Abstract:
A technique for minimizing motor polygon assembly output reflectivity using real time facet reflectivity measurements and mapping. An automatic power control sensor manages laser beams produced by the laser source associated with the system during overscan periods ‘outside’ of defined printing time. Errors are then recorded internal to the raster output scanner to minimize overall setup in the image output terminal.

Description:
TECHNICAL FIELD 
     Embodiments are generally related to image data processing. Embodiments are also related to the field of laser scanning. Embodiments are additionally related to minimizing MPA output reflectivity variation by real-time facet reflectivity measurement and mapping. 
     BACKGROUND OF THE INVENTION 
     Processes and devices used for electro photographic printers wherein a laser scan line is projected onto a photoconductive surface are known. In the case of laser printers, facsimile machines, and the like, it is common to employ a raster output scanner (ROS) as a source of signals to be imaged on a pre-charged photoreceptor (a photosensitive plate, belt, or drum) for purposes of xerographic printing. The ROS provides a laser beam which switches on and off as it moves, or scans, across a photoreceptor. 
     Commonly, the surface of the photoreceptor is selectively imaged and discharged by the laser in locations to be printed. On-and-off control of the beam to create the desired latent image on the photoreceptor is facilitated by digital electronic data controlling of the laser source. A common technique for effecting this scanning of the beam across the photoreceptor is to employ a rotating polygon mirror surface; the laser beam from the ROS is reflected by the facets of the polygon, creating a scanning motion of the beam, which forms a scan line across the photoreceptor. A large number of scan lines on a photoreceptor together form a raster of the desired latent image. Once a latent image is formed on the photoreceptor, the latent image is subsequently developed with a toner, and the developed image is transferred to a copy sheet, as in the well-known process of xerography. 
     While several exposure systems have been developed for use in electro photographic marking, one commonly used system is the raster output scanner (ROS). A raster output scanner is comprised of a laser beam such that the laser beam contains image information, a rotating polygon mirror having one or more reflective surfaces, a motor polygon assembly, etc. Some raster output scanners employ more than one laser beam. Usually in motor polygon assembly (MPA), errors may occur during manufacturing. Based upon these errors erratic beam reflectivity may occur from each facet in a ROS Imager MPA assembly that is then passed on to ROS outputs as dysfunctions in critical applications. 
     Laser scanning is based on a technique achieving both start-of-scan detection and dynamic beam intensity regulation in a multiple laser beam raster output scanner using a photodetector. The raster output scanner includes a source, or sources, of a plurality of laser beams or arrays, a rotating polygon having at least one reflecting facet for sweeping the laser beams to form a scan line path, and a photodetector for receiving illumination from the multiple laser beams and for converting those beams into beam-dependent electrical currents. The raster output scanner further includes a scan detection circuit for producing a start-of-scan signal, and a beam intensity circuit for producing an electrical output signal which depends upon the beam intensity of each laser beam. Optionally the raster output scanner also can include an optical fiber  102  that collects a portion of the light flux in the sweeping laser beams which directs the light flux onto the photo detector. Referring to  FIG. 1  (prior-art) the top view  100  of a raster output scanner used in the electro photographic printing machine is illustrated. The raster output scanning assembly  100  can include a plurality of laser diodes or array(s)  150  and  151  which produce laser beams  103  and  104 , respectively, are modulated according to image data from the data source and laser driver  152 . The image data from the data source and laser driver  152  might originate from an input scanner, a computer, a facsimile machine, a memory device, or any of a number of other image data sources. 
     The purpose of the data source and laser driver  152  is to excite lasers  150  and  151  with modulated drive currents such that the desired electrostatic latent image is interlaced on the photoreceptor in precise registration with uniform exposure. The output flux from laser diodes  150  and  151  are collimated by optical elements  154 , reflected by fold mirror  156 , and focused on reflective facets  157  of rotating polygon  158  by cylindrical lens  160 . The facets of rotating polygon  158  deflect the beams which are then focused into well defined spots focused on the surface of photoreceptor  10  by scan lens elements  162  and  164 . As the polygon rotates, the focused spots trace parallel raster scan lines on the surface of the photoreceptor. The sensor network  106  is positioned in the scan path to collect light flux from beams  103  and  104  at the beginning of the scan. Optionally, the input end of the optical fiber  102  is positioned in the scan path to collect light flux from beams  103  and  104  at the beginning of the scan. The optical fiber  102  transmits the intercepted flux to the sensor network  106 . Beam intensity signal  110  and the start of scan signals are configured from the sensor network  106  to the data source and laser driver  152 . The synchronized input  122  is configured to the sensor network  106 . 
     The present inventor has recognized a drawback of prior art of laser scanning is with lack in effectively controlling the output intensity variation of exposing beam(s) of a rotating polygon type image forming apparatus using control marks formed on a rotating surface portion of a polygon member or a motor polygon assembly. Ideally, control marks can be read by a reader during rotation of the polygon member, and the information read from the control marks is used to control the modulation of the exposing beam of the image forming apparatus to expose evenly spaced, uniformly sized, precisely oriented, geometrically straight scan lines of pixels on a photosensitive member. The control marks can include pixel clock information, intensity correction information, error correction information about individual facets of the polygon member, and motor speed control information. 
     BRIEF SUMMARY 
     The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed and is not intended to be a full description. A full appreciation of the various aspects of the embodiments can be gained by taking the entire specification, claims, drawings, and abstract as a whole. 
