JP2012251875A - Light intensity measuring device - Google Patents

Abstract

A light intensity measuring device capable of measuring the intensity of light generated by interaction with an object with a larger dynamic range and practical accuracy.
A light intensity measurement apparatus includes an irradiation system, a measurement system, and a neutral density filter. The irradiation system irradiates the test object with irradiation light. The measurement system measures the intensity of light generated by the interaction between the irradiation light and the test object. The neutral density filter attenuates at least one of the irradiation light and the light generated by the interaction at a plurality of different attenuation rates. Prior to the light measurement, the measurement system uses a photon counter to count the photons that make up the light that has been attenuated at multiple dimming rates, and the calibration value for the dimming rate obtained based on the photon counting results. The light intensity generated by the interaction is determined when the light is not dimmed at a plurality of dimming rates or is dimmed at the same dimming rate.
[Selection] Figure 1

Description

  The present invention relates to a light intensity measuring device and a light intensity measuring method.

  Conventionally, various physical quantities have been observed by measuring the intensity of scattered light. As a typical measurement method of scattered light, a photon count method (photon counting method) and an analog measurement method are known. The photon counting method is a method of measuring light intensity by counting the number of photon pulses generated according to light per unit time one by one. For this reason, the photon counting method is mainly used for observation of weak light. On the other hand, the analog measurement method is a light intensity measurement method in which the level of received light is converted into an electrical signal and directly measured. For this reason, the analog measurement method is used for observation of light having a relatively high intensity.

  For example, a measuring device that receives scattered light from the atmosphere or aerosol and measures the environment in the sky is known. In particular, as a detection device that receives scattered light from the atmosphere, a device that can perform highly accurate measurement by reducing the range that cannot be received by switching between the photon counting method and the analog measurement operation has been proposed. (For example, refer to Patent Document 1).

  In addition, a method for evaluating the polishing roughness and fine structure of the object surface by measuring the angular distribution of scattered light from the object surface is known. For example, when light is irradiated on the surface of the optical glass, scattered light corresponding to the roughness of the surface such as a polished surface or an antireflection film is generated. For this reason, the surface roughness can be evaluated by measuring characteristics such as the angular distribution of the intensity of the scattered light.

Japanese Patent Laid-Open No. 9-178852

  In recent years, with the progress of microfabrication technology and surface polishing technology, the miniaturization of the structure of the object surface and the increase in the specularity are progressing. Very weak scattered light is generated from an object surface having a fine structure or an object surface having a high specularity. Therefore, there is a need for a light intensity detection method that can detect the intensity of weak scattered light. In this respect, the photon counting method can detect with high sensitivity even scattered light having very weak intensity.

  However, the intensity of scattered light having a low reflection angle is orders of magnitude greater than the intensity of scattered light having a high reflection angle and a high angle. For this reason, the intensity of scattered light at a low angle may not be counted by the photon counting method because the dynamic range is saturated. On the contrary, in the analog measurement method, it is difficult to detect the intensity of weak scattered light from a high angle.

  From such a background, it is desired to develop a technique for measuring the intensity of scattered light over a wider angle range with a larger dynamic range. This is a common problem in measuring not only scattered light but also light generated by interaction with an object such as reflected light or transmitted light.

  An object of the present invention is to provide a light intensity measuring device and a light intensity measuring method capable of measuring the intensity of light generated by interaction with an object with a larger dynamic range and practical accuracy.

  The light intensity measurement device according to the present invention includes an irradiation system, a measurement system, and a neutral density filter. The irradiation system irradiates the test object with irradiation light. The measurement system measures the intensity of light generated by the interaction between the irradiation light and the test object. The neutral density filter attenuates at least one of the irradiation light and the light generated by the interaction with a plurality of different attenuation rates. Further, the measurement system counts the photons constituting the light attenuated at the plurality of attenuation rates using a photon counter prior to the measurement of the light generated by the interaction, and based on the photon counting result Based on the calibration values of the plurality of dimming rates obtained in the above, the irradiation light and the light generated by the interaction are not dimmed by the plurality of dimming rates or the irradiation light and the When at least one of the light generated by the interaction is attenuated at the same attenuation rate, the intensity of the light generated by the interaction is obtained.

  The light intensity measurement method according to the present invention includes a step of irradiating a test object with irradiation light, a step of measuring the intensity of light generated by the interaction between the irradiation light and the test object, A step of dimming at least one of the irradiation light and the light generated by the interaction with a plurality of different dimming rates. Then, prior to measurement of the light generated by the interaction, each photon constituting the light attenuated at the plurality of attenuation rates is counted using a photon counter, and obtained based on the photon counting result. Based on the calibration values of the plurality of dimming rates, both the irradiation light and the light generated by the interaction are not attenuated by the plurality of dimming rates or are generated by the irradiation light and the interaction The intensity of the light generated by the interaction when at least one of the light is attenuated at the same attenuation rate is obtained.

  According to the light intensity measuring device and the light intensity measuring method according to the present invention, it is possible to measure the intensity of light generated by interaction with an object with a larger dynamic range and practical accuracy.

The top view which shows the structure of the light intensity measuring apparatus which concerns on embodiment of this invention. The side view of the to-be-tested object and sample stage shown in FIG. The front view of the variable neutral density filter shown in FIG. The front view which shows an example of the variable attenuation filter which can change a light attenuation rate continuously. The front view which shows another example of the variable attenuation filter which can change a light attenuation rate continuously. The figure which shows the example which compared the design value and calibration value of the light attenuation rate of the variable neutral density filter shown in FIG. The schematic diagram which shows the effective dynamic range of the optical intensity measuring apparatus shown in FIG. The top view which shows the 1st modification of the light intensity measuring device shown in FIG. The top view which shows the 2nd modification of the light intensity measuring apparatus shown in FIG.

  A light intensity measurement device and a light intensity measurement method according to an embodiment of the present invention will be described with reference to the accompanying drawings.

(Configuration and function)
FIG. 1 is a top view showing a configuration of a light intensity measuring apparatus according to an embodiment of the present invention, and FIG. 2 is a side view of an object to be examined and a sample stage shown in FIG.

  The light intensity measuring apparatus 1 is an apparatus for measuring the intensity of scattered light generated as transmitted light by irradiating the inspection surface of the object O with light attenuated at a plurality of different extinction ratios. is there. For this purpose, the light intensity measuring apparatus 1 includes a sample stage 2 for installing the test object O, an irradiation system 3 for irradiating light to the test object O installed on the sample stage 2, and scattering from the test object O. It has a measurement system 4 that measures the intensity of light.

