The invention is particularly concerned with a golf training aid which is designed to assist a golfer in achieving proper alignment at address. It is recognised by skilled golfers that good alignment at address is one of the fundamental requirements for a competent stroke. Good alignment is generally achieved when the golfer's feet lie on a first imaginary line passing through the target, the ball lies on a second imaginary line parallel to the first line and the face of the golf club is at right angles to the second line. During the swing which is made, if the club face returns to its position at address and the swing in the hitting zone is along a line pointing to the target, the likelihood is that the ball will travel towards the target without sidespin that would generate a slice or hook.

Previous attempts to address the problem of poor alignment have generally taken the form of a mat which is laid on the ground and which is marked with various parallel lines and other illustrations. Generally the intention is that the parallel lines should be aimed at the target, with the other illustrations then being provided to show the golfer where his feet should be positioned and where the ball should be positioned. While golf practice mats of this type can certainly assist a player in training himself to set up properly at address, they tend to be bulky and inconvenient. In addition the player is obliged to play the ball off the mat, with or without a peg, and this generally does not truly represent the reality of playing a ball off natural turf.

It is an object of the present invention to provide a golf training aid which does not suffer from the disadvantages of training or practice mats as described above.

SUMMARY OF THE INVENTION According to the present invention there is provided a golf training aid comprising a pair of spectacles to be worn by a golfer, one or more spectacle lenses through which light can pass to the eyes of the golfer and image generation and projection means carried by the spectacles and arranged to project, onto at least one eye of the golfer, an image which will be visible to the golfer and which is superimposed on the golfer's normal field of view through the spectacle lenses, the image including a series of lines at least a first of which extends from side to side as viewed by the golfer and at least a second of which extends in a direction transverse to the first line, as viewed by the golfer.

The image may comprise a plurality of first lines and possibly a single or multiple second lines of varying length. Some or all of the lines themselves may be continuous or discontinuous. In the latter case, a line may be defined by, for instance, a row of dots.

In the preferred embodiment, the image generation and projection means comprises light collection means for collecting ambient light, reticle means arranged to receive light from the light collection means and to pass the image, and optical lens means to direct the image passed by the reticle onto the wearer's eye (s).

Other features of the invention are set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a plan view of a golf training aid according to this invention; Figure 2 shows a side view of the golf training aid; Figure 3 shows a front view of the golf training aid; Figure 4 shows a side view of the golf training aid worn by a golfer ; Figure 5 shows a front view of the golf training aid worn by the golfer ; Figure 6 shows a cross-sectional view, taken horizontally, of the golf training aid worn by the golfer ; Figures 7 (a) and 7 (b) illustratres the golf training aid in use during a full practice stroke; Figures 8 (a) and 8 (b) illustrates the golf training aid in use during putting stroke; Figure 9 diagrammatically illustrates one embodiment of lens system which can be used in the golf training aid of the invention; Figure 10 diagrammatically illustrates another embodiment of lens system which can be used in the golf training aid of the invention; and Figure 11 diagrammatically illustrates a reticle used in the golf training aid of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS The golf training aid 10 illustrated in Figures 1 to 6 is in the form of a pair of spectacles or eyeglasses, in this case dark glasses, which are worn by a golfer during practice. In the manner of conventional dark glasses, the aid 10 includes spectacle lenses 12 which are darkened, i. e. include filters to exclude certain light wavelengths and which are mounted in a frame 14.

Arms 16 extend rearwardly from the frame 14 and have cranked extremities 18 which in use locate behind the wearer's ears.

It will be noted that the frame 14 projects forwardly from the wearer's face by a distance somewhat greater than the distance by which conventional dark glasses frames would project. This is to provide space for the optical components described below. The frame 14 includes an upper, opaque wall 20 to prevent light from entering the wearer's eyes from directly above.

When worn in the manner of conventional dark glasses, light is transmitted through the lenses 12, from a substantially normal field of view, to both of the wearer's eyes.

Located within the space 22 between the lenses 12 and the wearer's eyes, on one side of the spectacles only, is an optical system indicated generally with the numeral 24. Figures 9 and 10 diagrammatically illustrate alternative optical systems which may be used.

Referring firstly to Figure 9, the numeral 26 generally indicates a reticle which is used to produce an image which will be projected onto one eye only of the user. Figure 11 diagrammatically illustrates a typical reticle which may be used. The reticle 26 includes a disc 27 of material which is opaque to visible light and which is formed with a pair of narrow, straight, parallel apertures 28 and a single, curved aperture 30 arranged transversely to the apertures 28. Located edgewise in the aperture 30 is a generally rectangular element 31. The element 31, which serves as a light collector, is made of a polymeric material incorporating a fluorescent dyestuff. An example of a suitable material for the light collector element 31 is LISA@ plastics material manufactured by Bayer AG.

