Abstract:
Provided are light absorption spectrum correction devices, methods of manufacturing the light absorption spectrum correction devices, and methods of correcting a light absorption spectrum. The light absorption spectrum correction device includes: a light source configured to emit light; an attenuated total reflectance (ATR) crystal layer configured to contact a subject and provide an optical passage along which the light emitted from the light source travels to the subject; a pressure sensor configured to detect a contact pressure applied to the ATR crystal layer by the subject; a spectrum detector and analyzer configured to detect light emitted from the ATR crystal layer, form a light absorption spectrum based on the detected light, and determine an intensity of the light emitted from the ATR crystal layer; and a spectrum correction device configured to correct the light absorption spectrum based on the contact pressure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Korean Patent Application No. 10-2014-0130326, filed on Sep. 29, 2014 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Apparatuses and methods consistent with exemplary embodiments relate to processing data obtained from a body under examination, and more particularly, to devices for correcting light absorption spectrum of a body under examination, methods of manufacturing the devices, and methods of correcting light absorption spectrums. 
         [0004]    2. Description of the Related Art 
         [0005]    Attenuated total reflectance (ATR) crystals are used in spectrum analysis using light in an infrared band. The ATR crystals may be utilized for measuring a biosignal in a non-invasive manner. 
         [0006]    In order to measure a biosignal in a non-invasive manner, a subject under medical examination may be brought into contact with ATR crystals. At this point, a contact pressure between the ATR crystals and the subject may be variable, and accordingly, the intensity of a light absorption spectrum with respect to the subject may also be variable. In the case of a general bench-top equipment, a light absorption spectrum can be measured by measuring a liquid or by applying a constant pressure to the subject. However, when the subject is a biological body (for example, a human body), it is difficult to maintain a constant contact pressure on the body. 
       SUMMARY 
       [0007]    One or more exemplary embodiments provide spectrum correction devices configured to reduce a variation of light absorption spectrum with a change in a contact pressure with respect to a body under examination. 
         [0008]    Further, one or more exemplary embodiments provide methods of manufacturing the spectrum correction devices. 
         [0009]    Further still, one or more exemplary embodiments provide methods of correcting a light absorption spectrum by using the spectrum correction devices. 
         [0010]    According to an aspect of an exemplary embodiment, there is provided a light absorption spectrum correction device including: a light source configured to emit light; an attenuated total reflectance (ATR) crystal layer configured to contact a subject and provide an optical passage along which the light emitted by the light source travels to the subject; a pressure sensor configured to detect a contact pressure applied to the ATR crystal layer by the subject; a spectrum detector and analyzer configured to detect light emitted from the ATR crystal layer, form a light absorption spectrum based on the detected light, and determine an intensity of the light emitted from the ATR crystal layer; and a spectrum correction device configured to correct the light absorption spectrum based on the contact pressure. 
         [0011]    The spectrum detector and analyzer is further configured to form the light absorption spectrum based on an intensity and a wavelength of the detected light. 
         [0012]    In the light absorption spectrum correction device, the spectrum correction device may be connected to the pressure sensor and the spectrum detector and analyzer. 
         [0013]    The light source, the pressure sensor, and the spectrum detector and analyzer may be provided on a same substrate. 
         [0014]    The pressure sensor may be provided on a substrate, and the light source and the spectrum detector and analyzer may be provided above the substrate. 
         [0015]    The ATR crystal layer may be disposed on the pressure sensor and in contact with the pressure sensor. 
         [0016]    The light absorption spectrum correction device may further include a material layer disposed between the ATR crystal layer and the pressure sensor, wherein the material layer has a refractive index less than that of the ATR crystal layer. 
         [0017]    The spectrum correction device may be only connected to the substrate. 
         [0018]    The spectrum correction device may include a data-base of contact pressure-light intensities. 
         [0019]    The light absorption spectrum correction device may further include a pressure arm configured to apply force to the subject, wherein the contact pressure corresponds to the force applied to the subject. 
