JPH0712946U - Refractive index distribution measurement cell - Google Patents

Abstract

(57) [Abstract] [Purpose] By adopting a structure that projects the laser light emitted from the cylindrical glass onto the emission window, it is necessary to have both transparency and the same refractive index as the outer wall of the glass. By making it possible to use a non-projection plate material as a constituent member of the exit window, the production cost can be reduced, and the measurement accuracy can be improved by the ease of production. [Structure] A light beam is incident on a cylindrical glass B used for a rodless lens or a preform for an optical fiber from a direction perpendicular to a central axis, and a light beam transmitted through the cylindrical glass B and emitted is projected. In the refractive index distribution measuring cell 2 which is inserted through the cylindrical glass B used in the refractive index distribution measuring device for observing the projected image with an image pickup device and analyzing it two-dimensionally, the exit window 22 is formed. It is composed of a screen that is inexpensive and easy to produce.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a refractive index distribution measuring cell used in a cylindrical glass refractive index distribution measuring device used for rodless lenses and optical fiber preforms.

[0002]

[Prior art]

 The cylindrical glass used as a rodless lens or optical fiber preform (base material) has a nearly squared refractive index in the direction perpendicular to the axis, and the refractive index in the direction along the axis. Accurately measure the refractive index distribution of the cylindrical glass before drawing, even if the refractive index is uniform or the core-clad type called single mode, which has a uniform refractive index in the direction along the axis. That is the condition for obtaining good quality rodless lens and optical fiber. Conventionally, the measuring device for measuring the refractive index distribution of a cylindrical glass is a laser oscillator that emits laser light from a direction perpendicular to the central axis of the cylindrical glass and the incident light from the laser oscillator The incident optical system that collects light to the minimum at the center of the cell, the filled cell that is mounted on the glass and has the incident window for the laser light and the exit window for the transmitted light, and the exit light scattered from the exit window of the cell. A projection screen, an image pickup device for observing the projected image of the screen, and a control unit and the like which is linked to the image pickup device and has a predetermined calculation means for two-dimensionally analyzing the observed projection image. ing. By the way, the cell forming a part of the measuring device in the above-mentioned prior art is filled with a matching oil having the same refractive index as that of the outer wall of the glass in the metal box, and the laser from the laser oscillator is filled in the box. It is constructed by providing an entrance window and an exit window, which are made of a material with the same refractive index, at the light entrance and exit parts, and refract the laser light from the laser oscillator from the entrance window. Is transmitted, and the transmitted light is transmitted from the emission window to the screen side, and an image is formed on the screen.

[0003]

[Problems to be solved by the device]

 Originally, the exit window needs to form a two-dimensional image on the screen without refracting or polarizing the refracted light in the glass as much as possible. High accuracy is required for parallelism and flatness. Therefore, the exit window is made of quartz that meets the condition that the refractive index is the same as that of the outer wall of the glass. However, in addition to the material cost, quartz has a very high production cost such as processing and finishing due to its hardness, which is a serious problem that the cell cannot be provided at a low price.

The present invention has been made in view of the above-mentioned conventional circumstances, and the object thereof is to adopt a structure in which a laser beam emitted from a cylindrical glass is projected onto an emission window portion, thereby improving transparency and A plate material for projection that does not need to have the same refractive index as the outer wall of glass can be used as a constituent member of the exit window to reduce the production cost, and improve the measurement accuracy due to ease of production. The purpose is to provide a cell for measuring the refractive index distribution that can be expected.

[0005]

[Means for Solving the Problems]

 The present inventor has made earnest studies on the molding material of the exit window, and if the projection image is formed on the exit window, the intention is to use an expensive and troublesome quartz in consideration of transmittance and refractive index. The present inventors have come to the present invention by discovering that a material that is inexpensive and easy to mold can be used. That is, according to the present invention, a light beam is incident on a cylindrical glass used for a rodless lens or a preform for an optical fiber from a direction perpendicular to a central axis, and a light beam transmitted through the cylindrical glass and emitted is transmitted. In the refractive index distribution measuring cell that penetrates the cylindrical glass used in the refractive index distribution measuring device for projecting the projected image, observing the projected image with the imaging device and analyzing it two-dimensionally, the exit window is screened. The point is that it is configured with.

