Method and apparatus for controlling charge on a photoconductor

Claim 2

In an electrophotographic reproduction apparatus including a member having a surface upon which an electrostatic latent image may be formed; means for charging the surface with an electrostatic charge; means for moving the surface relative to the charging means in a first direction; exposure means for exposing the charged surface to image-bearing radiation to form the latent image; measuring means for measuring the level of charge deposited on the surface by said charging means and charge-reducing means for reducing the level of charge on the surface to a referenced level, the improvement which comprises: first means for controlling the measuring means to cause the measuring means to measure the level of charge at each of a plural number of locations lying across the surface in a second direction transverse to the first direction and to provide a signal commensurate with each such measurement; and second means responsive to signals from the measuring means for controlling the charge-reducing means to selectively reduce the charge level at each of those transverse locations having a level of charge greater than said referenced level in accordance with the difference in charge level measurement for each such transverse location and the referenced level.

Claim 3

The apparatus according to claim 1 wherein the first means causes the measuring means to again measure the level of charge at each of the plural number of locations to check the results of operation of the charge-reducing means and if the level of charge at any location is greater than the referenced level the second means again adjusts the charge-reducing means based on the second measurements to selectively reduce the charge level at each of those locations having a level of charge greater than the referenced level and wherein the first means and the second means are operated iteratively until the charge level at each of the locations is no higher than the referenced level.

Claim 4

The apparatus according to claim 2 wherein the charging means deposits a negative electrostatic charge on the surface.

Claim 5

The apparatus according to claim 1 wherein the surface includes an area upon which the electrostatic latent image is to be formed; and includes third means responsive to measurement by the measuring means of a charge level lower than a referenced minimum level, for adjusting the charging means to increase the level of charge on the area so that all portions thereof in the area have a level of charge greater than the referenced minimum level.

Claim 6

The apparatus according to claim 4 wherein the first means causes the measuring means to again measure the level of charge at each of the plural number of locations to check the results of operation of the charging means and if the level of charge at any location is measured to be lower than the referenced minimum level the third means again adjusts the charging means based on these second measurements to increase the level of charge on the area so that all portions thereof in the area have a level of charge greater than the referenced minimum level and wherein the first means and the third means are operated iteratively until the charge level at each of the locations is greater than the referenced minimum level.

Claim 7

The apparatus according to claim 5 wherein the charging means deposits a negative electrostatic charge on the surface.

Claim 8

The apparatus according to claim 1 and wherein the surface is a photoconductive surface and the charge-reducing means comprises light source means for providing exposure of said photoconductor to nonimaging light at locations and in amounts needed to reduce the charge selectively at each of the locations to the aforesaid refereneced level.

Claim 9

The apparatus according to claim 7 wherein the surface includes an area upon which the electrostatic latent image is to be formed; and includes third means responsive to measurement by the measuring means of a charge level lower than a referenced minimum level, for adjusting the charging means to increase the level of charge on the area so that all portions thereof have a level of charge greater than the referenced minimum level.

Claim 10

The apparatus according to claim 8 and wherein the charging means deposits a negative electrostatic charge on the surface.

Claim 11

The apparatus according to claim 7 and wherein the light source means comprises a bank of lamps arranged in rows, extending in the second direction, and in columns, extending in the first direction, and each column of lamps is associated with the overlies a specific transverse location on the photoconductor, and wherein the second means selectively controls the number of rows of lamps which will be illuminated in each column in response to the level of charge measured by the measuring means for the respective transverse location.

Claim 12

The apparatus according to claim 10 wherein the first means causes the measuring means to again measure the level of charge at each of the plural number of locations to check the results of operation of the charge-reducing means and if the level of charge at any location is measured to be greater than the referenced level the second means again adjusts the charge-reducing means based on these second measurements to selectively reduce the charge level at each of those locations having a level of charge greater than the referenced level and wherein the first means and the second means are operated iteratively until the charge level at each of the locations is no higher than the referenced level.

Claim 13

The apparatus according to claim 11 wherein the charging means deposits a negative electrostatic charge on the surface.

Claim 14

The apparatus according to claim 12 wherein the surface includes an area upon which the electrostatic latent image is to be formed; and includes third means responsive to measurement by the measuring means of a charge level lower than a referenced minimum level for adjusting the charging means to increase the level of charge on the area so that all portions thereof have a level of charge greater than the referenced minimum level.

