Electrical Crosstalk Removal of Acousto-Optic Modulators

Abstract

A method for operating a multi-channel acousto-optic modulator comprises obtaining (S20) print data of a number of channels of the multi-channel acousto-optic modulator. High-frequency signals of each of the number of channels are modulated (S30) based on the print data. The modulated high-frequency signals are supplied (S40) to respective transducers of the multi-channel acousto-optic modulator via electrical input connectors. The modulation of the high-frequency signals comprises removing (S32) crosstalk of at least one channel. In this case, the modulated high-frequency signals are scaled by a predetermined coefficient and phase-shifted by a predetermined phase difference, and are compensated by the modulated high-frequency signals of at least electrically adjacent channels of the electrical input connectors. Also provided are a calibration method for the multi-channel acousto-optic modulator, a control device for the multi-channel acousto-optic modulator, and a pattern generator.

Description

Technical Field

[0001] The present technology generally relates to pattern printing, and more particularly to an apparatus and method for pattern printing using an acousto-optic modulator.

Background Art

[0002] In the field of pattern printing, it is common to use multiple channels to increase the printing speed. Therefore, it is necessary to modulate multiple channels simultaneously. One approach to managing such multi-channel modulation is to utilize an acousto-optic modulator (AOM). Acousto-optic modulation is commonly used in laser scanners and provides a reasonable compromise among cost, speed, and efficiency. An AOM uses acoustic waves in a crystal to create a diffraction grating. By changing the power of the applied RF signal, the amount of diffracted light changes proportionally. An acousto-optic multi-channel modulator can independently modulate multiple beams by integrating an array of transducers into a single acousto-optic crystal.

[0003] One problem that occurs when using a single common acousto-optic crystal is the risk of crosstalk between channels. "Crosstalk" may refer to acoustic crosstalk and / or electrical crosstalk. Acoustic crosstalk occurs within the acousto-optic crystal as interference between different acoustic waves. Electrical crosstalk can occur in the acousto-optic crystal itself via the connection cables from the source of the modulation signal. Electrical crosstalk can further be capacitive (electrostatic) and / or inductive (electromagnetic).

[0004] The problem of acoustic crosstalk has been addressed in various ways. One approach is disclosed in published International Publication No. WO 2020 / 120725, which introduced applying different frequencies to adjacent transducers.

[0005] Furthermore, a commonly used method to reduce electrical crosstalk is to space apart the electrical input connectors of adjacent channels on the crystal. One approach is to divide the AOM channels into two groups and separate them sufficiently on opposite sides of the device. In this way, crosstalk between channels physically adjacent on the crystal is reduced. However, there remains electrical crosstalk that cannot be avoided, for example, between channels that are not physically adjacent but electrically adjacent on the crystal.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] A general object of the present technology is to provide improved crosstalk reduction for an acousto-optic modulation apparatus and method for multi-beam pattern printing.

MEANS FOR SOLVING THE PROBLEMS

[0007] The above object is achieved by the methods and apparatuses of the independent claims. Preferred embodiments are defined in the m dependent claims.

[0008] Generally, in a first aspect, a method of operating a multi-channel acousto-optic modulator comprises obtaining print data for a number of channels of a multi-channel acousto-optic modulator. The high-frequency signal of each channel of the number of channels is modulated based on the print data. The modulated high-frequency signals are supplied to respective transducers of the multi-channel acousto-optic modulator via electrical input connectors. The modulation of the high-frequency signals comprises removing crosstalk of at least one channel. In this case, the modulated high-frequency signals are scaled by a predetermined factor and phase-shifted by a predetermined phase difference, and are compensated by the modulated high-frequency signals of at least electrically adjacent channels among the electrical input connectors.

[0009] In a second aspect, a method for calibrating a multi-channel acousto-optic modulator comprises operating one channel of the multi-channel acousto-optic modulator with a modulated high-frequency signal. Operating another channel of the multi-channel acousto-optic modulator with a modulated high-frequency signal that is scaled by a factor and phase-shifted by a phase difference. Measuring the intensity passing through another channel of the multi-channel acousto-optic modulator. Determining, as a calibration factor and a calibration phase difference used for crosstalk removal between two tested channels of the multi-channel acousto-optic modulator, the factor and the phase difference that give the lowest intensity as a predetermined factor and a predetermined phase difference. This predetermined factor and this predetermined phase difference are used for crosstalk removal between two tested channels of the multi-channel acousto-optic modulator.

