Capacitance sensor, acoustic sensor, and microphone
A capacitance sensor has a substrate, a vibration electrode plate formed over an upper side of the substrate, a back plate formed over the upper side of the substrate to cover the vibration electrode plate, and a fixed electrode plate arranged on the back plate facing the vibration electrode plate. At least one of the vibration electrode plate and the fixed electrode plate is divided into a plurality of regions. A sensing unit configured by the vibration electrode plate and the fixed electrode plate is formed in each of the divided regions. The plurality of sensing units output a plurality of signals having different sensitivities. At least some sensing units of the sensing units have vibration electrode plates having areas different from the areas of the vibration electrode plates in the other sensing units.
1. A capacitance sensor comprising:
a substrate;
a vibration electrode plate formed over an upper side of the substrate;
a back plate formed over the upper side of the substrate to cover the vibration electrode plate; and
a fixed electrode plate arranged on the back plate facing the vibration electrode plate,
wherein at least one of the vibration electrode plate and the fixed electrode plate is divided into a plurality of regions,
wherein a sensing unit configured by the vibration electrode plate and the fixed electrode plate is formed in each of the divided regions,
wherein the plurality of sensing units output a plurality of signals having different sensitivities,
wherein at least some sensing units of the sensing units have vibration electrode plates having areas different from the areas of the vibration electrode plates in the other sensing units,
wherein, of the sensing units, some sensing units having the vibration electrode plates having small areas have back plates in the regions of the corresponding sensing units having rigidity higher than rigidity of the back plates in the other sensing units having the vibration electrode plates having large areas,
wherein a plurality of openings to cause acoustic vibration to pass are formed in the back plate and the fixed electrode plate, and
wherein the sensing unit outputs a signal by a change in capacitance between the diaphragm and the fixed electrode plate that respond to the acoustic vibration.
2. A capacitance sensor comprising:
a substrate;
a vibration electrode plate formed over an upper side of the substrate;
a back plate formed over the upper side of the substrate to cover the vibration electrode plate; and
a fixed electrode plate arranged on the back plate facing the vibration electrode plate,
wherein at least one of the vibration electrode plate and the fixed electrode plate is divided into a plurality of regions,
wherein a sensing unit configured by the vibration electrode plate and the fixed electrode plate is formed in each of the divided regions,
wherein the plurality of sensing units output a plurality of signals having different sensitivities,
wherein each of the sensing units has a plurality of openings in the back plate and the fixed electrode plate,
wherein at least some sensing units of the sensing units have vibration electrode plates having areas different from the areas of the vibration electrode plates in the other sensing units, and
wherein, of the sensing units, at least one pair of sensing units having the vibration electrode plates having different areas are configured such that an aperture ratio of the opening in the sensing unit having the vibration electrode plate having a small area is smaller than an aperture ratio of the opening in the sensing unit having the vibration electrode plate having a large area.
3. The capacitance sensor according to claim 2 , wherein the aperture ratio of the back plate is adjusted by a hole diameter of the opening.
4. The capacitance sensor according to claim 3 ,
wherein at least one of the vibration electrode plate and the fixed electrode plate is divided into two regions in which the two sensing units are formed, and
wherein the hole diameter of the opening in the sensing unit having the vibration electrode plate having a small area is half or less of the hole diameter of the opening in the sensing unit having the vibration electrode plate having a large area.
5. The capacitance sensor according to claim 4 , wherein a hole diameter of the opening in the sensing unit having the vibration electrode plate having a small area is 10 μm or less.
6. The capacitance sensor according to claim 2 , wherein the aperture ratio of the back plate is adjusted by a distribution density of the openings.
7. The capacitance sensor according to claim 6 ,
wherein at least one of the vibration electrode plate and the fixed electrode plate is divided into two regions in which the two sensing units are formed, and
wherein an alignment pitch of the openings in the sensing unit having the vibration electrode plate having a small area is twice or more an alignment pitch of the openings in the sensing unit having the vibration electrode plate having a large area.
8. The capacitance sensor according to claim 2 , wherein the aperture ratio of the back plate is adjusted by hole diameters and a distribution density of the openings.
9. A capacitance sensor comprising:
a substrate;
a vibration electrode plate formed over an upper side of the substrate;
a back plate formed over the upper side of the substrate to cover the vibration electrode plate; and
a fixed electrode plate arranged on the back plate facing the vibration electrode plate,
wherein at least one of the vibration electrode plate and the fixed electrode plate is divided into a plurality of regions,
wherein a sensing unit configured by the vibration electrode plate and the fixed electrode plate is formed in each of the divided regions,
wherein the plurality of sensing units output a plurality of signals having different sensitivities,
wherein at least some sensing units of the sensing units have vibration electrode plates having areas different from the areas of the vibration electrode plates in the other sensing units, and
wherein, of the sensing units, at least one pair of sensing units having the vibration electrode plates having different areas are configured such that a thickness of the back plate in the sensing unit having the vibration electrode plate having a small area is larger than a thickness of the back plate in the sensing unit having the vibration electrode plate having a large area.
10. The capacitance sensor according to claim 1 ,
wherein the vibration electrode plate is divided into a plurality of regions, and
wherein a sensing unit configured by the vibration electrode plate and the fixed electrode plate is formed in each of the divided regions.
11. A microphone comprising the acoustic sensor according to claim 1 , and a circuit unit that amplifies a signal from the acoustic sensor to output the amplified signal to the outside.