Mask System for Radiograph Light Box

1. Field Of The Invention

This invention relates to apparatus for masking images and more specifically to apparatus for masking radiographs.

2. The Prior Art

X-ray film are conventionally viewed or illuminated for scanning by disposing the same against a diffuser plate behind which is located a lighting source. A mask system is commonly used to eliminate excess light around the borders of radiographs that are smaller than the illuminated area of the light box. Various types of mask systems such as plates and belts are disclosed in the prior art. However, such systems are generally complex structurally, require manual operations such as the manual positioning of plates and/or only mask on two sides of a rectangular area.

In accordance with the present invention apparatus for masking comprises a pair of spaced endless belts disposed in substantial perpendicular relationship adjacent a support for an image bearing medium. Each of the belts has spaced opaque regions and spaced aperture regions connecting the opaque regions. The belts are supported on rollers and are movable to selectively position portions of the opaque regions into alignment with the edge regions of the image support.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a top view of a light box for viewing radiographs;

FIG. 2 is a side view of the light box shown in FIG. 1 with one side wall removed;

FIG. 3 is a perspective view of the masking system shown in FIG. 1;

FIG. 4 is an enlarged perspective view of one of the masking belts shown in FIGS. 2 and 3;

FIG. 5 is a schematic side view showing one of the masking belts in a non-masking position;

FIG. 6 is a schematic side view similar to FIG. 5 showing one of the belts in a masking position; and

FIG. 7 is a top view of another embodiment of the masking belt.

Referring to FIGS. 1, 2 and 3 of the drawings, there is shown a light box comprising a housing 6 having a diffuser plate 8 in the upper surface thereof. A masking system in accordance with the invention comprises a pair of endless belts 10, disposed within the housing 6 in substantially perpendicular relationship. As shown in FIG. 3 each of the belts 10 extend around a pair of rotatable rollers 14. Each of the rollers 14 of each pair is rotatably mounted on a suitable supporting frame not shown by means of a shaft 16. One shaft 16 of each roller pair is extended to receive a gear 19 which is engaged by a gear 18 driven by an electric motor 20. The two belts 10 may be moved over their respective rollers 18 by selective energization of their respective motors 20.

The reach portions of each belt extending between their respective rollers are positioned over a transparent support plate 22 corresponding in size to the diffuser 8 and are effectively sandwiched between the support plate 22 and diffuser 8 as shown most clearly in FIG. 2. The support plate 22 thus holds the belts in contact with each other and the belt assembly in contact with the diffuser 8 to render the light transmission through the diffuser, belts and plate as effective as possible.

A light source 26 is positioned below the masking apparatus to illuminate a negative or other transparency placed on the diffuser 24. When so illuminated the image may be viewed, scanned, copied, etc.

Referring now to the specific structure of the belts 10 as shown in detail in FIG. 4, each belt 10 has a width corresponding to the width of the plate 22 and diffuser 8 and is provided with two spaced opaque portions 28 which are connected by transparent or aperture portions 30. Each of the transparent portions 30 has a length corresponding to the length of the plate 22 and diffuser 8.

When a belt is positioned to align its transparent portions with the diffuser 8, its opaque portions will extend around its respective rollers 14 as shown in FIG. 5. Thus the entire diffuser will be illuminated by the light source 26. However, if the belt 10 is moved as indicated in FIG. 6 to move the opaque sections into the image area the illuminated diffuser area will be effectively masked in either the X or Y direction depending on which belt 10 is moved. By simultaneously moving both belts masking in both the X and Y directions can be accomplished.

It will be readily apparent that as an alternative to a belt having continuous material the transparent or aperture sections could comprise cut out areas 34 in an opaque belt as shown in FIG. 7 with narrow edge positions 36 retained to provide belt continuity.

The apparatus disclosed thus provides a simple low cost means for masking a diffuser of a light box to render the light box capable of being used with radiographs of a variety of sizes. Also it will be apparent the masking system is not limited in application to light boxes. For example, it can readily be applied to a photographic printer to mask portions of negatives.

The invention has been described in detail with particular reference to certain embodiments thereof, but it will be understood that variations can be effected within the spirit and scope of the invention as defined in the appended claims.