United States Patent 5
`Haaret al.
`
`[54] APPARATUS FOR LIGHT REFLECTION
`MEASUREMENTS
`
`US005893364A
`
`(11) Patent Number:
`
`[45] Date of Patent:
`
`5,893,364
`Apr. 13, 1999
`
`5,598,843
`5,638,818
`
`
`..
`2/1997 Caisey et al.
`vase 600/476
`G/1997 Diab et al. ou... cecsesessesessesseeees 600/310
`
`(75]
`
`Inventors: Hans-Peter Haar, Wiesloch; Matthias
`4/1984
`0104772
`Essenpreis, Gauting; Rainer Fritsche.
`European Pat. Off.
`28 23 769 «12/1979
`Briihl, all of Germany
`Germany.
`2927814~~I/1981
`Germany .
`31 13248=3/1987
`Germany.
`Boehringer Mannheim GmbH.
`[73] Assignee:
`38 09 084AL
`9/1989
`Germany.
`Mannheim, Germany
`9103 974
`8/1991
`Germany.
`43 14 835
`11/1994
`Germany .
`[21] Appl. No.: 08/752,629
`0 631 137 A2
`12/1994
`Germany .
`43 37570=5/1995
`Germany.
`[22] Filed:
`Nov. 19, 1996
`1-138507
`5/1989
`Japan .
`2253 070=8/1992
`United Kingdom .
`[30]
`Foreign Application Priority Data
`
`FOREIGN PATENT DOCUMENTS
`
`.
`
`Nov. 29, 1995
`
`[DE]
`
`Germany ..........:.sccseene 195 44 501.5
`
`(SY) te C1. neeeeccccscccecorssecnnnnenenesenceneensens AGLB 5/00
`[52] U.S. C1. eeeeeeesecseenens 600/310; 600/476; 356/338
`[58] Field of Search 0... seein 600/3 10~317,
`600/322-324, 336. 473. 474. 476, 477;
`356/39-41, 337, 338; 435/4; 436/43
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`Primary Examiner—Ruth S. Smith
`Attorney, Agent, or Firm—Nikaido, Marmelstein, Murray &
`Oram LLP
`
`[57]
`
`ABSTRACT
`
`An apparatus for light transport measurements on a test
`object with a measuring head which includes a contact
`surface for placing against an interface of the test object.
`light irradiation device with a light transmitterfor irradiating
`light through the contact surface and an interface into the test
`object, and detection device with a light receiver for detect-
`2,706,927—4195S Wo...ssseescseensnccseorssnsenenerenes 38/14
`ing light leaving the test object. The contact surface com-
`6/1987 Sakurai etal............
`350/96.27
`4,671,612
`
`ww. 357/471
`...
`4,942.48!
`7/1990 Yoshinouchi et al.
`prises at least one optically transparent light passage point
`
`5,030,000=F/1991 Kamda ou... eeesccessessessseeonsveneces 356/40
`for the light, on which a large number of rigid light-
`+. 385/120
`
`5,052,776 10/1991 Fukushimaet al.
`.
`conducting elements are arranged, wherein an optical con-
`e+. 600/316
`5,077,476 12/1991 Rosenthal .........
`
`nection with a light transmitter or light receiver assigned to
`--- 600/476
`5/1993 Gratton et al.
`a light passage point is produced by the whole of the
`wee 385/120
`11/1993 Cook ........ee
`light-conducting elements of the light passagesite.
`-- 600/476
`.
`2/1994 Dhadwal etal.
`
`-- 600/476
`9/1994 Tiemann etal. .....
`9/1996 Simonsen et al.
