JP2013228270A - Cure degree measuring method for silane-based sealing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately measure a cure degree of a silane-based sealing material.SOLUTION: A cure degree measuring method for a silane-based sealing material comprises the steps of: irradiating measurement light containing at least one of a first wavelength included in a wavelength range ranging from 1500 nm to 1600 nm and a second wavelength included in a wavelength range ranging from 1980 nm to 2080 nm to a measuring object made of a silane-based sealing material, receiving transmission light or diffuse reflection light of the measuring object and obtaining an absorbance spectrum; extracting a feature amount in the first wavelength or the second wavelength from the absorbance spectrum; and determining whether or not the silane-based sealing material is cured by comparing the feature amount with a preset threshold value. The silane-based sealing material has an absorbance varying in response to a cure degree in the wavelength ranges. Accordingly, the cure degree of the silane-based sealing material can be appropriately measured by extracting the feature amount in the wavelength ranges and obtaining the cure degree of the silane-based sealing material on the basis thereof.

Description

  The present invention relates to a method for measuring the degree of cure of a silane-based sealing material.

  Conventionally, a method of measuring an absorption spectrum by irradiating a measurement object with infrared light and evaluating characteristics of the measurement object based on this result has been studied. For example, Patent Document 1 discloses a method for quantifying the glucose concentration in a living tissue using light absorption in the near infrared region. Patent Document 2 discloses a method for measuring the infrared spectrum of a paint applied to the surface of a steel sheet and evaluating the baking condition from the result.

Japanese Patent Laid-Open No. 10-325784 JP-A-8-196984

  By the way, for the purpose of improving water resistance and the like, a sealing material (sealing material) using a silane-based primer has attracted attention in building applications. However, a method for evaluating the degree of curing after applying the silane-based sealing material has not been studied.

  The present invention has been made in view of the above, and an object thereof is to provide a method capable of suitably measuring the degree of cure of a silane-based sealing material.

  In order to achieve the above object, a method for measuring the degree of cure of a silane-based sealing material according to the present invention is a light having a first wavelength included in a wavelength range of 1500 nm to 1600 nm with respect to a measurement object made of a silane-based sealing material. Or, by irradiating the measurement light including the light of the second wavelength included in the wavelength range of 1980 nm to 2080 nm, the transmitted light or diffuse reflected light from the measurement object is received, and the measurement object The step of acquiring the absorbance spectrum, the step of extracting the feature amount at the first wavelength or the second wavelength from the absorbance spectrum, and comparing the feature amount with a predetermined threshold value, thereby determining the degree of cure of the silane-based sealing material. And measuring.

  As a result of intensive studies, the inventors have found that the absorbance of the silane-based sealing material varies depending on the degree of cure in a wavelength range of 1500 nm to 1600 nm and a wavelength range of 1980 nm to 2080 nm. Therefore, the characteristic amount at the first wavelength included in the wavelength range of 1500 nm to 1600 nm or the second wavelength included in the wavelength range of 1980 nm to 2080 nm is extracted, and using this, the degree of cure of the silane-based sealing material By obtaining this, it becomes possible to suitably measure the degree of cure of the silane-based sealing material.

  Further, in the step of obtaining the absorbance spectrum of the measurement object, in the step of irradiating the measurement light including the light of the first wavelength and the light of the second wavelength, obtaining the absorbance spectrum, and extracting the feature amount, When it is set as the aspect which extracts the feature-value in a 1st wavelength and a 2nd wavelength, since the wavelength which contributes to the measurement of a cure degree increases, it becomes possible to measure the cure degree of a silane type sealing material more accurately. .

  Here, as a configuration that effectively exhibits the above-described operation, specifically, an aspect in which the feature amount is a difference in absorbance with respect to a baseline spectrum created based on the absorbance spectrum can be given.

  In addition, as another configuration that effectively exhibits the above-described operation, specifically, an aspect in which the feature amount is a second-order differential value according to the wavelength of the absorbance spectrum can be given.

  Moreover, it is good also as an aspect which obtains the light-absorption spectrum of a measuring object using the diffuse reflected light of a measuring object.

  In addition, the light source for irradiating the measurement object with the measurement light and the detection unit for receiving the transmission light from the measurement object are arranged to face each other with the measurement object interposed therebetween, and the measurement object is transmitted using the transmitted light. It is good also as a structure which obtains the light absorption spectrum.

