WO2005083450A1

WO2005083450A1 - Method of measuring the speed of an object

Info

Publication number: WO2005083450A1
Application number: PCT/SE2005/000256
Authority: WO
Inventors: Tommy De Captretz; Frans De Captretz; Sven Calander
Original assignee: Tommy De Captretz; Frans De Captretz; Sven Calander
Priority date: 2004-02-26
Filing date: 2005-02-22
Publication date: 2005-09-09
Also published as: SE0401058D0

Abstract

The invention discloses a method of measuring the speed of a moving object, preferably a shaft of a golf club, by measuring the time it takes for the object to pass through a measuring zone comprising at least two parallel, pulsed infrared light beams arranged perpendicular to a predicted line of travel for the moving object through the measurement zone.

Description

Method of measuring the speed of an object

TECHNICAL FIELD

The present invention relates to an optical, contact-less method of measuring the speed of a moving object and particularly the speed of a golf club immediately before the club head hits a golf ball during the downswing.

BACKGROUND

Golf has become a popular game for people of all ages over the whole world in recent years and the number of golf courses and active players are rapidly increasing. However, it is not the cheapest game to pursue and learning to master the proper technique with all the available clubs takes a lot of time and dedication from the golfer- to-be.

Because golf requires a lot of skill, which can only be acquired by training, many training devices have been introduced over the years in order to provide means to speed up the learning of a correct technique. For instance in publication US 4,630,829 titled "Compact golf swing training and practice device" published in 1986 Arthur A White discloses an invention of a battery powered practice device comprising a microprocessor controlled photo detector system for measuring various parameters of a golfer's swing including club head speed and swing time. However, the device has several drawbacks, e.g. it is rather clumsy by today's standards and the optical system must be adjusted for the ambient light conditions before using the device. The optical system is set up to detect the passage of a clxib head. The man-machine interface uses switches and control knobs, which, requires the golfer to change his stance before making a new swing.

Other prior art training and practice devices and methods can be studied in e.g. publications US 4,844,469, US 5,472,205, US 5,634,855, US 5,718,639,

US 5,935,014, US 5,976,022, US 6,261, 189 Bl and US 6,602, 144 Bl.

However, typical shortcomings in prior art methods and devices are that they are big, clumsy, cumbersome to set up, sensitive to light reflexes and changes in ambient light conditions, difficult to use indoors or outdoors, technically complicated, costly, complex to use, not weather proof and may require specially prepared clubs. Some devices require specially prepared tees and cannot easily be moved or used anywhere.

In view of these disadvantages there is a need for an easy and fool-proof method of measuring the swing performance of a golfer, which can be put to use indoors as well as outdoors and which will not be adversely affected by changes in ambient conditions.

SUMMARY The present invention discloses a method of measuring the speed of a moving object, preferably a shaft of a golf club, by measuring the time it takes for the object to pass through a measuring zone comprising at least two generally parallel, pulsed infrared light beams arranged generally perpendicular to a predicted line of travel for the moving object through the measurement zone.

An object of the invention is to make it possible to produce a swing meter device based on the disclosure. Such a device may be light, durable, weatherproof and extremely easy to set up so that it can be put to use outdoors as well as indoors, such that a golfer quickly and easily can carry out a practice session in his own back yard, or on a driving range or use the swing meter device in an actual round of golf.

The disclosed method uses preferably standard low-power IR optical devices as light source(s) and light receivers. The pulse train frequency is typically between 30 and 100 kHz, the exact frequency to be sleeted depending on what optical devices are available. The receiver detects only incoming light of a specific wavelength, if there is an element of pulsed light of the correct pulse frequency and light wavelength superimposed on a more or less steady, high or low influx of ordinary light. When the receiver detects pulsed light of the correct pulse frequency and light wavelength it will change its output state from "No light" to "Light". Thus, ambient light conditions and interfering, intermittent light reflexes will not affect a measuring system comprising two parallel beams of pulsed light going to the respective receivers. The distance between the beams, i.e. the receivers, and the IR beam pulse frequency sets a limit to the maximum object speed, which can be measured at any chosen, arbitrary measurement accuracy. Theoretically, the accuracy benefits from as high pulse frequency as possible.

