CS195673B2 - Method of picture record on the electrographic film and device for making the same - Google Patents

Abstract

1438870 Electro-photographic process COULTER INFORMATION SYSTEMS Inc 5 June 1973 [8 June 1972] 26889/73 Heading G2H An electro-photographic process comprises charging a photo-conductive film F at 24 to a peak voltage, immediately after charging imagewise exposing (e.g. using a projector 56) and, immediately after exposure, toning at 84; a photo-cell 32 detecting image light intensity in order to control the peak voltage in inverse relation to the light intensity. The process is particularly intended for making high resolution microimages. Preferably the film comprises a Mylar (TRM) base coated with indium oxide then CdS. As shown, differential amplifier 36 is connected to photo-cell 32 and an electrometer 34 to control a relay 42 connecting voltage source 46 to coronade 24. When amp 36 terminates charging a shutter 58 is opened to expose the film and is closed when the charge on an unexposed area sensed by electrometer 34 has decayed to a predetermined level. As soon as exposure is terminated, liquid toner is pumped to a head 84 and applied under the influence of an electrode 92, whose bias is optionally controlled by electrometer 34. A pump 109 removes excess toner and a heater 126 fixes the image, In Fig.3 (not shown) a rotating drum (109) carries the various processing stations past the film.

Description

The invention relates to a method for recording a high quality image on an electrophotographic film and to an apparatus for carrying out the method.

A relatively large number of recording devices based on the generation of an electrostatic image, whose function essentially consists in charging a pre-discharged photoconductive medium, in image exposure of the medium to light to produce a latent image on said medium, is known. a medium to produce a visible image on said medium and to fix the visible image either directly on said medium or on another surface, for example on paper, after previously transferring the visible image from said medium to said other surface. Most of the known devices operating on the above principle are known as office copying devices, in particular as xerographic copiers.

It has also been proposed to use the above techniques to create microimages on electrophotographic film. However, as far as is known, satisfactory results have not been achieved. One of the reasons why the above efforts have not been successful is that after shrinking the image to the microfilm size to create the images, the generated image needs to be magnified again for195873?

When the image is enlarged, not only the recorded information is magnified, but all imperfections of the recorded image are magnified to the same scale; generally, the recorded image needs to be magnified about 20 times.

In addition, in order to obtain an enlarged image with good resolution, i.e. about five lines per millimeter, the microimage system needs to have a resolution of about 100 lines per millimeter. However, the systems proposed so far are not able to achieve; when creating a microfilm image with such high resolution. In addition, by means of the prior art systems, it is not possible to obtain on the film an aggregate density and saturation that would be desirable for a high-quality electrophotographic microimage.

Until now, the individual steps of the electrophotographic procedure have been performed as a sequence of static, mutually independent processes. The photosensitive medium is first charged and then exposed to form an image. Light that strikes the portions of the medium corresponding to the light areas of the image causes the charge to dissipate from those portions of the medium, while the portions of the medium corresponding to the dark areas of the image retain their charge. In this way, a latent photographic image is created on the medium. Next on

195873 the medium applies a 'tinting' pigment that tends to adhere to those portions of the medium that have retained an electric charge, thereby converting the latent image into a visible image. Finally, the tinting pigment is melted to the medium so that the visible image becomes stable.

The above steps of the electrophotometric process are carried out at successive times, usually at various locations in the reproduction apparatus.

Because they are on their own. According to the known electrophotographic processes, the image is produced with a relatively low resolution on a relatively large image area, which results in a relatively low copying speed, i.e. a speed of about 1 to 10 seconds.

Typical photoconductive media such as. is, for example, selenium, showing dark discharge. Once charged, this medium has its usual initial stress, for example, about 5θ0 to. 600 'volts, there is a rapid decrease. voltage, such as speed. 50 to 100 volts per minute in about the first minute. Then, the rate of voltage drop decreases until the medium voltage stabilizes at a substantially constant residual value. ·. background, · · - straight · ______as -.30- to .50 ypltůpi ...., V. Conventional graphics systems, which, as already mentioned, are very slow, the medium is charged only when it is already charged. voltage reduction rate low. .