  The irradiation system 3 can be configured using a light source 5, a polarizer (optical polarizer) 6, a variable neutral density (ND) filter 7, and an iris (aperture) 8. One end of a single mode optical fiber 9 is connected to the output side of the light source 5. From the other end of the single mode optical fiber 9, a linear light path L <b> 1 of irradiation light is formed toward the test object O installed on the sample stage 2. On the optical path L1 of the linear irradiation light, a polarizer 6, a variable neutral density filter 7, and an iris 8 are sequentially arranged.

  On the other hand, the measurement system 4 includes a rotary stage 10, a first pinhole 11, a second pinhole 12, an objective lens 13, a dark box 14, a photon counter (photon counting method photodetector) 15, and an analog light intensity measurement device. 16 and the computer 17 can be used.

  The rotation stage 10 is a plate-like component having a rotation mechanism that rotates in the horizontal direction around the object to be examined O or the sample stage 2. On the rotary stage 10, the 1st pinhole 11, the 2nd pinhole 12, and the objective lens 13 are being fixed on the straight line in order. Further, the first pinhole 11, the second pinhole 12 and the objective lens 13 are covered with a dark box 14.

  For this reason, among the scattered light generated by passing through the test object O, the optical path L2 of the scattered light generated at a specific angle passes through the first pinhole 11, the second pinhole 12, and the objective lens 13. Are formed in a straight line. Then, by rotating the rotary stage 10, scattered light that has been transmitted through the test object O and generated at a specific angle can be incident on the objective lens 13.

  Furthermore, the objective lens 13 is connected to the photon counter 15 via an optical fiber 18 that penetrates the dark box 14. The photon counter 15 is detachably connected to the optical fiber 18 and can be replaced with an analog light intensity measuring device 16. A computer 17 is connected to the output side of the photon counter 15 and the analog light intensity measuring device 16.

  Next, the function of each component of the light intensity measuring device 1 will be described in detail.

  The light source 5 can be constituted by a laser light source such as a laser diode that emits laser light having a wavelength λ = 635 nm. The polarizer 6 is an optical element for obtaining linearly polarized light from the laser light emitted from the light source 5.

  The variable neutral density filter 7 is an optical element that can reduce the intensity of light with different attenuation ratios (transmittances).

  FIG. 3 is a front view of the variable neutral density filter 7 shown in FIG.

  As shown in FIGS. 1 and 3, the variable neutral density filter 7 can be configured by fixing a plurality of neutral density filters 19 having different attenuation ratios to a moving mechanism 20. A general neutral density filter is gray or black and has a neutral density depending on the density.

  The moving mechanism 20 is connected to the computer 17. The moving mechanism 20 has a function of disposing each of the neutral density filters 19 on the optical path L1 of the irradiation light or retracting from the optical path L1 of the irradiation light in accordance with a control signal from the computer 17.

  FIG. 1 and FIG. 3 show an example in which a rotating shaft with a ring-shaped attachment portion fixed is used as a moving mechanism 20, and a plurality of disc-shaped neutral density filters 19 are provided on the attachment portion on the circle at substantially equal intervals. . The moving mechanism 20 is not limited to the configuration examples shown in FIGS. 1 and 3, and a slide mechanism that translates a plurality of neutral density filters arranged on a line may be used.

  The variable neutral density filter 7 is configured to change the attenuation factor stepwise by changing the neutral density filter 19 arranged on the optical path L1 of the irradiation light by the moving mechanism 20. In addition, the irradiation system 3 may be provided with a variable neutral density filter 7 that can continuously change the light attenuation rate without changing it stepwise.

  FIG. 4 is a diagram illustrating an example of a variable neutral density filter capable of continuously changing the attenuation factor.

  As shown in FIG. 4, the variable neutral density filter 7A can be configured by fixing a ring-shaped neutral density filter 19A whose attenuation factor gradually changes in the circumferential direction to a moving mechanism 20A having a rotation axis. it can. In the variable neutral density filter 7A, the neutral density can be changed by changing the position of the neutral density filter 19A that crosses the optical path L1 of the irradiation light by the rotation of the moving mechanism 20A.

  FIG. 5 is a front view showing another example of a variable neutral density filter capable of continuously changing the attenuation factor.

  Further, as shown in FIG. 5, the variable attenuating filter 7B is also configured by fixing a band-shaped attenuating filter 19B whose gradual attenuation rate gradually changes in the longitudinal direction to a moving mechanism 20B that slides in the longitudinal direction. be able to. In this variable attenuating filter 7B, the attenuation factor can be changed by changing the position of the attenuating filter 19B crossing the optical path L1 of the irradiation light by sliding the moving mechanism 20B.

  The iris 8 provided in the subsequent stage of the variable neutral density filter 7 is an optical element that adjusts the size of the light irradiation area of the object to be examined O.

  As the first pinhole 11 and the second pinhole 12, for example, a hole having a diameter φ = 200 [μm] is used. By providing the first pinhole 11 and the second pinhole 12, the detection area of the scattered light can be limited to a predetermined range. For this reason, it becomes possible to measure the scattering characteristics of a desired minute region. In addition, by providing the first and second pinholes 11 and 12, it is possible to selectively make the scattered light traveling straight enter the objective lens 13.

  The objective lens 13 is an optical element for focusing the scattered light and making it incident on the optical fiber 18.

  The photon counter 15 is a detector that can detect scattered light having very weak intensity with high sensitivity by counting the number of photons per unit time output from the optical fiber 18. On the other hand, the analog light intensity measuring device 16 is a device that measures the intensity of light by converting the received light into a current proportional to the energy of the light.

  The computer 17 has a function of switching and executing the operation in the measurement mode of the light intensity measuring device 1 and the operation in the calibration mode. The measurement mode is a mode in which the angle distribution of the scattered light is acquired by sequentially measuring the intensity of the angle-resolved scattered light from the test object O while changing the angle of the scattered light. On the other hand, the calibration mode is a mode for obtaining a calibration value of the characteristic value of the irradiation system 3 including the light attenuation rate of the variable neutral density filter 7. Therefore, the calibration mode is carried out regularly or every measurement prior to the measurement mode in which the intensity of scattered light is measured.

  For this purpose, a program is read into the arithmetic unit of the computer 17, and the computer 17 functions as a light attenuation rate control unit 21, a characteristic value measurement unit 22, and a light intensity measurement unit 23. A circuit may be connected to the computer 17 as necessary.

