WO2003038791A2

WO2003038791A2 - Optical display device and method for addressing the pixels of the same

Info

Publication number: WO2003038791A2
Application number: PCT/HU2002/000111
Authority: WO
Inventors: Zoltán NÉMETH
Original assignee: Nemeth Zoltan
Priority date: 2001-10-31
Filing date: 2002-10-31
Publication date: 2003-05-08
Also published as: HUP0104625A2; HU0104625D0; WO2003038791A3; AU2002339207A1

Abstract

The invention relates to a method for addressing pixels of an optical device, wherein the pixel is activated, and with this, the energy status of that pixel is raised resulting in said addressing of the pixel. The improvement of the method is in that on said pixels to be addressed, a combination of electric and optical effects is applied and the raised energy status being necessary for said addressing is reached by simultaneous presence of said electric and optical effects. At the same time, the invention also relates to an optical device which utilises this method of addressing and which has at least one pixel, the pixel being connected to at least one addressing lead and the lead being connected to an electronic commanding unit. Therein, the improvement according to the invention is in that a photosensitive layer (3) is arranged between the pixel (2) and the addressing lead (4), and the photosensitive layer (3) is electrically insulating in its basic condition and it is electrically leading when in addressed condition by being illuminated by light.

Description

Optical Display Device and Method for Addressing the Pixels of the Same

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for addressing pixels of an optical device, wherein the pixel is activated, and with this, the energy status of that pixel is raised resulting in said addressing of the pixel. The procedure of addressing is understood herein as a process of differentiating this basic picture element from other pixels not being addressed. At the same time, the invention also relates to an optical device which utilises this method of addressing and which has at least one pixel, the pixel being connected to at least one addressing lead and the lead being connected to an electronic commanding unit. The invention can be used for addressing pixels of screens, displays, monitors, for reading optical detectors from pixel to pixel and for all application fields, where status and condition of elements arranged in a plane matrix is to be changed or read out independently from each other (e. g. in memories).

Description of the Related Art

Prior art addressing methods would involve either independent or multiplexed addressing. In case of independent addressing, the addressing information is led to each element independently from that of the other elements, through e. g. separate leads, radiations such as light or electrons directed to each element separately. In multiplexed addressing, the number of addressing leads (understood here in broad sense of the word) is less than that of the elements to be addressed and one lead is in connection with more than one element and the elements get activated upon the impact of effects of more

(usually two) addressing leads. In displays such as cathode ray tubes, usually independent addressing is applied which is bound to big space demand, therefore, it gets superseded by electronic addressing and most recently, by optical addressing. In devices with bigger number of electronically addressed elements, multiplexed addressing is most commonly used which can be realised in good quality only if the answer of the elements on the addressing signal is strongly non-linear since all elements connected to the same addressing lead receive a portion (usually the half) of the addressing effect and they would also get active if they wouldn't react non-linearly. This non-linearity is provided in the prior art either by the material of the liquid crystal itself (nematic liquid crystal) or by a thin film transistor connected to each element. Since the functional parts of these elements (in case of an LCD, e. g., the liquid crystal) cannot provide the needed non-linear characteristics or they can provide it only to the detriment of the functionality, solutions are needed which provide the non-linear response as part of the addressing method.

It has been proposed previously to apply the thin-film transistor technology to provide the non-linear response, e. g. in UK Patent Application No. GB2122419. It is however quite disadvantageous that a huge number of transistors are needed at each pixel's location increasing the complexity and cost with a limited yield in production.

Prior art would suggest to apply optical addressing, wherein a thin photosensitive material such as a photo-optical device resistor layer is used. On this layer, voltage is applied which gets to the element to be addressed on locations which are illuminated.