It has now been found that it is necessary to choose to obtain a high quality image. a completely different procedure. The main reason for this is that the surface on which the image is to be formed is a very matrix. - Also the requirements that are imposed on. resolution. and the saturation of the · microfilm image is considerably. higher than the requirements,. . put on-line _; · Ability. -and the saturation of larger xerographic copies. .

The invention is a method of recording an image on

- electrophotographic film containing. A layer of photoconductive material by charging the photographer. exposure of the film to the image,. by applying a tinting pigment to an electrophotographic film by removing excess tonal. . whose · · pigment; · · which does not adhere.- · c. Electrophotographic film, and optionally melting the tinting pigment adhering to the electrophotographic. said electrophotographic film, the essence of which is:. that · · se. measure the light produced by the image he has. be recorded on. electrophotpgraphic. film taking. the photoconductive layer is charged with simultaneous measurement. achieved. surface potential on a dark surface. the photoconductive layer and the intensity of the measured. light and the surface potential achieved by the photoconductive layer, with the charging being interrupted at the moment. when this comparison reaches a value known to correspond to the optimum surface potential for a given measured light intensity of the image, k. recording. optimizing the quality, said surface potential being inversely proportional to the light intensity of the recorded image, and then at a moment of time. when the optimum surface potential has been reached, the photoconductive layer exposes the image.

In the method of the invention, the photoconductive layer is exposed when the charging of the electrophotographic film is interrupted.

The photoconductive layer is preferably exposed. . for a fixed period of time, not related to surface. the photoconductive film potential reached during charging.

Applying toning. The pigment according to the invention is carried out in an electric field which is. formed near the film to accelerate the movement of the tinting pigment towards the film. .

The invention also provides an apparatus for performing the above method, comprising a charging member, an exposure member, and a flash member comprising a photoelectric cell for detecting light intensity. a. getting the first signal. proportional to said intensity, an electrometer for detecting instantaneous charge on the photoconductive layer and obtaining a second signal proportional to this charge. Calf,. the first charger switch. . and the first differential. amplifier · k. second signal; and k. obtaining a control signal proportional to this comparison to turn off the charging member in response to reaching the control signal at a value that corresponds to the optimum surface charge value of the photoconductive layer at a given light intensity of the image.

The device according to the invention preferably comprises. ’Bias circuit. formed by an electrode, a relay., a relay. coil and second. battery to accelerate electrically. movement of tinting pigment. . k. film. to achieve a uniform · - · distribution of this pigment on. The film, wherein the magnitude of the prestressing obtained is variable. depending on the. instantaneous · · charge to. · The film.

In the device according to the invention, the charging member is preferably formed. charging head, wire, first. derlection circuit, flip-flop, inverter. and a second differential amplifier,. an exposing member formed by a projector. and shutter, application. element, consisting of a first solenoid valve, a reservoir, a second derating circuit, a second monostabular multivibrator, a relay switch, a relay coil, a second battery, a first. distributor, first pipe. And a rotary clutch, and fuser. formed by a third differential circuit, a third monostable multivibrator, an infrared lamp and a reflector are located along the peripheral parts of the rotary drum, the apparatus further comprising a transporter. moving the film in engagement with said peripheral portions.

In the above embodiment, the film comprises a plurality of film fields, wherein: each film field is successively bringable to the _z position against the charging member, the exposure member, the depositing member, and the pulling member. during the relative movement. either with respect to said rotary hub.

The device according to the invention preferably comprises a tinting pigment separator comprising a second monostable multivibrator, a second solenoid valve, a vacuum pump, a hood, a second distributor and a third monostable multivibrator. to remove excess tinting pigment from the film.

In the apparatus of the invention, a first monostable multivibrator is coupled to the second differential amplifier to control the duration of the tinting time after exposure, said time being determined by a predetermined time. changing the size of the cartridge on said member. . ··

In the device according to the invention, the exposure member, preferably a projector disposed on the opposite side of the rotary drum relative to the film and arranged to project the image onto the film, and the operating position and tunnel el of the rotary drum aligned with said projector and filter. during a portion of each rotation of the rotary drum.

The device according to the invention preferably comprises a projector for projecting an image onto a film and an actuated shutter for exposing the film to the projected image at a selected time, depending on the instantaneous measured charge.

