rus
Issue #3/2021
A. V. Medvedev, A. V. Grinkevich, S. N. Knyazeva
Night Vision Goggles and Features of Their Use
Night Vision Goggles and Features of Their Use
DOI: 10.22184/1993-7296.FRos.2021.15.3.214.226
The article reviews a specific class of optical-electronic devices, which are the night vision goggles. They are not only improving the visibility in various difficult observation conditions but also freeing up the hands of the observer thus enabling various operations during the observation. There are two options of two-channel night vision goggles reviewed in the article featuring IR+TV and TV+SWIR channels, respectively, in terms of the benefits of their operation in the dark.
The article reviews a specific class of optical-electronic devices, which are the night vision goggles. They are not only improving the visibility in various difficult observation conditions but also freeing up the hands of the observer thus enabling various operations during the observation. There are two options of two-channel night vision goggles reviewed in the article featuring IR+TV and TV+SWIR channels, respectively, in terms of the benefits of their operation in the dark.
Теги: cabin equipment ir+tv goggles low-profile goggles night vision goggles swir range swir диапазон внутрикабинное оборудование низкопрофильные очки очки ночного видения тепло-телевизионные очки
Night Vision Goggles and Features of Their Use
A. V. Medvedev, A. V. Grinkevich, S. N. Knyazeva
ROMZ JSC, Yaroslavl region, Rostov
EVS CJSC, Moscow
ROMZ EDB JSC, Yaroslavl region, Rostov
The article reviews a specific class of optical-electronic devices, which are the night vision goggles. They are not only improving the visibility in various difficult observation conditions but also freeing up the hands of the observer thus enabling various operations during the observation. There are two options of two-channel night vision goggles reviewed in the article featuring IR+TV and TV+SWIR channels, respectively, in terms of the benefits of their operation in the dark.
Keywords: night vision goggles, SWIR range, cabin equipment, low-profile goggles, IR+TV goggles
The development of optoelectronic devices (OED) for observation and aiming is a natural process of evolution in the field of instrumentation. With the development of technologies, OED designs have been improved and today they fully provide all-day and all-weather observation. Among the variety of OEDs, a special class of devices can be distinguished – optoelectronic glasses, which allow not only to improve visibility, but also free the observer’s hands to perform various operations accompanying the observation.
One of the first representatives of the class of optoelectronic glasses were night vision goggles (NVG) and the first working versions of NVG accumulated the most advanced solutions of their time. One of the ONV samples, the manufacture of which is dated by the forties of the last century, is shown in Fig. 1.
A characteristic feature of the NVG of this period is the presence of an impressive infrared (IR) searchlight, usually placed on the chest, as well as a metal shoulder “backpack” with batteries and high-voltage voltage converters, the main task of which was to convert the low-voltage input voltage into voltage of tens of kilovolts for power supply of electro-optical converters.
Over time, already in the 60s, the desire to reduce dimensions led to a miniaturization of the IR illuminator and a decrease in its size and weight made it possible to move the illuminator from the chest to the observer’s head and fix it on a bracket common with the glasses, which undoubtedly increased the convenience of their use (Fig. 2).
The design of the bracket provided for the ability to “fold” the night goggles up quickly, which made it possible to conduct routine observation without tedious and time-consuming dismantling of the device. However, the battery box with electronic units fixed on the back remained unchanged for quite a long time.
But progress did not stand still and the appearance of small-sized electronic components made it possible to transfer almost all electronic components to the back of the head mount of the glasses, which turned into a small block that balances the actual night glasses, which are naturally located in front of the eyes.
This circumstance explains the rather high popularity of a number of NVG, developed at that time and are still actively used to perform special tasks. As an example, we can present the product ПНВ‑57Е (Fig. 3).
The photo shows that for all its advantages, the product is certainly far from perfect, since the low-voltage battery when using it “serves” the on-board network of the vehicle, and the standard headlights of the car are used as an IR searchlight, which are covered with IR filters.
