WO1995025971A2

WO1995025971A2 - Scanning apparatus and method

Info

Publication number: WO1995025971A2
Application number: PCT/GB1995/000681
Authority: WO
Inventors: Richard Mark Charles; Peter James Hedges
Original assignee: Amfax Limited
Priority date: 1994-03-24
Filing date: 1995-03-24
Publication date: 1995-09-28
Also published as: AU1957495A; GB9405835D0; GB9619831D0; GB2302186B; GB2302186A; WO1995025971A3

Abstract

An optical fibre (4) with a light-receiving end (18) is mechanically driven so that its end moves to scan an image, the optical fibre being driven to oscillate substantially at or near the natural resonant frequency of the fibre. The movement of the optical fibre is driven by at least one bimorph ceramic oscillator (20, 22). The light-receiving end of the fibre traces a scan path in the form of a time-varying Lissajous pattern.

Description

SCANNING APPARATUS AND METHOD

The present invention relates lo scanning apparatus and a method of scanning using a light conduit for transmission of light from an image or to a display, in which the light conduit is vibrated to produce a scanning movement so as lo scan an image or display plane. In particular, the invention relates to the use of an optical fibre, the end of which is vibrated.

Image scanning devices are known from FR2575889, FR2575887, FR2575883, GB1530443 and GB14I0903 in which an optical fibre is vibrated so that its light-receiving end scans an image plane in a Lissajous pattern. These devices involve complex and bulky apparatus to vibrate the fibres involving vibrating strips driven by electromagnetic coils and magnets. Other devices arc known from US 4385798, US 3941927, EP-A-0591848 and US 4410235, in which optical fibres are attached to and excited by vibrating bimorph strips.

In a first aspect, the present invention relates to an image scanning apparatus including a light conduit for transmission of light from the image to a detector or display, the conduit having an end portion having an end for receiving light, the end portion being mechanically driven by driver means so as to oscillate in at least one direction substantially at or near its natural resonani frequency, or a harmonic of the natural resonant frequency. By selecting such a frequency, a stable and relatively large oscillation is caused.

It is preferable to vibrate the light conduii substantially at or near its natural resonant frequency in both directions so that the scanning end follows a complex and time-varying scan pattern which takes the form of a Lissajous pattern. As the scan pattern varies with lime, the whole of the image is scanned. Crystal or ceramic transducers can be used, being vibrated in a regular manner producing an oscillation of the end portion of the light conduit in a predetermined manner. Such transducers are small. Thus, scanning devices according to the

invention are useful in a wide range of applications, for example, in industry and in medicine

to view inaccessible regions.

In a second aspect, the present invention relates to an image scanning apparatus including a conduit for transmission of light from the image to a detector or display, the conduit having an end portion including an end for receiving light, the end portion being driven by driver

means so as to oscillate in two directions, the frequencies at which the conduit end portion is driven in the two directions being determined according to the relation f, = n f,. (r - 1) / (r ÷ 1) Equation (A)

where f, is the frequency in a first direction, f, is the frequency in a different direction to the first, r is the desired resolution, and n is 1, or n is a positive integer for example 1, 2, 3 etc. The natural resonant frequency fr of the conduit end portion in a direction is preferably first

determined and entered into the above relation as either f, or f, enabling the other frequency, f₂ or f„ to be determined. A frequency difference value f, - f₂ is then obtained. The

frequencies f{, f,' are then selected as. e.g. f,'^{; •}= fr + modulus (f, - f₂) Equation (B)

f,' = fr - modulus (f, - f₂) Equation (C) To provide the resolution required more exactly, the f,' or f value can be substituted into

equation (A) as f, or f₂ respectively and the calculations repeated. This can be done several times, i.e. iteratively, to approach optimum frequency values.

The conduit is preferably an optical fibre, having an end portion which is of substantial length and free to oscillate. The driver means drives the fibre end portion at a region of the fibre substantially away from its end. The fibre is preferably of circular cross-section.

The two directions are preferably the perpendicular X and Y directions in the scanning plane.

Having selected the frequencies, the scanning fibre end follows a complex and time-varying

scan pattern which takes the form of a Lissajous pattern. The whole image can be scanned in this way. The scan pattern can vary with time.

In a third aspect, the present invention provides an image scanning apparatus including a light conduit for transmission of light from an image to a detector or display, the conduit having an end portion including an end for receiving light which is excited by driver means in two directions so as to oscillate substantially at or near natural resonant frequencies in the two directions or harmonics thereof, the excitation frequencies in the two directions selected to provide a predetermined resolution and/or scanning rate.

