Electrophotographic reproduction apparatus and method with selective screening

• US 4,740,818 A
• Filed: 12/11/1986
• Issued: 04/26/1988
• Est. Priority Date: 12/16/1985
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Smith, Dale, Hockey, David E., Day, Pierce B., Roztocil, Tomas, Swapceinski, John P., Steeves, John L., Tsilibes, George N.
• Primary Examiner(s): Moses, R. L.
• Application Number:
  US06/940,694
• Time in Patent Office: 502 Days
• Field of Search: 355/14 E, 355/14 R, 355/4, 355/7, 355/3 R, 355/77, 355/67, 355/71, 430/31, 430/396, 430/494, 358/283
• US Class Current: 399/181
• CPC Class Codes: G03G 15/04027 and forming half-tone image

Abstract

An electrophotographic reproduction apparatus and method are provided for reproducing an original document sheet that includes a continuous tone pictorial information area and a line-type information area. Rather than reproducing the entire document sheet with screening of both types of information, means are provided for selectively screening only the pictorial information area on the reproduction. The means of one preferred embodiment comprises a programmable illumination source that is programmed through inputs by the operator using a digitizing tablet to selectively image portions of a screen onto a charged photoconductive web prior to development of the electrostatic image formed on the web so that only the area on the web receiving the pictorial image is exposed to the screen. In another embodiment the programmable illumination source, such as LED'"'"'s, modulates the portion of the image frame receiving an optical exposure of the pictorial information with the screen type exposure so that the pictorial information only is reproduced with a screen pattern. In still another embodiment a sensor automatically senses and determines the image portions to be selectively screened.

Claims

1. In a method for electrophotographically reproducing an original document sheet having a continuous tone image on an area portion thereof wherein the image is to be reproduced as a halftone reproduction, the method including the steps of supporting the original document sheet at an exposure station, illuminating the original document sheet, imaging light reflected from or transmitted through the original document sheet onto a photoconductive member to form a developable electrostatic latent image of the document on an area of the photoconductive member;

and the improvement which comprises;

(a) providing signals related to the position of the continuous tone image area relative to a reference element; and

(b) forming in response to said signals an electrostatic latent halftone pattern image on the portion of the area of the photoconductive member which is to form the reproduction of the continuous tone image area.

2. The method according to claim 1 wherein the original document sheet also includes areas of line-type information and wherein a developable electrostatic latent image of this type of information is recorded on the photoconductive member on areas thereof not modulated by an electrostatic halftone pattern image.

3. The method according to claim 2 and including the step of developing the developable electrostatic latent images using opaque electroscopic toner and transferring the images to a copy sheet to provide on the copy sheet a halftone screened reproduction of the continuous tone image and a reproduction of the line-type information that is not modulated with a halftone pattern.

4. The method according to claim 3 and including the step of providing and storing signals related to the position of the original document sheet in a multi-sheet document stack, reproducing the multi-sheet document by moving serially the sheets of the multi-sheet document from a stack to an exposure platen, and then to a stack, counting the number of documents moved to the exposure platen and reproducing the aforesaid original document sheet in response to said count and the stored signals relating the position of the original document sheet in the stack.

5. The method according to claim 3 and wherein the photoconductive member is moved in a predetermined direction and the latent halftone pattern image is formed in step (b) by illuminating a source of illumination, independent of imaging light reflected from or transmitted through the original document sheet, through a halftone screen.

6. The method according to claim 5 and wherein the original document sheet includes more than one area of continuous tone images whose images are to be reproduced on different areas of the photoconductive member and including the step of selectively varying the exposures of the halftone pattern images by said source of illumination to provide different exposures of the latent halftone patterns formed on the areas of the photoconductive member.

7. The method according to claim 5 and including the step (c) wherein the source of illumination is activated to provide illumination of a spectral content that is substantially transparent to the halftone screen to substantially erase charge from a selected area of the photoconductive member to provide substantially no developable halftone pattern image in said selected area and wherein in step (b) the source of illumination is activated to provide illumination of a substantially different spectral content from that in step (c).

8. The method according to claim 7 and wherein the selected area is an interframe area on the photoconductive member.

9. The method according to claim 5 and wherein the halftone screen is movable between its position in step (b) to another position where it does not block illumination from the source of illumination and including the step (c) of providing signals related to the position of a different area on the photoconductive member that is to be erased of charge so as to form substantially no developable halftone image pattern in said different area and (d) maintaining the screen in said another position while illuminating the source of illumination to erase charge from the different area so as to form substantially no developable halftone image pattern in said different area.

