Infrared imaging devices play an important role in many fields. Infrared technology’s consumer applications are expected to expand. However, only a few optical materials can be used in the infrared region. Although germanium has excellent properties, it is unsuitable for the mass production of optical elements. Chalcogenide glass can be press-formed and exhibits high productivity; however, its transmission and other optical properties are not as good as those of germanium. Therefore, we invented an original chalcogenide glass material named FI-02 and developed optical elements using this material. FI-02 has excellent infrared transmission properties with a wider transmission wavelength range than germanium, and its refractive index of 3.4 at a wavelength of 10 m is a very high value as a glass material. Because FI-02 can be press-molded at low temperatures, it is ideal for the mass production of optical elements, such as aspherical lenses. Lens units for a far-infrared (FIR) camera made of FI-02 produce clearer, higher-contrast infrared images by taking advantage of the unique optical properties of the material. Furthermore, we present large-diameter lenses and diffractive elements for aerospace applications as examples of developments that capitalize on the properties of FI-02
Germanium and chalcogenide glasses are used as infrared lens materials, but there is no one that combines both excellent optical properties and mass production. Against this background, we worked on the development of a new infrared lens material, and a novel infrared lens material named FI-02 has been developed. FI-02’s most useful feature is its infrared transmission property. It can transmit up to 20-μm-wavelength infrared light and has a vast transmittance spectrum in the infrared region compared to germanium and conventional chalcogenide glass. In addition, FI-02 has a high refractive index of 3.47 (at a wavelength of 10 μm). This enables the fabrication of thin and high-performance infrared lenses. Furthermore, FI-02 can be processed through press molding. This enables making of high-performance lenses with high productivity. In an infrared lens unit using FI-02, infrared images are captured with better contrast as compared to those captured using the germanium or conventional chalcogenide glass lenses. This could be attributed to the good infrared transmission property of FI-02. In addition, we confirmed that using FI-02 with a high refractive index as an aspheric lens, it is possible to design a lens unit with unprecedented characteristics, such as a low-distortion ultra-wide-angle lens.
New chalcogenide glass (FI-02) has been developed successfully, with its most effective feature being its infrared (IR) transmittance. FI-02 can transmit up to 20-μm wavelengths of IR light and has a very wide transmittance spectrum in the IR region as compared to the germanium single crystal and conventional chalcogenide glass. Its excellent transmission property is expected to improve the brightness and clarity of IR images. In addition, FI-02 has a high refractive index of 3.47 (at a wavelength of 10 μm). This is the highest refractive index among glass materials, thus enabling the fabrication of thin and high-performance IR lenses. Furthermore, unlike crystal materials, FI-02 can be processed through press molding. This enables to make high performance lens with high productivity. To investigate the performance of FI-02 as an IR lens material, we made two types of IR lens units: focal length (FL) 10.5 mm (standard type) and FL 2.04 mm (super wide-angle type). In the standard lens unit, IR images were captured with better contrast as compared to those captured using the germanium or conventional chalcogenide glass lenses. This could be attributed to the good IR transmission property of FI-02. In the super wide-angle type, IR images were captured that were wider and less distorted as compared to those of the typical wide-angle IR lens unit. This was attributed to the advantage of the high refractive index of FI-02 and its ability to form aspherical shapes through press molding.
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