1. A multi-camera flat panel X-Ray detector, the detector comprising: a scintillator to convert X-Ray radiation generated by an X-Ray source into detectable radiation; at least one optical module, each optical module comprising a lens having a vignetting factor and an imaging sensor, wherein the imaging sensor is configured to acquire, during a linearization phase, at least two images related to the detectable radiation, at a field of view of the at least one imaging sensor, wherein the intensity of the X-Ray radiation generated by the X-Ray source is different for each of the at least two images, and wherein the lens is adapted to focus the detectable radiation onto the imaging sensor; a light energy measurement unit configured to measure, during the linearization phase, substantially simultaneously with the acquiring of each of the at least two images, at least two corresponding levels of energy of the detectable radiation, wherein the light energy measurement unit is substantially linear at the range of operation; and a processing unit comprising a processor and memory, wherein the processing unit is configured to: obtain the at least two images from the at least one imaging sensor; obtain the at least two levels of energy from the light energy measurement unit; and calculate an inverse response function to the at least one imaging sensor based on the at least two images and on the at least two levels of energy, wherein the inverse response function is calculated based on an equality between a relation between detectable radiation energy level present at a first area within a FOV of the at least one imaging sensor while acquiring a first image to detectable radiation energy level present at the first area while acquiring a second image and a relation between detectable radiation energy level present at a second area of a FOV of the at least one imaging sensor while acquiring the first image to the detectable radiation energy level present at the second area while acquiring the second image, and a relation between a level of detectable radiation energy detected by the light energy measurement unit while acquiring the first image to a level of detectable radiation energy detected by the light energy measurement unit while acquiring the second image.