A typical example of such a trial is a method in which a bright line light source is combined with a band pass filter (see, for example, a publication of JP-A No. 6-235900, a publication of JP-A No. 2-158289, a publication of JP-A No. 10-321025, a specification of USP 6307604, a specification of DE 3836955 A, a specification of DE 4222028 A, a specification of EP 578302 A, a specification of US 20