[0010] In a third aspect, a control unit for a multi-channel acousto-optic modulator comprises an input unit, a modulator arrangement, and a multi-channel output unit. The input unit is configured to obtain print data for a number of channels of the multi-channel acousto-optic modulator. The modulator arrangement has a multi-channel modulator control unit for modulating a high-frequency signal for each of the multi-channels based on the obtained print data. The multi-channel output unit is configured to supply the modulated high-frequency signal to each transducer of the multi-channel acousto-optic modulator via an electrical input connector. The modulator arrangement is configured to perform crosstalk removal that gives a modulated high-frequency signal for at least one channel, and the modulated high-frequency signal is compensated by the modulated high-frequency signals of at least electrically adjacent channels among the electrical input connectors, scaled by a predetermined factor, and phase-shifted by a predetermined phase difference.

[0011] In a fourth aspect, a pattern generator comprises a multi-channel acousto-optic modulator according to the third aspect and a control device for the multi-channel acousto-optic modulator.

[0012] One advantage of the proposed technology is to significantly reduce electrical crosstalk. Other advantages can be understood by reading the detailed description.

Brief Description of the Drawings

[0013] The present invention is best understood with reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals refer to like elements, and in which:

[0014]

Figure 1

Figure 2

Figure 3

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Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Best Mode for Carrying Out the Invention

[0015] Throughout the drawings, like or corresponding elements are designated by the same reference numerals.

[0016] To better understand the proposed technology, it is useful to start with a brief overview of a model system of a pattern generator 1 as shown in FIG. 1. The pattern generator 1 of this embodiment is merely an example of a system to which the present technology can be applied. The present technology can be used in any pattern generator that uses a multi-channel acousto-optic modulator.

[0017] The laser beam is generated by a laser device 30. A diffraction optical element (DOE) 32 splits the laser beam into a plurality of separate beams 90. A set of mirrors 34, 36, 38 and other optical elements direct the separate beams 90 to irradiate a photosensitive target 42 of a substrate holder 40 in order to create an exposure pattern 44 on the photosensitive target 42. Each of the respective lenses, mirrors, optical crystals, etc. has some error and an energy spread occurs. Print data 100 is supplied to a control unit 10 of a multi-channel acousto-optic modulator 20.

[0018] In the acousto-optic modulator 20, a transducer 24 is used to generate acoustic waves through an acousto-optic crystal 22. Depending on the interaction between the acoustic waves in the acousto-optic crystal 22 and the separate laser beams 90, the separate laser beams 90 can be turned on and off corresponding to the movement of the separate laser beams 90 over the photosensitive target 42, thereby creating the required pattern.

[0019] The control unit 10 supplies a high-frequency signal 102 modulated based on the print data to each transducer 24 of the multi-channel acousto-optic modulator 20 via an electrical input connector.

[0020] Separate laser beams 90 are moved over a photosensitive target by a plurality of mechanisms. The Y interferometer 50 utilizes a laser beam 54 from the laser light source 52 to determine the Y-direction position of the separate laser beams 90. The X interferometer 56 similarly determines the X-direction position. For this purpose, a mirror 58 of the movable print head is used. The print head of the X carriage is movable in the X direction along the X bridge 46 as indicated by the arrow 48, and the substrate holder 40 is stepwise movable in the Y direction with respect to the X bridge 46 as indicated by the arrow 78. Thus, the X carriage performs a scan in the X direction (scan strip). During the return stroke of the X carriage, the Y stage supporting the substrate holder 40 moves by one step length (scan strip width). Also, a micro sweep can be performed in the Y direction by sweeping the separate laser beams 90 as indicated by the arrow 72, thereby moving the irradiation spot 70 of the separate laser beams 90. The micro sweep is achieved in the present embodiment by an acousto-optic deflector 60 having an acousto-optic crystal 62. A sweep signal 66 adjusted by other operations and print data 100 is supplied to the transducer 64. In this way, exposure is performed by writing a plurality of micro sweeps in one scan strip. The AOD deflector crystal 62 generates the sweeps of all the separate beams 90 together and controls the power and linearity over the sweep.

