FR2895146A1 - Light amplifier device for nocturnal viewing apparatus of gun, has digital processing unit to control cyclic ratio for supplying photocathode, supply frequency of photocathode and gain adjustment and maximum current of screen - Google Patents

Abstract

The device has a light amplifier tube with a photocathode and an electron amplifying structure, and a high voltage electric supply block with a digital processing unit (30) including a microprocessor and a memory. The processing unit is arranged for controlling a voltage (V2) of the amplifying structure, a voltage (V1) of the photocathode, and a cyclic ratio for supplying the photocathode. The processing unit controls a supply frequency of the photocathode and an adjustment of gain and maximum current of a screen. An independent claim is also included for a high voltage supply block.

Description

The present invention relates to night vision devices. Such

  The apparatus includes a light amplifier tube and a high voltage power supply unit providing the voltages necessary for the operation of the tube.

  In existing night vision devices, the light amplifier tube includes a photocathode, an electron amplifying structure and a phosphorescent screen. The photocathode, which is for example based on silicon or germanium, releases electrons due to the reception of incident photons. The photons thus released by the photocathode are multiplied by the amplifying structure and accelerated towards the screen. The high-voltage power supply supplies the voltages necessary for the acceleration of the electrons released by the photocathode to the amplifying structure on the one hand and the acceleration of the electrons released by the amplifying structure towards the screen on the other hand.

  US Patents 5,949,069, 6,140,628, 6,288,386, 6,320,180, 6,898,890 and 6,429,416 relate to night vision devices. The amount of light that can be reviewed by a night vision device may vary significantly and night vision devices are generally equipped with an automatic brightness control system, also called ABC (Automatic Brightness). Control). The ABC is generally obtained through a regulation loop aimed at keeping the screen current substantially constant when it exceeds a certain threshold, by acting on the potential of the electron-amplifying structure. In addition, in order to extend the photocathode's life span, its potential is not maintained at a constant value depending on the incident light thanks to an automatic protection system called BSP (Bright Source Protection). In some night vision devices, the BSP relies on the reduction of the potential difference between the photocathode and the electron-amplifying structure when the current of the photocathode exceeds a certain threshold; however, such a decrease affects the quality of the image because the path of the electrons between the photocathode and the amplifying structure then deviates from an ideal rectilinear trajectory ensuring a clear image on the screen.

  To remedy this disadvantage, the potential difference between the photocathode and the electron-amplifying structure can be modulated, keeping a constant amplitude, according to a variable duty cycle, which depends on the amount of light seen by the vision apparatus. night. Such a process for feeding the photocathode, called auto-gating, is disclosed in US Pat. No. 4,195,222. US Pat. No. 5,883,381 describes a night vision apparatus in which the self-gating technique is implemented. before ABC. On the other hand, in US Pat. No. 6,278,104, ABC is used first and then self-gating is employed.

  Moreover, because of manufacturing tolerances, the light amplification tubes do not have all the same electrical characteristics, so that, in connection with the assembly, it is necessary to adjust the high-voltage power supply unit, in particular to gain power. and the screen current from which the ABC is implemented. For this purpose, mechanical potentiometers are provided on the high voltage power supply. Their presence is likely to cause temperature derivatives and increase the sensitivity of the apparatus to moisture, which is undesirable. The high-voltage power supplies used in some night vision devices include an oscillator that supplies low voltage to generate an alternating voltage that is energized by means of an elevator transformer. The pulse width modulation of the photocathode potential is performed at a frequency which depends on that of the oscillator. When the night vision device is used to observe a scene that is illuminated by a source of light itself modulated, which is the case for example in the presence of streetlights connected to the electrical network 50 or 60 Hertz, a phenomenon of beat is likely to occur, affecting the quality of the image produced. US Pat. No. 6,429,416 teaches a relatively complex solution to this problem, consisting of measuring a current of the amplifying structure, detecting a possible passage and modifying in this case the frequency of the supply voltage of the photocathode to another fixed value.