In a further aspect of the disclosed method more light beams parallel with the first two and preferably in the same plane may be arranged to increase the measuring distance of the measuring zone, whereby the maximum measurable speed of an object and/ or the measurement accuracy may be increased. Changes in speed within the measuring zone may also be measured when more beams and corresponding light receivers are introduced.

Preferably, the time it takes for an object to pass through the measuring zone is measured using a microprocessor counting well-defined clock pulses during the passage, e.g. by having a free-running counter and the count to be registered when the object breaks the first IR beam using the microprocessor, and to register for each of the light receivers the number of counted clock pulses when the object breaks each of the following beams. The time is then calculated by simply subtracting the count of one receiver from the count of a selected preceding receiver. Using previously entered information about the distances between the light receivers (beams), which information has been stored in memory, e.g. a non-volatile memory chip, the microprocessor can perform a calculation of the object speed in the different sections of the measuring zone and present the results by any preferred method, including a local or remote display, information screen, printer and/ or by a communication link to a remote data receiving system. The microprocessor may also store the measuring results locally in memory for later transfer to a readout system, e.g. a computer.

In another aspect of the invention a single light source may be used instead of two or more. Even though the resulting light beams are not perfectly parallel, the systematic measurement errors thus introduced are very small and can be predicted and compensated for, provided that the objects to be measured always move through the measurement zone in similar trajectories, reasonably close to the receivers and sufficiently remote from the light source.

In a different aspect of the invention the back swing time of a golf swing is measured i.e. the time from addressing the ball until the club hits the ball on the downswing.

A further object of the invention is to provide a user with more information relating to his or hers swing training. Means may be provided, e.g. by using an adapted microprocessor for the basic measurement tasks, which may permit the user to enter information regarding the specific clubs used, i.e. club type, loft, hit factor etc. This additional information may be used to compute the distance the ball will travel by using the club speed and the particular club data for a selected club as inputs to the computation. The additional information besides swing speed may then be presented and/ or stored locally or remotely, depending on how the method is implemented.

The present method is set forth by the independent claim 1 and the dependent claims 2 to 8, a use of the method is set forth in the independent claim 9 and the dependent claims 10 to 13 and a speed meter device for performing the method is set forth in the independent claim 14 and the dependent claims 15 to 18. BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further objects and advantages thereof, may best be understood by referring to the following detailed description taken together with the accompanying drawings, in which:

FIG. 1 illustrates the steps of the presented method in a flow diagram;

FIG. 2 illustrates in a top view the relative positions of a speed meter having several light receivers, a light source, a golf ball and a golf club head moving in the direction of the measuring zone;

FIG. 3 illustrates in a side view a speed meter, a light source and a golf ball, and

FIG. 4 illustrates in a side view a speed meter, showing approximate positions for 5 light receivers in the speed meter and an optional add-on measuring device.

FIG. 5 illustrates in a top view a speed meter and an integrated alphanumeric display.

DETAILED DESCRIPTION The present invention discloses a method of measuring the speed of a moving object, preferably a shaft of a golf club, by measuring the time it takes for the object to pass through a measuring zone comprising at least two pulsed, preferably infrared light beams. The presence or non-presence of the light beams are detected by at least two optical receivers with their respective optical axis positioned generally in parallel in the measurement zone with a fixed, pre-defined distance between them and generally perpendicular to a predicted line of travel for the moving object through the measurement zone. The method is illustrated in a flowchart in Figure 1.

