JP7521993B2 - Optical measurement device and optical measurement method - Google Patents

Description

The present invention relates to an optical measurement device and an optical measurement method.

In recent years, a technique has become known for measuring, for example, the film thickness of an object by measuring the transmittance or reflectance of the object based on the transmitted or reflected light generated from the object when light is irradiated onto the object.

For example, Patent Document 1 (JP 2015-59750 A) discloses the following film thickness measurement method. That is, the film thickness measurement method includes the steps of irradiating a measurement object with continuous light and obtaining a spectroscopic spectrum of the reflected or transmitted light, obtaining a power spectrum from the spectroscopic spectrum by Fourier transform, and determining the film thickness of the measurement object based on the midpoint between a first characteristic point for the peak on the shortest wavelength side and a second characteristic point for the peak on the longest wavelength side for the split peaks appearing in the power spectrum.

In addition, Patent Document 2 (JP 2009-198361 A) discloses a film thickness measurement device as follows. That is, the film thickness measurement device includes a measurement unit that irradiates a measurement object with white light, disperses the reflected or transmitted light obtained, and measures the spectrum, and a calculation unit that performs a predetermined calculation on the spectrum measured by the measurement unit to measure the film thickness of the measurement object. The calculation unit includes a first conversion unit that converts the spectrum in a preset wavelength band of the spectrum into a wavenumber range spectrum rearranged at a predetermined wavenumber interval, a second conversion unit that converts the wavenumber range spectrum converted by the first conversion unit into a power spectrum, and a calculation unit that determines the center of gravity of a peak that appears in the power spectrum converted by the second conversion unit and determines the thickness of the measurement object based on the center of gravity.

Patent Document 3 (JP Patent Publication 2011-133428A) discloses a retardation measurement device as follows. That is, the retardation measurement device is a retardation measurement device that irradiates a measured object with polarized light and measures the retardation of the measured object using the light returned from the measured object. The retardation measurement device includes a light source that outputs white light to be irradiated onto the measured object, a polarizing plate that polarizes the output light of the light source and receives the light returned from the measured object, a spectroscopic section that receives the light returned from the measured object and transmitted through the polarizing plate and generates a spectrum of this light, and a calculation section that receives the spectrum generated by the spectroscopic section, calculates the retardation from the spectrum, and outputs the retardation.

Patent Document 4 (JP Patent Publication 2012-112760 A) discloses the following film thickness measurement method. That is, the film thickness measurement method is a film thickness measurement method for measuring the film thickness of a birefringent object, and includes the steps of irradiating the object with polarized light, dispersing the light transmitted through the object to generate a spectrum, and measuring the retardation from the spectrum, and calculating the film thickness of the object from the measured retardation and the refractive index difference of the object.

JP 2015-59750 A JP 2009-198361 A JP 2011-133428 A JP 2012-112760 A

For example, Patent Document 1 discloses that in the power spectrum of the spectroscopic spectrum of reflected light or transmitted light from a measurement object, two peaks appear corresponding to two different optical film thicknesses in the measurement object. With the techniques described in Patent Documents 1 and 2, it may not be possible to accurately determine the film thickness of the measurement object based on such a power spectrum.

There is a need for technology that goes beyond the technologies described in Patent Documents 1 to 4 and that can measure the transmittance or reflectance of an object more accurately.

The present invention has been made to solve the above-mentioned problems, and its purpose is to provide an optical measurement device and an optical measurement method that can more accurately measure the transmittance or reflectance of a measurement object.

(1) In order to solve the above problem, an optical measurement device according to one aspect of the present invention includes an illumination optical system that illuminates an object to be measured with illumination light including multiple wavelengths, a light receiving optical system that receives measurement light, which is transmitted light or reflected light generated from the object to be measured by irradiating the object with the illumination light, and a polarizing plate, and is configured so that the polarizing plate can be positioned in either the illumination optical system or the light receiving optical system.

In this way, by providing a polarizing plate that can be positioned in either the irradiating optical system or the receiving optical system, and irradiating the measurement object with irradiation light that has passed through the polarizing plate, or receiving the measurement light that has passed through the polarizing plate, when measuring the transmittance spectrum or reflectance spectrum of a measurement object having birefringence, for example, it is possible to measure a transmittance spectrum or reflectance spectrum with reduced beat components, and compared to a configuration in which polarizing plates are provided in both the irradiating optical system and the receiving optical system, it is possible to suppress a decrease in the received intensity of the measurement light in the receiving optical system. Therefore, it is possible to more accurately measure the transmittance or reflectance of the measurement object.

(2) Preferably, the polarizing plate is fixedly provided to only one of the irradiation optical system and the light receiving optical system.

This configuration eliminates the need to move the position of the polarizing plate when measuring the transmittance or reflectance of an object to be measured, so measurement of the transmittance or reflectance of the object to be measured can be started with a simple configuration and simple operation.

(3) Preferably, the optical measurement device further includes an adjustment unit capable of adjusting the direction of the absorption axis of the polarizing plate in a direction on a plane intersecting the optical path of the irradiation light or the optical path of the measurement light.

This configuration allows the direction of the absorption axis of the polarizing plate to be adjusted relative to the optical axis of the birefringent object being measured, further reducing beat components in the generated transmittance spectrum or reflectance spectrum.

(4) In order to solve the above problem, an optical measurement method according to a certain aspect of the present invention is an optical measurement method using an optical measurement device having an irradiation optical system and a receiving optical system, and includes the steps of irradiating a measurement object with irradiation light including multiple wavelengths using the irradiation optical system, and receiving measurement light, which is transmitted light or reflected light generated from the measurement object by irradiating the measurement object with the irradiation light using the receiving optical system, and in the step of irradiating the measurement object with the irradiation light or the step of receiving the measurement light, the irradiation light transmitted through a polarizing plate is irradiated to the measurement object, or the measurement light transmitted through a polarizing plate is received.

In this way, by irradiating the measurement object with irradiation light transmitted through a polarizing plate or receiving the measurement light transmitted through a polarizing plate, when measuring the transmittance spectrum or reflectance spectrum of a measurement object having birefringence, for example, it is possible to measure a transmittance spectrum or reflectance spectrum with reduced beat components, and compared to a configuration in which polarizing plates are provided in both the irradiation optical system and the receiving optical system, it is possible to suppress a decrease in the received intensity of the measurement light in the receiving optical system. Therefore, it is possible to more accurately measure the transmittance or reflectance of the measurement object.

(5) Preferably, the polarizing plate is fixedly provided to only one of the irradiation optical system and the light receiving optical system.

This configuration eliminates the need for operations such as moving the position of the polarizing plate when measuring the transmittance or reflectance of the object to be measured, so measurement of the transmittance or reflectance of the object to be measured can be started with a simple configuration and simple operations.

(6) Preferably, the optical measurement method further includes a step of calculating the film thickness of the measurement object based on the reception results of each of the measurement lights in directions on a plane intersecting the optical path of the irradiation light or the measurement light when the directions of the absorption axes of the polarizing plate are different.

With this configuration, for example, when measuring the film thickness of a birefringent object, the film thickness of the object can be calculated more accurately by using the results of receiving the measurement light when the polarizing plate is positioned so that the absorption axis is parallel to the slow axis of the object, and the results of receiving the measurement light when the polarizing plate is positioned so that the absorption axis is parallel to the fast axis of the object.

The present invention makes it possible to measure the transmittance or reflectance of an object more accurately.