  Finally, it is desirable for a manufacturer to know the conditions of use of a night vision device for example to determine if a warranty clause is applicable in case of return of the device for alleged failure and / or for perform appropriate maintenance. U.S. Patent 6,898,890 discloses a method for controlling the life of a rifle equipped with a night vision apparatus, consisting of recording the operating time of the night vision apparatus and the number of hours of operation. shots. The invention aims in particular to provide a perfect night vision device, remediating all or part of the disadvantages of known devices. According to one of its aspects, among others, the invention relates to a light amplifier device comprising: - at least one light amplifier tube, - at least one high voltage electrical power supply unit, this block comprising at least one digital processing unit comprising at least one microprocessor and at least one m6-black.

  The amplifier tube may comprise: - a photocathode, and - an electron amplifying structure, which may comprise a microchannel wafer. The tube may also include a screen or alternatively a matrix sensor, for example CCD. The high voltage power supply may include an oscillator and at least one upconverter to raise an alternating voltage generated by the oscillator. The oscillator may oscillate at a substantially constant frequency, for example. The presence of at least one digital processing unit in the high voltage power supply can have many advantages depending on the functions that this digital processing unit is programmed to perform. According to an exemplary implementation of the invention, the digital processing unit may be arranged to exert control of the operation of the high voltage power supply. The digital processing unit may be arranged to perform at least one of the following functions: a control of the voltage of the photocathode, in order to control it as a function of the screen current, for example, a control of the duty cycle feeding the photocathode as a function of the screen current, for example, a control of the voltage of the amplifying structure, in order to regulate it as a function of the screen current, for example, a control of the frequency of feeding the photocathode, for example to avoid the aforementioned beat phenomena in case of observation of a scene illuminated by a source of modulated light - a measure of the screen current, for example synchronously with the frequency of The oscillator so that the measurement of the screen current occurs for example when it is substantially maximum, which improves the signal-to-noise ratio, - a setting of the gain and maximum current of screen, which can allow to avoid the re course to the mechanical potentiometers of anterior wax.

  The invention can make it possible to achieve relatively short photocathode feeding times, for example less than or equal to 100 nS. The digital processing unit may in particular be arranged in such a way as to vary the power supply frequency of the photocathode while keeping the duty cycle adapted to the search current.

  The joint regulation of the duty cycle and of the amplifying structure voltage can make it possible to modify both of them in a quasi-simultaneous manner, in order to keep the gain of the tube substantially constant during a discontinuous variation of the duty cycle or of the voltage of the amplifying structure. For example, the duty cycle can be varied discontinuously downwardly (respectively upward) and the amplifying structure voltage increased (respectively decreased) so as to maintain the gain substantially constant, then the voltage of the amplifying structure can be changed over a constant duty cycle duty range to control the gain. The regulation may for example comprise a phase in which the voltage of the amplifying structure is substantially constant and maximum and the substantially constant and maximum duty cycle, then at least one other phase in which both the voltage of the amplifying structure and the cyclic ratio of the photocathode voltage are controlled according to the amount of incident light. The digital processing unit may be arranged to record at least one operating parameter of the device, in particular at least one parameter chosen from: - at least one operating time, possibly several operating periods respectively associated with several current ranges of screen, at least one identifier of the device, a number of ignitions of the tube, - at least one information representative of a stress experienced by the tube, for example a quantity of electricity having crossed the screen. The digital processing unit can be further arranged to modify operating parameters of the device as a function of the aging of the tube, for example to modify the gain as a function of the amount of electricity that has passed through the screen.

  The microprocessor and the aforementioned memory may be part of the same component, for example a microcontroller, or may be separate components. The invention further relates, in another of its aspects, to a high-voltage power supply unit for a light-amplifying device, comprising: at least one printed circuit on which components are implanted, this printed circuit comprising zones of implantation separated by intermediate zones, the intermediate zones being devoid of components, the printed circuit being folded in these intermediate zones. Such a printed circuit makes it possible to avoid subjecting the components situated in the implantal zones; It has mechanical constraints, which improves reliability. This can facilitate the use of miniature components, such as CMS components. The subject of the invention is also an assembly comprising: an oscillator comprising two bipolar transistors whose bases are connected by a first winding transformer primary winding and whose collectors are connected by a second winding of the elevating transformer winding; first voltage multiplier stage at the terminals of a first secondary winding of the elevator transformer; a second voltage multiplier stage at the terminals of a second secondary winding of the elevator transformer. The first and second secondary windings can be connected by a noise compensation capacitor, which can facilitate the reading of the current of the screen.

