Germanium irlenses

Telephoto lens, for instance, helps create images with shallow depth of field. Cameras with a wide-angle lens, on the other hand, will produce images with more depth of field

Depth of Field is defined as the range of focus on a photograph or film. It is a basic technique that photographers, cinematographers, and camera operators use to create high-impact images that draw the audience’s attention.

Now for some fun stuff. We hear from plenty of our customers where their germanium windows are seeing action. Here are some highlights:

Aperture or F-stop is a camera setting that controls the DoF. The setting controls the amount of light that enters the film or digital sensor through an adjustable opening. The angle of light that strikes the film or sensor changes as the range of aperture changes. Aperture is measured by f-stops, which can be adjusted through the camera controls. The F-stop setting adjusts the ratio depending on the size of the lens that opens as well as the focal length.

Widen your aperture by setting your camera to a smaller F-number. Move closer to the subject and extend your focal length.

As you’d imagine, since germanium tags along with warfighters, it needs to be durable in all adverse conditions from desert, sea, high altitude, etc. The DLC coatings can take a serious beating with temperatures ranging from -80ºF to 160ºF, 24 hours of continuous sea spray, ocean immersion for over 24 hours and being immersed in a sandstorm. Additionally, the coatings can withstand heavy mechanical damage and chemical attacks.

What’s the secret to creating unique, striking images with perfect backgrounds? When composing an image, you have to control the distance between the foreground and the background of the subject that’s in focus. This technique is called Depth of Field (DoF) and it is a powerful principle that separates good photographs from stunning, unforgettable images that look professionally done.

If high transmission is the only consideration, you’d be best served to double coat your windows with BBAR over particular wavelength ranges and you can see transmissions all the way up to 99%. Now we’re talking!

In filmmaking and cinematography, depth of field gives filmmakers creative control over where the camera is focused on to direct what the audience sees in a scene. The technique helps set up an audience’s expectation in a specific part of the frame to elicit the right level of emotion and attention as the story unravels.

get wrecked! damage done to germanium windows by high power lasers. source: http://www.mdpi.com/2076-3417/10/10/3578/htm

Alternatively, you can use liquid CO2 from a specialized nozzle for cleaning though this requires additional cost in terms of equipment. While you will get a better, more controlled cleaning and can be used for stubborn stains, care must be taken to work in a controlled moisture-free environment and we do not recommend this for typical end-users.

To demonstrate deep DoF, a large depth of space will be shown in subjects such as landscapes. The technique helps make an entire frame appear to be sharp or in focus, from the foreground to the background.

Jasmine Katatikarn is the founder of Academy of Animated Art. She has 20+ years of experience in Feature Animation and VFX. Jasmine’s lighting credits include movies like Ice Age, Ferdinand, Peanuts, and Rio. Read more here.

GermaniumLens Price

Germanium ends up in some interesting places including defense aircraft navigation, reconnaissance and surveillance systems soaring in the stratosphere on an airplane or even as part of a satellite.

An uncoated germanium window is a decent IR generalist but specific optical coatings can really kick things up a notch. Diamond-Like Carbon (DLC) coatings can make this already hard material even more resistance to severe abrasions, environmental damage, mechanical strikes, thermal shock and whole other host of adversities.

A camera with a large F-stop has a large DoF. It will also require slower shutters speeds so more light enters the sensor, producing images with deeper depths of field. On the other hand, a camera with a small F-stop has faster shutter speeds so less light enters the sensor. This helps produce images with shallow depths of field.

Germaniumlens for thermal camera

Various BBAR coatings typically requested are 3-5µm, 3-12µm, 2-14µm and 8-12µm though we can do even more customization. You can fill out our custom request form and see what Firebird Optics can do for your application.

Germanium holds the high ground when it comes to transmission range getting that additional coverage from 7-16µm, which silicon lacks. On top of this, germanium has higher electrical conductivity making it a more suitable candidate as an optical component in laser systems.

Germaniumlens protector

The best way to clean the windows is to use either ethanol, isopropyl alcohol, methanol, reagent-grade acetone or lint-free lens cloths. You can also use nitric acid but this material, while okay for germanium can corrode other optics or mounts that may be nearby in your system.

