JP2010054392A - Light guiding apparatus for spectrally measuring small quantity of liquid - Google Patents

Abstract

[PROBLEMS] To realize a micro liquid crystal measuring apparatus having a simple structure capable of performing highly sensitive spectroscopic measurement for a sample solution having a refractive index lower than that of a transparent substrate flowing in a channel groove formed on a transparent substrate. .
A flow path groove 2 that is a flow path of a sample solution to be measured formed on a surface of a transparent substrate 1 and reflection grooves 3 and 4 formed on both sides of the flow path groove in parallel with the flow path groove. The material of the transparent substrate 1 has a refractive index larger than the refractive index of the sample solution, and the light flux of the detection light that has exited from the light source 5 and entered from the side surface of the transparent substrate 1 Is repeatedly reflected by the inner wall surface 6 of the reflection grooves 3 and 4, proceeds at least two times while crossing the flow channel groove 2, and is guided to the detector 12.
[Selection] Figure 1

Description

  The present invention relates to an apparatus for performing spectroscopic measurement on a very small amount of a liquid sample, and more specifically, high-sensitivity spectroscopy without performing surface treatment of the channel on a very small amount of liquid sample flowing through the microchannel. The present invention relates to a measurement apparatus that realizes measurement.

  In recent years, there has been an increasing need for highly sensitive optical measurement of a minute amount of liquid. One example is environmental analysis measurement, and it is necessary to spectroscopically measure a trace chemical substance contained in a sample liquid such as an aqueous solution with high sensitivity. Microanalysis is also required for measurement of biologically relevant chemical substances such as proteins and DNA. This is because it is difficult to secure the sample amount, and the test reagent used for the sample processing is expensive, and an increase in the necessary sample amount causes an increase in measurement cost.

  A microfluidic device is attracting attention as a system for handling such a minute amount of liquid. Here, the sample solution flowing through the minute groove is analyzed. Realization of highly sensitive spectroscopic measurement of the liquid in the microchannel is desired. As a method of spectroscopic measurement, a highly sensitive fluorescence method is widely used.

  However, in the fluorescence method, the detectable substance is limited to a fluorescent substance. The absorption method for measuring the absorbance is not limited to the measurement target, but is less sensitive than the fluorescence method. However, the absorption method is superior to the fluorescence method in that the substance to be measured is not limited to a fluorescent substance and the absorbance is proportional to the substance concentration, so a method for measuring with high sensitivity is required. .

  Specific means for performing spectroscopic measurement based on the absorbance of the liquid inside the microchannel and the problems that have been proposed will be further described below.

(1) Measurement of one-time transmission with respect to a microchannel When performing an analysis by absorbance using light crossing the microchannel, the absorbance is proportional to the solution concentration or the optical path length because it follows the Beer-Lambert rule. The depth of the microchannel is usually about 50 to 100 micrometers. Since the optical path length becomes very short, there is a problem that sufficient sensitivity cannot be obtained.

(2) Measurement using a waveguide system with a liquid flowing in the microchannel as a core If a light is passed through the channel in the direction of the channel, a sufficient optical path length is secured. However, the depth of the microchannel is usually about 50 to 100 micrometers, and it is practically impossible to transmit light in this size by converting it into parallel rays. Therefore, it is necessary to use a waveguide form similar to an optical fiber. Since this waveguide state is realized only when the refractive index of the liquid is higher than the refractive index of the base material forming the flow path, the combination of the base material and the solution is limited.

  The refractive index of the most widely used aqueous solution sample is about n = 1.33, whereas the refractive index of glass often used as a base material for forming a microchannel is n> 1.4. The combination cannot create a guided state. The biggest problem with this method is that it cannot be adapted to the most necessary combination.

(3) Measurement by a liquid core waveguide system in which the walls of the flow path are coated with a metal reflection layer or a low refractive index material A metal thin film that becomes a reflection layer on the surface of the groove structure (see Patent Document 1 and Patent Document 2) Alternatively, by forming a thin film of a medium having a refractive index smaller than that of water (see Non-Patent Document 1), even when an aqueous solution having a low refractive index is used as a sample solution, the waveguide having the liquid inside the groove as a core is used. Can make a state. Accordingly, a means for measuring by a liquid core waveguide system in which the walls of the flow path are coated with a metal reflection layer or a low refractive index material is also known.