A significant increase in the gain of new image intensifier tubes, as well as the emergence of new types of ultra-bright LEDs for the IR region, contributed to the transformation of a powerful IR illuminator into a miniature illuminator, the transparent plastic case of which was simultaneously an optical system, and the development at the end of the last century of miniature electronic components (high-voltage diodes and capacitors, small-sized transformers, etc.) made it possible to locate the high-voltage unit directly in the body of the image-converter, equipped with an effective device in the form of a microchannel plate (MCP). The result was a radical measurement of the layout solution of the NVG, all the components of which, as well as the accessories that ensure the operation, were placed in a single building (Fig. 4).
However, a common disadvantage of this design is a significant longitudinal overall dimension, which limits the breadth of their application. A significant overturning moment also adds significant discomfort, which puts a strain on the operator’s neck and facial muscles, causing him to fatigue.
Further efforts of the designers aimed at improving night glasses based on electron-optical converters went in the direction of rearranging the internal elements with a change in the optical scheme.
An example of such an approach are night goggles of the adjacent profile 1ПН105, often demonstrated at exhibitions in recent years (Fig. 5).
In glasses, the “forward” extension is significantly reduced, but the high overall size did not disappear, it simply changed direction – the vertical size increased and the impression of a snug fit to the observer’s forehead was created.
Among the variety of NVG options, a special place is occupied by goggles for aircraft pilots, designed for observing the space behind the cockpit of an aircraft at dusk and at night in conditions of natural night illumination (NNI) on terrain from 10–4 to 1.0 lux, and in some cases – with reduced transparency of the atmosphere, characterized by haze, fog, rain, etc.
A typical representative of NVG for pilots is the device “GEO-ONV1-01”, built on image intensifier tubes of generations II+ and III (Fig. 6).
When using NVG based on image intensifier tubes, it should be borne in mind that all indoor and outdoor lighting, including alarms and illumination of in-cab devices, illuminates the photocathodes of the image intensifier tubes. As a result of the research, the possibility of using color film light filters to narrow the operating spectral ranges of in-cab emitters in order to reduce their effect on NVG photocathodes was worked out [1]. However, this led to a limitation of the spectral characteristics of the image intensifier tube photocathode.
Another design solution based on the impulse adaptation method could be a more effective method. Here, the internal and external lighting equipment is connected to the in-cab lighting equipment and to the NVG through the synchronization unit, which provides operation in a pulsed mode and in time antiphase of the NVG with the lighting equipment, which makes it possible to exclude spurious illumination of the NVG in the dark [2].
All adaptation options require a structural complication of the in-cockpit electrical equipment, which leads to the need to create a specialized version of the aircraft adapted for night flights, and this reduces its reliability as a whole, not fully providing a comfortable pilot’s work.
However, there is a solution to this problem.
The elimination of complex, time-consuming and expensive methods of adaptation of the aircraft becomes possible if the pilot is provided with an OED using a spectral range that is different from the spectral range of radiation of the in-cabin equipment.
It is advisable to solve such a device in the form of an observation device with several working channels.
The most common combination is a combination of thermal imaging and television observation channels. These channels, being mutually complementary in many parameters, when combined into a coordinated observing system, make it possible to increase its efficiency, since they keep the system working in conditions when one of the channels is ineffective due to external conditions [3].
An example of such a device is the low-profile heat-television glasses IR-TV NVG, developed at the Rostov Optical and Mechanical Plant (Fig. 7).
IR-TV NVG is a multifunctional device that allows you to navigate and move around any terrain in difficult conditions, drive vehicles, carry out engineering and repair work, and also provide the ability to work with documents in complete darkness, as well as in rain, snow, fog, artificial and natural smoke.
The glasses are built according to the classical binocular scheme and have two working optical channels: television and thermal imaging, and two eyepiece outputs, with each of the objectives being installed coaxially with one of the eyepieces.
