WO2000021279A1

WO2000021279A1 - Optical image transmission

Info

Publication number: WO2000021279A1
Application number: PCT/GB1999/003103
Authority: WO
Inventors: Icaros Savvides
Original assignee: Icaros Savvides
Priority date: 1998-10-06
Filing date: 1999-10-05
Publication date: 2000-04-13
Also published as: GB9821630D0; GB2342524A; AU6100799A

Abstract

A plurality of optical fibres for the transmission of an optical image are arranged as a non-coherent bundle (10) in which the relative orientation of the fibres at an output end of the bundle differs from the relative orientation of the fibres at the other, image input end of the bundle, a processing device (15) being provided to receive an input signal from the output end of the optical fibres, and conversion means being provided for operating on a signal representative of said output end signal in a manner related to the differences between the relative orientations of the fibres at the respective ends of the bundle thereby to provide an output signal which is directly representative of the image at the input end of the fibre bundle.

Description

OPTICAL IMAGE TRANSMISSION

This invention relates to apparatus for the transmission of data such as data which defines an image, and to a method for the transmission of data such as that which defines an image. The invention relates in particular, though not exclusively, to apparatus comprising an optical image transmission device such as a flexible endoscope and to a method of use of a flexible endoscope or other optical image transmission device.

Endoscopes have many different applications and are used widely in the medical and industrial fields. They offer the only practical means of accomplishing certain tasks.

Many important applications of endoscopes require that the endoscope is of a flexible type.

To achieve flexibility between the input and output ends of the endoscope use is made of a bundle of optical fibres each of a small cross-section. In order that there is an accurate transmission of an image between input and output ends great care must be taken to ensure that the bundle is of a coherent type in which the fibres lie in the same orientation relative to one another at least at the respective ends of the bundle. Sometimes, for simplicity of manufacture and maintenance, the same orientation is preserved along the whole bundle length, but in other cases the fibres are laid spirally and allowed to move substantially randomly relative to one another at positions between their ends in order to provide a good level of flexibility, better than that attainable if the fibres are maintained in the same relative orientation along the whole of the bundle length.

The time and care needed to construct a fibre bundle of aligned fibres inevitably results in the endoscope being an expensive item of equipment. Care is therefore taken always to minimise the inevitable risk of damage to the fibre ends, and the resultant loss of optical quality, but very often the useful life of an endoscope is curtailed by damage to fibre ends.

One proposal has involved a method to refurbish a damaged end. However, refurbishment generally is only possible a small number of times before the bundle needs to be replaced, at significant cost. In accordance with one aspect of the present invention there is provided an apparatus for image transmission comprising a plurality of optical fibres arranged as a non-coherent bundle in which the relative orientation of the fibres at an output end of the bundle differs, typically in a substantially random manner, from the relative orientation of the fibres at the other, image input end of the bundle, a processing device to receive an input signal from the output end of the optical fibres, and conversion means for operating on a signal representative of said output end signal in a manner related to the differences between the relative orientations of the fibres at the respective ends of the bundle thereby to provide an output signal which is directly representative of the image at the input end of the fibre bundle.

It is envisaged that the conversion means typically will be an electronic type conversion means, but it is to be understood that other types of conversion means such as optical devices may be provided.

The processing device may be an electronic processing device which converts an input signal from the output end of the optical fibres to provide an electronic input signal to the conversion means.

Thus it is further envisaged that there may be associated with said output end of the fibre bundle an electronic processing device to receive an input signal from the output end of the optical fibres and to provide an output signal representative of the image at the input end of the fibre bundle, said electronic processing device comprising transducer means for receiving an optical signal from the output end of the fibre bundle and converting that signal to an electronic input signal, and that electronic conversion means may be provided for operating on said electronic input signal in a manner related to the differences between the relative orientations of the fibres at the respective ends of the bundle thereby to provide an electronic output signal which is directly representative of the image at the input end of the fibre bundle.

It is envisaged also that typically electronic conversion means will function to convert an electronic input signal in such manner that the electronic output signal is the same or substantially the same as that which would be provided if the optical fibres were in the form of a coherent bundle of aligned fibres that provide a visual output image directly representative of the input image as in a conventional endoscope.