  However, it is technically difficult to form a thin and uniform coating layer inside the minute groove, and there is a problem that the coating is likely to be peeled off by repeated use.

(4) Measurement by ARGOW system When a liquid sample with a low refractive index has a micro-groove structure without a surface reflection layer made of a high refractive index member such as glass, it is reflected by the end face of the high refractive index member. It is the non-resonant guided optical wave proposed by Schmidt et al. (See Non-Patent Document 1) that utilizes the fact that the traveling light beam repeatedly crosses the micro-groove region.

  This method uses total reflection of light on the upper and lower surfaces of two glass plates, which are base materials for forming a groove structure, and the number of times light crosses the microgroove through which the sample circulates depends on the thickness of the glass used. It is prescribed by Since the glass as a base material is extremely difficult to handle, it is necessary to have a thickness of 0.5 mm, preferably 1 mm or more. The thicker the thickness, the lower the number of times light passes through the liquid.

(5) Other Means As a spectroscopic device that has been used conventionally, there is a waveguide type spectroscopic device that uses an evanescent wave component (see Patent Document 3). In this method, when detection light travels while totally reflecting inside the high refractive index medium, measurement is performed using light that oozes about one wavelength outward from the outer edge of the high refractive index medium.

  Since the substance to be measured exists outside the high refractive index medium through which light is guided, the increase of the optical path length due to the waveguide does not contribute to the improvement of measurement sensitivity. This method is for performing spectroscopic analysis on a substance existing outside the high refractive index medium and within a distance of about one wavelength of the detection light, and measures a measurement target substance uniformly distributed in a solution sample. High sensitivity cannot be expected when performing.

  In addition, the waveguide by the high refractive index medium is also used for detecting with high sensitivity by selectively introducing fluorescence or scattered light from the measurement target substance immobilized on the surface (Patent Document). 4). These means are different in measurement object from the present invention aiming at performing high-sensitivity spectroscopic measurement of chemical components uniformly distributed in the solution.

JP 2006-53078 A See JP2008-70316. JP2007-101471A JP-A-2005-140682 See Takiguchi et al., Analytical Science, Vol. 22, No. 7, pp. 1017. Schmidt et al., Applied Physics Letters, 88, 15, 151109 / 1-3

  The object of the present invention is to solve the above-mentioned problems of the conventional means of spectroscopic measurement, and it flows through a channel groove formed in a transparent substrate and has a higher refractive index than that of the transparent substrate. It is intended to realize a micro liquid crystal measuring device having a simple structure that enables sensitive spectroscopic measurement.

  In order to solve the above-mentioned problems, the present invention forms a flow channel that is a flow path of a sample solution to be measured formed on the surface of a transparent substrate, and is formed on both sides of the flow channel in parallel to the flow channel. A waveguide micro-volume liquid spectroscopic measurement device having a reflective groove, wherein the material of the transparent substrate has a refractive index larger than the refractive index of the sample solution, and is incident from the side surface of the transparent substrate. The detected light beam is repeatedly reflected across the flow path groove and totally reflected by the inner wall surface of the reflection groove, and travels through the flow path groove at least twice and is guided to the detector. Provided is a waveguide type micro liquid crystal spectrometer.

  The transparent substrate is preferably formed of a transparent hard substrate formed of glass, calcium fluoride, silicon carbide, sapphire, alumina, crystal or diamond.

  The reflection grooves formed on both sides of the channel groove are preferably a single continuous groove structure or a groove structure composed of a plurality of grooves formed in a line on a straight line.

  The depth of the flow channel grooves and the reflection grooves is 10 to 1000 micrometers, and more preferably 150 to 1000 micrometers.

  The groove width of the channel groove is preferably 5 to 1000 micrometers.

  The groove width of the reflection groove is 1 micrometer or more, more preferably 1 to 50 micrometers. It is preferable that the reflection groove is arranged at a position separated by 10 to 1000 micrometers in parallel with the flow path groove.

The flow channel groove and the reflection groove have a strength range of 0.01 J from the back surface side of the transparent material to be processed by bringing a fluid substance having strong absorption at the laser wavelength into contact with the surface of the transparent material to be processed as the substrate material. / Cm ² / pulse to 100 J / cm ² / pulse is preferably produced by irradiating laser light whose shape is adjusted with a mask.