[0021] Accordingly, the printed pattern 44 on the photosensitive target 42 depends on appropriate modulation of the separate laser beams 90 being made to coincide with the micro sweep and other movement operations of the print head. The AOM modulator crystal 22 controls the power of the separate beams 90 and converts the pattern data 100 into exposure light. The present technology focuses on the control unit 10 of the multi-channel acousto-optic modulator 20 and its method.

[0022] FIG. 2 schematically shows an embodiment of the AOM 20. This AOM 20 may be used, for example, in a pattern generator as shown in FIG. 1. In this particular embodiment, the AOM 20 includes 15 channels. Each of the channels is defined by each of the transducers 24 mechanically connected to the acousto-optic crystal 22 to enable the transmission of acoustic waves to the acousto-optic crystal 22. Depending on the frequency of the acoustic wave, it is possible to affect the light passing in a direction perpendicular to the wave, that is, the light passing in the horizontal direction in the figure. Thereby, the on and off of the light beam can be switched. Each of the transducers 24 defines a channel of the AOM 20, and each of these channels is controlled more or less independently of each other. Separate single-frequency control signals to each of the transducers 24 determine the modulation of a single light beam passing through the AOM 20.

[0023] This approach generally functions very well. However, there is some crosstalk between the channels. One way to avoid crosstalk between adjacent channels of the AOM crystal oscillator 22 is to place the electrical input connectors of the adjacent channels on the crystal usually at locations far from each other. In the figure, it can be seen that the transducers are connected by two connectors 21A and 21B that are sufficiently separated on the opposing sides of the device having eight separate channels and seven separate channels 23 respectively. In one connector 21A that manages the first group of channels 23, the order of the channel connectors is 7, 5, 3, 1, 2, 4, 6, 8 as shown in the box on the right side. The numbers indicate the actual mechanical positions in the AOM crystal oscillator 22. Since the channel numbers indicate how the channels are arranged on the crystal, channel 1 is physically adjacent to 2, 2 is physically adjacent to 3, and so on. The order of the channels 23 in the group of connector 21B is 9, 11, 13, 15, 14, 12, 10 as shown in the box on the left side. In this way, the electrical crosstalk between physically adjacent channels is reduced. This is because the channel connectors are arranged in the above order. For this purpose, for example, channel 7 is electrically adjacent to 5, 5 is electrically adjacent to 3 and 7, 3 is electrically adjacent to 1 and 5, 1 is electrically adjacent to 2 and 3, 2 is electrically adjacent to 1 and 4, 4 is electrically adjacent to 2 and 6, 6 is electrically adjacent to 4 and 8, and 8 is electrically adjacent to 6. The same applies to the other groups.

[0024] Depending on how the channels are arranged, the crosstalk between adjacent channels on the crystal is reduced, but instead, unavoidable electrical crosstalk occurs between channels that are not adjacent on the crystal but are electrically adjacent. Therefore, it has been found that even when the light passing through the AOM is controlled to only one channel and all the surrounding channels are turned off, there is a certain amount of light passing through the electrically adjacent channels. This is shown in the photograph of Figure 3, where in this case, the light passing through different channels is detected.

[0025] In this experiment, an optical plane wave was sent through the modulator crystal and an RF signal was applied only to one of the modulator channels (channel 5 in this example). An imaging system was provided to image the acoustic waves generated in the crystal onto a camera sensor. This was done by filtering out the 0th diffraction order and allowing only the 1st diffraction order to pass through to the camera. When analyzing the image, in addition to the acoustic wave CH5 of channel 5, the acoustic waves CH3 of channel 3 and CH7 of channel 7 could also be clearly confirmed. These correspond to the channels electrically adjacent to channel 5 (CH5). In the figure, another acoustic wave with a significantly lower intensity corresponding to channel 1, which is electrically adjacent to channel 3 (CH3), can also be seen. The reason for the existence of these acoustic waves is that part of the energy of the high-frequency signal sent to channel 5 (CH5) is coupled to the electrical circuits of the adjacent channels and reaches the corresponding transducers, after which waves are generated in the crystal. It should also be noted that no light was detected in the physically adjacent channels between CH5 and CH7.