Claim 15

The apparatus according to claim 13 wherein the first means causes the measuring means to again measure the level of charge at each of the plural number of locations to check the results of operation of the charging means and if the level of charge at any location is measured to be lower than the referenced minimum level the third means again adjusts the charge-reducing means based on these second measurements to increase the level of charge on the area so that all portions thereof in the area have a level of charge greater than the referenced minimum level and wherein the first means and the third means are operated iteratively until the charge level at each of the locations is greater than the referenced minimum level.

Claim 16

The apparatus according to claim 1 and wherein the charging means deposits a negative electrostatic charge on the surface.

Claim 17

In an electrophotographic reproduction apparatus including a photoconductor; a corona charging station for charging an image area of the photoconductor with an electrostatic charge of a level suitable for forming an electrostatic latent image; means for moving the photoconductor in a first direction past said charging station; an exposure station located downstream of the charging station for illuminating the image area of the photoconductor with image-bearing radiation to form a latent electrostatic image in the area; a developing station for developing the latent image; a transfer station for transferring the developed image to a receiver; measuring means for measuring the level of charge deposited by said charging means and charge-reducing means for reducing the level of charge on the surface to a referenced maximum level; the improvement which comprises: first means for controlling the measuring means to cause the measuring means to measure the level of charge at each of a plural number of transverse locations lying across the photoconductor in a second direction transverse to the first direction; and second means responsive to the measurement by the measuring means of a charge level lower than a referenced minimum level at any of the measured locations for increasing the level of charge at all locations in the area to the referenced minimum level; and third means responsive to the measuring means for controlling the charge-reducing means to selectively reduce, in accordance with the difference in charge level measurement for each such transverse location and a referenced level, the charge level at each of those transverse locations having a level of charge greater than said maximum level to a level falling within the range between the aforesaid referenced minimum and maximum levels.

Claim 18

In an electrophotographic reproduction apparatus including a photoconductor; a corona charging station for charging an image area of the photoconductor with an electrostatic charge of a level suitable for forming an electrostatic latent image; means for moving the photoconductor in a first direction past said charging station; an exposure station located downstream of the charging station for illuminating the image area of the photoconductor with image-bearing radiation to form a latent electrostatic image in the area; a developing station for developing the latent image; a transfer station for transferring the developed image to a receiver; measuring means for measuring the level of charge deposited by said charging means and charge-reducing means for reducing the level of charge on the surface to a referenced maximum level; the improvement which comprises: first means for controlling the measuring means to cause the measuring means to measure the level of charge at each of a plural number of transverse locations lying across the photoconductor in a second direction transverse to the first direction; and second means responsive to the measurement by the measuring means of a charge level lower than a referenced minimum level at any of the measured locations for increasing the level of charge at all locations in the area to the referenced minimum level; and third means responsive to the measuring means for controlling the charge-reducing means to selectively reduce, in accordance with the difference in charge level measurement for each such transverse location and a referenced level, the charge level at each of those transverse locations having a level of charge greater than said maximum level to a level falling within the range between the aforesaid referenced minimum and maximum levels.

Claim 19

The apparatus according to claim 16 and wherein the corona charging station deposits a negative electrostatic charge on the surface.

Claim 20

The apparatus according to claim 17 and wherein the charge-reducing means comprises light source means for providing exposure of said photoconductor to nonimaging light at locations and in amounts needed to reduce the charge levels selectively at the locations to a level falling within the range between the referenced minimum and maximum levels.

Claim 21

The apparatus according to claim 18 and wherein the light source means comprises a bank of lamps arranged in rows, extending in the second direction, and in columns, extending in the first direction, and each column of lamps is associated with and overlies a specific transverse location on the photoconductor and wherein the third means selectively controls the number of rows of lamps which will be illuminated in each column in response to the level of charge measured by the measuring means for the respective transverse location.

Claim 22

The apparatus according to claim 19 wherein the first means causes the measuring means to again measure the level of charge at each of the plural number of locations to check the results of operation of the charge-reducing means and if the level of charge at any location is greater than the referenced maximum level the third means again adjusts the charge-reducing means to selectively reduce the charge level at each of those locations measured to have a level of charge greater than the referenced maximum level and wherein the first means and the third means are operated iteratively until the charge level at each of the locations is measured to be no higher than the referenced maximum level.

