JP2008185525A - Spectrometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce stray light as much as possible in a spectrometer wherein the F value of outgoing luminous flux is variable. <P>SOLUTION: A light trapping member 20 having a plurality of projecting pieces 21 along the direction of an optical axis C just before the exit slit 16 of the spectrometer is made replaceable and detachable, and can be replaced easily with a light trapping member 20 whose projecting pieces 21 are different in projection length. By attaching a member 20 having projecting pieces 21 of shorter projection lengths so as not to interrupt diffraction light when the F value of the outgoing luminous flux is small, and attaching a member 20 having projecting pieces 21 of longer projection lengths when the F value of the outgoing luminous flux is large, the clearance between the envelope of the luminous flux and the inner edge of each projecting piece 21 is narrowed to interrupt and prevent stray light from passing through this clearance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a spectroscope widely used in an optical apparatus such as a spectrophotometer, and more particularly to a technique for reducing stray light in the spectroscope.

  A spectroscope for taking out monochromatic light having a specific wavelength is widely used in optical devices such as a spectrophotometer. FIG. 3 is a schematic configuration diagram of a general spectroscope.

  Light including various wavelength components emitted from the light source 2 is condensed to the incident port 11 of the spectrometer 1 through the incident optical system 3 and taken into the spectrometer 1 through the entrance slit 12. This light is reflected by the reflecting mirror (collimating mirror) 13 and converged on the grating surface of the concave diffraction grating (wavelength dispersion element) 14. The light (diffracted light) wavelength-dispersed by the concave diffraction grating 14 is reflected by the reflecting mirror (focus mirror) 15 and condensed on the exit slit 16, and the diffracted light having a specific wavelength passes through the exit slit 16 and exits. The light is emitted from the port 17.

  In such a spectroscope 1, it is desirable to suppress as much as possible the emission of light having an undesired wavelength other than that defined by the diffraction formula of the concave diffraction grating 14, that is, stray light. For this reason, stray light has been conventionally reduced by various methods. For example, light that hits the edge of a reflector provided inside the spectroscope may be reflected in an undesired direction and become stray light. In view of this, it has been attempted to reduce stray light by reducing the reflected light in an undesired direction by providing a black shading band at the edge of the reflecting mirror. In addition, stray light may be reduced by installing an optical trap plate with a substance having a high light absorption rate attached to a portion where a relatively large amount of undesired light such as zero-order light strikes inside the spectrometer. (See, for example, Patent Document 1).

  By the way, in an optical apparatus using such a spectroscope, there is a case where it is desired to change a diaphragm (F value) of diffracted light to be extracted from the spectroscope depending on the purpose of the measurement. For example, in the spectroscope 1 having the above-described configuration, by changing the lens of the incident optical system 3 or the like, the aperture of the light taken into the spectroscope 1 from the incident port 11 is changed, and accordingly the diffraction emitted from the output port 17. The aperture of the light can also be changed. Of course, the variable range of brightness (that is, F value) as the spectroscope 1 varies depending on the size of the internal optical element, the optical path configuration, and the like.

  When it is desired to increase the analysis sensitivity, it is generally preferable to loosen the diffracted light aperture (decrease the F value) and increase the amount of light. On the other hand, in order to increase the resolution, the diffraction light is generally narrowed down. However, when the diffracted light is narrowed by narrowing the incident light, even if the amount of stray light is the same, the influence of the stray light is relatively increased, and the S / N of the diffracted light is lowered. Therefore, it is originally desirable to change the stray light removal structure in accordance with the extracted diffracted light aperture, but such a spectroscope has not existed in the past.

JP-A-2-254327

  The present invention has been made to solve the above problems, and provides a spectroscope capable of improving analysis accuracy by more effectively reducing stray light according to the diaphragm (brightness) of diffracted light. It is to be.

In order to solve the above problems, the present invention comprises an entrance slit, a wavelength dispersion element, and an exit slit, and the aperture of the diffracted light emitted from the exit slit is changed by changing the aperture of the light incident through the entrance slit. In a spectroscope that can be changed,
Provided on the optical path immediately before the exit slit is a stray light shielding optical trap having a projecting piece projecting in the optical axis direction from the outer edge of the luminous flux, and the projecting length of the projecting piece of the optical trap is taken out from the exit slit. It is characterized by a structure that can be changed according to the diffracted light aperture.

  Further, in the spectroscope according to a specific aspect of the present invention, the optical trap is detachable from the spectroscope main body, and the protruding length of the protruding piece according to the stop of the diffracted light taken out from the exit slit It can be set as the structure exchanged for the optical trap from which length differs.

  For example, when the diffracted light is darkened in order to increase the resolution, that is, when the focused light is emitted from the exit slit, the light flux passing through the optical trap is also reduced, so the projection length in the optical axis direction Even if an optical trap having a large protruding piece is used, the diffracted light is not blocked. On the other hand, if the projecting length of the projecting piece is increased, the incident angle range of light that can pass through the exit slit is narrowed and stray light is less likely to pass, and stray light removal performance is improved. That is, the stray light removal effect can be increased without blocking the desired diffracted light.

  On the other hand, for example, when the diffracted light is brightened to increase sensitivity, that is, when diffracted light with a loose aperture is emitted from the exit slit, an optical trap having a protrusion with a small protrusion length in the optical axis direction By using, diffracted light having a large luminous flux passing through the optical trap can be obtained without being blocked. Further, compared with a structure without an optical trap, the effect of removing stray light is obtained and the S / N is also good.

