Liquid quantity determination unit, photolithography apparatus, and liquid quantity determination method

A filling liquid storage unit for supplying a filling liquid between a plurality of optical components, comprising:

• an extension plate,
• the extension plate being mounted at an area where the plurality of optical components are in abutment with each other while arranging the side surfaces on the different levels, with a space to be filled with the filling liquid being interposed therebetween;
• the extension plate being overhung from the side surface of one of the optical components toward the portion of the optical components arranged on the different levels:
• and
• the filling liquid can be stored in a room defined by the extension plate, the bottom of one optical component, and the side surface of the other optical component.

A filling liquid storage unit for supplying a filling liquid between a plurality of optical components, comprising:

• a plurality of optical components being arranged on the different levels, with a space to be filled with the filling liquid being interposed therebetween, the lower optical component thereof being projected at a shelf;
• and
• an overflow preventing fence for the filling liquid being provided on the side surface of the shelf,
• wherein the filling liquid stored in a room defined by the shelf and the overflow preventing fence can be supplied from the end of the space opening toward the room.

A liquid quantity determination method suitable for determining the quantity of a filling liquid to be filled between a plurality of optical components, comprising the steps of:

• emitting an inspection beam substantially perpendicularly to an opposed surface of one of the pair of optical components facing each other, with the filling liquid being interposed therebetween;
• emitting the inspection beam to an arbitrary inspection point on the opposed surface;
• identifying a reflecting point of the inspection beam based on a reflected beam of the inspection beam emitted toward the opposed surface;
• and
• determining the presence or absence of the filling liquid at the inspection point based on the identified reflecting point.