         [0020]    According to an another aspect of an exemplary embodiment, there is provided a method of manufacturing a light absorption spectrum correction device including: forming an ATR measuring apparatus by disposing a pressure sensor, a light source, an ATR crystal layer, and a spectrum detector and analyzer on a substrate; and connecting a spectrum correction device to the ATR measuring apparatus. 
         [0021]    The pressure sensor, the light source, and the spectrum detector and analyzer may be formed on a same plane. In this case, the spectrum correction device may be connected to the substrate only. 
         [0022]    The light source and the spectrum detector and analyzer may be formed on a different plane from the pressure sensor. At this point, the spectrum correction device may be connected to the substrate and the spectrum detector and analyzer. 
         [0023]    According to an another aspect of an exemplary embodiment, there is provided a method of correcting a light absorption spectrum in a light absorption spectrum correction device including: measuring a contact pressure applied onto the device by a subject; measuring a light absorption spectrum with respect to the body under examination; and correcting the light absorption spectrum based on the measured contact pressure and the light absorption spectrum. 
         [0024]    The measuring of the light absorption spectrum may further include: recognizing that an ATR crystal layer is in contact with the subject; radiating light onto the subject through the ATR crystal layer; and detecting light emitted from the ATR crystal layer. 
         [0025]    The correcting of the light absorption spectrum may include: obtaining base data from the measured contact pressure and the light absorption spectrum; comparing the base data with a reference region of a graph that indicates a contact pressure-light intensity with respect to the subject; correcting the base data to be within the reference region in response to the base data being outside the reference region; and correcting the light absorption spectrum according to the corrected base data. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The above and/or other aspects will be more apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings, in which: 
           [0027]      FIG. 1  is a cross-sectional view of a light absorption spectrum correction device according to an exemplary embodiment; 
           [0028]      FIG. 2  is a graph showing an example of relationship between a contact pressure and light intensity; 
           [0029]      FIG. 3  is a cross-sectional view of a light absorption spectrum correction device according to another exemplary embodimentt; 
           [0030]      FIG. 4  is a cross-sectional view of a light absorption spectrum correction device according to another exemplary embodiment; 
           [0031]      FIG. 5  is a cross-sectional view of a light absorption spectrum correction device according to another exemplary embodiment; 
           [0032]      FIGS. 6 through 8  are cross-sectional views for explaining a method of manufacturing a spectrum correction device according to an exemplary embodiment; 
           [0033]      FIGS. 9 and 10  are cross-sectional views for explaining a method of manufacturing a spectrum correction device according to another exemplary embodiment 
           [0034]      FIG. 11  is a cross-sectional view for explaining another coupling method of an ATR crystal layer in the method of  FIG. 10 ; 
           [0035]      FIGS. 12 ,  13 ,  15 , and  16  are cross-sectional views for explaining a method of manufacturing a spectrum correction device according to another exemplary embodiment; 
           [0036]      FIG. 14  is a plan view of the spectrum correction device of  FIG. 13 ; 
           [0037]      FIG. 17  is a flow-chart for explaining a method of correcting light absorption spectrum according to an exemplary embodiment; and 
           [0038]      FIGS. 18 ,  19  and  20  are graphs showing methods of correcting a light absorption spectrum. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. 
         [0040]    First, a light absorption spectrum correction device (hereinafter, a correction device) according to an exemplary embodiment will be described. 
         [0041]      FIG. 1  is a cross-sectional view of a correction device according to an exemplary embodiment. 