10. The method according to claim 9 and wherein the different area is an interframe area on the photoconductive member.

11. The method according to claim 1 wherein the photoconductive member is moved in a predetermined direction and the latent halftone pattern image is formed in step (b) by illuminating a source of illumination, independent of imaging light reflected from or transmitted through the original document sheet, through a halftone screen.

12. The method according to claim 11 and including the step of (c) wherein the source of illumination is activated to provide illumination of a spectral content that is substantially transparent to the halftone screen to substantially erase charge from a selected area of the photoconductive member to provide substantially no developable halftone pattern image in said selected area and wherein in step (b) the source of illumination is activated to provide illumination of a substantially different spectral content from that in step (c).

13. The method according to claim 12 wherein the selected area is an interframe area on the photoconductive member.

28. The method according to any one of claims 1, 2, 3, 4, 14 or 24 and wherein the latent halftone pattern image is formed by exposing the photoconductive member to a selected point light source(s) to form a simulated latent halftone pattern image without light from said point light sources passing through a screen pattern.

29. The method of claim 28 and wherein the frequency of light output(s) is modulated in accordance with the member'"'"'s movement.

14. In a method for electrophotographically reproducing an original document sheet having a continuous tone pictorial image information content on an area thereof and image information content of another kind that is of non-continuous tone such as line-type information, the method including the steps of (a) exposing a photoconductive member having an electrostatiac charge thereon to light modulated with information of the original document sheet to form a developable latent electrostatic image of the information on the document sheet, (b) separately exposing the photoconductive member to light modulated by a halftone screen pattern before, during or subsequent to said first exposing step to form a screened latent electrostatic image of the halftone screen pattern only in those areas of the photoconductive member which comprise reproductions of continuous tone information found in the original document, (c) developing the latent electrostatic image, and (d) transferring the developed image to a copy sheet.

15. In an electrophotographic reproduction apparatus for reproducing an original document sheet having a continuous tone image on a portion thereof wherein the image is to be reproduced as a halftone reproduction, the apparatus including means for supporting the original document sheet at an exposure station, means including a photoconductive member for forming a developable electrostatic latent image when subjected to imaging radiation from the original document sheet;

means for illuminating the original document sheet and for imaging light from the original document sheet onto an area of the photoconductive member; and

the improvement which comprises;

first means providing signals related to the position of the continuous tone image area relative to a reference element on the original document sheet; and

programmable second means responsive to said signals for forming a developable electrostatic latent halftone pattern image on the portion of the area of the photoconductive member which is to form the reproduction of the continuous tone image area.

16. The apparatus according to claim 15 and including means for providing and storing signals related to the position of the original document sheet in a multi-sheet document stack, means for moving serially the sheets of the multi-sheet document to an exposure platen from a stack to an exposure platen and then to a stack, means for counting the number of documents moved to the exposure platen, and means for reproducing the aforesaid original document sheet in response to said count and the stored signals relating to the position of the original document sheet in the stack.

17. The apparatus according to claim 15 and wherein the original document sheet includes more than one area of continuous tone images whose images are to be reproduced on different areas of the photoconductive member and the programmable means includes means for selectively varying the exposures of the halftone pattern images on the photoconductive member to provide different exposure os the latent halftone patterns formed on the areas of the photoconductive member.

18. The apparatus according to claim 17 and wherein the means for selectively varying the exposures of the halftone pattern images comprises illumination means independent of the means for illuminating the original document sheet.

19. The apparatus according to claim 18 and including means for moving the photoconductive member in a predetermined direction and wherein the illumination means comprises a group of light emitting points arranged transversely to the direction of movement of the member;

and wherein the programmable means selectively illuminates the photoconductive member in response to said signals.

20. The apparatus according to claim 19 and wherein the photoconductive member includes a halftone screen integral therewith.

21. The apparatus according to claim 15 and including means for moving the photoconductive member in a predetermined direction and the programmable means includes illumination means for illuminating a halftone pattern on the portion of the photoconductive member which is to form the reproduction of the continuous tone image area, the illumination means comprising a group of light emitting points arranged transversely to the direction of movement of the photoconductive member;

and the programmable means selectively illuminates the photoconductive member in response to said signals.

22. The apparatus according to claim 21 and wherein the photoconductive member includes a halftone screen integral therewith.

23. The apparatus according to claim 21 and wherein the first means comprises a digitizing tablet.

24. The apparatus according to claim 19 and wherein the first means comprises a digitizing tablet.

25. The apparatus according to claim 15 and wherein the first means comprises a digitizing tablet.

26. The apparatus according to claims 15, 18, or 27 and including means for moving the photoconductive member in a predetermined direction and the programmable means includes point source exposing means for generating a simulated latent halftone pattern image without light from said point source exposing means passing through a screen.

