Measurement probe and bio-optical measurement system with contact detection

A measurement probe is configured to be detachably connected to a bio-optical measurement apparatus and includes: an illuminating fiber configured to irradiate body tissues with illumination light; light receiving fibers configured to receive return light of the illumination light reflected and/or scattered from the body tissues; an optical element configured to transmit the illumination light and the return light and to keep distances between the body tissues and distal ends of the illuminating fiber and the light receiving fibers, constant; and a contact detecting fiber configured to receive the return light to detect contact between a distal end face of the optical element and the body tissues, and detect the return light at a detection region on the distal end face through which the illumination light and the return light pass. The detection region is located outside an illumination region of the illuminating fiber.

BACKGROUND

1. Technical Field

The disclosure relates to a measurement probe detachably connected to a bio-optical measurement apparatus for measuring optical characteristics of body tissues. The disclosure also relates to a bio-optical measurement system.

2. Related Art

Conventionally, a bio-optical measurement system has been known which irradiates the body tissues with illumination light and estimates characteristics (property) of the body tissues based on a measured value of return light reflected or scattered from the body tissues. The bio-optical measurement system includes an optical measurement apparatus having a light source for irradiating the body tissues with the illumination light and a detection unit for detecting the return light from a measuring target and a measurement probe detachably connected to the optical measurement apparatus and for irradiating the body tissues with irradiation light and receiving the return light from the body tissues.

The measurement probe includes a fiber unit having an illuminating fiber and a light receiving fiber. The illuminating fiber is connected to the light source at one end thereof and is configured to irradiate the body tissues with the illumination light from the other end thereof. The light receiving fiber is connected to the detection unit at one end thereof and is configured to receive, at the other end thereof, return light from the body tissues irradiated by the illuminating fiber.

In the bio-optical measurement system, low-coherence enhanced backscattering (LEBS) is used in which the characteristics of the body tissues is detected by irradiating the body tissues with white low-coherent light having a short space coherence length from the distal end of the illuminating fiber of the measurement probe and measuring an intensity distribution of the scattered light of a plurality of angles by using a plurality of light receiving fibers (refer to WO 2007/133684).

Here, in the above-mentioned LEBS, the characteristics of the body tissues is detected in a state where the distal end face of the measurement probe is brought into contact with the body tissues (contact object). Therefore, a technique in which the distal end face of the measurement probe is surely brought into contact with the body tissues has been required.

A measurement probe is disclosed in which the distal end can be strongly pushed to the body tissues by providing a bellows-shaped elastic member at the distal end of the measurement probe as a member for surely bringing the distal end face of the measurement probe into contact with the body tissues (refer to JP 05-103773 A).

SUMMARY

In some embodiments, provided is a measurement probe configured to be detachably connected to a bio-optical measurement apparatus for performing optical measurement on body tissues. The measurement probe includes: an illuminating fiber configured to irradiate the body tissues with illumination light; a plurality of light receiving fibers configured to receive return light of at least one of the illumination light reflected and scattered from the body tissues and the illumination light reflected or scattered from the body tissues; an optical element configured to transmit the illumination light and the return light and to keep distances between the body tissues and distal ends of the illuminating fiber and the plurality of light receiving fibers, constant; and a contact detecting fiber configured to receive the return light to detect contact between a distal end face of the optical element and the body tissues, and configured to detect the return light at a detection region on the distal end face through which the illumination light and the return light pass, the detection region being located outside an illumination region of the illuminating fiber.

In some embodiments, a bio-optical measurement system includes a bio-optical measurement apparatus configured to perform optical measurement on body tissues, and a measurement probe configured to be detachably connected to the bio-optical measurement apparatus. The measurement probe includes: an illuminating fiber configured to irradiate the body tissues with illumination light; a plurality of light receiving fibers configured to receive return light of at least one of the illumination light reflected and scattered from the body tissues and the illumination light reflected or scattered from the body tissues; an optical element configured to transmit the illumination light and the return light and to keep distances between the body tissues and distal ends of the illuminating fiber and the plurality of light receiving fibers, constant; and a contact detecting fiber configured to receive the return light to detect contact between a distal end face of the optical element and the body tissues, and configured to detect the return light at a detection region on the distal end face through which the illumination light and the return light pass, the detection region being located outside an illumination region of the illuminating fiber. The bio-optical measurement apparatus includes: a detection unit configured to detect an intensity of the return light received by the contact detecting fiber; and a determination unit configured to determine that the distal end face has contacted the body tissues if decrease in the intensity of the return light detected by the detection unit is equal to or more than a predetermined threshold.

DETAILED DESCRIPTION

Exemplary embodiments of the measurement probe and the bio-optical measurement system according to the present invention will be described in detail below with reference to the drawings. The same reference signs are used to designate the same elements throughout the drawings. The drawings are schematic, and relationship between thickness and width of each member, a ratio of each member, and the like are different from those in reality. Also, a figure includes a part having the relationship of dimensions and ratio different from those of other figures. The present invention is not limited to the embodiments.

First Embodiment

Configuration of Bio-Optical Measurement System

FIG. 1is a schematic diagram of a configuration of a bio-optical measurement system according to a first embodiment of the present invention.FIG. 2is a schematic block diagram of the configuration of the bio-optical measurement system according to the first embodiment of the present invention.

A bio-optical measurement system1illustrated inFIGS. 1 and 2includes a bio-optical measurement apparatus2for detecting characteristics (property) of a measuring target by performing optical measurement on the measuring target such as body tissues which are scatterers and a measurement probe3detachably connected to the bio-optical measurement apparatus2. A side of a distal end of the measurement probe3is inserted into a subject.

Configuration of Bio-Optical Measurement Apparatus

First, a configuration of the bio-optical measurement apparatus2will be described. The bio-optical measurement apparatus2illustrated inFIGS. 1 and 2includes a power supply201, a light source unit202, a connector unit203, a first detection unit204, a second detection unit205, a third detection unit206, a fourth detection unit207, an input unit208, an output unit209, a recording unit210, and a control unit211. The power supply201supplies power input from outside to each element of the bio-optical measurement apparatus2.

The light source unit202irradiates the measuring target such as the body tissues with illumination light via the connector unit203and the measurement probe3. The light source unit202is configured of an incoherent light source such as a white light emitting diode (LED), a xenon lamp, a tungsten lamp, and a halogen lamp and a coherent light source such as a laser. The light source unit202is formed by combining it with an optical lens so that a light guiding efficiency to an optical fiber in the measurement probe3can be improved.

