Method for operating a radiation detector and radiation detector

Abstract

The invention describes a method for operating a radiation detector (5), in particular an X-ray radiation detector. The radiation detector (5) has a control device (2) for generating a control signal (S A ) for an illumination unit (4). The control signal (S A ) is generated by means of a pulsed current source (12) and a direct current source (14), wherein the pulsed current source (12) generates a pulsed signal portion (S P ) and the direct current source (14) generates a direct current component (S G ). The pulsed signal portion (S P ) and the direct current component (S G ) are superimposed for generating the control signal (S A ) and are delivered to the illumination unit (4). The invention also describes a radiation detector (5).​​​​​​​​​​​​​​

Description

Technical Field

[0001] The present invention relates to a method for operating a radiation detector. The present invention also relates to a radiation detector. Background Art

[0002] Imaging devices in medical diagnostics, such as x-ray devices, typically have a radiation detector, in particular an x-ray radiation detector, or x-ray detector for short.

[0003] X-ray detectors are usually designed as scintillator detectors or as detectors with direct converters.

[0004] A scintillator detector comprises a scintillator material. The scintillator material is excited by irradiation with X-ray radiation and emits the excitation energy in the form of light. The emitted light is then converted into an electrical signal, for example, by means of a photodiode and evaluated in an evaluation unit. Scintillator detectors typically have a plurality of scintillator elements arranged in an array. Similarly, photodiodes are also arranged in an array.

[0005] Detectors with direct converters usually have a semiconductor material, for example a cadmium telluride-based semiconductor, which converts radiation incident thereon, for example X-ray radiation, into an electrical signal.

[0006] The operating mode of a direct converter detector can be roughly simplified as follows: X-ray radiation impinging on a semiconductor generates charge carriers in the form of electron-hole pairs within the semiconductor. During operation, a voltage, the so-called bias voltage, is applied to the semiconductor. This voltage generates an electric field (E field) in the semiconductor. Due to the E field, the electron-hole pairs are subjected to forces that separate them from one another and move toward electrical contact elements, which are provided on the upper side of the semiconductor element and on the lower side of the semiconductor for applying the bias voltage. The charge pulses thus generated are then detected and evaluated by means of a recording unit. A precise description of the operating mode of a direct converter detector can be found, for example, in DE 2015 201 494 A1.

[0007] Direct-conversion detectors often exhibit polarization when irradiated with X-ray radiation, particularly at high X-ray intensities. Polarization describes undesirable changes in the E field within the semiconductor material of the detector. Therefore, polarization has a direct impact on detector properties, such as the charge carrier transport properties of the semiconductor material.

[0008] Polarization is often the result of defects, such as those in the form of vacuities that occur during semiconductor production. Furthermore, polarization is temperature-dependent with respect to the semiconductor material and / or the incident radiation. In other words, the polarization effect of a direct-conversion detector is, on the one hand, a production-dependent property, and, on the other hand, an operation-dependent property. The latter leads to an operation-dependent and, thus, time-dependent dependence of the polarization effect. This means that the polarization state of the detector can vary over time; for example, the detector may have a different polarization state before treatment than after treatment.

[0009] In particular, the signal characteristics of the received measurement signal change due to polarization. For example, the intensity of the measurement signal changes over time while the radiation intensity or radiation dose remains constant. This effect is also known as signal drift and has a negative impact on the functionality of the detector.

[0010] DE 10 2015 201 494 A1 describes a method for determining the polarization state of an X-ray detector (hereinafter referred to as detector) in order to reduce signal drift.

[0011] In this case, the detector is irradiated with a sequence of light pulses. The individual light pulses have different intensities. Furthermore, the intensity of the light pulses is determined at which the charge pulse generated by the detector exceeds a predefined threshold voltage. The threshold voltage is set, for example, by means of a signal detection unit. In other words, a relationship is established between the irradiation intensity and the threshold voltage determined to be exceeded. This relationship changes depending on the polarization state of the detector, from which the polarization state of the detector can be determined. Thus, the detector can be set to a certain signal drift by suitable measures, such as calibration, i.e., the detector can be set in such a way that a shift in the measurement signal is reduced and / or compensated.

