HK1045881B - Parallel-processing, optical distance-measuring device - Google Patents

Description

Parallel processing type optical distance measuring instrument

Technical Field

The invention relates to a device for determining the positional deviation of n points from n separate reference positions, comprising a source of electromagnetic radiation, a set of projection mirrors and a photosensitive detector, wherein n is a natural number and the positional information is converted into intensity information.

Background

For imaging flat or curved printing plates (Bebilderung), an array of light sources, and usually an array of lasers, is usually used in a plate exposure apparatus or printing apparatus or press. The n individual beams are generated by means of an array of lines which are generally perpendicular to the optical axis of the projection optics, the image points of which, starting from a light source, for example a laser diode, are formed by means of an objective optics, are located on a surface of a few millimeters by micrometers and are usually distributed substantially in a plane or rather in a straight line on the printing plate. A point or a point is understood here not only as a mathematical point but also as a multidimensional finite surface. The image points of one of the rays typically have a diameter of a few micrometers and are spaced from each other by several hundred micrometers. Since dust, other particles, etc. soil a substrate in a planar or curved shape, the printing plate is usually not flat but may form local bumps having a diameter of several millimeters. In general, not only are all n rays of the ray set designed identically, but also the individual projection lens groups of the array are designed such that the reference position of the image point or in other words its ideal position at the reference distance from the objective lens group lies approximately in one plane. However, due to the formation of the protuberances, it is necessary that the image point of each ray lies in a different plane than the plane defined by the reference positions, which plane is generally perpendicular to the straight line defined by the optical axis of the projection lens arrangement. In order to achieve the desired imaging effect also at these positions of the image field, it is necessary to vary the light power of the light source of the relevant array depending on the method used, or in the case of an image point at the reference position being the end of the beam of the light source, to vary the focus of the projection optics, for example by varying the object distance, the image width or by shifting the main plane of the projection optics. In both cases it is necessary to determine the position of the actual image point relative to the reference position, since this parameter is required as an input value to calculate the required power change or the required change of the projection mirror set. Typically, such ranging results are used to generate an adjustment signal. The adjustment signal can be generated, for example, by further processing of a photosensitive detector signal or by light intensity measurement. Optical distance meters are used in particular in autofocus devices.

US4546460 discloses an autofocus device for an optical system with a laser as light source, a light-reflecting layer and a photosensitive detector with at least two photosensitive regions. The laser beam is converged by the objective lens and projected on the light reflecting layer. The laser light reflected by the layer is projected onto the photosensitive detector surface through an objective lens and other optical elements. The displacement of the objective lens along the optical axis deflects the laser beam and the projected pattern on the surface of the photosensitive detector is moved in a certain direction. The pattern is present on the first photosensitive area if the objective lens is at a shorter distance from the light-reflecting layer than a predetermined distance. The pattern is also formed on the first photosensitive area if the objective lens is at a greater distance from the light-reflecting layer than the second predetermined distance. The pattern is formed on a second photosensitive area of the photosensitive detector if the objective lens is at a distance from the light-reflecting layer greater than the first predetermined distance but less than a second predetermined distance. The distance of the reflecting layer from the optical system can be deduced from the position of the measured pattern.

Furthermore, the focus of the projection lens group can be moved by moving the objective lens.

In such a configuration, it is disadvantageous that only the position of one of the points relative to one reference position can be determined and one focus moved.

For example, in US5302997, a structure is disclosed in which optical ranging elements are arranged in an array, which is used for automatic focus control and automatic exposure measurement of the associated optical system. In one image field, such an arrangement has a two-dimensional light-sensitive element in the center and a plurality of light-sensitive elements arranged in a line on both sides thereof. The pattern is projected onto the device by means of a lens system. Here, the light-sensitive elements arranged in a line acquire a small portion of the image field and are used to measure the intensity of the illuminating light, whereas the two-dimensional light-sensitive elements are formed from a number of separate areas and are used to generate autofocus signals.

In this arrangement, it is disadvantageous that the focus is controlled taking into account the position of only one of the points. Although the array of light sensitive elements is used for intensity measurement, the corresponding signals are only used for automatic exposure measurement.

In order to determine the positional deviation of the n image points from their reference position for an array of n light sources, in particular lasers, the device is not suitable, since a partial decomposition for the n image points is not possible and only a signal can be generated for the entire image field. Continuously measuring n deviations or distances means n times the measuring time, which is not acceptable for ideal use purposes and in particular for use purposes in a printing plate imaging device.

Disclosure of Invention

It is an object of the present invention to provide a device for determining the positional deviation of n points from their discrete reference positions which allows n deviations or distances to be measured quickly.

