JP2002131129A - Evert type spectroscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Evert type spectroscope which can correct astigmatism with simple structure. SOLUTION: The Evert type spectroscope has an incident optical part comprising a first cylindrical lens 1, a second cylindrical lens 2, a first slit 3, and a second slit 4: a diffractive grating 5: a collimator/camera mirror 6 which converts the luminous flux exiting the incident optical part into collimated light, reflects it back to the diffraction grating 5, collects, and reflects the light diffracted by the diffraction grating 5: and a linear array detector 7, which detects the reflected light. Of the pair of the cylindrical lenses, the light collecting direction of the former first cylindrical lens 1 is configured to be perpendicular to the diffraction direction, and the light collecting direction of the latter second cylindrical lens 2 is configured to be coincident with the diffraction direction. Astigmatism is corrected by adjusting the spacing between the pair of cylindrical lenses so that the amount of deviation of image formation position against the light collection direction for each of the pair of cylindrical lenses becomes nearly equal to the amount of deviation of focal point resulting from astigmatism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an evert type spectroscope, and more particularly to an evert type spectrometer capable of correcting astigmatism.

[0002]

2. Description of the Related Art In a Fasty-Ebert spectroscope, a single spherical mirror is used as an optical component because a collimator mirror for collimating a light beam and a camera mirror for forming an image of a diffracted light beam are both used. , A spectroscope having a simple structure including only a plane diffraction grating and an entrance slit. Since the number of optical components is small as described above, it has a feature of being resistant to misalignment and the like, and is used as a spectroscope mounted on an artificial satellite.

[0003]

However, in the Fasty-Evert type spectroscope, since the light beam is incident at a large angle with respect to the spherical mirror axis, the curvature of the spherical mirror projected in the light beam direction is changed in the spectral direction and the slit height direction. Because of the difference, the focal position also differs in the spectral direction and the slit height direction, and an aberration called astigmatism occurs. Therefore, when the detector is set at the focus position in the spectral direction, the incident slit image greatly extends in the slit height direction and protrudes from the light receiving surface of a normal detector, causing a problem that a large loss of light amount is caused. . Therefore, usually, in order to determine the field of view of the spectroscope, an incident optical unit using a spherical lens is provided in front of the entrance slit, and an observation target is imaged on the entrance slit.

The present invention has been made in view of the above problems, and a main object of the present invention is to provide an evert type spectroscope capable of correcting astigmatism without complicating the structure. is there.

[0005]

In order to achieve the above object, the present invention provides an incident optical section having a slit for narrowing incident light to a light beam having a predetermined width, diffracting means, and a light exiting from the incident optical section. In an evert type spectroscope having at least a reflecting mirror that converts a light beam into a parallel light and reflects the light diffracted by the diffracting means, and condenses the light diffracted by the diffracting means, the incident optical units are provided with respective predetermined directions. Cylindrical lenses that condense light only to the pair are arranged side by side in the direction of the incident light so that the condensing directions of the pair of cylindrical lenses are orthogonal to each other in a plane orthogonal to the incident light. Is set to.

In the present invention, it is preferable that the condensing direction of the cylindrical lens located at the preceding stage of the pair of cylindrical lenses is set so as to be orthogonal to the diffraction direction by the diffraction means.

Further, in the present invention, the shift amount of the imaging position of each of the light transmitted through the pair of cylindrical lenses with respect to the light collecting direction is substantially equal to the shift amount of the focus position of astigmatism. It is preferable that an interval between the pair of cylindrical lenses is set.

In the present invention, a plurality of the incident optical units are provided, and the incident light is divided into light in a predetermined wavelength range by a wavelength dividing means disposed in front of the incident optical unit. It may be configured to be incident on each of the plurality of incident optical units.

In the present invention, the first stage cylindrical lens may be constituted by a kinoform cylindrical lens.

As described above, the present invention provides a cylindrical lens in the incident optical section, thereby reducing astigmatism while retaining the advantage of a simple optical system that is strong in alignment, which is a feature of the Fasty-Evert type spectroscope. Can be corrected.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An evert type spectrometer according to the present invention, in a preferred embodiment thereof, comprises first and second espectors.
, An incident optical unit having first and second slits 3 and 4, a diffraction grating 5, and a light beam emitted from the incident optical unit is converted into parallel light and reflected by the diffraction grating. A collimator / camera mirror 6 for condensing and reflecting the light diffracted by the diffraction grating, and a linear array detector 7 for detecting the reflected light, and of the pair of cylindrical lenses, Is set so that the light collecting direction of the second cylindrical lens 2 at the subsequent stage coincides with the diffraction direction, and the image forming position of the pair of cylindrical lenses with respect to each of the light collecting directions. The astigmatism can be corrected by adjusting the distance between the pair of cylindrical lenses so that the shift amount of the focus position of the astigmatism becomes substantially equal to the shift amount of the focus position.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