  The dimming rate controller 21 controls the dimming rate of the variable dimming filter 7 and the measurement time of the light intensity at each dimming rate by giving a control signal to the moving mechanism 20 of the variable dimming filter 7. And a function of supplying the characteristic value measuring unit 22 and the light intensity measuring unit 23 with the control values of the dimming rate and measurement time of the variable neutral density filter 7.

  Particularly, when the photon counter 15 is connected to the optical fiber 18 as a light intensity detector, the light attenuation rate control unit 21 can detect at least the intensity of light incident on the photon counter 15 by the photon counter 15. A function of adjusting the light attenuation rate of the variable neutral density filter 7 so as to attenuate to the intensity is provided. The photon counter 15 can count the number of photons if the number of incident photons per second is approximately 1,000,000 or less.

  Therefore, in the measurement mode for measuring the angular distribution of the intensity of the scattered light from the test object O, the angle is resolved so that the photon counter 15 can count the number of photons of the scattered light having a high intensity from the test object O. The dimming rate and measurement time of the variable neutral density filter 7 are feedback-controlled by the dimming rate control unit 21 according to the intensity of the scattered light.

  On the other hand, in the calibration mode for calibrating the characteristic value of the irradiation system 3, the light attenuation rate and measurement time of the variable neutral density filter 7 are reduced so that the photon counter 15 can count the number of photons emitted from the irradiation system 3. It is controlled by the rate control unit 21. In the calibration mode, the range that can be taken by the number of photons of light emitted from the irradiation system 3 can be roughly predicted. Therefore, the variable dimming can be performed according to the range of the expected number of photons without measuring the light intensity. The dimming rate and measurement time of the filter 7 can be controlled. However, the dimming rate and measurement time of the variable neutral density filter 7 may be feedback controlled according to the intensity of light emitted from the irradiation system 3.

  Note that the control value of the light attenuation rate and the measurement time of the light intensity at each light attenuation rate is obtained from the light intensity measuring unit 23 or the characteristic value measuring unit 22 as specific information of the appropriate light attenuation rate and measuring time. Given to part 21.

  The characteristic value measuring unit 22 irradiates the light attenuation rate of the variable neutral density filter 7 and the output value of the intensity of light emitted from the light source 5 based on the photon counting result output from the photon counter 15 in the calibration mode. It has a function of measuring the characteristic value in the system 3 and a function of notifying the measured intensity value as a calibration value to the light intensity measuring unit 23.

  For example, each neutral density filter 19 that constitutes the variable neutral density filter 7 based on the count result of the photons after dimming output from the photon counter 15 corresponding to the design value of each neutral density ratio of the variable neutral density filter 7. The actual dimming rate can be measured. That is, when each neutral density filter 19 is arranged on the optical path L1 of the irradiation light, the photon count number detected by the photon counter 15 and when no neutral density filter 19 is arranged on the optical path L1 of the irradiation light. The calibration value of each light attenuation rate can be calculated as a ratio to the photon count detected by the photon counter 15.

  FIG. 6 is a diagram showing an example in which the design value and the calibration value of the attenuation factor of the variable attenuation filter 7 shown in FIG. 1 are compared.

  As shown in the left column of FIG. 6, the actual attenuation rate of the variable attenuation filter 7 that can variably set the attenuation rate to 6 values of 10%, 1%, 0.1%, 0.01%, 0.001%, 0.0001%. Was measured by the characteristic value measuring unit 22 of the computer 17. That is, the photon counter 15 is used to count the photons constituting the light attenuated at each attenuation rate, and the calibration value of the attenuation factor as a ratio with the number of photons of the light not attenuated is shown in FIG. Calculations were made as shown in the right column.

Here, the SN (signal to noise) ratio in the photon counter 15 is expressed by equation (1).
SN = Np (t) ^1/2 / (Np + 2Nd) ^1/2 (1)
In equation (1), Np is the count number of detected photons, Nd is the count number (dark count number) that occurs when no photons are input, and t is the measurement time.

  As shown in equation (1), it can be seen that the SN ratio of the photon counter 15 increases in proportion to the square root of the measurement time. Therefore, by setting the measurement time by the photon counter 15 to be long, it is possible to measure the light intensity with a high SN ratio.

  However, in order to obtain the calibration value of the attenuation factor of each attenuation filter 19 constituting the variable attenuation filter 7 with higher accuracy, it is desirable to make the SN ratio constant between different attenuation factors. Therefore, it is preferable to adjust the measurement time t to an appropriate time so that the SN ratio represented by the equation (1) is constant between different light attenuation rates.

  Therefore, the characteristic value measuring unit 22 is configured to select an appropriate light intensity corresponding to each light attenuation rate so that photons are counted at each measurement time t adjusted so that the SN ratio is constant between different light attenuation rates. The specific information of the measurement time t is configured to be notified to the light attenuation rate control unit 21. The calibration value shown in the right column of FIG. 6 is a value calculated by counting photons by the photon counter 15 at each measurement time t adjusted so as to be constant between dimming rates with different SN ratios.

  As shown in the right column of FIG. 6, the calibration value of the attenuation factor of the variable attenuation filter 7 includes a characteristic difference unique to each attenuation filter 19 and a slight difference in the light traveling direction of each attenuation filter 19. It can be confirmed that there is a variation according to conditions such as the inclination and the incident position of light on each of the neutral density filters 19. Therefore, it is possible to obtain the angular distribution of the intensity of the scattered light with practical accuracy by executing the measurement mode for measuring the intensity of the scattered light from the object to be detected using the calibration value of the dimming rate. Become.

  4 and 5, when the variable attenuation filter 7A, 7B capable of continuously changing the attenuation ratio is provided in the irradiation system 3, the variable attenuation is performed by the above-described method. It is possible to obtain a plurality of light attenuation rate calibration values at desired sampling positions of the filters 7A and 7B.

  In addition to the light attenuation rate, the characteristic value measuring unit 22 can also obtain a calibration value of the output value of the intensity of light emitted from the light source 5. That is, the actual output value and design value of the light source 5 may differ to a degree that cannot be ignored due to manufacturing errors or aging of the light source 5.

  Therefore, the attenuation rate of the variable attenuation filter 7 is fixed to an attenuation rate that allows the photon counter 15 to count photons, and the intensity of the light emitted from the irradiation system 3 after the attenuation is reduced to photon. By measuring with the counter 15, the actual output value of the light source 5 can be obtained with high accuracy. Specifically, the calibration value of the output value of the light source 5 provided in the irradiation system 3 can be obtained by multiplying the reciprocal of the light attenuation rate by the count value of the photons from the irradiation system 3.