[0012] For driving LEDs, certain requirements arise, such as certain requirements regarding the switching times of the components used for driving. To meet these requirements, complex and expensive components are currently used. Summary of the Invention

[0013] Based on this, the present invention is based on the object of enabling reliable operation of a radiation detector with the aid of a simple design.

[0014] According to the invention, this object is achieved by a method for operating a radiation detector having the features of an exemplary embodiment.

[0015] Advantageous embodiments, variants and improvements are the subject matter of the exemplary embodiments.

[0016] During operation, the radiation detector is irradiated with light by means of an irradiation unit, in particular an LED unit, for determining the polarization. This is used to set the radiation detector in a defined manner, as is known, for example, from DE 10 2015 201 494 A1.

[0017] The radiation detector is in particular an X-ray radiation detector, preferably a direct-conversion detector as described at the outset.

[0018] The illumination unit includes an operating device. The LED is operated using an operating signal generated by the operating device. The operating signal is advantageously formed by the superposition of two signal components. This means that the signal includes a pulsed signal component and, optionally, a DC component superimposed on the pulsed signal component. In this context, the term "optional" should be understood to mean that the LED can also be operated during operation using only the pulsed signal component. This is due to the fact that the operating device includes a direct current source (DC current source) and a pulsed current source.

[0019] Similarly, the pulse signal portion is generated by a pulsed current source, and the DC component is generated by a DC current source. Therefore, the two signal portions are initially generated separately. The pulse signal portion is then superimposed with the DC component and supplied to the LED. Similarly, the control signal is related to the current conducted through the LED. This current, hereinafter referred to as the LED current, is directly related to the LED's intensity. For example, if the LED current increases, the LED's intensity also increases.

[0020] To superimpose the pulse signal portion with the DC component, the value of the DC component is added to all values ​​of the pulse signal. In other words: viewed in a Cartesian coordinate system, the DC component "shifts" the pulse signal portion along the ordinate axis by the value of the DC component.

[0021] By applying the DC component of the control signal to the LED and, therefore, the semiconductor material of the radiation detector, the short-term drift of electron-hole pairs is reduced. This means that signal stability remains constant over time, as the radiation detector exhibits less signal drift than would be the case without applying the DC component of the control signal to the semiconductor material. This results in improved image quality.

[0022] In a first measurement, a pulse signal portion is used to generate a brief electron transport of electron-hole pairs within the semiconductor material of the radiation detector. This electron transport generates the charge pulse described above within the semiconductor material. This charge pulse generates a count event within a signal detection unit known from DE 10 2015 201 494 A1, such as an application-specific integrated circuit (ASIC), which is detected and stored by the ASIC. After a defined number of operating hours, preferably within a day, for example, three hours, the radiation detector is again loaded with the pulse signal portion in a second measurement, and the charge pulse is detected, along with count events. The count events detected and stored in the second measurement are then compared with the count events of the first measurement. The deviation between the two count events is then used as a correction value for the signal measured when the radiation detector is operated with X-ray radiation. This has the advantage of improving and / or preventing signal drift, particularly long-term drift, in the radiation detector.

[0023] The pulse signal portion has, in addition to its amplitude, a periodic pulse pattern, preferably a local wave signal, both of which are set by means of a pulse current source. A periodic pulse pattern is understood to mean that signal pulses, preferably local wave pulses, repeat at constant, recurring time intervals.

[0024] To this end, according to a preferred embodiment, the pulse current source has a first switching element, preferably an electronic load, for setting the amplitude and thus the pulse height of the pulse signal. Furthermore, the pulse current source has a second switching element, preferably a switch, connected in series with the first switching element, by means of which the pulse pattern of the pulse signal portion is set.

