image sensors, which can efficiently be integrated into easier-to-handle luminescence lifetime measuring systems. The principle of these modulatable CMOS image sensors, while initially being designed for distance measurements, shows a clear analogy to frequency-domain FLIM measurements, which was proven by researchers [1, 2]. Based on this principle a new CMOS image sensor has been developed, integrated into a camera system and has been investigated within a research project. The image sensor has a resolution of 1024 × 1024 pixels with a 5.6 μm pitch and can be modulated up to 50 MHz. First measurements show an effective dynamic range of larger than 1:1024 (corresponding to 10 bit dynamic). The maximum frame rate is in the range of 90 frames/s in dual-tap mode, resulting in an effective lifetime image frame rate for realistic measurements of approximately 22 frames/s. The camera system pco.flim, featuring that image sensor, generates all required modulation signals from 5 kHz to 50 MHz (sinusoidal and rectangular). It performs advanced pixel correction to generate linear and high-quality images, while the basic lifetime image processing is done in the computer. The modulation frequency can be freely adjusted within the specified range. The characteristics of the camera systems are presented, and first results are discussed using different representations of the data like for example the phasor approach [3], which has been established to provide a more global view to pixelwise fluorescence lifetime data and compare time- and frequency-domain results. Based on these results and the experiences of the on-going tests, it can be expected, that the pco.flim will significantly ease the introduction of luminescence lifetime imaging systems to broader applications.

Proceedings Article | 22 February 2002 Paper

Transparent oxygen optodes in environmental applications at fine scale as measured by luminescence lifetime imaging

Gerhard Holst, Ulrich Franke, Bjorn Grunwald

Proceedings Volume 4576, (2002) https://doi.org/10.1117/12.456961

KEYWORDS: Oxygen, Luminescence, 3D metrology, Environmental sensing, CCD cameras, Cameras, Ocean optics, Imaging systems, Calibration, 3D image processing

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Due to the MOdular Luminescence Lifetime Imaging system (MOLLI)that has been developed within the last few years it is possible to use oxygen sensors that are not optically isolated. Transparent planar optodes and dispersed nano-optodes for the first time enable a direct optical link between the chemical parameter to be measured (oxygen as an example) and the structure that is responsible for the distribution of the chemical parameter (ascidian and corals as an example). Since the transparency as a principal quality of the optode allows to record structural images. The spatial resolution of the MOLLI imaging system is determined by a)the area size of the view field that is imaged onto the amount of pixels of the CCD-chip (640x480 in our case)and b)by the spatial limitations of the sensing layer. The latter means in case of the planar optode the thickness of the sensing layer and in case of dispersed nano-optodes the thickness of the excitation light field. We present biological applications of transparent planar optodes (thickness approximately equals 5-10 micrometers ) at two areal resolutions,a)50 micrometers /pixel and b)6 micrometers /pixel and one application of nano-optodes at 80 micrometers /pixel. The first application shows the oxygen production of endolithic cells that live in the skeleton of massive corals measured in a cut coral sample that was illuminated through the planar oxygen optode with defined light energy levels to follow the oxygen production of these coral symbionts. Finally the oxygen production and consumption of coral symbionts are shown by dispersed oxygen nano-optodes in the medium. The specific set-up for the latter experiment will be discussed with the future implication of possible 3D measurements. Although the results all come from biological applications from coral reef environments obviously the measuring system and the transparent sensors can be applied to a variety of environmental topics. At the moment similar optodes are under development for parameters like pH,CO₂ and temperature.

