WO2007083991A1

WO2007083991A1 - Apparatus and method for performing optical analysis

Info

Publication number: WO2007083991A1
Application number: PCT/NL2006/000029
Authority: WO
Inventors: Henricus Josephus Cornelus Maria Sterenborg; Arjen Amelink; Johannes Antonius Maria Kuijpers
Original assignee: Erasmus University Medical Center Rotterdam
Priority date: 2006-01-19
Filing date: 2006-01-19
Publication date: 2007-07-26

Abstract

An optical analysis apparatus is provided with an exchangeable probe that contains an optical fibre for performing measurements or applying treatment. The apparatus has a base unit that contains a light source and/or a light detector for supplying to the optical fibre and/or detecting light from the optical fibre. The probe contains a computer readable information providing element. Before operation the base unit reads probe dependent probe information into the base unit from the information providing element that is part of the probe and controls operation of the base unit dependent on the probe information. In one embodiment the probe information comprises (or refers to) results of calibration measurements for the probe and supply of light to the probe and/or signal processing of signals received from the probe is corrected according to the results of the calibration measurements read using the information element. In other embodiments the information is used to prevent re-use of probes that have been used in operations that can compromise sterility.

Description

Apparatus and method for performing optical analysis

The invention relates to an optical analysis apparatus with an exchangeable probe that contains an optical fibre.

PCT patent application WO2005029051 discloses a device with a probe that contains two optical fibres. This device is used to measure a physical feature, such as a concentration of a substance (e.g. oxygenated blood) at a location near the distal end of the probe. A similar device is describe in an article published in Applied Optics VoI 43 No 15 pages 3048-3054, titled "Measurement of the local optical properties of turbid media by differential path-length spectroscopy" by. A. Amelink and H. J. CM. Sterenborg.

A measurement set-up is used wherein the probe is attached to a base unit that includes a light source, detectors and computation circuitry. The probe is included in the working channel of a clinical endoscope or biopsy device. The base unit feeds light to the proximal end of the probe to the distal end through a first fibre. The first fibre delivers the light to sample tissue or fluid near the distal end. Reflected or scattered light is collected at the distal end and led back through the first fibre and a second fibre in the probe, from which it is delivered at the proximal end. The base unit measures light properties of the light received from the first and second fibre and computes material properties of the sample tissue or fluid from the light properties.

For this purpose the base unit uses a mathematical formula that relates a wavelength dependent backscatter coefficient to wavelength dependent intensity of light from the second fibre, intensity of light fed to the first fibre, intensity of light that the measurement set-up measures from a highly reflective reference medium and a not or hardly reflective reference medium and a liquid that has an index of refraction that is approximately equal to that of the tissue that must be investigated..

This type of measurement requires accurate calibration of the properties of the optical fibres in the probe. Unfortunately, these properties may vary from probe to probe. Typically, a first and second calibration measurement are used wherein the probe is applied to a highly reflective reference medium and a not or hardly reflective reference medium respectively to measure the intensity. Such a calibration makes measurements cumbersome.

Moreover calibration can compromise sterility of the probe. Conventionally, probes are used only for one patient and subsequently discarded. Manufacturers supply sterilized probes, which are attached to the base unit for performing tests on a single patient. The calibration of the measurement set-up with reference media when a new probe is attached can compromise sterility.

The term "probe" as used herein is not limited to probes for measurement. Alternatively a treatment probe may be used, for supplying light to tissue through an optical fibre in the probe. This type of probe may also require calibration, for example to set the power level of light supplied to the probe so that a desired power density is realized in the tissue. Calibration for this purpose may also compromise sterility of the probe.

Further problems may arise if a probe has been reused. Thus, for example, used probes are typically not sterile any more. Another problem may arise if a base unit is able to operate in different modes for different probes, for example to perform different forms of analysis or treatment for different types of tissue. If the wrong mode of operation is used for a probe for a certain type of analysis or treatment undesirable results may occur.

Among others, it is an object to enable improved control over the use of optical fibre probes.