The measurement probe3is detachably connected to the connector unit203. The connector unit203propagates the illumination light irradiated by the light source unit202to the measurement probe3and propagates a plurality of light beams entered from the measurement probe3to the first detection unit204, the second detection unit205, the third detection unit206, and the fourth detection unit207.

The first detection unit204detects return light in which the illumination light irradiated from the measurement probe3is reflected and/or scattered from the measuring target and outputs the detection result to the control unit211. Specifically, the first detection unit204detects the intensity of the scattered light (spectrum) entered from the measurement probe3and outputs the detection result to the control unit211. The first detection unit204is formed by using a spectrometer, a light receiving sensor, a condenser lens, and the like.

The second detection unit,205is realized by having the similar structure to that of the first detection unit204. The second detection unit205detects the return light in which the illumination light irradiated from the measurement probe3is reflected and/or scattered from the measuring target and outputs the detection result to the control unit211.

The third detection unit206is realized by having the similar structure to that of the first detection unit204. The third detection unit206detects the return light in which the illumination light irradiated from the measurement probe3is reflected and/or scattered from the measuring target and outputs the detection result to the control unit211.

The fourth detection unit207is realized by having the similar structure to that of the first detection unit204. The fourth detection unit207detects the return light in which the illumination light irradiated from the measurement probe3is reflected and/or scattered from the measuring target and outputs the detection result to the control unit211.

The input unit208receives an input of a command signal for instructing the bio-optical measurement apparatus2to be started, a command signal for instructing the bio-optical measurement apparatus2to start measuring the measuring target, a command signal for instructing calibration processing, and the like, and then, the input unit208outputs the command signals to the control unit211. The input unit208is realized by using a push-type switch, a touch panel, and the like.

The output unit209outputs various information on the bio-optical measurement apparatus2, such as the measurement result of the measuring target, under the control of the control unit211. The output unit209is realized by using a display such as a liquid crystal display and an organic electro luminescence (EL) display, a speaker, and the like.

The recording unit210records various programs for operating the bio-optical measurement apparatus2, various data and various parameters to be used for optical measurement processing, and the like. The recording unit210temporarily records information under processing by the bio-optical measurement apparatus2. Also, the recording unit210records the measurement result of the measuring target by the bio-optical measurement apparatus2. The recording unit210is realized by using a volatile memory, a non-volatile memory, and the like. The recording unit210may be formed by using a memory card and the like attached from outside the bio-optical measurement apparatus2.

The control unit211totally controls the bio-optical measurement apparatus2by transferring the command information and the data corresponding to each element of the bio-optical measurement apparatus2. The control unit211is configured by using a central processing unit (CPU) and the like. The control unit211includes a determination unit211aand a calculation unit211b.

The determination unit211adetermines whether the detection result detected by the fourth detection unit207is equal to or more than a predetermined threshold. When the decrease in the detection result detected by the fourth detection unit207is equal to or more than the predetermined threshold, the determination unit211adetermines that the distal end face of the measurement probe3contacts the measuring target. On the other hand, when the decrease in the detection result detected by the fourth detection unit207is not equal to or more than the predetermined threshold, the determination unit211adetermines that the distal end face of the measurement probe3does not contact the measuring target.

The calculation unit211bperforms a plurality of calculating processes based on the detection results respectively detected by the first detection unit204, the second detection unit205, and the third detection unit206. Then, the calculation unit211bcalculates a characteristic value regarding the characteristics of the measuring target.

Configuration of Measurement Probe3

Next, the configuration of the measurement probe3will be described. A case will be described below where the number of detecting fibers is three. However, the same can be applied to a case where there is a plurality of detecting fibers in addition to the three detecting fibers.FIG. 3is a cross-sectional diagram of the measurement probe3.FIG. 4is a front view of the measurement probe3viewed from a side of the distal end.

The measurement probe3illustrated inFIGS. 2 to 4includes an illuminating fiber31, a first light receiving fiber32(first light receiving channel), a second light receiving fiber33(second light receiving channel), a third light receiving fiber34(third light receiving channel), and a contact detecting fiber35for passing through the measurement probe3. The contact detecting fiber35detects a contact of the distal end face of the measurement probe3relative to the body tissues. The measurement probe3includes a flexible part36having one end detachably connected to the connector unit203of the bio-optical measurement apparatus2and having flexibility, a fiber holding unit37which is connected to another end of the flexible part36and holds the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, the third light receiving fiber34, and the contact detecting fiber35, and a rod lens38(optical element) which is provided at the distal end of the fiber holding unit37. The contact detecting fiber35is inserted in and exposed from the rod lens38. When the flexible part36is connected to the connector unit203, the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, the third light receiving fiber34, and the contact detecting fiber35are respectively connected to the light source unit202, the first detection unit204, the second detection unit205, the third detection unit206, and the fourth detection unit207. Also, a connection mechanism which is connected to the connector unit203and is not shown is provided at one end of the flexible part36.

The illuminating fiber31is realized by using an optical fiber and irradiates the measuring target with the illumination light via the rod lens38. The illumination light is entered from the light source unit202via the connector unit203. The illuminating fiber31is a bundle of one or more optical fibers.

The first light receiving fiber32is realized by using the optical fiber. The first light receiving fiber32detects (receives) the return light of the illumination light reflected and/or scattered from the measuring target via the rod lens38and propagates the return light to the first detection unit204.

The second light receiving fiber33is realized by using the optical fiber. The second light receiving fiber33detects the return light of the illumination light reflected and/or scattered from the measuring target via the rod lens38and propagates the return light to the second detection unit205.

The third light receiving fiber34is realized by using the optical fiber. The third light receiving fiber34detects the return light of the illumination light reflected and/or scattered from the measuring target via the rod lens38and propagates the return light to the third detection unit206.

The contact detecting fiber35is realized by using the optical fiber. The contact detecting fiber35receives the return light of the illumination light and propagates the return light to the fourth detection unit207. Also, the contact detecting fiber35detects the contact of the distal end face of the measurement probe3with the measuring target (body tissues) by receiving the return light of the illumination light. The contact detecting fiber35is inserted in a hole which has been previously provided in the rod lens38and is provided on the side of the distal end of the rod lens38. The contact detecting fiber35may be integrally liquid-tightly formed of a resin and the like after being mounted in the rod lens38. One end of the rod lens38is cut into a D shape.

