WO1993016409A1

WO1993016409A1 - Method for transferring visual information

Info

Publication number: WO1993016409A1
Application number: PCT/FI1993/000033
Authority: WO
Inventors: Jouko Viitanen; Jukka Lekkala
Original assignee: Valtion Teknillinen Tutkimuskeskus
Priority date: 1992-02-11
Filing date: 1993-02-10
Publication date: 1993-08-19
Also published as: AU3454693A; FI920559A0; FI88754C; FI88754B

Abstract

The method according to the invention is intended for transmitting visual information. Visual information is optically transmitted from an information source (1) by emitting beams of light from an illuminator (10) onto a data transmitting first surface (2) and onto a data visualizing second surface (3) which forms a display surface, such as a viewing screen, display screen, scanning surface or the like. An optically anisotropic medium (4), such as a liquid crystal or the like, is arranged between the first surface (2) and the second surface (3). For the application of the method, a preferably closed structure (2, 3, 4, 65) is formed, wherein the said first (2) and second surface (3) are preferably essentially parallel and wherein organs (5) are arranged to direct the transmission of information between the said surfaces (2, 3), the function of the organs being at least partially based on changing the refractive index of the said medium (4). According to the invention, the organs (5) for controlling the transmission of the information are arranged to be operated by an arrangement at least partially transmitting optic energy into vibration of electron plasm, such as one based on the surface plasmon resonance phenomenon or the like. The structure is thus equipped with one or several electrical transformers (7) with electron plasm, such as a metal film, layer or the like.

Description

Method for transferring visual information

The invention relates to a method for transmitting

5 visual information, wherein visual information is e- optically transmitted from an information source, e.g. by emitting beams of light or from an illuminator or in a corresponding manner, on a data transmitting first surface and on a data visualizing second surface

10 which forms a display surface, such as a viewing screen, display screen, scanning surface or the like, wherein an optically anisotropic medium, such as a liquid crystal or the like, is arranged between the said first and second surface. For application of the

15 method, a preferably closed structure is formed, wherein the said first and second surface are prefer¬ ably essentially parallel and organs are arranged to direct the transmission of information between the said surfaces, the function of the organs being at

20 least partially based on changing the refractive index of the said medium.

Display elements utilizing liquid crystal materials are generally known and used in the industry of the

25 field. The types of liquid crystal display which are most commonly used at the present are based on rotating the plane of polarization of light, including twist- - ing nematic (TN) and electrically controlled bire¬ fringence (ECB) displays. Displays of this type are

30 described in several publications. Such displays can be classified as passive, because they do not neces¬ sarily require additional illuminators for viewing but the light of the environment is sufficient. For viewing in the dark, however, a specially arranged

35 background illumination is needed.

Also a display type based on total internal reflection (TIR) is known [Urisu, Green] but less popular in practical use. A TIR display is typically active, because it requires precisely collimated light, which is not possible using diffused illumination but specially arranged illuminators are needed. Illumina- tors of this kind can be arranged to be modulatable so that the number of gray shades of the image points can be even relatively high. However, this solution is expensive, particularly with a low multiplexing degree so that a large number of illuminators is needed.

Since a high resolution display can include several hundred thousand image points, a difficult problem with most types of liquid crystal displays lies in the control of the image points. Attempts have been made to increase the multiplexing degree e.g. by integrating active image-point guiding electronic switches for each image point in the display panel (active matrix or TFT displays) .

The present technology of liquid crystal display has several disadvantages. The multiplexing degree is limited, which means that the complexity of the display control electronics makes it expensive to manufacture displays with a high resolution. The limiting factor is either the decrease of contrast (typically with passive displays) or the slowness of the switching means of the liquid crystal (with active displays) . Using active matrix techniques, the weakening of contrast can be avoided in passive displays, but the technique of manufacturing the display panel is demanding and expensive, because separate control transistors or diodes must be manufactured for each image point. The number of grey or colour shades is limited in passive display types.

