Apparatus and system for spot position control in an optical output device employing a variable wavelength light source

A system for outputting an optical signal, comprising:

• a light source capable of emitting a beam of light at a selected one of at least two selectable wavelengths;
• beam deflecting means located in the path of said light beam for deflecting the beam of light an amount which depends on the wavelength of the beam of light;
• image plane means for receiving the light beam;
• and
• means for focusing the light beam to a spot on the image plane means;
• whereby, a shifting of the light beam from one to another of the at least two selectable wavelengths causes the beam deflecting means to change the amount that the beam is deflected and thereby reposition the spot on the image plane means.

A system for outputting an optical signal, comprising:

• a variable wavelength laser light source capable of emitting a beam of laser light at a selected one of at least two selectable wavelengths;
• means for selecting the one of at least two selectable wavelengths of the output of the laser light source;
• rotating output scanning means located in the path of said light beam for scanning the light beam in a raster fashion in a fast scan plane;
• a beam deflecting element located in the path of said light beam whose index of refraction varies as a function of the wavelength of light passing therethrough, for deflecting the beam of light in a slow scan plane, which is orthogonal to the fast scan plane, an amount which depends on the wavelength of the beam of light;
• image plane means for receiving the light beam;
• means for focusing the light beam to a spot on the image plane means;
• means for determining the existence and extent of any error in the position of the spot on the image plane means;
• means for determining the need for, and the extent of, the application of predetermined spot position correction;
• and
• means for application of such determinations of the existence and extent of any error and the need for, and extent of, the application of predetermined spot position correction to the means for selecting the wavelength of the output of the laser such that an appropriate shift of the light beam from one to another of the at least two selectable wavelengths is caused, and further that such a shift in wavelength causes the beam deflecting element to change the amount that the beam is deflected and thereby reposition the spot on the image plane means in the slow scan direction to compensate for the determined existence and extent of error and the determined needed application of predetermined spot position correction.

An improved printing apparatus, the improvement comprising:

• a variable wavelength laser light source capable of emitting a beam of laser light at a selected one of at least two selectable wavelengths;
• means for selecting the one of at least two selectable wavelengths of the output of the laser light source;
• rotating output scanning means located in the path of said light beam for scanning the light beam in a raster fashion in a fast scan plane;
• a beam deflecting element located in the path of said light beam whose index of refraction varies as a function of the wavelength of light passing therethrough, for deflecting the beam of light in a slow scan plane, which is orthogonal to the fast scan plane, an amount which depends on the wavelength of the beam of light;
• a photoreceptive element for receiving the light beam;
• means for focusing the light beam to a spot on the photoreceptive element;
• means for determining the existence and extent of any error in the position of the spot on the photoreceptive element;
• means for determining the need for, and extent of, the application of predetermined spot position correction;
• and
• means for application of such determinations of the existence and extent of any error and the need for, and extent of, the application of predetermined spot position correction to the means for selecting the wavelength of the output of the laser such that an appropriate shift of the light beam from one to another of the at least two selectable wavelengths is caused, and further that such a shift in wavelength causes the beam deflecting element to change the amount that the beam is deflected and thereby reposition the spot on the photoreceptive element in the slow scan direction to compensate for the determined existence and extent of error and the determined needed and extent of the application of predetermined spot position correction.