`........cece 128/633
`
`5,259,057
`3,284,149
`5,349,954
`5,551,422
`
`32 Claims, 5 Drawing Sheets
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`APPLE 1015
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`APPLE 1015
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`1
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`U.S. Patent
`
`Apr. 13, 1999
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`Sheet 1 of 5
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`5,893,364
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`UNIT
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`EVALU ATION
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`LIGHT
`DETECTOR
`
`Fig. 2
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`U.S. Patent
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`Apr. 13, 1999
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`Sheet 2 of 5
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`5,893,364
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`Fig. 3 2ic=2b2Ta
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`Fig. 4
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`Fig. 6
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`3
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`U.S. Patent
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`Sheet 3 of 5
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`Apr. 13, 1999
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`5,893,364
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`4
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`USS. Patent
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`Apr. 13, 1999
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`Sheet 4 of 5
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`5,893,364
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`U.S. Patent
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`Apr. 13, 1999
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`Sheet 5 of 5
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`5,893,364
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`Fig. 9
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`6
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`

`

`5.893.364
`
`1
`APPARATUS FOR LIGHT REFLECTION
`MEASUREMENTS
`
`FIELD OF THE INVENTION
`
`1. Background of the Invention
`The invention relates to an apparatus for light transport
`measurements with a measuring head which comprises a
`contact surface for placing against an interface of the test
`object.
`2. Description of the Related Art
`A particularly importantfield of application is light trans-
`port measurements on test objects which scatter the light
`strongly, in particularly on biological tissue, above all the
`skin of humansor animals. Light reflection measurements
`on the skin are mainly performed in medical-analytical
`investigations. A large number of methods have been pro-
`posed in which light of varying wavelengths (from the UV
`at about 200 nm up to the infrared at about 2500 nm) is used.
`Where methods of this kind are used for the analytical
`determination of the concentration of substances contained
`in the tissue (analytes). they are generally based on the
`principles of spectroscopy. Examples of such methods are
`described in EP-0 104 772 A2 and the printed publications
`cited there.
`
`A commonfeature of these methods is that light leaving
`a light transmitter (“primary light”) is irradiated through the
`contact surface of the measuring head andaninterface of the
`test object (in the case of the skin throughits surface) into
`the test object and light leaving the test object through an
`interface after interaction with said test object (“secondary
`light”) is detected. Thin test objects (for example the ear
`lobes) can be transilluminated by the light, i-e. the detection
`of the secondary light takes place at an interface which lies
`opposite the irradiation interface (“transport measurement”).
`A suitable light
`transport measuring instrument has two
`contact surfaces which are placed against the two opposite
`interfacesof the test object (cf. e.g. U.S. Pat. No. 2,706,927).
`The present invention can be realized on one or on both of
`the contact surfaces.
`
`The invention is particularly suitable for light transport
`measurements in which the irradiation of the primary light
`and the detection of the secondary light take place at the
`same interface. This is commonly called a measurement“in
`reflection”, although there is no reflection in the strict sense
`at the skin surface. Rather the light is also in this case
`irradiated into the inside of the test object where it travels
`from the irradiation site to a detection site, the light transport
`being determined by absorption and scattering in the test
`object. Such an apparatus can be designated as a contact
`reflectometer.
`In recent times contact reflectometers have also been used
`for methods which do not operate according to spectroscopic
`principles. For example, in WO 94/10901 a method and a
`corresponding contact reflectometer are described. which
`permit the analysis of glucose on the basis of the scattering
`properties in the tissue.
`The inventionis suitable for but is not limited to these and
`similar methods.
`It can in general be used successfully
`wherever light transport measurements have to be performed
`in direct contact with the test object and with particularly
`high accuracy. Non-biological test objects for which the
`invention is suitable are for example test strip surfaces
`whosecolor is characteristic of a particular analyte concen-
`tration.
`
`In order to permit the passage of the light. at least one
`partial area of the contact surface is optically transparent.
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`Sucha transparent section will be referred to here as the light
`passage site. In general separate light passage sites are
`provided in the contact surface for the irradiation of the
`primary light and for the detection of the secondary light.
`The accuracy requirements ofa suitable measuring device
`for the above-mentioned medical-analytical applications are
`extremely high. The total change in the secondary light as a
`function of the concentration of the analyte in the entire
`medically relevant concentration range is often only a few
`per cent. In order to determine the analyte concentration
`with sufficient accuracy from these small changes, a mea-
`suring accuracy of the reflectometer in the order of some
`0.1% is required. The main concern is the stability and
`long-term reproducibility of the measurement. Thusit is
`mostcritical that a particular light flux of the secondary light
`leaving the test object leads to the sameelectrical signal with
`maximum long term accuracy(at least over several hours, if
`possible over several days). In many cases such devices are
`to be provided to patients for the individual monitoring of a
`critical analyte (in particular glucose). Despite the high
`requirements, therefore, they must be manufactured at low
`cost.