[0025] The design is based on the consideration that the generation of the pulse signal portion is "distributed" between two switching elements in order to enable simple and cost-effective generation of the pulse signal portion. To set the pulse height of the pulse signal portion, the first switching element comprises a commercially available switch, preferably a transistor. The second switching element also comprises a commercially available switch, in particular a transistor. The difference between the switching of the first switching element and the switching of the second switching element can be seen in the switching times of the switches. In other words: from a circuit technology perspective, the switching of the first switching element has a slower switching time than the switching of the second switching element, via which the pulse pattern of the pulse signal portion is set. Therefore, only "fast-switching" components are required to generate the pulse signal portion.

[0026] To generate the pulse signal portion, the amplitude of the current is first set via the first switching element. This current then flows through the second switching element, where, for example, a square-wave signal with a defined edge steepness and a defined pulse width is formed by repeatedly switching the second switching element off and on again. Edge steepness is defined as the time period required for the control signal to reach its full amplitude value. For example, if the control signal has an edge steepness of 10 ns and an amplitude of 100 mA, the value of the control signal rises to 100 mA within 10 ns after switching on.

[0027] In this context, pulse width is understood to be the time period during which, for example, a square wave signal has its full amplitude before the signal drops back down. For example, if a square wave signal has a pulse width of 200 ns and an amplitude of 150 mA, then after increasing to an amplitude of 150 mA, the value of the square wave signal remains constant for, for example, 200 ns before dropping back down to a value of 0 A. The pulse width thus represents the "width" of the rectangle of the square wave signal.

[0028] The pulse signal portion of the control device preferably has a sequence of single pulses whose amplitudes increase. In other words: the signal is generated as a pulse signal portion, which has a sequence of single pulses. Each single pulse has an amplitude (pulse height). The pulse signal portion is preferably set so that the amplitude of the single pulse remains constant over a time interval, for example in the range of 1 μs to 5 μs. Subsequently, the subsequent pulse sequence has a higher amplitude. With this design, the amplitude of the single pulse increases in a step-shaped manner. Alternatively, each single pulse has a higher amplitude than the previous single pulse, which causes a ramp-shaped increase in the amplitude of the single pulse.

[0029] Preferably, as described at the outset, the value of the charge pulse is increased in circuit technology until it exceeds the value of a predetermined threshold voltage of the signal detection unit. In this case, exceeding is to be understood as meaning that the value of the charge pulse has at least the value of the predetermined threshold voltage, preferably a value greater than the value of the threshold voltage.

[0030] According to a particularly preferred embodiment, the absolute amplitude accuracy of the pulse signal components is not adjusted. This embodiment is based on the idea that, as already described, a comparison of the count events determined by at least two measurements is important for calibration and, therefore, for reducing signal drift. Detecting the relative amplitude change of the pulse signal components, particularly with respect to the ampere value, is preferred over detecting the absolute amplitude change for calibrating the radiation detector.

[0031] In other words: For example, if the difference in the amplitude of the control signal between the count events has a value of 20 mA, then 20 mA is required for calibration as the relative difference between the two measurements. Whether the determined difference of 20 mA is due to an amplitude difference of 100 mA to 120 mA or 60 mA to 80 mA is of secondary importance with regard to the method for reducing signal drift.

[0032] However, in at least two measurements, the pulse sequence expediently has the same ramp shape and the same starting value. The amplitude of the ramp shape preferably lies in the range of several hundred milliamperes.

[0033] The DC current source expediently has a third switching element, preferably an electronic load, by means of which the level of the direct current component is set.

[0034] This design has the advantage that, since the DC component is set by means of a separate switching element, it can be more easily introduced into and / or removed from the pulsed signal portion. Furthermore, this design offers advantages in terms of cost and circuitry. Conventional and, in particular, cost-effective components can be used for implementation.

[0035] According to a preferred refinement, the illumination unit, in particular an LED, is exposed to a DC component for the entire duration of the activation. Consequently, the semiconductor material of the radiation detector is illuminated with permanent light for the entire duration of the activation. The DC component is incorporated into the pulse signal portion to condition the semiconductor material. This allows for a more precise determination of the polarization.