Among others, it is an object to simplify the calibration procedure that is required for performing accurate measurements using a probe with optical fibres. An apparatus according to claim 1 is provided. Herein a base unit and an exchangeable probe are used that can be attached to the base unit and detached from it using connection part. The probe contains an information- providing element and at least one optical fibre. The base unit comprises a reading device arranged to read probe information from the information- providing element. In an embodiment the probe information is read automatically while the probe is attached to the base unit. The base unit contains a processor circuit which controls operation of the base unit dependent on the probe information. Thus, the operation can be adapted to individual probes. In an embodiment the probe information is used to correct light measurements results for light received from the probe, for example to compensate for transmission and/or reflection properties of the probe. In another embodiment the probe information is used to control properties of light supplied from the base unit to the probe, for example to compensate for transmission and/or reflection properties of the probe.

In another embodiment the probe information is used to enable or disable use of the probe, for example dependent on whether the probe has been used before. Information whether the probe has been used before may be stored in the probe by the base unit, when a writable information providing element is used. Alternatively, an identifier in the probe information may be used to retrieve and update this type of information about use of the specific probe in a database, the database being used to select between enabling and disabling use of the probe. In this way reuse of probes that are not sterile due to previous use can be disabled. In an embodiment the probe information provides for correction information about transmission and/or reflection by the optical fibre. The correction information may be stored in the probe or in a database that is accessible to the base unit, wherein the correction information for the probe is linked to an identifier that is stored in the information-providing element. In an embodiment the probe information identifies an internal reflection parameter for the optical fibre, for use to remove an effect of internal reflection from a detection result. In another embodiment the probe contains a first and second optical fibre, for supplying light to a sample medium through the first optical fibre and for receiving back light scattered by the sample medium through both the first and second fibre. In this embodiment a measurement of intensity of light from the second fibre is subtracted from a measurement of intensity of light from the first fibre. Thus, information about the sample medium near the distal face of the fibre is obtained. In this embodiment the correction information comprises identifies a ratio between light collection efficiencies of the first and second optical fibre of the probe. The measurement is corrected for the ratio between the light collection efficiencies identified by the probe information. Optionally also a correction is made for internal reflections in the first optical fibre, using probe information identified by the information-providing element.

These and other objects and advantageous aspects will become apparent from a description of exemplary embodiments using the following figures. Figure 1 shows a measurement set up

Figure 2 shows part of a base unit

Figure 3 shows a networked set up

Figure 1 shows a measurement set-up. The measurement set up contains a base-unit 10 and a probe 12 in the working channel 14 of a clinical endoscope or biopsy device. Base unit 10 comprises a light source 100, a detection arrangement 102, a first connector 104, a reading device 106 and a processing circuit 108. Light source 100 is arranged to supply light to first connector 104. Detection arrangement 102 is arranged to receive light from first connector 104 and to generate measurement signals that are indicative of the properties of the received light. Processing circuit 108 has inputs coupled to the detection arrangement 102 and reading device 106.

Probe 12 contains a first optical fibre 120, a second optical fibre 122, an information-providing element 124 and a second connector 126. Second connector 126 is shown coupled to first connector 104. A detachable form of coupling is used, for example a screw-on or click-on coupling. First optical fibre 120, second optical fibre 122, and information-providing element 124 are coupled to second connector 126 and arranged so that light from light source 110 is fed to first optical fibre 120, light from second optical fibre 122 is fed to detection arrangement 102 and reading device 106 is able to read data from information-providing element 124.

Although single fibres are shown for the sake of simplicity, it should be appreciated that further fibres may be arranged in parallel with first and/or second optical fibre 120, 122. The details of the fibres are not relevant for understanding the present invention. Such details can be found in

WO2005029051 and its references. For example, first optical fibre 120 may have a skewed distal surface to reduce internal reflections.

