Method of calibrating distances between imaging device and a rotating drum

摘要

Optimization of distances between each of an array of imaging devices and the surface of an oppositely disposed rotating drum is accomplished without disturbing the mechanical mounting of the imaging devices. For each device, an optimal distance from the recording construction is established; at this optimal distance, corresponding to substantially proper focus, maximum energy density is delivered to a recording medium on the drum. Rather than alter the actual device-to-drum distance to conform to this optimum, the optical paths between the devices and the drum are changed by varying the spacing between the radiation source (e.g., the end of a fiber-optic cable) and the assembly. This alters the point of focus, and therefore has the same practical effect as moving the device itself. The invention also provides a technique for determining the optimal device-to-drum distance by means of a sequence of imaged regions applied at different device-to-drum distances.