This results in active status of the element. European Patent Application No. EP

2 1 089 117 teaches to use this method with spatial light modulators with optical addressing, wherein the whole picture is projected onto the photosensitive layer and the device is used to modulate the read out light beam. Whereas US Patent No. 5,612,798 describes optically addressed liquid crystal display device having a matrix array of photocells applying independent addressing with a laser beam as normally used with cathode ray tubes. It is inevitably simpler and cheaper to apply optical addressing instead of thin film transistor technology and the resolution is much better, too. It turned out, however, that the contrast ratio of such displays is relatively low and the sensitivity of the photosensitive material may change form place to place. Therefore, the production costs of such devices with high quality demand are extremely high. Further, the addressing picture is to be produced somehow, for the purpose of which another electronically addressed display is also needed. If laser inscription from dot to dot is applied, the reduced contrast ratio causes huge problems, not to speak about material qualities (such as response time) and laser performance which make this solution practically non applicable.

As mentioned earlier, the cathodoluminescent devices such as vacuum fluorescent displays or field emission displays are commonly used as flat picture displays, however, the field emission needles with suitable durability are still not available. Around 1000 field emission needles are needed in one pixel to provide acceptable picture quality.

SUMMARY OF THE INVENTION

The main objective of the present invention is to provide a solution for addressing pixels of an optical device with better quality and with the application of simpler technical means, higher productivity than with the previously known solutions. The method shall result good quality and ergonomic displays being suitable for mass production.

The basic idea of this invention is to use in a multiplexed addressing system electric and optical addressing effects simultaneously, because if so, then a signal being proportional to the product of the electric signal and the optical signal will fall on the element to be addressed rather than the sum of these signals and with this, the non linear characteristics being necessary for the multiplexed addressing will be provided.

Hence, the invention relates to a method for addressing pixels of an optical device, wherein the pixel is activated, and with this, the energy status of the addressed pixel is raised. The improvement is in that on said pixels to be addressed, a combination of electric and optical effects is applied and the raised energy status being necessary for said addressing is reached by simultaneous presence of said electric and optical effects.

hi a preferred realisation of the method in this invention, said optical effect is applied on the pixel through a photosensitive layer which changes its electrical characteristics on the impact of light. The photosensitive layer may be impacted to an optical effect and with this, the electric effect gets insulated against the pixel, i another case, the photosensitive layer may be impacted to an optical effect and with this, the electric effect gets conducted to the pixel. The polarity of the electric effect may be changed in dependency from the change of the optical effect.

It is still preferred when a pixel changing its characteristics upon the impact of light is used, and optical characteristics of said pixel is changed by electrically addressing said pixel, and an effect being caused by the thus changing optical effect in the photosensitive layer reacts on the electric addressing and with this, a feed-back is produced in the addressing effect resulting the pixel being addressed.

hi another preferred realisation, cathodoluminescent device is used as said pixel, from a photo-cathode of which electrons are freed on the impact of said optical effect, and with this, an electric signal between the photo-cathode and a grid or an anode of the cathodoluminescent device is influenced and an intensity of a light caused on a cathodoluminescent screen of the device is controlled.

Further, it is preferred, when release of electrons is changed with the aid of a light borne in the cathodoluminescent device, in proportion to said light, and an electric field within the device is enlarged above a threshold value being characteristic for said device, and with this, the light emission of the device is intensified. The addressing electric effect may preferably be led to the cathodoluminescent device from both sides, and the value of each electric effect is separately smaller and the sum of the values of the electric effects is larger than the threshold value being characteristic for said device. The light emission of cathodoluminescent device may be controlled with an inside or outside current limiter influencing the electric field within the device.

It is preferred, when the pixels are arranged in a matrix and they form an optical display. In another preferred realisation, the pixels being capable of at least storing charge and being arranged in a plane are used as elements of a detector and it is connected to a charge counting means. The detector may be connected to an imaging optical system as well as to an amplifier and/or to a signal processing circuit, and with this, a camera can be produced.

The invention also relates to an optical device having at least one pixel, the pixel being connected to at least one addressing lead and the lead being connected to an electronic commanding unit.

Therein, the improvement according to the invention is in that a photosensitive layer is arranged between the pixel and the addressing lead, and the photosensitive layer is electrically insulating in its basic status and it is electrically leading when in addressed status by being illuminated by light.