Further, a use of at least one microprocessor, controlled by dedicated embedded software, is disclosed. The microprocessor and associated electronics is used to perform time measurements and to calculate secondary variables, based on pre-entered and stored parameters in nonvolatile memory, which may be accessed by the microprocessor. Such secondary variables are e.g. club head speed, ball speed, ball carry distance duffing etc. In a further aspect of the invention an operator interface - human-machine interface (HMI) - is disclosed allowing a user, preferably a golfer, to input, store and read out data, which may be used by the microprocessor as inputs to computations. A preferred method of interfacing is to use the optical receivers as input devices, to bring about a change of operating mode of the microprocessor. For instance, by breaking the light beam for a relatively long time to the first and/ or optionally other receivers may force the microprocessor to change its mode from a measuring mode to an interfacing mode. This type of interface may allow the user to read out information and to input/ or output information, e.g. about which club is used, without changing his or hers stance. Other methods of user interface may of course be used, e.g. keyboards or pushbuttons. However, such interfaces may require the user to change the stance or drop the club temporarily, which is detrimental to the learning process.

A simple menu system may guide the user to enter new or change old information in a memory associated with the microprocessor. Measurement and computation results may be output and presented to a user in several ways, e.g. by a local display or in a simple form by differently coloured LEDs or aural messages, and/or the information may be transferred to cellphones, Personal Digital Assistants or laptop computers, where it may be displayed and, if requested, stored. Optionally, a real time clock is incorporated to allow a time tag to accompany measurements and allow the user to follow the sequence of a training session in retrospect. Transfer of data to and from intelligent computerized systems may be arranged by cable or by infrared or radio data link transfer.

In a further aspect of the invention the implementation of a swing meter device based on the disclosure should allow the device to be adapted by the user to a left- or right-handed player. This implies that the local display, if implemented, must be arranged such that alphanumeric characters may be displayed turned the right way around for either a right-hander or a left- hander. The device must also have simple means for setting up the light receivers for either a right-hander or a left-hander. For instance, in a preferred embodiment the device may comprise dual sets of light receivers, one set on each side of the device, and the user selects left- or right-hander operation when switching on, which activates the correct set of receivers and leaves the other set inactive. Simultaneously, the display is arranged accordingly. The microprocessor may store the information locally such that the same operation mode is automatically started up the next time the device is put to use. If the device is configured for more than one user the information regarding left- or right-handed operation may be programmed into memory, such that correct operation is always there after selecting the current user.

The disclosed method measures time of passage for an object through the measurement zone. Preferably, standard low power IR optical devices are used as light source(s) and light receivers. These devices are made to transmit and/ or receive a train of pulses of infrared (IR) light of a specific wavelength only. Typically, such IR devices have a narrow spectral bandwidth and a peak power output for light sources and corresponding peak sensitivity for light receivers somewhere in the range 800 to 1000 nm wavelength. The pulse train frequency is typically today between 30 and 50 kHz, but higher frequency components are now in development, which may be advantageously used in this application in the near future. The exact frequency is determined in manufacture and the device given a device type number signifying the frequency and other relevant specifications. This type of optical receiver detects only incoming light of a specific wavelength, if there is an element of pulsed light of the correct pulse frequency and light wavelength superimposed on a more or less steady, high or low influx of ambient light of all wavelengths. Thus, ambient light conditions and interfering intermittent incident stray light will not affect a measuring system comprising two parallel beams of pulsed IR light and the respective receivers. Using standard IR devices as described has obvious cost advantages, but other optical devices working in other wavelength ranges, such as visible or ultraviolet light may alternatively be used. Only when an object breaks a beam of pulsed light, lasting for a certain minimum time period, i.e. a certain number of missed light pulses, will the receiver register this and change its output. The distance between beams, i.e. receivers, and the IR beam pulse frequency sets a limit to the maximum object speed, which can be measured at any chosen, arbitrary measurement accuracy. Theoretically, the accuracy benefits from as high pulse frequency as possible.

In a further aspect of the disclosed method more IR light beams generally parallel to the first two and in the same plane may be arranged to provide additional measurements within the measuring zone, whereby the maximum measurable speed of an object and/ or the measurement accuracy may be increased. If more than two beams are used it is further possible to measure acceleration or deceleration of the object within the measuring zone. Deceleration is normally caused by the club head hitting the ground prior to striking the ball and makes interesting information about "duffing" to a user, since the full power of the swing is not transferred to the ball in that case.

