JP3034382B2 - Microscopic total reflection attenuation measurement optical system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system for measuring attenuated total reflection, and more particularly to an optical system for measuring attenuated total reflection, which can clearly observe and position the measurement position of a minute sample without parallax.

[0002]

2. Description of the Related Art Conventionally, a total reflection surface such as a hemispherical prism, a triangular prism, a multi-reflection parallel flat plate having a large refractive index is closely attached to a sample, and the total reflection light is attenuated more sensitively due to non-uniformity near an interface of the sample. An attenuated total reflection measurement method (hereinafter, referred to as ATR measurement) for performing spectroscopic measurement or the like of a surface of a polymer film, a coating film, paper, or the like, which is difficult to measure by the transmission method, using the light receiving method is known. .

When performing ATR measurement on a minute sample, the position where the actual measurement of the sample is to be performed must be accurately determined by sample observation. To do so, conventionally, as described in, for example, US Pat. No. 5,093,580, the lens-shaped ATR crystal is separated from the sample, the sample is observed through the auxiliary lens and the objective lens, and the sample position with respect to the ATR crystal is determined. Next, the ATR crystal is brought into close contact with the sample, and thereafter, visible illumination light is made incident at the incident angle and the reflection angle position of the ATR measurement, and the measurement sample surface is observed.

[0004] Further, A
As a TR crystal, a prism P having a special shape as shown in FIG. 4 is used, a scale B is arranged on a surface A that is in close contact with the sample S, and the scale B passes through a surface D different from the measurement illumination light incident surface C of the prism P. There is known a method in which a measurement position is confirmed by a scale of a scale B while observing a sample S on which is superimposed.

[0005]

However, when the measurement sample surface is observed at a measurement angle that satisfies the condition of total reflection of the ATR crystal, as in US Pat. No. 5,093,580,
There is a problem that the state of the sample surface cannot be actually observed because the reflectance is too high. In addition, when an ATR crystal as shown in FIG. 4 is used, there are problems that the prism shape is complicated and a scale must be arranged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the purpose of observing the measurement position of a sample with a simple optical system without any parallax in micro ATR measurement of a minute sample. To provide a simple optical system.

[0007]

In order to achieve the above-mentioned object, the optical system for measuring attenuated total reflection according to the present invention has a plane of a hemispherical prism in close contact with the surface of a sample, and attenuates the total reflection light on the plane to reduce the amount of light reflected from the sample. In an optical system for measuring attenuated total reflection, which measures the attenuated total reflection, an objective lens for enlarging and projecting the sample surface in close contact with the plane through the spherical surface of the hemispherical prism is arranged. The reflected light is incident on the objective lens via an optical path on one side of the optical axis of the objective lens, the observation illumination light is incident on the plane of the hemispherical prism at an angle smaller than the total reflection angle, and the specular reflection light is reflected on the objective lens. Direction of the illumination light for measurement and the illumination light for observation with respect to the optical axis of the objective lens, and the optical axis of the objective lens in the plane of the hemispherical prism so as to enter the objective lens via the optical path on the other side of the optical axis of And it is characterized in that it is configured as a tilt against.

In this case, between the hemispherical prism and the objective lens, a light blocking means for selectively opening one of the optical path on one side and the optical path on the other side of the optical axis of the objective lens and blocking the other optical path. Is arranged, the background light is blocked during observation and measurement, which facilitates observation, and does not cause a decrease in measurement accuracy.

[0009]

