Fast, Flexible, Solid-State
LIQUID CRYSTAL TUNABLE FILTERS
Effortlessly tune to any wavelength in the visible (VIS) or
near-infrared (NIR) range—with no moving parts—using a
VariSpec™ Liquid Crystal Tunable Filter (LCTF) from CRi.
Large apertures and excellent imaging quality open up so
many possibilities. The industry-standard USB interface and
low-power requirement make integration with your existing
instrumentation easy.
APPLICATIONS
•
High-resolution remote sensing
•
Non-destructive QA/QC
•
Imaging spectroscopy
•
Biomedical research
•
Forensic analysis
MULTISPECTRAL IMAGING
Visible light is made up of a mixture of wavelengths that our eyes interpret
as “color”. Remarkably, although we can distinguish millions of different
colors or color combinations, we cannot perceive all the wavelength (or
“spectral”) information in our visual environment. This is because our eyes
(as well as conventional color films and color digital cameras) separate
visible light, no matter how spectrally complex, into only three color bins:
red, green, and blue (RGB).
Light with completely different spectral content can have precisely the same
RGB coordinates. For example, when we see a yellow color, we cannot tell
if it comes from a “pure” yellow color or from a mixture of red color and
green color. Multispectral imaging can.
BENEFITS
Multispectral imaging is a technique that provides images of a scene at
multiple wavelengths and can generate precise optical spectra at every
pixel. CRi’s VariSpec™ Liquid Crystal Tunable Filters (LCTF’s), which work
without moving parts or noise, represent an ideal technology for affordable,
precise, and robust multispectral imaging.
•
Precise, reproducible wavelength selection
•
Solid-state, no moving parts or vibration
•
Rapid switching time
•
Excellent image quality
•
Available in the VIS and NIR wavelength ranges
www.cri-inc.com
VariSpecTM Liquid Crystal Tunable Filters
VARISPEC LCTF TERMINOLOGY
Many of the terms used in this publication are defined in the context of CRi’s
tunable filter technology.
Bandwidth
The Full-Width at Half-Maximum (FWHM), measured as the spectral separation
between the two points where the filter’s transmission attain’s 50% of the peak
value. The passband center wavelength is the wavelength midway between
these two points. VariSpec filters come in a variety of bandwidths, which are
set during the design and manufacturing process and are not adjustable by
the end-user.
Center Wavelength
Not necessarily the highest point in the T curve, this is defined as midway
between the half-maxima points.
Off-Axis Performance at limit of Field-of-View (FOV)
Off-axis rays at the limit of the field-of-view (FOV) are permitted to be spectrally
shifted by up to Bandwidth/8 from the on-axis ray value. So, in the worst case,
the center ray could have a center wavelength which exceeds the ideal by
+Bandwidth/8, and an off-axis ray could be shifted by +Bandwidth/8 red of
that, or +Bandwidth/4 away from the ideal value.
CRi
Out-of-Band Transmittance or Contrast
The average ratio of transmission without the VariSpec filter in place to the transmission of unselected wavelengths with the filter in place. Typical performance is 0.01%.
Passband
The spectral region from [Center Wavelength - 1.2 * FWHM] to [Center Wavelength + 1.2 * FWHM].
Response Time
The time it takes to switch from one wavelength to another. Several factors affect this number, including the liquid crystal (LC) relaxation time from “charge” to “no charge”
states under various ambient temperatures and the calculation time of the electronics controller box, which must send the correct voltages to each LC element for each
change. Typically, this time is 50 ms to 150 ms.
Transmission
The percentage of linearly polarized light, oriented so that maximum transmission is attained, passing through the filter relative to the amount which entered. Since the
entrance element of the filter is a linear polarizer, transmission of randomly polarized light is half that of linearly polarized light in the correct orientation. VariSpec
transmission is wavelength-dependent.
Tuning accuracy
Founded in 1985, Cambridge Research & Instrumentation, Inc.
(CRi) is a photonics company and the leading provider of liquid
crystal based imaging technology.
CRi develops and manufactures high-performance instruments
and systems that employ multispectral and polarized-light imaging
and detection techniques for applications in diverse areas such
as pharmaceutical drug discovery; life sciences; clinical and
preclinical studies; and industrial process control.
CRi also offers a broad array of tunable, solid-state optical
components and modules for use in wavelength-selection,
polarization optics, and light- modulation in digital imaging
applications.
The tuning accuracy specification is that the center wavelength be correct within the actual Bandwidth/8 +/- 0.5 nm. Tuning accuracy is specified for on-axis rays.
Center Wavelengthactual = Center Wavelengthnominal +/-
(
Bandwidthnominal
8
Please contact us for more information:
TOLL-FREE
(USA):
1.800.383.7924
DIRECT (Worldwide): +1.781.935.9099
E-mail: sales@cri-inc.com
Website: www.cri-inc.com
)
+ 0.5 nm
Specifications
LC filter aperture
20 mm (All models), 35 mm (VIS 7-, 10-, and 20-nm models only)
Computer interface1
Universal Serial Bus (USB)
NUANCE™ & MAESTRO™ MULTISPECTRAL IMAGING SYSTEMS
Bandwidth (FWHM)
0.25-nm to 20-nm available
Wavelength range
VIS: 400—720 nm (7-, 10-, or 20-nm bandwidths)
VISR: 500—720 nm (0.25-nm bandwidth)
SNIR: 650—1100 nm (7-, or 10-nm bandwidths)
NIRR: 650—1100 nm (0.75-nm bandwidths)
LNIR: 850—1800 nm (6- or 20-nm bandwidths)
XNIR: 1200—2450 nm (7-nm FWHM)
For integrated solutions to
multispectral imaging, rely on
CRi’s powerful and robust
Nuance and Maestro Imaging
systems.
Wavelength accuracy
Bandwidth/8
Maximum optical input
500 mW/cm2
Wavelength accuracy
Bandwidth/8 +/- 0.5 nm
Operating temp range
10 to 40 °C
Storage temp range
-15 to 55 °C
Power supply
Provided by host computer’s USB port
Software
Software Developer’s Kit (SDK) and Programmer’s Guide for Windows® operating system;
LabVIEW™ sub-VIs; Matlab® m-files; USB drivers for Linux operating system
1
Compatible with USB 1.1/2.0 specification; USB Type-A to Type-B cable included
Nuance systems can be used for
brightfield or fluorescence
microscopy, remote sensing,
machine vision, macro-imaging,
and many other applications.
Maestro systems are used for invivo fluorescence imaging.
Contact CRi for more details.
CRi 35-B CABOT ROAD WOBURN, MA 01801
All trademarks mentioned in this publication are
the properties of their respective owners. VariSpec,
Nuance, and Maestro are trademarks of CRi.
www.cri-inc.com
Your local CRi agent or distributor is: