**1. Introduction**

78 Infrared Spectroscopy – Life and Biomedical Sciences

Ochsner, K. N., & Lieberman, M. D. (2001). The emergence of social cognitive neuroscience,

Preston, S. D., & de Waal, F. B. M. (2002). Empathy: Its ultimate and proximate bases.

Schroeter, M. L., Zysset, S., Kruggel, F., & Yves von Cramon, D. (2003). Age dependency of

Shimada, S., Hiraki, K., Matsuda, G., &, Oda, I. (2004). Decrease in prefrontal hemoglobin

Singer, T., Seymour, B., O'Doherty, J. P., Kaube, H., Dolan, R. J., & Frith, C. D. (2004).

*Science,* Vol. 303, No.5661, (February 2004), pp. 1157-1162, ISSN 0036-8075 Singer, T., Seymour, B., O'Doherty, J. P., Stephan, K. E., Dolan, R. J., & Frith, C. D. (2006).

*Nature,* Vol. 439, No.7075, (January 2006), pp. 466–469, ISSN 0028-0836 Suzuki, M., Gyoba, J., & Sakuta, Y. (2005). Multichannel NIRS analysis of brain activity

Villinger, A., & Chance, B. (1997). Non-invasive optical spectroscopy and imaging of human

Wager, T. D., Davidson, M. L., Hughes, B. L., Lindquist, M. A., & Ochsner, K. N. (2008).

Wicker, B., Michel, F., Henaff, M., & Decety, J. (1998). Brain regions involved in the

Vol.59, No.6, (September 2008), pp. 1037–1050, ISSN 1097-4199

*NeuroImage,* Vol.19, No.3, (July 2003), pp. 555–564, ISSN 1053-8119

1053-8119

525X

3940

ISSN 0166-2236

227, ISSN 1053-8119

490, ISSN 0926-6410

related fMRI study. *NeuroImage,* Vol.21, No.1, (January 2004), pp. 352–363, ISSN

*American Psychologist,* Vol.56, No.9, (September 2001), pp. 717–734, ISSN 0003-066X

*Behavioral and Brain Sciences,* Vol.25, No.1, (February 2002), pp. 1–20, ISSN 0140-

the hemodynamic response as measured by functional near-infrared spectroscopy,

oxygenation during reaching tasks with delayed visual feedback: A near-infrared spectroscopy study. *Cognitive Brain Research,* Vol. 20, No.3, (August 2004), pp. 480–

Empathy for pain involves the affective but not sensory components of pain.

Empathic neural responses are modulated by the perceived fairness of others.

during semantic differential rating of drawing stimuli containing different affective polarities, *Neuroscience Letters,* Vol.375, No.1, (February 2005), pp. 53–58, ISSN 0304-

brain function. *Trends in Neuroscience,* Vol.20, No.10, (October 1997), pp. 435-442,

Prefrontal-subcortical pathways mediating successful emotion regulation. *Neuron,* 

perception of gaze: A PET study. *NeuroImage,* Vol.8, No.2, (August 1998), pp. 221–

The infrared light analysis has become an indispensable part of life for humankind. The infrared measurement has been studied in the worldwide, because can be qualitative and quantitative analysis for trace samples. Today, infrared spectrophotometer has been installed in many laboratories and universities, and being used over a very wide field. So, the number of papers on infrared spectroscopy is so many. We also are one of a research group of infrared measurement. Our research policy is "non-destructive measurement using infrared light". In general, blood glucose measurements of the human body to extract blood, and to determine the composition of textile products will break down to samples. If we can measure these value in non-destructive, we can contribute to society. So I described our past "non-destructive measurement using infrared light" research in this document.

#### **2. Measurement system**

#### **2.1 FT-IR (Fourier Transform Infrared Spectrophotometer)**

In this study, measuring systems are used a FT-IR (IR-Prestige-21 : SHIMADZU, Travel-IR : SensIR Technologies) as in Fig.1. The block diagram of measurement system is shown in Fig.2. The broadband infrared light is interfering by Michelson interferometer, and sent to the sample place. In the sample place, we selected the best method (ATR method, diffuse reflection method, IR fiber probe method) by each sample. We are only using the MCT (mercury cadmium tellurium) detector in IR fiber probe method, using the DLATGS (Deuterated L-Alanine Triglycine Sulphate) detector in other method. Absorption infrared interference light is detected by the optical detector, appear on the PC as an interferogram signal. This signal transformed by Fourier transformation, we get the IR absorption spectrum. The horizontal axis of spectrum is wavenumber, and the vertical axis is absorbance.

#### **2.2 Attenuated Total Reflectance method (ATR method)**

ATR method is performed as follows. We place to the sample on the prism. At this time, if there is a gap, the S/N ratio is lower. Infrared light goes into the prism, and goes forward by repeating the total reflection. When IR light repeats total reflection in the prism, evanescent

Introduction of Non-Invasive Measurement Method by Infrared Application 81

The infrared light passes through the light source side fiber probe, and irradiated to the sample. The infrared light reflected from the sample goes into the detector side fiber probe, and detected by MCT detector. This method can be irradiated with infrared light directly on the sample for the movement of the measuring place. The fiber probe (REMSPEC IMM-07S) composed of 19 fibers (the light source side 7 and the detector side 12) made by the

The absorption spectrum has various information of sample by each wavelength. In other words, the absorption spectrum has multidimensional vector information. Therefore, it is to analyze the spectra by multivariate analysis. In multivariate analysis for the use of multiple explanatory variables, it is increasing the amount of information. Thereby to reduce noise to a relative, it is possible to build a greater precision calibration curve. We performed correction to the absorption spectrum, and used to the PLSR in quantitative analysis, and