Particularly in the manufacture of displays based on rotating the plane of polarization of light, the tolerances or the thickness of the liquid crystal layer are critical, which raises the expenses. The requirements of precision become significant par¬ ticularly with displays of large dimensions.

Further, the response time of most display types is relatively slow, which weakens the quality of the picture e.g. when viewing a video or television screen.

Finnish Patent Application Publication FI-906095 "Method for transmission of visual information" [Jouko Viitanen] discloses a method which is more developed in comparison with the prior art. The method is based on optical transmission of visual information, e.g. by means of optic fibres or the like, and oh changing the refractive index of the medium, such as a liquid crystal or the like, mechanically, i.e. acoustically. Consequently, the said method utilizes particularly the change in the refractive index due to the change of motive state in the medium and induced by mechanical means effective in the medium. In spite of the theore¬ tical advantages of the method there is no sufficient experience on its application into practice so far.

Using the method of the invention, a decisive improve¬ ment is achieved on the above-mentioned disadvantages of the techniques most commonly used at the present. Further, it provides a significant expansion also of the possible applications of the above-mentioned Finnish Publication. For achieving this, the method of the invention is primarily characterized in that the organs controlling the transmission of the informa¬ tion are arranged to be operated by an arrangement at least partially transmitting optic energy into vibra- tion of electron plasm, such as one based on the surface plasmon resonance phenomenon or the like, wherein the structure is equipped with one or several electric transformer with electron plasm, such as a metal film, layer or the like.

The most important advantage of the invention, a change in the orientation of a substantially thinner layer of the liquid crystal is required for switching the light by the method as compared with the methods of prior art. Thus particularly the return of the layer required for the switching to dormancy is accelerated. Further, the characteristic performance curve of the switching phenomenon is very sharp, which also accelerates the switching. Furthermore, the characteristic performance curve has a sharp peak corresponding to the maximum emission of light. Consequently, as compared with the structural prin¬ ciples of prior art, a relatively simple arrangement can be used to manufacture a display with only one active image point at a time. It is thus possible to provide the control eletronics in an inexpensive manner and rise the multiplexing level of the display high. Also, the thickness of the liquid crystal layer required in the display is not critical, which makes it very inexpensive to manufacture the applications of the method.

In the following description, the invention is de¬ scribed in detail with reference to the appended drawings. In the drawings,

Fig. 1 shows a cross-sectional view of an ad¬ vantageous embodiment of the method of the invention,

Fig. 2 illustrates the surface plasmon resonance phenomenon, and Fig. 3 shows the characteristic performance curve of the surface plasmon resonance phenomenon.

The method shown in Fig. 1 is intended for transmitting visual information. Visual information is transmitted from an information source 1 optically, by emitting beams of light or the like from an illuminator 10, on a data transmitting first surface 2 and on a data visualizing second surface 3 which forms a display surface 60, such as a viewing screen, display screen, scanning surface or the like. An optically anisotropic medium, such as a liquid crystal or the like, is arranged between the first surface 2 and the second surface 3. For application of the method, a preferably closed structure 2, 3, 4, 65 is formed, wherein the said first surface 2 and second surface 3 are essen¬ tially parallel and organs 5 are arranged to direct the transmission of information between the said surfaces 2, 3, the function of the organs 5 being at least partially based on changing the refractive index of the medium 4. According to the invention, the organs 5 controlling the transmission of the information are further arranged to be operated by an arrangement at least partially transmitting optic energy into vibration of electron plasm, such as one based on the surface plasmon resonance phenomenon or the like. The structure is thus equipped with one or several electromagnetic transformers 7 with electron plasm, such as a metal film 40, layer or the like.

The term surface plasmon resonance (SPR) refers to the phenomenon wherein the so-called evanescent wave present in total reflection of light is used for generating an electromagnetic wave in the electron plasm of the surface of a metal, i.e. a plasmon. By a suitable arrangement, the wave vector of the evanescent wave resonates with the wave vector of the electron plasm of the metal film, and the total light energy is transmitted into vibration of the electron plasm.

