The range-setting screen 20, which is illustrated in FIG. 3, includes a text box 21 for receiving the upper-limit value of the radius-ratio acceptable range, an OK button 22 for accepting the radius-ratio acceptable range, and a cancel button 23 for canceling the acceptance of the radius-ratio acceptable range. The text box 21 enables an input of a numerical value that one or more.

As illustrated in FIG. 2, the range accepting unit 18a determines whether the cancel button 23 is pressed or not (Step S102).

When determining that the cancel button 23 is pressed at Step S102, the range accepting unit 18a terminates the operations illustrated in FIG. 2.

When determining that the cancel button 23 is not pressed at Step S102, the range accepting unit 18a determines whether the OK button 22 is pressed or not (Step S103).

When determining that the OK button 22 is not pressed at Step S103, the range accepting unit 18a executes the process of Step S102.

When determining that the OK button 22 is pressed at Step S103, the range accepting unit 18a stores the numerical value received in the text box 21 as the radius-ratio-acceptable-range information 17d (Step S104).

After terminating the process of Step S104, the range accepting unit 18a terminates the operations illustrated in FIG. 2.