Control unit for an electric drive unit of an ophthalmic surgical handpiece and method for its operation, ophthalmic surgical device and system

Abstract

Control unit (1) for an electric drive unit (2) of an ophthalmic surgical handpiece (3) for processing an eye lens (52), which drives a treatment needle (14), comprising a generator unit (4) for providing an electrical control variable (5, 6) for the electric drive unit (2), wherein the generator unit (4) is configured to provide the control variable (5, 6) with a control oscillation, wherein the control oscillation has a first oscillation component at a first control frequency, wherein the first oscillation component is adjustable depending on a first ratio of a mechanical displacement amplitude of the treatment needle (14) to the electrical control variable (5, 6) at the first control frequency, wherein the generator unit (4) is further configured to provide the control oscillation of the control variable (5, 6) with at least one further oscillation component at a further control frequency different from each other control frequency,that the further oscillation component is adjustable depending on a further ratio of the mechanical displacement amplitude of the treatment needle (14) to the electrical control variable (5, 6) at the respective further control frequency. characterized in that the generator unit (4) provides the control variable (5, 6) such that a first period attributable to a forward movement of the treatment needle (14) is shorter than a second period attributable to a return movement of the treatment needle (14).

Description

The invention relates to a control unit according to the preamble of claim 1. Furthermore, the invention relates to an ophthalmic surgical device according to the preamble of claim 7. In addition, the invention relates to an ophthalmic surgical system according to the preamble of claim 8. Finally, the invention also relates to a method according to the preamble of claim 9. Ophthalmic surgical devices, in particular handpieces and control units for them, ophthalmic surgical systems with ophthalmic surgical devices, and corresponding procedures are used, among other things, to treat lens opacities in living beings, for example, humans or animals. Lens opacities are referred to in medicine as cataracts or clouding of the lens. One treatment option for lens opacities involves replacing the eye's natural lens with an artificial lens. One technique for treating lens opacities by replacing the natural lens with an artificial lens is phacoemulsification. An important component for performing phacoemulsification is the ophthalmic surgical handpiece, which will be referred to simply as the handpiece in the following. The handpiece comprises a treatment needle that is mechanically connected to a drive unit of the handpiece, so that the treatment needle can be driven by the drive unit in an oscillating motion during normal operation. An ophthalmic surgical handpiece, a control unit, and a method for controlling it are disclosed, for example, by US 2017 / 0134369 A1 and also by US 10 231 870 B2. Furthermore, it is known from US 10 231 870 B2 to actuate the treatment needle longitudinally by means of the drive unit, which in turn is actuated with a sawtooth alternating voltage. Furthermore, US 2005 / 0267504 A1 discloses a method for controlling an operating system based on an irrigation flow. It is known that the mechanical ultrasonic movement of a treatment needle in a handpiece can generate heat through friction during surgery on the eye. This can reduce the effectiveness of fragmenting the natural lens and result in significant local heat input into the eye, potentially causing irreversible damage. The invention is therefore based on the objective of improving a generic control device, a generic ophthalmic surgical device, a generic ophthalmic surgical system and a generic method in such a way that the control of the treatment needle can be carried out more precisely, so that in particular the aforementioned problems relating to heat input can be better reduced. The invention proposes a control unit, an ophthalmic surgical device, an ophthalmic surgical system and a method according to the independent claims as a solution. Advantageous further training opportunities arise from the characteristics of the dependent requirements. With regard to a generic control device, the invention, according to a first aspect, particularly proposes that the generator unit is further configured to provide the control oscillation of the control variable with at least one further oscillation component at a further control frequency different from each other control frequency, such that the further oscillation component is adjustable depending on a further ratio of the mechanical deflection amplitude of the treatment needle to the electrical control variable at the respective further control frequency. With regard to a generic ophthalmic surgical device, the invention, according to a second aspect, particularly proposes that the generator unit is further configured to provide the control oscillation of the control variable with at least one further oscillation component at a further control frequency different from each other control frequency, such that the further oscillation component is adjustable depending on a further ratio of the mechanical deflection amplitude of the treatment needle to the electrical control variable at the respective further control frequency. With regard to a generic ophthalmic surgical system, the invention, according to a third aspect, particularly proposes that the ophthalmic surgical device is designed according to the invention. With regard to a generic method, the invention, according to a fourth aspect, particularly proposes that the control oscillation of the control variable is provided with at least one further oscillation component at a further control frequency different from each other control frequency, wherein the further oscillation component is set depending on a further ratio of the mechanical deflection amplitude of the treatment needle to the electrical control variable at the respective further control frequency. The invention is based, among other things, on the finding that the ratio between the mechanical displacement amplitude of the treatment needle, particularly its cutting tip, and the corresponding control variable is frequency-dependent. This ratio is also called core admittance. It has been shown that core admittance is a frequency-dependent quantity. This has not been taken into account in the prior art. By ensuring that the control variable, which can encompass the control oscillation at two or more frequencies, is provided in such a way that the respective oscillation components are adjusted according to the respective frequency-specific core admittance, it is possible to adjust the control oscillation of the treatment needle much more precisely and accurately. The effect of the invention can be particularly evident when the electrical control variable is to exhibit a predefinable temporal curve profile in order to enable a specific movement of the treatment needle, especially its cutting tip. In one embodiment, the temporal curve profile can be achieved by superimposing oscillation components at different frequencies, for example, different phase angles and / or different amplitudes. If, in such a case, only the core admittance at a single frequency or control frequency is considered, this can result in the actual mechanical oscillation of the