[0026] According to the idea of this technology, this electrical crosstalk can be removed by adding a cancellation signal to the originally intended signal before sending it to the AOM. This cancellation signal is a scaled-down and phase-shifted version of the signals of the electrically adjacent channels. If there are two electrically adjacent channels, the respective cancellation signals can be added.

[0027] Figure 4 is an image of a situation similar to that of Figure 3, but a removal signal with an amplitude scaled to 1.7% (0.028% power) and a phase shifted by 203 degrees is added to Channel CH7, which contains a copy of the CH5 signal. The intensity of CH7 was significantly reduced. The phase shift was further varied, and in this particular case, a maximum removal was seen with a phase shift of 211 degrees. Theoretically, if the lengths, structures, etc. of all the connectors are exactly the same, the best removal is done at 180 degrees. However, in an actual setup, due to differences between the connectors, there can be a slight phase shift (in this case, 31 degrees) between electrically adjacent channels.

[0028] The same test was repeated while varying the scaling with a constant phase shift of 211 degrees. As shown in Figure 5, at an amplitude scaling of 2.9% (0.085% power), the light passing through Channel CH7 almost disappeared. The results were the same regardless of how the signal of Channel CH5 was configured as long as the removal signal was scaled and phase shifted.

[0029] This shows that electrical crosstalk can be removed. Since the crosstalk conditions of the device are constant during operation, the parameters for removing crosstalk (phase shift and scaling factor) are the same for each pair of channels. Therefore, it is possible to measure and calibrate separate devices for the removal of electrical crosstalk.

[0030] The method proposed in this way completely removes the electrical crosstalk between electrically adjacent channels. This method can remove crosstalk even when a pure phase control approach fails, for example, when the amplitude of the desired signal is zero and the amplitude of the crosstalk signal is maximum.

[0031] FIG. 6 schematically shows a control device 10 for a multi-channel acousto-optic modulator. The input section 9 is configured to acquire print data 100 of a large number of channels 23 of the multi-channel acousto-optic modulator. The modulator arrangement 8 has a multi-channel modulator control section 12 that modulates a high-frequency signal 101 for each of the large number of channels based on the acquired print data 100.

[0032] The modulator arrangement 8 is configured to perform crosstalk removal on at least one channel 23, and the crosstalk removal is compensated for by modulated high-frequency signals of at least electrically adjacent channels among the electrical input connectors, which are scaled by a predetermined coefficient and phase-shifted by a predetermined phase difference, and provides a modulated high-frequency signal. This compensation is added to the modulated high-frequency signal 101 to form a compensated high-frequency signal 102. This is typically performed at the signal compensation arrangement 14 for each channel.

[0033] The multi-channel output section 7 is configured to supply the modulated and compensated high-frequency signal 102 to each transducer of the multi-channel acousto-optic modulator via the electrical input connector 6.

[0034] Preferably, the modulator arrangement 8 is configured to perform crosstalk removal on all channels 23 of the electrical input connector 6.

[0035] Preferably, the modulator arrangement 8 is configured to perform crosstalk removal except for the electrically outermost channel 23X, and the crosstalk removal is compensated for by modulated high-frequency signals of two electrically adjacent channels among the electrical input connectors, which are scaled by respective predetermined coefficients and phase-shifted by respective predetermined phase differences, and provides a modulated high-frequency signal 102.

[0036] Various more detailed embodiments are further shown below.

[0037] FIG. 7 shows a flow chart of steps of an embodiment of a method for calibrating a multi-channel acousto-optic modulator. In step S10, one channel of the multi-channel acousto-optic modulator (denoted herein as channel N) is operated with a modulated high-frequency signal. In step S12, which is performed simultaneously, another channel of the multi-channel acousto-optic modulator (denoted herein as channel M) is operated with a modulated high-frequency signal that is scaled by a coefficient and phase-shifted by a phase difference.

