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OCT Images of Human Skin

Spectral Domain OCT Systems

Applicationof theHandheldProbe forIn VivoHuman SkinImagingPalm Skin with Callous

Back of HandFinger Pad

Available SystemsHyperion■ 100 nm Broadband SLD Centered

at 930 nm■ Axial Scan Rate: 110 kHz■ Axial Resolution: 6 µm■ Imaging Depth: 2.7 mm

Ganymede■ 100 nm Broadband SLD Centered

at 930 nm■ Axial Scan Rate: 29 kHz■ Axial Resolution: 6 µm■ Imaging Depth: 2.7 mm

Callisto ■ 100 nm Broadband SLD Centered

at 930 nm■ Axial Scan Rate: 1.2 kHz■ Axial Resolution: 7 µm■ Imaging Depth: 1.7 mm

All systems come with a handheld probethat contains an XY galvo mirror pair fortwo-dimensional scanning of the imagingbeam. As a result, each system can producecross-sectional, en face, and volumetricimages. For hands-free operation, a standon which the handheld probe can bemounted is also provided.

NEW110 kHz

A-Scan Rate

Spectral Domain Optical Coherence Tomography (SD-OCT) is based on Fourier DomainOCT technology. It utilizes a broadband super luminescent diode light source and a speciallydesigned spectrometer to measure the spectrally based interferometric signal. SD-OCT is idealfor real-time imaging of biological tissue, small animals, and materials. Thorlabs is dedicated toproviding imaging solutions to fit each customer’s needs. We have developed a broad range ofstandard SD-OCT systems and now offer a menu of options to customize our SD-OCTsystems to meet your specific needs. Additionally, to advance the value of our partnership in theimaging community, Thorlabs stands ready to develop application-specific solutions that can beintegrated into your systems.

Spectral Domain OCT System Features■ Cross-Sectional and Volumetric Imaging ■ Video Microscopy Imaging with Integrated CCD Camera in Handheld Probe■ Compact System Design Ready for OEM Applications■ Zero Image Distortion Over 10 mm x 10 mm Field of View■ Systems Available with Several Imaging Speeds and Sensitivities■ 930 nm Standard Systems Can be Customized for Output Centered at 850 nm

In vivo 930 nm Spectral Domain OCT images of human skin. All images are 4.0 mm (W) x 1.6 mm (D).

Mouse Lung Imaging

The 3D reconstruction of the sub-pleural area (Fig. A) and cross-sectionalimages of a ventilated mouse lung (Figs. B and C) are shown. These images weretaken with a modified Thorlabs 930 nm Spectral Domain system.

Images courtesy of Prof. Stefan Uhlig (Department of Pulmonary Pharmacology,Research Center Borstel, Germany) and E. Lankenau and G. Hüttmann(Institute of Biomedical Optics, University of Luebeck, Germany).

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Figure 1Schematic of an SD-OCT System with a Handheld Probe.

200 µm

Fig. A

Inspiration

Fig. B Fig. C

Expiration

Spectral Domain OCT Systems

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Principles of Spectral Domain OCTFigure 1 graphically depicts the basic design of the Thorlabs SpectralDomain OCT engine and probe. Within the OCT engine, light from abroadband SLD is divided, using a fiber-based Michelson interferometersetup, into reference and sample arm optical paths. The reference armpath is terminated with a mirror and consists of dispersion-compensatingoptics. Light retroreflected off the mirror is recoupled into the fiber opticbeamsplitter and combined with light returning from the external samplearm. The sample arm is a two-dimensional scanning handheld probeconsisting of two galvanometer scanners and focusing optics. Light thatis focused onto, and penetrates, the sample is back reflected off of thedifferent sample layers and recoupled into the sample arm fiber of theMichelson interferometer. The light returning from both arms

recombines to create an interference signal. Reflections from differentsample layers produce an interferogram with varying frequencies. Theresulting interferogram is a combination of reflections from all layers inthe sample. That interferogram is spectrally detected using a linear-kspectrometer consisting of a diffraction grating, a prism to spectrallydisperse the interferogram evenly as a function of wavenumber, and alinescan camera. The Fourier transform of the interferogram yields areflectivity plot as a function of depth within the sample (A-scan). 2Dcross-sectional and 3D volumetric images are created by scanning thegalvanometers in the sample arm probe to yield a series of A-scans in thelateral and transverse directions.

System DetailsThe Thorlabs Spectral Domain OCT imaging system is depictedschematically in Fig. 2. The base unit includes a broadbandsuperluminescent diode (SLD) light source, a spectrometer, analog anddigital timing circuitry, and drive electronics for the galvanometerscanners within the handheld probe.

An optical fiber is used to split the light into the reference and samplearm paths. The signal returning from the probe is recombined withreference arm light and directed toward the input of the spectrometerequipped with a high speed CCD sensor. The resolution of thespectrometer places a theoretical limit on the imaging depth, while thespectral width of the SLD places a theoretical limit on the axialresolution. However, actual results are sample dependent.

Data Acquisition and SoftwareThe base unit is connected to an included PC, which is equippedwith two high performance data acquisition cards. All required dataacquisition and processing is performed via the integrated softwarepackage, which contains a complete set of functions for controlling datameasurement, collection, and processing as well as for displaying andmanaging OCT image files. The software package includes a library ofparameter settings for sample applications. Alternatively, the softwareallows the user to modify the system parameters; for example, the lateralscanning range and the step width are both user controlled. In addition,the data sets can be saved and exported for further image processing anddata analysis.

