7. Hybrid Systems
Introduction
The increasing popularity of hybrid systems, combining the
best features of electronic imaging and micrographics, has created a demand
for equipment to link the two technologies. This chapter examines methods of
scanning film and converting film-images to digital data and also the
reverse process by which digital formats, including text and raster
graphics, can be converted to microfilm for archival storage with the
advantages of established storage life, freedom from technological
obsolescence and established legal acceptability.
Many permutations are viable. It is possible to microfilm
paper input and digitise it simultaneously to create both a film and a
bit-map image of each page. Alternatives include filming and scanning the
film image to provide digital input, or scan but delay filming until all
processing work is completed, at which point Computer Output on Microfilm
(COM) techniques can be employed to convert the digital data to any
microform. A wide range of hardware has been developed to enable these
operations.
Digital reader-printers
Digital reader-printers can
usually optically enlarge film images on to an integral screen for reference
or verification but they also incorporate a facility to scan the images for
input to an electronic document management system, printout via a
laser-printer or send it for direct fax transmission. Versions are available
for all microforms and some models can accept more than one film format.
Factors such as the choice of lenses, film carrier options
and the image retrieval methods available are similar to optical microfilm
reader-printers, but a much wider range of printout is available via a laser
or inkjet printer. Options typically include the ability to mask any part of
the image, correction of skewed images, superimposition of repetitive data
on prints and electronically variable enlargement.
These units are suitable for applications when there is a
need for a method of enlarging images from film but only occasional
necessity to convert them to electronic format.
Production film scanners
Production scanners for roll film, fiche or aperture cards are intended
for the rapid digitising of high volumes of data from film rather than
reference to or enlargement from specific images. A screen may be provided
for verification purposes, but if a facility for full size display is
required it is usually provided via a CRT monitor in order to show the
quality of the digitised data rather than an optical enlargement of the
microfilm image.
Applications include file conversion of microfilm
archives to electronic document management systems and the automation of
document scanning when assorted input is involved. If documents of different
sizes and quality are to be input to an electronic document management
system it may not be possible to batch scan and input may be very slow. By
microfilming the mixed input to produce standard images on roll film it is
possible to digitise the entire roll automatically at high speed. An
additional advantage of this method is the production of a film showing the
input in its original form which serves as a legally acceptable archival
record.
Engineering drawings can be handled in a similar manner by
first filming them on to 35mm roll and then scanning the roll. Special film
scanners are also available with hoppers which accept batches of aperture
cards. These units automatically scan the film, and extract data from
punching or marks on the cards.
Production film scanners are fast and relatively
expensive. It is necessary to have a long-term requirement for the scanning
of fairly high volumes of input to justify an in-house unit, but many
microfilm bureaux now offer film
scanning services at prices which make even low-volume input economic.
When documents need to be available for instant access it
is logical to hold them in digital format within electronic document
management systems, but the period of peak activity is usually of relatively
short duration. Thereafter the need for retrieval remains a possibility, but
in many applications the majority of the documents will never be referenced
again.
Despite advances in the capacity of digital storage, it is
still usually impractical to hold archival information on instant access
devices. Another problem is that as systems evolve it is time-consuming and
expensive to ensure that all digital archives held on outdated media or in
abandoned formats are converted. Repetitive conversion also carries an
attendant risk of data loss. The need to cater for large quantities of
archival material can act as a brake on system development.
COM (Computer Output Microfilm, also known as IOM - Image
Output Microfilm) offers a fast and economical method of converting digital
files to proven and archival microformats. In many cases it is sensible to
do this as part of the input process to ensure that an absolutely secure
back-up is always available. The master films should be preserved in a
remote archive, but exact copies can be produced inexpensively for use when
access from digital storage is terminated.
If a microfilmed document, thought to be archival, needs
to be re-input to an electronic document management system, it can easily be
scanned and digitised. Reader-scanners suitable for such applications can
also produce prints via a laser-printer if hard copy is preferable.
CAD PLOTTING
CAD applications are often "print bound" because paper
plotters are relatively slow. An alternative is to print direct too
microfilm, either in 35mm roll format or in aperture cards. When aperture
cards are employed, the recorder normally contains its own film processor in
order to deliver fully processed and titled aperture cards at speeds of up
to 35 cards per hour.
Specifications for hybrid equipment are included on this
site under film scanners for
aperture cards,
for fiche &
jackets, for
roll formats and for
multiple formats.
COM recorders for all formats and film plotters are listed under
digital to film recorders.
UK bureaux offering COM recording facilities are listed
under "Services/Data input and conversion"
(next
chapter) (back
to top)