treatment needle, especially its cutting tip, deviating significantly from the desired movement. The invention can eliminate, or at least reduce, this problem.The invention takes into account the different frequency-specific nuclear admittances for the various control frequencies when providing the electrical control signal. Preferably, the frequency-specific nuclear admittance is considered for each oscillation component. The deviation of the time-dependent curve of the electrical control signal therefore depends, among other things, on the respective frequency-specific nuclear admittances. Overall, the invention makes it possible not only to improve the efficiency of fragmenting the natural lens of the eye, but also to reduce heat input into the eye. Thus, the treatment of the eye can be improved overall. The control unit can be designed as a separately handled unit, which may have its own housing. The control unit can be stationary or mobile, particularly as a portable unit. If the control unit has its own housing, its components or assemblies may be at least partially enclosed within the housing. The control unit may also include an operating device or be designed to be connected to such a device. The operating device allows the control unit or the connected handpiece to be operated in a predefined manner. Furthermore, the control unit may also have an output interface to which a display device can be connected to show one or more operating states of the control unit or its settings. The drive unit can be designed as an electrostatic or electromagnetic drive unit. As an electrostatic drive unit, it can be piezoelectric. For this purpose, the drive unit can have one or more piezoelectric elements. The resulting piezoelectric drive unit utilizes the effect that the piezoelectric elements, to which, for example, an electrical voltage is applied as a control variable, change their mechanical dimensions, such as their length. The treatment needle is mechanically connected to the piezoelectric drive unit so that the desired drive effect can be achieved during intended operation.In contrast, an electromagnetic drive unit can incorporate an electromagnetic-mechanical transducer, which can be controlled, for example, by an alternating current. Using a magnetic field, a magnetizable actuator of the transducer can be actuated to generate the desired mechanical movement. The electric drive unit has electrical connections where it can be supplied with the electrical control signal, thus providing the desired mechanical movement for the treatment needle. The generator unit is preferably an electronic unit configured to provide the electrical control signal for the electric drive unit. For this purpose, the generator unit can include an electronic circuit, for example, an inverter or the like. Furthermore, the generator unit can, of course, also include a program-controlled computer unit, which is provided in addition to or as an alternative to the hardware circuit. The generator unit thus provides the electrical control signal. The generator unit is configured to provide the control oscillation of the control signal with a first oscillation component at a first control frequency. Preferably, the first control frequency is in the ultrasonic range, wherein the first control frequency is preferably greater than about 10 kHz, and particularly preferably in the range of about 40 kHz.The first control frequency can, for example, be set at a resonant frequency of the treatment needle. The first oscillation component, for example, a first amplitude, can be set by the generator unit depending on a first ratio of the mechanical displacement amplitude of the treatment needle to the electrical control variable at the first control frequency. This core admittance may have been determined separately before commencing intended operation. To provide the first oscillation component, the generator unit can include at least one suitable electronic oscillator, which is preferably adjustable to set the first control frequency in a predetermined manner. The signal provided by a first oscillator can then be fed to a first amplifier, whose gain can also be adjusted. To adjust the gain factor, the generator unit can include an amplitude factor unit that determines the associated first core admittance or the associated first ratio of the mechanical displacement amplitude of the treatment needle to the electrical control variable based on the first control frequency and adjusts the first amplifier accordingly. Adjusting the first amplifier can include adjusting its gain factor. Furthermore, the generator unit is designed to provide the electrical control signal with at least a second oscillation component at a second control frequency. For this purpose, the generator unit can have a separate second oscillator, which is preferably also adjustable, so that the desired second control frequency can be set using the second oscillator. The signal supplied by the second oscillator can then be fed to a second amplifier, which—similar to the first amplifier—has an adjustable gain factor. The second control frequency can be determined using the amplitude factor unit, and—as with the first control frequency—the gain factor of the second amplifier can be adjusted depending on a second core admittance or the mechanical displacement amplitude of the treatment needle relative to the electrical control signal at the second control frequency.This can be continued accordingly for other vibration components at other control frequencies. The electrical control signal therefore comprises not only a single oscillation component at the first control frequency, but also at least a second oscillation component at a second control frequency. Preferably, the first frequency is the lowest frequency. In this case, the first frequency can also be referred to as the fundamental frequency. The further control frequencies can be harmonics of the first control frequency, which is particularly advantageous. Preferably, separate adjustment is provided for each of the further oscillation components, depending on the respective individual frequency-specific additional core admittances at the respective further control frequencies. It is particularly advantageous for the electrical control signal to be provided as a single signal. Each oscillation component preferably comprises an oscillation according to a sinusoidal waveform. The invention thus makes it possible to adjust the electrical control variable in such a way that the vibration behavior of the treatment needle, in particular its cutting tip, can be very specifically adjusted within a wide range. For this purpose, the corresponding ratios or core admittances can be determined separately for the respective control frequencies, for example, for each individual handpiece or for each assembly of handpieces. The adjustment can be carried out using a frequency spectrum analyzer. To achieve a specific, predetermined type of oscillation of the treatment needle, the electrical control variable can provide several oscillation components with corresponding amplitudes and, if necessary, also taking into account their respective phase relationships. By considering the respective frequency-related core admittances, the desired mechanical oscillation of the treatment needle can then be set in virtually any way and with virtually any desired accuracy. This makes it possible to reduce or even completely avoid the problems present in the prior art. The generator unit provides the control variable such that