Lens adjustment for a light emitting diode print head

A method for adjusting a light emitting diode print head comprising a row of LEDs, an elongated lens array for focusing the images of the LEDs on an image plane, and a reference surface at each end of the row of LEDs for mounting the print head in a printer at a known location, comprising the steps of:

• emitting light from at least one LED near each end of the row;
• passing the light through an end of the lens array;
• analyzing the image of the light from one such LED with an image quality analyzer;
• adjusting the total conjugate of such an LED and the analyzer for maximizing image quality;
• adjusting the position of a first end of the lens array in the gap between the LEDs and the analyzer for maximizing image quality;
• and
• adjusting the position of the second end of the lens array in the gap between the LEDs and the analyzer for maximizing image quality.

A method for adjusting the optical elements of a light emitting diode print head comprising the steps of:

• adjusting the spacing between a row of LEDs and an image quality analyzer for maximizing quality of an image of an LED on the optical analyzer;
• adjusting the spacing of a first end of a lens array between the LEDs and the analyzer for maximizing quality of an image of an LED on the optical analyzer;
• and
• adjusting the spacing of a second end of the lens array between the LEDs and the analyzer for maximizing quality of an image of an LED on the optical analyzer;
• locking the spacing of the ends of the lens array in position;
• and
• locking a reference surface on the print head in a position determined by the spacing between the LEDs and the image quality analyzer.

An adjustment fixture for a light emitting diode print head comprising:

• means for securing a plate having a row of LEDs thereon in a selected position in the fixture;
• image analyzer means for analyzing the quality of an image of an individual LED on the plate;
• means for moving the analyzer in a direction parallel to the row of LEDs;
• means for moving the analyzer in a direction perpendicular to the row of LEDs;
• means for independently moving each end of a linear lens array between the row of LEDs and the analyzer in a direction perpendicular to the row of LEDs;
• and
• reference means on the analyzer for engaging a reference surface on the print head at a selected location.