TUNABLE OPTICAL RECEIVER

• US 20160377530A1
• Filed: 06/24/2016
• Published: 12/29/2016
• Est. Priority Date: 06/24/2015
• Status: Active Grant

• Current Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius Medical Care AG)
• Original Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius Medical Care AG)
• Inventors: Barrett, Louis L.
• Granted Patent: US 10,281,454 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61M 1/14 Dialysis systems; Artificial kidneys; Blood oxygenators semi-permeable membranes characterised by the material, manufacturing processes therefor B01D71/00; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
• CPC Class Codes: A61M 1/3627 Degassing devices; Buffer reservoirs; Drip chambers; Blood filters
• CPC Class Codes: A61M 2205/3313 used specific wavelengths
• CPC Class Codes: A61M 2230/20 Blood composition characteristics
• CPC Class Codes: A61M 2230/202 partial carbon oxide pressure, e.g. partial dioxide pressure (P-CO2)
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)
• CPC Class Codes: A61M 2230/207 hematocrit
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: G01J 1/46 using a capacitor
• CPC Class Codes: G01J 2001/4406 Plural ranges in circuit, e.g. switchable ranges; Adjusting sensitivity selecting gain values
• CPC Class Codes: G01J 2003/104 Monochromatic plural sources
• CPC Class Codes: G01J 2003/106 the two sources being alternating or selectable, e.g. in two ranges or line:continuum
• CPC Class Codes: G01J 2003/4334 by modulation of source, e.g. current modulation
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/108 for measurement in the infrared range
• CPC Class Codes: G01J 3/433 : Modulation spectrometry; Derivative spectrometry
• CPC Class Codes: G01J 3/4338 : Frequency modulated spectrometry
• CPC Class Codes: G01N 2021/3181 : using LEDs
• CPC Class Codes: G01N 21/31 : Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence
• CPC Class Codes: G01N 2201/0627 : Use of several LED's for spectral resolution
• CPC Class Codes: G01N 2201/0691 : Modulated (not pulsed supply)
• CPC Class Codes: G01N 2201/12 : Circuits of general importance; Signal processing
• CPC Class Codes: G01N 33/49 : Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80

Abstract

An embodiment of the disclosure provides a system for determining information on one or more constituents in a medium. The system includes N light emitters L₁ . . . L_N, wherein each light emitter L_r provides an amplitude modulated (AM) light at modulation frequency f_r into a flow path of the medium from one side of a containment vessel for the medium. The system further includes a photodetector, for receiving the AM light from each light emitter after it passes through the flow path of the medium, and converting the AM light to an electrical signal characterized by a summation of frequency components from each modulation frequency f_r. The system further includes one or more measuring circuits providing information about a concentration of one or more constituents in the medium determined from log ratios of a pair of amplitudes of f_y and f_z frequency components in the electrical signal.

Claims

1. A system for determining information on one or more constituents in a medium, the system comprising:

N light emitters L₁ . . . L_N, wherein each light emitter L_x is configured to provide an amplitude modulated (AM) light at modulation frequency f_x into a flow path of the medium from one side of a containment vessel for the medium, wherein each light emitter L_x uses a different modulation frequency f_x, and wherein Nis an integer greater than 1, and x is an integer greater than or equal to 1 and less than or equal to N;

a photodetector, configured to receive the AM light from each light emitter after it passes through the flow path of the medium, and convert the AM light to an electrical signal characterized by a summation of frequency components from each modulation frequency f_x; and

one or more measuring circuits, configured to provide information about a concentration of one or more constituents in the medium determined from log ratios of a pair of amplitudes of f_y and f_z frequency components in the electrical signal, wherein y and z are integers greater than or equal to 1 and less than or equal to N, and y is not equal to z.

2. The system according to claim 1, wherein the medium is blood moving through a blood chamber.

3. The system according to claim 2, wherein the blood chamber is part of a device for monitoring blood undergoing dialysis.

4. The system according to claim 1, further comprising:

a trans-impedance amplifier for receiving the electrical signal produced by the photodetector;

a blocking capacitor configured to remove a direct current (DC) offset from a voltage signal from the trans-impedance amplifier; and

the measuring circuits are further configured to determine values V_y and V_z related to amplitudes of f_y and f_z frequency components of the voltage signal, where the log ratios of V_y and V_z includes the information about the concentration of the constituents.

5. The system according to claim 1, wherein each measuring circuit comprises a bandpass filter configured to extract a filtered signal with a frequency value that corresponds to one of the f_x modulation frequencies.

6. The system according to claim 1, wherein each measuring circuit further comprises:

a diode configured to rectify an alternating current (AC) signal;

a lowpass filter configured to provide a smooth voltage signal from the rectified signal; and

a sampling circuit, configured to determine a value V_x related to the amplitude of the f_x frequency component in the electrical signal by selecting a voltage reading from the smooth voltage signal.

