DE4447756C2 - Measuring engraved area on printing cylinder in engraver - Google Patents

Abstract

The method for measuring a portion of an engraved area on a cylinder involves generating at least one dimension value corresponding to the portion, and displaying the portion and resulting valve on a monitor. The portion of the engraved area is videoed and an image is generated. An error value E corresponding to the difference between a set of predetermined set-up parameters and the actual measurement of the portion of the engraved cylinder (10) is then determined. The error value is then used to adjust the engraver to engrave an actual cut or etch in accordance with the parameters.

Description

This invention relates to engraving heads Patents 4,450,486 published by Buechler in general Art. Such engraving heads include a diamond stylus, which is carried by a holder which is attached to a Arm is attached by one in a rotary motion swinging shaft protrudes. A sine wave Drive signal is sent to a pair of opposite Electromagnets applied to the shaft with a fre frequency of around 3,000 to 5,000 Hz over a maximum Turn the angle of 0.25 ° back and forth.

There is a sliding block in one on the engraving head exactly known position in relation to the schwin attached graver. The engraving head is for Tilting movements held by a set of leaf springs are attached to a rear projecting rod. A DC motor turns the rod around the shoe in contact with a print roller to be engraved bring. If the shoe with the pressure roller in Kon is tact, the stylus swings from a position in which he just touches the pressure roller, up to a bottom sition about 100 µm from the surface of the Roller.

As soon as the slide shoe lies against the pressure roller, the sinusoidal drive signal becomes an image signal added to the vibrating stylus in con clock to drive with the platen roller, creating a row of wells of controlled depth in their upper  surface is engraved. The platen roller is about to rotate continuously with the swinging movement of the stylus, while an adjusting screw arrangement a generates axial movement of the engraving head, so that the Engraving head with the entire printing surface of the printing roller comes into engraving contact.

Engraving systems of the type used by Buechler teaches, the machine operator must start engraving a tiring trial at one end of the platen roller and perform the error setting procedure. This procedure includes the setting of the gain factor the amplifiers for the sinusoidal drive signal and the image signal to "black" pressure cups of a desired depth along with connection channels of another desired depth and clean, to produce non-engraved white cells. each Changing one of the run variables affects the others, and therefore hiring becomes one repetitive process.  

Post-published EP 0 595 324 A1 describes a real-time calibration method for a Engraving device known in which an engraved for calibrating the engraving device Cell is captured by a video camera and a desired cell dimension by a Image processing device is determined. This publication does not give any indication Channel width of a channel between two black cells as a setting parameter for a Drive signal to use.

It is the object of the invention, an engraving method and an associated one To create engraving device, which allow quick and easy adjustment to Wells of precisely controlled dimensions in the surface of an engraving printing roller or to engrave a gravure cylinder.

This object is achieved by an engraving process with the features specified in claim 1 and solved by an engraving device with the features specified in claim 10. Preferred embodiments result from the corresponding subclaims.  

The present invention provides a gra four device and an engraving method, wherein a Multiple parameter signals to one setting circuit for calculating engraving parameters be finished to the engraving response of the engraving stylus  to control an input image signal. An input AC signal and an input image signal fed to a multiplication circuit, in which they with Multiplication factors are multiplied by be generated on a computer. The computer creates also a signal for the white offset, which with the Output signals from the multiplication circuits is linked to a drive signal for the engraving to produce a prick. The stylus then engraves cells with the desired geometry.

Input signals are delivered to the computer the desired width for the black cells, a desired channel width, a desired width for the highlight cups and the image voltage level give, where these highlight cups of the desired Width must be engraved. The values of these parameters are used to set a set of equations solve which are the appropriate values for the two multi supply factors and the white offset.

A video camera is operated around a frame of image information to generate an image of a Includes a highlight cup, which is by means of a Image signal of a predetermined level has been engraved is. An image processing circuit measures the width of the well shown in this way and gives it to the computer. The computer then fits using an error term that is the difference between the expected cell width and the measured cell corresponds to the multiplication factors and the width White offset.

Brief description of the drawings

Fig. 1 is a schematic, partially perspective view of a programmable engraving system according to the present invention;

Figure 2 is a schematic representation of a series of cups engraved in a pressure roller;

Fig. 3 is a schematic representation of an AC and an image signal for controlling an engraving stylus and the resulting engraving movement;

Fig. 4 is a flow chart illustrating the method of well width control in accordance with the invention;

Figure 5 is a graphical representation of the maximum well depth resulting from 0-10 volt image input signals;

Fig. 6 is a schematic illustration of a picture frame including a highlight cup;

Figure 7 is a flow diagram of an algorithm for measuring well width; and

Fig. 8A and 8B collectively show a flow chart of another measuring algorithm.