         [0042]    As shown in  FIG. 1 , a pressure sensor  42  is provided on a substrate  40 . The substrate  40  may transmit a signal generated from the pressure sensor  42 . The substrate  40  may be a substrate on which an element (for example, a wire) for transmitting the signal is formed. The pressure sensor  42  is covered by a first material layer  44 . The first material layer  44  has an optical refractive index less than that of an attenuated total reflectance (ATR) crystal layer  50 . The first material layer  44  has a flat upper surface. The first material layer  44  may have a certain degree of elasticity. A light source  46  and a spectrum detector and analyzer  48  are formed on the first material layer  44 . The light source  46  and the spectrum detector and analyzer  48  are separated from each other. Since light emitted from the light source  46  reaches the spectrum detector and analyzer  48  through the ATR crystal layer  50 , the light source  46  and the spectrum detector and analyzer  48  may be disposed in consideration of the light passage. The pressure sensor  42  may be disposed between the light source  46  and the spectrum detector and analyzer  48 . The light source  46  and the spectrum detector and analyzer  48  are horizontally separated from the pressure sensor  42 . The light source  46  may be a light source generating light of various wavelengths (for example, an infrared ray), but is not limited thereto. The spectrum detector and analyzer  48  detects and analyzes a light absorption spectrum with respect to a subject  54  under examination by detecting light emitting from the ATR crystal layer  50 . As a result, a data of light intensity at a specific location (or wavelength) may be obtained from a detected light absorption spectrum. Information obtained in this way is transmitted to a spectrum correction device  56 . The subject  54  under examination may be a part of a human subject, for example, a skin, a finger, or a toe. 
         [0043]    The ATR crystal layer  50  may be disposed between the light source  46  and the spectrum detector and analyzer  48 . A bottom surface of the ATR crystal layer  50  contacts the upper surface of the first material layer  44 . Accordingly, a pressure applied to the ATR crystal layer  50  is transmitted to the pressure sensor  42  through the first material layer  44 . The surface of the ATR crystal layer  50  that contacts the subject  54  may be at a higher level than the light source  46  and the spectrum detector and analyzer  48 . The ATR crystal layer  50  may be fixed in a case  52 . The case  52  covers the light source  46  and the spectrum detector and analyzer  48  while fixing the ATR crystal layer  50 . The subject  54  may be brought into contact with an outer surface of the ATR crystal layer  50 . Light emitted from the light source  46  progresses through the ATR crystal layer  50  while being totally reflected in the ATR crystal layer  50 . Therefore, light that enters the ATR crystal layer  50  from the light source  46  may be incident at an angle that causes a total reflection in the ATR crystal layer  50 . The condition for total reflection when the subject  54  is on the ATR crystal layer  50  may vary from the condition for total reflection when the subject  54  is not on the ATR crystal layer  50 . Accordingly, when the subject  54  is on the ATR crystal layer  50 , a portion of the light incident on the upper surface of the ATR crystal layer  50  is reflected and other portion may be absorbed by the subject  54 . When a pressure (hereinafter, contact pressure) being applied to the ATR crystal  50  by the subject  54  is changed, properties of light absorbed by the subject  54  change. The properties of the absorbed light may include at least one of intensity, propagation direction, frequency or wavelength spectrum, and polarization. For example, as the contact pressure increases, the amount of energy being absorbed may increase. Also, the degree of light absorption of the subject  54  may vary according to the wavelength of light that is used. 
         [0044]    When the contact pressure is applied to the ATR crystal layer  50  by the subject  54 , the pressure sensor  42  measures the contact pressure, and the measured contact pressure is transmitted to the spectrum correction device  56 . 