By adjustment of at least one of the frequencies, the scanning resolution and/or scanning rate

can be altered. In particular, a low resolution/high frame rate scan can be altered to a high resolution/low frame rate scan by adjustment of the frequency difference. The low frame rate can be selected to be so low as to make the scan appear near static. In a fourth aspect, the invention relates to scanning apparatus for a display, the apparatus

including a light conduit for transmission of light to a display plane, the conduit having a light-transmitting end portion which is mechanically driven so as to scan the display plane,

and the light-transmitting end of the light conduit is driven so as to oscillate substantially at or near its resonant frequency or a harmonic thereof.

In an analogous manner to the image scanning apparatus, in the scanning apparatus for display, transducers, in particular, bimorph transducers, may be used to drive the scanning movement.

In a fifth aspect, the invention relates to scanning apparatus for a display, the apparatus including a light conduit for transmission of light to a display plane, the conduit having a light-transmitting end which is mechanically driven so as to scan the display plane, in which the light-receiving end follows a path of a time-varying Lissajous pattern in the display plane.

In its sixth aspect scanning apparatus for display can be used in combination with an image scanning apparatus for transmission of light from an image to provide an imaging and display system. The image scanning apparatus has a light conduit moving in a precisely determined manner. The same scan pattern can be replicated in the display, in particular by using ceramic or crystal bimorph transducers vibrating at the same frequencies and phases, and/or by providing optical fibres in the image scanning apparatus and display which have

substantially the same resonant frequency.

In its seventh aspect, the invention relates to image scanning apparatus and a method of scanning an image in which the scan takes the form of a Lissajous pattern. The scan path

overlaps or crosses over itself at several points at least. Accordingly, the resolution of the

image can be enhanced in those areas by averaging.

The image resolution is dependent on the relation of the cross-sectional area of the light

conduit to the image area to be scanned. As the scan path traced by the end of the light

conduit crosses itself many times, enhanced resolution is readily obtained by averaging.

In its eighth aspect, the invention relates to an image scanning apparatus comprising a light

conduit operative to transmit light to an image plane and from an image to a detector or

display, and driving means, the conduit having an end for light transmission and reception.

the end being mechanically driven by the driving means in use. so as to scan the image plane. Light from a light emitter follows a reverse optical path to that of received light. The emitter

may be modulated appropriately so as to illuminate only the area of interest. Particular wavelengths or energies of radiation could be used for example, to treat material or tissues

in a selected area.

In a ninth aspect, the invention provides an image scanning apparatus including a detector and light conduit for transmission of light from an image to the detector, the conduit having an end for receiving light which is driven by driver means so as to oscillate, the detector comprising a photon counter. The photon counter can be a photomultiplier tube. The detector can further comprise digital image processing circuitry. The use of photon counters gives enhanced sensitivity allowing the conduit end to be

oscillated more rapidly to provide an increased scanning frequency.

In a tenth aspect, the invention provides an image scanning apparatus including a light

conduit, such as an optical fibre, for transmission of light from the image to a detector or

display, the conduit having an end for receiving light which is driven by driver means so as

to oscillate and scan the image plane, the light conduit being sleeved by a tube to which the

conduit is fixed away from said conduit end, the tube being mounted so that it is free to be oscillated by reaction to movement of the conduit substantially out of phase with the conduit.

The tube preferably has a counter-motion to that of the conduit (i.e. it is an antiphase). An internally balanced structure is thus provided. The conduit and sleeve can be supported within

a further outer sleeve for protection. Support can be provided by an elastic plug.

In a eleventh aspect, the invention provides an image scanning apparatus including a light conduit, such as an optical fibre, for transmission of light from an image to a detector or display, the conduit having an end for receiving light which is driven by driver means, the

driver means applying force to the conduit at a region away from said end so as to oscillate

said end to scan the image plane, said region and said end being separated by a portion of the conduit at which the conduit is supported. The support is preferably provided by elastic support member. The elastic support member is preferably disposed within a sleeve. In use, the conduit preferably oscillates with respect to a pivot point disposed within the support

member.

In the twelfth aspect, the invention provides image scanning including a light conduit, such as an optical fibre, for transmission of light from the image to a detector or display, the

conduit having a light-receiving end which is driven so as to scan an image plane, the conduit

end being driven by at least one piezoelectric element so as to vibrate, in which the

piezoelectric element comprises piezoelectric material having been deposited directly on the

light conduit. Further steps in manufacture are preferably made after the deposition step. In

particular, piezoelectric material can be cut, preferably using a laser, so as to be made regular.