the first period, attributable to a forward movement of the treatment needle, is shorter than the second period, attributable to a return movement of the treatment needle. The forward movement of the treatment needle refers to a movement towards a maximum positive displacement of the treatment needle from a rest position, preferably a central one. In a longitudinal movement, the cutting tip of the treatment needle thus moves away from a housing of the handpiece, particularly from the drive unit, during the forward movement. The return movement is then the reverse; that is, the cutting tip of the treatment needle moves towards the housing, particularly the drive unit, of the handpiece. The forward and return movements can also be defined in a dual manner during a torsional oscillation of the treatment needle.Particularly when the treatment needle is moved longitudinally, this allows for a short forward movement of the needle, thus achieving good emulsification of the lens to be removed. Simultaneously, the longer return movement reduces heat exposure in the surgical area of ​​the eye. Preferably, the control parameter is provided such that a smooth transition from the forward movement of the cutting tip of the treatment needle to the return movement of the cutting tip of the treatment needle, and / or vice versa, can be achieved. According to a further development proposal, the control unit should have a storage unit in which individual values ​​for the respective ratios of the mechanical deflection amplitude of the treatment needle to the electrical control variable are stored, at least corresponding to the respective control frequencies. The storage unit allows these values ​​to be retrieved during normal operation. The storage unit can be at least partially integrated into the control unit. Furthermore, it is also possible that the storage unit is at least partially separate from the control unit and / or located within it, or that it communicates with the control unit via a communication link. For example, the storage unit can also be at least partially comprised of a database, preferably provided by the manufacturer.This allows for the centralized provision, maintenance, and updating of individual values ​​for the relationship between the mechanical deflection amplitude of the treatment needle and the electrical control variable. It also enables the subsequent provision of new individual values ​​for previously unsaved control frequencies. This significantly improves functionality. The storage unit can be designed as an electronic storage device, for example, a read-only memory (ROM), a random-access memory (RAM), a hard drive, a USB flash drive, a combination thereof, and / or similar devices. An advantageous embodiment may further provide that the storage unit is at least partially located within the ophthalmic surgical handpiece.This has the advantage that the individual values ​​for each individual ophthalmic surgical handpiece can be determined and stored within it. This makes it possible to manufacture the control unit independently of the required individual values ​​for the ratio of the mechanical deflection amplitude of the treatment needle to the electrical control input, and to adapt it individually to each ophthalmic surgical handpiece. Specifically, it can be designed so that when the handpiece is connected to the control unit, the storage unit within it is linked to the control unit via communication technology, thus making the values ​​determined for this specific ophthalmic surgical handpiece regarding the ratio of the mechanical deflection amplitude of the treatment needle to the electrical control input available to the control unit.This has the further advantage that when the ophthalmic surgical handpiece is changed, the individual values ​​for the ratio of the mechanical deflection amplitude of the treatment needle to the electrical control variable can also be automatically adjusted accordingly. With this design, the control unit typically has the values ​​for the ratio of the mechanical deflection amplitude of the treatment needle to the electrical control variable, assigned to the respective specific ophthalmic surgical handpiece, automatically available. It is further proposed that the generator unit be configured to superimpose several vibration components at different control frequencies to provide a predefined vibration shape of the controlled variable. In principle, the superposition can be implemented, for example, by an addition function. For this purpose, it can be provided that predefined suitable vibration components with their respective control frequencies are superimposed to realize the predefined vibration shape. Additionally or alternatively, the superposition can also include maximum value calculation, magnitude calculation, and / or other combinational functions. Preferably, the vibration components to be superimposed are sinusoidal vibrations.However, alternative configurations may also provide for the use of not only sinusoidal oscillations but also other oscillation shapes for superposition, such as rectangular oscillations, triangular oscillations or the like, in order to achieve a desired oscillation shape of the controlled variable. Furthermore, it is proposed that the generator unit be configured to perform the superposition at least partially as modulation. For this purpose, the control unit, in particular the generator unit, can include a modulator capable of implementing the desired modulation. Modulation methods can include, for example, amplitude modulation, frequency modulation, phase modulation, quadrature modulation, combinations thereof, and / or the like. The modulation can be implemented using a corresponding mathematical function. According to an advantageous embodiment, it is proposed that the control unit includes a sensor unit for detecting movement of the treatment needle, wherein the sensor unit is configured to output a sensor signal depending on the detected movement of the treatment needle, and wherein the generator unit is further configured to analyze the sensor signal spectrally with respect to the contained frequencies, taking into account the ratios of the mechanical displacement amplitude of the treatment needle to the electrical control variable at the respective control frequencies, and to determine the control variable depending on the analysis. The sensor unit can be configured as a separate unit that is communicatively connected to the control unit, in particular to an evaluation unit of the control unit.The evaluation unit, in turn, can be coupled via communication technology to the generator unit or a generator control unit of the control device in order to influence the provision of the control variable. The generator control unit serves, among other things, to provide one or more control signals for controlling the generator unit. Furthermore, the generator control unit, and in particular the evaluation unit, is preferably configured to access the storage unit so that the frequency-specific individual values ​​stored there for the ratio of the mechanical deflection amplitude of the treatment needle to the electrical control variable can be made available for evaluation.Furthermore, the sensor unit can be designed to be arranged with the handpiece, particularly in the area of ​​the treatment needle and / or the handpiece's drive unit, in order to detect the mechanical movement of the treatment needle, especially the cutting tip. The sensor unit can also be at least partially integrated