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®.
Small size and low weight are among the main drivers in modern military hand-held applications. Consequently, design-ers of such systems strive for combining multiple optical and electronic functions into the same piece of hardware. Present paper deals with the partial integration of an eye safe laser rangefinder into an optical channel for uncooled thermal imager using UMICORE's GASIR® optics. GASIR® is a chalcogenide glass with a transmission window from 0.8-15 µm, making it an effective material for use in near infrared, mid-wave infrared and far infrared applications.
Due to the fact that uncooled sensors in the LWIR spectral band require optics with low f/numbers and that laser range-finders typically need a larger receiver aperture - in order to comply with the maximum range requirement - this ap-proach at first sight promises favorable synergies. However, it soon turns out that such a dual band approach makes life for the rangefinder part of the job difficult - by imposing special surface types required for achieving optical specifica-tions of the thermal channel, which may deteriorate the beam quality of the laser light as well as by introducing special coatings with potentially insufficient transmission at the specific laser wavelength. Several design versions have been developed and evaluated with the purpose of finding optimal balance between image quality of the thermal channel and the laser rangefinder performance.
In this paper various optical and coating design aspects will be addressed together with the limitations of such a multi-spectral approach.
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.