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Infrared (IR) Filters, Infrared Coatings, Infrared Technology

Reynared Corporation Infrared Filters ImageReynard has been a leading supplier of infrared technology, including Infrared (IR) Filters, optics and infrared coatings for space and military needs, supporting various programs with production coatings, as well as development research with new coating materials and substrates.  Our experience in IR coatings range from the near infrared (NIR) to the far infrared (FIR, >25um) for anti-reflection, filters, beamsplitters, and mirrors. 

Leveraging our core technology of variable coatings, we have successfully made Infrared (IR) Variable Filter coatings in both a circular and linear format.  These filters are highly customized for specific customers and systems.  We look forward to talking with you about your specific infrared optic needs.

Commercial markets are beginning to recognize the advantages of infrared vision, and demand in the non-military market is rapidly growing.  We utilize our infrared knowledge to support this growing demand, and continue to deliver the highest quality optical products to all of our customers.  The biggest advantage of this demand trend is that we are able to produce standard IR range optics (NIR: 0.7-1.0um, SWIR: 1.0-2.5um, MWIR: 3-5um, and LWIR: 8-12um) at higher volume, which reduces the component individual price.

Night Vision Image Intensifiers:

Night Vision is the ability to see in low light conditions. One of the first instruments that allowed humans to extend the range of their night vision was an image intensifier tube (IIT), which intensifies low levels of light for human vision.  Though microbolometer and photon detector based cameras provide superior performance, IITs have found a low-cost commercial market for hunters and sailors. Reynard can provide Infrared(IR) Filters that allow IITs to block stray light that can blur (due to 'noise') an intensified image.

Infrared Security Cameras:

Security cameras are now available for homes and businesses that can extend the visible range into the  NIR (near infrared). These enhanced Infrared Cameras are typically based on a silicon detector and are available below $100 and up to many thousands of dollars. The price difference will depend on resolution, directivity and working environment.  These cameras have IR emitters that illuminate an area with NIR radiation (ie. 'light') of which the detector picks up and images the reflection, much as our eyes can see objects in the dark with a flashlight.

The optics in these cameras had to be extended from just the visible spectrum (400nm to 700nm), into the NIR (up to 900nm or 1000nm), without degrading the performance in the visible band.

High Performance Infrared Cameras:

Microbolometer based infrared cameras operate at room temperature and can image in the longwave infrared (LWIR) band from 8-12um.  Photon detector based infrared cameras can image in the midwave infrared (MWIR) band and/or LWIR band, among others, but require a cooled detector to do so.  Each of these technologies produces high-resolution, high-contrast images and are the state-of-the-art technology for night vision.

These camera systems use specialty optics to filter for single or multi-band wavelengths, and also require high-performance Infrared (IR) Anti-Reflection (AR) Coatings.  Uncoated infrared substrate materials pass as little as 40% of the wavelength band of interest.  The addition of an anti-reflection coating can bring this transmission up to over 95%.  For cameras with multiple lenses an AR coating could make the difference between a functional and a non-functional camera based on the number of photons reaching the detector.

Gas Sensing:

Most gases have their characteristic spectra in the infrared light range. Those spectra derive from the molecule’s composition in such a way that no two molecular gases have the same IR spectrum. IR spectra are the fingerprints of gases and allow gases to be uniquely identified. By transmitting a beam of infrared radiation through the air, or through any particular gas volume, and recording how much is transmitted at selected spectral lines, one may decide which gases are present and how much of each is there.

Reynard can specially design filters for broadband detection, or provide narrow band filters to select specified spectra.

Thermography:infrared2

Thermography is a process of temperature profiling of a surface or point. The principle underlying this characteristic of emissivity is that every object emits a certain amount of IR energy and the intensity of this IR radiation is a function of temperature. These scans are carried out from 0.8 to 10 microns. The basic IR system consists of an “IR energy detector” and a “Monitor”. The scanner is an opto-mechanical device which converts the IR energy received from an object surface to an electrical signal. These signals are further fed into the monitor where it is processed and presented in many forms like simple digital display to indicate temperature levels and a video display for thermal profile. The level of heat given off by human body makes it readily detectable to thermographic instruments.

Scene Discrimination (SWIR vs. MWIR vs. LWIR):

Infrared sensor development has been driven largely by the military. The primary spectral bands for infrared imaging are 0.9 to 1.7, 3 to 5 and 8 to 12 microns. These three bands differ dramatically with respect to contrast, background signal, scene characteristics, atmospheric transmission under diverse weather conditions, and optical aperture constraints.

Signal collected by the shortwave infrared (IR) SWIR (0.9 to 1.7) system have higher daytime contrast than either of the two other IR bands because the radiation is from a high-temperature sources such as the sun, moon, stars and synthetic sources.

Factors favoring the night time performance of the midwave infrared (IR) MWIR (3 to 5) systems are:  High contrast, great clear-weather performance, high transmission in high humidity conditions and high resolution for high object temperatures.
 
Factors favoring the night time performance of the longwve infrared (IR) LWIR (8 to 12) systems are:  Good performance at low object temperature, reduced background clutter from smoke from fires and flares, excellent performance in fog, dust and winter haze conditions, and high immunity to atmospheric turbulence.

Atmospheric Sounding:

An atmospheric sounding is a measurement of vertical distribution of physical properties of the atmospheric column such as pressure, temperature, wind speed and wind direction, liquid water content, ozone concentration, pollution, and other properties. Remote sensing soundings generally use passive infrared and microwave radiometers. These readings can come from:

  1. Airborne instruments
  2. Surface Stations
  3. Earth-observing satellite instruments such as Atmospheric Infrared Sounders (AIRS) and Advanced Microwave Sounder Unit (AMSU)

LIMB Sensor (horizon sensing):

The LIMB Sensor is based on a Quad Cell Photodiode for image stabilization. The generated photocurrent in each of the four sections of the photodiode is converted to voltage and processed in a microcontroller with 16 bits ADCs. The LIMB Sensor is used to remove motion of the image on the focal plane of a telescope. The detector takes the solar images and the Control Unit generates the pointing error signal. This generated signal is fed back to piezoelectric translators that drive the tip-tilt mirror in the telescope.