This PDF file contains the front matter associated with SPIE Proceedings volume 7556, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Polarimetric imaging of Stokes vector (I, Q, U, V) can provide 4 independent signatures showing the linear and circular polarizations of biological tissues and cells. Using a recently developed Stokes digital imaging system, we measured the Stokes vector images of tissue samples from sections of rat livers containing normal portions and hematomas. The derived Mueller matrix elements can quantitatively provide multi-signature data of the bio-sample. This polarimetric optical technology is a new option of biosensing technology to inspect the structures of tissue samples, particularly for discriminating tumor and non-tumor biopsy. This technology is useful for critical disease discrimination and medical diagnostics applications.

Pseudo-random single photon counting (PRSPC) is a new time-resolved method combining the spread spectrum timeresolved optical measurement method with single photon counting. A continuous wave laser diode is modulated with a pseudo-random bit sequence, while a single photon detector is used to record the pulse sequence in response to the modulated excitation. Periodic cross-correlation is performed to retrieve the impulse response. Compared with conventional time-correlated single photon counting (TCSPC), PRSPC enjoys many advantages such as low cost and high count rate without compromising the sensitivity and time-resolution. In this paper, we report a PRSPC system that can be used for high speed acquisition of the temporal spread function of diffuse photons. It can reach a photon count rate as high as 3Mcps (counts per second). Experimental work has been conducted to demonstrate the system performance.

Worldwide incidence and mortality rates due to cancer continue to rise, with the burden of disease increasingly shifting to developing countries. Several optical diagnostic methods are under development to enable earlier detection of cancer, however, these are primarily intended for use in healthcare facilities in industrialized countries. Using knowledge gained from early clinical studies with large-scale prototype systems, we have designed and tested low-cost, portable versions of these instruments. We propose that these systems may be used for early diagnosis and screening in developing countries, and that pilot clinical studies are warranted in these low-resource settings.

Video endoscopes with an imager located at the distal end possess a simplified opto-mechanical layout compared to classical setups since an optical relay system is not required. Together with the availability of low price miniature CMOS imagers, this enables for building low cost devices for single usage avoiding the necessity of withstanding autoclaving which is one of the major drivers in both, system fabrication and operating cost. The optical layout has to take into account geometrical as well as opto-electronic aspects and is therefore a trade-off between system diameter, sensitivity and resolution. Consequently, the image circle should be as close as possible to the outer diameter for optimum performance in terms of resolution and sensitivity which goes along with large pixel size. We propose systems designs and prototypes for f/4, 3mm outer diameter endoscopes with 70° and 110° field of view using a CMOS imager with 650x650 pixels of 2.8μm pitch. The final systems are based on a simplified and rugged integration using a single polymer lens made by injection molding, a GRIN lens and a dispensed lens made of UV curing material allowing for high performance paired with low fabrication cost. Additionally, a side view system angled at 30° is presented based on a tilting reflection prism requiring minimum construction space allowing for an outer diameter of 3mm.

In many areas of the world, current methods for diagnosis of infectious diseases such as malaria and tuberculosis involve microscopic evaluation of a patient specimen. Advances in fluorescence microscopy can improve diagnostic sensitivity and reduce time and expertise necessary to interpret diagnostic results. However, modern research-grade microscopes are neither available nor appropriate for use in many settings in the developing world. To address this need, we designed, fabricated, and tested a portable, battery-powered, bright field and fluorescence inverted field microscope, optimized for infrastructural constraints of the developing world. We characterized an initial prototype constructed with rapidprototyping techniques, which utilized low-cost, over-the-counter components such as a battery-powered LED flashlight as the light source. The microscope exhibited suitable spatial resolution (0.8 μm) in fluorescence mode to resolve M. tuberculosis bacilli. In bright field mode, malaria parasites were resolvable at 1000x magnification. The initial prototype cost 480 USD and we estimate that the microscope can be manufactured for 230 USD. While future studies are planned to evaluate ease-of-use and reliability, our current system serves as a proof of concept that combined fluorescence and bright field microscopy is possible in a low-cost and portable system.