Also, as illustrated inFIGS. 3 and 4, regarding the contact detecting fiber35, a detection region d5of the contact detecting fiber35on the distal end face of the rod lens38where the illumination light irradiated by the illuminating fiber31and the return light reflected from the measuring target pass through is arranged at a position outside an illumination region d1irradiated by the illuminating fiber31. In addition, the contact detecting fiber35is arranged in a position where the detection region d5of the contact detecting fiber35is located outer than each of detection regions d2to d4of the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34. In addition, the contact detecting fiber35is arranged such that a distance between the distal end of the contact detecting fiber35and the distal end of the illuminating fiber31in a direction along the distal end face of the rod lens38becomes longer than each of distances between the distal ends of the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34and the distal end of the illuminating fiber31. Also, the contact detecting fiber35is arranged such that a distance between the distal end of the contact detecting fiber35and the distal end face of the rod lens38becomes shorter than each of distances between the distal ends of the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34and the distal end face of the rod lens38.

The fiber holding unit37arranges the distal ends of the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34in an arbitrary array and holds them. InFIG. 3, a case will be illustrated where the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34are aligned in a straight line. Also, the fiber holding unit37holds the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34so that optical axes of them are arranged in parallel to one another. In addition, the fiber holding unit37holds the contact detecting fiber35. The fiber holding unit37is realized by using glass, resin, or metal.

The rod lens38is provided at the distal end of the fiber holding unit37. The rod lens38is realized by using glass, plastic, and the like having predetermined permeability. Specifically, a glass rod or plastic rod which has light transmission properties and does not have a light pass bending effect as that of the lens, or an optical lens or a refractive index distribution type lens (GRIN lens) having curvature is used for the rod lens38. When a lens is used for the rod lens38, the lens is arranged such that a focal plane of the lens is located at the respective distal ends of the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34. The rod lens38has a cylindrical shape so that distances between the distal ends of the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34and the measuring target become constant. It is appropriate that the distal end face of the rod lens38is obliquely formed relative to the optical axis of the illuminating fiber31so that the illumination light from the illuminating fiber31reflected from the distal end face of the rod lens38by Fresnel reflection does not directly enter all the detecting fibers. For the description, the surface is indicated by a surface perpendicular to the optical axis of the illuminating fiber31in the drawings.

As illustrated inFIG. 5, in the bio-optical measurement system1formed as described above, the measurement probe3is inserted into the subject via a treatment tool channel101aprovided in an endoscope apparatus101(endoscope scope) of an endoscope system100. The illuminating fiber31irradiates the measuring target with the illumination light. The first light receiving fiber32, the second light receiving fiber33, the third light receiving fiber34respectively detect the return light of the illumination light reflected and/or scattered from the measuring target at different scattering angles and respectively propagate the return light to the first detection unit204, the second detection unit205, and the third detection unit206. After that, the calculation unit211bcalculates the characteristic value of the measuring target based on the detection results respectively detected by the first detection unit204, the second detection unit205, and the third detection unit206.

Processing of Bio-Optical Measurement System

Next, processing performed by the above-mentioned bio-optical measurement system1will be described.FIG. 6is a flowchart of an outline of the processing performed by the bio-optical measurement system1.

First, as illustrated inFIG. 6, the determination unit211aobtains the intensity of the return light of the illumination light detected by the fourth detection unit207via the contact detecting fiber35(step S101) and determines whether the intensity of the return light of the illumination light obtained from the fourth detection unit207is equal to or more than a predetermined value (step S102). When the determination unit211ahas determined that the intensity of the return light of the illumination light obtained from the fourth detection unit207is equal to or more than the predetermined value (step S102: Yes), the bio-optical measurement system1proceeds to step S103to be described. On the other hand, when the determination unit211ahas determined that the intensity of the return light of the illumination light obtained from the fourth detection unit207is not equal to or more than the predetermined value (step S102: No), the bio-optical measurement system1returns to step S101.

FIGS. 7A to 7Dare schematic diagrams of a state where the measuring target is measured by using the measurement probe3.FIG. 8is a diagram of a relationship between the intensities of the return light respectively detected by the first detection unit204and the fourth detection unit207in the states illustrated inFIGS. 7A to 7Dand a distance between the distal end of the measurement probe3and the measuring target. Also, inFIGS. 7A to 7D, when the illumination light is irradiated from the illuminating fiber31, the return light includes not only the reflection from a surface of the measuring target, but also includes reflection and/or scattering inside the measuring target. However, for purposes of illustration and not limitation, the return light reflected and scattered from the surface of the measuring target is schematically illustrated. InFIG. 8, the vertical axis indicates the intensity (value), and the horizontal axis indicates the distance between the distal end of the measurement probe3and the measuring target. In addition, inFIG. 8, the curved line L1indicates the detection result of the first detection unit204, and the curved line L2indicates the detection result of the fourth detection unit207.

As illustrated inFIGS. 7A to 7DandFIG. 8, as the measurement probe3gradually gets closer to a measuring target SP1(FIG. 7A→4FIG. 7B→FIG. 7C), values respectively detected by the first detection unit204and the fourth detection unit207gradually increase. Specifically, the return light respectively detected by the first light receiving fiber32and the contact detecting fiber35is light in which the illumination light irradiated by the illuminating fiber31is spread with a predetermined angle. At the same time, since the scatter occurs on the surface of the measuring target SP1, the light becomes spread light diffused wider than that in a case where the light has been irradiated from the illuminating fiber31.

That is, the intensities of the return light respectively detected by the first light receiving fiber32and the contact detecting fiber35significantly depend on a distance between the measurement probe3and the measuring target SP1. Therefore, the intensity of the return light detected by the first light receiving fiber32gradually increases as the measurement probe3gets closer to the measuring target SP1(distance D1→distance D2→distance D3). On the other hand, the intensity of the return light detected by the contact detecting fiber35sharply decreases just before the measurement probe3contacts the measuring target SP1. As illustrated above-mentionedFIG. 4, regarding the contact detecting fiber35, the detection region d5for detecting the return light does not overlap with an illumination region d1of the illuminating fiber31so that this phenomenon occurs. In addition, when the intensity of the return light detected by the contact detecting fiber35is compared with that detected by the first light receiving fiber32, the intensity of the return light of the contact detecting fiber35previously decreases. This phenomenon is caused by a difference between the distances of the detection region of the contact detecting fiber35and the illumination region of the illuminating fiber31.