Claim 23

The apparatus according to claim 20 and wherein the first means and the third means are operated iteratively until the charge level at each of the locations is greater than the referenced minimum level.

Claim 24

In a method for depositing an electrostatic charge on an area of a surface so that the level of charge on the surface is suitable for forming an electrostatic latent image upon exposure to image-bearing radiation, the method inculding the steps of moving the surface in a first direction past a charging station and depositing charge on the surface; measuring the level of charge deposited on the surface; adjusting the level of charge on the surface to a referenced level; and the improvement which comprises: wherein in the step of measuring, measurements are made of the level of charge at each of a plural number of locations lying across the surface in a second direction transverse to the first direction; and wherein in the charge-adjusting step, the charge level is selectively adjusted at each of the locations having a level of charge differing from the referenced level in accordance with the charge level measurement for each such transverse location and the referenced level so as to produce a more generally uniform charge over the area.

Claim 25

In a method for depositing an electrostatic charge on an area of a surface so that the level of charge on the surface is suitable for forming an electrostatic latent image upon exposure to image-bearing radiation, the method inculding the steps of moving the surface in a first direction past a charging station and depositing charge on the surface; measuring the level of charge deposited on the surface; adjusting the level of charge on the surface to a referenced level; and the improvement which comprises: wherein in the step of measuring, measurements are made of the level of charge at each of a plural number of locations lying across the surface in a second direction transverse to the first direction; and wherein in the charge-adjusting step, the charge level is selectively adjusted at each of the locations having a level of charge differing from the referenced level in accordance with the charge level measurement for each such transverse location and the referenced level so as to produce a more generally uniform charge over the area.

Claim 26

The method according to claim 22 and including the steps of comparing a measured charge level for each of the locations with a referenced minimum level and adjusting the amount of charge deposited by said charging means on the area so that all points in the area have a level of charge greater than the referenced minimum level.

Claim 27

The method according to claim 23 and including the step of repeating iteratively the measuring, comparing, and charge-adjusting steps until the level of charge at each of the transverse locations is measured to be greater than the referenced minimum level.

Claim 28

The method according to claim 24 and wherein the steps of measuring and charge-adjusting are repeated iteratively until the level of charge at each transverse location is no greater than the referenced maximum level.

Claim 29

The method according to claim 23 and wherein the charging station charges the surface with a negative charge.

Claim 30

The method according to claim 22 wherein the surface is a photoconductor and the charge-adjusting step employs light to differentially reduce charge on the photoconductor.

Claim 31

The method of claim 23 and wherein measurements are made at each of a plural number of locations lying in the first direction and wherein in the charge adjusting step the charge level is selectively adjusted at each of the locations having a level of charge differing from the referenced level in accordance with the charge level measurement for such longitudinal location and the referenced level.

Claim 32

In an electrophotographic reproducing apparatus having a moving electrostatically charged member on which developable electrostatic images are formed, means for measuring the level of charge on the member and means for adjusting such level to a referenced level, the improvement which comprises: first means for positioning said measuring means to measure the levels of charge at each of a plural number of locations on the member spaced transversely in the direction of movement of the member, and to produce a signal representative of each such level; and second means responsive to each such signal and operatively associated with said adjusting means for selectively adjusting the charge level at transverse locations having a level of charge differing from the referenced level in accordance with the difference in charge level measurement for each such transverse location and the referenced level.

Claim 33

In an electrophotographic reproducing apparatus having a moving electrostatically charged member on which developable electrostatic images are formed, means for measuring the level of charge on the member and means for adjusting such level to a referenced level, the improvement which comprises: first means for positioning said measuring means to measure the levels of charge at each of a plural number of locations on the member spaced transversely in the direction of movement of the member, and to produce a signal representative of each such level; and second means responsive to each such signal and operatively associated with said adjusting means for selectively adjusting the charge level at transverse locations having a level of charge differing from the referenced level in accordance with the difference in charge level measurement for each such transverse location and the referenced level.

Claim 34

The apparatus of claim 29 wherein the member is a photoconductor and wherein the adjusting means and second means comprise light source means for providing exposure of said photoconductor to nonimaging light at locations and in amounts needed to reduce the charge levels selectively at the locations to a level falling within the range between referenced minimum and maximum levels.