27. The apparatus according to claim 26 and wherein the point source means exposing means comprises a series of light emitting point sources capable of forming a series of uniformly spaced exposed pixel areas that lie along a line transverse to the direction of the photoconductive member'"'"'s movement and the programmable means modulates the point sources with a frequency related to the member'"'"'s movement and the aforesaid spacing between pixel areas.

30. In a method for making electrophotographic reproductions, the method including the steps of providing from a first source light modulated with image information onto an electrostatically charged photoconductive member to form a developable electrostatic latent image of the image information on an area of the photoconductive member;

and the improvement which comprises;

(a) providing signals related to the position of an image area to be screened relative to a reference element; and

(b) forming in response to said signals an electrostatic latent halftone pattern image using a source independent of the first source on the portion of the area of the photoconductive member which is to form the reproduction of the image information to be screened.

31. The method according to claim 30 wherein the reproduction also includes areas of information that are not to be screened during the method of reproduction and wherein a developable electrostatic latent image of this type of information is recorded on the photoconductive member on areas thereof not modulated by an electrostatic halftone pattern image.

32. The method according to claim 31 and including the step of developing the developable electrostatic latent images using opaque electrostatic toner and transferring the images to a copy sheet to provide on the copy sheet a halftone screen reproduction of the information to be screened and a reproduction of information that is not modulated with a halftone pattern during the method of reproduction.

33. The method according to claim 31 and wherein the photoconductive member includes an integral halftone screen pattern and the latent halftone pattern image is formed in step (b) by illuminating a source of illumination, independent of imaging light reflected from or transmitted through the original document sheet, through the halftone screen.

34. In an apparatus for making electrophotographic reproductions from an electrostatically charged photoconductive member for forming a developable electrostatic latent image when subjected to imaging radiation;

first means for exposing an area of the photoconductive member with light modulated with image information; and

the improvement which comprises;

means providing signals related to the position of an image area to be screened relative to a reference element; and

second means independent of the first means and responsive to said signals for forming a developable electrostatic latent halftone pattern image on the portion of the area of the photoconductive member which is to form the reproduction of the image information.

35. The apparatus according to claim 34 and including means for moving the photoconductive member in a predetermined direction and the second means includes point source exposing means for generating a simulated latent halftone pattern image without light from said point source exposing means passing through a screen.

36. The apparatus according to claim 35 and wherein the point source means exposing means comprises a series of light emitting point sources capable of forming a series of uniformly spaced exposed pixel areas that lie along a line transverse to the direction of the photoconductive member'"'"'s movement and the programmable means modulates the point sources with a frequency related to the member'"'"'s movement and the aforesaid spacing between pixel areas.

37. In a method for electrophotographically reproducing an original document sheet having a multicolor continuous tone image on an area portion thereof within the image is to be reproduced as a halftone reproduction, the method including the steps of supporting the original document sheet at an exposure station, repeatedly illuminating the original document sheet, imaging light reflected from or transmitted through the original documet sheet onto a photoconductive member to form a plurality of developable electrostatic latent color-separation images of the document sheet on different image frames of the photoconductive member;

and the improvement which comprises;

(a) providing signals related to the position of the continuous tone image area relative to a reference element on the original document sheet; and

(b) forming in response to said signals electrostatic latent halftone-pattern color separation images on the portions of the image frames which are to form the reproductions of the continuous tone image area.

38. The method according to claim 37 wherein the original document sheet also includes areas of line-type information and wherein developable electrostatic latent images of this type of information are recorded on the image frames on areas thereof not modulated by an electrostatic halftone pattern image.

39. The method according to claim 38 and including the step of developing the developable electrostatic latent images using opaque electrostatic toners of different colors and transferring the images to a copy sheet to provide on the copy sheet a multicolor halftone screened reproduction of the continuous tone image and a reproduction of the line-type information that is not modulated with a halftone pattern.

40. The method according to claim 37 and wherein the photoconductive member is moved in a predetermined direction and the latent halftone pattern images are formed in step (b) by illuminating a source of illumination, independent of imaging light reflected from or transmitted through the original document sheet, through a halftone screen.

41. The method according to claim 40 and wherein the original document sheet includes more than one are of continuous tone images whose images are to be reproduced on different areas of an image frame and including the step of selectively varying the exposures of the halftone pattern images by said source of illumination to provide different exposures of the latent halftone patterns formed on the image frame.

42. The method according to claim 37 and wherein in step (a) the document sheet is automatically scanned to determine the relative position(s) of areas of continuous tone information on the document sheet.