         [0045]    The spectrum correction device  56  is connected to the substrate  40  and the spectrum detector and analyzer  48 . Based on data (hereinafter, base data) regarding the contact pressure transmitted from the pressure sensor  42  and the light intensity transmitted from the spectrum detector and analyzer  48 , the spectrum correction device  56  confirms whether the transmitted contact pressure and the light intensity are outside of a reference region or not. The confirmation may be achieved through comparison and analysis of the base data with respect to a database of contact pressure-light intensities that is stored in the spectrum correction device  56 . The database of contact pressure-light intensities that is stored in the spectrum correction device  56  may be formed from data of light absorption spectrums measured at various contact pressures on the subject  54 . A means (for example, a graph or an equation) for expressing the relationship between the contact pressure and the light intensity may be formed from the database of contact pressure-light intensities of the spectrum correction device  56 . When the means is a graph as depicted in  FIG. 2  and the base data (for example, a contact pressure) is P 1  or P 4 , which is outside of a reference region (for example, P 2 -P 3 ), the base data is determined as being outside of the reference region. When the base data is a light intensity, it may be determined as the same method as when the base data is the contact pressure. 
         [0046]    According to a result of the determination, the contact pressure of the base data is corrected into the range of the reference region, and the light intensity of the base data is also corrected to a light intensity corresponding to the contact pressure that is corrected into the reference region. Through the process of corrections, a light absorption spectrum measured from the subject  54  may be corrected to fit to the corrected light intensity, and the corrected result may be transmitted to a display device to be displayed. The correction of the light absorption spectrum may be performed in the spectrum correction device  56 . Hereinafter, devices except the spectrum correction device  56  may be referred to as an ATR measuring apparatus. 
         [0047]      FIG. 3  is a cross-sectional view of a light absorption spectrum correction device according to another exemplary embodiment. Only constituent elements of the light absorption spectrum correction device of  FIG. 3  that are different from those of  FIG. 1  will be described below. 
         [0048]    As shown in  FIG. 3 , a light source  46  may be attached to an inner sidewall of a case  52  facing a light incident surface of an ATR crystal layer  50 . A spectrum detector and analyzer  48  may be attached to a sidewall of the case  52  facing a light-emitting surface of the ATR crystal layer  50 . 
         [0049]      FIG. 4  is a cross-sectional view of a light absorption spectrum correction device according to another exemplary embodiment. Only constituent elements of the light absorption spectrum correction device of  FIG. 4  that are different from those of  FIG. 1  will be described. 
         [0050]      FIG. 4  illustrates a light source  46  and a spectrum detector and analyzer  48  disposed on a substrate  40  together with a pressure sensor  42 . The pressure sensor  42  is disposed between the light source  46  and the spectrum detector and analyzer  48 . A second material layer  60  is formed on the pressure sensor  42 . The second material layer  60  has a refractive index less than that of an ATR crystal layer  50 . The second material layer  60  may be formed of the same material as used to form the first material layer  44 . The second material layer  60  may cover an entire upper surface of the pressure sensor  42 . The ATR crystal layer  50  is formed on the second material layer  60 . A bottom surface of the ATR crystal layer  50  contacts the second material layer  60 . The ATR crystal layer  50  may be fixed by a case  62 . A portion of an upper surface of the ATR crystal layer  50  may contact the case  62 . A spectrum correction device  56  may be connected only to a substrate  40  of the ATR measuring apparatus. The spectrum correction device  56  may be connected to the pressure sensor  42  and the spectrum detector and analyzer  48  through the substrate  40 . Accordingly, the substrate  40  may include an element (for example, a wire) that connects the spectrum correction device  56  to the spectrum detector and analyzer  48 . 
         [0051]      FIG. 5  is a cross-sectional view of a light absorption spectrum correction device according to another exemplary embodiment. Only constituent elements of the light absorption spectrum correction device of  FIG. 5  that are different from those of  FIG. 1  will be described. 