Claim 35

The apparatus of claim 29 and wherein the adjusting means and second means comprise a plurality of point charging means arranged transversely to the direction of movement of the member for providing additional corona charge current to said member at locations and in amounts needed to add charge selectively at such locations to have the resultant charge at such locations fall within a range between a referenced minimum and maximum levels.

Claim 36

In an electrophotographic reproduction apparatus for moving along a path a web capable of retaining an electrostatic charge, and including means for adjusting such charges to a reference level, the improvement comprising: first means for detecting the levels of charge at spaced locations transverse to the direction of movement of the web and for producing signals representative of such levels; and second means responsive to such signals and operatively associated with said adjusting means for selectively adjusting the charge level, at each transverse location having a level of charge differing from the referenced level in accordance with the difference in charge level detected for each such transverse location and the referenced level.

Claim 37

In an electrophotographic reproduction apparatus for moving along a path a web capable of retaining an electrostatic charge, and including means for adjusting such charges to a reference level, the improvement comprising: first means for detecting the levels of charge at spaced locations transverse to the direction of movement of the web and for producing signals representative of such levels; and second means responsive to such signals and operatively associated with said adjusting means for selectively adjusting the charge level, at each transverse location having a level of charge differing from the referenced level in accordance with the difference in charge level detected for each such transverse location and the referenced level.

Claim 38

The apparatus of claim 32 wherein the web is a photoconductor and wherein the charge-reducing means and second means comprise light source means for providing exposure of said photoconductor to nonimaging light at locations and in amounts needed to reduce the charge levels selectively at the locations to a level falling within the range between the referenced minimum and maximum levels.

Claim 39

The apparatus of claim 32 and wherein the adjusting means and second means comprise a plurality of point charging means arranged transversely to the direction of movement of the member for providing additional corona charge current to said web at locations and in amounts needed to add charge selectively at such locations to have the resultant charge at such locations fall within a range between a referenced minimum and maximum levels.

Claim 40

The apparatus of claim 34 wherein the corona charge current has a negative charge.

Claim 41

In an electrophotographic reproducing apparatus having an electrostatically charged photoconductive member on which developable electrostatic images are to be formed on an image area of the member, means for measuring the level of charge on the member and adjusting means for providing signals for adjusting for nonuniformities in such level to a reference level representing a maximum charge level for points in the image area, the improvement which comprises: means for forming a narrow beam of radiation for exposure of the member on a point-by-point basis; means for impinging the beam upon the member at selected points; and means for modulating the beam on a point-by-point basis with electrical image information signals representing an image to be formed on the member and with signals for adjusting the level of charge on the member to the reference level to form a latent electrostatic image on the member with nonuniformities of charge adjusted at points not otherwise to receive an exposure based on image information signals for such points.

Claim 42

In an electrophotographic reproducing apparatus having an electrostatically charged photoconductive member on which developable electrostatic images are to be formed on an image area of the member, means for measuring the level of charge on the member and adjusting means for providing signals for adjusting for nonuniformities in such level to a reference level representing a maximum charge level for points in the image area, the improvement which comprises: means for forming a narrow beam of radiation for exposure of the member on a point-by-point basis; means for impinging the beam upon the member at selected points; and means for modulating the beam on a point-by-point basis with electrical image information signals representing an image to be formed on the member and with signals for adjusting the level of charge on the member to the reference level to form a latent electrostatic image on the member with nonuniformities of charge adjusted at points not otherwise to receive an exposure based on image information signals for such points.

Claim 43

The apparatus of claim 36 and wherein the scanning means scans the beam in point-by-point fashion across the image area of the member providing exposure at certain points in accordance with the image information signals; and the modulating means, at points on the image area of the member where no exposure is required by the image information signals, modulates the beam with signals for adjusting the level of charge on the member to the reference level.

Claim 44

The apparatus of claim 36 and including means for moving the member in a first direction and wherein the measuring means measures the levels of charge at a plural number of locations on the member spaced in a direction transverse to the first direction.

Claim 45

The apparatus of claim 38 and wherein the adjusting means and the modulating means cooperate to selectively adjust the charge level at points in transverse locations having a respective level of charge differing from the reference level in accordance with the difference in charge level measurement for each such transverse location and a referenced level.

Claim 46

The apparatus of claim 39 and including a corona charging station for charging the image area of the member with a negative electrostatic charge at least to a level suitable for forming developable electrostatic latent image.

