EP1640169B1 - Device to produce digital multi-colour images - Google Patents

Abstract

A device (1) has a transport device (4) for moving the material (2) in a forward (feed) direction (5) and an exposure head (8) which can move to and fro in a perpendicular direction relative to the feed direction (5) over the material (2), and in which the exposure head (8) has several exit ends of optical fibers (18) for generating picture elements on the material (2). Coupling units (17) are formed, through which are joined a first (14), a second (15), and a third (16) light source to a single optical fiber (18) in which the colors of the light of the three light sources (14, 15, 16) form a triplet of complementary basic colors. An independent claim is included for a method for generating a multi-colored image.

Description

The invention relates to an apparatus and a method for generating a multicolor image from data of a digital image on a photosensitive material, according to the features in the preambles of claims 1 and 22.

From the document US 6,452,696 B 1 discloses a method and apparatus for controlling a plurality of light sources in a digital printer. Digital image data are used to expose a photosensitive material by applying light point by point to the photographic paper. The light pulse for exposing a pixel on the photographic paper is in each case by a light-emitting diode (LED), according to the stored digital image information, generated and passed through an optical fiber in an exposure head, through which the light pulse is finally directed to the photographic paper. The outlet ends of a plurality of optical fibers are in a frame of the exposure head immediately adjacent to each other, strung together. The arrangement of the exit ends of the optical fibers is imaged by a lens system of the exposure head on the surface of the photographic paper, so that a plurality of pixels can be exposed simultaneously. The exposure head is moved across the photo paper so that at the same time a plurality of parts of pixels can be created during such movement. By means of a transport device, the photographic paper is then advanced by a length corresponding to the number of lines first produced, whereupon a further sequence of lines of pixels, through which the exposure head moving above the paper is transferred to the photographic paper. From the document US 6,452,696 B1 It is also known, by carrying out test exposures, to determine correction tables by which the non-uniform exposure effect, as a function of the exposure intensity and the exposure time, can be taken into account. Thus, the effect is corrected which is that the exposure effect having a first exposure intensity and a first exposure time is not equal to the exposure effect achieved, for example, by half the first exposure intensity over a period of twice the first exposure time. This effect is also called reciprocity failure. It is also already known that other corrections are required at the edges between two strips consisting of adjacent pixel lines, which are generated by the exposure head, than is the case with pixel lines in the interior of a strip is. To avoid banding and thus impairing the image quality.

From the patent application EP 072 840 A method is known for multiplexing channels for transmitting information by means of light waves transmitted through a step-index fiber, each channel consisting of light rays which propagate through successive total total reflections at the interface between the core and cladding in the fiber and as a function of their angle are arranged to the fiber axis such that they are located for each channel at each point in the fiber between two cones whose common vertex is formed by this point and which are rotationally symmetrical about a common axis parallel to the fiber axis. The two cones determine the part of the opening angle of the fiber associated with each channel, the aperture parts associated with all the channels being at most adjacent or preferably separated from each other by opening part of the fiber which are free of active radiation, with independent luminous fluxes in each channel in the Fiber input are fed by means that are specific to the angular geometry of each channel associated opening part. Finally, the light fluxes propagating in the channels are recovered at the fiber output by analogous specific means.

The Patent Application US 2002/134909 describes the calibration of the light-emitting elements in an optical printer. This is done by attaching the optical printer to an external monitor. This external monitoring device comprises a sensor mounting part, on which in a straight line, a plurality of photosensors are mounted. Further, there is a signal propagating circuit for processing the signals output from the photosensors and a reference voltage generating circuit. A comparison and control circuit for comparing the outputs of the signal processing circuit with the reference voltage outputs a signal based on the result of the comparison. The photosensors receive the light emitted from the light emitting elements of the optical printer which is to be subjected to calibration. The signal processing circuit includes a plurality of integrated circuits which receive the output signals from the plurality of photosensors and integrate these signals for a prescribed period of time. Finally, there is an arithmetic circuit for calculating the mean value of the output signal of the integration circuit and outputting the calibration voltage. -

It is the object of the invention to provide an apparatus for producing a multicolor image from data of a digital image on a photosensitive material capable of producing high quality images on photosensitive materials.

This object of the invention is achieved by the device according to the features of claim 1. The arrangement of a lens system has the advantage that the exit ends of the optical fiber need not be moved directly over the photosensitive material. By imaging the exit ends of the optical fibers with the proposed lens system, the inaccuracies due to the divergence of the exiting light beam from the optical fibers can be avoided. It is achieved by the mask that both the position and the shape of the pixels can be determined with high precision and mechanical inaccuracies in the assembly of the optical fibers in the exposure head are canceled out.

The advantage of the design of the device according to claim 2 is that due to the characteristic of the course of the spectral transmittance of the interference filter used, an optimum yield of light of the light sources used is achieved.