[0038] In step S14, the intensity passing through the other channel of the multi-channel acousto-optic modulator, i.e., channel M, is measured. In step S16, the coefficient and phase difference that give the minimum intensity are determined. This is typically done by repeating steps S12 and S14 with different scale factors and phase shifts, as indicated by the dotted arrow S15. These determined coefficients and phase differences that give the minimum intensity are assigned as the default coefficients and default phase differences for the pair of channels N and M used for crosstalk removal between the two tested channels of the multi-channel acousto-optic modulator.

[0039] Preferably, the default coefficients and default phase differences are determined for each pair of electrically adjacent channels.

[0040] Even if the electrical crosstalk with non-electrically adjacent channels is extremely small, this principle is, of course, applicable to all pairs of channels. Thus, in one embodiment, default coefficients and default phase differences are determined for each pair of channels. If the coefficient is very small, this may indicate that the electrical crosstalk is also very small and that removal between such channels may not be necessary. The default coefficients and default phase differences between different pairs of channels may be used for the operation of the multi-channel acousto-optic modulator.

[0041] FIG. 8 is a flowchart of steps of an embodiment of a method of operating a multi-channel acousto-optic modulator. In step S20, print data of a number of channels of the multi-channel acousto-optic modulator is acquired. In step S30, based on the print data, each high-frequency signal of the multi-channels is modulated. The step S30 of modulating the high-frequency signal sequentially includes crosstalk removal S32 for at least one channel. Thereby, the modulated high-frequency signal is scaled by a predetermined coefficient and phase-shifted by a predetermined phase difference, and is compensated by the modulated high-frequency signals of at least electrically adjacent channels of the electrical input connectors. In step S40, the modulated high-frequency signal is supplied to each of the transducers of the multi-channel acousto-optic modulator via the electrical input connectors.

[0042] Preferably, crosstalk removal is performed for all channels of the electrical input connector.

[0043] Also, it is preferable to perform crosstalk removal for all electrically adjacent channels. In most cases, a channel has two electrically adjacent channels, whereby electrical crosstalk compensation is performed from both of these electrically adjacent channels. For the channels related to the connectors provided on both sides of the connector, that is, for the outermost channels, there is only one electrically adjacent channel, and electrical crosstalk compensation is performed only for one electrically adjacent channel. Therefore, crosstalk removal preferably provides a modulated high-frequency signal that is compensated by the modulated high-frequency signals of two electrically adjacent channels of the electrical input connectors, scaled by each of a predetermined coefficient and phase-shifted by a predetermined phase difference, except for the electrically outermost channels.

[0044] The above-mentioned crosstalk removal can be implemented in various ways. It is possible to arbitrarily set the accurate and absolute phase of the modulation signal to a multi-channel acousto-optic modulator. The operation of the channels of the multi-channel acousto-optic modulator depends only on the applied frequency signal. Therefore, even if a phase shift of the signal supplied to a single channel of the multi-channel acousto-optic modulator is applied, the modulation characteristics of the channel do not change. The arrangement of the modulators can be designed such that each of the channels has a constant phase difference with respect to the electrically adjacent channels. When this phase difference is equal to the measured and calibrated predetermined phase shift, a simple setup of the signal compensation arrangement can be utilized. Since the basic phase shift between different channels is already set to a predetermined phase shift, the intended phase difference can be automatically achieved simply by adding the amplitudes proportional to the signals of the electrically adjacent channels.

[0045] Figure 9 is a partial flowchart showing an embodiment of step S32 for crosstalk removal between electrically adjacent channels. In step S33, the channels are arranged with a steady relative phase difference with respect to one or more electrically adjacent channels among the electrical input connectors. This steady relative phase difference is equal to each of the predetermined phase differences. In step S34, the printed data amplitude of each of the channels is summed with the printed data amplitude of the electrically adjacent channels scaled by a predetermined coefficient. In this way, RF modulation using the steady relative phase difference gives a full-channel signal including a removal signal having an appropriate phase difference with respect to the electrically adjacent channels.

[0046] As an example, a simplified approach is as follows. The data channel sums the main signal and the scaled adjacent signal and provides these for RF modulation. The distribution board has an appropriate set of phase differences. In the setup of the embodiment of Figure 2, in the ideal case, as shown in Table 1, all electrically adjacent channels are arranged with a 180-degree phase difference.

