Claims
- 1. An electrophotographic printing machine comprising:
an image-bearing member, having frame areas for receiving developed images, said frame areas separated by interframe areas; a charger for forming a latent image on said image-bearing member; a development station containing toner particles for developing said latent image so as to create a toner developed image on said image-bearing member, said toner image being created in said image frame area on an image-bearing member for subsequent transfer of said toner image to a receiver member; an optical detector for monitoring and measuring a low coverage of toner particles on said image-bearing member, said low coverage of toner particles relating to a background area of said toner image; a signal produced by said optical detector, representative of the coverage of toner particles on said image-bearing member; and a control device for controlling said electrophotographic printing machine when said low coverage of toner particles exceeds a certain coverage, said certain coverage including a threshold coverage and a pre-selected coverage.
- 2. An electrophotographic printing machine according to claim 1 wherein said low coverage of toner particles, relating to a background area of said toner image, monitored by said optical detector, is included in a control toner image control patch area on said imaging-bearing member, via toning of a control patch latent image by said development station, said control patch latent image toned by toner particles having a nature similar to said toner particles relating to said background area of said toner image, and said control patch area is located in an interframe area on said image-bearing member.
- 3. An electrophotographic printing machine according to claim 2, wherein said image-bearing member is movable so as to move said control toner image past said optical detector, and said development station toners said control patch latent image such that said control toner image includes a plurality of spaced toned strips, with said plurality of spaced toned strips being perpendicular to a direction of movement of said image-bearing member.
- 4. An electrophotographic printing machine according to claim 3, wherein said signal produced by detection of said plurality of spaced toned strips by said optical detector is a control AC signal.
- 5. An electrophotographic printing machine according to claim 4, wherein:
said control patch latent image is a plurality of mutually adjacent charged strips on said imaging member, said plurality of mutually adjacent charged strips being perpendicular to a direction of movement of said imaging member, each charged strip of said plurality of mutually adjacent charged strips having a predetermined width measured in said direction of movement of said imaging member; said plurality of mutually adjacent charged strips include a first number of charged strips each of which has a first charge density, said first charge density at a level to produce in said development station a first development electric field in a direction so as to inhibit toning by nominally charged toner particles; said plurality of mutually adjacent charged strips further include a second number of charged strips each of which has a second charge density, said second charge density at a level to produce in said development station a second development electric field in a direction so as to inhibit toning by nominally charged toner particles; said first charge density and said second charge density have differing magnitudes; said first number of charged strips and said second number of charged strips are mutually interleaved in alternating fashion, with associated electric fields there between; and said associated electric fields induce toning via dielectrophoretic forces so as to form said control toner image on said image-bearing member.
- 6. An electrophotographic printing machine according to claim 4, wherein said control device includes a synchronous detection circuit, and said control AC signal has a predetermined frequency, and wherein a reference AC signal, of a non-electrostatographic origin, is provided to said control device, said reference AC signal having a high signal-to-noise ratio and a reference frequency suitable for use with said predetermined frequency in a synchronous detection circuit, and said synchronous detection circuit produces a DC output having an amplitude proportional to said low coverage of toner particles.
- 7. An electrophotographic printing machine according to claim 4, further including a reference optical detector, and wherein said image-bearing member includes thereon a reference toner image formed in a reference patch area, via toning of a reference latent image by said development station, said reference patch area being located in an interframe area on said image-bearing member and is detected by said reference optical detector, said image-bearing member being movable to move said reference toner image past said reference optical detector so as to produce a reference signal, said reference toner image including a plurality of spaced toned reference strips perpendicular to a direction of movement of said image-bearing member, and said spaced toned reference strips of said reference toner image having a higher coverage of toner particles than said low coverage of toner particles.
- 8. An electrophotographic printing machine according to claim 7, wherein a reference AC signal results from detection by said reference optical detector of said plurality of spaced toned reference strips of said reference toner image.
- 9. An electrophotographic printing machine according to claim 8, wherein said background-control AC signal and said reference AC signal have a frequency in common and are substantially in phase one with the other.
- 10. An electrophotographic printing machine according to claim 9, wherein said control device further includes a signal-multiplying device, and said background-control AC signal and said reference AC signal are suitably filtered and multiplied in said signal-multiplying device so as to measure via synchronous detection a quantity proportional to said low coverage of toner particles.
- 11. An electrophotographic printing machine according to claim 1 wherein said low coverage of toner particles relating to said background area of said toner image is included in a composite toner patch image located in an interframe area on said image-bearing member; said composite toner patch image including a plurality of equally spaced toned strips, mutually parallel and perpendicular to a direction of movement of said image-bearing member; said plurality of equally spaced toned strips being inclusive of control toned strips and reference toned strips, said control toned strips having a lower coverage of toner than said reference-toned strips, said lower coverage substantially equal to said low coverage of toner particles relating to said background area of said toner image, said plurality of equally spaced toned strips further including a periodically repeating arrangement of strips, said periodically repeating arrangement of strips repeating adjacently in said direction of movement of said image-bearing member, said periodically repeating arrangement of strips including a reference toned strip and an integral number of control toned strips successively following said reference toned strip, with said integral number greater than or equal to 3; and said periodically repeating arrangement of strips having a lower frequency component from said reference-toned strips and a higher frequency component from said control toned strips.
