Optical glass is a very important material in the development of technology and
thus of the history of mankind as a whole. It first allowed access to the micro- and
macrocosm, when, about 400 years ago, the microscope and the telescope
were invented at almost the same time and location in the town Middelburg in the
Netherlands (Fig. 1.1). Although glass lenses were known before this time, only
the combination of two or more lenses forming optical instruments could
increase magnification to such an extent that new worlds were opened to human
vision and investigation.
Glass was the only bulk material capable of changing the direction of light
rays without impairing them by absorption or scattering that could be produced in
large volume with comparatively low cost. This property is still the basis of a
vast variety of optical systems in use today, not only for imaging but for light
management in general. Today's microscopes are highly sophisticated
instruments with outstanding precision mechanics, computer control, and
software assistance. But without the glass inside of them, they are worthless.
Quite obvious is the use of optical glass in consumer products such as
photography cameras, camcorders, and binoculars. The general public is also
familiar with applications in movie cameras and projectors. Much less known is
the fact that optical systems have widespread use in metrology, which is the
necessary precondition process in any manufacturing. The automotive industry
uses stationary, computer-numerical controlled 3D (CNC 3D) measurement
machines, which appear to work mechanically. However, a closer look shows
that these machines work with glass-ceramic-scale readout using small lenses.
Mobile machines provide 3D measurement directly at the workshop floor. In the
aviation- and ship-building industries, very large elements need to precisely fit
one another. This is also achieved with 3D measurement machines, so-called
laser trackers. In general industry, quite often large machines need to be precisely
aligned; this is achieved with optical systems. Products will be quality controlled
with telecentric optical lens systems. Machine vision systems are ubiquitous
nowadays. Theodolites are workhorses for civil engineering. Land surveying, the
application that boosted the development of optics 200 years ago, uses earthbound,
airborne, and spaceborne optical systems.