The conversion means may, for example, be of a kind adapted to receive pre-prepared information concerning the relative orientation of the fibres at respective ends of the bundle and thereby enable the signal to the conversion means to be converted into a signal directly or substantially directly representative of an image at the input end of the fibre bundle. Alternatively the conversion means may, for example, be of a kind adapted for use in a mapping or like operation whereby it receives information concerning a calibration image received by the input end of the fibre bundle, relates that to an input signal received by the transducer means from the output end of the fibre bundle, and stores for future use the details of that relationship. The conversion means may be adapted to store information concerning the positioning of a small spot of light, such as that of a laser source, moved progressively over the whole area of the input end to transmit through the individual fibres one at a time.

An example of an electronic type transducer device to receive an input signal from the output end of the bundle of optical fibres is a charge coupled device (known as a "CCD"), and which may be of a kind known per se for use in a cam corder. However, other types of light responsive devices may be used as the electronic transducer means.

The transducer means typically will be of a kind comprising an array of pixels, in which case preferably it provides at least one pixel for each fibre end. Electronic processing and filtering techniques may be employed to enhance image quality and compensate for any quality loss such as might arise due to fibre ends not lying in close alignment with respective pixel positions. Alternatively or additionally, there may on average be a plurality of pixel positions per fibre end, for example on average more than five (5) and preferably more than twenty (20) pixel positions per fibre end.

The apparatus may comprise position alignment means whereby the position of the electronic transducer means may be adjusted relative to the output end of the fibre bundle, for example by rotation, translation or a combination of those movements, to obtain that relative positioning which provides the best or at least an acceptable image transmission quality.

The fibre bundle typically will be flexible, but it is to be understood that this is not an essential requirement of the invention and that the invention may be applied to image transmission in applications in which there is a requirement for an optical link though not necessarily a link of a flexible type.

If the bundle is required to be flexible, the fibres preferably are positioned with a spiral lay, and may be free to position and re-position themselves randomly during flexing of the bundle. However, to maintain the validity of information held by the electronic conversion means the fibres should be maintained in a fixed orientation relative to one another at each of their respective ends.

The image transmission apparatus may comprise a pair of bundles of optical fibres, or one bundle having two end zones. Apparatus of that kind may be adapted for providing a three dimensional image or signal from which a three dimensional image may be derived.

The electronic output signal may, for example, be applied to a monitor for a visual display, optionally via a computer for image processing, or to a head mountable vision system e.g. to give binocular vision, or to a memory store.

In accordance with another aspect of the present invention a method of optical image transmission comprises providing a plurality of optical fibres arranged as a non-coherent bundle in which the relative orientation of the fibres at an output end of the bundle differs, typically in a substantially random manner, from the relative orientation of the fibres at the other, image input end of the bundle, providing at said output end a processing device for receiving an optical signal from the output end of the fibre bundle, the method further comprising a mapping operation to establish the differences between the relative orientations of the fibre ends at the two ends of the bundle and retaining the results of said mapping operation in the processing device whereby said device is then operable to provide an output signal substantially directly representative of the image at the input end of the fibre bundle.

The processing device may be an electronic processing device and may comprise an electronic type conversion means to perform said mapping operation. Alternatively other types of processing or conversion means may be employed, at least in part, and may for example comprise optical type processing devices.

The results of the mapping operation may be retained in an electronic processing device whereby said device is operable to provide an electronic output signal substantially directly representative of the image at the input end of the fibre bundle.

The method may comprise applying the result of the mapping operation to the electronic processing means foroperating on said electronic input signal, or it may comprise use of said electronic conversion means as a part of the mapping operation, whereby said conversion means operates on the electronic input signal in a manner related to the differences between the relative orientations of the fibre ends at the respective ends of the bundle thereby to provide an electronic output signal which is substantially directly representative of the image at the input end of the fibre bundle.

The characteristics of a fibre bundle, in respect of the relationship between the relative orientations of the individual fibres at the respective ends of the fibre bundle, may be pre-mapped in a calibration operation performed prior to operationally assembling that fibre bundle with an electronic processing device. The information of that characteristic may then be inputted into the electronic device, and in the event that a fibre bundle needs to be replaced, for example if damaged in service, that information may be replaced by a new set of calibration characteristics applicable to a replacement optical fibre bundle.

The invention envisages also that in an alternative method an electronic processing device may be employed as a part of the mapping operation conducted to establish the relevant characteristics of a newly assembled or a replacement fibre bundle.

