GB2128839A

GB2128839A - Image display apparatus

Info

Publication number: GB2128839A
Application number: GB08229495A
Authority: GB
Inventors: Mitsuru Rokunohe; Toshiyuki Nakajima; Kansei Iwata; Hiroyuki Tajima
Original assignee: Dainichi Nippon Cables Ltd
Current assignee: Dainichi Nippon Cables Ltd
Priority date: 1982-10-15
Filing date: 1982-10-15
Publication date: 1984-05-02

Abstract

Image display apparatus in which an incoherent optical fibre bundle is used to transmit an image of an object from its front end F to its remote end R. The front face is irradiated successively along the columns 5 of the bundle and the positions of the light emerging from face R stored, the front face is then irradiated along the rows of the bundle (not shown) and again the positions of the emergent light stored. The data thus obtained is correlated to produce a table of addresses of the fibres of the face R corresponding to those of face F which are stored in an address converter memory. The data stored in the memory is used to rearrange the pixels of the transmitted image into a coherent form. <IMAGE>

Description

SPECIFICATION Image display apparatus This invention relates to a display apparatus for displaying an optical image transmitted via a cable which is an optical fiber bundle.

The practice of adopting a cable comprising an optical fiber bundle obtained by bundling a plurality of optical fibers to transmit an optical image from one end of the bundle to the other by projecting the optical image with the aid of a lens, for example, on the front end face of the bundle and allowing the image to be transferred through the bundle and formed in the rear end face of the bundle has been in vogue.

For successful transmission of the optical image, however, the optical fiber bundle is required to be such that, at the opposite ends thereof, the individual optical fibers thereof are disposed geometrically in mutually corresponding positions. Otherwise, no faithful transmission of the optical image is obtained because the optical image in the front end face of the bundle and the optical image in the rear end face do not coincide with each other.

In the production of an optical fiber bundle of great length, the practice of imparting flexibility to the bundle, for example, by intertwisting individual optical fibers or strands of optical fibers so as to facilitate the handling of the bundle when the bundle is wound on a drum has found widespread acceptance. When the individual optical fibers are intertwisted or otherwise tamed as described above, however, there inevitably ensues the consequence that the geometric positions of the individual optical fibers differ in the opposite end faces of the bundle.When the number of optical fibers making up one optical fiber bundle is increased for the purpose of the improvement of the definition of an optical image to be transmitted, it often happens that optical fibers sustaining flaws such as chippings and fractures which are responsible to blots appearing in the displayed image may possibiy mingle with other flawless optical fibers in the bundle.

In the conventional optical image transmission, therefore, only a rather slender optical fiber bundle of small length is barely usable for medical observation of the internal organs such as the stomach and the esophague as a fiberscope (such as a gastroscope).

There is eager demand for application of the optical image transmission technique to remote monitoring of important phenomena occurring at places such as the interiors of nuclear reactors and blast furnaces which are hardly accessible by human beings. This demand is not easily met at present, in actuality, because manufacture of a long optical fiber bundle having as many optical fibers as desired and yet warranting perfect mutual conformity of the geometric positions of individual optical fibers in the opposite end faces of the bundle is extremely difficult for the reason given above.

An object of this invention is to provide an optical image display apparatus, which, even when used with an optical fiber bundle having the geometric positions of individual optical fibers thereof not mutually conforming in the opposite end faces, enables an optical image which has been projected on the front end face and transferred to the rear end face to be displayed to the original optical image.

Another object of this invention is to provide an optical image display apparatus for displaying an optical image transmitted via an optical fiber bundle, which apparatus, when used with an optical fiber bundle containing, in the optical fibers making up the bundle, those sustaining chippings or fractures, compensates for those elements of optical information which ought to have been conveyed by those defective optical fibers and eliminates otherwise possible blots from the displayed optical image.

Still another object of this invention is to provide an optical image display apparatus provided with a readily manufacturable address converter capable of converting the geometric addresses of individual optical fibers making up an optical fiber bundle in one end face of the bundle into the geometric addresses thereof in the other end face.

