JPH0575059B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an apparatus having means for optically measuring the characteristics of a thin film developed on a liquid surface and for controlling film formation. The present invention relates to an apparatus for measuring light absorption characteristics, which is the basis for analyzing various characteristics of thin films, and for controlling film formation.

That is, the present invention is utilized for characteristic analysis of a thin film spread on a liquid surface to be accumulated when forming a monomolecular cumulative film or the like.

[Summary of the Disclosure] This specification and drawings describe a beam light emitted from a probe light source in a thin film forming apparatus having means for optically measuring the characteristics of a thin film developed on a liquid surface and forming the film. a light splitting means for splitting into two;
means for converting the two-split light into two light beams whose directional components are symmetrical to each other to compensate for fluctuations in the beam light due to fluctuations in the probe light source; By using a device equipped with an optical element that guides the light beam to or near the liquid surface, and an optical position detector that receives the beam light, the influence of deviation in the light beam emission direction caused by fluctuations in the light source itself can be removed, and the This paper discloses a technology that improves the accuracy of measuring the light absorption characteristics of thin films, which has been developed in the past.

[Prior art] Conventionally, in the monomolecular film accumulation method (hereinafter referred to as the LB method; see Maruzen, New Experimental Chemistry Course, Vol. 18, pp. 498-507), which is called the Langmiur-Blodgett method after the inventor, The formed monomolecular film is transferred onto the surface of a substrate and layered one by one to create an ultra-thin film, so the characteristics of the thin film on the liquid surface are important.
It is natural that the structure and molecular orientation of the cumulative film transferred onto the substrate by the LB method are based on the state of the developed monomolecular film on the liquid surface, but this state is not directly transferred onto the substrate. There was a question as to whether there were any.

The liquid tank 101 and its procedure for obtaining a monomolecular cumulative film will be described below.

As shown in FIGS. 3 and 4, the liquid 10
An inner frame 121 made of, for example, polypropylene is suspended horizontally in the inner tank of a shallow and wide rectangular liquid tank 101 in which a liquid containing 2 is housed, and partitions water surfaces 103 and 103'. As the liquid 102, pure water is usually used. Inside the inner frame 121, a film forming frame 122 made of, for example, polypropylene is floated. The film forming frame 122 is a rectangular parallelepiped whose width is slightly shorter than the inner width of the inner frame 121, and is capable of two-dimensional piston movement in the left-right direction in the figure. Film forming frame 12
A weight 123 for pulling the film forming frame 122 to the right in the figure is connected to the frame 2 via a pulley 124. In addition, the magnet 1 fixed on the film forming frame 122
25 and a pair of magnets 126 which are movable from side to side in the figure above the film forming frame 122 and repel each other when approaching the magnet 125, thereby allowing the film forming frame 122 to move from side to side in the figure. It can be moved and stopped. Instead of such a weight 123 or a set of magnets 125, 126, there is also a method in which a rotary motor or a pulley is used to directly move the film forming frame 122.

Suction nozzles 128 connected to a suction pump (not shown) via suction pipes 127 are arranged on both sides of the inner frame 121 . This suction nozzle 128 quickly removes unnecessary monomolecular films from the previous process on the liquid surfaces 103 and 103' in order to prevent impurities from entering the monomolecular film or monomolecular cumulative film. It is used to remove Note that 120 is a substrate that is attached to a substrate holder 129 and is vertically moved up and down.

First, the film forming frame 122 is moved so that the liquid level 10
3, 103' is swept away and sucked out from the suction nozzle 128 to purify the liquid surface 103, 103'. A film forming frame 12 is placed on the left end of the liquid surfaces 103, 103' that have been cleaned in this way.
2, and drop a few drops of a solution of a membrane constituent material dissolved in a volatile solvent such as benzene or chloroform at a concentration of, for example, 5×10 ⁻³ mol/l onto the liquid surface 103 using a dropper or the like. When this solution spreads on the liquid surface 103 and the solvent evaporates, a monomolecular film forms on the liquid surface 103.
It will be left on top.

The monomolecular film exhibits two-dimensional behavior on the liquid surface 103. When the areal density of molecules is low, it is called a gas film of a secondary gas, and a two-dimensional ideal gas equation of state is established between the occupied area per molecule and the surface pressure.