In a thirteenth aspect, the invention provides image scanning apparatus including a light

conduit for transmission of light from the image to a detector or display, the conduit having

a light-receiving end which is driven so as to scan an image plane, the conduit being driven by at least one piezoelectric element so as to vibrate, in which at least one piezoelectric

element comprises photostrictive material. The photostrictive material can be PLZT. Photostrictive material operates by converting incident light energy into an electric field to

activate the piezo material.

The photostrictive material or elements preferably operate under the power of light transmitted via the light conduit. In image scanning apparatus for display, the light used to excite the

photostrictive materials can also be used to illuminate the image plane. The illuminating light can be sent to the image plane via a separate light conduit.

In its fourteenth aspect, the invention relates to an image scanning apparatus comprising a light conduit operative to transmit light from an image to a detector or display, and driving means, the conduit having an end for light reception, the end being mechanically driven by

the driving means in use. so as to scan the^" image plane, in which light from a laser is transmitted to the image plane via the light conduit. Light from the laser follows a reverse optical path to that of received light. The laser may be modulated appropriately so as to

illuminate only the area of interest. Particular wavelengths or energies of radiation could be

used for example, to treat material or tissues in a selected area. Sending light along the light conduit to the image plane is efficient. Only the area of the image being detected at a particular moment in time is illuminated.

A preferred embodiment of the invention will now be described by way of example with reference to the drawings, in which:

Figure 1 is a simplified schematic view of a camera having a scanning apparatus according to the present invention;

Figure la shows an enlarged view of the optical fibre and oscillators shown in Figure 1.

Figure 2 is a schematic representation of the scan pattern according to the present invention;

Figure 3 is a schematic representation of the scan pattern in the central portion of the image.

Figure 4 is a schematic sectional view of a probe part of a medical endoscope including a scanning apparatus according to the present invention.

Figure 5 is a schematic representation of apparatus for imaging and display, including two scanning apparatuses according to the present invention; Figure 6 is a schematic sectional view of another camera having scanning apparatus according

to the present invention; and

Figure 7 is a schematic sectional view of another camera having scanning apparatus according to the present invention.

As shown in Figure 1 , the camera 2 consists of an optical fibre 4 connected at its rear end 6, via connecting fibres 8, to three light detectors 10 of conventional type. Each light detector 10 has a colour filter 12 to filter either red, green or blue light before detection, so that red,

green and blue colour signals are produced by the three detectors 10. In another embodiment, the three detectors 10 and three filters 12 are replaced by a single detector to provide a single brightness (intensity) signal. The single detector may be an infra red radiation detector, allowing the camera to be used for night-vision.

The camera 2 includes a converging lens 14 at its aperture. The lens 14 acts to focus an image to be detected on to a focal plane 16. The optical fibre 4 has a front end 18 which lies in this focal plane 16 and receives light from the image. This light is transmitted along the optical fibre 4 to the detectors 10.

The front end 18 of the optical fibre 4 is moved within the focal plane 16 so as to scan the image. As the front end 18 moves, corresponding samples of the image are received and passed along the optical fibre 4, to be detected by the detectors. The fibre front end 8 moves within an area of approximately 1mm² within the focal plane.

The resolution with which the image is sampled at any particular instance is a function of the

diameter of the fibre 4. The preferred fibre diameter is 10 micrometres which is a good

compromise between resolution and light sensitivity. The optical fibre has a sleeve of 125

micrometres diameter to provide sufficient stiffness.

The front end 18 of the optical fibre 4 is moved by vibrating the optical fibre using two

bimorph ceramic actuators 20, 22. A first bimorph actuators 20, which has connecting leads

24 for supplying power, is connected to a fixture element 26. The fixture element 26 acts to

hold the rear end 28 of the first bimorph actuator 20 in a fixed position, such that the first

bimorph actuator 20 is driven to oscillate in the sideways (X) direction.

The second bimorph actuator 22 has a rear end 30 fixed to the front end 32 of the first

bimorph oscillator 20. The second bimorph actuator 22, which has connecting leads 24 for power supply, is fixed so as to oscillate in an up-down (Y) direction whilst being driven by the first bimorph actuator 20 to move also in the sideways (X) direction. In consequence, the front end 36 of the second bimorph actuator 22 vibrates in both X and Y directions within

the focal plane 16.

