Laser pulse generator, and method for generating a laser pulse

Abstract

The invention relates to a laser pulse generator (10) comprising: a) a pulse shape generating device (12) having - a pulse shape memory (16) for storing data and a digital-to-analogue converter (16) connected thereto, - a first connection (20) for supplying a clock signal (100), and - a second connection (22) for outputting an output signal (106), the digital-to-analogue converter (16) generating an output signal (106) in synchronisation with a clock signal (100) received at the first connection (20), which output signal is output at the second connection (22); b) a synchronisation circuit (30) which has a third connection (32) for connecting a trigger signal line (34) transmitting a trigger signal (104) and is connected to the second connection (22); and c) a clock stopping element (38) which is connected to the first connection (20), the synchronisation circuit (30) being designed to control the clock stopping element (38) depending on the trigger signal (104) and depending on the output signal (106) output at the second connection (22).

Description

[0001] Laser pulse generator and method for generating a laser pulse

[0002] The invention relates to a laser pulse generator with a pulse shape generation device, comprising a pulse shape memory for storing data and a digital-to-analog converter connected thereto, a first terminal for supplying a clock signal, and a second terminal for outputting an output signal. The digital-to-analog converter generates an output signal at the second terminal in synchronization with a clock signal received at the first terminal. Furthermore, the invention relates to a method for generating a laser pulse.

[0003] State of the art

[0004] Such a laser signal generator is known, for example, from CN 213547471 U and DE 10 2016 212 929 A1.

[0005] Laser diodes generate a laser pulse by controlling a laser diode driver with a laser pulse shape. Laser pulse shapes can be easily output via a digital-to-analog converter. The contents of a pulse shape memory are output via the digital-to-analog converter with an output clock. Pulse-on-demand triggering initiated by the user can result in output jitter, as the start event or trigger event does not necessarily correlate with the output clock of the memory or digital-to-analog converter.

[0006] Both DE 102016212 929 A1 and CN 213547471 U use a logic component, in particular an FPGA, to generate a laser pulse shape. With such logic circuits, it is not possible to generate nanosecond laser pulses with a length in the range of 25 nanoseconds without jitter.

[0007] Task

[0008] The object of the present invention is therefore to provide a laser pulse generator and a method for generating a laser pulse with which a laser pulse with low output jitter, in particular a laser pulse that can be shaped in nanosecond steps, can be generated.

[0009] Solution

[0010] This object is achieved according to the invention by a laser pulse generator with a) a pulse shape generation device, comprising

[0011] - a pulse shape memory for storing data and an associated digital-to-analog converter,

[0012] - a first terminal for supplying a clock signal,

[0013] - a second terminal for outputting an output signal, wherein the digital-to-analog converter generates an output signal at the clock of a clock signal arriving at the first terminal, which output signal is output at the second terminal, b) a synchronization circuit which has a third terminal for connecting a trigger signal line transmitting a trigger signal and is connected to the second terminal, c) a clock stop element which is connected to the first terminal, wherein the synchronization circuit is configured to control the clock stop element as a function of the trigger signal and the output signal output at the second terminal.

[0014] Advantageous embodiments, which can be used individually or in combination with one another, are the subject of the dependent claims. The laser pulse generator according to the invention can generate nanosecond laser pulses with an adjustable temporal shape. The temporal shape can be adjusted using the data stored in the pulse shape memory. The pulse shape memory can be filled via a microcontroller. The microcontroller can be connected to the pulse shape memory via a bus, in particular an SPI bus.

[0015] With the laser pulse generator according to the invention, it is particularly possible to perform the steps in which the laser pulse is to be formed in the range of a few nanoseconds or even in the sub-nanosecond range. The laser pulse can be requested arbitrarily, i.e., randomly. The request is made via the trigger signal on the trigger signal line. The jitter of the laser pulse generated in response to the output signal is less than two nanoseconds with the laser pulse generator according to the invention. The laser pulse generator is preferably designed without an FPGA (Field Programmable Gate Array) or comparable logic circuit.

[0016] The pulse shape memory can be integrated into the digital-to-analog converter. The contents of the pulse shape memory can be cyclically output in time with the clock signal, which can be in the range 50 MHz - 2.5 GHz. In response to a trigger signal and a specific state of the output signal, the clock signal can be stopped by appropriately controlling the clock stop element, which is preferably connected to a clock unit, in particular a clock signal generator. Subsequently, in particular after a predetermined time, the clock signal can be released again and passed in a defined manner to the digital-to-analog converter, so that an output signal corresponding to a laser pulse shape is generated with minimal jitter. This output signal can be passed to an amplifier connected upstream of a laser diode to generate a laser pulse.

[0017] The synchronization circuit can have a monitoring element for monitoring the output signal. In particular, the monitoring element can be configured to monitor an edge of the output signal or whether the output signal exceeds or falls below a reference value. This ensures that the clock signal is only stopped when the output signal of the digital-to-analog converter is at a specific point. This ensures that the clock signal is only stopped at each trigger event when the pulse shape memory is at a precisely defined point.