Various embodiments of information -providing element 124 may used. In one embodiment a flash memory is used with terminals coupled to second connector 126. In this embodiment connectors 104, 126 may be provided with mated electrodes and reading device 106 is a memory interface circuit. Processing circuit 108 may be arranged to address locations in the flash memory using reading device 106 as interface, or reading device 106 may be arranged to address standard locations. Instead of a flash memory, a PROM EPROM or any other type of non- volatile memory may be used.

In an alternative embodiment, a remotely readable circuit (e.g. an RF readable circuit using known RFID transponder technology) may be used as an information-providing element 124. In this embodiment connectors 104, 126 do not need mating electrodes and reading device 106 is a remote reading device located so that it can transmit signals to the remotely readable circuit and receive responses from the remotely readable circuit.

In another alternative embodiment an optically readable pattern such as a bar code may be used as an information-providing element 124. In this embodiment reading device 106 may be a scanner, a camera or the like, for optically reading the optically readable pattern. In this embodiment reading device 106, information-providing element 124 and connectors 104, 126 are arranged so that, when the connectors are mated, the reading device is capable of "seeing" information-providing element 124. Figure 2 schematically shows connection details of an embodiment.

In this embodiment detection arrangement 102 comprises a first, second and third detector 20, 22, 24. First connector 104 comprises a first and second fibre interface 26, 28, for first and second fibre 120, 122 respectively. In addition base unit 10 comprises a calibration interface 29. A reflector box 290 is coupled to calibration interface 29.

First and second source interface fibres 26a, 29a couple light source 100 to the fibre faces in first fibre interface 26 and to calibration interface 29 respectively. First detector 20 is coupled to a fibre face in first interface 26 via a first measurement interface fibre 26b. Second detector 22 is coupled to a fibre face in second fibre interface 28 for second fibre 122 via a second measurement interface fibre 28a. Third detector 24 is coupled to calibration interface 29 via a calibration interface fibre 29b.

First and second optical fibre 120, 122 and interface fibres 26a, b, 28a have fibre faces (preferably substantially perpendicular to the length of the fibres) facing each other. For the sake of simplicity, the fibres have been shown as lines, but it will be understood that the fibres have a finite diameter. The faces of the interface fibres 26a, b on one hand and first optical fibre 120 face each other in first interface 26 so that light from first source interface fibre 26a is transmitted to first optical fibre 120 and light from first optical fibre 120 is transmitted to measurement fibre 26b (and to first source interface fibre 26a, but this does not matter). Similarly the faces of the measurement fibre 28a and second optical fibre 122 face each other in second interface 28 so that light from second optical fibre 122 is transmitted to measurement fibre 28a (and to first source interface Preferably, first and second optical fibre 120, 122 have a different diameter compared with interface fibres 26a, b, 28a, 29a,b. This has the advantage that small relative position variations that may occur due to the exchangeable connection of probe 12 to base unit 10 have little or no effect on coupling. In an embodiment first and second optical fibre 120, 122 have a larger diameter than interface fibres 26a, b, 28a, 29a,b. Also preferably the faces of interface fibres 26a, b preferably directly face the faces of first and second optical fibre 120, 122 (that is, without intervening active optical elements such as lenses). This has the advantage that internal reflections from one interface fibres 26a, b to the other are minimal. First detector 20 measures light intensity of light returning from first interface 26 as a function of wavelength and passes measurement results to processing circuit 108. Second detector 22 measures intensity of light returning from second interface 28 as a function of wavelength. Third detector 24 measures the intensity of light reflected by reflector box 290 as a function of wavelength.

In normal operation sample measurement is performed, during which first sample measurement light source 100 is activated and light from light source 100 is passed to first optical fibre 120 via first source interface fibre 26a. First optical fibre 120 passes some of this light to the sample medium at the distal end of probe 12. The sample medium scatters back the light, into both first and second optical fibre 120, 122. The distal ends of the first and second optical fibre 120, 122 are located near each other sot that generally the scattered light collected by first and second optical fibre 120 comes from a same volume in the medium, except that first optical fibre also collects scattered light from a volume immediately in front of the distal end of the first optical fibre 120, which volume is not visible from the second optical fibre 122.

