Measurement and control of ink density

Claim 2

Apparatus for obtaining an indication of the density of color reproduction printed in ink of at least one color on sheet material and comprising: means for, when energized, transmitting light to simultaneously impinge upon at least one test surface area of said sheet material printed with a colored ink and upon an unprinted reference surface area; first and second light sensor means for respectively simultaneously receiving light reflected from said test surface area and said reference surface area and providing first and second electrical signals of magnitudes respectively representative of the amount of light received by said first and second sensor means; means for supporting said sheet material so as to receive light from said transmitting means; and control circuit means connected to said first and second sensor means and responsive to said first and second signals for providing an electrical output signal exhibiting a characteristic which varies in proportion to the level of the color density of said test surface area.

Claim 3

Apparatus as set forth in claim 1 wherein said supporting means comprises means for moving said sheet material past said transmitting means and said sensor means and light control means for periodically energizing said light means in synchronism with the movement of said sheet material.

Claim 4

Apparatus as set forth in claim 1, wherein said control circuit means includes gating means for activating said control circuit means only when a gating signal is applied thereto.

Claim 5

Apparatus as set forth in claim 3 including synchronizing means for applying said gating signals to said gating means.

Claim 6

Apparatus as set forth in claim 4 including light control means for energizing said light means in synchronism with said gating signals whereby said light means is energized in synchronism with activation of sAid control circuit means.

Claim 7

Apparatus as set forth in claim 4, wherein said gating means activates said control circuit means for a time duration dependent on the time duration of said gating signals and said synchronizing means comprises circuit means for providing each said gating signal for a predetermined period of time.

Claim 8

Apparatus as set forth in claim 2, having synchronizing means comprising third sensor means for sensing a mark located on said sheet material forwardly of said test area and circuit means for providing a gating signal in response thereto.

Claim 9

Apparatus as set forth in claim 7, including means for cyclically energizing said third sensor means for sensing a said mark for a predetermined period of time during each cycle of operation.

Claim 10

Apparatus as set forth in claim 8 wherein said sensor energizing circuit means is adjustable to vary said predetermined period of time.

Claim 11

Apparatus as set forth in claim 1 wherein said first and second light sensor means have a light receptive surface for receiving light reflected from said surface areas and means for directing air across at least one of said light receptive surfaces to maintain same relatively clean.

Claim 14

The method as set forth in claim 11 wherein the step of transmitting light includes periodically energizing a light source in synchronism with movement of said sheet material so as to sequentially transmit light to impinge upon said plurality of monitor areas.

Claim 15

The method as set forth in claim 12, wherein said first and second signals for each monitor area exhibit magnitudes representative of the instantaneous intensity level of light received by said first and second sensor means, respectively.

Claim 16

The method as set forth in claim 13, including the steps of integrating each of said first and second signals for a given period of time for each said monitor area and providing an output density signal representative of the color density of said test surface area as a function of said integrated signals.

Claim 17

The method as set forth in claim 14 including the steps of integrating said first and second signals for a plurality of said monitor areas and providing a steady state control signal having a magnitude dependent on the existing level of said output density signal.

Claim 18

The method as set forth in claim 15 including the step of utilizing said control signal for providing read out indications of the color density of said ink test surface area.

Claim 19

Apparatus for obtaining an indication of the density of color reproduction in ink of at least one color on sheet material and comprising: means for transmitting light to impinge upon at least a test surface area of said sheet material printed with a colored ink and a reference surface area comprising gas discharge flash lamp means for flashing a high intensity light beam of short duration so that portions thereof impinge upon said test surface area and said reference surface area; light sensor means for receiving said high intensiTy light as reflected from said surface areas and developing respective electrical output signals dependent upon the amount of light received; means for supporting said sheet material so as to be located to receive light from said lamp means and reflect light to said light sensor means; means connected to said sensor means for providing an output indication as to the color density of said test surface area in dependence upon said output signals; and means for triggering said flash lamp means into conduction.

