JP2006047270A - Wavelength-variable monochromatic light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength-variable monochromatic light source which can eliminate the problem of chromatic aberrations, while using a lens in an output optical system and which can adjust the irradiated area without decreasing the amount of light. <P>SOLUTION: The zoom lens (lens system 18) is used in the output optical system 3 of the wavelength variable monochromatic light source. There are provided a zoom-driving mechanism 23 for changing the focal length of the lens system 18 and a focusing mechanism 22 for performing focal point adjustment, by moving the overall or a part of the lens system 18 with respect to the optical axis direction thereof. Further, for the automatic control therefor, there are provided a half mirror 19, an image sensor 20, and a controller 21. Accordingly, chromatic aberrations can be eliminated by readjusting the focal point when the output wavelength is varied, and the irradiated area can be adjusted by the zooming. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wavelength tunable monochromatic light source used in absorption spectroscopic analysis or the like, and particularly to an output optical system thereof.

A spectroscope is used as a monochromatic light source whose wavelength can be arbitrarily selected within a certain range.
FIG. 4 shows a basic configuration example of the spectrometer. This is an optical system configured by arranging a light source, a mirror, and the like with a diffraction grating (grating) as a center, and is known as a Zerni-Turner spectrometer (see, for example, Patent Document 1).

  In the figure, light emitted from a light source 11 is collected by a collecting mirror 12, passes through an entrance slit 13, converted to parallel light by a collimator mirror 14, and sent to a grating 15. Here, of the wavelength-dispersed light, light in a predetermined wavelength range is collected by the imaging mirror 16, and an image of the entrance slit 13 (hereinafter simply referred to as an image) is formed on the projection surface 17. The projection surface 17 is a virtual surface, and in the case of spectroscopic analysis, a sample cell (not shown) is placed here, and the output monochromatic light is irradiated to the sample cell, and the luminous intensity of the light transmitted therethrough is measured. It is comprised so that it may detect with a light-receiving part (not shown). When the grating 15 is rotated around an axis perpendicular to the paper surface passing through the surface center of the grating 15, the wavelength of the light reaching the position of the exit slit 17a changes. can do.

  In some cases, the projection surface 17 is provided with an exit slit 17a through which monochromatic light is extracted. The monochromatic light output from the spectroscope is irradiated to an irradiation target (for example, a colorimeter cell) for the purpose of analysis and measurement. At that time, an optical fiber is used to guide the monochromatic light to the irradiation target. May be. In this case, a connection device for efficiently transmitting light from the spectroscope to the optical fiber is required.

FIG. 5 shows a configuration example of a conventional connection device for a spectroscope and an optical fiber.
In the figure, reference numeral 10 denotes a spectroscope, which is composed of an optical system as shown in FIG. 4, for example. Reference numeral 8 denotes an optical fiber, and only the end portion close to the spectroscope 10 is shown in the figure. Reference numeral 7 denotes a relay lens that transmits an optical image to another position while appropriately enlarging / reducing it. Here, an image of the exit slit 17a of the spectroscope 10 is transmitted to the end face of the optical fiber 8 to form an image again. Bear. Reference numeral 4 denotes a wavelength selection mechanism that selects the wavelength of the output light by rotating the grating 15 shown in FIG. 4, for example, one that is manually operated by an operator, or one that is automated using a motor or the like.
With such a configuration, the spectroscope 10 and the optical fiber 8 are connected via the relay lens 7, and the monochromatic light having the selected wavelength can be transmitted to an irradiation target (not shown). Although there are minor differences in the configuration of other conventional connection devices, the output light from the spectroscope 10 can be efficiently generated by forming the image of the exit slit 17a of the spectroscope 10 on the end face of the optical fiber 8. It is configured to be introduced into the optical fiber 8

  The optical system shown in FIG. 4 is divided into a light source unit 1 that collects and sends light from the light source 11, a spectroscopic optical system 2 that splits the light, and an output optical system 3 that projects and outputs the split light. For example, as shown in FIG. 7 of Patent Document 1, the spectroscopic optical system 2 and the output optical system 3 may be divided into two as a whole. Follow the category. As in the example of FIG. 5, when monochromatic light is extracted outside, the output optical system 3 is extended to the outside. That is, the relay lens 7 and the like in FIG. 5 can be considered as a part of the output optical system 3.