Not all cameras come with a DoF button but newer ones now come with this standard feature. When using the DoF button, the image may appear darker through the eyepiece but once the image is exposed, the correct exposure settings will be applied.

One common application for germanium is in night vision goggles. For these types of applications, both the inside and outside surfaces of the germanium is polished to a mirror finish and coated with multi-layered thin film filters to reduce any reflection of IR light. This enables optimal IR transmission essential to night vision/thermal imaging. As these windows will have excellent sensitivity at long range, this enables warfighters to retain long stand-off distances increasing safety and mission-effectiveness. Germanium is a literal life-saver.

We’ve already explored why you would pick germanium over sapphire but why would you pick germanium over silicon or vice versa?

Germaniumwindow

Silicon (Si) is germanium’s next door neighbor who frequently borrows sugar. Both have an atomic number of 14, absorb visible light and have sharp cut-offs making them also function as long pass filters. In addition, there is similarity with their transmission ranges with silicon transmitting from 1.2-7µm. However, this is where they begin diverging. Silicon is far lighter with a density of 2.33g/cm3, making it ideal for weight-sensitive applications and less than half the density of germanium. Moreover, it is more thermally resistant than germanium and with a Knoop Hardness of 1150 it is also harder and less brittle. Silicon also costs less making it a better candidate in several applications.

Germaniumglass

A camera can only focus on a small point in a space. Through this technique, you can determine how much of the image is in “acceptable focus” to the eyes. By understanding the intricacies of DoF, you can also focus on your subject and background at the same time.

On close-up shots, for example, the subject is more focused while the background is usually blurry. In macro photography, images usually have small depths of field. But in landscape shots, the depths of field are larger.

Narrow your aperture by setting your camera to a large F-number. Then, move farther away from the subject and shorten the focal length.

There are many ways to determine a scene’s depth of field. You can either search for DoF charts for your lenses and camera online, download apps that calculate DoF for you, or use your camera’s DoF button for a preview of the image.

Jasmine Katatikarn is the founder of Academy of Animated Art. She has 20+ years of experience in Feature Animation and VFX. Jasmine’s lighting credits include movies like Ice Age, Ferdinand, Peanuts, and Rio. Read more here.

Knowing how to sharpen or soften parts of your images is a great skill to master as an artist. With a shallow depth of field, you can bring the attention to the subject by separating it from the background. This technique is often used in wildlife photography, sports photography, and low light situations. But to focus as much of the scene in a frame, you’ll need maximum depth of field. This technique is often used in landscape photography to bring the viewers’ attention to the entire scene of the image, not just parts of it.

Germanium windows are optical windows that are completely impermeable to UV and VIS light giving them a dark, metallic appearance to the naked eye. However, when it comes to the IR range this is where germanium truly shines with an excellent, broad transmission range from 2-16μm making it an ideal candidate for Mid-Wave-IR (MWIR) and Long-Wave IR (LWIR) applications. The sharp transmission cut-off before 2µm also enables germanium to be used as a long pass filter, only transmitting wavelengths in excess of 2µm and fully blocking everything before it.

Germanium makes a good electromagnetic interference (EMI) shielding material and can shield IR systems on planes from other nearby signals that would render the system ineffective. This effectively creates an IR Faraday cage or as we like to refer to it, an aerospace tin foil hat. Typical resistance for EMI-grade germanium is approximately 4 Ohm per cm but this depends on the required level of spurious signal suppression. A germanium window made to these specs can effectively short out any errant signals and keep the IR system running well.

The distance of the subject will determine the depth of field of an image. Generally, the closer the subject is to the camera, the shallower the depth of field becomes. The further away the subject is to the camera, the deeper the depth of field becomes.

The lens helps control the aperture capabilities of the camera. Lens with high magnification capability produces images with smaller DoF. This goes even with large F-stop settings. The longer the camera lens, the shallower the DoF.

Germanium (Ge) is a shiny, hard element with a Knoop Hardness of 780kg/mm2 making it, along with its far stronger sister sapphire, the default candidate for applications where the environment is likely to put a beating on the material. For a full breakdown of how to wade through all of the major optical window choices check our optical window guide.