FIG. 1 is a diagram showing an example of the configuration of an optical measurement device according to a first embodiment of the present invention. FIG. 2 is a diagram showing an example of the configuration of the optical measuring device according to the first embodiment of the present invention. FIG. 3 is a diagram showing the configuration of a light receiving optical system in the optical measuring device according to the first embodiment of the present invention. FIG. 4 is a diagram showing the configuration of a processing device in the optical measuring device according to the first embodiment of the present invention. FIG. 5 is a diagram showing a transmittance spectrum generated by an optical measurement device according to a first comparative example of the first embodiment of the present invention. FIG. 6 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to the comparative example 1 of the first embodiment of the present invention. FIG. 7 is a diagram showing a transmittance spectrum generated by an optical measurement device according to a second comparative example of the first embodiment of the present invention. FIG. 8 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to the second comparative example of the first embodiment of the present invention. FIG. 9 is a diagram showing a transmittance spectrum generated by the optical measurement device according to the first embodiment of the present invention. FIG. 10 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to the first embodiment of the present invention. FIG. 11 is a diagram showing a transmittance spectrum generated by an optical measurement device according to a third comparative example of the first embodiment of the present invention. FIG. 12 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to the comparative example 3 of the first embodiment of the present invention. FIG. 13 is a diagram showing a transmittance spectrum generated by an optical measurement device according to Comparative Example 4 of the first embodiment of the present invention. FIG. 14 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to Comparative Example 4 of the first embodiment of the present invention. FIG. 15 is a diagram showing a transmittance spectrum generated by the optical measurement device according to the first embodiment of the present invention. FIG. 16 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to the first embodiment of the present invention. FIG. 17 is a diagram showing the relationship between the direction of the absorption axis of the polarizing plate in the optical measurement device according to the first embodiment of the present invention and the direction of the slow axis of the object to be measured. FIG. 18 is a diagram showing an example of a configuration of an optical measurement device according to the second modification of the first embodiment of the present invention. FIG. 19 is a flowchart defining an example of an operational procedure for calculating a film thickness of a measurement object in the optical measurement device according to the first embodiment of the present invention. FIG. 20 is a flowchart defining an example of an operational procedure for adjusting the direction of the absorption axis of the polarizing plate in the optical measurement device according to the first embodiment of the present invention. FIG. 21 is a diagram showing an example of the configuration of an optical measurement device according to the second embodiment of the present invention. FIG. 22 is a diagram showing an example of the configuration of an optical measurement device according to the second embodiment of the present invention. FIG. 23 is a diagram showing an example of a configuration of an optical measurement device according to a first modified example of the second embodiment of the present invention. In FIG. FIG. 24 is a diagram showing an example of the configuration of an irradiation optical system in an optical measurement device according to a modified example of the second embodiment of the present invention.

The following describes embodiments of the present invention with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated. In addition, at least some of the embodiments described below may be combined in any manner.

First Embodiment
[Optical measuring device]
FIG. 1 is a diagram showing an example of the configuration of an optical measurement device according to a first embodiment of the present invention.

Referring to FIG. 1, the optical measurement device 101 includes an irradiation optical system 10, a light receiving optical system 20, a processing device 30, an adjustment unit 51, a base member 4, a support member 6, and a polarizing plate 50. The base member 4 and the support member 6 fix the light receiving optical system 20. Note that the optical measurement device 101 is not limited to a configuration including the base member 4 and the support member 6, and may include other members for fixing the light receiving optical system 20 instead of or in addition to the base member 4 and the support member 6.

The polarizing plate 50 is configured so that it can be positioned in either the irradiation optical system 10 or the light receiving optical system 20. For example, the polarizing plate 50 is fixedly provided in only one of the irradiation optical system 10 or the light receiving optical system 20. In the example shown in FIG. 1, the polarizing plate 50 is fixedly provided in only the light receiving optical system 20.

Figure 2 is a diagram showing an example of the configuration of an optical measurement device according to a first embodiment of the present invention. Figure 2 shows a state in which a measurement target S, which is the measurement target of the optical measurement device 101, is placed.

Referring to FIG. 2, the optical measurement device 101 measures the transmittance of a measurement object S, such as a film, that passes through a target region R.

For example, the optical measuring device 101 automatically measures the transmittance spectrum at multiple measurement positions M on the measurement object S that is transported through the target region R in a manufacturing line for the measurement object S. That is, the optical measuring device 101 measures the transmittance spectrum at multiple measurement positions M on the measurement object S in-line.

More specifically, the optical measuring device 101 calculates the transmittance for each wavelength at the measurement position M of the transported measurement object S, for example, by periodically measuring the transmittance.

[Illumination optical system]
The irradiation optical system 10 linearly irradiates the measurement object S with irradiation light including a plurality of wavelengths. More specifically, the irradiation optical system 10 irradiates the irradiation light to a target region R, which is a linear region through which the measurement object S passes.

The irradiation optical system 10 includes a light source 11 and a line light guide 12.

The light source 11 emits light including multiple wavelengths. The spectrum of the light emitted by the light source 11 may be a continuous spectrum or a line spectrum. The wavelength of the light emitted by the light source 11 is set according to the range of wavelength information to be obtained from the measurement object S. The light source 11 is, for example, a halogen lamp.

The line light guide 12 receives light emitted from the light source 11 and emits the received light from a linear opening, thereby linearly irradiating the target region R with irradiation light. For example, a diffusion member or the like for suppressing unevenness in the amount of light is disposed on the emission surface of the line light guide 12 from which the irradiation light is emitted. The line light guide 12 is disposed directly below the surface on which the measurement target S is transported.

For example, when performing in-line measurement of the transmittance spectrum of the measurement target S, the irradiation optical system 10 irradiates the target region R with irradiation light at the measurement timing, and stops irradiating the target region R with irradiation light at timings other than the measurement timing. Note that the irradiation optical system 10 may be configured to continuously irradiate the target region R with irradiation light regardless of the measurement timing.

[Light receiving optical system]
The light receiving optical system 20 receives measurement light, which is transmitted light generated from the measurement object S when the measurement object S is irradiated with the irradiation light.

The light receiving optical system 20 includes a polarizing plate 50, an objective lens 21, an imaging spectrometer 22, and an imaging unit 23.

The light receiving optical system 20 is positioned opposite the line light guide 12, sandwiching the measurement object S.

The light receiving optical system 20 receives, as measurement light, the transmitted light that is transmitted through the target region R from the irradiation light emitted from the line light guide 12. Specifically, the light receiving optical system 20 receives, as measurement light, the transmitted light that is transmitted through the measurement object S passing through the target region R from the irradiation light emitted from the line light guide 12.

Figure 3 is a diagram showing the configuration of the light receiving optical system in the optical measurement device according to the first embodiment of the present invention.

Referring to FIG. 3, the imaging spectrometer 22 has a slit section 221, a first lens 222, a diffraction grating 223, and a second lens 224. The slit section 221, the first lens 222, the diffraction grating 223, and the second lens 224 are arranged in this order from the objective lens 21 side.

The imaging unit 23 is composed of an imaging element 231 having a two-dimensional light receiving surface. Such an imaging element 231 is, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The imaging unit 23 generates a two-dimensional image P based on the measurement light received from the imaging spectrometer 22. The two-dimensional image P generated by the imaging unit 23 includes wavelength information and position information.