`
`SUMMARY OF THE INVENTION
`
`The invention therefore addresses the problem to
`improve,
`in the case of an apparatus with the features
`explained above. the measuring accuracy in particular as
`regards the reproducibility of the link between the secondary
`light flux and the measured signal.
`The problem is solved for such a measuring device by the
`fact that the at least one light passage site in the contact
`surface comprises a large numberof rigid light-conducting
`elements, wherein the whole of the light-conducting ele-
`ments of a light passage site forms an optical connection
`with a particular light transmitter or light receiver assigned
`to the light passagesite.
`Thus the optical connection between the test object and a
`light receiver (detector) and/or between the test object and a
`light transmitter is produced in each case by a light passage
`site which is assigned to the respective transmitter/receiver.
`A plurality of light transmitters can be assigned to one light
`passagesite, as will be explained below. In certain circum-
`stances a plurality of receivers can also be assigned to one
`light passage site. This is expedient. for example, if a range
`of wavelength is used in which two different
`types of
`detector have to be used for different sections of the spec-
`trum (“tandem detector”).
`According to the invention the primary light leaving a
`particular light transmitter and/or the secondary light passed
`to a particular light receiver (detector) at the light passage
`site does not pass through an unsealed opening in the contact
`surface and is also not
`transmitted by a single light-
`conducting element, for example a light-conducting rod. but
`by a large number of light-conducting elements. Preferably
`at least 100, particularly preferably at
`least 1000.
`light-
`conducting elements are provided at a light passagesite. in
`particular at sites which are assigned to a light receiver. It is
`furthermore important that the light-conducting elements are
`rigid,
`i.e. no flexible light-conducting fibers shall be
`involved, as have been used on a large scale to date.
`In the known methodsthe light passage sites often have
`very small dimensions. A point-shaped light passage site of
`0.5 mm diameter can in the case of the invention neverthe-
`less comprise over 1000, possibly even about 10000. light-
`conducting elements. The elements preferably have a very
`small cross-section of less than 0.01 mm*. particularly
`preferably less than 0.002 mm*.
`
`7
`
`

`

`5,893,364
`
`3
`Suitable light-conducting elements which are packed
`closely parallel
`to one another, and are therefore rigid
`despite an extremely small cross-section. are manufactured
`as so-called fiber optic plates.
`The inventors have found that, when light-conducting
`elements according to the prior art are arranged between the
`opto-electronic converters (light
`transmitters and light
`receivers) and the test object, even extremely small
`mechanical changes in the sensor system or at the contact
`point with the interface of the test object (in particular of the
`skin surface) in many cases cause signal variations which
`are far higher than the desired measuring accuracy of about
`0.1%. Therefore it is often not possible to determine the
`desired analytical result in the medium with sufficient accu-
`racy or long term stability.
`The invention far better ensures that always the same
`fraction of the photons leaving the transmitter actually
`passes into the test object and—with the test object
`unchanged—-a likewise identical
`fraction passes to the
`detector after leaving the test object through the interface.
`Theoptical stability is in particular improved with respect to
`interference caused by minor irregularities at the surface of
`the test object (skin surface). At the same time the contact
`surface is closed, so that the interior of the measuring head
`is protected. Finally, the invention allows both the irradia-
`tion and the detection to be limited very precisely to par-
`ticular sections of the skin surface (“irradiation site” and
`“detection site” as defined in WO 94/10901).
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention will now be explained in detail by means of
`embodiments shown in the figures, where
`FIG. 1 showsa block diagram,partially in section, of an
`apparatus according to the invention,
`FIG. 2 showsa block diagram in cross-section of the main
`parts of a measuring head suitable for the invention,
`FIG. 3 shows a view onto a detector arrangement,
`FIG. 4 shows a highly magnified and abstract represen-
`tation explaining optical features critical for the invention,
`FIG. § shows an exploded view of the optical unit of a
`contact surface module for the invention,
`
`FIG. 6 showsa perspective view of a part of alternatively
`usable light irradiation means and
`FIG. 7 shows an exploded view of a contact surface
`module using a modified optical unit.
`FIG. 8 shows a cut-out view—partially in section and
`partially in perspective—of a further embodiment of the
`contact surface module.
