Advantages of Using lenses in Infrared Applications

Compared to many other forms of optical infrared lenses, meniscus lenses are rarely offered off-the-shelf. While meniscus infrared lenses are primarily used for focusing to small spot sizes or collimation applications, plano convex infrared lenses often offer a superior price-to performance ratio. There are scenarios, though, where meniscus infrared lenses provide significantly superior performance at only a moderate increase in price.

Spherical Aberration

Due to the spherical nature of a lens, spherical aberrations cause parallel rays at different distances from the optic axis to not converge at the same point. While spherical aberrations can be corrected by using multiple elements that overcorrect other elements, for many infrared lenses systems where materials are significantly more costly than visible materials, it is ideal to minimize the number of elements. In lieu of using multiple elements, it is possible to minimize spherical aberration for a single lens by shaping the lens into its best form.

For a fixed index of refraction and lens thickness, an infinite number of radii combinations exist that can be used to create a particular focal length lens. These combinations of radii create different lens shapes which directly result in spherical aberrations and coma due to the degree in which a ray bends as it travels through the lens.

Benefits of Meniscus Design

When working in the visible, glass indices typically range from 1.5 to 1.7 and the shape for minimum spherical aberration is nearly plano-convex. In the infrared lenses, however, higher index materials like germanium are typically used. Germanium, with its index of 4.0, greatly benefits from a meniscus lens design by significantly reducing spherical aberrations.

The minimum spherical aberration occurs when the ray is bent equally at both interfaces. While the first surface of a germanium meniscus lens causes light to bend slightly more than a comparable PCX lens, the second surface of a PCX lens causes light to bend significantly more, resulting in an overall increase in spherical aberration.

Which compares the performance of a 25 x 25mm germanium PCX lens to a 25 x 25mm germanium meniscus lens, it is easy to see how the PCX lens causes light to bend significantly more with respect to the lens surface than the comparable meniscus lens. This increase in bend causes an increase in spherical aberration. The germanium meniscus lens demonstrates a drastic decrease in resulting spot size, making it more ideal for use in demanding infrared lenses applications.

This article comes from edmundoptics edit released

Infrared camera and thermal imaging module

The long-wave thermal imaging modules for a wide variety of applications and are available with a choice of array sizes, pixel pitch and lens options. They can be delivered as self-contained camera units or as thermal imaging modules for integration into end-user products.

Our thermal imaging modules include the MIRICLE range, ultra low-power MicroCAM 2 and MicroCAM 3 cores with patented shutterless XTi Technology, MicroCAM irGO thermal imaging cameras, FevIR Scan fever screening system and MicroCAM HD high definition thermal imaging cameras.

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Thermal Monocular Camera for Long-Range Surveillance Detection

Thermal Monocular camera that “see” heat instead of light. Sometimes referred to as cameras, they produce an image that portrays objects using their temperature instead of their visible properties.

So how does thermal monocular camera see heat? All objects warmer than absolute zero (-273°C/-459°F) emit infrared radiation in the MWIR and LWIR wavelengths (3µm–14µm) in an amount proportional to the temperature of the object. Thermal Monocular camera focuses and detects this radiation, then translates the temperature variations into a greyscale image, using brighter and darker shades of grey to represent hotter and cooler temperatures, which gives a visual representation to the heat profile of the scene. Many thermal imagers can also apply color profiles to these images, showing hotter objects as yellow and cooler objects as blue for example, to make it easier to compare temperatures in the image.

In order to “see” radiated heat, special lenses and sensors are needed to focus and detect electromagnetic radiation in the MWIR (mid‑wave infrared) and LWIR (long‑wave infrared) ranges.

Thermal Monocular camera Sensors

To detect thermal energy, special FPAs (Focal Plane Arrays) are required. These can be divided into two types, cooled and uncooled detectors.

Cooled detectors exist to maximize detection performance. Since we’re detecting radiated heat, any heat from the camera components themselves makes it harder to see the image of the scene. Both our high-definition MCT (Mercury Cadmium Telluride or HgCdTe) sensors and our Indium Animonide (InSb) sensors incorporate a cryogenic cooling system to reduce the “noise” from the heat of the internal camera components and the sensor itself. This allows for detection of thermal energy with an accuracy as fine as 0.025°C.

Uncooled detectors are also available which are more affordable and compact due to the lack of a cryogenic cooler. We use vanadium oxide (VOx) detectors in our uncooled cameras and combine them with wide aperture lenses to maximize their performance (see below).

Lenses for Thermal Monocular camera

For visible light, glass lenses are typically used to focus light on a camera sensor, however glass is not transparent to thermal radiation. Instead, thermal lenses are constructed from a special metal called Germanium (Ge). This is a relatively rare element and thus is quite costly, with raw prices often as high as $2000 per kilogram. Depending on the type of sensor, lenses of different specifications are required.

Our cooled sensor thermal cameras are designed to have the best long-range detection. We have a wide variety of long-range continuous zoom lenses, allowing the operator to smoothly transition between wide angle and long range. Our germanium lenses are available in lengths of up to 1400mm, allowing us to reach detection ratings of over 50km.

Since uncooled thermal imagers are inherently less sensitive than cooled sensors, we maximize the quality of those images by using lenses with an extremely wide aperture of ƒ/1.0. This wide aperture allows more thermal energy through to the sensor for detection; twice as much energy as that of a lens with an aperture of ƒ/1.4, or four times as much as ƒ/2.0.

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Clip Thermal Weapon Sight on Scope

The thermal weapon sight clip on thermal rifle scope is a hardcore military weapon sighting system that will perform in the worst of conditions without fail. Designed as a multi-purpose infrared scope the thermal weapon sight works the way your mission profile demands. The thermal weapon sight can be used as a handheld thermal spotting scope, or a stand alone thermal weapon sight or an amazing clip on thermal scope. Built to withstand the rigors of combat the thermal weapon sight is waterproof and shock resistant. Complete kits are available to qualified purchasers with special pricing for law enforcement and military customers. Please contact us for more information.

The thermal weapon sight clip on rifle scope is the most versatile weapon sighting system available. This unique Military device really shines as a clip on weapon sight. Extensive research and precise optical calibration under the most demanding manufacturing processes allows the thermal weapon sight to “clip on” to the ront of your day scope.

That’s right IN FRONT of your optical rifle scope. The precision optical train of the thermal weapon sight maintains your point of impact through your day scope, through the thermal scope and out to your target. This means that you can easily switch between day shooting and night shooting without having to zero your weapon. Traditional thermal scopes are required to be zeroed to the weapon each time you swap with your dayscope or they require you to have two weapons one for day and one for night. With the thermal weapon sight when you need thermal weapon sight capabilities you just “clip it on” and away you go. The thermal weapon sight is an excellent mate to the ACOG 4x style of weapon sight but can be used with virtually any optical scope including red dot and holographic.

The thermal weapon sight operates on common CR123 batteries and has easy to use tactile buttons that can be operated with gloves on. The thermal weapon sight is a true Military Grade thermal imaging system that will satisfy even the most demanding mission applications.

This article comes from federalsensors edit released