JP2010014642A - Method and apparatus for measuring light intensity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method for measuring light intensity capable of deriving transmittance and reflectance of an optical element with high accuracy. <P>SOLUTION: The light intensity measuring apparatus 1 includes a first light detector 5 detecting a first light intensity of the light transmitting through a sample 4, a light detector 9 detecting a second light intensity (P0') of the light which does not transmit through the sample 4, a lock-in amplifier 12 measuring intensity difference (ΔP') between the first light intensity and the second light intensity, and a computing unit 14 computing transmittance of the sample 4 through operating process of formula T=1+(ΔP'/P0') using the intensity difference and the second light intensity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light intensity measurement method and a light intensity measurement device, and more particularly to a light intensity measurement method and a light intensity measurement device for measuring the transmittance of an optical element.

  2. Description of the Related Art Conventionally, a light intensity measuring device that measures the transmittance of an optical element having light transmittance is known (see, for example, Patent Document 1). This type of light intensity measuring apparatus has a configuration as shown in FIG. The light intensity measuring apparatus 100 includes a light source 101, a beam splitter 102, photodetectors 104 and 107, signal amplifiers 105 and 108, a reflection mirror 106, and a calculator 109.

  In the beam splitter 102, the first light and the sample 103 that pass through the first optical path L1 in which the sample (optical element) 103 to be measured having light transmittance is disposed are disposed on the beam splitter 102. The second light passing through the second optical path L2 that is not separated is separated.

  The photodetector 104 detects the first light intensity of the first light that has passed through the sample 103, and sends a first light intensity signal P1 '. The photodetector 107 detects the second light intensity of the second light that does not pass through the sample 103, and transmits a second light intensity signal P0 '.

  The calculator 109 receives the first light intensity signal P1 'and the second light intensity signal P0' and measures the transmittance T of the sample 103 based on the equation T = P1 '/ P0'.

JP 2002-162294 A

  By the way, an optical element having a high transparency, for example, a surface processing layer called a moth's eye, which has a concavo-convex shape finer than the light wavelength on the surface and has a reflectance reduced to 0.1% or less. The optical element which has is known. In order to measure the transmittance of such an optical element having a transmittance of 99.9% or more with high accuracy, the transmittance of the optical element is measured with, for example, an accuracy of four significant digits (99.99%). A light intensity measuring device for measurement is required.

  However, with the above-described conventional technology, it is difficult to measure the transmittance with a high accuracy of 4 significant digits (99.99%). The reason will be described below.

  If the resolution of the light intensity measuring device is, for example, 10 nW, this light intensity measuring device can measure with a resolution of 10 nW if there are no factors that affect the measurement. However, factors that affect the measurement include so-called light intensity fluctuations such as noise generated from electronic circuits constituting the light intensity measuring apparatus and light existing around the apparatus (for example, indoor light, outside light, etc.). .

  The light intensity fluctuation increases as the light intensity of the incident light from the light source increases, and the magnitude in a short time exceeds 10 nW. Therefore, the resolution of the light intensity measuring device is, for example, 10 nW. However, it cannot be measured with a resolution of 10 nW.

  In the above-described light intensity measuring apparatus 100, the transmittance T is calculated based on the formula T = P1 ′ / P0 ′, and the above-described light intensity fluctuation is not taken into account at all in this formula. In this case, the measurement accuracy is lowered due to the influence of the light intensity fluctuation.

  Therefore, it is conceivable to increase the measurement time in order to measure with high accuracy. However, since the power density of the light intensity fluctuation is high on the low frequency side, the measurement over a long period of time is affected by drift (change in the output voltage of the electronic circuit over time).

  In the above-described light intensity measuring apparatus 100, the first light intensity signal P1 ′ and the second light intensity signal P0 ′ output from the signal amplifiers 104 and 107, respectively, are merely calculated by the computing unit 108, so that it takes a long time. When measuring over a long period of time, it is difficult to improve the measurement accuracy due to the influence of the drift described above.

  In addition, regarding the light intensity measurement, only the transmittance measurement of the optical element used as the sample to be measured has been described here, but the same problem as described above also occurs in the reflectance measurement of the optical element.

  For the reasons described above, it has been difficult to measure the light intensity with four significant figures with the above-described prior art.

  Therefore, an object of the present invention is to measure the light intensity of an optical element with high accuracy.

  In the light intensity measurement method according to the first aspect of the present invention, the first light and the sample passing through the first optical path in which the sample to be measured having light transmittance is arranged are arranged for the incident light from the light source. A separation step that separates the second light that passes through the second optical path that has not been performed, a first light intensity of the first light that has passed through the sample, and a second light intensity of the second light. A detection step for detecting each, an intensity difference measuring step for measuring an intensity difference between the first light and the second light, and a transmittance calculation, calculation or calculation for calculating the transmittance of the sample based on the following Equation 1 Steps. Here, Equation 1 is T = 1 + (ΔP ′ / P0 ′), where T is the transmittance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  That is, in the light intensity measurement process, the transmittance is calculated based on the above formula 1 that reflects the difference in intensity between the first light and the second light.

  The light intensity measuring device according to the second aspect of the present invention is configured to receive incident light from a light source using first light and a sample that pass through a first optical path in which a sample to be measured having light permeability is arranged. A beam splitter that separates the second light that passes through the second optical path that is not arranged, and a first light intensity signal that transmits the first light intensity signal by detecting the first light intensity of the first light that has passed through the sample. A first light detecting means; a second light detecting means for detecting a second light intensity of the second light and transmitting a second light intensity signal; and an intensity difference between the first light and the second light. An intensity difference measuring means for outputting an intensity difference signal obtained by the measurement, an arithmetic means for receiving the second light intensity signal and the intensity difference signal, and measuring the transmittance of the sample based on the following Equation 1. It is made to have. Here, Equation 1 is T = 1 + (ΔP ′ / P0 ′), where T is the transmittance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  That is, in the light intensity measurement process by the light intensity measurement device, the transmittance is calculated based on the above formula 1 that reflects the difference between the first light intensity in the first optical path and the second light intensity in the second optical path. Is called.

