MXPA99009385A - Elastic radiation scatter-detecting safety device, analyzer apparatus provided with safety device, and method for controlling a laser excitation source - Google Patents

Abstract

A device for detecting elastically scattered radiation comprising:a source (16) of monochromatic radiation having a controllableoutput, a detector (56) for detecting the elastically scattered radiation from a specimen (12), and a signal conditioning circuit (68) comprising a transducer and comparator. The output of the transducer is compared to a threshold signal to produce a control output signal for source (16). The device is further included in a raman spectrometry apparatus that further includes an optical probe (32). The probe comprises a fluid-tight body that encloses three optical channels, preferabyl comprising fibers that carry monochromatic radiation to the speciment and separately collect inelastically and elastically scattered radiation from the specimen.

Description

SECURITY DEVICE THAT DETECTS RADIATION DISPERSION ELASTIC, ANALYZER APPARATUS PROVIDED WITH A DEVICE OF SECURITY, AND METHOD TO CONTROL A SOURCE OF LASER EXCITATION Field of the Invention The invention relates generally to laser excitation sources, particularly to a safety device and method for controlling a laser excitation source, and more particularly to a safety device that detects the dispersion of elastic radiation to control a source of excitation. laser included in a Raman spectrometry device.

Background of the Invention When the incident radiation interacts with matter, it can be subjected to a process called dispersion. As described in J.B. Ingle, Jr. and S.R. Crouch, "Molecular Scattering Methods," Chapter 16 in Spectrochemical Analysis. 1988, Prentice-Hall, Englewood Cliff NJ, pp. 494-499, the dispersion can be elastic, that is, the wavelength of the scattered radiation is unaltered from that of the incident radiation, or inelastic, that is, the scattered radiation has Ref. 031795 a wavelength different from that of the incident radiation.

In a form of elastic radiation scattering, referred to as Rayleigh scattering, the dimensions of the scattering particles, i.e., atoms and molecules, are much smaller than the wavelength of the incident beam. In general, the Rayleigh scattering is inversely proportional to the fourth power of the wavelength of the incident light. Liquids exhibit significantly greater Rayleigh dispersion than gases.

A type of inelastic radiation scattering is referred to as Raman scattering; the incident photons are dispersed with either a gain or loss of energy, and the energy difference between the scattered and incident radiation is commonly referred to as the Raman variation. The spectrum of the Raman variation represents the energy of several molecular vibrations and transmits the chemical and molecular information with respect to the studied matter. Raman spectrometry is widely used in the analysis of various materials and is able to provide both qualitative and quantitative information about the composition and / or molecular structure of chemical substances.

The Raman scattering signals are very weak, much weaker than the Rayleigh scattering signals. Typically a few photons of the Raman scattering exist among millions of elastically scattered photons. This small Raman signal between the elastically large scattered signals establishes several demands on the instrumentation design of any spectrometer used to observe the Raman spectrum.

A Raman spectrometry apparatus typically comprises a monochromatic light laser excitation source, a probe, and a fiber optic cable that includes the transmission and reception of fiber channels that connect the laser to the probe. The probe can be remotely located from the laser light source; it can, for example, be located inside a chamber, such as a reactor or a pipe where a chemical reaction is present comprising solids, liquids, gases, or mixtures thereof. The fiber-optic cable includes transmission and reception fibers. The laser output is transmitted through a transmission fiber channel to the probe, the probe comes out, and illuminates the material inside the reaction chamber. The Raman scattering resulting from the irradiation of the material is transmitted by a reception fiber channel to a detector and spectrograph included in the spectrometry apparatus.

The lasers are classified according to their power output, from "exempt" lasers of very low power of Class I to lasers of high power of Classes III and IV, whose output fluctuates from approximately 1 mW to greater than 500 mW. The lasers used as excitation sources for Raman spectrometry are frequently of Class III or IV and therefore have output energy levels that present a potential hazard. If the probe is accidentally removed from a material that is measured, the high laser output could damage the cornea or retina of an operator's eyes and could also ignite flammable substances in the surroundings, causing a fire or explosion. To ensure personal safety and minimize the hazards of fire or explosion, it would be highly desirable to have reliable control to automatically shut off the laser if the probe is removed from the material under examination or if an interruption occurs in a fiber-optic channel. Such control is provided by the present invention.

Brief Description of the Invention The present invention relates to a security device for use with an analyzer apparatus, in particular, a Raman spectrometry apparatus provided with an optical probe, and in addition it relates to a method using scattered detection of elastic radiation collected from a specimen illuminated by a laser excitation source to control the source of excitation.