In use, ambient light enters the space 22 through a side lens 32 mounted to the frame 12. The light falls on the collector element 31. A substantial amount of the resulting fluorescence of the dyestuff in the collector element material is totally internally reflected within the element and only escapes at the edges thereof. Thus a substantial proportion of light collected by the element 31 is transported to the aperture 30 and is passed by the reticle.

Although not shown in Figure 11, light collector elements similar to the element 31 can be provided for the apertures 28 as well, to ensure that the reticle passes a substantial amount of light through all the apertures 28,30.

Light passed by the reticle 26, i. e. an image corresponding to the apertures 28,30, is reflected by a curved reflector 34 towards the wearer's eye, which is located at a focal plane 36. The reflector 34 is in the nature of a beam splitter which is capable of reflecting light from the reticle towards the eye while at the same time passing light in a direction from right to left as viewed in Figure 9. Thus the wearer receives, in one eye only, an image corresponding to the apertures 28,30. At the same time, both the wearer's eyes receive light from the general field of view, in the case of one eye directly through the lens 12 and in the case of the other eye directly through the reflector 34 : It will accordingly be understood that the reticle and reflector 34 serve as an image generation and projection means to project an image onto one eye of the wearer while light from the general field of view is simultaneously received by both eyes. It will furthermore be understood that the projected image is visibly superimposed on the wearer's general view.

Those skilled in the art will appreciate that the aperture 30 is slightly curved to take account of spherical aberration effects attributable to the use of the curved beam splitter.

Figure 10 illustrates another optical system in which spherical aberration effects are reduced. In this case, the reticle 26 passes light which is reflected by a planar mirror 38 through a lens system 40 and onto a planar reflector or beam splitter 42 which refracts incident light to a parallel state and which reflects the parallel light rays to the wearer's eye at the plane 44.

The lens system 40 may for instance be provided by a Fresnel lens. With this type of configuration astigmatism and spherical aberrations are reduced or eliminated.

Figure 6 illustrates the training aid 10, with a lens system as shown in Figure 9, in a horizontal cross-section taken at the level of the wearer's eyeballs 38. As illustrated in this Figure, the frame 14 carries a nosepiece 45 which will rest in use, in the normal way, on the wearer's nose 48.

Extending from the nosepiece is a divider 49 which separates the left and right sides of the space 22 from one another, but it will be understood that this is not essential and that the space 22 may be continuous with a single lens, in the form of a unitary visor, in place of the dual lenses 12.

The use of the aid 10 in golf training will now be described with reference to Figures 7 (a) and 7 (b) and 8 (a) and 8 (b).

Referring firstly to Figures 7 (a) and 7 (b), the lines 50 and 52 are imaginary lines, visible to the wearer 55, in the image projected onto his eye. The parallel lines 50 are created by the apertures 28 in the reticle 26 and are seen by the wearer as straight lines extending from side to side across a part of his general field of view. The line 52, created by the aperture 30 in the reticle 26, is seen by the wearer as a straight line extending normal to the lines 50 across a part of his general field of view.

As a first step, the wearer stands behind a ball 60 which he is going to hit and lines up the ball with a distant target 62 towards which he wishes the ball to travel when hit. He does this by aligning the line 52 through both the target and the ball. He then lays a marker 54 on the ground, on the same line passing through the target and the ball, slightly ahead of the ball.

The wearer then takes up a stance, side-on to the target, as illustrated in Figure 7 (a), looking down at the ball. He adjusts his stance until the furthest of the two lines 50 which he can see, indicated by reference numeral 50.1, extends visibly through both the marker 54 and the ball and is accordingly aligned with the target. He then aligns his toes on the nearer of the two lines 50, indicated by the reference numeral line 50.2. Depending on the wearer's height and the length of his golf clubs, it may be necessary for him to swing his head up or down, in a vertical plane, to bring the lines 50. 1, 50.2 into appropriate positions for the necessary alignments to take place.

Having followed these steps, the wearer can now be sure that his feet are correctly aligned with the target and that if the face of the golf club is brought into contact with the ball along the line extending through the ball, marker and target with the club face square to that target line, the ball will be struck directly over the marker en route to the target.

It is recognised that a golf training aid as proposed by the invention and as described above will not be permitted, in terms of the Rules of Golf, to be used during actual play, and that it will be suitable for use during practice only. Nevertheless it is believed that if a golfer repeatedly practises the set- up routine described above, on the practice tee, he will acquire the ability, through muscle memory or otherwise, to achieve correct alignment at set- up during actual play on a golf course.

