JPS6067833A - Optical fiber inspector - Google Patents

Abstract

PURPOSE:To enable a highly accurate measurement at a high speed by arranging an inspector so as to measure various structural parameters of an optical fiber in the same condition as when light is actually transmitted. CONSTITUTION:A light emitting diode 5 projects one end face of an optical fiber 1' for inspection while a laser diode 6 is provided at the other end face thereof 1' to oscillate a laser light guided therethrough. A reflected image from the one end face is magnified by the optical system and taken by a photographing means 10. The video signal is converted into a digital signal with an A/D converter 14 and written into a frame memory FM with the writing operation controlled by a control circuit FMW. A microcomputer MCS uses the data written to determine a data on the brightness of the magnified image according to the specified signal processing sequence. The laser diode used for the light source enables the measurement of spot size and the refractive index distribution with the fiber set in the waveguide mode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an apparatus for measuring various structural parameters (eg, cladding diameter, core diameter, eccentricity, non-circularity) of an optical fiber.

[Prior art]

Conventional devices for measuring the structural parameters of optical fibers, such as cladding diameter, core diameter, eccentricity, and noncircularity, include, for example: a) using a normal lamp from one end of the test fiber; irradiate the fiber, observe the pattern of the passing light with a television camera through a microscope at the other end, and at the same time measure various parameters at the cross section of the fiber with a computer, or b) The same method as in the device a) above is used, but in addition to the "image rotation prism", the pattern image is completely rotated in addition to the optical system of the conventional microscope! l
There is an f'Lfc device configured to obtain two-dimensional information on various parameters.

t;i Another conventional device for measuring the entire refractive index distribution, which is another structural parameter, is an interference microscope device that measures the refractive index distribution in the core using differential interferometry. Various other methods for measuring refractive index distribution are known, but in conventional apparatuses, including the above-mentioned apparatus, a lamp used in ordinary microscopes is used as a light source. Also,
Most of the fibers to be measured are multimode fibers, and there was no measuring device with good measurement accuracy for single mode fibers.

The multimode fiber has a cladding diameter of 125 μm.
The core diameter is internationally standardized as 50 μm, but in the case of single-mode fibers, the core diameter itself is not completely specified because the distribution of light varies depending on the refractive index distribution within the core. The size of the light spot is completely specified. Here, the spot size refers to the width of the light pattern at the end that is 1/e2 of the maximum light intensity in the waveguide mode when the brightness distribution is a Gaussian distribution (the same applies hereinafter). Therefore, for single-mode fibers, there is no point in measuring all the core dimensions like in multi-mode fibers. The problem is the spot size of the covering light.

However, conventional measurement devices were not created with the assumption that they would measure all of the various characteristics of the fiber under exactly the same propagation conditions as the actual communication conditions, so the spot size of the light in the guided mode could not be measured, and there was no particularly good one for measuring the characteristics of single mode fiber.

[Summary of the invention]

The invention of the present application applies various structural parameters (cladding diameter, core diameter, eccentricity,
Refers to non-circularity, spot size, refractive index distribution, etc. (same hereinafter)? An optical fiber inspection device that uses a laser diode as a light source and can measure with high precision? provide.

[Embodiments of the invention]

In order to precisely measure all of the various structural parameters of an optical fiber, it is necessary to inspect and measure the optical fiber in the same state as it will be in during actual communication. In particular, for single mode fibers, it is required to accurately measure the spot size within the core and the entire refractive index distribution within that size, which has not been measured with conventional devices. Therefore, in such a single mode fiber, the spot size in the guided mode is more important than the core diameter as a measurement target. In view of this point, the optical fiber inspection device according to the invention of the present application is configured to have the following features.
ing.

a) Using a laser diode for light i, various structural parameters of the optical fiber under the same conditions as during actual optical transmission? Measure with high precision. That is, with a normal light source lamp, a waveguide mode can be obtained within the fiber.

By using a laser diode as a total light source, the spot size and refractive index distribution can be determined by making the fiber into a waveguide mode? can be measured. As the laser diode, a long wavelength laser with a wavelength of 1.8 μm is used for a single mode fiber, and a short wavelength laser with a wavelength λ of 085 μm is used for a multimode fiber.

However, since it is not necessary to use waveguide mode to measure the cladding diameter and core diameter, it may be used as an ordinary lamp light source.

b) Among various structural parameters, spot size and refractive index distribution are measured using two-dimensional '611J constant data? Also, if you want to measure other parameters with higher precision, what about two-dimensional measurement data? I need.