According to the invention, a device for determining deviations of the position of n points from n discrete reference positions thereof is proposed, where n is a natural number greater than or equal to 2, having a source of electromagnetic radiation, a projection optics group, whereby the electromagnetic radiation forms a light pad when passing through a part of the projection optics group, which light pad is projected obliquely at the position of all n points such that it illuminates the surface defined by the n points, wherein a deviation of the position of at least one of the n points on the surface from its reference position leads, by means of the projection optics group in a univocal relationship, to a further light path of the light reflected by the surface, which light path differs from the light path reflected by the point at the reference position, such that the position information of the n points is converted into path information of the electromagnetic radiation by means of the projection optics group; the device also has a photosensitive detector on which the reflected light is focused by means of an element of the projection lens group, wherein the photosensitive detector generates n signals simultaneously or in parallel in time, wherein each of the n signals is associated univocally with one of the n points, at least one further element of the projection lens group is provided, which is arranged in the beam path before the focused element and has a position-dependent transmission such that the path information of the light is converted into light intensity information by the projection lens group.

According to the invention, a method is also proposed for determining the deviation of the position of n points from n reference positions thereof, where n is a natural number greater than or equal to 2, the method comprising the steps of:

-electromagnetic radiation is projected on each individual one of the n points in the light pad;

-converting the position information of the spots into path information of the light beam;

-detecting reflected light of at least two of the n points differently;

wherein the method steps are performed simultaneously or in parallel in time for all n points,

in order to convert the positional information into intensity information, the path information of the light is converted into intensity information by means of an element having a position-dependent transmissivity.

In the inventive device for determining the positional deviation of n points from n discrete reference positions (dis junkten) thereof, which has a source of electromagnetic radiation, a set of projection mirrors and a photosensitive detector, n signals are generated by the detector simultaneously or in parallel in time, each of the n signals being unambiguously associated with one of the n points. For this purpose, light originating from the light source is directed onto the n spot surfaces by means of a suitable projection mirror group, said light being at least partially reflected by the n spot surfaces. The reflected light is directed to a photosensitive detector by means of a suitable set of projection mirrors. A signal, typically in electrical form, is generated corresponding to the intensity of the impinging light. It may be advantageous to measure n points or reflection points at a certain time. With the device according to the invention, n signals can be measured and generated quickly and easily, which can be taken into account for adjusting the intensity of an array of light sources, in particular for use in a printing plate imaging device, or for changing the focal position of a corresponding projection lens group for an imaging device with the array. Such an arrangement can be realized in a compact form and is also cost-effective, since only one electromagnetic radiation source is used, but at the same time the position of the n points or reflection points can be determined with corresponding resolution.

It is an object of the present invention to detect unevennesses of a printing plate to be imaged quickly and with local resolution, in particular to provide a device which is suitable for converting plate unevennesses into directly or indirectly detectable changes in the position of a light beam or a light beam region.

In a preferred embodiment, the electromagnetic radiation source is a separate electromagnetic radiation source which emits radiation which is polymerized or unpolymerized and whose light irradiates all n points while passing through the part of the projection lens group, the positional deviations of which from their respective reference positions are to be determined. The photosensitive detector has n mutually independent photosensitive elements. Precisely each of the n mutually independent light-sensitive elements is provided with a point or reflection point whose position deviation from a reference position is to be determined. These relate in particular to the spacing difference. In other words, the projection by the other part of the projection lens set after reflection of the light rays of the reflection surface (the n points are located in this region) is designed such that the light reflected by a region of one of the n points unambiguously realizes one of the n points independently of one another. The positional deviation of one of the n points from its reference position results in a different light path than the light path of the light reflected by the projection mirror group from the point of the reference position. Thus, the position information is converted into the path information. In the projection lens group, at least one element is provided which converts the path information for each light path belonging to one of the n points into a light intensity information by means of the projection lens group. For this purpose, it is particularly advantageous to use optical elements having a position-dependent transmission, which are continuously or discretely position-dependent. In other words, the inventive device for determining the positional deviations of n points from its n discrete reference positions may also be referred to as a parallel-processing optical distance meter.

The device for determining the positional deviation of n points from n discrete reference positions thereof according to the invention can be characterized in that, starting from the electromagnetic radiation source, a projection mirror arrangement with a plane of symmetry is used, said plane being parallel to the optical axis of the imaging device. Alternatively, it is advantageous to design the device according to the invention in such a way that its projection optics project a collimated light beam incident obliquely to the printing plate onto a detector. The intersection between the printing plate and the illuminating beam can occupy different positions in space depending on the deviation of the areas of the printing plate from the focal position. The reflected light beam is projected such that when the printing plate is mounted on the rotationally symmetrical member, positional information in one direction, and usually in the direction of the cylinder axis, is still obtained and the positional information in one direction is converted perpendicular thereto (determined by the position of the n points) into intensity information.