[0036] The individual pulses provided preferably have an edge steepness with a value in the range of 10 ns to 15 ns, in particular a maximum of 20 ns.

[0037] According to one expedient embodiment, the individual pulses are dimensioned such that they have a pulse width in the range of 80 ns to 120 ns and preferably in the range of 90 ns to 110 ns.

[0038] The described edge steepness and the described pulse width have proven suitable for generating electron transport in semiconductor materials of radiation detectors.

[0039] The object is also achieved by a radiation detector having the features of an exemplary embodiment.

[0040] The radiation detector described in the introduction, in particular an X-ray detector, has a control device for an irradiation unit, in particular an LED unit. The control device has a pulsed current source and a direct current source (DC current source).

[0041] The embodiment of the control device divided into a pulsed current source and a DC current source results in a simple and cost-effective construction.

[0042] Furthermore, the pulse current source and the DC current source are connected in parallel relative to one another. The parallel connection is based on the consideration that the superposition of the two signals is taken into account in the manner described.

[0043] The pulse current source expediently has a first switching element and a second switching element connected in series to the first switching element. The first switching element is used to set the amplitude (pulse height) of the pulse signal portion, and the second switching element is used to set the pulse pattern of the pulse signal portion.

[0044] For this purpose, the first switching element preferably has an electronic load—also called a current sink—and the second switching element preferably has a switch.

[0045] An electronic load is an electronic component or assembly consisting of components that are typically arranged in a circuit as an alternative to a load resistor. The difference between an electronic load and, for example, a (conventional) ohmic resistor can be seen in their adjustability. In other words: while an ohmic resistor connected to a voltage source flows a current with a constant value, the current flowing through an electronic load can be set within a defined value range, for example, using an electronic regulator.

[0046] Furthermore, the electronic load preferably has an electronic switch, in particular a transistor, for adjusting the current.

[0047] Both the electronic load of the first switching element and the switch of the second switching element preferably have electronic switches, in particular transistors.

[0048] The electronic switches provided in the switching elements differ in their switching times. The switching time is directly related to the transition frequency, which describes the switching frequency of the transistor. To set the pulse height of the pulse signal portion, the first switching element comprises an electronic switch, in particular a transistor, which preferably has a transition frequency with a value in the range of 100 MHz to 200 MHz. The slow transition frequency for the electronic switch is based on the consideration that, in order to set the pulse height of the pulse signal portion, a switching frequency within a specified value range is sufficient, in particular taking into account the preferred step-like increase in the pulse height.

[0049] The second switching element expediently comprises an electronic switch, in particular a transistor, having a switching frequency with a value in the range of 500 MHz to 2 GHz, in particular a value in the range of 1 GHz to 1.5 GHz. Preferably, the second switching element typically has a switching frequency that is, for example, at least 5 times, preferably 10 times, the required switching frequency, which is calculated from the required edge steepness. The second switching element is therefore designed to set a pulse pattern that preferably has an edge steepness with a value in the range of 10 ns to 20 ns.

[0050] The advantage is that, due to the separate generation of the pulse signal parts, cost-effective components can be used, in particular in the components of the first switching element, so that the actuation device still meets the same requirements as conventional, expensive actuation devices.

[0051] The DC current source preferably has a third switching element for setting the DC component. An electronic switch, in particular a transistor, is preferably provided in the third switching element. The electronic switch has a switching frequency with a value in the range of 100 MHz to 200 MHz. Due to the long-term irradiation of the semiconductor material, this design has the advantage of cost-effective production of the switching element due to simpler components, as opposed to fast switching times. Furthermore, the electronic switches of the first and third switching elements preferably have identical components.

[0052] The advantages and preferred embodiments listed with respect to the method apply analogously to the device, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] An exemplary embodiment of the present invention will be described in detail below with reference to the accompanying drawings, which show, in a partially greatly simplified diagram:

[0054] Figure 1 a circuit diagram showing an irradiation unit and a control device connected to the irradiation unit, and

[0055] Figure 2 A schematic detail of an actuation signal is shown.