'However, instead of rotating the optical system used in conventional equipment, or rotating the fiber itself for the TV left camera, we are using image processing technology to achieve precision that is equal to or higher than conventional methods. Two-dimensional measurements can be made with While conventional devices are equipped with some kind of rotation mechanism as described above, the inspection device disclosed in the present application does not require such a mechanism, and therefore has the advantage that its mechanism is simple.

C) Equipped with an automatic focus control mechanism that automatically changes the distance between the end face of the fiber and the objective lens in accordance with the focusing layer of the objective lens of the microscope when imaging the light pattern Kl emitted from the inspection fiber. I'm running away. As will be described in detail later, the control mechanism is that the edge of the emitted light pattern is detected and the focus control circuit is based on the differential coefficient of the edge.
The lens system fine movement device is configured to be driven through the lens system.

d) The infrared vidicon used to image the emitted light pattern is subject to the "burn-in" phenomenon, which is a deterioration caused by irradiating the same place with intense light for a long period of time, and is an important problem that affects the lifespan of the vidicon. However, in the inspection device that Honmaro discloses, the light I
By minimizing the total α-emission time, the above problems are alleviated, and the lifespan of the busicom is greatly extended. In other words, the output pattern from one fiber is subjected to two signal processing processes using image processing technology, and various structural parameters are processed on the side of the frame memory.
For example, the fiber needs to be irradiated with the V-za light for only 88 x 101 seconds), so the laser diode?
Switching is controlled by a microcomputer. As a result, there is no need to keep the laser diode oscillating continuously for a long time, and there is an advantage that not only the life of the vidicon but also the life of the laser diode is extended.

e) For single mode fiber, core M is approximately 10 μm
However, the diameter of ij is 125 μm, and the distance between the outer periphery of the core and the outer periphery of the cladding is nearly 60 m. Second, most of the light in the intra-core waveguide mode is concentrated in the core and propagates, so when observing the output light pattern at the fiber end face, the boundary between the outer periphery of the cladding and the air cannot be observed, and the cladding diameter This means that it cannot be measured. As a countermeasure for this, can we use a light emitting diode as a light source to illuminate the entire cladding? Used, Bee 1z 7 Pritsuta? The structure is such that the end face of the fiber is irradiated for a very short time through the fiber, and the reflected light is captured by a vidicon, making it possible to measure the cladding diameter.

f) In the fiber testing device according to the invention of the present application, once the fiber for testing is set in the device, various structural parameters are automatically measured and the results are displayed on a CRT or printer using a microcomputer. The control fQl system used is employed.

Next, are there drawings for specific embodiments of this invention? This will be explained in detail with reference to the following. FIG. 1 is an embodiment of the fiber inspection device according to the present invention. FIG. A laser diode LD with a single mode fiber f8 is used as a waveguide light source, and one end of a single mode fiber F (approximately i m) for inspection is fixed by a fiber support jig S1, facing the n2 single mode fiber f1. There are n. If the fiber for inspection is a single mode fiber, an infrared semiconductor laser for optical communication with a wavelength λ = 1.8 μm is used as the laser diode LD, whereas when inspecting a multimode fiber, A light emitting diode around 185 μm is used.

The laser light oscillated by the laser diode LD is transmitted to the inspection fiber VVCM via the single mode fiber FSK.
Waves. On the other hand, an image of the end face at the other end of the inspection fiber fixed by the support jig S is formed on the photocathode of the infrared vidicon camera C via the beam splitter Bs and the microscope Mi. At this time, the magnification of the objective lens of the P Micro Saw-1M is changed depending on whether the image to be observed is of the entire fiber or only the core, and when imaging the entire end face of the fiber including the cladding, the cladding part is illuminated. In order to do this, the end face is irradiated with visible light or infrared light from a light emitting diode LED (wavelength ^; V) through the beam sedge Bs2.

A focus control signal necessary for automatic focus adjustment is generated by a signal processing unit sp. Based on the focus control signal, the relative distance between the end face of the inspection single mode fiber F and the objective lens is adjusted to set the optimal focal length. After automatic focusing, the video signal obtained by the infrared vidicon IVC is converted into a digital signal in the signal processing unit sp, and written into the frame memory. After various signal processing described below, information on various structural parameters is obtained. .

The main parameters measured by the inspection device of this invention are cladding diameter, core diameter, spot size diameter, spot size roundness, eccentricity, non-circularity, refractive index distribution in the core and its two-dimensional distribution, etc. However, information regarding these parameters is obtained by software processing, regarding the frame memory as a two-dimensional matrix. That is,
Capturing the output pattern image from the inspection fiber,
From the brightness distribution on the line passing through the center of the pattern, each 97
Harameter glares. In this case, the twin can process brightness distributions on the fins in all directions, not just horizontal and vertical directions. Measurement accuracy is Microscope M
The core diameter of the single mode fiber (approximately 10 μm) and the spot size are determined by the resolution of the lens system and the image pickup tube, vidicon camera V'C, and are determined by the p1 optimal design.
It is possible to measure the cladding diameter with an accuracy of 0.1 μm or less.