`
`FIG. 9 shows a perspective view of the contact surface
`module of FIG. 8 in which the semi-conductor layer is
`shownin upright position to make its underside visible.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`The contact reflectometer shown in highly diagrammatic
`form in FIG. 1 consists essentially of a measuring head 1 and
`a signal processing and evaluation unit 2.
`The measuring head is in contact via contact surface 3 of
`a sample contact plate 4 with aninterface 5 of the test object
`6. Light irradiation means labeled overall as 7 and detection
`means 8 are located in the measuring head 1. They contain
`a light transmitter 20 (preferably a semiconductor light
`transmitter, in particular a light-emitting diode) and light
`detectors 21 (preferably semiconductor detectors, in particu-
`
`4
`lar photodiodes, phototransistors or avalanche-type
`photodiodes), which are connected to the signal processing
`and evaluation unit 2 via electrical leads 9 and 10 and a cable
`11.
`
`For the passage of the light the contact surface 3 (and the
`sample contact plate 4 as a whole) comprises light passage
`sites. wherein in the case shown onelight passagesite 13 is
`provided for the primary light irradiated into the test object
`6 and twolight passage sites 1da. 145 are provided for the
`detection of secondary light leaving the test object 6. The
`position and size of the respective primary light passage site
`13 (primary light passage location) and of the secondary
`light passage sites 1da and 14b (secondary light passage
`location} determines the site on the interface at which the
`light is irradiated into the test object (“irradiation site”) or
`from which emerging light is detected (“detection site”).
`The signal processing and evaluation unit 2 contains the
`electronic meansfor activating the light irradiation means 7
`and for deriving desired information concerning the inside
`of the test object 6 from theelectrical signals (test signals)
`generated by the detection means §. As already explained.
`the inventionis suitable for a large number of such methods
`and the signal processing and evaluation unit 2 contains the
`means respectively required for this purpose and explained,
`for example. in the publications mentioned above. Such
`means generally include electronic amplifier circuits (for
`example a lock-in amplifier) for the analog processing of the
`test signal of the detection means, together with a digital
`signal processing unit based on a microprocessor coupled
`thereto.
`
`FIG, 2 shows special features of the invention in highly
`abstract form. The contact plate 4 includes an optical fiber
`plate 16, which consists of a large number of closely packed.
`relatively short rigid light-conducting elements 15, in the
`form of optical fibers, running perpendicular to the contact
`surface 3. The length of the fibers. and hence the thickness
`of the optical fiber plate 16. preferably is not more than 5
`mm, particularly preferably not more than 2 mm. A thick-
`ness of about 1 mm has proven particular suitable.
`In the embodiment shown the optical fiber plate 16 is
`fitted directly between the walls of the housing 17 of the
`measuring head 1 in such a waythat it seals off the housing
`17 completely from thetest object 6. It is bonded directly to
`a semiconductor layer 19 by means of an index-adapted
`adhesive 18 said layer comprising at suitable points light-
`sensitive areas in the form of silicon detectors 21
`(photodiodes). This can be seen in overhead view in FIG.3.
`In the case shown,three detectors (light receivers) 21a, 21b
`and 21c are provided. Recesses are provided in alignment
`with these detectors. namely in a mask 22 which can be
`located optionally on the detector-side surface 16a or the
`sample-side surface 16b of the optical fiber plate 16. In the
`shown embodiment a covering layer 23 is provided on the
`sample-side surface 16b, which layer forms the mask 22 and
`comprises at
`the light passage sites 14a, 14b and 14c
`transparent partial areas 23a, 23b, 23c of an antireflection
`coating. while the remaining surface consists of black paint.
`The mask comprises a further transparent partial area 24,
`which defines the light passage site 13 for the irradiation of
`the light.
`The light irradiation means 7 and the detection means 8
`are carried by a printed circuit board 25 positioned between
`the walls of the housing 17. A recess 26 is provided in the
`fiber plate 16,
`through which connecting wires 27 are
`guided, which connect the detector contacts on the silicon
`layer 19 with the conductors of the printed circuit board 25.
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`5.893.364
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`5
`In the context of the invention it has been found that a
`mechanically stable construction of the optical unit is critical
`for the desired high measuring accuracy. Consequently a
`compact type of design is particularly preferred in which the
`following construction elements shown in FIG.2 are real-
`ized individually or in combination with one another:
`At least the detection sites, but preferably also the irra-
`diation sites, are provided in a single. common fiber
`plate 16.