According to the invention, a security device for detecting the elastically dispersed radiation comprises: a monochromatic radiation source substantially having a controllable output, detection means for detecting the elastically dispersed radiation, collected from a specimen illuminated by the radiation source monochromatically, and a signal conditioning circuit. The signal conditioning circuit comprises: transduction means for converting the elastically dispersed, detected radiation of the specimen into a transducer output signal, and a comparator for comparing the output signal of the transducer with a predefined threshold signal and generating a signal of control output which is representative of itself the output signal of the transducer is greater than, equal to, or less than the threshold signal. The control output signal is coupled to the monochromatic radiation source and causes the output of the radiation source which is reduced when the output signal of the transducer is smaller than the predefined threshold signal.

In a preferred embodiment of the invention, the source of monochromatic radiation substantially comprises a laser, the means for detecting the elastically dispersed radiation comprise a silicon photodetector, and the transduction means comprises a transimpedance amplifier. Also in a preferred embodiment, the security device further includes closure means comprising a relay and further comprising an on / off switch. In a preferred embodiment, the signal conditioning circuit further comprises a buffer amplifier coupled to the transducing means and a reference voltage source coupled to the buffer amplifier. The separator amplifier is selectively connected to the comparator to generate a test output to adjust a trigger point of the comparator.

Further in accordance with the present invention is an analyzer apparatus, preferably a Raman spectrometry apparatus comprising the described security device and an optical probe. In one embodiment, the analyzer apparatus further comprises a filter module that includes a band pass filter (PB) and a blocking filter, preferably a long pass filter (PL).

The optical probe comprises a fluid-tight body enclosing: a first optical channel for transporting the monochromatic radiation substantially from an excitation source for illuminating a specimen, a second optical channel for collecting the radiation dispersed elastically by the illuminated specimen, and a third optical channel to collect the radiation dispersed inelastically by the illuminated specimen. Each of the three optical channels comprises at least one optical fiber; in a modality described below, the third optical channel includes a plurality of optical fibers. In a particular embodiment, an optical fiber comprising the second optical channel and five optical fibers comprising the third optical channel are placed in a circular pattern substantially around an optical fiber comprising the first optical channel.

In a method for controlling a radiation source in an analyzer apparatus, a specimen that is analyzed by the apparatus is illuminated by an excitation source having a controllable output, preferably a laser. The elastically dispersed radiation of the illuminated specimen is collected, detected, and transduced into a transducer output signal representative of the scattered radiation. If the output signal of the transducer is smaller than a predefined threshold signal, a control output signal coupled to the laser causes its output to be reduced.

Brief Description of the Drawings FIG. 1 is a system diagram for a preferred analyzer apparatus, a Raman spectrometry apparatus, according to the invention.

FIG. 2 is a schematic representation of a bandpass filter included in the analyzer apparatus represented by FIG. 1.

FIG. 3 is a block diagram of the signal conditioning circuit included in the analyzer apparatus represented by FIG. 1.

FIG. 4 is a detailed schematic circuit diagram of the signal conditioning circuit shown in the block diagram of FIG. 3; in FIG. 4, the dotted lines indicate the optical fibers and the solid lines indicate the electrical conductors.

FIG. 5 is a partial sectional view of an optical probe useful for the analyzer apparatus represented by FIG. 1.

FIG. 6 is an enlarged end view of the optical fibers at the tip of the probe described in FIG. 5.

Detailed description of the invention As used herein, "optical" and "light" refers to electromagnetic radiation, whether or not it is visible to the human eye.

FIG. 1 shows a preferred analyzer apparatus 10 which evaluates a specimen of interest 12 and provides on a computer 14 an analyzer output indicative of the presence or amount of one or more chemical constituents of specimen 12. Analyzer apparatus 10, illuminates specimen 12 with narrow band light, collect the scattered light from specimen 12, optically isolate a Raman scattering component from the scattered light, and evaluate the Raman scattering component to verify the output of the analyzer. Simultaneously, according to one aspect of the invention, the apparatus 10 isolates an elastic dispersion component from the radiation dispersed by the specimen 12. If the elastic dispersion component falls below a threshold level, such as may result from, For example, disconnection or rupture of an optical fiber or separation of the specimen probe, the narrow band light illumination is interrupted. This interruption technique is particularly effective if the specimen 12 is a liquid, which may include a molten polymer composition, which has a significantly higher level of elastic dispersion than a gas, such as air.

The laser 16, shown in FIG. 1, essentially throws narrow, monochromatic band light at the fiber 18a of the beam splitter 1 by 2. Although the laser 16 may have an emission wavelength that fluctuates from the ultraviolet (UV) region to the visible region up to the In the infrared region (IR), a wavelength of approximately 810 nanometers (nm) for narrow band light is particularly useful for Raman spectrometry. The shorter wavelengths increase the amount of Raman scattering, but they can also produce unwanted fluorescence in certain specimens. Longer wavelengths are less likely to produce fluorescence, but would produce a lower Raman signal. A diode laser that produces light, having a wavelength between about 750 nm and 850 nm, is preferred.