FIG. 2 is a block diagram showing the configuration of the inspection apparatus shown in FIG. 1. Laser light from a laser diode (LD) (i) is guided to an optical fiber 1 fixed to a support jig 4,
One end of the inspection optical fiber 1', which is fixed by a support jig 3 so as to face the optical fiber 1', is further guided to the core.

On the other hand, the end image at the other end of the fiber 1' fixed by the support jig 2 is imaged on the photocathode of the infrared vidicon camera 10 via the beam sinter 7, the objective lens 8, and the imaging lens 9. Sanru. Is this partial "burning" of the photocathode? How to prevent it? In order to maintain the linearity of brightness for a long period of time at the same time, the entire end face image is captured in the frame memory (described later).
) V-me cycle (time for the infrared vidicon camera 10 to scan one screen: approximately 38 m5ec) Ta'/'j
The laser diode 6 is caused to oscillate by the LD switching circuit 16 under the control of the microcomputer in the microcomputer system MC8. When the inspection fiber 11 is a single mode fiber, the light emitting diode 5 and the beam splitter 7 are the end faces of the cladding portion where the laser light is not guided. It is provided for illumination. When the inspection fiber 1' is a multimode fiber, the laser diode 6 does not need to guide the laser light, and only the light emitting diode 5 that illuminates the fiber end face is required.

Illuminated cladding statue? The end image of the fiber 11 contained therein is magnified by an objective lens 8 according to the required magnification, and further imaged on the photocathode of an infrared vidicon 10 by an imaging lens 9. At this time, switching of the objective lens 8 and adjustment of the focal length are automatically performed. The supporting jig 2 on the exit side of the objective lens 8 or the inspection optical fiber 1' is moved under the control of a microcomputer so that the optimal focal length is obtained based on the image processing result of the video signal.
Ru. For example, a case will be described in which the objective lens 8 is moved. First, each time the optical fiber 1' for inspection is newly installed, the objective lens 8 is moved to the position closest to the optical fiber 11 by the lens system micro-a device based on instructions from the microcomputer. Next, the video signal at that position is taken into a frame memory, which will be described later, and the change rate of the video signal at a specific edge on the i-frame memory is determined in advance (1'), that is, the differential coefficient? Calculate using a microcomputer. The differential coefficients to be treated are mainly horizontal or vertical partial differential coefficients on the image. Is the differential coefficient of the video signal information about focus adjustment? Does the optimum focus adjustment occur at the point where the differential coefficient at the same location is maximum?
means. Based on this principle, the objective lens 8 is gradually moved by the lens system fine movement device FD to determine the optimum focal length.

Recording of the video signal into the frame memory FM is performed as follows. The video signal obtained by the infrared vidicon camera 10 is first converted into a wideband preamplifier. In this case, 14 AD converters and 1 video signal? Since it is necessary to directly digitize data in real time, it is necessary to use an AD converter suitable for high-speed conversion, such as a parallel comparison type with a maximum conversion time of 50 seconds or less. The number of conversion bits of the AD converter 14 is 8 bits, and the digital signal from there is sent to the frame memory write control circuit FMwK. The frame memory write control circuit FMW receives a timing signal from a memory control circuit MC and a CRT display timing generation circuit DT, which will be described later.A synchronization signal component is extracted by a synchronization separation circuit 18, and a horizontal synchronization signal is also sent to the frame memory write control circuit FMW. for a minute. Got 2t each synchronized communication 8! -Basically, in the CRT display timing/timing generation circuit DT, what is the data capture timing of the frame memory FM and the display timing for CRTK display? Vidicon camera 10 In synchronization with the color video signal, display and import timing including the address of frame memory FH or graphic memory GM are generated sequentially.
The output/memory output circuit MC controls the timing of loading/reading the frame memory FM and the graphic memory GM.

Frame memory FM has a resolution and gradation expression of about %1024XIQ24X8 bits? It has a memory capacity of 1 MB. Graphic memory GM usually has a resolution of 1024x1024xl bits? While the frame memory PM stores video images from the infrared vidicon camera 10, it is used to display arithmetic results and characters such as messages and commands from the microcomputer. Frame memo IJF
The content of liI is the frame memory interface F.
II Engineering F Communication C: Can be read and written from a microcomputer. On the other hand, frame memo UFM
Is the output video data? The state T that is not captured is always in the display mode, and is converted into an analog signal by the CRT display timing generation circuit. The DA converter 53 is also required to have a conversion speed comparable to or higher than that of the AD converter 14.

