Ganymede 930 nm OCT System
|GANYMEDE System Specifications|
|Center Wavelength||930 nm|
(A-Scan Line Rate)
|High-Speed Mode: 30 kHz|
Medium-Speed Mode: 10 kHz
High-Sensitivity Mode: 1.25 kHz
|Axial (Depth) Resolution (Air)||<5.8 µm|
|Lateral Resolution||8 µm|
|Maximum Field of View||10 mm x 10 mm x 2.7 mm|
|Maximum Pixels Per A-Scan||1024|
|Optical Power on Sample||1.5 mW|
Thorlabs' GANYMEDE™ OCT Imaging System
- A-Scan Rate of Up to 30 kHz
- General-Purpose OCT System with Video-Rate Imaging Speed
- Three Acquisition Modes for Flexibility in Imaging Speed and Sensitivity
- Ideal for Biological and Industrial Materials Imaging Applications
- Large Field of View: 10 mm x 10 mm x 2.7 mm
- Custom Configurations Available
Thorlabs' GANYMEDE™ OCT Imaging System offers three acquisition speed settings. In the High Speed mode with 30 kHz A-Scan rate, 1024 x 1024 pixel images can be displayed in video rate and with 91dB sensitivity. In contrast, the High Sensitivity Mode provides the ability to record images with a sensitivity of up to 106 dB at 1.25 kHz A-Scan rate. Increasing sensitivity, at the cost of imaging speed, enables higher contrast during imaging, thereby improving detection of very weakly resolved structures in the sample. The GANYMEDE Spectral Domain OCT System is an excellent general-purpose system for imaging biological samples as well as producing 2D cross-sectional images and 3D volume datasets.
The GANYMEDE utilizes a GigE data connection and is controlled via software preinstalled on a high-performance computer that is capable of online rendering and display of all measured 3D datasets. It also includes a 3D scanning probe with integrated video camera for volume imaging and live video display. The included stand and sample stage provide XY translation and rotation of the sample along with axial travel of the probe. The GANYMEDE system is fully functional right out of the box.
Optical Coherence Tomography (OCT) is a noninvasive optical imaging modality that provides real-time, 1D depth, 2D cross-sectional, and 3D volumetric images with micron-level resolution and millimeters of imaging depth. OCT images provide structural information of a sample, based on light backscattered from different layers of material within that sample. OCT imaging is considered to be the optical analog to ultrasound. OCT, however, achieves higher resolution through the use of near infrared wavelengths, at the cost of decreased penetration depth. In addition to high resolution, the non-contact, noninvasive advantage of OCT makes it well suited for imaging samples such as biological tissue, small animals, and industrial materials.
Click here for a full list of peer-reviewed publications using Thorlabs OCT imaging products.
OEM and Custom Requests
Thorlabs offers OEM products for easy integration into your imaging system. With ISO9001 certified production facilities and experienced OEM design engineers, we welcome OEM requests.
We also recognize that our customers have unique application requirements. For this reason, we stand ready to discuss how our OCT systems can be adapted to meet your needs. Please contact us to discuss the possibility of providing you with a customized OCT system.
The GANYMEDE OCT System includes a desktop PC and a 22" display. This processing system is set up with all the necessary data acquisition hardware, drive electronics, and software to begin imaging upon arrival.
- Processor: Quad Core
- Processor Speed: ≥ 3.3 GHz
- Memory: ≥ 8 GB
- Hard Drive: ≥ 500 GB
- Data Acquisition: GigE
*Computer Type Subject to Change without Notice
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The GANYMEDE SD-OCT engine is housed in a 420 mm x 320 mm x 149 mm (16.54' x 12.6' x 5.86') unit. It contains a 930 nm Superluminescent Diode Light Source and a Linear Array-Based Spectrometer. It also includes all associated drive electronics and controllers.
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High-performance data acquisition software is included with all OCT systems. The Windows-based software performs data acquisition, processing, scan control, and display of OCT images. See the Software tab for more details.
A Software Development Kit (SDK) is also available for C/C++ and LabVIEW-based interfaces. Please contact email@example.com for more details.
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All Thorlabs OCT systems include a hand-held probe and stand, as shown here. The probe provides X-Y scanning for three-dimensional data acquisition. A camera integrated in the probe provides live video imaging during OCT data acquisition. The probe easily slips onto the stand for imaging of small samples.
The probe stand consists of a post-mounted focus block which is attached to a specially designed 12" x 14" aluminum breadboard using a Ø1.5" P14 Post.
