Vanguard X Broadband wavelength Chalcogenide lenses and optics for multi spectral multi sensor imaging eoir systems
LWIR uncooled and MWIR cooled zoom thermal imaging Flir ir germanium chalcogenide optical broadband lenses by SPI
If your next project calls for an optic which transmits light broadband from multiple parts of the spectrum (visible, nir, vnir, swir, mwir, lwir), and weight, cost and complexity are concerns, you now have more options for the lens’ substrate material.
SPI’s Vanguard X Lenses and our optical engineering team has developed cutting-edge anti-reflective coatings for a new generation of optical substrates. These coatings maximize transmission of light through a number of new materials.
This permits efficient window and lens design for your multi-spectral eoir broadband imaging systems. Ideal for image fusion, image blending, sensor fusion and fuzed sensors and detectors all imaging through one common aperture lens
First is a new Chalcogenide glass which transmits from about 0.6um-12um. This material is inherently athermal, moldable or diamond-turnable, AR coatable, and is almost a direct replacement for ZnSe.
If your project calls for combining Image intensified night visions’ NIR light and thermal imaging’s LWIR energy; or SWIR or MWIR energy, this is a great candidate material; especially as the cost is in Germanium’s ballpark.
Next up is a newly processed Zinc Sulfide. The ingenious process results in a microstructure giving it great strength, in terms of modulus of rupture, and excellent transmission from NIR- LWIR (0.8um-12um). This material can be diamond turned, near-net formed,
traditionally polished and AR coated as well. If you require a resistant window or a polished, blowing sand-resistant dome, this material makes a good candidate. It transmits particularly well in the mid-wave portion of the spectrum(3-5um) and is cost-competitive with Germanium.
Contact SPI for assistance on your camera project. Share your problem and we can help develop a cost-competitive design solution including material selection and coating approach.
From there we can help develop and test your prototypes before moving into pilot, and then, volume production.
Contact [email protected] for additional info and pricing or call (702) 499-9551
LWIR IMAGE
MWIR IMAGE
VIS / NIR Image
I2 Image
Fabricating optics using chalcogenides can be challenging because of these glasses’ special optical, mechanical and economical characteristics. Diamond-turned machining is a viable option for addressing some of the issues with the conventional molding and polishing process.
Chalcogenide glass has gained attention in the optical engineering community as a versatile material for infrared thermal imaging and sensing applications, as well as for collimation of fiber and quantum cascade lasers.
SPI has the capability of designing and manufacturing lenses and windows made from this exotic material. Spherical and aspherical lenses also can be manufactured with some chalcogenide materials using injection molding.
Optical and thermal properties
Chalcogenide glass has attractive optical properties as an IR material because it is widely transparent between the short-wave (SWIR) and long-wave IR (LWIR) regions. Chalcogenide glass composed of the chalcogen elements sulfur (S), selenium (Se) and tellurium (Te) has a glass-transition temperature (Tg) characteristic of amorphous materials, even though its crystalline structure is not a continuous random network as observed in other amorphous materials, chalcogenide glasses are good candidates for VIS-NIR-SWIR-MWIR-LWIR applications. Their transparency in the IR spectrum is comparable to that in other broadband IR materials, such as zinc selenide (ZnSe) and zinc sulfide (ZnS) multispectral grade. Chalcogenide glasses exhibit a low rate of change in refractive index relative to temperature change. In comparison to germanium (Ge), which has a thermal change (dn/dt) at 10 µm that equals 39,600 × 10–6/K, IRG24 (Ge10As40Se50) has a dn/dt that is multiple magnitudes lower (dn/dt = 19.9 × 10–6/K @ 10 µm). Optical engineers take advantage of this characteristic when designing athermalized IR lens assemblies. As temperature changes, IR lens assemblies with chalcogenide materials will maintain focus throughout the operating temperature range (typically, −40 to +62 °C).
Molding process with chalcogenide glass
Chalcogenide glass is moldable, which adds another dimension to its versatility. For the molding process, SPI collaborate and will assist in initial investment that is required to manufacture the master mold. The molding process is rather economically unsuitable for low to medium quantities: Operating the injection molding machines is expensive, as is manufacturing the precision mold master for each lens. These initial setup costs typically are distributed over the thousands of units produced throughout its product life cycle.
Molding of glass lenses, unlike DTM, is restricted to diameters typically smaller than 25 to 30 mm. DTM also allows for much better form accuracy, and it produces better-quality aspheric and diffractive surfaces than the molding process. The mold masters for high-temperature press machines, which are made by single-point diamond turning, have good irregularity, but the molding process itself cannot duplicate the mold surface perfectly and exaggerates the irregularity on the finished glass surface.
In addition to the development of an AR coating for LWIR applications, the design of a multiwavelength mulrispectral broadband coating to accommodate the increasing number of SWIR needs also was carried out. SWIR film structure is different from the LWIR design, and coating materials must be transparent from SWIR to LWIR.
To summarize chalcogenide is a great contender for visible vis/ nir near infrared / SWIR short wave infrared, midwave infrared Mwir and long wave infrared LWIR applications. These optics will help reduce size weight and power SWaP for new advanced military multi sensor imaging systems, fire control system fcs, drivers vision enhanced dve and a wide array of military recon, surveillance, observation and targeting electro optical applications.