Table 1

[0047] By arranging them in electrical order, according to Table 2, the phase difference between electrically adjacent channels becomes apparent.

Table 2

[0048] In a realistic case, as seen in the above-described experiment, since the phase difference does not always become 180 degrees, for example, when Channel 5 needs to be 200 degrees lower than Channel 7 and 170 degrees higher than Channel 3, the table needs to be changed as follows (along with other experimentally determined phase shifts).

Table 3

[0049] In electrical order, the shift is as follows.

Table 4

[0050] FIG. 10 schematically shows an embodiment of the signal compensation arrangement 14. The printed data 100 of three electrically adjacent channels 101 N-1 , 101 N , 101 N+1 is provided at the input section to the signal compensation arrangement 14. In the adder 18, the printed data 101 N-1 is multiplied by the scale factor β N-1 in the multiplier 11 N-1 . Similarly, the printed data 101 N+1 is multiplied by the multiplier 11 N+1 having the scale factor β N+1 . The two scaled printed data and the printed data 101 N are added in the adder 15 to become corrected printed data. That is, in the adder 18, the printed data amplitude of each channel is multiplied by a predetermined coefficient β N+1Sum it with the printed data amplitudes of the electrically adjacent channels scaled by .

[0051] In the modulator 13 of the phase adjuster 16, the compensated printed data has a frequency f and a phase φ N and is RF modulated. The RF modulated signal 102 is for channels N-1 and channels N+1 and is supplied to an output for connection to the channels N of a multi-channel acousto-optic modulator via a connector where the channels are electrically adjacent. In other words, the phase adjuster 16 is configured to arrange channels having a constant relative phase difference equal to each of the predetermined phase differences for the electrically adjacent channels among the electrical input connectors.

[0052] Alternatively, all of its implementation can also be done on a distribution board. In that case, the distribution board needs to store three times the normal data.

[0053] FIG. 11 is a flowchart of an embodiment of step S32 for crosstalk removal between electrically adjacent channels. In step S35, supply a high-frequency signal modulated according to the printed data of the channels among the electrical input connectors and a modulated high-frequency signal according to the printed data of at least one other channel among the electrical input connectors. In step S36, scale the modulated high-frequency signal according to the printed data of at least one other channel by each of the predetermined coefficients and phase-shift the modulated high-frequency signal according to the printed data of at least one other channel by each of the defined phase differences. In step S37, add the high-frequency signal modulated according to the printed data of the channel and the modulated high-frequency signal scaled and phase-shifted according to the printed data of at least one other channel, thereby supplying the crosstalk-removed modulated high-frequency signal to each of the transducers.

[0054] FIG. 12 schematically shows an embodiment of the signal compensation arrangement 14. The compensation bridge 19 is connected to the output of the multi-channel modulator controller 12 and is configured to scale the high-frequency signals modulated according to the channel print data by respective predetermined factors and phase-shift the high-frequency signals modulated according to the channel print data by respective predetermined phase differences. The signal adder 17 is connected to one or more of the compensation bridges 19 and is configured to add the modulated high-frequency signals scaled and phase-shifted according to the channel print data from the one or more compensation bridges to the high-frequency signals modulated according to the channel print data of another channel. Each of the outputs of the signal adder 17 providing the cross-talk-removed modulated high-frequency signals is connected to each of the transducers via an electrical input connector.

[0055] As described above, electrical cross-talk cancellation can also be generalized to more channels than just electrically adjacent channels. Generally, the cross-talk is significantly reduced for each channel separating the two interfering channels. Thus, it is unlikely that the cross-talk exceeding the cross-talk of the two closest channels on both sides will provide a cross-talk large enough for compensation. However, theoretically, it can be done for all channels.

[0056] In other words, in one embodiment, cross-talk cancellation provides a modulated high-frequency signal that is compensated by the modulated high-frequency signals of more than two channels of the electrical input connectors, scaled by a predetermined factor and phase-shifted by a predetermined phase difference.