  According to the waveguide type micro liquid crystal spectrometer according to the present invention, in order to perform spectroscopic measurement on a sample solution having a lower refractive index than that of the transparent substrate flowing in the channel groove formed in the transparent substrate, the channel groove By forming a reflection groove as a reflection plate on both sides of the substrate, a plurality of detection light beams can cross the sample solution and be reflected by the reflection groove without forming a thin film as a reflection layer on the inner wall surface of the reflection groove. Since it is configured to generate a guided state that is repeated a number of times, highly sensitive spectroscopic measurement is possible.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a waveguide type micro liquid crystal spectrometer according to the present invention will be described below with reference to the drawings based on examples.

(Overview)
The waveguide type micro liquid crystal measurement device according to the present invention is a device that enables spectroscopic measurement of a sample solution flowing in a channel groove formed in a transparent substrate, and the transparent substrate material is a refractive index of the sample solution. Groove structures (hereinafter referred to as “channel grooves”) that serve as spectroscopic measurement targets and flow channels through which a liquid sample to be subjected to spectroscopic measurement flows (hereinafter referred to as “channel grooves”). , Referred to as “reflection groove”), a structure in which a waveguide state is formed to increase the sensitivity of spectroscopic measurement without forming a surface reflection layer on the wall surface in the reflection groove. It is a feature.

  Here, the waveguide state means that the detection light beam incident from the side surface of the transparent substrate is repeatedly reflected across the flow channel groove and totally reflected by the inner wall surface of the reflection groove, at least twice. A state of progressing while crossing.

  When quartz glass (refractive index: 1.46) is used as the material (base material) of the transparent substrate, by making the reflection groove hollow, the incident light flux with respect to the reflection groove exceeds 43.23 ° which is a critical angle. Total reflection. On the other hand, the critical angle when the aqueous solution sample is contained in the channel groove is 65.64 °, and the light beam passes through the solution unless the incident angle exceeds this angle.

  By setting the angle at which the incident light beam from the side surface of the transparent substrate is incident on the flow channel groove and the reflection groove inside the transparent substrate to an intermediate between the critical angle 43.23 ° and the critical angle 65.64 °. The light beam is totally reflected by the inner wall surface of the reflection groove, travels many times across the channel groove through which the sample solution flows, and is guided to the detector. As described above, the sample solution crosses the flow channel groove a plurality of times, the substantial optical path length increases, and as a result, the measurement sensitivity is improved.

  In this waveguide-type micro liquid crystal spectrometer, the arrangement of the flow channel grooves and the reflection grooves can be freely set within a range in which damage during processing does not occur, and is not limited by the thickness of the glass plate. Therefore, it is possible to increase the number of times of traversing the flow path and to improve sensitivity without making handling extremely difficult.

  FIGS. 1A and 1B are a plan view and a cross-sectional view taken along line AA of the waveguide type micro liquid crystal spectrometer of the present invention. This guided microscopic liquid spectroscopic measuring device (hereinafter also simply referred to as “spectrometric measuring device”) is a liquid sample to be subjected to spectroscopic measurement on the surface of a transparent hard transparent substrate 1 formed of quartz glass or the like. It is characterized in that it has a flow channel 2 as a flow channel for flowing the water, and reflection grooves 3 and 4 that are arranged on both sides of the flow channel 2 and are formed in parallel with the flow channel 2.

  As shown in FIG. 2, the light beam of the detection light used for the spectroscopic measurement is incident through the side surface of the transparent substrate 1 from the oblique rear side of the transparent substrate 1 of the spectroscopic measurement device and passes through the flow channel groove 2. At the same time, the light is repeatedly reflected by the inner wall surfaces 6 of the reflection grooves 3 and 4 on both sides to form a waveguide state. Hereinafter, the configuration of each part of the spectrometer of the present invention will be described in detail.

(Transparent substrate)
As the transparent substrate 1, a transparent hard transparent substrate of general glass, calcium fluoride, silicon carbide, sapphire, alumina, crystal, or diamond used for optical applications such as borosilicate glass can be used in addition to quartz glass. The transparent substrate 1 material is made of a material having a refractive index larger than that of the sample solution. In addition to borosilicate glass, general glass includes borosilicate crown glass, white plate glass, soda lime glass, lead glass, and the like.