Claim 47

In an electrophotographic reproduction apparatus including a photoconductive member having an image area upon which a developable electrostatic latent image may be formed; means for charging the image area with an electrostatic charge to a level greater than a reference level, said reference level representing a maximum nominal charge level for developing an image on the area; means for exposing the charged area to image-bearing radiation by scanning the area in point-by-point fashion with a narrow beam of radiation modulated with imaging information to form the latent image by discharging selected points in the area to charge levels substantially lower than the reference level; the improvement which comprises: means for modulating the beam with signals related to the difference between the level of charge applied to the member and the reference level to reduce the charge level to the reference level at points in the image area not selected for said discharging.

Claim 48

In an electrophotographic reproduction apparatus including a photoconductive member having an image area upon which a developable electrostatic latent image may be formed; means for charging the image area with an electrostatic charge to a level greater than a reference level, said reference level representing a maximum nominal charge level for developing an image on the area; means for exposing the charged area to image-bearing radiation by scanning the area in point-by-point fashion with a narrow beam of radiation modulated with imaging information to form the latent image by discharging selected points in the area to charge levels substantially lower than the reference level; the improvement which comprises: means for modulating the beam with signals related to the difference between the level of charge applied to the member and the reference level to reduce the charge level to the reference level at points in the image area not selected for said discharging.

Claim 49

In a method for forming a developable electrostatic latent image on an image area of a photoconductive member, the method including the steps of charging the area with an electrostatic charge to a level greater than a reference level, said reference level representing a maximum nominal charge level for developing an image on the area and exposing the charged area to image-bearing radiation by scanning the area in point-by-point fashion with a narrow beam of radiation modulated with imaging information to form the image by discharging selected points in the area to charge levels substantially lower than the reference level, the improvement which comprises the step of: modulating the beam with signals related to the difference between the level of charge applied to the area and the reference level to reduce the charge level to the reference level at points in the area not selected for said discharging.

Claim 50

In a method for forming a developable electrostatic latent image on an image area of a photoconductive member, the method including the steps of charging the area with an electrostatic charge to a level greater than a reference level, said reference level representing a maximum nominal charge level for developing an image on the area and exposing the charged area to image-bearing radiation by scanning the area in point-by-point fashion with a narrow beam of radiation modulated with imaging information to form the image by discharging selected points in the area to charge levels substantially lower than the reference level, the improvement which comprises the step of: modulating the beam with signals related to the difference between the level of charge applied to the area and the reference level to reduce the charge level to the reference level at points in the area not selected for said discharging.

Claim 51

In a method for forming a developable electrostatic latent image on an image area of an electrostatically charged photoconductive member, the method including the steps of measuring the level of charge on the member and adjusting the level to a predetermined reference level, said reference level representing a maximum nominal charge level for developing an image on the area, the improvement which comprises: scanning a narrow beam of radiation on the member; and modulating the beam when scanning the member with first signals representing an image to be formed on the member and with second signals for adjusting the level of charge on the member to the reference level to form a latent electrostatic image on the member.

Claim 52

In a method for forming a developable electrostatic latent image on an image area of an electrostatically charged photoconductive member, the method including the steps of measuring the level of charge on the member and adjusting the level to a predetermined reference level, said reference level representing a maximum nominal charge level for developing an image on the area, the improvement which comprises: scanning a narrow beam of radiation on the member; and modulating the beam when scanning the member with first signals representing an image to be formed on the member and with second signals for adjusting the level of charge on the member to the reference level to form a latent electrostatic image on the member.

Claim 53

The method of claim 43 and wherein in the scanning step the beam scans in point-by-point fashion across the image area of the member providing full exposure at certain points and no or less than full exposure at other points in accordance with the first signals and wherein at points on the image area of the member where no or less than full exposure is required by the first signals the beam is modulated with the second signals and adjusts the level of charge on the member to the reference level.

Claim 54

The method of claim 43 and wherein the member is moved in a first direction and in the step of measuring, measurements are made of the levels of charge at a plural number of locations on the member spaced in a direction transverse to the first direction.

Claim 55

The method of claim 45 and wherein the second signals modulate the beam to selectively adjust the charge levels at points in transverse locations having a respective level of charge for the location differing from the reference level.

Claim 56

The method of claim 45 and wherein the charged member is charged with a negative electrostatic charge at least to a level suitable for forming a developable electrostatic latent image.

