Use of performance parameters and temperature compensation for night vision devices

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 can 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, which are used to amplify low-intensity light or convert non-visible light into readily viewable images. One such image intensifier is an 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 by 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 exit 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 unfilmed). When electrons strike the input surface of the MCP, secondary electrons are generated within the MCP. That is, an MCP can generate hundreds of electrons for each electron that enters its 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 enables electron multiplication in the MCP.

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

[0006] A power supply integrated with or potted into the image intensifier tube is generally used to generate and provide the various potential differences described 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 a 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 includes the steps of: supplying, by a power supply, a control voltage to a microchannel plate of an image intensifier tube, the control voltage controlling the 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 the operating environment of the night vision device; adjusting the control voltage according to the compensation amount to obtain a compensated control voltage; and supplying, by the power supply, the compensated control voltage to the microchannel plate of the image intensifier tube. The method further includes the step of determining whether the night vision device has been used for a predetermined period of time, and is configured to supply 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 supply and an image intensifier tube in communication with the power supply. The method includes the steps of: supplying, by the power supply, a second control voltage to a microchannel plate of the image intensifier tube that controls a gain of the microchannel plate; determining whether a difference between the second control voltage and a first control voltage supplied 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 the 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 use time to obtain a third control voltage; and supplying, by the power supply, 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 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: supply, via the power supply, a control voltage to a microchannel plate of the light intensifier that controls the gain of the microchannel plate; determine, based on the value of the chronometer, whether the night vision device has been used in a stressed state for a predetermined time; and, if the night vision device has been used in a stressed state for the predetermined time, determine a compensation amount for applying the control voltage based on the stress exposure. Furthermore, based on the value of the temperature sensor, a change in the control voltage due to a change in temperature of the operating environment of the night vision device may exist regardless of whether or not there has been past stress exposure; the power supply adjusts the control voltage according to the compensation amount to obtain a compensated control voltage; and supply, via the power supply circuit, the compensated control voltage to the microchannel plate of the light intensifier. It is structured as follows. [Brief explanation 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. [Figure 2] FIG. 2 is a plot of output brightness versus light level according to an embodiment of the present invention. [Figure 3] FIG. 3 shows plots illustrating how the 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), according to an embodiment of the present invention. [Figure 5] FIG. 5 is a diagram illustrating how the photoresponse (PR) varies with the electric field strength between the photocathode and the MCP input, according to 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 is a diagram illustrating 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 is a diagram illustrating a normalized gain curve according to an embodiment of the present invention. [Figure 8B] FIG. 8B is a diagram illustrating 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 flowchart illustrating a series of operations or processes for controlling the performance of a night vision device, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Similar reference numbers are used throughout this disclosure to identify similar 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 stores, 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. The values ​​of these control voltages can be set by CPU 160 according to instructions received from control logic 180.

[0014] In a possible embodiment, CPU 160 controls circuitry that controls the application of voltages V1, V2, and V3 to photocathode 112, MCP 114, and anode 116, respectively. Operational amplifier 195 is configured to sense current I3 flowing through anode 116. Current I3 represents the brightness of light 10 being received by photocathode 112, where V1 and V2 are not modified to control the output brightness of the phosphor screen. The value of current I3 can be used by control logic 180 and CPU 160 to, for example, adjust the value of V1 or V2 (e.g., a higher V1 or V2 for higher brightness, a lower V1 or V2 for lower brightness). 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 for performance parameters with respect to temperature and / or usage.

[0016] Fixed Brightness Control

[0017] One function of power supply 150 and control logic 180 is to control the output brightness of intensifier tube 110 as a function of input light level, protecting the user from overly bright amplified scenes. In this regard, Figure 2 illustrates a plot of output brightness versus light level in accordance with an embodiment of the present invention. As shown, the output brightness remains approximately fixed (between predetermined brightness limits) above a predetermined level of received light, but nevertheless tends to increase slightly in the case of 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, embodiments 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 exhibits a brightness of approximately 2×10 -5 fc (foot-candles) after the screen current (I3) is fixed at a constant value. This constant brightness output is the result of the control logic 180 driving a control voltage (e.g., photocathode control voltage V1) to produce a zero difference between the screen current (I3) and a fixed value current, achieving the desired screen brightness. The operation of the control voltage is described below.