The resonance can be excited using an Otto, Kretschmann or Sarid configuration. Figure 2 shows the most commonly used Kretschmann configuration, where the p-polarized light I_; is emitted from a medium p with a higher optic density and totally reflected I_r at the interface of the medium p and a medium v with a lower optic density. At the interface, a thin (in the range of 50 nm) metal layer m has been vaporized, the plasmon B_sp being formed on the outer surface thereof. Upon measuring the reflection coefficient R (the ratio between the intensity of the reflected light I_r and the intensity of the incoming light I_; ) as a function of the angle Θ, a sharp resonance minimum can be observed, as illustrated in Fig. 3. The reso¬ nance (the depth and width of the peak) is dependent on the dielectric constants (eO, e2) of the media p, v, the dielectric function (el) and thickness of the metal , the wavelength of the light used, as well as the angle of incidence Θ. The best metals for inducing surface plasmon resonance are the precious metals silver and gold, by which a sharp resonance is ob- tained. With these metals, the real part of the dielectric function is high and negative, and the imaginary part is small and positive.

The resonance phenomenon increases the intensity of the electric field E of the evanescent wave which is generated in total reflection in the medium v outside the metal film m. The electric field E extends to a distance of a few hundred nanometres from the interface and is exponentially damped in either direction perpendicular to the interface. Because the electric field extends outside the interface, changes in the refractive index taking place in the outside medium v have an effect on the intensity of the electric field at the interface and thus on the resonance. Keeping all the other parameters constant and allowing a change to take place in the refractive index of the outside medium, transmission of the resonance will occur, as is shown by a broken line in Fig. 3. When measured using a constant angle (e.g. the angle corresponding to the sharpest gradient of the reso¬ nance) , the change can be observed as a change in the intensity. If the interfaces of the media are ideally even, the energy of the plasmon generated on the surface of the metal, i.e. the energy of incoming light at an angle corresponding to the resonance minimum, is converted to heat in the metal film m. In practice, however, the interfaces are uneven in a microscale. Part of the energy of the plasmon is thus transformed back into light which is emitted into the medium v.

Figure 1 shows a cross-sectional view of a display application of the method according to the invention in principle. The cross-section is so elected that it corresponds to part of one line, e.g. a horizontal line, of the display. In the embodiment shown, one line contains several image points 50. Constructions corresponding to other lines and other image points 50 of the line are identical with the illustrated detail.

As shown in Fig. 1, the light emitted from the il¬ luminator 10 with a modulatable intensity of light is led through a collimator 20 and a polarizer 21 to form a beam p-polarized in relation to the first surface 2. The light with a uniform direction is directed through a prism 30 in the first surface 2 to the successive metal layers 40 acting as electro- magnetic transformers 7. Depending on the refractive index of the liquid crystal 4 in connection with the metal layer 40 effective on the polarization component of the light in question, the light falling onto the metal layer 40 is either reflected with small losses or forms, according to the surface plasmon resonance phenomenon, an electric field E in the material of the metal layer 40 in which the energy of the light is almost totally absorbed. Such an electric field E emits the absorbed energy further as light 80 out of the structure through the liquid crystal 4 and a light-transparent front plate 60 acting as the second surface 3. A bright image point 80 is formed at the said point, whereas there is a non-illuminated image point 50 at the points of other metal layers from which the light is reflected back to the prism 30.

The refractive index of the liquid crystal 4 which is changed according to location and possibly also time, can be controlled by any known mechanism, e.g. an electric field, surface finishing, magnetic field or mechanical movement. In the application shown in

Fig. 1, the organs 9 for changing the refractive index are arranged to be electrically operated. Metal layers 40 arranged in succession are used as the first electrodes changing the refractive index of the medium 4 and layers 34 on the inner surface of the front plate 60 are used as the second electrodes, these being effected by a preferably adjustable control voltage U led from a power supply 70.