(Flow channel groove)
The flow channel groove 2 for introducing and flowing the liquid sample is formed as a micro-order groove, that is, a micro-groove in terms of width and depth. When the width of the channel groove 2 becomes narrower, it becomes difficult to introduce a liquid sample, and the optical path length for measurement decreases, and when the width becomes wider, the volume of the groove increases to increase the required amount of the liquid sample necessary for spectroscopy. To do. Therefore, the groove width is preferably 5 to 1000 micrometers, and more preferably 50 to 500 micrometers.

  The groove depth can be 10 to 1000 micrometers, but it is necessary to have a depth sufficient for the light beam of the detection light to pass through, so it is in the range of 150 to 1000 micrometers. It is preferable. Actually, a flow channel groove 2 having a width of 50 micrometers was produced by exposing a mask having an opening of 8.00 × 0.40 millimeters with a reduction of 1/8. An irradiation area having a length of 1.00 millimeters and a width of 50 micrometers is formed on the surface of the quartz glass.

  While irradiating the laser with a pulse repetition frequency of 80 health, the stage was reciprocated in the long axis direction of the groove in the range of 10.3 millimeters at a speed of 100 micrometers per second. The machining position was adjusted to be within the depth of focus by moving the 6.5 micrometer stage with respect to the focal direction for each stroke.

  In order to prevent the generation of cracks, the first five reciprocations of the flow channel groove 2 are adjusted to a laser irradiation intensity (fluence) of 1.0 joule per square centimeter, and then the laser irradiation intensity is set to 0.00 per square centimeter. Reduced to 9 joules and made 8 more round trips. By this operation, a channel groove 2 having a length of 10.3 millimeters, a width of 50 micrometers, and a depth of 200 micrometers was produced. However, each 1-mm part of the both ends of the flow-path groove | channel 2 is an inclined surface. The volume of the channel groove 2 is 93 nanoliters.

(Reflection groove)
The reflection grooves 3 and 4 formed on both sides of the channel groove 2 are parallel to each other and each have a vertical inner wall surface 6 excellent in smoothness. Thus, since the reflective grooves 3 and 4 have the vertical inner wall surface 6 excellent in smoothness, loss due to light scattering can be suppressed. The surface roughness of the inner wall surface 6 is preferably ¼ or less of the wavelength of the detection light, for example, 100 nanometers or less. Furthermore, it is necessary to have a depth sufficient for the light beam of the detection light to pass and reflect. The depth of the reflective grooves 3 and 4 is in the range of 10 to 1000 micrometers, more preferably 150 to 1000 micrometers.

The reflection grooves 3 and 4 that satisfy these conditions can be produced by a known laser-induced back surface wet processing method (see Japanese Patent No. 3012926). According to this processing method, a fluid substance having strong absorption at the laser wavelength is brought into contact with the surface of the transparent material to be processed, and the intensity range from the back surface side of the transparent material to be processed is 0.01 J / cm ² / pulse to 100 J. A fine structure such as a groove can be produced by irradiating laser light whose shape is adjusted with a mask up to / cm ² / pulse.

  Further, in this processing method, by controlling the stage position so that the processing surface is always within the focal depth of the lens of the irradiation optical system during laser irradiation, for example, the width is 7 micrometers and the depth is 420 micrometers. High aspect ratio reflective grooves 3 and 4 can be fabricated (see Kawaguchi et al., Jpn. J. Appl. Phys. 44 (2005) L176.).

  The reflection grooves 3 and 4 having a high aspect ratio thus obtained have a smooth inner wall surface 6 with a surface roughness of 100 nanometers or less, and can suppress loss due to light scattering.

  The reflection grooves 3 and 4 totally reflect the detection light. It is preferable that the width of each of the reflection grooves 3 and 4 is not less than twice the detection wavelength so that the evanescent light generated at this time reaches the opposing wall surfaces and no loss due to absorption or scattering occurs. Therefore, it is preferable that the reflection grooves 3 and 4 have a groove width of 1 micrometer or more. Further, the increase in the groove width makes the surrounding structure thin, and is liable to cause breakage during processing or installation of the upper plate 7 described later. Furthermore, the removal volume during processing increases, and more energy is required for processing. Therefore, the groove width of the reflection grooves 3 and 4 is preferably in the range of 1 to 50 micrometers.

