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Variable sized VCSEL ROS swath utilizing variable spaced diode array

IP.com Disclosure Number: IPCOM000210859D
Publication Date: 2011-Sep-12
Document File: 3 page(s) / 126K

Publishing Venue

The IP.com Prior Art Database

Abstract

Xerographic laser printers have used two dimensional arrays of Vertical Cavity Surface Emitting Lasers (VCSEL) in the raster Output Scanner (ROS) to create the image on the photoreceptor for many years. In the known VCSEL array, the spacing between the individual laser diode emitters is fixed. This idea proposes integrating a mechanism into the array that will allow for variable spacing between the diode elements in the array. This proposal will allow for certain inherent engineering problems to be resolved by using the variable spacing capability.

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Variable sized VCSEL ROS swath utilizing variable spaced diode array

Xerographic laser printers have used two dimensional arrays of Vertical Cavity Surface Emitting Lasers (VCSEL) in the raster Output Scanner (ROS) to create the image on the photoreceptor for many years.  In the known VCSEL array, the spacing between the individual laser diode emitters is fixed.  This idea proposes integrating a mechanism into the array that will allow for variable spacing between the diode elements in the array.  This proposal will allow for certain inherent engineering problems to be resolved by using the variable spacing capability.

This idea proposes a method to adjust the spacing of the diodes in a VCSEL ROS to adjust the magnification in the process direction. Precision piezoelectric linear actuators would be placed between all diodes or an actuator would be attached to the entire VCSEL diode structure, and a calibrated voltage would be applied to the actuators to make any needed adjustments in diode spacing. This run-time magnification control allows for the process magnification adjustments needed for tandem printing architectures, registration for dual sided printing, and other run time factors affecting process speed or ROS magnification. This solves the problem of banding induced by the imperfect overlap of the 32 wide beam VCSEL swaths that occur if the PR belt speed varies or if dual sided printing is needed. This solution could be superior to one-time manufacturing set-up of ROS magnification and to using slightly imperfect electronic magnification to handle photoreceptor belt speed variation or dual sided printing.

The set of laser diodes are scanned across the photoreceptor in a “swath”.   This “swath” of scan lines leads to several problems that must be overcome in order for the VCSEL ROS to be successfully integrated.  Each “swath” is followed by another.  The “swaths” of scan lines must be fit together in a manner that does not allow for image quality defects. If the photoreceptor speed (slow scan direction) is fixed, that creates its own set of problems.  One problem is known as Stitching Error. It is critical to space the swaths correctly in the process direction. Too little spacing will cause a bunching of the swaths, while too much spacing will result in excess non-imaged area between the swaths. Either of these conditions can lead to image artifacts including banding and beating.

Figure 2 shows a representation of two swaths of scan lines:

Another consideration is scan line overwrite. This is where line 1 of scan n+1 overlaps line 17 of scan n. This is done to balance laser power and overall smoothing of the scanned image. Figure 3 shows a representation of two swaths of scan lines with overwrite enabled:

Note that in either case, an interaction exists between scan line spacing and swath to swath spacing. This interaction leads to Stitch Error, which in turn will lead to undesir...