[0018] The synchronization circuit may include a control element connected to the clock stop element, which is connected to the third terminal. This ensures that the clock stop element is only stopped when a laser pulse is requested, i.e., when a trigger signal is present.

[0019] The control element can be designed as a logic module.

[0020] Advantageously, the control element can be connected to the monitoring element. Thus, both the trigger signal and the output signal of the monitoring element can be fed to the control element. Only when a corresponding signal combination is present can the clock signal be stopped by controlling the clock stop element accordingly.

[0021] Advantageously, the control element has a timing element. The timing element causes the clock signal to be released again after a predetermined time. The timing element can be programmable, allowing different predetermined times to be programmed.

[0022] A switching element controlled by the synchronization circuit, in particular the control element, can be connected to the second terminal. The switching element can be controlled such that the output signal is only forwarded to an amplifier when synchronization has occurred.

[0023] The invention also includes a method for generating a laser pulse, comprising the steps of: a) outputting data, in particular a digitally coded pulse shape, from a pulse shape memory to a digital-to-analog converter (DAC); b) generating an output signal in the DAC at the rate of a clock signal of a clock unit and outputting the output signal, wherein c) the clock signal is synchronized taking the output signal into account.

[0024] In this way, an output signal from which a laser pulse is generated can be generated with low jitter.

[0025] The output signal can be monitored, particularly with regard to its value or its edges. In particular, the clock signal can be stopped if the output signal falls below a specified value.

[0026] In response to a trigger signal, the clock signal can be suspended for a specified time. It can be provided that the clock signal is only suspended when, on the one hand, the trigger signal is present and, on the other hand, the output signal fulfills a specified condition.

[0027] In response to the trigger signal, the output signal can be forwarded to an amplifier connected upstream of a laser diode. This can occur with a time delay, namely when a specified time has elapsed after the trigger signal is applied and the output signal assumes a specified value.

[0028] Further features and advantages of the invention will become apparent from the following detailed description of an exemplary embodiment of the invention, based on the figures of the drawing, which show details essential to the invention, and from the claims. The features shown therein are to be understood to scale as necessary and are presented in such a way that the special features of the invention can be clearly seen. The various features can be implemented individually or in combinations in variants of the invention. List of Figures

[0029] The invention is explained in more detail below using an advantageous embodiment illustrated in the figures. However, the invention is not limited to this embodiment.

[0030] They show:

[0031] Fig. 1 : a schematic representation of a laser pulse generator; and

[0032] Fig. 2: Diagrams explaining the functionality of the

[0033] Laser pulse generator.

[0034] Figure 1 shows a laser pulse generator 10. The laser pulse generator has a pulse shape generation device 12. This has a pulse shape memory 14 and a digital-to-analog converter 16. In the illustrated embodiment, the pulse shape memory 14 is connected to a ring counter 18. The contents of the pulse shape memory 14 can be cyclically output using the ring counter 18 when a clock signal, in particular a clock signal > 50 MHz, is applied to a first terminal 20. The digital-to-analog converter 16 generates an analog output signal from the output data, which is output at the second terminal 22. The shape of the output signal is determined by the data stored in the pulse shape memory 14. The shape of the output signal can therefore correspond, in particular, to a laser pulse shape.The pulse shape generation device 12 has an interface 24 via which a microcontroller can be connected, which in turn can be used to fill the pulse shape memory 14 with data. The pulse shape memory 14 can have 64 memory locations.

[0035] Since the data memory content is output cyclically using the ring counter 18, temporal synchronization with an external signal is not possible. The pulse pattern in the pulse shape memory is output continuously. To nevertheless achieve synchronization, a synchronization circuit 30 is provided. The synchronization circuit 30 has a third terminal 32 for connecting a trigger signal line 34 transmitting a trigger signal. The synchronization circuit 30 has a control element 36, which is used to respond to the trigger signal transmitted on the signal line 34. The synchronization circuit 30, and in particular its control element 36, is connected to a clock stop element 38. The clock stop element 38 is connected to a clock signal generator 40 or can be connected to such a clock signal generator. In the illustrated embodiment, the clock signal generator 40 is connected to the first terminal 20 via the clock stop element 38.In response to the trigger signal transmitted on trigger signal line 34, control element 36 can control clock stop element 38 to prevent the clock signal from clock signal generator 40 from being applied to first terminal 20. Thus, the clock stop element 38 can deactivate the clock signal for digital-to-analog converter 16 and pulse shape memory 14. However, the clock signal should only be stopped when the output signal output at terminal 22 is at a specific point. This specific point can be detected via a monitoring element 42 of synchronization circuit 30. Monitoring element 42 is connected to terminal 22 for this purpose.