For example, the polarizing plate 50 is disposed on the optical path of the measurement light from the target region R to the objective lens 21. The polarizing plate 50 has an absorption axis. For example, the polarizing plate 50 is fixed on the optical path using a fixing member such as a bolt so that the direction of the absorption axis can be adjusted and the position relative to the light receiving optical system 20 is fixed.

The direction of the absorption axis of the polarizing plate 50 on the plane intersecting the optical path of the measurement light is adjusted by the adjustment unit 51, for example, before starting the in-line measurement of the transmittance spectrum of the measurement object S. Note that the direction may also be adjusted manually by the user.

The polarizing plate 50 absorbs the measurement light from the target region R that vibrates in a direction parallel to the absorption axis. The light that passes through the polarizing plate 50 is guided to the objective lens 21.

The objective lens 21 converges the measurement light from the target region R that has passed through the polarizing plate 50 and guides it to the imaging spectrometer 22.

The slit section 221 in the imaging spectrometer 22 includes a slit. The slit section 221 shapes the beam cross section of the measurement light incident on it via the objective lens 21 into a predetermined shape. The longitudinal length of the slit in the slit section 221 is set to a length corresponding to the length of the target region R, and the lateral width of the slit is set to a length corresponding to the resolution of the diffraction grating 223, etc.

The first lens 222 in the imaging spectrometer 22 converts the measurement light that has passed through the slit portion 221 into parallel light and guides the converted measurement light to the diffraction grating 223. The first lens 222 is, for example, a collimating lens.

The diffraction grating 223 in the imaging spectrometer 22 wavelength-expands (wavelength-expands) the measurement light in a direction perpendicular to the longitudinal direction of the measurement light. More specifically, the diffraction grating 223 wavelength-expands, i.e., disperses, the line-shaped measurement light that has passed through the slit portion 221 in a direction perpendicular to the line direction.

The second lens 224 in the imaging spectrometer 22 images the measurement light, which has been wavelength-expanded by the diffraction grating 223, on the light-receiving surface of the image sensor 231 in the imaging unit 23 as a two-dimensional optical spectrum that reflects the wavelength information and position information.

The imaging unit 23 transmits two-dimensional image data representing the two-dimensional image P formed on the light receiving surface of the imaging element 231 to the processing device 30 as a result of light reception in the light receiving optical system 20.

In the following, the D1 direction in FIG. 3 in the two-dimensional image P is referred to as the "position direction", and the D2 direction, which is a direction perpendicular to the position direction, is referred to as the "wavelength direction". Each point in the position direction corresponds to each measurement point X on the target region R. Each point in the wavelength direction corresponds to the wavelength of the measurement light from the corresponding measurement point X. In addition, the light receiving surface of the image sensor 231 has m channels as the resolution in the wavelength direction, and n channels as the resolution in the position direction. n is, for example, 1200.

[Processing device]
FIG. 4 is a diagram showing the configuration of a processing device in the optical measuring device according to the first embodiment of the present invention.

Referring to FIG. 4, the processing device 30 includes a receiving unit 31, a calculating unit 32, a memory unit 33, and a transmitting unit 34. The processing device 30 is, for example, a personal computer.

The receiving unit 31 receives two-dimensional image data from the imaging unit 23 in the light receiving optical system 20 and stores the received two-dimensional image data in the memory unit 33.

The calculation unit 32 generates a light reception spectrum S(λ), which is the relationship between the wavelength λ and the intensity of the measurement light in the target region R, based on the result of receiving the measurement light in the light receiving optical system 20. Then, the calculation unit 32 calculates the transmittance for each wavelength of the measurement object S passing through the target region R based on the generated light reception spectrum S(λ).

More specifically, the calculation unit 32 generates a light reception spectrum S(λ) based on the two-dimensional image data stored in the memory unit 33, and calculates the transmittance of the measurement object S for each wavelength λ based on the generated light reception spectrum S(λ).

For example, the calculation unit 32 calculates the transmittance spectrum ST(λ), which is the relationship between the wavelength λ and the transmittance in the measurement object S, based on a reference spectrum Str(λ), which is the light receiving spectrum S(λ) based on the measurement light generated from the target area R when the measurement object S is not present, and a measurement spectrum Stm(λ), which is the light receiving spectrum S(λ) based on the measurement light generated from the target area R when the measurement object S is present.

For example, the calculation unit 32 calculates the film thickness of the measurement object S based on the calculated transmittance spectrum ST(λ). More specifically, the calculation unit 32 generates a power spectrum by performing arithmetic processing such as a Fourier transform on the calculated transmittance spectrum ST(λ). Then, the calculation unit 32 determines the optical film thickness corresponding to the peak wavelength in the generated power spectrum as the film thickness of the measurement object S.

For example, the calculation unit 32 generates multiple reference spectra Str(λ) and multiple measurement spectra Stm(λ) for each measurement point X in the target region R, and calculates multiple transmittance spectra ST(λ) for each measurement point X based on each generated reference spectrum Str(λ) and each measurement spectrum Stm(λ). Then, the calculation unit 32 generates a film thickness distribution indicating the film thickness at each measurement point X of the measurement object S based on each calculated transmittance spectrum ST(λ).

The calculation unit 32 may be configured to calculate the hue of the measurement object S based on the calculated transmittance spectrum ST(λ).

(Adjustment of the absorption axis direction of the polarizing plate)
The adjustment unit 51 can adjust the direction of the absorption axis of the polarizing plate 50 in a direction on a plane intersecting the optical path of the measurement light. More specifically, the adjustment unit 51 can adjust the direction of the absorption axis of the polarizing plate 50 in a direction on a plane perpendicular to the optical path of the measurement light. The adjustment unit 51 is, for example, an electric actuator, a hydraulic actuator, a pneumatic actuator, a chemical actuator, a magnetic fluid actuator, or an electrorheological fluid actuator. As an example, the adjustment unit 51 adjusts the direction of the absorption axis of the polarizing plate 50 so that the angle between the absorption axis of the polarizing plate 50 and the optical axis of the measurement object S is between −10 degrees and 10 degrees, or between 80 degrees and 100 degrees.

For example, the adjustment unit 51 adjusts the direction of the absorption axis of the polarizing plate 50 so that a single peak that is not buried in the background appears in the power spectrum generated by performing arithmetic processing such as a Fourier transform on the transmittance spectrum of the measurement object S.

For example, before starting in-line measurement of the transmittance spectrum of the measurement object S, the adjustment unit 51 adjusts the direction of the absorption axis of the polarizing plate 50 according to a control signal from the processing device 30.

More specifically, before starting the in-line measurement of the transmittance spectrum of the measurement object S, the calculation unit 32 outputs a control signal to the transmission unit 34 to adjust the angle θa between a predetermined reference direction on a plane perpendicular to the optical path of the measurement light and the direction of the absorption axis of the polarizing plate 50 on that plane to an initial value angle θas.

When the transmission unit 34 receives a control signal from the calculation unit 32, it transmits the received control signal to the adjustment unit 51.

For example, when the adjustment unit 51 receives a control signal from the transmission unit 34, it adjusts the angle θa to the angle θas by rotating the polarizing plate 50 in accordance with the received control signal.