A further object of this invention is to provide an optical image display apparatus, which is adapted to receive the information of an optical image transmitted through an optical fiber bundle, store the information temporarily in a memory, read the information repeatedly out of the memory, and put it on the CRT display as a visible image.

Another further object of this invention is to provide an optical image display apparatus for displaying an optical image transmitted via an optical fiber bundle, which apparatus suits application to remote monitoring of phenomena occurring at places hardly accessible by human beings. An application of the invention will now be illustrated by way of example only, with reference to the accompanying drawings in which Figure 1 is a schematic diagram illustrating a conventional optical fiber bundle for transmission of an optical image.

Figure 2 and Figure 9 are block diagrams each illustrating an embodiment of this invention.

Figure 3 is a schematic diagram of a device for producing an address converter to be used in the present invention.

Figure 4 is a schematic diagram illustrating a procedure for the operation of the device of Figure 3.

Figure 5 is a model diagram illustrating the addresses of the positions of individual optical fibers of an optical fiber bundle in one end face of the bundle and the addresses of the positions of the same individual optical fibers in the other end face.

Figure 6 is a front view illustrating in detail the device for producing the address converter to be used in the present invention.

Figure 7 is a cross section of a simulator in the device of Figure 6, illustrating the inner structure thereof.

Figure 8 is a block diagram illustrating an electrical circuit in the simulator of the device of Figure 6.

Now, one embodiment of this invention will be described in detail below with reference to the accompanying drawings. Figure lisa schematic diagram illustrating a conventional optical fiber bundle for transmission of an optical image. In the diagram, 1 denotes an optical fiber bundle (bundle of optical fibers), F a front end of the optical fiber bundle, and Ra rear end thereof. The bundle 1 comprises an optical fiber bundle wherein the individual optical fibers, at the front end F and the rear end R, are disposed geometrically in mutually corresponding positions in the respective end faces.Transmission of an optical image by this bundle 1 is effected by projecting the optical image with the aid of a lens (not shown), for example, on the face of the front end F, whereby the small elements of the optical image impinging upon the optical fibers are conducted through the optical fibers to form a corresponding optical image in the face of the rear end R.

Figure 2 is a block diagram illustrating one embodiment of this invention. In this diagram, 21 denotes an object to be monitored, 22 a lens, and 2 a long flexible optical fiber bundle. By 10 is denoted a photoelectric converter, which is mutually a color TV camera consisting of a pickup tube and a control unit and which converts an optical image of the object 21 transmitted by the optical fiber bundle 2 to the rear end face R into analog electric signals R (red), G (green), and B (blue). An A/D converter 12 serves to convert the analog RGB electric signals from the photoelectric converter 10 into corresponding RGB signals in 64 levels (6 bits) of shade for each picture element (dot) of one scene which may be formed of 512 x 512 dots, for example.This A/D conversion proceeds at super-speed in the order of the 2-D (dimensional) addresses which are generated by a 2-D address generator 11.

The 2-D address generator 11 serves to generate 2-D addresses (X address and Y address) of each of the picture elements (dots) when the photoelectric conversion plane in the converter 10 is equally divided into 512 x 512 dots. These 2-D addresses are generated so that the displayed scene may be correctly scanned. A write control circuit 13 serves to store in a data buffer memory 14 the picture element information (RGB signals and corresponding information on shade) which has been digitalized for each picture element in the A/D converter 12.

An address converter 15 is a conversion table prepared in advance to fulfil the work of converting the addresses of the positions of the individual optical fibers of the optical fiber bundle in the face of the rear end R into the addresses of the positions of the same optical fibers in the face of the front end F. The method for preparing this address converter will be described with reference to Figure 3 and Figure 4.

Figure 3 is a schematic diagram of a device for producing the address converter and Figure 4 is a schematic diagram illustrating the operation of the device. In Figure 3,2 denotes a long flexible optical fiber bundle, which is provided at the front end Fthereofwith a simulator 3.