The graph ink memory GM can be read and written only from the microcomputer, and the microcoder signal and the double-stranded video data from the graphic memory GM are transmitted through the graphic memory interface GM, either individually or in combination by the CRT display control port DC. CRT in shape
Displayed above 15.

In addition to the constituent circuit blocks and functions described above, the system of the fC inspection device shown in FIG. 2 includes a keyboard 66 and a keyboard interface 661 for inputting various commands and information, and a A printer 60 and a printer interface 60' are provided. Furthermore, if necessary, floppy disk FD and floppy disk interface FDI can be used for backup and filing of measurement data.
It can be prepared as an option. In addition, for exchanging data with the host computer HC, GP-
IB interface G can also be installed.

In this system, the basic structural parameters of the optical fiber for inspection, such as the beam spot diameter, the circularity of the core, and the eccentricity of the core with respect to the cladding, are determined by software processing under the control of a microcomputer. The details of the processing will not be explained in detail later, but only an outline thereof will be described here. First, frame memory F
Sequentially read out all the data imported into M, and find the point with the maximum brightness.1. Ru. Of course, at the center of the beam, is the brightness of the beam spot a Gaussian distribution? If so, is the brightness 1/e' of the center brightness? The part to show? , and the beam spot diameter and its circularity can be determined from the obtained closed curve. Also, the edge of the cladding has the maximum coefficient of unevenness! As a set of parts having lf, the eccentricity of the cladding with respect to the beam pattern is determined from 7'L. moreover.

Regarding the refractive index, a relative refractive index distribution is determined from the luminance distribution within the core. The cladding diameter is (for light emitting diode 5)'6
It is measured from the brightness distribution of a spot obtained by irradiating the entire end face of the fiber 11. In addition.

If the brightness distribution of the beam spot of the core is not a Gaussian distribution, signal processing that is more complex than the above-mentioned signal processing is performed to find the one that corresponds to the above-mentioned closed curve.

Since such signal processing is software processing, it will not be discussed in more detail in this application.

Next, FIG. 3 shows a more detailed block diagram of the inspection apparatus shown in FIG. 2. In FIG. 3, parts with the same reference numerals as blocks in FIG. 2 indicate the same or equivalent parts as in FIG. 2, and no redundant explanation will be given.

The end face image of the inspection optical fiber 1' is
, objective l nozzle 8. An image is formed on the charging surface of the infrared vidicon camera 1o through a lens system consisting of an imaging lens 9, and a video signal 72 is obtained. As mentioned above, this platform uses a laser diode (L
L)) 6 is oscillated. This is done by the parallel output port 54 outputting a control signal 77 under the control of the CPU 56, which operates the LD/LED switching circuit 16 and controls the oscillation of the laser diode 6.

Light emitting diode (LED) 5 and beam splitter 7
is provided to illuminate the entire cladding, and is used not only to determine the cladding diameter and eccentricity of the core relative to the cladding, but also to determine parameters such as the cladding diameter and core diameter of multimode fibers. be done.

The obtained video signal 72 is amplified to an appropriate filtration amplitude (several VP-P) by the preamplifier 13, and the output luminance signal 74 is converted into a digital video signal 75 by the high-speed video converter 4. converted. The conversion bit number of the AD converter 14 is usually 8 bits, and the 1Iif signal is quantized into 256 steps, sampled at the same period as the indicated rate, and sent to serial input/parallel output shift registers 29 to 86 for each floor. is input bit by bit. Further, every 8 cycles of the shift clock 86 from the oscillation circuit 25, the edges of the latch clock 79 are latched into D flip flops 87 to 44, and eight sets of 8-bit RAMs 181 to 44 constitute a frame memory. 138
This is the input data. On the other hand, the video signal 74 amplified by the preamplifier 1B is applied to the sync separation circuit 18, and a composite sync signal below the black level is obtained as an output. The obtained composite synchronization signal 81 is divided into parts, one of which is outputted by the differentiation circuit 21 as a differential hull 782 in which only the horizontal synchronization signal is extracted, and further passed through the one-shot multi-by-break 22 to generate an H signal having a specified pulse width and timing. A reset pulse 84 is obtained.