Also advantageous are the development of the device according to claims 3 and 4, since thus a very high yield of light intensity of the light sources can be achieved.

The design of the device according to claim 5 has the advantage that the light sources, the interference filter and the entrance hatch of the optical fiber in the coupling unit can be arranged very compact and space-saving.

Also advantageous is the design of the device according to claim 6. This allows a simple assembly or connection of the optical fibers with the coupling unit.

Due to the development of the device according to claim 7, wherein the coupling units are arranged in a stationary light source unit, the advantage is achieved that the weight of the exposure head is thus kept as low as possible.

Also advantageous are the embodiments of the device according to claims 8 and 9, since with LEDs very precise, short light pulses can be generated so that correspondingly high speeds of the exposure head when moving over the photosensitive material are possible.

Due to the design of the device according to claim 10, continuously variable light pulses for exposure are available.

By forming the device with a measuring cell for measuring the light intensities of the exposure head according to claims 11 and 12, the advantage is achieved that the achievable light intensities of the exposure head can be easily checked and especially when using light emitting diodes as light sources whose nonlinear relationship between Drive current and light intensity measured and in the exposure of digital images, this relationship can be considered.

The development of the device according to claim 13, according to which a displacement sensor is designed to detect the position of the exposure head, the advantage is achieved that thus a very precise control of the pixel production is made possible according to the lateral position of the corresponding pixels.

Also advantageous are the developments of the device according to claims 14 and 15, since it is possible, the application of the pixels by alternately generating lines and inter-lines, by only every second line of the digital image is exposed and subsequently exposed to corresponding inter-lines to execute.

Due to the design of the device according to claims 16 and 17, an overlap of each successive lines or intermediate lines is possible in an advantageous manner, whereby image errors due to inaccuracies that could make noticeable by horizontal banding can be avoided.

By the formation of the device according to claims 18 and 19, the advantage is achieved, which thus also corresponds to the overlap of lines or inter-lines Overlapping in the lateral direction between each other within a line adjacent pixels is achieved. The formation of vertical stripes, which could be noticeable as corresponding artifacts are thus avoided.

Due to the development of the device according to claim 20, according to which lateral contours of the hatches in the mask approximately correspond to a Gaussian bell curve, it is achieved that even with imprecise feed movement of the transport device as even as possible a course of the total exposure between two adjacent lines or interstitial lines remains largely ,

The design of the device according to claim 21 has the advantage that masks with very high precision are available with the masks formed by coated glass flakes.

The object of the invention is solved independently by the method according to the features of claim 22. The advantage here is that with one third of the optical fibers, the Auslangen can be found and at the same time a higher accuracy of the exposure of the individual pixels of the digital image can be achieved.

Advantageous developments of the method are also described in claims 23 to 29.

For a better understanding of the invention, this will be explained in more detail with reference to the following figures.

Fig. 1

eine Vorrichtung zum Belichten eines fotosensitivem Materials mit digitalen Bildern;

Fig. 2

eine Prinzipdarstellung einer Einkoppeleinheit, gemäß Fig. 1;

Fig. 3

den über dem fotosensitiven Material angeordneten Belichtungskopf (gemäß Fig. 1), geschnitten dargestellt;

Fig. 4

die Maske des Belichtungskopfes gemäß Fig. 3;

Fig. 5

ein stark vergrößertes Detail der Maske mit zwei Luken, gemäß Fig. 4;

Fig. 6

einen vergrößerten Ausschnitt des photosensitiven Materials mit den darauf belichteten Zeilen und einer Zwischenzeile;

Fig. 7

ein Ablaufschema des Verfahrens zum Belichten von digitalen Bildern mit einer Korrektur des Intermittenz-Effektes.

In a simplified schematic representation:

Fig. 1

an apparatus for exposing a photosensitive material to digital images;

Fig. 2

a schematic diagram of a coupling unit, according to Fig. 1 ;

Fig. 3

the exposure head arranged above the photosensitive material (according to FIG Fig. 1 ) shown in section;

Fig. 4

the mask of the exposure head according to Fig. 3 ;

Fig. 5

a greatly enlarged detail of the mask with two hatches, according to Fig. 4 ;

Fig. 6

an enlarged section of the photosensitive material with the lines exposed thereon and an intermediate line;

Fig. 7

a flow chart of the method for exposing digital images with a correction of the Intermittenz effect.

By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, wherein the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and are to be transferred to the new situation mutatis mutandis when a change in position. Furthermore, individual features or combinations of features from the different exemplary embodiments shown and described can also represent independent, inventive or inventive solutions.

The Fig. 1 shows a device 1 for exposing a photosensitive material 2 with digital images 3 in a schematically simplified representation.

