JP2699753B2 - Spectrophotometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrophotometer for measuring the spectral reflectance characteristic of a solid sample mainly at a small angle of incidence and reflection, and more particularly to an accessory device thereof.

[0002]

2. Description of the Related Art For example, optical elements such as mirrors, lenses, and prisms, materials such as glass, which have a problem in optical characteristics, and spectral characteristics of solid samples such as thin films formed by vapor deposition or coating, such as reflection. Conventional spectrophotometers for measuring the rate characteristics include those shown in FIGS.

In the conventional example shown in FIG. 6, a sample to be measured 104 or a reflection reference sample 105 can be held in a reflection measuring section 106 of an integrating sphere 103. The measurement light beam 101 is reflected at an incident angle θ by any of the samples held in the integrating sphere 103, trapped on the inner surface of the integrating sphere, and detected by a photoelectric detector. In the measurement, first, the reflectance of the reflection reference sample 105 is set to 100%, and then the reflectance of the measurement sample 104 is measured at the incident angle θ with respect to the reflection reference sample. As the reflection reference sample, an aluminum-evaporated mirror having a known reflectance, barium sulfate powder, alumina ceramic, or the like is generally used.

The reference light beam 102 is incident on the integrating sphere in the same state both at the time of measuring the reflection reference sample and at the time of measuring the sample to be measured, and is measured. Therefore, the measurement is a so-called double beam measurement that takes the ratio of the measurement light beam S to the reference light beam R.

In the prior art shown in FIG. 7, a measuring light beam 101 is a reflecting mirror.
It is bent by 107 and irradiates the sample 104 or the reflection reference sample 105 supported by a sample holding mechanism (not shown). The irradiated light beam is reflected on the surface of the sample, bent again by the other reflecting mirror 108, and measured by the integrating sphere 103. The reference light beam 102 always enters the integrating sphere in the same state as in FIG. Sample 104 and reflection reference sample 10
5 and the ratio between the measurement light flux S and the reference light flux R are the same as in the conventional example of FIG.

[0006]

However, depending on the spectral reflectance characteristics of the solid sample and the purpose of the measurement, if the angle of incidence and reflection of the light beam on the sample must be extremely small,
Further, there are cases where it is necessary to measure the reflectance characteristics for vertically incident light. As a simple example, there is a case where it is desired to measure in advance the reflectance characteristics in an actual use condition of an interference filter designed and manufactured on the assumption that the interference filter is used for vertically incident light. When the reflectance measuring apparatus is designed to meet this purpose, first, in the conventional example shown in FIG. 6, when the angle θ between the sample surface and the measurement light beam S is 0 or a small angle close to 0, the sample surface The reflected luminous flux from the laser beam substantially returns along the same optical path as the incident measuring luminous flux, and exits from the entrance window 109 of the measuring luminous flux S to the outside of the integrating sphere, so that photometry cannot be performed. In addition, in the conventional example of FIG. 7, in order to reduce the incident angle θ of the measurement light beam to the sample (or to zero), the reflecting mirrors 107 and 108 approach each other, and the incident angle θ exceeds a certain angle. When the distance is reduced, the two mechanically interfere with each other, making the configuration of the device impossible. As described above, in the conventional example, it was extremely difficult to reduce the angle of incidence of the measurement light beam on the sample to a perpendicular (0 °) or an angle close thereto.

Accordingly, the present invention provides a spectrophotometer suitable for a case where the angle of incidence and reflection of a light beam on a sample must be extremely small or a case where the reflectance characteristics for vertically incident light must be measured. The purpose is. In the present invention, in particular, such a reflectance measurement can be performed by attaching an accessory dedicated to reflectance measurement in a normal spectrophotometer, and returning to a normal spectrophotometer by removing the accessory. It is an object of the present invention to provide a spectrophotometer that can be switched easily and easily.