When the angle θa is adjusted by the adjustment unit 51, the calculation unit 32 calculates the transmittance spectrum ST(λ) at a certain measurement position M on the measurement object S. For example, the calculation unit 32 calculates the transmittance spectrum ST(λ) at a portion located at the longitudinal end of the target region R at the measurement position M. Next, the calculation unit 32 generates a power spectrum by performing arithmetic processing such as a Fourier transform on the calculated transmittance spectrum ST(λ). Then, the calculation unit 32 calculates the difference D between the intensity of the largest peak and the intensity of the second largest peak in the generated power spectrum. The calculation unit 32 stores the calculated difference D in the storage unit 33.

After storing the difference D in the memory unit 33, the calculation unit 32 transmits a control signal to the adjustment unit 51 via the transmission unit 34 to change the angle θa to, for example, an angle rotated three degrees clockwise.

When the adjustment unit 51 receives a control signal from the calculation unit 32 via the transmission unit 34, it again adjusts the angle θa according to the received control signal.

When the angle θa is adjusted by the adjustment unit 51, the calculation unit 32 again calculates the transmittance spectrum ST(λ) at the measurement position M on the measurement object S, generates a power spectrum, and calculates the difference D in the power spectrum.

As described above, the calculation unit 32 repeats the change of the angle θa and the calculation of the difference D in the power spectrum a predetermined number of times, for example 60 times, and calculates the difference D for each angle θa. Then, the calculation unit 32 detects the angle θmax, which is the angle θa at which the difference D is maximum.

When the calculation unit 32 detects the angle θmax, it transmits a control signal to the adjustment unit 51 via the transmission unit 34 to set the angle θa to the angle θmax. The calculation unit 32 may be configured to detect one or more angles θth, which are the angles θa when the difference D is equal to or greater than a predetermined threshold value, and transmit a control signal to the adjustment unit 51 via the transmission unit 34 to set the angle θa to any one of the angles θth. The calculation unit 32 may also be configured to detect the angle θa when the sharpest single peak appears as the angle θmax based on an index indicating the sharpness of the peaks that appear in the power spectrum, and transmit a control signal to the adjustment unit 51 via the transmission unit 34 to set the angle θa to the detected angle θmax.

When the adjustment unit 51 receives a control signal from the calculation unit 32 via the transmission unit 34, it rotates the polarizing plate 50 in accordance with the received control signal so that the angle θa becomes the angle θmax.

The optical measuring device 101 starts in-line measurement of the transmittance spectrum ST(λ) of the measurement object S with the angle θa set to the angle θmax.

For example, the optical measurement device 101 is used to measure the film thickness of a measurement object S having birefringence. Specifically, the measurement object S is, for example, a stretched film of PET (Polyethylene Terephthalate). The stretched PET film has optical axes, for example, a slow axis Nx and a fast axis Ny, depending on the stretching direction and stretching ratio. The slow axis Nx and the fast axis Ny are, for example, perpendicular to each other. The slow axis Nx and the fast axis Ny of the measurement object S are an example of the optical axis of the measurement object S.

For example, the optical measurement device 101 is used to measure the film thickness of a measurement object S having polarization characteristics. Specifically, the measurement object S is, for example, a long polarizing film. The polarizing film is stretched in the manufacturing process and has an absorption axis in a direction corresponding to the stretching direction. The absorption axis of the measurement object S is an example of the optical axis of the measurement object S.

In the conventional optical measurement method, when measuring the film thickness of a measurement object S having birefringence or polarization characteristics, the film thickness of the measurement object S may not be measured accurately. Specifically, for example, in the conventional optical measurement method, due to the influence of the birefringence of the measurement object S, a beat component is included in the calculated transmittance spectrum, and in the power spectrum obtained by Fourier transforming the transmittance spectrum, multiple peaks may appear at different positions as peaks corresponding to the film thickness of the measurement object S, in which case it is difficult to accurately measure the film thickness of the measurement object S. Also, for example, in the conventional optical measurement method, due to the influence of the birefringence of the measurement object S, in the power spectrum, the peak corresponding to the film thickness of the measurement object S may be buried in the background, in which case it is difficult to accurately measure the film thickness of the measurement object S. Also, for example, in the conventional optical measurement method, due to the influence of the polarization diffraction property of the measurement object S, in the power spectrum, the peak corresponding to the film thickness of the measurement object S may be buried in the background, in which case it is difficult to accurately measure the film thickness of the measurement object S.

In addition, in the techniques described in Patent Documents 3 and 4, in order to measure the retardation of the object to be measured, a polarizing plate is arranged so that both the light irradiated to the object to be measured and the light output from the object to be measured pass through the polarizing plate. Therefore, since both the light irradiated to the object to be measured and the light output from the object to be measured are attenuated by the polarizing plate, it may not be possible to accurately measure the film thickness within the limited measurement time.

(Measurement Example 1)
Fig. 5 is a diagram showing a transmittance spectrum generated by an optical measurement device according to Comparative Example 1 of the first embodiment of the present invention. In Fig. 5, the vertical axis represents transmittance, and the horizontal axis represents wavelength. Fig. 5 shows a transmittance spectrum STc1(λ) at a measurement point on a measurement target S having birefringence, generated by an optical measurement device 101 not including a polarizing plate 50.

Figure 6 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to Comparative Example 1 of the first embodiment of the present invention. In Figure 6, the vertical axis represents intensity and the horizontal axis represents film thickness. Figure 6 shows the power spectrum Pwc1 obtained by Fourier transforming the transmittance spectrum STc1(λ) shown in Figure 5.

Referring to FIG. 6, in the power spectrum Pwc1 generated by the optical measurement device 101 of Comparative Example 1, the peaks that should appear according to the film thickness of the measurement object S are buried in the background, and the largest peak cannot be uniquely detected. For this reason, it is difficult to accurately measure the film thickness of the measurement object S.

Figure 7 is a diagram showing a transmittance spectrum generated by an optical measurement device according to Comparative Example 2 of the first embodiment of the present invention. In Figure 7, the vertical axis is transmittance and the horizontal axis is wavelength. Figure 7 shows a transmittance spectrum STc2(λ) at a measurement point on a birefringent measurement object S, generated by an optical measurement device 101 in which the angle between the absorption axis direction of the polarizing plate 50 and the slow axis Nx direction of the measurement object S is 45 degrees.

Figure 8 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to Comparative Example 2 of the first embodiment of the present invention. In Figure 8, the vertical axis represents intensity and the horizontal axis represents film thickness. Figure 8 shows the power spectrum Pwc2 obtained by Fourier transforming the transmittance spectrum STc2(λ) shown in Figure 7.

Referring to FIG. 8, in the power spectrum Pwc2 generated by the optical measurement device 101 according to the comparative example 2, similar to the power spectrum Pwc1, the peaks that should appear according to the film thickness of the measurement object S are buried in the background, and it may not be possible to uniquely detect the largest peak. In this case, it is difficult to accurately measure the film thickness of the measurement object S.

Figure 9 is a diagram showing a transmittance spectrum generated by an optical measurement device according to a first embodiment of the present invention. In Figure 9, the vertical axis represents transmittance, and the horizontal axis represents wavelength. Figure 9 shows a transmittance spectrum ST(λ) at a measurement point on a birefringent measurement object S, generated by an optical measurement device 101 adjusted so that the direction of the absorption axis of the polarizing plate 50 is parallel to the direction of the slow axis Nx of the measurement object S.

Figure 10 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to the first embodiment of the present invention. In Figure 10, the vertical axis represents intensity and the horizontal axis represents film thickness. Figure 10 shows the power spectrum Pw obtained by Fourier transforming the transmittance spectrum ST(λ) shown in Figure 9.

