JPH1114457A - Double-wavelength-region spectral scanning apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a double-wavelength-region spectral scanning apparatus in which the number of components is reduced, whose constitution is simple, which is made lightweight and compact and whose reliability is enhanced by a method wherein a rotation used to scan the wavelength of a diffraction grating and a rotation used to change a lattice face are performed by a single drive means. SOLUTION: In a double-wavelength-region spectral scanning apparatus, a double- wavelength region is spectrally scanned by using a diffraction grating. Two kinds of diffraction grating faces G1 , G2 whose diffraction characteristic is different are formed on both faces of a single parallel plane, and a double-sided diffraction grating 20 is constituted. Then, a shaft 21 is installed in the intermediate point between both grating faces G1 , G2 . The shaft 21 is coupled directly to a single drive means, e.g. to the output shaft of a step motor 22. A rotation used to scan the wavelength of the double-sided diffraction grating and a rotation used to change both lattice faces are performed. An origin slit 24 which is formed in a light-shielding blade 23 attached to the double-sided diffraction grating 20 is detected by a light interceptor 28, and the origin of the double-sided diffraction grating 20 is detected. Its detection signal is input to a CPU 32, and a spectral scanning operation is controlled continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for performing spectral scanning in two wavelength ranges, for example, a near infrared range and a near ultraviolet range.

[0002]

2. Description of the Related Art As an optical system for performing spectral scanning in two wavelength ranges, for example, a two-grating spectral optical system as shown in FIG. 7 has been conventionally known. In such an optical system, two plane diffraction gratings G ₁ and G ₂ having different diffraction characteristics are arranged in a back-to-back parallel manner on a switching table g mounted on a wavelength-scanning rotary table f for switching. _One of the plane diffraction gratings G ₁ and G ₂ used for spectroscopy is rotated by 180 ° by the mechanism h.

The above-mentioned switching table g and switching mechanism h are integrally rotated by a driving mechanism i of a rotating table f for wavelength scanning, while the monochromatic light after the spectral separation corresponds to the wavelength region. Thus, the light was selectively incident on _{one of} the _two detectors D ₁ and D ₂ due to the reciprocating operation of the switching mirror j.
Note that, in the same figure, a is a light source, b and e are slits, c and
d is a concave mirror.

[0004]

In the above-described conventional optical system, a rotating mechanism for wavelength scanning and a switching mechanism for switching the grating plane are separately provided, and the number of parts is small. However, the structure is complicated, the apparatus is large, the cost is high, and the number of movable parts is large.

The present invention has been made in view of such circumstances,
The number of parts is small, the configuration is simple, lightweight and compact,
It is an object of the present invention to provide a two-wavelength band spectral scanning device that can achieve low cost and high reliability.

[0006]

According to the present invention, means for solving the above-mentioned problems are constituted as follows. That is, according to the first aspect of the present invention, there is provided a two-wavelength band spectral scanning apparatus which performs a two-wavelength band spectral scanning by using a diffraction grating. A kind of diffraction grating surface is formed, a rotation axis is provided at an intermediate point between the two diffraction grating surfaces, and rotation for wavelength scanning and rotation for changing the grating surface are performed by a single driving means. It is characterized in that it can be carried out by driving the rotation shaft to rotate.

The rotation for wavelength scanning and the rotation for changing the grating plane can be operated by a single driving means, so that the configuration of the driving system is simplified, and the apparatus is lightweight and compact. And cost reduction, and the number of movable parts is reduced, so that reliability can be improved.

According to a second aspect of the present invention, the two types of diffraction grating surfaces in the first aspect of the invention are formed by bonding two replica gratings back to back.

According to a third aspect of the present invention, in the first aspect of the present invention, the two types of diffraction grating surfaces are formed by a replica grating formed simultaneously on both surfaces of a single plate-shaped substrate. And

According to a fourth aspect of the present invention, after spectroscopy by the two diffraction grating surfaces according to any one of the first to third aspects, two detectors corresponding to two wavelength ranges are provided. As means for selectively separating monochromatic light, a fixed dichroic mirror is used.