  Further, by making the conditions such as the characteristic value of the optical element not to be calibrated constant by the same method, the calibration value of the characteristic value of the optical element to be calibrated is based on the photon count value by the photon counter 15. Can be sought.

  The light intensity measurement unit 23 uses the photon counter 15 or the analog light intensity measurement value of the scattered light generated by irradiating the object O with the light attenuated by the variable attenuation filter 7 in the measurement mode. While acquiring from the measuring device 16, it has the function to give the specific information of the suitable light attenuation rate for feedback control to the light attenuation rate control part 21 based on the measured value of the intensity of scattered light.

  In the measurement mode, any one of the photon counter 15 and the analog light intensity measuring device 16 may be used as long as it is possible to measure the intensity of scattered light corresponding to the attenuation rate of the variable attenuation filter 7. The intensity of the scattered light is usually weak, and even the scattered light having a relatively high intensity can be reduced to scattered light having an intensity in a predetermined range by the variable neutral density filter 7. For this reason, if the photon counter 15 is used, the intensity of the scattered light that is reliably angle-resolved can be measured for each angle.

  However, when the intensity of the scattered light to be observed is sufficiently large, the measurement time can be reduced by measuring the intensity of the scattered light using the analog light intensity measuring device 16 as compared with the case where the photon counter 15 is used. It can be shortened. Therefore, the intensity of the scattered light after dimming by the variable neutral density filter 7 may be measured for each intensity range using both the photon counter 15 and the analog light intensity measuring device 16.

  In addition, an appropriate dimming rate to be given to the dimming rate control unit 21 for feedback control can be automatically determined by the light intensity measuring unit 23 based on the measured value of the intensity of scattered light. As a specific example, a threshold value is set for the intensity of scattered light when light is not dimmed in advance to divide the intensity range of scattered light into a plurality of ranges, and the intensity of scattered light in each intensity range is determined by the photon counter 15 or analog. The light attenuation rate that enables measurement within the dynamic range of the optical intensity measuring device 16 can be set to an appropriate light attenuation rate corresponding to each intensity range.

  Therefore, for example, an appropriate dimming rate can be obtained by threshold processing for determining which intensity range the actual scattered light intensity obtained by multiplying the measured value of the scattered light intensity by the reciprocal of the calibration value of the dimming rate. Can be determined automatically.

  In other words, the upper and lower thresholds are set in the range of intensities that can be measured within the dynamic range of the photon counter 15 or the analog light intensity measuring device 16, and the threshold is decreased when the upper threshold is exceeded. While the light rate is switched to a larger value, when the light rate is less than the lower threshold, the light attenuation rate can be determined to switch the light attenuation rate to a smaller value. That is, it is possible to provide a threshold value for the intensity of scattered light in the case where light is not attenuated, and to divide the range into intensity ranges corresponding to a plurality of light attenuation rates.

  In addition, when the variable attenuating filters 7A and 7B capable of continuously changing the attenuation rate as shown in FIGS. 4 and 5 are provided in the irradiation system 3, the photon counter 15 or the analog light intensity is provided. It is also possible to feedback control the dimming rate so that the measured value of the intensity of scattered light by the measuring device 16 becomes constant. In this case, a light attenuation rate inversely proportional to the measured value of the scattered light intensity is automatically set in the light intensity measurement unit 23 and the light attenuation rate control unit 21 as a control value of the light attenuation rate.

  In addition to the function of determining the attenuation rate according to the measured value of the intensity of scattered light, the light intensity measurement unit 23 includes the intensity of scattered light corresponding to a plurality of different attenuation rates of the variable attenuation filter 7. Based on the measurement result of the angle distribution and the calibration value of each attenuation ratio, the light that has not been attenuated by the plurality of attenuation ratios of the variable attenuation filter 7 or the light that has been attenuated by the same attenuation ratio is examined. A function for obtaining an angular distribution of the intensity of scattered light generated from the test object O when the object O is irradiated is provided.

  Specifically, the measured values of the intensity of the angle-resolved scattered light corresponding to the different dimming rates are respectively multiplied by the reciprocal of the calibration value of the dimming rate, thereby obtaining the plural dimming filters 7. A plurality of intermittent intensity data indicating the angular distribution of the intensity of the scattered light generated from the test object O when the test object O is irradiated with light that has not been attenuated by the light rate is calculated with practical accuracy. Can do. Further, by executing a stitching process for joining a plurality of intensity data, it is possible to generate angular distribution data having continuous intensity indicating the intensity of scattered light.

  That is, by using each dimming rate self-calibrated with high accuracy based on the photon count value in the photon counter 15, a plurality of intermittent light intensity data capable of executing the stitching process is obtained. Can do. In other words, the linearity can be obtained as long as it is between the calibration value of the attenuation rate with sufficient accuracy using the photon counter 15 and the measured value of the intensity of the scattered light. It is possible to join the light intensity data of the scattered light corresponding to the rate.

  Note that the measurement value of the intensity of scattered light corresponding to each light attenuation rate may be multiplied by the product of the reference light attenuation rate calibration value and the inverse of each light attenuation rate calibration value. In this case, when the object O is irradiated with light that has been attenuated at the same reference dimming rate, a plurality of intermittent intensities indicating the angle-resolved intensity of the scattered light generated from the object O is obtained. Data is obtained. Then, continuous angular distribution data indicating the angular distribution of the relative intensity of the scattered light can be generated by executing the intermittent intensity data stitching process.

  On the other hand, if the measured value of the intensity of scattered light corresponding to each attenuation ratio is multiplied by the reciprocal of the calibration value of each attenuation ratio, continuous angular distribution data indicating the angular distribution of the absolute intensity of the scattered light is obtained. Can be generated. When obtaining the absolute intensity distribution of the scattered light, the continuous angular distribution data indicating the intensity distribution of the scattered light is multiplied by a correction coefficient represented by the ratio of the calibration value to the design value of the output value of the light source 5. Thus, a more accurate angular distribution of scattered light intensity can be obtained.

  By such stitching processing in the light intensity measurement unit 23, a substantially large dynamic range is obtained in the light intensity measurement device 1.

  FIG. 7 is a schematic diagram showing an effective dynamic range of the light intensity measuring apparatus 1 shown in FIG.

  In FIG. 7, the vertical axis represents the intensity range of light that can be acquired. Even when the dynamic range unique to the photon counter 15 does not cover the range of the intensity of the scattered light to be measured, as shown in FIG. 7, the object O with different dimming rates ND1, ND2, and ND3 is used. By reducing the intensity of the irradiation light, it is possible to obtain the intensity of scattered light that has been angularly resolved over a wide range.

