Virtual golf systems are widely spreading which allow golfers to virtually play golf at low cost in downtown areas and the like.  The basic concept of such virtual golf systems is to acquire a number of photographed images of a golf ball upon being hit by a golfer, measure physical quantities of the golf ball on the basis of the trajectory, interval, size and the like thereof, perform a simulation of the shot, and display a result of the simulation on a screen.  In the virtual golf systems, it is important to acquire the photographed images of the golf ball as good as possible. 
In this connection, a technique for photographing a golf training session while adjusting the location or color of illumination to acquire more diverse images of a golf ball has been disclosed in Korean Laid-open Patent Publication No.  10-2009-0112538 (entitled, “APPARATUS FOR OBTAINING GOLF IMAGES USING ILLUMINATION CONTROL, AND GOLF PRACTICE SYSTEM BASED ON IMAGE PROCESSING USING IT”), the contents of which are incorporated herein by reference in its entirety.  However, various conventional techniques including the above one have not been concerned with a technique required to acquire golf ball images in a good state, which is necessary in accurately measuring a physical quantity of a golf ball, or a technique for measuring physical quantities of a golf ball using a mark sequence obtainable from a plurality of golf ball images. 
Therefore, the inventor(s) present a novel technique for accurately measuring physical quantities of a golf ball by analyzing a mark sequence appearing in golf ball images obtained from a high-speed camera capable of photographing many frames of images for a short time.