The first and second optical fibre 120, 122 feed back the collected light to first and second detector 20, 22, which measure the intensity of the scattered light as a function of wavelength. A result derived from the second detector 22 detectors is subtracted from a result derived from the first detector 20, so that the difference represents mainly the intensity of scattered light from a volume immediately in front of the distal end of the first optical fibre 120. For reasons set out in WO2005029051 this is a diagnostically useful signal.

A number of corrections are desirable to make the result more reliable. First of all, it is desirable to correct for internal reflection at the distal end of first optical fibre 120. In an embodiment this is realized by means of a first probe calibration measurements. Such probe calibration measurements are obtained for probe 12 before the probe is coupled to base unit 10.

Preferably the probe calibration measurements are performed at a specialized calibration site, in a form of serial production for a batch of different probes Preferably the probes 12 are sterilized after calibration, packaged and delivered to users, for connection to a base unit 10. By way of example the probe calibration measurements may be performed shortly after manufacture of probe 12.

In an embodiment the first probe calibration measurement is performed by coupling the probe under calibration to a calibration device with a structure similar to base unit 10. In the probe calibration measurement the distal end of the probe under calibration is placed in a reference medium (e.g. water), reflector box 290 is placed on calibration interface and light is supplied from the calibration device to the probe. The detection signals representing the intensity of reflected light at the first detector 20 in the calibration device is then measured. Calibration results derived from these detection signals are written to the information-providing element 124 of the probe under calibration.

During normal operation processing circuit 108 causes these calibration results to be read from information-providing element 124 and subtracted from measurement results derived from first detector 20 (or from a difference between results from first and second detector 20, 22). Thus a correction for internal reflections is realized.

Figure 3 shows an arrangement of an alternative embodiment, wherein the base unit 10 and a calibration device 30 are coupled to a database server 34 via a network 32 (probe not shown). In this embodiment information- providing element 124 stores an identifier that uniquely identifies the probe 12. Calibration device 30 writes results of the calibration with a link to the identifier to a database in database server 34. In this embodiment processing circuit 108 causes the identifier to be read from information-providing element 124 and use the identifier to retrieve the calibration results from the database. In this case there is no need to write calibration results to information- providing element 124, so that a read only information-providing element 124 may be used.

In one embodiment the calibration result of the probe calibration measurement, which is subtracted from the output signal of first detector 20 is simply the output signal of first detector 20 of the calibration device. This results in a reliable correction if light source 100 of base unit 10 and the light source of the calibration device have the same intensity as a function of wavelength and the first detectors 20 in base unit 10 and the calibration device have the same sensitivity. In an alternative embodiment the dependence on the intensity of the light source is removed by measuring the wavelength dependent intensity of the light sources of base unit 10 and the calibration device and modifying the correction to account for differences between the intensities. When the sensitivity (output signal value as a function of intensity) of the first detectors is known, this is a matter of normalizing the measurements from the first detectors of base unit 10 and the calibration device relative to one another to account for the ratio between the wavelength dependent intensities of the light sources before correction applied.

It should be noted that use of calibration results obtained with a reference medium (e.g. water) has the effect that the results during normal operation represent the difference between the effect of the sample medium and water. For many purposes this is sufficient. For example, the baseline scattering results from human tissue measurements correspond to those of water. Thus, the difference with the results for water provide a useful way of isolating the effect of a concentration of additional substances in the tissue.

However, if desired, the results during normal use may be corrected by adding the known response from the reference medium. Thus, a reference medium independent measurement can be obtained.