Referring to FIG. 10, in the power spectrum Pw generated by the optical measurement device 101 according to the first embodiment of the present invention, the largest peak pk can be uniquely detected, and the film thickness F of the measurement object S corresponding to the peak pk can be accurately measured.

(Measurement Example 2)
Fig. 11 is a diagram showing a transmittance spectrum generated by an optical measurement device according to Comparative Example 3 of the first embodiment of the present invention. In Fig. 11, the vertical axis represents transmittance, and the horizontal axis represents wavelength. Fig. 11 shows a transmittance spectrum STc3(λ) at a measurement point on a birefringent measurement object S, which is generated by an optical measurement device 101 in which the angle between the absorption axis direction of the polarizing plate 50 and the slow axis Nx direction of the measurement object S is 45 degrees.

Figure 12 is a diagram showing the power spectrum of the transmittance spectrum generated by an optical measurement device according to Comparative Example 3 of the first embodiment of the present invention. In Figure 12, the vertical axis represents intensity and the horizontal axis represents film thickness. Figure 12 shows the power spectrum Pwc3 obtained by Fourier transforming the transmittance spectrum STc3(λ) shown in Figure 11.

Referring to FIG. 12, in the power spectrum Pwc3 generated by the optical measurement device 101 according to Comparative Example 3, peaks pk1 and pk2 occur, and it may not be possible to uniquely detect the largest peak. In this case, it is difficult to accurately measure the film thickness of the measurement object S.

Figure 13 is a diagram showing a transmittance spectrum generated by an optical measurement device according to Comparative Example 4 of the first embodiment of the present invention. In Figure 13, the vertical axis is transmittance and the horizontal axis is wavelength. Figure 13 shows a transmittance spectrum STc4(λ) at a measurement point on a birefringent measurement object S, generated by an optical measurement device 101 in which the angle between the absorption axis direction of the polarizing plate 50 and the slow axis Nx direction of the measurement object S is 75 degrees.

Figure 14 is a diagram showing the power spectrum of the transmittance spectrum generated by an optical measurement device according to Comparative Example 4 of the first embodiment of the present invention. In Figure 14, the vertical axis represents intensity and the horizontal axis represents film thickness. Figure 14 shows the power spectrum Pwc4 obtained by Fourier transforming the transmittance spectrum STc4(λ) shown in Figure 13.

Referring to FIG. 14, in the power spectrum Pwc4 generated by the optical measurement device 101 according to Comparative Example 4, peaks pk1 and pk2 occur, similar to the power spectrum Pwc3. The peak pk2 in the power spectrum Pwc4 is smaller than the peak pk2 in the power spectrum Pwc3. However, in the power spectrum Pwc4, depending on the measurement conditions, etc., it may not be possible to uniquely detect the largest peak. In this case, it is difficult to accurately measure the film thickness of the measurement object S.

Figure 15 is a diagram showing a transmittance spectrum generated by an optical measurement device according to a first embodiment of the present invention. In Figure 15, the vertical axis represents transmittance, and the horizontal axis represents wavelength. Figure 15 shows a transmittance spectrum ST2(λ) at a measurement point on a birefringent measurement object S, generated by an optical measurement device 101 in which the angle between the absorption axis direction of the polarizing plate 50 and the slow axis Nx direction of the measurement object S is 90 degrees.

Figure 16 is a diagram showing the power spectrum of the transmittance spectrum generated by the optical measurement device according to the first embodiment of the present invention. In Figure 16, the vertical axis represents intensity and the horizontal axis represents film thickness. Figure 16 shows the power spectrum Pw2 obtained by Fourier transforming the transmittance spectrum ST2(λ) shown in Figure 15.

Referring to FIG. 16, in the power spectrum Pw2 generated by the optical measurement device 101 according to the first embodiment of the present invention, the largest peak pk1 can be uniquely detected, and the film thickness F of the measurement object S corresponding to the peak pk1 can be accurately measured.

Figure 17 shows the relationship between the direction of the absorption axis of the polarizing plate and the direction of the slow axis of the object to be measured in the optical measurement device according to the first embodiment of the present invention.

Referring to FIG. 17, the irradiation optical system 10 irradiates the measurement object S with irradiation light, which is natural light. The transmitted light that passes through the measurement object S includes light Lx that vibrates in a direction parallel to the slow axis Nx of the measurement object S, and light Ly that vibrates in a direction parallel to the fast axis Ny of the measurement object S.

For example, peak pk1 in power spectra Pwc3 and Pwc4 is a peak corresponding to light Lx, and peak pk2 in power spectra Pwc3 and Pwc4 is a peak corresponding to light Ly.

The optical measurement device 101 according to Comparative Example 3 receives light Lx attenuated by the polarizing plate 50 and light Ly attenuated by the polarizing plate 50. Here, since the angle between the direction of the absorption axis of the polarizing plate 50 in the optical measurement device 101 according to Comparative Example 3 and the direction of the slow axis Nx of the measurement object S is 45 degrees, the amount of attenuation of light Lx by the polarizing plate 50 and the amount of attenuation of light Ly by the polarizing plate 50 are approximately the same. Therefore, in the power spectrum Pwc3 generated by the optical measurement device 101 according to Comparative Example 3, a peak pk1 corresponding to light Lx and a peak pk2 corresponding to light Ly and having approximately the same magnitude as peak pk1 are generated.

The optical measurement device 101 according to Comparative Example 4 receives light Lx attenuated by the polarizing plate 50 and light Ly attenuated by the polarizing plate 50. Here, since the angle between the direction of the absorption axis of the polarizing plate 50 in the optical measurement device 101 according to Comparative Example 4 and the direction of the slow axis Nx of the measurement object S is 75 degrees, the attenuation of light Ly by the polarizing plate 50 is greater than the attenuation of light Lx by the polarizing plate 50. Therefore, in the power spectrum Pwc4 generated by the optical measurement device 101 according to Comparative Example 4, a peak pk1 corresponding to light Lx and a peak pk2 corresponding to light Ly and smaller than peak pk1 are generated.

In contrast, the angle between the direction of the absorption axis of the polarizing plate 50 in the optical measuring device 101 according to the first embodiment and the direction of the slow axis Nx of the object to be measured S is 90 degrees, so that, as shown in FIG. 17, the light Lx passes through the polarizing plate 50 without being attenuated by the polarizing plate 50, while the light Ly is absorbed by the polarizing plate 50. Therefore, in the power spectrum Pw2 generated by the optical measuring device 101 according to the first embodiment, a peak pk1 corresponding to the light Lx occurs, but no peak corresponding to the light Ly occurs, so that the largest peak pk1 can be uniquely detected, and the film thickness F of the object to be measured S corresponding to the peak pk1 can be accurately measured.

[Modification 1]
The calculation unit 32 calculates the film thickness of the measurement target S based on the results of receiving each measurement light when the absorption axis direction of the polarizing plate on a plane perpendicular to the optical path of the irradiation light is different.

For example, the calculation unit 32 determines, as the film thickness of the measurement object S, the average value of the film thickness Fmax1 calculated based on the light reception result by the light receiving optical system 20 of the measurement light generated from the measurement position M when the angle θa is set to the angle θmax, and the film thickness Fmax2 calculated based on the light reception result by the light receiving optical system 20 of the measurement light generated from the measurement position M when the angle θa is set to the angle (θmax + 90°).