- Ideal for Vibration-Sensitive Studies such as Doppler OCT Imaging
- 3/4" Thick Aluminum Breadboard Provides Increased Stability
- Breadboard Base has Side Grips and Recessed Feet for Easy Lifting and Transportation of the Stand
- Includes a Sample Stage with 1" X and Y Travel as well as Rotation
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Thorlabs offers a wide variety of OCT imaging systems, each with their own special set of specifications. To assist in narrowing down which OCT system(s) is best suited for your application, we have provided the guide below. This information is intended only as a guide. We encourage you to contact us to discuss your specific imaging requirements.
|Center Wavelength||930 nm (840 nm option also available)||1325 nm||1300 nm||1325 nm|
|Bandwidth (3 dB)||100 nm||150 nm||100 nm|
|A-Scan Line Rate||1.2 kHz||29 kHz||110 kHz||Up to 91 kHz||100 kHz||16 kHz|
|B-Scan Frame Rate*|
|2 fps||29 fps||55 fps||Variable||110 fps||25 fps|
|7 µm / 5.3 µm||5.8 µm / 4.5 µm||<7.5 µm / <5.6 µm||16 / 12 µm||12 µm / 9 µm|
|Lateral Resolution||8 µm||15 µm|| 25 µm|
|Sensitivity||105 dB||91 dB||86 dB||Up to 106 dB||100 dB|
|Maximum Field of View**|
(L x W x D)
|10 x 10 x 1.7 mm||10 x 10 x 2.7 mm||10 x 10 x 2.5 mm||10 x 10 x 12 mm||10 x 10 x 3 mm|
*Actual Frame Rate is dependent on processing and display parameters
**Depth Resolution and actual imaging depth are dependent on the optical properties of the sample being imaged.
- Interactive Click and Scan Video Mode
- High-Speed Volume Rendering Display
- Doppler Imaging
- Versatile Scan and Acquisition Control
High-performance data acquisition software is included with all Thorlabs OCT systems. This Windows®-based software package performs data acquisition, processing, scan control, and displays OCT images. Additionally, NI LabVIEW and C-based Software Development Kits are available that contain a complete set of libraries for measurement control, data acquisition, and processing, as well as storage and display of OCT images. Using the Thorlabs OCT LabVIEW or C SDKs provides the means for developing highly specialized OCT imaging software for each and every individual application.
Thorlabs' OCT software provides several scan and acquisition controls. The camera integrated in the probe of our OCT systems displays live video images in the application software. Users can now select points directly on the video display to define the scan line area for 2D imaging. Manual controls for scan length, size (in pixels), angle, and location are also available.
Thorlabs' OCT software provides numerous methods for archiving data. Output file formats include raw data directly from the detector, OCT image data, Doppler phase data, as well as complex data that is calculated after the FFT.
Users can specify data recording options such as length (in terms of time or number of frames), file names, and data formats (raw or processed) for one-click streaming. Additionally, a ring buffer can be configured for immediate in-memory storage and playback of the buffered 2D data. Images can be taken with a single click and saved as .bmp, .jpeg, .tiff, or .png files.
In Offline Mode, saved data can be processed (in case of raw data), reviewed, and exported into image stacks, video files, or converted into other data formats.
Thorlabs' GANYMEDE high-speed OCT system provides a choice of three different acquisition modes, ranging from high-speed to slow acquisition. in slow mode, the sensitivity in the image is maximized, thereby effectively providing higher structural detail. The high-speed mode provides video-like frame rates in 2D and fast volume rendering modes. The "medium" speed mode is a compromise of sensitivity and acquisition speed. Please note speed settings vary depending on system type.
In the 2D imaging mode, the probe beam scanns in one direction, thus acquiring cross-sectional OCT images, which are then displayed in real time. Line averaging before or after the Fast Fourier Transform (FFT) is available as well as OCT image averaging. Image display parameters, such as color mapping, can be controlled in this mode. We have also implemented an option for automatic display using the optimal dynamic range of the system. All tool panels can be unlocked and freely moved on the application window.
In the 3D imaging mode, the OCT probe beam scans sequentially across the sample to collect a series of 2D cross-sectional images, which are then processed to build a 3D image.
In the Thorlabs OCT software, 3D volume data sets can be viewed as orthogonal cross-sectional planes (see below) and volume renderings. The Sectional View, features clipping of cross-sectional images in all three orthogonal planes, independent of the orientation in which the data was acquired. The view can be rotated as well as zoomed in and out.