The laser 16 may have a multimodal output and may be capable of emitting 700 mW up to 1.2 optical power during operation. The laser 16 also includes a driver circuit with a control output on line 24 and, if it is a diode laser, a temperature control circuit as well. The control output of the laser 16 controls the amount or intensity of the narrow band light injected into the fiber 18a.

The beam splitter 20 divides the laser light thrown to the fiber 18a between the fibers 18b and 22a. The light can be equally or unevenly divided between the fibers 18b and 22a. The narrow band light is passed from the fiber 18b to the fiber 18c via the connector pair 26, which includes one end of the male connector that retains each fiber end, the connector ends are connected to each other inside a sleeve alignment insulator. Standard Type Equalization Adapter (SMA) connector pairs are preferred for their low cost and robustness, but other known styles, such as ST O FC are also contemplated. The fiber 18c is connected to the bandpass filter (PB) 28 of the filter module 30. The laser light is passed through the PB filter 28 and the fiber 18d to the probe 32, which is adapted to make contact with the specimen 12. The fibers 18c and 18d are preferably part of the assembled cable assemblies 34 and 36, respectively.

The analyzer apparatus 10 is preferably constructed to include a main analyzer unit 38, which is desirably located in a control room or other location that can provide the necessary electrical power and a favorable environment. The probe 32 is located at the site of the specimen 12, and the filter module 30 is positioned near the probe 32. The assembled fiber cable assemblies 34 and 36 connect, respectively, the main analyzer unit 38 to the filter module 30 and the filter module 30 to the probe 32. The cable assembly 34 can be ten or hundreds of meters in length.

Transmission radiation over long fiber optic cables can produce a large interference background signal resulting from Raman scattering in the fiber core and coating. This problem can be remedied by the use of properly placed optical filters, which can be either of two general types. A bandpass filter (PB), which allows only a very narrow range of wavelengths to be transmitted, is used with excitation radiation before interaction with a sample. The PB filter virtually eliminates all background radiation and allows a narrow, clean excitation beam to illuminate the sample.

A second type of filter, referred to as a blocking filter, essentially removes all the radiation at the incident wavelength, while allowing other wavelengths to pass. There are two general forms of blocking filters; one of these, referred to as a notch filter, is essentially the opposite of the bandpass filter PB. A notch filter rejects a narrow band, while allowing all other wavelengths to pass. The other form of blocking filter is a long-pass (PL) filter, which allows passing all wavelengths above a specific wavelength and rejecting all other wavelengths.

To eliminate the Raman scattering generated from the fibers 18a, 18b, and 18c by the laser light passing through them, which must be confused with the Raman dispersion of the specimen 12, the band pass filter (PB) 28 is provided in the filter module 30, which is placed as close as possible to the probe 32 to minimize. Raman dispersion generated by fibers resulting from fiber 18b. The band pass filter PB 28 passes narrow band light from the laser 16, but blocks the fiber-generated Raman scattering originating in the fibers 18a, 18b, and 18c penetrating the fiber 18d. The scattered Raman light generated by the fibers is outside the passband of the PB 28 filter and is thus rejected by the filter 28.

A preferred embodiment of the band pass filter PB is described in FIG. 2. The fiber connectors 39a and 39b, preferably of the SMA type, retain the ends of the fibers 18c and 18d against the 0.25 (GRIN) step gradient index lenses 40a and 40b, respectively. The GRIN lenses 40a and 40b serve to align and focus the radiation entering and passing the optical fiber 42, which is inserted between the lenses 40a and 40b and provides the desired spectral filtering characteristics.

The radiation rejected by a filter can be absorbed by the surrounding metal components and transformed into heat, or it can be reflected back to an optical fiber. The optical fibers are commonly coated with a layer of polyimide buffer and can be connected by epoxy adhesive materials. Both the polyimide and epoxy materials are frequently fluorescent, and radiation reflected back to an optical fiber coated or connected with such materials can induce fluorescence in the fiber. The resulting fluorescence signal can distort a radiation signal produced by specimen 12, especially when specimen 12 is highly dispersed.

In a different way to the optical fibers coated with polyimide buffer, the gold-coated fibers do not induce fluorescence. Optical fibers coated with gold are, however, more expensive than polyimide-coated fibers. It would be a waste to avoid the use of gold-coated fibers throughout the analyzer apparatus 10, it is advantageous to employ them in the construction of the probe 32, i.e. to use fibers coated with gold by the fibers 18d, 18e, 46a, 46b, 48a, and 48b.