Preferably, the time it takes for an object to pass through the measuring zone is measured using a microprocessor counting well-defined high frequency clock pulses during the passage, e.g. by having a free-running counter and the count to be registered when the object breaks the first IR beam, using the microprocessor, and to register for each of the light receivers the number of counted clock pulses when the object breaks each of the following beams. The time is then calculated by simply subtracting the registered count of one receiver from the registered count of a selected preceding receiver. Since each clock pulse represents a fraction of time, the difference in counts represents a time for the object to pass by. Using previously entered information about the distances between the light beams, which information has been stored in memory, e.g. a non- olatile memory chip, the microprocessor performs a calculation of the object speed in the different sections of the measuring zone and presents the results by any preferred method, including a local display or information screen, a printer and/ or by a communication link to a remote data receiving system. The microprocessor may also store the measuring results locally in memory for later transfer to a readout system, e.g. a computer where further processing of the measurement results may be done, if required. For instance, statistics over each session may be computed and overall statistics over several practice sessions may be produced.

In another aspect of the invention a single light source is used instead of two or more. Even though the resulting light beams defining the measurement zone may not be perfectly parallel, the measurement errors introduced are very small provided that the objects to be measured always move through the measurement zone in similar trajectories, reasonably close to the receivers and sufficiently remote from the light source. In a particular embodiment, illustrated in Figure 2, the angle 26 between the beams defining the measurement zone is less than 12 degrees and preferably less than 9 degrees and most preferably less than 6 degrees. The systematic measurement errors thus introduced depend e.g. on different clubs having different length shafts and therefore the shaft angle relative the ground plane during a swing differs between e.g. an iron club and a driver leading to different distances between shaft and light receivers for the different clubs. However, the measurement errors because of this and other similar phenomena are very small and the errors can be predicted and compensated for in the algorithms used by the microprocessor program. Typically, the total measurement error in club shaft speed is below 2 %.

In an alternative embodiment a separate light source associated with each receiver by pairing may be arranged when setting up the measuring zone, either by arranging the light sources in remote positions from the receivers, such that parallel light beams from the pairs result, generally in the same plane, or by arranging each light source /receiver pair very close together in virtually one and the same physical position and arranging a mirror on the far side of the measuring zone, such that the outgoing beam from the light source is reflected back into the corresponding receiver.

In a different aspect of the invention the back swing time of a golf swing is measured i.e. the time from addressing the ball until the club hits the ball on the downswing. The microprocessor stores the counter value, e.g. from a free-running counter, when the appropriate receiver(s) signals "no light", and again on the downswing. Time calculations are then performed in the same manner as before and the result is then indicated by the HMI.