Claim 20

Apparatus for obtaining an indication of the density of color reproduction in ink of at least one color on sheet material and comprising: means for transmitting light to impinge upon at least a test surface area of said sheet material printed with a colored ink and a reference surface area comprising gas discharge flash lamp means for flashing a high intensity light beam of short duration so that portions thereof impinge upon said test surface area and said reference surface area; light sensor means for receiving said high intensiTy light as reflected from said surface areas and developing respective electrical output signals dependent upon the amount of light received; means for supporting said sheet material so as to be located to receive light from said lamp means and reflect light to said light sensor means; means connected to said sensor means for providing an output indication as to the color density of said test surface area in dependence upon said output signals; and means for triggering said flash lamp means into conduction.

Claim 21

Apparatus as set forth in claim 17, wherein said flash lamp means exhibits the characteristic of flashing a light beam of high light intensity and relatively even spectral distribution.

Claim 22

Apparatus as set forth in claim 17, wherein said flash lamp means includes a self-extinguishing Xenon lamp.

Claim 23

Apparatus as set forth in claim 17, including means for directing a portion of said high intensity light beam so as to impinge on said reference surface area simultaneously with said light beam impinging on said test surface area, and said sensor means includes first sensor means responsive to light reflected from said test surface area for providing a first output signal and second sensor means responsive to light reflected from said reference surface area for providing a second output signal for use in providing said indication.

Claim 24

Apparatus for obtaining an indication of the density of a color reproduction printed in ink on material by comparing the reflectivity of the printed ink with the reflectivity of the material comprising: a gas discharge lamp for flashing a high intensity light beam of short duration, means for supporting said material in position to receive light from said lamp, and measuring means for receiving light from said lamp reflected by printed and unprinted portions of said material for measuring the reflected light and providing electrical signals indicating the reflectivity of said printed portion and said material and means for comparing said signals to provide a density measurement, said measuring means comprising means for exposing a reference area to light from said flash lamp simultaneously with the exposure of said printed portion and sensor means for simultaneously and individually measuring light from said printed portion and said reference area to obtain electrical signals for providing an output electrical signal which is independent of intensity of light from said lamp.

Claim 25

Apparatus for obtaining an indication of the density of a color reproduction printed in ink on material by comparing the reflectivity of the printed ink with the reflectivity of the material comprising: a gas discharge lamp for flashing a high intensity light beam of short duration, means for supporting said material in position to receive light from said lamp, and measuring means for receiving light from said lamp reflected by printed and unprinted portions of said material for measuring the reflected light and providing electrical signals indicating the reflectivity of said printed portion and said material and means for comparing said signals to provide a density measurement, said measuring means comprising means for exposing a reference area to light from said flash lamp simultaneously with the exposure of said printed portion and sensor means for simultaneously and individually measuring light from said printed portion and said reference area to obtain electrical signals for providing an output electrical signal which is independent of intensity of light from said lamp.

Claim 26

In a method for determining the density of ink printed on a sheet material wherein light is directed to printed and unprinted portions of the sheet material and the light reflected from the portions is measured to provide electrical signals indicating the reflectivity of a printed portion and an unprinted portion of the material and the signals are utilized to obtain the ratio of the reflectivity of the printed material and the reflectivity of the unprinted material to obtain a measurement of ink density, the improvement which comprises minimizing the effect of variations in light intensity on measurements by directing light to a printed area and to an unprinted reference area and simultaneously measuring the light reflected from the areas to obtain electrical signals which are affected in the same manner by light intensity and utilizing said signals to provide an ink density electrical output signal having a magnitude proportional to the ink density of said printed portion and which is essentially independent of light intensity.

Claim 27

In a method for determining the density of ink printed on a sheet material wherein light is directed to printed and unprinted portions of the sheet material and the light reflected from the portions is measured to provide electrical signals indicating the reflectivity of a printed portion and an unprinted portion of the material and the signals are utilized to obtain the ratio of the reflectivity of the printed material and the reflectivity of the unprinted material to obtain a measurement of ink density, the improvement which comprises minimizing the effect of variations in light intensity on measurements by directing light to a printed area and to an unprinted reference area and simultaneously measuring the light reflected from the areas to obtain electrical signals which are affected in the same manner by light intensity and utilizing said signals to provide an ink density electrical output signal having a magnitude proportional to the ink density of said printed portion and which is essentially independent of light intensity.