  Similarly, when obtaining an absorbance spectrum, the measurement object is placed on a reflector, and a light source that irradiates the measurement object with measurement light and a detection unit that receives the transmitted light from the measurement object are measured. It can also be set as the aspect which arrange | positions on the opposite side to a reflecting plate on both sides of a target object, and obtains the light absorbency spectrum of a measurement target object using transmitted light.

  ADVANTAGE OF THE INVENTION According to this invention, the method which can measure suitably the hardening degree of a silane type sealing material is provided.

It is a figure explaining schematic structure of the degree-of-curing measurement system concerning the present invention. It is a figure which shows an example of the measuring object used in a hardening degree measuring system. It is a figure explaining a hyperspectral image. It is a figure explaining the other structure of a hardening degree measuring system. It is a figure explaining the other structure of a hardening degree measuring system. It is a figure which shows an example of the light absorbency spectrum acquired by a cure degree measurement system. It is the figure which expanded and correct | amended a part of absorbance spectrum of FIG. It is the figure which expanded and correct | amended a part of absorbance spectrum of FIG. It is the figure which calculated | required the time change of the light absorbency according to hardening time based on FIG. It is the figure which calculated | required the time change of the light absorbency according to hardening time based on FIG. It is the figure which calculated | required the secondary differential value by the wavelength of the absorbance spectrum of FIG. It is the figure which expanded and corrected a part of spectrum of FIG. It is the figure which expanded and corrected a part of spectrum of FIG. It is the figure which calculated | required the time change of the light absorbency according to hardening time based on FIG. It is the figure which calculated | required the time change of the light absorbency according to hardening time based on FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(Configuration of curing degree measurement system)
A curing degree measurement system 100 including an image data analysis apparatus according to the present invention will be described with reference to FIG. The curing degree measurement system 100 according to the present embodiment cures a silane-based sealing material applied to an inspection target product 3 (showing the mounting position of the inspection target product in FIG. 1) distributedly placed on the belt conveyor 2. It is a device that measures the degree. As the inspection target product 3 of the curing degree measurement system 100 according to the present embodiment, for example, as shown in FIG. 2, a silane-based sealing material 33 that seals between the housing 31 and the lid portion 32 that covers the housing 31 is used. Can be mentioned. The silane-based sealing material here refers to a sealing material (sealing material) using a silane-based primer.

  The silane-based sealing material 33 is applied to the interface position between the casing 31 and the lid portion 32 in a fluid state, and then cured by a chemical reaction. The curing degree measurement system 100 measures the degree of curing of the silane-based sealing material 33 using the silane-based sealing material 33 as a measurement object. Specifically, the curing degree measurement system 100 calculates the spectrum of diffuse reflected light obtained by irradiating the measurement light to the measurement target position of the inspection target product 3 (the position where the silane-based sealing material 33 is applied). Based on the spectrum, the degree of cure of the silane-based sealing material 33 of the inspection object 3 is detected. The curing degree measurement system 100 includes a light source unit 10, a detection unit 20 (imaging unit), and an analysis unit 30 (control unit).

  The light source unit 10 irradiates measurement light having a certain wavelength band toward a predetermined irradiation area A1 on the belt conveyor 2. The wavelength range of the measurement light emitted by the light source unit 10 is appropriately selected according to the type of the silane-based sealing material 33 applied to the inspection target product 3 and the like. When near infrared light is used as measurement light, specifically, light having a wavelength range of 1500 to 1600 nm or 1980 to 2080 nm is preferably used.

  The irradiation region A1 is a partial region of the surface (mounting surface 2b) of the belt conveyor 2 on which the inspection target product 3 is placed. The irradiation area A1 extends in the width direction (x-axis direction) perpendicular to the traveling direction 2a (y-axis direction in FIG. 1) of the placement surface 2b, and covers from one end to the other end of the placement surface 2b. This is an area extending in a line. And the width | variety of irradiation area | region A1 in a direction (y-axis direction) perpendicular | vertical to the extension direction of irradiation area | region A1 shall be 10 mm or less.

