JPS61137044A - Apparatus for measuring light scattering - Google Patents

Abstract

PURPOSE:To measure the scattering of light containing a light scattering component having a large scattering angle with high sensitivity and high accuracy, by intermittently irradiate light and absorbing scattered light thereof to convert the same to molecular vibration energy before performing the frequency synchronous detection of said energy signal. CONSTITUTION:Light incident as shown by the arrow is converted to intermittent irradiation beam by a chopper 10 and converged to converged beam 2 by a lens 3 to irradiate matter 1 to be inspected. Scattered beam 3 is absorbed by the photosensitive surface of a microphone cell 11 and the gas in the hermetically closed microphone cell 11 is intermittently heated to generate a sonic wave which is, in turn, applied to the microphone cell 11 to be detected by microphone 12 and sent to a lock-in amplifier 15 being a molecular vibration measuring means to be subjected to frequency synchronous detection on the basis of the reference signal from the chopper 10 and the result thereof is recorded on a recorder 14.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an apparatus for analyzing the physical properties of an object surface and inside an object using light scattering, and particularly relates to a light scattering measurement apparatus that converts the scattered light into molecular vibrational energy and measures it. . [Prior Art] Conventionally, as shown in FIG. 3, an apparatus for analyzing the physical properties of an object surface and inside an object using light scattering irradiates a test object 1 with light 2 and transmits the scattered light 3 through an aperture. The light was guided to a photosensitive surface 6 of a photodetector (for example, Photomaru, Vinphoto, etc.) through a lens 4 with a large angle and an integrating sphere 5 to reduce the influence of light distribution. However, in this case, if the scattering angle was larger than the aperture angle, the protruding scattered components could not enter the lens, making measurement impossible. In order to detect the protruding scattered components, a method has been devised in which a transmission-type diffusion surface is placed near the test object and a photodetector is placed behind it, but the characteristics of the diffusion plate, the method of installing the photodetector, etc. This has made it difficult to measure with high accuracy and sensitivity. [Problems to be Solved by the Invention] In view of the above, the present invention aims to measure with high precision and high sensitivity, including light scattering components with large scattering angles, which are difficult to measure with conventional light scattering measurements. This is a problem that must be solved. [Means for Solving the Problems] In the present invention, the means taken to solve the problems include an intermittent light irradiation means that irradiates the test object with intermittent light, and a test object that uses the irradiation light to A photosensitive medium that absorbs scattered light intermittently emitted from the surface of the object according to the physical properties of the object and converts it into molecular vibrational energy; and an energy signal detection means that detects the intermittent energy signal generated in the medium. , molecular vibration measuring means for performing frequency synchronous detection of the energy signal using a reference signal from the intermittent light irradiation means. FIG. 1 is a basic configuration diagram of a light scattering measuring device according to the present invention. In FIG. 1, when a test object 1 is irradiated with intermittent light 2, scattered light 3 due to light within the test object is intermittently emitted from the surface of the test object at various emission angles. These scattered lights 3 are irradiated onto the photosensitive medium 7. The photosensitive medium 7 is made of a light-absorbing material, and the irradiated light energy is absorbed and becomes an intermittent molecular vibrational energy signal 8, which is guided to an energy signal detection means 9. Since the optical signal is converted into a molecular vibrational energy signal for any incident angle, by appropriately setting the size and position of the photosensitive medium 7, it is possible to easily detect even a case where the scattering angle is large. A known light source and chopper are used as the intermittent light irradiation means, and the photosensitive medium is preferably a light-absorbing material that has large absorption characteristics for the wavelength of the scattered light to be measured and has good thermal conductivity, such as carbon. A wide wavelength range can be covered by using a mixture mainly consisting of carbon and carbon. By measuring the spectral absorption characteristics of the light-absorbing material in advance, it is possible to correct the output signal and correct sensitivity unevenness for each wavelength. By adding irregularities to the surface of the light-absorbing material that are slightly larger than the wavelength of the scattered