Further, the materials of the structure are elected in a way that the refractive index n_e of the liquid crystal is higher and the refractive index n_c lower than the refractive index n_t required for inducing surface plasmon resonance in the electrodes 40. The surfaces of the electrodes 40 in contact with the liquid crystal 4 as well as the surfaces 35 are treated by a known liquid crystal technique in a manner that in successive sections I₁ , I₂ , I₃ being formed at points corresponding to the electrodes 40 in the liquid crystal, the refractive index of the fluid crystal molecules of the dormant section I₁ which are effective on the p-polarization component of the light travelling in the prism 30 are close to the index n₀. In an active section, the control voltage U causes reorientation of the liquid crystal in a way that the refractive index effective on the said polarization component is in the said section I₃ close to the index n_e . Consequently, after coupling of the control voltage U, the active section I₂ is at least for a moment in a state that the refractive index n_t effective on the polarized light is suitable for inducing surface plasmon resonance in the elec¬ trode 40.

In the structure, the optic energy transmitted on the first surface 35 of the electrode 40 and converted into electricity in the electrode 40 is returned by a transforming arrangement to optic energy in order to form an image point 80 to be illuminated by light reflected on the other surface 39 of the electrode 40. Further, as an advantageous embodiment the transforming arrangement is realized by roughening the back sur¬ faces 39 of the electrodes 40 partially uneven in a way that the intensity of the resonating electric field is further emitted as light 80.

The layers 37 and 36 used in the embodiment as the mechanical first and second control means are intended to improve the contrast of the image points 50 of the display. The electrodes 40 are typically so thin that they are light-permeable to some extent even though there were no resonance. The switching on of the light is induced e.g. by the roughness of the surfaces of the electrodes 40 due to poor manufacturing tech- niques. In order to prevent such non-intended emission, the structure of the display is arranged to be such that there are no directly illuminated absorbing parts 35 of the electrodes 40 visible in the display when viewed through the front plate 60. The non- transparent layers 37 cover the illuminated absorbing parts 35 of the electrodes 40, whereas the reflecting layers 36 prevent illumination of the reflecting parts 39 of the electrodes. Choosing the lengths of the layers 36 and 37 sufficiently short and making the absorbing parts 35 of the electrodes 40 as even as possible and their reflecting parts 39. rough, the dampening of the light emitted from the resonance is prevented.

It is not necessary to illuminate directly the entire area of one line or line group of the display by the illuminator 10 and the optics conneted therewith. As shown in Fig. 1, if no surface plasmon resonance is induced in a certain electrode 40, typically more than 90% of the light falling on it is reflected further. The other surfaces 38 of the prism 30 and the layer 36 are manufactured in a way that total reflection takes place in them, wherein almost all the luminosity is reflected further. The prism 30 can thus be made very thin to allow even several dozens of reflections depending on the luminosity reserve of the illumina¬ tor 10. It is possible to take into account the dissipation of the reflections in a multiplex display e.g. in a way that the signal amplitude of the modula¬ tor 11 modulating the illuminators 10 is arranged to be greater at those moments of time when the momentary resonance is taking place at the outermost image points.

As illuminators 10, it is advantageous to use light- emitting diodes (LED) which can be modulated at a sufficiently wide band width and v/hich are available in all light components of a full colour system: red, green and blue. In practice, however, it is difficult to manufacture inexpensive illuminators 10 which could be modulated and whose beam were colli ated into a width of one line only. Thus it is advantageous to arrange the display to be multiplexed also in a way that one illuminator 10 illuminates several lines of the type described above simultaneously, but only one line is active at a time.

The invention is not limited to the embodiment presen¬ ted above and in the drawings, but it can be modified within the basic idea even to a substantial degree, as will be described in the following:

In the embodiment described above, a colli ator is used between the illuminator and the polarizer which makes the beams parallel. However, it is also possible to use an illuminator which has not been collimated. In such a case resonance is only induced at a point with a suitable angle of incidence of the beams and suitable orientation of the liquid crystal. Thus only a few or one common electrode can be used instead of several electrically operated electrodes. With a suitable range of angles of incidence of the beams, the changing control voltage of the electrodes can be used to induce a local emission with a changing location always at the point with a suitable orienta- tion of the liquid crystal. For example a monotonously changing control voltage produces a uniform scanning image point. Thus a display based on the scanning principle can be constructed without 'using separate control for each image point. In this case it is not possible, however, to use indirect illumination of the image points but the entire display area must be directly illuminated by the illuminator.