On the other hand, the Vsync component is extracted by the integrating circuit 23, and an integrated PALNU signal 88 is obtained. This is similarly waveform-shaped using the one-shot multi-by-flake 24 to generate the V reset pulse 85. In this example, the timing is generated with the simplest timing. That is, by measuring the video signal 72 output from the infrared vidicon camera 10 and the video signal to be displayed on the CRT 15, the frame memory 13
1 to 138 can be written and displayed at the same timing. Furthermore, in this embodiment, in order to prevent conflict between access to the frame memory or graph ink memory from the CPU 56 and access for display (or writing) on the CRT 15, the timing of the latch clock 79 of the CPU 56 is made the same. Toshi, CP
From the perspective of the U 56, a state is realized in which accesses related to the CRT 15 are being performed by cycle stealing (see FIG. 5, which will be described later).

86 is output. Further, the dot counter 26 counts down in character units (shift register load cycle) to obtain a character clock 90. Next, the character counter 27 counts one line, and at the same time a blank signal (not shown) is generated.
, a horizontal periodic signal (Hsync) 88 is obtained. At the same time, a vertical synchronization signal (Vsync) is output from the line counter 28 provided for counting one frame.
I got 89. The count values of these counters are used as a CRT display atlas 98 for displaying or writing the contents of the frame memories 181 to 138 or the graphic memory 64. The CRT display address 98 and CPTJ address 96 (described later) are switched by the address multiplexer 68, and at the same time, the frame memories 131-138. A time-division memory address 139 is generated to be added to the address terminal of the Guinaminoku RAM constituting the graphic memory 64. Control of reading/writing of frame memory, switching of address multiplexer 68, latch timing of DFFs 87 to 44, or shift register 45
The generation of road clocks .about.52 and the like are performed by the timing control circuit 55.

FIG. 4 is a circuit diagram showing in detail the circuit configuration of the timing control circuit 55 and its peripheral parts in FIG. 3, and FIG. Based on the dot counter output 92 and shift clock 86, an inverter 280 and an AND element 200 create a load clock (LC) 87, and a D flip-flop 201 generates a signal 216 which is the basic timing of the I<A S signal 224. and its inverse, the signal 218
is generated. Further, the signal 216 is delayed by the D flip-flop 202 to obtain a switching signal S W 219 for obtaining a time division address. The frequency-divided output 215 of the dot counter 26 is used as it is as a switching signal CPU/CRT 215 for address signals related to the CPU 56 and the CRT 15. The inverter 208 has a shift clock 8
This is provided to reverse the polarity of the edge 6. Each signal making up memory control signal 104 is generated by gates 204-212. AND gate 2
05 is provided to decode the upper address of the address bus 96, and one address signal of positive logic or negative logic is input thereto to define the addresses of the frame memories 181 to 138. In this example, AND gate 2
05 determines the address area seen from the CPU 56 of the frame memory. Regarding the RAS signal 224, first, the gate 206 makes address decoding valid only when the Qc signal 215 is at the H level (that is, during the valid period of the CPU 56), and when the Qc signal 215 is at the L level, it is in display or write mode. So RAS signal 2
The above logic is realized by the OR gate 207 so that 24 becomes valid.

Output 228 of OR gate 207 and flip-flop 20
1 ζ output 218 through NAND gate 208 to RA
An S signal 224 is created. Further, the CAS signal 225 is added to each memo every month by inverting Q114HM' 214 of the dot counter 26 as it is by the inverter 209.

Regarding the write signal, in the case of a frame memory, the write operation is limited to the image of the infrared vidicon camera in this embodiment, so the CPU 56
By writing the bit of the frame memory capture signal 94, the WR(F) signal 229 of the NAND gate 212 becomes valid and a write operation is performed. Regarding graphic memo 1, like frame memory,
address signal 226 is applied to AND gate 210;
The address camera of the graph ink memory 64 as seen from the CPU 3O is defined. The graphics memory 64 is a CPU
It is used to output the results processed by the CPU 56 in the form of graphics or characters, and can be read from or written to by the CPU 56. In addition to the above, in the timing control circuit 55, the Qc multiplied signal from the dot counter 26 is directly used as a latch lock 79 and a CPU clock (not shown).

Since the video data 8o is written to the frame memory as an 8-bit block for each gradation through the video AD converter 14 and the FF 19, the memory cycle time is equal to the cycle of the shift clock even including the access by the CPU 56. Since the memory size is four times that of the previous one, it is possible to use memory with long access times and cycle times.

Frame memory reading from the CPU 56 takes 8
Lower address of address bus 96 (Ao AI A2
) (not specifically shown) to specify the number of dots from the left of the 8 bits on the screen. This makes it easy to specify X and Y on the screen as a linear address, and also allows access to any point in one access. Further, the selected 8-bit data can be read by the CPU 56 via the three-state buffer 59.

