Transmitting light with photon energy information Number:7,522,786 from the United States Patent and Trademark Office (PTO) owispatent

Title: Transmitting light with photon energy information

Abstract: In detection and sensing, light is transmitted through layers or structures that vary laterally, such as with a constant gradient or a step-like gradient. After transmission, a position of a transmitted portion of the light or of output photons can be used to determine wavelength change or to obtain other photon energy information. The light can be received, for example, from a stimulus-wavelength converter such as an optical fiber sensor or another optical sensor. A component that propagates the light from the converter to a transmission structure can spread the light across the transmission structure's entry surface. At the exit surface of the transmission structure, photosensor components can sense or detect transmitted light or output photons, such as with a photosensor array or a position sensor. A photosensed quantity can be compared, such as with another photosensed quantity or with a calibration quantity. A differential quantity can be obtained using photosensed quantities.

Patent Number: 7,522,786 Issued on 04/21/2009 to Kiesel,   et al.

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Inventors:	Kiesel; Peter (Palo Alto, CA), Schmidt; Oliver (Palo Alto, CA)
Assignee:	Palo Alto Research Center Incorporated (Palo Alto, CA)
Appl. No.:	11/316,241
Filed:	December 22, 2005

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Current U.S. Class:	385/12 ; 356/451; 356/454; 359/326
Current International Class:	G02B 6/00 (20060101); G01J 3/45 (20060101); G02F 1/35 (20060101)
Field of Search:	385/12

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Primary Examiner: Le; Uyen Chau N
Assistant Examiner: Prince; Kajli
Attorney, Agent or Firm: Leading-Edge Law Group, PLC Beran; James T.

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Claims

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What is claimed is:

1. A detection system, comprising: an optical sensor that outputs a narrow band of optical wavelengths when illuminated with a broad band of optical wavelengths, the narrow band of optical wavelengths changing over time; and a detector that includes at least one layer with laterally varying transmission properties, the detector receiving light output by the optical sensor; in response to a change over time of the narrow band of optical wavelengths output by the optical sensor, the detector transmitting a portion of the received light at a position of the at least one layer, the position having a change over time; the detector using the position's change over time to determine change over time of the narrow band of optical wavelengths output by the optical sensor.

2. The system of claim 1, further comprising: an optical fiber that receives light output from the optical sensor and guides the light to the detector.

3. The system of claim 1 in which the at least one layer includes a graded Fabry-Perot cavity with two sets of distributed Bragg mirrors and, between them, a laterally graded cavity; the light output by the optical sensor being spread across approximately an entire surface of one of the distributed Bragg mirrors.

4. The system of claim 1 in which the optical sensor is one of a two-dimensional grating sensor, a guided mode resonant fiber sensor, or a photonic crystal sensor.

5. The system of claim 1 in which the detector further includes an IC with at least one of a photosensor array with CCD readout, a photosensor array with CMOS readout, and a position sensor.

6. The system of claim 1, further comprising: a differential amplifier connected to receive two signals from the detector; the differential amplifier providing a differential signal that changes over time in response to changes in the narrow band of optical wavelengths output by the optical sensor.

7. The apparatus of claim 1 in which the narrow band of wavelengths output by the optical sensor changes over time in response to changes over time in a stimulus, the stimulus including at least one of temperature, pressure, strain, stress, flow, level, speed or rpm, position, orientation, motion, acceleration, presence or absence of an analyte, rain, thickness, liquid quality, breakage, or magnetic field.

8. Apparatus comprising: a stimulus-wavelength converter that provides light within a photon energy range that includes first and second peak energy values about which the converter provides light in response to first and second values of a stimulus, respectively; the light provided by the stimulus-wavelength converter changing over time between the first and second peak energy values in response to change over time between the first and second values of the stimulus; a transmission structure with entry and exit surfaces, the exit surface including first and second positions; the transmission structure being a layered structure with a laterally varying energy transmission function; and a propagation component that propagates light from the converter to the transmission structure's entry surface; the transmission structure providing photons at the first and second positions of the exit surface in response to light received at its entry surface with the first and second peak energy values, in response to a change over time between the first and second peak energy values, the transmission structure providing photons at the first and second positions with relative quantities that change over time, a change over time in the relative quantities indicating a change over time between the first and second peak energy values.

