Many devices have been designed to measure the speed of the golf club head but all have significant disadvantages to their use. Apparatus currently available from-' Beltonics uses the Doppler effect to perform this measurement, but the device is relatively expensive, limiting it availability to the average golf player. US patent No.

4,477, 079 in the name of White, teaches a method of determining the speed using two photo-detectors looking along parallel paths that the golf club passes through just before the point of impact. The device uses ambient light, such that as the club head passes in front of the photo-detectors, the light reaching them is temporarily diminished, thus they are able to detect the passing of the gold club head. By measuring the time between the golf club head passing the first and second photo- detectors it is possible to calculate the speed at which the club is travelling at that time. The problem with this device is that because it relies on ambient light, on days with low light levels, for example when it is cloudy, the photo-detectors are not reliable at determining when the club head passes in front of them. In addition, in artificially lit areas, the lights frequently flicker, again causing problems for the detection of the club head.

US Patent No. 5,257, 084, Marsh, teaches a system utilising infra-red light reflected from a reflector attached to the golf club. The disadvantage of this system is that it requires the alteration of the golf club, affecting it's balance and thus it's swing.

US Patents Nos. 5,108, 105 Shimizu and 5,114, 150 Matsumura teach devices using a magnetic system to determine the speed of the club. The golf club is provided with magnetic materials that can be sensed by magnetic sensors, generally provided in

a mat placed on the ground under the swing of the golf club. The disadvantage with this system is that special golf clubs are required, fitted with the necessary magnetic materials, and the user must place a special mat, with associated detection equipment, on the ground where he is to swing.

US Patent No. 6,227, 984 Blankenship also teaches a device mounted in a mat.

This device teaches the use of light sensors sensing the passing overhead of the club head. The difficulty with this device is that unless the club head passes very close to the sensors, the measurement will lack accuracy due to the wide field of view of the sensors.

US Patent No. 5,634, 855, King, teaching a system incorporating two light sources and two detectors. The system is arranged such that as the golf club is swung, it passes between the light sources and the detectors, crossing and thereby interrupting the light beam reaching the detectors. The time between the two light beams being crossed can be used to determine speed of the golf club. This requires a mechanical connection between light sources and detectors in the light path, which is not conducive to fabricating a compact and easily transportable device.

The object of the present invention is to provide an improved device for measuring golf club speed, which does not require alteration to the golf club and easily is portable.

According to the invention there is provided apparatus for the measurement of speed of an object between two points, the apparatus comprising: a least one light source; at least one detector or detecting changes in light levels; a processor, including timing means, for processing and timing information obtained from the detector; and a display for displaying the processed information.

Preferably the light source (s) will be a laser diode. Alternatively, other light sources such as LEDs may be used, but these will generally be shaped via apertures and/or lenses.

Generally two light sources will be used. However, where one source is used, the apparatus may include means for splitting the light from the source into two beams.

Generally a single detector will be used. However, two detectors may be used.

In addition, the detector (s) will usually further incorporate collection optics to limit the angular range from which light is detected. In addition, the detector may incorporate a filter to allow detection of light in the range produced by the light source. Conveniently the detector (s) may be set to ignore light levels up to a threshold and measure changes in light levels above that threshold.

In one embodiment a single light source is used in combination with two detectors. In this embodiment the light source is shaped to be as broad as possible, and the collection option for the detector only accept light from a very narrow angular range.

Preferably the processor also controls the switching on and off of the light source (s). In addition the processor is programmed to switch on the timer on receipt of a change of light level signal from the detector, or a first detector, and switch the timer off on receipt of a second change of light level signal from the detector, or from a second detector. The processor is also programmed to determine speed by calculation, in which the distance between the two beams or two detectors by the time measured by the counter.

To help understanding of the invention, a specific embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a speed meter according to the prior art; Figure 2 is a timing diagrams for the meter of Figure 1;

Figure 3 is a speed meter according to the present invention; Figure 4 is a timing diagram for the meter of Figure 3; Figure 5 is a further sp eed meter according to the present invention; Figure 6 is a timing diagram for the meter of Figure 5; Figure 7 is a third speed meter according to the present invention; Figure 8 is a fourth speed meter according to the present invention; and Figure 9 is a schematic of the electronics of a speed meter according to the present invention.