  The light intensity measuring device according to the third aspect of the present invention functions as the first light when passing through the sample to be measured having optical transparency and functions as the second light when not passing through the sample. A light source that emits light, sample moving means for moving the sample on or off the optical path through which the first light and the second light pass, driving means for driving the sample moving means, Light detecting means for detecting a first light intensity of the first light and transmitting a first light intensity signal; detecting a second light intensity of the second light; and transmitting a second light intensity signal; and An intensity difference measuring means for outputting an intensity difference signal obtained by measuring an intensity difference between the first light and the second light, the second light intensity signal and the intensity difference signal are received. And a calculation means for calculating the transmittance of the sample on the basis thereof. Here, Equation 1 is T = 1 + (ΔP ′ / P0 ′), where T is the transmittance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  That is, in the light intensity measurement device, the difference in intensity between the first light and the second light obtained by moving the sample on or off the optical path through which the first light and the second light pass is reflected. The transmittance is calculated based on Equation 1 above.

  The light intensity measuring device according to the fourth aspect of the present invention functions as the first light when passing through the sample to be measured having optical transparency and functions as the second light when not passing through the sample. A light source that emits light, an optical path changing unit that alternately changes an optical path in which the sample is arranged and an optical path in which the sample is not arranged, a driving unit that drives the optical path changing unit, and the first light Detecting the first light intensity of the second light, transmitting a first light intensity signal, detecting the second light intensity of the second light, and transmitting a second light intensity signal; and the first light An intensity difference measuring means for outputting an intensity difference signal obtained by measuring an intensity difference between the second light and the second light, and receiving the second light intensity signal and the intensity difference signal, and transmitting the transmittance based on the following Equation 1 And an arithmetic means for measuring. Here, Equation 1 is T = 1 + (ΔP ′ / P0 ′), where T is the transmittance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  Therefore, in the light intensity measurement apparatus, the above formula 1 reflects the difference between the first light intensity and the second light intensity obtained by alternately changing the optical path where the sample is arranged and the optical path where the sample is not arranged. Based on the above, the transmittance is measured.

  In the light intensity measurement device according to the fifth aspect of the present invention, the light from the light source is not disposed with the first light passing through the first optical path where the sample to be measured is disposed. A beam splitter that separates the second light that passes through the second optical path, and a first light detection that detects the first light intensity of the first light reflected from the sample and transmits a first light intensity signal. A second light detecting means for detecting a second light intensity of the second light and transmitting a second light intensity signal; and measuring an intensity difference between the first light and the second light. Intensity difference measuring means for outputting the intensity difference signal obtained, and calculation means for receiving the second light intensity signal and the intensity difference signal and measuring the reflectance of the sample based on the following Equation 2. It is a thing. Here, Formula 2 is R = 1 + (ΔP ′ / P0 ′), where R is the reflectance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  That is, in the light intensity measurement process by the light intensity measurement device, the reflectance is calculated based on the above formula 2 that reflects the difference between the first light intensity in the first optical path and the second light intensity in the second optical path. Is called.

  In this light intensity measurement method, incident light from a light source is converted into first light that passes through a first optical path in which a sample to be measured having optical transparency is arranged, and a second optical path in which no sample is arranged. A separation step for separating the second light passing through the sample, a detection step for detecting a first light intensity of the first light transmitted through the sample and a second light intensity of the second light, respectively. An intensity difference measuring step for measuring the intensity difference between the first light and the second light, and a transmittance calculating step for calculating the transmittance of the sample based on the following Equation 1. Here, Equation 1 is T = 1 + (ΔP ′ / P0 ′), where T is the transmittance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  Since the influence of the light intensity fluctuation can be reduced by the combination of the intensity difference measurement between the first light and the second light and the transmittance calculation based on Equation 1, the measurement accuracy can be improved.

  The present light intensity measuring apparatus uses incident light from a light source as a first light passing through a first optical path in which a sample to be measured having optical transparency is arranged and a second optical path in which no sample is arranged. A beam splitter that separates the second light that passes through the sample, first light detection means that detects a first light intensity of the first light that has passed through the sample and sends a first light intensity signal, and A second light detecting means for detecting a second light intensity of the second light and transmitting a second light intensity signal; and an intensity difference obtained by measuring an intensity difference between the first light and the second light. An intensity difference measuring means for outputting a signal; and an arithmetic means for receiving the second light intensity signal and the intensity difference signal and calculating the transmittance of the sample based on the following Equation 1. . Here, Equation 1 is T = 1 + (ΔP ′ / P0 ′), where T is the transmittance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  Since the influence of the light intensity fluctuation can be reduced by the combination of the intensity difference measurement between the first light and the second light and the transmittance calculation based on Equation 1, the measurement accuracy can be improved.

  In the invention described in claim 3, the first light intensity signal and the second light intensity are provided between the first light detection means and the second light detection means and the intensity difference measurement means. Since the switching means for alternately outputting the signals to the intensity difference measuring means is provided, it is possible to reduce the influence of the more remarkable fluctuation on the light intensity measurement at a low frequency. Although the fluctuation is described here, the fluctuation component has fluctuations of the light intensity itself, there are various origins such as fluctuations in the output current of the photodetector and fluctuations in the output voltage of the circuit. Hereinafter, there is a place where it is simply described as “light intensity fluctuation”, but this single word represents all fluctuation components and does not mean “light intensity fluctuation” exclusively.