JP 2001-289713 A

  The optical system shown in FIG. 4 is a reflective optical system mainly configured by using a mirror as an optical element, but there is also a refractive optical system mainly configured by using a lens. Refractive optical systems have the advantage of being more resistant to vibration than reflective optical systems, but have the problem of chromatic aberration (a phenomenon in which the focal length varies depending on the wavelength). That is, when a lens is used in the output optical system, even if adjustment is made so that the image is correctly formed on the projection surface at a certain wavelength, the image is blurred and spreads at other wavelengths, so the so-called vignetting occurs at the exit slit, and the output light quantity Decrease. For this reason, although the refractive optical system has a characteristic of being resistant to vibration, it has hardly been applied to a wavelength variable monochromatic light source.

  The problem of chromatic aberration also occurs in the relay lens 7 in FIG. For example, in FIG. 5, when a single lens is used and the focal length F1 is 200 mm when the wavelength is 550 nm, the focal length F2 is 160 nm at the wavelength 200 nm. That is, in general, in an optical system as shown in FIG. 5, when the output wavelength of the spectroscope 10 is changed, the monochromatic light image emitted from the relay lens 7 is blurred and spreads larger than the end face of the optical fiber 8, and the light Energy transmission loss occurs.

  As a general-purpose monochromatic light source, it is desirable that the irradiation area (the size of the image formed on the projection surface) can be adjusted according to the size of the irradiation target (sample cell or light receiving unit). Although there is an example in which a variable stop is provided in the optical path in order to strongly change the irradiation region, adjustment of the irradiation region by the stop is accompanied by a decrease in the amount of output light.

  The present invention has been made in view of such circumstances, and a first object of the present invention is to provide a wavelength-tunable monochromatic light source that has no optical energy loss due to chromatic aberration while using a lens in the output optical system. is there. A second object of the present invention is to provide a wavelength-tunable monochromatic light source that can adjust the irradiation area without reducing the amount of light.

  As a basic configuration for solving the above-described problems, the present invention uses a variable focal length lens system, a so-called zoom lens, as an output optical system, and a zoom drive mechanism for changing the focal length of the lens system and the lens system. And a focusing mechanism that moves all or part of the focusing mechanism in the optical axis direction. With this configuration, it is possible to correct the focal shift (chromatic aberration) that occurs when the output wavelength is changed by changing the focal length of the lens system (zooming), and also to adjust the irradiation area. It becomes possible.

  In the second aspect of the present invention, in addition to the above basic configuration, output light divided by an optical path dividing means such as a half mirror is projected on an image sensor, and the output image signal is processed to obtain focus information or irradiation area information. A control device that controls the zoom drive mechanism by taking out and feeding back this is configured. Thus, it is possible to automatically adjust the focal length of the lens system when the wavelength is changed to correct chromatic aberration, and it is possible to automatically adjust the irradiation area.

  A third aspect of the present invention is configured to include a control device that processes the output image signal of the image sensor to extract focus information and feeds back the focus information to control the focusing mechanism. Thereby, the focus can be automatically adjusted when the irradiation area is set.

  Further, a fourth aspect of the present invention is a drive mechanism that moves the projection surface (for example, the end surface of the optical fiber) along the output side optical axis of the relay lens when the output light is transmitted to the irradiation target via an optical fiber or the like. Control means for controlling this in conjunction with the wavelength selection mechanism of the spectroscope is provided. By configuring in this way, when changing the wavelength of monochromatic light, it can be focused by changing the distance between the relay lens and the projection surface according to the change in focal length based on the change in wavelength, Transmission loss of light energy due to image blurring can be prevented.

  Since the present invention is configured as described above, it becomes possible to solve the problem of chromatic aberration peculiar to the refractive optical system while using a refractive optical system that is resistant to vibration. It is possible to provide a wavelength tunable monochromatic light source whose wavelength range is expanded to a maximum. In addition, since the irradiation area can be adjusted, it is possible to provide a variable wavelength monochromatic light source with excellent versatility.

  FIG. 1 shows an embodiment of the present invention. The present invention relates to the output optical system 3, and the light source unit 1 and the spectroscopic optical system 2 which are not directly related to the present invention are schematically shown in FIG. The light source unit 1 and the spectroscopic optical system 2 schematically shown are the same as those in the conventional example shown in FIG. 4, or are configured by replacing a reflective optical element such as a mirror in FIG. 4 with a refractive optical element such as a lens. is there.

In FIG. 1, reference numeral 18 denotes a lens system configured to function as a convex lens having a variable focal length by combining a plurality of lenses, and is generally known as a zoom lens, and is a zoom driving mechanism driven by a motor or the like. The zooming (changing the focal length) is performed according to 23. Reference numeral 22 denotes a focusing mechanism that is similarly driven by a motor or the like and moves the lens system 18 in the optical axis direction to perform focus adjustment. 17 is a virtual projection surface as in FIG. 4, 19 is a half mirror installed in the output optical path of the lens system 18, and 20 is a plurality of light receiving elements (pixels) arranged in a plane to output image information. For example, the image sensor includes a charge coupled device (CCD). The image sensor 20 and the projection surface 17 are arranged equidistant from the half mirror 19, and the output light of the lens system 18 is divided by the half mirror 19 to form the same image on the surface of the image sensor 20 and the projection surface 17.
Reference numeral 21 denotes a control device configured by a computer, which processes an image signal sent from the image sensor 20 and controls the focusing mechanism 22 and the zoom drive mechanism 23.

