SAE ARP 4168B-2017 Night Vision Goggle (NVG) Compatible Light Sources.pdf

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1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there

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3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497

4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/ARP4168B AEROSPACE RECOMMENDED PRACTICE ARP4168 REV. B Issued 1988-09 Revised 2017-08 Supersedi

5、ng ARP4168A Night Vision Goggle (NVG) Compatible Light Sources RATIONALE This document shows recommended industry practices, requirements and design recommendations for Night Vision Goggle (NVG) compatible light sources within the crew station. The most recent revision to this document was to update

6、 the reference documents, add more technical details and expand design recommendations for LEDs. The recommendations contained within this document apply to both military and civilian aircraft. 1. SCOPE This ARP covers three common light sources, incandescent, electroluminescent and light emitting d

7、iode that, when NVG filtered, can be used to illuminate NVG compatible aerospace crew stations. It is recognized that many other different light sources can also be used for this purpose. Also see 2.1.1 for other SAE documents that cover particular applications within the crew station environment. T

8、his ARP sets forth recommendations for the design of NVG compatible lighting, utilizing these light sources, that will meet the requirements of MIL-L-85762 Lighting, Aircraft, Interior, Night Vision Imaging System (NVIS) Compatible. This also includes the replacement document MIL-STD-3009: Lighting,

9、 Aircraft, Night Vision Imaging System (NVIS) Compatible. Although this ARP concentrates on lamp light sources for illumination, the information contained within this ARP may be directly applied to incandescent, electroluminescent and light emitting diode information display devices. Regardless of t

10、he light source, the focus of this document is the understanding that the radiometric energy that can be amplified by the Night Vision Goggles (NVGs) must be filtered to such an extent that it will not impact the operational use of the NVGs while still allowing sufficient visible (photometric) energ

11、y to be viewed by the pilot. 1.1 Purpose This SAE Aerospace Recommended Practice recommends certain basic considerations which the design engineer should observe when designing NVG compatible lighting. Key design issues include the right type of light source to use, how to match the filter to the li

12、ght source and what trade offs need to be made in optimizing the design. Each of the various light sources have different spectral distributions from the 380-980NM wavelengths and therefore the filter selection must take that into consideration. For example, most LED light sources are very saturated

13、 (with the exception of white LEDs) and require little filtering in the near Infra-Red (IR) wavelengths to allow NVIS compatibility. However, incandescent light sources have the majority of their radiometric energy within the near IR wavelengths (780-930NM) and therefore require significant filterin

14、g that will in most situations also impact chromaticity and photometric outputs. 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications

15、 shall be the issue in effect on the date of the purchase order. In the SAE INTERNATIONAL ARP4168B Page 2 of 14 event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws a

16、nd regulations unless a specific exemption has been obtained. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org. ARP881 Lamps for Aircraft Lighting ARP1048 Ins

17、trument and Cockpit Illumination for General Aviation Aircraft ARP4169 Night Vision Goggle (NVG) Filters ARP4822 Night Vision Imaging System (NVIS) Compatible Illuminated Pushbutton Switches and Indicators ARP4967 Night Vision Imaging Systems (NVIS) Integrally Illuminated Information Panels AS5452 N

18、ight Vision Goggles (NVG) Compatible Lighting for Civil Aircraft 2.1.2 U.S. Military Specifications and Standards Copies of these documents are available at http:/quicksearch.dla.mil. MIL-DTL-6363 Lamps, Incandescent, Aircraft Service General Specifications for MIL-DTL-7788 Panels, Information, Inte

19、grally Illuminated MIL-HDBK-310 Global Climatic Data for Developing Military Products. MIL-L-85762 Lighting, Aircraft, Interior, Night Vision Imaging System (NVIS) Compatible MIL-PRF-19500/708 Displays, Diode, Light Emitting, Solid State, Red, Numeric and Hexadecimal, with on Board Decoder/Driver Ty

