Callisto 930 nm OCT Imaging System
|CALLISTO System Specifications|
|Center Wavelength||930 nm|
(A-Scan Line Rate)
|Axial (Depth) Resolution (Air)||<7.0 µm|
|Lateral Resolution||8 µm|
|Maximum Imaging Depth||1.6 mm|
|Imaging Speed (512 Lines/Frame)||2 fps|
|Maximum Pixels Per A-Scan||512|
Thorlabs' High-Sensitivity CALLISTO™ OCT Imaging System
- High Sensitivity for Increased Contrast OCT Imaging
- Ideal for Imaging Static or In Vitro Samples
- Custom Configurations Available
Thorlabs' CALLISTO™ High-Sensitivity OCT Imaging system has one of the highest sensitivities of any of Thorlabs' OCT systems. The sensitivity directly corresponds to the smallest refractive index change in the sample that can be resolved. Hence, in a layered sample, the images produced by the Callisto will have high contrast between the layers. The Callisto operates at a maximum A-Scan rate of 1.2 kHz, which results in 2 fps with 512 lines per frame. The Callisto is a great tool for teaching labs in the fields of imaging, biophysics, biology, and biomedical engineering.
The CALLISTO is the ideal OCT system for imaging static samples due to its sensitivity of 105 dB and imaging rate of 1200 lines per second. The high sensitivity achieved with this imaging system enables distinction between layers of similar material that cannot be visualized by using other OCT systems at higher speeds, especially at greater depths. Click here to see the difference between an OCT image of a grape taken with the CALLISTO OCT Imaging System (top) compared to the high-speed but lower sensitivity HYPERION OCT System at 110 kHz (bottom). Image size: 6.3 mm x 1.7 mm.
The CALLISTO system utilizes a USB data connection and is controlled via software preinstalled on the provided computer. It also includes a 3D scanning, common path probe with an integrated video camera for volume imaging and live video display. The included stand and sample stage provides XY translation and rotation of the sample along with axial travel of the probe. The CALLISTO 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. We encourage you to send us samples for product testing so our engineers can customize one of our OCT systems to suit your individual applications. Please use the "Contact Us" button on the upper right-hand side of the page for more information.
Click on the Callisto OCT Imaging System Components, shown below, for further details.
The Callisto OCT System includes a notebook PC with a 15.6" display. This processing system is set up with all the necessary data acquisition hardware, drivers, and software to start imaging upon arrival.
- Processor: Dual Core
- Processor Speed: ≥ 2.5 GHz
- Memory: ≥ 4 GB
- Hard Drive: ≥ 250 GB
- Data Acquisition: USB
*Computer Type Subject to Change without Notice
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Callisto SD-OCT Engine
The Callisto 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 930 nm Superluminescent Diode Light Source and Linear CCD Array-Based Spectrometer. It also includes all associated drive electronics and controllers.
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High Performance Software
High-performance ThorImage OCT data acquisition software is included with all SD 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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Hand-Held Probe and Stand
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 cameraintegrated 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.
|930 nm (840 nm option also available)||1325 nm||1300 nm||1325 nm||1300 nm||1325 nm|
|100 nm||150 nm||170 nm||100 nm||100 nm|
|1.2 kHz||29 kHz||110 kHz||Up to 91 kHz||Up to 76 kHz||100 kHz||16 kHz|
|2 fps||29 fps||55 fps||Variable||110 fps||25 fps|
|7 µm||5.8 µm ||<7.5 µm ||5.5 µm||12 µm||16µm ||12 µm |
|5.3 µm||4.5 µm||<5.6 µm||4.2 µm||9.0 µm||12 µm||9 µm|
|8 µm||15 µm||13 µm|| 25 µm|
|Sensitivity||105 dB||91 dB||86 dB||Up to 106 dB||Up to 103 dB||>103 dB||100 dB|
|Max Field |
(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 3.5 mm||10 x 10 x 7 mm||10 x 10 x 12 mm||10 x 10 x 3 mm|
ThorImage OCT Software Index
- Interactive Scan Position Control through Video Display (Draw and Scan)
- Advanced Dataset Management
- High-Speed Volume Rendering of 3D Data
- Doppler and Speckle Variance Imaging
- Versatile Scan and Acquisition Control
ThorImage OCT is high-performance data acquisition software that is included with all Thorlabs Spectral Domain OCT systems. This 64-bit Windows-based software package is capable of data acquisition, processing, scan control, and displaying OCT images. Additionally, NI LabVIEW and C-based Software Development Kits (SDKs) are available, which contain a complete set of libraries for measurement control, data acquisition and processing, as well as storage and display of OCT images. The SDKs provide the means for developing highly specialized OCT imaging software for every individual application.