Description of the preferred embodiment

In Fig. 1, an engraving printing roller 10 is Darge, which is arranged for the purpose of rotation by a drive motor 12 and the engraving by an engraving prick. During the engraving process, the stylus sticks to and away from the pressure roller 10 to produce a series of cups which are arranged along a track 30 . A lead screw motor 14 rotates a lead screw 56 to cause movement of the plunger in a direction parallel to the axis of the roller 10 . If the adjusting screw spindle motor 14 moves continuously, then the track 30 will have a helical shape. Discontinuous excitation of the motor 14 creates a series of spaced circular tracks 30 .

The stylus is driven by an electromagnetic drive member 61 , which operates in response to a drive control signal on line 60 , in engraving contact with the printing roller 10 . The electromagnetic drive member 61 may be configured as generally disclosed in Buechler U.S. Patent 4,450,486.

The signal on line 60 has an AC component, an image component and a component of the white offset, capable of producing an engraving process as described below. The AC component comes from an AC input signal which is applied to a multiplier and multiplied by a multiplication factor Ka which is obtained on a line from a computer 34 . The AC product signal from the multiplier is provided to a summing link where it is linked to a signal from another summing link. The summing connection links a displacement signal WD on a line from the computer 34 with an output signal from a second multiplier. The function of the second multiplier is to multiply an input image signal by a factor Kd generated by the computer 34 on a line.

The computer 34 generates the parameters Ka, Kd and WD by solving a set of three equations as described below. A control panel 32 is provided to allow entry of values for five constants that appear in the three equations. This. Constants are the width of the black cells BW, the width of the highlight cells HW, the image voltage Vh corresponding to HW, a stylus constant Ks and the voltage for the black cells Vmax. If desired, a shoe offset S can also be entered.

As discussed in more detail below, the AC component of the signal on line 60 causes the stylus to oscillate in a sinusoidal manner relative to the platen 10 , at a wavelength that depends on the surface speed of the platen. The speed of the drive motor 12 must be set so that an engraving track 30 is generated which has an odd number of half wavelengths during a full engraving revolution. The Com puter 34 transmits a lead screw signal to the lead screw motor 14 via a line 24 . This signal is adjusted so that the lead screw motor 14 advances the stylus an axial distance equal to half the width of a black cup plus half the width of a connecting channel plus the width of a partition during each full revolution of the pressure roller 10 .

The equations for Ka, Kd and WD take one linear relationship between the input image signal and the resulting width of an engraved cup on. While this is sufficient in many cases is accurate assumption, it happens that adjustments required are. If so, you can use tabella corrections are carried out as described in the An message with the current input number 08 / 022,127, of the main application thereof, is taught, the open is cited here for the purpose of reference.

Another problem is the drift. Although computer 34 may be correctly programmed and may initially produce the correct well width, changes in gain in analog components or mechanical changes in the positioning of the shoe that carries the stylus may include a customizable correction term in the calculation of Ka, Kd and WD algorithm required. For this purpose, a video camera 46 is provided, which is set to track 30 . The camera 46 sees a portion of the track 30 illuminated by a strobed lamp 58 and provides frames of image feedback information to an image processor 41 . From a well counter 42 on line 55 , strobe signals for the lamp 58 are supplied with the correct frequency and phase.

Although not shown in the embodiment of the invention, the strobed lamp 58 is an integral part of the video camera 46 so that the strobe lights up through a lens (not shown) of the video camera. Moreover, the video camera 46 is an auto focus camera that can focus printing rollers 10 of any size. The image processor 41 is able to control the autofocus property when, for example, the printing roller 10 is exchanged for a printing roller of a different radius. The image processor 41 incorporates conventional circuitry to ensure that the image is in focus. The Näpf chenzähler 42 counts the pulses that are generated by a clock generator 47 with four times the alternating current frequency. A clock pulse is generated at this frequency every quarter wavelength of an engraving stylus oscillation.

The geometric shape of typical black cells, the connecting channels for black cells, the highlight cells and the partitions is shown in FIG. 2. This illustration shows a series of wide, deep black cells 70 and a series of shallower and narrower highlight cells 76. The cells shown comprise sections of three adjacent Gavur tracks 30 . The black cells 70 have a maximum width BW. The control signal for the stylus is set in such a way that 70 connecting channels 72 are produced between the successively engraved black cells. The channels 72 have a width CW, while the highlight cups 76 have a width HW. The arcuate edges of the cups 70 result from the vertically oscillating stitch of the stylus during a rotary movement of the pressure roller 10 located underneath. As also shown in FIG. 2, a row of successively engraved black wells 70 can be separated by a wall 74 from a row of successively engraved wells 70 (also shown as black wells) in an adjacent engraving track 30 .