The bimorph actuators 20, 22 are fitted to the optical fibre 4. The frequencies at which the bimorph actuators 20. 22 are operated are selected so as to vibrate the assembly of the

bimorph activities and optical fibre at or near its natural resonant frequencies in both X and

Y directions. The natural frequencies of vibration of the assembly of the bimorph activities and optical fibre

in the two directions depend predominantly on the stiffness, mass, and cross-section of the

fibre and. as shown in Figure la, the distance between the fibre front end 18 and a rigid

fixture region part-way along the length of the fibre 4. Of course, with a fibre having the

preferred circular cross-section, this dependence is independent of X-Y orientation.

As shown in Figure 1A, the fibre 4 includes further portions 3, 5 which are fixed to, and

oscillated by, the bimorph oscillators 20, 22. These also contribute to a minor extent to the

natural resonant frequencies of the fibre in the X and Y directions. Specifically, the fibre

portion 3 together with the attached bimorph 22. which oscillates in the Y direction, affect

the overall natural resonant frequency in the Y direction. The fibre portion 5 and bimorph

20 also contribute to the natural resonant frequency in the X direction.

In an alternative embodiment (not shown) the optical fibre fits within a bore through the

bimorph oscillators.

Vibrating the fibre 4 at or near its resonant frequencies in this way results in the position of

the fibre front end 18 being accurately known at any time. This enables the light samples to be displayed directly using a display having the same scan pattern. Specifically, a fibre can

be vibrated at its two ends so as to scan identical paths, as defined by equations (D) and (E). Light is received at one end and passed directly to the other end for transmission to a display. Light amplification can be undertaken if necessary. Alternatively, the light samples can be detected and stored as X, Y and light intensity data in a memory or framestore. The data can then be read out so as to be converted to signals of any predetermined scan pattern format, such as the conventional raster scan format.

As the overall resonant frequencies in the X and Y directions are slightly different, the first

bimorph actuator 20 is set to vibrate at a slightly different frequency than the second bimorph actuator 22. The fibre front end 18 vibrates sinusoidally in both X and Y directions. In the X and Y directions, the fibre end 18 follows a path defined by

x = A sin 2 πf_xt Equation (D)

y = A' sin 2 πf t Equation (E)

where A and A' are amplitudes, t is time, x is distance in the x direction, y is distance in the

y direction. f_x is frequency in the x direction, and f_y is frequency in the y direction.

To explain how the fibre scans, Figure 2 which shows the paths which the fibre end 18 would

take if instantaneous phase values were fixed. Figure 2 gives an idea of how the scan is built

up. As phase is time-varying in a selectable manner, the whole image plane can be scanned with a predictable resolution.

The path taken by the fibre end 18 in the central portion of an image plane is shown in Figure

3, where individual lines are numbered to indicate their order in the scan sequence. Each square bounded by the scan lines represents the ability of the scan to resolve images or display images. For example, if the square is 1/512 of the total image/display in both orthogonal directions then the resolution can be said to be 512 by 512. This equates to 256

line pairs.

Using the scanning method adopted, it is the centre part of the image plane which has the least resolution. It is for this reason the centre of the image is considered for the practical

purpose of calculating the frequencies required to obtain a desired image/display resolution.

The frequencies in the x and y directions at which to oscillate the fibre end 18 are determined

according to

f_x = n f_y . (r - 1) / (r + 1) (Equation F) where f_x is the frequency in the X direction

f_v is the frequency in the Y direction r is the desired resolution, and

n = 1, or n is a positive integer for example 1, 2, 3 etc.

In practice, the natural resonant frequency of the fibre end 18 is found and substituted in the above relation as f_x or f_y. The other frequency f_v or f_x is determined from which a frequency differency modulus f_x - f_y is calculated. The frequencies for driving the fibre are then selected

as f = f_r + modulus (f_x - f_y) Equation (G)

f = f_r - modulus (f_x - f_y) Equation (H)

To obtain the desired resolution more precisely, f or f_y' can be substituted into Equation (D) so as to obtain a revised frequency difference and hence revised f_x and f_y. Several such

iterations can be made if necessary.

The frequency difference f_x - f_y is a measure of the frame repeat rate. As regards resolution, image scanning resolution is dictated by the physical size of the image

plane and the size of the optical conduit. For example, scanning a 1mm by 1mm image plane

with a 10 microns diameter optical fibre gives a basic resolution of 100 x 100. If the image

were 5mm by 5mm scanning, using the same fibre would give a basic resolution of 500 x

500. In practice, higher resolutions are obtained due to oversampling the image, i.e. the path

taken by the scanning fibre end overlaps itself somewhat.

Display resolution can. in some circumstances, limit the resolution of the displayed image.

