X-ray vidicon. The X-ray vidicon system consists of a specially designed television camera which is
sensitive to X-rays. It has a specially coated face which is capable of imaging X-radiation. This coating is amorphous,
which provides the capability of very, very fine resolution. The results of this type of inspection are displayed on a
television monitor. The sensitive area of the television vidicon tube is generally very small, on the order of 3/8 by 1/2
inch. When this small area is viewed on a 17-inch television monitor, a magnification of 30 times results, thus very high
detail resolution is accomplished. These system are used primarily for the Inspection of very fine detail, such as in the
inspection of microelectronic circuits. This system is capable of resolving a wire the diameter of a human hair.
Photoradiography. Photoradiography is a combination of fluoroscopy and photography. in this method,
the Image of a fluoroscopic or fluorescent screen is photographed by a conventional camera on small or miniature-type
film rather than by direct contact. is method has the advantage over fluoroscopy in that the film has the property to
integrate and react to the total light emitted by the fluoroscopic screen during the time of exposure, whereas the
integration time of the eye is relatively short. Furthermore, the resultant film can be viewed with transmitted light and the
photographic process can be used to enhance the contrast of the fluorescent image. In general, this system permits
radiographic sensitivity of about four to five per cent. The photoradiography accessory is available as an assembly and
usually consists of a light-tight hood, a fluorescent screen assembly and the camera.
Various type cameras are available, some of which employ sheet film and others using 70-mm roll film.
Polaroid radiograph. If a convenient, permanent image is required and the time required for conventional
film radiography is prohibitive, alternatives may be considered. One of these is polaroid radiography. Just as polaroid
photography facilitates very rapid development of photographic images, there are available polaroid X-ray films which
provide the same advantages. These require the special polaroid film holders and a film processor If the larger sizes are
used. In some cases, the typical polaroid 4 by 5 inches adapter can be used. Polaroid radiographic films are used just
as regular films are used in conventional film radiography. They have their own characteristic curves and an appropriate
exposure technique should be used.
However, after the exposure has been made, rather than process the films by conventional techniques, they are dry
developed as polaroid photography is, and results are available after about one minute. Presently available polaroid
films provide for either viewing by reflected or transmitted light. Polaroid radiographs provide nearly instant
interpretation and also provide a permanent image. However, polaroid radiographs are low in contrast and detail
resolution compared to conventional film techniques. Polaroid radiographs can be made to establish the geometrical
alignment of the X-ray beam with the part before a typical film radiograph is exposed. This technique is useful in those
cases where critical alignment is required.
5-8. Film Exposure and Processing. Film exposure and processing are explained in the following paragraphs.
Exposure. Exposure is the time the silver salts on the film are exposed and acted upon by radiation. The
intensity of the reaction is directly proportional to the amount of radiation received.
Processing. Processing consists of the various steps necessary to have a clear radiographic image. Processing
is done either manually or automatically.
Manual film processing. The developing procedure for manual film processing is depicted in figure 5-1 and
explained in the following paragraphs.
Immerse the film and its hanger in the developing solution. Agitate the hanger by hand at one minute
intervals. This must be done the entire developing time.
Remove the film from the developer and immerse in the stop bath for about one minute.
Remove the film from the stop bath solution and Immerse in the fixing solution.
Remove the film from the fixing bath and immerse in the wash water for the recommended time.
Dry the film.
Remove the film from the film hanger (2) Automatic film processing. The advantages of automatic
processors are speed and control of the development process. Automatic processing is particularly advantageous when
large volumes of film need to be processed. Automatic processing also provides for greater uniformity of development,
thus providing more consistent results. However, because the processing cycle is faster and the chemical temperatures
are higher In automatic processing than they are with manual processing, the use of automatic processing will have a
noticeable effect on the radiographic technique Ap-