Next, from this gas film state, the film forming frame 122 is gradually moved to the right to gradually reduce the area of the liquid surface 103 where the monomolecular film is developed and increase the areal density, thereby increasing the intermolecular interaction. It becomes stronger and changes from a liquid film of a two-dimensional liquid to a solid film of a two-dimensional solid. In this solid film, the molecules are arranged and oriented neatly, resulting in a high degree of order and uniform ultra-thin film properties. At this time, the monomolecular film that has become a solid film can be attached to the surface of the substrate 120 and transferred. Moreover, a monomolecular cumulative film can be obtained by stacking and transferring a monomolecular film to the same substrate multiple times. Incidentally, as the substrate 120, for example, glass, synthetic resin, ceramic, metal, etc. are used.

There are roughly two types of methods for transferring the monomolecular film from the liquid surface 103 to the surface of the substrate 120. One is the vertical dipping method and the other is the horizontal deposition method. The vertical immersion method is a method in which the monomolecular film is transferred by moving the substrate 120 up and down in the direction across the film, that is, in the vertical direction, while applying a constant surface pressure suitable for cumulative operation to the monomolecular film on the liquid surface 103. This is the way to take it. The horizontal adhesion method is to apply liquid level 1 from above while keeping the substrate 120 horizontal.
03 as close as possible, tilt it slightly, and touch the monomolecular film from one end to attach it.

In order to perform the transfer operation under conditions of a monomolecular film suitable for transfer to the substrate 120,
Measurement of the surface pressure of monolayers has been carried out. Generally, the surface pressure of a monomolecular film suitable for transfer is 15 to 30 dyn/cm. Outside this range, the arrangement and orientation of molecules may be disturbed and the film may easily peel off. However, in special cases, for example, depending on the chemical structure of the membrane constituents, temperature conditions, etc., a suitable surface pressure value may fall outside of the above range, so the above range is only a rough guide.

The surface pressure of the monomolecular film is automatically and continuously measured by a surface pressure measuring device (not shown). Surface pressure measuring instruments include those that apply a method of indirectly determining the surface tension from the difference in surface tension between the liquid surface 103' that is not covered with a monomolecular film and the liquid surface 103 that is covered with a monomolecular film; There are methods that directly measure the two-dimensional pressure applied to the film forming frame 122 that separates the liquid surface 103' not covered with a monomolecular film from the liquid surface 103 covered with a monomolecular film and floats. , each with its own characteristics. In addition to the surface pressure, the occupied area per molecule of the monomolecular film and the amount of change thereof are also usually measured. The occupied area and the amount of change thereof are determined from the left and right movement of the film forming frame 122.

The movement of the film forming frame 122 described above is controlled based on the surface pressure of the monomolecular film measured by the measuring device. That is, a driving device (not shown) for moving the counter magnet 126 from side to side is controlled by a surface pressure measuring device so that the monomolecular film always maintains a constant surface pressure selected within a range suitable for the transfer operation. It is controlled based on the measured surface pressure of the monolayer. This movement control of the film forming frame 122 is performed not only after dropping the solution of the film constituent material until the start of the monomolecular film transfer operation, but also continuously during the transfer operation. For example, in a transfer operation, as the monolayer is transferred to the substrate 120, the surface density of the monolayer molecules on the liquid surface 103 decreases, and the surface pressure also decreases. Therefore,
It is necessary to move the film forming frame 122 to reduce the developed area of the monomolecular film and to correct the decrease in surface pressure to maintain a constant surface pressure.

As mentioned above, various delicate adjustments are required to obtain a monomolecular cumulative film. However, what conditions are optimal has to be determined through various experiments, and whether the monomolecular film on the liquid surface 103 is in a state suitable for accumulation depends on the surface pressure. It was only possible to confirm this indirectly through methods such as methods, and it lacked accuracy.

Next, a method for measuring light absorption characteristics, which is the basis for directly measuring the characteristics of such a thin film, will be explained.

Conventionally, as a method for measuring the light absorption characteristics of a certain sample, there is a method of determining the light absorption characteristics from transmittance or reflectance. However, when a sample is irradiated with light, there is scattered light in addition to transmitted light and reflected light, and in order to achieve even higher accuracy, it is important to directly measure the absorption component of light in evaluating light absorption characteristics. .

A method for directly measuring the absorption component of light is a measurement method that utilizes the fact that when a sample is irradiated with light intermittently, the light energy absorbed by the sample is intermittently converted into heat through a non-radiative relaxation process. Photoacoustic Spectroscopy (PAS) and Photothermal Radiometry:
PTR).