Proceedings Article | 22 February 2002 Paper

Simple plastic fiber-based optode array for the in-situ measurement of ground air oxygen concentrations

Martin Koelling, Henrik Hecht, Gerhard Holst

Proceedings Volume 4576, (2002) https://doi.org/10.1117/12.456952

KEYWORDS: Sensors, Oxygen, Luminescence, Pyrite, Light emitting diodes, Mirrors, Connectors, Phase only filters, Mining, Oxidation

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Proceedings Article | 14 February 2002 Paper

SPR fiber optic microsensor: system and applications

Bjoern Grunwald, Gerhard Holst

Proceedings Volume 4578, (2002) https://doi.org/10.1117/12.456110

KEYWORDS: Sensors, Refractive index, Spatial resolution, Calibration, Gold, Metals, Microsensors, Polymers, Fiber optics, Reflectivity

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Proceedings Article | 14 February 2002 Paper

DSP-based measuring system for temperature-compensated fiber optical oxygen sensors

Christian Stehning, Gerhard Holst

Proceedings Volume 4578, (2002) https://doi.org/10.1117/12.456078

KEYWORDS: Oxygen, Digital signal processing, Temperature metrology, Sensors, Luminescence, Signal processing, Modulation, Fiber optics sensors, Fiber optics, Signal to noise ratio

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Proceedings Article | 9 December 1999 Paper

Fiber optic microsensor for refractive index and salinity based on SPR

Bjoern Grunwald, Gerhard Holst

Proceedings Volume 3860, (1999) https://doi.org/10.1117/12.372994

KEYWORDS: Refractive index, Sensors, Gold, Microsensors, Reflectivity, Spatial resolution, Refraction, Surface plasmons, Metals, Cladding

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Proceedings Article | 9 December 1999 Paper

Luminescence lifetime imaging system using imaging fibers to measure the 2D distribution of O2 in biological samples

Gerhard Holst, Bjoern Grunwald, Ingo Klimant, Michael Kuehl

Proceedings Volume 3860, (1999) https://doi.org/10.1117/12.372952

KEYWORDS: Oxygen, Endoscopes, Luminescence, Optical fibers, Imaging systems, Sensors, Cameras, Data modeling, Calibration, CCD cameras

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Proceedings Article | 18 June 1998 Paper

MICROX II: a new generation of portable measuring systems for micro-optodes

Gerhard Holst, Michael Kuehl, Oliver Kohls

Proceedings Volume 3483, (1998) https://doi.org/10.1117/12.309650

KEYWORDS: Sensors, Ocean optics, Luminescence, Microsensors, Light emitting diodes, Beam splitters, Oxygen, Optical fibers, Light sources, Fiber couplers

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Proceedings Article | 18 June 1998 Paper

Micro-optodes: the role of fibre tip geometry for sensor performance

Oliver Kohls, Gerhard Holst, Michael Kuehl

Proceedings Volume 3483, (1998) https://doi.org/10.1117/12.309651

KEYWORDS: Ocean optics, Sensors, Oxygen, Luminescence, Sensor performance, Microsensors, Optical fibers, Optics manufacturing, Cladding, Fiber optics

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Proceedings Article | 7 May 1997 Paper

Characterization and application of temperature micro-optodes for use in aquatic biology

Gerhard Holst, Michael Kuehl, Ingo Klimant, Gregor Liebsch, Oliver Kohls

Proceedings Volume 2980, (1997) https://doi.org/10.1117/12.273525

KEYWORDS: Sensors, Oxygen, Temperature metrology, Microsensors, Spatial resolution, Calibration, Ruthenium, Luminescence, Environmental sensing, Ocean optics

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Proceedings Article | 31 March 1997 Paper

Development and comparison of pH microoptodes for use in marine systems

Oliver Kohls, Ingo Klimant, Gerhard Holst, Michael Kuehl

Proceedings Volume 2978, (1997) https://doi.org/10.1117/12.269958

KEYWORDS: Sensors, Absorption, Ocean optics, Calibration, Microsensors, Luminescence, Fiber optics sensors, Light emitting diodes, Sol-gels, Oceanography

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Proceedings Article | 10 December 1996 Paper