As for the graphics memory 64, it simply uses data buffers 68 . This can be done via the three-state buffer 67.

8-bit parallel-to-serial conversion shift registers 45 to 52 are provided at the output of the frame memory for display on a CRT of these memories, and can output 8-bit gradation data sequentially. . The data is applied to a high-speed video DA converter 53, and an analog 256-gradation monochrome video signal is generated. In this case, the DA converter requires a high-speed video DA converter with set and ring times of several tens of nanoseconds. As for the binary image in the graphic memory 64, the graphic memory output 101 is sequentially shifted and outputted by the shift register 65, and a graphic memory video signal 102 is obtained. These data and Hsyn
cl word 88 and Vsync signal 89 are applied to video mixing circuit 20, thereby converting video signal 7 for display.
6 is obtained and the data is displayed on the CRT 15.

In the above explanation, we briefly touched on image capture mainly from the frame memory, data reading by the CPU 56, and CRT display. Next, focal length adjustment will be explained. Optical fiber support jig 2,
8, it is necessary to optimize focusing by moving the lens system in almost all cases. For this reason, this inspection apparatus system has a built-in automatic focal length adjustment function, so that various parameters can be measured while always capturing an optimally focused image into the frame memory.

As an example, in this inspection apparatus system, automatic focus adjustment is performed by the procedure described below with reference to FIGS. 6 and 7. Figure 6 is a graph showing the relationship between the amount of movement of the lens system and the luminance differential coefficient at a certain position on the fiber end face. Find a point where the difference in luminance differential coefficients is reversed in a small step, and then gradually change the basic step to Ai ■ Thus N=N
÷K.

K: integer). The operation of reversing the stamping motor 12 and returning the lens system that has gone too far (A=-A) is repeated. If N becomes smaller than the minimum step Nm1n, the position of the lens system is within the minimum step error from the optimal position (corresponding to the FE point in FIG. 6), and the automatic focus adjustment process ends.

Next, the process of calculating the maximum brightness differential coefficient will be explained. 8th
Figure (a) shows a one-dimensional area (N
Direct brightness distribution A between the two points =0 and N=ONtAx,
It is a graph showing a point a+b on B where the maximum luminance differential coefficient is obtained. Moreover, FIG. 9 is a flowchart for calculating the maximum brightness differential coefficient.

This example assumes a maximum brightness factor for the horizontal dimension of the frame memory image. Movement of the lens system due to automatic focus adjustment is achieved by the CPU 56 outputting a stepping motor control signal 78 to the parallel output port 54, which applies a signal to the stepping motor drive circuit 17 and rotates the stamping motor 12 by a specified number of steps. As a result, the axial fine movement device 11 slides to move the lens system (objective lens 8, focusing lens 9, infrared vidicon camera 10).

In this way, frame memory 1 can be adjusted in the optimal focus adjustment state.
The images captured in ROMs 81 to 138 are mainly stored in RA by software written in ROM Allo 2.
Variables are placed in M58 for processing, and the results are output to parallel input/output capotro 1 and printed on printer 60. Further, these commands are inputted from the keyboard 66 and are sent back to C through the parallel input/output capotro 1.
This will be communicated to P U 56.

[Toss Insufficient White] The 97 Eyepa inspection device according to the present invention described above uses light with a wavelength of 1.8 μm from visible light as a means for imaging the light pattern emitted from the inspection fiber. An infrared vidicon camera was used. However, depending on the type of inspection fiber, there may be trenches, or depending on the purpose of the inspection, various structures may be used. Alternative makeup can be measured. It is also possible to use a solid-state imaging device such as a charge-coupled device (CCD).

Furthermore, the same effect can be obtained by using a single photodetector that is sensitive in the wavelength region of 1.3 μm, which is the wavelength λ of the laser light when inspecting a single mode fiber. An example in which such a photodetector is used as an imaging means will be described below with reference to FIGS. 10 to 15. FIG. It is. In order to image the beam patterns p and P obtained at the end face of the inspection fiber, a single photodetector is scanned vertically and horizontally (X, Y directions) on a plane parallel to the end face at a predetermined scanning timing. Flooding means is incorporated into the inspection equipment. In this case, either the X or Y direction may be selected as the horizontal scanning direction. By this scanning, the emitted light and the wind turn are imaged two-dimensionally, and after signal processing similar to that in the embodiment shown in Fig. 3, the desired inspection results are obtained. In this case, the dimensional scanning timing and the quimming of the IIX output from the photodetection SD are the same operations as the extraction of the image IIX from the photocathode of the busicon under the control of the CPU in Fig. 3. It will be held in

z 11 Figure 1 Plural photodetectors 1) A one-dimensional array from D is aligned horizontally or vertically in one direction (Y direction in the figure) in a plane parallel to the end surface of the inspection fiber, with a predetermined primary It is a schematic diagram in the case of scanning by a scanning drive means at the scanning timing of the original direction. The signals from the one-dimensional array at a certain location are processed according to the predetermined signal JJ-extraction scan timing. At this time, the inspection apparatus is configured such that the signal processing timing at which the data corresponding to the frame memory is stored and the mechanical scanning timing by the scanning driving means are executed by the CPU according to a predetermined control program.