Optical Coherence Microscopy (OCM) utilizes a higher NA microscope objective in the sample arm of a low coherence interferometer than in Optical Coherence Tomography (OCT) to achieve axially and laterally high-resolution optical tomographic images. An increase in NA, however, leads to a dramatically decreased depth of focus (DOF), and hence shortens the imaging depth range so that high lateral resolution is maintained only within a small depth region around the focal plane. One solution to increase the depth of imaging while keeping a high lateral resolution is dynamic-focusing. Utilizing the voltage controlled refocus capability of a liquid lens, we have recently presented a solution for invariant high-resolution imaging using the liquid lens embedded within a fixed optics hand-held custom microscope. An implementation of the microscope for optical imaging using a broadband light source centered at 800 nm has been completed. Subsequently, we have developed Gabor-Domain Optical Coherence Microscopy (GD-OCM) that utilizes the high speed imaging of spectral domain OCT, the high lateral resolution of OCM, and the ability of real time refocusing of our custom design variable focus objective. In this paper, we provide an overview of the technology developed and highlight resent results. We also provide linkages to current related research in our group all directed at finding expedient pathways to the clinical settings.

We present an overview of our contributions and directions of research in the domain of optical scanners, with regard to their perspectives of use in optical coherence tomography (OCT). The performances, advantages and drawbacks of the different types of scanning systems are summarized. Both 1-D and 2-D scanners for various applications in OCT, from swept source filters to flying the beam over the target are considered. We briefly present our developments of polygon mirror (PM) scanners. We study galvoscanners (GS) in order to increase their duty cycle in general and for high speed scanners in particular. The limitations in reaching such goals are discussed. Based on these advancements, 2-D scanners, i.e. the double GS and the PM+GS solutions are approached with regard to their optimum driving functions. The 2-D Risley prism scanner is also considered, as the best choice when compactness is of prime importance. We finally briefly discuss the tendency towards miniaturization and recent developments in MEMS scanners. A trade-off is thus accomplished between recent developments and requirements of scanning devices for OCT in order to achieve the most appropriate results for a certain application. The current and future tendencies in the field are discussed.

Spectral domain optical coherence tomography (SD-OCT) systems achieve higher sensitivities compared to time domain OCT systems. However, one of the main challenges in SD-OCT is the obscuring object structure called "ghost image" or "mirror image" that arises from the Fourier transform of a real function. We have designed and developed a phaseshifting- based full-range SD-OCT system that we refer to as the dual detection full range SD-OCT. The proposed technique simultaneously obtains the quadrature components of a complex spectral interference. Therefore, the technique enables full range imaging without any loss of speed and is intrinsically less sensitive to movements of the subject. In this paper, we demonstrate that the dual detection technique can be applied to Doppler imaging without loss in the velocity dynamic range since the phase information of the acquired spectra is preserved. The dual detection full range SD-OCT provides a superior signal-to-noise ratio over a conventional SD-OCT since the most sensitive region around the zero path delay is usable. This capability improves the image quality of not only the structural image but also the Doppler image.

We present a novel instrumentation for wide dynamic range optical investigations based on a time-gated silicon Single- Photon Avalanche Diode (SPAD) in a Time-Correlated Single-Photon Counting (TCSPC) setup. The detector is gatedon and off in less than 200 ps and kept-on for detecting photons only within short time slots. Such technique is particularly useful in applications where a large amount of unnecessary photons precedes or follows the optical signal to detect, such as in time-resolved NIR spectroscopy, optical mammography, and optical molecular imaging. In particular, in time-resolved reflectance spectroscopy, when the source-detector separation is decreased, the detection electronics easily saturates, due to the huge amount of "early" photons, diffused by superficial layers. Instead, our setup is able to reject those photons and to detect only "late" photons, thus allowing to increase the injected power and to drastically widen the investigation dynamic range, while remarkably speeding up the acquisition. We acquired Instrument Response Functions (IRFs) at multiple wavelengths between 600 nm and 1000 nm and we achieved up to 10⁸ dynamic range in a very short measurement time (few minutes). Moreover, we tested the instrumentation with SPADs of different active areas and we compared the performances.

The goal of this article is to present a novel method for spectral characterization and calibration of spectrometers and hyper-spectral imaging systems based on non-collinear acousto-optical tunable filters. The method characterizes the spectral tuning curve (frequency-wavelength characteristic) of the AOTF (Acousto-Optic Tunable Filter) filter by matching the acquired and modeled spectra of the HgAr calibration lamp, which emits line spectrum that can be well modeled via AOTF transfer function. In this way, not only tuning curve characterization and corresponding spectral calibration but also spectral resolution assessment is performed. The obtained results indicated that the proposed method is efficient, accurate and feasible for routine calibration of AOTF spectrometers and hyper-spectral imaging systems and thereby a highly competitive alternative to the existing calibration methods.