According to a fifth aspect of the present invention, the driving means is controlled and driven in response to a detection signal from the position detecting means for the two diffraction grating surfaces according to any one of the first to fourth aspects of the present invention. And a control means for outputting a control signal for controlling the rotation for the wavelength scanning and the rotation for changing the diffraction grating surface by a preset control program. It is characterized by:

According to a sixth aspect of the present invention, the control program according to the fifth aspect includes at least a step of detecting the origins of the two diffraction grating surfaces based on an origin detection signal from the position detecting means. Moving one of the diffraction grating surfaces up to the scanning start position, performing one of the diffraction grating surfaces in a stepwise sequential spectral scanning, and moving the other diffraction grating surface up to the scanning start position. The method is characterized in that a step of performing the step of sequentially performing spectral scanning by the other diffraction grating surface is sequentially incorporated with time.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the two-wavelength band spectral scanning device of the present invention will be described in detail. Figure 1 shows Czerny
Reference numeral 1 denotes a light source, 2 denotes a light source lens, 3 denotes an entrance slit, 4 denotes a collimating mirror, G ₁ ,
G ₂ is a diffraction grating surface, 6 is a camera mirror, 7 is an exit slit,
10 is a dichroic mirror (dichroic mirror), 11, 1
Reference numeral 3 denotes a detection lens, and reference numerals 12 and 14 denote detectors. Both diffraction grating surfaces G _{1 and} G ₂ have different diffraction characteristics and are formed on both surfaces of a single parallel plane to constitute a double-sided diffraction grating 20. And a rotating shaft 21 is provided at an intermediate point between the two lattice planes,
The rotating shaft 21 is directly connected to a single driving means, for example, the output shaft of a step motor 22, so that the double-sided diffraction grating 20 can be rotated for wavelength scanning and rotated for changing the grating surface. .

A light-shielding blade 23 is integrally attached to the double-sided diffraction grating 20. An origin slit 24 formed in the light-shielding blade 23 is detected by an optical interrupter (position detecting means) 28, so that the double-sided diffraction grating 20 is detected. Lattice 2
A zero (0) origin can be detected, and the detection signal is input to a CPU (control means) 32 via an interface 31, and a control output is sent from the CPU 32 to a control circuit 33 for driving the step motor 22 via the interface 31. In addition, as described later, the apparatus is configured so that spectral scanning in two wavelength ranges can be continuously controlled according to a preset control program.

The spectral scanning in two wavelength ranges will be described.
The wide-wavelength light emitted from the light source 1 is condensed on the entrance slit 3 by the optical lens 2, and is collimated by the collimating mirror 4.
And one diffraction grating surface G in the double-sided diffraction grating 20
₁ (for example, 300 grooves / mm for near-infrared region, blaze wavelength 1.5 μm). The diffraction grating surface G ₁ is rotated about the rotation axis 21 with respect to the parallel light beam 29 by the step motor 22, and the diffracted light forms an image on the exit slit 7 by the camera mirror 6, and passes through the wavelength band light. Is incident on a dichroic mirror 10 and is condensed by a detection lens 11 on a detector 12 for the near infrared region.

When the spectral scanning reaches a second wavelength range, for example, a near ultraviolet range, the double-sided diffraction grating 2 is
0 is rotated by 180 ° and the other diffraction grating surface G ₂ (for example, 6
00 lines / mm, and a blaze wavelength of 0.3 μm) are arranged in the parallel light flux 29 and the stepping motor 22 rotates the rotating shaft 2.
1 rotated by a predetermined step the diffraction grating surface G ₂ is relative to the parallel light flux 29 around the, diffracted light camera mirror 6
An image is formed on the exit slit 7, and the wavelength band light passing therethrough is reflected on the surface of the dichroic mirror 10 and is condensed by the detection lens 13 on the detector 14 for the near ultraviolet region.

The light-shielding blade 23 integrated with the double-sided diffraction grating 20 is for detecting the reference point of the double-sided diffraction grating 20, and the position of the origin slit 24 is detected by the optical interrupter 28. Accordingly, to be able to verify that the diffraction grating surface G ₁ is in the position of the reference origin, the diffraction grating surface G being scanned by integrating the feed pulse for driving from the origin (step number)
₁ (or G ₂ ) and the rotation angle, that is, the spectral wavelength,
It can be easily managed by software.