A further object of the invention is to provide a user with more information relating to his or hers swing training. Means are then provided, e.g. by using an adapted microprocessor for the basic measurement tasks, which permits the user to enter information regarding the specific clubs used, i.e. club type, loft, hit factor etc. This additional information is used to compute the distance the ball will travel using the club speed and the particular club data for a selected club as inputs to the computation. The additional information besides swing speed may then be presented and/ or stored locally or remotely, depending on how the method is implemented. A preferred embodiment of a speed meter device is illustrated in Figure 2, 3, 4 and 5 showing respectively a top view, a side view, a front view and again a top view of the device, where like numbers indicate like items in the different views. The speed meter device comprises at least two light receivers 12 and 14, characterized by being sensitive to an incident pulse train of light of a specific pulse frequency and of a specific light wavelength, at least one stand-alone light source 31 capable of emitting a corresponding pulse train of light, an electronic package incorporating at least one microprocessor running a dedicated embedded main software program, optional input and output devices and a power supply, preferably batteries. The receivers are preferably enclosed together with the electronic components and a power supply in a weatherproof casing 32, which may be used indoor or outdoor and which is mechanically robust. The receivers are sufficiently spaced apart in the casing to create the measuring zone, i.e. light beams 22 and 24. Optionally in a particular embodiment more receivers 11, 13 and 15 of same type as receivers 12 and 14 are added in the casing in defined positions as shown in Figure 2, such that the speed of e.g. a club shaft 34 (fixed to club head 33) can be measured accurately in each of the measurement sections created by the addition of extra receivers 11 and 13, i.e. light beams 21 and 23. The measuring zone defined by light beams 21 and 22 may generate information about the club speed in that zone compared to the speed in the following zone defined by light beams 22 and 24 and thus information is gained regarding in what zone the golfer reaches the highest club speed in a swing. Also, by adding the readings from zone 21/22 to that of zone 22/24 a more accurate club speed can be computed, which may be especially important when a driver is used, because drivers achieve the highest speed of all clubs. Receiver 13 is used to compute the speed in the zone defined by light beams 23 and 24, which is particularly useful for some clubs e.g. putters, where the swing is very limited and the speed is low. An optional receiver 15 is used to detect when the club has hit the ball 36 and then moves on to break light beam 25. Receiver 15 triggers the computation of the measuring results from the completed swing and the results are optionally stored in memory and/ or presented to the user by means of an appropriate operator interface. A single, stand-alone light source is preferred and preferably provided with its own mounting arrangement, such as a tripod, and power supply, e.g. batteries, see Figure 3. No cables need be run between the remotely placed light source 31 and the electronic package of the speed meter device 32. In a preferred embodiment the light source is switched on manually, but a built-in timer switches off automatically after a certain adjustable time of inactivity by the user to conserve battery power if the user forgets to switch off after a training session. In a different embodiment the light source is further provided with an IR-interface or equivalent cable-less communications port and electronic means therefore, so it can be switched on and off remotely from the main microprocessor having a corresponding port. The input/output devices are of two kinds:

1. A local set for the user during a training session, such as a. A display capable of indicating various measurement and computation results directly after the user has completed a golf stroke. The display is preferably an alphanumeric display, but a simple system of differently coloured LEDs may suffice to indicate the quality of a stroke. Optionally audible signals, even preprogrammed messages may be implemented. See Figure 5 for an illustration of a particular embodiment of the speed meter device 32 comprising also an alphanumeric display 37. b. A keyboard or pushbuttons may be arranged in the speed meter for the user to enter a simple menu system to input user data or to read out results from previous golf strokes, but preferably an optical detection system is implemented using one or more of the existing light beams to change the mode of the microprocessor from measuring mode to read-out and/ or set-up mode by simply breaking at least one of the beams for a longer time than is normal for an object to pass by the beam. By breaking the beam or beams in different ways the user can scroll through a simple menu system to set the meter up or read out the information he or she needs before going back to the measuring mode again.

2. At least one communication port, which can be cable, IR or wireless depending on customer preference, is preferably provided to allow data to be transferred in both directions either during a practice session or optionally later at a different time and place. In an advanced version of the speed meter it is possible to share the meter with several people by configuring the speed meter for different users and the individual clubs for each user, which information is stored in a non-volatile memory to keep the integrity. As a further option the meter is provided with memory capacity for storing results from many training sessions, which can be downloaded into any computer when convenient and analyzed, using standard or proprietary software.

A separate measuring device is offered as an optional device 16, see Figure 4, which is added on to the speed meter device 32, either by reserving a space for the additional device in the existing casing or more preferably having the optional device in a separate casing. The optional measuring device is furnished with multiple light receivers of the same type as in the speed meter, preferably arranged in a rectangular pattern. The same light source or light arrangements as for the speed meter are used to establish the light beams necessary for performing measurements. The objectives for the optional device are to measure the speed of an object, normally a golf ball, being hit by a club head and the angle of the ball in relation to the horizontal ground plane. The optional device preferably has a built-in dedicated independent microprocessor executing a dedicated embedded software program and associated supportive electronics for the measuring and computing tasks relating to the ballistic trajectory of the ball. The information from the optional measuring device is transferred to the speed meter in order to be further manipulated and suitably displayed for the benefit of the user on the normal operator interface of choice. Local storage and/ or transmission to other clients using the means provided by the speed meter are further obvious possibilities.

