We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
Fig. 2. View with reading-arm cover removed.
the first step into reading position. Each actuation of a lever on the mechanism moves the holder one step to the left, in the manner of a typewriter carriage. The number of the step being read is indicated by a scale along the front edge of the holder. For sensitometric procedures in which only certain selected steps are read on each strip, the indexing mechanism will accommodate a special strip holder that stops only at the desired positions.
In Fig. 2 the cover of the reading arm has been removed to show the type 1P42 measuring phototube, its load resistor, and a cathode-follower amplifier stage. The figure also shows, in the sample plane below the phototube, a transparent circular disk containing an opaque insert. The optical system of the densitometer projects a uniform spot of light on the insert from below. An
aperture at the center defines the size and shape of the measured area on the sample. When the reading arm is raised, an auxiliary lamp comes on and brightly illuminates a white background surface, which is visible to the operator through the transparent disk and through the defining aperture. This viewing arrangement is an invaluable aid in finding the exact spot on the sample that is to be read, particularly when the density is high. The transparent disk is interchangeable with others having defining apertures of different sizes and shapes. The largest area that can be measured is, of course, determined by the size of the phototube window, which is 5 mm in diameter. The aperture normally used is 5 mm in diameter. Much smaller apertures can be employed, at the expense of a reduction in the usable density range.
K. G. Macleish: Color Densitometer
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