The process according to the invention comprises performing the individual stages of the xerographic process in the form of a series of interrelated stages, some of which are carried out in parallel and all of which are carried out in a considerably shortened period of time. compared to o. methods known per se. In addition, all stages of the xerographic process are carried out at the moment when the charge of the photoconductive medium is discharged, ie. at the beginning of the dark discharge curve of the photoconductive medium. In order to achieve the best possible results, it is desirable that the photoconductive film to be treated has sufficient sensitivity, and that it is desirable. showed a sufficiently fast discharge for the dark. For this purpose, a film consisting of a polyester-based substrate, a middle layer of indium oxide (0.05 µm thick) and a top layer of cadmium-type n, (0.3 µπι thick) was developed. This film exhibits rapid dark discharge, i.e., initially about 800 volts per second. Listed. film is transparent, so the image is. on it, it can be projected directly, as explained below.

The film, or rather its photoconductive layer, is charged, whereby the charge and light conditions are controlled by an exposure meter such that the photoconductive layer is charged to the optimum charge value for a given light condition.

In contrast to known methods, the film is subjected to a very high charge voltage, i.e. an impact, which is often significantly higher than the voltage corresponding to the saturation of the photoconductive medium. In other words, while known xerographic methods include charging the medium to saturation, which is when the charge is already equal to the charge that is spontaneously removed from the medium, the medium of the method of the invention is rapidly charged to a voltage which. it far exceeds the saturation voltage, the only limitation of this voltage being that the film is not charged to a voltage higher than the voltage at which the film would break. This allows the photoconductive medium to be charged in a very short period of time, for example within 500 microseconds.

Once the photoconductive film has been charged to said desired maximum voltage, the film is image-exposed under automatic exposure meter control, in relation to reaching said maximum charge.

This is followed by the application of a tinting pigment in relation to the selected controlled voltage on the surface of the photoconductive film, ensuring that the desired maximum density, i.e., the desired density, is achieved. maximum blackening, and. continuous gray scale, ie. Halftone, in the recorded image. It will still be discussed in detail later in the description.

Toning. the pigment is applied very quickly and uniformly to the surface of the film. The tinting pigment is also applied under prestressing in close proximity; to accelerate the movement of the pigment pigments. in that direction. to the surface of the photoconductive film to achieve uniform distribution of said particles, and to minimize lateral migration of the particles, which could cause a very well-known edge effect, a characteristic of conventional xerographic reproduction.

Finally, the excess tinting pigment is optionally immediately removed from the surface of the photoconductive film and the remaining tinting pigment is applied to said surface of the photoconductive film. film melts, so the whole process is finished before the tension on powc.hu fo. the conductive film drops to the minimum background value.

If the procedure is as described above, then it is obtained. microimage on film high resolution, good contrast and exceptionally clear background. As a result, when the image is enlarged to a large format for viewing or copying the image, the resulting enlarged image retains a good resolution, the image being relatively free of impurities. The method according to the invention is of course. can also be used to record larger images while maintaining all the above advantages.

In the following, preferred embodiments of the method and apparatus will be described.

1 is a functional block diagram of an image recording system for an electrophotographic film according to the invention; FIG. 2 is a graph which illustrates the process according to the invention in more detail; 1, FIG. 3 is a schematic representation of other embodiments of the invention; and. FIG. graph,. which. illustrates the function of the system shown in FIG. 3. It can be seen from FIG. 1 that in a given system it moves the film strip F, which may be a microfilm, namely. for using a conventional film feed device. Said film F is a film of the above-mentioned photoconductive type and comprises a transparent plastic backing, a photoconductive layer 12 'and an intermediate conductive layer 14. A pair of flexible ground contacts 16a and 16b slides along opposite edges of the intermediate conductive layer. 14 in order that the intermediate conductive layer has zero potential. <

In order to remove any charge present on the photoconductive layer 12, each film field F of the film F passes through. Before further processing of the film F along the grounded discharge head 18.

