a method of obtaining a series of images of a three - dimensional object . the method includes the steps of transmitting pulsed terahertz radiation through the entire object from a plurality of angles , optically detecting changes in the transmitted thz radiation using pulsed laser radiation , and constructing a plurality of imaged slices of the three - dimensional object using the detected changes in the transmitted thz radiation . the thz radiation is transmitted through the object as a two - dimensional array of parallel rays . the optical detection is an array of detectors such as a ccd sensor .