JPH109955A - Spectroscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spectroscope in which the wavelength of light whose polarization is extinguished can be computed on the basis of the angle of incidence of a luminous flux on a dielectric by a method in which a parallel luminous flux to be spectrally diffracted is made incident on the surface of a plane dielectric and its reflected light is measured through a polarizer. SOLUTION: Light which is radiated from a light source is condensed by a collimator 5, and it is converted into a parallel luminous flux so as to be incident on a dielectric plate 2. In a central base 3, and angle position in which the normal line on the surface of the plate 2 agrees with the optical axis of the collimator 5 so as to face the collimator is set at an angle of incidence of 0, and data on the angle position is fetched by a control device 11. A turning arm 4 is turned at an angle double that of the central base 3, and the light from the light source 6 reflected by the plate 2 is always incident on a photodetector 8 so as to be detected. The device 11 sends a signal to a polarizer driving device 9, a polarizer 7 is changed over to the S- component transmission direction and the P-component transmission direction of reflected light from the plate 2 at every angle position of the central base 3, it sends out the output of the photodetector 8 in the respective directions, and the output is stored in a memory 12 together with data on the angle position of the central base 3 at this time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spectroscope that does not use a diffraction grating or a prism.

[0002]

2. Description of the Related Art A spectroscope has conventionally used a light dispersion element such as a diffraction grating or a prism.

[0003]

A conventional spectroscope using the above-mentioned light dispersing element has a structure in which an image of an entrance side slit of the spectroscope is formed on a spectrum image plane, and an image of the entrance slit is formed into an image. In the optical configuration, aberration is accompanied.
In particular, the imaging system of a spectroscope usually utilizes concave reflection, and since the concave surface is used off-axis, astigmatism is inevitable. In the case of using a concave diffraction grating, the magnitude of the aberration changes depending on the wavelength, and there is a problem that even if the aberration can be reduced at one wavelength, the aberration at another wavelength cannot be reduced.

[0004]

SUMMARY OF THE INVENTION The present invention does not use a spectral element and does not need to form a spectral image.
Provided is a spectroscope that does not have a problem of aberration of an optical system.

[0005]

Means for Solving the Problems In a configuration in which light to be measured is made incident on a dielectric surface and light reflected from the dielectric surface is measured through a polarizer, the angle of incidence of the light to be measured on the dielectric surface is variable. As measuring the intensity of the P-polarized component of the reflected light at each incident angle, for example, calculating the wavelength of the light exhibiting the peak from Brewster's law from the incident angle with respect to the downward peak of the measured value. did.

In the above configuration, the P-polarized light component of the light reflected from the dielectric surface becomes 0 when the incident angle θ is the Brewster's angle determined by the refractive index n (λ) of the dielectric with respect to the wavelength λ. . Considering the case where the measured light is mixed with the background light and the bright line, the S component of the reflected light from the dielectric always reflects all the wavelength components of the measured light almost uniformly regardless of the incident angle. Therefore, the photometric output monotonically increases with the incident angle from the state where the incident angle is 0 (normal incidence). On the other hand, the reflectance of the P-polarized component decreases near the wavelength where the incident angle θ of the measured light becomes the Brewster angle. When the intensity is higher than the wavelength of, the reduction rate of the measured intensity of the P-polarized light component in the reflected light with respect to the entire measured light becomes larger than when the incident angle is another angle.

