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Home Products Liquid Crystal Tunable Filters ThorLabs Kurios Liquid Crystal Tunable Filters
ThorLabs Kurios Liquid Crystal Tunable Filter

ThorLabs Kurios® Liquid Crystal Tunable Bandpass Filters provide a continuously tunable center wavelength (CWL) in the 420 - 730 nm (VIS) range or the 650 - 1100 nm (NIR) range. 

The KURIOS-WB1, KURIOS-WL1, and KURIOS-XE2 offer a fixed bandwidth for any given center wavelength. Alternatively, the KURIOS-VB1(/M) has user-selectable bandwidth settings of Narrow (10nm), Medium (18nm), and Wide (32nm). The switching time varies depending upon the initial and final wavelengths and on the Kurios' bandwidth setting (for -VB1 only).

With an included controller that provides Trigger In, Trigger Out, and Analog In functionality, these tunable optical bandpass filters are ideal for applications that perform multispectral or hyperspectral imaging. For example, they can be used in conjunction with a monochrome scientific CCD camera to obtain images with a much higher accuracy for color representation than using a color CCD camera with a Bayer mosaic. This technique produces true spectral imaging and can thus show spectral features that would otherwise be impossible to detect.

Kurios filters consist primarily of liquid crystal cells that are sandwiched between polarizing elements. Their integrated design enables quick and vibrationless tuning. For added operational stability, a closed-loop temperature control servo is used to maintain the filter head's operating temperature. An LED on the filter head displays red when the head is warming up and green when it is ready to be used.

KURIOS LCTF controller box

Wavelength Control

Center wavelength is controlled manually via the front panel of the LCTF controller and allows programmable switching sequences. The controller offers three BNC connectors (Trigger In, Trigger Out, and Analog In) allowing the LCTF to be synchronized with a number of different devices such as scientific cameras or motion control stages. Each Kurios LCTF is factory calibrated and includes a switching time map to allow the user to optimize the system to their specific system requirements.

The Trigger In connector allows Kurios to be controlled by another device via a TTL signal. It can be used, for instance, to synchronize Kurios with a scientific camera, such that every time the camera captures an image, the filter is immediately advanced to the next wavelength in the sequence. Kurios triggers on the falling edge of the 5 V TTL signal.

The Trigger Out connector outputs a TTL signal that has the same duration as the calibrated switching time of the filter. This signal can be used, for example, to monitor the switching time and to cause events to coincide with or follow the switching event, such as imaging or shuttering.

The Analog In connector allows the center wavelength to be set by a 0 to 5 V signal from an external voltage source and changed by an internal or external trigger. 0 V corresponds to the minimum wavelength of 420 nm or 650 nm, while 5 V corresponds to the maximum wavelength of 730 nm or 1100 nm.

Kurios' Sequence Preload Function, which is accessible from the front panel, the included GUI, and a command-line interface, permits the user to define a sequence of wavelengths (up to 1024 values). Providing an internal or external trigger switches the wavelength to the next value in the sequence. This function can be used, for example, in combination with the Trigger Out and Trigger In connectors to trigger a camera at the completion of each wavelength switch and then accept a trigger from the camera once the image is obtained. This sequence is stored within the controller's non-volatile memory, enabling the user to close the software GUI or unplug the USB cable without loss of the preloaded sequence. However, powering off the controller will cause the non-volatile memory to reset.

The Bandwidth button on the front of the controller toggles through various operating modes. For the KURIOS-VB1(/M), this button toggles between Narrow, Medium, and Wide (the three selectable bandwidths), as well as beam-blocking mode ("Black"). For the fixed bandwidth models, the Bandwidth button toggles between the only bandwidth available and Black mode. 

Transmission and Polarization

The liquid crystal optics in Kurios filters are not sensitive to the direction of propagation, allowing the filter to be used in either direction. The first element in the filter head is a linear polarizer and each face is marked with a white line  that indicates the transmitted polarization direction. For maximum transmission, the input beam should be linearly polarized and aligned with this polarization axis. Please note that since Kurios is structured like Lyot and Solc filters, the polarization axis rotates by 90° through the filter head. To obtain the specified attenuation of out-of-band wavelengths, the input beam should be well collimated, since the filter head's field of view is ±6°.

A lens-tube-mounted premium 750 nm shortpass filter is included with our KURIOS-WB1, KURIOS-WL1, and KURIOS-VB1 Tunable Filters for visible wavelengths. Use of this filter is recommended to protect the filter head components from excessive IR illumination.

Mounting Options

These tunable filters are post mountable via three 8-32 (M4) taps on the sides of the housing. In addition, four 4-40 tapped holes on the front and back faces provide compatibility with our 30 mm or 60 mm cage systems, depending on the model. The front and back faces of the housing are internally SM1- (1.035"-40) or SM2- (2.035"-40) threaded. These threads accommodate Ø1" and Ø2" lens tubes, respectively. To connect the KURIOS-WB1, KURIOS-XE2, or KURIOS-VB1 filter to a camera, use our SM1A39 SM1-to-C-Mount thread adapter together with an appropriate tube lens.

ThorLabs Kurios Fixed VIS LCTF

Visible Wavelength Fixed Bandwidth Liquid Crystal Tunable Filter

  • Wavelength Range: 420 - 730 nm
  • Bandwidth at λ 550 nm: 35 nm FWHM
  • Switching Time: <50 ms
  • Polarized Transmission: 45%

ThorLabs offers two options for fixed bandwidth liquid crystal tunable filters in the visible wavelength: the KURIOS-WB1 (20mm aperture) and the KURIOS-WL1 (35mm aperture). To eliminate transmission in the near-IR