In one exemplified embodiment of this invention, the optical device has an optical addressing means emitting directed light and having a light source illuminating at least one pixel or a predetermined group of pixels. The pixel may have an electrode means storing electric charge. It is also preferred when the pixel has a second electric lead connected to the pixel on the side being opposite to the side having the photosensitive layer on it.

A further preferred embodiment is, wherein the pixel has a light influencing means which is optically coupled to the photosensitive layer being in electric connection to the addressing lead. During the illumination of certain (groups of) pixels, an electric signal with changing polarity may be switched on. In this embodiment, the (groups of) pixels being sensitive to polarity may be illuminated after one another and they may be connected to the addressing lead(s) with changing polarity. It is still another preferred embodiment, wherein after all pixels being disconnected form the addressing leads, an electric signal impulse having a polarity opposite to that of the addressing electric signal is applied in the addressing leads.

A further preferred embodiment is, wherein the pixel is a cathodoluminescent device arranged between the two addressing leads, and the cathodoluminescent device has a photo-cathode emitting electrons upon the impact of addressing light and a luminescent screen catching electrodes impacting the screen in dependency from an electric signal between the photo-cathode and an anode of the device.

It is a preferred embodiment, wherein the optical device is formed as a light source. Alternately, a group of pixels may be formed as a screen with multiplexed addressing.

Various other optional or preferred features are set out in the detailed description forming part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

Realisations and embodiments of this invention will now be described by way of example with reference to the accompanying drawings, in which

Fig. 1 illustrates a preferred embodiment of the optical device as in this invention in a back elevational view;

Fig. 2 is a cross section along line II-II of Fig. 1,

Fig. 3 is a cross section along line IH-III of Fig. 1,

Fig. 4 shows another preferred embodiment of the optical device as in this invention in a back elevational view; Fig. 5 is a cross sectional view along line V-V of Fig. 4,

Fig. 6 is a cross section along line VI- VI of Fig. 4,

Fig. 7 shows till another preferred embodiment of the optical device as in this invention in a back elevational view;

Fig. 8 is a cross sectional view along line VITI-VIII of Fig. 7, Fig. 9 is a cross sectional view along line LX-LX of Fig. 7,

Fig. 10 is a voltage-current diagram of a preferred embodiment of this invention formed as a cathodoluminescent device, Fig. 11 shows the electron series of a preferred embodiment formed as a cathodoluminescent device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figs. 1 to 3 show, for the sake of simplicity, an LCD display 1 formed as a matrix of 3x3, altogether nine elements as a realisation of the method in this invention. Pixels 2 forming the LCD display 1 are per se well known and commercially available elements, therefore, they are not described in more detail here. They include all parts which are commonly needed for forming a picture on LCD display 1. The pixels 2 being side by side in a row in the picture are referred to in the description as a row of pixels, the pixels 2 being below each other in a column are referred to as a column of pixels.

On the back side of each pixel 2 a photosensitive part, in this example a photosensitive layer 3 is arranged. With regard to functionality, it is important to galvanically insulate photosensitive layer 3 of pixels 2 being in the same column from those in the adjacent column. In this example, each photosensitive layer 3 of each pixel 2 is insulated against adjacent photosensitive layer 3 in the row and in the column as well. Each column of photosensitive layer 3 is connected to an addressing lead 4 which is common for pixels 2 in this column. Addressing leads 4, in turn, are connected to a commanding unit 5. At the back side of the LCD display 1 carrying addressing leads 4, an optical system 6 is arranged (see Figs. 2 and 3), with which a light strip 7 is projected on the backside of LCD display 1 carrying addressing leads 4.