A series of cells designed as shown in Figure 2 will print a graphic pattern that defines a diagonally extending grid. The tangent of the screen angle corresponds to the ratio of the width of the black cells to the wavelength of the stitch movement of the stylus. The stitch wavelength is a function of the surface speed of the platen 10 and the vibration frequency of the stylus.

Thus, the screen angle can be adjusted by adjusting the speed of the drive motor 12 , but such an adjustment must be made step by step in order to maintain an odd number of half wavelengths around the circumference of the printing roller. Alternatively, the screen angle can be adjusted by adjusting the width of the black cells and the operating speed of the adjusting screw motor 14 .

The drive signal for the stylus and the resulting vertical movement of the stylus are shown in FIG. 3. The drive signal is obtained by adding an AC signal 80 to an image signal 82 . The image signal 82 shown has, for example, an image level for white spots 86 , an image level for black spots 88 and an image level for brightest spots (highlight level) 90 . The image signal and the alternating current signal are linked with a displacement, so that the stylus is lifted out of the contact area with the roller surface during the entire time in which the image signal 82 has a white level 86 . The minimum elevation for white spots is WD.

When the image signal 82 changes from a white level to a black level, the stylus moves into engraving contact with the roller as shown by the stylus position line 84 . In this state, the stylus swings back and forth between a minimum depth CD and a maximum depth BD. If the stylus is in the depth CD, it engraves a connecting channel 72 . When the image signal 82 changes to a highlight level, as indicated by the reference symbol 90 , the stylus oscillates between a position outside the area of the engraving contact with the roller 10 and an engraving position with a maximum depth HD. The alternating current signal 80 , the image signal 82 and the signal for the white offset are generated by the setting circuit 34 .

In general, a set of predetermined setting parameters (BW, SW, Vh, Ks and Vmax) can be entered into the control panel 32 . These predetermined setting parameters generally correspond to the desired dimensions for, for example, the highlight cup 76 or cup 70 . These parameters are received by the computer 34 , which in turn generates a plurality of excitation signals (Ka, WD and Kd) in response to this. The input signals control the depth of the stylus at all times. In the described embodiment, the computer 34 determines the depth of the stylus using the following equations.

D (t) = Ka.A. (sin (ω.t) - 1) - WD + Kd.V (t)

wherein:
Ka = gain of the AC amplifier
A = maximum value of the AC reference signal
ω = frequency of the AC reference signal
t = time
WD = white offset
Kd = amplification factor of the image intensifier
V (t) = image voltage at the input (function of time).

The maximum depth of the black cells can be seen if sin (ω.t) = 1 and V (t) = Vmax. Therefore, the depth of the black cells is given by:

BD = Kv.Vmax - WD (1)

The channel depth CD is when sin (ω.t) = 0 and V (t) = Vmax. The channel depth is therefore given by:

CD = Ka.A - WD + Kv.Vmax (2)

The depth of the highlight cup HD is generated at sin (ω.t) = 1 and V (t) = highlight voltage Vh. Therefore:

HD = Kv.Vh - WD (3)

When engraving with a stylus that has an engraving tip angle, the depths BD, CD and RD correspond to Ks.Bw, Ks.Cw and Ks.HW, respectively, where Ks is a stylus constant, given by the equation:

Ks = 1 / (2.TAN (tip / 2)).

When performing the above substitution, equations (1) - (3) can be rewritten such that

Kv = Ks. (BW - HW + E) / (Vmax - Vh) (4)

WD = Kv.Vmax - Ks.BW (5)

Ka = (Ks.CW + WD - Kv.Vmax) / A (6)

receives, where E is an error used to do this the solution for errors found in HW correct.

Equations (4) - (6) can be solved one after the other. Thus, the value for Kv obtained by solving equation (4) can be used in solving equations (5) and (6), and the value for WD obtained from equation (5) can be used in equation (6). The computer 34 does this to calculate Kv, WD and Ka. Alternatively, the screen angle (SA) and the wavelength (WL) of the piercing stylus movement can be used as setting parameters. In this case, BW can be derived from the equation:

BW = WL.tan (SA)

calculate. This BW value is then used in the calculation the engraving parameter used.

