The present invention discloses a control method of recording speed in an optical disc drive. The trailing and leading edges of the choke and throttle valves, respectively, preferably overlap during wide open throttle operation to separate a single intake passage bore into an air intake passage above the choke and throttle valves and an airfuel intake passage below the choke and throttle valves. The stationary film-producing mechanism comprises a loop with an opening through which air travels, a film-forming edge, a bubble-releasing edge, a first orifice on an exterior surface of the loop, and a second orifice on an interior surface of the loop. The potential shift circuit initializes output signals in response to a shift pulse, and outputs the output signals to the reset gate electrodes in response to a reset pulse. The software 7 for conducting high-pass filter processing and smoothing processing is installed in the data processing unit 6, and the data on the wave height and current direction and speed are output, while the errors are being removed from the three-dimensional position data recorded in the data recording unit 4.