[0056] In the figures, components having the same function are denoted by the same reference numerals. DETAILED DESCRIPTION

[0057] Figure 1 1 shows a simplified circuit diagram of an embodiment variant of a control device 2 for an irradiation unit 4, in particular an LED unit 6. The irradiation unit 4 serves to irradiate a radiation detector 5. The radiation detector 5 is the X-ray radiation detector described at the outset.

[0058] In this context, the LED unit 6 is understood to be an arrangement of a plurality of individual LEDs arranged in an array. Furthermore, the illumination unit 4 has a power supply unit 8 for supplying a supply voltage to the LED unit 6 and the control device 2. The control device 2 and the illumination unit 4 are electrically connected to each other via a line 10. The LED unit 6 has conventional LEDs or alternatively infrared LEDs.

[0059] The control device 2 and the irradiation unit 4 are designed to irradiate a semiconductor material of a radiation detector, in particular an X-ray radiation detector. By means of the irradiation, the polarization state of the radiation detector can be determined.

[0060] In order to irradiate the semiconductor material, the control signal S A The LED unit 6 is acted upon, the control signal being generated by means of the control device 2 .

[0061] For this purpose, the control device 2 in the exemplary embodiment has a pulsed current source 12 and a direct current source (DC current source) 14 .

[0062] Therefore, the control signal S A It has two signal parts: pulse signal part S P and DC component S G The pulse signal part and the DC component are added together in the node 16 of the control device to generate the actual control signal S A .

[0063] The pulse current source 12 is used to generate the pulse signal portion S P To this end, the pulse current source 12 has a first switching element 18 a and a second switching element 18 b connected in series to the first switching element 18 a .

[0064] The first switching element 18a has a first electronic load 20a for setting the pulse signal S G The first electronic load 20a has a first electronic switch 22a, which in the embodiment is a transistor, for example a BC817 transistor. In addition, the first electronic load 20a has a first control unit 24a, which in the embodiment is a digital-to-analog converter, for controlling the first electronic switch 22a.

[0065] The second switching element 18b has a switch 21 for setting the pulse signal S G The switch 21 particularly comprises a second electronic switch 22b, which in the exemplary embodiment is a transistor, for example a transistor of the type BFU590G. Furthermore, the second switching element 18b comprises a second control unit, which in the exemplary embodiment is a field programmable gate array (FPGA), for regulating and setting the pulse pattern. The second control unit is connected to the second electronic switch 22b.

[0066] The differences between the two switching elements 18 a , 18 b can be seen essentially in the different requirements regarding the switching times, in particular the transition frequencies, of the two electronic switches 22 a , 22 b .

[0067] The requirements for the switching time of the second electronic switch 22b result from the requirements for the maximum permissible edge steepness of the pulse pattern to be set. In one embodiment, the pulse signal portion has a pulse pattern in the manner of a square wave signal.

[0068] The second electronic switch 22b preferably has a transition frequency with a value in the range of 500 MHz to 2 GHz, in particular with a value in the range of 1 GHz to 1.5 GHz. With the aid of a transition frequency with a value in the aforementioned range, an edge steepness with a value in the range of 10 ns to 20 ns can be achieved.

[0069] Higher switching frequencies are also conceivable; for example, in this exemplary embodiment, the second electronic switch 22 b comprises a transistor of the type BFU590G, which has a switching frequency of 8.5 GHz.

[0070] According to the preferred embodiment, the pulse signal portion S is increased G The pulse height (amplitude) of the individual pulses is designed to increase in a staircase-like manner. This results in a switching time or transition frequency of the first electronic switch 22a that is smaller than the transition frequency of the second electronic switch 22b. This is based on the consideration that, to achieve the staircase-like shape, the pulse height (amplitude) of the individual pulses is increased only after a pulse train that corresponds to a multiple of the duration of the individual pulses. In one embodiment, the transition frequency of the first electronic switch 22a of model BC817 is 170 MHz.