  In other words, the intensity range of scattered light that can be obtained is connected by dimming the irradiated light with different dimming rates ND1, ND2, ND3 and multiplying the measured value of the light intensity by the inverse of each dimming rate ND1, ND2, ND3 By combining them, an effective range wider than the range unique to the photon counter 15 can be obtained.

(Operation and action)
Next, the operation and action of the light intensity measuring device 1 will be described.

  First, a calibration mode for obtaining a calibration value of the characteristic value of the irradiation system 3 is selected. Therefore, the test object O is not installed on the sample stage 2, and the rotary stage 10 is positioned at a position where the optical path from the output side of the single mode optical fiber 9 to the objective lens 13 is a straight line. A photon counter 15 is connected to the optical fiber 18.

  Then, at least the dimming rate of each neutral density filter 19 provided in the variable neutral density filter 7 is calibrated. Therefore, the intensity of light that is not attenuated by the variable neutral density filter 7 is measured by the photon counter 15. Specifically, all the neutral density filters 19 are retracted from the optical path L1 of the irradiation light by driving the moving mechanism 20. Then, a sufficiently low intensity laser beam that can be counted by the photon counter 15 is emitted from the light source 5.

  Then, the laser light enters the single mode optical fiber 9 as irradiation light, and the irradiation light that has passed through the single mode optical fiber 9 enters the polarizer 6. Irradiation light incident on the polarizer 6 becomes linearly polarized light and enters the iris 8 without passing through any of the neutral density filters 19. Irradiation light that has entered the iris 8 and whose irradiation region size has been adjusted enters the objective lens 13 on the sample stage 2 through the first pinhole 11 and the second pinhole 12.

  The irradiation light incident on the objective lens 13 is narrowed down and enters the optical fiber 18. Irradiation light that has entered the optical fiber 18 enters the photon counter 15. Then, the photon counter 15 counts photons constituting the irradiation light. Further, the photon counting result is output to the computer 17.

  Next, the intensity of light attenuated by the variable attenuation filter 7 at a plurality of attenuation rates is sequentially measured by the photon counter 15. Specifically, the characteristic value measurement unit 22 of the computer 17 sets the photon counting time adjusted so that the S / N ratio is constant between the different attenuation rates to the appropriate light intensity corresponding to each attenuation rate. Notify the dimming rate control unit 21 as the measurement time. Then, the light attenuation rate control unit 21 controls the moving mechanism 20 of the variable dark filter 7, and the light reducing filter 19 to be calibrated is positioned at a position crossing the optical path L1 of the irradiation light by driving the moving mechanism 20. .

  Next, the light source 5 emits a laser beam having the same intensity as the intensity of the laser beam irradiated for measuring the intensity of the light that is not attenuated by the variable neutral density filter 7. Then, the irradiation light enters the photon counter 15 in the same flow as in the case of measuring the intensity of light that is not attenuated by the variable neutral density filter 7. However, since the irradiation light passes through the neutral density filter 19 to be calibrated, it is attenuated at the actual neutral density rate of the neutral density filter 19.

  Then, the photon counter 15 counts photons constituting the dimmed irradiation light. This counting is continued until the moving mechanism 20 is driven by the control from the light attenuation rate control unit 21 and the light attenuation filter 19 to be calibrated is changed to another light attenuation filter 19. That is, photons are counted for the measurement time notified from the characteristic value measurement unit 22 to the light attenuation rate control unit 21. Then, the photon counting result is output to the computer 17.

  When the measurement time notified from the characteristic value measuring unit 22 to the dimming rate control unit 21 elapses, the moving mechanism 20 is driven by the control from the dimming rate control unit 21, and the dimming filter 19 to be calibrated is different. It is changed to the neutral density filter 19. Then, the counting result of the photons constituting the irradiation light dimmed at different dimming rates by all the neutral density filters 19 in the same flow is sequentially output to the computer 17.

  The photon counting time is adjusted so that the SN ratio is constant between different light attenuation rates. For this reason, the computer 17 obtains photon counting results corresponding to different attenuation rates with the same SN ratio.

  Next, the characteristic value measurement unit 22 divides each count value of photons corresponding to different attenuation rates by the count value of photons of irradiation light that has not been attenuated. Thereby, the actual dimming rate of each neutral density filter 19 can be calculated. The calculated value of the light attenuation rate is given from the characteristic value measurement unit 22 to the light intensity measurement unit 23 as a calibration value of the light attenuation rate.

  Furthermore, the output value of the laser light emitted from the light source 5 is calibrated by the characteristic value measuring unit 22 as necessary. In this case, the photon count value of the irradiation light that has not been dimmed can be used as the calibration value of the output value of the light source 5. Further, the calibration coefficient of the output value of the light source 5 can be obtained as the ratio of the calibration value of the light source 5 to the design value.

  When the operation of the light intensity measurement apparatus 1 in the calibration mode is completed, a measurement mode for measuring the angular distribution of the intensity of scattered light from the object to be examined O is selected. For this reason, the test object O is installed on the sample stage 2. The rotary stage 10 is positioned at an initial position where the angle-resolved scattered light from the test object O can enter the objective lens 13. Further, a photon counter 15 or an analog light intensity measuring device 16 is connected to the optical fiber 18.

  Here, the case where the angular distribution of scattered light is measured using the photon counter 15 will be described. However, the analog light intensity measuring device 16 may be used at an angle where the intensity of the scattered light becomes sufficiently large in order to shorten the measurement time.

  In the measurement mode, the moving mechanism 20 is driven by the control from the light attenuation rate control unit 21, and the light attenuation rate of the variable light attenuation filter 7 is set to a default value. Then, laser light is emitted from the light source 5 as in the calibration mode. For this reason, the irradiation light attenuated by the attenuation factor of the variable attenuation filter 7 is incident on the test object O. As a result, scattered light having an intensity corresponding to the dimming rate of the variable neutral density filter 7 is generated from the test object O due to factors such as surface roughness of the test object O and variations in refractive index.

  Of the scattered light, the scattered light passing through the optical path L <b> 2 of the scattered light formed on the rotary stage 10 enters the objective lens 13. The scattered light incident on the objective lens 13 is limited to a predetermined range by the first pinhole 11 and the second pinhole 12. As a result, the scattered light angle-resolved with higher resolution can be incident on the photon counter 15.