In operation, let us suppose that the first pixel 2 in the first row of pixels 2 and the third pixel 2 in the third row of pixels 2 of LCD display 1 shall be addressed (switched on). For this, light strip 7 of optical system 6 will first illuminate the first row of pixels 2 of LCD display 1. Upon impact of the light, photosensitive layer 3 of the first row will get electrically conductive. Simultaneously, an electric signal is switched by commanding unit 5 onto addressing lead 4 of the first column, which is needed to get pixels 2 be switched on. From among the three pixels 2 of the first column, only the first pixel 2 will be switched on, since the non-illuminated photosensitive layer 3 insulate the pixels 2 from addressing leads 4. Thereafter, the light strip 7 of optical system 6 will be switched off. The resistance of photosensitive layer 3 of the first row will newly get high, thus, the voltage led to the first pixel 2 of the first row will remain caught there, and the switched-on status of this pixel 2 will remain maintained. After this, the light strip 7 of optical system 6 will be projected on the second row of pixels 2 of LCD display 1. The commanding unit 5 will hold the addressing lead 4 on a voltage level corresponding to the switched-off status; all pixels 2 in this row remain unswitched and non-addressed. Thereafter, light strip 7 of optical system 6 slides on the third row and illuminates it. Simultaneously, an electric signal is switched by commanding unit 5 onto addressing lead 4 of the third column, which is needed to get pixels 2 of this column be switched on. With this, however, only the third pixel 2 of the third row and the third column will switch on and be addressed. After being the light strip 7 of optical system 6 switched off, this pixel 2 remains also in stable switched-on status. These pixels 2 are now addressed, and for a new addressing procedure, the steps as above shall be repeated, always both of the electric and optical effects shall be applied upon pixels 2 to be addressed: electric signal shall be led to the column and light be applied on the row wherein the pixels 2 to be addressed are contained.

The embodiment shown in Figs. 1 to 3 can also be used in detectors. In this case, each pixel 2 contains at least one part being capable for storing charges (such as an electrode) and means to raise the sensitivity of the detector or for converting the signal to be detected into light, depending on the application wherein the detector is used. For medical application, e. g., the arrangement can be used in an X-ray detector, wherein a scintillation material is applied which converts the incoming X-ray photons into light with a frequency corresponding (or near) to the sensitivity of the photosensitive material. In simple optical detectors, however, usual and optional colour filters are regarded as part of pixels 2. In operation of this embodiment, voltage is applied on all addressing leads 4 for the duration of the exposure. The radiation to be detected illuminates some points of the photosensitive layers 3 of pixels 2. On these places, charge will be forwarded to pixels 2 from addressing leads 4. Thereafter, the detector is shadowed against the radiation to be detected, thus, charges on pixels 2 remain caught there. After this, the detector is illuminated for row by row by optical system 6, the photosensitive layer 3 gets electrically conductive and in addressing leads 4, an electric signal being proportional to the charges stored in pixels 2 being just illuminated will be measurable.

In the embodiment of the device as shown in Figs. 4 to 6, the elements of the matrix of LCD display 1 has means being able to influence the light, and each element is connected to at least two addressing leads 4 and 8. The LCD display 1 has in this example, too, 3x3, i. e. nine pixels 2 and it is formed for getting the pixels 2 dark as a result of the voltage applied on them. Addressing leads 4 on the backside of LCD display 1 in form of transparent column electrodes and addressing leads 8 on the front side of LCD display 1 in form of transparent row electrodes surround pixels 2 from both sides. Each pixel 2 is connected to one column electrode and one row electrode, i. e. to two addressing leads 4, 8. LCD display 1 is illuminated from the front side, pixels 2 are transparent if voltage is not present and through this, light gets onto photosensitive layers 3, they get conductive. If on both addressing leads 4, 8 belonging to a given pixel 2 voltage impulse is led, the transparency of pixel 2 gets worse (the pixel 2 gets darker), less light gets on photosensitive layer 3 and its resistance gets higher. As a result, the charge captured in pixels 2 will be discharged slower, thus, pixels 2 remain longer dark. The voltage on pixels 2 gets lower first slower (great resistance), and then it falls suddenly to zero (small resistance). The higher the addressing voltage is, the greater is the darkening at the beginning and the slower gets the charge captured in pixels 2 discharged. Thus, with the voltage switched onto pixels 2 not only the amplitude of the darkening but its duration can also be influenced, i. e. the fill factor can be modulated. The response given to the voltage will thus be strongly non-linear what the human reception is concerned, since at the frequencies being characteristic for LCD display 1, the raise of the fill factor is deemed as a further darkening effect by our eyes. Therefore, the disturbing darkening of other pixels 2 connected to the same addressing lead 4 and addressing lead 8 will remain small, imperceptible.