Embodiment 1 First, an evert type spectroscope according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a view schematically showing a configuration of an evert type spectroscope according to a first embodiment of the present invention.
FIG. 3 is a diagram showing a state of image formation in directions orthogonal to each other by a cylindrical lens. FIGS. 3A and 3B are diagrams showing the effect of the present embodiment. FIG. 3A is a spot diagram obtained by an evert type spectroscope of the present embodiment, and FIG. 3B is a spot diagram obtained by a conventional evert type spectrometer. It is.

In this embodiment, a lens having a different focal length and a different focal position is used in combination with the incident optical section,
It corrects the astigmatism peculiar to the Fasty-Evert type spectroscope. Specifically, a first cylindrical lens 1 and a second cylindrical lens 2
Are combined to offset the astigmatism by shifting the focal positions of the vertical and horizontal cylindrical lenses by the difference between the focus positions due to astigmatism.

The details will be described below with reference to the drawings. As shown in FIG. 1, an incident light beam 8 is condensed by an incident optical unit including a first cylindrical lens 1, a second cylindrical lens 2, a first incident slit 3, and a second incident slit 4. You. The condensed light is collimated by a collimator / camera mirror 6 and then split by a diffraction grating 5. Then, the split light is output to the collimator / camera mirror 6.
Is reflected again, and an incident slit image is formed.

In the Evert type spectroscope having such a configuration,
Since an incident slit image is formed at a different position for each wavelength, a spectrum can be obtained by acquiring the incident slit image of each wavelength with the linear array detector 7.
Note that, as a reference coordinate system, the direction of the incident light beam 8 is the Z axis,
In a plane including the incident light 8, the center of the diffraction grating 5, and the center of the collimator / camera mirror 6, the direction orthogonal to the incident light 8 is represented by X
Y axis so as to form a right-handed system orthogonal to the X axis and Z axis.
Take the axis.

Next, the optical path of the incident optical section, which is a feature of the present embodiment, will be described with reference to FIG. The first cylindrical lens 1 condenses light in the Y direction (a direction orthogonal to the diffraction direction) as shown in the lower part of FIG. 2 to the first entrance slit 3 and the second cylindrical lens 2 to the upper part of FIG. As shown, the light is condensed in the X direction (diffraction direction) and the second
The observation target is imaged on each of the entrance slits 4.
Here, the first entrance slit 3 has a role of narrowing the field of view in the Y direction and a role of determining the size of the image in the Y direction in the linear array detector 7. Similarly, the second entrance slit 4 has a field of view in the X direction. And the role of determining the size of the X-direction image in the linear array detector 7.

In the following description, the size of the slit in the X direction is “slit width”, the size of the slit in the Y direction is “slit height”, and the size of the image in the X direction is “slit of the slit image”. If the size of the image in the Y direction is referred to as the “height of the slit image”, the size of the image is defined not only by these slit dimensions but also by aberrations.

Here, since the X direction is the direction in which the light is split by the spectroscope, the size of the image in the X direction determines the spectral resolution. Since the spectral resolution is important for the spectroscope, the spectral resolution is reduced. The linear array detector 7 is set at the best focus position in the X direction so as to maximize it. However, in the structure of a normal Fastie-Evert type spectroscope,
Linear array detector 7 at the best focus position in the X direction
Is adjusted, the best focus position in the Y direction shifts due to astigmatism, and the height of the slit image increases.

However, in the configuration of the present embodiment, the second field of view of the spectroscope in view of the X direction and the demand for the spectral resolution require
The position and the focal length of the cylindrical lens 2 and the position and the slit width of the second entrance slit 4 are uniquely determined, whereas the arrangement of the first cylindrical lens 1 and the first entrance slit 3 Since it is specified only by the requirement of the Y-direction visual field, there is a certain degree of freedom. Therefore,
By moving the first cylindrical lens 1 to an optimum value, the "difference 9 between the focal positions of the first cylindrical lens 1 and the second cylindrical lens 2" is adjusted, and the Y direction is also set to the best focus. Can be.