Then, the film field F quickly charges to the maximum voltage that is determined by the prevailing lighting conditions. This happens in the film process. The frame F * along the charging head 22. The charging head 22 has a recess 22a in its side wall 26, adjacent to the film F, corresponding in size to the area of the film field F ‘. This recess 22a extends in parallel to the film 'F wire 24 for corona discharge. If this wire connects to a relatively high potential that is negative to ground, a corona discharge will occur near the wire. The corona discharge causes the portion of the photoconductive layer 12 corresponding to the film frame to be negatively charged.

Film F charges very quickly to 'voltage that is dependent on prevailing lighting conditions at a given time. This ensures that the 'image' created on the 'F' film has a uniform toning, despite changing light conditions. This aspect of the invention is more readily understood from Figure 2, which is a graph depicting stress on the surface of film F over time.

Each film, or rather its photoconductive layer, has a characteristic dark discharge curve. In other words, if the film is charged to the selected maximum voltage, then the voltage drops exponentially to reach the background value, ie 50 to 100 · volts. If the film is charged to the first maximum voltage P, then the initial rate of voltage reduction immediately after charging is very high, as shown in Figure 2 by the first dashed line A. This means that a relatively small period of time, i.e. a small amount of light causes a relatively large charge drop 's surface of film F.

On the other hand, if the film is charged with a second maximum voltage P ', for example, to a voltage of 200 volts, the voltage drop rate is much slower, as shown in the second dashed line. B. In other words, to produce the same charge loss with the film surface, a longer period of time, and hence greater, is required; ’Amount of light. It goes without saying that the stresses are selected only by way of example, and that these stresses will vary from case to case according to the nature of the photoconductive layer used.

It can be seen from Figure 1 that a photoelectric cell 32 is disposed near the film field F so that when the film field is exposed, the average of the film element 32 is sensed. the amount of light incident on the film F In the present case, said output causes the film to charge in an inversely proportional manner to the amount of light incident. Charge. On the surface of film F, it is in turn picked up by an electrometer 34, which is built into the rechargeable head of the head 22. The electrometer 34 senses a voltage that is proportional to the surface tension. • a dark corner outside the image area. ·. '. ;.

As a result, its output follows the dark discharge curve. · Output of said photoelectric cell. 32 is connected to the first via an adjustable resistor 37. a high gain differential amplifier 36 to which an electrical output is also connected. subway '34; as the voltage on both inputs of the first differential amplifier 36 becomes low, its output voltage drops rapidly. 'Adjustable' resistance '37 that changes' output. current from the photoelectric cell 32 provides a reference setting. ’· ·,’ ·,

The output of the first differential amplifier 36 is connected to an exciter 38 that is. · In turn coupled to coil 42a of relay 42, the other end of which is coupled via the 'first switch' 44 to ground. The coil 42a controls the second switch 42b which connects the corona discharge wire 24 in the charging head 22 to the negative voltage source. which in this case is the first battery 46. The first switch 44 is normally off, as is the second switch 42b. The first switch 44 turns on when the film field is correctly positioned in front of the charging head 22 as shown in Figure 1. The switch can be turned on manually or automatically. using a mechanism that moves incrementally. film. In any case, the switch is connected during charging.

Switching on the first switch 44 results in the coil 42a. the relay 42 that starts will be energized. engages the second switch 42b of relay 42. This results in a corona discharge on the wire 24, starting to charge the film surface F. Once the film surface F has been charged, the charge value on the surface of the non-illuminated portion of the film F is sensed by an electrometer. 34, wherein the voltage at its output is proportional to said charge, in which the voltage at said output is equal to the voltage applied to the first differential amplifier 36 of the photoelectric cell 32, voltage at the output of the exciter 38, as a result of which the relay 42 is no longer energized. As a result, the second switch 42b is turned off, thereby terminating the charging of the film surface F.

If the photoelectric cell 32 senses a very intense light incident on the film field F, then a relatively low voltage is applied to the input of said differential amplifier 36. That is, the relatively small charge applied to the surface of the film field F má results in the equalization of the voltage at the output of the photoelectric cell 32 with the voltage at. output from the electrometer 34, and that charging is therefore completed relatively quickly. In this case, the film surface F will be charged at a relatively low second maximum voltage -P *. Conversely, if the photoelectric cell 32 senses less intense light impinging on the film field F ‘, a higher voltage is applied to the input of the first differential amplifier 36 from the photoelectric cell 32. As a result, the surface of the film F needs to be charged with a greater charge to obtain a voltage at the output of the electrometer 34 that would terminate charging. In this case, film F is charged to a higher first maximum voltage P.

