JP2001116618A - Spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spectrometer capable of measuring plural spectral lines with high resolution by use of diffraction gratings. SOLUTION: In this spectrometer, parallel light from a collimator lens 16 is diffracted by a holographic grating 18, and the diffracted light (first diffraction light) is incident on an echellette grating 19. The first diffraction light is diffracted by the retro-disposed echellette grating 19, and the diffracted light (second diffraction light) is newly incident on the holographic grating 18. The second diffraction light is diffracted by the holographic grating 18, and the diffracted light (third diffraction light) returns to the collimator lens 16 and is reflected by a mirror 15 to converge on a sensor 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrometer having detection means for inputting light having a plurality of spectral lines having different wavelengths and detecting the output of the light.

[0002]

2. Description of the Related Art A conventional spectrometer is disclosed in JP-A-11-1.
The one disclosed in Japanese Patent No. 32848 is known. In the spectrometer described in this publication, a partially reflecting mirror is positioned between a dispersive optical element such as a diffraction grating (grating) and a collimating optical element.

In this spectrometer, when light whose wavelength is to be detected is converted into a parallel beam by a collimating optical element and is incident on a diffraction grating, the light diffracted by the diffraction grating returns to the collimating optical element. A part of the returning light is reflected by the partial reflection mirror and is incident on the diffraction grating again, so that the light diffracted by the diffraction grating returns to the collimating optical element again.

That is, a part of the parallel beam passes through the partial reflection mirror, is diffracted by the diffraction grating (first diffraction beam), and is reflected by the partial reflection mirror.
Diffracted by the diffraction grating (second diffraction beam).

[0005] When the second diffracted beam passes through the partial reflection mirror, the light intensity of 70% of the transmitted second diffracted beam is measured by a photometer.

As described above, the spectrometer described in the above publication measures a beam having a double dispersion value by diffracting at least part of a parallel beam at least twice by a diffraction grating.

[0007]

By the way, in the spectrometer described in the above publication, a specific arrangement for realizing a retro arrangement with a large diffraction angle (an arrangement in which incident light and output light with respect to the grating are in the same direction) is realized. No mention is made of a diffraction grating (grating), but an echelle grating is suitable for a diffraction grating for realizing a retro configuration.

However, when this echelle grating is used, there are the following problems.

That is, in order to realize a grating having a large diffraction angle and a retro-arrangement, it is necessary to increase the number of grooves, but it is difficult to manufacture an echelle grating by increasing the number of grooves. is there. Therefore, in order to increase the diffraction angle with a small number of groove lines, it is necessary to use diffracted light having a higher diffraction order. As a result, the wavelength of the diffraction light of a certain diffraction order and the diffraction light of the next diffraction order are required. Wavelength difference (that is, FSR) with respect to the wavelength of.

Here, the wavelength of the incident light incident on the grating is λ1, the diffraction order is m1, and the relationship between the incident light and the diffracted light having the wavelength λ2 and the diffraction order m2 is expressed by the following equation (1). If satisfied, the light is diffracted in the same direction.

M1 · λ1 = m2 · λ2 (1) When the equation (1) is satisfied, the wavelength difference Δλ between the wavelengths λ1 and λ2 (that is, FSR) is represented by the equation (2).

Δλ = λ1 / (m1 + 1) (2) When diffracting incident light using an echelle grating, if the diffraction order m1 is set to a very large value, for example, 100, then m1 · λ1 = m2 All wavelengths λ2 satisfying λ2 (m2 is an integer) are observed at the same position as wavelength λ1. Therefore, when there are a plurality of spectra in a wavelength range close to the wavelength λ1, it is difficult to identify the spectra.

More specifically, for example, when an iron (Fe) hollow cathode lamp is made incident on an echelle grating having a groove line number of 85.34 lines / mm, the 93rd light having a wavelength λ1 of 248.3271 nm is used. As shown in FIG. 11, the angle difference between the diffraction angle of the folded light and the diffraction angle of the 55th-order diffracted light having a wavelength λ2 = 419.9098 nm is 0.018.
Only different.

As described above, in the above-described spectrometer having a small FSR, since the angle difference between the diffraction angles of the diffracted lights of adjacent diffraction orders is very small, a plurality of emission spectrum lines are formed like an iron (Fe) hollow cathode lamp. In some cases, since the respective diffracted lights overlap, these diffracted lights cannot be separated, and as a result, it becomes difficult to identify the correspondence between individual spectra.

That is, the actual spectrum is shown in FIG.
Even in the case where the light is distributed as shown in (a), in the spectrometer having a small FSR, since the angle difference between the diffraction angles of the diffracted lights of the adjacent diffraction orders is very small, it is measured by the photometer. This results in a plurality of spectra having different wavelengths as shown in FIG.