Other types of calibration data for performing other corrections may be written alone, or combination with the calibration result for correcting for internal reflection. In one embodiment data is provided in order to correct for difference between the light collection efficiency of the first and second optical fibre. In this embodiment, at the time of probe calibration measurement, the probe under measurement is coupled to a calibration device that may be similar in structure to base unit 10 and light from a light source is supplied from outside the probe under measurement to the distal end of first and second optical fibre 120, 122. Preferably a setup is used wherein light supplied to both has the same wavelength dependent intensity, which can be easily realized because the distal ends are located closely together. The resulting output signals from the first and second detector 20,

22 in the calibration device are measured and calibration information about these measurements is written to information-providing element 124 or a data base wherein information from information-providing element 124 is linked to the information. The calibration information may include for example a ratio between detected intensities at the first and second detector in the calibration device. In this case, during normal operation, the intensities obtained from first and second detector 20, 22 of base unit 10 are corrected according to the calibration information, for example by scaling one intensity according to the ratio. In a further embodiment, a correction for relative sensitivity differences between at least the first detector 20 and second detector 22 in the base unit 10 and the calibration device is provided. In this embodiment light from a light source is supplied to the interfaces 26, 28 at first connector 104 of the calibration device. The resulting wavelength detection signals from first and second detector 20, 22 are recorded. From these detection signals relative correction factors for the relative sensitivity of the first detector 20 and second detector 22 of the calibration device are determined as a function of wavelength. The calibration information obtained for the probe is then corrected for these relative correction factors. A similar procedure is followed for base unit 10, to obtain relative correction factors as a function of wavelength for the first detector 20 and the second detector 22 in base unit 10. These relative correction factors are used to perform a relative correction of the results from the detectors obtained when probe 12 is used. It is emphasized that this embodiment is optional: such a correction can be avoided if accurately matched detectors are used. Also various other forms of (relative) calibration of the detectors may be used. In another embodiment, as illustrated in figure 2, a calibration interface 29 and a reflector box 290 are used to correct for fluctuations of the intensity of light source 100. Simultaneously with measurements using first detector 20 and second detector 22, or essentially at the same time in terms of the speed of any expected fluctuations, a measurement form third detector 24 is obtained, of the intensity as a function of wavelength of light from light source 100 that is reflected by reflector box 290. Preferably, a diffuse reflector with a wavelength independent reflection coefficient is used but this is not necessary. Also, instead of a configuration with a reflector box a fibre running from light source 100 to third detector 24 may be used. Intensity measurements from first detector 20 and second detector 22 are then normalized as a function of wavelength according to the intensity measurements from third detector 24. This may be applied to measurements in the calibration device and the measurements in base unit 10. Thus, the effect of intensity fluctuations, including wavelength dependent relative fluctuations is eliminated.

It should be noted if no such correction is needed calibration interface 29 and reflector box 290 may be omitted from base unit. Also, as mentioned, other arrangements for performing reference measurement on light from light source 100 may be used.

In a further embodiment, the relative sensitivity of first, second and third detector 20, 22, 24 of the base unit or calibration device is calibrated using a further measurement which is performed when no probe is attached to the base unit or calibration device and reflector box 290 is temporarily. During the further measurement, reference light from outside the device is applied to interfaces 26, 28 and calibration interface 29. The resulting intensity measurements as a function of wavelength from detectors 20, 22, 24 are recorded. A ratio between the results from first and second detector 20, 22 on one hand and third detector 24 on the other hand is used to correct other measurements from the first and second detectors, in conjunction with the normalization that is used to eliminate the effect of fluctuations in the light source. Thus, a calibration normalized against the reference light is realized. It should be noted that such a normalized calibration is optional. Relative measurements may suffice, or other forms of calibration of the detectors may be used.

In an embodiment detectors 20, 22, 24 are arranged so that their output signals as a function of wavelength are each proportional to the received intensity. In this case no further correction is needed. In another embodiment an arrangement is used wherein detectors 20, 22, 24 output signals proportional to an offset plus intensity from first and second optical fibre 120, 122. The offset may be due for example to spurious light in base unit 10, or it may be inherent in the detectors. In this embodiment preferably a first and second sub-measurements are used for each measurement, a first measurement wherein processing circuit 108 has switched light source 100 on and a second measurement wherein processing circuit 108 has switched light source 100 off.