In the event that a small error occurs in the positioning of the shoe on the pressure roller 10 , the computer 34 can be given an additional setting parameter S. If this parameter is entered, it is treated as a depth offset, which is multiplied by Ks before the solution described above is added and added to BW, CW and NW.

Referring now to FIG. 5. It can be seen that the maximum well depth is directly proportional to the image input signal. As shown in the figure, a maximum image input signal of 10 volts produces the maximum well depth BD required to engrave a black well. In the example shown, the computer 34 was given a highlight light width HW = 0.25.BW. So with HD the highlight cup depth corresponds to 25% of BD. The figure also reflects setting Kh to 3 volts. Under these conditions, an image signal with an amplitude that corresponds to 30% of a "black" image signal generates a puncture with a depth that speaks only 25% of the depth of a black cell ent. It follows that the maximum well depth for an image input signal of approximately 0.7 volts becomes zero. For image signals that are below this value, the stylus remains outside the contact area with the roller. In the case of a "white" image input signal, the stylus is withdrawn by a minimum distance WD from the engraving roller, which represents the white offset.

During the initial setting of the pressure roller 10 for the engraving or even after the beginning of the engraving, it may be desirable to set the predetermined setting parameters BW, HW, Vh, Ks and Vmax and their associated excitation signals Kd, WD and Ka accordingly to adapt to the specified setting parameters and an actual measurement of a section of an engraved area ( FIG. 2). This is made easier by the provision of a closed control system that can be self-adjusting and self-monitoring. To implement this closed control system, it is necessary to calculate an error value that generally corresponds to the difference between the specified setting parameters and an actual measurement of the section of the engraved area on the printing roller. Once the error value is averaged, the computer 34 can adapt the predetermined setting parameters and the corresponding exciter signals Ka, WD and Kd in response to the error value E.

It is important that the camera 46 can be adjusted to view a specific position of lane 30 . It should be noted that a single well is strobed while the engraving machine is engraving. For this purpose, the stich is allowed to grave a test track at one end of the roller 10 . Although it is possible for an operator to be able to look at a monitor or display (not shown) and operate a cursor control key (not shown) on the keyboard mentioned above, the computer 34 is able to automatically strobe a flash and image to take with the video camera 46 . The image processor receives the new image and measures the width of the strobed cell and its associated channel. This information is sent to the computer 34 as a well size feedback information. Since there is a distance between the stylus and the camera mount 46 , the computer 34 must store a count for the cell position distance between the camera 46 and the stylus. The computer uses this position offset count to time strobes on line 55 to include certain wells that have been engraved at certain known times.

Fig. 4 illustrates the overall process involved in the controlled engraving and error correction system according to an embodiment of the present invention. The process begins at an entry point, designated by reference number 100 . The first step is to enter the setting parameters Bw, HW, Vmax, Vh and Ks (block 102 ). These parameters can be read from a plate file or entered into the keyboard by an operator. In the case of an input by an operator, the specified setting parameters can be obtained by visual assessment of cells in a manually controlled test track, which is engraved on one end of the pressure roller 10 . Regardless of the type of input, the predetermined setting parameters are stored in the computer 34 for the setting control. The computer 34 then sets the value of the error term E to zero (block 104 ) and calculates the engraving drive parameters Kd, WD and Ka using the equations (4) - (6) above (block 106 ). This puts the system on standby to start engraving.

As soon as the engraving drive parameters are available, the computer 34 generates the excitation or control signals which cause image data in the form of pixel data to be read from a corresponding data file (block 108 ). Further control signals acti vate the drive motor 12 , the adjusting screw spindle motor 14 and the working head 16 , and the engraving begins (block 110 ). The computer 34 then begins to check the progress of the engraving process (point 112 ). The system exits at point 114 when the process is complete.

In one embodiment, the error value E can be determined using a predetermined setting parameter, namely Vh. In general, the error correction system calculates the error value E by comparing the most common Vh value for a plurality of wells that have actually been engraved up to a Vh value that can be obtained by taking an actual measurement on a preselected engraved well 606 ( Fig. 6) is determined. It is assumed that a most frequently occurring Vh value corresponds to the system setting parameter or specified setting parameters. Therefore, the computer 34 keeps a record of the frequency of occurrence of different Vh values (block 116 ) and compares the set Vh value with the value for Vh which occurs most frequently. If it is determined that the set value deviates from the most frequently occurring value by more than a prescribed minimum value, then the specified setting parameters and the corresponding excitation signals are adapted. In the described embodiment, a corresponding new HW value can be calculated. This calculation involves solving the equation:

HW = (Kd.Vh - WD) / Ks.

