Pixel clock generating apparatus, optical writing apparatus using a pixel clock, imaging apparatus, and method for generating pixel clocks

Abstract

A pixel clock generating apparatus comprises a data offset circuit and a pixel generator. The data offset circuit defines multiple data blocks, each data block consisting of a predetermined number of successive clocks, and produces phase data for each data block. The phase data represents an amount and a direction of phase shift to be carried out for a certain clock in each data block. The pixel generator receives the phase data from the data offset circuit and generates a phase-shifted pixel clock a predetermined number of times in each data block based on the phase data.

1 - 24 . (canceled)  
   
   
       25 : An optical writing apparatus comprising: 
 a first light source;    a deflector configured to deflect light flux emitted from the first light source;    a photosensitive unit on which an image is optically formed;    two or more detectors configured to detect the light flux and produce detection signals;    an optical guide positioned between the deflector and the photosensitive unit and configured to guide the light flux deflected by the deflector to the photosensitive unit and said two or more detectors; and    a pixel clock generating unit configured to create phase data and generate a pixel clock based on the phase data, the phase data being corrected based on a scanning time required for the light flux to scan between said two or more detectors and designating phase shift timing.    
   
   
       26 : The optical writing apparatus according to  claim 25 , wherein the optical guide includes a scanning lens and a transparent member having a first surface positioned closer to the deflector, and a portion of the light flux is reflected from said first surface and guided to said two or more detectors.  
   
   
       27 : The optical writing apparatus according to  claim 26 , wherein the transparent member has a second surface positioned closer to the photosensitive unit, and reflectance of the first surface is set greater than that of the second surface.  
   
   
       28 : The optical writing apparatus according to  claim 26 , wherein the transparent member is a parallel flat plate, and has an overlapped area on the surface, in which the light flux guided to the photosensitive unit and the light flux guided to said two or more detectors overlap each other.  
   
   
       29 : The optical writing apparatus according to  claim 26 , wherein the transparent member is a dustproof flat glass plate.  
   
   
       30 : The optical writing apparatus according to  claim 26 , wherein the photosensitive unit has an effective writing area, and the transparent member is tilted with respect to a plane perpendicular to the light flux guided to a center of the effective writing range.  
   
   
       31 : The optical writing apparatus according to  claim 25 , wherein the pixel generating unit further has a high-frequency generator for generating a high-frequency reference signal, and said phase shift timing is synchronized with the high-frequency reference signal.  
   
   
       32 : An optical writing apparatus comprising: 
 a light source;    a photosensitive unit having a writing start position and a writing end position;    a deflector configured to deflect light flux emitted from the light source toward the photosensitive unit;    an optical guide configured to guide the light flux deflected from the deflector to the photosensitive unit and let the light flux scan between the writing start position and the writing end position;    first and second detectors positioned corresponding to the writing start position and the writing end position and configured to detect the light flux as the light flux scans on the photosensitive unit; and    a pixel clock generating unit configured to produce and adjust phase data based on a change in scanning time required for the light flux to scan between the detectors, and to generate a phase-shifted pixel clock whose phase has been shifted based on the phase data.    
   
   
       33 : The optical writing apparatus according to  claim 32 , wherein the pixel clock generating unit defines multiple data blocks within an effective scanning period, each of the data blocks consisting of successive clocks, and gives the phase data for each of the data blocks.  
   
   
       34 : The optical writing apparatus according to  claim 32 , wherein the pixel clock generating unit defines the data blocks so that the number of clocks in each data block is variable depending on the amount of said change.  
   
   
       35 : The optical writing apparatus according to  claim 32 , wherein the pixel clock generating unit defines a first data block corresponding to the writing start position, a second data block corresponding to the writing end position, and a third data block corresponding to an area between the writing start position and the writing end position, and gives the phase data to each of the first through third data blocks.  
   
   
       36 : The optical writing apparatus according to  claim 32 , wherein the pixel clock generating unit changes a frequency of the pixel clock so as to shift a dot offset characteristic of the optical writing apparatus as a whole.  
   
   
       37 : The optical writing apparatus according to  claim 32 , wherein the light source is a multi-beam light source.  
   
   
       38 : The optical writing apparatus according to  claim 32 , wherein the pixel clock generating unit has a high-frequency clock generator for generating a high-frequency reference signal, and said phase-shifted pixel clock is generated in synchronization with the high-frequency reference signal.  
   