         [0052]    Referring to  FIG. 5 , a first material layer  44  is formed around a pressure sensor  42 . The first material layer  44  may have the same height as the pressure sensor  42 . Upper surfaces of the pressure sensor  42  and the first material layer  44  are flat. A case  72  is formed above the first material layer  44 . The case  72  may contact the entire upper surface of the first material layer  44  and the entire upper surface of the pressure sensor  42 . A light source  46  and a spectrum detector and analyzer  48  are disposed on an inner bottom surface of the case  72 . The location relationship of the light source  46  and the spectrum detector and analyzer  48  may be the same as that of the light source  46  and the spectrum detector and analyzer  48  of  FIG. 1 . The case  72  between the light source  46  and the spectrum detector and analyzer  48  has a concave portion. An ATR crystal layer  50  is mounted on the concaved portion of the case  72 . A sloped portion of the concaved portion of the case  72  facing the light source  46  may be an opening-portion for light incident. Also, a sloped portion of the concaved portion of the case  72  facing the spectrum detector and analyzer  48  may be an opening-portion for light emission. A bottom surface of the concaved portion of the case  72  may be parallel to an upper surface of the pressure sensor  42 . A height of an upper surface of a circumference of the concaved portion of the case  72  may be at the same level as the upper surface of the ATR crystal layer  50 . 
         [0053]    In the ATR measuring apparatuses described above, the ATR crystal layer  50  may directly contact the pressure sensor  42 . However, at this point, there may be a wearing problem as a result of direct contact. 
         [0054]      FIGS. 6 through 8  are cross-sectional views for explaining a method of manufacturing a spectrum correction device according to an exemplary embodiment. 
         [0055]    Referring to  FIG. 6 , a pressure sensor  42  is formed or mounted on a substrate  40 . After forming a first material layer  44  that covers the pressure sensor  42  on the substrate  40 , an upper surface of the first material layer  44  is planarized. The first material layer  44  may have a refractive index less than that of an ATR crystal layer  50  to be formed in a subsequent process. 
         [0056]    Referring to  FIG. 7 , a light source  46  and a spectrum detector and analyzer  48  are formed or disposed on the first material layer  44 . The light source  46  and the spectrum detector and analyzer  48  are disposed so that the pressure sensor  42  is located between the light source  46  and the spectrum detector and analyzer  48 . The ATR crystal layer  50  is disposed on the first material layer  44  between the light source  46  and the spectrum detector and analyzer  48 . The ATR crystal layer  50  is located above the pressure sensor  42 . A bottom surface of the ATR crystal layer  50  contacts an upper surface of the first material layer  44 . The ATR crystal layer  50  may be attached to the first material layer  44  by using an adhesive. The refractive index of the adhesive may be less than that of the ATR crystal layer  50 . The ATR crystal layer  50  is separated from the light source  46 . The ATR crystal layer  50  is also separated from the spectrum detector and analyzer  48 . The ATR crystal layer  50  may be disposed so that a sloped light incident surface faces the light source  46  and a sloped light emitting surface faces the spectrum detector and analyzer  48 . 
         [0057]    Referring to  FIG. 8 , the ATR crystal layer  50  is fixed by a case  90 . The light source  46  and the spectrum detector and analyzer  48  are covered by the case  90 . Next, the spectrum correction device  56  is connected to the pressure sensor  42  through the substrate  40 . The spectrum correction device  56  is also connected to the spectrum detector and analyzer  48 . When the spectrum detector and analyzer  48  and the substrate  40  are connected via a connection means, such as a conductive plug, the spectrum correction device  56  may be connected only to the substrate  40 . 
         [0058]    Next, a method of manufacturing a spectrum correction device according to another exemplary embodiment will be described with reference to  FIGS. 9 and 11 . Differences from the method described above with reference to  FIGS. 6 through 8  will be mainly described hereinafter. 
         [0059]    Referring to  FIG. 9 , a case  52  is mounted on an upper surface of a first material layer  44  that covers the pressure sensor  42 . The case  52  includes a groove  52 G onto which an ATR crystal layer  50  will be mounted. The groove  52 G is located above the pressure sensor  42 . A bottom of the groove  52 G is opened and the first material layer  44  is exposed through the bottom of the groove  52 G. A light source  46  is mounted on an inner sidewall of the case  52  before mounting the case  52 , and a spectrum detector and analyzer  48  may be mounted on the other inner sidewall of the case  52  facing the inner sidewall. 
