Patent Number: 052025667
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A typical computer is shown at 10 with its video display terminal (VDT) indicated at 12. In front of the VDT is the protective hood 14 of the present invention. The hood comprises a frame 16, which in the preferred embodiment is the hood enclosure 18 itself, although were the invention limited to protection from emitted radiation only without the glare-reduction function, the hood could be abbreviated greatly, leaving only the frame structure necessary to support the reflectors as described below, and as suggested by FIGS. 4 and 8. The enclosure 18 defines a pair of sidewalls 20 which are parallel and spaced adequately to fit alongside the left and right edges of the VDT, as shown in FIG. 2. The sidewalls of the VDT are held in place by means of a first reflector 21, which has an aluminum tray 22, which is pivotally mounted by its flanges at 26 by a bolt and nut combination 28 and 30 which permits rotation, but which can be locked at any particular position by tightening the bolts. The second reflector 32 is also pivotally adjustable with the same bolt-and-nut combination 28 and 30. The pivotal reflectors are adequate supported to hold the two sidewalls together. The hood is held to the VDT by means of a bail 36, which has inwardly-directed ends 38 which engage in any pair of bail holes 40 bored into the sidewalls of the hood as shown in FIGS. 1 and 5. The crossbar portion of the bail seats in a selected one of the three grooves 42 in the attachment or mounting block 44, which is securely held on to the top of the VDT by means of a double-sided adhesive coated foam slab 46. The action of the reflectors is as follows. Both reflectors are rotated into adjusted position such that the viewer sees the image approximately as indicated in FIG. 8. The aluminum tray 22 of the reflector 21 is also grounded AS INDICATED AT 48 to the VDT ground to short-circuit the electrical components of the EMF and help eliminate static. The tray also has a ferromagnetic screen 23 bonded to its upper surface, which is intended to shield the operator from the magnetic field component of the EMF from the VDT. On top of the ferromagnetic screen is a layer of lead foil 50, which will absorb most of the X-rays, reflecting some of them. On top of the foil shield is a reflective surface 24, which could be a chromed, polished glass surface or any other kind of highly reflective surface, which will pass most EMF and X-rays, and absorb some UV and reflect some. It is not critical that the first reflector 21 absorb all or most of the harmful radiation, as long as it doesn't transmit it. All radiation reflected from the first reflector is reflected to the second reflector 32, which is where the remaining separation occurs. The second reflector, unlike the first reflector 21, comprises a sheet of plastic such as polycarbonate or allyldiglycol carbonate, marketed as an eyeglass lens material under the trademark CR-39.TM., with a highly polished reflective surface darkened with an organic (non-metallic) dye such as black azo dye. The preferred embodiment is treated with a black azo dye to a very dark density so that 95% to 97% of visible light which passes across the surface into the material is absorbed, but visible light reflection is maximized. The surface of the second reflector reflects visible light in the range of 400-700 nanometers in wavelength, but passes through all other wavelengths, so that all high-frequency radiation such as UV and X-rays harmlessly pass through this reflector to be dissipated in the environment, away from the operator. This action is best shown in FIG. 8. In this figure, rays indicated at a are emitted from the VDT and impinge on the first reflector 21. At 21, the EMF is largely absorbed, and the UV and X-rays partially absorbed. Non-absorbed radiation, including substantially all of the visible spectrum, is reflected as rays b to the second reflector 32. At the second reflector, high-frequency, harmful radiation is passed through as rays d, and the visible image is reflected to the viewer, as indicated at c. As seen in both FIGS. 3 and 8, the harmful radiation from the VDT screen is intercepted by the reflector combination so that the worker's body is in the shadow of the reflectors and thus shielded. These figures show an exaggerated posture in which the operator appears to be looking up, but the reflectors would ordinarily be arranged so that the operator is looking straight ahead and assumes the same posture, looking straight ahead or somewhat downward as he or she would were the enclosure not there. It will be noted that the bail 36 is multiply adjustable in the grooves 42, and the first and second reflectors both pivot. In any event, the VDT has a general longitudinal or axial axis and the reflectors do not deflect the VDT image left or right of that axis, but only upwardly and rearwardly in a vertical plane by the first reflector, and forwardly in the same basic vertical plane, which is parallel to the longitudinal axis of the VDT, with the second reflector. The ray diagram of FIGS. 4 and 8 are diagrammatic only, but with the multiple adjustability of the unit, which has been tried on the job, for any known type of computer VDT, the reflector and the hood itself can be adjusted properly so that full screen viewing is possible without any substantial gaps which could pass radiation to the body. The eyes and body do not actually face the VDT directly. It should be noted that the upper and lower reflectors could be reversed in function, with the upper reflector receiving the light first and reflecting it to the lower reflector, but this arrangement tends to protect the eyes only, and is geometrically awkward, so that the illustrated embodiment works better. The hood 14, in addition to having the sidewalls 20 and the reflectors, is intended to virtually eliminate all glare by excluding ambient light from the screen of the VDT. This is accomplished in the preferred embodiment by means of a top wall 52 which slides forward and rearwardly in channels 54, and a rear wall 56 which slides up and down in rear wall channels 58. The rear wall is preferably provided with a plurality of adjustment slots 60 which seat the rear edge of the top wall 52 as shown in FIG. 5, so that the rear wall is adjustable to accommodate the positioning of the hood on any particular VDT. The combination of the top wall and rear wall, together with the sidewalls and the first reflector 24 effectively eliminate most ambient light from the VDT screen. All of the wall members are black and dull-finished to eliminate internal reflection. As described above, the first, lower reflector is made of a normal silvered glass or plastic pane and will partially transmit and partially reflect harmful radiation. The upper reflector, being made of highly polished polycarbonate or CR-39 tinted to a density of 92-97 percent with an organic pigment such as black azo dye, reflects only visible light. Although the bulk of glare and extraneous light is eliminated by the dark hood, there are other factors that must be considered when protecting the operator from glare-induced eye strain. First, not all of the glare is eliminated by the hood. Also, often there is light that could be coming from an angle (such as the light from ceiling fixtures) which tends to interfere with vision. This light causes the pupils to constant contract, straining the eyes. To counter this, a pair of eyeglasses 62 with lenses 64 having an annular gradient 66 is provided. These glasses, which could be either prescription or not, have a clear center which measures about 1 cm. to 2 cm., and outside of the center they have a steep gradient tint that may vary from full light transmission at the center to as little as 10% transmission at the edges. This configuration accommodates the optical facts of computer use, in which only the very central portion of the field of vision is used anyway, about a 15 degree solid angle. Light impinging on the eyes at greater angles serves to constrict the pupil without providing any useful visual information, resulting in the apparent dimming of the useful image. Therefore, glasses having a clear central portion wide enough to allow viewing the VDT screen but excluding other light enhances the image in conjunction with the beneficial effects of the darkened hood described above. A computer operator can sit in front of a VDT equipped with the hood disclosed herein, wearing the glasses described herein, for hours on end in many instances without reporting any eye discomfort whatsoever. The same operator, when the hood and glasses are removed, report eye distress within an hour or two if the operator has sensitive eyes. There is thus no doubt that the elimination of glare plays a major part in the reduction of eye strain complaints among workers, so that the double function of the disclosed system produces immediate advantages in addition to elimination or reduction of the as yet unknown deleterious effects of various electromagnetic rays which do not fall within the visible spectrum.