In the above-described spectrometer having a small FSR, a plurality of spectra of distant orders are measured in a state of being close to each other. Therefore, as shown in FIG. And the waveform of the spectrum S1 overlaps with the waveform of the spectrum S2 to be measured, so that there is a problem that the measurement of the baseline portion cannot be performed accurately.

By the way, when light having a plurality of emission spectral lines is incident on the echelle grating, there is the above-mentioned problem. However, when light having one emission spectral line is incident on the echelle grating. , The output of the light can be detected.

Therefore, in order to solve the above-mentioned problem, as a means for converting a plurality of emission spectrum lines into one emission spectrum line, that is, as a so-called one-line method, as shown in FIG. Before the light is incident on the spectrometer 1, 1 is set between the two lenses 2 and 3.
A configuration in which a pre-dispersion element in which two prisms 4 are arranged is provided.

The pre-dispersion element disperses the light that has passed through the lens 3 by the prism 4 and then passes the light through the lens 2 so that the one-lined light is transmitted to the slit 1 a of the spectrometer 1. It is designed to be incident.

However, since the resolution of one prism 4 is not sufficient (spectral quantity is insufficient), it is not possible to completely remove the overlap of the spectra as described above. In order to improve the resolution, it is conceivable to use a plurality of prisms, but there is a problem that the prism configuration becomes large.

Moreover, since the light passes through the prism,
Since a thermal change (temperature change) occurs here, the refractive index of the prism also changes with this temperature change. Therefore, 1
There is a possibility that the light transmitted through the prism at the set position does not pass through the slit 1a. That is, the spectrum may not be measured.

As a means for forming one line, another grating spectroscope 5 as shown in FIG. 15 can be used instead of the prism. This spectroscope 5
The light that has passed through the slit 6 is reflected by the concave mirror M1 to be incident on the grating 7, and the light diffracted by the grating 7 is reflected by the concave mirror M2 and then reflected by the reflecting mirror 8 to form one line. The emitted light is made to enter the conventional spectroscope 1 through the entrance slit 9.

However, in this method, although the resolution by the spectrometer 1 is sufficiently obtained, the amount of light of one line is reduced, and it becomes difficult to measure the light intensity by the photometer of the spectrometer 1.

In the spectrometer disclosed in the above publication, the light transmitted through the partial reflection mirror is diffracted by the grating. Therefore, the light transmitted through the partial reflection mirror reduces the light intensity of the spectrum to be measured. , The S / N ratio deteriorates. For example, if light is diffracted three times by the grating, the light intensity of the light diffracted three times is only 0.55% of the light intensity of the incident light.

Further, in the spectrometer disclosed in the above-mentioned publication, a spectrum not diffracted by the grating, a spectrum diffracted once, and a spectrum diffracted twice are observed adjacent to each other. Due to being strong, as shown in FIG. 13, the baseline portion of the spectrum S1 diffracted once and the baseline portion of the spectrum S2 diffracted twice overlap, and the baseline of the spectrum of the light whose wavelength has been measured is obtained. There is a problem that cannot be measured accurately.

It is an object of the present invention to provide a spectrometer capable of measuring a plurality of spectral lines with high resolution using a diffraction grating.

[0027]

Means for Solving the Problems, Functions and Effects In order to achieve the above object, according to a first aspect of the present invention, detecting means for inputting light having a plurality of spectral lines having different wavelengths and detecting the output of the light In the spectrometer having, the first diffraction grating which is formed with grooves having a number of grooves capable of detecting the output of a spectral line of a specific wavelength by the detection means, and which can be used at a low diffraction order, A second diffraction grating having a number of grooves smaller than the number of groove lines in the first diffracted photon and being usable in a retro configuration, wherein the first diffraction grating specifies one of the plurality of spectral lines. Is selected, and the light of the selected spectral line is diffracted into higher-order diffracted light by the second diffraction grating.

According to a second aspect, in the first aspect,
The light having the plurality of spectral lines is diffracted by the first diffraction grating into lower-order diffraction light, and the diffracted light is converted into higher-order diffraction light by the second diffraction grating. Diffracted, returning the diffracted light to the first diffraction grating, and detecting the output of the diffracted or reflected light from the first diffraction grating by the detection means. .

Further, in the third invention, in the first invention or the second invention, the first diffraction grating is one of a holographic grating, an ion-etched grating, a blazed grating, an echelette grating, and a concave grating. And the second diffraction grating is one of an echelle grating and a blazed grating.