The simulator 3 is not given any detailed description. In short, it functions to emit light and moves it along the face of the front end F of the optical fiber bundle from one side to the other, so that the light enters the individual optical fibers.

In Figure 4, S denotes a luminescent line of a width At (nearly equal or smaller than the cross-sectional diameter of one optical fiber). The luminescent line is generated by the simulator 3.

In Figure 4 (a), the luminescent line S parallel to they axis is positioned at the leftmost side of the front end Fto deliver light to three optical fibers. At this time, light ought to show correspondingly from the three optical fibers on the rear end R. Thus, the addresses of the positions of these three optical fibers are put into a memory. Then, as shown in Figure 4 (b), the luminescent line S is shifted by a predetermined minute interval At in the direction of the x axis to deliver light, this time, to five optical fibers. Similarly to the former instant, light ought to show correspondingly from five optical fibers on the rear end R. The addresses of the positions of these five optical fibers are put into the memory. In the same manner, the luminescent line S is successively shifted by equal intervals in the direction of the x axis, to scan the front end F.

Then, the luminescent line S is laid down and shifted successively by minute intervals At in the direction of they axis parallelly to the x axis, with the addresses of the positions of optical fibers showing light on the rear end R at the successive shifts of the luminescent line S being put into the memory. After the two scannings of the front end F by the luminescent line S one each in the direction of the x axis and they axis, all the addresses of the locations of light-showing optical fibers on the rear end Rare consolidated to find the relationship between the addresses of the positions of optical fibers on the front end F and those on the rear end R.

Of course, the light emitted from the simulator 3 need not be a visible light but may be an invisible light.

The effect produced by successively shifting the luminescent line S as described above may be equally brought about by gradually expanding the illuminated area of the front end F of the bundle.

The aforementioned determination of the relationship between the addresses of the positions of optical fibers on the front end F and those on the rear end R depending on the results of the two scannings will be described more specifically below with reference to Figure 5. Figure 5 is a model diagram illustrating the addresses of the positions of the individual optical fibers of the optical fiber bundle on the front end F and the rear end R; the addresses on the front end F are shown in (i) and those on the rear end R in (ii) respectively.

For better comprehension, it is assumed that in Figure 5 (i), the front end F of the optical fiber bundle comprises a total of nine optical fibers shown by letters "a" through "i" and that, as shown in Figure 5 (ii), the positions of optical fibers showing on the rear end Rare denoted by the letters "A" through "I".

The luminescent line being parallel to they axis is to be shifted to scan the front end Ffirst in the direction of the x axis.

In the first stage, it is assumed that lights show in the fiber positions G, E, and Con the rear end R when light of luminescent line enters the fiber positions a (x1, yl), b (x1, y2), and c (xl, y3) on the front end F. Then it is shown that G, E, and C severally have the address xl at least on the front end F side because a, b, and c share the address xl in common.

In the second stage, if lights show in the fiber positions A, H and F on the rear end R when light of luminescent line enters the fiber positions d (x2, y1), e (x2, y2), and f (x2, y3) on the front end F, then it is known that A, H, and F share the address x2 in common at least on the front end F side.

In the third stage, if lights show in the fiber positions B, D and I on the rear end R when light of luminescent line enters the fiber positions g (x3, y1), h (x3, y2), and i (x3, y3) on the front end F, then it is known that B, D, and I share the address x3 in common at least on the front end F side.

Now, the luminescent line being parallel to the x axis is laid down and shifted to scan the front end F downwardly from the upper side in the direction of they axis.

In the fourth stage, it is assumed that lights show in the fiber positions E, F, and B on the rear end R when light of luminescent line enters the fiber positions a (x1, y1), d (x2, yl), and g (x3, y1). Then it is known that E, F, and B share the address yl in common at least on the front end F side.

In the fifth stage, if lights show in the fiber positions A, G, and I on the rear end R when light of luminescent line enters the fiber positions b (x1, y2), e (x2, y2), and h (x3, y2) on the front end F, it is known that these fiber positions A, G, and I share the address y2 in common at least on the front end F side.