The ability to display information from any of the spectral ranges on two displays provides a stereoscopic effect, which significantly increases the convenience and information content of observation and reduces eye fatigue.
The design parameters of the optical components provide equalization of the image formats, which makes it possible to combine images obtained in different spectral ranges and display the combined image from each of the channels in different percentages.
The device uses special high-aperture optics with protection against backlighting, digital and optical zoom is implemented, for reading documents and topographic maps, a built-in wide-angle IR illumination with indication of the inclusion of the IR illuminator is provided.
However, no matter how wide the capabilities of the thermal television glasses are, it is not possible to use them for observation from the cockpit through the thermal imaging channel, since the cockpit glass does not allow thermal imaging wavelengths to pass through, and this requires the use of remote rotary thermal imaging cameras, as well as systems tracking and synchronizing their rotation with the rotation of the pilot’s head [4].
The possibility of unobstructed observation through protective and windshields of vehicles is provided in a universal version of the NVG with a classic television channel in the visible range of the spectrum and a channel in the short-wave IR range from 0.9 to 1.7 microns, called in Western terminology the SWIR range.
The SWIR channel, in contrast to thermal imaging, not only provides observation through ordinary glass [5], but also allows you to get an image even through heavily tinted glass of a car (Fig. 8).
The SWIR channel is built on a photodetector based on InGaAs material, which most effectively provides night observation and observation in bad weather conditions through cockpit glazing. Evaluation of the effectiveness in terms of range shows that night vision devices with InGaAs photodetectors at low illumination levels of less than 2 × 10–3 lux, in conditions of haze, weak fogs and dust (at a meteorological visibility range Sm ≈ 2.5 km), at order surpass the OED on the image intensifier tubes [6].
Thus, using two such channels, it is possible to obtain an almost universal version of the NVG for piloting and driving various vehicles, since the SWIR channel is almost always compatible with the glazing of cabins and does not require additional adaptation of the vehicle to the proposed NVG, and a television channel with the usual visibility expands NVG capabilities and provides high resolution with the possibility of additional electronic magnification.
A variant of the design of universal NVG, using an original layout solution, which reduces the “extension” of the lenses forward and provides a “flatter” profile of the device, is shown in Fig. 9.
Previously, the NVG is installed (fixed) in front of the observer’s eyes so that the exit pupils of the eyepieces are aligned with the observer’s eyes.
Due to the difference in the light diameters of the SWIR and TV channels, as well as different fields of view for HD (40°) and VD (30°), the mirror prism has an asymmetric shape, and the protective glass has an elongated shape, while the SWIR and TV channels are displaced relative to each other in the horizontal plane by a certain amount Δx. The calculated dimensions of the faces of the mirror prism, the distance and, accordingly, the value Δx, can be determined according to the outline diagram shown in Fig. 10.
If we express the value of the segment О1О5 by two ratios through the dimensions of the left branch and through the dimensions of the right branch, then the following formulas will be valid:
(1)
for the left branch, and:
(2)
for the right branch, where:
О1 is the top of the mirror prism;
О2, О3, О4 are the points lying on the axis passing through the top of the mirror prism and perpendicular to the optical axes of the objectives;
О5 is the point of intersection of the optical axis of the lens of the left branch with the perpendicular axis passing through the top of the mirror prism;
ω1, ω2 are the angles of the field of view of the left and right branches, respectively;
А1, А2 are the distances from the light diameter of the first objective lens (or from the entrance pupil of the objective) to the top of the mirror prism O1 for the left and right branches, respectively.
After equating the right-hand sides of the formulas, the final expression for Δx takes the form:
. (3)
The formula is valid in the absence of vignetting, and setting the permissible vignetting will allow us to ensure acceptable dimensions of the device when designing.
A variant of such an arrangement, which has the weight of the optics of all channels with microdisplays and two CR123A batteries of ~134 g, can provide a low profile at a level of ~45 mm in depth (Fig. 11).