The PAS method can be divided into the microphone method and the piezoelectric element method depending on the type of detector, but the microphone method requires the sample to be placed in a sealed sample chamber.
The piezoelectric element method has problems with the placement of the detector and sample, and both methods are unsuitable for measuring samples in unique environments, such as measuring thin films spread on the liquid surface. Furthermore, since the PTR method uses an infrared detector, it has the disadvantage of being susceptible to atmospheric changes such as water vapor.

On the other hand, photothermal deflection spectroscopy is a method for directly measuring the absorption components of light.
There is a method called Deflection Spectroscopy (PDS). This PDS method utilizes the fact that in addition to heat generation due to light absorption by the sample, a temperature distribution occurs within and near the sample, causing a change in the refractive index, which deflects the incident light. That is, the measurement site of the sample is irradiated with excitation light that generates a temperature distribution due to heat generation when the light is absorbed and changes the refractive index, and probe light that measures the amount of deflection caused by the excitation light. The light absorption characteristics of the sample are measured from the wavelength and the amount of deflection of the probe light. This method allows the sample and detection system to be set independently, making it suitable for on-site measurements and remote measurements. There are two types of this PDS method, transverse type and collinear type, depending on the arrangement of the excitation light and probe light. It measures the amount of deflection of the probe light, and often uses a position sensitive detector (PSD) as the detector.

FIG. 5a shows an example of a vertical type, in which excitation light 111 emitted from an excitation light source 110 becomes intermittent light at a chopper 112, is focused by a lens 134, and is placed on the sample 10.
4' is irradiated. On the other hand, the probe light 106 emitted from the probe light source 105 is passed through the area of the sample 104' that is irradiated with the excitation light 111 by an optical path adjuster 117 consisting of a lens 135 and a mirror, and is passed through the area of the sample 104' that is irradiated with the excitation light 111. The amount of deflection when the beam is deflected as shown by the broken line is measured. FIG. 5b shows an example of the horizontal type, which is the same as the vertical type except that the probe light 106 is irradiated parallel to the surface of the sample 104'.

The theoretical treatment of this PDS method is to solve the heat conduction equation within the sample, and the amount of deflection measured as the deflection angle φ is determined by the excitation light intensity, the temperature coefficient of refractive index (n/T), and the passage of the probe light. It is proportional to the temperature gradient (T/x) etc. in the region where A term proportional to the light absorption coefficient of the sample is included in (T/x).
Further, (n/T) can take either a positive or negative value depending on the sample, which indicates that the deflection angle can also be both positive and negative.

FIG. 6 is a longitudinal sectional view showing an example of the structure of a one-dimensional PSD. In FIG. 6, the one-dimensional PSD consists of a uniform resistance layer 4 of a P layer on the surface of a flat silicon 3, electrodes X ₁ and X ₂ are arranged on both sides, and an N layer 5 on the back surface. A common electrode 6 is provided.

FIG. 7 is a schematic diagram showing the principle of operation.
The photo-generated charge corresponding to the incident position of the light Q is transferred to the resistive layer 4 as a photocurrent corresponding to its energy.
reaches the position Q and the extraction electrodes X ₁ and X ₂ at both ends.
It is divided in inverse proportion to the distance to and output from each electrode. If the photocurrent due to incident light is I _L , the currents I _x1 and I _x2 output from the electrodes X ₁ and X ₂ are as follows: I _x1 = I _L・R _x2 / (R _x1 + R _x2 ) I _x2 = I _L・R _x1 / (R _x1 + R _x2 ), and since the resistance between X ₁ and _{X 2} maintains a uniform distribution, the following equations are established between the resistance between X ₁ and _{X 2} and the length L. holds true.

R _x1 + R _x2 = L R _x1 = x R _x2 = L-x Therefore, the signal taken out from each electrode is represented by L and x, and I _x1 = I _L・(L-x)/L I _x2 = I _L・x/L. That is, information about the incident position of light and the light intensity can be obtained from the X ₁ and X ₂ electrodes.

Furthermore, if we take the ratio of the sum and difference of I _x1 and I _x2 and use this as the position signal P, we get P=I _x1 −I _x2 /I _x1 +I _x2 =L−2 _x /L, and x= Corresponding to 0 to L, position signals unrelated to light intensity changes can be obtained continuously, such as x = 0, P = 1 x = 1/2, P = 0 x = L, P = -1. become.