Optical aberrations present an important problem in optical measurements. Geometrical calibration of an imaging system is therefore of the utmost importance for achieving accurate optical measurements. In hyper-spectral imaging systems, the problem of optical aberrations is even more pronounced because optical aberrations are wavelength dependent. Geometrical calibration must therefore be performed over the entire spectral range of the hyper-spectral imaging system, which is usually far greater than that of the visible light spectrum. This problem is especially adverse in AOTF (Acousto- Optic Tunable Filter) hyper-spectral imaging systems, as the diffraction of light in AOTF filters is dependent on both wavelength and angle of incidence. Geometrical calibration of hyper-spectral imaging system was performed by stable caliber of known dimensions, which was imaged at different wavelengths over the entire spectral range. The acquired images were then automatically registered to the caliber model by both parametric and nonparametric transformation based on B-splines and by minimizing normalized correlation coefficient. The calibration method was tested on an AOTF hyper-spectral imaging system in the near infrared spectral range. The results indicated substantial wavelength dependent optical aberration that is especially pronounced in the spectral range closer to the infrared part of the spectrum. The calibration method was able to accurately characterize the aberrations and produce transformations for efficient sub-pixel geometrical calibration over the entire spectral range, finally yielding better spatial resolution of hyperspectral imaging system.

We have investigated a potential technique based on spatially resolved reflectance to determine optical properties (OPs) in two-layer turbid media. Reflectance from two-layer tissue was simulated for a wide range of OP combinations (μ_a = 1-22.5, μs' = 5-42.5 cm^-1) using a condensed Monte Carlo (MC) model and utilized to train neural network (NN) inverse models. Experimental data from two-layer tissue phantoms with top layer thicknesses (D) ranging from 0.22 to 0.66 mm were collected at three UV-Vis wavelengths. Estimation accuracy was compared to simulated results with added noise. The mean error in experimental determination of μa ranged from 1.5 to 5.9 cm^-1 and mean error for μs' ranged from 2.1 to 12.1 cm^-1 as a function of D. Although numerous realistic challenges remain, this initial experimental study of an unconstrained two-layer diffuse reflectance based OP estimation approach provides support that such a technique has a strong potential to provide accurate in situ measurements in layered tissues.

Noninvasive and real-time analysis of tissue properties, in particular, the quantitative assessment of blood content and light scattering properties of mucosa is useful in a wide variety of applications. However, the nature of interactions between contact fiber-optic probes and the tissue surface presents a challenging problem with respect to the variability of in vivo measurements, for example affects due to variations in the pressure and angle of the probe tip on the tissue surface. Previously, pressure and angle effects have been investigated for other modalities (i.e. diffuse reflectance and Raman spectroscopy). We present an evaluation of this variability, as well as the length of time in contact with tissue for polarization-gated spectroscopy. The evaluation is based on the quantification of mucosal blood content at superficial depths (within 100 to 200 microns of tissue surface) for in vivo measurements of oral mucosa. Measurements are presented for different pressures, angles and time scales and the variability due to these factors is assessed.

A currently available 2-D high-resolution, optical molecular imaging system was modified by the addition of a structured illumination source, Optigrid^TM, to investigate the feasibility of providing depth resolution along the optical axis. The modification involved the insertion of the Optigrid^TM and a lens in the path between the light source and the image plane, as well as control and signal processing software. Projection of the Optigrid^TM onto the imaging surface at an angle, was resolved applying the Scheimpflug principle. The illumination system implements modulation of the light source and provides a framework for capturing depth resolved mages. The system is capable of in-focus projection of the Optigrid^TM at different spatial frequencies, and supports the use of different lenses. A calibration process was developed for the system to achieve consistent phase shifts of the Optigrid^TM. Post-processing extracted depth information using depth modulation analysis using a phantom block with fluorescent sheets at different depths. An important aspect of this effort was that it was carried out by a multidisciplinary team of engineering and science students as part of a capstone senior design program. The disciplines represented are mechanical engineering, electrical engineering and imaging science. The project was sponsored by a financial grant from New York State with equipment support from two industrial concerns. The students were provided with a basic imaging concept and charged with developing, implementing, testing and validating a feasible proof-of-concept prototype system that was returned to the originator of the concept for further evaluation and characterization.