The device 1 has for this purpose a transport device 4, with the aid of which the photosensitive material 2 can be moved in the feed direction 5. The photosensitive material 2 is formed by, for example, photographic paper or a film. With the aid of a transport roller 7 operated by a motor 6, the material 2 is moved or positioned underneath an exposure head 8. The exposure head 8 can be moved back and forth along guides 9 oriented transversely or perpendicular to the feed direction 5 with the aid of an exposure head drive 10. For the exposure of the material 2 with the exposure head 8, the latter is alternately moved back in the direction 11 and in the direction 12, the material 2 being moved further in the feed direction 5 between the transverse movements of the exposure head 8 and being repositioned. There is such a line by line or pointwise exposure of the photosensitive material 2 by 8 light pulses are directed to the material 2 by the exposure head.

The generation of the light pulses takes place in a light source unit 13 with light sources 14, 15, 16, which are preferably each formed by a light-emitting diode (LED). It is provided, for example, that the light source 14 of the generation of red light, the light source 15 of the generation of green light and the light source 16 of the generation of blue light, so that generates a triple of complementary primary colors by a triple of light sources 14, 15, 16 can be. The light sources 14, 15, 16 are to a coupling unit 17 summarized, wherein the light is merged or coupled into a single optical fiber 18. The light source unit 13 has a number of a plurality of such coupling units 17, the light of which is guided into the exposure head 8 through the optical fibers 18, which are combined to form a fiber bundle 19. According to the number of optical fibers 18, it is thus possible to simultaneously expose a number of lines corresponding to the number of coupling units 17 on the photosensitive material 2, wherein each pixel can be exposed simultaneously with the three primary colors. By appropriate mixing of the color components of the light sources 14, 15, 16 in that their light intensity is continuously variable, it is thus possible to produce any desired color on a pixel.

To generate the light pulses, each of the light sources 14, 15, 16 of each of the coupling units 17 has a drive circuit 20. Each of these drive circuits 20 comprises at least one digital / analog converter 21 and a timer 22. The execution of the exposure process of the device 1 by means of a central controller 23, the information of the digital image 3 in control signals for the transport device 4, the exposure head 10 and the driving circuits 20 for the light sources 14, 15, 16 converts. To determine the current position of the exposure head 8 or the fiber ends of the optical fibers 18, the controller 23 is connected to a displacement sensor 24 in connection.

The device 1 additionally comprises a measuring cell 25 for measuring the light intensities of the exposure head 8. In particular, in the case that the light sources 14, 15, 16 are formed by LEDs, by measuring the light intensities by means of the measuring cell 25, the strong, non-linearity of Connection, between drive current and light emission are measured. The correction parameters derived from this are taken into account during the exposure. However, by periodically repeating corresponding measurements with the measuring cell 25, it is also possible to compensate for changes as a result of the aging or the thermal loads on the LEDs. This measuring cell 25 is preferably arranged in the region of a parking position of the exposure head 8 outside the actual exposure range of the device 1, so that measurements on the measuring cell 25 can also be carried out automatically.

The Fig. 2 shows a schematic diagram of one of the coupling units 17, according to Fig. 1 ,

On a frame 26 of the coupling-in unit 17, a fiber holder 27 for the inlet-side end of the optical fiber 18 is arranged. The optical fiber 18 is additionally attached in a socket 28, which can be inserted into the fiber holder 27 and fixed there. The fiber holder 27 has at one end a, corresponding to the longitudinal extension of the socket 28 of the optical fiber 18, aligned entrance hatch 29, through which the light of the light sources 14, 15, 16 enters or is coupled into the optical fiber. The light sources 14, 15, 16 are each held in a holder or a tube 30, 31, 32 and their light is focused in each case by a lens 33, 34, 35. The tubes 30, 31, 32 or optical axes 36, 37, 38 of the lenses 33, 34, 35 are aligned approximately star-shaped. The optical axis 38 of the lens 35 is aligned parallel and in alignment with respect to an optical axis 39 of the entrance hatch 29. In contrast, the optical axes 36, 37 of the lenses 33, 34 with respect to the optical axis 39 of the engagement hatch 29 are obliquely aligned and passes the light of the light sources 14, 15 by deflection or reflection at an interference filter 40 or 41 in the entrance hatch 29th the fiber holder 27. The optical axes 36, 37 close with the optical axis 39 of the entrance hatch 29 preferably an angle of 60 °. This allows a very compact arrangement of the tubes 30, 31, 32 and the interference filter 40 with respect to the fiber holder 27th

