JPS61259135A - Method for measuring leaked light of image guide - Google Patents

Abstract

PURPOSE:To measure a local leaked light state reaching one core of an image guide, by allowing light to be locally incident to the incident end of the image guide by an optical fiber and measuring the emitted light at the emitting end of said optical fiber. CONSTITUTION:The light emitted from a light source 8 is guided to the incident end of an image guide 10 by a single mode fiber 9. The core diameter and the number of apertures of the fiber 9 coincide with that of the image guide and, by regulating the position of the fiber 9 by a fine adjustment stand, only one arbitrary core of the guide 10 can be excited. At this time, the pinhole plate on the emitting end surface of the guide 10 is moved and the intensity of the transmitted light from a pinhole 12 is measured by a light receiving element 13 to measure the intensity distribution of emitted light. By this method, the intensity of leaked light when light was incident to a certain one core is cleared and, by calculating the sum total when each core was excited, the leaked light intensity of the image guide is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a light leakage measurement method for an image guide using an optical fiber, which can accurately measure the local light leakage state of an image guide.

[Prior Art] Light leakage from an image guide has a large effect on image contrast, and it is extremely important to accurately measure the light leakage state.

The method shown in FIG. 5 is generally used to measure light leakage of conventional image guides. That is, a part of the input IMtIN surface of the image guide 1 is covered with the knife 2, white light is applied to it from the light source 3, and the light intensity distribution in the radial direction at the output end surface of the image guide 1 is measured. A pinhole plate 4 that can move in the radial direction is provided on the output end surface of the image guide 1, and a light receiving element 6 is provided behind the pinhole 5 of the pinhole plate 4, and the light receiving element 6 measures the intensity of the received light. A power meter 7 is connected.

If there is no light leakage in image guide 1,
The light intensity is zero at the portion of the output end face of the image guide 1 corresponding to the portion covered by the knife 2. Therefore, the slope of the rate of change in light intensity at the output end face corresponding to the portion covered by the knife 2 and the portion not covered, respectively, becomes infinite. However, in reality, there is light leakage in the image guide 1, so the above-mentioned slope becomes smaller accordingly, and the less steep the slope, the greater the light leakage.

[Problems to be Solved by the Invention] The light leakage measurement method of the image guide 1 using the knife 2 described above is suitable for observing a rough trend of the light leakage state. However, from this measurement result, MTF (
modulation transfer function
In order to obtain a contrast index such as ion), complex calculations are required. Further, it is difficult to know the degree of light leakage in a certain local part of the image guide 1 from this measurement result alone, and furthermore, it is impossible to measure the light leakage of a certain core.

[Object of the Invention] The present invention has been made to solve the problems of the prior art described above, and an object of the invention is to be able to accurately measure the local light leakage state of an image guide, and to improve the contrast coefficient, etc. An object of the present invention is to provide a method for measuring light leakage of an image guide, which can easily determine the index.

[IN essential points of the invention] In order to achieve the above object, the present invention locally injects light into the input end of an image guide using an optical fiber,
The light leakage state of the image guide is determined by measuring the intensity of the light emitted from the output end of the image guide, and it is characterized by the fact that point excitation of the input end surface of the image guide is possible by using an optical fiber. shall be.

[Examples] Examples of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, 8 is a light source, and the light emitted from the light source 8 is guided to the input Dj E of the image guide 10 by a single mode fiber (hereinafter abbreviated as 8M fiber) 9. The output end of the 8M fiber 9 is butted against the input end of the image guide 10 as close as possible without colliding with the input end.

Further, the output end of the 8M fiber 9 is fixed to a fine movement table (not shown) or the like, so that it can be moved on the input end surface of the image guide 10 while maintaining the abutted state. The core diameter of the 8M fiber 9 is the same as that of the image guide 10, and the numerical aperture of the 8M fiber 9 is equal to the numerical aperture of the input end of the image guide 10 (including the fiber lens at the input end). Image guide 10
At the output end of the pinhole plate 11 is movable on the output end surface.
is provided. Pinhole 12 on pinhole plate 11
A light receiving element 13 for measuring the intensity of transmitted light from the pinhole 12 is integrally attached to the pinhole plate 11 behind the light receiving element 13, and a power meter 14 is attached to the light receiving element 13.
is connected.

The diameter of the pinhole 12 is approximately the same as the diameter of a pixel consisting of the core and cladding of the image guide 1o.