The television observation branch provides observation of the outdoor environment during the day and the in-cab equipment in day and night conditions due to the coincidence of the working spectral ranges of the in-cab emitters and the television photodetector.
The SWIR channel of the spectral range provides night observation without the influence of illumination from the in-cabin lighting equipment due to the different operating spectral ranges of the television channel, in-cabin emitters and a SWIR range photodetector. The working spectral range of the television channel and modern LED in-cab emitters is in the range from 0.45 to 0.85 µm, and the SWIR channel has a spectral range of wavelengths from 0.9 to 1.7 µm, which provides the necessary spectrum spacing.
The characteristics of night vision goggles in comparison with serial devices of types 1ПН74 and 1ПН105 are shown in Table 1. The functional diagram of the NVG is shown in Fig. 12. The given functional diagram is universal and can be the basis for an NVG in any version of the spectral performance of the observation channels.
In the considered version of NVG, two matrices are used as photodetectors – SWIR matrix FUK36M manufactured by NPO Orion JSC with a format of 640 × 512 pixels, which has a high sensitivity in the short-wave infrared range of 0.9–1.7 microns, and a CMOS matrix EV76C660 by Teledyne e2v with a 1280 × 1024 pixel format, providing a high-quality image when the illumination changes from 5 × 10–2 to 5 × 104 lux.
The processor unit, the main computing core of which is the Xilinx XC7A75T programmable logic array, provides processing of incoming video information and its subsequent output to microdisplays.
AMOLED microdisplays SXGA‑120 R5 manufactured by eMagin Corporation in 1280 × 1024 format allow displaying incoming video information and entering service data.
The power supply generates the voltages necessary for the operation of the NVC, and also makes it possible to charge the batteries from an external power source. Two Li-Ion accumulators of 16340 size, 1200 mAh capacity are used as power sources.
An important feature of two-channel NVG is the use of domestic photodetectors. The Moscow enterprise “Orion” has developed and is producing a new module – 640 × 512 elements with a pitch of 15 µm, the parameters of which are presented in Table 2. The module includes a matrix of photosensitive elements made of InGaAs.
The Moscow enterprise Pulsar is completing R&D work to create a complete analogue of the EV76C660 CMOS matrix. The controls allow you to select different modes of NVC operation: image output only from the SWIR matrix, image output only from the CMOS matrix, combined image output, as well as the image output from the CMOS matrix in the electronic zoom mode of 2 krt, which makes the device almost a universal option for numerous applications.
It should be especially noted that the integrated image output mode provides the possibility of simultaneous observation of the image of the in-cab lighting equipment through a television channel and images of the terrain at all levels of natural night illumination through the SWIR channel without being influenced by illumination from the in-cab lighting equipment.
REFERENCES
RF patent No. 2133973. Method of illumination of instrument equipment and transparencies of light signaling of an aircraft when observing them through aerobatic night vision goggles / Belikova V. N., Vinokurov S. A., Gordienko Yu.N., Gruzevich Yu.K., Dyatlov A. L., Soldatenkov V. A., Khusnetdinov A. R.
RF patent № 2325308 C2. Device for impulse adaptation of lighting equipment, mainly aircraft to night vision devices / Padalko G. A., Pokotilo S. A., Golovatenko V. P., Shchedrina T. V., Loktionov V. I.
Medvedev A. V., Grinkevich A. V., Knyazeva S. N. Image intensifier or television matrix? Aspects of the effectiveness of the application. Photonics. 2020; 14 (5): 394–411.
Gruzevich Yu. K. Optoelectronic night vision devices. M.: FIZMATLIT. 2014. 276 p. – ISBN 978-5-9221-1550-6.
Ptitsyn A. What we see and what we do not see. Photonics. 2015; 3 / 51: 142–151.
Gusarova N. I., Koshavtsev N. F., Popov S. V. Advantages of using solid-state photodetectors for the spectral range of 1.4–1.7 microns in night vision devices. Advances in Applied Physics. 2014; 2 (3).