Figs. 7 to 11 show examples of the method and the device in this invention, wherein pixels 2 of LCD display 1 are cathodoluminescent devices. In the cathodoluminescent device, the light is produced by a fluorescent material (luminophor) induced by free electrons accelerated in vacuum. Pixels 2 in this example contains a photo-cathode 9 and a fluorescent luminophor layer 10 (serving as a luminescent screen). From this pixels 2, a 3x3 matrix is shown in the figures. Photo-cathode 9 has the role of the photosensitive means of the addressing.

During optical addressing, the light impacting on pixels 2 frees electrons from photo- cathode 9 and the electrons impacting the luminophor layer 10 (luminescent screen) generate light in dependency from the electric signal between photo-cathode 9 and a grid, or in the example of the figures, between photo-cathode 9 and the luminophor layer 10 serving as an anode, at the same time.

In the solution of Figs. 7 to 9, the role of the addressing light is fulfilled by the light borne in luminophor layer 10 which results in an optical feed-back. In this system, the light intensity grows over a threshold voltage very strongly if the voltage will further be raised. The electrons get more accelerated, more photons are produced, these free more electrons from the photo-cathode 9, and so on. Fig. 10 shows the voltage vs. current (U-I) diagram of this system. Below threshold voltage U0, current is not flowing through pixels 2 since the electrons don't generate enough photons for replacing themselves and thus, their number reduces quickly to zero. At the voltage U0, electrons of a given number generate exactly as many photons as is needed to reproduce the original photon population. Above U0, the current would rise like an avalanche if there wouldn't be applied an outer current limiter. In case of the current limiter R, the current will raise according to the formula (U-U0)/R. In the figure, dotted lines show the asymptotic linears 1 = 0 and I = (U-U0)/R. Fig. 11 illustrates the electron multiplication mechanism of pixels 2. Lines 11 show the movement of electrons, dotted lines 12 refer to movement of photons. Photons start at a place 13 (Fig. 11 /a) where photo-cathode 9 has been illuminated in the previous phase. These places are shown at 14 (Fig. 11/b) and 15, 16 (Fig. 11/c). The light emission strength of the system can be determined by the aid of inner or outer current limiter means. If with such a pixel 2 a resistance in connected in series, greater voltage falls as a result of the increasing current and smaller voltage gets onto pixel 2 - the system controls down. As a matter of course, a transistor can be used as a controllable current limiter. If onto the transistor and pixel 2, a voltage U is jointly applied, on pixel 2 falls a voltage UO and on the transistor a relatively small voltage (U-UO). With a controlling signal applied onto base of the transistor, the resistance between emitter and collector of the transistor and thus, the current flowing through the whole system, with this, the light strength can be controlled. A grid within the vacuum space and connected to a suitable potential may function as an inner current limiter, as is usual in case of grids of vacuum tubes. In case of a positive voltage between photo-cathode 9 and the grid, electrons can move in direction of the luminophor, but in case of a suitable negative voltage, they cannot. In case of voltage in between theses values, only a part of the borne electrons will get into motion.

The system as described as an exemplified embodiment of the invention can find utilisation as a light source replacing light tubes. With this, the environment pollution caused by the mercury filling as well as the glow cathode or the field emission cathode of the light tubes can be left away, the light power is easily controllable, whilst it has a quite simple construction. Since the system is strongly non-linear, it is perfectly suitable as pixels 2 of a LCD display 1 with multiplexed addressing.

