Use method of performance parameter for night-vision device and temperature compensation

Abstract

To provide a method for controlling performance of a night-vision device.SOLUTION: A control method contains: a step of supplying a control voltage for controlling a gain of a micro channel plate to the micro channel plate of an image intensifier tube by a power supply; a step of determining a compensation amount for being adapted to the control voltage on the basis of a change of the control voltage caused by a change of a temperature of an operation environment of the night-vision device; a step of adjusting the control voltage in accordance with the compensation amount to acquire a compensation control voltage; and a step of supplying the compensation control voltage to the micro channel plate of an optical intensifier tube by the power supply. The method further contains a step of determining whether the night-vision device is used for a predetermined time, and is constructed so as to supply the compensation control voltage only after the predetermined time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to night vision devices, to power sources for night vision devices, and more particularly to digital and software techniques for maintaining the performance of night vision devices subjected to extended use and temperature extremes. [Background technology]

[0002] Night vision devices may be used in many industrial and military applications. For example, such devices are used to enhance the night vision of pilots, to photograph celestial bodies, and to provide night vision to soldiers or patients with retinitis pigmentosa (night blindness). The devices often incorporate image intensifiers that are used to amplify low intensity light or convert non-visible light into readily viewable images. One such image intensifier is the image intensifier tube.

[0003] Image intensifier tubes typically include a photocathode with, for example, a gallium arsenide (GaAs) active layer and a microchannel plate (MCP) disposed within a vacuum housing. Visible and infrared energy, for example, can strike the photocathode and be absorbed in the cathode active layer, thereby generating electron / hole pairs. The generated electrons are emitted into the vacuum cavity and amplified by the MCP.

[0004] More specifically, as electrons leave the photocathode, they are accelerated toward the input surface of the MCP by a potential difference between the MCP's input surface and the photocathode, which is approximately 200-900 volts depending on the MCP-to-cathode spacing and the MCP configuration (filmed or un-filmed). When electrons strike the input surface of the MCP, secondary electrons are generated within the MCP; that is, the MCP can generate hundreds of electrons for each electron that enters the input surface. The MCP is also exposed to a potential difference between its input surface and its output surface, typically about 700-1200 volts. This potential difference allows for electron multiplication in the MCP.

[0005] As the multiplied electrons exit the MCP, they are accelerated through the vacuum cavity towards the phosphor screen (or other anode surface) by a further potential difference between the phosphor screen and the output surface of the MCP. This latter potential may be on the order of about 4200 to 5400 volts.

[0006] A power supply integrated or potted with the image intensifier tube is generally used to generate and provide the various potential differences discussed above, and also to provide control voltages to the various components of the image intensifier tube. The power supply and intensifier tube are expected to operate under a variety of lighting conditions, including, for example, relatively low light conditions, relatively high light conditions, over a variety of temperature ranges, and for extended periods of time. Configuring and controlling the power supply to handle all of these conditions is difficult. Summary of the Invention

[0007] Described herein is a method for controlling the performance of a night vision device, the method including the steps of: providing, by a power source, a control voltage to a microchannel plate of an image intensifier tube, the control voltage controlling a gain of the microchannel plate; determining a compensation amount to apply to the control voltage based on a change in the control voltage due to a change in temperature of an operating environment of the night vision device; adjusting the control voltage according to the compensation amount to obtain a compensated control voltage; and providing, by a power source, the compensated control voltage to the microchannel plate of the image intensifier tube. The method further includes determining if the night vision device has been used for a predetermined period of time, the method being configured to provide the algorithmically determined compensation control voltage to the microchannel plate only after the predetermined period of time.

[0008] In another embodiment, a method for controlling the performance of a night vision device is provided. The night vision device includes a power source and an image intensifier tube in communication with the power source. The method includes the steps of: providing, by the power source, a second control voltage to a microchannel plate of the image intensifier tube, the second control voltage controlling the gain of the microchannel plate; determining whether a difference between the second control voltage and a first control voltage provided at an earlier time than the second control voltage is less than a predetermined value; determining whether the night vision device has been used for a predetermined time if the difference is less than a predetermined value; adjusting the second control voltage only after the night vision device has been used for the predetermined time to compensate for changes in the second control voltage resulting from time of use to obtain a third control voltage; providing, by the power source, the third control voltage to the microchannel plate of the image intensifier tube; Includes.