Referring first to Figure 1, thereshown is a device for measuring the speed of a golf club according to the prior art. Ambient light 100 from the sun or lighting fixtures scatters from features surrounding a golf player with a fraction of the light being emitting in the direction of two lenses 102 and 103 that collect light and focus it on two photo-detectors 104 and 105. The detection system is designed so that only light within a predetermined angular range defined by dashed lines 112 and 113 reached the detector. In use the detection system is placed near the ground in front of a golf ball 109. When a player desires to hit the ball he swings the club head in direction 108, thereby causing the club head to intercept the light path of detector 104 when the club head is in position 106. As the swing progresses towards the ball 109, the club head moves to position 107, where it intercepts the light path of detector 105.

Referring now to Figure 2, the timing diagram thereshown, has time indicated along the horizontal axis. The movement of the club head causes photo-detector 104 to produce a signal 200 that has a transition from high value to low value. Similarly as the club head reaches position 107, the signal 201 from photo-detector 105 transitions from a high value to a low value.

Referring to both Figures 1 and 2, processor 110 includes circuitry including a timer counter that is started at time a T1, when the first high to low transition is detected and stops the counter at time a T2, when the second high to low transition is detected. The magnitude 206 of the counter timer T when it is stopped corresponds to the transit time of the club head over the distance W (114). The club head speed v can then be determined by the processor from the known calculation v = W/T and displayed on electronic display 111.

An essential problem with this passively illuminated approach is that if the background illumination level changes rapidly or falls below some threshold value, then the entire device fails to work.

Referring now to Figure 3, which shows a speed-measuring device according to the present invention. Light beams 302 and 303 are sent from light sources 300 and 301 along substantially parallel paths separated by distance W (315). Generally the light sources will be low cost laser diodes, such as approximately 1 mW in a red beam from a 650 nm laser. However, other light sources such as light emitting diodes (LEDs) could be used. The beams of such other light sources can be shaped through the use of apertures or lenses to a small transverse size to increase the precision of timing measurements. The light from each light source can be turned on or off by circuitry in processor 308.

Between lasers 300 and 301 is situated a photo-detector 305 which may be equipped with collection optics 304 to collect light from within a predetermined angular range as illustrated by dashed lines 306 and 307. In operation the player swings the golf club head along direction 316 towards the ball 317. Near position 313 light from laser 300 hits the club head. Part of the light is reflected and collected by optics 304 and enters detector 305, where it produces a transition corresponding to an increased light level. As the club head continues to swing it reaches position 314 where it crosses the second light beam 303. Light from this beam is then scattered onto detector 305 resulting in a second transition corresponding to an increased light level. The two light transitions can be used to determine the club speed in several ways.

The accuracy of the measurement is related to the width of the light beams 302 and 303 in relation to the distance, W, between them. Although the detailed result is dependent on how received light signals are processed, a first order estimate of the fractional uncertainly of a speed measurement is given as d/W, where d is the width of the light beam. For a laser beam the diameter may be, for example, 2mm, and with a distance, W, of for example 50 mm, giving an uncertainly of approximately 4%. If an un-shaped LED were used as a light source, the full divergence angle from the LED

may be 20° or greater. At a distance of 10cm the light beam width is then 3.5 cm. As a result sources 5 cm apart would have overlapping beams, indicating the need for shaping of the beams.

In the preferred embodiment as shown in Figure 3, the light sources are generally held in an off situation expect when they are being used. This is a safety precaution and also conserves energy. Figure 4 is a timing diagram of the device of Figure 3. The speed meter of Figure 3 is set for the golf club to be swung in a particular direction. Where the golf club is to be swung, as illustrated, light source 300 is first turned on at time TO indicated by line 400. As the light beam 302 is not being scattered by the club head, the detector records a relatively low light level as shown in line 402 on Figure 4. As the club head moves and intersects light beam 302 at time T1, the light is scattered and the detector 305 receives an increased light level.

Once this has occurred light source 300 has completed its function for this particular swing and is turned off by the processor 308. At the same time the processor 308 turns on light source 301, and starts a counter timer. When the club head intersects beam 303 at time T2, the photo-detector 305 records a second increase in the light level. At that time the processor turns off the second light source 301 and the counter timer. The speed v of the club head can now be calculated by the calculation v = W/T, where W is the distance between the light sources, and T is the time between the first and second increase in light levels recorded by the detector, as recorded by the counter timer. The speed can then be shown on the display 312. The processor can then be reset and re-started for another swing of a golf club.

Where the golf club is to be swung in the opposite direction to that described above, it is necessary that light source 301 is switched on initially, with light source 300 being turned on after the club head has passed though light beam 303 scattering light to the detector 305. To achieve this the processor is programmed such that the direction of the swing can be entered, determining which light source is illuminated initially. This may be by means of a switch.