  The use of two transistors can improve the electrical efficiency. The invention further relates, in another of its aspects, to a control circuit of a potential difference between a photocathode and an amplifier structure according to a duty cycle determined by the sending of control signals by a processing unit. digital, this modulation circuit comprising: - moire two transistors respectively commandos in saturation by positive and negative pulses, - a pulse transformer whose primary receives pulses of current as a function of the control signals and whose secondary is connected said transistors. This pulse transformer comprises for example both primary and secondary moire five turns, better one or two turns, allowing to have very short pulse durations, so to modulate the duty cycle very quickly. The secondary may include, for example, double primary turns. The pulse transformer may comprise a torus on which the turns are wound. The potential difference between the photocathode and the amplifying structure can be modulated according to voltage bands whose temporal width is determined by the value of the duty cycle. The control signals may be transmitted with a frequency higher than one of the voltage bands. This frequency may be high enough that the photocathode voltage does not vary substantially in the low state, ie when the photocathode is blocked and has substantially no electrons, given the capacitance of the photocathode. of the photocathode, between two control signals.

  The digital processing unit may be operable to vary the number of control signals sent to refresh the photocathode voltage to maintain it at a substantially constant potential.

  By varying this number around a predefined value determined by the screen current, the duty cycle can be modified. The control signals can be sent in such a way as to vary the power supply frequency of the photocathode in order to avoid a beat phenomenon when viewing a scene illuminated by a modulated light source. The variation can be continuous and be done without detection of the current of the amplifying structure, which brings a significant simplification compared to the teaching of the aforementioned US Pat. No. 6,429,416. According to another of its aspects, the high-voltage power supply unit comprises at least two electrical contacts allowing the exchange of information with an external programming device, for example to read values of operating parameters recorded in the memory of ( The invention further relates, in another of its aspects, independently or in combination with the above, to a light amplifier device comprising: a light amplifier tube comprising a photocathode, and an amplifying structure and a display device, for example a screen or a matrix sensor, in particular a CCD, a digital processing unit arranged to: - modulate the potential of the amplifying structure, Periodically recoding a dui-6e of application of a potential difference between the photocathode and the amplifying structure according to a rap. variable cyclic port. In an exemplary embodiment of the invention, in an operating phase of the device, the amplitude of the potential difference on the amplifying structure is maintained at a maximum level and the duty cycle is maintained equal to the unity of the device. the amount of incident light exceeds a predefined threshold.Also in an exemplary embodiment of the invention, in a phase of operation of the device, the digital processing unit is arranged to: - select a duty cycle among many, to act on the amplitude of the potential difference on the amplifying structure.

  The duty cycle is for example chosen from several gauges, the passage from one caliber to the next corresponding for example to a division by two of the duty cycle or to an incrementation or decrementation of the interval between two voltage crenels on the photocathode of a multiple of the time interval corresponding to a voltage window. The action on the magnitude of the voltage of the amplifying structure is effected, for example, in a voltage range corresponding to a decrease of about half of the screen intensity. The voltage range is for example less than 100 V, for example between 25 and 75 V.

  The processing unit can store a table of values indicating, for each variation of the duty cycle, the voltage to be applied to the amplifying structure to compensate for the variation in gain due to the variation of the ratio and to maintain a substantially constant gain for the tube. The invention further relates, in another aspect, to a method for controlling the gain of a light amplifier tube comprising a photocathode and an amplifying structure, in which the gain of the tube is regulated by acting periodically at a time. on the duty cycle of the photocathode voltage and the magnitude of the potential difference on the amplifying structure. In an exemplary embodiment of the invention, the action on the voltage of the amplifying structure is exerted after selecting one of several cyclic ratios. The invention will be better understood on reading the following detailed description, non-limiting examples of implementation thereof, and on examining the accompanying drawings, in which: FIG. schematically, in perspective, an example of a high-voltage power supply unit and an associated programming apparatus; FIG. 3 represents a view from above of an example of a light-emitting device; printed circuit, before folding of the power supply unit, FIG. 4 is a simplified diagram of the electronic circuit of the high voltage power supply unit, FIG. 5 represents isolation of the oscillator and the voltage multiplier stages, FIG. the control circuit of the photocathode, FIG. 7 represents the control circuit of the amplifying structure, FIG. 8 represents the isolation of the current reading circuit, FIG. 9 represents an example of the evolution of the luminosity of the screen as a function of the amount of incident light, FIG. 10 represents an example of an evolution of the voltage of the amplifying structure as a function of the amount of incident light, FIG. FIG. 12 shows an example of an evolution of the duty cycle as a function of the amount of incident light, and FIG. 12 shows schematically the steps of a control loop according to an exemplary embodiment of the invention.