  Further, the groove depth of the reflection grooves 3 and 4 needs to be deep enough to reflect the light beam of the detection light, and is therefore 10 to 1000 micrometers, more preferably 150 to 1000 micrometers. It is preferable that the depth is in the range of meters and the depth is approximately the same as that of the channel groove 2.

  As described above, the reflection grooves 3 and 4 are formed in parallel with the flow path groove 2 and at a position close to the flow path groove 2 within a range in which damage during processing does not occur. The number of times the light beam of the detection light crosses the flow path groove 2 can be increased by the reflection grooves 3 and 4 approaching the central flow path groove 2, but between the flow path groove 2 and the reflection grooves 3 and 4. The formed wall structure 8 becomes thin and easily breaks during processing or when the upper plate 7 is installed.

  Therefore, the distance between the reflective grooves 3 and 4 is in the range of 10 to 1000 micrometers, and more preferably 100 to 500 micrometers. This distance may be changed from the detection light introducing portion (side surface of the substrate) as the wave guides.

  Moreover, the reflection grooves 3 and 4 are not a single continuous groove structure (single groove) but a plurality of shorter grooves 9 that are about 1/10 of the width of the detection light in order to prevent breakage. You may produce so that it may arrange in a line on a straight line at intervals of about micrometer.

  The reflection grooves 3 and 4 including the plurality of grooves 9 will be described below. When the reflective grooves 3 and 4 were manufactured, scanning was not performed in a straight line in the groove direction, and a plurality of grooves 9 having a length of 1 millimeter were formed on the straight line at an interval of 50 micrometers. Each groove 9 was produced with a width of 10 micrometers by exposing a mask having an opening of 8.000 × 0.080 millimeters with a reduction of 1/8.

  The plurality of grooves 9 were produced by performing irradiation for 257 seconds at a pulse repetition frequency of 80 Hz and an irradiation fluence of 1.0 joule, respectively. During irradiation, the processing position was moved at a speed of 0.6 micrometers per second as the processing progressed. By repeating this operation 13 times, a total of 13 grooves were produced on both sides of the flow channel groove 2.

  In this way, the reflection grooves 3 and 4 in which the plurality of grooves 9 are arranged in a line on a straight line are formed on both sides of the flow path groove 2 so as to be parallel to each other at positions separated by 500 micrometers. The depth of each groove 9 constituting the obtained reflection grooves 3 and 4 was 200 micrometers.

(Upper plate)
As shown in FIGS. 3 (a) and 3 (b), the upper plate 7 is placed on the flow path groove 2 and the transparent substrate 1 having reflection grooves 3 and 4 formed on the surfaces thereof on both sides. Has been. The upper plate 7 is a polydimethylsiloxane (PDMS) plate having a thickness of 1 millimeter. In the upper plate 7, through holes 10 and 11 having a diameter of 0.75 mm are formed at two positions with a gap of 9 mm. The through holes 10 and 11 formed in the upper plate 7 are entrances and exits for the sample solution, and are formed so as to be positioned at both ends of the flow channel groove 2.

  As for the upper plate 7, a PDMS plate can be used as described above, or quartz glass or general glass can be used and bonded using a hydrofluoric acid treatment method or a heat fusion method. In this device, the upper plate 7 is not directly related to the wave guide. Therefore, even a medium having a higher refractive index than that of the solution sample can be used without any problem.

  The through holes 10 and 11 formed in the PDMS plate are used as sample solution introduction and discharge ports as shown in FIG. When the sample solution is dropped onto one through hole, the sample solution is filled into the flow channel groove 2 (micro groove) by capillary action, and is ready for spectroscopic analysis by waveguide. A PEEK tube or a terfun tube can be fixed on the through-hole and used for sample circulation.

  Further, instead of passing through the through holes 10 and 11 of the upper plate 7, a micro flow channel (not shown) for further supplying a sample solution is formed on the transparent substrate 1, and the sample is passed through the sample distribution groove through the micro flow channel. It is also possible to supply In this case, the depth of the groove for supplying the sample is set to 50 micrometers or less, and interference with the light beam to be guided can be prevented by using a sufficiently shallow groove as compared with the groove for spectroscopic measurement.