The use of the interference filter 40, 41 for deflecting the beam path of the light sources 14, 15 offers the advantage that light losses can be kept particularly low. Such interference filters are formed by alternating-layer systems, ie multiple layers with alternating high and low refractive indices. Since the layers are virtually free of absorption, a nearly lossless division of a spectral range to reflection and transmission is possible, the limit being determined by a steep edge of the transmission curve. For deflecting the red light of the light source 14, a filter is used for the interference filter 40 whose spectral transmittance for red light is almost zero, while light of a smaller wavelength range, such as the green light of the light source 15 and the blue light of the light source 16 Interference filter can pass almost unattenuated. The red light of the light source 14, however, is reflected and passes through the entrance hatch 29 in the optical fiber 18. Analogously, a filter is used as the interference filter 41 whose spectral transmittance for green Light is almost equal to 0, while the blue light of the light source 16 can pass almost lossless through the interference filter 41. The green light of the light source 15 is thus reflected to the interference filter 41 and passes through the engagement hatch 29 in the optical fiber 18. The peculiarity of the coupling unit 17 is thus that for the deflection of the beam path of the first light source 14 toward the entrance hatch 29 for the Optical fiber 18, an interference filter 40 is used whose spectral transmittance for the wavelength of the light of the light source 14 is almost 0, while the spectral transmittance for the wavelengths of light of the other light sources 15, 16, which must pass through the interference filter 40, almost equal 1 is. The second indifference filter 41, on the other hand, has a spectral transmittance which is almost equal to 0 for the wavelength of the light of the second light source 15, while the spectral transmittance of the light of the light source 16 which must pass through this indifference filter 41 is almost equal to 1.

For the arrangement of the light sources 14, 15, 16 in the respective tubes 30, 31, 32 can also be provided that their position with respect to the longitudinal extent of the respective tube 30, 31, 32 can be adjusted. Likewise, the position of the tubes 30, 31, 32 with respect to the frame 26 in the longitudinal extension of the tubes 30, 31, 32 are adjusted. This ensures that the light intensity that reaches the entrance hatch 29 of the fiber holder 27 has the maximum achievable value.

The Fig. 3 shows the exposure head 8 arranged above the photosensitive material 2 (according to FIG Fig. 1 ), cut shown.

The photosensitive material 2 is guided in the region below the exposure head 8 via a table or a plate 42 with a flat upper side. This ensures that the material 2 is aligned parallel to the exit ends of the optical fibers 18. From the stationarily arranged light source unit 13 (FIG. Fig. 1 ), the optical fibers 18 carry the light in the exposure head 8. The optical fiber 18 each end in a socket 43 which are mounted in a carrier 44. The light from the optical fibers 18 is directed by the interposition of a lens system 45 on the photosensitive material 2. Between the material 2 facing the outlet ends 46 of the optical fibers 8 and the lens system 45, a mask 47 is arranged with hatches 48 or interposed.

By using this mask 47 inaccuracies in the positioning of the exit ends 46 of the optical fibers 18 are compensated. Both the insertion of the optical fibers 18 in the sockets 43 and the insertion of these sockets 43 in the carrier 44 is associated with mechanical inaccuracies that can be completely eliminated by the mask 47 provided with the hatches 48 and thus only inaccuracies of manufacture the mask 47 itself remain. The hatches 48 in the mask 47 in each case act as diaphragms for the light emerging from the exit ends 46 and can thus be determined very precisely both the shape of the individual pixel points and their relative distance. By the hatches 48 of the mask 47 are imaged by the lens system 45 in the ratio 1: 1 on the material 2, on the material 2, the same accuracy of the mutual distances and the shape of the pixels can be achieved.

The Fig. 4 shows the mask 47 of the exposure head 8 according to Fig. 3 ,

The hatches 48 are distributed in a grid-shaped manner on the mask 47, so that with respect to a direction perpendicular to the directions 11, 12 of the movement of the exposure head 8 successive hatches 48 are offset by a hatch distance d 49. In the illustrated embodiment, a total of 41 hatches 48 are provided, so that when moving the exposure head 8 in one of the directions 11, 12 41 lines 40 of pixels on the material 2 can be exposed. In the Fig. 4 This is indicated by the lines 50 shown in the upper area of the mask 47 for the direction of movement 11 by way of example. For the sake of simplicity, the lens system 45 (FIG. Fig. 3 ) occurring image reversal in the further description disregarded. Around the exit ends 46 of the optical fibers 18 (FIG. Fig. 3 ) to be able to position each other over one of the gaps 48 without mutual spatial obstruction, the hatches 48 are in each case also successively in the lateral direction, ie with respect to the directions 11, 12, offset from each other in successive rows 50. When activating the light sources 14, 15, 16 of different optical fibers 18, this lateral displacement of the hatches 48 by a corresponding time delay of the transmission of the data of the digital image 3 to the drive circuit 20 (FIG. Fig. 1 ). The mask 47 is preferably formed from a glass sheet provided with a coating. For exact mounting in the exposure head 8, the mask 47 also has centering marks 51.