  The light source unit 10 includes a light source 11 that emits near-infrared light, an irradiation unit 12, and an optical fiber 13 that connects the light source 11 and the irradiation unit 12. As the light source 11, for example, a halogen lamp can be used, which outputs broadband light in the near-infrared light region.

  Near-infrared light generated by the light source 11 is incident on one end face of the optical fiber 13. This near-infrared light is guided through the core region of the optical fiber 13 and is emitted from the other end face to the irradiation unit 12.

  The irradiation unit 12 irradiates near-infrared light emitted from the end face of the optical fiber 13 to the irradiation region A1 on which the inspection target product 3 is placed. Since the irradiation unit 12 receives near infrared light emitted from the optical fiber 13 and emits it in a one-dimensional line corresponding to the irradiation region A1, a cylindrical lens is preferably used as the irradiation unit 12. The near-infrared light L1 shaped in a line shape in the irradiation unit 12 in this way is irradiated from the irradiation unit 12 to the irradiation region A1.

  The near infrared light L1 output from the light source unit 10 is diffusely reflected by the inspection target product 3 placed on the irradiation area A1. A part of the light enters the detection unit 20 as diffusely reflected light L2.

The detection unit 20 has a function as a hyperspectral sensor that acquires a hyperspectral image. Here, the hyperspectral image in this embodiment is demonstrated using FIG. FIG. 3 is a diagram for explaining the outline of the hyperspectral image. As shown in FIG. 3, the hyperspectral image is an image composed of _N pixels P _{1 to} P _N. Specifically it shows the two pixel P _n and P _m as them example in FIG. Each of the pixels P _n and P _m includes spectral information S _n and S _m including a plurality of intensity data. And the intensity data is data indicating a spectral intensity at a particular wavelength (or wavelength band), 3, 15 intensity data has been held as the spectral information S _n and S _m, superposition of these It is shown in the state. As described above, the hyperspectral image H is characterized by having a plurality of intensity data for each pixel constituting the image, so that a three-dimensional image having both a two-dimensional element as an image and an element as spectral data. Configuration data. FIG. 3 also shows the placement position of the product 3 to be inspected. That, P _n is the pixel of the captured object of inspection 3 in FIG. 3, P _m is the pixel of the captured background (e.g., a belt conveyor). In the case of the inspection target product 3 shown in FIG. 2, the part provided with the silane-based sealing material, which is the measurement target, is limited to a part, so the actual inspection target product 3 in FIG. 3 is shown. Not all pixels at the position are pixels that image the measurement object.

  Returning to FIG. 1, the detection unit 20 according to the present embodiment includes a camera lens 24, a slit 21, a spectroscope 22, and a light receiving unit 23. The detection unit 20 has a visual field region 20 s extending in a direction (x-axis direction) perpendicular to the traveling direction 2 a of the belt conveyor 2. The visual field area 20s of the detection unit 20 is a linear area included in the irradiation area A1 of the placement surface 2b, and is an area where the diffusely reflected light L2 that has passed through the slit 21 forms an image on the light receiving unit 23.

  The slit 21 is provided with an opening in a direction parallel to the extending direction (x-axis direction) of the irradiation region A1. The diffuse reflected light L2 that has entered the slit 21 of the detection unit 20 enters the spectroscope 22.

  The spectroscope 22 splits the diffusely reflected light L2 in the longitudinal direction of the slit 21, that is, the direction perpendicular to the extending direction of the irradiation area A1 (y-axis direction). The light split by the spectroscope 22 is received by the light receiving unit 23.

  The light receiving unit 23 includes a light receiving surface in which a plurality of light receiving elements are two-dimensionally arranged, and each light receiving element receives light. As a result, the light receiving unit 23 receives light of each wavelength of the diffusely reflected light L2 reflected at each position along the width direction (x-axis direction) on the belt conveyor 2. Each light receiving element outputs a signal corresponding to the intensity of received light as information on a two-dimensional planar point composed of a position and a wavelength. A signal output from the light receiving element of the light receiving unit 23 is sent from the detection unit 20 to the analysis unit 30 as image data related to the hyperspectral image. As the light receiving unit 23, for example, a CCD can be used.