As the engraving progresses, periodic checks are made to determine if the system is engraving HW-sized light bulbs in response to image input signals with the Vh voltage. When the time for a measurement comes, as indicated by the check at point 122 , the system proceeds to block 124 . This block includes strobeing a lamp 58 which causes the camera 46 to generate a frame of image information. The image processor 41 is also strobed to measure the width of a spotlight that appears in the image frame and is known to be engraved in response to an image voltage Vh. The error term E is equated with the difference between the actually measured HW value and the current setting for HW. The system then proceeds to block 127 where the predetermined setting parameters such as Kd, WD and Ka are recalculated in the computer 34 using the new value of E. This causes the error value E to be eliminated or reduced. The system then returns to block 108 .

The video camera 46 is mounted on a frame 57 , which is carried by the adjusting screw 56 . The camera 46 is adjustable in relation to the frame 57 so that it generates frames of image information that are directed to track 30 .

Preferably, the camera 46 includes a CCD array that generates a new frame of image information with each flash of the lamp 58 .

It is important that the camera 46 is set to see a specific portion of lane 30 . For this purpose, the stylus is set in motion to engrave a test track at one end of the roller 10 . The computer 34 stores this position count and uses it to time the strobe pulses on line 55 for receiving certain wells that have been engraved at certain known times.

FIG. 6 illustrates a typical frame of image information 600 that includes a highlight cup 606 that has PC clock counts engraved prior to generating the strobe that generated frame 600 . Frame 600 contains a series of horizontal lines that are too numerous to be displayed. Exemplary horizontal lines are identified by reference numerals 602 . These lines are a subsampling of the well image captured by the strobe. The actual cell dimensions are measured on these lines.

The image processor 41 processes the lines 602 sequentially from top to bottom. The image information goes through a localized threshold operation (not shown). Pixels that are lighter than the threshold are considered white, while pixels that are darker than the threshold are considered black. In the embodiment just described, the threshold values are set at a preselected gray level.

While each line of image information is processed by threshold operation, it is examined for the occurrence of black / white and white / black transitions. FIG. 6 illustrates black / white transitions by symbols denoted by reference number 610 , while white / black transitions by symbols denoted by reference number 611 . This creates a series of boundary lines, as illustrated in FIG. 6 by reference numerals 604 , 605 , 606 , 607 , 608 and 609 . These boundary lines define a white area 650 .

The image processor 41 recognizes the white region 650 through a black / white transition 610 , followed by a white / black transition 611 . For each such transition pair, the image processor 41 creates a first linked list. For example, if programming is done in the C language, such a linked list can be represented by a unit known as a structure. Each such linked list contains the X coordinates of the left and right boundaries of the white area indicated by the transition pair. The linked lists of each scan line 602 are linked to the linked lists of the previous scan line by comparing the boundary points.

For the first six image lines 602 of FIG. 6, only a white span (and a chained list) appears. On the seventh horizontal line, however, with the reference number 602 a, two additional transition points 611 d, 610 d appear. These two new transition points mark the limits of a highlight cup 60 . It can be seen that the appearance of the highlight cup 60 in the white area 650 causes a “split”. The image processor 41 responds to this split by creating a second and a third linked list to replace the previously processed first linked list.

As soon as a split is observed, the image processor knows that a highlight cup 606 is present. The image processor then compares the left boundary of the third concatenated one. Right border list of the second linked list to determine the width of the highlight cup 606 . The width of the highlight cup is calculated for each scan line 602 and compared to the width of the highlight cup calculated for the previous scan line. Each time a comparison is made, the image processor 41 stores the larger value. This process continues until the middle black area disappears (at 602 b) and the two legs of the white area 650 merge. At this point, the measurement is ended and the processor stores the observed maximum value for HW. The image processor 41 passes this HW value on to the computer 34 . The computer 34 assigns the communicated HW value to the special engraving command that was sent to the stylus PC clock counts before the strobe that generated the frame. For this purpose, the computer 34 queries the image information that is supplied to the multiplier 38 .

Fig. 7 shows the measurement process set out above in the form of a flow chart. Thus, the HW measurement begins at a starting point 136 and continues with a scanning step at Bock 138 . As discussed above, frame detection or sampling is initiated by a strobe signal on line 55 . It should be noted that the roller could be stationary (ie not rotating) during the process of recording, measuring, and correcting errors. It should also be noted that the system and method of measurement can be used independently to provide means for measuring portions of actual punctures in roller 10 . Thus, the measuring system and the measuring method per se could be used to measure the actual dimensions for the purpose of being displayed on a monitor (not shown) so that, for example, a subsequent manual adjustment can be carried out in order to correct any errors.

