Patent ID: 7301703

Claim:
A tunable filter comprising: a fixed substrate provided with a first hollow section and a second hollow section formed in one surface thereof, and capable of transmitting light having a shorter wavelength than infrared light; a movable substrate having a electrically conductive property and provided with a movable section and disposed to the fixed substrate so that the movable section faces bottom surfaces of the first and the second hollow sections; a movable reflecting film provided to a surface of the movable section, the surface facing the bottom surfaces of the first and the second hollow sections; a fixed reflecting film provided to the bottom surface of the first hollow section defining a first gap with the movable reflecting film; and a drive electrode provided to the bottom surface of the second hollow section defining a second gap with the movable section and for displacing the movable section with respect to the fixed substrate, by coulomb force generated by a potential difference from the movable section, to vary the length of the first gap, wherein light entering the first gap from the outside is repeatedly reflected by the movable reflecting film and the fixed reflecting film for outputting light having a wavelength corresponding to the length of the first gap, and the movable section is provided, at an area to which the movable reflecting film is disposed, with a light transmitting section capable of transmitting light having a shorter wavelength than infrared light and for inputting/outputting light from/to the outside, the light transmitting section having a substantially cylindrical shape.