In this case the detector results obtained with the sub-measurement with light source 100 off are subtracted from the detector results obtained with the sub-measurement with light source 100 on. Thus the effect of the offset is eliminated. This may be applied to all normal measurements and all calibration measurements. Optionally, the detector results obtained from the sub-measurement with light source 100 off may be shared for a plurality of measurements. Although processing circuit 108 has been shown in a box labelled base unit 10, it should be appreciated that this processing circuit 108 may be a device on its own, such as a PC (personal computer) or any other computer, coupled to the detector arrangement and the reading device via any suitable interface (e.g. a USB interface or a PCI bus). Alternatively processing circuit 108 may be integrated in base unit, for example in the form of a firmware programmed microcomputer or a signal processor.

Although specific examples have been given for scattering measurements using a probe with a first and second optical fibre, it should be understood that the use of information-providing element 124 and reading device 106 is not limited to such measurements. For example, these elements may also be used for a probe with a single fibre, to represent transmission properties and/or internal reflection properties of this fibre. Similarly these elements may be used for a probe with more fibres.

Preferably, information-providing element 124 is used to represent both calibration information to correct for internal reflections (e.g. at the distal end) from first optical fibre 120 and relative transmission efficiency through first and second optical fibre 120, 122 as a function of wavelength of the transmitted and reflected light. However, in other embodiments only wavelength independent information about internal reflection and relative transmission efficiency may be represented. This may be done for example when these parameters do not vary over the wavelength range of interest, or if the wavelength dependence can be reconstructed by processing circuit 108 by means of a mathematical model. In another embodiment, calibration information for only relative transmission efficiency or for only internal reflection is provided. This may be done for example if no correction for one of these properties is needed, or if the correction can be computed by processing circuit 108 by means of a mathematical model.

Although specific examples have been given of calibration measurement procedures it should be realized that other procedures may be used. For example, instead of using light with identical properties from a single light source to supply light to the distal end of both fibres of the probe or to the interfaces of the base unit or calibration device, alternatively light of different constitution may be used, with known relation between the light at different interfaces or fibres. The calibration can easily be corrected using such a relation.

Preferably information-providing element 124 is located so that reading device 106 is able to read information from information-providing element 124 when probe 12 is attached to the base unit 10 by the connectors. Thus it is ensured that calibration information can be obtained without special action from the user and that the information for the right probe will be used. However, alternatively the information-providing element 124 may be provided so that an additional reading action from the user is needed, for example holding a part of probe 12 near reading device 106. In this case, preferably, base unit 10 is provided with a detector (e.g. a micro-switch, or some optical detector not shown, or using signals from detectors 20, 22 that indicate the presence and absence of optical fibres 120, 122) to detect the detachment and/or preferably attachment of probes from base unit 10. Preferably processing circuit 108 is configured to output a query signal in response to detection, for causing the user to perform the additional reading action.

Preferably, the corrections using the calibration information for the probe and/or calibration data for the base unit are performed when the signals from first and second detectors 20, 22 are received. Alternatively, some or all of the calibration measurements may be performed subsequently, the correction being performed only after all required calibration measurements have been made. When, in this case, probe calibrations are performed subsequently an identifier from information-providing element 124 is used to ensure that the normal operation measurements and the probe calibration measurements for the same probe are combined. In addition or alternatively the apparatus may be used to control intensity of light supplied to an optical fibre 120, to enable or disable the apparatus and/or to select a mode of operation.

In a first embodiment processing circuit 108 is configured to control the intensity of light supplied to first optical fibre 120, for example by controlling energy supplied to light source 100, or by controlling an optional attenuator (not shown) between light source 100 and first optical fibre 120. Optionally the intensity as a function of wavelength is controlled. In this embodiment processing circuit 108 is configured to control the intensity dependent on information obtained using information-providing element 124 (e.g. directly, or by means of information from a database selected using information from information-providing element 124).