Fig. 5 shows a greatly enlarged detail of the mask 47 with two hatches 48, according to Fig. 4 ,

The illustrated section shows two hatches 48 and dashed lines indicated exposure strips 52, as they are generated by the passage of the hatches 48 in the direction 11 on the photosensitive material 2. According to the invention, during a first movement of the exposure head 8 (FIG. Fig. 1 ) over the material 2 of the lines of the digital image 3 to be generated only every second line 50 is generated. After the material 2 has been correspondingly moved further in the feed direction 5, the generation of corresponding intermediate lines 53 ensues, during a second movement of the exposure head 8, on the basis of the data of the digital image 3. With respect to the feed direction 5, successive lines 50, 53 thus have a line spacing z 54 whose value is equal to half the hatch distance d 49. This method of applying nested lines 50 and intermediate lines 53 is also referred to as interlacing. In this case, preferably an exposure head 8 is used with an odd number of optical fibers 18 or of hatches 48, so that the transport device 4 can be operated with a respective same feed length in the extent of the product of the number of optical fibers 18 and half of the hatch distance d 49 (feed length = Number of optical fibers * d / 2).

According to the invention, each hatch 48 perpendicular to the direction 11, 12 of the movement of the exposure head (8) has a height 55 whose value is greater than the line spacing z 54. As a result, the exposure strips 52 of lines 50 and exposure strips 56 of FIG Intermediate lines 53 between each successive lines 50 and intermediate lines 53 overlap each other. This can be avoided unwanted streaking. For hatches 48 whose height 55 is equal to the theoretically maximum value of the height of a pixel, namely equal to the line spacing z 54, it can lead to unexposed hatches as a result of not sufficiently precise forward movement of the material 2 by the transport device 4, which is a strip in the Make picture noticeable. Furthermore, it is provided that a width 57 of the hatch 48 has a value which is greater than the line spacing z 54. Both the height 55 and the width 57 of the hatch 48 thus extend beyond the maximum theoretical areal extent of a pixel. This corresponds just to a square with a side length which is equal to the line spacing z 54. By thus selected width 57 of the hatch 48 is consequently also an overlap between adjacent Pixels within a line 50, 53 reached. The lateral overlap with respect to the direction 11, 12 is additionally increased by the fact that the exposure head 8 is moved continuously over the photosensitive material 2 ( Fig. 1 ). This overlap of the exposure areas of individual pixels in the lateral direction 11, 12 results from the path traveled by the exposure head 8 or the hatch 48 during the duration of an exposure pulse. The maximum duration of an exposure pulse is equal to the transit time for covering the width of an exposure point corresponding to FIG Line spacing z 54. For the duration of the exposure pulses, a value between 60% and 95%, in particular 90%, of the propagation time for the width of an exposure point or the transit time for the distance of the line spacing z 54 is preferably selected.

Regarding the shape of the hatch 48, it is provided that lateral contours 58, 59 correspond at least approximately to a Gaussian bell curve. Points of material 2 near the maximum width of the hatch 48, i. in an area near the width 57 of the hatch 48, are thus exposed to the exposure of a light pulse much longer than is the case for other points. This is symbolically indicated by exposure curves 60 of the exposure strips 52 and exposure curves 61 of the exposure strips 56, respectively. It is easy to see that in areas where exposure strips 52 and exposure strips 56 overlap one another, the exposure curves 60, 61 overlap, resulting in an overall exposure curve with approximately constant progression and no abrupt changes. Also, inaccuracies that may occur as a result of not exactly running feeds through the transport device 4, thereby have only a very small effect on the overall exposure curve and are therefore practically unrecognizable in the appearance of the finished exposed image. The height 55 as well as the width 57 of the hatch 48 are preferably equal to 1.8 times the line spacing z 54.

• Stärke: einstellbare Korrekturwirkung
• T-Differenz: aktuelles Zeitintervall
• T-Nominal: Referenz-Zeitinterfall

Because of the overlap of the exposure strips 56 of interstitial lines 53 with the exposure strips 52 of the lines 50, locations of the material 2 that are in the overlap area are exposed twice in succession. Since the exposure effect is different in such a case in the second exposure process, as when a location is exposed for the first time, it is provided according to the invention that a compensation by a correction of the light intensities and / or the pulse duration of the light pulses is made. The different exposure effect of two on each other The following exposures of a photosensitive material is known as the so-called Intermittenz effect of photophysical exposure systems. The calculation of the correction values for the intensity of the exposure takes place by means of a function of the form: $$\mathrm{CORR}=\mathrm{St}\ddot{\mathrm{a}}\mathrm{strength}*\log \left(\mathrm{T}-\mathrm{difference}/\mathrm{T}-\mathrm{Nominal}\right)$$

• Strength: adjustable correction effect
• T difference: current time interval
• T-Nominal: reference time interval

The values for "Thickness" and "T-Nominal" can be determined by test exposures. T difference stands for the time duration between the first exposure process and the second exposure process at the same location of the material 2.

