1. A photoacoustic gas sensor comprising:
a housing having a predetermined physical form factor;
a photoacoustic gas sensing chamber carried in the housing; and
processing circuitry carried in the housing and communicatively coupled to the sensing chamber, to process signals from the sensing chamber to produce an output signal responsive to at least one gas sensed by the photoacoustic gas sensor, said output signal emulating the characteristic gas response output signal of a catalytic bead pellistor gas sensor.
2. A photoacoustic gas sensor as in claim 1 where the housing defines a gas diffusion port and a flame arrestor which covers the port, at least in part.
3. A photoacoustic gas sensor as in claim 1 where the housing defines a gas diffusion port which is covered by a gas permeable member.
4. A photoacoustic gas sensor as in claim 3 where the gas permeable member comprises a flame arrestor.
5. A photoacoustic gas sensor as in claim 1 which includes at least one of an ambient acoustic sensor, a thermal sensor, a pressure sensor or a humidity sensor carried by the gas sensor housing.
6. A photoacoustic gas sensor as in claim 5 where the processing circuitry includes circuitry for producing output signals compensated by outputs from the at least one of an ambient acoustic sensor, a thermal sensor, a pressure sensor, or an humidity sensor carried by the gas sensor housing.
7. A photoacoustic gas sensor as in claim 5 which includes circuitry to generate a normalized output signal based on at least one of; the type of gas sensed, the gas concentration range, or a preferred sensor output range.
8. A photoacoustic gas sensor as in claim 5 which includes circuitry to generate a linearized output signal based on the type of gas and gas concentration.
9. A photoacoustic gas sensor as in claim 6 where the processing circuitry includes programmable circuitry and at least one pre-stored data table for carrying out the processing.
10. A photoacoustic gas sensor as in claim 9 which includes a storage unit load able with a data table.
11. An integrated photoacoustic gas sensor comprising:
a gas sensing chamber;
a source of radiant energy which directs the energy into the sensing chamber;
a plurality of sensors carried in the gas sensor body, including at least one acoustic signal sensor, a thermal sensor, a pressure sensor and a humidity sensor;
control circuits coupled to the sensors to process photoacoustic or ambient environment-related signals from at least some of the sensors to produce at least one of a compensated, normalized or linearized gas concentration-indicating output signal.
12. An integrated photoacoustic gas sensor as in claim 11 where the control circuits include pre-stored data and executable instructions pertaining to at least one of the compensation, normalization, or linearization of a sensor output signal corresponding to a sensed gas concentration.
13. An integrated photoacoustic gas sensor as in claim 11 which includes processing circuitry and executable instructions to produce an output signal responsive to a target gas to be detected, said output signal emulating the gas response output signal characteristics of a catalytic bead pellistor gas sensor.
14. An integrated photoacoustic gas sensor as in claim 13 carried in a gas sensor body comprising a cylindrical housing of outside diameter 20.4 mm\xb10.3 mm, and height 16.6 mm\xb10.3 mm.
15) A photoacoustic gas sensor as in claim 12, where the control circuits include digital transmit and receive interface circuitry disposed to provide external bi-directional digital communications for the gas sensor.
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. Method for the realization of a confocal fluorescence in vivo in situ image, the method using an image guide made of several thousands of optical fibres and consisting of the point by point scanning of a tissue in a subsurface plane, each point corresponding to an excitation signal emitted by a continuous source, deflected and injected into one of the optical fibres of said bundle then focussed on the exit of said fibre in said plane, each point emitting in return a fluorescence signal collected by said optical fibre, then detected and digitized to form an image element, characterized in that the excitation signal is deflected at a speed corresponding to acquisition of a number of images per second sufficient for a real-time use and in that the fluorescence signal is detected at a detection frequency corresponding to a minimum sampling frequency of the fibres one-by-one.
2. Method according to claim 1, characterized by a numerical aperture of the focussing optics between approximately 0.5 and 1.
3. Method for the realization of a high-resolution fluorescence image using an image guide made of several thousands of optical fibres, an excitation signal being emitted by a continuous source, deflected and injected by turns into one of the optical fibres of said image guide and a fluorescence signal emitted in response being collected by the same optical fibre as that used for the excitation, then detected and digitized to form an image element, characterized in that the end of the fibres is intended to be placed bare directly in contact with the surface of the tissue to be imaged, each fibre being able to produce a divergent beam which is able to excite a microvolume of tissue situated at the surface to a maximum depth depending in particular on the core diameter of the optical fibres and in that the excitation signal is deflected at a speed corresponding to acquisition of a number of images per second sufficient for a real-time use and in that the fluorescence signal is detected at a detection frequency corresponding to a minimum sampling frequency of the fibres one-by-one.
4. Method according to claim 1, characterized in that the deflection speed of the excitation beam is adjusted by determining a rapid-resonance frequency of a resonating line mirror and a slow-resonance frequency of a galvanometric frame mirror.