   
       39 : The optical writing apparatus according to  claim 32 , wherein: 
 the light source includes a first light source unit configured to emit a writing beam and a second light source configured to emit a reference beam; and    the optical guide guides the writing beam onto the photosensitive unit and guides the reference beam to the first and second detectors.    
   
   
       40 : The optical writing apparatus according to  claim 39 , wherein a path length of the reference beam is substantially the same as that of the writing beam.  
   
   
       41 : The optical writing apparatus according to  claim 39 , wherein the first light source and the second light source have substantially the same wave length.  
   
   
       42 : The optical writing apparatus according to  claim 39 , wherein the first light source and the second light source are arranged in a laser array.  
   
   
       43 : The optical writing apparatus according to  claim 33 , wherein the pixel generating unit shifts timing of generating a phase-shifted clock for each of the data blocks when the light flux scans a next line on the photosensitive unit.  
   
   
       44 . (canceled)  
   
   
       45 : An imaging apparatus comprising: 
 an optical writing unit configured to optically form a latent image; and    an image reproducing unit configured to reproduce the latent image as a visible image, the optical writing unit comprising: 
 a first light source;  
 a deflector configured to deflect light flux emitted from the first light source;  
 a photosensitive unit on which an image is optically formed;  
 two or more detectors configured to detect the light flux and produce detection signals;  
 an optical guide positioned between the deflector and the photosensitive unit and configured to guide the light flux deflected by the deflector to the photosensitive unit and said two or more detectors; and  
 a pixel clock generating unit configured to create phase data and generate a pixel clock based on the phase data, the phase data being corrected based on a scanning time required for the light flux to scan between said two or more detectors and designating phase shift timing.  
   
   
   
       46 : An imaging apparatus comprising: 
 an optical writing unit configured to optically form a latent image; and    an image reproducing unit configured to reproduce the latent image as a visible image, the optical writing unit comprising: 
 a light source;  
 a photosensitive unit having a writing start position and a writing end position;  
 a deflector configured to deflect light flux emitted from the light source toward the photosensitive unit;  
 an optical guide configured to guide the light flux deflected from the deflector to the photosensitive unit and let the light flux scan between the writing start position and the writing end position;  
 first and second detectors positioned corresponding to the writing start position and the writing end position and configured to detect the light flux as the light flux scans on the photosensitive unit; and  
 a pixel clock generating unit configured to produce and adjust phase data based on a change in scanning time required for the light flux to scan between the detectors, and to generate a phase-shifted pixel clock whose phase has been shifted based on the phase data.  
   
   
   
       47 . (canceled)  
   
   
       48 : An imaging apparatus comprising: 
 multiple optical writing units corresponding to multiple colors, each configured to optically form a latent image of an associated color; and    an image reproducing unit for reproducing a color image based on the latent images formed by the optical writing units, each of the optical writing units comprising: 
 a first light source;  
 a deflector configured to deflect light flux emitted from the first light source;  
 a photosensitive unit on which the latent image is formed;  
 two or more detectors configured to detect the light flux and produce detection signals;  
 an optical guide positioned between the deflector and the photosensitive unit and configured to guide the light flux deflected by the deflector to the photosensitive unit and said two or more detectors; and  
 a pixel clock generating unit configured to create phase data and generate a pixel clock based on the phase data, the phase data being corrected based on a scanning time required for the light flux to scan between said two or more detectors and designating phase shift timing.  
   
   
   
       49 : An imaging apparatus comprising: 
 multiple optical writing units corresponding to multiple colors, each of the optical writing units being configured to optically form a latent image of an associated color; and    an image reproducing unit for reproducing a color image based on the latent images formed by the optical writing units, each of the optical writing units comprising: 
 a light source;  
 a photosensitive unit having a writing start position and a writing end position;  
 a deflector configured to deflect light flux emitted from the light source toward the photosensitive unit;  
 an optical guide configured to guide the light flux deflected from the deflector to the photosensitive unit and let the light flux scan between the writing start position and the writing end position;  
 first and second detectors positioned corresponding to the writing start position and the writing end position and configured to detect the light flux as the light flux scans on the photosensitive unit; and  
 a pixel clock generating unit configured to produce and adjust phase data based on a change in scanning time required for the light flux to scan between the detectors, and to generate a phase-shifted pixel clock whose phase has been shifted based on the phase data.  
   
   
   
       50 - 63 . (canceled)