Patent ID: 8387884
Filing Date: 2013-03-05
Classification: G06K

Abstract:
1. A variable focus imaging lens assembly for an imaging system of an imaging-based bar code reader, the imaging system generating image frames of a field of view of the imaging system and including an imaging sensor array, the variable focus imaging lens assembly comprising: a lens assembly focusing light from the field of view onto the sensor array, the lens assembly including a lens movable along a path of travel; a drive mechanism driving the moving lens along the path of travel; a focusing system establishing a reference point for the moving lens along the path of travel corresponding to a reference focal plane within the field of view; a projection assembly including a light source and an optic element, the projection assembly being configured to project light from the light source onto the optic element to generate a virtual target image in the form of backward propagating light originated from the optic element, the virtual target image being located at a predetermined position within the field of view and coincident with the reference focal plane, the predetermined position being a known distance from the lens assembly along an optic axis of the lens assembly; and the focusing system energizing the drive mechanism to drive the moving lens along the path of travel, analyzing successive image frames generated by the imaging system to determine an acceptable in-focus resolution of an image of the virtual target image of the light source and establishing the moving lens reference point at a position of the moving lens providing the acceptable in-focus resolution of the image of the light source virtual target image.