  Thus, according to the spectroscope according to the present invention, it is possible to increase the stray light reduction effect without blocking the diffracted light according to the brightness (F value) of the diffracted light extracted from the exit slit of the spectroscope. It becomes.

  A spectrometer according to an embodiment of the present invention will be described with reference to the drawings. The basic configuration of the spectrometer 1 according to the present embodiment is the same as that in FIG. 3 described above, but the stray light is blocked at the optical path immediately before the exit slit 16, specifically at the position indicated by the dotted line A in FIG. A light trap member 20 is attached.

  FIG. 1 is a schematic sectional view showing the structure and principle of the optical trap member 20. The optical trap member 20 has a plurality (three in this example) of projecting pieces 21 projecting from the outer periphery toward the optical axis C of the light beam converged toward the exit slit 16. Between adjacent projecting pieces 21, there is a recess 22 that is recessed in a direction perpendicular to the optical axis C. The projecting piece 21 itself is made of a material having a high light absorption rate, or a member having a high light absorption rate is attached to the surface thereof. As shown in FIG. The stray light Lb hits the projecting piece 21 and is repeatedly reflected and absorbed while proceeding to the back of the recess 22. Therefore, it is avoided that such stray light passes through the exit slit 16.

  When light with a small aperture (small F value) is incident on the spectroscope 1, the exit slit is formed with a relatively large incident angle as shown, for example, as "bright (low F value)" in FIG. The diffracted light is condensed on 16. In this case, in order not to block the diffracted light, the protruding length of the protruding piece 21 of the optical trap member 20 needs to be relatively small.

  On the other hand, when light with a large aperture (a large F value) is incident on the spectroscope 1, for example, as shown as “dark (large F value)” in FIG. 1, the exit slit has a relatively small incident angle. The diffracted light is condensed on 16. In this case, if the protruding length of the projecting piece 21 is small as described above, a gap between the outer edge of the light beam of the diffracted light and the inner end of the projecting piece 21 is increased, and for example, as shown by the arrow of the stray light La The stray light located outside the outer edge of the light beam passes through the exit slit 16. Therefore, when the incident angle of the diffracted light is small as described above, an optical trap member 20 having a projecting piece 21 having a large projecting length as shown by a dotted line in FIG. 1 is used. Thereby, the diffracted light can be allowed to pass through without removing the stray light La.

  FIG. 2 is a sectional view showing the mounting structure of the optical trap member 20. A positioning pin 32 is erected on the outside of the housing wall 31 on the emission port 17 side of the spectrometer 1, and the positioning pin 32 is inserted into a hole drilled in the optical trap member 20, thereby The position is determined. Furthermore, the position of the slit member 33 is also determined by inserting the positioning pin 32 into the hole formed in the slit member 33 provided with the exit slit 16 inside.

  As the optical trap member 20, for example, a plurality of protrusion lengths of the projecting pieces 21 for F value: 3, F value: 4, F value: 8, F value: 16, and the like differ depending on the diaphragm of the light flux. Prepare a thing, and a user replaces | exchanges the optical trap member 20 suitably according to the specification of the spectrometer 1 at that time. 2A shows an example in which the F value of the outgoing light beam is small, and FIG. 2B shows an example in which the F value of the outgoing light beam is large. By replacing only the optical trap member 20, the diffracted light is not blocked. Stray light can be reduced as much as possible.

  In the above embodiment, the protruding length of the protruding piece 21 is changed by exchanging the optical trap member 20 itself. However, for example, the protruding piece 21 is configured to be slidable and the user protrudes by sliding. The length may be changeable.

  Moreover, since the said Example is an example of this invention, even if it changes, corrects, and is added in the range of the meaning of this invention, it is included by the claim of this application.

The schematic sectional drawing which shows the structure and principle of the optical trap member in the spectrometer by one Example of this invention. Sectional drawing which shows the mounting structure of the optical trap member in the spectrometer of a present Example. The schematic block diagram of a spectrometer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Spectroscope 11 ... Incident port 12 ... Entrance slit 13 ... Reflector (collimator mirror)
14 ... Concave diffraction grating 15 ... Reflector (focus mirror)
16 ... Exit slit 17 ... Output port 20 ... Light trap member 21 ... Projection piece 22 ... Recess 2 ... Light source 3 ... Incoming optical system 31 ... Housing wall surface 32 ... Positioning pin 33 ... Slit member

Claims (2)

In a spectrometer that includes an entrance slit, a wavelength dispersion element, and an exit slit and can change the aperture of diffracted light emitted from the exit slit by changing the aperture of light incident through the entrance slit.
Provided on the optical path immediately before the exit slit is a stray light shielding optical trap having a projecting piece projecting in the optical axis direction from the outer edge of the luminous flux, and the projecting length of the projecting piece of the optical trap is taken out from the exit slit. A spectroscope having a structure that can be changed according to the diaphragm of the diffracted light.   The optical trap can be attached to and detached from the spectroscope main body, and the optical trap has a structure that is replaced with an optical trap having a different protrusion length of the protruding piece according to the diaphragm of the diffracted light extracted from the exit slit. The spectroscope according to claim 1.

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