The method for correcting the intermittency effect thus consists in first producing at least one first line 50 of pixels 53 during a first movement of the exposure head 8 and subsequently producing at least one second line 53 of pixels 62 during a second movement of the exposure head the first row 50 and the second row 53 at least partially overlap each other. Before generating the second line 53, corrected image data for the second line 53 is calculated by compensating for the changed exposure effect of the second exposure process for each of the pixels 62. This compensation is effected by a change in the intensity and / or by the change in the pulse duration of the corresponding exposure pulse by a value which is proportional to the logarithm of the ratio of the time interval between the exposure of the pixel 63 and the exposure of the pixel 63 and a reference time interval.

The Fig. 6 shows an enlarged section of the photosensitive material 2 with the lines 50 exposed thereon and an intermediate line 53.

Based on this representation, the correction of the above-mentioned Intermittenz effect will be described in more detail. A pixel 62 of the intermediate line 53 and in each case a pixel 63 of the two adjacent rows 50 are indicated by a respective dashed square with the side length corresponding to the value of the line spacing z 54. As by the also marked Outlines of the hatches 48 should be illustrated, the exposure is carried out according to the image data of the digital image 3 ( Fig. 1 ), beyond the range of the theoretical maximum areal extent of the pixels 62, 63. The consequence is that, already in the description to Fig. 5 explained overlap of the exposure strips 52, 56 (FIG. Fig. 5 ).

Assume now that the exposure of the photosensitive material 2 to the lines 50 during movement of the exposure head 8 (FIG. Fig. 1 ) corresponding to the direction 11 (according to FIG Fig. 6 from left to right). Corresponding to the lateral position of the pixels 63, they are exposed at a first time, whereupon the exposure head 8 moves to the right edge of the image until the corresponding lines 50 have been completely exposed. There is then an advance of the photosensitive material 2 in the feed direction 5, so that subsequently the intermediate lines 53 can be exposed. The feeding head 8 ( Fig. 1 ) changes its direction of movement in direction 12 (according to Fig. 6 from right to left) and the exposure of the intermediate line 53 until the pixel 62 is finally exposed at a second time. By measuring or calculating the time difference between the first time of exposure of the pixels 63 and the second time of exposure of the pixel 62, it is possible to calculate a correction value for the light pulse required to expose the pixel 62 and to control the light sources 14, 15, 16 ( Fig. 1 ) to take into account. The time difference corresponds to a path 64 of the exposure head 8, as determined by detecting the position of the exposure head 8 by means of the displacement sensor 24 (FIG. Fig. 1 ) and the speed of movement can be determined. For an exact determination of the corresponding time intervals, strictly speaking, the delay difference due to the lateral displacement of the hatches 48 would also have to be considered. However, this difference in transit time is negligible in relation to the total runtime. There is thus a detection of the time sequence of the exposure course during exposure of the photosensitive material 2 and a calculation of the time interval for exposing adjacent pixels 62, 63 of successive lines 50 and intermediate lines 53 and on the basis of the time interval thus determined a correction for the compensation of so-called intermittency effect. The calculated correction value is converted to the image data of the digital image 3 before the corresponding exposure cycle is executed (FIG. Fig. 1 ) added.

Fig. 7 shows a flowchart of the method for exposing digital images 3 with a correction of the Intermittenz effect.

Starting from the image data of a digital image 3, in a first step 71, the image data is divided into image data corresponding to lines 50 and image data corresponding to intermediate lines 53 (FIG. Fig. 5 and 6 In a further step 72, a recording of the movement sequence of the exposure head 8 and the advancing movement of the photosensitive material 2 (FIG. Fig. 1 ). In a step 73, on the basis of this information, time intervals or differential times for adjacent pixels 62, 63 for lines 50 and intermediate lines 53 are determined. In a step 74, correction values for the exposure of the intermediate lines 53 are then calculated and thus new corrected image data for the intermediate lines 53 is determined. In a subsequent step 75 then the control of the light sources 14, 15, 16, by the image data to the lines 50 and the intermediate lines 53 are alternately transferred to the drive circuit 20.

The exemplary embodiments show possible embodiments of the device or the method for generating a multicolored image from data of a digital image, it being noted at this point that the invention is not limited to the specifically illustrated embodiments of the same, but rather also various combinations of the individual embodiments are possible with each other and this possibility of variation due to the teaching of technical action by objective invention in the skill of working in this technical field expert. There are therefore also all possible embodiments, which are possible by combinations of individual details of the illustrated and described embodiment, the scope of protection.