Drawings

Further advantages and advantageous refinements of the invention are described in conjunction with the figures and their description.

Fig. 1 is a schematic illustration of the light path through an advantageous embodiment of the device according to the invention.

Fig. 2 shows how a deviation of the position of the reflection point leads to different light paths through an advantageous embodiment of the device according to the invention.

Fig. 3 is a schematic illustration of an advantageous embodiment of the device according to the invention with additional means for determining the intensity of the reflected light.

Fig. 4 is a schematic representation of an advantageous alternative embodiment of the device according to the invention with spatially dependent graduated transmissive optical elements.

Fig. 5 is a schematic view of the light path through an alternative embodiment of the apparatus of the present invention with an obliquely incident parallel (Kollimiert) illumination beam.

Fig. 6 is a schematic illustration of the creation of a light pad (Lichtteppich) on a printing plate as a light-reflecting line.

Fig. 7 is a schematic diagram illustrating the conversion of position information into intensity information in the apparatus of the present invention.

Fig. 8 is a schematic illustration of the light path in an alternative embodiment of the device according to the invention and in the part of the projection optics located behind the light pad.

Fig. 9 is a schematic illustration of a first advantageous development of an alternative embodiment of the device according to the invention.

Fig. 10 is a schematic illustration of a second advantageous development of an alternative embodiment of the device according to the invention.

Detailed Description

Fig. 1 shows an advantageous embodiment of the device according to the invention in a schematic representation of the light path. In a preferred embodiment, the light source 1 is a diode laser. The light emitted by the laser is converted into a laser beam 3 by a first set of projection optics 2, preferably with a non-rotationally symmetrical, non-spherical optical element, such as a cylindrical lens, the width of which covers the recording surface defined by an imaging device (not shown), typically n (here 4) image points of a diode laser array, and the height of which is chosen such that the divergence of the beam in the propagation direction is negligible. The laser beam is focused off-axis onto the printing plate 5 by an objective lens group, here a cylindrical lens 4, so that a narrow light pad 6 is projected on the printing plate. In fig. 1 a flat printing form is shown, but it can generally, without limitation, be a printing form with a macroscopically curved surface, which curvature is negligible microscopically or locally for the projection of the inventive device. The laser deviation of a point is in particular a distance deviation from a reference plane. The width of the light pad 6 is the same as the width of the recording surface of the printing plate 5 determined by the n image points of the imaging device. The light reflected by the printing plate 5 is converted into parallel light by the objective lens group 4 and converted into a laser beam 7. The laser beam 7 impinges on an optical element having a position dependent transmission, preferably a gray scale wedge 8, the gray scale wedge 8 being transmissive in relation to the distance from the optical axis OA of the projection system and generally being more transmissive at near distances than at far distances. For the optical element, the refraction of the light rays upon entry and exit is negligible. The transmitted light, which is optionally also reduced in intensity, is focused by a focusing lens group (here a cylindrical lens) 9 onto a photosensitive detector 10. In a preferred embodiment, the photosensitive detector has n photodiodes 11.

In the operating state of the device, the light pads 6 on the printing plate 5 can also be located at spatially separated positions of the n image points of the light source of the imaging device. The printing plate 5 can thus be moved relative to one another so that a point of its surface first falls into the light pad 6 having the size of the surface defined by the n image points and then falls below the surface of the imaging device n image points P. Since the translation or rotation parameters are known, the actual distance present during imaging can be deduced from the above measurements.

The geometry shown in fig. 1 is only one preferred embodiment of the invention. It is also conceivable to add further optical elements for beam shaping, in particular. Here, reflective optical elements prove suitable.