light, it is possible to not only improve complete diffusivity and eliminate the effects of the scattering angle, but also increase absorption efficiency. . The energy signal detecting means used is one that corresponds to the molecular vibration energy signal generated in the medium. For example, for sound waves, a microphone etc. is used, and for heat waves, a thermocouple etc. is used.6 As a molecular vibration measuring means. A loaf-in amplifier is used. The object to be tested is not limited to solids, but may also be liquids.By shining light onto the surface of the liquid, we can detect the development of a single molecule so-called LB film (Langmuir-Prodgett film) on the liquid surface, and the interface between adsorbed molecules. It can also be applied to the evaluation of fine particles in nearby liquids. [Function] In Fig. 1, it was stated that the energy signal detection means used corresponds to the molecular vibrational energy signal generated in the medium, but the form of the molecular vibrational energy signal is determined by the photoacoustic effect as follows. It changes like this. FIG. 2 is a diagram showing the basic principle of the photoacoustic effect. In Fig. 2, the photoacoustic effect consists of four processes, and shows a state in which energy propagates through a material when the material absorbs light. Shows the process of being absorbed by hitting an absorbing substance,
Process B shows a process in which this energy becomes intermittent heat through a non-radiative relaxation process and propagates in the material as heat waves. Process C shows a case where a heat wave that reaches the surface of a material intermittently heats the gas in contact with the material and generates a sound wave,
In process D, thermal waves traveling through a substance are converted into elastic waves,
The present invention attempts to select a desired form of molecular vibrational energy from any stage of the above process and detect a desired signal using an energy signal detection means. Therefore, it is possible to detect with high sensitivity by using photoacoustic means, which is a phenomenon that shows an acoustic response, temperature distribution on one surface, etc. Scattering to be analyzed by the present invention includes so-called elastic scattering in which the scattered light is not accompanied by a wavelength shift, and inelastic scattering in which the scattered light is accompanied by a wavelength shift such as Raman scattering and Prillouin scattering. For example, an analysis that uses both the
One method is to use all of the scattered light as an information source. The scattered light in this case includes light of all wavelength components, and is a simple method for determining refractive index fluctuations and the presence of fine particles on the surface and inside of the object to be measured. Regarding analysis using inelastic scattering, for example, by analyzing Raman scattering (or laser Raman spectroscopy) generated using monochromatic light such as laser light, it is possible to analyze molecular structure theory in minute parts inside the test object. For example, by changing the frequency of scattered light caused by a change in lattice vibration, it is possible to analyze a phase transition.In particular, by changing the temperature of the object to be measured and using the analytical method of the present invention, it is possible to obtain information on phase transitions. Various information can be obtained regarding local changes in . Furthermore, in Prillouin scattering, the information source is scattered light with a wavelength shift caused by the interaction between phonons within the test object and the irradiated light, so if this is analyzed spectrally, it is possible to determine, for example, the phase of a crystal sample. It is effective for analyzing transition and glass transition of polymeric materials. [Examples] Hereinafter, the present invention will be explained in detail with reference to Examples and drawings. FIG. 4 is a block diagram showing an example of a light scattering measuring device embodying the present invention, in which the energy signal is a sound wave generated by the process C, and the energy signal detection means is a microphone. In FIG. 4, a known light source and chopper 10 are used as the intermittent light irradiation means constituting the light scattering measuring device, the photosensitive medium is the photosensitive surface 7 of the microphone cell 11, and the energy signal detection means is the microphone 12. The irradiated light beam 2 interrupted by the chopper 10 is guided to the object 1 by the lens 13, and the scattered light 3 is absorbed by the photosensitive surface 7 of the microphone cell 11, and the gas 14 inside the sealed microphone cell 11 is absorbed by the photosensitive surface 7 of the microphone cell 11. is heated intermittently to generate sound waves. This sound wave is detected by the microphone 12 attached to the microphone cell 11, and the microphone 12
The signal is sent to the lock-in amplifier 15, which is a molecular vibration measuring means, and the chopper IO cuts off the measurement light beam 2.