[0009] In yet another embodiment, a power supply for a light intensifier of a night vision device is provided. The power supply includes a power supply circuit configured to provide a control voltage to the image intensifier, a chronometer, a temperature sensor, a memory configured to store a control logic, and a processor in communication with the chronometer, the temperature sensor, and the memory. The processor is configured to execute the control logic to provide, by the power supply, a control voltage to a microchannel plate of the light intensifier that controls a gain of the microchannel plate, and determine whether the night vision device has been used in a stressed state for a predetermined time based on the value of the chronometer, and if the night vision device has been used in a stressed state for a predetermined time, determine a compensation amount for applying the control voltage based on the stress exposure. Furthermore, a change in the control voltage due to a change in temperature of the operating environment of the night vision device based on the value of the temperature sensor may exist regardless of whether there has been a past stress exposure, and the power supply adjusts the control voltage according to the compensation amount to obtain a compensated control voltage, and provides, by the power supply circuit, the compensated control voltage to the microchannel plate of the light intensifier. It is structured as follows. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 illustrates, in block diagram form, a digitally controlled power supply and associated image intensifier in accordance with an embodiment of the present invention. [Diagram 2] FIG. 2 is a plot of output brightness versus light level according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a plot showing how three control voltages of a power supply respond to changes in temperature without active compensation. [Figure 4] FIG. 4 shows the response of a multiplier tube in output gain (measured at room temperature) to changes in V3 (anode voltage), in accordance with an embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram illustrating how the photoresponse (PR) changes with changing electric field strength between the photocathode and the MCP input, in accordance with an embodiment of the present invention. [Figure 6] FIG. 6 illustrates spectral response curves for three operating temperatures according to an embodiment of the present invention. [Figure 7] FIG. 7 illustrates normalized gain as a function of time for the reliability of several tested multiplier tubes, in accordance with an embodiment of the present invention. [Figure 8A] FIG. 8A illustrates a normalized gain curve according to an embodiment of the present invention. [Figure 8B] FIG. 8B is a diagram showing the voltage difference added to the room temperature V2 set point to maintain the same gain as a function of time in accordance with an embodiment of the present invention. [Figure 9] FIG. 9 is a flow chart illustrating a series of operations or processes for controlling performance of a night vision device in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Like reference numbers are used throughout this disclosure to identify like elements.

[0012] Figure 1 illustrates, in block diagram form, a digitally controlled power supply and associated image intensifier in accordance with an embodiment of the present invention. Specifically, Figure 1 illustrates an image intensifier tube 110 that is powered and controlled by a digitally controlled power supply 150. The intensifier tube 110 includes a photocathode 112, a microchannel plate (MCP) 114, and an anode 116 that includes a phosphor layer 118.

[0013] Digital power supply (or simply "power supply") 150 includes a battery 155 or other energy source that provides power used by power supply 150 itself and transmitted to multiplier tube 110. Power supply 150 further includes a central processing unit (CPU) 160 and memory 170 that store, among other things, control logic 180 and state variables (or settings) 185 (described further below). Battery 155 provides power for each of control voltages V1, V2, and V3, which are applied to components of multiplier tube 110. Values ​​of these control voltages can be set by CPU 160 according to instructions received from control logic 180.

[0014] In a possible embodiment, the CPU 160 controls circuits that control the application of voltages V1, V2, V3 to the photocathode 112, the MCP 114, and the anode 116, respectively. An operational amplifier 195 is configured to sense a current I3 flowing through the anode 116. The current I3 represents the brightness of the light 10 being received at the photocathode 112, where V1 and V2 are not modified to control the output brightness of the phosphor screen. The value of the current I3 can be used by the control logic 180 and the CPU 160 to, for example, adjust the value of V1 or V2 (e.g., higher V1 or V2 for higher brightness, lower V1 or V2 for lower brightness). The power supply 150 also includes a temperature sensor 164 and a chronometer 165.

[0015] An advantage of the digitally controlled power supply 150 is that the control scheme for adjusting the output brightness of the tube 110 as a function of the input light 10 can be selected after the power supply is assembled, unlike conventional analog power supplies where the control scheme is hardwired into the power supply. The digital control of the power supply 150 allows for the adjustment of different parameters or settings to activate specific features and / or ensure that the night vision device complies with, for example, export restrictions. The digital control of the power supply 150 can also be used to compensate performance parameters in terms of temperature and / or usage.

[0016] Fixed Brightness Control

[0017] One function of the power supply 150 and control logic 180 is to control the output brightness of the intensifier tube 110 as a function of the input light level, to protect the user from overly bright amplified scenes. In this regard, FIG. 2 illustrates a plot of output brightness versus light level according to an embodiment of the present invention. As shown, the output brightness is approximately fixed (between predetermined brightness limits) above a given level of received light, but nevertheless tends to increase slightly for a typical analog power supply due to the inherent behavior of analog circuitry, as shown by curve 210.