On the other hand, an AR-coated germanium will feel right at home in a low power pulsed laser setup. One particularly noteworthy application is in quantum cascade lasers (QC), which is used in high-end materials science. Quantum cascades are used by such institutions as the Max Planck Institute of Quantum Optics in Garching to produce ribbons and strip structures as well as to produce new materials for use in medical applications. Pretty cool stuff!

Germaniumtransmission vs temperature

Another consideration is germanium’s density. At 5.33g/cm3 it does not float like a butterfly and sting like a bee. It’s heavy. Quite heavy and this will need to be considered when designing weight-sensitive systems.

One cautionary detail to note is that your germanium window will not appreciate being exposed to high temperatures. In fact, there is an inverse relationship to temperature and transmission when it comes to this material. As your temperature goes up, the transmission properties will drop precipitously, a property known as thermal runaway. Anything over 100ºC is not recommended. By the time it reaches 200ºC it is nearly opaque at all wavelengths. If you need a high temperature window, you’re better suited to stick with a material like MgF2, YAG or our old friend sapphire.

One of the more common applications we see at Firebird Optics for germanium windows is in low power CO2 laser systems. With a Laser Induced Damage Threshold (LIDT) of 10 J/cm2, germanium windows are not suited for high power or continuous wave (CW) lasers. Part of the reason for this is higher powered lasers cause temperature increases, dramatically dropping transmission properties over 100ºC and eventually damaging the substrate itself once temperatures near 600ºC are reached.

When not in use, we recommend storing your germanium windows wrapped in lens tissue with humidity below 30% and between 15 and 25ºC. While germanium is pretty tough stuff, these are the ideal conditions that will prolong the life of your window.

An image’s DoF is measured from the closest in-focus point to the farthest in-focus point. Depth of Field could either be deep or shallow.

One very common scenario we see germanium utilized is inside high and low speed wind tunnels for jet propulsion studies. Typically, these windows are much larger than stock configurations reaching sizes in excess of 190-200mm.

Germanium irprice

Frequently, DLC coatings are often paired with Broadband AR Coatings (BBAR) to not only up the mechanical performance but also the transmission properties. Typically, a window is coated on one side with DLC and the other side with BBAR (typically in the 7-14μm range to boost both of these properties in tandem. This combination can increase the transmission to well over 85% in the target wavelength range. Optical windows treated in this manner will pass a variety of tests including MIL-C-675-C, MIL-STD-810 and APCM-01071.00001 and can survive salt water, humidity, high and low temperatures and hard smacks.

High refractive index enables excellent performance for lenses, ATR optics or beamsplitters. For optical windows, AR coatings can be added to boost performance.

Shallow depth highlights the main subject of the image by softening the background or putting it out of focus. This technique is usually applied in portraits. By blurring the background, the visual distractions are minimized, allowing observers to focus on the main subject of the scene.

Firebird Optics manufactures these types of windows in various geometries, coatings and can also produce lenses, prisms and various other optical components from germanium. Now back to your regularly scheduled programming…

The aperture setting ranges from f/1.8-f/64 and you have to use the right lens to capture different aperture ranges. A wider aperture (f/1.4, f/2, etc.) helps create a blurred or soft focus image. On the other hand, a narrower aperture (f/8, f/11, etc.) creates a deeper DoF, creates a sharply focused image.

You definitely don’t want to breathe in germanium dust so care must be taken while handling these optics. Using gloves whenever possible and washing hands should be part of any standard operating procedure.

Since germanium windows have a high index of refraction of approximately 4.0 in the range of 2-16μm, transmission with minimal refraction is guaranteed but without any additional coatings only around 50% of the beam is able to pass through. Those are rookie numbers and in most applications we’ll need to boost our window signals via various coatings. While this may be a disadvantage for optical windows this property comes in handy for novel lens designs and ATR optics where refraction is desired.

In fact, at an eye-popping Knoop Hardness of 2000kg/mm2, one might wonder, why wouldn’t I just use sapphire windows instead of germanium? While sapphire is the undisputed champion of robust optics in the UV/VIS and mid-IR with a wavelength range that dips into the far UV range at 150nm, it can only be used up to 4.5µm. This leaves germanium as the best and only choice for brutally tough IR applications. This is typically why you will see germanium windows and lenses serving in places as inhospitable as outer space, battlefields and in the middle of high-powered CO2 laser systems. More on this later.