The above effect will be described with reference to FIG. FIG. 3A shows a spot diagram around a wavelength of 360 nm obtained by the evert type spectroscope of this embodiment. For comparison, FIG. 3B shows a spot diagram of a normal Fastie-Evert type spectroscope using a single lens as an incident lens. As can be seen from FIG. 3, the image size (image height) in the Y direction is very large in a normal Fastie-Evert spectroscope, whereas the image obtained by the detector of the present embodiment has an image height It can be seen that the astigmatism has been greatly reduced and the astigmatism has been greatly improved.

As described above, according to the evert type spectroscope of the present embodiment, two cylindrical lenses are arranged in combination in the incident optical section, and the focal positions of the vertical and horizontal cylindrical lenses are determined by astigmatism. Astigmatism can be offset by shifting the focus position only.

[Embodiment 2] Next, an evert type spectroscope according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a view schematically showing a configuration of an evert type spectroscope according to the second embodiment of the present invention.
FIG. 5 is a view of FIG. 4 as viewed from the Z direction. FIG. 6 is a diagram showing spot diagrams in each wavelength band of the evert type spectroscope of the present embodiment. In this embodiment,
It is an object of the present invention to provide an evert type spectroscope capable of coping with a wide wavelength range using a plurality of incident optical units and a plurality of rows of linear array detectors.

In general, since the degree of astigmatism in an Evert type spectroscope differs depending on the wavelength, the focal points of the first cylindrical lens 1 and the second cylindrical lens 2 shown in FIG. The optimum value of the "position difference 9" also differs depending on the wavelength. Therefore, when acquiring a spectrum over a wide wavelength range, the system according to the first embodiment has a problem that astigmatism increases again in a region where the wavelength is significantly different from the spectrum at a wavelength of 360 nm.

Therefore, for example, a wavelength of 300 to 420 nm
In order to reduce the aberration over a relatively wide wavelength range such as the range of the above, the incident light beam 8 is divided into light beams of several wavelength ranges, and in each wavelength range, the “first cylindrical lens 1 and the second cylindrical lens” in FIG. It is necessary to optimize the “difference 9 in the focal position of the lens 2”. In this embodiment, as shown in FIG.
For example, the luminous flux 11 having a wavelength of 300 to 340 nm
a, luminous flux 11b having a wavelength of 340 to 380 nm, wavelength 380
The light beam is divided into light beams in three wavelength ranges of a light beam 11c of ~ 420 nm.

Each of the light beams 11a, 11b, and 11c split by the wavelength selection element 10 is guided by a plane mirror 12 to an incident optical unit optimized so that astigmatism is minimized in each wavelength region. I will Light rays after the incident optical section are similar to those in the system of the first embodiment described above. The light rays are collimated by the collimator / camera mirror 6 shown in FIG.

As shown in FIG. 5, to prevent the spectra in each wavelength range from being mixed on the linear array detectors 7a, 7b, 7c, the incident optical unit 13 in each wavelength range is used.
a, 13b, and 13c are respectively shifted by several mm in the Y direction, and corresponding to the respective incident optical units 13a, 13b, and 13c,
The three linear array detectors 7a, 7b, 7c are also arranged in parallel at a distance of several mm in the Y direction.

The effect of the Evert type spectroscope having such a configuration will be described with reference to FIG. FIG. 6 shows a spot diagram of the Evert type spectroscope of the present embodiment obtained near the center wavelength of each wavelength range. As for each center wavelength, (a) is 320 nm, (b) is 360 nm, and (c) is )
Is 400 nm. As can be seen from FIG. 6, it can be seen that a very good image-forming property with little astigmatism is shown in a wide wavelength range having a central wavelength of 320 to 400 nm. In the configuration of the present embodiment, the linear array detectors 7a, 7
Since b and 7c are divided into three parts and installed in parallel, the size of the linear array detector can be reduced.

[Embodiment 3] Next, an evert type spectroscope according to a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a diagram showing characteristics of the kinoform lens. The evert type spectrometer of this embodiment uses a kinoform lens to make it possible to respond to a wide wavelength range.
It is an object to provide an Evert spectroscope.

The kinoform lens 16 can have both a lens function and a diffraction function by imprinting a mark on the surface. By optimizing the engraving pattern, it is possible to change the focal length for each wavelength. Therefore, as shown in FIG. 7, a kinoform lens is used as the front cylindrical lens, and the “first cylindrical lens 1 and the second cylindrical lens 1” of FIG.
It is possible to make an optimal design so as to reduce astigmatism due to the difference “9” in the focal position of the cylindrical lens 2 ”.

As described above, by using the kinoform lens as the front cylindrical lens, the first lens described above can be used.
In addition, astigmatism can be further reduced as compared with the second embodiment.