7. The system according to claim 1, further comprising:

a blocking capacitor configured to remove a DC offset from the electrical signal;

a multiplier, configured to generate a mixed output signal by multiplying the electrical signal without DC offset and a matching signal, wherein the matching signal has a frequency equal to one of the modulation frequencies f₁ . . . f_N, and

wherein the one or more measuring circuits is one measuring circuit, the measuring circuit comprising a bandpass filter and a processor,

the processor configured to select the frequency of the matching signal, and the bandpass filter configured to extract a filtered signal from the mixed output signal, the filtered signal having a frequency equal to twice the matching signal'"'"'s frequency, and

wherein the measuring circuit determines values V_y from the filtered signal when the matching frequency is f_y and V_z from the filtered signal when the matching frequency is f_z, and V_y and V_z are related to the amplitudes of the f_y and f_z frequency components in the electrical signal, where the log ratios of V_y and V_z includes the information about the concentration of the constituents.

8. The system according to claim 1, further comprising:

a blocking capacitor configured to remove an offset from the electrical signal;

a multiplier, configured to generate a mixed output signal by multiplying the electrical signal without DC offset and a matching signal, wherein the matching signal has a frequency equal to one of the modulation frequencies f₁ . . . f_N; and

wherein the one or more measuring circuits is one measuring circuit, the measuring circuit comprising a lowpass filter and a processor,

the processor configured to select the frequency of the matching signal, and the lowpass filter configured to extract a filtered signal from the mixed output signal, the filtered signal being a DC signal, and

wherein the measuring circuit determines values V_y from the filtered signal when the matching frequency is f_y and V_z from the filtered signal when the matching frequency is f_z, and V_y and V_z are related to the amplitudes of the f_y and f_z frequency components in the electrical signal, where the log ratios of V_y and V_z includes the information about the concentration of the constituents.

9. The system according to claim 1, further comprising:

a blocking capacitor configured to remove an offset from the electrical signal;

a multiplier, configured to generate a mixed output signal by multiplying the electrical signal without DC offset and a matching signal, wherein the matching signal has a frequency equal to one of the modulation frequencies f₁ . . . f_N plus an offset frequency, and

wherein the one or more measuring circuits is one measuring circuit, the measuring circuit comprising a bandpass filter and a processor,

the processor configured to select the frequency of the matching signal, and the bandpass filter configured to extract a filtered signal from the mixed output signal, the filtered signal having a frequency equal to the offset frequency, and

wherein the measuring circuit determines values V_y from the filtered signal when the matching frequency is f_y plus the offset frequency and V_z from the filtered signal when the matching frequency is f_z plus the offset frequency, and V_y and V_z are related to the amplitudes of the f_y and f_z frequency components in the electrical signal, where the log ratios of V_y and V_z includes the information about the concentration of the constituents.

10. The system according to claim 1, wherein the measuring circuit is further configured to provide a phase difference between a phase of an f_x frequency component of the electrical signal and a phase of a current driving the L_x emitter.

11. The system according to claim 10, wherein the measuring circuit is further configured to determine a change in the phase difference, wherein the change in the phase difference provides information about a change in the composition of the medium.

12. A method for determining information on one or more constituents in a medium, the method comprising:

varying, by a driving circuit, current provided to N light emitters L₁ . . . L_N in a sinusoidal manner so that each light emitter L_x provides an amplitude modulated (AM) light at modulation frequency f_x into a flow path of the medium from one side of a containment vessel for the medium, wherein each light emitter L_x uses a different modulation frequency f_x, and wherein N is an integer greater than 1, and x is an integer greater than or equal to 1 and less than or equal to N;

receiving, by a photodetector, the AM light from each light emitter after it passes through the flow path of the medium and converting the AM light to an electrical signal characterized by a summation of frequency components from each modulation frequency f_x;

extracting, by a measuring circuit, log ratios of the amplitudes of f_y and f_z frequency components in the electrical signal to determine information about a concentration of one or more constituents in the medium, wherein y and z are integers greater than or equal to 1 and less than or equal to N, and y is not equal to z.

13. The method according to claim 12, wherein the medium is blood moving through a blood chamber.

14. The method according to claim 13, wherein the blood chamber is part of a device for monitoring blood undergoing dialysis.

15. The method according to claim 12, further comprising:

receiving, by a trans-impedance amplifier, the electrical signal produced by the photodetector;

removing, by a blocking capacitor, a direct current (DC) offset from a voltage signal from the trans-impedance amplifier; and

determining, by the measuring circuit, values V_y and V_z related to amplitudes of f_y and f_z frequency components of the voltage signal, where the log ratios of V_y and V_z includes the information about the concentration of the constituents.