  The analysis unit 30 obtains the spectrum of the diffuse reflected light L2 from the input signal, and measures the degree of curing based on the obtained spectrum. When measuring the degree of cure of the silane-based sealing material 33 of the inspection target product 3, the inspection is performed according to the following principle. In the wavelength range of 1500 to 1600 nm and the wavelength range of 1900 to 2080 nm in the wavelength range of the measurement light output from the light source 11, the spectrum shape varies depending on the hardness of the silane-based sealing material. Accordingly, in the hyperspectral image H by the diffuse reflection light L2 diffusely reflected by the silane-based sealing material 33 in the inspection target product 3, the spectrum information that is included for each pixel and is composed of a plurality of intensity data is referred to, and the above wavelength range The degree of cure is determined based on the peak shape of the spectrum at. Alternatively, the second derivative of the spectrum of the diffuse reflected light L2 is obtained, and based on this, the degree of cure of the silane-based sealing material is determined. The result of analysis by the analysis unit 30 is notified to the operator of the curing degree measurement system 100 by, for example, outputting the result to a monitor connected to the analysis unit 30 or a printer.

  The analysis unit 30 includes a CPU (Central Processing Unit), a RAM (Random Access Memory) and a ROM (Read Only Memory) that are main storage devices, a communication module that performs communication with other devices such as a detection unit, a hard disk, and the like. The computer is provided with hardware such as an auxiliary storage device. And the function as the analysis unit 30 is exhibited when these components operate | move. An outline of analysis processing by the analysis unit 30 and a specific method thereof will be described later.

  It should be noted that the configuration of the light source unit 10 and the detection unit 20 in the curing degree measurement system 100 can be variously changed.

  For example, as illustrated in FIG. 4, the light source unit 10 and the detection unit 20 are disposed so as to face each other with the inspection target product 3 interposed therebetween, and the near infrared light L <b> 1 is irradiated from the light source unit 10 to the inspection target product 3. By doing so, it is good also as a structure by which the transmitted light L3 which permeate | transmitted the to-be-inspected goods 3 is received by the detection unit 20.

  As in the modification of FIG. 4, the light source unit 10 and the detection unit 20 are arranged on the same side with respect to the inspection target product 3 even when the transmitted light from the inspection target product 3 is measured. Also good. An example is shown in FIG. In this case, the near-infrared light L1 is emitted from the light source unit 10 after the inspection target product 3 is placed on the reflection plate 40, thereby transmitting the inspection target product 3 while being reflected by the reflection plate 40. The light L3 is received by the detection unit 20. The reflecting plate 40 is preferably a plate having a low wavelength dependency of reflectance. For example, a standard reflecting plate made of Teflon (registered trademark) or a gold-plated plate can be used.

  Like said modification 1-3, the structure of the light source unit 10 for detecting the hyperspectral image H and the detection unit 20 can be changed suitably.

(Measurement method using a curing degree measurement system)
Next, a method for measuring the degree of cure using the above-described degree of cure measurement system will be described. First, using the light source unit 10 and the detection unit 20 described above, the diffuse reflection light spectrum or the transmission light spectrum of the product 3 to be inspected is acquired. Thereafter, analysis is performed in the analysis unit 30 using the obtained spectrum.

When the degree of curing performed in the analysis unit is evaluated, data processing is performed on the diffuse reflected light spectrum or transmitted light spectrum of the inspection object 3 using the following two methods.
(1) A straight line connecting absorbances at two wavelengths sandwiching a specific wavelength used for evaluation of the degree of cure is used as a base line, and an incremental spectrum from the base line is obtained.
(2) A secondary differential spectrum is obtained from the absorbance spectrum of diffusely reflected light or transmitted light.
Then, based on the spectrum after the processing of (1) or (2) is performed, by comparing the increment or the second derivative value at the wavelength used for the determination of the degree of curing with a predetermined threshold value, The degree of cure of the silane sealant is evaluated. In addition, what is necessary is just to set an optimal value suitably as a threshold value according to the desired degree of hardening.

  Hereinafter, it demonstrates in detail based on an Example.