         [0060]    Next, referring to  FIG. 10 , an ATR crystal layer  50  is mounted on and attached to the groove  52 G of the case  52 . A bottom surface of the ATR crystal layer  50  is parallel to an upper surface of the first material layer  44 . Both side slopes that connect the bottom and upper surfaces of the ATR crystal layer  50  may be parallel to slopes of the groove  52 G of the case  52 . After mounting the ATR crystal layer  50 , a spectrum correction device  56  is connected to remaining elements, that is, the ATR measuring apparatus. The spectrum correction device  56  may also be connected to the substrate  40  and the spectrum detector and analyzer  48 . 
         [0061]    As depicted in  FIG. 11 , a set may be formed by mounting the ATR crystal layer  50  on the case  52  before mounting the case  52  on the first material layer  44 , and the set may be mounted or contacted on the upper surface of the first material layer  44 . 
         [0062]    Another method of manufacturing a spectrum correction device according to another exemplary embodiment will now be described with reference to  FIGS. 12 through 16 . 
         [0063]    Referring to  FIG. 12 , a light source  46 , a pressure sensor  42 , and spectrum detector and analyzer  48  are formed or mounted on a substrate  40 . The light source  46  and the spectrum detector and analyzer  48  are respectively located on both sides of the pressure sensor  42 . The light source  46  and the spectrum detector and analyzer  48  are separated from the pressure sensor  42 . A second material layer  60  covers an upper surface of the pressure sensor  42 . The pressure sensor  42  may be mounted on the substrate  40  after separately forming the pressure sensor  42 . At this point, the pressure sensor  42  may be mounted on the substrate  40  in a state that an upper surface of the pressure sensor  42  is covered by the second material layer  60 . 
         [0064]    Next, referring to  FIG. 13 , a case  62  that covers the light source  46 , the pressure sensor  42 , the second material layer  60 , and the spectrum detector and analyzer  48  are aligned on the substrate  40 . The ATR crystal layer  50  is attached to an inner ceiling of the case  62 . The ATR crystal layer  50  is attached to the inner ceiling of the case  62  through an upper surface of the ATR crystal layer  50 . At this point, a portion of the upper surface of the ATR crystal layer  50  (for example, a rim portion) may be attached to the ceiling of the case  62  and the remaining upper surface of the ATR crystal layer  50  may be exposed to the outside. For this purpose, as depicted in  FIG. 14 , a portion of the case  62  that corresponds to the upper surface of the ATR crystal layer  50  may be opened. That is, a through hole  62   h  may be formed in the portion of the case  62  to correspond to the upper surface of the ATR crystal layer  50 . The majority of the upper surface of the ATR crystal layer  50  may be exposed through the through hole  62   h.    
         [0065]    The case  62  on which the ATR crystal layer  50  is then mounted is lowered towards the substrate  40  to mount on or combine with the substrate  40 . As depicted in  FIG. 15 , the case  62  may be mounted on or combined with the substrate  40  so that a bottom surface of the ATR crystal layer  50  contacts the second material layer  60 . In this process, without forming the second material layer  60 , the bottom surface of the ATR crystal layer  50  may directly contact an upper surface of the pressure sensor  42 . 
         [0066]    Next, as depicted in  FIG. 15 , a spectrum correction device  56  is connected to the substrate  40 . 
         [0067]    As depicted in  FIG. 16 , the second material layer  60  may be attached to the bottom surface of the ATR crystal layer  50 . In this case, the case  62  is mounted on or combined with the substrate  40  by lowering the case  62  so as to bring the second material layer  60  in contact with the pressure sensor  42 . 
         [0068]    Alternatively, after mounting the ATR crystal layer  50  on the second material layer  60  that is formed on the upper surface of the pressure sensor  42 , the case  62  may be mounted on or combined with the substrate  40  to fix the mounted ATR crystal layer  50 . 