[0006]

[Action]

 According to the above technical means, the exit window is composed of a screen. Therefore, it is not necessary to combine transparency with the same refractive index as the outer wall of the glass, and a projected image is formed directly on the screen that is easy to produce and finish, and the projected image is taken by the imaging device as needed. The refractive index distribution can be measured by enlarging and analyzing it two-dimensionally.

[0007]

[Effect of device]

 As described above, the present invention is a cell for measuring the refractive index distribution, which is made of quartz, which is a material that has both transparency and a refractive index similar to that of the outer wall of glass, and does not have an exit window but a screen. Therefore, it is possible to provide the cell for measuring the refractive index distribution, which has a low material cost, can be formed with a material having no hardness, and which can be easily manufactured and finished, and which can reduce the refractive index distribution. Moreover, since it is not necessary to dispose screens spaced apart from each other at a predetermined interval in the exit window, there is no error in disposing the screen, and the processing is easy and highly accurate, and the distance from the cell core can be set accurately. High accuracy of refractive index distribution measurement can be expected.

[0008]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show a refractive index distribution measuring cell of this embodiment. FIG. 1 shows a schematic view of a measuring device using the cell for measuring the refractive index distribution of this example.

This measuring apparatus A is a cylindrical glass B which is a measurement target of a laser beam 1 ′ oscillated from a He—Ne laser oscillator 1 through an incident optical system 6 and an incident window 12 of a refractive index distribution measuring cell 2. Is introduced into the same cell 2 while gradually descending or rising so as to traverse vertically, and the transmitted light transmitted through the matching oil 3 and the cylindrical glass B to be measured is emitted through the exit window 22 of the same cell 2. The image is projected as a projection image, and the image is sequentially observed by the image pickup device 4 that gradually descends in synchronization with the laser oscillator 1, and the control unit 5 determines the projected image (image formation) obtained by the image pickup device 4. This is a system for calculating the refractive index distribution in the above, and although not described in detail, a configuration other than that in which the exit window 22 part is composed of a screen, that is, the image pickup device 4 is a TV camera and the calculation built in the control part 5 About means Has the same configuration as the conventional one.

The refraction index distribution measuring cell 2 has a through hole having a diameter equal to that of the cylindrical glass B to be measured in a pair of opposing side plate portions of a box body 2 ′ surrounding six metal surfaces (see FIG. (Not shown), the glass B is inserted into the through hole (not shown), and a sealing material (not shown) that is in close contact with the peripheral surface of the glass B is provided around the edge of the glass B to make it watertight. Of the side wall portion 2-1 which has the same property as the outer wall portion b of the glass B and has the same refractive index as that of the outer wall portion b of the glass B. A long hole 2-2 is formed in the side plate portion 2-1 facing the glass plate, and the long hole 2-2 is covered in a watertight manner with an entrance window 12 formed of quartz having the same refractive index as the glass B. In the opposite side plate portion 2-1 as well, a long hole 2-3 having a wider vertical and horizontal width than the above long hole 2-2 is formed. Are formed by Hifuta watertight form the long hole 2-3 by screen 22.

The screen 22 is made of a generally known material such as clouded glass, and emits light emitted from the laser oscillator 1 and scattered through the cylindrical glass B as shown in FIG. 1 to form a projected image.

In this case, the projected image is smaller than that formed by a screen that is separated from the exit window by a predetermined distance as in the related art, but the image magnifying function of the image pickup device 4 magnifies the projected image. It is sufficient to perform a two-dimensional analysis similar to.

[Brief description of drawings]

FIG. 1 is a schematic view of a measuring apparatus incorporating a cell for measuring a refractive index distribution of this example.

FIG. 2 is an enlarged cross-sectional view showing a usage state of the cell for measuring the refractive index distribution of the present embodiment.

[Explanation of symbols]

A: Measuring device 2: Refractive index distribution measuring cell 1: Laser oscillator B: Cylindrical glass 12: Entrance window 22: Exit window (screen) 3: Matching oil 4: Imaging device 5: Control unit

Claims (1)

[Scope of utility model registration request] 1. A light beam is incident on a cylindrical glass used for a rodless lens or a preform for an optical fiber from a direction perpendicular to a central axis, and a light beam emitted through the cylindrical glass is projected. In the refractive index distribution measuring cell which penetrates the cylindrical glass used in the refractive index distribution measuring device for observing the projected image with an image pickup device and analyzing it two-dimensionally, the exit window is constituted by a screen. A cell for measuring a refractive index distribution, which is characterized in that