In one embodiment processing circuit 108 is configured to control the intensity so that a predetermined nominal intensity will be received back from the sample at first connector. Thus, less correction of the measurements is needed. In another embodiment processing circuit 108 is configured to control the intensity so that a desired nominal intensity will be delivered at the distal end of the probe, by compensating the intensity at the connector for measured transmission and/or reflection losses of the first optical fibre 120. This may be useful to control treatment of tissue at the distal end of first optical fibre 120. It may be noted that in this case second optical fibre may not be needed in this case. The required calibration data may be obtained for example by measuring intensity delivered at the distal end via the probe when the probe is in a calibration set-up and subsequently sterilizing the probe. In this case a result of the measurements is written into information providing element 124 or in a database, for use during normal operation.

Optionally the delivered intensity at the connector is measured with third detector 24 and the intensity is controlled so that this measurement corresponds to a level that will result in a desired output intensity at the distal end for the probe that is used (taking account of losses that are particular for the probe). If necessary processing circuit 108 can compensate for the sensitivity of its third detector 24 and/or the response behavior of its light source 100.

As another option the delivered intensity may be measured with second optical fibre 122 and the intensity is controlled so that this measurement corresponds to a desired output intensity at the distal end for the probe that is used, after correction for the effect on the measurement due to losses that are particular to the probe.

In another embodiment processing circuit 108 is configured to respond dependent on information about previous use of the probe. In an embodiment processing circuit 108 is configured to maintain this information, for example to write this information to information providing element 124 when the probe is used, or to write to a database using an identifier obtained from information providing element 124. In a further embodiment a writable information providing element 124 is used for this purpose, containing a non- volatile memory for example. When processing circuit 108 detects previous use, it preferably causes base unit 10 to generate an alarm signal and disables operation. The alarm signal my be an audio signal for example, or a visual signal, or the absence of an approval signal from base unit 10. Thus, use of non-sterile probes is counteracted. In addition or alternatively processing circuit 108 disables operation using the probe in this case, operation being enabled only if the information indicates that the probe has not been used before.

In another embodiment processing circuit 108 is configured to select between different modes of operation dependent on a type of the probe. For example, different types of probe may be provided to cooperate with base unit 10 in different ways, for example to investigate different types of tissue or to apply different types of light treatment. In this case processing circuit 108 implements the different ways of cooperation by operating in different modes (e.g. applying mode dependent light intensity, or performing mode dependent computations on detected light intensity to produce a measurement result). In this embodiment processing circuit 108 is configured to read information about the type of the probe from information providing element 124, and to switch to a selected one of the modes dependent on the information about the type.

Claims

1. An optical analysis apparatus, comprising a base unit and an exchangeable probe,

- the probe having a distal end and a proximal end, the probe comprising an information-providing element, a first connection part for connecting and disconnecting the proximal end of the probe to the base unit, and at least one optical fibre coupled between the first connection part and the distal end, for guiding light between the base unit and a sample region adjacent the distal end;

- the base unit comprising a second connection part, for detachably connecting to the first connection part, a light supply and/or detection arrangement for supplying light to the optical fibre and/or detecting light received from the optical fibre through the second connection part, a reading device arranged to read probe information from the information-providing element and a processing circuit coupled to the reading device, the processing circuit being configured to obtain the probe information from the reading device and to control operation of the analysis apparatus dependent on the probe information.

2. An optical analysis apparatus according to claim 1, wherein the processing circuit is configured to effect a correction for an effect of a reflection and/or transmission parameter of the optical fibre, dependent on the probe information.

3. An optical analysis apparatus according to claim 1, wherein the processing circuit is configured to activate a selective one of a plurality of different modes of operation of the optical analysis apparatus, dependent on the probe information.

4. An optical analysis apparatus according to claim 1, wherein the processing circuit is configured to select between disabling and enabling operation of the optical analysis apparatus and/or to generate a human perceptible alarm signal, dependent on the probe information.

5. An optical analysis apparatus according to claim 2, wherein the base unit comprises a light detection arrangement for measuring intensity of light received from the optical fibre through the second connection part, the processing circuit being configured to receive a signal from the detection arrangement and to correct a result derived from said signal using information about the reflection and/or transmission parameter, dependent on said probe information.