Fig. 2 is a schematic diagram illustrating how the offset of the printing plate position and the resulting offset of the position of the reflection point cause different light paths by the device according to the invention. For the sake of simplicity of discussion, a sagittal section through the device of the invention, precisely perpendicular to the line defined by the light section 6, is drawn without general limitation. The light beam 21 is radiated from the left side parallel to the optical axis 22. It is refracted towards the optical axis 22 by the lens 23. The intersection of the planes 25 with the optical axis 22 is set as an operating point or reference position. In general, if the beam 21 has different half-axes in the meridional and sagittal directions, a light pad 24 appears on the plane 25. The light reflected by the plane 25 is in turn converted by the lens 23 into a light beam 26, which propagates parallel to the optical axis 22. The beam 21 refracted by the lens 23 intersects a plane 27 in the optical pad 28, which plane 27 is located between the lens 23 and the reference surface 25. The light reflected by the light pad 28 is converted by the lens 23 into a light beam 29, which propagates parallel along the optical axis 22. The distance of the beam 29 from the optical axis is smaller than the distance of the beam 26. A plane 210 further from the lens 23 than the plane 25 intersects the light beam 21 in the light pad 211 refracted on the lens 23, the light from the light pad 211 being converted by the lens 23 into a light beam 212 propagating parallel to the optical axis 22 along. Beam 212 is at a greater distance from the optical axis than beam 26. As shown in fig. 2, in such a configuration, the position, i.e., the distance from the front and rear planes of the reference plane 25, into which the light reflected by the planes is converted, is in a function (complementary) of the distance of the parallel light beams from the projection mirror group from the optical axis 22. In other words, the position information of the plane 27 or 210 from the reference plane 25 is converted into the path information of the distance of the parallel light beams 26, 29, and 212. The path information can be encoded as the light intensity of the light beams 26, 29 and 212 by means of an optical element 213 which transmits depending on the distance from the optical axis 22. The light beam 214 advantageously has a smaller intensity than the light beam 215, for example after passing through an optical element 213 having a position-dependent transmission, while the light beam 215 has a smaller intensity than the light beam 216. In other words, the path information contained by the position of the parallel light beams from the optical axis is converted into intensity information, so that the light beams 214, 215 and 216 can be projected onto a not shown detector by a not shown projection mirror group, wherein information about the position of the reflection plane is still obtained.

The conversion of the path position information described in connection with fig. 2 into the intensities of all n points P is simultaneously achieved by the preferred embodiment of the device according to the invention shown in fig. 1. For this purpose, the optical projection system (abboldungssystem) of fig. 1 can be a set of projection lenses which produce a light pad 6 on the printing plate 5, which light pad has different half axes in the sagittal and meridian directions. Furthermore, the surface of the light pad 6 covers the surface defined by the n image points P of the imaging device. The light reflected by the light cross section 6 is projected by means of a set of projection mirrors onto a detector surface 10, each of which is assigned to one of the n photodiodes 11. In other words, on the detector, the projection of the light section 6 is divided into at least n parts, so that there is a distinction between the regions in which two of the n points are located. Here, each portion is unambiguously associated with one of the n image points P of the light source of the imaging device. The signals are generated by the detectors substantially in time, in particular in the range of the detector motion parameter characteristic, simultaneously or in parallel, wherein each of the n signals corresponds unambiguously to one of the n points. If a portion of the light cross-section 6 has a different distance from the projection mirror group 4, in other words the reflection takes place in a plane whose position deviates from the position of the reference plane, this portion is matched to the corresponding intensity information relating to the function in the device according to the invention. In this way, a parallel processing optical rangefinder can be realized.

Fig. 3 shows an advantageous further development of the device according to the invention. In fig. 3, the inventive device with additional optical elements for determining the intensity of the light reflected by the printing plate is schematically shown. Fig. 3 first shows the elements 1-11 described in fig. 1. In addition, a beam splitter 12 is added to the beam path of the laser beam 7, through which a light beam 13 is coupled out. The light beam is projected by means of a cylindrical lens 14 onto another photosensitive detector 15. The photosensitive detector 15 has n photodiodes 16. The beam splitter 12 may have any known division factor (teilungsverhaleltnis) between transmitted and reflected light. An important point in this arrangement is that, independently of the position of the printing plate 5 from the objective lens group 4 and thus of the light cross-section 6, which leads to different optical paths of the reflected light beam, the intensity of the reflected light beam, i.e. the intensity of the light beam 7, can be determined from the division factor of the beam splitter 12 and the known intensity of the light from the light source 1. By corresponding to the ratio of the intensity signals of the photodiodes 11, 16, an adjustment signal can be generated from the photosensitive detector 10 signal which is independent of the existing reflected beam power, in particular with respect to the actual light power of the light source 1.

Fig. 4 shows schematically an alternative embodiment of the device according to the invention with optical elements for the spatial axial distance-dependent graduated transmission. Graded transmissions of 0 and 1 are particularly advantageous. In order to utilize this transmission, the light beam 7 is transmitted in such a way that half of the light beam ends up propagating through the transmission stage 0 when it is reflected at the reference position on the light section 6 of the printing plate 5. The positional deviation of the reflection plane is converted into positional information of the reflected parallel light beam as already described. Depending on the distance of the reflected parallel beam from the optical axis OA, more or less a portion is lost from the entire beam by the transmission order 0. In this way, the intensity information leaves traces in the light beam. Since the entire transmitted light is projected or focused on the detector, the intensity modulation of the focusing effects, such as edge diffraction, the fresnel integral, is negligible in the case of focused light.