[0018] On the other hand, with digital control, an embodiment of the present invention can generate an output brightness versus light level curve 220 that is similar to curve 210, but without the slow rise of curve 210. That is, curve 220 shows a linear increase in brightness from approximately 2×10 -5 It is shown that the brightness remains truly fixed after fc (foot-candles). This stable brightness output is the result of the control logic 180 driving a control voltage (e.g., photocathode control voltage V1) to produce zero difference between the screen current (I3) and a fixed value current to achieve the desired screen brightness. The operation of the control voltage is described below.

[0019] temperature compensation

[0020] Under extreme operating conditions, for example -50°C to +50°C, the tube 110 and power supply 150 are expected to maintain stable gain at low light levels and limit output brightness at higher light levels. As mentioned above, some of the parameters and control processes within the power supply 150 are achieved by adjustment of the voltage (V1 and V2) and I3 current settings. Under some conditions, in an embodiment, the gain correction algorithm is <2×10 -4 fc light level and >2×10 -4 It has two operating ranges, corresponding to light levels of fc and fc. -4fc), the output of the intensifier 110 can be controlled by varying the MCP voltage (V2). However, when the intensifier is exposed to a high enough light level, the image becomes too bright (>2×10 -4 fc illumination) and the total light output is capped by limiting the value of I3. As explained in connection with Figure 2, it is possible to keep the I3 current below a user-defined limit. This method is called Automatic Brightness Control (ABC) and ensures that the screen current (I3) does not exceed a set point until all adjustment parameters reach their lowest control settings. At a light level that produces this level of screen current, the power supply first controls the brightness of the output by varying V2 to a maximum allowable current value I3, which corresponds to the maximum allowable output brightness at a fixed temperature. max As the light level increases, V2 eventually decreases to a minimum value. Once V2 reaches the first lower limit, the light output is adjusted by decreasing the duty factor of the cathode or V1 voltage.

[0021] Under lighting levels where ABC is not active, gain temperature compensation is performed by modifying the MCP voltage or V2. At all higher light levels, instead of modifying V2 to change the output brightness, the allowed screen current is changed to control the light output in environments hotter or colder than room temperature. Control logic 180 in power supply 150 is configured to control the supply voltage, which may vary with temperature. In this regard, a temperature sensor 164 is provided and may be part of CPU 160 or may be a separate component in communication with CPU 160 (FIG. 1) as shown.

[0022] The change in voltage output seen over temperature is driven by changes in the photomultiplier components, changes in the interface between the photomultiplier tube and the power supply (which is non-ideal but sometimes exists), and changes in the voltage provided by the power supply. For example, FIG. 3 is a plot showing how the three control voltages of power supply 150 respond to changes in temperature without active compensation. The plotted lines in FIG. 3 represent the average response of 12 power supplies. As can be seen, the swing in V3 from -50°C to +50°C is over 100 volts around the room temperature (RT) value.

[0023] FIG. 4 shows the response of the multiplier in output gain (measured at room temperature) to changes in V3 (anode voltage) when paired with a multiplier tube.

[0024] The dependence of phosphor light intensity as a function of temperature is shown below:

number

[0025] Depending on the activation energy (Ea), the intensity of the phosphor may increase as the temperature decreases or may be close to constant. In phosphor systems according to embodiments, the intensity of the phosphor increases as the temperature decreases. According to embodiments, data regarding phosphor efficiency changes is collected and used by control logic 180 to compensate power supply 150 over a range of operating temperatures.

[0026] The photocurrent to the input of MCP 114 is controlled by the effect of V1 voltage on emission probability and the change in material properties as a function of temperature. V1 varies by approximately 20 volts over the temperature range as shown in Figure 3. The photoresponse (PR) varies with the change in electric field strength between the photocathode 112 and the input of MCP 114. Since the spacing does not change with temperature, the photocathode current varies as shown in Figure 5.

[0027] The dependency in FIG. 5 is described by equation (2) below:

number

[0028] In equation (2), QE is the quantum efficiency and E is the electric field controlled by V1 and the spacing between the cathode output and the MCP input. The only other factor in this equation is β, a measure of the emission probability at the cathode surface. As temperature changes, the photocathode bandgap also changes, with the bandgap increasing as temperature decreases. A larger bandgap typically results in a higher emission probability and a larger β. However, a larger bandgap also shifts the spectral cutoff frequency upwards, meaning the cathode becomes less sensitive to longer wavelength photons. These two shifts are shown in the spectral response curves for the three operating temperatures in Figure 6, bottom.