  In the invention described in claim 4, the intensity difference measuring means is a lock-in amplifier, and the lock-in amplifier synchronizes with the switching operation of the switching means in the first light and the second light. Since the light intensity difference is measured, it is possible to reduce the influence of the significant light intensity fluctuation generated at a low frequency on the light intensity measurement.

  In the invention described in claim 5, an optical modulator is disposed between the light source and the beam splitter, and a signal reflecting the light intensity detected in the two optical paths is alternately supplied to the light intensity difference measuring means. Light switching is used as a supply method. Accordingly, there is an advantage that the switching portion is not affected by electrostatic or inductive noise as compared with the case of switching the electric signal.

  In the invention described in claim 6, the light functioning as the first light when passing through the sample to be measured having optical transparency and functioning as the second light when not passing through the sample. A light source that emits; a sample moving unit that moves the sample on or out of an optical path through which the first light and the second light pass; a driving unit that drives the sample moving unit; Light detecting means for detecting a first light intensity of light and transmitting a first light intensity signal; detecting a second light intensity of the second light; and transmitting a second light intensity signal; and An intensity difference measuring means for outputting an intensity difference signal obtained by measuring an intensity difference between the light and the second light; receiving the second light intensity signal and the intensity difference signal; And a calculation means for calculating the transmittance of the sample. Here, Equation 1 is T = 1 + (ΔP ′ / P0 ′), where T is the transmittance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  In this case, only one optical path is provided in the apparatus, and only one photodetector and signal amplifier are provided, so that the light intensity can be measured with high accuracy with a simple configuration.

  In the invention described in claim 7, the light functioning as the first light when passing through the sample to be measured having optical transparency and functioning as the second light when not passing through the sample. A light source that emits light, an optical path changing unit that alternately changes an optical path in which the sample is arranged and an optical path in which the sample is not arranged, a driving unit that drives the optical path changing unit, and a first of the first light Light detecting means for detecting a light intensity and transmitting a first light intensity signal; detecting a second light intensity of the second light; and transmitting a second light intensity signal; and the first light and the second light An intensity difference measuring means for outputting an intensity difference signal obtained by measuring the intensity difference of the light, the second light intensity signal and the intensity difference signal are received, and the transmittance is calculated based on the following Equation 1. And an arithmetic means. Here, Equation 1 is T = 1 + (ΔP ′ / P0 ′), where T is the transmittance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  In this case, since the optical means of changing the optical path is used to switch the light intensity signal supplied to the intensity difference measuring means, it is not affected by electrostatic or inductive noise, so that electrical fluctuations are generated. As a result, measurement accuracy can be improved.

  In the invention described in claim 8, the incident light from the light source is converted into the first light passing through the first optical path in which the sample to be measured is disposed and the second light in which the sample is not disposed. A beam splitter for separating the light into second light passing through the optical path; first light detection means for detecting a first light intensity of the first light reflected from the sample and transmitting a first light intensity signal; A second light detecting means for detecting a second light intensity of the second light and transmitting a second light intensity signal; and an intensity obtained by measuring an intensity difference between the first light and the second light. An intensity difference measuring means for outputting a difference signal; and an arithmetic means for receiving the second light intensity signal and the intensity difference signal and calculating the reflectance of the sample based on the following Equation 2. is there. Here, Formula 2 is R = 1 + (ΔP ′ / P0 ′), where R is the reflectance, P0 ′ is the second light intensity, and ΔP ′ is the intensity difference between the first light and the second light.

  Even when the reflectance is measured in this way, the influence of fluctuation can be reduced by the light intensity measurement based on the above-described Equation 2, so that the accuracy of the reflectance measurement can be increased.

  In the invention described in claim 9, there is provided a sample arrangement changing means for changing the position or arrangement of the sample with respect to the first light between the beam splitter and the first light detecting means. Therefore, measure the amount of change in transmittance depending on the polarization direction determined by the optical system located on the light source side from the sample and the direction of the sample held in the sample arrangement changing means, or the incident angle of light to the sample, The optical anisotropy of the sample can be measured with high accuracy.

  In the invention described in claim 10, there is provided sample arrangement changing means for changing the position or arrangement of the sample with respect to the first light between the beam splitter and the first light detecting means. Therefore, the amount of change in reflectance depending on the polarization direction determined by the optical system located on the light source side from the sample and the direction of the sample held in the sample arrangement changing means, or the incident angle of the light to the sample is measured, The optical anisotropy of the sample observed in the measurement of the reflection arrangement can be measured with high accuracy.

  Hereinafter, a light intensity measuring apparatus according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the light intensity measuring apparatus according to the first embodiment.

  The light intensity measuring device 1 includes a light source 2, a beam splitter 3, photodetectors 5 and 9, signal amplifiers 6 and 10, a reflection mirror 7, a variable density filter 8, a switch 11 as a switching means, and a lock as an intensity difference measuring means. An in-amplifier 12, a switching circuit 13, and an arithmetic unit 14 as a transmittance calculation unit are provided.

  The beam splitter 3 converts the incident light from the light source 2 into the first light passing through the first optical path L1 in which the sample 4 to be measured having optical transparency is arranged and the second in which the sample 4 is not arranged. And the second light passing through the optical path L2. In the light intensity measuring device 1, the light T to the first optical path L1 and the second optical path L2 is set so that the transmittance T when passing through the second optical path L2 is 1 (100%). The branching ratio and the gain of each electronic circuit constituting the device are adjusted. For example, the variable density filter 8 has a function of adjusting the transmittance value calculated by the calculator 14 to 1 (100%) when the first light reaches the detector 5 directly without placing a sample. Have. Such adjustment of the branching ratio and gain is the same in the second, fourth and sixth embodiments described later.