An example of a suitable method for mapping the relevant characteristics of a non-coherent fibre bundle comprises systematically moving a small spot of light, such as that of a fine laser beam, over the input end of the fibre bundle so that it transmits sequentially in defined order through the respective fibres, one at a time, and then comparing the positions at which that beam of light emerges from the other end of the bundle a sensed by pixels or like sensor positions of the electronic transducer means to provide mapping information.

The electronic processing device may, for example, comprise a frame store and signals received sequentially from individual pixels at the electronic transducer means may be sequentially re-arranged in the frame store having regard to the characteristics of the fibre bundle as established in the mapping operation thereby to provide a re-arranged sequence of signals corresponding directly or substantially directly in sequence with those which would have been obtained if the transducer means had directly scanned the original image in the absence of the interposed non-coherent optical fibre bundle.

Embodiments of an image transmission apparatus of the invention will now be described, by way of example only, with reference to the accompanying drawing which shows schematically parts of an apparatus of the invention, in an exploded form, and block diagrams representing image processing stages. An optical fibre bundle 10 of an endoscope having conventional end fittings and a sleeve (not shown) comprises a plurality of individual glass fibre filaments 11 held in a fixed orientation relative to one another at each of their respective ends 12,13. The bundle is of a non-coherent type in which the orientations at the two ends differ. Between the ends the fibres extend with a spiral lay and are free to move in orientation relative to one another during flexing of the endoscope.

An electronic processing device of the apparatus comprises a CCD type transducer 15 which is associated with the output end 13 of the fibre bundle via an optical coupler device 16, and acts as an optical sensor.

The sensor provides a digital type output signal which comprises individual signal elements obtained by sequential scanning and digitising of the outputs of the individual pixels 17 of the sensor. That digital type output signal is then processed in an electronic conversion means that re-arranges the order of the individual signal elements. The conversion means is pre-programmed with mapping information concerning the relative orientations of the fibres at the respective ends 12, 13 of the fibre bundle, that re-arrangement of signal elements being undertaken having regard to the mapping information thereby to provide an electronic output signal in which the sequence of the signal elements is the same as that which would arise , in the absence of the conversion means, only if the fibres were in the same orientation at the respective ends of the fibre bundle.

Thus, for example, the ordered sequence of the fibres shown as A - D at the input end 12 is randomly arranged at the output end 13, and is read in that random order by the optical sensor 15, as depicted in the sequence block 18. The electronic conversion means operates on the output of the sensor to re-order the signal elements and result in the signal elements from the fibres A - D again being in the original sequence as indicated in the memory translation matrix shown in block 19. In consequence an output display 20 provides an image representative of that at the input end 12 of the endoscope.

If the fibre bundle is re-furbished to result in a change of end orientations, or is replaced by another bundle, it is merely necessary to update the conversion information held byihe electronic conversion means, i.e. to update the memory translation matrix. That can be accomplished at much lower cost than the provision of a replacement fibre bundle of a coherent type having the same fibre orientation at each of the respective ends.

Claims

Claims:

1. Apparatus for image transmission comprising a plurality of optical fibres arranged as a non-coherent bundle in which the relative orientation of the fibres at an output end of the bundle differs from the relative orientation of the fibres at the other, image input end of the bundle, a processing device to receive an input signal from the output end of the optical fibres, and conversion means for operating on a signal representative of said output end signal in a manner related to the differences between the relative orientations of the fibres at the respective ends of the bundle thereby to provide an output signal which is directly representative of the image at the input end of the fibre bundle.

2. Apparatus according to claim 1 , wherein the conversion means is an electronic type conversion means.

3. Apparatus according to claim 1 or claim 2, wherein the processing device is an electronic type processing device operable to convert an input signal from the output end of the optical fibres to an electronic input signal to the conversion means.

4. Apparatus according to any one of the preceding claims, wherein an electronic type processing device is associated with said output end of the fibre bundle to receive an input signal from the output end of the optical fibres and to provide an output signal representative of the image at the input end of the fibre bundle, said electronic processing device comprising transducer means for receiving an optical signal from the output end of the fibre bundle and converting that signal to an electronic input signal, and an electronic type conversion means for operating on said electronic input signal in a manner related to the differences between the relative orientations of the fibres at the respective ends of the bundle thereby to provide an electronic output signal which is directly representative of the image at the input end of the fibre bundle.