[0032]

As described above, according to the Evert type spectroscope of the present invention, two cylindrical lenses whose light converging directions are orthogonal to each other are arranged in combination in the incident optical section, and each of the cylindrical lenses is arranged. Is shifted by the difference between the focus positions due to astigmatism, the astigmatism can be canceled.

By using a kinoform lens as the front cylindrical lens, the focal length can be adjusted for each wavelength, and astigmatism can be further reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an evert type spectroscope according to a first embodiment.

FIG. 2 is a diagram showing an optical path in an incident optical unit of the Evert type spectroscope according to the first embodiment.

FIGS. 3A and 3B are diagrams showing an effect of the first embodiment, and FIG. 3A is a spot diagram of an evert type spectroscope of the present embodiment,
(B) is a spot diagram of a conventional Evert type spectroscope.

FIG. 4 is a diagram showing a configuration of an evert type spectroscope according to a second embodiment.

FIG. 5 is a cross-sectional view of a Evert type spectroscope according to a second embodiment, taken along a plane orthogonal to incident light.

FIG. 6 is a diagram illustrating the effect of the second embodiment, and is a spot diagram in different wavelength bands of the Evert type spectroscope of the present embodiment.

FIG. 7 is a diagram illustrating an optical path of a kinoform lens used in an evert spectroscope according to a third example.

[Description of Signs] 1 First cylindrical lens 2 Second cylindrical lens 3 First entrance slit 4 Second entrance slit 5 Diffraction grating 6 Collimator / camera mirror 7 Linear array detector 7a Linear array detector (wavelength 300 7b Linear array detector (wavelength 340 to 380 nm) 7a Linear array detector (wavelength 380 to 420 nm) 8 Incident light 9 Difference in focal position between first cylindrical lens and second cylindrical lens 10 Wavelength sorting element 11a Light flux having a wavelength of 300 to 340 nm 11b Light flux having a wavelength of 340 to 380 nm 11a Light flux having a wavelength of 380 to 420 nm 12 Planar mirror 13a Incident optical unit (wavelength 300 to 340 nm) 13b Incident optical unit (wavelength 340 to 380 nm) 13c Incident optical unit (wavelength 380) ~ 420n m) 14a Center line of the incident optical unit 13a 14b Center line of the incident optical unit 13b 14c Center line of the incident optical unit 13c 15a Light beam having a wavelength of 300 nm 15b Light beam having a wavelength of 300 nm 16 Kinoform lens

Claims (7)

[Claims] 1. An incident optical section having a slit for narrowing incident light into a light beam having a predetermined width, a diffracting means, and converting a light beam emitted from the incident optical section into parallel light and reflecting the parallel light onto the diffracting means. An evert type spectroscope having at least a reflecting mirror for condensing the light diffracted by the diffracting means, wherein a cylindrical lens for condensing light only in a predetermined direction is provided in the incident optical section in the incident light direction. An evert type spectroscope, wherein a pair of juxtaposed parallel lenses is arranged such that the light condensing directions of the pair of cylindrical lenses are orthogonal to each other in a plane orthogonal to the incident light. 2. A method according to claim 1, wherein said pair of cylindrical lenses includes:
2. The Evert type spectroscope according to claim 1, wherein the light condensing direction of the cylindrical lens located at the preceding stage is set so as to be orthogonal to the direction of diffraction by the diffraction means. 3. The pair of cylindrical lenses so that the amount of shift of the imaging position of each of the light transmitted through the pair of cylindrical lenses with respect to the focusing direction is substantially equal to the amount of shift of the focus position of astigmatism. The Evert type spectroscope according to claim 1 or 2, wherein an interval is set. 4. The apparatus according to claim 3, wherein said first-stage cylindrical lens is formed so as to be movable in said incident light direction, and said shift of said image-forming position is adjusted by movement of said first-stage cylindrical lens. Evert type spectrometer. 5. A plurality of said incident optical units are provided, and said incident light is divided into light of a predetermined wavelength range by a wavelength dividing means disposed in a stage preceding said incident optical unit. 5. The light incident on each of
An Evert type spectrometer according to any one of the above. 6. A shift amount of the focus position of astigmatism with respect to a center wavelength of light incident on each of the incident optical units, wherein a shift amount of the image forming positions of the pair of cylindrical lenses included in each of the incident optical units is different from each other. The evert type spectrometer according to claim 5, wherein the amount is set to be substantially equal to the amount. 7. The evert type spectroscope according to claim 1, wherein said first stage cylindrical lens is constituted by a kinoform cylindrical lens.