In the sixth stage, if lights show in the fiber positions C, D, and H on the rear end R when light of luminescent line enters the fiber positions c (xl, y3), f (x2, y3) and i (x3, y3) on the front end F, it is known that these fiber positions C, D, and H share the address y3 in common at least on the front end F side.

Consolidation of the foregoing results ascertains that there exists the following relationship between the positions of the individual optical fibers on the rear end R and the front end R.

A (X1, < e (x2, y2) B(X1,Y2)g (x3,y1) C(X1,Y3)c(xl,y3) D (X2, e i(x3, y3) E (X2, Y2) e a (x1 , y1 ) F(X2,Y3)~d (x2,yl) G (X3, Yl)b(xl, y2) H (X3, Y2) < f (x2, y3) I (X3, Y3) < h (x3, y2) The address converter 15 in Figure 2 is obtained by tabulating the relationship between the positions of the individual optical fibers on the front end F and the rear end R which has been ascertained as described above.By the use of this address converter 15, on the rear end R of the optical fiber bundle, the information obtained at the fiber position A is stored in the address (x2, y2), the information obtained at B is stored in the address (x3, yl), and this procedure is repeated thereafter until the information obtained at I is stored in the address (x3, y2). Then, by reading out the memorized information in the order of the addresses, the optical image formed on the front end F is faithfully reproduced on the display.

Now, in Figure 2, a memory 16 which may be a refresh memory is a circuit for memorizing, in the order of scanning addresses, the information which has undergone address conversion in the address converter 15.

ATV synchronizing signal generator 17 is a circu it for generating horizontal and vertical synchronizing signals when raster scanning is made on a CRT (cathode ray tube) 20. A read controller 18 is a circuit for reading out the information written in a refresh memory 1-6 and delivering it to a B/A converter 19 by keeping pace with the TV synchronizing signals from the circuit 17. The D/A converter 19 is a circuit for converting a train of digital picture-element signals brought in from the refresh memory 16 into color video signals and delivering the produced color video signals to the CRT 20.

Although the operation may be already apparent from the foregoing description, it will be described briefly below for the sake or precaution. The image of an object 21 to be monitored which is situated in a position such as the interior of a nuclear reactor which is not accessible by human beings is formed in the face of the front end F of the optical fiber bundle 2 with the aid of a lens 22, for example. The optical image is transmitted through the optical fiber bundle 2 to the photoelectric converter 10, there to be converted into electric signals under the control of the address generator 11. The electric signals are then converted into digital signals at the A/D converter 12. The digital signals are subsequently written in the data buffer memory 14 under the control of the write controller 13.In the address converter 15, the information which has been read out of the data buffer memory by read control means which is not shown in the dig ram undergoes address conversion in accordance with the relationship found in advance between the positions of the individual optical fibers on the front end F and the rear end R of the optical fiber bundle 2 and then written in the refresh memory 16. The read controller 18 reads out the information from the refresh memory 16 under the control of the TV synchronizing signal generator 17. The information is converted into analog signals in the DIA converter 19. The analog signals are delivered to be displayed on the CRT 20. Consequently, the optical image of the object 21 under surveillance is displayed on the CRT 20 and watched.

Figure 6 is a front view illustrating in detail the device to be used for producing the address converter illustrated in Figure 3. In this diagram, 4 denotes an adapter, 5 an image pickup device, 6 a controller, and 7 a monitor device.

To the front end F of a long flexible optical fiber bundle 2 is attached the simulator 3. The image pickup device 5 is attached to the rear end R of the bundle through the medium of the adapter 4. The image pickup device 5 and the controller 6 are interconnected with a line L1. Further, the controller 6 is connected through a control line L2 to the simulator 3. The controller 6 forwards control signals through the control line L2 to the simulator 3 to generate a luminescent line and cause the luminescent line to scan the front end F of the optical fiber bundle 2.