The present embodiment configured as described above operates as follows.
The light emitted from the light source unit 1 and split by the spectroscopic optical system 2 is incident on the lens system 18 of the output optical system 3, where it is condensed and imaged on the projection surface 17, but is simultaneously reflected by the half mirror 19. The same light forms the same image on the surface of the image sensor 20. This image is converted into an image signal by the image sensor 20, sent to the control device 21, and processed by a computer inside the image to extract focus information. The focus information is obtained by, for example, comparing the brightness between adjacent pixels in the vicinity of the contour of the image, and focusing is performed at a point where the difference becomes maximum. Focus adjustment can be performed by controlling the focusing mechanism 22 based on such focus information and performing feedback control to move the lens system 18 back and forth. Autofocus technology already established in the camera field can be applied to such focus adjustment.
If the focus is thus achieved on the image sensor 20, a focused image can be obtained on the projection surface 17 that is equidistant from the image sensor 20 from the half mirror 19.

  When adjusting the irradiation area, the image signal from the image sensor 20 is processed to extract irradiation area information. As the irradiation area information, for example, the area of the irradiation area can be obtained by summing up the number of pixels receiving light, and this is compared with the set value, and the zoom drive mechanism 23 is controlled so that the difference becomes smaller. To do. When zooming of the lens system 18 is performed by the zoom drive mechanism 23, the focal length changes and the size of the projected image changes, so that the size of the image connected to the projection surface 17 is set by this feedback control. Can be automatically adjusted to match. In addition, since a focus will shift | deviate if a focal distance changes by zooming, focus adjustment by said focusing mechanism 22 is used together. Further, the feedback control system for adjusting the irradiation area does not need to be constantly operated, and may be configured to operate by operating a switch or the like (not shown) only when the setting is changed.

  In this way, when the output wavelength is changed in the state where the irradiation area is set and focused at a certain wavelength, the focus shift occurs due to the chromatic aberration of the lens system 18. When correcting chromatic aberration, the image signal from the image sensor 20 is processed to obtain the same focus information as in the focus adjustment described above, and this is fed back to control the zoom drive mechanism 23 for focusing. At this time, the focusing mechanism 22 should not be moved. By focusing in this way by zooming, the change in the focal length due to the wavelength is corrected by changing the focal length of the lens system 18, so that the chromatic aberration can be reduced without changing the image size (irradiation area). Can be resolved.

The above is a description of the case where the focus and irradiation area are automatically adjusted by feedback control. However, it is also possible for the operator to make a manual adjustment.
That is, the apparatus is configured to display an image signal from the image sensor 20 on an appropriate display device (not shown), and the operator manually operates the focusing mechanism 22 and the zoom drive mechanism 23 while viewing this display. Adjustment is made so that the size of the focal image (irradiation area) becomes a desired size, and when the output wavelength is changed, the zoom drive mechanism 23 may be manually operated to readjust the focus.

In addition, when taking out monochromatic light outside, what is necessary is just to provide the projection surface 17 with the variable slit (not shown) which can change the magnitude | size of a slit according to an irradiation area.
Also, the half mirror 19 can be replaced with other optical path dividing means.
Further, the focus adjustment of the lens system 18 can be designed so as to be performed by moving only a part of the lenses constituting the lens system 18 without moving the entire lens system back and forth. 22 can be further reduced in size and simplified.

FIG. 2 shows another embodiment of the present invention. In the figure, the same components as those in FIG.
In this embodiment, the difference from the conventional configuration shown in FIG. 5 is that the drive mechanism 5 that moves the projection surface 9 (the end surface of the optical fiber 8) along the emission side optical axis of the relay lens 7 and the drive mechanism 5 Control means 6 for controlling is provided. The control means 6 has a built-in computer and controls the drive mechanism 5 so as to move the projection surface 9 to the in-focus position corresponding to the wavelength in response to the wavelength signal from the wavelength selection mechanism 4.