20、pes 4N51, 4N52, 4N53, 4N54 Jan and Jantx MIL-STD-750 Test Method Standard For Semiconductor Devices MIL-STD-810 Environmental Engineering Considerations and Laboratory Tests MIL-STD-3009 Lighting, Aircraft, Night Vision Imaging System (NVIS) Compatible SAE INTERNATIONAL ARP4168B Page 3 of 14 2.2 Def

21、inition Night vision goggle compatible lighting is the condition in which the spectral wavelengths, luminance level and uniformity of the cockpit lighting do not interfere with the operation of night vision goggles while still maintaining the same (or nearly the same) level of photometric output as

22、the previously non-NVIS compatible light source. This is done with a complimentary set of cut-off filters with one set on the NVGs only allowing radiant energy from 625nm or 665nm (depending on the Class version of the NVG) and above to enter the intensifier tubes. The complimentary filters over the

23、 visible light sources within the crew station are then added to greatly reduce the radiant energy in the far red chromaticity and near Infra-red region to the extent that it is far less than the possible radiometric energy within that wavelength coming from outside the crew station. This allows the

24、 goggles to only amplify the radiant energy originating outside the crew station area while allowing the operator to view the crew station under the goggles with the unaided eye. Class C (or Leaky Green) filtered NVGs also allow a small amount of radiant energy within the 540nm to 550nm bandwidth so

25、 care must be taken not to use LEDs that have their peaks within this energy band or this will be detectable by this Class version of NVGs). 3. RECOMMENDATIONS When designing for NVG compatible lighting, the designer must consider that all light sources require varying degrees of optical filtration

26、to restrict emissions above 600 nm. The degree of restriction is dependent upon the color and NVIS Radiance (NR) as defined in MIL-L-85762A (or MIL-STD-3009). This is necessary since night vision goggles are most sensitive to long wavelength emission. Without the proper filtration, the light source

27、will degrade or shut down the operation of a night vision goggle. NVG filtered lighting must be dimmable to levels as low as 0.1 fL in order to allow use without NVGs since that is the typical luminance level that pilots have set their cockpit lighting when fully dark adapted. If a combination of NV

28、G light sources is utilized in a single piece of equipment, it is desirable to have one control that will dim all the light sources simultaneously. When using a common dimming circuit, considerations should be given to the luminance tracking characteristics of the different light sources. The possib

29、le requirement for sunlight readability should also be considered when selecting the light sources. When modifying a crew station for NVG operation, it is very important that the existing brightness levels, dimming setting and color match as closely to the legacy system to ease the transition to gog

30、gle and non-goggle operation. The only exception to the color requirement would be to allow green chromaticity to replace Aviation White for panel lighting. This exception is to reduce the overall amount of radiant energy within the crew station to improve NVG performance. Another slight change in c

31、hromaticity from the Aviation color to the NVIS color is for red. Since the spectral distribution of Aviation Red is within the wavelength area that is normally amplified by the NVGs, the NVIS Red color requirements is shifted to be more Orange in color. Recently, the use of red LEDs have allowed a

32、closer match to Aviation Red due to the saturated nature of LEDs as compared to incandescent lamps. 3.1 Incandescent Lamps 3.1.1 Lamp Types Some typical military specifications for incandescent lamps that are used in aerospace vehicle panels are listed in Table 1. The size and type of lamp should be

33、 selected to meet the specific requirements of the application. Military specified lamps should be used whenever possible. Additional tighter tolerance of brightness ranges should also be considered (i.e., 15% brightness range versus 25%). These tighter tolerance lamps will cost more, but will ensur

34、e that your brightness levels are being met with the more difficult NVIS filter application. Please refer to MIL-DTL-6363 since the lamp part numbers contained in Table I are obsolete but are still referred to due to their common use on existing aircraft. However, in some instances it may be necessa

35、ry to deviate from MIL specifications in order to meet special lighting and packaging requirements. SAE INTERNATIONAL ARP4168B Page 4 of 14 Table 1 - Military specifications for Incandescent Lamps Military Specification Lamp Type MS 90452 MS 24367 MS 90451 MS 24515 MS 3338 MS 25237 MS 25238 MS 15570