In a corresponding manner, the first mechanical control means which are not light-permeable and the second mechanical control means which intensify or dampen the reflection are only used to improve the contrast of the display; however, the contrast may be sufficient without these layers. Also, the position of the layers may vary, wherein e.g. the layer functioning as the second mechanical control means can be located on the way of the previously incoming light in a way that it prevents the illumination of certain parts of the electrodes. The said layer can be manufactured of any reflecting or dampening material. Also, the reflecting parts of the electrodes can be made thicker than the other parts or formed in another way to provide sufficient dampening of light permeation.

For controlling the image points, an electric arrange¬ ment can be used to form an electric field by coupling the successive metal layers together, wherein each two metal layers next to each other are used as the first and the second electrode. Thus, e.g. by electing suitably small dimensions of the electrodes, the control voltage coupled between them orientates also the liquid crystal of the electrodes which is in contact with the back surface directed towards the front plate.

In the embodiment presented, the construction used is based on a previously known method for generating surface plasmon resonance according to the so-called Kretschmann configuration. There are, however, also other commonly known configurations, e.g. the Otto and Sarid configurations, with which resonance can be generated. The surface structures used in these configurations differ slightly from the one presented above. In particular, said Sarid configuration is advantageous, because it can be used to provide greater intensification of the electric field as compared with the con iguration presented. However, it has the disadvantage of requiring at least one additional dielectric surface between the electrodes and the prism. It is obvious that when applying the method of the invention, also other known methods can be used for generating surface plasmon resonance than those presented above without changing the basic principle of the invention.

In the application presented above, light is connected with the resonating electrodes by means of a prism. It is, however, also possible to use other known methods for the same purpose, e.g. a grating prepared on the outer surface of the first surface, wherein the illumination is directed to this surface.

The presented operation can naturally be also reversed without changing the principle of the invention, i.e. light is connected through the liquid crystal layer and it radiates through a prism or another suitable covering plate. This can be arranged e.g. by choosing suitable refractive indices of the prism and the liquid crystal as well as suitable material and thickness of the electrodes.

Further, in the embodiment presented above, the unevenness of the reflecting parts of the metal layer is utilized as the arrangement for transforming optic energy, wherein the light is emitted because of the roughness of their surfaces. Also other known trans¬ forming arrangements can be used for emitting illumina¬ tion, e.g. a grating produced in the metal layer for this purpose, or a fluorescent substance mixed into the liquid crystal which is excited by the electric field of the electrodes and emits the excited energy as illumination.

In the embodiment presented above, each pair of electrodes is equipped with electric control of its own. However, it may be advantageous to arrange the control in a way that the corresponding electrodes of successive pairs of electrodes are connected by resistance films with a known resistance, and the chain thus formed is terminated in a known voltage. If the chain is controlled at its one end by a voltage with an amplitude increasing as a function of time, the voltage corresponding to resonance is achieved by different electrodes at different times. By choosing suitable resistance values and a suitable number of connected electrodes, it is possible to arrange resonance to be found in only one pair of electrodes at a time. Thus the number of control stages of electrodes can be reduced.

In the present embodiment, each of the electrodes is arranged as a rectangular strip for simplicity. In practice, however, it is usually more advantageous to form the electrodes e.g. in the shape of fingers in a way that that the fingers of the pairs of elec¬ trodes are interlocked. Using such an arrangement, it is possible to construct image points of desired size without a need to change the intensity of the electric field required for the coupling.

Naturally, it is possible to use not only a liquid crystal but also other materials as the medium, provided that the anisotropy of the dielectric constant can be controlled by an electric, magnetic or mechan¬ ical arrangement. It is thus also possible to utilize e.g. the commonly known Kerr or Pδckels effects.