It is necessary that the film · F be charged to the exact maximum voltage co; maybe the fastest. It. 6e performs by subjecting the film F to a relatively high voltage, which may be higher than the voltage corresponding to the saturation of the photoconductive layer, and which may even approach the voltage corresponding to the charge at which the photoconductive layer 12 is pierced. according to the invention, since - immediately after it has been charged - the film F is exposed, so that the charge on the film F is reduced - before the actual conductivity of the photoconductive layer 12 can occur.

As soon as the film field F ‘is charged to the selected maximum voltage as described above, it is immediately imaged. The parts of the film frame - F ‘on which light falls, and these parts of the film frame correspond to the bright areas of the image, quickly discharge.

On the other hand, those parts of the film frame F ‘that do not receive light - these parts correspond to the dark parts of the image to be reproduced - retain their charge. In other words, - provided that film F is charged to a voltage corresponding to the first maximum voltage. P, the charge drops on the film frame surfaces F ‘on which light falls, very rapidly, as indicated in Figure 2 by the C curve, while on the non-illuminated surfaces - shown. F ‘The charge is discharged according to the curve indicated by the first dashed line A.! · .. ·. According to the method of the invention, the film field F ‘is exposed up to. the moment when the charge on its surface,. sensed by the electrometer 34 drops to a predetermined point on curve C. From this point on, the usual reduction occurs - the voltage to the minimum background value - as shown in FIG.

Said point is chosen such that the charge on the film F corresponding to the latent image is able to bind a sufficient amount of tinting pigment particles - which are applied to the film during the tinting pigment deposition stage to achieve a good degree of contrast between blacks and white areas of the image.

In other words, if the film 'F - is exposed only for a short period of time, for example, when the discharge is dark. reaches 500 volts in Figure 2. is the contrast - between the light and dark portions of the image formed on the film frame F ', less than when the film is exposed. longer.

It can be seen from Figure 2 that this is due to the fact that even discharging the film surface - F in the dark is initially relatively fast. As a result, the charge on the non-illuminated areas of the film frame F ‘decreases - at the beginning of the exposure- almost as fast as the charge on the non-illuminated areas of the film frame F‘ decreases. As a result, if the exposure is relatively short, the charge difference on the illuminated and non-illuminated areas of the film frame F ‘is minimal.

On the other hand, if the exposure is longer, the charge difference on the illuminated and non-illuminated areas of the film frame F ‘is substantially greater. For example, if the film is exposed until the charge 'on the non-illuminated portions of the film' F 'drops to 480 volts, the charge on the illuminated areas of the film' F 'drops simultaneously to approximately 180 volts, as shown in Figure 2. As a result, they have unlit parts of the film box F '. the tendency to bind more tint pigment than the illuminated portions, and the contrast of the resulting image is therefore much more pronounced. Thus, the illuminated areas will be illuminated in said resulting image. also whiter. -. ,

Thus, it is possible to select the point at which the exposure ends; to regulate very precisely not only the degree of whiteness of the unlit parts of the latent image, but also the density of halftones and the gray scale of the image. Film sensitivity · F is selected automatically based on measured light conditions.

It can be seen from Figure 1 that in the system according to the invention, film F is exposed by means of a conventional projector 56 which projects the image to be reproduced onto the film field F ‘. A shutter 58 is provided between the projector 56 and the film F to control the exposure duration. This shutter 58 - is normally closed. The shutter opens as soon as the - - charging - - film - F,

This is mediated by a drop in the output voltage of the first differential amplifier 36. The first detector circuit 62 detects non-.

a negative transition of the output of the first differential amplifier 36 - and sends a signal to. first, the flip-flop input 64. Flip-flop output; ·; it then opens the shutter 58;

The charge · on the unlit - parts of the film frame F ‘decreases according to the first. 2. whereby the charge is measured at any time by an electrometer 34. The output of the electrometer 34 is connected to a second high-gain differential amplifier 66, to which also an output from an adjustable the reference voltage source 66. The output of the second differential amplifier 66 is in turn connected via an inverter 72 to the second input of the flip-flop 64. The adjustable source 66 is set to terminate the exposure when the charge on the unlit portion of the F-field reaches · select. determined by electrometer. 34.. As soon as this point is reached, the voltage at the output of the second differential amplifier 66 drops, thereby resetting the flip-flop-64 and closing the shutter 56.