- 12. An electrophotographic printing machine according to claim 11 wherein said composite toner patch image is moved with said image-bearing member in a direction past said optical detector, said signal produced by said optical detector is a composite AC signal inclusive of said lower frequency component and said higher frequency component; and wherein said control device further includes a synchronous detection circuit, said composite AC signal being divided and thereafter conducted into a control branch and a reference branch of said synchronous detection circuit, said reference branch suitably filtering said composite AC signal so as to leave said lower frequency component, said lower frequency component being passed through a frequency-multiplying device so as to produce a reference branch signal having a frequency substantially the same as said higher frequency component; said control branch suitably filtering said composite AC signal to leave said higher frequency component so as to produce a control branch signal, and said control branch signal and said reference branch signal being multiplied together in a signal-multiplying device, and the resulting multiplied signal being passed through a low pass filter so as to produce an output signal having a DC component, said DC component of a magnitude proportional to said low coverage of toner particles.
- 13. An electrophotographic printing machine according to claim 1, wherein, said toner image is a test image located in an image frame area on said receiver member, said test image including a color sub-image, said color sub-image included in a plurality of color sub-images, said color sub-image having a respective color; said color sub-image including a respective plurality of control strips having said respective color, said respective plurality of control strips having a respective post-transfer low coverage of toner particles after transfer to said receiver member, said respective post-transfer low coverage of toner particles relating to a respective background area on a toner image; said test image on said receiver member is moved with said receiver member at a steady rate past said optical detector, said respective plurality of control strips being perpendicular to a direction of movement of said receiver member; and wherein said color sub-image further includes a respective plurality of reference strips having said respective color, said respective plurality of reference strips having a respective post-transfer reference coverage of toner particles, said respective post-transfer reference coverage of toner particles being relatively high, said respective plurality of reference strips being perpendicular to said direction of movement of said receiver member; and wherein said control device further includes a synchronous detection circuit, and said signal produced by said optical detector is an AC signal which includes a plurality of control components having a control frequency, a respective control component included in said plurality of control components is produced via detection by said optical detector of said respective plurality of control strips, said respective control component having an amplitude proportional to said respective post-transfer low coverage of toner particles, said AC signal further including a plurality of reference components having a reference frequency, said reference frequency lower than said control frequency, a respective reference component included in said plurality of reference components is produced via detection by said optical detector of said respective plurality of reference strips, said respective reference component having an amplitude proportional to said respective post-transfer reference coverage, and said respective reference component and said respective control component are processed in said synchronous detection circuit, which synchronous detection circuit has an output proportional to said respective post-transfer low coverage of toner particles relating to said respective background area on said toned imaging member.
- 14. A method for measuring a low coverage of toner particles on an image-bearing member, said method for use in an electrostatographic machine, said image-bearing member having thereon a toner image located in an image frame, said toner image including a background area in which a coverage of background toner particles may be present, said image-bearing member having thereon a non-image area, said non-image area exclusive of said image frame, said non-image area having thereon a control toner image and a reference toner image, a detector of said control toner image being provided for producing a control toner image signal, a detector of said reference toner image provided for producing a reference toner image signal, said method including the steps of:
forming said control toner image in said non-image area on said image-bearing member, said control toner image including toned control strips, said toned control strips having a coverage substantially the same as said coverage of background toner particles in said image areas; moving said control toner image, on said image-bearing member, in a given direction past said detector for producing said control toner image signal, said toned control strips being perpendicular to said given direction, wherein said control toner image signal is a control AC signal; forming said reference toner image in said non-image area on said image-bearing member, said reference toner image including toned reference strips, said toned reference strips having said reference toner coverage; moving said reference toner image, on said image-bearing member, in said given direction past said detector for producing said reference toner image signal, said toned reference strips being perpendicular to said given direction wherein said reference toner image signal is a reference AC signal; past said detector for producing said reference toner image signal; and processing said control AC signal and said reference AC signal in a synchronous detection circuit having a DC output, said DC output having an amplitude proportional to said control toner coverage.
- 15. The method of claim 14 wherein said control toner image and said reference toner image are co-formed in a composite toner patch image in said non-image area, said composite toner patch image including said toned control strips and said toned reference strips, and said control AC signal and said reference AC signal are included in a composite AC signal conducted to said synchronous detection circuit.
CROSS REFERENCE TO RELATED APPLICATION
[0001] Reference is made to and priority claimed from U.S. Provisional Application Ser. No. 60/477,481, filed Jun. 10, 2003, entitled DETECTION OF BACKGROUND TONER PARTILCES.
Provisional Applications (1)
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Number |
Date |
Country |
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60477481 |
Jun 2003 |
US |