  The photon counter 15 counts the photons that constitute the scattered light. Then, the photon counting result is output to the computer 17. Then, the light intensity measurement unit 23 determines whether or not the photon counting result is normally obtained within the range determined by the threshold. If the photon count value is within the threshold value, the light intensity measurement unit 23 acquires the photon count value as the angle-resolved intensity of the scattered light.

  On the other hand, when the photon counting result is larger than the range determined by the threshold or when the photon counter 15 is saturated within the measurement range of the photon counter 15, the light intensity measurement unit 23 is larger than the current dimming rate. The dimming rate is given to the dimming rate control unit 21 as specific information of the dimming rate for feedback control. On the contrary, when the photon counting result is smaller than the range determined by the threshold or when it is less than the noise and is not obtained as a normal count value, the light intensity measurement unit 23 is set to be less than the current dimming rate. A small dimming rate is given to the dimming rate control unit 21 as specific information of the dimming rate for feedback control.

  Then, the light attenuation rate control unit 21 controls the moving mechanism 20 to change the light attenuation rate of the variable light attenuation filter 7 to the light attenuation rate specified as the specific information of the light attenuation rate. Then, the photon counter 15 again counts the photons constituting the scattered light by applying the changed attenuation rate. That is, feedback control is performed so that the dimming rate becomes an appropriate dimming rate based on the photon count value. Further, the counting result of the counted photons is output from the photon counter 15 to the light intensity measuring unit 23.

  By repeatedly determining the threshold value of the photon counting result and changing the attenuation rate, the photon counting result is finally obtained as the angle-resolved intensity of the scattered light within the range determined by the threshold value. Acquired by the unit 23.

  Next, the rotary stage 10 is rotated by a predetermined step angle, and is positioned at a position where another angle-resolved scattered light from the test object O can enter the objective lens 13. Then, the laser beam is irradiated again from the light source 5, and the photon counting and the light attenuation rate feedback control are executed. Thereby, the count value of the photon within the range defined by the threshold value is acquired by the light intensity measurement unit 23 as the intensity of the scattered light subjected to another angle resolution.

  Further, the rotary stage 10 is sequentially rotated by a predetermined step angle, and the intensity of the scattered light that is angle-resolved in each angle direction by the same flow is acquired by the light intensity measurement unit 23. As a result, the light intensity measurement unit 23 obtains the scattered light intensity as a count value of photons included in a predetermined range for each angle of the rotary stage 10.

  However, the count value of each photon corresponds to one of a plurality of different light attenuation rates. A count value of a plurality of photons corresponding to the same attenuation rate becomes intermittent intensity data indicating an angular distribution of the intensity of scattered light.

  Next, the light intensity measurement unit 23 multiplies the intermittent intensity data indicating the angular distribution of the intensity of the scattered light by the reciprocal of the calibration value of the attenuation factor. As a result, a plurality of intermittent intensity data indicating the angular distribution of the intensity of the scattered light generated from the test object O when the test object O is irradiated with the irradiation light that has not been attenuated by the variable neutral density filter 7 is practical. Calculated with reasonable accuracy.

  Next, the light intensity measurement unit 23 stitches together a plurality of intermittent intensity data calculated by multiplying the reciprocal of the calibration value of the corresponding dimming rate by stitching processing. As a result, it is possible to obtain continuous measurement data indicating the angular distribution of the intensity of scattered light generated from the test object O when the test object O is irradiated with irradiation light that has not been attenuated by the variable neutral density filter 7. it can.

  Further, when the calibration coefficient of the output value of the light source 5 is acquired in the characteristic value measurement unit 22, the light intensity measurement unit 23 scatters the calibration coefficient of the output value of the light source 5 acquired from the characteristic value measurement unit 22. Multiply the continuous measurement data showing the angular distribution of light intensity. As a result, continuous measurement data indicating an accurate angular distribution of scattered light intensity corresponding to the design value of the output value of the light source 5 can be obtained.

  Then, the user can accurately evaluate the object surface of the object to be examined O and the structure of the object by referring to the angle distribution of the intensity of the scattered light or by data analysis processing based on the angle distribution of the intensity of the scattered light. Is possible.

  In other words, the light intensity measuring apparatus 1 as described above reduces the intensity of scattered light to be detected with the variable attenuation filter 7 at different attenuation ratios, so that the photon counter 15 and the analog light intensity measuring device 16 At least one of them can detect scattered light. Furthermore, the light intensity measuring device 1 calibrates the light attenuation rate of each neutral density filter 19 based on the photon count value by the photon counting method capable of detecting the light intensity with high accuracy. is there.

(effect)
For this reason, according to the light intensity measuring device 1, even if the scattered light has a wide intensity range, the dynamic range is not saturated, and the angular distribution of the intensity of the scattered light is obtained by the photon counter 15 or the analog light intensity measuring device 16. Can be requested.

  Further, the intermittent intensity data of the scattered light can be accurately obtained by using the calibration value of each neutral density filter 19 obtained with high accuracy based on the photon count value by the photon counter 15. That is, even if there is a manufacturing error in each of the neutral density filters 19, linearity can be obtained between the neutral density and the intensity of scattered light.

  As a result, it is possible to connect intermittent intensity data measured at different dimming rates. That is, the effective dynamic range can be made larger than the actual dynamic range.

  For this reason, it becomes possible to measure the intensity by angle-resolving scattered light in a wider angle range. Then, based on the angle-resolved distribution of scattered light from the object to be measured O measured by the light intensity measuring device 1, the polished object surface with a small surface roughness and the structure of the object formed by microfabrication are accurately obtained. Can be evaluated.

  Incidentally, in the light intensity measuring apparatus 1 that irradiates the test object O with the light of the wavelength λ = 635 nm from the light source 5 as the test object O is a flat plate made of borosilicate glass, the effective dynamic range is 11 digits. It was confirmed that it could be enlarged. In the light intensity measuring apparatus 1, the angle range of the scattered light to be measured can be set in the range of −60 ° to + 20 ° due to the large effective dynamic range. The step amount of the scattered light measurement angle at this time was 0.25 °, and the number of photons of the scattered light was counted by the photon counter 15 with the detection time of the scattered light at each measurement angle as 1 s. Further, the measurement of the intensity of the scattered light was started when the intensity of the irradiation light from the light source 5 was sufficiently stabilized.