Figures 8 (a) and 8 (b) illustrate the use of the training aid of the invention during a putting stroke. The same procedure as is described above is used to achieve correct alignment at address. However in this case the club face will be moving far slower than during a full stroke with a club other than the putter, so that the further line 50.1 can also visibly assist the wearer of the training aid to bring the face of the putter towards the ball along the correct target line, and also to ensure that the putter face is square to that line at impact.

Figures 7 (a) and 7 (b) and 8 (a) and 8 (b) also show a number of short lines 53 which are presented to the wearer's eye in the projected image, which are spaced apart from one another and which extend at right angles to the lines 50.1,50.2. In both cases, the wearer of the training aid can use these lines to ensure that his feet are spaced apart by the correct distance at address and also to ensure that the ball is at the correct position relative to his feet. So, for instance, with a longer club such as a wood or long iron, the ball will usually be positioned further forward in the stance than would be the case with a short iron, and with a putter the ball will usually be positioned midway between the feet in the stance. An added benefit which arises in the case of the putting stroke illustrated in Figures 8 (a) and 8 (b) is that the wearer can use the lines 53 to gauge and refine the length of his backswing and follow-through for putts of different length.

It will be understood that the short lines 53 are generated in the image received by the golfer's eye by appropriate modification of the reticle 26, and in particular by the provision of further slit-like apertures corresponding to these lines.

To assist the golfer using the training aid to take up the same stance and position the ball consistently for particular shots, the projected image may include identification markings associated with the short lines 53. The lines may for instance have individual, recognisable symbols or alphanumeric characters located visibly alongside them. Such identification markings would also assist the user, when practising putting, to regulate the length of his backswing and follow though to consistent values.

Specific mention has been made of a light source including one or more light collectors of flat proportions which collect and concentrate ambient light for passage through the reticle. In another embodiment of the invention the light collector (s) could be provided by one or more lengths of polyoptic fibre, i. e. fibre which has the ability to collect light along its length and convey the collected light, by internal reflection, to its ends. In this case the end (s) of the fibre (s) could be located adjacent the apertures of a reticle. Alternatively, a plurality of fibre ends could themselves be arranged to define the image which is to be projected on the eye. In yet other alternatives, other types of light source could also be used. The light source could, for instance, be an LED or other powered light source with an appropriate power source, such as batteries. Gaseous tritium light sources are also within the scope of the invention. Still further the invention envisages that the projected image could be an LCD (liquid crystal display).

In the example described above, the entire image is projected onto one eye only. It is within the scope of the invention for a part of the image to be projected to one eye and another part of the image to be projected to the other eye. So, for instance, it would be possible to project, say, the horizontal line (s) to one eye and the vertical line (s) to the other eye. Such an arrangement would typically require independent image generation and projection means for the two eyes.

In yet another modification envisaged by the invention, the light generation and projection means, eg the light source and optical system in the above example, could be located above the eye rather than to the side. In situations where the user of the training aid wears a hat, cap or peak with a forwardly projecting brim this may however be less desirable than the described arrangement in which light is collected from the side, because the brim may reduce the amount of direct sunlight reaching the light collector (s).

It will be understood that in, the examples described above, the projected image is visible throughout the golf stroke. In situations where the golfer finds the image distracting while he is actually making a stroke, it is possible to include a means whereby the image is removed when the stroke is to be made. Where the light source is, say, an LED version as mentioned above, the training aid may include an on/off switch to switch off the power supply. Since it would be undesirable for the user, having taken up a correct stance and grip, to operate the switch manually, it is envisaged that the switch could be orally operated. It could for instance include suitable hard wiring extending from the power source to a small switch which is inserted in the mouth between the upper and lower rows of teeth and which is then operated by clenching the teeth.

In embodiments where the image generation and projection means includes a light collector and optical system as illustrated in the drawings, the image could be removed by a shutter moved into a position to obstruct the image when the stroke is to be played. Movement of the shutter to an image obstructing position could once again be initiated orally.

In sophisticated versions of the invention, the image generation and projection means could be adjustable to enable a user to position the lines which he sees at positions which he personally prefers. This could involve apparatus arranged to move or reorientate refracting and/or reflecting components of the optical system to selected positions.

In embodiments where the lens (es) 12 are darkened to enable the golf training aid to serve as dark glasses, the filter incorporated in the lens (es) may also be selected, in relation to the colour of the projected image, to enhance the contrast between the image the general field of view, thereby improving the visibility of the image.