Returning again to FIG. 1, the fiber 18d is freely connected to the probe 32 by a pair of connector 44 located at the proximal end 32a of the probe 32 and passes narrow band light to the fiber 18e, which extends from the connector pair 44 to the distal end 32b of the probe 32. The fibers 46a and 48a are also housed in the probe 32; 48a may comprise a plurality, five in a particular embodiment, of fibers 48a. The line that * represents the fibers 48a, and some other lines in FIG. 1, are shown thick to indicate multiple optical fibers in particular embodiments. The fiber 46a is connected to a pair of connector 50 at the proximal end 32a, and at the distal end 32b is welded or otherwise held in place together with the fibers 18e and 48a. At the end 32b, the fibers are polished to a mirror finish and are arranged as shown in FIG. 6. The welding material 52 retains the ends of the fiber in place and seals the probe at the end 32b.

The narrow band light leaves the fiber 18e and illuminates the specimen 12 in a detection zone 54, which is defined by the superposition of the conical outlet of the fiber 18e and each of the fibers 48a. The fibers 46a and 48a collect a part of the scattered light, which includes a relatively strong elastic component having the same wavelength as the narrow band light of the laser 12, together with a relatively weak Raman component whose wavelength differs of that of the laser light 12. In a particular embodiment, the analyzer apparatus 10 uses five fibers 48a to reinforce the detected Raman component and a single fiber 46a to detect the elastic component by continuity.

The scattered light passing through the fiber 46a is guided to the detector 56 via the connector 50, the fibers 46b-e, pairs of the connector 58 and 60, and a bandpass filter (PB). The bandpass filter BP 62 passes the wavelength of the narrow band light and is substantially identical to the bandpass filter PB previously described 28. The purpose of the bandpass filter PB 62 is to prevent light solar, ambient light, or any extraneous light collected by fiber 46a is confused by elastically scattered light. The bandpass filter PB 62 has the additional effect of preventing the weaker Raman component from penetrating the detector 56. The amplifier 64 is coupled to the detector 56 to provide an output signal from the amplified detector on line 66.

Advantageously, the output of the detector 56, which is representative of the elastic dispersion component, is fed back through the signal conditioning circuit as a laser control input signal to the laser 16 on the line 24. The circuit 68 compares the detector output signal on line 66 with a predefined threshold signal. If the detector output signal is above the threshold signal, it indicates that the optical system of the analyzer apparatus 10 is intact, the signal conditioning circuit 68 provides an output signal on the line 24 which keeps the laser 16 in its relatively high, normal output level. Yes, on the other hand, the output signal of the detector is below the threshold signal, indicates a disconnection or removal of the fiber from probe 32 of specimen 12, circuit 68 provides an output signal on line 24 that disconnects the laser 16, or at least controls it to a lower intensity level. This lower intensity level can be adjusted, such that the intensity of light emitted from the fiber of the probe 18e, and preferably of the fiber 18b, is within a class 1 operation BSI / EN 60825-1, ie , direct observation not dangerous. In this way, the analyzer apparatus 10 can operate at high laser light levels during normal operation and can automatically be turned off if a discontinuity is detected by the detector 56, thereby avoiding the hazard in the eyes of an operator.

The signal conditioning circuit 68 is responsible for the differentiation between the transient losses in the elastic dispersion signal, such as can be caused by small bubbles 69 of air or other gas passing through the detection zone 54, and the long life losses in the signal resulting from the disconnection or separation of the fiber from probe 32 of specimen 12. Circuit 68 continues to drive laser 16 at its high operating intensity level, in the presence of transient losses true, but turn off the laser to the lowest intensity level for long life losses. This differentiation function prevents unnecessary interruptions during the operation of the analyzer apparatus 10.

Referring again to FIG. 1, the fibers 48a are not supported on the probe 32, except at the distal end 32b, where they are arranged around the emission fiber 18e, and at the proximal end 32a, where they are attached together at the male connector end 70a , as shown in FIG. 5. The other male connector end 70b of the pair 70 of FIG. 1 retains a single fiber 48b in alignment with the fibers 48a, where the fiber 48b has a diameter large enough to capture the light emitted from all the fibers 48a. For example, if the fibers 48a are approximately 100 μm in core diameter, the fiber 48b can be approximately 300μm in core diameter. This arrangement greatly simplifies the interconnections in the analyzer apparatus 10; using a large fiber 48b rather than five separate small fibers to collect the light from the fibers 48a allows a reduction of four fifths in the number of connector pairs and filters required to transmit the radiation from the Raman scattering of the probe 32 to the main analyzer unit 38. The scattered light is transported by the fiber 48b to the input slot of the optical spectrograph 72 via a blocking filter, preferably a long pass filter PL 74, fibers 48c-e, and pairs of connector 76 and 78. The long-pass filter PL 74 is similar in construction to the bandpass filter PB 28 shown in FIG. 2, except that the band pass filter PB 28 is manufactured to block the narrow band light of the laser 16 and to pass longer wavelengths. For a laser having a wavelength of, for example, 810 nm, the spectral transmission of the long pass filter PL 74 is preferably less than 10"6 to 810 nm and increases up to half of its maximum transmittance to about 833 nm The filter module 30 is preferably mounted near the probe 32 to keep the fiber 48b short, less than about one meter, so that no appreciable fiber-generated Raman component can be produced in the fiber 48b by elastic scattered light. Long-pass filter PL 74 blocks any elastic scattered light that penetrates fibers 48c-e.