In the present invention, the double-sided diffraction grating 20 is used.
Is rotated / rotated by a single step motor 22 to perform spectral scanning in two wavelength ranges. For this purpose, one diffraction grating surface G ₁ and the other diffraction grating surface G ₂ With the center of rotation / rotation P (rotation axis 2
1 (center of 1) (see FIG. 3). This is because the imaging characteristics in the ray traveling direction are greatly affected by the offset amount between the lattice plane and the rotation axis, and it is better to set a certain amount of offset r rather than the ideal state of offset 0 that has been conventionally considered. This is because it has been confirmed that good imaging characteristics can be obtained as a result depending on the design conditions of the optical system. That is,
By forming the double-sided diffraction grating 20 relatively thin and setting an appropriate offset r, good imaging characteristics can be secured, and the characteristics of the present invention can be utilized.

The spectral scanning in the two wavelength ranges by the double-sided diffraction grating 20 can be performed with very good operability, for example, according to the flow shown in FIG. 2 by a control program preset and stored in the CPU 32. Note that X represents the count amount, and the numerical value represents one rotation of the step motor 22 at 8000.
In a specific example in the case of steps, both diffraction grating surfaces G ₁ , G ₂
Extracts 80 wavelengths.

[0020] First, with the start of the wavelength scan, by the light interrupter 28 to confirm the reference origin of the diffraction grating surface G ₁ (S1, S2), is incremented the diffraction grating surface G ₁ to the scan start position (S3). Was then incremented steps for the wavelength scanning (S5), whether, for example, lookup tables that do diffraction grating surface G ₁ is located in the photometric wavelength position confirmed by (LUT) or the like (S6)
After that, the detector 12 (or 14) is selected and the detection output is taken in (S7). The above steps S5 to S7 are repeated repeatedly until the number of steps reaches a first predetermined value (1590 <x <1610) (S4), thereby performing near-infrared spectral scanning.

Next, it is determined whether or not the scanning is performed on the diffraction grating surface G ₂ (S 8). If not, the scanning is advanced to the scanning start position of the diffraction grating surface G ₂ (S 9). Until the step number reaches the second predetermined value (5950 <x <5970) (S4), the steps S5 to S7 are repeated and the near-ultraviolet spectral scanning is performed. After repetition, S8
And x> 4000, and confirms the stop of scanning (end) in S10, and ends the flow. However, if the scanning is not completed in S10, the remaining number of one rotation (8000 steps) is determined in S11 (step S11). That is, step 2040 is advanced.

As described above, since the direct drive system using the single step motor 22 is employed, a simple and lean control program can be implemented with good operability, and the number of movable parts is reduced with the compactness of the apparatus. Therefore, the causes of troubles are reduced, and highly reliable spectral scanning can be realized at low cost.

FIGS. 4A and 4B show an example in which the light-shielding blade 23 shown in FIG. 1 is replaced by a disk-shaped light-shielding plate 26. Simpler than if. That is, by reading the number of steps from the time when the reference origin is detected, the positions of the diffraction grating surfaces G ₁ and G ₂ at any time can be detected, and the reference origin can be calculated back from the position. it can. The original signal for detecting the reference origin is the diffraction grating surface G
_1, unlike the light shielding blade system 1 capable of also serving as a position detecting status signals G _2, may be managed only accumulated walking notation x, corresponds to the flow of FIG. In this case, also in this case, the output shaft of the step motor 22 has a simple configuration in which the output shaft is directly connected to the double-sided diffraction grating 20.

FIG. 5 shows a modified example of the detection and focusing optical system, in which the two detection lenses 11 and 13 shown in FIG.
The light is condensed on the detectors 12 and 14 via the dichroic mirror 10 fixedly arranged by the condensing concave mirrors 15.

FIG. 6 shows a double-sided diffraction grating 2 used in the present invention.
0 is a schematic view showing an example of a manufacturing method of the first adhesive.
8 is formed by bonding back together and integrating them. Although not shown, by forming two types of replica gratings on both surfaces of a single plate-like substrate, a double-sided diffraction grating with less distortion deformation can be manufactured.