9. The apparatus of claim 8 in which the stimulus-wavelength converter includes one of an optical fiber, a photonic crystal, a laser cavity, a fluorescent analyte, a fiber Bragg grating, and a Fabry-Perot structure.

10. The apparatus of claim 8 in which the stimulus-wavelength converter provides light about the first and second peak energy values in response to the first and second values of the stimulus, respectively; the stimulus including at least one of temperature, pressure, strain, stress, flow, level, speed or rpm, position, orientation, motion, acceleration, presence or absence of an analyte, rain, thickness, liquid quality, breakage, or magnetic field.

11. The apparatus of claim 8 in which the stimulus-wavelength converter provides light from a fiber end facet, from a point-like source, or from a broad area source.

12. The apparatus of claim 8 in which the transmission structure is a coating with a constant transmission gradient or a step-like transmission gradient.

13. A system that includes the apparatus of claim 8, the system further comprising: one or more photosensing components that sense quantities of photons from the first and second positions of the exit surface; and circuitry that compares sensed quantities of photons from the first and second positions; the circuitry providing a differential signal indicating results of comparing sensed quantities of photons from the first and second positions; the differential signal changing over time in response to the stimulus-wavelength converter's changing over time between the first and second peak energy values.

14. The system of claim 13 in which the circuitry includes a processor.

15. A method of using the apparatus of claim 8, comprising: with the propagation component, propagating output light from the stimulus-wavelength converter to the transmission structure's entry surface; and in response to a change from the first value to the second value of the stimulus, changing relative quantities of photons provided at the first and second positions of the transmission structure's exit surface.

16. The method of claim 15 in which the act of propagating the output light comprises at least one of transmitting, guiding, spreading, collimating, focusing, and imaging the output light.

17. A method of producing the apparatus of claim 8, the method comprising: producing the apparatus so that, in response to a change between the first and second peak values resulting from a change between the first and second values of the stimulus, the transmission structure changes relative quantities of photons provided at the first and second positions.

18. The apparatus of claim 8 in which the propagation component spreads the light from the converter across the transmission structure's entry surface sufficiently that a change over time between the first and second peak energy values results in a detectable change over time in relative quantities of photons provided at the first and second positions.

19. Apparatus comprising: a transmission structure with entry and exit surfaces, the transmission structure being a layered structure with a laterally varying energy transmission function; in response to light received at the entry surface that has distributions across a range of photon energies, the distributions changing over time; the transmission structure providing output photons at positions of the exit surface, the output photons being provided in quantities that change over time in response to change over time in the distributions; a photosensor component that photosenses quantities of photons provided at positions of the exit surface; and circuitry that responds to the photosensed quantities by providing differential quantities, each differential quantity comparing photosensed quantities from a respective one of the distributions, the differential quantities indicating change over time in the distributions.

20. The apparatus of claim 19 in which the transmission structure is a coating over the photosensor component.

21. The apparatus of claim 19 in which the circuitry includes a processor.

22. The apparatus of claim 19 in which the photosensor component comprises: an IC that includes a photosensor array with CCD readout, a photosensor array with CMOS readout, or a position sensor.

23. A method of using the apparatus of claim 19, the method comprising: receiving light at the entry surface of the transmission structure, the light having distributions within a range of photon energies; in response to the received light, providing output photons at positions of the transmission structure's exit surface; with the photosensing components, photosensing quantity of output photons provided at positions of the transmission structure's exit surface; and with the circuitry, using the photosensed quantities to obtain at least one differential quantity that compares photosensed quantities from the same one of the distributions.

24. A method of using a transmission structure that is a layered structure with a laterally varying energy transmission function; the method comprising: receiving light at the transmission structure's entry surface, the received light having distributions within a range of photon energies, the distributions changing over time; in response to the received light, providing output photons at positions of the transmission structure's exit surface, the output photons being provided in quantities that change over time in response to change over time in the distributions; photosensing quantities of output photons provided at positions of the transmission structure's exit surface; and using the photosensed quantities to obtain differential quantities, each differential quantity comparing photosensed quantities from a respective one of the distributions, the differential quantities indicating change over time in the distributions.