The height of the light cross-section illuminating the printing plate can be selected depending on whether the positionally graded transmissive optical element has a graded transmissive characteristic or a transmissive characteristic that varies in a small spatial region, such as a knife edge (Messerschneide) or a single-sided coated mirror with a narrow transition between transmissive and non-transmissive portions, or comprises a gray-scale wedge with a wide transition. In the case of a knife edge, the light cross section should be so high that the knife edge also divides the light cross section pattern in the detector plane at maximum deflection of the printing plate, i.e. always transmits 1% to 99%. In the case of a gray-scale wedge, the illuminating light beam has a small height, so that the entire light cross section is always emitted by the gray-scale wedge, the position of which can be determined as precisely as possible by the gray value.

As light source 1, any laser can be used, which in the preferred embodiment can be a diode laser or a solid-state laser. Alternatively, a light source emitting unpolymerized light may be used. The plate advantageously reflects the light beam wavelength well. In a preferred embodiment, the wavelength lies in the red spectral region, for example 670 nm. Generally, a laser is used in a continuous oscillation state. However, pulse operation is advantageous in order to increase the insensitivity to other unwanted reflections.

The topology shown in the figure and the geometry of the projection optics can be supplemented by further optical elements, such as spherical and aspherical lenses, anamorphic lenses, mirrors, etc., for advantageous beam shaping of the light beam 3 or the light beam 7.

In an advantageous further development of the invention, the control signal is decomposed into an average value, which is calculated from the sum of the intensities measured on the n photodiodes. The average value is used as a universal adjustment value for the focal line motion of the imaging device. The difference between each photodiode adjustment signal and the average value serves as an adjustment signal for each laser of the imaging device laser array.

In another alternative embodiment, the number of photodiodes in the photosensitive detector is smaller than the number of laser beams of the imaging device. In this case, the control signal generated by the intensity of the radiation on the particular photodiode is used as a control signal for a plurality of parallel laser beams. If the number of photodiodes in the photosensitive detector is greater than the number of imaging device laser beams, for example, the average of a plurality of adjustment signals of adjacent photodiodes can be used for one laser beam. The above-mentioned graphical division of the light cross-section may also be smaller or larger than a number predetermined by the number n of light sources of the operating device.

In an advantageous development of the invention, micro-optical elements are used. For example, the focusing cylindrical lenses 9 and 14 may be constituted by a plurality of optical elements and may have an array of lenses.

In order to avoid the incidence of the laser beam of the imaging device into the photosensitive detector of the device according to the invention, a corresponding optical bandpass filter is provided which transmits only the wavelength of the light source 1 for generating the reflection point in the parallel-processing optical distance meter. In an alternative embodiment of the invention, it is a photosensitive detector with a photocell, a photomultiplier, or a charge-coupled display (CCD).

Such an inventive device may be configured to be separate from the imaging device of the printing plate or be fully or partially integrated with the imaging device. In other words, the components of the projection lens assembly of the device of the present invention and the imaging device can be used together.

Fig. 5 schematically shows the light path through an alternative embodiment of the device according to the invention. The map coordinates x, y, z of the coordinate system 502 represent the position of the cylinder 504, for example in a so-called external drum printing plate exposure apparatus or a direct imaging printing press. Here, the axis of rotation 505 is in the x-direction, the z-direction is defined by the optical axis along which light from the imaging device light source 522 is directed onto the printing plate 510 received on the cylinder 504, and the y-direction represents a third spatial direction, which is perpendicular to the x, z-directions. Illumination beam 506, which is typically a collimated beam of light source 508, such as a laser, is projected onto printing plate 510 by means of a cylindrically symmetric mirror array 507. The projection of illuminating beam 506 forms a light pad 509 on plate 510. The light pad 509 is preferably a rectangular and as uniformly illuminated area as possible, having a width equal to the width of the area to be detected. Preferably, illumination beam 506 is directed at plate 510 at a 45 degree angle and reflected perpendicular to the direction of incidence. The light pad 509 is projected into a conversion plane 514 by means of the intermediate mirror group 511. An optical element having a position-dependent transmission lies in this conversion plane 514. Which achieves focusing on the photosensitive detector 520 by means of another set of projection lenses 519. Furthermore, in an advantageous development, as shown in fig. 5, a beam splitter 512 is arranged in the beam path before the conversion plane 514. On the same beam path 516, the portion of the light is coupled out by means of a projection mirror 517 onto a photosensitive detector 518.