Claims

1. A method of optically measuring the speed of an object in a generally linear motion, the method suitable for use indoors as well as outdoors in varying ambient light conditions, characterized by the steps of arranging a measurement zone comprising at least a first and a second light beam going from at least one, generally monochromatic light source to at least a first and a second light receiver positioned at a predefined distance from each other, the beams generally in parallel and generally perpendicular to a predicted line of travel of the object through the measurement zone; selecting the at least one, generally monochromatic light source to be pulsating, emitting a continuous train of light pulses of a selected, constant pulse frequency; selecting the at least first and second light receivers to have a spectral sensitivity in a spectral band with a peak sensitivity at the emitted wavelength of light from the at least one, generally monochromatic light source and said receivers further adapted to detect only the emitted pulse train frequency in the beam of the selected at least one, generally monochromatic light source, thereby making detection of a presence or non- presence of the light beams unaffected by changes in ambient light conditions and insensitive to intermittent incident interfering stray light, and measuring the elapsed times from when the object breaks the first light beam to when it breaks the following light beams in turn, whereby the speeds of the object may be calculated for the whole or for parts of the measurement zone, depending on the number of beams and the predefined distances between corresponding, consecutive light receivers.

2. The method according to claim 1, characterized by the further step of selecting standard, low power IR infrared optical devices presenting peak performances at a common, particular wave length within a wavelength range of 800 to 1000 nm for light sources and light receivers alike.

3. The method according to claim 2, characterized by the further step of selecting IR optical devices specified for high frequency pulsing of infrared light tuned to a common pulse frequency not less than 30 kHz and preferably not less than 40 kHz.

4. The method according to claim 1, characterized by the further step of arranging the measurement zone to comprise more than two light beams by the addition of one or more light receivers in the same plane as the other receivers, thereby creating two or more consecutive measurement sections, which together constitute a measurement zone, whereby the speed of the object may be calculated individually per measurement section, and presenting differences in measured speeds between the measurement sections and optionally the measured speeds per section to a user.

5. The method according to claim 1, characterized by the further step of using a single IR infrared optical device as light source; positioning the light source at an adequate distance from the light receivers such that the light beams going from the light source to the receivers, said beams constituting the measurement zone, present an angle of less than 12 and preferably less than 6 degrees.

6. The method according to claim 1 , characterized by the further step of measuring a back swing time of a golf swing i.e. the time from addressing a golf ball until the golf club head hits the ball on the downswing, and presenting the back swing time to a user.

7. The method according to claim 1, characterized by the further step of outputting measurement and computation results to a user may be arranged by a digital or graphic display or optionally in a simple form by differently coloured lights or aural messages or a combination thereof.

8. The method according to claim 1, characterized by the further step of transferring information about measurement and computation results to cellphones, Personal Digital Assistants, laptop computers or remote computer systems where it may be displayed and, if requested, stored and further combined and processed with previously stored data, and arranging one-way or otionally two-way digital communication between a local speed meter device and cellphones, Personal Digital Assistants, laptop computers or intelligent computerized systems by an interconnecting cable or by infrared link or radio link using prior art digital signal transfer.

9. A use of at least one microprocessor with embedded software adapted for a method of measuring the speed of an object in linear motion through a defined measurement zone by using at least two optical receivers as primary input variables, characterized in that the optical receivers are selected to be sensitive only to a beam of pulsed light of a particular, selected wavelength and of a certain pulse train frequency only; each receiver signals the microprocessor when an object breaks a respective pulsed light beam into the receiver; when a first receiver in the measurement zone signals a broken first beam the microprocessor starts to count and register clock pulses until a next receiver in the measurement zone signals the microprocessor that its light beam has been broken, whereby the microprocessor stores the counted pulses at that point for each receiver in turn until a last receiver gives a signal that its light beam has been broken; the microprocessor, controlled by the embedded software, calculates the speed of the object by dividing pre-entered constants defining distances between the respective light receivers with the number of counted pulses representing a time interval for the object to pass each sector of the measurement zone, and the microprocessor and the embedded software may present, store and communicate the results of measurements and calculations in one or more ways depending on what hardware and software is implemented in an embodiment of a speed meter device.