AUTHORS
Medvedev Alexander Vladimirovich, design@romz.ru, General Designer, Rostov Optical and Mechanical Plant OJSC (ROMZ OJSC), Rostov Veliky, Yaroslavl Region, Russia.
Grinkevich Alexander Vasilievich, lyu1455@yandex.ru, ZAO “EVS”, Moscow, Russia.
Knyazeva Svetlana Nikolaevna, ksn 61@yandex.ru, Design Engineer, Design Bureau of OJSC “Rostov Optical and Mechanical Plant, (OJSC ”ROMZ“), Rostov the Great, Yaroslavl Region, Russia.
A. V. Medvedev, A. V. Grinkevich, S. N. Knyazeva
ROMZ JSC, Yaroslavl region, Rostov
EVS CJSC, Moscow
ROMZ EDB JSC, Yaroslavl region, Rostov
The article reviews a specific class of optical-electronic devices, which are the night vision goggles. They are not only improving the visibility in various difficult observation conditions but also freeing up the hands of the observer thus enabling various operations during the observation. There are two options of two-channel night vision goggles reviewed in the article featuring IR+TV and TV+SWIR channels, respectively, in terms of the benefits of their operation in the dark.
Keywords: night vision goggles, SWIR range, cabin equipment, low-profile goggles, IR+TV goggles
The development of optoelectronic devices (OED) for observation and aiming is a natural process of evolution in the field of instrumentation. With the development of technologies, OED designs have been improved and today they fully provide all-day and all-weather observation. Among the variety of OEDs, a special class of devices can be distinguished – optoelectronic glasses, which allow not only to improve visibility, but also free the observer’s hands to perform various operations accompanying the observation.
One of the first representatives of the class of optoelectronic glasses were night vision goggles (NVG) and the first working versions of NVG accumulated the most advanced solutions of their time. One of the ONV samples, the manufacture of which is dated by the forties of the last century, is shown in Fig. 1.
A characteristic feature of the NVG of this period is the presence of an impressive infrared (IR) searchlight, usually placed on the chest, as well as a metal shoulder “backpack” with batteries and high-voltage voltage converters, the main task of which was to convert the low-voltage input voltage into voltage of tens of kilovolts for power supply of electro-optical converters.
Over time, already in the 60s, the desire to reduce dimensions led to a miniaturization of the IR illuminator and a decrease in its size and weight made it possible to move the illuminator from the chest to the observer’s head and fix it on a bracket common with the glasses, which undoubtedly increased the convenience of their use (Fig. 2).
The design of the bracket provided for the ability to “fold” the night goggles up quickly, which made it possible to conduct routine observation without tedious and time-consuming dismantling of the device. However, the battery box with electronic units fixed on the back remained unchanged for quite a long time.
But progress did not stand still and the appearance of small-sized electronic components made it possible to transfer almost all electronic components to the back of the head mount of the glasses, which turned into a small block that balances the actual night glasses, which are naturally located in front of the eyes.
This circumstance explains the rather high popularity of a number of NVG, developed at that time and are still actively used to perform special tasks. As an example, we can present the product ПНВ‑57Е (Fig. 3).
The photo shows that for all its advantages, the product is certainly far from perfect, since the low-voltage battery when using it “serves” the on-board network of the vehicle, and the standard headlights of the car are used as an IR searchlight, which are covered with IR filters.
A significant increase in the gain of new image intensifier tubes, as well as the emergence of new types of ultra-bright LEDs for the IR region, contributed to the transformation of a powerful IR illuminator into a miniature illuminator, the transparent plastic case of which was simultaneously an optical system, and the development at the end of the last century of miniature electronic components (high-voltage diodes and capacitors, small-sized transformers, etc.) made it possible to locate the high-voltage unit directly in the body of the image-converter, equipped with an effective device in the form of a microchannel plate (MCP). The result was a radical measurement of the layout solution of the NVG, all the components of which, as well as the accessories that ensure the operation, were placed in a single building (Fig. 4).