  The first light passes through the sample 4 and is input to the photodetector 5. The second light is reflected by the reflection mirror 7 and input to the photodetector 9 through the variable density filter 8.

  The photodetector 5 detects the first light intensity P <b> 1 ′ of the first light transmitted through the sample 4. The signal amplifier 6 sends out a first light intensity signal obtained by amplifying the first light intensity P1 '. The photodetector 9 detects the second light intensity P0 'of the second light. The signal amplifier 10 transmits a second light intensity signal obtained by amplifying the second light intensity P0 '. P1 'and P0' are observation amounts including fluctuations.

  The switch 11 is connected between the photodetector 6 and the lock-in amplifier 12 (hereinafter referred to as “first connection”) and between the photodetector 10 and the lock-in amplifier 12 according to the switching control signal output from the switching circuit 13. The connection (hereinafter referred to as “second connection”) is switched alternately in a short time (with a short cycle).

The switching control signal is, for example, a rectangular wave AC signal having a frequency f ₀ that takes two states of high and low, and functions as a signal that controls the switching operation of the switch 11. For example, when the switching control signal is in a high state, the switch 11 operates to maintain the first connection state, and the first light intensity signal is sent to the lock-in amplifier 12. When the switching control signal is in the low state, the switch 11 operates to maintain the second connection state, and the second light intensity signal is sent to the lock-in amplifier 12.

The lock-in amplifier 12 is a measuring device that detects a fluctuation component of the frequency f ₀ synchronized with the reference signal from the input signal waveform and outputs the magnitude thereof. However, the light intensity measuring apparatus 1 is configured such that the first light intensity signal and the second light intensity signal are alternately input to the lock-in amplifier 12 at the frequency f ₀ . Therefore, the output of the lock-in amplifier is given by the magnitude of the input fluctuation accompanying the change of the first light intensity signal and the second light intensity signal, that is, the difference in intensity between the first light intensity and the second light intensity, ΔP ′. It is done.

  The calculator 14 receives the second light intensity signal and the intensity difference signal, and calculates the transmittance T of the sample 4 based on the following formula (1).

T = 1 + (ΔP ′ / P0 ′) (1)
When the transmittance measurement is performed using the light intensity measuring apparatus 1 described above, the influence of fluctuation is reduced for the reason described later, and the light intensity measurement (transmittance measurement) can be performed with high accuracy.

  In order to verify that highly accurate measurement is provided by the present invention, first, the magnitude of the fluctuation of the transmittance measurement value obtained by the conventional measuring apparatus is confirmed. As a comparative example, FIG. 7 shows a configuration commonly used in a spectrophotometer. However, there are a measurement optical path and a reference optical path for placing a sample, and the light intensities P1 ′ and P0 ′ are measured and the transmittance is measured. T is given by the right side of the following formula (A).

T = P1 '/ P0' (A)
When no sample is placed, the light branching ratio to each optical path or the gain of the circuit is adjusted so that T = 1 (100%) is obtained.

  Here, the dash on the shoulder of the light intensity P is attached as a mark representing the measured value. If the measured value is divided into a fluctuation portion δ that becomes 0 on average over time and a portion that does not, the result is P1 ′ = P1 + δ1, P0 ′ = P0 + δ0. Therefore, P1 / P0 that does not include fluctuation is desired as the transmittance value, but (P1 + δ1) / (P0 + δ0) is used instead.

  Since both δ1 and δ0 are of the same magnitude, this ratio, that is, the relative magnitude of fluctuation reflected in the value of T, is (√2) δ0 / P0 (hereinafter, “fluctuation (a)”) Call it).

Subsequently, referring to FIG. 1, the amount of fluctuation included in the transmittance measurement value according to the present invention is calculated. It is the same as the comparative example described above in that two optical paths for measurement and reference are provided. The intensity signals P1 ′ and P0 ′ are alternately input to the lock-in amplifier using an analog switch, and the intensity difference ΔP ′ is measured by detection synchronously with the switching of the analog switch. If this fluctuation is written as ε, ΔP ′ = P1−P0 + ε. Here, when the fluctuation included in the transmittance calculation formula, T = 1 + (ΔP ′ / P0 ′) according to the method of the present invention is examined,
T = 1 + (ΔP ′ / P0 ′) = 1+ (P1−P0 + ε) / (P0 + δ0)
≒ P1 / P0 + ε / P0 + (1-P1 / P0) ・ (δ0 / P0) ・ ・ ・ ・ （B）
Here, when moving to the second row of the above formula (B), an approximation was performed in which only the first-order contributions of ε / P0 and δ0 / P0, which are smaller amounts than 1, were considered. The fluctuation of the measured value obtained by this method is ε / P0 + (1−P1 / P0) · (δ0 / P0) (hereinafter, the second and third terms of the last side of the above formula (B). , Referred to as “fluctuation (b)”).

  The magnitudes of fluctuations (a) and (b) included in the measurement values obtained by the conventional method and the method of the present invention can be compared as follows. When alternating intensity comparisons are made for two optical paths in a relatively short time period, the measurement is at a higher frequency than the DC measurement, and the effect of significant fluctuations is greatly reduced at a lower frequency, so ε is greater than δ0. The amount is quite small. Also, in the last term (1-P1 / P0) · (δ0 / P0) of fluctuation (b), the first factor (1-P1 / P0) is the difference between the two quantities close to 1, so this term The magnitude is much smaller than (δ0 / P0). Therefore, the fluctuation contribution (b) to the transmittance given by the equation (B) of the present invention is compared with the fluctuation (√2) δ0 / P0 given as shown in (a) with respect to the calculated value based on the conventional method. Can be quite small.