  First, as a product 3 to be inspected, a silane-based sealing material applied to the surface of a preparation (glass plate) so as to have a thickness of 2 mm was prepared. In this case, the entire inspection target product is the measurement target. Further, the configuration shown in FIG. 5 was adopted as the measurement optical system of the curing degree measurement system 100. That is, the inspection target product 3 is placed on the reflective material, the measurement light is irradiated from the light source unit 10 provided on the opposite side of the reflective material to the inspection target product 3, and the same side as the light source unit 10 is provided. The provided detection unit 20 is configured to receive the light transmitted through the inspection target product 3. Using the curing degree system 100 having the above-described configuration, when the silane-based sealing material is applied to the surface of the preparation and every time one hour has elapsed from the application, the measuring object 3 is irradiated with the measurement light. The hyper spectrum was obtained by receiving the transmitted light from the inspection target product 3 obtained in step 1 with the detection unit 20. This was repeated every 8 hours after application. The absorbance spectrum of the transmitted light obtained as a result is shown in FIG.

  Next, the case where the process (1) is performed on the absorbance spectrum obtained by the above method will be described. A straight line connecting the absorbance at a wavelength of 1480 nm and the absorbance at 1600 nm was used as a baseline, and a spectrum based on an increment from the baseline was created. FIG. 7 shows the result of obtaining a difference from the incremental spectrum of 0h (at the time of applying the sealing material) with respect to the incremental spectrum of 1 to 8h after applying the sealing material after the correction based on the baseline. . Similarly, FIG. 8 shows the result of correction similar to that in FIG. 7 with the straight line connecting the absorbance at the wavelength of 2007 nm and the absorbance at 2063 nm as the baseline. In the process (1), the difference from the 0h incremental spectrum becomes a feature amount, and the degree of curing is evaluated using this feature amount.

  Next, FIG. 9 shows the result of obtaining the change in absorbance (difference from 0h incremental spectrum) with time at a predetermined wavelength (first wavelength) included in 1500 to 1600 nm based on FIG. Show. In FIG. 9, the change of the light absorbency according to hardening time is shown about the case of wavelength 1531.8nm, 1538.1nm, 1544.3nm, 1550.6nm, 1556.9nm, 1563.1nm. Moreover, the result of having calculated | required the change of the light-absorption with time passage in the predetermined wavelength (2nd wavelength) contained in 198-2080 nm based on FIG. 8 is shown in FIG. In FIG. 10, the change of the light absorbency according to hardening time is shown about the case of wavelength 2018.9nm, 2025.1nm, 2031.4nm, 2037.6nm, 2043.8nm. In addition, the wavelength which calculates | requires the change of a light absorbency may be a wavelength different from the said wavelength, and can be suitably selected from the wavelength range of 1500-1600 nm or 1280-2080 nm. Further, only one of the wavelength range of 1500 to 1600 nm and the wavelength range of 1980 to 2080 nm may be used. By using both wavelength ranges, the influence of errors and the like is reduced, and the silane system is more preferably used. It becomes possible to evaluate the hardening of the sealing material.

  9 and 10, the difference from the absorbance at 0 h (at the time of application) changes with the elapsed time after application. Therefore, the threshold value of the increase in absorbance from 0 h at a predetermined wavelength is determined in advance, and the degree of cure of the silane-based sealing material is cured using the determination of whether the difference in absorbance of the inspection object 3 exceeds the threshold value. It can be determined whether or not.

  Next, a case where the process (2) is performed on the absorbance spectrum obtained by the above method will be described.

  FIG. 11 shows the result of obtaining the second derivative with respect to the absorbance spectrum of FIG. In the present embodiment, the secondary differentiation was performed by the Savitzky-Golay method (quadratic function approximation, front and rear five-point correction). And what was taken out about the range of wavelength 1500-1600nm among the results of calculating | requiring the difference of the spectrum of 1-8h after sealing material application | coating and the spectrum of 0h (at the time of sealing material application | coating) based on FIG. Show. Similarly, what was taken out in the wavelength range of 1960 to 2080 nm is shown in FIG. In the process (2), the difference between the second derivative value and the value at time 0h becomes a feature value, and the degree of curing is evaluated using this feature value.