FIGS. 1 to 3 show the first to third aspects of the present invention.
This will be described with reference to FIG.

As shown in FIG. 1, the first grating 18 has a large number of groove lines and can be used at a low diffraction order. This first grating 18
It is assumed that a holographic grating having a groove line number of 3600 lines / mm is used (hereinafter referred to as a holographic grating 18).

The incident beam width W1 of the beam to the holographic grating 18 and the outgoing beam W2 of the beam emitted from the holographic grating 18 have a relationship of W1 <W2, for example, W2 / W1 = 9.8.
6 is set.

The second grating 19 is of a retro arrangement (an arrangement in which the directions of incident light and diffracted light are substantially the same).
Is used. As the second grating 19, an echelle grating having the number of groove lines of 35.34 lines / mm is used (hereinafter, referred to as "the second grating 19").
Echel grating 19).

The holographic grating 1
When the spectrometer 10 is viewed from the direction indicated by the arrow A in FIG. 1, the groove 8 and the echelle grating 19 are positioned such that their groove lines are spatially parallel to each other as shown in FIG. Are placed in a relationship.

Here, the reason why a grating having a large number of groove lines and usable at a low diffraction order, for example, a holographic grating, is used as the first grating is that a holographic grating having 3600 groove lines / mm is used. 18, the wavelength λ1 = 248.3
When light having a wavelength of 271 nm and a wavelength of λ = 419.9098 nm is diffracted, the difference between the diffraction angles of the two diffracted lights is 41.5 degrees, as shown in FIG.
This is because light of the wavelength λ1 or the wavelength λ2 can be easily identified.

Next, the operation of the spectrometer 10 having such a configuration will be described with reference to FIG.

The collimated light from the collimating lens 16 incident on the holographic grating 18 is diffracted by the holographic grating 18 at an angle of a diffraction angle that changes according to the wavelength of the light, and the diffracted light (first light) Is incident on the echelle grating 19.

The first diffracted light is diffracted by the echelle grating 19 arranged in the retro direction, and the diffracted light (second diffracted light) enters the holographic grating 18 again.

The second diffracted light is further diffracted by the holographic grating 18, and the diffracted diffracted light (third diffracted light) returns to the collimating lens 16, is reflected by the mirror 15 and is reflected by the sensor 17. Collect light.

As described above, according to the first to third inventions, the wavelength range is limited by the first grating, and the light in the limited wavelength range is expanded to a high resolution by the second grating. By returning the light enlarged to the high resolution to the first grating and diffracting the same, a high-resolution spectrometer in which diffracted lights of different diffraction orders do not overlap can be realized.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a spectrometer according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a configuration diagram showing a configuration of a spectrometer 10 according to the present embodiment.

As shown in the figure, the spectrometer 10 includes a light source 1
1, optical fiber 12, slit 13, two mirrors 1
4, 15, a collimating lens 16, a sensor 17, a first grating 18 and a second grating 19.

The light source 11 is a light source that emits light having a plurality of emission spectra having different wavelengths. This light source 11
Can use either an iron (Fe) lamp, a mercury (Hg) lamp, or a platinum (Pt) lamp.

The slit 13 has a slit width of, for example, 25
The light from the lamp, which has a thickness of μm and is guided by the optical fiber 12, is guided to the mirror.

The mirror 14 reflects the incident light from the slit 13 and guides it to the collimating lens 16.
The mirror 15 reflects light incident through the collimating lens 16 and guides the light to the sensor 17.

The collimating lens 16 emits the incident light as collimated light, that is, parallel light.

As the sensor 17, a line sensor is used.
Specifically, it can be configured using a one-dimensional or two-dimensional image sensor or a diode array.

The line sensor has a plurality of light receiving channels, and the light detection position on the line sensor is determined according to the channel number at which the light of the maximum intensity is detected. Since the incident position on the line sensor differs depending on the wavelength on the line sensor, the wavelength of light can be detected from the light detection position of the line sensor. Therefore, the wavelength of the light is determined from the channel number where the light is detected.

The wavelength (unit: nm) corresponding to the channel interval (unit: μm) of the line sensor is called a dispersion value.

As the first grating 18, a grating having a large number of groove lines and usable at a low diffraction order is used. Specifically, a holographic grating, an ion-etched grating, a blazed grating, an echelette grating, or a concave grating can be used.

In this embodiment, a holographic grating having 3600 grooves / mm is used as the first grating 18 (hereinafter referred to as a holographic grating 18).

The beam width W1 of the beam incident on the holographic grating 18 and the output beam W2 of the beam emitted from the holographic grating 18 have a relationship of W1 <W2, for example, W2 / W1 = 9.8.
6 is set.