For example, if a 512 x 512 display device is used together with a scanned image of 1mm

by 1 mm scanned with a fibre of 10 microns diameter, to ensure high resolution it is

necessary to scan with 5.12 times oversampling. A 512 by 512 display device used to display

an image detected from a 5.12 mm by 5.12 mm plane scanned by a 10 micron diameter fibre

will basically give 512 by 512 resolution with no oversampling.

The apparatus shown in Figure 1 can be used for display, basically by reversing the direction

of light along the optical fibre 4.

As shown in Figure 5, an image scanner 42, which includes image scanning apparatus as described, is connected via an optical signal amplifier 44 to a display 46. The display includes similar scanning apparatus including an optical fibre 4 and associated bimorph transducers 20,22. The optical fibre 4 in the display has the same natural resonant frequency

as the one in the scanner.

In the image scanning apparatus or the scanning apparatus for display, the optical fibre 4 is vibrated at or near its resonant frequency in both directions so that the fibre front end 18

follows a complex and slowly varying scan pattern which takes the form of a Lissajous

pattern. The Lissajous pattern depends on both the frequency relationship between the

frequencies in the up-down (Y) and sideways (X) directions at which the fibre 4 is vibrated,

and also on the phase difference between the vibrations in the two directions. The overall pattern can be fixed such that the same path is taken repeatedly to scan the image.

Alternatively, the scan pattern can vary with time.

The frequency difference which can be very small such as one hundredth of one Hertz, is

adjusted so as to control both the resolution and frame rate of the scanning. A fine

adjustment of the frequency difference alters the Lissajous scan path such that resolution can

be simply and accurately controlled. By altering the frequency difference, the apparent frame

rate can be adjusted from near-static to a high frame rate.

By using a complex Lissajous scan pattern, the path traced by the fibre front end 18 crosses

over itself many times. By processing the signals from detectors 10, it is possible to average video signals representative of the received light samples where the paths cross so as to

provide video signals relating to an image with enhanced resolution.

Other image-processing is possible. In particular, by storing and averaging video signals from successive scans it is possible to provide a display image which is effectively a continuously updated weighted average of the present and previous scans. This acts to enhance the image being displayed by effectively smoothing noise. Alternatively, providing the display plane with a fluorescent screen in which fluorescence lasts for longer than the time taken for one scan, has similar averaging effect.

The preferred camera 2 has a very small size, approximately 2mm diameter by 15mm long,

which allows a wide range of uses.

As shown in Figure 4, the probe part of a medical endoscope, including a scanning device according to the present invention, has an illuminating tubular wall 40 down which light is

passed to illuminate the area to be imaged adjacent the endoscope front end 42. The scanning device is held within the tubular wall 40 and protected by it. The receiving front end 18 of

the optical fibre 4 is disposed near the endoscope front end 42.

In an alternative endoscope which includes a scanning device according to the present invention, illuminating light can be directed to the target area down the optical fibre itself. Thus, a separate illuminating wall is not required. By appropriately modulating a light emitter, only a selected area in the image plane receives light, and so is imaged.

As the optical fibre end is continuously moving, the illumination can be fairly intense without

damage to materials in the image plane. Alternatively, an emitter of high energy radiation such as a laser can be used in conjunction with the scanning device, for example, for

microsurgery.

In some medical procedures, drugs are administered to a body and a certain wavelength of light can be used, such as UV light, to effectively activate the drug in a selected region of the body. The scanning device according to the present invention can be used to provide such activating light to the selected region whilst allowing imaging of the region either before and

after, or at substantially the same time. The area for treatment could be viewed and selected

under microprocessor control, for example, using a mouse or light pen in conjunction with

a Visual Display Unit.

The scanning device can also be used for medical analysis such as pulse oximetry. By

illuminating with light of certain wavelengths, the received light provides a measure of blood

oxygen level or flow. The resultant image would show the various oxygen level area in the

target area.

In a further embodiment, illuminating light is provided by a separate composite optical fibre including several narrow diameter conductors. These would allow selective illumination of

small image regions.

Referring back to the camera shown in Figure 1, the detectors 10 are preferably digital photon

counters such as photon multiplier tubes. These are very light-sensitive such that higher frequencing scanning can be undertaken than would otherwise be the case. Such detectors can be used as part of a digital image processing/display system.