  By adopting the present invention, an improvement of almost two digits was possible, and it was possible to discriminate between 99.99% and 99.98% transmittance. Samples having transmittances of 99.99% and 99.98% were prepared with a dilute solution of color ink.

  Next, a light intensity measurement apparatus according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the light intensity measuring apparatus according to the second embodiment.

  The light intensity measuring device 20 includes a light source 2, a polarizer 21, an optical modulator 22, a polarizing beam splitter 23, photodetectors 5 and 9, signal amplifiers 6 and 10, a reflection mirror 7, a variable density filter 8, and a lock-in amplifier 12. , A modulation circuit 24, an adder 25, a light intensity signal monitor 26, and an arithmetic unit (not shown).

  The polarizer 21 makes incident light from the light source 2 incident on the light modulator 22 as linearly polarized light having a photoelectric field vector in the (1, 0, 0) direction in the illustrated coordinate system.

  The optical modulator 22 is used with its main axis aligned in the (1, 1, 0) direction and the (1, -1, 0) direction. This optical modulator has an electric field vector in the principal axis direction, ie, (1, 1, 0) direction and (1, -1, 0) direction, and two linearly polarized light components having the same frequency ω propagating in the Z axis direction. In the meantime, a phase difference from 0 to π / 2 can be generated.

  The polarization beam splitter 23 transmits light in the z direction when the electric field vector of incident light is in the (1, 0, 0) direction, and the electric field vector of incident light is in the (0, 1, 0) direction. Has a function of reflecting incident light at right angles to the -x direction.

  The modulation circuit 24 has a function of sending a modulation signal to the optical modulator 22 at a predetermined timing and periodically changing the phase difference of incident light between 0 and π / 2. At that timing, a synchronization signal is sent to the lock-in amplifier 12.

  Here, when the phase difference is 0, since the electric field vector of the light transmitted through the optical modulator 22 remains in the (1, 0, 0) direction, the linearly polarized light is transmitted through the polarization beam splitter 23 and the sample. 4 passes the first optical path L1 in which 4 is disposed. On the other hand, when the phase difference is π / 2, since the photoelectric field vector transmitted through the optical modulator 22 is in the (0, 1, 0) direction, the linearly polarized light is reflected at a right angle by the polarization beam splitter 23 and the sample. It passes through the second optical path L2 where 4 is not arranged.

  The photodetector 5 detects the first light intensity P <b> 1 ′ of the first light transmitted through the sample 4. The signal amplifier 6 sends out a first light intensity signal obtained by amplifying the first light intensity P1 '. The photodetector 9 detects the second light intensity P0 'of the second light. The signal amplifier 10 transmits a second light intensity signal obtained by amplifying the second light intensity P0 '.

  The adder 25 receives the first light intensity signal and the second light intensity signal and outputs a signal voltage obtained by adding both signals.

  The lock-in amplifier 12 receives a signal voltage corresponding to the sum of the light intensities obtained by the detectors 5 and 9 placed in the two optical paths L1 and L2 from the adder 25, but is common to the optical paths L1 and L2. Since light from one light source is introduced alternately, the sum of the light intensities received by the detectors 5 and 9 is constant when the sample is not placed in the optical path L1, that is, locked as the output of the adder 25. The signal voltage input to the in-amplifier 12 has a constant value. Therefore, the lock-in amplifier does not feel the fluctuation component of the modulation frequency in the input signal.

  However, when a loss occurs in the light intensity reaching the detector 5 due to the sample placed in the optical path L1, even if the signals from the detector 5 and the detector 9 are added, the intensity balance completely complements each other. Therefore, the output of the adder 25 varies with the optical path switching frequency. The lock-in amplifier measures and outputs the magnitude of the fluctuation, but the magnitude of the fluctuation is not directly corrected and is proportional to the magnitude of the optical loss caused by the sample. As a result, it is detected in the optical path 1 and the optical path 2. Measurement of the difference in light intensity, ΔP ′, is realized.

  The light intensity signal monitor 26 monitors the second light intensity signal in the second optical path L2, and sends the second light intensity signal to the calculator.

  The computing unit receives the second light intensity signal and the amplified intensity difference signal, and calculates the transmittance T of the sample 4 based on the above mathematical formula (1).

  As described above, in the second embodiment, the optical modulator 22, the polarization beam splitter 23, and the modulation circuit 24 are used to switch the first optical path L1 and the second optical path L2, and the sample is arranged on the optical path. The light intensity measurement is performed alternately between the case where it is performed and the case where it is not.

  According to the light intensity measurement device 20 according to the second embodiment, compared with the case where the electrical signal reflecting the light intensity is switched by the switch 11 in the first embodiment described above, It has the effect of not being affected by inductive noise. Further, since the intensity of the light beam itself related to the measurement is modulated, there is an advantage that it can be separated from the background light (this is not modulated) reaching the photodetector.

  Next, a light intensity measuring apparatus according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing the configuration of the light intensity measuring apparatus according to the third embodiment. In the third embodiment, the light intensity measurement is alternately performed when the sample is disposed in the single optical path L and when the sample is not disposed using the sample moving mechanism 31.

  The light intensity measuring device 30 includes a light source 2, a sample moving mechanism 31, a photodetector 32, a signal amplifier 33, a drive circuit 34, a lock-in amplifier 12, and a calculator (not shown).

  Incident light from the light source 2 functions as first light when the sample moving mechanism 31 moves the sample 4 onto the optical path L, and the sample moving mechanism 31 moves the sample 4 to a region outside the optical path L. When it is made to function, it functions as the second light.