into the handpiece, particularly the drive unit, which, for this purpose, is preferably capable of providing the sensor signal during breaks in normal operation, depending on the mechanical vibration of the treatment needle. In the case of a piezoelectric drive unit, the sensor unit can, for example, be a separate piezoelectric element within the drive unit.In addition, there is of course the possibility that the sensor unit uses other methods to detect the mechanical movement of the treatment needle, such as optical detection methods, magnetic detection methods and / or the like. The generator control unit, particularly when it includes the evaluation unit, is designed to analyze the sensor signal spectrally with respect to its contained frequencies. For this purpose, a frequency analysis unit may be provided, capable of performing a spectral analysis using a Fourier transform, a Laplace transform, and / or similar methods. In this way, a frequency spectrum of the sensor signal can be obtained, which can then be evaluated taking into account the frequency-specific relationship between the mechanical deflection amplitude of the treatment needle and the electrical control variable. This signal can then be used by the generator control unit to better adapt the control variable provided by the generator unit to the treatment needle.In particular, it is possible to compare this signal, which can be an actual signal, with a target signal, which can also be defined based on the individual values ​​stored in the memory unit for the ratios of the mechanical deflection amplitude of the treatment needle to the electrical control variable at different control frequencies. This also makes it possible to compensate for deviations from the target signal for the control variable, which may be caused, for example, by the generator unit, electrical cables, the handpiece, and / or the like. For this purpose, a comparison unit can be provided, which may be included in the generator control unit, especially the evaluation unit. Both the evaluation unit and the sensor unit are preferably electronic units that may include an electronic hardware circuit.Furthermore, at least the evaluation unit can also include or be formed by a computer unit. The sensor signal is preferably an electrical sensor signal, for example a voltage signal, a current signal, or the like. It can be an analog or a digital signal. Furthermore, it is proposed that the individual values ​​for the ratio of the mechanical deflection amplitude of the treatment needle to the electrical control variable be determined, at least for the control frequencies, during a calibration process. Although the calibration process can, in principle, be performed during normal operation, it is preferably carried out outside of normal operation. The calibration process can be performed using the control unit to which the respective handpiece is connected. This can be provided during the manufacture of the respective handpiece or similar device. This allows functional properties of the handpiece to be recorded and documented during manufacturing. Alternatively, the calibration process can, of course, also be performed on a calibration device specifically designed for this purpose.For example, a high-speed camera can be used to capture the movement of the treatment needle for calibration purposes. The high-speed camera can transmit corresponding image data to the evaluation unit, which determines the mechanical movement of the treatment needle. Based on this mechanical movement, a frequency spectrum can then be determined, as previously explained for the control variable. The control variable used to capture this mechanical movement of the treatment needle can also be spectrally analyzed, so that a frequency spectrum can be generated for this as well. The frequency spectra determined in this way can then be used to determine the values ​​for individual conditions. The values ​​obtained in this manner are then preferably stored in the storage unit.Alternatively, the individual values ​​for the ratio of the mechanical deflection amplitude of the treatment needle to the electrical control signal can also be determined without a corresponding high-speed camera, for example, by simply determining the individual values ​​for the ratio of the mechanical deflection amplitude of the treatment needle to the electrical control signal from knowledge of the corresponding amplitudes during a purely harmonic oscillation. For calibration, a camera is sufficient that can estimate the oscillation amplitudes with sufficient accuracy at selectively adjustable frequencies. Such cameras are readily available and inexpensive. Furthermore, this method avoids the need for a Fourier transform when determining the individual values ​​for the ratio of the mechanical deflection amplitude of the treatment needle to the electrical control signal, although this transformation may be required later. The advantages and effects specified for the control unit according to the invention naturally apply equally to the ophthalmic surgical device, the system, and the method according to the invention, and vice versa. In principle, device features can therefore also be formulated as method features, or vice versa. Further features of the invention will become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations without departing from the scope of the invention. Thus, embodiments of the invention that are not explicitly shown and explained in the figures, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed. Embodiments and combinations of features that do not exhibit all the features of an originally formulated independent claim are also to be considered disclosed.Furthermore, embodiments and combinations of features, in particular those set out above, are to be considered disclosed which go beyond or deviate from the combinations of features set out in the cross-references of the claims. The figures show: Fig. 1 a schematic representation of an embodiment of an ophthalmic surgical system with an embodiment of an ophthalmic surgical device comprising an ophthalmic surgical handpiece connected to a control unit of the ophthalmic surgical device; Fig. 2 a schematic representation of a simplified and reduced block view of the ophthalmic surgical device according to Fig. 1; Fig. 3 a schematic representation of the movement of a cutting tip of the treatment needle according to Fig. 1; Fig. 4 a schematic block view of the control unit and the handpiece connected to the control unit according to Fig. 2; Fig. 5 a schematic diagram representation of a spectral analysis of a mechanical movement of the cutting tip of the treatment needle according to Fig. 3; Fig. 6 a schematic diagram representation of a spectral analysis of a control voltage for the piezoelectric drive unit according to Fig. 4.2, so that the cutting tip of the treatment needle performs a mechanical movement according to Fig. 5; Fig. 7 a schematic diagram of an approximately triangular mechanical movement of the cutting tip of the treatment needle according to Fig. 3; and Fig. 8 a schematic diagram of a mechanical movement of the cutting tip of the treatment needle according to Fig. 3 that approximates the triangular shape according to Fig. 7. In the figures, the same reference symbols denote the same features and functions. Figure 1 shows a schematic representation of an ophthalmic microsurgical system, or ophthalmic surgical system 35, for phacoemulsification on a human eye 36. The representation in Figure 1 symbolically