  Next, FIG. 14 shows the result of determining the change in absorbance (difference from the second derivative value of 0h) over time at a predetermined wavelength included in 1500 to 1600 nm based on FIG. FIG. 14 shows the change in absorbance (secondary differential value) according to the curing time in the case of wavelengths 1538.1 nm, 1544.3 nm, 1550.6 nm, and 1556.9 nm. Moreover, the result of having calculated | required the change of the light absorption with time passage in the predetermined wavelength contained in 1980-2080 nm based on FIG. 13 is shown in FIG. FIG. 15 shows the change in absorbance (secondary differential value) according to the curing time for the cases of wavelengths 2018.9 nm, 2025.1 nm, 2031.4 nm, 2037.6 nm, and 2043.8 nm.

  In both FIG. 14 and FIG. 15, the difference from the absorbance (second-order differential value) at 0 h (during application) changes with the elapsed time after application. Accordingly, a threshold value for the increment of absorbance (secondary differential value) from 0 h at a predetermined wavelength is determined in advance, and a determination is made as to whether the difference in absorbance of the product to be inspected 3 exceeds the threshold value. It can be determined whether or not is cured.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment, A various change can be made.

  For example, in the above-described embodiment, the configuration in which the analysis unit 30 is incorporated in the curing degree measurement system 100 has been described. However, the apparatus configuration can be changed as appropriate, and can be used by being incorporated in another system, for example. Moreover, the analysis unit 30 does not need to be connected to the detection unit 20 that captures image data as in the above embodiment, and can be used alone.

  Moreover, in the said embodiment, although the predetermined threshold value was set to one and the case where it was determined whether the silane type sealing material hardened | cured by the comparison with the said threshold value was demonstrated, like FIG. In addition, the degree of cure of the silane-based sealing material may be measured by utilizing the fact that the absorbance gradually changes according to the degree of curing of the silane-based sealing material, and by setting some threshold values.

DESCRIPTION OF SYMBOLS 100 ... Curing degree measuring system, 2 ... Belt conveyor, 3 ... Inspection object, 10 ... Light source unit, 11 and 11A ... Light source, 12 ... Irradiation part, 13 ... Optical fiber, 20 ... Detection unit, 21 ... Slit, 22 ... Spectroscope, 23 ... light receiving unit, 24 ... camera lens, 30 ... analysis unit, 33 ... silane-based sealing material (measurement object).

Claims (7)

Measurement including a light having a first wavelength included in a wavelength range of 1500 nm to 1600 nm or a light having a second wavelength included in a wavelength range of 1980 nm to 2080 nm with respect to a measurement object made of a silane-based sealing material. Irradiating light to receive transmitted light or diffuse reflected light from the measurement object, and obtaining an absorbance spectrum of the measurement object;
Extracting a feature quantity at the first wavelength or the second wavelength from the absorbance spectrum;
Measuring the degree of cure of the silane-based sealing material by comparing the feature amount with a predetermined threshold;
Method for measuring degree of curing of silane-based sealing material containing In the step of obtaining the absorbance spectrum of the measurement object, the measurement spectrum including the light of the first wavelength and the light of the second wavelength is irradiated to obtain an absorbance spectrum,
The method for measuring the degree of cure of a silane-based sealing material according to claim 1, wherein in the step of extracting the feature amount, feature amounts at the first wavelength and the second wavelength are extracted.   The method for measuring the degree of cure of a silane-based sealing material according to claim 1, wherein the feature amount is a difference in absorbance with respect to a baseline spectrum created based on the absorbance spectrum.   The method for measuring the degree of cure of a silane-based sealing material according to claim 1 or 2, wherein the feature amount is a second-order differential value depending on a wavelength of the absorbance spectrum.   The method for measuring the degree of cure of a silane-based sealing material according to any one of claims 1 to 4, wherein an absorbance spectrum of the measurement object is obtained using diffuse reflected light of the measurement object. A light source that irradiates measurement light to the measurement object and a detection unit that receives transmitted light from the measurement object are arranged to face each other with the measurement object interposed therebetween,
The method for measuring the degree of cure of a silane-based sealing material according to any one of claims 1 to 4, wherein an absorbance spectrum of the measurement object is obtained using the transmitted light. The measurement object is placed on a reflector, and a light source that irradiates measurement light to the measurement object and a detection unit that receives transmitted light from the measurement object sandwich the measurement object. Placed on the opposite side of the reflector,
The method for measuring the degree of cure of a silane-based sealing material according to any one of claims 1 to 4, wherein an absorbance spectrum of the measurement object is obtained using the transmitted light.