  FIG. 1 schematically shows a night vision apparatus 1 comprising a light amplifier tube 2 connected to a high-voltage power supply unit 3, itself fed from a low-voltage electrical source 4. voltage composed for example of one or more batteries or accumulators. The light amplifier tube 2 comprises a photocathode 6, an electron-amplifying structure 7 and a screen 8. In a variant that is not illustrated, the screen is replaced by a CCD matrix sensor. The high-voltage power supply unit 3 makes it possible to supply voltages VI, V2 and V3 which, on the one hand, make it possible to accelerate the electrons between the photocathode 6 and the input face of the amplifying structure 7 and, on the other hand, between the output face of the latter and the screen 8. In the example considered, the input face of the amplifying structure 7 is at potential V2 and its output face has ground, the voltage V2 being negative, but it could be otherwise without departing from the scope of the present invention. The photocathode voltage V1 may vary according to the amount of incident light, according to a pulse width modulation, its potential V1 passing for example at the potential V2 when the photocathode is blocked and has a potential V2-AV when the photocathode must emitting electrons, the voltage AV may vary depending on the tubes and being for example of the order of 200 V in the example. The potential VI of the photocathode can vary substantially following a nipple-shaped voltage, for example in a manner that will be detainee further.

  The screen voltage V3 is for example approximately + 6.2 kV, being for example substantially constant. The voltage V2 of the input face of the amplifying structure varies for example from -1 200 V to 0 V, depending on the amount of incident light, for example as will be specified later. The output face is substantially 0 V in the example considered, but it could be otherwise. The high-voltage power supply unit 3, for example, as shown in FIG. 2, has a generally semi-annular shape, defining a central housing 10 for the amplifying tube 2. The power supply unit 3 may comprise a printed circuit 12 in an insulating resin 13. Supply and output wires 16 are provided for connecting the power supply unit 3 respectively to the electrical source 4 and the amplifier tube 2. The power supply unit 3 may also include electrical contacts. 18 and 19 allowing an exchange of information between the power supply unit 3 and a programming device 20 comprising plugs 21 to be electrically connected to the contacts 18 and 19, as shown in FIG. 2. The programming apparatus 20 may comprise a display 23 and a user interface 24 comprising for example keys and / or adjustment buttons. The programming apparatus 20 may include a microcomputer, as appropriate.

  The printed circuit 12 has been shown in FIG. 3. This circuit comprises, in the example considered, zones 13 for the implantation of the components, separated by intermediate zones 14 devoid of components, around which the printed circuit 12 is folded. In this way, the CMS components present in the zones 13a are not subjected to mechanical stresses liable to damage them. FIG. 4 shows a diagram of the electronic circuit of the high-voltage power supply unit.

  This comprises: a digital processing unit 30 comprising for example a microcontroller, for example of the PIC type, having a microprocessor and an integrated memory, - an oscillator 33 arranged to generate a sinusoidal voltage from the power supply 4 a first voltage multiplier stage 35 associated with a first winding of a secondary 36 of a voltage-raising transformer, enabling delivery of the screen supply voltage V3, and a second voltage multiplier stage 38, associated with a second winding 39 of the secondary elevator transformer. This second stage 38 supplies a circuit 40 for controlling the photocathode voltage V1 6 and a circuit 42 for controlling the voltage V2 of the amplifying structure 7. The power supply unit 3 also comprises a circuit 44 for reading the current of the screen 1F, connected to the digital processing unit 30. The oscillator 33 has been shown in FIG. 5. The oscillator 33 comprises, in the example considered, two bipolar transistors 45 whose bases are connected by a first winding. primary of the elevator transformer and whose collectors are connected by a second winding 47 of the primary of this elevator transformer. The oscillator 33 also comprises a resistor 48 which allows the start of the oscillations as well as capacitors 49 connecting the bases to the ground GND and resistors 50 connecting the emitter islands to the ground. The frequency of the oscillator is for example 80 kHz.