25. The method of claim 24 in which the photosensed quantities are indicated by first and second currents provided by a position sensor in response to the distributions, the differential quantities comparing the first and second currents.

26. The method of claim 24 in which the act of using the photosensed quantities includes obtaining a first differential quantity in response to received light with a first distribution and obtaining a second differential quantity in response to received light with a second distribution.

27. The method of claim 26 in which the first distribution is received at the entry surface before the second distribution is received; the first differential quantity being obtained before the second distribution is received.

28. The method of claim 26 in which the first and second distributions are received concurrently at the entry surface, first and second sets of positions of the exit surface providing photons in response to the first and second distributions, respectively; the first and second differential quantities being obtained from photosensed quantities of output photons from the first and second sets of positions, respectively.

29. The method of claim 26 in which the first and second distributions include first and second peak energy values, respectively; the method further comprising: detecting a transition between the first and second peak energy values based on a transition between the first and second differential quantities.

30. The method of claim 26 in which the received light is output light from a stimulus-wavelength converter; the first and second distributions being provided by the converter in response to first and second values of a stimulus.

31. A method of using a transmission structure that is a layered structure with a laterally varying energy transmission function, the method comprising two or more operations, each operation including: at the transmission structure's entry surface, receiving a respective distribution of output light from a stimulus-wavelength converter, the respective distribution being within a range of photon energies; in response to the respective distribution, providing at each of a number of positions of the transmission structure's exit surface a respective quantity of output photons; photosensing the respective quantities of output photons provided at a set of two or more positions of the transmission structure's exit surface; and using the photosensed quantities to obtain a respective set of one or more differential quantities, each of which compares photosensed quantities from two or more of the positions in the set; the operations including first and second operations, the first operation's respective distribution being received at the transmission structure's entry surface at a first time in response to a first value of a stimulus; the second operation's respective distribution being received at the transmission structure's entry surface at a second time in response to a second value of the stimulus, the second time being after the first time; the stimulus value changing between the first and second times so that the first and second values of the stimulus are different from each other; the second operation's set of differential quantities being different from the first operation's set of differential quantities, the difference between the sets of differential quantities indicating that the stimulus value changed between the first and second times.

32. The method of claim 31 in which the act of using the photosensed quantities comprises comparing a photosensed quantity with another photosensed quantity of photons or with a calibration quantity of photons.

33. The method of claim 31 in which the act of using the photosensed quantities comprises using analog photosensed quantities from at least two of the positions to obtain the respective set of differential quantities.

34. The method of claim 31 in which the act of using the photosensed quantities comprises: converting photosensed quantities from at least two of the positions to digital values; and using the digital values to obtain the respective set of differential quantities.

35. The method of claim 34 in which the act of using the digital values comprises combining digital values from two subsets of the positions and comparing the combined digital values to obtain the respective set of differential quantities.

36. The method of claim 31 in which the act of using the photosensed quantities obtains at least one of absolute photon energy information and relative photon energy information.

37. A system comprising: one or more sources that provide output light with respective photon energy distributions that change over time; a transmission structure that has an entry surface at which it receives light and an exit surfaces at which it provides output photons in response, the transmission structure having a laterally varying energy transmission function; and a component that spreads the output light from each of the one or more sources across the transmission structure's entry surface; the component spreading the output light from each source in such a way that a change in the respective photon energy distribution over time results in a detectable change over time in quantities of the output photons provided at different positions in response to the output light from the source.

