In order to visualize the internal structure of a spray cloud injected from a diesel nozzle, a computed tomography diagnostic technique was applied. A compact type of CT systems was developed, an Industrial Television Video Camera was used for the detector and a small computer was adopted for reconstruction of image data. A noninstrusive measurement technique was developed. At first, the algorithm for data reduction was discussed, followed by the effects of filter function on reconstruction data. The modified Sheff and Logan's filter function was recommended for the reconstruction of images such as diesel spray clouds.