In 1964, just a few years after the invention of the laser, a fluid velocity measurement based on the frequency shift of scattered light was made and the laser Doppler technique was born. This comprehensive review paper charts advances in the development and applications of laser Doppler vibrometry (LDV) since those first pioneering experiments. Consideration is first given to the challenges that continue to be posed by laser speckle. Scanning LDV is introduced and its significant influence in the field of experimental modal analysis described. Applications in structural health

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ABSTRACT:The perception of 'feel' during a ball-implement impact is considered a significant determinant in equipment selection. Previous studies in golf have found that the perceived time for which the ball and clubface are in contact is a factor in the 'feel' of the shot. This factor appears to have become more significant with the development of the latest metal 'woods'. The purpose of this study was to investigate whether golfers' perceptions of impact duration correspond to measured values or whether the perceptions are created by other factors. A technique has been developed to measure the duration of impact by creating an electrical circuit in which the ball and clubface form a 'switch', completing the circuit whilst contact is maintained between the two bodies. Measurements were taken of the duration of impact between five different types of clubhead and two different constructions of golf ball. Further tests, also reported in this paper, investigated the effect of both clubhead speed at impact and ball compression on the impact duration. The results suggest that the ball has a greater effect on impact duration than the type of clubhead with lower compression balls producing longer impact durations than higher compression balls and two piece balls producing shorter impact durations than three piece, wound balls. It was also found that the duration of impact decreased as the clubhead speed at impact was increased. Finally, results suggest that there is no correlation between the perception of the golfer and the actual duration of impact and therefore other factors are responsible for creating this perception.

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