  The sample moving mechanism 31 has a function of moving the sample 4 on the optical path L or moving it to a region outside the optical path L. As a specific moving method of the sample moving mechanism 31, for example, there is a method of blocking the optical path L by attaching a plate-like sample to a rotating body and rotating it like an impeller.

  The drive circuit 34 drives the sample moving mechanism 31 at a predetermined timing, and a synchronization signal is sent to the lock-in amplifier 12 at that timing.

  When the sample 4 moves on the optical path L by the sample moving mechanism 31, the first light passes through the sample 4 and is input to the photodetector 32. When the sample 4 is moved to an area off the optical path L by the sample moving mechanism 31, the second light is input to the photodetector 32 without passing through the sample 4.

  The light detector 32 detects the first light intensity P1 'of the first light transmitted through the sample 4 and detects the second light intensity P0' of the second light. The signal amplifier 33 sends out a first light intensity signal obtained by amplifying the first light intensity P1 'and a second light intensity signal obtained by amplifying the second light intensity P0'.

  The lock-in amplifier 12 receives the input first light intensity signal and second light intensity signal, and changes the same frequency component as the reference signal supplied from the drive circuit 34 in synchronization with the movement operation of the sample moving mechanism 31. By detecting, the intensity difference ΔP ′ between the first light intensity P1 ′ and the second light intensity P0 ′ is measured, and the obtained intensity difference ΔP ′ is output.

  The computing unit receives the second light intensity signal and the intensity difference signal, and calculates the transmittance T of the sample 4 based on the above equation (1).

  According to the light intensity measuring apparatus 30 according to the third embodiment, only one optical path is provided, and only one optical detector 32 and one signal amplifier 33 are provided. Strength measurement can be performed with high accuracy.

  Next, a light intensity measuring apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the light intensity measuring apparatus according to the fourth embodiment.

  The light intensity measuring device 40 includes a light source 2, a movable mirror 41 as an optical path changing means, a drive circuit 42, photodetectors 5 and 9, signal amplifiers 6 and 10, a variable density filter 8, an adder 25, and a light intensity signal monitor 26. , A lock-in amplifier 12 and a computing unit (not shown).

  The incident light from the light source 2 functions as the first light when the optical path through which the movable mirror 41 transmits the incident light is changed to the first optical path L1 in which the sample 4 is disposed, and the optical path through which the incident light passes. Is changed to the second optical path L2 in which the sample 4 is not arranged, it functions as the second light.

  The movable mirror 41 has a function of receiving incident light from the light source 2 and changing an emission direction from the movable mirror 41, that is, a function of alternately changing the first optical path L1 and the second optical path L2.

  The drive circuit 42 rotates the movable mirror 41 at a predetermined timing, and a synchronization signal is sent to the lock-in amplifier 12 at that timing.

  When the optical path of the incident light is changed to the first optical path L1 by the movable mirror 41, the incident light (first light) passes through the sample 4 and is input to the photodetector 5. When the optical path of the incident light is changed to the second optical path L <b> 2 by the movable mirror 41, the incident light (second light) is input to the photodetector 9 without passing through the sample 4.

  The photodetector 5 detects the first light intensity P <b> 1 ′ of the first light transmitted through the sample 4. The signal amplifier 6 sends out a first light intensity signal obtained by amplifying the first light intensity P1 '. The photodetector 9 detects the second light intensity P0 'of the second light. The signal amplifier 10 transmits a second light intensity signal obtained by amplifying the second light intensity P0 '.

  The adder 25 receives the first light intensity signal and the second light intensity signal and outputs a signal voltage obtained by adding the both.

  The lock-in amplifier 12 receives a signal voltage corresponding to the sum of the light intensities obtained by the detectors 5 and 9 placed in the two optical paths L1 and L2 from the adder 25, but is common to the optical paths L1 and L2. Since the light from one light source is alternately introduced by the movable mirror 41, the sum of the light intensities received by the detectors 5 and 9 is constant when the sample is not placed in the optical path L1, that is, the adder 25. The signal voltage input to the lock-in amplifier 12 as an output is a constant value. Therefore, the lock-in amplifier does not feel the fluctuation component of the operating frequency of the movable mirror 41 in the input signal.

  However, when a loss occurs in the light intensity reaching the detector 5 due to the sample placed in the optical path L1, even if the signals from the detector 5 and the detector 9 are added, the intensity balance completely complements each other. Therefore, the output of the adder 25 varies with the frequency of switching the optical path by the movable mirror 41. The lock-in amplifier measures and outputs the magnitude of the fluctuation, but the magnitude of the fluctuation is not directly corrected and is proportional to the magnitude of the optical loss caused by the sample. As a result, it is detected in the optical path 1 and the optical path 2. Measurement of the difference in light intensity, ΔP ′, is realized.

  The light intensity signal monitor 26 monitors the second light intensity signal in the second optical path L2, and sends the second light intensity signal to the calculator.

  The computing unit receives the second light intensity signal and the intensity difference signal, and measures the transmittance T of the sample 4 based on the above equation (1).

  According to the light intensity measuring device 40 according to the fourth embodiment, compared with the case where the electrical signal reflecting the light intensity is switched by the switch 11 in the first embodiment described above, It has the effect of not being affected by inductive noise.

  Next, a light intensity measuring apparatus according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 5 is a block diagram showing the configuration of the light intensity measuring apparatus according to the fifth embodiment.