Although the above is a one-dimensional case, the same can be considered for a two-dimensional position detector, and the position signal can be obtained using the block diagram of the operating circuit shown in FIG.

Here, according to the operating principle of PSD, if there are two or more points of light incidence, position signals weighted in proportion to the respective light intensities are obtained. Furthermore, even when the light beam is spread out, a position signal of the center of gravity of the light intensity can be obtained.

[Problems to be Solved by the Invention] However, if the PDS method described above is directly applied to the measurement of a monomolecular film spread on a liquid surface, there are inconveniences that arise because the thin film that is the sample is an ultra-thin film. It was hot. In other words, in measurements using such a PSD, fluctuations in the emission angle of the light source itself have a large effect on measurement accuracy, and in particular, in measurements using a gas laser as the probe light, it is difficult to perform highly accurate position detection. It has been difficult to obtain desired light absorption characteristics.

The present invention eliminates the influence of such fluctuations in the light source itself, increases measurement accuracy to the limit of PSD resolution, and improves measurement accuracy even in extremely thin and unique environments such as a monomolecular film spread on a liquid surface. Regarding the sample,
It is an object of the present invention to provide a thin film forming apparatus that can measure its light absorption characteristics with high accuracy and sensitivity.

[Means for Solving the Problems] The present invention provides an excitation light source that emits excitation light, a light intensity modulator that modulates the intensity of the emitted excitation light in front of a measurement site of a thin film, and a light intensity modulator that emits a beam light. A probe light source, a spectrometer that divides the emitted beam light into two, an optical element that vertically inverts the passing position of at least one of the two divided beam lights, and a beam light that has passed through the optical element. means for converting the other beam into two beams whose directional components are symmetrical to each other to compensate for fluctuations in the beam light due to fluctuations in the probe light source;
The present invention is characterized in that the thin film forming apparatus includes an optical element that guides the light beams to the measurement site or the vicinity thereof, and an optical position detector that receives the light beams.

[Function] When the excitation light is absorbed by the thin film that is the sample, the refractive index of the measurement site and its vicinity changes between when the excitation light is irradiated and when it is not irradiated, so this can be detected as the amount of deflection of the probe light. The non-absorption properties can be measured by A feature of the principle of this PDS method is that the PDS output ultimately obtains a signal at the center of gravity of the light intensity distribution.

FIG. 9 is a coordinate diagram illustrating the principle of the compensation method according to the present invention. FIG. 9a shows that on a plane perpendicular to the average emission direction of the light beam emitted from the light source,
The X-Y coordinate axes are orthogonal to each other.
The amount of deflection of the emitted light is indicated by an arrow 12. If the above coordinate axes are inverted using the required optical system, the projection will be as shown in Figure 9b.
X'-Y', and the amount of deflection of the emitted light also becomes as shown by arrow 13. When these mutually inverted light beams are irradiated onto the target irradiation surface, their coordinates are point symmetrical 12 with respect to the origin 0, as shown in FIG. 9c.
a, 13a, and if the intensities of both light beams are equal, the center of gravity of the light beam energy always coincides with the origin. Therefore, if you use an optical system that satisfies the above conditions, even if the light source fluctuates,
The intensity center of the irradiation beam will be compensated for unaffected.

Figure 10 is a schematic configuration diagram of a basic device for one-dimensionally verifying the effect based on the above principle.
The light beam from the Ne light source 14 is transferred to the half mirror 15
The amplitude of the divided secondary light beams is divided by , and the divided secondary light beams are irradiated onto an optical position detector 18 by mirrors 16 and 17, respectively, and fluctuations of the light source 14 are recorded. FIG. 11 is a graph of the measurement results of the amount of positional deviation of the light beam with the above configuration, where the vertical axis shows the detection position P of the light beam, and the horizontal axis shows the time t. In FIG. 10, when the light beam is directly irradiated onto the optical position detector 18 without passing through the optical system consisting of the half mirror 15 and mirrors 16 and 17, fluctuations as shown in a in FIG. 11 are recorded,
When compensated according to the present invention, the result is as shown in FIG. 11b, and it can be seen that the light source fluctuation is removed.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing a first embodiment of the present invention. This example is for measuring the deflection of probe light in the vertical direction in the figure using a one-dimensional PSD.