`The mask 22 is connected firmly to the fiber plate. As an
`alternative to the coating mentioned above, a selec-
`tively black-tinted glass plate. which is bonded to the
`optical fiber plate 16 by mastic or by a hot melt process
`is also suitable as the mask and as the test-object-side
`seal of the fiber plate 16.
`The detectors are connected firmly and immovably to the
`detector-side surface 16a of thefiber plate, in particular
`by bonding or a similar permanent fixing method.
`The detectors 21 are arranged on a common semiconduc-
`tor substrate 19. Thereby an identical characteristic
`curve of the detection sensitivity is obtained. Bonding
`of the semiconductor plate to the fiber plate in addition
`improves the mechanical and optical stability.
`Three light-conducting elements 15 can be seen in FIG. 4
`in a view which is highly magnified and not to scale. Two
`light beams are shown diagrammatically, wherein the light
`beam 29 symbolizes the path of photons which emerge at an
`angle a of virtually 90°. referred to the interface 5, and
`therefore impinge on the walls 30 of the light-conducting
`elements 15 at an acute angle B, while the light beam 31
`leaves the interface 5 at a more acute angle a. so that the
`angle of incidence B of the photons on the wall 3 is greater
`in this case. In the invention the optical conditions of the
`light
`transmission in the light-conducting elements 15
`should be such that the:light is fully reflected at the walls of
`the light-conducting elements 15 down to very small angles
`of emergence & (i.e. up to the highest possible angles of
`incidence B of the light beams on the walls 30). This
`property is termed the numerical aperture NA: NA=n-sin B.
`In technical terms the optical aperture is determined—in the
`case ofthe rigid light-conducting elements used according to
`the invention—by the reflection properties at the elements’
`walls, which in turn depend on the ratio of the refractive
`indices at the wall and the possible existence of an additional
`reflective layer on the wall. Preferably the light-conducting
`elements have a numerical optical aperture of more than 0.5.
`The photons emerge from a strongly scattering test object
`6 isotropically (ie. uniformly distributed across a wide
`angular range) through the contact surface 5. As a result of
`the optical conditions prevailing in the invention, all these
`photonsoratleast a fraction thereof, which is constantin the
`long term arrive at the respective detector 21.
`The light-conducting elements of a light passage site
`conduct the light separately from one another, and are thus
`essentially insulated optically from one another. If the opti-
`cal insulation is incomplete, the measuring accuracy and
`reproducibility is affected, although perfectly good results
`are achieved with an optical crosstalk of less than 20%,
`whereas on the other hand an optical crosstalk of less than
`1% can be obtained without any difficulty even with the
`extremely close arrangement of rigid light-conducting ele-
`ments in an optical fiber plate.
`The optical insulation of the light-conducting elements 15
`is symbolized in FIG. 4 by gaps 32. In an actual fiber plate
`16 the light-conducting elements 15 are packed far more
`densely than shownin FIG.4. and the gaps 32 are therefore
`much smaller.
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`In the optical unit 39 shown in FIG. § which formsa part
`of a contact surface module and which is suitable in par-
`ticular for analytical investigations of human skin. an optical
`fiber plate 16 is sandwiched between two masks 40, 41.
`wherein both masks 40. 41 comprise at the same points of
`the surface of the fiber plate 16 (therefore in alignment with
`one another), transparent partial areas 23a, 23b, 23c for
`detectors 21@. 21d, 21c, and a transparent partial area 24 for
`the irradiation of light. The masks 40, 41 can consist of black
`ink which is applied by screen-printing. Particularly prefer-
`ably a photosensitive layer is used for the mask. in which the
`optical openings are produced by an exposure process (as
`with the manufacture of semiconductor boards). This
`method can be easily incorporated in the manufacturing
`process. No changeof the production tool is necessary after
`generating the mask layer. Therefore, precise assembly is
`facilitated.