In a further embodiment, as shown in Figure 6, the optical fibre 4 and attached bimorphs 20, 22 are held within a protective inner tube 48. The inner tube 48 has a countermotion to the

vibration of the bimorphs 20, 22. As the inner tube 48 has greater mass than the birmorphs 20. 22 it provides a vibrating fibre with a stable support. In consequence, fixture to a heavy

base plate is not required. In the Figure 6 embodiment, the optical fibre 4, bimorphs 20, 22 and inner tube 48 are

supported coaxially within an outer tube 50 by a silicon rubber support plug 52. The end 54

of the inner tube 48 away from the fibre scanning end 18 is embedded in the support being

52. As no base plate is required, the camera can be made very small.

In a further embodiment, as shown in Figure 7, the fibre 4 which has bimorphs 20, 22

mounted thereon is supported within a protective tube 54 by a silicon rubber bung 56. The

fibre 2 is supported such that the bimorphs 20. 22 and the scanning end 18 of the fibre 2 are

on opposite sides 58. 60 of the bung 56. Exciting the fibre 4 results in a pivotal action around a point in or near the bung 56. The masses of vibrating parts on the two sides 58, 60 of the bung are selected so as to approximately balance.

Besides bimorph transducers, other transducers could be used providing they are able to provide the required mechanical movement when provided with a suitable electrical stimulating signal. In particular, some embodiments of the invention include piezoelectric

actuators. Piezoelectric material can be grown onto the optical fibre, or otherwise deposited on the fibre. Crystals can then be cut, in particular using a laser to do the cutting, so as to provide a regular shaped crystal oscillator.

Bimorph crystals can also be grown directly on optical fibres.

Further embodiments of the invention include photostrictive actuators. Some do not require an external power source, the photostrictive actuators being powered by light transmitted

down the optical fibre, in either direction. Crystal or ceramic transducers, for example

Claims

multimorphs or simple ceramic devices could be used.In a further embodiment (not shown) use of selective red, green and blue light strobe emitterwould allow colour pictures to be obtained even where a monochrome detector is used inplace of red, green and blue light detectors.In a still further embodiment (not shown), a second optical fibre is used, also connected tothe front end 36 of the second bimorph oscillator, so as to vibrate in synchrony with the firstoptical fibre. This enables 3-D, i.e. stereoscopic imaging. In other embodiments of theinvention the optical fibre 4 is replaced by a bundle of optical fibres.The term "light" is used in this patent specification to include Infra-red radiation, ultra violet radiation and electromagnetic radiation of all other wavelengths which can be transmitted viaa light conduit such as an optical fibre, and detected. CLAIMS

1. Image scanning apparatus comprising a light conduit for transmission of light from an

image to a detector or display, and driving means, the conduit having an end portion having

an end for receiving light, the end portion being mechanically driven by the driving means,

in use, so as to oscillate within a scanning plane, the driving means being operative to drive the conduit end portion to oscillate in at least one direction substantially at or near its natural

resonant frequency.

2. Image scanning apparatus according to claim 1, in which the driving means acts to oscillate the conduit end in two orthogonal directions substantially at or near the natural

resonant frequency.

3. Image scanning apparatus according to claim 2 or claim 3, in which the conduit end follows a path of a time-varying Lissajous pattern in the scanning plane.

4. Image scanning apparatus according to any of the claims 1 to 3, in which the light

conduit is an optical fibre.

5. Image scanning apparatus according to any preceding claim, in which the driving means comprising at least one ceramic transducer or crystal transducer operative to oscillate

the conduit end in at least one direction.

6. Image scanning apparatus according to claim 5, in which at least one transducer is a

bimorph ceramic transducer.

7. Image scanning apparatus according to claim 5 or claim 6, in which the driving means

comprises two transducers which operate to vibrate in different directions to oscillate the

conduit end in both directions.

8. Image scanning apparatus according to claim 7, in which the two transducers vibrate

in orthogonal directions.

9. Image scanning apparatus according to claim 7 or claim 8, in which the two transducers each have two ends and are joined together at respective first ends, one of the

second ends is held fast, and the other second end, which vibrate in use, is attached to and

drives the oscillation of the light conduit.

10. Image scanning apparatus according to any preceding claim, in which the oscillation in each direction is driven by a bimorph ceramic transducer.

1 1. A method of scanning an image by mechanically driving a light-receiving end of a light conduit, the light-receiving end being oscillated in at least one direction in a scanning plane, substantially at or near its natural resonant frequency.

12. A method of scanning according to claim 11, in which the light-receiving end is oscillated in two orthogonal directions in the scanning plane substantially at or near its natural resonant frequency.

13. A method of scanning according to claim 1 1 or claim 12, in which the light-receiving end follows a path of a time-varying Lissajous pattern in the scanning plane.