         [0069]    A method of correcting a spectrum by using a spectrum correction device according to an exemplary embodiment will now be described with reference to  FIG. 17  and the spectrum correction device  56  described above. 
         [0070]    As shown in  FIG. 17 , first, a contact pressure between the ATR crystal layer  50  and the subject  54  under examination is measured (S 1 ). The contact pressure may be measured by using the pressure sensor  42 . A value (data) measured by the pressure sensor  42  may be transmitted to the spectrum correction device  56 . Next, a light absorption spectrum with respect to the subject  54  is measured and/or detected (S 2 ). The measurement and/or detection of the light absorption spectrum with respect to the subject  54  may be simultaneously achieved while measuring the contact pressure. The light absorption spectrum with respect to the subject  54  may be formed by detecting light of various wavelengths that are emitted through a light-emitting surface of the ATR crystal layer  50  by using the spectrum detector and analyzer  48 . After the light absorption spectrum is formed, information regarding light intensities in a specific wavelength or a specific wavelength band through analysis of the formed light absorption spectrum is obtained. Information obtained in this way may be transmitted to the spectrum correction device  56 . A spectrum correction is performed by using the data of contact pressure and light intensities that are transmitted to the spectrum correction device  56  (S 3 ). As described above, the spectrum correction may be achieved by comparing a graph that is formed from the database of contact pressure-light intensities stored in the spectrum correction device  56  and the base data (data regarding the contact pressure and light intensities) transmitted to the spectrum correction device  56 . The corrected light absorption spectrum may be displayed to a user through a display device (S 4 ). 
         [0071]    An example of correcting a light absorption spectrum will be described with reference to  FIGS. 18 through 20 . 
         [0072]      FIG. 18  shows a contact pressure-light intensity correction curve, which is stored in an element (for example, the spectrum correction device  56 ), when a wavelength of incident light is λ 0 . 
         [0073]    As shown in  FIG. 18 , when contact pressures are P 00 , P 11 , and P RR , light intensities of spectrums are respectively I 00 , I 11 , and I RR . P RR  is a reference contact pressure and I RR  is a light intensity at P RR . Accordingly, when the wavelength of light used is λ 0  and the contact pressures are P 00  and P 11 , the measured light intensity (the absorption spectrum) may be corrected to the light intensity I RR  when the reference contact pressure is P RR  along the curve of  FIG. 18 . 
         [0074]    For example, as depicted in  FIG. 19 , a first spectrum measured at various wavelengths when the contact pressure is P 00  is SP 1  and a second spectrum measured at various wavelengths when the contact pressure is P 11  is SP 2 , the correction of the first and second spectrums SP 1  and SP 2  may be performed as follows. 
         [0075]    First, at a wavelength λ 0 , the light intensities I 00  and I 11  of the first and second spectrums SP 1  and SP 2  are corrected to the light intensity I RR  when the reference contact pressure is P RR . At this point, if the amounts of correction of the light intensities I 00  and I 11  of the first and second spectrums SP 1  and SP 2  are ΔI 1  and ΔI 2  respectively, light intensities at remaining wavelengths of the first and second spectrums SP 1  and SP 2  are also corrected by the same correction amounts ΔI 1  and ΔI 2 . As a result, the first and second spectrums SP 1  and SP 2  may be corrected as depicted in  FIG. 20 . In  FIG. 20 , SP 1 ′ and SP 2 ′ respectively represent the first and second spectrums SP 1  and SP 2  after corrections. 
         [0076]    According to at least one of the above-described exemplary embodiments, the variation of a light absorption spectrum according to a contact pressure on a subject under examination is corrected (a strong light intensity is corrected to a weak light intensity, and a weak light intensity is corrected to a strong light intensity). Accordingly, although a contact pressure on the subject is outside a desired range, the light absorption spectrum may be displayed within a reference region. 
         [0077]    While one or more exemplary embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.