[0029] The height of the maximum indicates an improved emission probability, and the spectral shift to the right indicates a shift in the bandgap. Once convoluted with the 2,856 K source spectrum, this leads to an equivalent photocurrent from the photocathode with a change in temperature if the cathode voltage remains fixed.

[0030] Several operating values ​​change in an image intensifier assembly as temperature changes (as described above). Generally, power supplies and intensifier tubes operate more efficiently at lower temperatures than at room temperature and worse (noisier) at higher temperatures. The official U.S. government test for behavior at high and low temperatures, the Temperature Extremes test, has three functional temperatures at which measurements are taken: baseline temperature or room temperature (~23°C), high temperature (nominal +50°C) and low temperature (nominal -50°C). Left uncorrected, the various shifts combine to cause a noticeable change in output brightness with temperature. The degree of change in output brightness (gain) is enough that an intensifier assembly whose gain is within specification at room temperature will be out of specification at low temperatures, with a typical 70% increase in output brightness.

[0031] The gain of the MCP114 is expected to change 0.1% per temperature change. Since the MCP gain does not vary with temperature, but only with V2(T), adjustment of this variable is fairly well controlled, which is why it is chosen as the gain control parameter for the lower light levels.

[0032] In one embodiment, the night vision device is constructed based on a linear relationship between operating voltage and luminous output, referred to as the Imputed Brightness Relationship, derived from empirical data to model the change in output brightness with changes in temperature driving voltage change.

[0033] If the luminance B is given in foot Lamberts or fl, then the relationship of B to V1, V2 and V3 is: Note that the numerical coefficients represent a percentage luminous output change.

number

[0034] This equation is known as the imputed brightness relationship and shows that V2 is the strongest contributor to output brightness among the three operating voltages. Thus, for every volt change in V2, the output brightness changes by 1.5%, but for a volt change in V3, there is a 0.05% gain change. Although the change to V3 is larger in magnitude (see FIG. 3), the output brightness change per volt change in V3 is 30 times smaller than for a volt change in V2 voltage. In one embodiment, the power supply changes in operating voltage as a function of ambient temperature are obtained during final testing of each power supply, and these changes can also be used to modify the MCP voltage (V2) with temperature.

[0035] Figures 3 and 4 show that at -50°C, the intensifier output brightness increases without any increase in the I3 sensing current set point, primarily due to changes in the V2 and V3 voltages. This does not take into account the change in image tube phosphor efficiency that changes with temperature.

[0036] To control the low light level gain over a temperature range, one algorithm is a linear correction of V2 as a function of temperature, where the slope is greater than a simple slope adjusted only to compensate for that one change. As mentioned above, there are changes with temperature in the power supply and sometimes the interface and the intensifier. The increased slope m accounts for all these changes including V3 changes, phosphor efficiency changes, V1 changes (which increase the photoresponse and MCP gain), and V2 changes. This linear relationship is shown in Equation (4):

number

[0037] Brightness change in the ABC range (>2×10 -4 To compensate for fc, the power supply 150 reduces the I3 sensing current as a function of temperature and is expressed as a first-order linear equation:

number

[0038] In equation (5), m is the gain slope of the correction factor that best accounts for the slope of the gain change as a result of the efficiency change from all sources as a function of temperature.

[0039] In a manufacturing environment, it is impractical to characterize each component and each power supply due to efficiency variations over temperature. Thus, a general empirical relationship is used to account for the normal behavior of the multiplier tube and the inherent variations of individual power supplies (from final test data at the power supply levels mentioned above).

[0040] Also, the rate of change of gain is greater above room temperature than at lower temperatures. V2 is the gain at light levels <2×10 -4 Modulated at fc, I3 max is 2 x 10 -4For light levels above fc, the image intensifier assembly is modulated. Thus, four linear gain change coefficients are employed to keep the luminous output of the image intensifier assembly constant for low and high levels of light over the range of -50°C to +50°C. The coefficients, which substitute for the m value in equations (4) and (5), are as follows:

[0041] C1 = Low light level from 23°C to +50°C (<2×10 -4 fc) coefficient; V2 varies (6) C2 = low light level from 23°C to -50°C (<2×10 -4 fc) coefficient; V2 varies (7) C3 = High light level (>2×10 -4 Coefficient for fc; I3 max Change (8) C4 = high light level from 23°C to -50°C (>2×10 -4 Coefficient for fc; I3 max Change (9)

[0042] To determine the coefficients, the image intensifier assembly was evaluated at +50°C, 23°C and -50°C. At these temperatures the gain is measured (light output / light input at fl / fc).

[0043] In the model described below, the terms adopted are as follows:

[0044] G x is the gain at temperature level x (10).