Immediately. - after finishing the exposure, the tinting film F ‘is applied to the film frame. · Pigment. Toning. pigment - is applied in the presence of an electric field that drives the tinting pigment particles in the direction of the film F. This field not only accelerates the application of the tinting pigment, but also distributes the tinting pigment particles over all charges. parts of the film frame F ‘, so that it minimizes the occurrence of the edge effect, which is a characteristic phenomenon of copies prepared by conventional xerographic ones. progresses· .

In the system according to the invention, the start of the application of the tinting pigment is initiated by a signal from the inverter 72. which is connected to a first monostable multivibrator 76 having a variable time. constant. The outlet of the first monostable multivibrator 76 is in turn connected to a normally closed first solenoid valve 76, which is connected in a line between the liquid tinting pigmeter reservoir 62 and the tinting pigment dispenser 64 located near the film field F ‘.

As soon as the first monostable multivibrator 76 is actuated, the first solenoid valve 76 opens, resulting in a tinting flow. pigment to the dispenser 64 tinting. · Pigment. The tinting pigment dispenser 64 has a first slot 64a that is dimensionally identical to the film field F ‘, so that the liquid tinting pigment is distributed over the entire surface of the film field F‘.

An electrode 92 extends along the edge of the first slot 64a. This electrode is connected via a relay switch 94k. one terminal of the voltage source, which is a second battery 96, the other terminal of which is connected to ground. The output of the first monostable multivibrator 76 is

3 also connected when the relay coil -94ar, controls the relay switch 94 so that when it is the first. monostable, · multivibrator, 76 running, · -relayed on · ·. - This will make the connection. A strong positive potential on said electrode, which thus aids in driving the tinting particles. a pigment towards the film F to achieve the aforementioned more uniform tone. vání. ·· .;

Tinting pigment particles adhere to the k. film parts. fields' F not illuminated during exposure,.,. with less adherence to. those - parts of the film frame - F ‘that have been affected by a smaller amount of light. - If it is. voltage may be desirable. which is used during the application of the tinting pigment. to accelerate particle movement. pigment towards - film - F,. changed - in '. indirectly - depending on the output of the electrometer 34 - so that the auxiliary voltage increases as the charge on the surface of the film F decreases - along the curves in Figure 2. when the charge is on the unlit parts of the film. If the field F ‘is relatively low, a sufficient amount of tinting pigment is obtained to produce a sufficiently black image. .

The deposition of the tinting pigment is discontinued after the resetting to the initial position of the first mono-stable multivibrator 76, the time interval being dependent on. time constant of the first monostable multivibrator 76. Once the first monostable multivibrator is selected. 76 turns off, its output voltage drops. This transition is - detected by the second derivative - 102 and signaled to the second monostable multivibrator 104s. variable time constant.

Output of the second. the monostable multivibrator 10 is connected to a second solenoid valve 106 connected in a line between the vacuum pump 169 and the hood 112, which is open towards the film field F The second monostable multivibrator is started. as a result, the opening of the second electromagnetic valve 106 results in the air being pumped out of the space in which the film F is located. it achieves aspiration of excess tint pigment - from illuminated portions of the film frame F ‘having little or no charge and evaporation of the solvent of the tint pigment, thereby converting the latent image on the film frame F‘ into a visible image.