[0026]

As described above, according to the two-wavelength spectral scanning apparatus of the present invention, two types of diffraction grating surfaces having different diffraction characteristics are formed on both surfaces of a single parallel plane, and both diffraction gratings are formed. By rotating the rotation axis provided at the intermediate point between the surfaces by a single driving means, rotation for wavelength scanning,
The rotation for changing the grating plane is performed, so that the grating constant and the blaze wavelength corresponding to each wavelength region can be set on the two kinds of grating planes, and a complicated and expensive grating switching mechanism like the conventional one. As a result, operability is improved, reliability is improved, high overall performance is obtained, and light weight, compactness, and low cost can be achieved.

Also, if the two replica gratings are bonded back to back to form a double-sided diffraction grating, the offset between the grating surface and the rotation axis position can be set appropriately, and the imaging aberration in wavelength scanning is within the allowable range. Inside, and the accuracy can be improved.

Furthermore, by simultaneously forming a replica grating on both sides of a single plate-shaped substrate, a double-sided diffraction grating with less distortion deformation can be manufactured.

Further, if a fixed dichroic mirror is used as a means for selectively separating monochromatic light in a wavelength range corresponding to two detectors after spectroscopy, it is possible to omit a movable part and a driving mechanism, Light utilization efficiency can be improved. In addition, if a composite detector that can cover two wavelength regions to be subjected to spectral scanning with one detector can be used, it goes without saying that a dichroic mirror or a second detection and focusing system is not required. .

Further, a simple and lean control program can be set for a single driving means, and spectral scanning over two wavelength ranges can be realized with extremely high operability. High spectral scanning can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a two-wavelength band spectral scanning device of the present invention.

FIG. 2 is a flowchart illustrating an example of a control flow of spectral scanning in the same two wavelength ranges.

FIG. 3 is an explanatory diagram of setting of an offset between both diffraction grating surfaces.

FIG. 4A is a plan view of a light shielding plate integrated with the double-sided diffraction grating, and FIG. 4B is a front view.

FIG. 5 is another plan layout view of the dichroic mirror.

FIG. 6 is a sectional view of the double-sided diffraction grating.

FIG. 7 is a configuration diagram showing an example of a conventional two-wavelength band spectral scanning device.

[Explanation of symbols]

G ₁ , G ₂ : diffraction grating surface, 10: dichroic mirror, 20: double-sided diffraction grating, 21: rotating shaft, 22: driving means, 23: light shielding blade, 28 ... position detecting means, 32 ... control means.

Claims (6)

[Claims] 1. A two-wavelength band spectral scanning apparatus which performs two-wavelength band spectral scanning using a diffraction grating, wherein two types of diffraction grating surfaces having different diffraction characteristics are formed on both surfaces of a single parallel plane. A rotation axis is provided at an intermediate point between the two diffraction grating surfaces, and rotation for wavelength scanning and rotation for changing the grating surface are rotationally driven by a single driving means. A two-wavelength band spectral scanning device, characterized in that it is configured to be able to perform the above-mentioned operations. 2. The two-wavelength band spectral scanning device according to claim 1, wherein the two types of diffraction grating surfaces are formed by bonding two replica gratings back to back. 3. The two-wavelength band spectral scanning apparatus according to claim 1, wherein the two types of diffraction grating surfaces are formed by replica gratings formed simultaneously on both surfaces of a single plate-shaped substrate. 4. A method for selectively separating monochromatic light from two detectors corresponding to two wavelength ranges after spectral separation by the two diffraction grating surfaces, wherein a fixed dichroic mirror is used. The two-wavelength band spectral scanning device according to claim 1, wherein: 5. A control means for receiving a detection signal from a position detecting means of the two diffraction grating surfaces and outputting a control signal for controlling and driving the driving means, wherein the wavelength is controlled by a preset control program. 5. The two-wavelength band spectroscopy according to claim 1, wherein a rotation for scanning and a rotation for changing a diffraction grating surface can be continuously operated. Scanning device. 6. The control program includes at least:
A step of detecting the origin of the two diffraction grating surfaces by an origin detection signal from the position detecting means, a step of stepping one of the diffraction grating surfaces to a scanning start position, and a step of sequentially performing the one of the diffraction grating surfaces. The step of performing the spectral scanning in a step, the step of moving the other diffraction grating surface up to the scanning start position, and the step of sequentially performing the spectral scanning by the other diffraction grating surface sequentially, The two-wavelength band spectral scanning device according to claim 5, wherein the spectral scanning device is incorporated.