At this time, the positions of light-showing optical fibers on the rear end R of the bundle 2 are picked up by the image pickup device 5. The addresses of these positions are supplied to the controller 6. At the controller 6, the address conversion table of the positions of the individual optical fibers of the optical fiber bundle 2 on the front end F and the rear end R is produced on the basis of the received data of addresses in the manner as described above. The monitor device 7 is a cathode ray tube display (CRT display) to be used for the purpose of monitoring.

Figure 7 is a sectional diagram illustrating the inner structure of the simulator 3 and Figure 8 is a block diagram illustrating the electric circuit of the simulator 3.

Reference is now made to Figure 7. A CRT (cathode ray tube) 31 is for the generation of a luminescent line.

This luminescent line is focussed by a lens 32 on the face of the front end F of the optical fiber bundle 2. By 33 is denoted a printed-circuit board containing necessary electric circuits.

Now with reference to Figure 8, 61 denotes an interface, 62 and X-Y deflection signal generator, 63 a luminescent signal generator, 64 a video amplifier, and 65 a deflection amplifier.

The control signal issued from the controller (6 in the diagram of Figure 6) is delivered via the interface 61 to the X-Y deflection signal generator 62. In response thereto, the generator 62 issues X and Y deflection signals for the luminescent line and directs this signal toward the deflection amplifier 65. Simultaneously, the luminescent signal generator 63 issues a luminescent signal which is amplified by the video amplifier 64 and applied to the electrode of the CRT 31. On the other hand, the output from the deflection amplifier 65 is applied to the deflection coil of the CRT 31. The generation of the luminescent line and the scanning with this luminescent line in the CRT 31 are readily materialized by the prior art as described above.

In the embodiment of this invention illustrated in Figure 2, the optical fiber bundle 2 has large length. If any of the optical fibers in this bundle sustains a fracture somewhere along its length, that particular optical fiber appears as a blot in the reproduced optical image and impairs the quality of the displayed image. The optical fiber bundle 2 generally may be produced by first preparing unit strands each consisting of a plurality of optical fibers, then intertwisting a plurality of such unit strands, and then if necessary, subjecting the resultant bundle to drawing. When the optical image is observed at one end of the optical fiber bundle, the fibers of the peripheral region of each unit strand suffers loss because of residual strain in intertwisting or drawing and shows dark shade. This phenomenon impairs the definition of the picture image.

Another embodiment of th is invention offers a solution to this problem. This embodiment will be described below with reference to Figure 9.

Figure 9 is a block diagram illustrating the embodiment of this invention just mentioned. The circuit configuration of this diagram differs from that of Figure 2 in respect that it additionally incorporates the group of circuits 9 enclosed with a chain line. In other words, the addition of the group of circuits 9 to the circuit configuration of Figure 2 completes the circuit configuration of Figure 9. This group 9 consists of a level comparator 91, a neighbor address generator 92, a read controller 93, a video prorcessor 95, and a data register 94.

In Figure 9, the level comparator 91 is a circuit for rating the level of the data which have undergone address conversion in the address converter 15. It writes the data in the refresh memory 16 when it has found the level of the data is a predetermined standard range of level. When the level is not found to be within the stated range, that is, the data is a defective one, the level comparator 91 conveys the address of the data to the neighbor address generator 92. In response, the neighbor address generator 92 issues addresses of the data points surrounding the address received from the level comparator 91. Based on the addresses given by the generator 92, the read controller 93 reads out from the refresh memory 16, the data at the data points (4 points, for example) surrounding the defective data point of insufficient level and stores the read-out data in the register 94. In the video processor 95, the average value (not necessarily average), for example, of the data of the four points stored in the data register 94 is determined by calculation. This value is written in the address of the defective data point in the refresh memory 16.

If the defective data point happens to be on the zero level due to a fracture in one of the optical fibers making up the optical fiber bundle, the defective data are corrected by the data of the neighbor data points on condition that the data of the neighbor data points are normal. In this manner, the present embodiment of this invention is capable of improving the quality of picture image. The dark shade in the peripheral region of each unit strand is corrected in entirely the same manner.