`The use of two masks on both sides of the fiber plate 16
`is advantageous. The mask on the detector-side surface 16a
`of the fiber plate 16 can be generated with particular high
`precision and this method step can be incorporated in the
`manufacturing process as described. On the other hand a
`dark mask on the sample-side surface 16 of thefiber plate
`16 is often also advantageous—irrespective of the precise
`position of the light passage sites—in order to absorb light
`components which leave the sample surface between the
`irradiation and detection sites. Such a mask can be produced
`with slightly less precision and be applied for example by a
`printing method.
`In FIG. § the detector-side fiber plate 41 comprises an
`additional recess 42 for accommodatingthe electrical wiring
`for the connection between the detectors 21a, 21b. 21¢ and
`the measurementelectronics.
`In the embodiment shown in FIG. 5 the light irradiation
`means 7 are so constructed that light of a plurality of
`different wavelengths can be irradiated at a single point in
`the test object which is defined by the transparent point 24
`in the masks 40, 41. To this end four light-emitting diodes
`46 to 48 are arranged within an Ulbricht cylinder 44, which
`is closed in a downward direction (towards the fiber plate
`16) by a layer 45 silvered on its inside. The light emitting
`diodes radiate light of different wavelengths and are secured
`to a covering plate 50 closing the Ulbricht cylinder in an
`upward direction.
`Instead of the Ulbricht cylinder 44 another optical ele-
`ment can be used, which causes the light from the various
`light-emitting diodes 46 to 49 to impinge as isotropically as
`possible at the same point on the surface ofthefiber plate 16.
`An optical element of this kind is termed a “beam com-
`biner”. Preferably a beam-combiner element suitable for the
`invention should comprise an optical cavity whose walls
`reflect (diffusely or specularly), so that the light emerging
`from light transmitters which are attached at various points
`on the walls of the cavity is distributed isotropically in the
`cavity.
`The dimensionsof the cavity in relation to the maximum
`light exit distance (distance between the light exit points
`furthest from one another) of the light transmitters are
`important for a sufficiently isotropic light distribution. Pref-
`erably the minimum distance of the light transmitters from
`the light exit opening of the beam-combiner element(i.e.
`from the light entry opening of the assigned light passage
`site) should be three times as great and the minimum mean
`diameter of the cavity should be at least twice as great as the
`maximum light exit distance. The optical cavity of the
`beam-combiner element does not necessarily have to be
`empty. For example, a truncated-cone-shaped componentof
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`5,893,364
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`7
`a transparent plastics material is suitable, which forms a
`conical light conductor 51 that is silvered on its generated
`surface 52 in order to achieve a diffusion effect. A beam
`combiner of this kind is shown in FIG.6.
`The embodiment shown in FIG. 5 with one light passage
`site for the primary light and a plurality of light passage sites
`for the secondary light makes it possible to determine the
`reflection properties of a test object for several differenttest
`distances between the respective irradiation site of the
`primary light and the respective detection site of the sec-
`ondary light. This is advantageous in particular with inves-
`tigations in which not only the optical absorption behaviour
`(absorption coefficient 1,). but also the scattering behaviour
`of the test object (scattering coefficient 1,) is to be investi-
`gated. Such methods are described in the international patent
`applications WO 94/10901, WO 95/12348 and WO
`95/324 16. It can alternatively also be advantageous to work
`with a plurality of inradiation sites and only one detection
`site or with a combination of several irradiation and several
`detection sites.
`In the contact plate module shown in FIG. 7 the optical
`unit 39 comprises for example two beam combiners as part
`of the light irradiation means 7a. 7b. Two transparent areas
`24a, 24b are provided accordingly for the primary light on
`the underside ofthe fiber plate 16, which define two different
`irradiation sites on the skin surface. In addition five trans-
`parent areas 23 are provided for the detection. corresponding
`to five different detection sites on the skin surface.
`FIG. 7 shows furthermore a suitable structural arrange-
`ment in which the fiber plate 16 is located in a corresponding
`recess 54 in a skin contact plate 55, which preferably is made
`from metal or glass. Such an arrangement, in which only a
`part of the skin contactplate consists of an optical fiber plate,
`is advantageous with respect to the cost. For example, the
`optical unit 39 may be connected as shown to the skin
`contact plate 54 in a firm and stable manner by means of a
`holding plate 56 and screws 57.