36、 MS 25478 MS 25235 T-3/4, 5.0 Volt, Wire Terminals T-1, 5.0 Volt, Wire Terminals T-1, Short Length, 5.0 Volt, Wire Terminals T-1, 5.0 Volt, Based T-1, 28.0 Volt, Based T-1 3/4, 2.5 to 28.0 Volt, Based G-5, 28.0 Volts, Based G-6, 6.0 to 28.0 Volts, Based S-8, 6.0 to 28 Volts, Based S-11, 28.0 Volts,

37、Based 3.1.2 Design Considerations 3.1.2.1 Light Output Incandescent lamps emit light by the resistance heating of a tungsten wire filament to incandescent temperatures above 1200 K inside a vacuum or inert gas filled envelope. They are broadband emitters that follow the typical blackbody radiation c

38、urves. Most subminiature lamps operate in the 1600 to 2400 K filament color temperature range as shown in Figure 1. Less than 8% of the energy emitted is within the visible spectrum from blue to red. The remaining energy is in the infrared where NVIS systems are most sensitive. When properly filtere

39、d, incandescent light sources will meet the NR and color requirements of MIL-L-85762A or MIL-STD-3009. Incandescent lamps range from 0.001 mean spherical candelas (MSCD) to 1.0+ MSCD in the subminiature sizes. A NVG filter will reduce the available light and should shift the observed spectral distri

40、bution from white to the desired NVG color. Thus, incandescent lamps must be selected to provide sufficient illumination through the NVG filter. In general, the number of lamps required for a NVIS version of a panel and/or instrument will be greater due to the lower transmission levels of NVIS filte

41、rs versus Aviation color filters. 3.1.2.2 Size of Lamp The physical size of the lamp must fit within the available space. Miniature and subminiature incandescent lamps are available in a wide range of sizes from less than 0.030 inches to more than 1.5 inches in diameter. The selected lamp should be

42、configured with the proper base design to meet maintenance requirements. 3.1.2.3 Power Dissipation The designer needs to select an incandescent lamp that is compatible with available power. Either AC or DC power may be used. Typical incandescent lamps in aerospace applications use 5.0 or 28 V, 0.02

43、to 1.0 A. Please consider the additional power loads with an increase in the number of lamps with NVIS compatible crew stations. This may require changes in the current load of the step down transformers used to supply power to the lamps. 3.1.2.4 Thermal Considerations Ambient temperatures of -55 to

44、 +100 C will normally not affect the life or operation of standard incandescent lamps. It is recommended that the designer allow for sufficient heat dissipation, where applicable, in order to maintain the proper lamp surface temperature. SAE INTERNATIONAL ARP4168B Page 5 of 14 3.1.2.5 Dimming Incand

45、escent lamps are voltage operated devices. The light output is dimmed by reducing the applied voltage. The dimmed light output varies exponentially, as determined by Equation 1. 5.3)()( V o l t a g eR a t e dV o l t a g eDi m me dM S C DOu t p u tL i g h tOu t p u tL i g h tR a t e dM S C DOu t p u

46、tL i g h tL i g h tDi m me d (Eq. 1) As an incandescent lamp is dimmed, a spectral shift occurs towards longer wavelengths. This is due to the shift in color temperature when lamps receive lower voltage levels thereby changing the spectral distribution of the lamp output. This spectral shift causes

47、a color shift towards red, a change in the spectral relationship with respect to the filters transmission characteristic and will affect the NR value. These effects must be factored into the overall lighting system design to assure that the spectrum (color) of the NVG filtered incandescent lamp is w

48、ithin the desired NVIS color range at the dimmed brightness level specified in MIL-L-85762A or MIL-STD-3009. This is critical when measuring for chromaticity compliance since they are taken in the dim level luminance levels. The filter selection must take this spectrum shift of the lamp into account

49、 so it will still be in compliance with the selected color requirement at this lower brightness value. 3.2 Electroluminescent (EL) Lamps 3.2.1 Lamp Types AC thick-film electroluminescent lamps use phosphors to convert electrical energy into light energy. Only a small amount of infrared energy is emitted by an EL lamp. AC thick-film EL lamps are available in a wide array of colors with the most common