The light emitted from the light source 8 is input to the image guide 10 through the 8M fiber 9. Since the core diameter and numerical aperture of the 8M fiber 9 match those of the image guide 10, the 8M fiber 9 is By adjusting the position, it is possible to ensure that only any one core of the image guide 10 is excited. Therefore, at this time,
The appearance of the output end face of the image guide 11 in which the pixels 15 consisting of the core and the cladding are arranged correctly is shown in the second diagram.
As shown in the figure. In FIG. 2, 15a is a core pixel excited by the SM fiber 9. In FIG. At this time, if the pinhole plate 11 is moved in a certain radial direction on the output end face of the image guide 10 so as to pass through the pixel 15a, the measurement result of the intensity distribution of the output light as shown in FIG. 3 can be obtained. can get. In Figure 3, the peak of maximum light intensity at the center is a
is due to the light emitted from the core pixel 15a excited by the 8M fiber 9, and the beaks b on both sides indicate the light modulation from the pixel 15 that is in contact with the pixel 15ak:1ljl.

From this measurement result, when light is incident on one core, the light leakage intensity to the surrounding cores and cladding can be determined, and when light is incident on all cores of the image guide 10, each core,
The light leakage intensity of Klazudobe is determined as the sum of the excitation of each core. If the value obtained by normalizing the light leakage intensity obtained in this way by the light intensity of the core is l, then the contrast coefficient C is given by the following equation.

FIG. 4 shows an embodiment in which a half mirror 16 is installed at the output end of the image guide 10, and the reflected light is viewed by a television camera 17. In this case, at the same time as the intensity measurement, it is possible to observe the position of the measurement point and the state of light leakage from the light emitting end surface body of the image guide 10.

In the above embodiment, the core diameter of the 8M fiber 9 and the core diameter of the image guide 10 are made the same, but the core diameter of the 8M fiber 9 may of course be made smaller than the core diameter of the image kite 10. Conversely, if an SM fiber or a multimode fiber having a core diameter larger than the core diameter of the image guide is used, the state of light leakage in a predetermined local area of the image guide can be measured. In addition, in the above embodiment, the numerical aperture of the 8M fiber 9 and the numerical aperture of the entrance end of the image guide 10 were made equal, but by using a 3M fiber with a larger aperture than the numerical aperture of the image guide, the lens It is possible to measure the state of light leakage when a high-angle light beam is coupled to the image guide due to axis misalignment in the optical system. Furthermore, by appropriately setting the v-length of the 3M fiber, it is possible to measure the state of light leakage when light in a certain wavelength range passes through the image guide.

[Effects of the Invention] In summary, the present invention provides the following excellent effects.

(1) It is possible to accurately measure the state of light leakage locally in the image guide up to one core.

(2) Since light leakage can be locally measured down to each core, indicators such as the contrast coefficient can be determined with high precision using simple calculations from the measurement results.

(3) By simply changing the groove path parameters such as the core diameter, numerical aperture, and vfla of the optical fiber, the light leakage state when the optical axis is shifted, the light leakage state when various measurement regions are excited, or the light leakage state at a specific wavelength can be adjusted. It is possible to measure the state of light leakage when light in the area passes through the image guide.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of a measurement system for implementing the light leakage measurement method according to the present invention, FIG. 2 is an enlarged end view of a part of the image guide output end face of the rryJ measurement system, and FIG. Fig. 1 is a graph showing the light intensity distribution in the radial direction of the output end face of the image guide, Fig. 4 is a configuration diagram showing an example of a measurement system for carrying out the method of this invention, and Fig. 5 is an image of the conventional image. It is a block diagram which shows the measurement system of the light leakage measurement method of a guide. In the figure, 1 is an image guide, 2 is a knife, 3 is a light source, 4 is a pinhole plate, 5 is a pinhole, 6 is a light receiving element, 7 is a power meter, 8 is a light source, 9 is a single fiber, and 10 is a Image guide, 11 is a pinhole board,
12 is a pinhole, 13 is a light receiving element, 14 is a power meter, 15 is an image guide pixel, and 16 is a half mirror.
117 is a television camera.

Claims (5)

[Claims] (1) An image guide characterized in that light is locally incident on the input end of the image guide through an optical fiber, and the intensity of the emitted light at the output end of the image guide is measured to determine the light leakage of the image guide. How to measure light leakage. (2) A method for measuring light leakage of an image guide according to claim 1, wherein light is made to enter one core at an input end of the image guide through the optical fiber. (3) The method for measuring light leakage of an image guide according to claim 1 or 2, wherein the optical fiber is a single mode fiber. (4) The method for measuring light leakage of an image guide according to claim 3, wherein the numerical aperture of the single mode fiber is equal to the numerical aperture of the end of the image guide. (5) The method for measuring light leakage of an image guide according to claim 3 or 4, wherein the core diameter of the single mode fiber is less than or equal to the core diameter of the image guide.