The fibers 18a-e, 46a, 48a, 48e, and 22a-d are preferably fibers of relatively small diameter (100 μm core diameter); while fibers 48b-d are preferably fibers of relatively large diameter (300 μm core diameter). The fibers 46b-e may be either small or large diameter, but preferably are not smaller than the fiber 46a. All can be cataloged by gradient, or, preferably, cataloged by step for increased levels of light. A plurality of fibers 48e is held in connector pair 78, preferably in a "six about one" pattern for optimal coupling to fiber 48d, while the input loop to spectrograph 72 is held in a linear array .

Referring again to FIG. 1, the diamond reference 80 is provided in a main analyzer unit 38. The narrow band light is transported by the fibers 18a, 22a, and 22b from the laser 16 to the diamond surface 80. The bandpass filter PB 82, substantially identical to bandpass filters PB 28 and 62, blocks the Raman scattering generated by fibers. Preferably, six fibers 22c around the fiber 22c on the diamond surface capture the scattered light of the diamond 80. The long-pass filter PL 84, substantially identical to the long-pass filter PL 74, blocks the scattered elastic light of the fibers 22d .

Preferably, a plurality of fibers 22d is arranged in a "six about one" pattern in the long-pass filter PL 84 and in a linear configuration in the input slot of the spectrograph 72.

The linear network of fibers 22d and 48e are colinearly arranged in the input slot of spectrograph 72. Spectrograph 72 may be, for example, a spectrograph model SP-150, available from Acton Research Corp., provided with a graduated grid having 400 slots / mm and marked 750 nm. A network of the detector 73 having a network of, for example, 750 pixels x 240 pixels, simultaneously verifies the scattered light spectrum Raman spatially separated from the specimen 12 and the diamond reference 80. The network output of the detector 73 is fed to computer 14 through line 75. The collection of programs that are contained in computer 14 is prepared to use the Raman spectrum of specimen 12 together with the Raman spectrum of the diamond and a predetermined calibration to determine the composition of the specimen 12, as described in US Pat. Nos. 5,455,673, 5,610,836, and 5,638,172, and in U.S. Application. Copendent Serial No. 08/947/689, METHOD FOR STANDARIZING RAMAN SPECTROMETERS TO OBTAIN STABLE AND TRANSFERABLE CALIBRATIONS, filed on October 9, 1997 by Carman et al., the descriptions of all of which are incorporated herein by reference.

The computer 14 may be equipped with a transceiver 86, which may be an antenna or an infrared transmitter / receiver. The instructions can be sent to, and the information received from, the computer 14 using a second computer, for example, a laptop 88 equipped with a transceiver 90 similar to the transceiver 86. Such communication can be carried out through of a wireless fiber free space circuit 91, allowing one to move freely from one place to another with the computer 88, and thereby allow for greater flexibility and choice in a mounting location for a main analyzer unit 38. Transceivers 86 and 90 can be PC / MCIA cards, known in the computer industry. The computer 88 can be provided with a keyboard and a mouse to transmit the questions and commands to the computer 14. This arrangement would allow a reduction in the size, weight, and electrical requirements of the main analyzer unit 38.

A preferred embodiment of probe 32, schematically described in FIG. 5, has a body including terminal terminal 32c, body 32d, and connector housing 32e, all made of stainless steel or other suitable inert materials capable of withstanding temperatures of several hundred ° C. The terminal terminal 32c, the body 32d, and the connector housing 32e are rotationally symmetrical about the axis of the probe 32f and are connected by the solder joints 92 and 94, as shown. The outer surface comprising the terminal terminal 32c, the weld joint 92, and the body 32d is polished to a smooth finish to allow sealing within the core of a standard fitting pipe or other container holding the specimen 12. The probe 32, in particular the terminal terminal can be constructed by the method described in Buchanan et al., US Application Serial No. 08 / 450,597, ROBUST SPECTROSCOPIC OPTICAL PROBÉ, SUBMITTED ON MAY 25, 1995, now U.S. Pat. No. 5,657,404, the description of which is incorporated herein by reference.