  The light intensity measuring device 50 includes a light source 2, a beam splitter 3, photodetectors 5 and 9, signal amplifiers 6 and 10, three reflection mirrors 7, 7 and 7, a variable density filter 8, a switch 11, a lock-in amplifier 12, The switching device 13 and the arithmetic unit 52 are provided. Here, one of the three reflecting mirrors 7, 7, and 7 is arranged in the front stage of the first optical path L1, the other one is arranged in the rear stage of the first optical path L1, and the other one is the second optical path L1. Is disposed in the optical path L2.

  The beam splitter 3 converts the incident light from the light source 2 into the first light passing through the first optical path L1 in which the sample 51 to be measured having light reflectivity is arranged and the second in which the sample 51 is not arranged. And the second light passing through the optical path L2. In the light intensity measuring apparatus 50, the light intensity measuring apparatus 50 gives a reflectance value of 1 (100%) when there is no loss of light by the sample in the first optical path L1. The branching ratio of light to the first optical path L1 and the second optical path L2 and the gain of each electronic circuit constituting the device are adjusted. For example, the variable density filter 8 has a function of adjusting the light intensity measurement device 50 to provide a reflectance value of 1 (100%) when there is no light loss due to the sample in the first optical path L1. have.

  Here, the incident light reflected by the front reflection mirror 7 disposed in the first optical path L1 that has passed through the beam splitter 3 and reflected is reflected by the sample 51 and then disposed in the first optical path L1. Are reflected by the reflection mirror 7 and are incident on the photodetector 5. The number of reflection mirrors 7 required on the route (first optical path L1) until the incident light reaches the photodetector 5 through the sample 51 is not limited to the above two, but the attenuation of light is performed. Considering this, it is desirable to use a small number.

  The second light is reflected by the reflection mirror 7 disposed in the second optical path L <b> 2 and input to the photodetector 9 through the variable density filter 8.

  The photodetector 5 detects the first light intensity P <b> 1 ′ of the first light reflected by the sample 51. The signal amplifier 6 sends out a first light intensity signal obtained by amplifying the first light intensity P1 '. The photodetector 9 detects the second light intensity P0 'of the second light. The signal amplifier 10 transmits a second light intensity signal obtained by amplifying the second light intensity P0 '.

  The switch 11 alternately switches the first connection and the second connection in a short cycle according to the switching control signal output from the switching circuit 13. By such switching operation by the switch 11, the first light intensity signal and the second light intensity signal are alternately sent to the lock-in amplifier 12.

  The lock-in amplifier 12 receives the input first light intensity signal and the second light intensity signal, measures the intensity difference ΔP ′ between the first light intensity P1 ′ and the second light intensity P0 ′, and obtains the obtained intensity difference ΔP. 'Is output.

  The calculator 52 receives the second light intensity signal and the intensity difference signal, and calculates the reflectance R of the sample 51 based on the following formula (2). In addition, Numerical formula (2) respond | corresponds to Numerical formula (A) of Claim 8 of a claim.

R = 1 + (ΔP ′ / P0 ′) (2)
When the light intensity measurement of the optical element is performed using the light intensity measurement device 50 described above, the influence of fluctuation is reduced for the same reason as in the first embodiment, and the light intensity measurement (reflectance measurement) is performed. It can be performed with high accuracy.

  Next, a light intensity measuring apparatus according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing a configuration of a light intensity measuring apparatus according to the sixth embodiment.

  Compared with the first embodiment described above, this embodiment is provided with a sample arrangement changing mechanism 61 between the beam splitter 3 and the photodetector 5 for changing the position and the arrangement angle of the sample 4. It is the same except for. Therefore, the description of the same configuration as in the first embodiment is omitted.

  The present embodiment is characterized in that a sample arrangement changing mechanism 61 is provided as sample arrangement changing means for changing the position of the sample 4 with respect to incident light, and the dependence of transmittance on the arrangement, that is, the optical anisotropy can also be measured. is there.

  A polarizer 21 is disposed between the light source 2 and the beam splitter 3.

  The light intensity measuring device 60 measures the transmittance depending on the polarization direction determined by the polarizer 21 and the direction of the sample 4 arranged in the sample arrangement changing mechanism 61.

  The dependence on the orientation of the sample 4 is determined by the sample arrangement changing mechanism 61. Specifically, as shown in FIG. 6, as shown in FIG. 6, the sample 4 with respect to the incident light having the polarization direction is rotated by rotating the plate-like sample 4 arranged on the XY plane with the Z axis as the rotation axis. Change the direction of.

  Therefore, by changing the direction of the sample 4 with respect to the incident light using the sample arrangement changing mechanism 61, the transmittance value depending on the polarization direction and the direction of the sample 4 arranged in the sample arrangement changing mechanism 61 is measured. Can do.

  Although the present embodiment has been described with respect to transmittance measurement, the reflectance that depends on the polarization direction and the direction of the sample 4 arranged in the sample arrangement changing mechanism 61 can also be measured. The configuration in this case is the same as that in which the sample arrangement changing mechanism 61 is provided instead of the sample 51 in the above-described fifth embodiment.

  Each of the above-described embodiments is merely an example of a preferred embodiment of the present invention, and the present invention can be implemented with various modifications without departing from the gist thereof.