Fig. 6 illustrates schematically how a light pad is produced on the printing plate as a reflection line and how the position information is converted into path information of the reflection light. Fig. 6 shows an illuminating light beam 601 which is directed onto a printing plate, for example, at an angle of 45 degrees and is reflected substantially perpendicular to the direction of incidence. The plate may have different positions in the z-direction (normal 603). A first intersection 602 is created at a first position of plate 608, a second intersection 604 is created at a second position 609 of plate 608, and a third intersection 606 is created at a third position of plate 608. For example, in fig. 6, a situation is shown in which the printing plate 608 is in a position in which the illuminating light beam 601 is reflected as a light beam 612 within the intersection line 604. If plate 608 is absent, the beam may continue to propagate as illumination beam 605. The three intersecting lines 602, 604 and 606 are drawn by way of example to lie in a line plane 610. In other words, if plate 608 changes its position in the z-direction, normal 603, the possible positions of intersection lines 602, 604 or 606 form a plane in space defined by the direction of incidence of the illuminating beam and one of the intersection lines, e.g. second intersection line 604.

The conversion of the position information into intensity information in the device of the invention is illustrated schematically in connection with fig. 7. Fig. 7 schematically shows how a light section 702 is located on the printing plate 701. The position of the light section 702 is converted into path information of the reflected light beam 704 in the line plane 705 by means of reflection conversion indicated by arrows. Projection converter 706 converts this information as image spot 708 into conversion plane 707. The conversion plane 707 has optical elements 709 with a position dependent transmission. It influences the intensity information 710 in such a way that a certain light intensity is measured in a detection plane 711 on a photodiode 713 of a photosensitive detector 712. To generate the brightness signal 715, a signal converter 714 is generated depending on the measurement of each photodiode 713. Thus, a signal 716 for each region within the optical cross-section is generated as a function of position. The information in the brightness signal 715 can then be transmitted serially or in parallel as an adjustment signal to a device that matches the optical parameters of the imaging beam to the unevenness of the printing plate.

Fig. 8 shows a schematic illustration of the light paths in an embodiment of the projection mirror assembly arranged behind the light pad. In the partial drawing 8a cross section in the yz plane is drawn, whereas in the partial drawing 8b a cross section along the x coordinate is drawn. In the partial drawing of fig. 8a, a first printing plate position 801 and a second printing plate position 803 are depicted with a line plane 802, which have two intersection points, namely a first reflection point 812 and a second reflection point 814. The first reflection point 812 and the second reflection point 814 are projected into a conversion plane 806 by means of a rotationally symmetrical projection mirror group 804, preferably a spherical lens. An optical element having a position dependent transmission lies in the conversion plane 806. From there, the projection onto a photosensitive detector 810 is effected by means of a further rotationally symmetrical projection mirror arrangement, wherein the first reflection point 812 is assigned a first detection point 816 and the second reflection point 814 is assigned a third detection point 820. Alternatively, the partial view of fig. 8b shows the case with a first probe point 816 and a second probe point 818 along an x-coordinate cross section.

Fig. 9 shows a schematic view of a first advantageous development of an alternative embodiment of the device according to the invention. The partial drawing 9a shows a section in the yz plane, and in the partial drawing 9b, the situation is shown in a section along the x-axis. In a first position 901 the surface of the plate intersects one line plane 902 at a first reflection point 914 and in a second position 903 the surface of the plate intersects the line plane 902 at a second reflection point 916. The first reflection point 914 and the second reflection point 916 are projected by means of an at least two-part projection mirror arrangement (which is formed by the first cylindrically symmetrical projection mirror arrangement 904 and the second cylindrically symmetrical projection mirror arrangement 908) onto a conversion plane 910 on which the optical element with position-dependent transmission lies. Here, the first cylindrically symmetric projection mirror group 904 and the second cylindrically symmetric projection mirror group 908 have axes of symmetry which are substantially perpendicular to each other. By means of the third cylindrically symmetric projection lens set 912, the first reflection point 914 is projected onto the first detection point 918, and the second reflection point 916 is projected onto the second detection point 920, which are coincident in the partial diagram 9a of fig. 9. The partial diagram 9b of fig. 9 shows how the projections in the x-direction and the yz-direction are separated from one another by a sectional diagram in the x-direction. The light beam coming from the first reflection point 914 in this direction is influenced by the first cylindrically symmetric projection mirror group 904 and projected into the first detection point 918. Accordingly, light from the second reflection point 916 is projected onto the second detection point 920 via the first cylindrically symmetric projection lens group 904.