FIG. 12 is a schematic diagram when an emitted light pattern is imaged by a plurality of photodetectors arranged in a plane. In this case, the light-receiving plane made up of multiple photodetectors corresponds to the light-receiving surface of the vidicon camera, and no mechanical scanning driving means is required to extract the video signal, and the entire scanning method is electrical. The purpose can be achieved by In this embodiment, instead of using several ``41'' single photodetectors, charge-coupled devices (
It is also possible to use a single solid-state imaging device such as a CCD (CCD).

FIG. 13 shows a single mode 71 coupled to a photodetector.
It is a schematic diagram in the case where the IPA f is arranged near the end face of the output side of the optical fiber for inspection, and the output light patterns p and P are imaged. If the end face of the single mode fiber facing the output side end face of the inspection optical fiber is considered as the light receiving surface, it is possible to image the emitted light pattern in the same way as in the case of FIG.

FIG. 14 is a schematic diagram when an emitted light pattern is imaged using a one-dimensional array composed of single mode fibers f and f coupled to each of a plurality of photodetectors. In this case, the purpose is achieved by mechanical and electronic processing similar to that shown in FIG. In the one-dimensional array described above, the resolution cannot be improved unless the cores of adjacent fibers are brought close to each other to such an extent that they do not optically couple with each other.

For example, when making a fiber bundle, the distance between the cores is approximately 2
A one-dimensional array is made with a thickness of about 0 μm.

FIG. 15 is a schematic diagram in the case of using a two-dimensional tilted arrangement using a single mode fiber coupled to a photodetector.

Signal processing in this case is performed in accordance with the case shown in FIG. In the case of FIG. 15, as in FIG. 14, it is necessary to fabricate and use a fiber in which the core spacing of each fiber is made close to the extent that no coupling occurs. This example is
Although it corresponds to a conventional image fiber, since it is a detection means that essentially utilizes the core portion of a single mode fiber, much better results can be obtained in terms of accuracy (resolution).

Above theory Fy+ 1. The embodiments shown in FIGS. 10 to 15 have the following features compared to the case where a vidicon camera is used.

1) There is no burn-in like in image pickup tubes, and the linearity is good.

-11) In the case of a 7-eye pie photodetector, in addition to i) above, the light receiving surface is small, less than 1O/1m, and the resolution is lower than that of an image pickup tube or This is better than when using a conventional CCD, resulting in improved measurement accuracy.

In the case of the embodiments shown in FIGS. 10 to 15, focusing is required when exchanging the inspection fiber or changing the magnification of the objective lens of the optical system. Automatic focus adjustment can be performed with the same configuration as in the embodiment. In other words, automatic focus adjustment is performed by making the optical system that magnifies the pattern image of the end face movable in the X dimension with respect to the end face of the optical fiber for inspection. to the optical system
919 sections are made so that they can be moved dimensionally.

〔Effect of the invention〕

As explained below, this FJ has the effect of being able to emit light in the same state as during actual optical transmission. Furthermore, care has been taken to prevent the phenomenon of "one-time burn-in" of the vidicon camera, which has the effect of extending its lifespan.

[Brief explanation of drawings]

