Fluorescence detecting apparatus

A fluorescence detecting apparatus for detecting whether or not a protective film is properly formed on the front side of a workpiece, by using fluorescence emitted from said protective film, said protective film being formed to protect the front side of said workpiece from processing dust generated in applying a laser beam to the front side of said workpiece to process said workpiece, said protective film being formed of a resin containing an absorbing agent capable of absorbing said laser beam, said fluorescence detecting apparatus comprising:

• a holding section configured to hold said workpiece;
• and
• light detecting means for detecting said fluorescence emitted from said protective film to thereby detect the formed condition of said protective film;
• said light detecting means including
• an excitation light applying section configured to apply excitation light to said protective film, said excitation light having an absorption wavelength to said absorbing agent contained in said protective film,
• a light detecting section configured to detect said fluorescence emitted from said absorbing agent due to the absorption of said excitation light,
• a filter for removing light having wavelengths other than the wavelength of said fluorescence emitted from said absorbing agent, and
• a reflecting mirror having a reflecting surface for reflecting said fluorescence emitted from said protective film toward said light detecting section;
• said reflecting surface being formed by a part of a curved surface forming a spheroid having two foci, one of said two foci being positioned at a target area of said protective film where said excitation light is applied;
• whereas the other focus being positioned at said light detecting section.