In some embodiments, an optical bandpass filter is provided either in front of the detector 305, at position 318 or in front of the collection optics 304. This allows transmission of light having a wavelength of approximately that of the light sources,

while blocking other light. This eliminates deleterious noise from the detector 305, resulting in more defined signals.

Figure 5 shows an alternative embodiment of the speed meter according to the present invention. Corresponding elements have corresponding numbers for ease of understanding. In this embodiment, one light source 500 is used to generate two light beams 302 and 303. The light source 500 is intercepted by a partially reflecting and partially transmitting beam splitter 502, producing two beams. The transmitted beam is then re-directed using a mirror 503 to produce two parallel beams 302 and 303.

As these beams 302 and 303 are from the same light source and will be switched on and off together, the timing diagram of Figure 6 is somewhat different to that showing in Figure 4, corresponding to the speed meter of Figure 3. The light beams are shown in the top two lines 600,601 and as they originate in a single source 500, they are turned on at the same time. In the third line 602 of Figure 3, the distance W between the beams 302,303 is less than the size of the gold club head.

Thus the head intercepts the first beam alone 302, then both beams and finally the second beam 303 alone, resulting in light to the detector as shown. In this case it is suitable to use an edge detector which detects the changes in intensity of the light.

This detects pulses as shown in the fourth line 603 of Figure 6. These pulses are detected at times T1 and T2 corresponding to the start of crossing of the beams by the club head, from which the time to travel between these points can be measured and thus the speed of the club head.

This second embodiment has the advantage over the first and preferred embodiment in that only one light source is needed. However, the beam splitter and mirror are also required, and the signal processing required to establish the presence of two steps is also potentially more complicated.

Figure 7 shows a further embodiment according to the present invention. This embodiment utilises two sets of detectors 700, collection optics 701 and light sources 703. The light beams 704 are directed such that when light scatters from the club head it falls within the acceptance angle of the detection systems 702. This arrangement produces a single low to high transition for each detector which can be

used to start and stop a timer counter and thus calculate the speed of the club head as described with reference to the precious embodiments.

A further embodiment according to the invention is shown in Figure 8.

Detectors 805 and collection options 806 are arranged so that the detector fields of view 800,801, are relatively narrow. The beam from light source 807 is expanded using optics 802 to produced a wide beam, 803,804. The detectors receive one light pulse each as the club head moves though first one detector field of view and then the other. As a result the speed of the club head can be calculated as before.

In order to achieve reliability of the speed meters according to the invention it is necessary to suppress any interference with the detector due to ambient light levels, or noise. Such background light noise can be reduced by spectrally filtering the light incident on the detector, as described in the first embodiment. Discrimination can also be enhanced through synchronous detection where the light source is amplitude modulated at a particular range of frequencies, for example 10kHz to 10MHz. Figure 9 is a schematic of electronic circuitry to operate a speed meter of Figure 3.

Pushing panel button 901 wakes the micro-controller 903 from sleep mode and powers up the system. Oscillator 902 drives laser circuit 904 at a frequency of, for example 300 kHz. On micro-controller wake-up light source 905 is enabled through signal 916 and starts pulsing at 300 kHz. Photodiode 907 receives light scattered from club 906. Trans-impedance amplifier 908 provides photodiode current to voltage conversion with-5k ohm trans-impedance gain. DC bias due to constant background light sources is stripped by AC coupling to bandpass amplifier stage.

Low-Q bandpass amplifier 909 selects only signals in the range 250 kHz to 350 kHz for additional gain and attenuates out of band signals. This eliminates interference from flickering light sources, such as fluorescent and other types of gas discharge lighting. Peak signal detector 910 rectifies 300 kHz back-scattered return signals. 2 kHz low pass filter 911 provides running average of the signals with ~500, us time constant. This determines the average return signal from slowly changing background targets such as clothing, grass, etc. The background level is used to set the detection threshold in the threshold detector 913. When a club 906 enters the laser beam, the 40 kHz low pass filter 912, having a 25 ms time constant, responds very quickly to the

sudden signal change. Being much faster than the 2 kHz low pass response, the threshold detector 913 is triggered by the abrupt signal change, and signals the micro- controller 903 that the club has been detected. The microprocessor then switches off laser diode 905 and instead switches on laser diode 915 through enable signal 917 and laser driver 914. When a second abrupt change is detected in the signal from the photo-detector 907, the time difference between the laser beam intercepts is recorded, the club speed is calculated and the result is shown on the display 918.

The invention is not intended to be restricted to the details of the above- described embodiment. For instance, it is possible to use the devices described above to measure the speed of objects other than golf clubs.