For the sake of order, it should finally be pointed out that, for better understanding of the structure of the device, these or their components have been shown partially unevenly and / or enlarged and / or reduced in size.

The problem underlying the independent inventive solutions can be taken from the description.

Above all, the individual in the Fig. 1 . 2 ; 3 . 4 . 5 ; 6 . 7 shown embodiments form the subject of independent solutions according to the invention. The relevant objects and solutions according to the invention can be found in the detailed descriptions of these figures.

REFERENCE NUMBERS

1

contraption

2

material

3

image

4

transport means

5

feed direction

6

engine

7

transport roller

8th

exposure head

9

guide

10

Exposure Head Drive

11

direction

12

direction

13

direction

14

Light source unit

15

light source

16

light source

17

coupling unit

18

Optical fiber

19

fiber bundles

20

drive circuit

21

Digital / analog converter

22

timer

23

control

24

encoder

25

cell

26

frame

27

fiber mount

28

version

29

admission Luke

30

tube

31

tube

32

tube

33

lens

34

lens

35

lens

36

optical axis

37

optical axis

38

optical axis

39

optical axis

40

interference filters

41

interference filters

42

plate

43

version

44

carrier

45

lens system

46

exit end

47

mask

48

hatch

49

Hatch distance d

50

row

51

centering mark

52

exposure strips

53

intermediate line

54

Line spacing z

55

height

56

exposure strips

57

width

58

contour

59

contour

60

exposure curve

61

exposure curve

62

pixel

63

pixel

64

path

70

step

71

step

72

step

73

step

74

step

Claims (29)