[0057] FIG. 13 schematically shows an embodiment in which crosstalk from more than two channels on each side is compensated. In other words, the modulator arrangement 8 is configured to perform crosstalk removal, and the crosstalk removal is compensated by modulated high-frequency signals of at least electrically adjacent channels of the electrical input connectors, which are scaled by a predetermined coefficient and phase-shifted by a predetermined phase difference, to provide a modulated high-frequency signal.

[0058] The idea of crosstalk compensation of the present invention has been proven to substantially completely remove electrical crosstalk between electrically adjacent channels. Furthermore, there is an implementation that can be easily realized without changing the hardware. The necessary changes can be implemented only in software / firmware.

[0059] The above-described embodiments should be understood as some exemplary examples of the present invention. It is understood by those skilled in the art that various modifications, combinations, and changes to the embodiments can be made without departing from the scope of the present invention. In particular, if technically possible, different component solutions in different embodiments can be combined in other configurations. However, the scope of the present invention is defined by the appended claims.

Claims

Claim 1 A method for operating a multi-channel acousto-optic modulator (20), comprising: obtaining (S20) print data (101) of a number of channels (23) of the multi-channel acousto-optic modulator (20); modulating (S30) high-frequency signals (102) of each of the number of channels (23) based on the print data (101); feeding (S40) the modulated high-frequency signals (102) to respective transducers (24) of the multi-channel acousto-optic modulator (20) via an electrical input connector (6); wherein the step of modulating (S30) the high-frequency signals (102) comprises crosstalk removal (S32) for at least one channel (23), and the modulated high-frequency signals are compensated by modulated high-frequency signals of at least electrically adjacent channels (23) of the electrical input connector, which are scaled by a predetermined coefficient (β) and phase-shifted by a predetermined phase difference (φ). Claim 2 The method according to claim 1, wherein the crosstalk removal (S32) is performed on all channels (23) of the electrical input connector (6). Claim 3 The method according to claim 1 or 2, wherein the crosstalk removal (S32) provides a modulated high-frequency signal (102) compensated by modulated high-frequency signals of two electrically adjacent channels (23) of the electrical input connector (6), which are scaled by respective predetermined coefficients (β) and phase-shifted by respective predetermined phase differences (φ), except for the electrically outermost channels (23X). Claim 4 The crosstalk removal (S32) comprises: arranging (S33) the channels (23) having a constant relative phase difference equal to each of the predetermined phase (φ) differences in the electrically adjacent channels (23) of the electrical input connector (6); summing (S34) the print data amplitudes of each of the channels (23) with the print data amplitudes of the electrically adjacent channels (23) scaled by the predetermined coefficient (β); The method according to any one of claims 1 to 3, characterized by comprising the above steps. Claim 5 The crosstalk cancellation (S32) is characterized in that the modulated high-frequency signals of two electrically adjacent channels (23) of the electrical input connector (6), which are scaled by respective predetermined coefficients (β) and phase-shifted by a predetermined phase difference (φ), are compensated, and the method according to any one of claims 1 to 3, which provides a modulated high-frequency signal.

6. The crosstalk cancellation (S32) is supplying (S35) a high-frequency signal modulated according to the print data (101) of a channel (23) of the electrical input connector (6) and a high-frequency signal modulated according to the print data (101) of at least one other channel (23) of the electrical input connector (6); scaling the modulated high-frequency signal (101) by each of the predetermined coefficients (β) according to the print data of the at least one other channel (23) and phase-shifting the modulated high-frequency signal (101) by each of the predetermined phase differences (φ) according to the print data of the at least one other channel (23) (S36); adding (S37) the modulated high-frequency signal according to the print data of the channel (23) and the modulated high-frequency signal according to the print data of the at least one other channel (23), which has been scaled and phase-shifted, to provide the crosstalk-cancelled modulated high-frequency signal (102) supplied to each of the transducers; The method according to any one of claims 1, 2, 3 or 5, characterized by comprising the steps.