The Rendering View provides a volumetric rendering of the acquired volume dataset. This view enables quick 3D visualization of the sample being imaged. Planes of any orientation can be clipped out to expose internal structures within the volume. Users can zoom in/out, rotate, as well as save a snapshot of the rendering display as an image in BMP, JPEG, TIFF, or PNG format.
Utilizing the full potential of our high-performance software in combination with our GANYMEDE high-speed OCT system, we have developed a Fast Volume Rendering Mode for the Thorlabs OCT software. In this mode, high-speed volume renderings can be displayed in real-time, providing rapid visualization of samples in three dimensions. This mode is available on all SDOCT systems except for the Callisto.
Doppler OCT imaging comes standard with all OCT systems. In the Doppler Mode, phase shifts between adjacent pixels are averaged to calculate the Doppler frequency shift induced by particle motion or flow. The Doppler Mode is activated by a button on the software toolbar. The number of lateral and axial pixels can be modified to change velocity sensitivity and resolution during phase shift calculation. The Doppler images are displayed in the main window with a user-selectable color map indicating forward- or backward-directed flow, relative to the OCT beam.
Doppler OCT Imaging
Doppler OCT is an extension of OCT that enables imaging of particle motion within a sample. In Fourier Domain OCT (FD-OCT) systems, there are no additional hardware requirements for implementation of Doppler imaging. Doppler OCT imaging capability is embedded in the software provided with all Thorlabs’ OCT systems and is ideal for functional vascular imaging, studying embryonic cardiac dynamics, or monitoring vascular treatment response. It is also useful for general flow velocimetry used in microfluidic channel monitoring.
Principles of Doppler OCT
The Fourier transform of the interferogram acquired in FD-OCT imaging (A-scan) produces a complex signal [I(z) + iQ(z)], where the magnitude of that signal is used to create the structural OCT image. The complex portion of the signal contains information based on the phase of the interferogram. Any change in phase between consecutively acquired A-scans can be attributed to a Doppler frequency shift induced by particle motion.
In Thorlabs’ implementation of Doppler OCT, Doppler frequency shifts are calculated based on spatially averaging phase shifts within a sliding 2D window and using a Kasai autocorrelation function (see reference below). The Doppler frequency shiftfD caused by moving particles is related to the phase shift between A-scans, as described in the following expression:
where Δφ is the average phase shift within the sliding 2D window and fA is the A-scan rate of the OCT system. The Thorlabs Doppler Imaging Mode displays the phase shift induced by moving particles using a standard Doppler colormap where red to yellow (violet to blue) indicates flow in the direction toward (away from) the OCT sample beam.
The mean velocity <ν> of the moving particles, at any depth, can be quantified by knowing θ, the angle between the OCT sample beam and flow vector:
Here, λo is the center optical wavelength of the OCT sample beam and n is the index of refraction of the sample.
C. Kasai, K. Namekawa, A. Koyano, R. Omoto et al . “Realtime two-dimensional blood flow imaging using an autocorrelation technique,” IEEE Trans. Sonics. Ultrason. 32 458-464 (1985).
A stationary observer will observe a Doppler shift in the frequency of light emitted from a source moving toward or away from the observer.When the light source is moving toward the observer, the observed frequency of light will be blue-shifted, meaning the perceived frequency of the light will be higher than the actual frequency emitted by the source. Higher frequencies correspond to shorter wavelengths. Conversely, if the light source is moving away from the observer, the observed frequency of light will be redshifted to lower frequencies. In Doppler OCT, the Doppler effect caused by moving particles in a sample is determined by measuring a shift in the phase between consecutive OCT interference fringe signals.
Fig. A shows the 3D surface reconstruction of the tadpole heart, while Fig. B demonstrates the complex blood flow pattern of the heart via a 3D color Doppler map.
Thorlabs’ Swept Source OCT Imaging System (OCS1300SS) with Doppler Imaging was used by researchers at the University of Toronto to study the cardiovascular system of living tadpoles. The series of images below show in vivo cross-sectional SS-OCT images of a beating tadpole heart superimposed with Doppler blood flow images. An optical Doppler cardiogram was obtained using a gated technique to increase the effective frame rate and improve the signal-to-noise ratio. The gating technique provides ultra high-speed visualization of the heart blood flow pattern in developing African frog embryos in both 3D and 4D (i.e., 3D + time) modes. This allows detailed visualization of the complex cardiac motion and hemodynamics in the beating heart.