[0007] The above-mentioned place will be described with reference to the drawings. FIG. 2A
Is the spectral spectrum of the light to be measured, and the horizontal axis is the double scale of the wavelength and the Brewster angle of the dielectric used for light of each wavelength. FIG. 2E shows that P for a certain wavelength of light in the dielectric.
The relationship between the incident angle of polarized light and S-polarized light and the reflectance is shown, and the angle at which the P-polarized light reflectance is 0 is the Brewster angle. FIG. 2B shows the spectral spectrum of the S component of the reflected light at a certain incident angle, which is obtained by multiplying FIG. 2A by the S-polarized reflectance at the incident angle, and has substantially the same shape as the spectral spectrum to be measured. The measured S-polarized component intensity is shown in FIG.
It corresponds to the area under the curve of B. This corresponds to the fact that the reflectance of the S-polarized light monotonically increases while the incident angle changes from 0 to 90 °, and changes as shown in FIG. 3A. FIG. 2C shows the spectral spectrum of the P-polarized light component of the reflected light at a certain incident angle θ. The spectral intensity is low near the wavelength λ where the incident angle θ is the Brewster angle, and is zero at the wavelength λ. FIG. 2D is concave at a wavelength where the angle θ ′ is the Brewster angle in the spectral spectrum of the reflected light P component at another incident angle θ ′. The measured intensity of the P-polarized light component is the area under the curves shown in FIGS. 2C and 2D, and the shaded portions in each figure are dimmed from the measured intensity when there is no phenomenon such as Brewster reflection. Indicates the amount. Since the area of the dimming portion is large where the spectral intensity is large, comparing FIG. 2C and FIG. 2D, the measured intensity of P-polarized light is larger in the case of C than in the case of D. For this reason, the change in the intensity of the P-polarized light component of the reflected light when the incident angle is changed is as shown in FIG. 3B, which is a form obtained by subtracting the spectrum of the incident light from the measured intensity of the S-polarized light component. The degree of the depression reflects the spectrum of the light to be measured. Since the dent appears sharply at a position corresponding to the Brewster angle of the bright line light, the wavelength of the bright line light is determined from the angle.

[0008]

FIG. 1 shows an example of an embodiment of the present invention. In this figure, 1 is a goniometer, 2 is a plate-shaped dielectric plate and is installed on a center base 3 of the goniometer, 4 is a rotating arm, and the center base 3 and this arm ,
It can be rotated at twice the rotation angle. A collimator 5 is a light source 6 for the light to be measured, for example, a plasma flame of an inductively coupled plasma device or a glow discharge tube. A polarizer 7 and a photodetector 8 are installed on the rotating arm 4, and the polarizer 7 can be rotated about its optical axis by a polarizer driving device 9 mounted on the rotating arm 4. It has become. Reference numeral 10 denotes a goniometer driving device which rotates the center base 3 by a predetermined angle in accordance with a command from the control and data processing device 11. The rotating arm 4 is driven by a double angle in conjunction with the center base 3.

Light emitted from the light source 6 is collected by the collimator 5, converted into a parallel light beam, and made incident on the dielectric plate 2. The center base 3 is set such that the angular position when the surface normal of the dielectric plate 2 is aligned with the optical axis of the collimator 5 and faces the collimator 5 is the incident angle 0, and the data of the angular position is taken into the control device 11. ing. The actual rotation of the center table does not need to start from the angular position of 0 °, and the angular range determined by the measurement wavelength range before and after the angular position of 50 ° can be rotated. The rotation angle range is previously input to the control device as an instruction.
For example, when BaF10 of optical glass is used as the dielectric, the refractive index is 1.655 and the wavelength is 365 n at a wavelength of 1014 nm.
m, the refractive index is 1.707, and each Brewster's angle is 5
Since they are 8 ° 52 ′ and 59 ° 31 ′, the upper wavelength range can be measured by changing the incident angle in the range of 58 ° to 60 °. Since the rotating arm 4 rotates at twice the angle of the center base 3, the light of the light source 6 reflected by the dielectric plate 2 always enters the photodetector 8 and is detected. The control device 11 sends a signal to the polarizer driving device 9 to switch the polarizer 7 between the S component transmission direction and the P component transmission direction of the reflected light from the dielectric plate 2 at each angular position of the center base 3. The output of the photodetector 7 is read in each direction, and stored in the memory 12 together with the data on the angular position of the center base 3 at that time. In this way, the preset rotation angle range of the center base 3 is turned, for example, by 1 '.