In order to solve the above-mentioned problems, in the spectrophotometer of the present invention, there is a space for installing the sample to be measured on the measurement light beam of the spectrophotometer, and the sample to be measured is installed here. In addition to being able to perform transmission measurement, it is also possible to perform reflection measurement by installing the sample to be measured on the measurement light beam of the reflection measurement unit with the reflection measurement unit for reflection measurement attached to the sample installation space part. In a spectrophotometer capable of being provided in the detachable reflection measurement unit,
A semi-transmissive mirror that branches the measurement light beam in two directions of reflection and transmission, and one of the light beams branched by the semi-transparent mirror, which is provided in the detachable reflection measurement unit, is incident on the sample to be measured at a small incident angle, and A holding mechanism for holding the sample to be measured so that the reflected light beam from the sample to be measured is branched again by the semi-transparent mirror, and when the detachable reflection measuring unit is attached to the spectrophotometer, Positioning means for positioning the reflection measurement unit on the spectrophotometer so that the measurement light beam irradiates the semi-transparent mirror, and when a detachable reflection measurement unit is attached, the reflected light beam re-branched by the semi-transparent mirror Alternatively, a detection mechanism is provided at a position where one of the transmitted light beams is guided, and a detection mechanism provided at a position where a straight-forward measurement light beam from the spectrophotometer is guided when the reflection measurement unit is not attached. To.

[0009]

The measurement light beam is split into transmitted light and reflected light in two directions by a semi-transparent mirror mounted at an appropriate position and angle by mounting the reflection measuring section at a predetermined position by the positioning means. Perpendicular to (0
°) The reflected light reflected from the sample surface of a sample supported at or at a small angle close to it and returning along almost the same optical path as the incident light is split again by the semi-transparent mirror, and one of them is introduced into the detector. Is used to measure the spectral reflectance characteristics of the solid sample with respect to incident light at a small angle near or perpendicular to it. Then, by removing the reflection measurement unit and moving the detection mechanism in accordance with the removal, the measurement light beam that goes straight can go straight and enter the detection mechanism as it is, and measurement as a normal spectrophotometer becomes possible. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described with reference to the drawings.
FIG. 1 is a schematic view of an embodiment of the present invention, and FIGS. 2 and 3 are plan views each showing a detailed structure.

The detection mechanism comprises an integrating sphere 1 and a photoelectric detector (not shown), and can be fixed to one of two positions A and B in FIG. At the time of reflection measurement, the integrating sphere is attached at the position A in FIG. The measuring light beam 2 is branched into reflected light bent in a right angle direction and transmitted light traveling straight by a semi-transmissive mirror 6 installed on the optical path at an angle of 45 ° with respect to the optical axis. On the other hand, the sample 4 or the reflection reference sample 5 is held by a holding mechanism (not shown) such that its surface is perpendicular to the light beam. The light beam perpendicularly incident on the surface of the sample follows the original optical path after being reflected by the surface, is again split by the semi-transparent mirror 6 into reflected light and transmitted light, and the transmitted light of the split light beam is bent by the reflecting mirror 7. Is introduced into the integrating sphere 1 for photometry. With this configuration, it is possible to measure the spectral reflectance of a light beam that is perpendicularly incident on the sample surface without mechanical interference of the optical element.

The light beam 12 transmitted through the semi-transparent mirror among the measurement light beams is bent by the reflecting mirror 8 and absorbed by the optical trap 9. This is to prevent the transmitted light 12 from being irregularly reflected by the inner wall of the apparatus or the like, entering the integrating sphere 1, and causing a measurement error.

The reference light beam 3 is directly incident on the integrating sphere 1, and double beam photometry is performed to obtain a photometric ratio between the two light beams S and R. The reflectance of the sample 4 can be measured as a relative value with respect to the reflection reference sample 5.