Fig. 10 is a schematic view of a second advantageous development of an alternative embodiment of the device according to the invention. In the partial drawing 10a of fig. 10a cross section in the yz plane is drawn, while in the partial drawing 10b of fig. 10 an x-direction cross section is drawn. In a first position 1001, the surface of the printing plate intersects the rectilinear plane 1002 at a first reflection point 1014, while in a second position 1003 the surface of the printing plate intersects the rectilinear plane 1002 at a second reflection point 1016. The first reflection point 1014 and the second reflection point 1016 are projected onto a conversion plane 1006 by means of a rotationally symmetric projection mirror group 1004. An optical element having a position-dependent transmission lies in the plane. From there, a projection lens group with at least two segments, which is formed by a first cylindrically symmetrical projection lens group 1008 and a second cylindrically symmetrical projection lens group 1010, whose axes of symmetry are approximately perpendicular to each other, is projected onto a detection plane 1012. A first detection point 1018 corresponding to the first reflection point 104 and a second detection point 1020 corresponding to the second reflection point 1016 coincide within the plane. In the partial diagram 10b of fig. 10, a cross section in the orthogonal, i.e. x-direction is shown. The first reflection point 1014 and the second reflection point 1016 are projected into the conversion plane 1006 by means of the rotationally symmetric projection mirror group 1004. From there, the first cylindrically symmetric projection mirror group 1008 causes a first reflection point 1014 to be projected onto a first detection point 1018 and a second reflection point 1016 to be projected onto a second detection point 1020.

Such an inventive device can be used not only in a plate exposure device but also in a printing unit or printing press, in particular a direct imaging printing unit or printing press.

Description of the reference numerals

P-point; OA-optical axis; 1-a light source; 2-a projection lens group; 3-a laser beam; 4-an objective lens group; 5-printing plate; 6-light pad; 7-a laser beam; 8-elements with position-dependent transmission; 9-a cylindrical lens; 10-a photosensitive detector; 11-a photodiode; 12-a beam splitter; 13-a light beam; 14-a cylindrical lens; 15-a photosensitive detector; 16-a photodiode; 21-a light beam; 22-optical axis; 23-a lens; 24-a light pad; 25-a reference plane; 26-a light beam; 27-plane; 28-light pad; 29-a light beam; 210-plane; 211-a light pad; 212-a light beam; 213-optical elements with position-dependent transmission; 214-a light beam; 215-a light beam; 216-a light beam; 502-coordinate system; 504-a roller; 505-a rotation axis; 506-irradiating the light beam; 507-a cylindrically symmetric mirror group; 508-a light source; 509-light pad; 510-printing plate; 512-a beam splitter; 511-middle lens group; 514-conversion plane; 516-same optical path; 517-projection lens group; 518-a photosensitive detector; 519-a projection lens group; 520-a photosensitive detector; 522-an imaging light source; 524-projection lens group; 601-an illumination source; 602-intersection first position; 603-normal direction; 604-second location of intersection; 605-continuation of the illuminating beam; 606-third position of intersection; 608-printing plate; 610-line plane; 612-reflected light beam; 701-printing plate; 702 — optical cross section; 703-reflection conversion; 704 — path information in the reflected beam; 705-line plane; 706-projection conversion; 707-a conversion plane; 708-mottling; 709-an optical element having a position dependent transmission; 710-intensity information; 711-detection plane; 712-a photosensitive detector; 713-photodiode; 714-signal conversion; 715-a luminance signal; 716-signals of each point; 801-plate first position; 802-line plane; 803-plate second position; 804-a rotationally symmetric projection mirror group; 806-conversion plane; 808-a rotationally symmetric set of projection mirrors; 810-a photosensitive detector; 812-a first reflection point; 814-second reflection point; 816-a first probe point; 818-a second probe point; 820-a third probe point; 901-plate first position; 902-line plane; 903-plate second position; 904-a first cylindrically symmetric set of projection mirrors; 906-detection plane; 908-a second set of cylindrically symmetric projection mirrors; 910-a conversion plane; 912-a third cylindrically symmetric projection mirror group; 914-first reflection point; 916-second reflection point; 918 — a first probe point; 920-a second probe point; 1001-plate first position; 1002-line plane; 1003-plate second position; 1004-a rotationally symmetric set of projection mirrors; 1006-conversion plane; 1008-a first set of cylindrically symmetric projection mirrors; 1010-a second cylindrically symmetric set of projection mirrors; 1012-probing plane; 1014-first reflection point; 1016-second reflection point; 1018 — first probe point; 1020-second detection point.