The second grating 19 is arranged in a retro manner (an arrangement in which the directions of incident light and diffracted light are substantially the same).
Is used. Specifically, an echelle grating or a blazed grating can be used.

In this embodiment, as the second grating 19, an echelle grating having a groove number of 35.34 lines / mm is used (hereinafter referred to as an echelle grating 19).

The holographic grating 1
When the spectrometer 10 is viewed from the direction indicated by the arrow A in FIG. 1, the groove 8 and the echelle grating 19 are positioned such that their groove lines are spatially parallel to each other as shown in FIG. Are placed in a relationship.

Next, the reason why a grating having a large number of groove lines and usable at a low diffraction order, for example, a holographic grating, is used will be described.

Here, the wavelength of the incident light incident on the grating is λ1, the diffraction order is m1, and the relationship between this incident light and the diffracted light having the wavelength of λ2 and the diffraction order of m2 satisfies the above equation (1). Then, the wavelength difference Δλ between the wavelength λ1 and the wavelength λ2 (that is, FSR) is given by the above equation (2), that is, Δλ = λ
It is represented by 1 / (m1 + 1).

For example, a holographic grating is used to diffract incident light using a grating that increases the value of the wavelength difference Δλ (that is, FSR).

That is, in the case of the holographic grating 18, when the diffraction order m1 = 1 is used, the wavelength difference Δλ is λ1 / 2. For example, wavelength λ1 = 248
nm, the wavelength difference Δλ = 124 nm and the wavelength λ2 = 12
Although 4 nm overlaps, the light of wavelength λ2 is not output because it is absorbed by air.

The wavelength λ1 = 2 by the holographic grating 18 having 3600 grooves / mm.
48.3271 nm and wavelength λ2 = 419.9098n
When the light having the wavelength m is diffracted, the angle difference between the diffraction angles of the two diffracted lights becomes 41.5 degrees as shown in FIG. 3, and the light of the wavelength λ1 or the wavelength λ2 is easily identified by the sensor 17. it can.

That is, in the case of the holographic grating 18, since the angle difference between the diffraction angles of the two diffracted lights is large as described above, the FSR also increases as shown in FIG. Is condensed on the sensor 17 which measures in a predetermined range width, whereby the spectrum can be easily identified.

The light intensity output as a signal from the sensor 17 can be represented by the product of the diffraction efficiencies of the first and second gratings, for example, the diffraction efficiency of the first grating (holographic grating 18). Is assumed to be 30% and the diffraction efficiency of the second grating (the echelle grating 19) is assumed to be 50%, the light output when these gratings are diffracted three times in total (the output of the light detected by the sensor 17). Is
30% / 50% / 30% = 4.5% (relative intensity to the light intensity of light incident on the holographic grating 18).

As described above, in the present embodiment, the relative intensity of the light output when diffracted three times by the grating is 4.5%, and is three times by the diffraction grating (grating) of the spectrometer described in the above publication. An output nearly ten times as high as the relative intensity of the output light of 0.55% when diffracted is obtained.

The reason that the spectrometer 10 can obtain an output nearly ten times as compared with the conventional one is that not only the above-mentioned first and second gratings are used but also the spectrometer described in the above-mentioned publication. This is because the partial reflection mirror is not used, so that the loss (decrease in the amount of light) due to the partial reflection mirror can be suppressed.

Further, since the partial reflection mirror is not used, the intensity of the spectrum detected by the sensor 17 depends only on the diffraction efficiency of the grating, so that the light intensity is measured at a high S / N ratio. be able to.

As described above, in this embodiment,
Since the spectrum can be easily identified and the light intensity of the light having the spectrum can be nearly ten times higher than that of the conventional one, the grating having a large number of groove lines and being usable at a low diffraction order as the first grating. (For example, a holographic grating).

On the other hand, as described above, if the first
In the case where an echelle grating is used as the grating of the above, if the diffraction order m1 = 100, then m1 · λ1
= M2 · λ2 (m2 is an integer), since all wavelengths λ2 are observed at the same position as λ1, if there are multiple spectra in the wavelength range close to wavelength λ1, the identification of those spectra is It becomes difficult.

That is, in the case of the echelle grating, the FSR is small as shown in FIG.
In this case, the spectra of light of different orders come close to each other, and the light of these two wavelengths is measured in a predetermined range width in the sensor, which makes it difficult to distinguish these spectra.

Next, the operation of the spectrometer 10 having such a configuration will be described with reference to FIG.

As shown in FIG. 1, the light emitted from the light source 11 is guided to the slit 13 via the optical fiber 12, where it is diffracted and then reflected by the mirror 14.