Frequency synchronized detection is performed based on the reference signal from the recorder 16, and the result is output to the recorder 16. It has been theoretically confirmed that the intensity of the photoacoustic signal detected in this manner is proportional to the intensity of the scattered light irradiated onto the light absorbing material. Therefore, the scattered light intensity can be measured quantitatively. Note that measurement becomes more stable if the incident light intensity is monitored and fluctuations in the irradiated light intensity are removed. Moreover, the light scattering distribution can also be measured by moving the light irradiation position of the test object. The light may be irradiated onto the object to be inspected not only from the direction shown in FIG. 4 but also from any arbitrary direction. FIGS. 5 and 6 are structural diagrams showing the photosensitive medium in this example. In FIG. 5, the part of the sealed microphone cell 11 that receives the incident light is made of a partition wall 17 made of a soundproofing material that does not absorb light, and the light absorbing material 7 is arranged inside the partition wall 17. In FIG. 6, a light-absorbing material 7 is placed on the light incident side of a partition wall 17 formed of a material with a large thermal diffusion length, and the partition wall 17 transfers the heat generated by the light-absorbing material 7 to the inside of the cell. It has a configuration that heats the gas intermittently. The thickness of these partition walls is preferably equal to or less than the thermal diffusion length. For thermal diffusion length, the thermal conductivity α of the substance is

[Cl21S] and the intermittent frequency f [Hz], le = (α/π
Since it is calculated as f)'(c zen), using silver (α=1.7), f =
If it is 50 Hz, then g=l(mml). FIG. 7 is a block diagram showing another example of a light scattering measuring device embodying the present invention. In this embodiment, the energy signal detection means is a piezoelectric detection means.In FIG. The energy signal detecting means is a piezoelectric element 18.The irradiation light beam 2 interrupted by the chopper 1O is guided to the test object 1 by a lens 13, and the scattered light 3 is absorbed by light. It is absorbed by the substance 7, becomes intermittent molecular vibrations, is converted into elastic energy in the process of being transmitted to the piezoelectric element 18, and is detected by the piezoelectric element 18. The signal from this piezoelectric element 18 is sent to the lock-in amplifier 15, - Frequency synchronized detection is performed based on the reference signal from the chopper 10 that intermittents the measurement beam 2, and the result is sent to the recorder 1.
6 is output. It has been theoretically confirmed that the intensity of the piezoelectric signal detected in this way is proportional to the intensity of scattered light irradiated onto the light-absorbing material. Therefore, the scattered light intensity can be measured quantitatively. FIG. 8 is a structural diagram showing an example of the energy signal detection means in this embodiment. In FIG. 8, light absorbed by the light absorbing substance 7 becomes intermittent molecular vibrations, which are converted into elastic energy and detected by the piezoelectric element 18. Note that a rear plate 13 is inserted between the light absorbing material 7 and the piezoelectric element 18 to facilitate uniform transmission of light. Further, if the rear plate 18 and the light absorbing material 7 are integrated and the piezoelectric element 18 is made removable, it is convenient when measuring light absorbing materials with different characteristics. FIG. 9 is a configuration diagram showing another example of a light scattering measuring device embodying the present invention, in which the energy signal is obtained by directly detecting the temperature change on the surface of the light-absorbing material generated by the process B using a thermocouple. This is an example. In FIG. 9, a known light source and chopper 10 are used as the intermittent light irradiation means constituting the light scattering measuring device, the photosensitive medium is formed of a light absorbing material 7, and the energy signal detection means 20 is composed of a thermocouple. The irradiation light beam 2 interrupted by the chopper 1O is guided to the test object 1 by the lens 13, and the scattered light 3 is absorbed by the light absorbing material 7 and becomes intermittent heat, which generates energy signal detection means consisting of a thermocouple. 20, it is converted into an electrical signal. The signal from this energy signal detection means 20 is sent to a lock-in amplifier 15, where it is subjected to frequency synchronized detection based on a reference signal from a chirotsuba 10 that cuts off the measurement light beam 2, and the result is output to the recorder 1B. It has been theoretically confirmed that the intensity of the thermoelectric signal detected in this manner is proportional to the intensity of scattered light irradiated onto the light-absorbing substance. Therefore, the scattered light intensity can be measured quantitatively. FIG. 1θ and FIG. 11 are structural diagrams showing an example of the energy signal detection means in this embodiment. In FIG. 10, the heat generated by the light absorbing substance 7 is transferred to a thermal conductor 21.