[0045] The difference in gain is ΔG where x and y are the two temperature levels. xy =G x -G y is given as:

[0046] Tx is the temperature at level x

[0047] TR = Room temperature or 23℃ (12)

[0048] T H = High temperature, nominal 50°C (13)

[0049] T C = Low temperature or nominal -50°C (14)

[0050] The temperature difference is ΔT xy =T x -T y where x and y are the two temperature levels. (15)

[0051] The gain change per volt of V2 is δ v and holds a value of 0.015. (16)

[0052] Change in V2 from temperature x to temperature y, ΔV xy (17)

[0053] The normalized gain change per degree Celsius is given by Θ, where the normalization factor is the room temperature gain G R (18)

[0054] Light level < 2×10 -6 The basic form of the model of V2 changes in response to fc is:

number

[0055] A linear coefficient Cn is used for two temperatures x and y. To derive the low light coefficient, we first use the 2×10 -4 The gain change for fc is calculated. In this example, a low temperature of -50°C is used.

[0056]

number

[0057] The temperature changes are as follows:

Number

[0058] Also, the gain change of fl / fc per °C (or K) is as follows:

Number

[0059] To normalize the gain change with respect to the baseline room temperature gain, this quantity is divided by the room temperature 2×10 -6 divided by the fc gain, and is shown as the per-degree fractal gain change normalized by the baseline gain obtained in the term called Θ.

Number

[0060] To give the V2 change necessary to keep the cold gain the same as the room temperature gain, Θ is divided by δV. This quantity is the linear coefficient for the gain change between room temperature and cold temperature.

Number

Number

[0061] Then, the V2 change is such that T2 < T R and is C2 times the temperature change at a given temperature T2 such that the light level is <2×10 -6 fc.

Number

[0062] Similarly, the expression for the change in V2 for 23°C < T2 + 50°C is

Number

[0063] High light condition 2×10 -4 For fc, a similar approach is taken, except that the change in screen current is included. Note that the luminous gain and screen current values ​​are linearly proportional, so the following ratios are assumed to be equal: x is the screen current at temperature x. (28) shows the relationship between the screen current at room temperature (x=R) and the increased temperature (x=2).

number

[0064] And the change in screen current δ I ·I has the following form:

number

number

number

[0065] Here, δ I is the linear coefficient of luminous gain (C n ) and the screen current for T R The product of the temperature difference from and ΔT 2R T2 and T R is the temperature difference between

[0066] Here, C n Note that has the same form as the coefficient of the voltage term:

number

number

number

number

[0067] Light level ≥ 2 x 10 -4 At temperatures below TR, where fc, the model I2 = δ I I1+I1 becomes:

number

[0068] Also, if the light level is >2×10 -4 At temperatures above TR, where fc:

number

[0069] Therefore, to correct the luminous output over temperature at light levels high enough for ABC to be invoked, generalized versions of equations (37) and (38) are used.

number

[0070] Again, the linear control equation above is the most basic version of temperature compensation. More complex algorithms can be implemented with even more parameters.

[0071] Usage Compensation

[0072] During operation of the photointensifier 110, its response tends to degrade as the amount of charge extracted from the MCP 114 increases. Accelerated reliability testing can be designed to subject the photointensifier 110 and associated power supply 150 to elevated temperature and high light conditions to determine the mean time between failures. In this case, failure is a degradation of performance to a predefined minimum level. Three criteria can be evaluated during reliability testing: gain, SNR, and EBI (Equivalent Background Intensity). In general, EBI tends to degrade as the reliability test continues, and in most cases, its value is below specification. SNR usually degrades during reliability testing, although not at the same rate as gain. Thus, low gain is a typical failure mode for image intensifiers. The V2 and I 3ABC Temperature compensation helps to control to some extent the amount of current extracted from MCP 114 under different light levels.

[0073] The first step in developing a usage compensation technique is to have the multiplier I 3ABC The point is reached to understand that the gain of the MCP 114 decays over time as a function of the charge extracted. Using a digitally controlled power supply 150 including a chronometer 165, the power supply 150 can increment a counter for conditions that put the multiplier under stress, i.e., conditions that force the ABC current limit. The power supply 150 can be integrated into the CPU 160, can be a separate component, or can even be part of the control logic 180. The next step is to determine how much the MCP V2 voltage must be adjusted as charge is extracted from the MCP 114 and whether temperature plays a role in the gain decay. The final step is the development of an algorithm or model that covers the majority of multipliers manufactured but has limitations in adjustments for the outlying units of the distribution.