The light reflected by the mirror 14 becomes parallel light by passing through the collimating lens 16, and the parallel light enters the holographic grating 18.

The incident parallel light is diffracted by the holographic grating 18 at an angle of the diffraction angle that changes according to the wavelength of the light, and the diffracted light (first diffracted light) is converted into an echelle grating 19.
Incident on.

The first diffracted light is diffracted by the echelle grating 19 arranged in a retro manner, and the diffracted light (second diffracted light) again enters the holographic grating 18.

The second diffracted light is diffracted again by the holographic grating 18, and the diffracted light (third diffracted light) is transmitted to the collimating lens 16.
The light is reflected by the mirror 15 and condensed on the sensor 17.

Next, the spectrometer of the present embodiment and a conventional Zellni-Turner type spectrometer will be described based on a specific design example.

First, the spectrometer of this embodiment will be described.

1. As the light source, one of an iron (Fe) lamp, a mercury (Hg) lamp, and a platinum (Pt) lamp is used.

The vacuum wavelength of the iron (Fe) lamp is 248.4221 nm, 248.4935 nm and 248.8893 nm, and the vacuum wavelength of the mercury (Hg) lamp is 248.275 nm and 248.34.
7 nm and 248.457 nm, and platinum (Pt)
The vacuum wavelength in the lamp is 248.176 nm, 24
8.792 nm and 248.949 nm.

2. Design Example (a) Wavelength to be Measured λ = 248 nm (b) First Grating A holographic grating having 3600 groove lines / mm is used. The first-order light (first-order diffracted light) diffracted by the holographic grating is used.

(C) Second grating An echelle grating having a groove number of 85.34 lines / mm is used. The blaze angle is 78.7 degrees. 93 order light (93 order diffracted light) diffracted by this echelle grating is used. (D) The focal length of the lens is 500 mm.

(E) The slit width is 25 μm.

(F) Sensor channel (ch) width = 25
μm.

(G) The incident angle of the incident light on the holographic grating is 84.21 degrees.

Under the above conditions, the wavelength (dispersion value) per sensor channel is 0.094 pm / ch.

This means that a plurality of spectral lines can be realized with high resolution, and that a plurality of spectra can be separated and a baseline of the spectrum can be accurately measured.

In the holographic grating, the ratio between the input beam width W1 and the output beam W2 is W2
/W1=9.86, and the output beam width is obtained by expanding the input beam width by about 10 times.

This means that the beam width of the light incident on the holographic grating disposed before the echelle grating can be reduced.
Therefore, the effective range of the collimating optical element (for example, a collimating lens) for forming parallel light to the holographic grating can be reduced, and the collimating optical element can be downsized.

Next, a case where a holographic grating is used in a conventional spectrometer having a Zellni Turner type arrangement will be described.

(A) Method: Czerny-Turner type arrangement (b) First grating A holographic grating having 3600 grooves / mm is used. The first-order light (first-order diffracted light) diffracted by the holographic grating is used.

(C) The focal length of the concave mirror is 1500 mm.

(D) The slit width is 25 μm.

(E) Sensor channel (ch) width = 25
μm.

(F) The incident angle of the incident light on the holographic grating is 84.21 degrees.

Under the above-described conditions, the wavelength (dispersion value) per sensor channel is 0.92 pm / ch, and the size of the spectrometer is about three times as long as that of the present embodiment (the focal length is three times).
Despite this, the variance value can only be realized by one order of magnitude worse. That is, even if the grating used in the conventional spectrometer is a holographic grating similar to that of the present embodiment, the dispersion value is 1 despite the fact that the spectrometer size is three times as described above. Unfortunately, a high-resolution spectrometer cannot be realized.

As described above, according to the present embodiment,
The wavelength range is limited by the first grating, the light in the limited wavelength range is expanded to high resolution by the second grating, and the light expanded to high resolution is further returned to the first grating and diffracted. By doing
It is possible to realize a high-resolution spectrometer in which diffracted lights of different diffraction orders do not overlap.

The relative intensity of the light detected by the sensor 17 is 4.5%, and the relative intensity of the light detected by the photometer in the spectrometer described in the above publication is 0.55%.
%, An output nearly 10 times higher can be obtained.

Further, the ratio of the incident beam width W1 to the output beam W2 in the holographic grating is expressed as W2
Since / W1 is set to 9.86, the effective diameter of the collimating lens can be reduced, and the size of the collimating lens can be reduced.

[Second Embodiment] FIG. 5 shows a configuration diagram of a spectrometer 20 according to a second embodiment.