  Using the spectroscopic device of the above example, an ethanol solution of rhodamine 6G was introduced into the microchannel, and a green laser beam having a wavelength of 532 nanometers was used as the light source 5 to confirm the state of the waveguide by the fluorescence. .

  As the light source 5 for the spectroscopic analysis, any known light source 5 can be used. For example, light obtained by making various lamp lights collimated into thin light beams by slits, laser light, or light from a light emitting diode. Can be used as the light source 5.

  As for the detector 12, any measuring device capable of sensing light can be used for detecting light, but generally a photodiode, a linear CCD sensor, a CMOS camera, a CCD camera, or the like is preferably used. .

  As described above, the best mode of the waveguide-type micro liquid crystal spectrometer according to the present invention has been described based on the embodiments. However, the present invention is not limited to such embodiments, and It goes without saying that there are various embodiments within the technical scope.

  Since the waveguide type micro liquid crystal spectrometer according to the present invention has the above-described configuration, it is an apparatus that performs high-sensitivity spectroscopic measurement for micro liquids whose needs have been increasing in recent years. Alternatively, it is used for measurement of biologically related chemical substances such as proteins and DNA. It can utilize as a detection part of a liquid chromatography regarding such an analysis. It is also possible to incorporate such analysis operations on the same transparent substrate as an analysis site in a microfluidic device in which one plate is integrated.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the waveguide type micro-volume liquid-spectrometer apparatus Example based on this invention, (a) is a top view of the board | substrate with which the flow-path groove | channel and the reflective groove were formed, (b) is sectional drawing. is there. It is a top view explaining the effect | action (waveguide state) of the Example of this invention. It is a figure which shows the Example of this invention which installed the upper board, (a) is a top view, (b) is sectional drawing. It is a figure explaining the effect | action of the Example of this invention which installed the upper board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Channel groove 3, 4 Reflection groove 5 Light source 6 Inner wall surface of reflection groove 7 Upper plate 8 Wall structure between channel groove and reflection groove 9 Plural grooves 10, 11 upper plate constituting reflection groove Through-hole formed in the wall (entrance to the channel groove)
12 Detector

Claims (7)

A waveguide type comprising a channel groove that is a channel of a sample solution to be measured formed on the surface of a transparent substrate, and reflection grooves formed in parallel to the channel groove on both sides of the channel groove A micro-volume liquid spectrometer,
The material of the transparent substrate has a refractive index larger than the refractive index of the sample solution,
The detection light beam incident from the side surface of the transparent substrate is repeatedly reflected across the flow path groove and totally reflected by the inner wall surface of the reflection groove, and proceeds to the detector at least twice while crossing the flow path groove. A guided-wave micro liquid crystal spectrometer characterized by being guided.   2. The waveguide type micro liquid crystal spectrometer according to claim 1, wherein the transparent substrate is a transparent hard substrate formed of glass, calcium fluoride, silicon carbide, sapphire, alumina, crystal or diamond.   Each of the reflection grooves formed on both sides of the flow channel groove is a continuous groove structure or a groove structure composed of a plurality of grooves formed on a straight line at intervals. The waveguide type micro liquid crystal spectrometer according to claim 1 or 2.   The waveguide microscopic liquid spectrometer according to any one of claims 1 to 3, wherein each of the flow channel groove and the reflection groove has a depth of 10 to 1000 micrometers.   5. The waveguide type micro liquid crystal spectrometer according to claim 1, wherein the groove width of the flow channel is 5 to 1000 micrometers.   The waveguide according to any one of claims 1 to 5, wherein the reflection groove having a groove width of 1 micrometer or more is disposed at a position separated by 10 to 1000 micrometers in parallel with the flow path groove. Type micro liquid crystal spectrometer. The flow channel groove and the reflection groove have a strength range of 0.01 J from the back surface side of the transparent material to be processed by bringing a fluid substance having strong absorption at the laser wavelength into contact with the surface of the transparent material to be processed as the substrate material. ^{/ cm 2 / pulse~100J / cm 2} / waveguide type according to claim 1, characterized in that it is produced by irradiating a laser beam shape is adjusted by the mask pulse fine Small liquid spectroscopic measurement device.