1. A photovoltaic cell comprising:
a semiconductor lamina having a first textured surface and a second surface substantially parallel to the first textured surface, wherein
at least 50 percent of the first textured surface area is first faces and second faces, wherein the first faces are at an angle between about 5 and about 30 degrees from horizontal, and the second faces are at least seventy degrees from horizontal, wherein the photovoltaic cell comprises the semiconductor lamina,
wherein the semiconductor lamina has a thickness between the first and second surfaces, the thickness averaging between about 1 and about 50 microns,
wherein the semiconductor lamina is substantially monocrystalline semiconductor material.
2. The photovoltaic cell of claim 1 wherein the semiconductor material is silicon.
3. The photovoltaic cell of claim 1 wherein the spacing of the first faces is periodic.
4. The photovoltaic cell of claim 3 wherein the first faces comprise a first subset of first faces having a first orientation, and a second subset of first faces having a second orientation different from the first orientation, wherein the first subset of first faces comprises about half of the first faces.
5. The photovoltaic cell of claim 3 wherein the first faces are at a pitch of between about 0.3 micron and about 3 microns.
6. The photovoltaic cell of claim 1 wherein the spacing of the first faces is not periodic.
7. The photovoltaic cell of claim 1 wherein vertical peak-to-valley distance of the first textured surface does not exceed about 3000 angstroms.
8. The photovoltaic cell of claim 1 wherein the semiconductor lamina comprises at least a portion of the base of the photovoltaic cell.
9. The photovoltaic cell of claim 1 wherein the second surface of the semiconductor lamina is affixed to a receiver element, and wherein the second surface of the semiconductor lamina, or a surface of the receiver element, or a layer disposed between the second surface and the receiver element, is reflective.
10. The photovoltaic cell of claim 9 wherein, in the completed photovoltaic cell, the majority of light initially enters the semiconductor lamina at the first textured surface.
11. The photovoltaic cell of claim 1 wherein, in the completed photovoltaic cell, the majority of light initially enters the semiconductor lamina at the second surface.
12. A photovoltaic cell comprising:
a semiconductor lamina having a first textured surface and a second surface substantially parallel to the first textured surface, wherein
at least 50 percent of the first textured surface comprises first faces and second faces, wherein
the first faces are at an angle between ten and twenty-five degrees from horizontal, and the second faces are at least seventy degrees from horizontal, wherein
distribution of the first faces is not periodic, wherein
the photovoltaic cell comprises the semiconductor lamina,
wherein the semiconductor lamina has a thickness between the first and second surfaces, the thickness averaging between about 1 and about 50 microns,
and wherein the semiconductor material is monocrystalline.
13. The photovoltaic cell of claim 12 wherein the semiconductor material is silicon.
14. The photovoltaic cell of claim 12 wherein the semiconductor lamina is between about 0.5 and about 20 microns thick.
15. The photovoltaic cell of claim 12 wherein the semiconductor lamina is between about 1 and about 10 microns thick.
16. The photovoltaic cell of claim 12 wherein, in the completed photovoltaic cell, the majority of light enters the semiconductor lamina at the first textured surface.
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 method of communicating with an ingestible capsule, comprising:
detecting the location of the ingestible capsule;
focusing a multi-sensor acoustic array on the ingestible capsule; and
communicating an acoustic information exchange with the ingestible capsule via the multi-sensor acoustic array.
2. The method of claim 1, wherein the communicating step comprises at least one of:
transmitting, via the multi-sensor acoustic array, an acoustic information exchange to the ingestible capsule; and
receiving, via the multi-sensor acoustic array, an acoustic information exchange from the ingestible capsule.
3. The method of claim 1, wherein determining the location comprises:
receiving an acoustic signal from the ingestible capsule;
determining a phase delay for each sensor in the multi-sensor array that produces a maximum gain of the acoustic signal; and
deriving the location of the ingestible capsule from the determined phase delays.
4. The method of claim 3, wherein determining a phase delay comprises:
detecting the acoustic signal; and
adjusting the phase delay for each sensor to maximize an amplitude of the acoustic signal.
5. The method of claim 4, wherein adjusting the phase delay comprises:
changing the phase delay by a given amount;
measuring the amplitude of the acoustic signal; and
repeating the changing and measuring steps until the amplitude of the acoustic signal is maximized.
6. The method of claim 4, wherein adjusting the phase delay comprises:
detecting the phase of the acoustic signal; and
adjusting the phase delay of each sensor until the signals received by each sensor are coherent.
7. The method of claim 1, wherein detecting the location comprises:
determining the location of the ingestible capsule through a successive approximation.
8. The method of claim 9, wherein determining the location further comprises:
determining the location of the ingestible capsule using a previously known location as a starting point for the successive approximation.
9. The method of claim 1, wherein communicating occurs periodically, continuously, or based on a given event.
10. A sensor array configured to communicate with a movable object, comprising:
a plurality of acoustic transducers configured to receive an acoustic signal from the movable object; and
a plurality of delays, each delay coupled to a corresponding one of the plurality of acoustic transducers,
wherein each delay is adjusted according to a phase of an information signal received by the corresponding acoustic transducer.
11. The sensor array of claim 10, wherein the acoustic transducers are spaced apart by approximately one-half the wavelength of the received information signal.
12. The sensor array of claim 10, wherein each acoustic transducer has a width approximately equal to one-quarter the wavelength of the received information signal.
13. The sensor array of claim 10, wherein each delay is determined through a successive approximation.
14. An ingestible capsule, comprising:
a sensor that receives a stimulus inside the gastrointestinal tract of an animal;
a bidirectional acoustic information communications module that transmits an acoustic information signal containing information from the sensor; and
an acoustically transmissive encapsulation configured to have a size that is ingestible, wherein the acoustically transmissive encapsulation substantially encloses the sensor and communications module.
15. The device of claim 14, the communications module comprising:
a receiver that receives an acoustic information signal;
a modulator that modulates a carrier frequency with the sensor output signal to generate an acoustic information signal;
a transmitter that transmits an acoustic information signal generated by the modulator.
16. The device of claim 14, the communications module comprising:
a radiating element coupled to an output of the communications module.
17. The device of claim 16, wherein the radiating element is a piezoelectric element.
18. The device of claim 17, wherein the radiating element is two or more piezoelectric elements spaced apart by a distance that is half the wavelength of the modulated signal.
19. The device of claim 17, wherein the radiating element emits a locationing signal that allows a detector to locate the device.
20. The device of claim 14, wherein the communications module is configured to suspend transmission of the acoustic information signal while information is obtained by the sensor.
21. The device of claim 14, wherein the communications module is configured to transmit an acoustic locationing signal prior to transmission of the acoustic information signal.
22. The device of claim 14, wherein the communications module is configured to transmit and receive an electromechanically modulated acoustic information signal.
23. A method of transmitting information acoustically, comprising:
applying a base voltage to a piezoelectric device to cause the piezoelectric device to ring at a drone frequency;
applying a voltage higher than the base voltage to the piezoelectric device to cause the piezoelectric device to ring at a first frequency that is different from the drone frequency; and
applying a voltage lower than the base voltage to the piezoelectric device to cause the piezoelectric device to ring at a second frequency that is different from the first frequency and the drone frequency,
wherein the first frequency represents a \u201c1\u201d bit and the second frequency represents a \u201c0\u201d bit in the transmitted information signal.
24. The method of claim 23, further comprising:
receiving information to be modulated into a transmitted information signal; and
applying a higher voltage and a lower voltage in sequence to generate the transmitted information signal.
25. The method of claim 23, wherein the base voltage is applied to separate bits in the transmitted information signal.