Claims (20)

1. A device for determining the deviation of the position of n points (P) from n discrete reference positions thereof, wherein n is a natural number greater than or equal to 2, said device having a source of electromagnetic radiation (1), a set of projection mirrors (2, 4, 9), whereby the electromagnetic radiation forms a light pad (6) when passing through a part of the set of projection mirrors, the light pad is projected obliquely at the position of all n points (P) so that the light pad (6) illuminates the plane defined by the n points (P), wherein a deviation of the position of at least one of the n points on the surface from its reference position leads, by means of the set of projection mirrors, in a one-to-one correspondence to a further light path of the light reflected by the surface which is different from the light path of the light reflected by said point (P) on the reference position, so that the position information of the n points (P) is converted into the path information of the electromagnetic ray by the projection mirror group; the device also has a photosensitive detector (10) on which the reflected light is focused by means of an element (9) of the projection lens group, characterized in that the photosensitive detector generates n signals simultaneously or in parallel in time, wherein each of the n signals is associated with one of the n points (P) in a one-to-one correspondence, at least one further element (8) of the projection lens group is provided, which is arranged in the beam path before the focused element (9) and has a position-dependent transmission, such that the path information of the light is converted into light intensity information by the projection lens group.

2. The device according to claim 1, characterized in that the source (1) is a single radiation source.

3. A device as claimed in claim 1 or 2, wherein the n points are in a plane or in a line.

4. Device as claimed in claim 1 or 2, characterized in that the set of projecting mirrors (2, 4, 9) has aspherical optical elements.

5. A device as claimed in claim 1 or 2, characterized in that the photosensitive detector (10) is formed by a plurality of mutually independent photosensitive elements.

6. A device as claimed in claim 5, characterized in that the light-sensitive element (11) is a photodiode, a photocell, a photomultiplier or a charge-coupled display.

7. A device as claimed in claim 5, characterized in that at least two of the n points are arranged for at least two of the n mutually independent light-sensitive elements (11) in exactly one-to-one correspondence.

8. The device according to claim 1 or 2, characterized in that the radiation source (1) emits at least one wavelength of infrared or visible light.

9. A device as claimed in claim 1, characterized in that the further element (8) is a gray-scale wedge or an edge.

10. The device as claimed in claim 1 or 2, characterized in that the part of the set of projecting mirrors disposed behind the light pad has at least two optical elements (904, 908) having mutually orthogonal axes of symmetry of cylindrical symmetry.

11. A device as claimed in claim 1 or 2, characterized in that an intermediate image is generated in a conversion plane (1006) in which the optical element (8) having a position-dependent transmission lies.

12. A device as claimed in claim 1 or 2, characterized in that the set of projection mirrors has at least one beam splitter (12) in the reflected beam path.

13. A device as claimed in claim 12, characterized in that at least one further photosensitive detector is provided with a plurality of individual photosensitive elements, wherein each of the mutually individual elements corresponds to at least one or exactly one of the n points (P).

14. A distance meter having a device according to claim 1 or 2.

15. An imaging device having n individually controllable lasers and mutually independent sets of projection mirrors and an autofocus system which can perform focus displacements independently of each other for at least two of the n individually controllable lasers, where n is a natural number, characterized in that the autofocus system is adjusted on the basis of the measurement results of a distance meter as claimed in claim 14.

16. A printing plate exposure apparatus, characterized in that it has at least one imaging device according to claim 15.

17. A printing unit having an imaging device according to claim 15.

18. A printing press having at least one printing unit according to claim 17.

19. A method of determining deviations of the positions of n points (P) from their n reference positions, where n is a natural number greater than or equal to 2, the method comprising the steps of:

-electromagnetic radiation is projected on each individual one of the n points (P) in the light pad (6);

-converting the position information of the points (P) into path information of the light beam;

-detecting reflected light differently for at least two of the n points (P);

wherein the above-mentioned method steps are carried out for all n points (P) simultaneously in time or in parallel,

in order to convert the positional information into intensity information, the light path information is converted into intensity information by means of an element (8) having a position-dependent transmittance.

20. A method of determining a deviation of a position of n points from its reference position according to claim 19, having the additional step of measuring the instantaneous intensity of the reflected electromagnetic radiation for at least one of the n points, characterized in that a comparison of the intensity of the reflected light measured on the corresponding photosensitive element of the detector with the instantaneous intensity of the reflected electromagnetic radiation is performed.