We can extract the maximum information from the spectrum by performed correction to the absorption spectrum. We used to the spectral correction to the normalization and the differential. In the normalization correction, the absorbance of the designated peak is "1", and the coefficient "1/(absorbance of the specified peak)" is multiplied to the absorbance of each wavenumber. For example, there are the measured spectra of sample including material A and B. When you want to get the results of material A, the information of material B in the spectrum is the noise. In here, normalized to all spectra by the absorption peak of material B, and appears only information of material A. In this correction, that can

On the other hand, the differential correction is a correction of the slope of the spectrum, it is possible to eliminate the effects of baseline. Also, if the wavenumber of several absorption peaks is very close, is able to separate these peaks. The first differential correction is calculated at the slope of each wavenumber in spectrum, the intensity of absorption peaks wavenumber is "0". Derivative spectrum half-width of the higher orders is narrowed, and the noise increases for in lower S/N ratio. For these reasons, we used first differential correction in this study.

We are using PLSR for a quantitative analysis. PLSR has not the Multilinear regression (MLR) exists multicollinearity, Measurement accuracy of PLSR is better than Principal Components Regression (PCR) in a small number of factors. In the PLSR, the explanatory variables are the infrared spectra, the objective variables are the reference values. The explanatory variables and the objective variables are assumed to each have an error margin, extracted to PLS factors, calculate a regression, and new objective variables are calculated. Next, a similar calculation using the new objective variables and explanatory variables, add a PLS factor, re-calculate the objective variables. A number of PLS factors increase, and the

chalcogenide glass. A fiber diameter is 500 μm, and a fiber probe diameter is 5 mm.

used to the SIMCA method and the KNN method in the pattern analysis.

**2.4 IR fiber probe method** 

**3.1 Spectral correction** 

be minimized by measurement error.

**3.2 Partial Least Squares Regression (PLSR)** 

Standard Error of Calibration (SEC) is smaller.

**3. The spectrum analysis method** 

Fig. 1. FT-IR (IR-Prestige-21 (A), Travel-IR(B))

Fig. 2. The block diagram of measurement system

lights goes into the sample. Evanescent light attenuates by absorbance in sample surface set on the prism. The absorbed infrared light from the sample is detected.

In the ATR prism, we use the ZnSe prism of plate type and the prism of diamond mounted on ZnSe. Optical path length of the evanescent light to go into the sample is shown in equation 1.

$$\mathbf{dp} = \lambda / 2 \text{nm} \sqrt{\sin 2\theta} \text{-(tn/m)}^2 \text{l}^{1/2} \tag{1}$$

dp: depth of penetration of evanescent light, θ: angle of incidence

λ: Wavelength, n1: refractive index of ATR prism, n2: refractive index of sample

By the equation 1, optical path length of evanescent light in the sample will get longer as the long wavelength side. Therefore, the absorption by the sample is strong in the long wavelength side. Accordingly, coefficient of divide "Absorbance of standard wavenumber" by "Absorbance of each wavenumber" is multiplied by the absorbance at each wavelength. In this calculation, optical path length of the evanescent light is standardize, and to correct the absorbance of spectrum. This calculation method is "ATR correction".

#### **2.3 Diffuse reflection method**

If the infrared light irradiated to powder or fibers, we can be measured the diffused reflection light from sample inside and the regular reflection light from sample surface. Infrared light penetrate inside the sample, then repeated the transmission and reflection, and come out of sample. In diffuse reflection method, this light is measured. We used to the UP-IR (Pike Tech) in this method. 30mm diameter hole is in the top of the UP-IR, the sample is placed to cover the hole.

#### **2.4 IR fiber probe method**

80 Infrared Spectroscopy – Life and Biomedical Sciences

lights goes into the sample. Evanescent light attenuates by absorbance in sample surface set

Michelson interferometer Sample place Detector

Absorption spectrum Fourier Transformation Interferogram

In the ATR prism, we use the ZnSe prism of plate type and the prism of diamond mounted on ZnSe. Optical path length of the evanescent light to go into the sample is shown in

dp=λ/2πn1[sin2θ-(n2/n1)2]1/2 (1)

By the equation 1, optical path length of evanescent light in the sample will get longer as the long wavelength side. Therefore, the absorption by the sample is strong in the long wavelength side. Accordingly, coefficient of divide "Absorbance of standard wavenumber" by "Absorbance of each wavenumber" is multiplied by the absorbance at each wavelength. In this calculation, optical path length of the evanescent light is standardize, and to correct

If the infrared light irradiated to powder or fibers, we can be measured the diffused reflection light from sample inside and the regular reflection light from sample surface. Infrared light penetrate inside the sample, then repeated the transmission and reflection, and come out of sample. In diffuse reflection method, this light is measured. We used to the UP-IR (Pike Tech) in this method. 30mm diameter hole is in the top of the UP-IR, the sample

Fig. 1. FT-IR (IR-Prestige-21 (A), Travel-IR(B))

(A) (B)

Fig. 2. The block diagram of measurement system

equation 1.

**2.3 Diffuse reflection method** 

is placed to cover the hole.

on the prism. The absorbed infrared light from the sample is detected.

dp: depth of penetration of evanescent light, θ: angle of incidence

λ: Wavelength, n1: refractive index of ATR prism, n2: refractive index of sample

the absorbance of spectrum. This calculation method is "ATR correction".

The infrared light passes through the light source side fiber probe, and irradiated to the sample. The infrared light reflected from the sample goes into the detector side fiber probe, and detected by MCT detector. This method can be irradiated with infrared light directly on the sample for the movement of the measuring place. The fiber probe (REMSPEC IMM-07S) composed of 19 fibers (the light source side 7 and the detector side 12) made by the chalcogenide glass. A fiber diameter is 500 μm, and a fiber probe diameter is 5 mm.