For example, when the angle θa is set to the angle θmax, the direction Da of the absorption axis of the polarizing plate 50 is parallel to the slow axis Nx of the object to be measured S, and when the angle θa is set to the angle (θmax + 90°), the direction Db of the absorption axis of the polarizing plate 50 is parallel to the fast axis Ny of the object to be measured S.

More specifically, the optical measuring device 101 includes an irradiation optical system 10a and an irradiation optical system 10b aligned along the transport direction of the measurement object S, and a light receiving optical system 20a and a light receiving optical system 20b aligned along the transport direction of the measurement object S.

The irradiation optical system 10a and the irradiation optical system 10b irradiate the irradiation light to the measurement position M on the measurement object S.

The light receiving optical system 20a receives measurement light generated from the measurement position M by the irradiation optical system 10a irradiating the measurement position M with irradiation light. The light receiving optical system 20b receives measurement light generated from the measurement position M by the irradiation optical system 10b irradiating the measurement position M with irradiation light.

The direction Da of the absorption axis of the polarizing plate 50 in the light receiving optical system 20a and the direction Db of the absorption axis of the polarizing plate 50 in the light receiving optical system 20b are perpendicular to each other. More specifically, the absorption axis of the polarizing plate 50 in the light receiving optical system 20a has an angle θa set to an angle θmax, and the absorption axis of the polarizing plate 50 in the light receiving optical system 20b has an angle θa set to an angle (θmax + 90°).

The calculation unit 32 determines the average value of the film thickness Fmax1 calculated based on the light reception result by the light receiving optical system 20a of the measurement light generated from the measurement position M, and the film thickness Fmax2 calculated based on the light reception result by the light receiving optical system 20b of the measurement light generated from the measurement position M, as the film thickness of the measurement object S.

[Modification 2]
In the optical measurement device 101 according to the first embodiment of the present invention, the polarizing plate 50 is configured to be fixedly provided only to the light receiving optical system 20, but this is not limited thereto. The polarizing plate 50 may be configured to be fixedly provided only to the irradiation optical system 10.

Figure 18 shows an example of the configuration of an optical measurement device according to variant 2 of the first embodiment of the present invention.

Referring to FIG. 18, in the optical measurement device 101, the light receiving optical system 20 does not include a polarizing plate 50, while the irradiation optical system 10 includes a polarizing plate 50.

More specifically, for example, the polarizing plate 50 is disposed on the optical path of the irradiation light from the line light guide 12 to the target region R. For example, the polarizing plate 50 is fixed on the optical path using a fixing member such as a bolt so that the direction of the absorption axis of the polarizing plate 50 is adjustable and the position relative to the irradiation optical system 10 is fixed.

The adjustment unit 51 adjusts the direction of the absorption axis of the polarizing plate 50 on a plane perpendicular to the optical path of the irradiated light.

In the optical measurement device 101 according to the second modification, like the optical measurement device 101 according to the first embodiment of the present invention, the largest peak pk can be uniquely detected in the generated power spectrum Pw, and the film thickness F of the measurement object S corresponding to the peak pk can be accurately measured.

[Operation flow]
The optical measurement device according to the embodiment of the present invention includes a computer including a memory, and a processor such as a CPU in the computer reads out from the memory and executes a program including some or all of the steps in the following flowcharts. The program for this device can be installed from outside. The program for this device is distributed in a state stored on a recording medium.

Figure 19 is a flowchart that defines an example of the operational procedure for calculating the film thickness of a measurement object in an optical measurement device according to the first modification of the first embodiment of the present invention.

Referring to FIG. 19, first, before starting the in-line measurement of the transmittance distribution of the measurement object S, the optical measurement device 101 adjusts the direction of the absorption axis of each polarizing plate 50 of the light receiving optical system 20a, 20b so that a single peak not buried in the background appears in the power spectrum generated by performing arithmetic processing such as Fourier transform on the transmittance spectrum of the measurement object S. Specifically, the optical measurement device 101 sets the angle θa between a predetermined reference direction on a plane perpendicular to the optical path of the measurement light and the direction of the absorption axis of the polarizing plate 50 in the light receiving optical system 20a to an angle θmax. In addition, the optical measurement device 101 sets the angle θa between a predetermined reference direction on a plane perpendicular to the optical path of the measurement light and the direction of the absorption axis of the polarizing plate 50 in the light receiving optical system 20b to an angle (θmax + 90°) (step S102).

Next, after starting the in-line measurement, the optical measuring device 101 waits for the measurement timing, which is the timing to perform the measurement (NO in step S104), and at the measurement timing (YES in step S104), irradiates the measurement object S with irradiation light in a linear manner. Specifically, the optical measuring device 101 uses the irradiation optical systems 10a and 10b to irradiate the measurement position M on the measurement object S with irradiation light in a linear manner (step S106).

Next, the optical measuring device 101 receives the measurement light, i.e., the transmitted light, which is generated from the measuring object S by irradiating the measuring object S with the irradiation light and which has passed through the polarizing plate 50. Specifically, the optical measuring device 101 receives the transmitted light that passes through the measuring object S using the light receiving optical systems 20a and 20b (step S108).

Next, the optical measuring device 101 calculates the transmittance spectrum ST(λ) based on the result of receiving the measurement light. Specifically, the optical measuring device 101 calculates the transmittance spectrum ST(λ) based on the result of receiving the light by the light receiving optical system 20a, and the transmittance spectrum ST(λ) based on the result of receiving the light by the light receiving optical system 20b (step S110).

Next, the optical measuring device 101 calculates the film thickness at the measurement position M of the measurement object S based on each calculated transmittance spectrum ST(λ). Specifically, the optical measuring device 101 determines the average value of the film thickness Fmax1 calculated based on the light reception result by the light receiving optical system 20a and the film thickness Fmax2 calculated based on the light reception result by the light receiving optical system 20b as the film thickness at the measurement position M of the measurement object S (step S112).

In addition, in the optical measuring device 101 according to the first embodiment of the present invention, when calculating the film thickness of the object to be measured using a pair of the irradiation optical system 10a and the receiving optical system 20a, it is not necessary to set the direction of the absorption axis of the polarizing plate 50 in the receiving optical system 20b (step S102), irradiate the irradiation light using the irradiation optical system 10b (step S106), receive the transmitted light using the receiving optical system 20b (step S108), and calculate the transmittance spectrum ST(λ) based on the light reception result by the receiving optical system 20b (step S110). Instead, it is sufficient to determine the film thickness Fmax1 calculated based on the light reception result by the receiving optical system 20a as the film thickness at the measurement position M of the object to be measured S (step S112). Furthermore, when calculating the film thickness of a measurement object using the optical measurement device 101 according to the second modification of the first embodiment of the present invention, in step S106, the optical measurement device 101 linearly irradiates the measurement object S with irradiation light that has passed through the polarizing plate 50, and in step S108, receives the measurement light that has not passed through the polarizing plate 50.

Figure 20 is a flow chart that defines an example of an operational procedure for adjusting the direction of the absorption axis of a polarizing plate in the optical measurement device according to the first embodiment of the present invention. Figure 20 shows the details of step S102 in Figure 19.

Referring to FIG. 20, first, the optical measurement device 101 adjusts the angle θa to the initial value, angle θas, by rotating the polarizing plate 50 (step S202).