However, a common disadvantage of this design is a significant longitudinal overall dimension, which limits the breadth of their application. A significant overturning moment also adds significant discomfort, which puts a strain on the operator’s neck and facial muscles, causing him to fatigue.
Further efforts of the designers aimed at improving night glasses based on electron-optical converters went in the direction of rearranging the internal elements with a change in the optical scheme.
An example of such an approach are night goggles of the adjacent profile 1ПН105, often demonstrated at exhibitions in recent years (Fig. 5).
In glasses, the “forward” extension is significantly reduced, but the high overall size did not disappear, it simply changed direction – the vertical size increased and the impression of a snug fit to the observer’s forehead was created.
Among the variety of NVG options, a special place is occupied by goggles for aircraft pilots, designed for observing the space behind the cockpit of an aircraft at dusk and at night in conditions of natural night illumination (NNI) on terrain from 10–4 to 1.0 lux, and in some cases – with reduced transparency of the atmosphere, characterized by haze, fog, rain, etc.
A typical representative of NVG for pilots is the device “GEO-ONV1-01”, built on image intensifier tubes of generations II+ and III (Fig. 6).
When using NVG based on image intensifier tubes, it should be borne in mind that all indoor and outdoor lighting, including alarms and illumination of in-cab devices, illuminates the photocathodes of the image intensifier tubes. As a result of the research, the possibility of using color film light filters to narrow the operating spectral ranges of in-cab emitters in order to reduce their effect on NVG photocathodes was worked out [1]. However, this led to a limitation of the spectral characteristics of the image intensifier tube photocathode.
Another design solution based on the impulse adaptation method could be a more effective method. Here, the internal and external lighting equipment is connected to the in-cab lighting equipment and to the NVG through the synchronization unit, which provides operation in a pulsed mode and in time antiphase of the NVG with the lighting equipment, which makes it possible to exclude spurious illumination of the NVG in the dark [2].
All adaptation options require a structural complication of the in-cockpit electrical equipment, which leads to the need to create a specialized version of the aircraft adapted for night flights, and this reduces its reliability as a whole, not fully providing a comfortable pilot’s work.
However, there is a solution to this problem.
The elimination of complex, time-consuming and expensive methods of adaptation of the aircraft becomes possible if the pilot is provided with an OED using a spectral range that is different from the spectral range of radiation of the in-cabin equipment.
It is advisable to solve such a device in the form of an observation device with several working channels.
The most common combination is a combination of thermal imaging and television observation channels. These channels, being mutually complementary in many parameters, when combined into a coordinated observing system, make it possible to increase its efficiency, since they keep the system working in conditions when one of the channels is ineffective due to external conditions [3].
An example of such a device is the low-profile heat-television glasses IR-TV NVG, developed at the Rostov Optical and Mechanical Plant (Fig. 7).
IR-TV NVG is a multifunctional device that allows you to navigate and move around any terrain in difficult conditions, drive vehicles, carry out engineering and repair work, and also provide the ability to work with documents in complete darkness, as well as in rain, snow, fog, artificial and natural smoke.
The glasses are built according to the classical binocular scheme and have two working optical channels: television and thermal imaging, and two eyepiece outputs, with each of the objectives being installed coaxially with one of the eyepieces.
The ability to display information from any of the spectral ranges on two displays provides a stereoscopic effect, which significantly increases the convenience and information content of observation and reduces eye fatigue.
The design parameters of the optical components provide equalization of the image formats, which makes it possible to combine images obtained in different spectral ranges and display the combined image from each of the channels in different percentages.
The device uses special high-aperture optics with protection against backlighting, digital and optical zoom is implemented, for reading documents and topographic maps, a built-in wide-angle IR illumination with indication of the inclusion of the IR illuminator is provided.