Claim 57

The method of claim 43 and wherein in the step of measuring the measurements are made along both longitudinal and transverse tracks on the member and data for charge level at a location in a particular longitudinal track and transverse track is stored and wherein each of the second signals are generated in response to a position signal indicating the beam is to expose a location representing the intersection of a longitudinal and transverse track for which a charge level measurement is made.

Claim 58

In an electrophotographic reproducing apparatus having an electrostatically charged photoconductive member on which developable electrostatic images are to be formed on an image area of the member, means for measuring the level of charge on the member and adjusting means for providing signals for adjusting such level to a reference level, said reference level representing a maximum nominal charge level for use in developing an image on the area, the improvement which comprises: first means for forming a narrow beam of radiation and exposing the member to such beam; and second means for modulating the beam when exposing the member with electrical image information signals representing an image to be formed on the member and with electrical signals for adjusting the level of charge on the member to the reference level to form a latent electrostatic image on the member.

Claim 59

In an electrophotographic reproducing apparatus having an electrostatically charged photoconductive member on which developable electrostatic images are to be formed on an image area of the member, means for measuring the level of charge on the member and adjusting means for providing signals for adjusting such level to a reference level, said reference level representing a maximum nominal charge level for use in developing an image on the area, the improvement which comprises: first means for forming a narrow beam of radiation and exposing the member to such beam; and second means for modulating the beam when exposing the member with electrical image information signals representing an image to be formed on the member and with electrical signals for adjusting the level of charge on the member to the reference level to form a latent electrostatic image on the member.

Claim 60

The apparatus of claim 49 and wherein the first means exposes the member in point-by-point fashion across the image area of the member providing exposure at certain points in accordance with the image information signals; and the second means, at points on the image area of the member where no exposure is required by the image information signals, modulates the beam with signals for adjusting the level of charge on the member to the reference level.

Claim 61

The apparatus of claim 49 and including means for moving the member in a first direction and wherein the measuring means measures the levels of charge at a plural number of locations on the member spaced in a direction transverse to the first direction.

Claim 62

The apparatus of claim 51 and wherein the adjusting means and the second means cooperate to selectively adjust the charge level on the member at points in transverse locations having a respective level of charge differing from the reference level in accordance with the difference in charge level measurement for each such transverse location and the reference level.

Claim 63

The apparatus of claim 52 and including a corona charging station for charging the image area of the member with a negative electrostatic charge at least to a level suitable for forming a developable electrostatic latent image.

Claim 64

In an electrophotographic reproduction apparatus including a photoconductive member having an image area upon which a developable electrostatic latent image may be formed; means for charging the image area with an electrostatic charge to a level greater than a reference level, said reference level representing a maximum nominal charge level for developing an image on the area; means for exposing the charged area to image-bearing radiation by exposing the area in point-by-point fashion with a narrow beam of radiation modulated with imaging information to form the latent image by discharging selected points in the area to charge levels substantially lower than the reference level; the improvement which comprises: means for modulating the beam with signals related to the difference between the level of charge applied to the member and the reference level to reduce the charge level to the reference level at points in the image area receiving substantially no image exposure.

Claim 65

In an electrophotographic reproduction apparatus including a photoconductive member having an image area upon which a developable electrostatic latent image may be formed; means for charging the image area with an electrostatic charge to a level greater than a reference level, said reference level representing a maximum nominal charge level for developing an image on the area; means for exposing the charged area to image-bearing radiation by exposing the area in point-by-point fashion with a narrow beam of radiation modulated with imaging information to form the latent image by discharging selected points in the area to charge levels substantially lower than the reference level; the improvement which comprises: means for modulating the beam with signals related to the difference between the level of charge applied to the member and the reference level to reduce the charge level to the reference level at points in the image area receiving substantially no image exposure.

Claim 66

In a method for forming a developable electrostatic latent image on an image area of a photoconductive member, the method including the steps of charging the area with an electrostatic charge to a level greater than a reference level, said reference level representing a maximum nominal charge level for developing an image on the area, exposing the charged area to image-bearing radiation by exposing the area in point-by-point fashion with a narrow beam of radiation modulated with imaging information to form the image by discharging selected points in the area to charge levels substantially lower than the reference level and the improvement which comprises the step of: modulating the beam with signals related to the difference between the level of charge applied to the area and the reference level to reduce the charge level to the reference level at points in the area not selected for said discharging.