On the other hand, the temperature at the reference thermoconductor 22 is detected by another thermocouple 23b, the difference signal between the two is obtained by the detection signal processing section 24, and the signal is sent to the lock-in amplifier 15. It shows the structure to send. In FIG. 11, thermocouples are arranged at predetermined locations on the light-absorbing material 7 so that the heat distribution can be measured simultaneously, and the intensity distribution of the scattering power can be determined according to each light distribution angle. FIG. 12 is a configuration diagram showing another example of a light scattering measuring device embodying the present invention, in which the energy signal reflects the change in refractive index near the surface due to the radiant heat wave from the light-absorbing material generated in the step of process B. This is an embodiment in which detection is performed as a deflection of a light beam. In FIG. 12, a known light source and a chopper 10 are used as the intermittent light irradiation means constituting the light scattering measuring device, the photosensitive medium is formed of a light absorbing material 7, and the energy signal detection means is a photothermal deflection detection means 25. be. The irradiation light beam 2 interrupted by the chopper 10 passes through the lens 13
The scattered light 3 is absorbed by the light-absorbing material 7, becomes intermittent heat, changes the refractive index near the surface of the light-absorbing material, and changes the direction of light passing through that region. It is deflected and converted into an electrical signal by the photothermal deflection detection means 25. The electrical signal from the photothermal deflection detection means 25 is sent to the lock-in amplifier 15, where it is subjected to frequency synchronization detection based on a reference signal from the chopper IO which cuts off the measurement light beam 2, and the result is output to the recorder 1B. The intensity of the photothermal deflection signal detected in this manner increases as the intensity of the scattered light irradiated onto the absorbing substance increases, and this relationship has also been theoretically confirmed. Therefore, the scattered light intensity can be measured quantitatively. Figure $13 is a structural diagram showing an example of the photothermal deflection detection means in this embodiment. In Figure 13. The scattered light passes through the transparent flat plate 28, is absorbed by the light absorbing material 7 present on the surface of the flat plate 2B, and generates intermittent heat. This heat changes the refractive index near the surface of the light-absorbing material, and the probe light beam 27 passes through that area.
The direction changes intermittently. The probe light beam 27 is preferably a laser beam or the like with good directivity and a small beam diameter; in the figure, it is emitted from a light source 28,
It is arranged so that it is refracted by a mirror 29 and passes near the light absorbing material. This probe light beam 2
7 is detected by the position sensor 30, converted into an electrical signal, and sent to the lock-in amplifier 15, thereby measuring the intensity of the scattered light. FIG. 14 is a structural diagram showing another example of the photothermal deflection detection means. In FIG. 14, the probe light beam 27 is passed over the surface of the light-absorbing material 7 in a matrix pattern, and the amount of deflection at each position is detected by the corresponding position sensor 30, which shows the temperature distribution on the surface of the absorbing material. In other words, the light distribution of scattered light can be obtained. The probe light beam 27 is. Scanning may be performed using a rotating mirror or the like, or separate light sources may be set at each corresponding position and measurement may be performed at once. Note that by filling the region where the light beam is deflected with a material whose refractive index changes significantly with temperature changes, a heated region with a large refractive index change due to a slight temperature change is formed, which greatly changes the path of the light beam. is possible,
Highly sensitive measurements are possible. FIG. 15 is a configuration diagram showing another example of a light scattering measuring device embodying the present invention, in which an energy signal is generated by detecting radiant heat waves caused by temperature changes on the surface of a light-absorbing material generated in the process B using an infrared detector. This is an example of detection. In FIG. 15, a known light source and chip 10 are used as the intermittent light irradiation means constituting the light scattering measurement device, the photosensitive medium is formed of a light absorbing material 7, and the energy signal detection means 31