According to the present invention, an objective lens for projecting the sample surface in close contact with the plane through the spherical surface of the hemispherical prism is arranged, and the illumination light for measurement is totally reflected by the plane of the hemispherical prism, and the optical axis of the objective lens is adjusted. The illumination light for observation is incident on the plane of the hemispherical prism at an angle smaller than the total reflection angle through the optical path on one side, and the specularly reflected light passes through the optical path on the other side of the optical axis of the objective lens. Since the directions of the illumination light for measurement and the illumination light for observation with respect to the optical axis of the objective lens, and the inclination of the plane of the hemispherical prism with respect to the optical axis of the objective lens are set so that the light enters the objective lens through
The identity of the position of the sample observed through the objective lens with the position of the sample measured by the photodetector of the measurement system is guaranteed, and there is no parallax. Moreover, the optical path followed by the measurement light satisfies the total reflection condition of the total reflection attenuation measurement, while the optical path followed by the observation light is observed at an angle smaller than the critical angle and satisfying the specular reflection condition. Can be clearly observed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the ATR measuring optical system according to the present invention will be described below. In order to observe the measurement position of the micro sample adhered to it via the ATR crystal, as described above,
When observed at a measurement angle that satisfies the condition for total reflection of the ATR crystal, the reflectivity is too high and the appearance of the sample surface cannot be clearly observed. Therefore, it is conceivable to observe the sample surface with scattered light from an angle that does not cause total reflection. However, in this case, there is a problem that scattering from a stepped portion of the sample or the like is too strong and the sample surface is difficult to see.

Therefore, the observation illumination light is made incident on the sample surface at an angle smaller than the critical angle of the ATR crystal and at an angle where the illumination angle and the observation angle satisfy the same specular reflection condition, and the measurement position of the micro sample is observed. As a result, it was found that the sample surface could be clearly observed. In the present invention, the measurement optical system is configured so as to satisfy such observation conditions and to always observe the same position as the measurement light emission position without parallax.

FIG. 1 is an optical path diagram of one embodiment of an ATR measuring optical system according to the present invention. A hemispherical prism 1 is used as an ATR crystal, and the hemispherical prism 1 is fixed in a state in which it is in close contact with a sample S. Observation and measurement are performed with magnification of 2. That is, the sample S is disposed obliquely with respect to the optical axis a of the microscope optical system, and the hemispherical prism 1 having a high refractive index is pressed against the surface of the sample S. In this case, the light coming from the sample S passing through the hemispherical prism 1 forms an image at the position of the mask 3 through the Cassegrain objective lens 2, the measurement position is limited by the mask 3, and the light is reflected by the half mirror or the switching mirror 4. The light is divided into two light paths, the observation light is enlarged by the eyepiece 6, and the measurement position of the sample S is observed. Further, the measurement light is photoelectrically converted by the photodetector 5 and, in the case of Fourier spectroscopy, is subjected to Fourier transform and spectral analysis is performed.

In the present invention, the critical angle θ _{c of the} hemispherical prism 1 (the refractive index of the hemispherical prism 1 is n ₁ ,
Assuming that the refractive index of the sample S is n ₂ , sin θ _c = n ₂ /
the n _1. ) Greater than β (see FIG. 2; N in FIG. 2).
Represents the normal line of the sample S surface. ), Light emitted from the surface of the sample S is used, and as observation light incident on the objective lens 2, an angle α smaller than the critical angle θ _{c is obtained} from the above-described discovery.
In FIG. 2, light emitted from the surface of the sample S is used.
To do so, as shown in FIG. 1, the measurement light (double arrow)
Is one side of the optical axis a of the microscope optical system (left side in the figure)
Only, the observation light (single arrow) is incident on the objective lens 2 by following only the optical path on the opposite side (right side in the figure) of the optical axis a. Then, the incident directions of the illumination light for measurement 8 and the illumination light for observation 7 with respect to the sample S are set so as to satisfy such an angular relationship and satisfy the specular reflection condition, and the inclination of the sample S with respect to the optical axis a is set. Set.

Since the ATR measuring optical system is arranged as described above, the position of the sample S observed from the eyepiece 6 through the objective lens 2 and the mask 3 and the position of the sample S measured by the photodetector 5 are determined. Identity is guaranteed (no parallax).
Moreover, the optical path followed by the measurement light satisfies the condition for total reflection of the ATR measurement, while the optical path followed by the observation light is observed at an angle smaller than the critical angle and that satisfies the specular reflection condition. Can be observed.

When the other optical path is open at the time of observation and measurement, light entering through the optical path becomes a background, which makes observation difficult and reduces measurement accuracy. Therefore, as shown in FIG. 3A, at the time of observation, a light-shielding plate 11 having an opening 10 is inserted in front of the objective lens 2, and only observation light enters the objective lens 2 through the opening 10. Also, at the time of measurement, as shown in FIG. 3B, the opening 10 of the light shielding plate 11 is moved so as to be positioned in the optical path of the measurement light, and only the measurement light enters the objective lens 2. It is good to do so.