14. Image scanning apparatus including a conduit for transmission of light from the image to a detector or display, the conduit having an end portion including an end for receiving light, the end portion being driven by driver means so as to oscillate in two directions, the frequencies at which the conduit end portion is driven in the two directions being determined according to the relation f, = f₂. (r - l) / (r + l) where f, is the frequency in a first direction, f₂ is the frequency in a different direction to the first, and r is the desired resolution.

15. Image scanning apparatus according to claim 14, in which the conduit end portion is driven is at least one direction substantially at or near its natural resonant frequency.

16. Image scanning apparatus according to claim 14 or claim 15, in which the natural resonant frequency fr of the conduit end portion in a direction is first determined and entered into the relation as either f, or f₂ enabling the other frequency, f₂ or f,, to be determined.

17. Image scanning apparatus according to claim 16, in which a frequency difference value

f, - f, is obtained, to provide updated driving frequencies f , f selected as

f = fr + modulus (f, - f₂)

f = fr - modulus (f, - f₂)

18. Image scanning apparatus according to claim 17, in which the f or f value is

substituted into equation (A) as f, or f₂ respectively and the calculations repeated, to approach

the resolution required more exactly.

19. Image scanning apparatus according to claim 18. in which updating of f and fv

values is undertaken iteratively to approach optimum frequency values.

20. Image scanning apparatus according to any of claims 14 to 19, in which the conduit

is an optical fibre, having an end portion which is of substantial length and free to oscillate.

21. Image scanning apparatus according to any of claims 14 to 20, in which the driver means drives the fibre at a region of the fibre substantially away from its end.

22. Image scanning apparatus according to any of claims 14 to 21, in which the fibre is

of circular cross-section.

23. Image scanning apparatus according to any of claims 14 to 22, in which, the two

directions are the perpendicular X and Y directions in the scanning plane.

24. Image scanning apparatus according to any of claims 14 to 23, in which, having

selected the frequencies, the scanning fibre end follows a complex and time-varying scan

pattern which takes the form of a Lissajous pattern.

25. Image scanning apparatus according to claim 24, in which, the whole image is scanned.

26. Image scanning apparatus according to claim 24 or claim 25, in which the scan pattern can vary with time.

27. Image scanning apparatus including a light conduit for transmission of light from an image to a detector or display, the conduit having an end portion including an end for

receiving light which is excited by driver means in two directions so as to oscillate substantially at or near natural resonant frequencies in the two directions, the excitation

frequencies in the two directions selected to provide a predetermined resolution and/or

scanning rate.

28. Image scanning apparatus according to claim 27, in which by adjustment of at least

one of the frequencies, the scanning resolution and/or scanning rate is alterable.

29. Image scanning apparatus according to claim 28, in which a low resolution/high frame rate scan is alterable to a high resolution/low frame rate scan by adjustment of the frequency

difference.

30. Image scanning apparatus according to any of claims 27 to 29, in which a low frame

rate can be selected to be so low as to make the scan appear near static.

31. Scanning apparatus for a display, the apparatus comprising a light conduit for

transmission of light to a display plane, and driving means, the conduit having a light- transmitting end which is mechanically driven by the driving means in use. so as to scan the

display plane, in which the driving means is operative to drive the conduit end to oscillate

substantially at or near its natural resonant frequency.

32. Scanning apparatus according to claim 31, in which the driving means comprises at least one bimorph ceramic transduce operative to oscillate the conduit end in at least one

direction.

33. Scanning apparatus according to any of claim 31 or claim 32, in which the light-

receiving end follows a path of a time-varying Lissajous pattern in the display plane.

34. Scanning apparatus for a display, the apparatus comprising a light conduit for transmission of light to a display plane, and driving means, the conduit having a light-

transmitting end which is mechanically driven by the driving means in use, so as to scan the display plane, in which the light-receiving end follows a path of a time-varying Lissajous

pattern in the display plane.

35. Scanning apparatus according to claim 34, in which the driving means comprises at least one bimorph ceramic transducer operative to oscillate the conduit end in at least one

direction.

36. Scanning apparatus according to claim 34 or claim 35, in which the driving means is

operative to drive the conduit end to oscillate substantially at or near its natural resonant frequency.

37. An image scanning and display apparatus comprising image scanning apparatus

according to any of claims 1 to 10. or 14 to 20 in combination with a scanning apparatus for display according to any of claims 31 to 36.

38. Image scanning apparatus including means to scan an image according to a scan pattern which substantially takes the form of a Lissajous pattern, the path of the scan pattern including crossovers and/or overlaps, in which image data relating to each region of said crossovers and/or overlaps is averaged to enhance image resolution.

39. A method of scanning an image according to a Lissajous scan pattern which includes crossovers and/or overlaps, including averaging image data at said crossovers and/or overlaps

to enhance image resolution.