We demonstrate the use of Beam Profile Reflectometry (BPR) to measure coating thicknesses on small, highly curved devices such as cardiac stents. BPR has long been used in the semiconductor industry as a powerful technique for measuring the thickness and refractive index of transparent films. The method uses a diffraction-limited focused laser beam to provide light at multiple angles-of-incidence simultaneously within a sub-micron measurement area. By analyzing the reflected light as a function of angle-of-incidence and polarization, robust and deterministic measurements of film-thickness and refractive index can be obtained taking proper account of birefringence. For the current work, the technique has been implemented in a compact desktop configuration suitable, for example, for the in-line monitoring of coating thickness and composition as part of a stent manufacturing process. Provision is made for the alignment and manipulation of the small and fragile samples, and for the location of the measurement spot at the appropriate site on the stent's surface. Validation measurements on stent-like reference samples, comparing results from the technique with destructive measurements on the same samples, show correlation of better than 99% over a range of coating thicknesses and sample morphologies down to curvature radii of ~50μm.

We developed a multi-parameter detection system that integrates both a quartz crystal microbalance (QCM) and a surface plasma resonance (SPR) system. A QCM is known to possess the capabilities of measuring both mass loading by frequency shift and stiffness by damping factor of the adsorption layer. However, the mass measured by using a QCM includes not only the true mass of the adsorption layer but also the water. On the other hand, a SPR is a well known technique which can be used to measure the true mass loading of the adsorption layer. By integrating these two techniques, we can simultaneously measure properties such as stiffness, conformation, and mass loading of the adsorption layer. To simplify the chip manufacturing procedures, this new detection system adopts a prism couple method which consists of a He-Ne laser, a prism, quartz and a power meter. In consideration of the light transmission issue, one side of the quartz was coated with ITO instead of gold. Preliminary results showed that this set-up can perform QCM and SPR techniques simultaneously. The experimental results matched well with the theoretical predictions.

Lighting subsystems to drive 21st century bioanalysis and biomedical diagnostics face stringent requirements. Industrywide demands for speed, accuracy and portability mean illumination must be intense as well as spectrally pure, switchable, stable, durable and inexpensive. Ideally a common lighting solution could service these needs for numerous research and clinical applications. While this is a noble objective, the current technology of arc lamps, lasers, LEDs and most recently light pipes have intrinsic spectral and angular traits that make a common solution untenable. Clearly a hybrid solution is required to service the varied needs of the life sciences. Any solution begins with a critical understanding of the instrument architecture and specifications for illumination regarding power, illumination area, illumination and emission wavelengths and numerical aperture. Optimizing signal to noise requires careful optimization of these parameters within the additional constraints of instrument footprint and cost. Often the illumination design process is confined to maximizing signal to noise without the ability to adjust any of the above parameters. A hybrid solution leverages the best of the existing lighting technologies. This paper will review the design process for this highly constrained, but typical optical optimization scenario for numerous bioanalytical instruments and biomedical devices.

Background: Accurate assessment of tumor boundaries and intraoperative detection of therapeutic margins are important oncologic principles for minimal recurrence rates and improved long-term outcomes. However, many existing cancer imaging tools are based on preoperative image acquisition and do not provide real-time intraoperative information that supports critical decision-making in the operating room. Method: Poly lactic-co-glycolic acid (PLGA) microbubbles (MBs) and nanobubbles (NBs) were synthesized by a modified double emulsion method. The MB and NB surfaces were conjugated with CC49 antibody to target TAG-72 antigen, a human glycoprotein complex expressed in many epithelial-derived cancers. Multiple imaging agents were encapsulated in MBs and NBs for multimodal imaging. Both one-step and multi-step cancer targeting strategies were explored. Active MBs/NBs were also fabricated for therapeutic margin assessment in cancer ablation therapies. Results: The multimodal contrast agents and the cancer-targeting strategies were tested on tissue simulating phantoms, LS174 colon cancer cell cultures, and cancer xenograft nude mice. Concurrent multimodal imaging was demonstrated using fluorescence and ultrasound imaging modalities. Technical feasibility of using active MBs and portable imaging tools such as ultrasound for intraoperative therapeutic margin assessment was demonstrated in a biological tissue model. Conclusion: The cancer-specific multimodal contrast agents described in this paper have the potential for intraoperative detection of tumor boundaries and therapeutic margins.