In the above description, the hemispherical prism 1 has a high refractive index. Specifically, zinc selenide, zinc sulfide, titanium bromide iodide (KRS
-5) is used. Further, a Cassegrain objective lens is used as the objective lens 2, but is not limited thereto.
Various known reflection objective lenses and refraction objective lenses can be used. Further, the illumination light for measurement usually uses infrared light, but is not limited thereto, and may be visible light or ultraviolet light.

Although the ATR measuring optical system of the present invention has been described based on the embodiments, the present invention is not limited to these embodiments, and various modifications can be made.

[0018]

As is apparent from the above description, according to the ATR measurement optical system of the present invention, the objective lens for enlarging and projecting the sample surface in close contact with the plane through the spherical surface of the hemispherical prism is arranged, and the illumination light for measurement is provided. Is totally reflected by the plane of the hemispherical prism, enters the objective lens via the optical path on one side of the optical axis of the objective lens, and the observation illumination light is incident on the plane of the hemispherical prism at an angle smaller than the total reflection angle. The direction of the measurement illumination light and the observation illumination light with respect to the objective lens optical axis, and the plane objective of the hemispherical prism so that the specularly reflected light enters the objective lens via the optical path on the other side of the optical axis of the objective lens. Since the tilt with respect to the lens optical axis is set, the identity of the position of the sample observed through the objective lens with the position of the sample measured by the photodetector of the measurement system is guaranteed, and there is no parallax. Moreover, the optical path followed by the measuring light is A
Since the optical path that the observation light follows satisfies the total reflection condition of the TR measurement and is observed at an angle that satisfies the regular reflection condition at an angle smaller than the critical angle, the sample surface can be clearly observed.

[Brief description of the drawings]

FIG. 1 is an optical path diagram of one embodiment of an ATR measuring optical system according to the present invention.

FIG. 2 is an enlarged view of the vicinity of a sample in FIG.

FIG. 3 is an optical path diagram showing a main part of another embodiment.

FIG. 4 is a diagram for explaining a conventional example.

[Explanation of symbols]

 S ... Sample 1 ... Hemispherical prism 2 ... Objective lens 3 ... Mask 4 ... Half mirror or switching mirror 5 ... Photodetector 6 ... Eyepiece 7 ... Observation illumination light 8 ... Measurement illumination light 10 ... Aperture 11 ... Shield plate a …optical axis

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiromichi Hattori 3-1-2 Musashino, Akishima-shi, Tokyo Japan Inside Electronic Co., Ltd. (72) Hiroshi Terashima 3-1-2 Musashino, Akishima-shi, Tokyo Japan (56) References JP-A-4-116452 (JP, A) JP-A-5-10872 (JP, A) US Patent 5093580 (US, A) (58) Fields investigated (Int. Cl. ^7, DB name) G01N 21/00 - 21/01 G01N 21/17 - 21/61 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. An optical system for measuring attenuated total reflection by measuring the total reflection attenuation characteristic of a sample by attenuating the total reflection light on the flat surface of a hemispherical prism in close contact with the surface of the sample.
An objective lens for enlarging and projecting the sample surface in close contact with the plane through the spherical surface of the hemispherical prism is arranged, and the illumination light for measurement is totally reflected by the plane of the hemispherical prism and passes through the optical path on one side of the optical axis of the objective lens. Incident on the objective lens,
Observation illumination light is incident on the plane of the hemispherical prism at an angle smaller than the total reflection angle, and the specular reflection light is incident on the objective lens via the optical path on the other side of the optical axis of the objective lens,
An optical system for measuring attenuated total internal reflection, wherein the directions of the illumination light for measurement and the illumination light for observation with respect to the optical axis of the objective lens and the inclination of the plane of the hemispherical prism with respect to the optical axis of the objective lens are set. 2. Between the hemispherical prism and the objective lens,
2. The light-shielding means according to claim 1, wherein a light-blocking means for selectively opening one of the optical path on one side and the optical path on the other side of the optical axis of the objective lens and blocking the other optical path is arranged. Microscopic total reflection attenuation measurement optical system.