Please visit our homepage www.thorlabs.com and clickon the link to our on-line Image Gallery for OCT images,applications, and links to publications.

Spectral Domain OCT Systems

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PC

Fiber OpticCoupler

Spectrometer

Base Unit

Analog Front End and Digital Logic & Clocking

Image Sensor

SLDLight Light

ReferenceArm

Light

Light

Signal & Datalines

High-Speed Signal Processing Software

High Level Application Software

High-Speed DAQ Board

Multichannel I/O board

Galvanometer Driver

CollimatingLens

Objective

Sample

X-YGalvanometer

Scanners

Figure 2Schematic showing all the major component parts of the SD-OCT system

Spectral Domain OCT Systems

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Cochlear ImagingAn anatomical drawing of human cochlea (Fig. A) and theOCT scan of the lateral part of an exposed cochlea (Fig. B)imaged with a modified Thorlabs’ Spectral Domain systemand a Möller-Wedel HR1000 microscope.

Ref: Pau, H. W., Lankenau, E., Just, T., Behrend, D., and Hüttmann, G.Acta Oto-Laryngologica 127, 907-13, 2007.

SVST

Fig. A

SV ST

Fig. B

Standard 930 nm SD-OCT SystemsHyperion: High-Speed ImagingThe Hyperion SD-OCT system provides the fastest OCT imaging capability on the market at 110 kHz. It takes advantage of the outstandingperformance of the Basler Sprint CMOS camera to acquire 110,000 lines (A-scans) per second. The Hyperion is capable of image acquisition ratesup to 214 frames per second (i.e., less than 5 ms per frame). Real-time 3D imaging with 256 x 256 x 512 pixels can be achieved at 1 volume persecond. As a tradeoff for speed, the Hyperion has the lowest sensitivity of Thorlabs’ SD-OCT systems at 87 dB. The high-speed capability of theHyperion, however, makes it well suited for monitoring rapid, dynamic processes as well as for process control applications. Thorlabs’ standardHyperions has a center wavelength of 930 nm and is capable of imaging up to 2.7 mm in the sample with 6 µm axial resolution.

Ganymede: Video-Rate ImagingThe Ganymede is the optimal choice for a general purpose SD-OCT system with 91 dB sensitivity and imaging at 29,000 lines per second or56 frames per second (512 lines/frame). At this rate and sensitivity, the Ganymede can image live biological samples and acquire volume data sets inless than 5 seconds. Thorlabs’ standard Ganymede has a center wavelength of 930 nm and is capable of imaging up to 2.7 mm in the sample with6 µm axial resolution.

Callisto: High-Sensitivity ImagingThe linear CCD array used in the Callisto has the highestsensitivity of any of Thorlabs’ SD-OCT systems. Thesensitivity corresponds to the the smallest detectable changein the index of refraction in a sample. Images produced usingthe Callisto will have higher contrast between sample layerscompared to the Hyperion and Ganymede systems. TheCallisto operates at 1.2 kHz A-scan rate, which results in2 frames per second (512 lines/frame). With the highestsensitivity but slow imaging speed, the Callisto is best suitedfor imaging static or in vitro samples. Thorlabs’ Callisto has acenter wavelength of 930 nm and is capable of imaging upto 1.7 mm in the sample with 7.2 µm axial resolution.

Custom SD-OCT SystemsIn addition to our standard SD-OCTsystems described above, Thorlabs offers avariety of options for customers to designtheir own SD-OCT systems based on theirunique imaging requirements. Weencourage customers to contact Thorlabsto discuss how we can meet your uniqueOCT imaging needs.

Data Acquitition Cards■ Analog/Digital Conversion Rate:

100 MS/s*■ Analog/Digital Resolution: 14 Bit■ Analog/Digital Channels: 2■ Analog Output Rate: 1 MS/s*■ Analog Output Resolution:

16 Bit■ Analog Output Channels: 4

Computer■ CPU: Intel® Processor■ Memory: 2 GB■ Operating System: Windows®

XP Professional■ Hard Drive: 250 GB SATA■ Optical Drive: 16x DVD +/- RW■ Monitor: 19" LCD, 1280 x 1024* MS/s = 1x106 Samples per Second

Common SD-OCT System Specifications

*Axial Resolution and Maximum Imaging Depth may vary depending on the absorption and scattering characteristics of the sample.†Optical Power is the power output from the base unit (engine). **Imaging Speed is based on 512 A-scans per Frame‡The Sensitivity specification is for a single A-scan and is dependent on the application.

SD-OCT Engine Callisto Ganymede Hyperion

Center Wavelength 930 ± 10 nmSpectral Width (FWHM) 100 ± 5 nmAxial Scan Rate 1.2 kHz 29 kHz 110 kHzAxial Resolution* in Air 7.0 µm 5.8 µm 5.8 µmAxial Resolution* in Water 5.3 µm 4.4 µm 4.4 µmMaximum Imaging Depth* 1.7 mm 2.7 mm 2.7 mmMaximum Optical Power† 3 mWImaging Speed** 2 fps 56 fps 214 fpsMaximum Pixels per A-scan 512 1024 1024A-scan Sensitivity‡ 105 dB 91 dB 86 dB