40. Image scanning apparatus comprising a light conduit operative to transmit light to an image plane and from an image to a detector or display, and driving means, the conduit having an end for light transmission and/or reception, the end being mechanically driven by the driving means in use, so as to scan the image plane, a light source operative to provide

light to illuminate the image plane via the light conduit, in which the light source is adapted

to provide light for both illuminating and treating materials or tissues in the image plane.

41. Image scanning apparatus according to claim 40, in which the light source is

modulated in use to irradiate a selectable area of interest.

42. Image scanning apparatus according to claim 40 or claim 41. in which the wavelength

of light is selectable.

43. Image scanning apparatus including a detector and light conduit for transmission of light from an image to the detector, the conduit having an end for receiving light which is driven by driver means so as to oscillate, the detector comprising a photon counter.

44. Image scanning apparatus according to claim 43, in which the photon counter is a

photomultiplier tube.

45. Image scanning apparatus according to claim 43 or claim 44, in which the detector further comprises digital image processing circuitry.

46. Image scanning apparatus including a light conduit for transmission of light from the image to a detector or display, the conduit having an end for receiving light which is driven

by driver means so as to oscillate to scan the image plane, the light conduit being sleeved by a tube to which the conduit is fixed away from said conduit end, the tube being mounted so that it is free to be oscillated by reaction to movement of the conduit substantially out of

phase with the conduit.

47. Image scanning apparatus according to claim 46, in which, in use the tube has a counter-motion to that of the conduit.

48. Image scanning apparatus according to claim 46 or 47, in which the conduit and sleeve

are supported within a further outer sleeve for protection.

49. Image scanning apparatus according to claim 45, 47 or 48, in which support is by an

elastic plug.

50. Image scanning apparatus including a light conduit for transmission of light from an image to a detector or display, the conduit having an end for receiving light which is driven by driver means, the driver means applying force to the conduit at a region away from said end so as to oscillate said end to scan the image plane, said region and said end being separated by a portion of the conduit at which the conduit is supported.

51. An image scanning apparatus according to claim 50, in which an elastic support

member provides the support to the conduit.

52. An image scanning apparatus according to claim 50 or claim 51 in which the elastic

support member is disposed within a sleeve.

53. An image scanning apparatus according to any of claims 50 to 52, in which, in use,

the conduit oscillates with respect to a pivot point disposed within the support member.

54. Image scanning apparatus including a light conduit, such as an optical fibre, for

transmission of light from the image to a detector or display, the conduit having a light-

receiving end which is driven so as to scan an image plane, the conduit end being driven by at least one piezoelectric element so as to vibrate, in which the piezoelectric element

comprises piezoelectric material having been deposited directly on the light conduit.

55. Image scanning apparatus according to claim 54, in which after deposition piezoelectric material is cut so as to be made regular.

56. Image scanning apparatus according to claim 55, in which the cutting step is

undertaken using a laser.

57. Image scanning apparatus including a light conduit for transmission of light from the image to a detector or display, the conduit having a light-receiving end which is driven so as

to scan an image plane, the conduit being driven by at least one piezoelectric element so as to vibrate, in which at least one piezoelectric element comprises photostrictive material.

58. Image scanning apparatus according to claim 57, in which the photostrictive material

is PLZT.

59. Image scanning apparatus according to claim 57 or claim 58, in which the photostrictive material or elements operate under the power of light transmitted via the light conduit.

60. Image scanning apparatus according to any of claims 57 to 59 for display, light is applied to excite the photostrictive materials and also to illuminate the image plane.

61. Image scanning apparatus according to any of claims 57 to 60, in which the illuminating light is sent to the image plane via a separate light conduit

62. Image scanning apparatus comprising a light conduit operative to transmit light from an image to a detector or display, and driving means, the conduit having an end for light reception, the end being mechanically driven by the driving means in use, so as to scan the image plane, in which light from a laser is transmitted to the image plane via the light conduit

63. Image scanning apparatus according to claim 62, in which light from the laser follows a reverse optical path lo that of received light.

64. Image scanning apparatus according to claim 62 or claim 63 in which the laser is modulated to illuminate only the area of interest.

65. Image scanning apparatus according to any of claims 62 to 64, in which wavelengths and energies of radiaiion are selected to treat material or tissues in a selected area.

66. Image scanning apparatus substantially as hereinbefore described with reference to the

drawings.

67. A method of scanning an image substantially as hereinbefore described with reference to the drawings.

68. Scanning apparatus for a display substantially as hereinbefore described with reference

to the drawings.