The spectrometer 20 shown in the figure has the same configuration as the spectrometer 10 shown in FIG. 1 except that the collimating lens 16 is omitted and a concave mirror 21 is added. Note that, in the same figure, portions that perform the same functions as the components illustrated in FIG. 1 are denoted by the same reference numerals.

The operation of the spectrometer 20 having the following configuration will be described with reference to FIG.

As shown in FIG. 5, the light emitted from the light source 11 is guided to the slit 13 via the optical fiber 12, where it is diffracted and then reflected by the mirror 14.

The light reflected by the mirror 14 is reflected by the concave mirror 2
At 1, the light is reflected as parallel light and enters the holographic grating 18.

After that, as described in the first embodiment, the parallel light reflected by the concave mirror 21 is diffracted by the holographic grating 18, and this diffracted light (first diffracted light) is Grating 1
9 is incident.

The first diffracted light is diffracted by the echelle grating 19, and the diffracted light (the second
Is incident again on the holographic grating 18, and the second diffracted light is further diffracted by the holographic grating 18 (third diffraction).
Is done.

The third diffraction light by the third diffraction is as follows:
After being reflected by the concave mirror 21, the light is reflected by the mirror 15 and condensed on the sensor 17.

As described above, according to the second embodiment, the use of the concave mirror 21 instead of the lens eliminates the chromatic aberration caused by this lens, and makes it possible to measure light of any wavelength.

[Third Embodiment] FIG. 6 shows a configuration diagram of a spectrometer 30 according to a third embodiment.

The spectrometer 30 shown in the figure has a configuration in which the optical fiber 12, the two mirrors 14 and 15 are deleted, and the lens 31 is added to the configuration of the spectrometer 10 shown in FIG. Note that, in the same figure, portions that perform the same functions as the components illustrated in FIG. 1 are denoted by the same reference numerals.

The holographic grating 18 is
The collimating lens 16 is arranged so that the parallel light passing therethrough is incident thereon, and is arranged such that the outgoing light is emitted to the lens 31 located in a direction different from the incident direction of the incident light.

That is, the first diffraction order of the holographic grating 18 is set to “+1 order”, and the second diffraction order is set to “+2 order”.

The operation of the spectrometer 30 having the following configuration will be described with reference to FIG.

As shown in FIG. 6, the light emitted from the light source 11 is guided to the slit 13, is diffracted there, passes through the collimating lens 16, and is converted into parallel light by the holographic grating 18. Incident.

This parallel light is diffracted by the holographic grating 18, and the diffracted light, that is, the diffracted light of the “+ 1st” diffraction order (first diffracted light) is
The light enters the echelle grating 19.

The first diffracted light is diffracted by the echelle grating 19, and the diffracted light (second
Is incident on the holographic grating 18.

The second diffracted light is diffracted by the holographic grating 18, and the diffracted light, that is, the diffracted light of the “+ 2nd” diffraction order (which becomes the third diffracted light) passes through the lens 31. After that, the light is focused on the sensor 17.

As described above, according to the third embodiment, the first diffraction order of the holographic grating 18 is set to “+ 1st order”, and the second diffraction order is set to “+ 2nd order”. Since the light emission direction is different from the light emission direction, an image with less aberration can be formed on the sensor surface, and a highly accurate spectrum can be measured.

In the above-described embodiment, the diffraction order in the holographic grating 18 is “+1”.
Although the diffraction of the combination of the "next order" and the "+ 2nd order" has been described, other combinations of orders such as "+ 1st order" and "-1st order" and "+1" and "0th order" are also possible. is there.

With this functional configuration, “0”
When the “next” is used, the light intensity of the output light (light detected by the sensor 17) increases, although the variance value slightly deteriorates. Further, by detecting the diffracted light having a higher diffraction order such as “+ 2nd order” by the sensor 17, it is possible to measure the spectrum with higher accuracy.

[Fourth Embodiment] FIG. 7 shows a configuration diagram of a spectrometer 40 according to a fourth embodiment.

The spectrometer 40 shown in the same drawing has the same structure as the spectrometer shown in FIG. 1, except that the collimating lens 16 is omitted.
The configuration is such that a concave grating 41 is added instead of the holographic grating 18. Note that, in the same figure, portions that perform the same functions as the components illustrated in FIG. 1 are denoted by the same reference numerals.

The operation of the spectroscope 40 having the following configuration will be described with reference to FIG.

As shown in FIG. 7, the light emitted from the light source 11 is guided to the slit 13 via the optical fiber 12, reflected by the mirror 14, and then reflected by the concave grating 4.
Incident on 1.

Light incident on the concave grating 41 is
The light is diffracted by the concave grating 41 at an angle of the diffraction angle that changes according to the wavelength of the light, and the diffracted light (first diffracted light) enters the echelle grating 19.