  An MOS transistor 85 is used to generate a synchronization signal SYN to the digital processing unit 30, this synchronization signal taking the logic value 1 as the oscillator voltage minima pass and taking the logic value 0 ninon. The signal SYN may be useful for synchronizing the reading of the iF screen current with the frequency of the oscillator and for reading the screen current when the latter is substantially maximum, as explained below.

  The first voltage amplifier stage 35 is associated with a first winding 51 of the secondary of the elevator transformer and has a number of diodes and capacitors connected together so as to raise the voltage. The second voltage multiplier stage 38 is associated with a second winding 52 of the secondary of the elevator transformer and delivers several intermediate voltages for supplying in particular the control circuit 42 of the amplifying structure. A low-noise noise compensation capacitor 53, for example of the order of 4.7 pF in the example considered, connects the windings 51 and 52. This capacitance facilitates the reading of the iF screen current. The circuit 40 for controlling the photocathode is shown in FIG. This circuit is arranged, in the example considered, to generate voltage gates.

  A voltage pulse VI is triggered by the sending of a signal PULSE_START by the digital processing unit 30 and the voltage V2 of the photocathode is triggered by the sending of a PULSE_STOP signal from the unit. The aforementioned control signals are rejected by current amplifiers 60 connected to the primary 61 of a pulse transformer whose secondary 62 controls, via a resistor 63, two MOS transistors 64 and 65 becoming respectively on the reception of signals PULSE_START and PULSE_STOP. When the transistor 64 is on, the voltage V1 is reduced to V2-AV, the transistor 65 being blocked. When the transistor 65 is on, the transistor 64 being blocked, the voltage V1 is substantially the voltage V2, which can vary for example from 0 to -1 200 V. AV is for example about 200 V, this voltage can be obtained by the capacitance load 1112 connected to the secondary 52 of the elevator transformer and to the diodes 110 and 111. The time width of the voltage gates during which the voltage V1 is substantially maximum, for example equal to A. V2-200 V, then equal to V2, in a duty cycle is controlled by the digital processing unit 30 so that the screen current iF exceeds a predefined value.

  In the example considered, the frequency of the PULSE_START control signals is greater than that of the voltage jacks defining the duty cycle so that the photocathode voltage remains substantially constant, given its inherent capacitance, between two signals. PULSE_START.

  The dui-6e separating two PULSE START signals thus serving to refresh the photocathode voltage is, for example, a few hundred μs, while the duration of a voltage loop V 1 is for example of the order of one ms or mo ins. The frequency of the PULSE_STOP signals is also chosen to be large enough to maintain the voltage substantially at V2 during the second search, taking into account the inherent capacitance of the photocathode. Thus, the digital processing unit 30 can act on the duty cycle c by changing the number of consecutive pulses PULSE_START then PULSE_STOP sent to the control circuit 40.

  The invention can make it possible to have a duty ratio corresponding to a very small nickle time, for example less than or equal to 100 nS. A threshold of dui-6th minimum is generated by sending after a pulse PULSE_STOP a pulse PULSE_START followed by a new impulse PULSE STOP.

  In order to avoid the phenomenon of beats in case of observation of a scene illuminated by a modulated light, the pulses can be sent in such a way as to vary the frequency of the voltage slots of V1, the variation in frequency being, for example, the order of 10%. The frequency may vary continuously, regardless of the screen current.

  The pulse transformer comprises for example two turns in the primary and four turns in the secondary, being coil on a ferrite core, and thus has a relatively low time constant. This low time constant allows a relatively fast regulation of the duty cycle as a function of the screen current.

  The invention is not limited to the use of a pulse transformer and the control of the transistors 64 and 65 could be carried out differently, for example optoelectronic way, provided to have sufficiently fast components.

  FIG. 7 shows the control circuit 42 making it possible to generate the variable voltage V2. This circuit 42 comprises two MOS transistors 80 and 81 branches in series so that no one sees at its terminals a voltage greater than the gate voltage of the transistor 81, of the order of 750 V. The transistor 80 is controlled by the digital processing unit 30 via an opto-coupler 83. Depending on a control signal sent by the digital processing unit 30 to opto-coupler 83, the voltage V2 can be controlled. from 0 to -1 200 V in the following example.