In this way, when the decrease in the intensity of the return light detected by the fourth detection unit207via the contact detecting fiber35is equal to or more than the predetermined value, the determination unit211adetermines that the distal end face of the measurement probe3contacts the measuring target SP1. On the other hand, when the decrease in the intensity of the return light detected by the fourth detection unit207via the contact detecting fiber35is not equal to or more than the predetermined value, the determination unit211adetermines that the distal end face of the measurement probe3does not contact the measuring target SP1. Specifically, the determination unit211acompares the intensities of the two beams of temporally successive return light detected by the fourth detection unit207with each other and determines whether the decreased value or gradient is equal to or more than the predetermined value when the intensity of the return light has decreased. Accordingly, the determination unit211adetermines whether the distal end face of the measurement probe3contacts the measuring target SP1. When the intensity of the return light of the illumination light detected by the fourth detection unit207continues to decrease for a certain time after it has continued to increase for a certain time, the determination unit211amay determine that the distal end face of the measurement probe3contacts the measuring target SP1.

The procedure returns toFIG. 6, and the description after step S103will be continued.

In step S103, the control unit211makes the output unit209output information indicating that the distal end of the measurement probe3has contacted the measuring target SP1. Specifically, the control unit211makes the output unit209output an icon and the information indicating that the distal end of the measurement probe3has contacted the body tissues. The control unit211may make the output unit209output as voice and the like for indicating that the distal end of the measurement probe3has contacted the body tissues.

Subsequently, the calculation unit211bcalculates the characteristics of the measuring target SP1based on the values of the return light from the measuring target SP1respectively detected by the first detection unit204, the second detection unit205, and the third detection unit206(step S104). In this case, the output unit209may output the calculation result by the calculation unit211b. After step S104, the bio-optical measurement system1terminates this procedure.

According to the first embodiment described above, since the contact detecting fiber35is arranged such that the detection region d5of the contact detecting fiber35is arranged outside the illumination region d1of the illuminating fiber31, it is possible to determine whether the distal end face of the measurement probe3surely contacts the body tissues.

Also, according to the first embodiment, when the decrease in the intensity of the return light detected by the fourth detection unit207via the contact detecting fiber35is equal to or more than the predetermined value, the determination unit211adetermines that the distal end face of the measurement probe3contacts the measuring target SP1. On the other hand, when the decrease in the intensity of the return light detected by the fourth detection unit207via the contact detecting fiber35is not equal to or more than the predetermined value, the determination unit211adetermines that the distal end face of the measurement probe3does not contact the measuring target SP1. Accordingly, it is possible to determine whether the distal end face of the measurement probe3surely contacts the body tissues.

In the first embodiment, the distal end face of the contact detecting fiber35has been exposed. However, a different optical member such as cover glass may be provided, for example, on the distal end face of the contact detecting fiber35and the rod lens38.

First Modification of First Embodiment

Next, a first modification of the first embodiment will be described.FIG. 9is a cross-sectional diagram of a measurement probe according to the first modification of the first embodiment.

In a measurement probe3aillustrated inFIG. 9, the contact detecting fiber35is held by the fiber holding unit37in the same line as each of the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34. Specifically, the contact detecting fiber35is held by the fiber holding unit37so that a distance between the distal end and the distal end face of the rod lens38is the same as a distance between each of distal ends of the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34and the distal end face of the rod lens38. In addition, the contact detecting fiber35detects the return light of the illumination light irradiated by the illuminating fiber31via the rod lens38. Also, the contact detecting fiber35is held by the fiber holding unit37so that the detection region d5of the contact detecting fiber35on the distal end face of the measurement probe3a(numerical aperture θ3) is arranged outside the illumination region d1on the distal end face of the measurement probe3airradiated by the illuminating fiber31(numerical aperture θ1).

According to the first modification of the first embodiment described above, the measurement probe3acan be manufactured with a simple structure. In addition, the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, the third light receiving fiber34, and the contact detecting fiber35of the measurement probe3acan be integrated together by using a single fiber bundle.

Second Modification of First Embodiment

Next, a second modification of the first embodiment will be described.FIG. 10is a cross-sectional diagram of a measurement probe according to the second modification of the first embodiment.

A measurement probe3billustrated inFIG. 10further includes a diaphragm39for shielding a part of the illumination light irradiated by the illuminating fiber31in addition to the elements of the first embodiment described above.

The diaphragm39has an annular shape and is formed by using a light shielding member. The diaphragm39includes an aperture part39a, and the measuring target SP1is irradiated with a part of the illumination light irradiated by the illuminating fiber31by the aperture part39a. The diaphragm39isolates an illumination region of the illumination light irradiated by the illuminating fiber31from a detection region of the contact detecting fiber35. Specifically, the diaphragm39shields a part (most part) of the illumination light irradiated by the illuminating fiber31not to enter the contact detecting fiber35.

According to the second modification of the first embodiment described above, since the diaphragm39isolates the illumination region of the illumination light irradiated by the illuminating fiber31from the detection region detected by the contact detecting fiber35, the measurement probe3bcan be miniaturized. In addition, the size of the illumination region by the illuminating fiber31can be freely set regardless of the numerical aperture of the illuminating fiber31.

Second Embodiment

Next, a second embodiment of the present invention will be described. A bio-optical measurement system according to the second embodiment includes a measurement probe having a configuration different from that of the first embodiment which has been mentioned above. Specifically, the measurement probe according to the second embodiment includes a plurality of contact detecting fibers. Therefore, in the following description, after the configuration of the measurement probe according to the second embodiment is described, processing performed by the bio-optical measurement system according to the second embodiment will be described. The same reference signs are used to designate the same elements as those of the above-mentioned bio-optical measurement system1according to the first embodiment, and the explanation thereof will be omitted.

Configuration of Measurement Probe

FIG. 11is a cross-sectional diagram of the measurement probe according to the second embodiment. A measurement probe3cillustrated inFIG. 11includes a plurality of contact detecting fibers35ato35cin addition to the elements of the above-mentioned measurement probe3according to the first embodiment described above.

