Method for spot position control in an optical output device employing a variable wavelength light source and an optical beam deflecting element

In an optical output system wherein a beam of light is generated and focused to a spot on an image plane, a method of positioning the spot so as to compensate for slow scan direction spot position error, comprising the steps of:

• generating a beam of light;
• deflecting the beam of light by way of an optical beam deflecting element such that the optical beam deflecting element deflects the path of the beam of light by an amount that is determined by the wavelength of the light beam;
• determining the existence and extent of error, if any, in the slow scan direction position of the spot on the image plane;
• generating a signal which is proportional to the determined existence and extent of error in the slow scan direction position of the spot;
• and
• varying the wavelength of the beam of light by an amount which is determined, at least in part, by the signal, such that the amount that the beam of light is deflected by the optical beam deflecting element is varied to achieve correction of the positional error in the slow scan direction.

In an optical output system wherein a beam of light is generated and focused to a spot on an image plane, and further wherein the spot is scanned in a raster fashion across the image plane, a method of positioning the spot on the image plane so as to compensate for recurrent slow scan direction spot position error introduced by the various elements of the optical output system, comprising the steps of:

• determining the existence and extent of recurrent slow scan direction spot position error;
• storing in a memory apparatus data from which a signal may be generated which may be applied to correct for the recurrent slow scan direction spot position error;
• and,
• for each scan line,
• determining whether the spot position is one which must be corrected;
• generating a beam of light at a first wavelength if the spot position is one which need not be corrected, and generating a beam of light at a second wavelength, determined at least in part by the signal generated by the stored data, if the spot position is one which must be corrected;
• and
• deflecting the beam of light by way of an optical beam deflecting element such that the optical beam deflecting element deflects the path of the beam of light by an amount that is determined by the wavelength of the light beam, and further such that at the second wavelength of light the beam of light is deflected by the optical beam deflecting element an amount sufficient to correctly position the spot in the slow scan direction on the image plane.