The fibers 18e, 46a, and 48a, shown in FIG. 6, extend from their respective male connector ends 44a, 50a, and 70a at the proximal end of the probe 32a to the distal end 32b, as shown in FIG. 5. Each of the fibers is preferably cataloged per step and includes a core / coating of doped silica or silica and also a thin outer cushion layer of gold, nickel, or other inert metal throughout its entire length. The ends of the 44a male connector, 50a, and 70a are attached to connector housing 32e to allow probe 32 to disconnect and reconnect conveniently to cable assembly 36 to facilitate installation and service. It is also fixed to the housing 32e of the connector 96 for the temperature sensor 98, which is optionally included in the probe 32. The temperature sensor 98 is preferably positioned near the distal end 32b for diagnostic purposes to ensure that the probe does not exceed its nominal temperature. Alternatively, the output of the sensor 98 can be used as an approximate indication of the temperature of the specimen 12; thus, the probe 32 may be useful for a dual purpose as a probe for the fibro-optic chemical analysis and as a thermometer for the specimen. Although known fiber-optic temperature sensors can be used by sensor 98, electrical sensors are preferable for their simplicity; especially preferable for its low cost and reliability is a thermocouple such as, for example, a type K thermocouple. The output of the sensor 98 can be verified with a handheld device coupled directly to the connector 96, or with the computer 14, in which case a Additional channel, such as a pair of twisted wires may be included in cable assemblies 34 and 36 of FIG. 1.

As shown in FIG. 6, the optical fibers in the probe 32 can be effectively combined in a "six about one" configuration. The central fiber 18e transmits the signal from the laser 16 to the specimen 12. The fiber 46a transmits the elastic scattering signal, and the five fibers 48a transmit the Raman scattering signals to the main analyzer unit 38.

With reference to the schematic diagram of FIG. 3, which represents the signal conditioning circuit 68, the light dispersed elastically at the wavelength of the laser 16 is coupled by one or more optical fibers generally indicated as 140 to the silicon photodetector 56, which is sensitive to the wavelength of the laser light 16 and produces a current proportional to the amplitude of the surprising laser light photodetector 56. The current is amplified by a transimpedance amplifier 156, which has a short time constant, to produce an output voltage signal Vs.

The voltage signal Vs is an input to the comparator 158, the other input to the comparator 158 is a constant voltage Vt supplied by the reference voltage source 160. The reference voltage source 160 is coupled to the separator amplifier 162, which is selectively operable by the trigger point switch 164 for adjusting the trigger point of the comparator 158. More specifically, the separator amplifier 162 generates an analog output rating that is proportional to the difference between the output voltage of the transimpedance amplifier Vs and the reference voltage Vt. The analog output of separator amplifier 162 is used to test the circuit system and adjust the trigger point of comparator 158.

The relay 166 is coupled between a power source, not shown, and the laser 16, which is energized initially by pressing the push button of the start and stop switch 170. By keeping the start and stop switch 170 in a depressed position, the power is temporarily supplied to the laser 16 until the signal conditioning circuit is operational. If the elastically dispersed light is present at sufficient amplitude, such that Vs is greater than Vt, the output of the comparator 158 is sufficiently high to keep the relay 166 closed, thereby supplying power to the laser 16. A light scattering signal elastic releases relay 200 and turns off laser 16.

The signal conditioning circuit 68 operates rapidly, such that even a momentary loss of the elastic scattering signal, in the order of about 10 to 20 milliseconds, will cause the relay 166 to release and turn off the laser 16. The delay time it is regulated by adjusting the transimpedance amplifier 156, in particular, the capacitor Cl shown in the circuit diagram of FIG. 4. The components Rl and Cl form a low pass filter for the transimpedance amplifier 156. By adjusting one or the other component, the delay time of the transimpedance amplifier 156 can be varied. It is important to have a short delay time to avoid unnecessary stopping of the laser 16 in response to a false interruption of the elastic scattering signal. False interruptions are typically caused by bubbles 69 or other irregularities in the specimen 12. The comparator 158 has a certain amount of hysteresis that can be adjusted by changing the value of the resistor R8. The reference level at which the comparator 158 operates is adjusted using the potentiometer 210, which sets the output voltage Vt of the reference voltage source 160 at node 214. The detector voltage Vs appears at node 212, and the voltage Vt is subtracted from the voltage Vs at node 216. The rest is compared to a ground reference voltage by comparator 158. If the remainder is greater than the earth, comparator 158 has a high output, indicating that the laser 16 is illuminating the specimen 12. If the remainder is zero or less than the earth, the comparator 158 has a low output, which indicates that the laser 16 is not illuminating the specimen 12, either because of a break in a fiber optics in the analyzer apparatus 10 or removal of the probe 32 from the medium of the specimen 12.

The output of comparator 158 drives the base of bipolar transistor Q2. If the output is high, the transient Q2 is in operation, and the current of Vcc maintains the contact Kl of the relay 166 in the closed position. If the output of the comparator 158 is low, the transistor Q2 is turned off, the current flow to the contact Kl is interrupted and the relay 166 is opened. The opening of the relay 166 causes the power supply to the laser 16 either to be reduced to a harmless level or to be completed. The diode D3 receives a visual indication of the action of the relay, while the diode D4 indicates that the safety device is powered with power. The start and stop switch 170 and the comparator 158 together form a wired OR circuit. If either the input is high, the relay 166 closes and the high power is supplied to the laser 16. If both inputs are low, the relay 166 is opened and the laser 16 is turned off or has its power reduced to an inoffensive level.