Immediately after said removal of excess tinting pigment, and after evaporation of the solvent, tinting is performed. - a pigment that - remains on the film - F, fuses to. film: F to obtain a permanent visible image. The resetting of the second monostable multivibrator 104 to its initial state is detected by the third derivative circuit 120. The output of this third divider circuit 120 is used to trigger the third monostable. multivibrator 12 $, - whose Vý195673

The 18-degree control of the heater, which in Figure 1 is an infrared bulb 126, is provided with a reflector 128 that 'directs the heat' to the 'film' F. After a certain period of time has elapsed, the length of which is determined by the setting of the third monostable multivibrator 124, the heating element is switched off, thereby terminating the development process. ·

The electrophotographic film may be processed by the method of the invention on a straight line comprising a plurality of functional positions shown in Figure -1, which are positioned along said line, perpendicular to the feed direction of the film F. When the film F is moved, this film F gradually moves to the individual functional positions.

Figure 3 shows an embodiment of a system according to the invention in which most of the functional poles shown in Figure 1 are arranged on the periphery of a cylindrical rotary drum 110. This rotary drum 110 is mounted on a hollow shaft 111 rotated by a servomotor 112. The film-F is pulled along the perimeter of the rotary drum 110 'field-by-field from right to left through the operative position-113. The individual elements of the device of Figure 3 are similar to those shown in Figure'. 1, have the same reference numerals.

On the way - to the operational position - 113, - each film field F ‘passes along the discharge head 18 which removes any residual charge from the film - F. When the film field F 'reaches the operating position 113, the rotary drum 110 rotates one revolution counterclockwise, thereby gradually adjusting the individual functional positions against the film field F at the operating position 113 .

First, film F is charged by corona discharge from wire 24, the charge on film F being measured by an electrometer 34, as described above. Then, the film frame F ‘is exposed. In this case, the shutter 58 of Figure 1 is replaced by a tunnel 114 that extends diametrically through the rotary drum 110. When the rotary drum 110 is in the position shown in Figure 3, the tunnel 114 is aligned with the optical axis O of project 56, which exposes the film field F *. In the present case, the optical system is adequately curved to compensate for the curved image plane in which the film field F F is located.

The length of the exposure is dependent on the angular velocity of the rotary drum 110. This can be - regulated by controlling the speed of the servomotor 112 using the same inputs that control the shutter 58.

As the slot 84a moves along the film field F ‘, a tinting pigment is applied to the surface of the film field F‘. It is connected to the slot 84a inside the rotary drum 110. a first -distributor 116, wherein the tinting pigment is supplied to the first distributor 116 by the first. via a line 118 which extends through a shaft 111 and which is connected via a rotary coupling 115 to a tinted pigment container 82. An electrode 92 is disposed around the slot 84a to accelerate the movement of the tinting pigment particles toward the film F as described above.

Immediately after the application of the tinting pigment, the excess tinting pigment is removed from the film F by rotating the second slit 112a along the film frame F 'located in the operating position 113. A second' slit 112a 'is connected within the rotary drum 110 a distributor 122 which is connected via a second pipe 125 and a rotary coupling 115 with a vacuum pump 109.

By moving - the slots - 112a 'along the film frame - complete rotation of the rotary drum' 110 is completed. The heating element in the form of an infrared bulb 126, located directly behind the film frame F 'in the operating position 113, is then engaged. in the above manner to fuse the residual tinting pigment, to the surface of the field F ', thereby completing the process. Thereafter, the feed of the film F is actuated by moving to the operating position 113 another film field F ‘of the film F.

The duration of charge, exposure and application of the tinting pigment can be controlled by varying the speed of the rotating drum during the operating cycle.

Figure 4 is a graph showing how the angular velocity of the rotary drum 110 can be varied during each part of each operating cycle to change the duration of operation of each operating position on the film field -F '. are obtained in a manner similar to that of the apparatus shown in Figure 1.

In a similar manner, the individual functional positions may be arranged 'along' the periphery of the rotary disk. The film to be processed advances along said disc near its periphery, while the disc is rotated in order to gradually bring the respective functional positions to the opposite position relative to the film field F in the operative position. . The operation of this device is similar to that shown in Figure 3.