It is a block diagram shown about the composition of the light intensity measuring device concerning a 1st embodiment. It is a block diagram shown about the structure of the light intensity measuring apparatus which concerns on 2nd Embodiment. It is a block diagram shown about the structure of the light intensity measuring apparatus which concerns on 3rd Embodiment. It is a block diagram shown about the structure of the light intensity measuring apparatus which concerns on 4th Embodiment. It is a block diagram shown about the structure of the light intensity measuring apparatus which concerns on 5th Embodiment. It is a block diagram shown about the structure of the light intensity measuring apparatus which concerns on 6th Embodiment. It is the block diagram which showed the structure of the conventional light intensity measuring apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 20, 30, 40, 50, 60 ... Light intensity measuring device, 2 ... Light source, 3 ... Beam splitter, 4, 51 ... Sample, 5, 9, 32 ... Photo detector, 6, 10, 33 ... Signal amplifier , 7 ... reflection mirror, 8 ... variable density filter, 11 ... switch, 12 ... lock-in amplifier, 13 ... switching circuit, 14, 52 ... computing unit, 21 ... polarizer, 22 ... optical modulator, 23 ... polarizing beam splitter , 24 ... modulation circuit, 25 ... adder, 26 ... light intensity signal monitor, 31 ... sample moving mechanism, 34, 42 ... drive circuit, 41 ... movable mirror, 61 ... sample arrangement changing mechanism

Claims (10)

Incident light from the light source passes through a first optical path through which a sample to be measured and a sample having optical transparency are arranged, and a second optical path through which a second specimen is not arranged. A separation step that separates into light;
A detection step of detecting a first light intensity of the first light transmitted through the sample and a second light intensity of the second light, respectively.
An intensity difference measuring step for measuring an intensity difference between the first light and the second light;
A light intensity measurement method comprising: a calculation step of calculating the transmittance of the sample based on the following formula 1.
(1) T = 1 + (ΔP ′ / P0 ′)
However,
T: transmittance P0 ′: second light intensity ΔP ′: difference in intensity between the first light and the second light. Incident light from the light source is converted into first light that passes through a first optical path in which a sample to be measured having optical transparency is arranged and second light that passes through a second optical path in which no sample is arranged. A beam splitter that separates
First light detection means for detecting a first light intensity of the first light transmitted through the sample and transmitting a first light intensity signal;
Second light detection means for detecting a second light intensity of the second light and transmitting a second light intensity signal;
An intensity difference measuring means for measuring an intensity difference between the first light and the second light;
A light intensity measuring apparatus comprising: an arithmetic unit that receives the second light intensity signal and the intensity difference signal and calculates and calculates the transmittance of the sample based on the following Equation 1.
(1) T = 1 + (ΔP ′ / P0 ′)
However,
T: transmittance P0 ′: second light intensity ΔP ′: difference in intensity between the first light and the second light. The first light intensity signal and the second light intensity signal are alternately supplied to the intensity difference measuring means between the first light detecting means and the second light detecting means and the intensity difference measuring means. The light intensity measuring device according to claim 2, further comprising a switching unit. The intensity difference measuring means is a lock-in amplifier,
The light intensity measurement device according to claim 3, wherein the lock-in amplifier measures a difference between the first light intensity and the second light intensity in synchronization with a switching operation of the switching means. An optical modulator is disposed between the light source and the beam splitter;
The light intensity measurement apparatus according to claim 2, wherein the optical power that the beam splitter distributes to the first optical path and the second optical path is switched by the action of an optical modulator. A light source that emits light that functions as first light when passing through a sample to be measured having light permeability and functions as second light when not passing through the sample;
Sample moving means for moving the sample on or off the optical path through which the first light and the second light pass;
Driving means for driving the sample moving means;
Light detecting means for detecting a first light intensity of the first light and transmitting a first light intensity signal; detecting a second light intensity of the second light; and transmitting a second light intensity signal;
An intensity difference measuring means for measuring an intensity difference between the first light and the second light and outputting an intensity difference signal;
A light intensity measurement apparatus comprising: an arithmetic unit that receives the second light intensity signal and the intensity difference signal and calculates the transmittance of the sample based on the following Equation 1.
(1) T = 1 + (ΔP ′ / P0 ′)
However,
T: transmittance P0 ′: second light intensity ΔP ′: difference in intensity between the first light and the second light. A light source that emits light that functions as first light when passing through a sample to be measured having light permeability and functions as second light when not passing through the sample;
An optical path changing means for alternately changing an optical path where the sample is arranged and an optical path where the sample is not arranged;
Driving means for driving the optical path changing means;
Light detecting means for detecting a first light intensity of the first light and transmitting a first light intensity signal; detecting a second light intensity of the second light; and transmitting a second light intensity signal;
Intensity difference measuring means for measuring an intensity difference between the first light and the second light and outputting an intensity difference signal;
A light intensity measuring device comprising: an arithmetic unit that receives the second light intensity signal and the intensity difference signal and measures the transmittance based on the following Equation 1.
(1) T = 1 + (ΔP ′ / P0 ′)
However,
T: transmittance P0 ′: second light intensity ΔP ′: intensity difference between the first light and the second light
And The incident light from the light source is separated into first light that passes through the first optical path where the sample to be measured is arranged and second light that passes through the second optical path where the sample is not arranged. A beam splitter,
First light detection means for detecting a first light intensity of the first light reflected from the sample and transmitting a first light intensity signal;
Second light detection means for detecting a second light intensity of the second light and transmitting a second light intensity signal;
An intensity difference measuring means for measuring an intensity difference between the first light and the second light and outputting an intensity difference signal;
A light intensity measurement apparatus comprising: an arithmetic unit that receives the second light intensity signal and the intensity difference signal and measures the reflectance of the sample based on the following Equation 2.
(2) R = 1 + (ΔP ′ / P0 ′)
However,
R: reflectance P0 ′: second light intensity ΔP ′: difference in intensity between the first light and the second light. The light intensity measurement apparatus according to claim 2, further comprising a sample arrangement changing unit that changes a position and arrangement of the sample with respect to the first light between the beam splitter and the first light detection unit. The light intensity measurement apparatus according to claim 8, further comprising a sample arrangement changing unit that changes a position and arrangement of the sample with respect to the first light between the beam splitter and the first light detection unit.

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