Tunable interference filter, optical module, and photometric analyzer

A tunable interference filter comprising:

• a first substrate;
• a second substrate opposed to the first substrate;
• a first reflection film provided on the first substrate;
• a second reflection film provided on the second substrate and opposed to the first reflection film via a gap;
• an electrostatic actuator including a first drive electrode provided on the first substrate and a second drive electrode provided on the second substrate and opposed to the first drive electrode;
• and
• a gap detection electrode including a first detection electrode provided on the first substrate and a second detection electrode provided on the second substrate and opposed to the first detection electrode,
• wherein the second substrate includes a movable part provided with the second reflection film and a holding part that holds the movable part close to or away from the first substrate,
• in a plan view of the first substrate and the second substrate as seen from a substrate thickness direction, the movable part is formed in a circular shape and the holding part is formed along an outer circumference of the movable part,
• the first drive electrode includes a first partial drive electrode and a second partial drive electrode provided along a virtual circle around a center point of the movable part in the plan view,
• a first lead drive electrode extending from the first partial drive electrode toward an outer peripheral edge of the first substrate and a second lead drive electrode extending from the second partial drive electrode toward the outer peripheral edge of the first substrate are provided on the first substrate,
• the second drive electrode includes a first opposed drive region overlapping with the first partial drive electrode and a second opposed drive region overlapping with the second partial drive electrode in the plan view,
• the first detection electrode includes a first partial detection electrode and a second partial detection electrode provided along a virtual circle around the center point of the movable part in the plan view,
• a first lead detection electrode extending from the first partial detection electrode toward the outer peripheral edge of the first substrate and a second lead detection electrode extending from the second partial detection electrode toward the outer peripheral edge of the first substrate are provided on the first substrate, and
• the second detection electrode includes a first opposed detection region overlapping with the first partial detection electrode and a second opposed detection region overlapping with the second partial detection electrode in the plan view.