Determination of extreme density values of photographic originals

Claim 1

In an apparatus for determining the extreme density values of the originals in a strip of photographic originals, of the type provided with evaluating means for receiving an electric signal having a value dependent upon the density of the originals and determining extreme values of the signal, in combination, transport means for transporting the strip in a predetermined travel direction along a predetermined travel path; and electromechanical scanning means operative for scanning each original in direction transverse to said travel direction during travel of the original in said direction using a scanning spot of substantially constant surface area and generating a corresponding electrical signal having a density-dependent value, said scanning means comprising a light source for illuminating the original being scanned, a photoelectric transducer positioned to receive light transmitted from the illuminated original, and beam-shaping means intercepting the path of the light for determining the shape of said scanning spot, said beam-shaping means including a stationary light shield positioned in the path of light from said light source and having a slit extending in direction transverse to said travel direction for establishing the limits of a scan line to be traversed by said scanning spot, and a rotating disk provided with apertures which during rotation of said disk move through the light from said source to define a scanning spot which travels along the scan line established by said slit, said apertures being of equal angular breadth measured relative to the rotation axis of said rotating disk and being equiangularly spaced from one another, the angular spacing between adjoining ones of the apertures of the rotating disk being such that during the transitional time interval at the end of a line scan operation when the scanning spot defined by one aperture reaches and begins to disappear into one end of the scan line the scanning spot defined by the next aperture simultaneously therewith begins to appear at the other end of the scan line, adjoining apertures of the rotating disk accordingly being operative for simultaneously transmitting to the photoelectric transducer the light transmitted through the two ends of the scan line during the transitional time interval, said scanning means comprising means for rotating said disk at such a speed that each scanning spot produced by one of said apertures of said rotating disk travels from one to the other end of said scan line within a time no greater than that in which the strip is transported a distance equal to the breadth of the scanning spot as measured in said travel direction of the strip.

Claim 8

A method of scanning the successive originals in a strip of such originals during longitudinal travel of the strip in order to determine the extreme density values of the originals, comprising scanning each original during longitudinal travel of the strip using a scanning spot which repeatedly traverses a stationary scan line extending transverse to the direction of strip travel and has a scanning speed such that the scanning spot travels from one to the other end of the stationary scan line in a time less than the time in which the strip travels a distance equal to the breadth of the stationary scan line, the scanning spot when at the end of the scan line disappearing into the end of the scan line with a progressive decrease in cross-sectional area but simultaneously reappearing at the start of the scan line with a corresponding progressive increase in cross-sectional area, so that during the progressive disappearance of the scanning spot into the end of the scan line and simultaneous progressive reappearance of the scanning spot from out the start of the scan line the combined cross-sectional areas of the parts of the scanning spot at the end and at the start of the scan line will be substantially constant and substantially equal to the cross-sectional area which the scanning spot has when traversing the middle portion of the scan line.

Claim 9

A method of scanning the successive originals in a strip of such originals during longitudinal travel of the strip in order to determine the extreme density values of the originals, comprising scanning each original during longitudinal travel of the strip using a scanning spot which repeatedly traverses a stationary scan line extending transverse to the direction of strip travel and has a scanning speed such that the scanning spot travels from one to the other end of the stationary scan line in a time less than the time in which the strip travels a distance equal to the breadth of the stationary scan line, the scanning spot when at the end of the scan line disappearing into the end of the scan line with a progressive decrease in cross-sectional area but simultaneously reappearing at the start of the scan line with a corresponding progressive increase in cross-sectional area, so that during the progressive disappearance of the scanning spot into the end of the scan line and simultaneous progressive reappearance of the scanning spot from out the start of the scan line the combined cross-sectional areas of the parts of the scanning spot at the end and at the start of the scan line will be substantially constant and substantially equal to the cross-sectional area which the scanning spot has when traversing the middle portion of the scan line.