The first diffracted light is diffracted by the retro-arranged echelle grating 19, and the diffracted light (second diffracted light) again enters the concave grating 41.

The second diffracted light is again diffracted by the concave grating 41 (third diffraction), and the diffracted light (third diffracted light) is reflected by the mirror 15 to be detected by the sensor. Light is condensed at 17.

As described above, according to the fourth embodiment, by using a concave grating as the first grating, the functions of the lens and the grating can be combined with one element, and thus the components of the spectrometer can be used. And the adjustment for detecting light of a specific wavelength is facilitated by the reduction in the number of components.

[Fifth Embodiment] FIG. 8 shows a configuration diagram of a spectrometer 50 according to a fifth embodiment.

The spectrometer 50 shown in the figure has a configuration in which the collimating lens 16 and the lens 31 are deleted from the spectrometer shown in FIG. 6, and a concave grating 51 is added instead of the holographic grating 18. I have. Note that, in the same figure, portions that perform the same functions as the components illustrated in FIG. 6 are denoted by the same reference numerals.

As in the case of the sixth embodiment, the concave grating 51 is arranged so that the light emitted from the slit 13 is incident, and the sensor 17 positioned in a direction different from the incident direction of the incident light. It is arranged so that outgoing light is emitted.

That is, the first diffraction order of the concave grating 51 is set to “+1”, and the second diffraction order is set to “+”.
Secondary ".

The operation of the spectrometer 50 having the following configuration will be described with reference to FIG.

As shown in FIG. 8, when light from the slit 13 enters the concave grating 51, the light is diffracted by the concave grating 51, and the diffracted light, that is, the “+ 1st” diffraction order The (first diffracted light) enters the echelle grating 19.

The first diffracted light is diffracted by the echelle grating 19, and the diffracted light (second
Is incident on the concave grating 51.

The second diffracted light is transmitted to the concave grating 5
1 and the diffracted light, ie, “+”
Diffracted light of the “second order” diffraction order (which becomes third diffracted light) is focused on the sensor 17.

In the above embodiment, the diffraction orders of the concave grating 51 are “+1 order” and “+2 order”.
Although the diffraction of the combination of “next order” has been described, other combinations of orders such as “+1 order” and “−1 order” and “+1” and “0 order” are also possible.

As described above, according to the fifth embodiment, the same effects as those of the third and fourth embodiments can be expected.

[Sixth Embodiment] FIG. 9 shows a configuration diagram of a spectrometer 60 according to a fifth embodiment.

The spectrometer 60 shown in the figure has a configuration in which a second holographic grating 61 is added in place of the echelle grating 19 in the configuration of the spectrometer shown in FIG. Has become. Note that, in the same figure, portions that perform the same functions as the components illustrated in FIG. 6 are denoted by the same reference numerals.

In this embodiment, the light incident on the holographic grating is diffracted four times, and the light incident on the echelle grating is diffracted once.

The operation of the spectrometer 60 having the following configuration will be described with reference to FIG.

As shown in FIG. 9, the parallel light from the collimating lens 16 incident on the holographic grating 18 is diffracted by the holographic grating 18 at an angle of the diffraction angle that changes according to the wavelength of the light. The diffracted light (first diffracted light)
The light enters the holographic grating 61.

The first diffracted light is diffracted by the holographic grating 61, and the diffracted light (second diffracted light) enters the echelle grating 19.

The second diffracted light is diffracted by the echelle grating 19, and the diffracted light (third diffracted light)
Is incident on the holographic grating 61 again.

The third diffracted light is diffracted by the holographic grating 61 (to become a fourth diffracted light), and further diffracted by the holographic grating 18 (to become a fifth diffracted light).

The fifth diffracted light is transmitted to the collimating lens 1
6, the light is reflected by the mirror 15 and condensed on the sensor 17.

As described above, according to the sixth embodiment, the first and second holographic gratings 1
The wavelength range is limited by 8 and 61, the light whose wavelength range is limited by the echelle grating 19 is expanded to a high resolution, and the light expanded to the high resolution is further divided into first and second holographic gratings 18. , 61 and diffracted, it is possible to realize a high-resolution spectrometer in which orders do not overlap.

[Seventh Embodiment] FIG. 10 shows a configuration diagram of a spectrometer 70 according to a seventh embodiment.

The spectrometer 70 shown in the figure has a configuration obtained by changing the arrangement of the holographic grating 18 and the echelle grating 19 in the configuration of the spectrometer shown in FIG. Note that, in the same figure, portions that perform the same functions as the components illustrated in FIG. 6 are denoted by the same reference numerals.