5. Apparatus according to claim 4, wherein the electronic conversion means is operable to convert an electronic input signal in such manner that the electronic output signal is the same or substantially the same as that provided by optical fibres in the form of a coherent bundle of aligned fibres that provide a visual output image directly representative of the input image as in a conventional endoscope.

6. Apparatus according to any one of the preceding claims, wherein the conversion means is adapted to receive pre-prepared information concerning the relative orientation of the fibres at respective ends of the bundle and thereby enable the signal to the conversion means to be converted into a signal directly or substantially directly representative of an image at the input end of the fibre bundle.

7. Apparatus according to any one of claims 1 to 5, wherein the conversion means is of a kind adapted for use in a mapping or like operation whereby it is operable to receive information concerning a calibration image received by the input end of the fibre bundle, relate that to an input signal received by the transducer means from the output end of the fibre bundle, and store for future use the details of that relationship.

8. Apparatus according to any one of the preceding claims, wherein the conversion means is adapted to store information concerning the positioning of a small spot of light moved progressively over the whole area of the input end to transmit through the individual fibres one at a time.

9. Apparatus according to any one of the preceding claims, wherein an electronic type transducer device to receive an input signal from the output end of the bundle of optical fibres is a charge coupled device.

10. Apparatus according to any one of the preceding claims, wherein the transducer means comprises an array of pixels in which at least one pixel is provided for each fibre end.

11. Apparatus according to claim 10, wherein there are more than five (5) pixel positions per fibre end.

12. Apparatus according to any one of the preceding claims, and comprising position alignment means operable to adjust the position of the electronic transducer means relative to the output end of the fibre bundle.

13. Apparatus according to any one of the. preceding claims, wherein the fibre bundle is flexible.

14. Apparatus according to claim 13, wherein the fibres extend with a spiral lay and are free to position and re-position themselves randomly during flexing of the bundle at positions between the ends of the bundle, the fibres being maintained in a fixed orientation relative to one another at each of their respective ends.

15. Apparatus according to any one of the preceding claims, and comprising a pair of bundles of optical fibres, or one bundle having two end zones.

16. Apparatus for optical image transmission according to claim 1 , and substantially as herein before described with reference to the accompanying drawings.

17. An endoscope comprising apparatus according to any one of the preceding claims

18. Method of optical image transmission comprising providing a plurality of optical fibres arranged as a non-coherent bundle in which the relative orientation of the fibres at an output end of the bundle differs, typically in a substantially random manner, from the relative orientation of the fibres at the other, image input end of the bundle, providing at said output end a processing device for receiving an optical signal from the output end of the fibre bundle, the method further comprising a mapping operation to establish the differences between the relative orientations of the fibre ends at the two ends of the bundle and retaining the results of said mapping operation in the processing device whereby said device is then operable to provide an output signal substantially directly representative of the image at the input end of the fibre bundle.

19. Method according to claim 18, wherein use is made of an electronic type processing device which comprises an electronic type conversion means to perform said mapping operation.

20. Method according to claim 18 or claim 19, wherein the results of a mapping operation are retained in an electronic processing device and said device is then employed to provide an electronic output signal substantially directly representative of the image at the input end of the fibre bundle.

21. Method according to any one of claims 18 to 20, wherein the result of the mapping operation is applied to the electronic processing means for operating on said electronic input signal.

22. Method according to any one of claims 18 to 20, wherein the electronic conversion means is employed as a part of the mapping operation whereby said conversion means operates on the electronic input signal in a manner related to the differences between the relative orientations of the fibre ends at the respective ends of the bundle to provide an electronic output signal which is substantially directly representative of the image at the input end of the fibre bundle.

23. Method according to any one of claims 18 to 20, wherein the characteristics of a fibre bundle, in respect of the relationship between the relative orientations of the individual fibres at the respective ends of the fibre bundle, are pre-mapped in a calibration operation performed prior to operationally assembling that fibre bundle with an electronic processing device.

24. Method according to any one of claim s 18 to 20, and comprising mapping the relevant characteristics of a non-coherent fibre bundle by systematically moving a small spot of light, such as that of a fine laser beam, over the input end of the fibre bundle so that it transmits sequentially in defined order through the respective fibres, one at a time, and then comparing the positions at which that beam of light emerges from the other end of the bundle a sensed by pixels or like sensor positions of the electronic transducer means to provide mapping information.

25. Method according to claim 18 and substantially as herein before described.