The operation of this embodiment configured as described above will be described below.
Now, when monochromatic light of wavelength λ1 is output from the spectroscope 10, the end face of the optical fiber 8 is at a distance L1 from the relay lens 7, and an accurate focused image is formed on the end face. To do. When the operator operates the wavelength selection mechanism 4 to change the output wavelength from the spectroscope 10 to λ2, the wavelength signal is input to the control means 6. The control unit 6 stores in-focus position information experimentally obtained for various wavelengths in advance in the built-in computer, or is configured to calculate the in-focus position using a pre-stored calculation formula. . Thereby, the focus position L2 with respect to the wavelength λ2 is immediately obtained, and the drive mechanism 5 is controlled so that the optical fiber 8 is moved to this position (position indicated by a dotted line in FIG. 2). As a result, an in-focus image is obtained on the end surface (projection surface 9) of the optical fiber 8, so that the output light is transmitted to the optical fiber 8 without loss.

An example of a specific configuration of the drive mechanism 5 in FIG. 2 is shown in FIG.
In FIG. 3A, the output shaft of the pulse motor 56 controlled by the control means 6 is directly connected to a screw 54 to be screwed with the nut 53, and the support plate 52 connected to the nut 53 has a holding tool. The optical fiber 8 is held via 51.
In such a configuration, when the pulse motor 56 rotates in either the forward or reverse direction in response to a control signal from the control means 6, the screw 54 also rotates, and the nut 53 that is screwed to the screw 54 is on the nut guide base 57. Is driven in the left-right direction in the figure, and the optical fiber 8 moves along the optical axis accordingly. With such a mechanism, the end face of the optical fiber 8 can be moved to a position where a focused image can be obtained. The piezo element 55 performs fine adjustment of the focus by slightly expanding and contracting according to the applied voltage from the control means 6. FIG. 5B is a view of the holder 51 as viewed from the optical axis direction, in which the optical fiber 8 is held through four piezo elements 58 at substantially the center of the annular holder 51. By appropriately adjusting the voltage applied to the piezo element 58, the optical axis can be adjusted (the center of the optical fiber 8 is aligned with the optical axis).

  Note that the control means 6 in FIG. 2 is not necessarily impossible to use a structure in which the wavelength selection mechanism 4 and the drive mechanism 5 are mechanically linked by a mechanism such as a cam without necessarily using a computer. Further, a structure different from that shown in FIG. 3 can be designed as the drive mechanism 5, and the projection surface 9 is not limited to the end face of the optical fiber 8.

  The present invention can be used in an apparatus that performs analysis, measurement, and other light irradiation using monochromatic light.

It is a figure which shows one Embodiment of this invention. It is a figure which shows other embodiment (Example 1) of this invention. 3 is a diagram illustrating a partial configuration example in Embodiment 1. FIG. It is a figure which shows the basic composition of a spectrometer. It is a figure which shows an example of the conventional structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source part 2 Spectroscopic optical system 3 Output optical system 4 Wavelength selection mechanism 5 Drive mechanism 6 Control means 7 Relay lens 8 Optical fiber 9 Projection surface 10 Spectrometer 11 Light source 12 Condensing mirror 13 Entrance slit 14 Collimator mirror 15 Grating 16 Imaging Mirror 17 Projection surface 17a Exit slit 18 Lens system 19 Half mirror 20 Image sensor 21 Control device 22 Focusing mechanism 23 Zoom drive mechanism 51 Holder 52 Support plate 53 Nut 54 Screw 55 Piezo element 56 Pulse motor 57 Nut guide stand 58 Piezo element

Claims (5)

In a tunable monochromatic light source configured to wavelength-disperse light from a light source with a spectroscope and project and output light in a part of the wavelength range to the projection surface through the output optical system, the output optical system is set to a focal length Variable wavelength system comprising a variable lens system, a zoom drive mechanism for changing the focal length of the lens system, and a focusing mechanism for moving all or part of the lens system in the optical axis direction Monochromatic light source. An optical path splitting means installed in the optical path of the output light of the lens system, an image sensor on which the light split from the output light of the lens system is projected by the optical path splitting means, and an output image signal of the image sensor is processed The tunable monochromatic light source according to claim 1, further comprising a control device that performs feedback control of the zoom drive mechanism. The wavelength tunable monochromatic light source according to claim 2, further comprising a control device that processes an output image signal of an image sensor and feedback-controls the focusing mechanism. A spectrometer that disperses light from a light source and selectively outputs light in a part of the wavelength range, and a wavelength selection mechanism that selects an output wavelength of the spectrometer, and relays the output light of the spectrometer In a wavelength tunable monochromatic light source configured to project and output to a projection surface via a lens, a drive mechanism that moves the projection surface along the optical axis on the emission side of the relay lens, and in conjunction with the wavelength selection mechanism A wavelength tunable monochromatic light source comprising control means for controlling the drive mechanism. The wavelength-tunable monochromatic light source according to claim 4, wherein the projection surface is an end surface of the optical fiber.

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