     It is, therefore, one aspect of the present invention to provide for an improved image data processing. 
     It is another aspect of the present invention to provide for improved system performance in using a raster output scanner. 
     It is a further aspect of the present invention to provide a solution that minimizes motor polygon assembly (MPA) output reflectivity differences by real time facet reflectivity measurement and mapping. 
     The aforementioned aspects and other objectives and advantages can now be achieved as described herein. In this present method the errors in MPA manufacturing diminishes erratic beam reflectivity that may occur from each facet in a ROS Imager MPA and that are passed on to ROS outputs (dysfunctions) in critical applications. Accordingly, a laser beam is passed to facets of the rotating polygon mirror that is configured with MPA then to an automatic power controller (APC) that provides the sensing during the process of image data scanning. The output beam is then sent from the APC when scanning is in process while the over scanning period is being defined as the process progress. 
     This present solution minimizes MPA output reflectivity by real time facet reflectivity measurement and mapping. The polygon facets are set setup with the help of the motor polygon assembly. A automatic power control (APC) sensor looks at the beam of the laser during over scan periods ‘outside’ of printing time. Errors are recorded internal to the ROS to minimize overall setup in image output terminal (IOT) manufacturing. The graphical output when analyzed from the processing of this method gives better output. The percentage of rise in the digitized signal can be analyzed with the rotation of the polygon facets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the embodiments and, together with the detailed description, serve to explain the embodiments disclosed herein. 
         FIG. 1  illustrates a prior art the top view  100  of a raster output scanner used in the electro photographic printing machine is illustrated, in motor polygon assembly (MPA) facet reflectivity mapping, which can be implemented in accordance with a preferred embodiment. 
         FIG. 2  illustrates a perspective view with the formed graphical analysis of the method adopted with motor polygon assembly (MPA) facet reflectivity mapping, which can be implemented in accordance with a preferred embodiment. 
         FIG. 3  illustrates a block diagram of the system, in motor polygon assembly (MPA) facet reflectivity mapping, which can be implemented in accordance with a preferred embodiment. 
         FIG. 4  illustrates a high-level flow chart showing the functional steps with a motor polygon assembly (MPA) facet reflectivity mapping, in accordance with a preferred embodiment. 
         FIG. 5  illustrates the graphical representation of the response waveform of a raster scanner system, in accordance with a preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof. 
     Referring to  FIG. 2 , illustrated is a perspective view  200  with the formed graphical analysis of the method adopted with motor polygon assembly (MPA) facet reflectivity mapping, which can be implemented in accordance with a preferred embodiment. A rotating polygon mirror  202  is kept adjacent to its facets, in which the laser beam is transmitted. The rotating polygon is configured with the help of the polygon motor driver and the response is generated to the automatic power control (APC)  206 . The laser beam  204  is sent to the facets of the rotating polygon. The output beam  208  is configured and sent with the help of the automatic power control (APC). During the process the formed graphical output  210  is shown. The percentage of change  212  is analyzed in the vertical axis of the graph and the polygon facets  216  are analyzed in the horizontal axis of the graph. The raw portion  214  is shown in the graph. The digitized signal  218 ,  220  can also figured out from the graph representation. 
     Referring to  FIG. 3 , illustrated is a block diagram  300  of a system, in motor polygon assembly (MPA) facet reflectivity mapping, which can be implemented in accordance with a preferred embodiment. It is understood that the generated laser beam  204  is sent to the motor polygon assembly  202  which consists of the polygon motor driver  302  wherein the facets of the polygon mirror  304  can be configured with the help of the polygon motor driver. The polygon motor driver is used in the functionality of the rotation of the facets of the polygon mirror. The motor polygon assembly can be configured to the automatic power control (APC)  206  sensor and sets up the output beam  208 . The data source and laser driver  306  is setup with the input device  322 . The data source and laser driver  306  is connected to the laser beam  204  and the main control section  308  that includes a memory  312 . The main control section (CPU) is configured with the motor polygon assembly  202  and it sets up the generation of the laser beam  204 . The main control section (CPU) is also integrated to the integrator  314  that connects the light beam sensing unit  310  with the light beam sensor output processing circuit  316 . The light beam sensor output processing circuit forms the interface for the output unit that is configured with the raster output scanners (ROS) wherein the IOT  318  is set up for the processing of the image data. 
     Referring to  FIG. 4 , illustrated is a high-level flow chart  400  showing the functional steps with a motor polygon assembly (MPA) facet reflectivity mapping, in accordance with a preferred embodiment. As depicted at block  402 , initialization can occur. Next, as indicated at block  404 , the automatic power control (APC) sensor looks at the beam of laser. Thereafter, as described in block  406 , the APC sets up during the over scan periods outside of the printing time. The errors formed are recorded internal to the raster output scanners (ROS) to minimize overall setup in IOT manufacturing as depicted in block  408 , following processing of the operation involves real time facet reflectivity measurement &amp; mapping with MPA as depicted in block  410  and finally minimizes MPA output reflectivity as described in block  412 . 
     Referring to  FIG. 5 , illustrated is a graphical representation  500  of the response waveform of a raster scanner system, in accordance with a preferred embodiment. The percentage of rise is analyzed in the vertical axis of the graph and the polygon facets are analyzed in the horizontal axis of the graph. The raw portion is shown in the graph. The digitized signal is also figured out from the graph representation. 
     It can be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.