The plurality of contact detecting fibers35ato35cis realized by using optical fibers. The contact detecting fibers35ato35cdetect return light of illumination light and propagate the return light to a fourth detection unit207. The plurality of contact detecting fibers35ato35cis inserted into a hole which has been previously provided in a rod lens38and is provided on a side of a distal end of the rod lens38. The plurality of contact detecting fibers35ato35cmay be integrally formed of a resin and the like after being mounted in the rod lens38. One end of the rod lens38is cut into a D shape.

Also, each of the plurality of contact detecting fibers35ato35cis held by a fiber holding unit37so that detection regions d10to d12on the distal end face of the rod lens38are arranged at positions outside an illumination region d1irradiated by an illuminating fiber31. In a fourth detection unit207, a plurality of light receiving elements corresponding to the plurality of contact detecting fibers35ato35cmay be provided, and a single light receiving element may detect the intensities of the return light of the illumination light respectively received by the plurality of contact detecting fibers35ato35cby periodically switching the fiber to be detected.

Processing of Bio-Optical Measurement System

Next, the processing performed by the bio-optical measurement system1according to the second embodiment will be described.FIG. 12is a flowchart of an outline of the processing performed by the bio-optical measurement system1.

First, as illustrated inFIG. 12, a determination unit211aobtains the intensities of the return light of the illumination light detected by the fourth detection unit207via the contact detecting fibers35ato35c(step S201) and determines whether the plurality of intensities obtained from the fourth detection unit207is equal to or more than a predetermined value (step S202). When the determination unit211ahas determined that the plurality of intensities obtained from the fourth detection unit207is equal to or more than the predetermined value (step S202: Yes), the bio-optical measurement system1proceeds to step S203to be described. On the other hand, when the determination unit211ahas determined that the plurality of intensities obtained from the fourth detection unit207is not equal to or more than the predetermined value (step S202: No), the bio-optical measurement system1proceeds to step S201.

FIG. 13is a diagram of relationship between the intensities of the return light respectively detected by the first light receiving fiber32, the second light receiving fiber33, the third light receiving fiber34, and the contact detecting fibers35ato35cand a distance between the distal end of the measurement probe3cand a measuring target SP1. InFIG. 13, the vertical axis indicates the intensity (value), and the horizontal axis indicates a distance between the distal end of the measurement probe3cand the measuring target SP1. In addition, inFIG. 13, a curved line L11indicates the intensity of the return light detected by the first light receiving fiber32, and a curved line L12indicates the intensity of the return light detected by the second light receiving fiber33. A curved line L13indicates the intensity of the return light detected by the third light receiving fiber34, and a curved line L21indicates the intensity of the return light detected by the contact detecting fiber35a. A curved line L22indicates the intensity of the return light detected by the contact detecting fiber35b, and a curved line L23indicates the intensity of the return light detected by the contact detecting fiber35c.

As illustrated inFIG. 13, as the measurement probe3cgradually gets closer to the measuring target SP1, the intensities of the return light respectively detected by the first light receiving fiber32, the second light receiving fiber33, the third light receiving fiber34, and the contact detecting fibers35ato35cgradually increase. Specifically, the return light respectively detected by the first light receiving fiber32, the second light receiving fiber33, the third light receiving fiber34, and the contact detecting fibers35ato35cis light in which the illumination light irradiated by the illuminating fiber31is spread with a predetermined angle. At the same time, since the scatter occurs on the surface of the measuring target SP1, the light becomes spread light diffused wider than that in a case where the light has been irradiated from the illuminating fiber31.

That is, the intensities of the return light respectively detected by the first light receiving fiber32, the second light receiving fiber33, the third light receiving fiber34, and the contact detecting fibers35ato35csignificantly depend on the distance between the measurement probe3cand the measuring target SP1. Therefore, the intensities of the return light respectively detected by the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34gradually increase as the measurement probe3cgets closer to the measuring target SP1. On the other hand, the intensities of the return light detected by the contact detecting fibers35ato35csharply decrease just before the measurement probe3ccontacts the measuring target SP1. The detection regions d10to d12of the respective contact detecting fibers35ato35cdo not overlap with the illumination region d1of the illuminating fiber31, and accordingly, this phenomenon occurs.

In addition, when the intensities of the return light respectively detected by the contact detecting fibers35ato35care compared with one another, positions where the intensity of the return light decreases are in an order of the distances from the illuminating fiber31from the longer one. This phenomenon is caused by a difference between the distances of the detection regions d10to d12of the respective contact detecting fibers35ato35cto the illumination region d1of the illuminating fiber31. That is, regarding the position where the intensity of the return light of the illumination light sharply decreases, the order of the decrease in the intensity of the return light becomes earlier as the distance between the detection regions d10to d12of the contact detecting fibers35ato35cand the illumination region d1of the illuminating fiber31is longer.

In this way, the respective detection regions d10to d12of the contact detecting fibers35ato35care arranged not to overlap with the illumination region d1of the illuminating fiber31, and the contact detecting fibers35ato35crespectively having a different distance from the illuminating fiber31to one another are arranged. Accordingly, the contact of the measurement probe3cwith the measuring target SP1can be accurately detected. For example, according to the conventional method, when the contact state between the measurement probe3cand the measuring target SP1is detected by using the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34, it is preferable to detect the contact state by providing a threshold relative to the intensity of the return light. However, variations of the intensities of the return light becomes large according to the state of the measuring target SP1, the angle between the measurement probe3cand the measuring target SP1, the state of the illuminating fiber31(for example, decrease in light quantity of light source, connection state of fiber, and transmittance of fiber), and the state of the detecting fiber (for example, sensitivity of detector, connection state of fiber, and transmittance of fiber). That is, according to the conventional method, it is necessary to set the threshold of the intensity of the return light to a value in view of the above-mentioned variation. Therefore, the contact state between the measurement probe3cand the measuring target SP1cannot be accurately detected.

In order to address such a situation, in the second embodiment, when the decrease in the plurality of intensities of the return light respectively detected by the fourth detection unit207via the contact detecting fibers35ato35cis equal to or more than the predetermined value, the determination unit211adetermines that the distal end of the measurement probe3ccontacts the measuring target SP1. On the other hand, when the decrease in the plurality of intensities of the return light respectively detected by the fourth detection unit207via the contact detecting fibers35ato35cis not equal to or more than the predetermined value, the determination unit211adetermines that the distal end of the measurement probe3cdoes not contact the measuring target SP1. As a result, the contact of the measurement probe3cwith the measuring target SP1can be surely detected without depending on variation in the intensities of the return light respectively detected by the contact detecting fibers35ato35c.