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Description

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The present application is related to the following applications, each of which is hereby incorporated by reference in its entirety: "Chip-Size Wavelength Detector", U.S. patent application Ser. No. 10/922,870, now issued as U.S Pat. No. 7,310,153; "Biosensor Using Microdisk Laser", U. S. patent application Ser. No. 10/930,758, now published as U.S. Patent Application Publication No. 2006/0046312; "Anti-resonant Waveguide Sensors", U.S. patent application Ser. No. 10/976,434, now issued as U.S. Pat. No. 7,268,868; "Photosensing Throughout Energy Range and in Subranges", U.S. patent application Ser. No. 11/316,438, now issued as U.S. Pat. No. 7,291,824; "Sensing Photon Energies of Optical Signals", U.S. patent application Ser. No. 11/315,926; "Sensing Photon Energies Emanating From Channels or Moving Objects", U.S. patent application Ser. No. 11/315,992; "Providing Light To Channels Or Portions", U.S. patent application Ser. No. 11/316,660; "Sensing Photon Energies Emanating from Channels", U.S. patent application Ser. No. 11/315,386; "Obtaining Analyte Information", U.S. patent application Ser. No. 11/316,303; and "Propagating Light to be Sensed", U.S. patent application Ser. No. 11/315,387, now issued as U.S. Pat. No. 7,315,667.

BACKGROUND OF THE INVENTION

The present invention relates generally to transmission of light through structures, and more particularly to transmission of light that includes photon energy information.

Fuhr, P. L., "Measuring with Light", Sensors Magazine Online, May 2000, pp. 1-11, available at www.sensorsmag.com/articles/0500/26/, describes sensors that are sometimes referred to as fiber-optic sensors. Fiber-optic sensors have advantages over conventional electrical- and electromechanical-based sensors, stemming mainly from the fact that the fibers are made of nonconducting glass and photons, not electrons, are the signal propagation elements; as a result, the sensors are immune to electromagnetic interference (EMI) and can operate in harsh environmental conditions, offering a geometric versatility that allows unobtrusive sensing. More than 60 different parameters can be measured using fiber-optic sensors. In extrinsic fiber-optic sensors, the optical fiber acts as a transmit/receive light conduit, with signal modulation occurring outside of the fiber, such as in a modulation region that receives light of known parametric values and provides light with a changed characteristic. In intrinsic fiber-optic sensors, on the other hand, an external perturbation directly interacts with the optical fiber and modulates the light signal in the fiber, such as by changing the optical fiber's waveguide controlling boundary conditions.

Various types of optic-fiber sensors as described by Fuhr have been developed. Many fiber-optic sensors are based on Fiber Bragg Gratings (FBGs), which can be fabricated by exposing a photosensitive optical fiber to a periodic pattern of strong ultraviolet light or by etching a periodic pattern directly into the core of the fiber, forming a periodic modulation of the refractive index along the core. Plastic optical fibers (POF) have been applied to sensing in the form of diffracting structures in single- and multi-mode POF with various fabrication techniques. Photonic crystal sensors are the two- and three-dimensional analogs to FBGs, with a periodic modulation of the refractive index in all directions resulting in special reflection and transmission properties. In addition to other applications, various fiber-optic sensors and other optical sensors have been proposed for use in biosensing.

In fiber-optic sensors that indicate stimulus change in the form of wavelength shift in output light, additional systems have been developed for detecting the wavelength shift. Some examples include a broadband light source in combination with a spectrum analyzer and, alternatively, a tunable laser with a narrow line width, sweeping periodically across the reflectivity peak or resonance dip of the sensor cavity.

Othonos, A., and Kalli, K., Fiber Bragg Gratings, Artech House Publishers, Boston, 1999, pp. 304-330, provide an overview of readout techniques for FBGs.

U.S. Pat. No. 5,166,755 describes a spectrometer apparatus in which a spectrum resolving sensor contains an opto-electronic monolithic array of photosensitive elements and a continuous variable optical filter. The filter can include a variable thickness coating formed into a wedge shape on a substrate or directly on the surface of the array. If polychromatic light passes through the variable filter and is spectrally resolved before incidence on the array, the output of all the elements in the array provides the spectral contents of the polychromatic light. High spectral resolving power is obtained by subtracting the output signals of adjacent elements in the array. Non-imaging applications include measurement of spectral transmission through samples; for molecular absorption and emission spectra; for spectral reflectance measurements; for pollution and emission control by measuring transmission or absorption; for astronomical spectral analyses of stell