Returning back to the embodiment shown in Figs. 7 to 9, the outer current limiter therein is a transistor connected to each of addressing leads 4 and addressing leads 8 and contained in unit 5. The addressing electric effect (voltage) is led to the device from both sides through addressing lead 4 and addressing lead 8. Each of the electric voltages separately is smaller than the threshold value being characteristic for the device, but the sum of these addressing voltage values is greater than this threshold value. Only pixels 2 will get shine, which receive a total of addressing voltages which is higher than the threshold value, and the intensity of the light can be controlled by the value of the sum of voltages above the threshold value received through addressing lead 4 and addressing lead 8.

When the photosensitive layer 3 is not illuminated, some leakage current still may flow through. If so, some portion of the addressing electric signal would get on pixels which are not intended to be addressed and the contrast ratio would get worse. To avoid this, the influence of the leakage current shall be lessened. However, it is sufficient to held the average value of the leakage current near to zero.

In sense of the invention, it is preferred to apply onto the addressing lead 4 and addressing lead 8 electric signals with alternating polarity during the subsequent illuminations. With this, on elements without illumination, the average value of the leakage current will be near to zero and the contrast ration will be better. If, in another example, the elements used in the system are sensitive to polarity of the electric field, they can be connected to addressing lead 4 and addressing lead 8 with different polarity in each row, providing that the signal coming through addressing lead 4 and addressing lead 8 will reach them with correct polarity.

If in the latter example, the elements being sensitive to polarity of the electric field are used but the above described solution cannot be utilised, impulses with reversed polarity are applied in addressing leads 4 and addressing leads 8 in periods of illumination (e. g. in intervals of non-illuminating), when all elements are separated from addressing leads 4 and addressing leads 8. With this, the amount of charge collected on pixels 2 which are not intended to be addressed will be minimised. Namely, these impulses result a leakage current with opposite direction. The magnitude of the compensating impulses are chosen for being the average value of the leakage current near to zero.

In another embodiment, the unit 5 controlling the whole system contains a memory circuit, wherein information on responses of the elements being given as a reaction to equal addressing signals is saved. On basis of this stored information, the addressing signal will be modified by unit 5 to compensate the unequal quality of the elements of the system. If for example, one of the pixels 2 gives to the same signal a response which is with 15 percent stronger than that of the other ones (e. g. it gets darker than the other pixels 2), then this information is stored in the memory of unit 5 and with this, the next addressing signal will be modified to generate a response within the acceptable range. With this solution, the picture produced with LCD display 1 will be more uniform even with pixels 2 having different qualities.

As is apparent now, the most important feature of the invention is in that the number of addressing leads 4, 8 needed for addressing increases only with the square root of numbers of elements to be addressed, without the need of sophisticated controlling means such as transistors or the like, the production yield is increasing, the costs can be reduced. On the other hand, the invention provides a simple and powerful solution to generate free electrons in a cathodoluminescent device. The application of compensation against leakage current and against uneven quality of elements in the system is a quite important advantage when the contrast ratio and the picture quality of the solution are considered.

Claims

CLAIMS:

1. Method for addressing pixels of an optical device, wherein the pixel is activated, and with this, the energy status of the addressed pixel is raised, characterised in that on said pixels to be addressed, a combination of electric and optical effects is applied and the raised energy status being necessary for said addressing is reached by simultaneous presence of said electric and optical effects.

2. Method as claimed in Claim 1, characterised in that said optical effect is applied on the pixel through a photosensitive layer which changes its electrical characteristics upon the impact of light.

3. A method as claimed in Claim 2, characterised in that the photosensitive layer is impacted to an optical effect and with this, the electric effect is insulated against the pixel.

4. A method as claimed in Claim 2, characterised in that the photosensitive layer is impacted to an optical effect and with this, the electric effect is conducted to the pixel.

5. A method as claimed in Claim 3 or 4, characterised in that polarity of the electric effect is changed in dependency from the change of the optical effect.