However, no matter how wide the capabilities of the thermal television glasses are, it is not possible to use them for observation from the cockpit through the thermal imaging channel, since the cockpit glass does not allow thermal imaging wavelengths to pass through, and this requires the use of remote rotary thermal imaging cameras, as well as systems tracking and synchronizing their rotation with the rotation of the pilot’s head [4].
The possibility of unobstructed observation through protective and windshields of vehicles is provided in a universal version of the NVG with a classic television channel in the visible range of the spectrum and a channel in the short-wave IR range from 0.9 to 1.7 microns, called in Western terminology the SWIR range.
The SWIR channel, in contrast to thermal imaging, not only provides observation through ordinary glass [5], but also allows you to get an image even through heavily tinted glass of a car (Fig. 8).
The SWIR channel is built on a photodetector based on InGaAs material, which most effectively provides night observation and observation in bad weather conditions through cockpit glazing. Evaluation of the effectiveness in terms of range shows that night vision devices with InGaAs photodetectors at low illumination levels of less than 2 × 10–3 lux, in conditions of haze, weak fogs and dust (at a meteorological visibility range Sm ≈ 2.5 km), at order surpass the OED on the image intensifier tubes [6].
Thus, using two such channels, it is possible to obtain an almost universal version of the NVG for piloting and driving various vehicles, since the SWIR channel is almost always compatible with the glazing of cabins and does not require additional adaptation of the vehicle to the proposed NVG, and a television channel with the usual visibility expands NVG capabilities and provides high resolution with the possibility of additional electronic magnification.
A variant of the design of universal NVG, using an original layout solution, which reduces the “extension” of the lenses forward and provides a “flatter” profile of the device, is shown in Fig. 9.
Previously, the NVG is installed (fixed) in front of the observer’s eyes so that the exit pupils of the eyepieces are aligned with the observer’s eyes.
Due to the difference in the light diameters of the SWIR and TV channels, as well as different fields of view for HD (40°) and VD (30°), the mirror prism has an asymmetric shape, and the protective glass has an elongated shape, while the SWIR and TV channels are displaced relative to each other in the horizontal plane by a certain amount Δx. The calculated dimensions of the faces of the mirror prism, the distance and, accordingly, the value Δx, can be determined according to the outline diagram shown in Fig. 10.
If we express the value of the segment О1О5 by two ratios through the dimensions of the left branch and through the dimensions of the right branch, then the following formulas will be valid:
(1)
for the left branch, and:
(2)
for the right branch, where:
О1 is the top of the mirror prism;
О2, О3, О4 are the points lying on the axis passing through the top of the mirror prism and perpendicular to the optical axes of the objectives;
О5 is the point of intersection of the optical axis of the lens of the left branch with the perpendicular axis passing through the top of the mirror prism;
ω1, ω2 are the angles of the field of view of the left and right branches, respectively;
А1, А2 are the distances from the light diameter of the first objective lens (or from the entrance pupil of the objective) to the top of the mirror prism O1 for the left and right branches, respectively.
After equating the right-hand sides of the formulas, the final expression for Δx takes the form:
. (3)
The formula is valid in the absence of vignetting, and setting the permissible vignetting will allow us to ensure acceptable dimensions of the device when designing.
A variant of such an arrangement, which has the weight of the optics of all channels with microdisplays and two CR123A batteries of ~134 g, can provide a low profile at a level of ~45 mm in depth (Fig. 11).
The television observation branch provides observation of the outdoor environment during the day and the in-cab equipment in day and night conditions due to the coincidence of the working spectral ranges of the in-cab emitters and the television photodetector.
The SWIR channel of the spectral range provides night observation without the influence of illumination from the in-cabin lighting equipment due to the different operating spectral ranges of the television channel, in-cabin emitters and a SWIR range photodetector. The working spectral range of the television channel and modern LED in-cab emitters is in the range from 0.45 to 0.85 µm, and the SWIR channel has a spectral range of wavelengths from 0.9 to 1.7 µm, which provides the necessary spectrum spacing.