In FIG. 1, 101 is a liquid layer, 102 is a liquid, and a thin film 104 serving as a sample is developed on the surface 103 of this liquid 102. Note that the illustrated thin film 104 is a schematic representation of a monomolecular film. Further, a probe light source 7 is provided on the side of the liquid tank 101. The light beam 8 emitted from the probe light source 7 is separated into two light beams 8a and 8d by a beam splitter, and then combined again into one light beam 8e by a mirror 20 and a half mirror 21, which is placed directly below the liquid surface 103. liquid level 10
It is irradiated in a direction parallel to 3. Further, an optical position detector 107 is provided at a position opposite to the probe light source 7 with the liquid tank 101 interposed therebetween, for detecting the position of the probe light 8e sent thereto. The signal of this optical position detector 107 is transmitted to the driver 10
8 to the lock-in amplifier 109.

On the other hand, an excitation light source 110 is provided slightly below the probe light source 7. This excitation light source 110
is the angle at which the thin film 104 is totally reflected on the liquid surface 103 on which the excitation light 11 is applied from the liquid 102 side.
1 is irradiated toward the measurement site of the thin film 104. A chopper 112 for irradiating the excitation light 111 as intermittent light is provided at a position along the optical path of the excitation light 111. In addition, excitation light source 1
An absorber 113 for absorbing the excitation light 111 is provided at a position where the excitation light 111 emitted from the liquid tank 10 and totally reflected by the liquid surface 103 exits the liquid tank 101 .

The chopper 112 is connected to a lock-in amplifier 109, and the signal from the detector 107 can be synchronously detected using a signal indicating the intermittent state of the excitation light 111 sent from the chopper 112 as a reference signal. Probe light source 7, excitation light source 1
10, chopper 112 and lock-in amplifier 1
09 are each connected to the measurement controller 114. The measurement controller 114 controls the optical path and wavelength of the probe light 8e and the excitation light 111, as well as the chopper 11.
2 controls the intermittent interval of the excitation light 111, and calculates the light absorption characteristic based on the signal from the lock-in amplifier 109.

Note that the liquid tank 101 receives at least the probe light 8.
If a transparent window is provided in the part that becomes the optical path of e and the excitation light 111, it is not necessary to make the whole part transparent. Further, if the liquid 102 has a small absorption with respect to the excitation light 111, the probe light 8e
Even if it has some direct influence on the measurement, it will not have a bad effect on the measurement, but it is preferable that it be transparent. Further, FIG. 1 shows only the light control system and the liquid layer section, and the film forming section and surface pressure control section shown in FIGS. 3 and 4 are omitted.

Next, the action will be explained. First, the excitation light 111 emitted from the excitation light source 110 is transmitted to the chopper 112.
The liquid level 10 of the liquid tank 101 is modulated into intermittent light by
The measurement site of the thin film 104 spread on the liquid surface 103 is irradiated from below the liquid surface 103. At this time, the excitation light 11
1 is incident with an incident angle larger than the critical angle of the liquid 102, is totally reflected at the liquid surface 103, passes through the liquid 102, and exits the liquid tank 101. Only a very small amount of light, on the order of a wavelength, seeps into the gas phase on the liquid surface 103 as an evanescent wave during total reflection. Excitation light 111 emitted from liquid tank 101 is absorbed by absorber 113, and unnecessary light is cut out. In the region on the measurement site where the intermittent excitation light 111 is reflected, the thin film 104 on the liquid surface 103 absorbs the light, and due to a non-radiative radiation process,
Heat is emitted intermittently, which causes intermittent changes in the refractive index in the vicinity.

On the other hand, since the probe light 8e emitted from the probe light source 7 passes directly below the liquid surface 103 in parallel to the liquid surface 103, it passes through a region where the refractive index changes intermittently due to the irradiation with the excitation light 111. become. When the probe light 8e passes near the measurement site where the refractive index changes intermittently, the optical path is deflected as shown by the dotted line according to the changed refractive index distribution, and the PSD light is received by the optical position detector 107. Detected on the surface. At this time, assume that the beam of the probe light fluctuates by a minute amount due to fluctuations in the probe light source 105. This minute amount is sufficiently small compared to the excitation light irradiation area, and the amount of deflection due to absorption by the sample does not change.As shown in the partially enlarged view of FIG. 2, the beam light 8a moves to the beam light 8'. The probe light directed toward the sample 104 is beam light 8c' and 8, which move symmetrically around beam 8e.
becomes d′. Therefore, the optical position detectors 107 are moved in mutually symmetrical directions on the PSD light-receiving surface as well, centering on the position corresponding to the amount of deflection due to absorption of the sample when there is no light source fluctuation.
Based on the measurement principle of PSD, the output is constant at a value corresponding to the absorption of the sample, and the influence of fluctuations in the probe light source is eliminated.

