Density measuring apparatus

Claim 3

The method of claim 1 including the step of utilizing said fourth electrical signal to control the exposure in the making of a reproduction on photosensitive material from said image bearing medium.

Claim 4

An image reproduction apparatus including: scanning means for scanning an original in a raster pattern to produce a first electrical signal whose varying level is representative of the density of successive incremental areas of said image bearing medium; clamping means for clamping a portion of said first electrical signal to a predetermined signal level to produce a second electrical signal having a signal level varying about said predetermined signal level; converting means for converting said level varying second electrical signal into a frequency varying third electrical signal having a frequency dependent on the variation of said second signal level from said predetermined level; summing means for summing the number of cycles of said third signal over a complete raster scan of said image bearing medium to obtain a fourth electrical signal which is representative of the average density of said image bearing medium; modifying means connected to said scanning means for modifying said first electrical signal; control means connected to said summing means for controlling said modifying means to effect modification of said first electrical signal as a function of said fourth electrical signal to produce a fifth electrical signal; and electrooptical means controlled by said fifth signal for producing a reproduction of said image bearing medium on photosensitive material.

Claim 5

An image reproduction apparatus including: scanning means for scanning an original in a raster pattern to produce a first electrical signal whose varying level is representative of the density of successive incremental areas of said image bearing medium; clamping means for clamping a portion of said first electrical signal to a predetermined signal level to produce a second electrical signal having a signal level varying about said predetermined signal level; converting means for converting said level varying second electrical signal into a frequency varying third electrical signal having a frequency dependent on the variation of said second signal level from said predetermined level; summing means for summing the number of cycles of said third signal over a complete raster scan of said image bearing medium to obtain a fourth electrical signal which is representative of the average density of said image bearing medium; modifying means connected to said scanning means for modifying said first electrical signal; control means connected to said summing means for controlling said modifying means to effect modification of said first electrical signal as a function of said fourth electrical signal to produce a fifth electrical signal; and electrooptical means controlled by said fifth signal for producing a reproduction of said image bearing medium on photosensitive material.

Claim 6

The apparatus of claim 3 wherein said electrooptical means includes a flying spot scanning cathode ray tube.

Claim 7

The apparatus of claim 3 wherein said control means includes manually operable means for manually controlling said control means.

Claim 8

The apparatus of claim 3 wherein said means for scanning an image bearing medium in a raster pattern includes means for producing a beam of radiant energy and for causing the beam of radiant energy to scan said image bearing medium point-to-point in a raster pattern to produce a modulated beam of energy modulated by the point-to-point density of said image bearing medium; and further includes optoelectrical means for sensing said modulated beam of energy and for producing said first electrical signal.

Claim 9

The apparatus of claim 6 wherein said image bearing medium is a transparency and said beam of radiant energy is modulated by the transmission of said radiant energy through said transparency.

Claim 10

The apparatus of claim 6 wherein said producing means produces a beam of radiant energy in the visible spectrum.

Claim 11

The apparatus of claim 6 wherein said producing means includes a flying spot scanning cathode ray tube.

Claim 12

The apparatus of claim 6 wherein said optoelectrical means includes a logarithmic amplifier.

Claim 13

The apparatus of claim 10 wherein said optoelectrical means includes a resistive matrix.

Claim 14

The apparatus of claim 3 wherein said predetermined signal level is representative of the color gray and wherein said converting means includes a voltage controlled oscillator which converts a voltage varying second electrical signal into a frequency varying third electrical signal.

Claim 15

The apparatus of claim 12 wherein said summing means includes a counter.

Claim 16

The apparatus of claim 13 wherein said modifying means includes an attenuator and wherein said control means includes logic means for controlling the attenuation of said first electrical signal by said attenuator as a function of the count of said counter.