GRIN materials can help compensate chromatic aberrations and enhance athermalization in an optical system, leading to more lightweight and compact lens assemblies, often with a lower number of elements. For several years, Umicore and ISCR in Rennes have developed GRIN materials for systems, using several approaches to modify the index in a chalcogenide glass. We will mention two of the most promising paths in this review: partial and spatially controlled crystallization by fast heating of the perimeter of a glass rod and ionic exchange which modifies locally the glass composition, leading to local changes in refractive index.
In recent years, a growing interest has settled for optical materials and fibers for the mid infrared (mid-IR) region. This interest originates from societal needs for health and environment for instance, and also from demand for defence applications. Indeed, the mid-IR spectral region contains the atmospheric transparent windows (3-5 μm) and (8-12 μm) where thermal imaging (military and civilian) can take place. The elaboration of chalcogenide microstructured optical fibers (MOFs) permits to combine the mid infrared transmission of chalcogenide glasses up to 18 μm to the unique optical properties of MOFs thanks to the high degree of freedom in the design of their geometrical structure. In this context, additive manufacturing of glass materials appears as an attractive technique to achieve more elaborate designs that can hardly be obtain using more common methods such as the stack-and-draw or molding. Taking advantages of the specific physical properties of chalcogenide glasses such as low Tg and extrusion temperature, we have shown that chalcogenide preforms can be rapidly obtained by fused deposition modeling (FDM) using a customized RepRap-style 3D printed fed with chalcogenide glass rods. Such as-prepared preforms can be drawn into chalcogenide optical fibers. Those early-stage results open a new way for the elaboration of chalcogenide MOFs.
In this paper we present techniques for measuring efficiently the optical properties of chalcogenide glasses. In particular we discuss methods for measuring refractive index and the variation of refractive index with temperature. We then apply these techniques to a new glass composition and demonstrate a high index of 3.26 @10 μm and a large thermo-optic coefficient of 1.99 ⋅ 10−4 K−1. These properties make this glass a good candidate for replacing germanium.
The last twenty years have seen a dramatic improvement in the performance of infrared detectors, especially those with uncooled microbolometer arrays. These make new commercial applications possible, from the Internet of things to drones for crop monitoring. Such emerging markets are constantly pushing the requirements on the existing technology to improve cost, performance, weight and size. In this context, gradient index (GRIN) lenses can offer a new degree of freedom compared to their homogeneous counterparts. For example, recent papers have shown how GRIN lenses could help reduce the number of elements in a system, by helping correct lens chromatism and athermalization. While the interest in using GRIN is obvious, mastering their fabrication with infrared materials remains highly challenging. Encouraging progress has been made in that direction, for instance by stacking different materials or by laser writing. Very recently, it has been demonstrated that partial crystallization of chalcogenide glass allows for tuning the refractive index. In this paper, we introduce a new technique based on the controlled formation of nano-crystallites in chalcogenide glass to fabricate the first macroscopic radial GRIN in the infrared. We also propose a simple way to test the index gradient value by interferometry and demonstrate GRIN with index contrast of ▵n ~ 3⋅10-2 between the center and the edge of the disk. The process is easily repeated and opens the possibility for a rapid transfer to the industry.
Chalcogenide glasses are compounded from chalcogen elements, such as sulphur, selenium, and tellurium. These
glasses are applied to commercial applications, e.g., night vision, because they transmit infrared in the spectral range of
0.8-16μm. Chalcogenide glasses have greater advantages over germanium (Ge), i.e., their wide spectral range of high
transmissivity and their small temperature dependence of the refractive index.
We have developed the Compact Infrared Camera (CIRC) with an uncooled infrared array detector (microbolometer)
for space applications. The CIRC has been scheduled to launch in 2013 to demonstrate the usability of a microbolometer
as a space application. The optics of the CIRC adopts two different kinds of materials for athermal optics. One is
germanium, and the other is GASIR1® which is a chalcogenide glass (Ge22As20Se58) developed by Umicore. However,
the radiation tolerance of GASIR® has not been investigated in the past.
We carried out irradiation tests to investigate the radiation tolerance of GASIR1®. We irradiated GASIR1® with
gamma-rays (Co60, 1.17 MeV and 1.33 MeV) up to 3Mrad. We measured the transmissivity and refractive index in the
infrared range before and after irradiation. In this paper, we report the results of the irradiation tests of GASIR1®.