Multi-infusion systems are used frequently at intensive care units to administer several liquid therapeutic agents to patients simultaneously. By passively combining the separate infusion lines in one central line, the number of punctures needed to access the patient's body, is reduced. So far, the mutual influence between the different infusion lines is unknown. Although the flow properties of single infusion systems have been investigated extensively, only a few research groups have investigated the flow properties of multi-infusion systems. We showed in a previous study that applying multi-infusion can lead to fluctuations in syringe pump infusions, resulting in uncontrolled and inaccurate drug administration. This study presents a performance analysis of multi-infusion systems as used in the Neonatology Intensive Care Unit. The dynamics between multiple infusion lines in multi-infusion systems were investigated by simulation experiments of clinical conditions. A newly developed real-time spectral-photometric method was used for the quantitative determination of concentration and outflow volume using a deconvolution method of absorption spectra of mixed fluids. The effects for common clinical interventions were studied in detail. Results showed mutual influence between the different infusion lines following these interventions. This mutual influence led to significant volume fluctuations up to 50%. These deviations could result in clinically dangerous situations. A complete analysis of the multiinfusion system characteristics is recommended in further research to estimate both the presence and severity of potential risks in clinical use.

Electrosurgical equipment used during surgery generate smoke consisting of particles, vapor, aerosols and potentially harmful biological agents. Smoke evacuation systems are used more commonly and various types are available. A special image enhancement technique was used to study the behavior of surgical smoke and the effectiveness of smoke evacuation systems. Three different smoke evacuation systems were investigated. Rapid vac (Valleylab Boulder CO) The Buffalo silent whisper turbo (Buffalo, NY) ERBE IES 300 ( Tübingen, Germany) A back scatter illumination technique in combination with a high speed camera was applied to image the dynamics of a smoke plume generated by vaporizing a homogenous meat paste irradiated with the beam of a 10 W cw CO₂ laser moving at a constant speed. The three different smoke evacuation systems with their individual nozzles, were held 2 cm above the surface of the meat paste and were switched on and off at fixed intervals to mimic a clinical situation. For images analysis, software was developed to count 'smoke pixels' in the video frames as a quantification tool. For the observer's eye, there were no differences between the systems. However, images quantification showed significantly less 'smoke' for the Buffalo system. It is expected that the performance in a clinical situation is also influenced by additional conditions like nozzle design, airflow and noise level. Noise levels were measured at the tip of the nozzle, 80 cm from the tip, 140 cm from the tip. The Buffalo system is the loudest system at every distance measured.

One of the most commonly performed ophthalmic surgeries is the replacement of the eye lens by a synthetic intraocular lens. Because of the trend to match the intraocular lens with the properties of the individual eye, intricate designs for IOLs have been developed. Multifocal, diffractive as well as aspheric designs demand for elaborate measurement and analysis options. Various measurement methods have evolved including techniques which analyze the image itself or the emerging wavefront. In order to understand the advantages of these different methods intraocular lenses of various designs have been measured and analyzed under miscellaneous conditions. Measurement results of this comparison will be presented.

In this study, a new HMS (Health Monitoring System) device is developed for diabetic patient. This device mainly consists of I) 3D blood vessel searching unit and II) automatic blood glucose measurement (ABGM) unit. This device has features such as 1)3D blood vessel location search 2) laptop type, 3) puncturing a blood vessel by using a minimally invasive micro-needle, 4) very little blood sampling (10μl), and 5) automatic blood extraction and blood glucose measurement. In this study, ABGM unit is described in detail. It employs a syringe type's blood extraction mechanism because of its high accuracy. And it consists of the syringe component and the driving component. The syringe component consists of a syringe itself, a piston, a magnet, a ratchet and a micro-needle whose inner diameter is about 80μm. And the syringe component is disposable. The driving component consists of body parts, a linear stepping motor, a glucose enzyme sensor and a slider for accurate positioning control. The driving component has the all-in-one mechanism with a glucose enzyme sensor for compact size and stable blood transfer. On designing, required thrust force to drive the slider is designed to be greater than the value of the blood extraction force. Further, only one linear stepping motor is employed for blood extraction and transportation processes. The experimental result showed more than 80% of volume ratio under the piston speed 2.4mm/s. Further, the blood glucose was measured successfully by using the prototype unit. Finally, the availability of our ABGM unit was confirmed.