[0036] Thus, when the monitoring element 42 detects that the output signal is at a specific point and a corresponding trigger signal is present, the clock stop element 38 is controlled by the control element 36 to stop the clock. At the same time, the switching element 44 is controlled, in particular, closed, by the control element 36 to output the next pulse from the pulse shape generation device 12 to the amplifier 46 when the clock restarts at terminal 20.

[0037] After a predetermined time, for example, 100 nanoseconds, the clock stop element 38 is controlled again by the control element 36 to release the clock signal again. The clock signal now controls the ring counter 18 and the digital-to-analog converter 16 again. The pulse shape stored in the pulse shape memory 14 is output again until a specific point in the pulse pattern is reached and the monitoring element 42 reacts again. As a result, the control element 36 receives a reset command and controls the switching element 44 again to prevent the output signal from being passed to the amplifier 46. The switching element 44 is controlled, in particular opened, by the control element 36 in such a way that the output signal of the pulse shape generation device 12 is prevented from being passed on to the amplifier 46 and via it to the laser diode 48.

[0038] A laser diode 48 is driven by the amplifier 46.

[0039] The operation is described using the diagrams in Figure 2. The signal 100 corresponds to the signal output by the clock signal generator 40 at point I in Figure 1. The signal 102 corresponds to the signal at point II on the first terminal 20. The signal 104 corresponds to a trigger signal at point III in Figure 1.

[0040] Signal 106 corresponds to the output signal at point IV of Figure 1 at the second terminal 22. Signal 108 corresponds to the signal at point V of Figure 1. Signal 110 corresponds to the signal at point VI at the input of the laser diode 48.

[0041] Accordingly, if the control element 36 detects a rising edge 104a of the trigger signal 104 and the monitoring element 42 further signals that the signal 106 at the second terminal 22 is below a predetermined reference value, the control element 36 controls the clock stop element 38 to prevent the clock signal 100 from being output to the pulse shape generation device 12. This point in time is marked by the line 112. After a predetermined time t0, which can be stored in the time element 50, has elapsed, the control element 36 controls the clock stop element 38 again so that the clock signal is again output to the pulse generation device 12. At the same time, the control element 36 controls the switching element 44 so that the output signal 106 can be output to the amplifier 46. The output signal 106 is generated again from point 114 onwards due to the renewed clock signal being present.Amplifier 46 amplifies output signal 106 and supplies signal 110 to laser diode 48. If monitoring device 42 again detects that output signal 106 is at a specific position, in particular, falls below a specific value, control element 36 is reset and switching element 44 is opened, which occurs at point 116. The features disclosed in the above description, claims, and drawings can be important both individually and in combination for the implementation of the invention in its various embodiments.

Claims

Patent claims Laser pulse generator (10) with a) a pulse shape generation device (12), comprising - a pulse shape memory (16) for storing data and a digital-to-analog converter (16) connected thereto, - a first terminal (20) for supplying a clock signal (100), - a second terminal (22) for outputting an output signal (106), wherein the digital-to-analog converter (16) generates an output signal (106) in time with a clock signal (100) arriving at the first terminal (20), which output signal is output at the second terminal (22), characterized in that b) a synchronization circuit (30) is provided which has a third terminal (32) for connecting a trigger signal line (34) transmitting a trigger signal (104) and is connected to the second terminal (22), c) a clock stop element (38) is provided which is connected to the first terminal (20), wherein the synchronization circuit (30) is configured to control the clock stop element (38) as a function of the trigger signal (104) and the output signal (106) output at the second terminal (22). Laser pulse generator according to claim 1, characterized in that the synchronization circuit (30) has a monitoring element (42) for monitoring the output signal (106).Laser pulse generator according to claim 1 or 2, characterized in that the synchronization circuit (30) has a control element (36) connected to the clock stop element (38) and connected to the third terminal (32). Laser pulse generator according to claim 3, characterized in that the control element (36) is connected to the monitoring element (42). Laser pulse generator according to one of the preceding claims, characterized in that the control element (36) has a time element (50). Laser pulse generator according to one of the preceding claims, characterized in that a switching element (44) is connected to the second terminal (22), which is controlled by the synchronization circuit (30), in particular the control element (42). Method for generating a laser pulse, comprising the steps of: a) outputting data, in particular a digitally coded pulse shape, from a pulse shape memory (14) to a digital-to-analog converter (DAC) (16), b) generating an output signal (106) in the DAC (16) in time with a clock signal (100) of a clock unit and outputting the output signal (106), characterized in that c) the clock signal (100) is synchronized taking the output signal (106) into account.Method according to claim 7, characterized in that the output signal (106) is monitored, in particular with regard to its value or its edges. Method according to claim 7 or 8, characterized in that, in response to a trigger signal (104), the clock signal (100) is suspended for a predetermined time (t0). Method according to one of claims 7 to 9, characterized in that, in response to the trigger signal (104), the output signal (106) is forwarded to an amplifier (46) connected upstream of a laser diode (48).

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