The material constituting the semi-transmissive surface of the semi-transmissive mirror 6 is determined by the measurement wavelength range and the like, but the ratio of the transmittance to the reflectance is close to 1: 1 and the absorption is as small as possible.
It is desirable that the transmittance has a small wavelength dependence. Specific materials include, for example, chromium deposited on a quartz substrate,
Metal thin films such as inconel and aluminum are exemplified. In particular, the chromium thin film has a substantially flat wavelength characteristic in the ultraviolet, visible, and near infrared regions. When chromium is deposited by controlling the film thickness so that the reflectance and the transmittance are almost equal, the reflectance is as follows:
The transmittance: absorption ratio is approximately 3: 3: 4.

In the present embodiment, since the measurement light beam is reflected once and transmitted once by the semi-transparent mirror, considering the absorption, if the reflectance of the sample 4 is 100%, the amount of light incident on the integrating sphere is It is about 1/10 of the original measurement light flux. With this level of dimming, the use of a high-sensitivity high-detector or the reduction of the reference height bundle with a filter or the like to balance the light amounts of S and R does not greatly affect the measurement accuracy. Can be measured.

In the case where the measurement wavelength range is limited, the measurement light flux 1:
It is possible to branch to 1. In this case, the amount of light incident on the integrating sphere 7 is about 1/4 of the original measurement light beam, and high-accuracy measurement with less noise can be performed as compared with the case of the chromium film.

Further, when a semi-transmissive mirror for phase-dividing a light beam, such as one obtained by partially depositing aluminum on a quartz substrate or depositing aluminum on a quartz plate having a large number of small holes, is used, the semi-transparent mirror is deposited. By suitably designing the optical system so that the pattern is not formed on the sample surface, the same effect as that of the multilayer semi-transparent mirror can be obtained in a wider wavelength range.

In this embodiment, the integrating sphere 1 can be attached to two positions A and B along the reference light beam 3. Of these positions, position A is a position for measuring the above-mentioned vertically incident light by reflection, while position B is a position where the reflection measuring section is removed together with the mounting base 10, and the measuring light beam 2 going straight on is directly incident on the integrating sphere. It is determined to be the position. The advantages of such a configuration will be described below.

In general, as a spectral characteristic of a solid sample, a spectral transmittance is often measured in addition to a reflectance.
It is also desirable that the measurement device be able to easily switch between reflection and transmission measurements. In the example of FIG. 1, in order to measure the transmittance while the integrating sphere 1 is kept at the position A for reflection measurement, the methods of FIGS. 4 and 5 can be considered.

In the method shown in FIG. 4, a transmission measurement reflecting mirror 13 is placed at the position of the reflection measurement sample shown in FIG. 1, and the transmission measurement sample 13 is placed immediately before the measurement light beam 2 incident on the integrating sphere 1 along the same path as in FIG. 14
And measure its transmittance. According to this method, the transmittance can be measured without a major change of the apparatus,
Due to the light amount loss due to the semi-transparent mirror, the energy inherent in the measurement light is wasted, and there may be a problem such as an increase in noise and a limitation on the wavelength range. These are acceptable to some extent in the special measurement of reflection at normal incidence, but may exceed the permissible limit in a very common transmittance measurement.

On the other hand, in the example shown in FIG. 5, a reflecting mirror 13 for measuring transmission is provided in place of the semi-transmitting mirror shown in FIG. 1 or FIG. The transmittance of the sample is measured. According to this method, the transmittance can be measured with a light amount substantially equal to the original light amount while reducing the loss of the measurement light beam. On the other hand, it is necessary to accurately position and exchange the two optical elements of the semi-transmissive mirror and the reflecting mirror, and replacing the optical element alone may cause problems such as contamination and damage at the time of attachment and detachment. Furthermore, the size and shape of the sample that can be measured due to the spatial constraints of components such as the optical trap 9 are limited.