An infrared detector is used. The irradiation light beam 2 interrupted by the chopper 10 is guided by the lens 13 to the test object l, and the scattered light 3 is absorbed by the light absorbing material 7 and becomes intermittent radiant heat, which is converted into an electric signal by the infrared detector. is converted to The electrical signal from this infrared detector is sent to a lock-in amplifier 15, where it is subjected to frequency synchronous detection based on a reference signal from a chopper 10 that cuts off the measurement light beam 2, and the result is output to a recorder 16. The intensity of the thermal radiation signal detected in this manner increases as the intensity of the scattered light irradiated onto the absorbing substance increases, and this relationship has also been theoretically confirmed. Therefore, the scattered light intensity can be measured quantitatively. FIG. 18 is a structural diagram showing an example of the energy signal detection means in the above embodiment. In FIG. 18, the scattered light is absorbed by the light-absorbing material 7 and generates heat intermittently, thereby intermittently warming the entire rear plate 32, which has good thermal conductivity. Since the rear plate surface is heated, radiant heat waves corresponding to the temperature at that time change intermittently. This is detected by forming an image on the entrance window of the infrared detector 34 using a lens 33 made of a material that transmits infrared radiation. As shown in FIG. 17, the scattered light is transmitted through the transparent flat plate 2B, absorbed by the light absorbing material 7 present on the surface of the flat plate, and the thermal radiation radiated from the surface of the light absorbing material is detected by the lens 33. If the detector 34 is integrated and detected while scanning along the surface of the light absorbing material as shown by the arrow 35 in the figure, information corresponding to the light distribution of scattered light can be obtained. FIG. 18 is a graph showing that the light absorption rate depending on the wavelength differs for each substance. By using different wavelength characteristics of the light absorbing material 7 shown in the basic configuration diagram of FIG. 1 as shown in FIG. 18, it is possible to measure the scattered light intensity of each corresponding wavelength, and Measurement of elastic scattering becomes possible. FIG. 18 is a structural diagram in which a filter is interposed in the scattered light path between the test object and the photosensitive medium. As shown in FIG. 18, a similar measurement is possible by placing a filter 3B before the scattered light is absorbed by the light absorbing substance 7 and controlling the measurement wavelength range of the scattered light. If a polarizing filter is used as the filter, it is also possible to obtain polarization characteristics of scattered light. FIG. 20 shows an example in which high-sensitivity and high-precision light scattering measurement is made possible by arranging a reflection plate 37 on the back surface of the light-absorbing material 7 to reduce the effective thickness of the absorption layer. It is. FIG. 21 shows an embodiment in which the light-absorbing substance is formed into a layered structure, and substances 7a to 7c having different spectral absorption characteristics are arranged in each layer.By arranging the substances in this way, signals of each wavelength can be measured simultaneously. becomes possible. That is, in each layer, light energy having different wavelength characteristics is converted into molecular vibrational energy and transmitted to the energy signal detection means, but at that time, there is a phase delay corresponding to the distance from each layer to the energy signal detection means. arise. Therefore, when obtaining a signal of scattered light by frequency synchronous detection, it is possible to separate signals from each layer by detecting each corresponding phase shift. FIG. 22 shows an example in which the present invention is applied to light scattering by a monomolecular film on a liquid surface. In FIG. 22, irradiation light 2 is incident from below the liquid surface and is incident at an angle at which it is totally reflected at the liquid interface. On the total reflection interface, the light energy is transmitted as an evanescent wave to the monomolecular film 33 on the liquid surface and the adsorbed substance, thereby causing light scattering 3. The light scattering characteristics due to the monomolecular film 39 and the light adsorbing substance can be detected by detecting the energy signal using the energy signal detecting means 9 placed above the liquid surface based on each of the methods described above. FIG. 23 is an example of evaluating the light scattering characteristics below the liquid surface in the LB film forming apparatus. By measuring the light scattered by the scattering factor 40 in the liquid, the state of the monomolecular developing solution can be detected, and film formation can be controlled based on this information. In addition, the