Once the frame is scanned, the image processor checks the line number at point 140 . When the lower edge of the frame has been reached, exit at point 142 . If it assumes that the lower border of the frame has not been reached, the program continues at block 144 where it determines the transition points 610 , 611 . Then, at block 146, the program captures the white areas for use in the linked lists described above. Next, at point 148 , the program looks for a split. If a split is detected, then the two resulting linked lists are provided with an identifier at block 152 and a flag is set at block 154 .

The program checks the state of the flag at point 156 and jumps down to block 164 if the result is negative. This means that the top of a highlight cup 606 has not yet been reached and there is no need to measure a cup width. Thus, the program simply increments the line number at block 164 and returns to point 140 .

If the check at point 156 indicates that the flag has been set, then the program looks for a merge at point 158 . If a fusion is detected, the program leaves the measuring routine. If no merging has occurred, the program checks the separating distance between the two legs of the white area 650 . This point is compared at point 160 with the previously stored separating distances. If the new separating distance is greater than any previously saved distance, then HW is equated with this distance. According to FIG. 6, the first separation distance is the distance between the points is 611 d and 610 d. This distance increases until the program reaches points 611 a and 610 a. At this point the separation distance is at a maximum and no further adjustments are made to HW.

The image processor 41 then feeds the measured HW value back to the computer 34 , and this is compared with the most frequently occurring HW value. If the difference is below a specified threshold value or is zero, then no adjustment is made to the specified setting parameters. If, on the other hand, there is a difference between the measured HW value and the most frequently occurring HW value, the computer 34 adapts the specified setting parameters until the engraving machine sticks wells which fall into the specified setting.

Thus, the embodiment just described includes a method of measuring a portion 67 ( FIG. 2) of an engraved area 69 on the roller 10 while the roller 10 is rotating or while the roller 10 is stationary. The method uses an image processor 41 , a video camera 46 and a strobe 58 . The method includes the steps of capturing section 67 of engraved surface 69 and generating a correspondingly speaking video image (of the type shown in FIG. 6). These steps are performed using the image processor 41 , which is used to process the video image data to determine the actual dimensions of the portion captured by video.

Fig. 8 shows another embodiment in which the well width BW, the channel width CW, the width of the highlight well HW and the error value E are measured and determined by a similar technique. In this embodiment, the image processor 41 detects the presence of the white area 650 through the black / white transition 610 , followed by a white / black transition 611 . The actually measured and strobed well is generally assumed in the center of the scanning frame 600 .

At this point, the image processor 41 begins a fill process, starting from a location somewhere within the well 606 and starting to fill in memory locations associated with or corresponding to the well 606 with gray scale values. The image processor first selects a black pixel, which is preferably located in the center of the cup 606 . The image processor 41 then "fills" the selected pixel and all adjacent black pixels with a halftone or gray value that is somewhere between the white and black values that are typically stored.

This filling process continues until all pixels within the well 606 are filled with a halftone value. It should be noted that when the halftone value reaches either an upper edge 621 ( FIG. 6) or a lower edge 623 of the scanning frame 600 , the image processor recognizes that it is the limits of a well 70 ( FIG. 2) and one Channel 72 measures. On the other hand, if the inserted pixels do not reach the upper 621 or lower edge 623 of the scanning frame 600 , then the image processor 41 considers the measured cup as a highlight cup 76 ( FIG. 2). When the halftones reach the edges 625 and 627 of the raster, the image processor 41 recognizes that no well has been measured.

For the sake of explanation, it is assumed, as above, that the image processor 41 measures a highlight cup 76 ( FIG. 2) and 606 ( FIG. 6) which was strobed by means of the video camera 46 and the strobed lamp 58 . When the image processor 41 completes the filling of wells 606 , it usually stores all black / white transition points and white / black transition points in memory.

After the image processor 41 finishes filling wells 606 , the black / white and white / black transition points are located. These transition points generally correspond to the boundary lines or the wall of 606 ( Fig. 6). The image processor 41 then examines these transition points and uses each horizontal scan line 602 to determine the left and right (referring to FIG. 6) transition points. These transition points correspond to the points like points 615 and 617 around the. Border of cells 606 .

After all border crossing points have been determined, the maximum and minimum distances between transition points lying on the same horizontal scan line 602 are determined. These values are typically subtracted from the image processor 41 , yielding values associated with the distance between the walls of the highlight cup 606 . The image processor 41 then scales these values to the pixel sizes of the video camera 46 ( FIG. 1).