[0071] Typically, the transition frequency of an electronic switch has a value that is 10 times the value of the desired edge steepness, converted to frequency, that is to be achieved by the electronic switch. For example, to achieve an edge steepness of 10 ns, corresponding to a frequency of 100 MHz, the electronic switch has a transition frequency of 1 GHz.

[0072] The DC current source 14 is configured to generate a DC component S G For this purpose, the DC current source 14 has a third switching element 18c. In order to set the DC component S G The third switching element 18c has, on the one hand, a third control unit 24c, for example a digital-to-analog converter, and, on the other hand, a current sink 20b. The current sink 20b has a third electronic switch 22c, for example a transistor of type BC817. In addition, the third switching element 18c has a control circuit for analog regulation of the DC component S GThe operational amplifier 26. By means of the third control unit 24c, for example, the DC component S G The amplitude of the DC component is set by the third electronic switch 22c in a switchable manner to be delivered to the pulse signal part S G .

[0073] Typically and preferably, the DC component S G The LED unit 6 is permanently loaded. Therefore, requirements are imposed on the third electronic switch 22c with regard to switching times and / or transition frequencies, which are preferably met by means of conventional transistors, for example bipolar transistors of the type BC817.

[0074] In addition, the pulsed current source has a current limiter element 28, for example an emitter resistor, for compensating for temperature drift of the first electronic switch 22a. Temperature drift is generally understood to be a temperature-dependent current increase of a transistor.

[0075] Furthermore, the DC current source has a current measuring element 29, for example a shunt resistor, for detecting the DC component S G level.

[0076] For a better understanding, the method already described in DE 10 2015 201 494 A1 is briefly discussed again below:

[0077] The LED is loaded with pulsed signal components. Due to the increased amplitude of the individual pulses and, consequently, the LED current flowing through the LED, the light from the LED has an increased intensity. The increased intensity of the LED light generates an increased number of charge carrier pairs in the semiconductor material of the radiation detector 5, which results in a higher charge pulse. After each increase in the amplitude of the individual pulses and, therefore, after each increase in the charge pulses, the charge pulses are compared with a pre-set threshold voltage of the signal detection unit. For example, if the charge pulses have a value less than the threshold voltage, a counting event is detected in the signal detection unit, and the amplitude of the individual pulses is increased using the control device 2. After the increase, the charge pulses are compared again with the threshold voltage. For example, if the value of the charge pulses exceeds the value of the threshold voltage, a counting event is used as a value for evaluating the polarization of the radiation detector. A counting event is to be understood as how often the individual pulses are increased until the value of the charge pulses exceeds the value of the threshold voltage.

[0078] Because polarization changes over time and the effects of radiation on the polarization state of the radiation detector, the method for determining polarization is preferably performed once before and once after patient treatment. The same value is set for the threshold voltage in both measurements. For example, in the measurement after treatment and, therefore, after the radiation detector has been exposed to X-ray radiation, the threshold voltage can be exceeded more quickly or more slowly. The difference between the number of individual pulses added until the threshold voltage is exceeded in the pre-treatment measurement and the number of individual pulses added until the threshold voltage is exceeded in the post-treatment measurement is interpreted as signal drift and can subsequently be reduced, for example, using a calibration method.

[0079] Figure 2 The control signal S A In this case, the value I of the control signal is plotted on the vertical current axis in relation to the time t plotted on the horizontal time axis. In one embodiment, the control signal S A The pulse signal portion S has a square wave signal pattern. P In addition, the pulse signal part S P With the DC component S G Superposition. Pulse signal part S P The superposition of the pulse signal part S P "Shift" the DC component S in the direction of the current axis G Therefore, the control signal S A With a total amplitude GA. The total amplitude GA is composed of the DC component S G and the pulse signal part S P The sum of the values ​​of the amplitude (pulse height) is formed.