Having thus described the present invention in detail, those skilled in the art will appreciate that modifications, additions, changes, and additional alterations may be made to the described embodiment without departing from the spirit and scope of the invention as mentioned in the following claims. .

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, the content of the following is claimed as property.

Claims (46)

1. A safety device for detecting the elastically dispersed radiation, characterized in that the device comprises: a monochromatic radiation source substantially having a controllable output; detection means for detecting the elastically dispersed radiation collected from a specimen illuminated by the monochromatic radiation source substantially; Y a signal conditioning circuit comprising: transducing means comprising a transimpedance amplifier for converting the elastically detected scattered radiation, collected from the specimen into a transducer output signal representative of the elastically detected scattered radiation; Y a comparator for receiving a predefined threshold signal and the transducer output signal, and generating a control output signal coupled to the monochromatic radiation source substantially, the control output signal is representative of the transducer output signal is greater than, equal to, or less than the threshold signal.

2. The security device according to claim 1, characterized in that the source of monochromatic radiation substantially comprises a laser.

3. The security device according to claim 2, characterized in that the monochromatic radiation substantially has a wavelength of about 750 to 850 nm.

4. The security device according to claim 1, characterized in that the detection means comprise a silicon photodetector.

5. The security device according to claim 1, characterized in that it also comprises: closing means responsive to the comparator control output signal to reduce the output of the monochromatic radiation source substantially when the output transducer signal is smaller than the predefined threshold signal.

6. The safety device according to claim 5, characterized in that the closing means comprise a relay.

7. The security device according to claim 6, characterized in that the closing means further comprise a switch on and off.

8. The security device according to claim 1, characterized in that the comparator has an adjustable trigger point.

. The security device according to claim 8, characterized in that the signal conditioning circuit further comprises a separating amplifier coupled to the transducing means and a reference voltage source coupled to the separating amplifier, the separating amplifier is selectively connected to the comparator to generate a test output to adjust the trigger point of the comparator.

10. The safety device according to claim 1, characterized in that the specimen is a liquid.

11. An analyzer apparatus provided with a safety device for controlling a source of excitation radiation, characterized in that the apparatus comprises: a monochromatic radiation excitation source substantially having a controllable output; an optical probe that interconnects the excitation source with a specimen, the optical probe comprises: a first optical channel for transmitting the radiation of the excitation source to illuminate the specimen; a second optical channel for collecting the radiation dispersed elastically by the illuminated specimen, and a third optical channel for collecting the radiation dispersed inelastically by the illuminated specimen; first detection means for detecting the radiation dispersed elastically by the illuminated specimen; second detection means for detecting the radiation dispersed inelastically by the illuminated specimen; a signal conditioning circuit comprising: transduction means for converting the elastically dispersed, detected, collected radiation from the specimen into a transducer output signal coupled to the monochromatic radiation source substantially, the control output signal is representative of whether the transducer output signal is greater than , equal to, or less than the threshold signal, - and closing means sensitive to the control output signal of the comparator to reduce the output of the monochromatic radiation source substantially when the output signal of the transducer is smaller than the predefined threshold signal.

12. The analyzer apparatus according to claim 11, characterized in that the apparatus comprises a Raman spectrometer provided with a computer and an optical spectrograph.

13. The analyzer apparatus according to claim 12, characterized in that the Raman spectrometer is further provided with a diamond reference material.

14. The analyzer apparatus according to claim 11, characterized in that the monochromatic radiation excitation source substantially comprises a laser.

15. The analyzer apparatus according to claim 14, characterized in that the monochromatic radiation substantially has a wavelength of about 750 nm to 850 nm.

16. The analyzer apparatus according to claim 11, characterized in that the first, second, and third optical channels of the probe, each comprising at least one optical fiber.

17. The analyzer apparatus according to claim 16, characterized in that the third optical channel further comprises a plurality of optical fibers.

18. The analyzer apparatus according to claim 11, characterized in that it also comprises a filter module.

19. The analyzer apparatus according to claim 18, characterized in that the filter module comprises: a bandpass filter positioned between the excitation source and the first optical channel of the probe in close proximity to the probe, and a blocking filter positioned between the third optical channel of the probe and the first detection means.

20. The analyzer apparatus according to claim 19, characterized in that the band pass filter and the blocking filter each comprise two lenses of gradient index.

21. The analyzer apparatus according to claim 11, characterized in that the first detection means for detecting the radiation dispersed elastically by the illuminated specimen comprises a silicon photodetector.

