Radiographic Image Detection Device

Other objects and advantages of the present invention will become more apparent from the following detailed description when taken with the accompanying drawing of an enlarged isometric view of a portion of a radiographic image detection device of the present invention.

Referring now to the drawing, there is illustrated a solid-state, image detection device, generally indicated as 10, comprised of a semiconductive matrix 11 covered by a protective layer 12. In the semiconductive matrix 11, radiation sensitive areas 13 are arranged in a matrix of rows and columns. Each radiation sensitive area 13 is surrounded by an area insensitive to radiation in which control lines are present which carry control signals under the influence of which image information in the form of charges generated by the radiation in each radiation sensitive area 13 is transported to a side of the device to be read out in a manner known, per se. The protective layer 12 of an initial thickness d is provided in a manner known per se, with a plurality of parallel grooves in rows and columns 14a,. . . , 14d and 15a,. . . , 15d, respectively. It should be noted that the dimensions of the grooves shown in the drawing are not to scale relative to the dimension of the protective layer 12. The grooves enclosed lands or land portions, one of which is denoted by the reference numeral 16, of the material of the protective layer 12, which may be, e.g. SiO.sub.2 or Si.sub.3 N.sub.4, or a mixture thereof. The grooves are positioned above the insensitive areas surrounding the sensitive areas 13 thereby leaving the lands or land portions 16 disposed above the radiation sensitive areas 13.

After the grooves have been made in the protective layer 12, the device is subjected to vapor deposition of cesium iodide (CsI). Cesium iodide (CsI) crystals (one of which is denoted by referenced numeral 17) are formed on respective land or land portion 16 whereby crystals on adjacent lands or land portions 16 possess different crystal orientations. As the vapor deposition process continues and the CsI layer became thicker, the CsI layers on adjacent lands or land portions 16 in fact grow relative to each other, because with increasing thickness the dimensions also increased parallel to the surface of the device 10 but without growing into each other because of the different crystal orientations of the CsI on adjacent lands or land portions 16. There is only a minimum of interchange of light between the CsI crystals on adjacent lands or land portions 16.

As a result, any X-ray radiation, for example, penetrating a CsI crystal 17 from above in the direction of arrow 18 generates light within that crystal 17. At any site wherein X-ray radiation generates light, such light is essentially sent out in all directions and could reach a multitude of sensitive areas 13 thereby giving rise to a poor signal-to-noise ratio (i.e. low contrast) of the image read out from the device 10. However, due to a minimum of interchange of light between adjacent crystals, let alone crystals remote from such adjacent crystals, any light generated by X-ray radiation entering a respective crystal 17 will reach the sensitive area associated with such crystal 17 or not reach any sensitive area at all. Thus, the signal-to-noise ratio will be greatly improved. By matching the pattern of lands 16 to the matrix pattern of sensitive areas 13 of the semiconductive matrix 11, no crystals result between the sensitive areas 13.

It is known from previous attempts (See e.g. Japanese patent application No. 59-122988) to generate an undefined crack-pattern in the CsI layer. Thereby, inevitably a portion (in case of the Japanese application), about 75% of the crystals do not form above the sensitive areas. By providing a protective layer 12 with a pattern of grooves and lands matching the pattern of insensitive and radiation sensitive areas 13, respectively, a greatly enhanced efficience radiographic image detection device is achieved, because any X-ray radiation, be it directed to a sensitive area or be it directed to the insensitive area surrounding such sensitive area gives rise to light that reaches the sensitive area.

The grooves formed in the protective layer 12 are of a width of 10 to 20 micrometers and a depth of 10 to 20 micrometers suitable for obtaining different crystal orientations of CsI which may be applied by vapor deposition on the lands or land portions 16 of the protective layer 12.

Although for TDI applications use will be made of a matrix image-recording element comprised of a number of rows and a number of columns, it is also possible for other radiographic applications, in particular when a high source load is of no disadvantage, to use the matrix comprised of only one row of image-recording elements located next to each other, each image-recording element forming a "column". The advantages of the method according to the present invention with such a matrix comprised of one row are the same as those with a matrix comprised of several rows.

While the invention has been described in connection with an exemplary embodiment thereof, it will be understood that many modifications will be apparent to those of ordinary skill in the art; and that this application is intended to cover any adaptations of variations thereof. Therefore, it is manifestly intended that this invention be only limited by the claims and the equivalents.