[0074] 7 is a diagram illustrating normalized gain as a function of time for the reliability of several tested multiplier tubes 110, in accordance with an embodiment of the present invention. The dashed line is the average of five filmed multiplier tubes, and the solid line is five individual unfilmed multiplier tubes.

[0075] For the filmed tube, the gain increases or remains the same during the initial stages of testing. It can be seen that the unfilmed tube loses gain almost immediately when placed under stress. Again, these curves are from a typical accelerated reliability test involving high light pulses and elevated temperatures. To determine the coefficients of the compensation algorithm, the filmed tube was exposed to the same light levels with and without temperature and the V2 voltage was reset to maintain gain over time.

[0076] The curves in FIG. 8A show normalized gain curves with the dashed curve at elevated temperature and the solid curve at room temperature, each curve being an average of five tubes. Some of the spread in normalized gain is due to the repeatability of the gain measurement equipment. FIG. 8B shows the voltage difference preferably added to the room temperature V2 set point to maintain the same gain as a function of time in a reliability test. After about 500 hours of testing at room temperature, the V2 adjustment is about 1.2 volts per 100 hours and the elevated temperature adjustment is 1.8 volts per 100 hours. In conclusion, increasing the temperature increases the decay rate, so any use compensation algorithm preferably takes this into account. As pointed out above, unfilmed tubes experience a decay in gain almost immediately, whereas filmed tubes have an initial period during which the gain increases or may be the same. Thus, the algorithm or model is preferably configured to not apply the correction factor until a predetermined period has passed, i.e., a delay in the V2 increase. Finally, some of the distributions may experience a slower decay. Applying full correction to such a device may result in the corrected gain being outside the upper tolerance limits. In this case, the algorithm or model preferably caps the allowed voltage change to the maximum correction, after which point the power supply 150 will not increase V2 and the multiplier gain will begin to decrease. With the foregoing in mind, in one embodiment, the parameters of the exemplary algorithm used are: delay , ΔV2, δ(T), ΔV 2max , Δt, where t delay is the time that must elapse before the algorithm is applied, ΔV2 is the correction added to the V2 setpoint as a function of time, δ(T) is the correction due to temperature, Δt is the amount of time in high light conditions, and ΔV 2max is the maximum allowable V2 adjustment. With these parameters, an example compensation algorithm would be: [Outside 1] TIFF2025016463000027.tif35115

[0077] One skilled in the art will appreciate that other algorithms or models are possible, using different and / or more parameters.

[0078] FIG. 9 is a flow chart illustrating a series of operations, methods, or processes for controlling the performance of a night vision device, according to an embodiment of the present invention. As described, the night vision device includes a power source and an image intensifier tube in communication with the power source. At 902, the method includes providing, by the power source, a control voltage to a microchannel plate of the photointensifier tube, which controls the gain of the microchannel plate. At 904, the method includes determining a compensation amount to apply to the control voltage based on a change in the control voltage caused by a change in temperature of the operating environment of the night vision device. At 906, the method includes adjusting the control voltage according to the compensation amount to obtain a compensation control voltage. At 908, the method includes providing, by the power source, a compensation control voltage to the microchannel plate of the image intensifier tube. In one embodiment, taking into account usage, the method may further include determining whether the night vision device has been used for a predetermined period of time, the method being configured to provide a compensation control voltage to the microchannel plate of the photointensifier tube only after the night vision device has been used for the predetermined period of time.

[0079] In summary, the embodiments described herein provide a digitally controlled power supply for a photomultiplier tube that provides an enhanced control process for controlling the performance of a night vision device by, among other things, taking into account and compensating for time of use and operating environment temperature.

[0080] Although the disclosed invention has been illustrated and described herein as embodied in one or more specific examples, it is not intended to be limited to the details shown, since various modifications and structural changes may be made within the scope of the claims and their equivalents without departing from the scope of the invention. Moreover, various features from one of the embodiments may be incorporated into another of the embodiments. It is therefore appropriate that the appended claims be construed broadly in a manner consistent with the scope of the disclosure as set forth in the following claims.