A. Mariampillai, B.A. Standish, N.R. Munce, C. Randall, G. Liu, J.Y. Jiang, A.E. Cable, I.A. Vitkin, V.X.D. Yang, “Doppler optical cardiogram gated 2D color flow maging at 1000 fps and 4D in vivo visualization of embryonic heart at 45 fps on a swept source OCT system”, Optics Express15 , 1627 (2007).
Optical Coherence Tomography Tutorial
Optical Coherence Tomography (OCT) is a noninvasive optical imaging modality that provides real-time, 1D depth, 2D cross-sectional, and 3D volumetric images with micron-level resolution and millimeters of imaging depth. OCT images consist of structural information from a sample based on light backscattered from different layers of material within the sample. It can provide real-time imaging and is capable of being enhanced using birefringence contrast or functional blood flow imaging with optional extensions to the technology.
Thorlabs has designed a broad range of OCT imaging systems that cover several wavelengths, imaging resolutions, and speeds, while having a compact footprint for easy portability. Also, to increase our ability to provide OCT imaging systems that meet each customer’s unique requirements, we have designed a highly modular technology that can be optimized for varying applications.
Retina Cone Cells
OCT is the optical analog of ultrasound, with the tradeoff being lower imaging depth for significantly higher resolution (see Figure 1). With up to 15 mm imaging range and better than 5 micrometers in axial resolution, OCT fills a niche between ultrasound and confocal microscopy.
In addition to high resolution and greater imaging depth, the non-contract, noninvasive advantage of OCT makes it well suited for imaging samples such as biological tissue, small animals, and materials. Recent advances in OCT have led to a new class of technologies called Fourier Domain OCT, which has enabled high-speed imaging at rates greater than 700,000 lines per second.1
Fourier Domain Optical Coherence Tomography (FD-OCT) is based on low-coherence interferometry, which utilizes the coherent properties of a light source to measure optical path length delays in a sample. In OCT, to obtain cross-sectional images with micron-level resolution, and interferometer is set up to measure optical path length differences between light reflected from the sample and reference arms.
There are two types of FD-OCT systems, each characterized by its light source and detection schemes: Spectral Domain OCT (SD-OCT) and Swept Source OCT (SS-OCT). In both types of systems, light is divided into sample and reference arms of an interferometer setup, as illustrated in Fig 2. SS-OCT uses coherent and narrowband light, whereas SD-OCT systems utilize broadband, low-coherence light sources. Back scattered light, attributed to variations in the index of refraction within a sample, is recoupled into the sample arm fiber and then combined with the light that has traveled a fixed optical path length along the reference arm. A resulting interferogram is measured through the detection arm of the interferometer.
The frequency of the interferogram measured by the sensor is related to depth locations of the reflectors in the sample. As a result, a depth reflectivity profile (A-scan) is produced by taking a Fourier transform of the detected interferogram. 2D cross-sectional images (B-scans) are produced by scanning the OCT sample beam across the sample. As the sample arm beam is scanned across the sample, a series of A-scans are collected to create the 2D image.
Similarly, when the OCT beam is scanned in a second direction, a series of 2D images are collected to produce a 3D volume data set. With FD-OCT, 2D images are collected on a time scale of milliseconds, and 3D images can be collected at rates now below 1 second.
Spectral Domain OCT vs. Swept Source OCT
Spectral Domain and Swept Source OCT systems are based on the same fundamental principle but incorporate different technical approaches for producing the OCT interferogram. SD-OCT systems have no moving parts and therefore have high mechanical stability and low phase noise. Availability of a broad range of line cameras has also enabled development of SD-OCT systems with varying imaging speeds and sensitivities.
SS-OCT systems utilize a frequency swept light source and photodetector to rapidly generate the same type of interferogram. Due to the rapid sweeping of the swept laser source, high peak powers at each discrete wavelength can be used to illuminate the sample to provide greater sensitivity with little risk of optical damage.
FD-OCT Signal Processing
In Fourier Domain OCT, the interferogram is detected as a function of optical frequency. With a fixed optical delay in the reference arm, light reflected from different sample depths produces interference patterns with the different frequency components. A Fourier transform is used to resolve different depth reflections, thereby generating a depth profile of the sample (A-scan).
1V.Jayaraman, J. Jiang, H.Li, P. Heim, G. Cole, B. Potsaid, J. Fujimoto, and A. Cable, "OCT Imaging up to 760 kHz Axial Scan Rate Using Single-Mode 1310 nm MEMs-Tunable VCSELs with 100 nm Tuning Range," CLEO 2011 - Laser Applications to Photonic Applications, paper PDPB2 (2011).