depicts some components of the system 35 for a simplified explanation of the basic general operating principle of the system 35. System 35 comprises a device unit 53, which may be, for example, a console or the like. A control unit 38 is preferably arranged in or on the device unit 53. Furthermore, a fluidics system 39 is preferably arranged in the device unit 53, which includes a pump and a control unit for controlling the pump and connected components. The fluidics system 39 comprises an irrigation device with an irrigation branch 40 and an aspiration device with an aspiration branch 41. The irrigation device has a container 42 for rinsing fluid, for example, a BSS solution, which is a fluid for irrigation, and which is directed to a phacoemulsification handpiece. The phacoemulsification handpiece is an ophthalmic surgical handpiece 3, hereinafter referred to simply as the handpiece. The aspiration device is connected to the handpiece 3.The handpiece 3 has a drive unit 2 with piezoelectric elements 43, by which a hollow needle 14, serving as the treatment needle of the handpiece 3, is mechanically vibrated. The hollow needle 14 has a cutting tip 58 (Fig. 3) which is brought into contact with the eye lens 52 for the purpose of emulsifying this eye lens 52. An ultrasound unit 54 of the device unit 53 comprises, in this case, at least one control unit 1 with at least one AC voltage generator 4 as a generator unit and with a generator control unit 8 (Fig. 2). The device unit 53 further comprises a control unit 55. The control unit 55 can also be configured to control a vitrectomy handpiece 46, which may in particular be a component of the ophthalmic surgical system 35. The vitrectomy handpiece 46 is preferably also connected to the fluidic system 39, in particular by an aspiration line 47. In addition, a further instrument control unit 48 may be provided, which controls a preferably further existing surgical instrument 49, for example for diathermy. Furthermore, the system 35, and in particular the device unit 53, may comprise further modules and control units as well as systems, which are symbolically represented by the unit 50. The ophthalmic surgical system 35 further preferably comprises a foot control panel 51, which is connected to the device unit 53.The foot control panel 51 allows functions of the ophthalmic surgical system 35 to be set. Figure 1 also schematically shows a natural lens 52 in a human eye 36. In an alternative embodiment, the ophthalmic surgical system 35 may have a tank 44 (Fig. 1) separate from the container 42. In a further embodiment, the separate tank 44 may be arranged in the handpiece 3. It may also be provided that a first separate tank 44 is arranged in the handpiece 3 and a further separate tank 56 is arranged externally to the handpiece 3. This further separate tank 56, external to the handpiece 3, may be fluid-conductingly connected to the first separate tank 44 arranged in the handpiece 3. Fig. 2 shows a simplified schematic block view of an ophthalmic surgical device 37 of the ophthalmic surgical system 35 according to Fig. 1. The ophthalmic surgical device 37 comprises the handpiece 3. The piezo-based drive unit 2 serves as a mechanical drive for the treatment needle 14 of the handpiece 3. In alternative embodiments, a magnetically based drive unit can be provided instead of or in addition to the piezo-based drive unit 2. The drive unit 2 is designed to excite the treatment needle 14 to mechanical vibrations such that a mechanical vibration is generated in a frequency range of approximately 20 kHz to approximately 80 kHz, preferably in a range of approximately 40 kHz. The vibration amplitude can be approximately 100 µm. The handpiece 3 also includes an EEPROM 12 as a data storage device for storing handpiece-specific data. This handpiece-specific data can include, for example, at least identification data that is unique to each individual handpiece 3. The ophthalmic surgical handpiece 3 also includes a communication interface 15, which is connected to the EEPROM 12 and serves to establish a communication link between the EEPROM 12 and the control unit 1. The ophthalmic surgical device 37 further comprises the control unit 1, which serves to operate the handpiece 3 in a predefined manner. The control unit 1 is therefore designed for the handpiece 3, which can be driven by the piezo-based drive unit 2, for manipulating an ocular lens 52. For this purpose, the control unit 1 is provided with a power supply interface 13, which includes a communication interface 11. The handpiece 3 also includes a power supply interface 16, which includes the communication interface 15. The power supply interface 13 is detachably connected to the power supply interface 16 of the handpiece 3 via a power supply line 18 and a plug connection (not shown). This allows the control unit 1 to be connected to different handpieces 3. The control unit 1 includes the controllable AC voltage generator 4, which is connected to the supply interface 13 via electrical lines 19 and provides an AC voltage 57 as a control variable for the drive unit 2. A corresponding electrical connection is provided on the handpiece side so that the drive unit 2 can be connected to the supply lines 19. The AC voltage has an adjustable amplitude in a range of approximately 20 V to approximately 30 V. The amplitude of the AC voltage 57 is adjustable depending on a control signal 6. The control signal 6 is provided by the generator control unit 8. Although the control variable is formed by an AC voltage in this configuration, in alternative embodiments the control variable can also be formed by another suitable variable, preferably electrical, such as an alternating current or the like.The type of control variable is preferably chosen to suit the design of the drive unit 2. To set the amplitude of the AC voltage 57, the control unit 1 has a power supply 20 which provides a supply voltage 17 for the AC voltage generator 4. The amplitude control signal 6 allows the value of the supply voltage 17, and consequently the amplitude of the AC voltage provided by the AC voltage generator 4, to be set. A further control signal 5 allows the control oscillation of the AC voltage 57 provided by the AC voltage generator 4 to be set. To determine the control signals 5, 6, the AC voltage generator 4 includes a voltage sensor 7 as a sensor unit, which is connected to the electrical lines 19. The voltage sensor 7 provides an electrical voltage or feedback voltage 10 as a sensor signal, which represents an electrical operating condition variable and depends on an operating state of the handpiece 3, in particular the treatment needle 14. To detect the feedback voltage 10, the AC voltage generator 4 is briefly deactivated. The feedback voltage 10 is supplied to a generator control unit 8 of the control device 1, which provides the control signals 5 and 6 depending on the feedback voltage 10. Simultaneously, the AC voltage generator 4 can be controlled by the generator control unit 8 such that it is briefly deactivated for the purpose of detecting the feedback voltage 10. The deactivation period is approximately 450 µs. This period is repeated at intervals of approximately 10 ms. The generator control unit 8 further comprises an evaluation unit 9 of the control device 1, which is configured to determine state variables or operating variables of the control device 1, in particular with regard to the feedback voltage 10 and the AC voltage 57, so that the control signals 5, 6 can be set accordingly. In addition, a