Determining the cause of printer image artifacts

1. A method of determining the cause of artifacts in images produced by an electrophotographic (EP) printer, comprising:

providing the EP printer with:

a print engine for producing an image on a receiving member, the print engine including a plurality of rotatable imaging components;

a plurality of runout sensors for measuring the distance between a respective reference point and the surface of the respective rotatable imaging component along a respective reference axis; and

an artifact sensor for detecting one or more artifacts, or the absence of artifacts, in the produced image;

producing a reference image using the print engine, detecting zero or more artifact(s) in the reference image using the artifact sensor, and storing information identifying the detected artifact(s) in a memory;

producing one or more image(s) using the print engine;

producing a test image using the print engine and detecting zero or more artifact(s) in the test image using the artifact sensor;

determining whether at least one of the detected artifacts in the test image does not correspond to one of the zero or more artifact(s) detected in the reference image using the stored information;

if one of the artifact(s) does not correspond:

selecting one of the non-corresponding image artifact(s) in the test image;

determining a characteristic frequency spectrum of the selected image artifact;

rotating at least two of the rotatable imaging components and, while each rotatable imaging component is rotating, measuring the respective distances of the component at a plurality of angles of rotation of the imaging component using the respective runout sensor;

automatically determining a respective characteristic frequency spectrum of each measured imaging component using the corresponding measured distances; and

automatically comparing the characteristic frequency spectrum of the selected image artifact in the test image to the respective characteristic frequency spectra of one or more of the measured imaging component(s) to determine which imaging component(s) are causing the image artifact.

2. The method according to claim 1 , further comprising reporting the determined cause of the artifact to an operator using an interface.

3. The method according to claim 1 , further comprising, if one of the artifact(s) in the test image does not correspond to one of the zero or more artifact(s) detected in the reference image:

automatically determining whether one or more of the non-corresponding image artifact(s) is periodic; and

if a selected one of the artifact(s) is not periodic:

rotating the rotatable imaging components;

while each rotatable imaging component is rotating, measuring the respective distances at a plurality of angles of rotation of the imaging component using the respective runout sensor, the plurality of angles including angles in at least two revolutions of the imaging component; and

automatically determining, using a processor, which of the imaging component(s) has measured distances that are aperiodic over the measured revolutions, so that that cause of the selected image artifact is identified to include the component(s) having such aperiodic distances.

4. The method according to claim 1 , further comprising, for each characteristic frequency spectrum of one of the measured imaging components, selecting one or more frequencies of interest in the characteristic frequency spectrum and filtering the characteristic frequency spectrum of the selected image artifact in the test image with the selected frequencies of interest before comparing the spectrum of the artifact to the spectrum of the component.

5. A method of identifying malfunctions in an electrophotographic (EP) printer, comprising:

providing the EP printer with:

a print engine for producing an image on a receiving member, the print engine including a plurality of rotatable imaging components; and

a plurality of runout sensors for measuring the distance between a respective reference point and the surface of the respective rotatable imaging component along a respective reference axis;

a first rotating step of rotating the rotatable imaging components and, while each rotated imaging component is rotating, measuring the respective distances at a plurality of angles of rotation of the imaging component as reference distances using the respective runout sensor;

for each measured imaging component, storing the measured reference distances or information identifying the reference distances in a memory;

producing one or more images using the print engine;

a second rotating step of rotating one or more of the rotatable imaging components and, while each rotated imaging component is rotating, measuring the respective distances at a plurality of angles of rotation of the imaging component as test distances using the respective runout sensor; and

comparing the stored reference distances to the respective test distances and determining that a component whose test distances do not correspond to the respective reference distances is malfunctioning.

6. The method according to claim 5 , further comprising reporting the determined cause of the fault to an operator using an interface.

7. The method according to claim 5 , further including

determining respective reference frequency spectra of the measured reference distances for each component; and

determining respective test frequency spectra of the measured test distances for each component;

wherein the comparing step includes comparing the respective reference frequency spectra and test frequency spectra.