22. The analyzer apparatus according to claim 11, characterized in that the second detection means for detecting the radiation dispersed elastically by the illuminated specimen comprises a multi-channel network detector.

23. The analyzer apparatus according to claim 22, characterized in that the multichannel network detector is a charge coupling device or a photodiodic network.

24. The analyzer apparatus according to claim 11, characterized in that the transducing means comprise a transimpedance amplifier.

25. The analyzer apparatus according to claim 11, characterized in that the closing means comprise a relay and a switch on and off.

26. The analyzer apparatus according to claim 11, characterized in that the comparator has an adjustable trigger point, and the signal conditioning circuit further comprises a separator amplifier coupled to the transducing means and a reference voltage source coupled to the separator amplifier. , the separator amplifier is selectively connected to the comparator to generate a test output to adjust the trigger point of the comparator.

27. The analyzer apparatus according to claim 11, characterized in that the specimen is a liquid.

28. An optical probe for simultaneously and separately collecting the inelastically and elastically dispersed radiation from a specimen illuminated with radiation from a substantially monochromatic radiation excitation source, characterized in that the probe comprises: a fluid-tight body comprising: a connector housing placed at a proximal end of the probe, a terminal terminal placed at a distal end of the probe, and a body placed between and sealingly connected to the connector housing and the terminal terminal, Each of the connector housing, terminal terminal, and body is rotationally symmetric about an axis of the probe, a first optical channel for transmitting monochromatic radiation substantially from an excitation source to illuminate a specimen positioned near the distal end of the probe. probe, the first optical channel is placed within the body of the probe and extends from the proximal end to the distal end of the probe; a second optical channel for collecting the radiation dispersed elastically by the illuminated specimen, the second optical channel being positioned within the body of the probe and extending from the proximal end to the distal end of the probe; Y a third optical channel for collecting the radiation dispersed elastically by the illuminated specimen, the third optical channel is placed within the body of the probe and extends from the proximal end to the distal end of the probe.

29. The optical probe according to claim 28, characterized in that it is adapted for use with a Raman spectrometry apparatus.

30. The optical probe according to claim 28, characterized in that the connector housing is provided with three connector pairs, one of each of the connector pairs is connected to each of the first, second, and third optical channels.

31. The optical state according to claim 28, characterized in that the first, second, and third optical channels each comprise at least one optical fiber.

32. The optical probe according to claim 31, characterized in that each optical fiber comprises a thin, non-fluorescent outer cushion layer.

33. The optical probe according to claim 32, characterized in that the outer shock layer comprises gold.

34. The optical probe according to claim 31, characterized in that each optical fiber is an optical fiber cataloged per step.

35. The optical probe according to claim 31, characterized in that the third optical channel further comprises a plurality of optical fibers.

36. The optical probe according to claim 31, characterized in that it also comprises a filter module, the filter module comprises a band pass filter placed between the excitation source and the first optical channel and a blocking filter placed between the third optical channel and a detector for the elastically dispersed radiation.

37. The optical probe according to claim 36, characterized in that the first and third optical channels are each respectively connected to the bandpass and blocking filters by at least one optical fiber.

38. The optical probe according to claim 37, characterized in that each optical fiber comprises a thin, non-fluorescent outer cushion layer.

39. The optical probe according to claim 38, characterized in that the buffer layer comprises gold.

40. The optical probe according to claim 37, characterized in that each optical fiber is an optical fiber cataloged per step.

41. A method for controlling a radiation source in an analyzer apparatus, characterized in that the method comprises: illuminating a specimen that is examined by the analyzer apparatus using a monochromatic radiation source substantially having a controllable output; collecting the elastically dispersed radiation from the specimen illuminated by the monochromatic radiation source substantially; detect the elastically dispersed radiation, collected from the illuminated specimen; using a transimpedance amplifier, transducing the elastically dispersed, detected radiation of the specimen into an output signal of the transducer representative of the elastically dispersed radiation, detected; comparing the output signal of the transducer with a predefined threshold signal; Y generating a control output signal coupled to the monochromatic radiation source substantially, the control output signal causes the output of the monochromatic radiation source to be reduced substantially, using the closing means comprising a relay and a power switch. turn on and off, when the output signal of the transducer is smaller than the threshold signal.

42. The method according to claim 41, characterized in that the analyzer apparatus comprises a Raman spectrometry apparatus, the apparatus is provided with an optical probe for interconnecting a source of laser radiation with the specimen, a multichannel network, and an optical spectrograph.

43. The method according to claim 42, characterized in that the source of laser radiation provides monochromatic radiation substantially having a wavelength of about 750 nm to 850 nm.

44. The method according to claim 41, characterized in that the detection of the elastically dispersed radiation is carried out using a silicon photodetector.

45. The method according to claim 41, characterized in that the comparison of the output signal of the transducer is carried out using a comparator.

46. The method according to claim 41, characterized in that the specimen is liquid.