FIGS. 2 and 3 show detailed plan views of this embodiment in which these problems are solved. In FIG. 2, the integrating sphere 1 is set at the position A in FIG. 1, and the reflection measuring unit 10 is accurately positioned on the measuring unit base 15 by a positioning pin (not shown) or the like, and is attached by the screw 17. This attachment / detachment operation can be easily attached / detached with good reproducibility by loosening the screw 17, and can be performed without fear of damage or contamination of each optical element by covering the entire reflection measurement unit 10 with a cover or the like. . Reference numeral 18 denotes a sample holder.
FIG. 3 shows the reflection measuring unit 10 in the example of FIG.
Is removed, and the integrating sphere 1 is moved to the position B shown in FIG. 1 on the detection base 16. In this state, since the measurement light beam 2 is directly incident on the integrating sphere 1, the transmittance of the transmission measurement sample 14 placed at the integrating sphere entrance window can be measured without loss of light quantity. Since the reference light beam 3 has two positions A and B along the reference light path, the integrating sphere 1 has the same incident angle in each case.
And is measured. According to the arrangement shown in FIG. 3, the size and shape restrictions observed when the detection unit is located at the position A are greatly relaxed in the sample to be measured for transmission, so that a large sample, a thick sample, a deformed sample, etc. Can be measured.

In the above embodiment, the angle of incidence of the light beam on the sample is set to 0 ° (ie, perpendicular incidence). However, by appropriately setting the position and angle of the optical element such as the size, for example, 5 ° or less. Needless to say, it is possible to measure the reflectance with respect to the small incident angle of reflection.

[0024]

Since the present invention is configured as described above, it is possible to measure the reflectance of a solid sample for a small incident angle or a vertical angle close to the solid sample, and also to reduce the light amount by a simple operation. It is also possible to change the arrangement for transmission measurement without the need.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of the present invention.

FIG. 2 is a plan view of an embodiment of the present invention (when measuring reflectance).

FIG. 3 is a plan view of an embodiment of the present invention (when measuring transmittance).

FIG. 4 is a schematic diagram showing an example in which the present invention is applied to transmittance measurement.

FIG. 5 is a schematic diagram showing an example in which the present invention is applied to transmittance measurement.

FIG. 6 is a schematic view showing an example of a conventional reflection measurement.

FIG. 7 is a schematic diagram showing an example of a conventional reflection measurement.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Integrating sphere 2 Measurement light beam 3 Reference light beam 4 Sample 5 Reflection reference sample 6 Semi-reflection mirror 7 Reflection mirror 8 Reflection mirror 10 Reflection measurement unit 11 Reflection light 12 Transmission light 13 Transmission measurement reflection mirror 14 Transmission measurement sample 15 Measurement unit base 16 Detector base

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-27844 (JP, A) JP-A-60-242308 (JP, A) JP-A-2-96640 (JP, A) JP-A-1- 308930 (JP, A) JP-A-4-125431 (JP, A) JP-A-62-132152 (JP, A) JP-B-41-16719 (JP, B1) JP-B-61-8936 (JP, B2)

Claims (1)

(57) [Claims] 1. A space for installing a sample to be measured is provided on the measurement light beam of the spectrophotometer. By installing the sample to be measured there, transmission measurement can be performed, and a reflection measuring unit for reflection measurement can be provided. In a spectrophotometer that can also perform reflection measurement by setting a sample to be measured on the measurement light beam of the reflection measurement unit while being attached to the measurement sample installation space portion, provided in the detachable reflection measurement unit A semi-transmissive mirror that divides the measurement light beam in two directions of reflection and transmission, and one of the light beams that is provided in the detachable reflection measurement unit and is branched by the semi-transparent mirror enters the sample to be measured at a small incident angle. And a holding mechanism for holding the sample to be measured so that a reflected light beam from the sample to be measured is branched again by the semi-transparent mirror; and a spectrophotometer when the detachable reflection measurement unit is attached to the spectrophotometer. from Positioning means for positioning the reflection measuring unit on the spectrophotometer so that the constant light beam is irradiated on the semi-transparent mirror; and when a detachable reflection measuring unit is attached, the reflected light beam branched again by the semi-transparent mirror. Or a detection mechanism provided at a position where one of the transmitted light beams is guided, and provided at a position where a straight-ahead measurement light beam from the spectrophotometer is guided when the reflection measurement unit is not attached. Spectrophotometer.