Next, the optical measurement device 101 calculates the transmittance spectrum ST(λ) at a certain measurement position M on the measurement object S, and generates a power spectrum by performing arithmetic processing such as a Fourier transform on the calculated transmittance spectrum ST(λ) (step S204).

Next, the optical measurement device 101 calculates the difference D between the intensity of the largest peak and the intensity of the second largest peak in the generated power spectrum, and stores the calculated difference D in the memory unit 33 (step S206).

Next, if the number of times steps S204 and S206 have been processed is less than the predetermined number of times (NO in step S208), the optical measurement device 101 adjusts the angle θa to an angle rotated 3 degrees clockwise by rotating the polarizing plate 50 (step S210), and repeats steps S204 and S206.

Next, when the number of times steps S204 and S206 have been processed reaches a predetermined number (YES in step S208), the optical measuring device 101 detects the angle θmax, which is the angle θa at which the difference D is maximum (step S212).

Next, the optical measurement device 101 rotates the polarizing plate 50 so that the angle θa becomes the angle θmax (step S212).

In the optical measurement device 101 according to the first embodiment of the present invention, the irradiation optical system 10 is configured to irradiate irradiation light onto the target region R, which is a linear region through which the measurement target S passes, but this is not limited to this. The irradiation optical system 10 may also be configured to irradiate irradiation light onto a point-like target position.

In addition, although the optical measurement device 101 according to the first embodiment of the present invention is configured to include the adjustment unit 51, this is not limited to this. The optical measurement device 101 may be configured not to include the adjustment unit 51. In this case, as an example, the direction of the absorption axis of the polarizing plate 50 is fixed in advance so as to be parallel to the direction of the slow axis Nx or fast axis Ny of the measurement object S on a plane perpendicular to the optical path of the measurement light.

In addition, in the optical measurement device 101 according to the first embodiment of the present invention, the adjustment unit 51 is configured to adjust the direction of the absorption axis of the polarizing plate 50 according to the control signal received from the transmission unit 34, but this is not limited to the configuration. The adjustment unit 51 may be configured to have a mechanism that can manually adjust the direction of the absorption axis of the polarizing plate 50, not limited to automatic adjustment. In this case, the user manually adjusts the angle θa in steps S202 and S210 of FIG. 20.

In addition, in the optical measurement device 101 according to the first embodiment of the present invention, the polarizing plate 50 is configured to be placed on the optical path of the measurement light from the target region R to the objective lens 21, but this is not limited to this. The polarizing plate 50 may be configured to be placed between the objective lens 21 and the slit portion 221, between the slit portion 221 and the first lens 222, or between the first lens 222 and the diffraction grating 223.

Next, other embodiments of the present invention will be described with reference to the drawings. Note that the same or corresponding parts in the drawings will be given the same reference numerals and their description will not be repeated.

In addition, in the optical measurement device 101 according to the first embodiment of the present invention, the polarizing plate 50 is configured to be fixedly provided to only one of the irradiation optical system 10 and the light receiving optical system 20, but this is not limited to this.

For example, the optical measurement device 101 may be configured to include a polarizing plate 50A, which is a polarizing plate 50 provided in the irradiation optical system 10, and a polarizing plate 50B, which is a polarizing plate 50 provided in the light receiving optical system 20. More specifically, the polarizing plate 50A is arranged on the optical path OP1 of the irradiation light from the line light guide 12 to the target area R by, for example, a stand S1 having a support clamp, and the polarizing plate 50B is arranged on the optical path OP2 of the measurement light from the target area R to the objective lens 21 by, for example, a stand S2 having a support clamp. In this case, when starting the film thickness measurement of the measurement object S, the polarizing plate 50A is moved to a position off the optical path OP1 by the user, or the polarizing plate 50B is moved to a position off the optical path OP2, depending on, for example, the type of the measurement object S. In addition, the polarizing plate 50A or the polarizing plate 50B may be mounted on an actuator (not shown) that receives a control signal from the processing device 30, and may be configured to be automatically moved in accordance with the operation of the actuator.

For example, the optical measurement device 101 may be configured to include a polarizing plate 50C, which is a movable polarizing plate 50 provided in either the irradiation optical system 10 or the light receiving optical system 20. More specifically, the polarizing plate 50C is mounted on an actuator (not shown) that receives a control signal from the processing device 30, and is automatically moved between the optical path OP1 and the optical path OP2 in accordance with the operation of the actuator, thereby being placed on the optical path OP1 or the optical path OP2. Note that the polarizing plate 50C may be configured to be automatically moved between the optical path OP1 and a predetermined position off the optical path OP1 in accordance with the operation of the actuator, thereby being placed on the optical path OP1 or at the predetermined position. Alternatively, the polarizing plate 50C may be configured to be automatically moved between the optical path OP2 and a predetermined position off the optical path OP2 in accordance with the operation of the actuator, thereby being placed on the optical path OP2 or at the predetermined position.

Second Embodiment
As compared with the optical measuring device 101 according to the first embodiment, the present embodiment relates to an optical measuring device 102 that uses reflected light generated from a target region R. Contents other than those described below are the same as those of the optical measuring device 101 according to the first embodiment.

[Optical measuring device]
FIG. 21 is a diagram showing an example of the configuration of an optical measurement device according to the second embodiment of the present invention.

Referring to FIG. 21, the optical measurement device 102 includes an irradiation optical system 10, a light receiving optical system 20, a processing device 30, an adjustment unit 51, a base member 4, a support member 6, and a polarizing plate 50. The base member 4 and the support member 6 fix the light receiving optical system 20. Note that the optical measurement device 102 is not limited to a configuration including the base member 4 and the support member 6, and may include other members for fixing the light receiving optical system 20 instead of or in addition to the base member 4 and the support member 6.

The polarizing plate 50 is configured so that it can be positioned in either the irradiation optical system 10 or the light receiving optical system 20. For example, the polarizing plate 50 is fixedly provided in only one of the irradiation optical system 10 or the light receiving optical system 20. In the example shown in FIG. 21, the polarizing plate 50 is fixedly provided in only the light receiving optical system 20.

Figure 22 is a diagram showing an example of the configuration of an optical measurement device according to a second embodiment of the present invention. Figure 22 shows a state in which a measurement target S, which is the measurement target of the optical measurement device 102, is placed.

Referring to FIG. 22, the optical measurement device 102 measures the reflectance spectrum of the measurement object S passing through the target region R.

For example, the optical measurement device 102 automatically measures the reflectance spectrum at multiple measurement positions M on the measurement object S that is transported through the target area R in a manufacturing line for the measurement object S. That is, the optical measurement device 102 measures the reflectance spectrum at multiple measurement positions M on the measurement object S in-line.

More specifically, the optical measurement device 102 calculates the reflectance for each wavelength at the measurement position M of the transported measurement object S, for example, by periodically measuring the reflectance.

[Illumination optical system]
The irradiation optical system 10 linearly irradiates the measurement object S with irradiation light including a plurality of wavelengths. More specifically, the irradiation optical system 10 irradiates the irradiation light to a target region R, which is a linear region through which the measurement object S passes.

The line light guide 12 of the irradiation optical system 10 is positioned so that the angle of incidence of the irradiation light passing through the target area R on the measurement object S is θ.

[Light receiving optical system]
The light receiving optical system 20 receives measurement light, which is reflected light generated from the measurement object S when the measurement object S is irradiated with irradiation light.

The light receiving optical system 20 is positioned on the same side of the measurement object S as the line light guide 12, and in a position where it can receive reflected light from the measurement object S at a reflection angle of θ.