Thionine as an indicator for use as a hydrogen sulfide optode

Oliver Kohls, Ingo Klimant, Gerhard Holst, Michael Kuehl

Proceedings Volume 2836, (1996) https://doi.org/10.1117/12.260606

KEYWORDS: Luminescence, Sensors, Oxygen, Microsensors, Hydrogen, Fiber optics, Sol-gels, Matrices, Light emitting diodes, Silicon

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Proceedings Article | 29 September 1995 Paper

Novel measuring system for oxygen micro-optodes based on a phase modulation technique

Gerhard Holst, Michael Kuehl, Ingo Klimant

Proceedings Volume 2508, (1995) https://doi.org/10.1117/12.221754

KEYWORDS: Oxygen, Luminescence, Light emitting diodes, Sensors, Phase measurement, Phase modulation, Modulation, Signal processing, Fiber optics, Glasses

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Proceedings Article | 29 September 1995 Paper

Oxygen micro-optrodes and their application in aquatic environments

Ingo Klimant, Gerhard Holst, Michael Kuehl

Proceedings Volume 2508, (1995) https://doi.org/10.1117/12.221753

KEYWORDS: Oxygen, Luminescence, Sensors, Microsensors, Calibration, Spatial resolution, Light emitting diodes, Silicon, Fiber optics, Optical fibers

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Proceedings Article | 8 May 1995 Paper

Hybrid fiber optical sensor for determining the oxygen partial pressure and the oxygen flux in biomedical applications

Dietrich Luebbers, Thomas Koester, Gerhard Holst

Proceedings Volume 2388, (1995) https://doi.org/10.1117/12.208511

KEYWORDS: Sensors, Oxygen, Skin, Head, Fiber optics sensors, Blood circulation, Calibration, Fiber optics, Hybrid fiber optics, Luminescence

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The development and improvement of oxygen sensors is continuously matter of research because it is important to quantify oxygen concentrations in biological systems. The presented hybrid fiberoptical sensor combines the common advantages of fiber optic sensors e.g. flexible connection to the place of interest and potential separation between place of measurement and measuring device with the special advantage of the optical analysis that does not consume the analyte oxygen. The O₂ sensing was tested by using (1) solutions with the dissolved oxygen indicator dye (tris(1,10-phenantroline) ruthenium (II) chloride hexahydrate), and (2) and O₂ flux optode. The O₂ flux optode consist of an oxygen permeable membrane (test membrane) combined with oxygen optodes to measure the pO₂ differences across the membrane. The O₂ flux can be calculated from the pO₂ gradient across the test membranes and its permeability. The developed measuring systems `FLOX' detects the phase shift between the sinusoidally modulated excitation light and the resulting fluorescence of the indicator. The phase shift is caused by the fluorescence lifetime that depends on the oxygen concentration. Many investigations have shown that measurements of lifetime are preferable to measurements of intensity because of higher stability. The FLOX system uses a blue light emitting diode (LED, (lambda) _peak equals 450 nm) as light source together with optical filters and a photo multiplier tube as detector. The coupling between the place of measurement and the FLOX is performed by a bifurcated fiber bundle in which single multimode fibers are statistically mixed. Its measuring end could be either immersed directly in an aqueous solution of the fluorophore or provided with a special sensor head for the measurement of the oxygen flux into a surface, for example into the surface of the human skin. First measurements demonstrated the applicability of the FLOX system to measure the O₂ flux into human skin; for example an about 20 - 50% increase of the O₂ flux after stop of the circulation could be clearly shown.

Proceedings Article | 18 May 1993 Paper

O2-flux-optode for medical application

Gerhard Holst, Dietrich Luebbers, Edgar Voges

Proceedings Volume 1885, (1993) https://doi.org/10.1117/12.144712

KEYWORDS: Sensors, Luminescence, Diffusion, Skin, Oxygen, Phase measurement, Glasses, Modulation, Silicon, Light emitting diodes

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Showing 5 of 18 publications

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