`In the embodiment of FIG. 7 two light sources (light
`irradiation means 7a and 7b) are assembled together with a
`plurality of detectors to a commonoptical fiber plate 16. The
`invention allows configurations of this kind with a plurality
`of irradiation sites and a plurality of detection sites which are
`of particularly compact design and simultaneously excellent
`measuring accuracy. In this way a chessboard-type arrange-
`ment of many irradiation sites and detectionsites is possible
`with a relatively simple design.
`Such an embodiment is shown in FIGS. $ and 9 which
`also show further preferred embodiments which can be used
`individually or in combination.
`FIG, $ showsa cout-out of a sample contact plate 4 which
`consists of an optical fiber plate 16 and a silicon semi-
`conductor layer 19 which is bonded to fiber plate 16 by
`means of a layer 18 of index-adapted adhesive. As in FIG.
`2, detectors 21 are integrated into semi-conducting layer 19.
`Aplurality of detectors 21 (in this case 6x6 detectors having
`a surface area of 0.25~0.25 mm each) are arranged on the
`underside 19a of layer 19 in a chessboard-type arrangement
`having a dimension of 10 mm.
`In this embodiment also light-transmitters 20 are fixed to
`semi-conducting substrate 19, namely by bonding to its
`upper surface 19d. They are contacted by a wirebond-
`method and connected via thin layer leads 60 and contacts
`61 to the signal processing and evaluation unit2. In a similar
`manner as in the embodimentof FIG.5 and 6, a plurality of
`light-transmitters of different wavelengths—embodied as
`light-emitting diodes—are provided for each light passage
`site 13 of the primary light. These radiate the light essen-
`
`10
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`15
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`20
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`25
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`30
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`35
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`45
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`50
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`55
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`65
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`8
`irradiation is
`Isotropical
`tially sidewards and upwards.
`accomplished by means of a beam combiner element 62.
`The optical cavity of the beam combiner is in this case
`closed by a reflecting dome-shaped cover.
`At each light passage site 13 for the primary light, a light
`passage channel 63 between the surfaces of silicon layer 19
`is provided via which the primary light travels to the light
`passage site 13. The inner surface of channel 63 is light-
`reflecting by means of a metallization. Alternatively. also a
`light-guiding rod which is inserted into a bore of a silicon
`layer could be used. In this case, the inner side of the bore
`should have a light-absorbing coating.
`A further special feature of the embodiment shownrefers
`to the fact that at each light passage site a surface-light
`barrier 65 is provided. It is formed by an optical locking
`ditch. This is a ring-shaped groove which is provided (for
`example by engraving) in the upper surface offiber plate 16,
`the depression being preferably filled with an optically
`absorbing substance. Thereby. optical cross-talk of the pri-
`mary light at the surface of fiber plate 16 is eliminated.
`With such optical light barriers 65 no mask on the upper
`surface of fiber plate 16 is necessary whereas on the skin-
`side of fiber plate 16 a mask 46 should preferably be present.
`As a further means for minimizing any remaining optical
`cross-talk inside fiber plate 16, a jacket 68 surrounding light
`passage site 13 and consisting of an absorbing substance is
`provided which perferably has a cylindrical shape. For |
`example, during the production of fiber plate 16, glass fibers
`of black color can be incorporated to form the jacket surface
`surrounding the light passagesite.
`We claim:
`
`1. An apparatusfor light transport measurements on a test
`object for generating medical analysis data on a concentra-
`tion of an analyte in the test object. said apparatus compris-
`ing:
`a measuring head, said measuring head including a con-
`tact surface for contacting an interface of the test
`object;
`at least one light irradiation means connected to the
`measuring head for irradiating primary light into the
`test object through the contact surface and the interface,
`said irradiation means comprising a light transmitter;
`at least one detection means connected to the measuring
`head for detecting secondary light emerging from the
`test object through theinterface and the contact surface,
`said detection means comprising a light receiver; and
`a signal processing unit connected to the detection means
`for processing a signal which is output by the detection
`means to yield an analytical result, wherein said ana-
`lytical result corresponds to the concentration of the
`analyte in the test object,
`wherein said contact surface includes at least one opti-
`cally transparent primary light passage means for con-
`ducting light therethrough from said light transmitter to
`which it is optically connected, and at least one opti-
`cally transparent secondary light passage means for
`conducting light therethrough to said light receiver to
`which it is optically connected, wherein a size and
`position of a site on the int