Also, the distance between the measurement probe3cand the measuring target SP1does not always vary at fixed intervals. For example, when the positions of the measurement probe3cand the measuring target SP1have moved rapidly from the positions where the distance between them is short to the positions where the distance between them is long, there may be a position where the intensity of the return light sharply decreases. However, according to the third embodiment, when the positions of the measurement probe3cand the measuring target SP1have moved rapidly from the positions where the distance between them is short to the positions where the distance between them is long, the intensities of the return light respectively detected by the contact detecting fibers35ato35cvary in the same way in a case where the respective intensities of the return light of the contact detecting fibers35ato35care compared with each other. On the other hand, in the state where the measurement probe3ccontacts the measuring target SP1, the intensities of the return light decrease in an order of the contact detecting fiber35c, the contact detecting fiber35b, and the contact detecting fiber35a.

In this way, the determination unit211adetermines the contact state between the measurement probe3cand the measuring target SP1by determining the change of the intensities of the return light respectively detected by the contact detecting fibers35ato35c. That is, when the intensities of the return light have decreased in an order of the contact detecting fiber35c, the contact detecting fiber35b, and the contact detecting fiber35a, the determination unit211adetermines that the distal end of the measurement probe3chas contacted the measuring target SP1. On the other hand, when the respective intensities of the return light of the contact detecting fiber35c, the contact detecting fiber35b, and the contact detecting fiber35ahave decreased or changed in the same way, the determination unit211adetermines that the distal end of the measurement probe3chas not contacted the measuring target SP1.

The procedure returns toFIG. 12, and the description after step S203will be continued.

According to the second embodiment described above, since the detection regions d10to d12of the respective contact detecting fibers35ato35care arranged at positions outside the illumination region d1of the illuminating fiber31, it is possible to determine whether the distal end face of the measurement probe3csurely contacts the measuring target SP1.

Also, according to the second embodiment, when the decrease in the plurality of intensities of the return light respectively detected by the fourth detection unit207via the contact detecting fibers35ato35cis equal to or more than the predetermined value, the determination unit211adetermines that the distal end face of the measurement probe3ccontacts the measuring target SP1. On the other hand, when the decrease in the plurality of intensities of the return light respectively detected by the fourth detection unit207via the contact detecting fibers35ato35cis not equal to or more than the predetermined value, the determination unit211adetermines that the distal end face of the measurement probe3cdoes not contact the measuring target SP1. As a result, the contact of the measurement probe3cwith the measuring target SP1can be surely detected without depending on variation in the intensities of the return light respectively detected by the contact detecting fibers35ato35c.

In addition, according to the second embodiment, even when such foreign substances as dust adhere on the distal end face of the measurement probe3c, it is determined whether the intensity of the return light rapidly decreases by using the contact detecting fibers35ato35c. Accordingly, it is possible to determine whether the distal end face of the measurement probe3ccontacts the measuring target SP1or foreign substances adhere on the distal end face of the measurement probe3c.

First Modification of Second Embodiment

Next, a first modification of the second embodiment will be described.FIG. 14is a cross-sectional diagram of a measurement probe according to a first modification of the second embodiment.FIG. 15is a front view of the measurement probe according to the first modification of the second embodiment viewed from the side of the distal end of the measurement probe.

A measurement probe3dillustrated inFIGS. 14 and 15further includes a plurality of contact detecting fibers35dto35i(detection regions d14to d16) in addition to the elements of the measurement probe3caccording to the second embodiment described above. The contact detecting fibers35dto35iare realized by using the optical fibers similarly to the above-mentioned contact detecting fibers35ato35c. The contact detecting fibers35dto35idetect the return light of the illumination light and propagate the return light to the fourth detection unit207. Also, the contact detecting fibers35ato35iare arranged around the illumination region d1irradiated by the illuminating fiber31. Specifically, the contact detecting fibers35ato35iare arranged at predetermined intervals in a radial direction of a surface perpendicular to the longitudinal direction along the measurement probe3d, and for example, three of them are arranged side by side. The contact detecting fibers35ato35iare arranged at a predetermined interval (angle), for example, an interval of 120°.

According to the first modification of the second embodiment described above, even when the intensity of the return light has rapidly decreased by dust and foreign substances on one of the distal ends of the measurement probe3d, the determination unit211adetermines whether the distal end of the measurement probe3dcontacts the measuring target SP1based on the intensities of the return light detected by all the contact detecting fibers35ato35i. Accordingly, the contact with the measuring target SP1can be accurately determined.

Second Modification of Second Embodiment

Next, a second modification of the second embodiment will be described.FIG. 16is a front view of a measurement probe according to the second modification of the second embodiment viewed from the side of the distal end of the measurement probe.

A measurement probe3eillustrated inFIG. 16further includes a plurality of contact detecting fibers35dto35lin addition to the elements of the measurement probe3caccording to the second embodiment described above. The contact detecting fibers35dto35lare realized by using the optical fibers similarly to the above-mentioned contact detecting fibers35ato35c. The contact detecting fibers35dto35ldetect the return light of the illumination light and propagate the return light to the fourth detection unit207. Also, the contact detecting fibers35ato35lare arranged side by side by three in a radial direction of the measurement probe3eand arranged at respective positions which are rotationally symmetric having the center of the measurement probe3eas an axis. Specifically, the contact detecting fibers35ato35lare arranged by three at a predetermined interval, for example, an interval of 90°.

According to the second modification of the second embodiment described above, even when the intensity of the return light has rapidly decreased by dust and foreign substances on one of the distal ends of the measurement probe3e, the determination unit211adetermines whether the distal end of the measurement probe3econtacts the measuring target SP1based on the intensities of the return light detected by all the contact detecting fibers35ato35l. Accordingly, the contact with the measuring target SP1can be accurately determined.

Third Modification of Second Embodiment

Next, a third modification of the second embodiment will be described.FIG. 17is a cross-sectional diagram of a measurement probe according to the third modification of the second embodiment.

In a measurement probe3fillustrated inFIG. 17, the contact detecting fibers35ato35care held by the fiber holding unit37in the same lines as each of the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34. In addition, the contact detecting fibers35ato35cdetect the return light of the illumination light irradiated by the illuminating fiber31via the rod lens38. In addition, the detection regions d10to d12of the respective contact detecting fibers35ato35con the distal end face of the measurement probe3fare held by the fiber holding unit37so as to be arranged outside the illumination region d1irradiated by the illuminating fiber31on the distal end face of the measurement probe3f.