16

Claims (12)

Subject A method of recording an image onto an electrophotographic film comprising a layer of photoconductive material. charging the electrophotographic film, exposing the film to the image, depositing the tinting pigment on the electrophotographic film, removing excess tinting pigment that does not adhere to the electrophotographic film, and optionally fusing the tinting pigment. adhered to an electrophotographic film, to said electrophotographic film, characterized in that the light produced by the image to be recorded on the electrophotographic is measured. the film, wherein the photoconductive layer is charged while measuring the surface potential achieved on the dark surface of the photoconductive layer and compared; the measured light intensity and the achieved surface potential of the photoconductive layer, and charging. interrupts. when this comparison reaches a value known to correspond to the optimum surface potential for a given measured light intensity of the image to achieve optimal recording quality, said surface potential being inversely proportional to the light intensity of the recorded image and in the moment, . . when . has reached said optimum surface potential, the photoconductive layer exposes said image. . 2. The method according to claim 1, wherein the photoconductive layer is exposed when the charging of the electrophotographic film is interrupted. ... 3. The method according to item 1 or 2, marked. by exposing the photoconductive layer for a fixed period of time not related to. the surface potential of the photoconductive layer achieved during charging. .. = 4. A method according to claims 1 to 3, characterized in that the application of the tinting pigment is carried out in an electric field, which is provided in the vicinity of the film, to accelerate the movement of the tinting pigment towards the film. 5. An apparatus for carrying out the method according to claim 1, comprising a charging member, an exposure member and a deposition member, comprising a photoelectric cell (32) for detecting an intensity of light and obtaining a first signal proportional to said intensity; ) for detecting instantaneous charge on the photoconductive layer and obtaining a second signal proportional to this charge, the relay (42),. a first charger switch (44) and a first differential amplifier (36) for comparing the first and second signals and obtaining a control signal proportional to the comparison to turn off the charger in response to achieving a control signal of a value corresponding to the optimum surface charge value of the photoconductive layer at a given light intensity of the image. 6. A device according to claim 5, characterized in that it comprises a bias voltage circuit. VYN.ÁLEZU .... an electrode (92), a relay switch (94), a relay coil (94a), and a second battery (96 '), to the electrical. accelerating the movement of the tinting pigment towards the film (F) to achieve uniform distribution of the pigment on the film. (F), the magnitude of the prestressing obtained being variable depending on the instantaneous charge value on the film (F). 7. Device according to claim 5, characterized in that the charging member comprises a charging head (22), a wire (24), a first derivative circuit (62), a tilting circuit. (64), an inverter (72) and a second differential amplifier · · (66), · an exposing member consisting of a projector (56) and · a shutter (58), a dispensing member consisting of a first solenoid valve (78), a cartridge (82) ; A second derivative circuit (102), a second monostable multivibrator (104), a relay switch (94), a relay coil (94a), a second battery (96), a first distributor (116), a first line ( 118) a β rotating coupling (115), and an attracting device comprising a third differential circuit (120), a third monostable multivibrator (124), a heating element preferably comprising an "infrared lamp" (126) and a reflector (128) are disposed along the peripheral portions of the rotary drum (110), the apparatus further comprising a transporter for moving the film (F) in engagement with said peripheral portions. Device according to Claim 5, characterized in that the film (F) · comprises a plurality of film frames (F '), each film frame (F' J being sequentially operable into position against the charging member, the exposure member, the coating member and a melting device during relative movement relative to said rotary drum (110). 9. The apparatus of item 5, characterized in that it comprises a tinting pigment separator comprising a second monostable multivibrator (104), a second solenoid valve (1013), a vacuum pump (109), a fume hood (112), a second distributor (122) and a third monostable multivibrator (124) to remove excess tinting pigment from the film (F). Device according to claim 5, characterized in that a second monostable multivibrator (76) is connected to the second differential amplifier (66) to control the duration of the tinting time after exposure, said time being determined by a predetermined change in charge size to that member. Device according to Claim 9 or 10, characterized in that the exposure member comprises a projector (56) disposed on the opposite side of the rotary drum (110) with respect to the film (F) and arranged to project the image onto the film (F). an "operating position" (113) and a tunnel (114) · in a rotating drum (110) aligned with 193673 by a projector (56) and a film (F) during a portion of each rotation of the rotary support member. 12. Apparatus according to claim 9 or 10, comprising a projector (56) for having an image on the film (F) and a controllable shutter (58) for exposing the film (F) to the projected image for a selected time depending on the instantaneous charge measured. .