[0081] [Appendix 1] 1. A method for controlling performance of a night vision device, comprising: the night vision device comprises a power source; and an image intensifier in communication with the power source; The method comprises: providing a control voltage to a microchannel plate of the image intensifier tube by the power supply, the control voltage controlling a gain of the microchannel plate; determining an amount of compensation to apply to the control voltage based on a change in the control voltage due to a change in temperature of an operating environment of the night vision device; adjusting the control voltage according to the compensation amount to obtain a compensated control voltage; providing the compensation control voltage to the microchannel plate of the image intensifier tube by the power supply; Including, method. [Appendix 2] determining whether the night vision device has been used for a predetermined period of time; applying the compensation control voltage to the microchannel plate of the image intensifier only after the night vision device has been in use for the predetermined period of time; Further comprising: Method described in Appendix 1. [Appendix 3] The predetermined time is about 500 hours. Method described in Appendix 2. [Appendix 4] The step of determining whether the night vision device has been used for a predetermined period of time comprises: monitoring a chronometer in communication with a central processing unit of the power supply or associated with control logic within the power supply; Method described in Appendix 3. [Appendix 5] adjusting the control voltage includes adding a correction factor to the control voltage. Method described in Appendix 1. [Appendix 6] the correction factor is based on the amount of time the night vision device is exposed to high light conditions, a correction added to the control voltage set point as a function of time, and a temperature correction; Method described in Appendix 5. [Appendix 7] The high light condition is 2×10 -4 corresponds to a light level greater than fc, Appendix 6 The method described. [Appendix 8] The temperature change of the operating environment of the night vision device is not less than a range of -50°C to +50°C; Method described in Appendix 1. [Appendix 9] the coefficients used to determine the amount of compensation are selected based on the temperature and light level of the operating environment of the night vision device; Method described in Appendix 1. [Appendix 10] The coefficients are: 2×10 -4 The first factor is used for light levels below fc and temperatures from 23°C to +50°C, 2×10 -4 A second factor used for light levels below fc and temperatures between 23°C and -50°C, 2×10 -4 A third factor is used for light levels greater than fc and temperatures between 23°C and +50°C, and 2×10 -4A fourth factor is used for light levels greater than fc and temperatures between 23°C and -50°C. One of the Method described in Appendix 9. [Appendix 11] 1. A method for controlling performance of a night vision device, comprising: the night vision device comprises a power source and a photomultiplier tube in communication with the power source; The method comprises: providing, by the power supply, a second control voltage to a microchannel plate of the photomultiplier tube, the second control voltage controlling a gain of the microchannel plate; determining whether a difference between the second control voltage and a first control voltage provided at an earlier time than the second control voltage is less than a predetermined value; if the difference is less than a predetermined value, determining if the night vision device has been used for a predetermined amount of time; adjusting the second control voltage only after the night vision device has been used for a predetermined period of time to compensate for changes in the second control voltage resulting from time of use to obtain a third control voltage; providing, by the power supply, the third control voltage to the microchannel plate of the photomultiplier tube; A method comprising: [Appendix 12] The predetermined time is about 500 hours. Method described in Appendix 11. [Appendix 13] determining whether the night vision device has been used for a predetermined period of time includes monitoring a chronometer in communication with a central processing unit of the power supply or associated with control logic within the power supply; Method described in Appendix 11. [Appendix 14] adjusting the second control voltage includes adding a correction factor to the second control voltage. Method described in Appendix 11. [Appendix 15] the correction factor is based on the time the night vision device is exposed to high light conditions and is a correction added to the control voltage set point as a function of time; and a temperature correction. Method described in Appendix 14. [Appendix 16] The high light condition is 2×10 -4 corresponds to a light level greater than fc, Method described in Appendix 15. [Appendix 17] 1. A power supply for a light intensifier of a night vision device, comprising: The power source includes: a power supply circuit configured to provide a control voltage to the light multiplier; The chronometer, A temperature sensor; a memory configured to store control logic; a processor in communication with the chronometer, the temperature sensor, and the memory, the processor comprising: providing a control voltage to the microchannel plate of the photomultiplier by the power supply, the control voltage controlling the gain of the microchannel plate; determining whether the night vision device has been used for a predetermined period of time based on the value of the chronometer; determining an amount of compensation to apply to the control voltage based on a change in the control voltage caused by a change in temperature of the operating environment of the night vision device based on a value of the temperature sensor when the night vision device has been used for a predetermined period of time; Adjusting the control voltage according to the compensation amount to obtain a compensated control voltage; a processor configured to execute control logic that causes the power supply circuit to provide the compensation control voltage to the microchannel plate of the photomultiplier tube; A power supply. [Appendix 18] The predetermined time is about 500 hours. A power source as described in Appendix 17. [Appendix 19] the processor is configured to adjust the control voltage by adding a correction factor to the control voltage. A power source as described in Appendix 17. [Appendix 20] The correction factor is 2×10 -4 a correction added to the control voltage set point as a function of time based on the time of exposure to a high light condition exceeding fc, the correction being a temperature correction; Power source as described in Addendum 19.