In the example described, and as can be seen in Fig. 6, there is the greatest difference between black / white and white / black transitions at points 610 a and 611 a. The distance between these at points 610 a and 611 a represents the maximum separate the distance and consequently the width of the highlight cup HW. The image processor 41 recognizes that this is a highlight cup because no semitones have reached the upper edge 621 or the lower edge 623 of the scanning frame 600 .

It should be noted that the channel width CW of channel 72 ( FIG. 2) and the well width HW of wells 70 are similarly determined by the image processor 41 . For example, a minimum distance determined by the image processor would correspond to the channel width CW. If the image processor 41 determines that the minimum distance is below zero, then there is no channel and it is assumed that a highlight well, such as well 606 in FIG. 6, is measured. As with the maximum distance, the minimum distance between black / white and white / black transitions located on the same line 602 is scaled to the magnification and pixel sizes of video camera 46 ( FIG. 1).

Reference is now made again to the example just described. As soon as the highlight well HW has been measured, it is fed back to the computer 34 and the error value E is determined. The computer 34 receives the highlight bowl width HW and compares it with the HW value, which corresponds to the predetermined setting parameters. If the error value E is below the predefined threshold or is zero, then there is no mismatching to the predefined setting parameters, since the engraving machine engraves the highlight cups 76 ( FIG. 2) which have the actual dimensions, which generally correspond to those of the predefined setting parameters the required dimensions.

On the other hand, if the error value E is above the predetermined threshold, then an error adjustment is carried out. In this regard, the computer 34 determines that the actual engraved highlight cup 76 ( FIG. 2) has dimensions that differ from the dimensions that correspond to the predetermined setting parameters. As mentioned earlier, the computer 34 can use the most common HW values to determine the error value E. In this case, the error value E would correspond to the difference between the HW value and the most frequently occurring HW value, which has been stored in the memory for a large number of strobed and measured highlight cells 76 .

In the embodiment just described, the computer 34 initiates several measurements of the highlight cup 76 of the same size in order to verify the error value E. The computer 34 then adjusts one or more of the predetermined setting parameters BW, HW, Vh, Ks, Vmax and S in order to eliminate the error value E.

Fig. 8 explains the measurement process according to this embodiment. The measurement process begins at start block 170 and continues at block 172 with the scanning of a data frame. This is similar to the measuring process described above with reference to FIG. 7. After the data frame has been scanned, the data is divided into a plurality of localized sectors at block 174 . Using a variety of smaller localized sectors in this embodiment of the invention enables image processor 41 and computer 34 to process data faster. Threshold points are determined for each localized sector. A threshold operation is performed on each sector so that white / black and black / white transition points can be located within that sector. This process continues until all black / white and white / black transition points have been found for each sector in the scan frame and finally for the entire well measured at block 176 . At block 180 , the image processor 41 begins filling out the memory by filling in all the black depressions for the measured well. Then, at block 182, the image processor 41 identifies the largest and smallest transition points on a particular scan line.

At point 184 , the image processor 41 checks whether the memory fill has reached the page margins 625 and 627 ( FIG. 6). When the margins 625 and 627 have been reached, the image processor 41 recognizes that no well or channel has been measured (block 186 ). If the side edges 625 and 627 have not been reached, the image processor 41 determines at point 188 whether the fill has reached the upper edge 621 or the lower edge 623 . If the upper edge 621 or the lower edge 623 has been reached, the image processor 41 calculates the channel width CW and the well width BW at block 190 using the maximum and minimum values determined at block 186 . If the top edge 621 or the bottom edge 623 has not been reached, the image processor determines the highlight well HW at block 192 . After all these dimensions have been determined, the image processor exits at point 194 , whereupon an error value E is determined by the computer 34 in the manner described above. An error detection and correction system is advantageously provided that is suitable for creating a closed control circuit system for the engraving of highlight cups 76 ( FIG. 2), cups 70 and channels 72 in an engraving engraving machine. The error detection and correction system enables the determination of an error value E and its return to the computer 34 , whereupon feedback adjustments can be made to one or more of the predetermined setting parameters. This allows the engraving machine to engrave actual stitches, cups and channels in accordance with specified setting parameters.

It should be noted that during the initial adjustment or during normal loading drive of the engraving machine can be used. Consequently can the system and method described here a "Real time" display of actual dimensions and a "real time" correction for each error value E ge währleisten.