display device can be connected to a display interface 21 of the control device 1. The display device allows the operator or user to view the operating states of interest. The display device is not shown in the figures. For this purpose, the evaluation unit 9 comprises a program-controlled computer unit that implements the necessary functions of the evaluation unit 9 and the generator control unit 8. Additionally, a hardware circuit can be provided as needed. Furthermore, an operating device 22 is connected to the control unit 1, in particular to the generator control unit 8, by means of which the operator can set the control signals 5, 6, depending on the current progress of the operation or the current operational situation. Communication interface 11 and communication interface 15 are wired together via supply line 18. This allows a communication connection to be established between the control unit 1 and the handpiece 3. This connection enables, among other things, the reading of identification data from the handpiece 3's EEPROM 12 and its provision to the generator control unit 8. The generator control unit 8 is connected to communication interface 11 for other purposes as well. Furthermore, the generator control unit 8 can store specific operating data for each handpiece 3 in its EEPROM 12. This allows the data to be individualized for each handpiece 3 and used to individually configure the control unit 1. For example, when the handpiece 3 is connected to the control unit 1, the corresponding data can be read from the EEPROM 12 and transmitted to the generator control unit 8. The generator control unit 8 can then control the AC voltage generator 4 accordingly, enabling a predefined function of the handpiece 3. Upon completion of an operation, the generator control unit 8 can store the data relating to the handpiece 3 back in its EEPROM 12 for later use. This allows for improved operation of the handpiece 3 with a specific control unit 1. Fig. 3 shows a schematic representation of how the cutting tip 58 of the treatment needle 14 moves mechanically during normal operation. The movement shown in Fig. 3 is a movement of the cutting tip 58 in a longitudinal direction, i.e., in the direction of the longitudinal extension of the treatment needle 14. However, the following explanations are equally applicable to torsional or rotary movements. During normal operation, the treatment needle 14, and in particular its cutting tip 58, is driven longitudinally by the drive unit 2.The cutting tip 58 thus performs a back-and-forth movement, the forward movement of the cutting tip 58 being a movement in which the cutting tip 58 moves away from the drive unit 2, whereas the opposite movement, the return movement, is a movement in which the cutting tip 58 moves towards the drive unit 2. In a path diagram shown in Fig. 3, a position s=0 is schematically depicted, which denotes a rest position of the cutting tip 58 when the drive unit 2 is not driving the treatment needle 14 outside of normal operation. Fig. 4 shows a further schematic block diagram of the control unit 1 and the handpiece 3 connected to the control unit 1, illustrating the respective functional blocks. To explain the details, this illustration assumes, for example, that the alternating voltage 57 comprises the oscillation of four control frequencies, namely frequencies f1 to f4, as further explained below with reference to Figs. 6 and 7. Figure 4 shows that the handpiece 3 comprises not only the treatment needle 14 and the piezoelectric drive unit 2, but also the memory unit 12, which in this case is designed as an EEPROM. The memory unit 12 stores, for example, individual values ​​for core admittances q1 to q4 assigned to respective control frequencies f1 to f4, for instance, in the form of a lookup table. The frequency f1 is assigned the core admittance q1, the frequency f2 the core admittance q2, and the frequency f3 the core admittance q3. The same applies to f4 and q4. Depending on requirements, the resulting table can be continued accordingly for further control frequencies. These individual values ​​in the memory unit 12 are determined specifically for the handpiece 3. Determining these values ​​can preferably be done during a calibration process outside of normal operation of the handpiece 3, preferably during the manufacture of the handpiece 3.For this purpose, the mechanical movement of the treatment needle 14, in particular its cutting tip 58, can be recorded with a suitable high-speed camera and analyzed with respect to mechanical and temporal parameters using an evaluation unit connected to the camera. The resulting motion sequence can then be spectrally analyzed, for example, by performing a Fourier transform, in particular a discrete Fourier transform, using a suitable program-controlled computer unit. A corresponding Fourier transform can also be performed for the alternating voltage 57 as a control variable. This makes it possible to determine the corresponding ratios or nuclear admittances q in a frequency-specific manner and to store them accordingly in the storage unit 12. However, this is not shown in the figures.Alternatively, the Fourier transform can be omitted when determining the corresponding ratios or core admittances q if the calibration for the individual harmonic oscillations is performed separately. However, a corresponding Fourier transform is then required later, that is, when analyzing a recorded motion pattern into its individual oscillation components. In the present embodiment, the control unit 1 comprises oscillators 23, 24, 25, and 45, which are adjustable in this configuration. The oscillators 23, 24, 25, and 45 are implemented in this configuration by electronic hardware circuits. In alternative embodiments, however, they can also be at least partially implemented by or encompassed by a program-controlled computer unit. The oscillators 23, 24, 25, and 45 are, in this configuration, part of the generator control unit 8. Each of the oscillators 23, 24, 25, and 45 provides an oscillator signal, which in this configuration is an alternating voltage signal with a predefined amplitude and a control frequency that is set differently for each oscillator. The generator control unit 8 also includes an oscillator control unit 26, which is configured to control the oscillators 23, 24, 25, and 45 with respect to the frequency to be set and to adjust the oscillators 23 to 25 and 45 accordingly with respect to the frequencies to be set. Furthermore, as can be seen in Fig. 4, the oscillator control unit 26 is communicatively coupled to the storage unit 12 of the handpiece 3. A nuclear admittance determination unit 30 of the generator control unit 8 is also communicatively coupled to the storage unit 12 of the handpiece 3. The nuclear admittance determination unit 30 determines the respective nuclear admittances q1 to q4 for the frequencies f1 to f4. The nuclear admittance determination unit 30 provides these values ​​to an amplitude factor unit 34, which is also included in the generator control unit 8.The amplitude factor unit 34 receives the corresponding AC voltage signals with normalized amplitudes from oscillators 23 to 25 and 45. The amplitude factor unit 34 receives the corresponding frequency-specific core admittances q1 to q4 from the core admittance determination unit 30. Taking the core admittances q1 to q4 into account, the amplitude factor unit 34 determines the respective amplitude values ​​for oscillation at the respective frequencies f1 to f4. These amplitude values ​​are used to