43. In a method for making electrophotograhic reproductions, the method including the steps of (a) exposing a plurality of image frames of a photoconductive member having a electrostatic charge thereon to image forming illumination to form a plurality of developable latent color separation electrostatic images of the information to be reproduced which includes information that is to be reproduced with a screen pattern and information that is not to be reproduced with a screen pattern, (b) separately exposing at least some of the same image frames to light modulated by a halftone screen pattern before, during or subsequent to said first exposing step to form a screened latent electrostatic images of the halftone screen pattern only in those areas of each image frame which are to reproduce the information that is to be reproduced with the screen pattern;

and (c) developing the latent electrostatic images using toners of different colors and (d) transferring the developed images to a copy sheet.

44. In a method for electrophotographically reproducing an original document having a continuous tone image on an area thereof, wherein the image is to be reproduced as a halftone reproduction, the method including the steps of supporting the original document at an exposure station, illuminating the original document, imaging light reflected from or transmitted through the original document onto a photoconductive member to form a developable electrostatic latent image of the document on a predetermined area of the photoconductive member;

developing the developable image and the improvement which comprises;

automatically sensing the relative position(s) of areas of continuous tone information on the document and generating signals relative thereto; and

forming in response to said signals an electrostatic latent halftone pattern image on the portion(s) of the predetermined area(s) which is (are) to form the reproduction(s) of the continuous tone image area(s).

45. The method according to claim 44 wherein the original document sheet includes areas of line-type or alphanumeric information and wherein a developable electrostatic latent image of this type of information is recorded on the photoconductive member on areas thereof not modulated by an electrostatic halftone screen pattern image.

46. The method according to claim 45 and including the step of developing the developable electrostatic latent images using opaque electrostatic toner and transferring the images to a copy sheet to provide on the copy sheet a reproduction having a halftone reproduction of an image and a reproduction of line-type or alphanumeric information that has not been modulated with a halftone screen pattern image.

47. In a method for electrophotographically reproducing an original document sheet having both a continuous tone image information content on an area thereof and image information content of another kind that is of non-continuous tone such as line-type information, the method including the steps of:

a. illuminating the original document sheet;

b. exposing a photoconductive member having a uniform electrostatic charge thereon to light reflected from or transmitted through the original document sheet to form a developable latent electrostatic image of the information on the document sheet;

c. exposing the photoconductive member to light modulated by a halftone screen pattern before, during or subsequent to said first exposing step to form a screened latent electrostatic image of the information on the document sheet;

d. developing the latent electrostatic image, and

e. transferring the developed image to a copy sheet, the improvement which comprises;

the step of automatically sensing the relative position(s) of areas of continuous tone information, on the document sheet and generating signals relative thereto and

wherein in step c., the electrostatic latent image is formed, in response to said signals, with a halftone screen pattern only in those areas which comprise reproductions of continuous tone information found in the original document sheet.

48. In an electrophotographic reproduction apparatus for reproducing an original document sheet having a continuous tone image on an area thereof wherein the image is to be reproduced as a halftone reproduction, the apparatus including means for supporting the original document sheet at an exposure station, means including a photoconductive member for forming a developable electrostatic latent image when subjected to imaging radiation from the original document sheet;

means for illuminating the original document sheet and for imaging light from the original document sheet onto a predetermined area of the photoconductive member to form the developable image;

means for developing the developable image and the improvement which comprises;

means for automatically sensing the relative positions of areas of continuous tone information on the document sheet and for generating signals relative thereto;

means responsive to said signals for forming a developable electrostatic latent halftone pattern image on the portion of the predetermined area which is to form the reproduction of the continuous tone image area.

49. The apparatus of claim 48 and wherein the sensing means comprises image sensing means for sensing illumination from the original document sheet.

50. The apparatus of claim 49 and wherein the apparatus includes means for illuminating the document sheet with a preflash prior to illuminating the document sheet with a mainflash and wherein the apparatus further includes means for developing a latent electrostatic image formed on the photoconductive member with the mainflash and not developing a latent electrostatic image formed on the photoconductive member with the preflash;

and wherein the sensing means senses the preflash illumination from the original document sheet.

51. The apparatus of claim 49 and wherein the automatic sensing means senses imaging illumination from the original document sheet that passes through the photoconductive member.

52. The apparatus of claim 48 and wherein the automatic sensing means senses the document sheet as it is being moved into the exposure station.

53. The apparatus of claim 48 and wherein the apparatus includes means for illuminating the document sheet with a preflash prior to illuminating the document sheet with a mainflash and wherein the apparatus further includes means for developing separate latent electrostatic images of the document sheet formed on the photoconductive member with the preflash and mainflash;

and wherein the sensing means senses the developed image on the photoconductive member when sensing the relative position(s) of areas of continuous tone information on the developed image made using the preflash.