@Figure 1 is a schematic diagram showing an embodiment of the optical fiber inspection apparatus according to the present invention, @2 Figure is a block diagram showing the configuration of the inspection apparatus shown in Figure 1, and Figure 3 is the inspection apparatus shown in Figure 2. A more detailed block diagram of 41''/1- is a circuit diagram of the timing control circuit 55 of Figure 3 and its peripheral parts, and Figure 5 is a timing diagram of signals of the corresponding part of the circuit of Figure 4. Figure 6 is a graph showing the relationship between the amount of movement of the lens system and the brightness differential coefficient at the end of the fiber, Figure 7 is a flowchart for automatic focus adjustment, and Figure 8 (a) is a graph showing the frame memory image. Figures 8(b) and 8(c) representing the one-dimensional head area of
are graphs showing the point at which the maximum brightness differential coefficient is obtained during focus adjustment, Figure 9 is a flowchart for determining the maximum brightness differential coefficient, and Figure 10 is a graph showing the point at which the maximum brightness differential coefficient is obtained, and Figure 10 is a graph showing the point at which the maximum brightness differential coefficient is obtained when adjusting the focus. FIG. 11 is a schematic diagram of a case in which a one-dimensional array consisting of a plurality of photodetectors is used, and FIG. 12 is a schematic diagram of a case in which a plurality of photodetectors arranged in a plane is used.
FIGS. 13 to 15 are schematic diagrams in the case of using a single mode fiber coupled to a dog-dog optical detector. In the figure, LD: Raded diode, F50: single mode fiber, F: inspection optical fiber, BS: beam splitter, LED: light emitting diode, M...
Microscope, IVC... Infrared 1a digital camera, Sl, S2... Support jig, SP... Signal processing section, 1... Optical fiber 1, 1'... Optical fiber for inspection, 7・・・Beamsp main path, DT...CRT table X timing generation circuit, FM・
...Frame memory, FMW...Frame memory write control circuit, MC5...DC...CRT display control circuit. ” Note that the same reference numerals in each figure indicate the same or corresponding parts2.Representative Patent Attorney Takaharu Higashijima Figure 6 Figure 7 Figure 8 ((1) Figure 9

Claims (1)

[Scope of Claims] (1) A light emitting diode for illuminating one end face of an optical fiber for inspection, an optical system for enlarging a reflected image from the end face, and an image capturing the enlarged image from the optical system. an analog/digital converter for converting a video signal from the imaging means into a digital signal, a frame memory for writing the digital signal, and a frame memory for controlling the writing operation of the frame memory. An optical system comprising: a write control circuit; and a microcomputer containing a control program that uses the data written in the frame memory to obtain data regarding the brightness of the enlarged image through a predetermined signal processing procedure. Fiber inspection equipment. (2) provided on the other end surface of the inspection optical fiber;
An optical fiber inspection apparatus according to claim 1, further comprising a beam splitter provided near the one end face for oscillating and passing a laser beam guided therein. . (3) The optical fiber inspection apparatus according to claim 1 or 2, wherein the imaging means is an infrared vidicon camera. (4) The imaging means is a semiconductor photodetector, and a scanning drive for capturing the enlarged image by scanning the semiconductor photodetector vertically and horizontally at a predetermined scanning timing along a plane parallel to the one end surface. An optical fiber inspection device according to claim 1 or 2, characterized in that it comprises means. (5) The imaging means is a semiconductor photodetector and a single-mode fiber coupled thereto, and the light-receiving surface of the single-mode fiber is scanned vertically, horizontally, and vertically at predetermined scanning timing along a plane parallel to the one end surface. The optical fiber inspection apparatus according to claim 4, characterized in that it comprises a scanning drive means for scanning and capturing the enlarged image. (6) The front end imaging means is a one-dimensional array-like imaging means composed of a plurality of semiconductor photodetectors, and the front-end imaging means is a one-dimensional array-like imaging means that is arranged in a direction perpendicular to the one-dimensional direction of the one-dimensional array. The light according to claim 1 or 2, further comprising a scanning drive means for capturing the enlarged image by moving it with a predetermined scanning direction along a plane parallel to the end surface l. Fiber inspection equipment. (7) The imaging means is a one-dimensional array-like imaging means composed of a plurality of sets of semiconductor photodetectors and single mode fibers coupled thereto, and the -dimensional array-like imaging means is Claims @Claim 1, further comprising a scanning drive means for capturing the enlarged image by moving it at a predetermined scanning timing along a plane parallel to the one end surface in a direction perpendicular to the direction of Or the optical fiber inspection device according to item 2. (8) The imaging means is an imaging means in which a plurality of semiconductor photodetectors are arranged in a planar manner, and the imaging means is characterized in that the image is taken at a predetermined scanning timing. Or the optical fiber inspection device according to item 2. (9) The imaging means is an imaging means in which a plurality of sets of semiconductor photodetectors and single mode fibers coupled thereto are arranged in a plane, and the enlarged image is taken at a predetermined scanning timing. An optical fiber inspection device according to claim 1 or 2. Q0 Claims 1 or 2 include an automatic focus adjustment mechanism configured to be movable in eight dimensions so as to automatically perform focusing when capturing the enlarged image. The optical fiber inspection device described. 0]) The optical fiber according to claim 10, wherein the automatic focus adjustment mechanism is configured to be able to move the optical system three-dimensionally with respect to the one end surface. Inspection equipment. (6) The automatic focusing mechanism is configured to be able to move the one end surface eight-dimensionally (ζ) with respect to the optical system. Phi) <Inspection equipment. [N person-F color]