Claims

Claims :

1. Method for transmitting visual information, wherein visual information is optically transmitted 5 from an information source (1), e.g. by emitting beams of light from an illuminator (10) or in a corresponding manner, on a data transmitting first surface (2) and on a data visualizing second sur¬ face (3) which forms a display surface, such as a

10 viewing screen, display screen, scanning surface or the like, wherein an optically anisotropic medium (4), such as a liquid crystal or the like, is arranged between the said first (2) and second surface (3) , wherein for the application of the method, a preferably

15 closed structure (2, 3, 4, 65) is formed, wherein the said first (2) and second surface (3) are preferably essentially parallel and wherein organs (5) are arranged to direct the transmission of information between the said surfaces (2, 3), the function of the

20 organs being at least partially based on changing the refractive index of the said medium (4) , charac¬ terized in that the organs (5) for controlling the transmission of the information are arranged to be operated by an arrangement at least partially tranε-

25 mitting optic energy into vibration of electron plasm, such as one based on the surface plasmon resonance phenomenon or the like, wherein the structure is equipped with one or several electrical transformer (7) with electron plasm, such as a metal film, layer or

30 the like.

,

2. Method according to claim 1, wherein one or several optic transformers (8) , such as a prism, s grating or the like, is arranged in connection with

35 one or several electrical transformers (7) , charac¬ terized in that in the said structure, the refractive index of the optically anisotropic medium (4) , such as a liquid crystal or the like, which is in contact with one or several electrical transformers (7) on the side opposite to the optic transformer (8) , is changed by organs (9) for changing the refractive index, such as by known chemical, electric, mechanical or cor- responding arrangements, wherein the energy of the information optically transmitted to the electrical transformer (7) can be essentially totally transmitted into an electric field (E) , such as an electromagnetic wave, or plasmon or the like, to be generated in the electron plasm of the electrical transformer (7) .

3. Method according to claim 1 or 2, characterized in that in the said structure, the optic energy transmitted onto the first surface (35) of the said one or several electrical transformers (7) and trans¬ formed in the electrical transformer (7) into an electric field (E) is returned by a transforming arrangement into optic energy for transmitting infor¬ mation from the other surface (39) of the electrical transformer (7) in order to form an image point (80) or the like illuminated optically, such as by means of a beam.

4. Method according to claim 3, characterized in that the said transforming arrangement is formed by arrangements included in said one or several electrical transformers (7) and based on the roughness of the electrical transformer (7) , a grating or the like formed therein, and/or the properties of the medium (4) , such as fluorescent substances or the like contained therein.

5. Method according to claim 1 or 2, wherein the second surface (3) in the said structure is at least partially formed of a plate (60) manufactured of a substantially light-permeating material, such as glass, plastic or the like, characterized in that the first surface (2) of the said structure is sub- stantially formed of the said one or several electrical transformers (7) , such as a metal film, plate (40) or the like preferably manufactured of a noble metal, such as gold or silver, and at least one optic trans- former (8) , such as a prism (30) , grating or the like.

6. Method according to one of claims 1-5, charac¬ terized in that the minimum refractive index (n₀) of the medium (4) in the structure is arranged to be equal to, or preferably lower than the value required by the surface plasmon resonance to be generated in the electrical transformer (7) and/or the maximum refrac¬ tive index (n_e) equal to, or preferably higher than the value required by the surface plasmon resonance to be generated in the electrical transformer (7) , wherein by changing the refractive index, the refrac¬ tive index (n_t) can be made at least momentarily suitable for generating surface plasmon resonance.

7. Method according to claims 4 and 5 or 6, characterized in that the said transforming arrange¬ ment is formed to be operated by arrangements included in one or several electrical transformers (7) , wherein at least the part (35) of the first surface of the electrical transformer (7) absorbing incoming optic energy is made substantially even and at least the part (39) of the second surface of the electrical transformer (7) emitting optic energy is made substan- tially uneven.