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Various acquisition parameters can be adjusted in ThorImage OCT.
ThorImage OCT provides numerous scan and acquisition controls. The camera integrated in the probe of our OCT system provides live video images in the application software. Defining the scan line for 2D imaging or the scan area for 3D imaging is accomplished through the easy-to-use "Draw and Scan" feature by clicking on the video image. The scan pattern can also be adjusted by specifying parameters in the controls of the software. Additionally, one can further set processing parameters, averaging parameters, and the speed and sensitivity of the device using device presets. By using a high-speed preset, video-like frame rates in 2D and fast volume rendering in 3D are possible, whereas high-sensitivity acquisition is enabled by choosing a preset with a lower acquisition speed.
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The Sample Monitor can be used to define the scan pattern using the "Draw and Scan" feature.
ThorImage OCT provides advanced dataset management capabilities, which allow opening several datasets simultaneously. Datasets are uniquely defined using an identifier consisting of study (or test series) name and an experiment number. Grouping of datasets is possible using the same study name. The "Captured Datasets" list shows an overview of all open datasets, including the study name, the acquisition mode, and preview pictures of the still video image and the OCT data.
Datasets can be exported in various image formats, such as PNG, BMP, JPEG, PDF, or TIFF. Formats suited for post-processing purposes, such as RAW/SRM, FITS, VTK, VFF, and 32-bit floating-point TIFF, are also supported.
The OCT file format native to ThorImage OCT allows OCT data, sample monitor data, and all relevant metadata to be stored in a single file. ThorImage OCT can also be installed and run on computers without an OCT system installed in order to view data.
Third Party Applications
If ImageJ is installed on the computer with ThorImage OCT installed, opening acquired OCT data in ImageJ is one mouse click away, as shown in the image below. This enables a flawless workflow when requiring the advanced image processing functionality provided by ImageJ. Clicking the Explorer button shown below will open the folder and select the file in Windows Explorer where the currently active dataset is stored.
Export buttons are accessible in the Action Toolbar of ThorImage OCT.
In the 2D imaging mode the probe beam scans 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 B-Scan averaging. Image display parameters, such as color mapping, can be controlled in this mode. We have also implemented an option for automatic calculation of the optimum contrast and brightness of the displayed OCT images.
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 ThorImage OCT software, 3D volume datasets can be viewed as orthogonal cross-sectional planes (see below) and volume renderings.
The Sectional View features 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 to expose structures within the volume. The 3D image can be zoomed in and out as well as rotated. Furthermore, the coloring and dynamic range settings can be adjusted.
Utilizing the full potential of our high-performance software in combination with our high-speed OCT systems, we have included a Fast Volume Rendering mode in ThorImage OCT, which serves as a preview for high-resolution 3D acquisitions. In this mode, high-speed volume renderings can be displayed in real-time, providing rapid visualization of samples in three dimensions.
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Doppler dataset showing the velocity of a rotated plastic stick.
Doppler OCT imaging comes standard with all OCT systems. In the Doppler mode, phase shifts between adjacent A-scans are averaged to calculate the Doppler frequency shift induced by particle motion or flow. The number of lateral 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 color map indicating forward- or backward-directed flow, relative to the OCT beam.
ThorImage OCT 4.0 introduces a new acquisition mode, which uses the variance of speckle noise to calculate angiographic images. It can be used to visualize three dimensional vessel trees without requiring significant blood flow and without requiring a specific acquisition speed window. The speckle variance data can be overlaid on top of intensity pictures providing morphological information. Different color maps can be used to display the multimodal pictures.
Video Showing Screencast of ThorImage OCT Rendering Capabilities
In this video, OCT images of a finger are acquired and manipulated in the 3D volume and cross section modes.
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).