In this manner, the optical position detector 107 receives the probe light 8e intermittently and sends the receiving position of the probe light 8e to the lock-in amplifier 109 via the driver 108. The lock-in amplifier 109 is
At the same time as the signal from the detector 107 is received, the signal from the chopper 112 is also received, and by synchronizing both signals, the light reception position signal of the probe light 8e when the excitation light 111 is irradiated and the light reception position signal of the probe light 8e when the excitation light 111 is irradiated are
1 and the light reception position signal of the probe light 8e during non-irradiation are separated with a good S/N ratio and sent to the measurement controller 114. Based on this sent signal, the measurement controller 114 determines the amount of deflection of the probe light 8e for the wavelength of the excitation light 111 at that time, and calculates the light absorption characteristic based on this. Furthermore, by performing similar measurements while sequentially changing the wavelength of the excitation light 111, the spectral absorption characteristics of the thin film 104 can be obtained.

In this measurement, the measurement part is the measurement controller 1
The optical path of the excitation light 8e can be freely selected by adjusting the optical path of the excitation light 111 at 14, and accuracy can be ensured by adjusting the optical path of the probe light 8e using the measurement controller 114 depending on the position of the liquid level 103. Further, it is also possible to automatically make all necessary adjustments to the probe light source 7, excitation light source 110, and chopper 112 by the measurement controller 114, thereby simplifying the operation.

The light energy absorbed by the thin film 104 is determined from the light intensity distribution of the excitation light 111 at the measurement site, the characteristics of the refractive index change due to heat of the liquid 102, the incident beam position of the probe light 8e, and the amount of deflection at that time. Therefore, by monitoring the irradiation energy of the excitation light 111 onto the thin film 104 with a photo sensor or the like, the absolute light absorption characteristics of the thin film 104 can be obtained from both. Then, by changing the wavelength of the excitation light 111, absolute spectral absorption characteristics can be obtained. In addition, the relative intensity at each wavelength of the excitation light 111 is determined in advance, and the probe light 8e corresponding to the wavelength is
Relative spectral absorption characteristics can be obtained by simply determining the amount of deflection. The relative value and absolute value of the light absorption characteristic may be appropriately selected depending on the purpose of measurement.

FIG. 12a is a block diagram showing a second embodiment of the present invention. This embodiment is for measuring the deflection of probe light in any direction using a two-dimensional PSD, and includes a beam splitter 19 and a half mirror 2.
An image rotator 22 is placed between the beam splitter 19 and one of the probe light beams 8d split by the beam splitter 19, and its upper and lower passing positions are reversed in a direction perpendicular to the splitting direction of the beam splitter 19. is configured to do so. The other configurations are exactly the same as in FIG. 1.

FIG. 12b is a side view of the measurement system shown in FIG.
The optical path of the light beam 8d passing through is shown. The light source fluctuation component along the splitting direction of the beam splitter 19 is removed by the principle explained in FIG.
The light source fluctuation component in the direction perpendicular to the light source is not affected by the beam splitter 19, as is clear from FIG. 12b, and therefore, as shown in the partially enlarged view of FIG. Taking advantage of the position reversal, the direction of fluctuation of the fluctuated light beam 8d' is reversed, and the shift is compensated for based on the principle of the present invention. in this way,
By combining both components, it is possible to compensate for the deviation of the light beam even if the light source fluctuates in any arbitrary direction.

Note that the image rotator 22 receives the probe light 8c, which is split into two by the beam splitter 19.
It may be placed in any optical path of 8d.

FIG. 14a is a block diagram showing a third embodiment of the present invention, in which measurement is performed using one-dimensional PSD. In each of the above embodiments, the excitation light was incident from below the liquid surface, but in this embodiment, the excitation light was introduced from below the liquid surface.
As shown in the figure, the excitation light is made to enter from above the liquid surface.

