LED printhead with relay lens to increase depth of focus

摘要

LED printhead apparatus and printing systems are presented in which an LED array and a first high angle lens array are housed in an LED printbar assembly and a second low angle lens array is provided between the first lens array and a photoreceptor belt or drum in order to relay the output of the first lens array to the photoreceptor to provide a larger depth of focus and to reduce waterfront and tolerance issues near the photoreceptor.

主权项

1. A printhead apparatus for generating an image on a portion of a photoreceptor traveling along a path in a path direction in a host printing system, the printhead apparatus comprising:
an LED array comprising a plurality of LEDs individually operative according to received image data to produce light output along a first direction; a first self-focusing lens array having a plurality of gradient index lens elements with varying indices of refraction along the first direction, the first self-focusing lens array having a first side facing the LED are and receiving the light output from the LED array at first ends of the gradient index lens elements, and a second side providing a second light output at second ends of the gradient index lens elements for one-to-one erect imaging of the light output from the LED array; and a second self-focusing lens array having a plurality of gradient index lens elements with varying indices of refraction along the first direction, the second self-focusing lens array having a first side facing the second side of the first self-focusing lens array and receiving the second light output from the first self-focusing lens array at first ends of the gradient index lens elements, and a second side facing the photoreceptor and providing a third light output at second ends of the gradient index lens elements for one-to-one erect imaging of the second light output from the first self-focusing lens array onto the photoreceptor of the host printing system; wherein the first lens array has a first image conjugate distance and a first object conjugate distance, wherein the second lens array has a second image conjugate distance and a second object conjugate distance, and wherein the first side of the second lens array is spaced along the first direction from the second side of the first lens array by a first distance approximately equal to the sum of the first image conjugate distance and the second object conjugate distance.