information on each part can be patterned by narrowing down the irradiation light beam diameter as necessary, removing the influence of scattered light beams within the object, and scanning the irradiation light beam along a predetermined surface within the object. You can also. Then, by computer processing the electrical signals and scanning signals obtained in this way and displaying them on a display, microscopic information can be captured in a patterned manner. [Effects of the Invention] As explained above, according to the present invention, elastic and inelastic light scattering, including light scattering components with large scattering angles that were conventionally difficult to measure, can be measured with high sensitivity and high sensitivity. Can be measured accurately. Therefore, it is not only possible to detect refractive index fluctuations and the presence of fine particles within the test object, but also to obtain molecular structural information, and it can also be applied to LB film deposition equipment. This makes an extremely large contribution to the analysis of physical properties.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a diagram of the principle of photoacoustic effect, Fig. 3 is a block diagram of a conventional example, Figs. 4, 7, 9,
Figures 12 and 15 are configuration diagrams of embodiments of the present invention;
Figure 6, Figure 8, Figure 1θ, Figure 11, Figure 13,
16, 17, and 19 to 23 are longitudinal sectional views of the energy signal detection means of each embodiment, FIG. 14 is a configuration diagram of the photothermal deflection detection means, and FIG. 18 is the absorption characteristics of the absorbing substance. It is a diagram. ■...Test object, 2...Irradiation light beam, 3...Scattered light, 7...Photosensitive medium. 9, 20.31.34...Energy signal detection means, 10...Chopper, 11...Microphone cell,
12... Microphone, 15... Lock-in amplifier, 16... Recorder, 17... Partition wall (heat transfer material)
, 18... Piezoelectric element, 18... Rear plate, 23... Thermocouple, 25... Photothermal deflection detection means, 30... Position sensor, 32... Rear plate (thermal transfer material), 34...Infrared detector, 3B...Filter, 37...Reflector, 38...
-Liquid, 38... Monomolecular film, 40... Scattering factor.

Claims (1)

[Scope of Claims] 1) Intermittent light irradiation means for irradiating intermittent light onto a test object, and the irradiation light absorbs scattered light emitted intermittently from the surface of the test object according to the physical properties of the test object. and a photosensitive medium for converting into molecular vibrational energy, an energy signal detection means for detecting an intermittent energy signal generated in the medium, and frequency synchronized detection of the energy signal using a reference signal from the intermittent light irradiation means. A light scattering measuring device comprising: molecular vibration measuring means. 2) The light scattering measuring device according to claim 1, wherein the energy signal is a sound wave, and the energy signal detection means is a photoacoustic detection means. 3) The light scattering measuring device according to claim 1, wherein the energy signal is an elastic wave, and the energy signal detection means is a piezoelectric detection means. 4) The light scattering measuring device according to claim 1, wherein the energy signal is a conductive heat wave, and the energy signal detection means is a heat detection means. 5) The light scattering measuring device according to claim 1, wherein the energy signal is a radiant heat wave, and the energy signal detection means is a means for detecting optical deflection caused by the radiant heat wave. 6) The light scattering measuring device according to claim 1, wherein the energy signal is a radiant heat wave, and the energy signal detection means is a photothermal radiation detection means. 7) The light scattering measuring device according to claim 1, characterized in that one or more types of light absorbing substances having different spectral absorption characteristics are superimposed as a photosensitive medium. 8) Claim 1, characterized in that a predetermined filter is interposed in the scattered light path between the test object and the photosensitive medium.
6. The light scattering measuring device according to any one of items 6 to 6. 9) The light scattering measuring device according to claim 1, characterized in that a reflective object is attached to the light absorption rear surface of the photosensitive medium. 10) The photosensitive medium has a layered structure, the energy signal detection means is provided with means for detecting the phase of the energy signal corresponding to each layer, and the means for simultaneously measuring different spectral characteristics of the phase-shifted color scattered light is provided with a molecular structure. The light scattering measuring device according to claim 1, characterized in that it includes vibration measuring means.