16. The method according to claim 12, further comprising extracting, by a bandpass filter, a filtered signal with a frequency value that corresponds to one of the f_x modulation frequencies.

17. The method according to claim 12, further comprising:

rectify an alternating current (AC) signal;

providing a smooth voltage signal from the rectified signal; and

determining a value V_x related to the amplitude of the f_x frequency component in the electrical signal by selecting a voltage reading from the smooth voltage signal.

18. The method according to claim 12, further comprising:

removing a DC offset from the electrical signal;

generating, by a multiplier, two mixed output signals by multiplying the electrical signal without DC offset and two matching signal, wherein the two matching signal have frequencies f_y and f_z;

extracting, by a bandpass filter, two corresponding filtered signals from the two mixed output signal, the two filtered signals having frequencies equal to 2×

f_y and 2×

f_z; and

determining, by the measuring circuit, values V_y from the filtered signal when the matching frequency is f_y and V_z from the filtered signal when the matching frequency is f_z, and V_y and V_z are related to the amplitudes of the f_y and f_z frequency components in the electrical signal, where the log ratios of V_y and V_z includes the information about the concentration of the constituents.

19. The method according to claim 12, further comprising:

removing a DC offset from the electrical signal;

generating, by a multiplier, two mixed output signals by multiplying the electrical signal without DC offset and two matching signal, wherein the two matching signal have frequencies f_y and f_z;

extracting, by a lowpass filter, two corresponding filtered signals from the two mixed output signal, the two filtered signals being DC signals; and

determining, by the measuring circuit, values V_y from the filtered signal when the matching frequency is f_y and V_z from the filtered signal when the matching frequency is f_zj and V_y and V_z are related to the amplitudes of the f_y and f_z frequency components in the electrical signal, where the log ratios of V_y and V_z includes the information about the concentration of the constituents.

20. The method according to claim 12, further comprising:

removing a DC offset from the electrical signal;

generating, by a multiplier, two mixed output signals by multiplying the electrical signal without DC offset and two matching signal, wherein the two matching signal have frequencies f_y plus an offset frequency and f_z plus the offset frequency;

extracting, by a bandpass filter, two corresponding filtered signals from the two mixed output signal, the two filtered signals having frequencies equal to the offset frequency; and

determining, by the measuring circuit, values V_y from the filtered signal when the matching frequency is f_y plus the offset frequency and V_z from the filtered signal when the matching frequency is f_z plus the offset frequency, and V_y and V_z are related to the amplitudes of the f_y and f_z frequency components in the electrical signal, where the log ratios of V_y and V_z includes the information about the concentration of the constituents.

21. The method according to claim 12, further comprising:

determining, by the measuring circuit, a phase difference between a phase of an f_x frequency component of the electrical signal and a phase of a current driving the L_x emitter.

22. The method according to claim 21, further comprising:

determining, by the measuring circuit, a change in the phase difference, wherein the change in the phase difference provides information about a change in the composition of the medium.

24. The non-transient computer readable medium according to claim 12, wherein the processor further performs the method of:

providing two matching signals with frequencies f_y and f_z to a multiplier, so that the multiplier generates two mixed output signals by multiplying the electrical signal without DC offset and the two matching signals; and

extracting log ratios of values V_y and V_z to determine the information about the concentration of the constituents, wherein V_y is determined from a filtered signal in one mixed output signal with frequency 2×

f_y when the matching frequency is f_y and V_z is determined from a filtered signal in the other mixed output signal with frequency 2×

f_z when the matching frequency is f_z, and V_y and V_z are related to the amplitudes of the f_y and f_z frequency components in the electrical signal.

23. A non-transient computer readable medium containing program instructions for determining information on one or more constituents in a medium, such that when the instructions are executed by a processor coupled to N light emitters L₁ . . . L_N and a photodetector, the processor performs the method of:

varying driving current provided to the N light emitters in a sinusoidal manner so that each light emitter L_x provides an amplitude modulated (AM) light at modulation frequency f_x into a flow path of the medium from one side of a containment vessel for the medium, wherein each light emitter L_x uses a different modulation frequency f_x, and wherein N is an integer greater than 1, and x is an integer greater than or equal to 1 and less than or equal to N;

extracting log ratios of amplitudes of f_y and f_z frequency components in an electrical signal to determine information about a concentration of one or more constituents in the medium, wherein y and z are integers greater than or equal to 1 and less than or equal to N, and y is not equal to z;

wherein the electrical signal is generated by a photodetector receiving the AM light from each light emitter after it passes through the flow path of the medium and converting the AM light to an electrical signal characterized by a summation of frequency components from each modulation frequency f_x.