1. Device (1) for generating a multi-colour image from data of a digital image (3) on a photosensitive material (2), with a conveyor system (4) for moving the material (2) in a feed direction (5), and with an exposure head (8) which can be moved backwards and forwards across the material (2) in a direction (11, 12) extending perpendicular to the feed direction (5), and the exposure head (8) has a several outlet ends (46) of light-conducting fibres (18) for generating pixels (62, 63) on the material (2), and coupling units (17) are provided by means of which a first light source (14), a second light source (15) and a third light source (16) are respectively connected to a single light-conducting fibre (18), and the colour of the light of the first light source (14), the colour of the light of the second light source (15) the colour of the light of the third light source (16) form a trio of complementary basic colours, characterised in that a mask (47) with exposure apertures (48) is disposed in the exposure head (8) between the outlet ends (46) of the light-conducting fibres (18) and a lens system (45) for reproducing the outlet ends (46) of the light-conducting fibres (18) on the material (2).
2. Device as claimed in claim 1, characterised in that the coupling unit (17) for connecting the light sources (14, 15, 16) to an inlet port (29) of the light-conducting fibres (18) comprises a first interference filter (40) and a second interference filter (41), and the light of the first light source (14) is reflected on the first interference filter (40), and the light of the second light source (15) is reflected on the second interference filter (41) and passes through the first interference filter (40), and the light of the third light source (16) passes through the second interference filter (41) and through the first interference filter (40).
3. Device as claimed in claim 1 or 2, characterised in that the light sources (14, 15, 16) are each disposed in a tube (30, 31, 32), each equipped with a lens (33, 34, 35) for focusing the light of the light sources (14, 15, 16) on the fibre inlet port (29) for the light-conducting fibre (18).
4. Device as claimed in claim 3, characterised in that the position of the light sources (14, 14, 16) in the respective tubes (30, 31, 32) can be adjusted with respect to the longitudinal extension of the respective tube (30, 31, 32).
5. Device as claimed in claim 3 or 4, characterised in that the optical axes (36, 37) of the lenses (33, 34) of the first and the second light sources (14, 15) each subtend an angle of 60° with an optical axis (39) of the inlet port (29), and an optical axis (38) of the lens (35) is oriented parallel with the optical axis (39).
6. Device as claimed in one of claims 2 to 5, characterised in that the inlet port (29) is disposed in a fibre holder (27) and the light-conducting fibre (18) secured in a socket (28) can be inserted in the fibre holder (27) and fixed in the fibre holder (27).
7. Device as claimed in one of claims 2 to 6, characterised in that the coupling units (17) are disposed in a stationary light source unit (13).
8. Device as claimed in one of the preceding claims, characterised in that the light sources (14, 15, 16) are light-emitting diodes (LEDs).
9. Device as claimed in one of the preceding claims, characterised in that the trio of basic colours is red, green and blue.
10. Device as claimed in one of the preceding claims, characterised in that each of the light sources (14, 15, 16) is connected to a control circuit (20), and the control circuit (20) comprises at least one digital-analogue converter (21) and a timer (22).
11. Device as claimed in one of the preceding claims, characterised in that it has a measuring cell (25) for measuring the light intensities of the exposure head (8).
12. Device as claimed in claim 11, characterised in that the measuring cell (25) is disposed outside of the exposure area of the exposure head (8) when the latter is in an idle position.
13. Device as claimed in one of the preceding claims, characterised in that it has a distance transmitter (24) for detecting the position of the exposure head (8).
14. Device as claimed in one of the preceding claims, characterised in that exposure apertures (48) disposed one after the other are offset with respect to a direction extending perpendicular to the directions (11, 12) of movement of the exposure head (8) by an aperture spacing d (49).
15. Device as claimed in one of the preceding claims, characterised in that the aperture spacing d (49) has a value equal to twice a line spacing z (54) of lines of the digital image (3) to be generated.
16. Device as claimed in one of the preceding claims, characterised in that the exposure apertures (48) have a height (55) perpendicular to the direction (11, 12) of movement of the exposure head (8), the value of which is greater than the line spacing z (54).
17. Device as claimed in claim 16, characterised in that the height (55) is equal to 1.8 times the line spacing z (54).
18. Device as claimed in one of the preceding claims, characterised in that the exposure apertures (48) have a width (57) by reference to the direction (11,12) of movement of the exposure head (8), the value of which is greater than the line spacing z (54).
19. Device as claimed in claim 18, characterised in that the width (57) is equal to 1.8 times the line spacing z (54).
20. Device as claimed in one of the preceding claims, characterised in that the exposure apertures (48) are shaped with lateral contours (58, 59) at least approximately conforming to a Gaussian bell curve.
21. Device as claimed in one of the preceding claims, characterised in that the mask (47) is made from a glass leaf provided with a coating.
22. Method of generating a multi-colour image from data of a digital image (3) on a photosensitive material (2), and the material (2) is moved by a conveyor system (4) in a feed direction (5), and pixels (62, 63) are generated on the material (2) by an exposure head (8) which is able to move backwards and forwards across the material (2) in a direction (11, 12) extending perpendicular to the feed direction (5) and has a plurality of outlet ends (46) of light-conducting fibres (18), and the light of a first light source (14), the light of a second light source (15) and the light of a third light source (16) is directed through a single light-conducting fibre (18), and the colour of the light of the first light source (14), the colour of the light of the second light source (15) and the colour of the light of the third light source (16) form a trio of complementary basic colours, characterised in that a mask (47) with exposure apertures (48) is disposed in the exposure head (8) between the outlet ends (46) of the light-conducting fibres (18) and a lens system (45) for reproducing the outlet ends (46) of the light-conducting fibres (18) on the material (2).
23. Method as claimed in claim 22, characterised in that a first interference filter (40) and a second interference filter (40) are used to introduce the light into the light-conducting fibres (18), and the light of the first light source (14) is reflected on the first interference filter (40), and the light of the second light source (15) is reflected on the second interference filter (41) and passes through the first interference filter (40), and the light of the third light source (16) passes through the second interference filter (41) and through the first interference filter (40).
24. Method as claimed in one of claims 22 to 23, characterised in that, during the course of a first movement of the exposure head (8), only every second line (50) of the lines of the digital image (3) to be produced is generated, after which the material (2) is advanced further in the feed direction (5) and intermediate lines (53) are then generated during the course of a second movement of the exposure head (8).
25. Method as claimed in claim 22 or 24, characterised in that the exposure apertures (48) have a height (55) perpendicular to the direction (11, 12) of movement of the exposure head (8), the value of which is greater than the line spacing z (54), and exposed strips (52) of lines (50) and exposed strips (56) of intermediate lines (53) are generated, and exposed strips (52, 53) of successively following lines (50) and intermediate lines (53) partially overlap one another.
26. Method as claimed in claim 25, characterised in that, prior to generating the intermediate lines (53), corrected image data is computed for the intermediate lines (53) by compensating, for each and every image pixel (62) of the intermediate lines (53), the altered exposure effect of the second exposure process which follows the first exposure process after a time interval, , and such compensation takes place by changing the intensity and/or by changing the pulse duration by a value which is proportional to the logarithm of the ratio between the time interval and a reference time interval (value ∼ log(time interval/reference time interval)).
27. Method as claimed in claim 26, characterised in that test exposures are run and from these, the reference time interval and a proportionality factor are determined for the value of the change in intensity and/or a proportionality factor is determined for the value of the change in pulse duration for the specific photosensitive material (2).
28. Method as claimed in one of claims 22 to 27, characterised in that the light sources (14, 15, 16) are light-emitting diodes (LEDs).
29. Method as claimed in claim 28, characterised in that the light intensities of the exposure head (8) for different control currents of the LEDs are measured with a measuring cell (25) and correction parameters for compensating non-linearities of the LEDs are determined.

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