The characteristics of night vision goggles in comparison with serial devices of types 1ПН74 and 1ПН105 are shown in Table 1. The functional diagram of the NVG is shown in Fig. 12. The given functional diagram is universal and can be the basis for an NVG in any version of the spectral performance of the observation channels.
In the considered version of NVG, two matrices are used as photodetectors – SWIR matrix FUK36M manufactured by NPO Orion JSC with a format of 640 × 512 pixels, which has a high sensitivity in the short-wave infrared range of 0.9–1.7 microns, and a CMOS matrix EV76C660 by Teledyne e2v with a 1280 × 1024 pixel format, providing a high-quality image when the illumination changes from 5 × 10–2 to 5 × 104 lux.
The processor unit, the main computing core of which is the Xilinx XC7A75T programmable logic array, provides processing of incoming video information and its subsequent output to microdisplays.
AMOLED microdisplays SXGA‑120 R5 manufactured by eMagin Corporation in 1280 × 1024 format allow displaying incoming video information and entering service data.
The power supply generates the voltages necessary for the operation of the NVC, and also makes it possible to charge the batteries from an external power source. Two Li-Ion accumulators of 16340 size, 1200 mAh capacity are used as power sources.
An important feature of two-channel NVG is the use of domestic photodetectors. The Moscow enterprise “Orion” has developed and is producing a new module – 640 × 512 elements with a pitch of 15 µm, the parameters of which are presented in Table 2. The module includes a matrix of photosensitive elements made of InGaAs.
The Moscow enterprise Pulsar is completing R&D work to create a complete analogue of the EV76C660 CMOS matrix. The controls allow you to select different modes of NVC operation: image output only from the SWIR matrix, image output only from the CMOS matrix, combined image output, as well as the image output from the CMOS matrix in the electronic zoom mode of 2 krt, which makes the device almost a universal option for numerous applications.
It should be especially noted that the integrated image output mode provides the possibility of simultaneous observation of the image of the in-cab lighting equipment through a television channel and images of the terrain at all levels of natural night illumination through the SWIR channel without being influenced by illumination from the in-cab lighting equipment.
REFERENCES
RF patent No. 2133973. Method of illumination of instrument equipment and transparencies of light signaling of an aircraft when observing them through aerobatic night vision goggles / Belikova V. N., Vinokurov S. A., Gordienko Yu.N., Gruzevich Yu.K., Dyatlov A. L., Soldatenkov V. A., Khusnetdinov A. R.
RF patent № 2325308 C2. Device for impulse adaptation of lighting equipment, mainly aircraft to night vision devices / Padalko G. A., Pokotilo S. A., Golovatenko V. P., Shchedrina T. V., Loktionov V. I.
Medvedev A. V., Grinkevich A. V., Knyazeva S. N. Image intensifier or television matrix? Aspects of the effectiveness of the application. Photonics. 2020; 14 (5): 394–411.
Gruzevich Yu. K. Optoelectronic night vision devices. M.: FIZMATLIT. 2014. 276 p. – ISBN 978-5-9221-1550-6.
Ptitsyn A. What we see and what we do not see. Photonics. 2015; 3 / 51: 142–151.
Gusarova N. I., Koshavtsev N. F., Popov S. V. Advantages of using solid-state photodetectors for the spectral range of 1.4–1.7 microns in night vision devices. Advances in Applied Physics. 2014; 2 (3).
AUTHORS
Medvedev Alexander Vladimirovich, design@romz.ru, General Designer, Rostov Optical and Mechanical Plant OJSC (ROMZ OJSC), Rostov Veliky, Yaroslavl Region, Russia.
Grinkevich Alexander Vasilievich, lyu1455@yandex.ru, ZAO “EVS”, Moscow, Russia.
Knyazeva Svetlana Nikolaevna, ksn 61@yandex.ru, Design Engineer, Design Bureau of OJSC “Rostov Optical and Mechanical Plant, (OJSC ”ROMZ“), Rostov the Great, Yaroslavl Region, Russia.
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