Original documents are digitized using equipment appropriate to image acquisition conditions and the physical constraints of each document.
There are two main image acquisition techniques, each of which uses hardware that varies in line with the constraints of the document: digitization by taking photographs and digitization by scanning.
Digitization by taking photographs
A digital camera photographs the document one page at a time.
The distance between the camera and the page must be accurately analyzed so as to optimize image definition.
This technique is used when digitizing small or medium-sized documents
Two types of machine are used for digitization by taking photographs:
A machine with a V-shaped cradle for fragile documents
, consisting of a camera facing each side of the cradle and a page-turning robot
to minimize human intervention.
A machine consisting of an equalizer tray
for documents that can be digitized flat
(some paperbacks and books with flexible bindings).
Digitization by scanning
Digibook 2000LC, Suprascan A0 device
Sensors scan the document and reconstruct the image a pixel at a time.
This technique is used to digitize large or bulky documents
(maps and atlases, brochures, registers, press publications, some manuscripts, etc.).
The sensor is fitted to a moving arm. The distance between the sensor and the document being digitized is adjustable. The entire document is scanned.
Pages are manually turned
by an operator.
A V-shaped cradle may be used for documents with fragile bindings.
Manuscripts and posters
The majority of manuscripts and posters are digitized using machines consisting of a digital camera mounted on a bracket above a work surface that can be adjusted to suit various document types (e.g. a table for flat documents, a V-shaped cradle for documents with a reduced angle of opening, an equalizer tray for thick bindings, etc.). These machines can handle documents of a wide variety of sizes (up to A0) but which require specific adjustments (on a per document or even per capture basis).