Schott: high transmission glass for digital projection

The future of cinema is digital and three-dimensional. The epic 3-D film Avatar has raked in global revenue of USD 2.7 billion since December 2009, ranking as the single most successful movie of all t…

The future of cinema is digital and three-dimensional. The epic 3-D film Avatar has raked in global revenue of USD 2.7 billion since December 2009, ranking as the single most successful movie of all time. Projecting it onto screens that are around 30 meters in width requires a luminous flux of 27,000 lumens or more. Prisms made of special glass offer high light yield and deliver a perfect picture. Schott has now developed a version of its N-BK7 glass that offers extremely high transmission (HT) especially for the prisms used in digital projectors. According to the company, its new N-BK7HT guarantees a minimum transmission of 99.6% at a wavelength of 400 nm and a thickness of 25 mm. Within the visible spectrum range of between 400 and 700 nm, the absorption coefficient is three times lower than with standard N-BK7, generating less heat and reducing the risk of image errors. Schott continually works on improving the properties of its glasses and expanding the range of possibilities with respect to processing. In addition, being able to offer sound advice on applications provides the basis for the success of Schott. By expanding its prism manufacturing capabilities, the international technology group is not only in a position to produce the appropriate raw glass products, but also polished or coated prisms, for instance, of up to 200 mm in size. Moreover, prisms can be coated according to client needs, for example with dichroic or anti-reflective coatings. N-BK7 and N-BK7HT are suited for manufacturing highly homogenous optical components of up to 1 meter in diameter. Highly transparent N-BK7HT is also ideal for use in components in which light needs to travel inside the material for distances of up to 150 mm and more, such as prisms, for example. The properties of this glass change only very slightly even when exposed to solar radiation with a UV portion, thus also making it ideal for use in concentrator photovoltaics. Schott AG will be presenting N-BK7 and N-BK7HT and other innovations at its booth at this year“s Optatec, in Franfurt, 15-18 June.