determine the respective frequency-specific individual AC voltages. The individual AC voltages are then fed to a superposition unit 31 of the generator control unit 8, which superimposes the individual AC voltages to form a common AC voltage.This total alternating voltage is supplied to a control signal unit 29, which generates the corresponding control signals 5, 6 and provides them to the alternating voltage generator 4 to generate the alternating voltage 57. In the present embodiment, the voltage sensor 7 is further provided to output the feedback voltage 10 in a predetermined manner – as explained above – which is also supplied to the generator control unit 8. The feedback voltage 10 is supplied to a frequency analyzer 33, which analyzes the feedback voltage 10 of the voltage sensor 7 with respect to its frequency components. For this purpose, a Fourier transform or a discrete Fourier transform can also be provided. The frequency analyzer 33 is further configured to perform a comparison function. The feedback voltage 10, analyzed with respect to its frequency spectrum, can be further analyzed taking into account the nuclear admittances q1 to q4 provided by the nuclear admittance determination unit 30. This allows an actual signal to be provided.This actual signal can be compared with a predefined target signal to determine a differential control signal. This can then be used to determine the controlled variable. This allows for control of the AC voltage 57, thus reducing undesirable influencing effects, for example from the AC voltage generator 4 or similar devices. The generator control unit 8 further comprises a waveform generator 32, by means of which a temporal waveform for the mechanical movement of the treatment needle 14, in particular the cutting tip 58, can be set or specified. With the waveform generator 32, it is possible to specify the temporal waveform of the mechanical reciprocating movement of the treatment needle 14 or the cutting tip 58. The waveform can be, for example, a triangular waveform, a sawtooth waveform, a sinusoidal waveform, and / or the like. The waveform generator can be set accordingly using the operating device 22. The frequency analyzer 33 can also be used here to determine the control signals 5, 6. Using its comparison function and taking into account the core admittances q1 to q4 for the frequencies f1 to f4, the frequency analyzer 33 can determine whether the feedback voltage 10 contains the desired components to the desired extent. This makes it possible to provide a target signal with the curve shape generator and to follow the curve shape of the mechanical movement of the treatment needle 14 or the cutting tip 58 specified by the curve shape generator 32 as accurately as possible, because the feedback voltage 10 can deliver a corresponding value depending on an actual mechanical movement of the treatment needle 14 or the cutting tip 58. Figures 5 and 6 illustrate the potential effects of the invention. Figure 5 shows a standardized schematic diagram depicting a spectral analysis of the mechanical movement of the cutting tip 58 for a predetermined intended operation in a further embodiment. The mechanical movement shown in Figure 5 includes the oscillation of four frequencies: f1, f2, f3, and f4. The diagram in Figure 5 shows the corresponding amplitude components s relative to each other for these frequencies. Fig. 6 shows, in a schematic diagram similar to Fig. 5, a frequency spectrum for an alternating voltage u as a control variable, which generates the mechanical movement of the cutting tip 58 according to Fig. 5. It can be seen that the alternating voltage 57 here comprises the same frequency components f1 to f4. However, it is evident that the frequency spectrum according to Fig. 6 is required to generate the frequency spectrum according to Fig. 5. A comparison between the diagrams according to Fig. 5 and Fig. 6 shows that the relative oscillation components at the respective control frequencies are different. This is because the correspondingly assigned core admittances require a corresponding adjustment of the relative amplitude values ​​of the alternating voltage 57 in order to achieve the frequency spectrum according to Fig. 5.It is evident that the nuclear admittance is taken into account in a frequency-specific manner, which explains why, for example, the relative amplitude component at the control frequency f1 is significantly larger in the diagram according to Fig. 5 than in the diagram according to Fig. 6. For the control frequency f2, this is already the opposite. This is a consequence of the nuclear admittance differing at the control frequency f2 compared to the nuclear admittance at the control frequency f1. The same applies to the control frequencies f3 and f4. This explains why the invention makes it possible to control the movement of the cutting tip 58 or the treatment needle 14 significantly better than is possible with the prior art. Fig. 7 shows a schematic displacement-time diagram of the mechanical movement of the treatment needle 14, in particular its cutting tip 58, represented by graph 59. Fig. 7 shows that the cutting tip 58 performs an approximately triangular back-and-forth movement. Fig. 7 shows that the forward movement occurs during a period t1, while the return movement takes place during a period t2. Fig. 7 shows that the period t1 is considerably shorter than the period t2. It has been shown that, particularly with longitudinal movements, a rapid forward movement combined with a slow backward movement can significantly reduce heat input. Therefore, this movement proves to be particularly advantageous in this respect. However, graph 59 represents an idealized form of motion that can hardly be realized in practice. Fig. 8 shows, in a schematic displacement-time diagram like Fig. 7, an approximate motion with graph 60, which achieves comparable functionality to the motion according to graph 59 in Fig. 7. It can be seen that graph 60 shows an essentially mathematically continuous motion, unlike graph 59. A displacement-time function of this motion is preferably mathematically continuously differentiable, or smooth. This motion can be achieved, for example, by modulation. The modulation can be carried out, for example, according to the following formula: s0 denotes an amplitude of the mechanical displacement of the treatment needle and can, for example, assume a value of up to approximately 100 µm. a is a weight and can determine the difference between the fast forward motion and the slow backward motion.A typical value for a can, for example, be in the range of approximately 0.1 to approximately 0.75. Preferably, it can be approximately 0.5. ω contains the frequency in a known manner. This time course can be provided by means of the waveform generator 32. By processing this signal by means of the generator control unit 8 using frequency analysis, taking into account the frequency-specific core admittances, the AC voltage generator 4 can be set to provide a corresponding AC voltage 57, so that the desired time course of the oscillation of the treatment needle 14 can be achieved. Although the invention has been explained using longitudinal motion as an example, it is of course equally applicable to torsional motions, in particular torsional vibrations, as well as combinations of torsional and longitudinal motions. The invention is therefore not limited to use exclusively in longitudinal motions. The exemplary embodiments serve solely to illustrate the invention and are not intended to limit it.