In FIG. 14a, the probe light beam 8a emitted from the probe light source 7 is reflected by the half mirror 11.
8 into two light beams 8f and 8g,
8f is a probe light that is directly below the liquid level 103 and reaches the liquid level 1.
03 and the optical position detector 107
toward the PSD light-receiving surface. On the other hand, 8g serves as a reference light, which is reflected by a mirror 117, totally reflected by the liquid surface 103 in the reference area where the excitation light 111 is not irradiated, and also directed toward the PSD light receiving surface of the optical position detector.
On the PSD light receiving surface, 8f is irradiated to the S position and 8g is irradiated to the R position.

If the beam moves from 8a to 8a' as shown in FIG. 15 due to fluctuations in the probe light source, then
On the PSD light receiving surface, the beam irradiation positions move in opposite directions in the direction of the arrow shown in FIG. 14b.
This optical path is illustrated by the broken line in FIG.
When such fluctuations occur, the PSD output will always represent a constant midpoint position (M in the figure) from the measurement principle, assuming that the S and R light intensities are the same. The effect is removed.

FIG. 16a is a block diagram showing a fourth embodiment of the present invention. In this embodiment, the one-dimensional PSD used in the above-mentioned embodiment FIG. 14 is replaced with a two-dimensional PSD to measure the amount of deflection two-dimensionally. The beam is configured to rotate in a direction perpendicular to the plane of the paper. The other configurations are exactly the same as in FIG. 1.

FIGS. 16b and 16c show the measurement system shown in FIG. 16a viewed from the side, with b and c showing the optical path 8f and 8g, respectively. The position on the PSD light-receiving surface in this case is shown in Figure d. In d, 8
Assuming that f is irradiated at the position shown in S and 8g is irradiated in the position shown in R, if 8a shifts due to light source fluctuation, S, R
move in the directions of the arrows, but the average midpoint position M does not change, and the output from the PSD is always constant, so the influence of light source fluctuations is removed.

[Effects of the Invention] As explained above, according to the present invention, it is possible to eliminate the influence of deviation in the emission direction of the light beam due to fluctuations in the light source itself, and it is possible to increase measurement accuracy to the limit of the PSD's original resolution. This allows us to measure the light absorption characteristics of extremely thin samples under unique environments, such as a monomolecular film spread on a liquid surface, with high precision and sensitivity, and to control film formation. It is possible to provide a thin film forming apparatus that can perform the following steps.

[Brief explanation of the drawing]

1, 12, 14, and 16 are configuration diagrams showing each embodiment of the present invention, FIG. 2, FIG. 13,
FIG. 15 is an explanatory diagram of an inverted beam, FIGS. 3 and 4 are configuration diagrams of a conventional LB film forming apparatus, FIG. 5 is a configuration diagram of a conventional PSD apparatus, and FIG. 6 is a structural diagram of a PSD element. Fig. 7 is a diagram of the operating principle of the PSD element, Fig. 8 is a block diagram of the operating circuit, Fig. 9 is an explanatory diagram of the principle of the present invention, Fig. 10 is a configuration diagram of the verification mechanism of the principle, and Fig. 11 is This is a graph of the verification results. 15, 21...Half mirror, 16, 17, 2
0...Mirror, 19...Beam splitter, 22
...Image rotator, 101 ...Liquid layer, 10
2...Liquid, 103, 103'...Liquid level, 104
... Thin film, 104' ... Sample, 7,105 ... Probe light source, 18,107 ... Optical position detector, 1
08... Driver, 109... Lock-in amplifier, 110... Excitation light source, 114... Measurement controller.

Claims (1)

[Claims] 1. An excitation light source that emits excitation light, a light intensity modulator that modulates the intensity of the emitted excitation light in front of the measurement site of the monolayer, a probe light source that emits a beam light, and an emission light source that emits excitation light. a light splitting means for splitting the split light beam into two; and a light splitting means for splitting the split light into two light beams whose directional components are symmetrical to each other to compensate for fluctuations in the beam light due to fluctuations in the probe light source. What is claimed is: 1. A monomolecular film forming apparatus comprising: a means for forming a monomolecular film; an optical element that guides the light beams to the measurement site or the vicinity thereof; and an optical position detector that receives the light beams. 2. The thin film forming apparatus according to claim 1, wherein total reflection of the liquid surface on which the thin film is formed is utilized when forming the compensating light beam.