The treatment of keratoconus and corneal ulcers by collagen cross-linking using ultraviolet type A irradiation, combined with photo-sensitizer Riboflavin (vitamin B2), is a promising technique. The standard protocol suggests instilling Riboflavin in the pre-scratched cornea every 5min for 30min, during the UVA irradiation of the cornea at 3mW/cm² for 30 min. This process leads to an increase of the biomechanical strength of the cornea, stopping the progression, or sometimes, even reversing Keratoconus. The collagen cross-linking can be achieved by many methods, but the utilization of UVA light, for this purpose, is ideal because of its possibility of a homogeneous treatment leading to an equal result along the treated area. We have developed a system, to be clinically used for treatment of unhealthy corneas using the cross-linking technique, which consists of an UVA emitting delivery device controlled by a closed loop system with high homogeneity. The system is tunable and delivers 3-5 mW/cm², at 365nm, for three spots (6mm, 8mm and 10mm in diameter). The electronics close loop presents 1% of precision, leading to an overall error, after the calibration, of less than 10% and approximately 96% of homogeneity.

The goal of this work is to develop a safe software construction means for an XML based data standard for a class of medical devices, cytometry instruments. Unfortunately, the amount of empirical evidence to archive this goal is minimal. Therefore, technologies associated with high reliability were employed together with reuse of existing designs. The basis for a major part of the design was the Digital Imaging and Communications in Medicine (DICOM) standard and the Flow Cytometry Standard (FCS). Since the DICOM Standard is a Class II device, the safety of software should be maximized. The XML Schema Definition Language (XSDL) has been used to develop schemas that maximize readability, modularity, strong typing, and reuse. An instance and an instrument XML schema were created for data obtained with a microscope by importing multiple schemas that each consisted of a class that described one object. This design was checked by validating the schemas and creating XML pages from them.

We present a common-path optical frequency domain imaging (CP-OFDI) system for non-invasive evaluation of various pearls. By adopting a high speed ready-to-ship scanning light source and a common-path lensed fiber probe, with the help of a rotation stage, real-time display of whole circumference of a pearl could be achieved. The common-path lensed fiber probe was fabricated by simply forming a focusing lens directly on the tip of an optical fiber, thus the fiber lens acted as a reference reflector as well as a focusing lens. The focal length of the lensed fiber probe was over 600 μm in free space and the average imaging depth reached up to 3 mm, which was deep enough to examine the internal structure of the pearl. The sensitivity of the system was experimentally obtained as 100dB. With an implemented system, the presence of nucleus and the nacreous laminated pattern were confirmed and analyzed. Experimental results show that the CP-OFDI system has great potential for identifying and grading pearls non-invasively but precisely.

Near-infrared spectroscopy is a promising, rapidly developing, reliable and noninvasive technique, used extensively in the biomedicine and in pharmaceutical industry. With the introduction of acousto-optic tunable filters (AOTF) and highly sensitive InGaAs focal plane sensor arrays, real-time high resolution hyper-spectral imaging has become feasible for a number of new biomedical in vivo applications. However, due to the specificity of the AOTF technology and lack of spectral calibration standardization, maintaining long-term stability and compatibility of the acquired hyper-spectral images across different systems is still a challenging problem. Efficiently solving both is essential as the majority of methods for analysis of hyper-spectral images relay on a priori knowledge extracted from large spectral databases, serving as the basis for reliable qualitative or quantitative analysis of various biological samples. In this study, we propose and evaluate fast and reliable spectral calibration of hyper-spectral imaging systems in the short wavelength infrared spectral region. The proposed spectral calibration method is based on light sources or materials, exhibiting distinct spectral features, which enable robust non-rigid registration of the acquired spectra. The calibration accounts for all of the components of a typical hyper-spectral imaging system such as AOTF, light source, lens and optical fibers. The obtained results indicated that practical, fast and reliable spectral calibration of hyper-spectral imaging systems is possible, thereby assuring long-term stability and inter-system compatibility of the acquired hyper-spectral images.