[0080] In one embodiment, the pulse signal portion S P It has an amplitude A, an edge steepness F, and a pulse width B. The edge steepness F defines the pulse signal portion S P From the output value (in one embodiment, the output value is the DC component S G The time for the edge steepness F to rise to the full value of its amplitude A. In one embodiment, the edge steepness F has a maximum value of 20 ns. The pulse width B defines the time during which the control signal S A Or pulse signal part S P In the pulse signal part S P The time for which the pulse width has its amplitude before falling to its initial value to form a pulse pattern. In one embodiment, the pulse width has a value in the range between 100ns and 120ns.

Claims

1. A method for operating a radiation detector (5), wherein the radiation detector (5) is irradiated with light by means of an irradiation unit (4), wherein the irradiation unit (4) is controlled by means of a control device (2), It is characterized by: The control device (2) has a direct current source (14) and a pulse current source (12), wherein the irradiation unit (4) is driven by a control signal (S A ) to control, and the control signal (S A ) has a pulse signal part (S P ) and DC component (S G ), the pulse signal part (S P ) is generated by the pulse current source (12), the DC component (S G ) is generated by the DC current source (14).

2. The method according to claim 1, It is characterized by: The pulse signal part (S P ) has an amplitude (A) and a pulse mode, and the pulse current source (12) has a first switching element (18a) and a second switching element (18b), the second switching element (18b) being connected to the first switching element (18a), wherein the amplitude (A) is set by means of the first switching element (18a), and the pulse mode is set by means of the second switching element (18b).

3. The method according to claim 2, It is characterized by: The pulse signal part (S P ) has a sequence of single pulses, wherein the amplitude (A) of the single pulses increases.

4. The method according to claim 2 or 3, It is characterized by: Discard the pulse signal part (S P )’s amplitude (A).

5. The method according to any one of claims 1 to 3, It is characterized by: The DC current source (14) has a third switching element (18c), wherein the DC component (S G ) is set by means of the third switching element (18c).

6. The method according to any one of claims 1 to 3, It is characterized by: During the entire duration of the actuation, the DC component (S G ) loading the irradiation unit (4).

7. The method according to claim 3, The individual pulses have an edge steepness (F) of a maximum of 20 ns.

8. The method according to claim 3, The single pulse has a pulse width (B) in the range of 80 ns to 120 ns.

9. The method according to claim 1, The irradiation unit (4) is an LED unit (6).

10. The method according to claim 1, The DC component (S G ) is superimposed on the pulse signal part (S P )superior.

11. The method according to claim 3, The single pulse has a pulse width (B) in the range of 90 ns to 110 ns.

12. A radiation detector (5) comprising a control device (2) for an irradiation unit (4), It is characterized by: The control device (2) has a pulse current source (12) and a direct current source (14), The pulse current source (12) and the direct current source (14) are configured to control the irradiation unit (4) so ​​that the irradiation unit (4) is irradiated by means of a control signal (S A ) to control the irradiation unit (4), wherein the control signal (S A ) has a pulse signal part (S P ) and DC component (S G ), the pulse signal part (S P ) is generated by the pulse current source (12), the DC component (S G ) is generated by the DC current source (14).

13. The radiation detector (5) according to claim 12, It is characterized by: The pulse current source (12) has a first switching element (18a) and a second switching element (18b), wherein the second switching element (18b) is connected to the first switching element (18a), wherein the first switching element (18a) is configured to set the pulse signal portion (S P ) of the amplitude (A), and the second switching element (18b) is configured to set the pulse signal portion (S P ) pulse mode.

14. The radiation detector (5) according to claim 13, It is characterized by: The transition frequency of the second switching element (18b) has a value that is five times the value of the transition frequency determined from the required edge steepness (F).

15. The radiation detector (5) according to any one of claims 12 to 14, It is characterized by: The DC current source (14) has a function for adjusting the DC component (S G ) of the third switching element (18c).

16. The radiation detector (5) according to claim 12, The irradiation unit (4) is an LED unit (6).

17. The radiation detector (5) according to claim 12, The DC component (S G ) is superimposed on the pulse signal part (S P )superior.

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