1. A measuring apparatus comprising:
an acoustic wave detecting unit that detects acoustic waves generated from a subject irradiated with light; and
a member that is disposed between the acoustic wave detecting unit and the subject and has an acoustic speed value smaller than an average acoustic speed value inside the subject;
wherein a thickness of the member is greater than a value obtained by dividing the acoustic speed value inside the subject by the minimum frequency detectable by the acoustic wave detecting unit.
2. The measuring apparatus according to claim 1,
wherein the minimum frequency detectable by the acoustic wave detecting unit is a frequency detected with half sensitivity with respect to a frequency detectable with the maximum sensitivity of the acoustic wave detecting unit.
3. The measuring apparatus according to claim 1, further comprising:
a signal processing unit that acquires a subject information based on the detected acoustic waves,
wherein, when determining a generated location of the acoustic waves, the signal processing unit acquires the subject information by calculating a distance up to the generated location of the acoustic waves based on a variation in an incident angle of the acoustic waves on the acoustic wave detecting unit according to a ratio of the acoustic speed value inside the member to the average acoustic speed value inside the subject.
4. The measuring apparatus according to claim 1, further comprising:
a first holding plate; and
a second holding plate that holds the subject together with the first holding plate between the member and the subject,
wherein the member is disposed on the second holding plate.
5. The measuring apparatus according to claim 1, wherein the member has a sheet-like shape.
6. The measuring apparatus according to claim 1,
wherein the shape of the member is varied depending on the shape of the subject.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A multi-stage ignition type gas generator, comprising:
a housing having a gas discharge port;
a first combustion chamber provided inside the housing;
a second combustion chamber provided inside the housing separately from the first combustion chamber;
a third combustion chamber provided inside the housing and through which a gas generated in at least one of the first combustion chamber and the second combustion chamber passes before reaching the gas discharge port;
a first partition wall separating the first combustion chamber and the third combustion chamber and defining a first communicating port that communicates the first combustion chamber and the third combustion chamber;
a second partition wall separating the second combustion chamber and the third combustion chamber and defining a second communicating port that communicates the second combustion chamber and the third combustion chamber;
first restriction means that seals the first communicating port, the first restricting means allowing communication between the first combustion chamber and the third combustion chamber only by a gas pressure generated in the first combustion chamber;
second restriction means that seals the second communicating port, the second restriction means allowing communication between the second combustion chamber and the third combustion chamber only by a gas pressure generated in the second combustion chamber;
a first gas generating agent accommodated in the first combustion chamber for generating a first combustion gas for inflating an air bag;
a second gas generating agent accommodated in the second combustion chamber for generating a second combustion gas for inflating the air bag;
a third gas generating agent accommodated in the third combustion chamber for generating a third combustion gas for inflating the air bag;
a first ignition means for directly igniting and burning the first gas generating agent;
a second ignition means for directly igniting and burning the second gas generating agent; and
shielding means, which prevents at least one of the first communication port and the second communication port from being obstructed by at least one of the first gas generating agent, the second gas generating agent, and the third gas generating agent,
wherein, the first gas generating agent and the second gas generating agent are different in at least one of combustion heat, combustion temperature, all gas output, and gas output per unit time in combustion of the gas generating agent.
2. The multi-stage ignition type gas generator as claimed in claim 1, wherein the first restriction means seals the first communicating port from the third combustion chamber side.
3. The multi-stage ignition type gas generator as claimed in claim 2, wherein the first restriction means at least one of deforms, destructed by fire, detaches from the first partition wall, displaces, ruptures, and breaks only by combustion of the first gas generating agent and opens the first communicating port.
4. The multi-stage ignition type gas generator as claimed in claim 3, wherein the first restriction means is selected from the group consisting of a metal tape, a cover, and a check valve that closes the first communicating port.
5. The multi-stage ignition type gas generator as claimed in claim 1 or 2, wherein the first ignition means includes a first igniter and the second ignition means includes a second igniter for initiating operation of the gas generator, and the first igniter and the second igniter are attached to a single common igniter collar attached to the housing.
6. The multi-stage ignition type gas generator as claimed in claim 1 or 2, further comprising:
a coolant that defines the third combustion chamber therein,
wherein, the first combustion gas, the second combustion gas, and the third combustion gas pass through the coolant before being discharged from the discharge port.
7. The multi-stage ignition type gas generator as claimed in claim 1 or 2, wherein the shielding means is made of one of a wire mesh and a multi-perforated plate.
8. The multi-stage ignition type gas generator as claimed in claim 1, wherein the second restriction means seals the second communicating port % from the third combustion chamber side.
9. The multi-stage ignition type gas generator as claimed in claim 1, wherein the shielding means is made of one of a wire mesh and a multi-perforated plate.