5. Method according to claim 1, characterized in that optical deflection, injection, focussing and detection means are used having a degree of achromaticity which allows the collection of photons over the whole of the emission band of the excited fluorophore.
6. Method according to claim 1, characterized by a quantum efficiency of detection at the fluorescence wavelengths to be detected of at least 50%.
7. Method according to claim 1, characterized by a prior step of detecting the placement of the fibres of the image guide which are intended to be used.
8. Method according to claim 1, characterized by a prior step of determining the real injection rate particular to each fibre.
9. Method according to claim 8, characterized by a prior step of determining the collected flux corresponding to the background image.
10. Method according to claim 9, characterized by a step of correcting the digitized signal coming from a fibre by subtraction of the flux corresponding to the background image and adaptation to the real rate of injection which is particular to said fibre.
11. Method according to claim 10, characterized by a step of reconstructing the image from the corrected signal.
12. Method according to claim 11, characterized in that the step of reconstructing the image comprises a Gaussian low-pass filtering.
13. Apparatus for in situ in vivo fibred optic confocal fluorescence imaging for the implementation of the method according to claim 1, comprising:
the image guide (6);
the source (1) emitting continuously at the excitation wavelength of at least one targeted fluorophore,
means for rapid scanning (4) and injection (5) fibre by fibre over time of the excitation beam produced by the source (1) by lines and by columns in a XY plane corresponding to the entry section of the image guide (6);
means (3) for separating the excitation wavelength and the fluorescence wavelengths;
means for detection (11) of the fluorescence signal; and
means (12) for processing the detected signal allowing the realization of an image;
an optical head (7) being arranged at the distal end, intended to be brought into contact with the observed tissue (13), allowing the excitation beam to be focussed.
characterized in that:
the scanning means are suitable for moving the excitation beam at a speed corresponding to the obtaining of an image in real time; and
the detection means have a pass-band whose frequency is fixed as a function of the minimum one-by-one fibres sampling frequency.
14. Apparatus for in situ in vivo fibred high-resolution confocal fluorescence imaging for the implementation of the method according to claim 3, comprising:
the image guide (6);
the source (1) emitting continuously at the excitation wavelength of at least one targeted fluorophore,
means for rapid scanning (4) and fibre-by-fibre injection (5) of the excitation beam produced by the source (1) in a XY plane corresponding to the entry section of the image guide (6);
means (3) for separating the excitation wavelength and the fluorescence wavelengths;
means (11) for detecting the fluorescence signal; and
means (12) for processing the detected signal allowing the realization of an image;
characterized in that the end of each fibre is adapted for producing a beam which is divergent and is intended to be placed bare directly in contact with the surface of the tissue to be observed;
and in that the scanning means are suitable for moving the excitation beam at a speed corresponding to the obtaining of an image in real time; and the detection means have a pass-band whose frequency is fixed as a function of the minimum sampling frequency of the fibres one-by-one.
15. Apparatus according to claim 13, characterized in that the excitation beam produced by the source (1) is of the longitudinal monomode type presenting an optimum wave front quality for the injection into a slightly multimode optical fibre.
16. Apparatus according to claim 13, characterized in that, the section of a fibre being circular, the excitation beam produced by the source is circular so as to optimize the injection into a fibre.
17. Apparatus according to claim 13, characterized by means (2) for shaping the beam used on the exit of the source (1) in order to shape the excitation beam so as to adapt it to the injection means (5) in the image guide (6).
18. Apparatus according to claim 13, characterized in that the means for separating the excitation and fluorescence wavelengths comprise a dichroic filter (3) having a maximum efficiency at the excitation wavelength.
19. Apparatus according to claim 13, characterized by rejection means (8) placed upstream of the detection means (11) and suitable for eliminating the excitation wavelength.
20. Apparatus according to claim 13, characterized in that the scanning means (4) comprise a resonating line mirror (M1), a galvanometric frame mirror (M2), a first afocal optical system (AF1) with unitary magnification adapted for the conjugation of the two mirrors and a second afocal system (AF2) with unitary magnification adapted for the conjugation of the rotation planes of the two mirrors with the injection plane in one of the fibres.
21. Apparatus according to claim 13, characterized in that the optical means of the optical head (7), the scanning means (4), the injection means (5) and the detection means present a degree of achromaticity adapted for the collection of the photons over the whole of the width of the spectral band of the fluorescence signal.
22. Apparatus according to claim 13, characterized in that the injection means (5) comprise two optical units (E1, E2), the first unit (E1) being adapted for correcting the optical aberrations at the edge of the field of the scanning means (4) and the second unit (E2) being adapted for carrying out the actual injection in one of the fibres of the image guide (6).
23. Apparatus according to claim 22, characterized in that the first optical unit (E1) comprises a doublet and the second optical unit (E2) comprises two doublets followed by a lens.
24. Apparatus according to claim 13, characterized by a filtering hole (10) placed in front of the detection means (11) whose diameter is chosen so that the image of a fibre fits into it.
25. Apparatus according to claim 24, characterized by means (9) for focussing the fluorescence signal on the filtering hole (10).