Claims

1. An image display apparatus, comprising an optical fiber bundle consisting of a number of optical fibers and serving to conduct an optical image formed on the front end thereof to the rear end thereof, photoelectric conversion means for dividing said optical image formed in the face of said rear end into elements of light information assigned to the addresses of geometric positions of individual optical fibers of said optical fiber bundle in said rear end face, converting said elements of light information into electric signals, and issuing said electric signals, an address conversion means for memorizing the relationship between the addresses of geometric positions of said individual optical fibers in the face of a front end of said optical fiber bundle and the addresses of geometric positions of said individual optical fibers in the face of said rear end, rearranging said electric signals supplied from said photoelectric conversion means in corresponding with said addresses of positions of said individual optical fibers in the face of rear end of said optical fiber bundle, in the order according to said addresses of positions of individual optical fibers in said front end face of said optical fiber bundle, and issuing the rearranged electric signals, and a display device for displaying two-dimensionally said electric signals rearranged by said address conversion means thereby faithfully reproducing said optical image formed in said front end face of said optical fiber bundle.

2. An image display apparatus according to Claim 1, which further comprises a memory for memorizing as data said rearranged electric signals supplied from said address conversion means and means for reading out of the memory said data to be displayed on said display device.

3. An image display apparatus according to Claim 2, which further comprises comparator means for rating the magnitude of said rearranged electric signals from said address conversion means, and means for storing as data in said memory such an electric signal found by said comparator means as possessing a specified magnitude and, upon detection by said comparator means of such a defective electric signal not possessing said specified magnitude, reading out data stored in such addresses in said memory corresponding to the addresses of positions surrounding the address of position at which said defective electric signal ought to have appeared on said display device, performing a predetermined processing on said data, and writing in said memory the data resulting from said processing as data representing said defective electric signal.

4. An image display apparatus according to Claim 3, wherein said predetermined processing is an arithmetic operation for finding an average value of said data.

5. An image display apparatus according to any of Claims 2 to 4, wherein said memory for memorizing electric signals as data is a refresh memory.

6. An image display apparatus according to any of Claims 1 to 5, wherein said display device is a CRT display.

7. An image display apparatus according to any of Claims 1 to 3, wherein said address conversion means is a look up table which memorizes and tabulates the relationship between the addresses of the positions of individual optical fibers on one end of the optical fiber bundle and the addresses of the positions of said optical fibers on the other end, and said relationship is obtained by scanning one end face of said optical fiber bundle with light to inject light into corresponding optical fibers, detecting the positions of optical fibers showing light in the other end face during said scanning, memorizing and tabulating the results of said detection.

8. An image display apparatus according to any of Claims 1 to 3, wherein said address conversion means is a look up table which memorizes and tabulates the relationship between the addresses of positions of individual optical fibers on one end of said optical fiber bundle and the addresses of positions of said optical fibers on the other end, and said relationship is obtained by injecting light simultaneously to the end faces of all the optical fibers sharing in common each of the x addresses in an x-y two-dimensional address coordinates plane formed on one end face of said optical fiber bundle, memorizing upon each entry of light, the addresses of positions of the optical fibers showing light in a two-dimensional address coordinates plane formed at the other end face of said optical fiber bundle, then injecting again light simultaneously to the end faces of all the fibers sharing in common each of they addresses in said x-y two-dimensional address coordinates plane, memorizing upon each entry of light, the addresses of positions of the optical fibers showing light in the two-dimensional address coordinates plane formed at the other end face of said optical fiber bundle, and consolidating the results of said first and second memorization.

9. An image display apparatus according to Claim 7 or Claim 8, wherein the light to be used for scanning said front end face of said optical fiber bundle and injected into relevant optical fibers is a visible light or invisible light.

10. An image display apparatus substantially as herein described with reference to and as illustrated in the accompanying drawings. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~