Kent Optronics
Switchable & Tunable Notch Filter

Made from all electro-optically active components, the S-TNF filter product can be electrically switched between notch blocking and transparent non-blocking states.

Data Sheet


The S-TNF™ series filters are one-of-a-kind products - they are switchable & tunable notch filters. Their performance is superior to the competitive products offered in the marketplace - they have 2X higher transmittance over a super-wide spectral range in the non-blocking state. This is critical for capturing images under weak illumination. The filters:

  • Feature all active components made from liquid crystal and
  • Do not rely on light absorption mechanism

The S-TNF™ products can be used either as system components or standalone devices. Their typical applications include laser protection, spectral filtering, laser beam directing, beam splitting, remote sensing, vision-aids, etc...

The S-TNF™ series has high optical density at the notch wavelength in the active blocking state, > 40% transmittance outside the notch band, and a switching time of ~5 ms.

sensor with s-tnf

sensor with commercial filter

S-TNF™ enables a sensor
to see a scene under weak
illumination condition

The same sensor has difficulty in
seeing this weak scene with a
commercial tunable notch filter

sensor jammed by green laser

sensor recovered

Sensor is jammed by the
green laser radiation

The sensor is recovered by
the S-TNF™ filter

The S-TNF™ series come with a compact power supply that is either battery or 110/220 V wall-plug powered. Customer options include the selection of spectral range, operational mode (manual or computer control), substrate material, shape and aperture. All products are offered at a competitive price. Contact us for a price quote with your specific application requirements.

spectrum in blocking


Transmission in Blocking State

VNIR spectrum non-blocking

SWIR spectrum non-blocking

Non-blocking Transmission (VNIR)

Non-blocking Transmission (SWIR)

S-TNF™ Specifications

Spectral Region 0.4 - 2.7 μm
Transmittance (blocking inactive) ~80%
Scene spectral neutrality (blocking inactive) Neutral
Polarizing properties Polarization Insensitive
Tunable narrowband blocking wavelength > 300 nm (continuously tunable blocking)
Tunable narrowband blocking optical density high over bandwidth
Angular range for broadband transmission (parallel light operation) > 25° in air
Angular range for tunable narrowband blocking (parallel light operation) > 25° in air
Clear aperture Diameter: 5 - 50 nm (circular)
Area: 5 x 5 to 50 x 50 mm2 (square)
Thickness < 10 mm
Operating temperature range -5°C to 55°C without heating mechanism;
-40°C to 55° C with heating mechanism
Survival temperature range -51°C to 120°C
Laser damage threshhold > 1 J/cm2 (5 ns pulsed @ 532 nm)
> kW/cm2 (CW @ 532 nm)
Uniformity of retardance < 0.1 OD across the clear aperture
Wavelength distorsion < 0.5 wavelength at 633 nm
Parallelism < 2 arcminutes
Response time 5.3 ms switching to blocking mode
Rate of change of temperature Survive a rate of change of temperature of 3°C per minute
Driving voltage Polarizer: 280V RMS
Retarder: 0 - 1.5V RMS
Computer interface USB interface w/PC
Weight < 100g (filter only)
Substrate material Glass, quartz and plastic (PC)
Cable length 1 m
Input power to the driver 110V or 220V/50 - 60Hz AC or 9V battery
Total power consumption < 4W
Power supply weight 200g