The interest in new infrared materials has grown rapidly during the last decade, one reason being the increasing cost of traditional Germanium, with in the meantime, a decrease of the cost of infrared detectors.
In response to this Umicore has developed the GASIR® range of optical materials. A key strength of the new material is that it can be molded, leading to particularly cost effective solutions for high volume requirements. This paper reviews the GASIR®1 material relative to some of the existing materials and presents a case study of an optical design using GASIR®. In particular the effect of thermal cycling on survivability and performance are examined.
The case study includes Umicore's recently developed iDLC(tm) coating. This coating complies with the specifications for "Diamond Like Carbon" coatings and can thus suit a broad range of applications such as thermography, fire fighting, etc.
Umicore, known for its activities in the infrared materials and molded optics, this year launches a new infrared glass
called GASIR® 3. This material can be molded using Umicore's proprietary molding technology and allows serving a
wide range of new markets. Examples are a new automotive commercial application and sensing applications with their
need for very small optics.
Parallel to the materials development, a new coating has been developed by Umicore that allows the use of GASIR®
molded optics in extremely harsh environments. The extreme performance of this new type of coating which complies
with the toughest military specs will also be described.
A novel IR transmissive hard coating that offers protection to harsh environmental conditions on GASIR® and other
IR materials for thermal imaging and sensing applications.
iDLC has been developed to maximise both spectral and environmental performance for GASIR®. This coating can be
applied to the outside surface of molded optics and windows and offers high spectral efficiencies from 1.4μm to 15μm.
The ability to deposit a multi-layer structure allows broad band high efficiency anti-reflection coatings to be produced.
Compared to conventional DLC, this coating offers significantly less absorption, lower reflection and thus allows
higher transmission over a wide spectral band.
Tests have shown that the coating offers exceptional resistance to abrasion, salt spray and humidity.
The process used to manufacture iDLC has been configured for production volumes and offers a process for a wide
range of applications on IR electro-optic materials.
Umicore IR Glass has developed an industrial process to manufacture low cost chalcogenide glasses. These materials
called GASIR® are transparent in the 3-5 and 8-12 μm atmospheric windows which allows to use them in all the
sensing and thermal imaging applications where Germanium and ZnSe usually stands.
During the past 5 years, Umicore has developed and produced with and for its customers various GASIR ® optics in
low and medium volume for military and civilian applications. But from the beginning of last year, the company is also
very active in the automotive market. For that reason, a huge work of development on optics quality has been done to
comply with automotive requests.
Umicore's GASIR ® optics are used for instance in the night vision system that BMW launched in September 2005 on
its 7-series. This system which will be described in this paper was developed by Umicore's customer, automotive
TIER1 producer Autoliv.
During many years high volume commercial applications of infrared optics have been slowed down by several cost factors. The development of focal plan arrays and uncooled detectors has allowed to greatly reduce the cost of infrared detectors. In the meantime, Umicore IR Glass has developed an industrial process to manufacture low cost chalcogenide glasses with well controlled properties. These glasses called GASIR 1 and GASIR 2 are transparent in the NEAR and FAR infrared atmospheric windows and are mouldable into high quality finished spherical, aspherical and diffractive lenses. The moulding process allows high volume production of cost effective infrared optics. After the development of several optics in GASIR for medium volume series, Umicore is opening the first high volume factory entirely dedicated to GASIR optics for driving vision enhancement (DVE). This new facility will have a capacity of several tens of thousands of optics per year.
Umicore IR Glass has developed an industrial process to manufacture low cost chalcogenide glasses with well controlled properties. These materials called GASIR® 1 and GASIR® 2 are transparent in the 3-5 and 8-12 μm atmospheric windows allowing a great range of applications in thermal imaging.
In the past two years, several optics based on Germanium existing optics (60 mm and 100 mm) have been redesigned for GASIR® glass and are now produced as standards in medium volume series.
This year Umicore is passing another step in the production of infrared moulded optics by opening the first high volume factory entirely dedicated to GASIR® optics for driving vision enhancement (DVE). This new facility will have a capacity of several tens of thousands of optics per year.
In this article, the first results of performance of the corresponding optics will also be presented.