8. Method according to one of claims 5-7, charac¬ terized in that the structure is equipped with at least substantially non-transparent first mechanical control means (37) , such as one or several barrier plate, coating or the like, which are used to prevent at least light from penetrating directly through the absorbing part (35) of the electrical transformer (7) .

9. Method according to one of claims 2-8, charac¬ terized in that the organs (9) for changing the refractive index are arranged to be electrically operated, wherein at least one electrical transformer (7) or a part thereof is used as one or several electrolytes (40) or the like for changing the refract¬ ive index of the medium (4) , effected by a preferably adjustable control voltage (U) led from a power supply (70) .

10. Method according to claim 9, wherein one or several optic transformers (8) of the said structure, e.g. arranged on the first surface (2) thereof, is used for transforming optic energy by means of a beam in order to form several image points (50) , optic points or the like in one or several lines of a multiplex display, scanning surface or the like, wherein the structure is equipped with sections ( I. , 1₂ , I₃ ) next to each other, wherein the refractive index of the medium (4) in each section is changed irrespectively of the other sections, characterized in that the sections (I, , I₂ , I₃ ) are formed by the changing control voltage (U) of one or several elec- trical transformers (7) , wherein a local emission with a changing location is achieved in the line active at the moment of time.

11. Method according to claim 10, characterized in that the sections (I₁ , I₂ , I₃ ) are formed by the monotonously changing control voltage (U) of one or several electrical transformers (7) , wherein a con¬ tinuous scanning movement of beams is achieved in the line active at the moment of time.

12. Method according to claims 5-11, wherein one or several optic transformers (8) included in the first surface (2) of the said structure are used to transmit at least part of the optic energy indicrectly, such as by reflecting beams to be reflected from the illuminator (10) in the optic transformer (8) by the principle of total internal reflection substantially without loss, or in a corresponding manner, for illuminating several image points (50) in one or several lines of a multiplex display or the like by beams, wherein the structure is equipped with sec¬ tions (I₁ , 1₂ , I₃ ) next to each other, wherein the refractive index of the medium (4) in each sectioin is changed irrespective of the other sections, characterized in that the sections ( I. , I₂ , I₃ ) are formed by means of two or more electrical transformers (7) which are arranged at least in the direction of the optic energy to be transmitted at a distance from each other.

13. Method according to claim 12, characterized in that dissipations of beams caused in the optic transformer (8) in connection with a multiplex display or the like are compensated in forming at least indirectly illuminated image points located substan¬ tially outermost from the illuminator (10) .

14. Method according to claim 13, wherein the beams of light to be reflected from the illuminator (10) including the information source (1) are formed by one or several light sources (10) , such as a light emitting diods (LED) , preferably a wide band radiator equipped with colour filters, modulated by a modula¬ tor (11) , characterized in that dissipations caused by reflections in the optic transformer (8) of beams are compensated by the modulator (11) , wherein preferably the amplitude of the signal modulating the illuminator (10) is arranged to be higher in forming the image points outermost from the illuminator (10) .

15. Method according to one of claims 5-14, charac¬ terized in that the structure is equipped with second mechanical control means (36) , such as one or several reflecting/damping plate, coating or the like, for intensifying the reflection of the optic energy at least in the optic transformer (8) and/or for preventing the penetration of the light directly at least through the transforming part (39) of the electrical transformer (7) .

16. Method according to one of claims 12-15, wherein the beams of light to be reflected from the illumina¬ tor (10) including the said information source (1) are formed by one or several light sources (10) , such as a light emitting diode (LED) , preferably a wide band radiator equipped with colour filters or the like, modulated by the modulator (11) , and polarized by a polarizer (21) to be p-polarized or the like in relation to the first surface (2) , and/or collimed by a collimator (20) into a beam with a width of at least one line or the like, characterized in that in connection with a multiplex display or the like, beams collimed in connection with the illuminator (10) are used to illuminate two or more lines or parts thereof simultaneously, wherein only one line is used actively for illuminating one image point (80) therein at a time.