Claims

1. 1. A method for controlling performance of a night vision device, comprising: the night vision device comprises a power source and a photomultiplier tube in communication with the power source; The method comprises: providing a control voltage to a microchannel plate of the photomultiplier tube by the power supply, the control voltage controlling a gain of the microchannel plate; determining an amount of compensation to apply to the control voltage based on a change in the control voltage due to a change in temperature of an operating environment of the night vision device; adjusting the control voltage according to the compensation amount to obtain a compensated control voltage; providing the compensating control voltage to the microchannel plate of the photomultiplier tube by the power supply; The compensation control voltage is calculated by: V(t)=V(t ｐｒｅｖｉｏｕｓ )+Δt*ΔV*δ(T) where V(t) is the compensation control voltage at a given time t, ΔV is the correction added to the set point of the control voltage, δ(T) is the correction due to temperature, and Δt is the time the night vision device is exposed to high light conditions. method.

2. The method further comprises: determining whether the night vision device has been used for a predetermined period of time; and applying the compensating control voltage to the microchannel plate of the photomultiplier tube only after the night vision device has been in use for a predetermined period of time. The method of claim 1.

3. The predetermined time is about 500 hours. The method of claim 2.

4. determining whether the night vision device has been used for a predetermined period of time includes monitoring a chronometer in communication with a central processing unit of the power supply or associated with control logic within the power supply; The method of claim 3.

5. adjusting the control voltage includes adding a correction factor to the control voltage. The method of claim 1.

6. the correction factor is based on the time the night vision device has been exposed to high light conditions, a correction added to the control voltage set point as a function of time, and a temperature correction; The method of claim 5.

7. The high light state is 2×10 －４ corresponds to a light level greater than fc, The method of claim 6.

8. The temperature change of the operating environment of the night vision device ranges from −50° C. to +50° C. The method of claim 1.

9. the coefficients used to determine the amount of compensation are selected based on the temperature and light level of the operating environment of the night vision device; The method of claim 1.

10. The coefficients are: 2 x 10 －４ A first factor used for light levels below fc and temperatures between 23°C and +50°C; 2 x 10 －４ A second factor used for light levels below f c and temperatures between 23° C. and −50° C. 2 x 10 －４ A third factor used for light levels greater than fc and temperatures between 23°C and +50°C, and 2 x 10 －４ A fourth coefficient used for light levels greater than f and temperatures between 23° C. and −50° C.

10. The method of claim 9.

11. 1. A power supply for a light intensifier of a night vision device, comprising: The power source includes: a power supply circuit configured to provide a control voltage to the light multiplier; The chronometer, A temperature sensor; a memory configured to store control logic; a processor in communication with the chronometer, the temperature sensor, and the memory, The processor, providing a control voltage to the microchannel plate of the photomultiplier by the power supply, the control voltage controlling the gain of the microchannel plate; determining whether the night vision device has been used for a predetermined period of time based on the value of the chronometer; determining an amount of compensation to apply to the control voltage based on a change in the control voltage caused by a change in temperature of the operating environment of the night vision device based on a value of the temperature sensor when the night vision device has been used for a predetermined period of time; Adjusting the control voltage according to the compensation amount to obtain a compensated control voltage; providing the compensation control voltage to the microchannel plate of the photomultiplier by the power supply circuit; The compensation control voltage is calculated by: V(t)=V(t ｐｒｅｖｉｏｕｓ )+Δt*ΔV*δ(T) where V(t) is a compensation control voltage at a given time t, ΔV is a correction added to the set point of the control voltage, δ(T) is a correction due to temperature, and Δt is the time the night vision device is exposed to high light conditions. power supply.

12. The predetermined time is about 500 hours.

12. The power supply of claim 11.

13. the processor is configured to adjust the control voltage by adding a correction factor to the control voltage.

12. The power supply of claim 11.

14. The correction factor is 2×10 －４ a correction added to the control voltage set point as a function of time based on the time of exposure to a high light condition exceeding f c , and a correction due to temperature.

14. The power supply of claim 13.

15. The temperature change of the operating environment of the night vision device is greater than or equal to the range of −50° C. to +50° C.; 12. The power supply of claim 11.

16. the coefficients used to determine the amount of compensation are selected based on the temperature and light level of the operating environment of the night vision device; 12. The power supply of claim 11.

17. The coefficients are: 2 x 10 －４ A first factor used for light levels below fc and temperatures between 23°C and +50°C; 2 x 10 －４ A second factor used for light levels below f c and temperatures between 23° C. and −50° C. 2 x 10 －４ A third factor used for light levels greater than fc and temperatures between 23°C and +50°C, and 2 x 10 －４ A fourth coefficient used for light levels greater than f and temperatures between 23° C. and −50° C.

17. The power supply of claim 16.

Images