1. A method, comprising:
accessing a plurality of measurements of a subject, the plurality of measurements resulting at least in part from detection of ultrasound radiation by an ultrasound imaging device comprising at least one source and at least one sensor and operating in a transmissive modality;
obtaining a system of linear equations based at least in part on geometry information indicating location of the at least one source and the at least one sensor; and
generating, using at least one processor, at least one volumetric image of the subject from the plurality of measurements by using a compressive sensing image reconstruction process involving identifying a solution to the system of linear equations.
2. The method of claim 1, wherein identifying the solution to the system of linear equations comprises using a sparsity constraint to identify the solution.
3. The method of claim 1, wherein identifying the solution to the system of linear equations comprises using a three-dimensional basis.
4. The method of claim 3, wherein the three-dimensional basis is a three-dimensional discrete cosine basis, a three-dimensional discrete sine basis, or a three-dimensional wavelet basis.
5. The method of claim 1, wherein the at least one source includes a first source and the at least one sensor includes a first sensor, and wherein the ultrasound imaging device comprises a plurality of sources and a plurality of sensors, and wherein said generating comprises using geometry information indicating location of the first source and the first sensor.
6. The method of claim 5, wherein the at least one volumetric image comprises a plurality of voxels, and wherein said generating comprises using the geometry information to calculate a value indicative of a length of a portion of a line through a voxel in the plurality of voxels, wherein the line intersects the voxel, and wherein the line connects the first source and the first sensor.
7. The method of claim 1, wherein the plurality of measurements comprises a plurality of time-of-flight measurements andor a plurality of attenuation measurements.
8. The method of claim 7, wherein the plurality of measurements comprises the plurality of time-of-flight measurements and the plurality of attenuation measurements, and wherein said generating comprises using Kramers-Kronig relations to calculate the at least one volumetric image.
9. The method of claim 1, wherein the plurality of measurements resulted at least in part from the detection, by the ultrasound imaging device, of ultrasound radiation forward scattered from the subject.
10. A method, comprising:
accessing a plurality of measurements of a subject, the plurality of measurements resulting at least in part from detection of ultrasound radiation by an ultrasound imaging device having at least one source and at least one sensor and operating in a transmissive modality;
obtaining a system of equations based at least in part on location of the at least one source and the at least one sensor; and
generating, using at least one processor, at least one volumetric image of the subject from the plurality of measurements by using a compressive sensing image reconstruction process involving identifying a solution to the system of equations.
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 waveguide type variable optical attenuator, comprising:
a substrate for forming a waveguide for optical signal propagation;
a waveguide element comprising a first arm waveguide and a second arm waveguide arranged on a surface of the substrate for constituting a portion of the waveguide and cladding for covering the first and second arm waveguides and the surface of the substrate;
an output side waveguide connecting the first arm waveguide with the second arm waveguide and arranged to couple light from the first arm waveguide with light from the second arm waveguide; and
a heater arranged on a surface of the waveguide element for heating the first and second arm waveguides, wherein:
the first and second arm waveguides and the output side waveguide constitute one optical interference circuit, the first and second arm waveguides are connected thermally to each other by a high thermal-conductivity member that covers the heater, the high thermal-conductivity member being different from the heater.
2. The waveguide type variable optical attenuator according to claim 1, wherein:
a length L of a spacing between the first and second arm waveguides at a center part is substantially equal to or more than that of a spacing in which optical characteristics of the first and second arm waveguides are affected by each other.
3. The waveguide type variable optical attenuator according to claim 1, wherein:
when a temperature of the first arm waveguide adjacent to the heater during heater electrical conduction is T1, a temperature of the second arm waveguide during heater electrical conduction is T2, and
a temperature of the first and second arm waveguides during no heater electrical conduction is T3, T1>T2>T3.
4. The waveguide type variable optical attenuator according to claim 2, wherein:
the length L is set to a range 30 \u03bcm\u2266L\u2266250 \u03bcm.
5. The waveguide type variable optical attenuator according to claim 1, wherein:
the substrate comprises a quartz glass substrate.
6. The waveguide type variable optical attenuator according to claim 1, wherein:
a thermal conductivity \u03b1 of the high thermal-conductivity member is set to thermal expansivity ranging 100 WmK\u2266\u03b1\u2266500 WmK.
7. The waveguide type variable optical attenuator according to claim 1, wherein:
the high thermal-conductivity member covers the first arm waveguide, and extends to a region adjacent to the second arm waveguide.
8. The waveguide type variable optical attenuator according to claim 1, wherein:
the high thermal-conductivity member is arranged on the surface of the waveguide element via an electrical insulation layer, and the heater is covered with the electrical insulation layer, the electrical insulation layer arranged between the high thermal-conductivity member and the heater.
9. The waveguide type variable optical attenuator according to claim 1, wherein:
the high thermal-conductivity member extends on or over a center line between the first and second arm waveguides.
10. The waveguide type variable optical attenuator according to claim 1, wherein:
the heater is a single heater.
11. The waveguide type variable optical attenuator according to claim 1, wherein:
the high thermal-conductivity member covers the first arm waveguide, but not the second arm wave guide.
12. The waveguide type variable optical attenuator according to claim 4, wherein:
the high thermal-conductivity member extends over a half point of the spacing between the first and second arm waveguides.
13. A waveguide type variable optical attenuator, comprising:
a substrate for forming a waveguide for optical signal propagation;
a waveguide element comprising a first arm waveguide and a second arm waveguide arranged on a surface of the substrate for constituting a portion of the waveguide and cladding for covering the first and second arm waveguides and the surface of the substrate;
an output side waveguide connecting the first arm waveguide with the second arm waveguide and arranged to couple light from the first arm waveguide with light from the second arm waveguide; and
a single heater arranged on a surface of the waveguide element for heating the first and second arm waveguides, wherein:
the first and second arm waveguides and the output side waveguide constitute one optical interference circuit, the first and second arm waveguides are connected thermally to each other by the heater.
14. The waveguide type variable optical attenuator according to claim 13, wherein:
the heater extends on or over a center line between the first and second arm waveguides.