Viewing Apparatus This invention relates to viewing apparatus for viewing an electronic display. In particular, but not limited to liquid crystal displays. Conventional cathode ray tube (CRT) electronic displays emit a powerful glare which can cause severe eye strain, contingent fatigue and in certain cases lasting damage to the viewer's eyes. With liquid crystal displays (LCD) the glare is reduced by comparison with a CRT display, but an additional problem of miniaturization of the image is encountered since LCD displays are more difficult to manufacture and more expensive for the same size of screen. LCD displays are commonly used for computer screens, personal organisers, calculators, translators, electronic books and portable or fixed television screens. While devising lighter and smaller electronic viewing devices the size of the display screen and the characters or image displayed thereon, tend also to be reduced. The user is then required to view smaller images, whilst still having some problems with glare and reflected light from the display.

In accordance with the present invention, viewing apparatus for viewing an electronic display comprises a lens support, and at least one magnifying lens mounted in the lens support, the lens including a filter wherein the magnification and filter characteristics of the lens are predetermined in accordance with the type of display to be viewed.

The present invention provides viewing apparatus for a user which compensate for the inherent glare and reflected light resulting from a particular screen which the user is viewing, and also provides appropriate magnification.

The or each lens may be fixed in the lens support, but preferably is removably mounted on the lens support. This allows a user to fit a lens support and then change the lenses according to the particular display to be viewed.

The lens support may comprise a frame which the user wears directly, adapted to receive the lens, but preferably the lens support is adapted for attachment to a conventional spectacle frame. By attaching the lens support to the user's ordinary spectacle frame there is no requirement to compensate for individual user's eyesight. The filter may be incorporated into the lens, but preferably the filter is applied as a coating.

In accordance with a second aspect of the present invention, a set of lenses for use separately with a common lens support wherein the lenses are adapted for different electronic displays.

An example of viewing apparatus in accordance with the present invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 shows one example of a frame for use in the present invention;

Figure 2 shows a lens suitable for use inrthe example of Figure 1; Figure 3 shows a second example of a frame for use in the present invention;

Figure 4 shows a pair of lenses suitable for use in the frame of Figure 3;

Figure 5 shows a frame and lens attached to a pair of conventional spectacles, and

Figure 6 shows an adjustable frame with variable angle for the lens.

In Figure 1 a frame 1 is shown, suitable for supporting a pair of lenses 2 such as those shown in Figure 2. The lenses are typically made of optical glass or plastic 3 and edged with a metal surround 4. The metal surround is provided with extensions 5 and 6 which cooperate with grooves 7 and 8 respectively in the frame 1. The surround 4 cooperates with a groove 9 in the frame 1. The extensions 5 and 6 can be arranged to have a snap fit into the grooves 7 and 8. The shape of the frame 1 and its

corresponding lenses may be varied to some extent to give a choice of style.

In Figure 3 an alternative frame is shown. In this case grooves 10 allow the lens 11 to be slid into place and extensions 12 cooperate with grooves 13 on the upper side of the frame in arms 14 of the frame. In the example of Figure 4 the lens 11 is formed as a single piece. An edge 15 of the lens which forms a bridge or nose piece is machined to provide a comfortable surface for the wearer. For a lens or lenses manufactured from plastics the extensions may also be formed e.g. by moulding from plastics rather than having to add a metal surround 4 to the lens.

The magnification of the lens is defined during manufacture and for convenience its value may be marked on a surface of the surround 4 or one of the extensions 5,6. Glare and reflected light from the screen is reduced by providing a filter in the lens 2 either in the form of a coating or incorporated in the material during construction.

Glare caused by light in the room or sunlight reflecting off the screen may be cut down by providing circular polarising filters in combination with linear polarising filters in the lens structure so that only light generated by the screen itself is received by the viewer.

An anti-glare coating provided on the surface of the lenses improves contrast of the image being viewed and reduces eye strain, the thickness and refractive index of the coating determining the effectiveness. There may be multiple coatings of different refractive index.

In Figure 5, a pair of conventional spectacles 16 are shown onto which is superimposed a lens 17 according to an example of the present invention (shown by a dashed outline) . The lens 17 is supported on the bridge 19 of the spectacles by a clip 18 which holds the lens 17 in place and can be easily removed when the user is no longer looking at the screen.

The lenses and frames may be provided in a removable form as described with respect to Figures 1 to 5 or as a complete pair of spectacles with particular lenses fixed into the frames. The removable lens arrangement will typically be in the form of a common frame which can receive separate ones of a set of lenses according to the electronic display to be viewed. In the case of fixed lenses 2, these will be adapted to a particular display screen so that any user of that screen would use the same spectacles to view it.

In determining the characteristics of magnification and reflectance for the lenses for any chosen display, the display would typically be monitored using a sensor and values of reflectance measured from the screen using conventional methods would be input to a processor which could then calculate the necessary parameters for the lens filter to compensate for diffuse and/or specular reflection and combine these with predetermined magnification levels for the size of screen and typical output image/character size. This information could be provided by the suppliers of the display or derived from the operator's knowledge of the display.

The relevant parameters which may be altered include magnification; polarisation; transmissivity; material thickness, refractive index and shape; colour tint and lens coating.

The type of polarisation necessary to cope with the ambient light reflected off the screen may be, for example, linear, right or left handed circular polarisation, or elliptical polarisation.

For monochrome screens, light at the desired frequency should be allowed to pass, whereas light which has been reflected off the screen and has different frequencies to that of the screen originating light should be stopped. The operation of colour and monochrome screens may also cause a pulsing effect which with time causes stress due to the continual requirement of the eye to accommodate. Light

at the frequency of this pulsed light can also be excluded by filtering out frequencies of light other than those which are desired to pass through the lens.

The thickness and refractive index of the material from which the lenses are manufactured affects the focusing of light being viewed. For different colours of light, a material of a particular refractive index has a different bending power causing dispersion. In certain cases a standard thickness moulding may be provided in which the material refractive index is altered to give the desired focus for a particular screen. The lens material may be glass, with standard, or low silica content for low dispersive power, or polycarbonate or other material typically used in known clip-on anti-glare screens. The lenses incorporating the appropriate filter may be produced from polished glass, by lamination or by providing multi-layer coatings onto a substrate of conventional material, such as glass, by evaporation e.g. of magnesium chloride or zinc sulphide. A tint, either light or dark can be added to the lens to improve contrast for monochrome or colour screens respectively, and to reduce the intensity of light passing through the lens.

Other frame shapes or arrangements for mounting the lenses may be used without detracting from the invention. An example of this is to provide adjustment of the join between the lens support 22 and arms 21, shown in Figure 6, so that for a given height of user in a standard working position the angle of the lens to the incident light and the eye is adjustable. Settings 20 may be marked on the arm 21 so that the processor calculates and indicates the correct setting for the circumstances.