[0019] temperature compensation

[0020] Under extreme operating conditions, for example, from -50°C to +50°C, the multiplier 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 noted above, some of the parameters and control processes within power supply 150 are achieved by adjusting the voltage (V1 and V2) and I3 current settings. Under certain 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 lighting), 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, called Automatic Brightness Control (ABC), prevents the screen current (I3) from exceeding its 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 output brightness by varying V2, and then adjusts the maximum allowable current value I3, which corresponds to the maximum allowable output brightness at a fixed temperature. max , keeping the screen current (linearly related to output brightness) below . As the light level increases, V2 eventually decreases to a minimum value. Once V2 reaches the first lower limit, the luminous 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 allowable screen current is varied to control the light output in environments hotter or colder than room temperature. Control logic 180 within power supply 150 is configured to control the supply voltage, which can vary with temperature. In this regard, a temperature sensor 164 is provided and may be part of CPU 160 or, as shown, may be a separate component in communication with CPU 160 (FIG. 1).

[0022] The observed change in voltage output 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, Figure 3 shows a plot illustrating how the three control voltages of power supply 150 respond to changes in temperature without active compensation. The plotted lines in Figure 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] Figure 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 or remain close to constant as the temperature decreases. 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) changes with changes in the electric field strength between the photocathode 112 and the input of MCP 114. Since the spacing does not change with temperature, the photocathode current changes 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 increases the emission probability and increases β. However, as the bandgap increases, the spectral cutoff frequency also shifts upward, meaning the cathode becomes less sensitive to longer wavelength photons. These two shifts are illustrated in the spectral response curves for 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 discussed above). Generally, power supplies and intensifier tubes operate more efficiently at lower temperatures than room temperature and poorly (noisier) at higher temperatures. The official U.S. government test for high and low temperature behavior, 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 sufficient to cause an intensifier assembly whose gain is within specification at room temperature to go 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. Because 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 lower light levels.

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

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

number

[0034] This equation, known as the imputed brightness relationship, shows that V2 is the strongest contributor to output brightness among the three operating voltages. Thus, for each 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. While the change to V3 is larger in magnitude (see FIG. 3), the change in output brightness per volt change in V3 is 30 times smaller than for a volt change in the V2 voltage. In one embodiment, 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 output brightness of the intensifier tube 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 changes in the picture tube phosphor efficiency that change with temperature.

[0036] To control 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 multiplier tube. The increased slope m accounts for all of these changes, including V3 change, phosphor efficiency change, V1 change (which increases photoresponse and MCP gain), and V2 change. 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 efficiency changes 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 aforementioned power supply levels).

[0040] Also, the rate of change of gain is greater at temperatures 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 -4The image intensifier assembly is modulated for light levels above fc. Thus, four linear gain variation coefficients are employed to maintain constant luminous output for low and high light levels 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 (<2×10 -4 Coefficient for fc; V2 varies (6) C2 = low light level (<2 × 10 -4 fc) coefficient; V2 changes (7) C3 = High light level (>2×10 -4 Coefficient for fc; I3 max Changes (8) C4 = High light level (>2×10 -4 Coefficient for fc; I3 max Changes (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 used are:

[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°C (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 V2 volt is δ v and holds the value of 0.015. (16)

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

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

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

number

[0055] The linear coefficients Cn are used for two temperatures x and y. To derive the low light coefficients, we first calculate 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 normalized by the baseline gain obtained in terms of the term Θ, showing the per-degree fractal gain change.

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: where I 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 is of the form:

number

number

number

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

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

number

number

number

number

[0067] Light level ≥=2×10 -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 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 photomultiplier 110, its response tends to degrade as the amount of charge extracted from the MCP 114 increases. Accelerated reliability testing can be designed to expose the photomultiplier 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 predetermined minimum level. Three criteria can be evaluated during reliability testing: gain, SNR, and EBI (equivalent background intensity). Generally, EBI tends to degrade as the reliability test continues, and in most cases, its value is below specification. SNR also degrades during reliability testing, although usually not at the same rate as gain. Therefore, low gain is a typical failure mode for image intensifiers. The V2 and I mentioned above 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 3ABC The key to success is understanding that the gain of the MCP 114 decays over time as a function of the charge extracted. Using a digitally controlled power supply 150 with a chronometer 165, the power supply 150 can increment a counter for conditions that stress the multiplier, i.e., conditions that force ABC current limiting. The power supply 150 can be integrated into the CPU 160, be a separate component, or 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 to develop an algorithm or model that covers the majority of manufactured multipliers but has limitations on adjustment for 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, according to 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 either increases or remains the same during the initial stages of testing. The unfilmed tube can be seen to lose 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 Figure 8A show normalized gain curves, with the dashed curve at elevated temperature and the solid curve at room temperature, and each curve is an average of five multiplier tubes. Part of the spread in the normalized gain is due to the repeatability of the gain measurement equipment. Figure 8B shows the voltage difference preferably added to the room temperature V2 setpoint to maintain the same gain as a function of time during a reliability test. After approximately 500 hours of testing at room temperature, the V2 adjustment is approximately 1.2 volts per 100 hours, and the elevated temperature adjustment is 1.8 volts per 100 hours. Consequently, increasing temperature increases the rate of decay, and any compensation algorithm preferably takes this into account. As noted above, unfilmed multiplier tubes experience almost immediate gain decay, while filmed tubes have an initial period during which the gain may increase or remain the same. Therefore, the algorithm or model is preferably configured not to apply the correction factor until a predetermined period has passed, i.e., a delay in the V2 increase. Finally, some portions of the distribution may experience a slower decay. Applying full correction to such a device may result in the corrected gain falling 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 power supply 150 will not increase V2 and the gain of the multiplier will begin to decrease. With the foregoing in mind, in one embodiment, the parameters of the exemplary algorithm used are: t 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] TIFF0007756218000026.tif35115

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

[0078] FIG. 9 is a flowchart illustrating a series of operations, a method, or a process 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 supply and an image intensifier tube in communication with the power supply. At 902, the method includes providing, by the power supply, a control voltage to a microchannel plate of the photointensifier tube that 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 due to 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 compensated control voltage. At 908, the method includes providing, by the power supply, a compensated control voltage to the microchannel plate of the image intensifier tube. In one embodiment, taking usage into account, the method can further include determining whether the night vision device has been used for a predetermined period of time, the method being configured to provide a compensated 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 taking into account and compensating for, among other things, the duration of use and the temperature of the operating environment.

[0080] While 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 and range of equivalents of the claims without departing from the scope of the invention. Moreover, various features from one embodiment may be incorporated into another embodiment. Accordingly, it is appropriate that the scope of the appended claims be accorded the broadest interpretation 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: applying a control voltage to a microchannel plate of the image intensifier tube by the power supply, the control voltage controlling the gain of the microchannel plate; determining an amount of compensation to apply to the control voltage based on changes in the control voltage due to changes in temperature of the 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 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 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, and is a correction added to the control voltage set point as a function of time; and is 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 between 23°C and +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 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: applying a second control voltage to the microchannel plate of the photomultiplier tube by the power supply, 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 applied earlier than the second control voltage is less than a predetermined value; If the difference is less than a predetermined value, determining whether 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 use time to obtain a third control voltage; applying the third control voltage to the microchannel plate of the photomultiplier tube by the power supply; 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 has been exposed to high light conditions and is a correction added to the control voltage set point as a function of time; and is 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 supply a power supply circuit configured to provide a control voltage to the light multiplier; A chronometer and 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; When the night vision device has been used for a predetermined period of time, 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 based on the value of the temperature sensor; 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; Provided with a power supply. [Appendix 18] The predetermined time is about 500 hours. Power supply 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. Power supply 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 duration of exposure to a high light condition exceeding fc, the correction being a temperature correction; Power supply as described in Appendix 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: applying a control voltage to a microchannel plate of the photomultiplier tube by the power supply, the control voltage controlling the gain of the microchannel plate; determining an amount of compensation to apply to the control voltage based on changes in the control voltage due to changes in temperature of the 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 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 compensation 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 approximately 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 and is a correction added to the control voltage set point as a function of time; and is 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 coefficient 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 fc 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 fc 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 supply a power supply circuit configured to provide a control voltage to the light multiplier; A chronometer and 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; When the night vision device has been used for a predetermined period of time, 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 based on the value of the temperature sensor; 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 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. power supply.

12. The predetermined time is approximately 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 fc, the correction being a temperature correction; 14. The power supply of claim 13.

15. The temperature change in the operating environment of the night vision device is greater than or equal to a 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 coefficient 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 fc 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 fc and temperatures between 23°C and -50°C; 17. The power supply of claim 16.

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