In various embodiments, the invention relates to a method for identifying the presence of particular bacteria in a sample. The ball can be thrown between different players and each player catching the ball can change the shape of any of the appendages to a fixed position before the ball is thrown again. In addition, the processing unit may read out the recorded original image signal from the first recording unit and perform still image signal processing upon the read out original image signal while suspending the moving image signal processing. The phase of the return of the first and second signals are determined.