in 1957 Early
digital fax machines such as the
Bartlane cable picture transmission system preceded digital cameras and computers by decades. The first picture to be scanned, stored, and recreated in digital pixels was displayed on the Standards Eastern Automatic Computer (
SEAC) at
NIST. The advancement of digital imagery continued in the early 1960s, alongside development of the
space program and in
medical research. Projects at the
Jet Propulsion Laboratory,
MIT,
Bell Labs and the
University of Maryland, among others, used digital images to advance
satellite imagery, wirephoto standards conversion,
medical imaging,
videophone technology,
character recognition, and photo enhancement. Rapid advances in
digital imaging began with the introduction of
MOS integrated circuits in the 1960s and
microprocessors in the early 1970s, alongside progress in related
computer memory storage,
display technologies, and
data compression algorithms. The invention of computerized axial tomography (
CAT scanning), using
x-rays to produce a digital image of a "slice" through a three-dimensional object, was of great importance to medical diagnostics. As well as origination of digital images,
digitization of analog images allowed the enhancement and restoration of
archaeological artifacts and began to be used in fields as diverse as
nuclear medicine,
astronomy,
law enforcement,
defence and
industry. Advances in microprocessor technology paved the way for the development and marketing of
charge-coupled devices (CCDs) for use in a wide range of
image capture devices and gradually displaced the use of analog
film and
tape in photography and videography towards the end of the 20th century. The computing power necessary to process digital image capture also allowed
computer-generated digital images to achieve a level of refinement close to
photorealism.
Digital image sensors The first semiconductor image sensor was the CCD, developed by
Willard S. Boyle and
George E. Smith at Bell Labs in 1969. While researching MOS technology, they realized that an electric charge was the analogy of the magnetic bubble and that it could be stored on a tiny
MOS capacitor. As it was fairly straightforward to
fabricate a series of MOS capacitors in a row, they connected a suitable voltage to them so that the charge could be stepped along from one to the next. The CCD is a semiconductor circuit that was later used in the first
digital video cameras for
television broadcasting. Early CCD sensors suffered from
shutter lag. This was largely resolved with the invention of the
pinned photodiode (PPD). It was a
photodetector structure with low lag, low
noise, high
quantum efficiency and low
dark current. The NMOS APS was fabricated by Tsutomu Nakamura's team at Olympus in 1985. The
CMOS active-pixel sensor (CMOS sensor) was later developed by
Eric Fossum's team at the
NASA Jet Propulsion Laboratory in 1993. By 2007, sales of CMOS sensors had surpassed CCD sensors.
Digital image compression An important development in digital
image compression technology was the
discrete cosine transform (DCT), a
lossy compression technique first proposed by
Nasir Ahmed in 1972. DCT compression is used in
JPEG, which was introduced by the
Joint Photographic Experts Group in 1992. JPEG compresses images down to much smaller file sizes, and has become the most widely used image file format on the
Internet. ==Mosaic==