While the procedure described here and the Form of the device for implementing this method in preferred embodiments in practice represent, it is understood that the invention not on this exact procedure and this exact Device shape is limited and that each change can be made without the scope of protection leave the invention, which is in the attached Pa is defined.

Claims (15)

1. Engraving method in which an engraving stylus is driven by a signal-controlled electromagnetic drive ( 61 ) in order to generate an engraving from a plurality of engraved cells on a rotatably drivable printing roller ( 10 ), the drive being controlled by a computer ( 34 ) for the operation of the engraving stylus, characterized ,
that setting parameters, the width (BW) of a black bowl ( 70 ), the width (HW) of a highlight bowl ( 76 ), the channel width (CW) of a two black bowls ( 70 ) connecting channel ( 72 ) and an image Voltage levels (Vmax, Vh) are entered into the computer and
that a drive signal for the engraving stylus is generated by the computer ( 34 ) based on an input image signal as a function of the input setting parameters. 2. The method according to claim 1, characterized in that from the Setting parameters (BW, HW, CW) automatically control parameters (Kd, WD, Ka) are calculated using the control parameters (Ka, Kd) AC multiplication factor and an image multiplication factor are and the parameter (WD) is a white offset signal, and that the Engraving is created by ver the control parameters (Kd, WD, Ka) be applied to the movement of the engraving stylus in response to control an input signal (V (t)).   3. The method according to claim 1 or 2, characterized in that depth setting values (BD, HD, CD) for wells and channels ( 70 , 76 ; 72 ) to be engraved are also entered into the computer ( 34 ) as setting parameters. 4. The method according to claim 2, characterized in that the computer ( 34 ) is used to calculate the control parameters (Kd, WD, Ka) from the setting parameters (BW, HW, CW). 5. The method according to any one of the preceding claims, characterized in that the setting parameters (BW, HW, CW; BD, HD, CD) are entered via a desk ( 32 ). 6. The method according to any one of the preceding claims, characterized in that an AC and a DC signal for producing the engraving are generated and that the computer ( 34 ) is used to generate a plurality of adjustment signals for adjusting the AC and the DC signal , 7. The method according to any one of the preceding claims, characterized in that one of the setting parameters is used to generate a white offset signal (WD) and that the white offset signal is combined with the AC signal and the input signal (V (t)) such that the Engraving stylus for small values of the input signal does not come into contact with the pressure roller ( 10 ). 8. The method according to claim 6 or 7, characterized in that an AC and a DC signal for controlling the movement of the engraving stylus are generated on the basis of the setting parameters, so that cells ( 76 ) of defined brightness are engraved with the dimensions entered. 9. The method according to any one of the preceding claims, characterized in that the image voltage signal value (Vh) corresponds to the width dimension (HW) of the highlight cup ( 76 ). 10. Engraving device for performing the method according to one of the preceding claims, comprising a signal-controlled, electromagnetically drivable engraving head ( 61 ) with a parallel to an engraved, rotatably drivable pressure roller ( 10 ) movable engraving stylus ( 20 ) for generating an engraving on the pressure roller and a computer ( 34 ) electrically connected to the engraving head for processing parameters supplied to it and for generating an engraving signal for controlling the engraving stylus, characterized in that the following setting parameters can be entered into the computer ( 34 ): the desired width (BW) a black cell ( 70 ), the desired width (CW) of a connecting channel ( 72 ) between two black cells ( 70 ), the desired width (HW) of a highlight cell and an image voltage level (Vmax, Vh), and the computer ( 34 ) is set up is a drive signal for the Gra fourstichel based on an input image signal al depending on the setting parameters. 11. The device according to claim 10, characterized in that the computer ( 34 ) generates multiplication factors (Ka, Kd) from the setting parameters, which are applicable to an AC signal and an input signal (V (t)). 12. The apparatus according to claim 11, characterized by multiplier means ( 36 , 38 ) for multiplying the multiplication factors (Ka, Kd) by the AC signal and the input signal (V (t)). 13. The apparatus according to claim 10, characterized in that other adjustment parameters consist of an engraving tool constants (Ks), a highlight cell which (76) voltage corresponding input Span (Vh) and a shoe displacement (S). 14. The apparatus according to claim 10, characterized in that depth setting values (BD, HD, CD) for wells and channels ( 70 , 76 ; 72 ) to be engraved are also entered into the computer ( 34 ) as setting parameters. 15. The device according to one of claims 10 to 14, characterized in that an image processor ( 41 ) electrically connected to the computer ( 34 ) is provided in order to generate image feedback information which comprises at least a portion of the print roller ( 10 ) corresponds to the engraving generated.