10. The use according to claim 9, characterized in that the measurement zone is arranged to comprise three light beams defined by three light receivers positioned at predefined distances from each other, thus creating two measurement sections, whereby the speed of the object may be calculated by the microcomputer individually per measurement section, and the difference in measured speed between the measurement sections is presented to a user on a local display and optionally by an aural message.

11. The use according to claim 9, characterized in that the embedded microprocessor program is adapted to discern the direction of object motion through the measurement zone by detecting which light beam is broken first, whereby the microprocessor may measure the swing time, i.e. the time from addressing a golf ball until the golf club head hits the ball on the downswing, and the back swing time is presented to the user by any preferred method.

12. The use according to claim 9, characterized in that the embedded microprocessor program is adapted to other modes of operation besides the measurement mode; a local or remote input mode may be called up by a user as needed, whereby stored constants relating to user data, club data and optionally weather conditions may be entered or edited before being used in computations during a training session, and an output mode may be called up by a user as needed, whereby stored measurement and computation data regarding a last training session is presented to the user locally and optionally transferred to remote read-out and/ or computerized storage systems.

13. The use according to claim 9, characterized in that the embedded microprocessor program is arranged to let a user select a set of light receivers for right-handed or left-handed speed meter operation and furthermore to adapt a local display, if fitted, for correct indication to a right-handed or left-handed user;

14. A speed meter device for optically measuring the speed of an object in a generally linear motion, the device being suitable for use indoors as well as outdoors in varying ambient light conditions, characterized in that the speed meter device comprises at least one, stand-alone, generally monochromatic light source emitting a pulsating, continuous train of light pulses of a selected, constant pulse frequency; at least a first and a second light receiver in a common, stand- alone housing having a spectral sensitivity in a spectral band with a peak sensitivity at the emitted wavelength of light from the at least one light source and said receivers further adapted to detect only the emitted pulse train frequency in a respective beam of the selected at least one, generally monochromatic light source, thereby making detection of a presence or non- presence of the light beams unaffected by changes in ambient light conditions and insensitive to intermittent incident interfering stray light; at least one microprocessor in the common housing, said microprocessor provided with embedded software adapted for a method of measuring the speed of an object in linear motion through a defined measurement zone constituted by the at least first and second light beams according to claim 1 ; at least one input device whereby the user may start and stop the speed meter device and provide selected input data necessary for carrying out computations by the microprocessor, and at least one output device controlled by the microprocessor and the embedded software, whereby results of measurements and calculations from the swinging may be presented to the user, and optionally stored and communicated to other digital devices depending on what hardware and software is implemented in a selected embodiment of the speed meter device.

15. The speed meter device according to claim 14, characterized in that the measurement zone is arranged to comprise three or more light beams defined by corresponding three or more light receivers positioned at predefined distances from each other in the common, stand-alone housing, thus creating two measurement sections, whereby the speed of the object may be calculated and presented to the user by the microcomputer individually per measurement section.

16. The speed meter device according to claim 14, characterized in that the embedded microprocessor program is adapted to discern the direction of object motion through the measurement zone by detecting which light beam is broken first, whereby the microprocessor may measure the swing time, i.e. the time from addressing a golf ball until the golf club head hits the ball on the downswing, and the microprocessor presents the back swing time to the user by any preferred method.

17. The speed meter device according to claim 14, characterized in that the embedded microprocessor program is adapted to other modes of operation besides the measurement mode; a local or remote input mode may be called up by a user as needed, whereby stored constants relating to user data, club data and optionally weather conditions may be entered or edited before being used in computations during a training session, and an output mode may be called up by a user as needed, whereby stored measurement and computation data regarding a last training session is presented to the user locally and optionally transferred to remote read-out and/ or computerized storage systems.

18. The speed meter device according to claim 14, characterized in that the embedded microprocessor program is arranged to let a user select a set of light receivers in the common, stand-alone housing for right- handed or left-handed speed meter operation and furthermore to adapt a local display, if fitted, for correct indication to a right-handed or left-handed user;