7. A method for calibrating a multi-channel acousto-optic modulator (20), comprising: operating (S10) one channel (23) of the multi-channel acousto-optic modulator (20) with a modulated high-frequency signal; operating (S12) another channel (23) of the multi-channel acousto-optic modulator (20) with the modulated high-frequency signal, which is scaled by a coefficient and phase-shifted by a phase difference; measuring (S14) the intensity passing through the another channel (23) of the multi-channel acousto-optic modulator (20); As a calibration coefficient and a calibration phase difference used for crosstalk removal between two tested channels (23) of the multi-channel acousto-optic modulator, a step of determining a coefficient and a phase difference that give the lowest intensity (S16). A method comprising the above. **Claim 8** The method according to claim 7, characterized in that the calibration coefficient and the calibration phase difference are determined for each pair of electrically adjacent channels (23). **Claim 9** The method according to claim 7 or 8, characterized in that the calibration coefficient and the calibration phase difference are determined for each pair of channels (23). **Claim 10** A control unit (10) of a multi-channel acousto-optic modulator (20), an input unit (9) for acquiring print data (100) of a number of channels (23) of the multi-channel acousto-optic modulator (20), a modulator arrangement (8) having a multi-channel modulator control unit (12) for modulating a high-frequency signal (102) of each of the number of channels (23) based on the acquired print data (100), a multi-channel output unit (7) for supplying the modulated high-frequency signal (102) to each transducer of the multi-channel acousto-optic modulator (20) via an electrical input connector (6), comprising the modulator arrangement (8) is configured to perform crosstalk removal on at least one channel (23), and the crosstalk removal is scaled by a predetermined coefficient (β) and phase-shifted by a predetermined phase difference (φ), and is compensated by the modulated high-frequency signals of at least electrically adjacent channels (23) of the electrical input connector, and provides a modulated high-frequency signal, a control unit. **Claim 11** The control unit according to claim 10, characterized in that the modulator arrangement (8) is configured to perform crosstalk removal on all channels (23) of the electrical input connector (6). **Claim 12** The modulator arrangement (8) is configured to perform crosstalk cancellation except for the electrically outermost channel (23X), and the crosstalk cancellation is scaled by each of a predetermined coefficient (β) and phase-shifted by a predetermined phase difference (φ), and is compensated by modulated high-frequency signals of two electrically adjacent channels (23) among the electrical input connectors (6), and provides a modulated high-frequency signal (102). The control unit according to claim 10 or 11, characterized in that.

13. The modulator arrangement (8) is The print data (101 Ｎ of each channel (23) has its amplitude added to the print data amplitudes (101 Ｎ－１ , 101 Ｎ＋１ ) of the electrically adjacent channels (23) scaled by the predetermined coefficient (β) in an adder (18), and A phase adjuster (16) configured to arrange the channels (23) having a constant relative phase difference equal to each of the predetermined phase (φ) differences in the electrically adjacent channels (23) among the electrical input connectors (6); The control unit according to any one of claims 10 to 12, characterized by comprising.

14. The modulator arrangement (8) is configured to perform crosstalk cancellation, and the crosstalk cancellation is scaled by each of a predetermined coefficient (β) and phase-shifted by a predetermined phase difference (φ), and is compensated by modulated high-frequency signals of at least electrically adjacent channels (23) among the electrical input connectors (6), and provides a modulated high-frequency signal (102). The control unit according to any one of claims 10 to 12, characterized in that.

15. The modulator arrangement (8) is A compensation bridge (19) connected to the multi-channel modulator control unit (12) and configured to scale the modulated high-frequency signal (101) by each of the predetermined coefficients (β) according to the printed data of the channels (23) and phase-shift the modulated high-frequency signal (101) by each of the predetermined phase differences (φ) according to the printed data of the channels (23); A signal adder (17) connected to one or more of the compensation bridges (19) and configured to add the scaled and phase-shifted modulated high-frequency signals from one or more of the compensation bridges (19) to the modulated high-frequency signals modulated according to the printed data of another channel (23). Each of the output parts of the signal adder (17) supplies the cross-talk removed modulated high-frequency signal (102) and is connected to each of the transducers (24) via the electrical input connector (6), and the control unit according to any one of claims 10, 11, 12 or 14, characterized in that.

16. A pattern generator (1) comprising a multi-channel acousto-optic modulator (20) and a control unit (10) for the multi-channel acousto-optic modulator (20) according to any one of claims 10 to 15.

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