According to the third modification of the second embodiment described above, the measurement probe3fcan be made with a simple structure. In addition, the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, the third light receiving fiber34, and the contact detecting fibers35ato35cof the measurement probe3fcan be integrally formed by using a single fiber bundle.

Fourth Modification of Second Embodiment

Next, a fourth modification of the second embodiment will be described.FIG. 18is a cross-sectional diagram of a measurement probe according to the fourth modification of the second embodiment.

A measurement probe3gillustrated inFIG. 18further includes an optical member38afor protecting the distal end faces of the contact detecting fibers35ato35cand the distal end face of the rod lens38in addition to the elements of the measurement probe3caccording to the second embodiment described above.

The optical member38a(second rod lens) is formed of a similar member to that of the rod lens38. A glass rod or plastic rod which has light transmission properties and does not have a light pass bending effect as that of the lens, or an optical lens or a refractive index distribution type lens (GRIN lens) having curvature is used for the optical member38a. The optical member38ahas a disc-like shape and prevents liquid and the like from entering a gap between the contact detecting fibers35ato35cand the rod lens38. The distal end face of the optical member38amay be obliquely notched relative to the longitudinal direction of the measurement probe3g. In addition, the optical member38amay be formed to have no difference between refractive indexes of materials of the rod lens38and the optical member38aso that unnecessary light reflected from the distal end face of the rod lens38does not reach the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34before the illumination light reaches the measuring target SP1in a bonding part between the rod lens38and the optical member38a. In addition, the rod lens38may be obliquely formed relative to the longitudinal direction of the measurement probe3gsimilarly to the optical member38a.

According to the fourth modification of the second embodiment described above, the liquid for entering the gap between the contact detecting fibers35ato35cand the rod lens38can be surely prevented. Accordingly, when the measurement probe3gis cleaned or used for the subject, impurities such as water can be surely prevented from entering the above-mentioned gap.

Fifth Modification of Second Embodiment

Next, a fifth modification of the second embodiment will be described.FIG. 19is a cross-sectional diagram of a measurement probe according to the fifth modification of the second embodiment.

A measurement probe3hillustrated inFIG. 19further includes a contact detecting fiber35din addition to the elements of the measurement probe3caccording to the second embodiment described above. In addition, the measurement probe3hincludes a rod lens41instead of the rod lens38and the optical member38aaccording to the fourth modification of the above-mentioned second embodiment.

The rod lens41is provided on the distal end of the fiber holding unit37and is realized by using glass, plastic, and the like having predetermined permeability. The rod lens41has a cylindrical shape so that a distance between each of the distal ends of the illuminating fiber31, the first light receiving fiber32, the second light receiving fiber33, and the third light receiving fiber34and the measuring target becomes constant. Also, the rod lens41holds the contact detecting fibers35ato35dso that the distal ends thereof are exposed. The rod lens41includes a disk-shaped bottom41a, a wall part41bextending from a circumference of the bottom41aalong the longitudinal direction of the measurement probe3h, and a cylindrical distal end part41c. The bottom41a, the wall part41b, and the distal end part41care integrally formed by bonding with, for example, an adhesive. Accordingly, a space is formed in the rod lens41. In addition, the optical member38ais provided on the side of the distal end of the rod lens41.

According to the fifth modification of the second embodiment described above, the contact detecting fibers35ato35dcan be easily mounted on the distal end of the rod lens41by forming a space K1in the rod lens41.

Third Embodiment

Next, a third embodiment of the present invention will be described. A bio-optical measurement system according to the third embodiment has a different configuration from that of the bio-optical measurement system1according to the above-mentioned first embodiment. Specifically, the bio-optical measurement system according to the third embodiment further includes a light source unit for irradiating illumination light to detect a contact between a measurement probe and a measuring target and an illuminating fiber. Therefore, the configuration of the bio-optical measurement system according to the third embodiment will be described below. The same reference signs are used to designate the same elements as those of the above-mentioned bio-optical measurement system1according to the first embodiment, and the explanation thereof will be omitted.

Configuration of Bio-Optical Measurement System

FIG. 20is a block diagram of a functional configuration of the bio-optical measurement system according to the third embodiment of the present invention. A bio-optical measurement system1aillustrated inFIG. 20includes a bio-optical measurement apparatus2afor detecting characteristics (property) of the measuring target by performing optical measurement on the measuring target such as body tissues which are scatterers and a measurement probe3idetachably connected to the bio-optical measurement apparatus2a. A side of a distal end of the measurement probe3iis inserted into a subject.

Configuration of Bio-Optical Measurement Apparatus

First, the configuration of the bio-optical measurement apparatus2awill be described. The bio-optical measurement apparatus2aillustrated inFIG. 20includes a contact light source unit212in addition to the elements of the bio-optical measurement apparatus2of the first embodiment described above. In addition, the bio-optical measurement apparatus2aincludes a control unit213instead of the control unit211of the bio-optical measurement apparatus2of the first embodiment described above.

The contact light source unit212irradiates the measuring target such as the body tissues with the illumination light (contact illumination light) via a connector unit203and a measurement probe3iunder the control of the control unit213. The contact light source unit212is configured of an incoherent light source such as a white LED, a xenon lamp, a tungsten lamp, and a halogen lamp and a coherent light source such as a laser. In addition, the contact light source unit212is formed by combining it with an optical lens so that a light guiding efficiency to the optical fiber in the measurement probe3ican be improved.

The control unit213totally controls the bio-optical measurement apparatus2aby transferring command information and data to each element of the bio-optical measurement apparatus2a. The control unit213is formed by using a CPU and the like. The control unit213includes a determination unit211a, a calculation unit211b, and an illumination controller211c.

The illumination controller211ccontrols the contact light source unit212and the light source unit202based on the determination result of the determination unit211a. Specifically, when the determination unit211adetermines that the distal end of the measurement probe3idoes not contact the measuring target, the illumination controller211ccauses the contact light source unit212to emit the illumination light for detecting the contact. On the other hand, when the determination unit211adetermines that the distal end of the measurement probe3icontacts the measuring target, the determination unit211astops the illumination light for detecting the contact irradiated by the contact light source unit212and causes the light source unit202to emit the illumination light.