(Modification)
In the light intensity measuring apparatus 1 shown in FIG. 1, the optical path L of the linear irradiation light formed from the one end of the single mode optical fiber 9 toward the test object O placed on the sample stage 2 through the variable attenuation filter 7. Although the example arrange | positioned above was shown, the variable attenuation filter 7 can also be arrange | positioned in the middle of the single mode optical fiber 9. FIG.
FIG. 8 is a top view showing a first modification of the light intensity measuring apparatus 1 shown in FIG.
In the light intensity measuring apparatus 1A shown in FIG. 8, the arrangement position of the variable neutral density filter 7 is different from that of the light intensity measuring apparatus 1 shown in FIG. Since other configurations and operations are not substantially different from those of the light intensity measuring apparatus 1 shown in FIG. 1, only the irradiation system 3A is illustrated, and the same components are denoted by the same reference numerals and description thereof is omitted.
In the light intensity measuring apparatus 1A shown in FIG. 8, the irradiation system 3A is provided with a first single mode optical fiber 9A, a second single mode optical fiber 9B, a fiber end fixture 30, and a coupling lens 31. One end of the first single-mode optical fiber 9A is connected to the light source 5 side, and the other end is connected to the fiber end fixture 30. On the other hand, one end of the second single mode optical fiber 9 </ b> B is connected to the fiber end fixture 30, and irradiation light is irradiated from the other end toward the test object O.
The fiber end fixture 30 is an instrument that fixes each end of the first single mode optical fiber 9A and the second single mode optical fiber 9B facing each other and being separated from each other by a predetermined distance. For this reason, the second single mode optical fiber 9B is arranged apart from the first single mode optical fiber 9A.
In addition, the coupling lens 31 is disposed between the first single mode optical fiber 9A and the second single mode optical fiber 9B. The coupling lens 31 is a lens for focusing the irradiation light output from the end portion of the first single mode optical fiber 9A so as to make it incident on the second single mode optical fiber 9B stably and with little loss.
Then, the irradiation light emitted from the light source 5 once exits from the end of the first single mode optical fiber 9A into the space, and then enters the second single mode optical fiber 9B again via the coupling lens 31. Incident.
Further, the variable neutral density filter 7 is disposed in a gap formed between the first single mode optical fiber 9A and the second single mode optical fiber 9B by the fiber end fixture 30. That is, each of the neutral density filters 19 constituting the variable neutral density filter 7 is irradiated with irradiation light formed between the first single mode optical fiber 9A and the second single mode optical fiber 9B by driving the moving mechanism 20. It can be arranged on the optical path L1 or retracted from the optical path L1 of the irradiation light.
FIG. 8 shows an example in which two coupling lenses 31 are arranged and the variable neutral density filter 7 is arranged between the coupling lenses 31, but only one coupling lens 31 may be provided. However, if two coupling lenses 31 are arranged, the irradiation light is applied to the thin second single-mode optical fiber 9B, which is usually about several μm in diameter, without using a special lens having an extremely short focal length. It is possible to make the light incident. If the variable neutral density filter 7 is sandwiched between the two coupling lenses 31, parallel irradiation light enters the variable neutral density filter 7.
Of course, the variable neutral density filters 7A and 7B capable of continuously changing the attenuation rate as shown in FIG. 4 and FIG. 5 are used as the first single mode optical fiber 9A and the second single mode optical fiber 9B. You may provide between.
According to the light intensity measuring apparatus 1A having such a configuration, it is possible to obtain the same effect as that of the light intensity measuring apparatus 1 shown in FIG. In addition, in the light intensity measuring apparatus 1A shown in FIG. 8, the irradiation light can be reduced between the first single mode optical fiber 9A and the second single mode optical fiber 9B. Therefore, even if the light reduction surface of the variable neutral density filter 7 is not strictly perpendicular to the optical axis of the irradiation light, the second single mode optical fiber 9B is caused by the inclination of the variable neutral density filter 7. There is no effect on the direction of the optical axis of the irradiation light directed toward the test object O.
Further, even if the light attenuation surface of the variable attenuation filter 7 is inclined with respect to the traveling direction of the irradiation light, the change in the attenuation factor due to the inclination of the variable attenuation filter 7 can be calibrated in the calibration mode. . Therefore, according to the light intensity measuring apparatus 1A shown in FIG. 8, the angular distribution of the scattered light from the test object O can be measured more accurately.
As described above, the variable neutral density filter 7 may be provided in the irradiation systems 3 and 3A as shown in FIGS. That is, the variable neutral density filter 7 can be provided in the optical path L2 of the scattered light instead of on the optical path L1 of the irradiation light toward the test object O or in addition to the optical path L1 of the irradiation light. In other words, the light intensity measuring device can be configured using a variable neutral density filter that attenuates at least one of irradiation light and angle-resolved scattered light at a plurality of different attenuation rates.

  Further, a plurality of neutral density filters 19, 19A, 19B having the same or different attenuation ratios are respectively provided on the optical path (L1 + L2) from the light source 5 to the photon counter 15 including the optical path L1 of the irradiation light and the optical path L2 of the scattered light. They can also be arranged in series so that they can be retracted by the moving mechanisms 20, 20A, 20B. Even in this case, the intensity of the scattered light incident on the photon counter 15 or the analog light intensity measuring device 16 can be reduced with a desired light attenuation rate.

  On the other hand, the light intensity measuring device may be configured by providing a neutral density filter 19 having a single attenuation rate so as to be retractable from the optical path L1 of the irradiation light or the optical path L2 of the scattered light. In this case, the dimming rate is 0% when the neutral density filter 19 is not arranged on the optical path L1 of the irradiation light or the optical path L2 of the scattered light. Then, the angular distribution of the intensity of the scattered light is easily measured with the two light attenuation ratios when the neutral density filter 19 is disposed on the optical path L1 of the irradiation light or on the optical path L2 of the scattered light and when it is retracted. can do.

  FIG. 9 is a top view showing a second modification of the light intensity measuring apparatus 1 shown in FIG.

  In the light intensity measuring apparatus 1B shown in FIG. 9, the angle-resolved scattered light generated from the test object O, not the irradiation light directed toward the test object O, is attenuated at different attenuation rates. 1 is different from the light intensity measuring apparatus 1 shown in FIG. Since other configurations and operations are not substantially different from those of the light intensity measuring apparatus 1 shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted.

  In the light intensity measurement apparatus 1B, two neutral density filters 19C having the same or different attenuation rates are connected in series on the optical path L2 of the scattered light between the first pinhole 11 and the second pinhole 12. Has been placed. Each neutral density filter 19C can be moved by the moving mechanism 20C between a position crossing the scattered light path L2 and a retracted position not crossing the scattered light path L2. For this reason, the variable neutral density filter 7C is substantially formed by each neutral density filter 19C and the moving mechanism 20C.