The diffraction angle of the diffracted light (first diffracted light) diffracted by the holographic grating 18 is 0.
Degree, that is, the holographic grating 18 is oriented in the normal direction of the holographic grating 18.
Adjust the installation angle.

The first diffracted light is the echelle grating 1
9 is incident. The first diffracted light is diffracted by the echelle grating 19, and the diffracted light (second diffracted light) is again transmitted to the holographic grating 18
Incident on.

In this arrangement, the angle of incidence of the second diffracted light on the holographic grating 18 is 0 degree, so that the light (first reflected light) specularly reflected by the holographic grating 18 is again subjected to the echelle grating. It is incident on 19.

The first reflected light is diffracted by the echelle grating 19, and the diffracted light (third diffracted light) enters the holographic grating 18 again. The third diffracted light is diffracted by the holographic grating 18, and the diffracted light (fourth diffracted light) enters the collimator lens 16 and is reflected by the mirror 15.
And is detected by the sensor 17.

In this case, the second diffracted light is specularly reflected by the holographic grating 18, and at the same time, the second diffracted light is diffracted by the holographic grating 18, enters the collimating lens 16, is reflected by the mirror 15, and is reflected by the sensor 17. Is detected by

In order to separate the second diffracted light returning to the sensor 17 from the light returned to the sensor 17 by the fourth diffracted light, the installation angle of the echelle grating 19 is slightly shifted from the retro arrangement, and The second diffracted light and the fourth diffracted light can be imaged at different positions on the sensor 17.

As described above, according to the seventh embodiment, the echelle grating 19 diffracts twice and the holographic grating 18 diffracts twice, so that a higher resolution is obtained as compared with the first embodiment. (High dispersion)
Can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a first embodiment.

FIG. 2 is a diagram illustrating an arrangement relationship between a first grating and a second grating;

FIG. 3 is a diagram for explaining characteristics of a holographic grating.

FIG. 4 is a diagram for explaining the relationship between the number of groove lines of the grating and FSR.

FIG. 5 is a configuration diagram showing a configuration of a second embodiment.

FIG. 6 is a configuration diagram illustrating a configuration of a third embodiment.

FIG. 7 is a configuration diagram showing a configuration of a fourth embodiment.

FIG. 8 is a configuration diagram showing a configuration of a fifth embodiment.

FIG. 9 is a configuration diagram illustrating a configuration of a sixth embodiment.

FIG. 10 is a configuration diagram showing a configuration of a seventh embodiment.

FIG. 11 is a diagram for explaining features of the echelle grating.

FIG. 12 is a diagram for explaining an actual spectrum and a spectrum observed by a spectrometer having a small FSR.

FIG. 13 is a diagram illustrating characteristics in a state where two spectra overlap each other.

FIG. 14 is a diagram showing a configuration in a case where a unit for making one line is provided in the spectrometer disclosed in the official gazette.

FIG. 15 is a diagram showing a configuration in a case where a unit for making one line is provided in the spectrometer disclosed in the official gazette.

[Explanation of symbols]

 10, 20, 30, 40, 50, 60 Spectrometer 11 Light source 12 Optical fiber 13 Slit 14, 15 Mirror 16 Collimating lens 17 Sensor 18, 61 Holographic grating 19 Eschel grating 21 Concave mirror 41, 51 Concave grating

Claims (3)

[Claims] 1. A spectrometer having detection means for inputting light having a plurality of spectral lines having different wavelengths and detecting the output of the light, wherein the detecting means detects an output of a spectral line having a specific wavelength. Grooves of the number of groove lines that can be formed,
A first diffraction grating that can be used with a low diffraction order, and a second diffraction grating in which grooves that are smaller than the number of groove lines in the first diffraction photon are formed and that can be used in a retro configuration. A first diffraction grating selects a spectral line having a specific wavelength from the plurality of spectral lines, and diffracts the light of the selected spectral line into higher-order diffracted light by the second diffraction grating. A spectrometer characterized by: 2. The light having the plurality of spectral lines is diffracted by the first diffraction grating into low-order diffraction light, and the diffracted light is diffracted by the second diffraction grating into a high-order diffraction light. Diffracted into the next diffracted light, the diffracted light is returned to the first diffraction grating, and the output of the diffracted or reflected light from the first diffraction grating is detected by the detection means. The spectrometer according to claim 1, wherein: 3. The first diffraction grating is any one of a holographic grating, an ion-etched grating, a blazed grating, an echellet grating, and a concave grating, and the second diffraction grating is an echelle grating. 3. The spectrometer according to claim 1, wherein the spectrometer is one of a grating and a blazed grating.