Configuration of Measurement Probe

Next, the configuration of the measurement probe3iwill be described. A case will be described below where the number of detecting fibers is three. However, the same can be applied to a case where there is a plurality of detecting fibers in addition to the three detecting fibers.FIG. 21is a cross-sectional diagram of the measurement probe3i.

The measurement probe3iillustrated inFIG. 21further includes a contact illuminating fiber50in addition to the elements of the measurement probe3according to the first embodiment described above. The contact illuminating fiber50propagates the illumination light irradiated by the contact light source unit212and emits the illumination light from the distal end of the measurement probe3i. An illumination region d20(contact illumination region) on the distal end face of the measurement probe3iirradiated by the contact illuminating fiber50is held by the fiber holding unit37so as to be arranged outside the illumination region d1irradiated by the illuminating fiber31.

The bio-optical measurement system1aformed in this way is used by using the endoscope system100illustrated inFIG. 5similarly to the above-mentioned first embodiment.

Processing of Bio-Optical Measurement System

Next, processing performed by the above-mentioned bio-optical measurement system1awill be described.FIG. 22is a flowchart of an outline of the processing performed by the bio-optical measurement system1a.

As illustrated inFIG. 22, first, the illumination controller211ccauses the contact light source unit212to emit the contact illumination light (step S301).

Subsequently, the illumination controller211cstops irradiation of the contact illumination light by the contact light source unit212(step S304) and causes the light source unit202to emit the illumination light (step S305).

According to the third embodiment described above, the contact illuminating fiber50for emitting the illumination light to detect whether the distal end of the measurement probe3icontacts the measuring target SP1is provided in addition to the illuminating fiber31. Accordingly, the contact with the measuring target SP1can be detected without being limited by the numerical aperture of the illuminating fiber31.

Also, according to the third embodiment, the illumination controller211ccontrols the irradiations by the contact light source unit212and the light source unit202based on the determination result by the determination unit211a. Therefore, the contact with the measuring target SP1can be detected without having an effect of the other illumination light, and the characteristics of the measuring target SP1can be obtained.

There is one contact detecting fiber35in the third embodiment. However, a plurality of contact detecting fibers may be employed.

In addition, in the third embodiment, the above-mentioned optical member38aof the fourth modification of the second embodiment may be provided at the distal end of the rod lens38.

First Modification of Third Embodiment

Next, a first modification of the third embodiment will be described.FIG. 23is a cross-sectional diagram of a measurement probe3jaccording to the first modification of the third embodiment.

The measurement probe3jillustrated inFIG. 23has similar elements to those of the above-mentioned measurement probe3iaccording to the third embodiment. The measurement probe3jis held by the fiber holding unit37and arranged such that the illumination region d20of the contact illuminating fiber50on the distal end face of the measurement probe3joverlaps with a part of the illumination region d1irradiated by the illuminating fiber31. In addition, the measurement probe3jis held by the fiber holding unit37and arranged such that the illumination region d20of the contact illuminating fiber50on the distal end face of the measurement probe3jdoes not overlap with the detection region d5of the contact detecting fiber35.

According to the first modification of the third embodiment described above, the measurement probe3jis held by the fiber holding unit37and arranged such that the illumination region (irradiation region) of the contact illuminating fiber50on the distal end face of the measurement probe3joverlaps with a part of the illumination region irradiated by the illuminating fiber31. Accordingly, it is possible to reduce the diameter of the measurement probe3j.

Second Modification of Third Embodiment

Next, a second modification of the third embodiment will be described.FIG. 24is a cross-sectional diagram of a measurement probe3kaccording to the second modification of the third embodiment.FIG. 25is a front view of the measurement probe3kaccording to the second modification of the third embodiment viewed from a side of the distal end.

The measurement probe3killustrated inFIGS. 24 and 25has similar elements to those of the above-mentioned measurement probe3iof the third embodiment and includes contact detecting fibers35aand35band a contact illuminating fiber50. The measurement probe3kis held by the fiber holding unit37and arranged such that the illumination region d20of the contact illuminating fiber50on the distal end face of the measurement probe3kdoes not overlap with the illumination region d1irradiated by the illuminating fiber31. Also, the measurement probe3kis held by the fiber holding unit37and arranged such that the detection regions d10and d11of the respective contact detecting fibers35aand35bon the distal end face of the measurement probe3kdo not respectively overlap with the illumination region d20of the contact illuminating fiber50and the illumination region d1irradiated by the illuminating fiber31.

According to the second modification of the third embodiment described above, the contact illuminating fiber50for emitting the illumination light to detect whether the distal end of the measurement probe3kcontacts the measuring target SP1is provided in addition to the illuminating fiber31. Accordingly, the contact with the measuring target SP1can be detected without being limited by the numerical aperture of the illuminating fiber31.

Third Modification of Third Embodiment

Next, a third modification of the third embodiment will be described.FIG. 26is a cross-sectional diagram of a measurement probe according to the third modification of the third embodiment.FIG. 27is a front view of the measurement probe according to the third modification of the third embodiment viewed from the side of the distal end.

A measurement probe31illustrated inFIGS. 26 and 27has similar elements to those of the measurement probe3iaccording to the third embodiment described above and includes the contact detecting fibers35aand35band the contact illuminating fiber50. The measurement probe31is held by the fiber holding unit37and arranged such that the illumination region d20of the contact illuminating fiber50on the distal end face of the measurement probe31does not overlap with the illumination region d1irradiated by the illuminating fiber31. Also, the measurement probe31is held by the fiber holding unit37and arranged such that the detection regions d10and d11of the respective contact detecting fibers35aand35bon the distal end face of the measurement probe31do not respectively overlap with the illumination region d20of the contact illuminating fiber50and the illumination region d1irradiated by the illuminating fiber31.

According to the third modification of the third embodiment described above, the contact illuminating fiber50for emitting the illumination light to detect whether the distal end of the measurement probe31contacts the measuring target SP1is provided in addition to the illuminating fiber31. Accordingly, the contact with the measuring target SP1can be detected without being limited by the numerical aperture of the illuminating fiber31.

In the description of the flowchart herein, the anteroposterior relation of the processing of each step has been defined by using expressions such as “first”, “after that”, and “subsequently”. However, an order of the necessary processing to carry out the present invention is not uniquely defined by those expressions. That is, the order of the processing in the flowchart described herein can be changed within a consistent range.

According to some embodiments, it is possible to determine whether a distal end face surely contacts body tissues.