Claim 67

In a method for forming a developable electrostatic latent image on an image area of a photoconductive member, the method including the steps of charging the area with an electrostatic charge to a level greater than a reference level, said reference level representing a maximum nominal charge level for developing an image on the area, exposing the charged area to image-bearing radiation by exposing the area in point-by-point fashion with a narrow beam of radiation modulated with imaging information to form the image by discharging selected points in the area to charge levels substantially lower than the reference level and the improvement which comprises the step of: modulating the beam with signals related to the difference between the level of charge applied to the area and the reference level to reduce the charge level to the reference level at points in the area not selected for said discharging.

Claim 68

In a method for forming a developable electrostatic latent image on an image area of an electrostatically charged photoconductive member, the method including the steps of measuring the level of charge on the member and adjusting the level to a reference level suitable for developing selected points of the image area receiving substantially no image exposure, the improvement which comprises: exposing a narrow beam of radiation on the member; and modulating the beam, when exposing the member, with first signals representing an image to be formed on the member and with second signals for adjusting the level of charge on the member to the reference level to form a latent electrostatic image on the member.

Claim 69

In a method for forming a developable electrostatic latent image on an image area of an electrostatically charged photoconductive member, the method including the steps of measuring the level of charge on the member and adjusting the level to a reference level suitable for developing selected points of the image area receiving substantially no image exposure, the improvement which comprises: exposing a narrow beam of radiation on the member; and modulating the beam, when exposing the member, with first signals representing an image to be formed on the member and with second signals for adjusting the level of charge on the member to the reference level to form a latent electrostatic image on the member.

Claim 70

The method of claim 56 and wherein in the exposing step the beam exposes in point-by-point fashion, the image area of the member providing full exposure at certain points and no or less than full exposure at other points in accordance with the first signals and wherein at points on the image area of the member where no or less than full exposure is required by the first signals the beam is modulated with the second signals and adjusts the level of charge on the member to the reference level.

Claim 71

The method of claim 56 and wherein the member is moved in a first direction and in the step of measuring, measurements are made of the levels of charge at a plural number of locations on the member spaced in a direction transverse to the first direction.

Claim 72

The method of claim 58 and wherein the second signals modulate the beam to selectively adjust the charge levels at points in transverse locations having a respective level at points in transverse locations having a respective level of charge for the location differing from the reference level in accordance with the difference in charge level measurement for each such transverse location and the referenced level.

Claim 73

The method of claim 59 and wherein the member is charged with a negative electrostatic charge at least to a level suitable for forming a developable electrostatic latent image.

Claim 74

In a method for depositing an electrostatic charge on an area of a surface so that the level of charge on the surface is suitable for forming an electrostatic latent image upon exposure to image-bearing radiation, the method including the steps of moving the surface in a first direction past a charging station and depositing charge on the surface, measuring the level of charge deposited on the surface; adjusting the level of charge on the surface to a referenced level; and the improvement which comprises: wherein in the step of measuring, measurements are made of the level of charge at each of a plural number of locations lying across the surface in a second direction transverse to the first direction; and wherein in the charge-adjusting step the photoconductor is exposed simultaneously at the same location to light that is modulated in accordance with image information for forming the latent image and to charge-reducing information for selectively reducing the charge at the location in accordance with a difference between the respective measurement of the level of charge for the particular location and the referenced level.

Claim 75

In a method for depositing an electrostatic charge on an area of a surface so that the level of charge on the surface is suitable for forming an electrostatic latent image upon exposure to image-bearing radiation, the method including the steps of moving the surface in a first direction past a charging station and depositing charge on the surface, measuring the level of charge deposited on the surface; adjusting the level of charge on the surface to a referenced level; and the improvement which comprises: wherein in the step of measuring, measurements are made of the level of charge at each of a plural number of locations lying across the surface in a second direction transverse to the first direction; and wherein in the charge-adjusting step the photoconductor is exposed simultaneously at the same location to light that is modulated in accordance with image information for forming the latent image and to charge-reducing information for selectively reducing the charge at the location in accordance with a difference between the respective measurement of the level of charge for the particular location and the referenced level.

Claim 76

The method according to claim 61 and wherein the light comprises emissions from a laser that is scanned across the photoconductor.