Claims

Control unit (1) for an electric drive unit (2) of an ophthalmic surgical handpiece (3) for processing an eye lens (52), which drives a treatment needle (14), comprising a generator unit (4) for providing an electrical control variable (5, 6) for the electric drive unit (2), wherein the generator unit (4) is configured to provide the control variable (5, 6) with a control oscillation, wherein the control oscillation has a first oscillation component at a first control frequency, wherein the first oscillation component is adjustable depending on a first ratio of a mechanical displacement amplitude of the treatment needle (14) to the electrical control variable (5, 6) at the first control frequency, wherein the generator unit (4) is further configured to provide the control oscillation of the control variable (5, 6) with at least one further oscillation component at a further control frequency different from each other control frequency,that the further oscillation component is adjustable depending on a further ratio of the mechanical displacement amplitude of the treatment needle (14) to the electrical control variable (5, 6) at the respective further control frequency. characterized in that the generator unit (4) provides the control variable (5, 6) such that a first period attributable to a forward movement of the treatment needle (14) is shorter than a second period attributable to a return movement of the treatment needle (14). Control unit (1) according to claim 1, characterized by a storage unit (12) in which individual values ​​for the respective ratios of the mechanical deflection amplitude of the treatment needle (14) to the electrical control variable (5, 6) are stored, at least as assigned to the respective control frequencies. Control unit (1) according to claim 1 or 2, characterized in that the generator unit (4) is further configured to superimpose at least several oscillation components at different control frequencies in order to provide a predefinable oscillation shape of the control variable (5, 6). Control unit (1) according to claim 3, characterized in that the generator unit (4) is further configured to perform the superposition at least partially as modulation. Control unit (1) according to one of the preceding claims, characterized by a sensor unit (7) for detecting a movement of the treatment needle (14), wherein the sensor unit (7) is configured to output a sensor signal (10) depending on the detected movement of the treatment needle (14), and wherein the generator unit (4) is further configured to analyze the sensor signal (10) spectrally with respect to contained frequencies taking into account the ratios of the mechanical deflection amplitude of the treatment needle (14) to the electrical control variable (5, 6) at the respective control frequencies and to determine the control variable (5, 6) depending on the analysis. Ophthalmic surgical device (37) comprising: - an ophthalmic surgical handpiece (3) for manipulating an ocular lens (52), which can be driven by means of a drive unit (2); and - a control unit (1) which can be connected to the ophthalmic surgical handpiece (3) at least in intended operation, wherein the control unit (1) comprises a generator unit (4) for providing an electrical control variable (5, 6) for the electrical drive unit (2), wherein the generator unit (4) is configured to provide the control variable (5, 6) with a control oscillation, wherein the control oscillation has a first oscillation component at a first control frequency, wherein the first oscillation component is adjustable depending on a first ratio of a mechanical displacement amplitude of the treatment needle (14) to the electrical control variable (5, 6) at the first control frequency, wherein the generator unit (4) is further configured to control the control oscillation of the control variable (5,6) to provide at least one further oscillation component at a further control frequency different from each other control frequency, such that the further oscillation component is adjustable depending on a further ratio of the mechanical displacement amplitude of the treatment needle (14) to the electrical control variable (5, 6) at the respective further control frequency. characterized in that the generator unit (4) is further configured to provide the control variable (5, 6) such that a first period attributable to a forward movement of the treatment needle (14) is shorter than a second period attributable to a return movement of the treatment needle (14). Ophthalmic surgical system (35) for processing an eye lens (52), comprising at least: - an irrigation device (6), - an aspiration device (7), and - an ophthalmic surgical device (37), characterized in that the ophthalmic surgical device (37) is configured according to claim 6. Method for operating an electric drive unit (2) of an ophthalmic surgical handpiece (3) for operating a treatment needle (14), which is used for processing an eye lens (52), wherein an electrical control variable (5, 6) with a control oscillation is provided by means of a generator unit (4), wherein the control oscillation has a first oscillation component at a first control frequency, wherein the first oscillation component is set depending on a first ratio of a mechanical displacement amplitude of the treatment needle (14) to the electrical control variable (5, 6) at the first control frequency, wherein the control oscillation of the control variable (5, 6) with at least one further oscillation component is provided at a further control frequency different from each other control frequency,wherein the further oscillation component is adjusted depending on a further ratio of the mechanical displacement amplitude of the treatment needle (4) to the electrical control variable (5, 6) at the respective further control frequency, characterized in that the generator unit (4) provides the control variable (5, 6) such that a first period attributable to a forward movement of the treatment needle (14) is shorter than a second period attributable to a return movement of the treatment needle (14). Method according to claim 8, characterized in that the individual values ​​for the ratio of the mechanical deflection amplitude of the treatment needle (14) to the electrical control variable (5, 6) are determined at least for the first and at least one second frequency during a calibration process.

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