KEYWORDS: Lenses, Germanium, Thermography, Coating, Infrared radiation, Optics manufacturing, Glasses, Modulation transfer functions, Night vision, Single point diamond turning
Sustainable mobility is a major public concern, making increased safety one of the major challenges for the car of the future. About half of all serious traffic accidents occur at night, while only a minority of journeys is at night. Reduced visibility is one of the main reasons for these striking statistics and this explains the interest of the automobile industry in Enhanced Night Vision Systems.
As an answer to the need for high volume, low cost optics for these applications, Umicore has developed GASIR. This material is transparent in the NEAR and FAR infrared, and is mouldable into high quality finished spherical, aspherical and diffractive lenses. Umicore's GASIR moulded lenses are an ideal solution for thermal imaging for cars (Night Vision) and for sensing systems like pedestrian detection, collision avoidance, occupation detection, intelligent airbag systems etc.
Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. CEA/LETI developments are focused on the improvement of their sensitivity enabling the possibility to reduce the pixel pitch and the decrease of the system cost by using smaller optics. We present the characterization of a 160 x 120 infrared focal plane array with a pixel pitch of 35 μm. The amorphous silicon based technology is using recent process enhancement developed by CEA/LETI and transferred to ULIS. ULIS developed for this device a low cost package. The readout integrated circuit structure is using an advanced skimming function to enhance the pixel signal exploitation. This device is well adapted to high volume infrared imaging applications where spatial resolution (in term of pixel number) is less important than cost. The electro-optical characterization is presented. Besides, a unique and high precision molding technology has been developed by Umicore IR Glass to produce low cost chalcogenide infrared glass lenses with a high performance level. Spherical, aspherical and asphero-diffractive lenses have been manufactured with very accurate surface precision. The performances are comparable to those of an optic made with aspherical germanium. This new glass named GASIR offers an alternative solution to germanium for thermal imaging, especially for medium and high volumes applications. These two key technologies are well adapted to develop infrared driver vision enhancement (DVE) system for commercial application. A European project named ICAR has been setting up to exploit these advantages. An overview of the project will be given.
Umicore IR Glass has developed an industrial process to manufacture low cost chalcogenide glasses with well controlled properties. These materials called GASIR 1 and GASIR 2 are transparent in the 3-5 and 8-12 μm atmospheric windows allowing a great range of applications in thermal imaging. A high precision industrial moulding process has been developed and set up allowing to mould GASIR material directly into high quality finished spherical, aspherical and diffractive lenses. This process is especially attractive for medium and high volume applications. Specific antireflection coatings have also been developed offering a maximum transmission of 98% when coated with high efficiency coating. Several optics from 17.5 mm F/1 to 100 mm F/1.25 focal length based on existing germanium optics have been redesigned especially for GASIR 1 and GASIR 2 glasses. The lenses have been manufactured using Umicore’s moulding technology. These chalcogenide moulded optics are used in various applications like imaging, process control, military applications and their performances (modulation transfer function has been measured) are reviewed and compared to the existing solutions made of traditional IR optics.
Umicore IR Glass is a company specialising in the production of chalcogenide glasses and moulded optics. The standard glass compositions are GASIR1 (Ge22As20Se58) and GASIR2 (Ge20Sb15Se65). These materials are transparent in the 3-5 μm and 8-12 μm bands. An industrial process has been developed to produce these two glasses with well controlled properties. The reproducibility of refractive index is for example better than 2.0 x 10-4 at 10 μm.
A unique and high precision moulding technology has been developed to produce low cost chalcogenide glass lenses with high performance levels. Spherical, aspherical and asphero-diffractive lenses are manufactured with very accurate surface precision. The form defect of the moulded surfaces can be less than 0.4 μm with a typical roughness of 10 nm.
When depositing an antireflection coating onto the moulded lenses, the reflection losses are reduced, raising the transmission to 98%, compared to 70% for uncoated lenses. A durable coating has also been developed as a protection for exposed lenses. Coated asphero-diffractive GASIR optics, used in infrared cameras give good quality images. The performance is comparable to that of an optical system with aspherical germanium.
GASIR offers a cost-effective alternative to germanium for thermal imaging, especially for medium to high volume applications, both commercial and military.
Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. CEA / LETI developments are focused on the improvement of their sensitivity enabling the possibility to reduce the pixel pitch in order to decrease the total system cost by using smaller optics. We present the characterization of a 160 x 120 infrared focal plane array with a pixel pitch of 35 μm. The amorphous silicon based technology is the latest one developed by CEA / LETI and transferred to ULIS. ULIS developed for this device a low cost package based on existing technologies. The readout integrated circuit structure is using an advanced skimming function to enhance the pixel signal exploitation. This device is well adapted to high volume infrared imaging applications where spatial resolution is less important than device cost. The electro-optical characterization is presented. Besides, A unique and high precision molding technology has been developed by Umicore IR Glass to produce low cost chalcogenide infrared glass lenses with a high performance level. Spherical, aspherical and asphero-diffractive lenses have been manufactured with very accurate surface precision. The performances are comparable to those of an optic made with aspherical germanium. This new glass named GASIR2 offers an alternative solution to germanium for thermal imaging, especially for medium and high volumes applications. These two key technologies are well adapted to develop infrared enhanced driver vision (EDV) system for commercial application. A European project named ICAR has been setting up to exploit these advantages. An overview of the project will be given.
Umicore IR Glass is a company specialising in the production of chalcogenide glasses and moulded optics. The standard glass compositions are GASIR1 (Ge22As20Se58) and GASIR2 (Ge20Sb15Se65). These materials are transparent in the 3-5 μm and 8-12 μm bands. An industrial process has been developed to produce these two glasses with well controlled properties. The reproducibility of refractive index is for example better than 1.5 x 10-4 at 10 μm. A unique and high precision moulding technology has been developed to produce low cost chalcogenide glass lenses with high performance levels. Spherical, aspherical and asphero-diffractive lenses are manufactured with very accurate surface precision. The form defect of the moulded surfaces can be less than 0.3 μm with a typical roughness of 10 nm. When depositing an antireflection coating onto the moulded lenses, the reflection losses are reduced, raising the transmission to 98%, compared to 70% for uncoated lenses. A durable coating has also been developed as a protection for exposed lenses. Coated asphero-diffractive GASIR optics, used in infrared cameras give good quality images. The performance is comparable to that of an optical system with aspherical germanium. GASIR offers a cost-effective alternative to germanium for thermal imaging, especially for medium to high volume applications, both commercial and military.
Sulfide glasses based on GeGaS are stabilized by the addition of a fourth element: antimony. They show very weak crystallization upon heating as compared to standard GeGaS glass. Because of the low phonon energy inherent in sulfide glasses, the 1.3 micrometers emission of Dy3+ ions can be observed. This transition is characterized in terms of emission cross-section and quantum efficiency. Refractive indices are measured for various concentrations of cesium halides in standard GeGaS glass.
TeX glass fibers with a core-cladding structure are prepared by one of three methods: modified crucible method, preform method, or double crucible method. The raw elements are purified in order to eliminate some oxide impurities. They are then all distilled. The Te-Se-As- I system was chosen for the core and cladding glasses because of its stability against crystallization. The numerical aperture (N.A.) of the fiber is typically between 0.15 and 0.4. The diameter ratio of the core and cladding can be varied in the range of 0.15 - 0.9. These fibers are covered with a thermal plastic, to improve their mechanical properties. The optical losses of the fibers are measured between 2 and 13 micrometers by the cut-back method. The modified crucible method was the best to reduce the loss due to structural imperfections at the interface of the core and cladding. The lowest loss of 0.5 dB/m was achieved in the 7 - 9 micrometer region. Many applications of TeX glass fibers are actually tested in our laboratory such as thermal imaging, laser power delivery and remote spectroscopy. This last technology allows in-situ detection and quantification of several chemical compounds which have their characteristic absorptions in the 3 - 13 micrometer region.
The TeX glasses are attracting much attention as materials for low loss mid-IR optical fibers and are consequently good candidates for thermal imaging, laser power delivery, and more recently remote sensing. The TeX glass fiber, transmitting in a wide optical window, has a minimum attenuation in the 9-10 micrometers region. Fibers with an attenuation of less than 0.5 dB/m have been repeatly obtained. These fibers are coated with a UV curable or thermal plastic, in order to improve their mechanical properites. The IR remote spectroscopy using TeX fibers is one of the most promising applications. This technology allows to perform in situ, real-time, and on-line analysis of chemical and biological compounds. The study of industrial processes such as fermentations has been performed by this method, based on the use of these IR TeX fibers.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.