  FIG. 8 shows the circuit 44 for reading the 1F screen current. In the example considered, the screen current iF is read by measuring the voltage across a resistor 90 of high value connecting a first point 93 common to the first secondary winding 51 and the capacitor 53 and a second point 94 has a reference voltage obtained by means of a voltage divider 95.

  The voltage across the resistor 90 is read through a first 96, a second 97 and a third 98 operational amplifiers used as followers. The output of the first amplifier 96 is connected to the input of the second amplifier via the resistance of a filter RC having a time constant which makes it possible to eliminate the very fast fluctuations of the iF screen current. A low-filtered voltage is measured between the output 121 of the second amplifier 97 and a reference 120 by the processing unit and the value thus read can serve to regulate the voltage V2 and the duty cycle T. The output of the second amplifier 97 is connected to the input of the third amplifier 98 through the resistance of an RC filter which has a relatively high time constant in order to deliver a signal which can be used to count the amount of electricity passed through the screen during operation of the light amplifier tube. A capacitance 102 in parallel with the resistor 90 makes it possible to average the signal and to reduce the amplitude of the voltage used to read the current in order to avoid saturating the operational amplifiers 96 A. 98 during the regulation.

  The digital processing unit 30 is arranged to provide, in the example considered, the following functions. First, the digital processing unit 30 can record information representative of the amount of electricity circulating through the screen and can thus provide information on the stress experienced by the amplifier tube. Not only the total amount of electricity can be recorded, but also the maximum value of the screen current and, if so, the duration during which a current falling within a range of predetermined current values has circulated.

  The voltage delivered by the amplifier 98 can thus be stored and / or used to increment an electricity quantity meter. The digital processing unit 30 can record information indicative of the stress experienced by the light amplifier tube, which is a function of the screen current.

  The digital processing unit 30 can also record the number of ignitions of the power supply, the number of hours of operation and an identifier such as for example a serial number. The digital processing unit 30 may be arranged to exchange information with the programming apparatus 20 through contacts 18 and 19, for example by an I2C protocol or any other communication protocol. This exchange of information can take place especially during the manufacture of the device, in order to program the gain of the tube and the maximum iF screen current. The tube is for example exposed to a known light and the values of the gain and maximum current are programmed in the digital processing unit 30.

  The exchange of information can take place also after a period of use of the device, in case of maintenance or return for failure, to read values of parameters relating to the use of the tube and thus to verify that it has been correctly used. The digital processing unit 30 may also be arranged to provide at least one correction factor depending on the aging of the tube. The gain and the maximum screen current can for example evolve according to the stress experienced by the tube, according to predefined laws. The maximum iF current can increase as the tube ages. During the operation of the device, the screen current iF croft in a first phase substantially proportional to the amount of incident light, as shown in Figure 9, the slope of the line being a function of the gain of the tube. Then, when the amount of incident light crosses a predefined threshold, the maximum screen current must be kept substantially constant. The digital processing unit 30 may be arranged to control the voltage V 2 as a function of the amount of incident light so as to have, in the first operating phase, a maximum voltage V 2 in absolute value, as shown in FIGS. 9 and 10. as long as light is insufficient for the screen current to reach its maximum value. The digital processing unit 30 may also be arranged to control the duty cycle of the voltage VI so as to have, in the first phase, a duty cycle corresponding to a continuous supply of the photocathode, as illustrated in FIGS. 9 and 11. In the first phase of operation, when the amount of incident light continues to increase, the digital processing unit 30 controls the voltages V1 and V2 so that the iF screen current remains acceptable.

  In an exemplary embodiment of the invention, the digital processing unit 30 may be operable to perform a control loop illustrated in FIG. 12, selecting a duty cycle i from a plurality of predefined values, thereby providing a control coarse and then acting on the voltage V2, which ensures a finer regulation.

  The duty cycle is for example selected from a number of gauges of between 10 and 20, for example equal to 14. Of a gauge to the other, the duty ratio T is for example halved, but the variation i d one caliber to another could be different. The peak value of the current iF can be used for example by the processing unit to determine the size. Once the selected duty cycle has been selected, a control of the screen current is made by acting on the value of the voltage V2.