The output of the photodetector 8 for the S-polarized light is read out from the data stored in the memory 12 by the above-described operation, and the angular position of the center base 3 is set on the horizontal axis to display the display device 13.
FIG. Similarly, FIG. 3B shows the output of the photodetector 8 for P-polarized light.

The data processing actually performed by the control device calculates (S-polarized light measurement intensity-P-polarized light measurement intensity) / (S-polarized light measurement intensity) for each angular position of the center base from the data stored in the memory 12. It is displayed on the display device 13 as a curve in which the angle of the center base is set on the horizontal axis. This is the curve C in FIG. This curve has substantially the same shape as the spectrum of the light source 6 as described above. The peak protruding upward in this curve is the peak of the bright line light. The analyst reads the center wavelength of this peak and inputs it to
Calculates the wavelength of the bright line light as follows. If the angle of the center base 3 just read is θ, this is the incident angle from the collimator 5 to the dielectric plate, and the refractive index n of the bright line light with respect to the dielectric plate 2 is determined by Brewster's law.
N = tan θ On the other hand, since a table of the refractive index wavelength characteristics of the dielectric plate 2 is stored in the control device in advance, the wavelength of the target bright line light is subtracted from the above n according to the table, and this is displayed on the display device 13. Is output to

Although the data processing described above corresponds to the elemental analysis based on the emission line spectrum, as described above, the curve of FIG. 3C has substantially the same shape as the spectrum of the light source. The refractive index is converted into a wavelength by a refractive index wavelength characteristic table, and the refractive index is converted into a wavelength by using FIG.
Curve can be drawn. This data processing can be applied to analysis by continuous spectrum such as absorption spectrum analysis. The polarizer may be placed anywhere on the optical axis from the collimator to the photodetector 8.

In the above-described configuration, the S-polarized light and the P-polarized light are measured at each position of one of the rotating arms 4, but the rotating arm 4 is moved while rotating the polarizer at a high speed, and the photodetector is moved. When an AC component synchronized with the rotation of the polarizer is extracted from the output of No. 8,
The amplitude is the difference between the S-polarized light intensity and the P-polarized light intensity.
The curve of C is drawn.

FIG. 4 shows another embodiment of the present invention. In this example, no goniometer is used, and the reflected light from the dielectric 2 is focused on the image sensor 80 through the lens 14. When the dielectric plate 2 is rotated, the focal point on the image sensor moves. Therefore, when the output of the image sensor is read by turning the dielectric plate while switching the direction of the polarizer 7, the output of A and B in FIG. The data shown is obtained. When a goniometer is used, the rotation range of the rotation arm is narrow, so that the configuration in FIG. 4 can be used instead of the configuration in FIG. Other parts corresponding to the respective parts of the configuration in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and each description is omitted.

[0015]

The spectrometer of the present invention does not use a light dispersing element and always uses all of the spectrum light for measurement. Therefore, the spectroscope is a bright spectrometer despite the use of dielectric surface reflection. Since there is no imaging system, a spectroscope having no aberration can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a graph for explaining the principle of the present invention.

FIG. 3 is a graph of a measurement result in the embodiment.

FIG. 4 is a schematic plan view of an optical system according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Goniometer 2 Dielectric plate 3 Center base 4 Rotating arm 5 Collimator 6 Light source 7 Polarizer 8 Photodetector 9 Polarizer drive device 10 Goniometer drive device 11 Control and data processing device 12 Memory 13 Display device

Claims (1)

[Claims] 1. A means for injecting a parallel light beam to a dielectric and its surface, a photodetector for receiving the reflected light of the parallel light by the dielectric, and the parallel light incident means to the photodetector via the dielectric. The polarizer disposed on the optical path, the parallel beam incident means, the photodetector, and the polarizer are always driven with respect to the dielectric surface while maintaining a positional relationship corresponding to incident light and reflected light. Means and the driving means for measuring the intensity of the P-polarized light of the reflected light while changing the angle of incidence of the incident light beam on the dielectric, and analyzing the P-polarized light based on Brewster's law based on the measurement result of the P-polarized light. A spectroscope comprising means for calculating spectrum data.