6. An optical analysis apparatus according to claim 5, wherein the base unit comprises a light source arranged to supply light to the proximal end and the detection arrangement comprises a measurement detector arranged to receive light from the proximal end that has passed through the optical fibre, the probe information identifying an internal reflection parameter for the optical fibre, the processing circuit being configured to remove an effect of internal reflection from said result according to the internal reflection parameter.

7. An optical analysis apparatus according to claim 5, comprising a reference detector arranged to receive light from the light source, the processing circuit being coupled to the reference detector, the processing circuit being configured to adapt a relative weight of the signal form the detection arrangement and correction for the reflection parameter, dependent on a reference signal from the reference detector.

8. An optical analysis apparatus according to claim 5 wherein the probe comprises a first and second optical fibre, the base unit comprising a light source arranged to supply light to the first optical fibre at the proximal end, the detection arrangement comprising a first and second measurement detector, the first measurement detector being arranged to receive light end that has passed through the first optical fibre from the proximal end, the second measurement detector being arranged to receive light from the second optical fibre, the probe information identifying a ratio between light collection efficiencies of the first and second optical fibre of the probe, the processing circuit being configured to form the result by subtracting results obtained from the first and second detector, correcting for the ratio between the light collection efficiencies identified by the probe information.

9. An optical analysis apparatus according to claim 8 wherein the probe information furthermore identifies an internal reflection parameter for the first optical fibre in the probe, the processing circuit being configured to remove an effect of internal reflection from said result according to the internal reflection parameter.

10. An optical analysis apparatus according to claim 5, wherein the correction information defines corrections as a function of wavelength.

11 An optical analysis apparatus according to claim 5, wherein the correction information is stored in the information-providing element.

12. An optical analysis apparatus according to claim 5, wherein the information-providing element stores an identifier, the processing circuit being configured to use the identifier to retrieve the correction information from a data base that contains the correction information linked to the identifier.

13. An optical analysis apparatus according to claim 1, wherein the information-providing element is a writable element, the processing circuit being configured to write further probe dependent information into the information providing element.

14. An optical analysis apparatus according to claim 1, wherein the information-providing element and the reading device are mutually arranged so that the reading device is capable of reading the probe dependent information while the first connection part is attached to the second connection part, the processing circuit being configured to obtain the probe information while the first connection part is attached to the second connection part.

15. A probe for use in an apparatus according to claim 1, the probe comprising a first connection part for connecting and disconnecting the probe to the base unit, an information-providing element for providing machine readable probe dependent information and at least one optical fibre coupled to the first connection part, for guiding light between the base unit and a sample region.

16. A base unit for use an apparatus according to claim 1, the base unit comprising a second connection part, for detachably connecting to the first connection part, a reading device arranged to read probe information from the information-providing element and a processor circuit configured to control operation of the base unit dependent on the probe information.

17. A method of using an optical probe that comprises at least one optical fibre, the method comprising

- connecting the probe to a base unit that contains a light source and/or a light detector for supplying to the optical fibre and/or detecting light from the optical fibre; - reading probe dependent probe information into the base unit from an information providing element that is part of the probe;

- controlling operation of the base unit dependent on the probe information.

18. A method according to Claim 17, comprising

- using the probe information to retrieve further probe information from a database and using the further information to control the operation.

19. A method according to Claim 17, comprising

- reading the results of calibration measurements for the probe determined by the probe information;

- supplying light to the probe and/or receiving a measurement of an intensity of light that has passed through the optical fibre;

- correcting an intensity of the light supplied to the fibre and/or the measured intensity according to the results of the calibration measurements read using the information element.

20. A method according to Claim 17, comprising - selecting a mode of operation of the base unit dependent on the probe information;

- activating the base unit in the selected mode.

21. A method according to Claim 17, comprising selecting between enabling and disabling operation of the base unit dependent on the probe information, and/or generating an alarm signal.

22. A computer program product comprising a program of instructions for a base unit of an apparatus according to Claim 1, the instructions, when executed by the processor circuit, causing the processor circuit to - read probe dependent probe information from an information providing element that is part of the probe;

- control operation of the base unit dependent on the probe information.