Claim 77

In an electrophotographic reproducing apparatus having a moving electrostatically charged photoconductive member on which developable electrostatic images are formed, means for measuring the level of charge on the member and means for adjusting the level to a referenced level, the improvement which comprises: first means for positioning said measuring means to measure the levels of charge at a plural number of locations on the member spaced transversely in the direction of movement of the member, and to produce signals representative of such levels; and second means responsive to such signals and operatively associated with said adjusting means for selectively adjusting the charge level at transverse locations having a level of charge differing from the referenced level; and wherein said adjusting means and second means comprise: means for producing a laser beam; means for scanning the beam transversely across the photoconductive member; and means for modulating the beam when scanning each location with signals representing an image to be formed on the photoconductor at the location and signals representing a difference between the respective level of charge measured for said location and the referenced level.

Claim 78

In an electrophotographic reproducing apparatus having a moving electrostatically charged photoconductive member on which developable electrostatic images are formed, means for measuring the level of charge on the member and means for adjusting the level to a referenced level, the improvement which comprises: first means for positioning said measuring means to measure the levels of charge at a plural number of locations on the member spaced transversely in the direction of movement of the member, and to produce signals representative of such levels; and second means responsive to such signals and operatively associated with said adjusting means for selectively adjusting the charge level at transverse locations having a level of charge differing from the referenced level; and wherein said adjusting means and second means comprise: means for producing a laser beam; means for scanning the beam transversely across the photoconductive member; and means for modulating the beam when scanning each location with signals representing an image to be formed on the photoconductor at the location and signals representing a difference between the respective level of charge measured for said location and the referenced level.

Claim 79

In an electrophotographic reproduction apparatus for moving along a path a photoconductive web capable of retaining an electrostatic charge, and including means for adjusting such charges to a referenced level, the improvement comprising: first means for measuring the level of charge at each of several spaced locations transverse to the direction of movement of the web and for producing a signal representative of each measurement; second means responsive to the respective signal representing the level of charge at a particular transverse location and operatively associated with said adjusting means for selectively adjusting the charge level, at each respective transverse location having a level of charge differing from the referenced level; and wherein said adjusting means and second means comprise: means for forming a laser beam; means for scanning the beam transversely across the photoconductive web; and means for modulating the beam when scanning each location with signals representing an image to be formed on the photoconductor at the respective location and respective signals representing a difference between the level of charge measured for said location and the referenced level.

Claim 80

In an electrophotographic reproduction apparatus for moving along a path a photoconductive web capable of retaining an electrostatic charge, and including means for adjusting such charges to a referenced level, the improvement comprising: first means for measuring the level of charge at each of several spaced locations transverse to the direction of movement of the web and for producing a signal representative of each measurement; second means responsive to the respective signal representing the level of charge at a particular transverse location and operatively associated with said adjusting means for selectively adjusting the charge level, at each respective transverse location having a level of charge differing from the referenced level; and wherein said adjusting means and second means comprise: means for forming a laser beam; means for scanning the beam transversely across the photoconductive web; and means for modulating the beam when scanning each location with signals representing an image to be formed on the photoconductor at the respective location and respective signals representing a difference between the level of charge measured for said location and the referenced level.

Claim 81

An electrostatographic reproduction apparatus which comprises: a member having a surface upon which an electrostatic latent image may be formed; means for charging the surface with a primary electrostatic charge; means for moving the surface relative to the charging means in a first direction; means for measuring the primary electrostatic charge level and providing first signals relative to the measurement of the charge level and second signals associated with the location of the reading relative to a reference spaced from said location in said direction of movement of the member; and means responsive to said first and second signals for reducing the primary charge level at selected points to a reference level to provide a more uniform electrostatic charge; means for forming an electrostatic latent image on the member; and means for developing the latent image.

Claim 82

An electrostatographic reproduction apparatus which comprises: a member having a surface upon which an electrostatic latent image may be formed; means for charging the surface with a primary electrostatic charge; means for moving the surface relative to the charging means in a first direction; means for measuring the primary electrostatic charge level and providing first signals relative to the measurement of the charge level and second signals associated with the location of the reading relative to a reference spaced from said location in said direction of movement of the member; and means responsive to said first and second signals for reducing the primary charge level at selected points to a reference level to provide a more uniform electrostatic charge; means for forming an electrostatic latent image on the member; and means for developing the latent image.