The light receiving optical system 20 includes a polarizing plate 50, an objective lens 21, an imaging spectrometer 22, and an imaging unit 23.

The polarizing plate 50 is disposed on the optical path of the measurement light from the target region R to the objective lens 21. The polarizing plate 50 has an absorption axis.

The light receiving optical system 20 receives, as measurement light, the light reflected by the measurement object S from the irradiation light emitted from the line light guide 12. Specifically, the light receiving optical system 20 receives, as measurement light, the light reflected by the measurement object S passing through the target region R from the irradiation light emitted from the line light guide 12.

[Processing device]
The calculation unit 32 in the processing device 30 generates a light reception spectrum S(λ), which is a relationship between the wavelength λ and the intensity of the measurement light in the target region R, based on the result of receiving the measurement light in the light receiving optical system 20. Then, the calculation unit 32 calculates the reflectance for each wavelength of the measurement target S passing through the target region R based on the generated light reception spectrum S(λ).

More specifically, the calculation unit 32 generates a light reception spectrum S(λ) based on the two-dimensional image data stored in the memory unit 33, and calculates the reflectance of the measurement object S for each wavelength λ based on the generated light reception spectrum S(λ).

For example, when a reflector is placed in the target area R, the calculation unit 32 calculates the reflectance spectrum SR(λ) of the measurement object S based on a reference spectrum Srr(λ), which is the light receiving spectrum S(λ) based on the measurement light generated from the reflector placed in the target area R, and a measurement spectrum Srm(λ), which is the light receiving spectrum S(λ) based on the measurement light generated from the target area R when the measurement object S is present.

For example, the calculation unit 32 calculates the film thickness of the measurement object S based on the calculated reflectance spectrum SR(λ). More specifically, the calculation unit 32 generates a power spectrum by performing arithmetic processing such as a Fourier transform on the calculated reflectance spectrum SR(λ). Then, the calculation unit 32 determines the optical film thickness corresponding to the peak wavelength in the generated power spectrum as the film thickness of the measurement object S.

For example, the calculation unit 32 generates multiple reference spectra Srr(λ) and multiple measurement spectra Srm(λ) for each measurement point X in the target region R, and calculates multiple reflectance spectra SR(λ) for each measurement point X based on each generated reference spectrum Srr(λ) and each measurement spectrum Srm(λ). Then, the calculation unit 32 generates a film thickness distribution indicating the film thickness at each measurement point X of the measurement object S based on each calculated reflectance spectrum SR(λ).

In addition, in the optical measurement device 102 according to the second embodiment of the present invention, similar to the optical measurement device 101 according to the modified example of the first embodiment of the present invention, the calculation unit 32 in the processing device 30 may be configured to calculate the film thickness of the measurement object S based on the reception results of each measurement light when the directions of the absorption axis of the polarizing plate on the plane intersecting the optical path of the irradiation light are different.

[Modification 1]
FIG. 23 is a diagram showing an example of a configuration of an optical measurement device according to a first modified example of the second embodiment of the present invention. In FIG.

Referring to FIG. 23, the line light guide 12 has a half mirror 121. The line light guide 12 irradiates the target area R with irradiation light reflected by the half mirror 121. In this case, for example, the line light guide 12 is disposed directly above the surface on which the measurement object S is transported so that the angle of incidence of the irradiation light passing through the target area R on the measurement object S is 0°. In other words, the irradiation optical system 10 of the optical measurement device 102 is a coaxial epi-illumination system.

The light receiving optical system 20 receives the reflected light from the measurement object S due to the irradiation of the measurement object S with the irradiation light via the half mirror 121. In this case, for example, the light receiving optical system 20 is placed in a position where it can receive the reflected light from the measurement object S with a reflection angle of 0°, that is, in a position facing the target region R across the line light guide 12.

[Modification 2]
In the optical measurement device 102 according to the second embodiment of the present invention, the polarizing plate 50 is fixedly provided only in the light receiving optical system 20, but this is not limiting. The polarizing plate 50 may be fixedly provided only in the irradiation optical system 10.

Figure 24 shows an example of the configuration of an irradiation optical system in an optical measurement device according to a modified example of the second embodiment of the present invention.

Referring to FIG. 24, in the optical measurement device 102, the light receiving optical system 20 does not include a polarizing plate 50, while the irradiation optical system 10 includes a polarizing plate 50.

More specifically, the polarizing plate 50 is disposed on the optical path of the illumination light from the line light guide 12 to the target region R.

In the optical measuring device 102 according to the second embodiment of the present invention, the optical measuring device 102 according to the first modification, and the optical measuring device 102 according to the second modification, the largest peak pk can be uniquely detected in the generated power spectrum Pw, and the film thickness F of the measurement object S corresponding to the peak pk can be accurately measured, just like the optical measuring device 101 according to the first embodiment of the present invention.

The above-described embodiments should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims.

REFERENCE SIGNS LIST 10 Irradiation optical system 20 Light receiving optical system 30 Processing device 31 Receiving section 32 Calculation section 33 Storage section 34 Transmitting section 50 Polarizing plate 51 Adjustment section 101, 102 Optical measurement device

Claims (4)

1. An optical measurement device, comprising:
an irradiation optical system that irradiates an object to be measured with irradiation light including a plurality of wavelengths;
a light receiving optical system that receives measurement light, which is transmitted light or reflected light generated from the measurement object by irradiating the measurement object with the irradiation light;
A polarizing plate,
The polarizing plate is configured to be capable of being positioned in either one of the irradiation optical system or the light receiving optical system ,
The optical measurement device further comprises:
an adjustment unit capable of adjusting a direction of an absorption axis of the polarizing plate in a direction on a plane intersecting an optical path of the irradiation light or an optical path of the measurement light;
The object to be measured has birefringence,
(a) an angle between the absorption axis of the polarizing plate and the slow axis of the object to be measured is -10 degrees or more and 10 degrees or less, and an angle between the absorption axis of the polarizing plate and the fast axis of the object to be measured is 80 degrees or more and 100 degrees or less, or (b) an angle between the absorption axis of the polarizing plate and the slow axis of the object to be measured is 80 degrees or more and 100 degrees or less, and an angle between the absorption axis of the polarizing plate and the fast axis of the object to be measured is -10 degrees or more and 10 degrees or less . The optical measurement device according to claim 1, wherein the polarizing plate is fixedly provided to only one of the irradiation optical system and the light receiving optical system. An optical measurement method using an optical measurement device including an irradiation optical system and a light receiving optical system,
A step of irradiating a measurement object with irradiation light including a plurality of wavelengths using the irradiation optical system;
receiving measurement light, which is transmitted light or reflected light generated from the measurement object by irradiating the measurement object with the irradiation light, using the light receiving optical system;
In the step of irradiating the measurement object with the irradiation light or the step of receiving the measurement light, the irradiation light transmitted through a polarizing plate is irradiated onto the measurement object, or the measurement light transmitted through a polarizing plate is received ;
The optical measurement method further comprises:
An optical measurement method comprising a step of calculating a film thickness of the object to be measured based on the reception results of each of the measurement lights when the absorption axis direction of the polarizing plate is different in a direction on a plane intersecting an optical path of the irradiation light or the measurement light. The optical measurement method according to claim 3 , wherein the polarizing plate is fixedly provided in only one of the irradiation optical system and the light receiving optical system.

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