  For a given duty cycle, the voltage V2 can vary for example over a range of 50 V to perform the fine adjustment, which allows to vary the screen current by about 50%. When a change in size corresponding to a decrease of i, the voltage V2 can be increased so as to compensate for this decrease and to avoid a too abrupt transition of the screen current. Conversely, the voltage V2 can be reduced during an increase of i in passing from one template to another. The regulation of the voltages V1 and V2 can be carried out in a manner other than that just described. The digital processing unit can for example regulate the screen current by acting not on the foil on the duty cycle and on the voltage V2 but on the one up to a certain threshold of current of screen and then on the other when this threshold is exceeded. Thus, in one example, the voltage V2 is decreased as a function of the incident illumination keeping the duty cycle constant, then the duty cycle is decreased keeping V2 constant. In an alternative embodiment of the invention, the sinusoidal voltage at the input of the up-converter transformer is synthesized by the digital processing unit, which makes it possible, for example, to vary it.

  It is not beyond the scope of the present invention when the amplifying structure is supplied by positive and negative voltages, the amplifying structure being for example as described in US Pat. No. 5,949,063. The amplifying structure may for example comprise an ionic barrier. . The expression including a >> shall be understood as being synonymous with having at least one, unless the contrary is specified.

Claims (17)

  1. A light amplifier device (1) comprising: at least one light amplifier tube (2), at least one high-voltage power supply unit (3), this block 5 comprising: at least one digital processing unit (30); ) comprising at least one microprocessor and at least one memory.   2. Device according to claim 1, wherein the tube (3) comprises at least one photocathode (6) and at least one electron-amplifying structure (7). 10   3. Device according to claim 2, the tube comprising at least one screen (8).   4. Apparatus according to one of the preceding claims, wherein the digital processing unit (30) is arranged to perform the control of the voltage (V2) of the amplifying structure. 15   Apparatus according to any one of the preceding claims, wherein the digital processing unit (30) is arranged to control the voltage (V1) of the photocathode.   Apparatus according to any one of the preceding claims, wherein the digital processing unit (30) is arranged to control the photocathode power cycling ratio (z).   7. Apparatus according to any one of the preceding claims, wherein the digital processing unit (30) is arranged to perform a screen current measurement (iF) synchronously with the frequency of an oscillator for generating a voltage. alternative that is elevated by means of an elevator transformer. 25   8. Apparatus according to any one of the preceding claims, wherein the digital processing unit (30) is arranged to record at least one operating parameter of the device, including at least one parameter selected from: at least one operating sixth-6e , possibly several operating periods respectively associated with ranges of screen current, at least one identifier of the device, a number of ignitions, at least one information representative of a stress suffered by the tube, in particular a quantity of electricity crossing the screen.   9. Apparatus according to any one of the preceding claims, wherein the digital processing unit (30) is arranged to change the operating parameters of the device according to the aging of the tube, including changing the gain depending on the amount of electricity having crossed the screen.   10. The device of claim 2, the digital processing unit being arranged to perform a joint regulation of a duty cycle of the photocathode voltage and a voltage of the amplifying structure.   11. Device according to claim 10, the amplifying structure voltage being controlled so as to avoid a sudden transition of the gain of the tube during a change of duty cycle.   12. Apparatus according to any one of the preceding claims, wherein the microprocessor and the memory are part of the same component, including a microcontroller.   13. Apparatus according to any one of the preceding claims, the processing unit being arranged to continuously vary the frequency of the supply voltage of the photocathode.   14. High voltage power supply unit for a light amplifier device, comprising at least two electrical contacts (18, 19) allowing the exchange of information with an external programming device (26), in particular for reading parameter values. of operation stored in a memory of a digital processing unit.   A light amplifying device comprising: a light amplifier tube having a photocathode and an electron amplifying structure, a digital processing unit arranged to: - modulate the amplitude of the potential difference on the amplifying structure, Periodically modulate the voltage applied to the photocathode in a variable duty cycle.   16. Apparatus according to claim 14, the processing unit being arranged to vary the frequency of the voltage applied to the photocathode, especially in a continuous manner.   17. A device according to claim 15 or 16, wherein in an operating phase, the digital processing unit is arranged to select one of a plurality of cyclic ratios, to act on the magnitude of the potential difference of the amplifying structure. .21. Device according to claim 19 or 20, wherein in an operating phase, the digital processing unit is arranged to: - select one of several cyclic ratio, act on the amplitude of the potential difference of the amplifying structure.