  Even with the light intensity measuring apparatus 1B having such a configuration, the same effect as that of the light intensity measuring apparatus 1 shown in FIG. 1 can be obtained. In addition, according to the light intensity measuring apparatus 1B shown in FIG. 9, the angle is resolved at the light attenuation rate corresponding to the intensity of the scattered light angle-resolved by the first pinhole 11 and the second pinhole 12. Scattered light can be selectively reduced.

  In addition, the variable neutral density filter 7C can be easily configured using a plurality of neutral density filters 19C having the same attenuation ratio. On the other hand, if a plurality of neutral density filters 19C having different attenuation ratios are arranged so as to be retractable in series in the traveling direction of the irradiation light and the scattered light, the neutral density filters 19C having different attenuation ratios can be combined with the neutral density filters 19C. Irradiation light and scattered light can be dimmed at a dimming rate larger than the number of 19C. For this reason, the number of photons counted by the photon counter 15 for obtaining the calibration value of the light attenuation rate of each neutral density filter 19C and the amount of data processing in the computer 17 for obtaining the calibration value of the light attenuation rate are reduced. Can do.

  Further, the moving distance of each neutral density filter 19C can be reduced. For this reason, the positioning error of each neutral density filter 19C by the moving mechanism 20C can be reduced. As a result, it is possible to obtain a more accurate calibration value of the light attenuation rate.

(Other embodiments)
Although specific embodiments have been described above, the described embodiments are merely examples, and do not limit the scope of the invention. The novel methods and apparatus described herein can be implemented in a variety of other ways. Various omissions, substitutions, and changes can be made in the method and apparatus described herein without departing from the spirit of the invention. The appended claims and their equivalents include such various forms and modifications as are encompassed by the scope and spirit of the invention.

  For example, in the above-described embodiment, the example in which the angular distribution of the scattered light from the test object O is measured by the light intensity measuring devices 1, 1 </ b> A, and 1 </ b> B is shown. In addition to the intensity of simple scattered light that is not angularly distributed, the intensity of light generated by the interaction between the irradiated light and the object to be inspected, such as transmitted light and reflected light, can be measured with a light intensity measuring device equipped with various mechanisms and functions. It can also be measured. Further, the intensity of the scattered light generated by the light reflected by the test object can be measured by the light intensity measurement device, not only the scattered light generated by the light transmitted through the test object.

  When the light intensity distribution is a measurement target of the light intensity measurement device, the light intensity distribution can be measured even when the intensity difference between the maximum intensity and the minimum intensity of light is large. In addition, when the intensity of non-distributed light is a measurement target of the light intensity measurement device, the light intensity is measured as data that can be compared with the intensity of light from various objects that generate different light with a large difference in intensity. It can be measured by a measuring device.

  Furthermore, not only visible light having a wavelength of about 760 nm to 830 nm, but also the intensity of invisible light such as infrared light having a wavelength of about 0.7 μm to 1 mm and ultraviolet light having a wavelength of about 10 nm to 400 nm is measured by a light intensity measuring device. be able to. Further, when the test object is a phosphor, the intensity of light generated by the fluorescence can be measured.

DESCRIPTION OF SYMBOLS 1, 1A, 1B Light intensity measurement apparatus 2 Sample stage 3, 3A Irradiation system 4 Measurement system 5 Light source 6 Polarizer 7, 7A, 7B, 7C Variable attenuation filter 8 Iris 9, 9A, 9B Single mode optical fiber 10 Rotating stage 11 1st pinhole 12 2nd pinhole 13 Objective lens 14 Dark box 15 Photon counter 16 Analog light intensity measuring device 17 Computer 18 Optical fibers 19, 19A, 19B, 19C Neutral filter 20, 20A, 20B, 20C Moving mechanism 21 Light attenuation rate control unit 22 Characteristic value measurement unit 23 Light intensity measurement unit 30 Fiber end fixture 31 Coupling lens O Test object L1 Optical path of irradiated light L2 Optical path of scattered light

Claims (6)

An irradiation system for irradiating a test object with irradiation light; and
A measurement system for measuring the intensity of light generated by the interaction between the irradiation light and the object to be examined;
A neutral density filter that attenuates at least one of the irradiation light and the light generated by the interaction at a plurality of different attenuation rates;
Prior to the measurement of the light generated by the interaction, the measurement system counts the photons constituting the light attenuated at the plurality of attenuation rates using a photon counter, and based on the photon counting result Based on the calculated calibration values of the plurality of attenuation ratios, when the irradiation light and the light generated by the interaction are not attenuated at the plurality of attenuation ratios, or the irradiation light and the mutual A light intensity measuring device configured to obtain an intensity of light generated by the interaction when at least one of light generated by the action is attenuated at the same attenuation rate. The irradiation system is disposed apart from the light source, the first optical fiber connected to the light source side, and the first optical fiber, and emits irradiation light toward the object to be inspected. With fiber,
The light intensity measuring device according to claim 1, wherein irradiation light is attenuated between the first optical fiber and the second optical fiber by the neutral density filter.   By arranging a plurality of neutral density filters so that they can be retracted in series on the optical path, at least one of the irradiation light and the light generated by the interaction is configured to be attenuated at a plurality of different dimming rates. The light intensity measuring device according to claim 1 or 2.   The measurement system counts photons constituting light emitted from the irradiation system using a photon counter prior to measurement of light generated by the interaction, and obtains it based on the photon counting result from the irradiation system. Based on the calibration value of the output value of the light source provided in the irradiation system, the irradiation light and the light generated by the interaction are not attenuated at the plurality of attenuation ratios or the irradiation light And at least one of the light generated by the interaction is configured to determine the intensity of the light generated by the interaction when the light is attenuated at the same attenuation rate. The light intensity measuring device described.   5. The light intensity measurement according to claim 1, wherein the measurement system is configured to measure an angular distribution of intensity of scattered light generated from the test object as light generated by the interaction. 6. apparatus. Irradiating a test object with irradiation light; and
Measuring the intensity of light generated by the interaction between the irradiation light and the object to be examined;
Dimming at least one of the irradiation light and the light generated by the interaction at a plurality of different dimming rates,
Prior to the measurement of the light generated by the interaction, each of the photons constituting the light attenuated at the plurality of attenuation rates is counted using a photon counter, and the plurality of photons obtained based on the counting result of the photons Based on the calibration value of the dimming rate of the light, when neither the irradiation light nor the light generated by the interaction is dimmed by the plurality of light attenuation rates, or the light generated by the irradiation light and the interaction A light intensity measurement method for obtaining an intensity of light generated by the interaction when at least one of the light is attenuated at the same attenuation rate.

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