6. A method as claimed in Claim 2, characterised in that a pixel changing its characteristics upon the impact of light is used, and optical characteristics of said pixel is changed by electrically addressing said pixel, and an effect being caused by the thus changing optical effect in the photosensitive layer reacts on the electric addressing and with this, a feed-back is produced in the addressing effect amking the pixel being addressed.

7. A method as claimed in Claim 1, characterised in that a cathodoluminescent device is used as said pixel, from a photo-cathode of which electrons are freed as a result of impact of said optical effect, and with this, an electric signal between the photo- cathode and a grid or an anode of the cathodoluminescent device is influenced and an intensity of a light caused on a cathodoluminescent screen of the device is controlled.

8. A method as claimed in Claim 2, characterised in that release of electrons is changed with the aid of a light borne in the cathodoluminescent device, in proportion to said light, an and electric field within the device is enlarged above a threshold value being characteristic for said device, and with this, the light emission of the device is intensified.

9. A method as claimed in Claim 8, characterised in that the addressing electric effects are led to the cathodoluminescent device from both sides, and the value of each electric effect is separately smaller and the sum of the values of the electric effects is larger than the threshold value being characteristic for said device.

10. A method as claimed in Claim 8 or 9, characterised in that the light emission of the cathodoluminescent device is controlled with an inside or outside current limiter influencing the electric field within the device.

11. A method as claimed in any one of Claimsl to 10, characterised in that the pixels are arranged in a matrix and they form an optical display.

12. A method as claimed in any one of Claimsl to 11, characterised in that the pixels being capable of at least storing charge and being arranged in a plane are used as elements of a detector, and the detector is connected to a charge counting means.

13. A method as claimed in Claim 12, characterised in that the detector is connected to an imaging optical system as well as to an amplifier and/or to a signal processing circuit, and with this, a camera is produced.

14. Optical device having at least one pixel, the pixel being connected to at least one addressing lead and the lead being connected to an electronic commanding unit, characterised in that a photosensitive layer (3) is arranged between the pixel (2) and the addressing lead (4), and the photosensitive layer (3) is electrically insulating in its basic condition and it is electrically leading when in addressed condition by being illuminated by light.

15. An optical device as claimed in Claim 14, characterised in that it has an optical addressing means emitting directed light and having a light source illuminating at least one pixel (2) or a predetermined group of pixels (2).

16. An optical device as claimed in Claim 14 or 15, characterised in that the pixel (2) has means such as at least one electrode for storing electric charge.

17. An optical device as claimed in Claim 14, characterised in that the pixel (2) has a second electric addressing lead (8) connected to the pixel (2) on the side being opposite to the side having the photosensitive layer (3) on it.

18. An optical device as claimed in Claim 14, characterised in that the pixel (2) has a light influencing means which is optically coupled to the photosensitive layer (3) being in electric connection to the addressing lead (4, 8).

19. An optical device as claimed in any one of Claims 14 to 18, characterised in that during the illumination of certain pixels (2) or groups of pixels (2), an electric signal with changing polarity is switched on.

20. An optical device as claimed in Claim 19, characterised in that pixels (2) or groups of pixels (2) being sensitive to polarity are illuminated after one another and they are connected to at least one addressing lead (4, 8) with changing polarity.

21. An optical device as claimed in any one of Claims 14 to 20, characterised in that after all pixels (2) being disconnected form the addressing leads (4, 8), an electric signal impulse having a polarity opposite to that of the addressing electric signal is applied in the addressing leads (4, 8).

22. An optical device as claimed in Claim 17, characterised in that the pixel (2) is a cathodoluminescent device arranged between the two addressing leads (A, 8), and the cathodoluminescent device has a photo-cathode (9) emitting electrons upon the impact of addressing light and a luminescent screen (10) catching electrodes impacting the screen (10) in dependency from an electric signal between the photo- cathode (9) and an anode of the device.

23. An optical device as claimed in Claim 17, characterised in that it is formed as a light source.

24. An optical device as claimed in Claim 17, characterised in that a group of pixels (2) is formed as a screen with multiplexed addressing.