OPTICAL STORAGE OF DIGITIZED NONDESTRUCTIVE TESTING RADIOGRAPHS

Abstract

Publisher Summary This chapter describes optical storage of digitized nondestructive testing radiographs. Digitization is the conversion of continuous, analog radiographic information into a discreet, digital form. Radiographic images are characterized by two forms of information: visible light transmission through the film and the spatial variation in transmission in two dimensions. Both these parameters are captured and converted. The hardware required to store digitized film images includes the following: digitizer, host computer, data compression hardware, and optical disk drive. The host computer's main function is to move data from the digitizer, through the data compression system, and onto the optical disk. The development of lossless data compression, implemented in hardware, makes optical storage practical in a wide range of nondestructive testing (NDT) applications by reducing the time required to compress the large data sets from 70 micron radiographic images digitized to 12 bits. Data compression, implemented in hardware, allows increased system speed because the compression and decompression algorithms are performed faster. The data is decorrelated by the host before being sent to the data compression board in order to attain the highest compression. The main advantages of digital film storage are image quality preservation, lower cost storage, and faster, more efficient retrieval. Once the image is digitized, information about it is entered into a database so that the image can be tracked and easily retrieved when needed. Finally, the storage requirements of optical media are more easily met than those of film.