1、 AEROSPACE RECOMMENDED PRACTICE Night Vision Imaging System (NVIS) Compatible Illuminated Pushbutton Switches and Indicators 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 entire
2、ly voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites
3、 your written comments and suggestions. Copyright 2006 SAE International All rights reserved. No part of this publication 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 writ
4、ten permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org Issued 2006-06 ARP4822 RATIONALE Warning, caution and advisory push-button switches and indic
5、ators are considered by pilots to be one of the most important items in the aircraft crew station. Due to the different colors, these push-button switches and indicators are particularly difficult in an NVG green-lighted compatible crew station. This specific technology, which is utilized to deal wi
6、th the design of these devices is covered in this document. 1. SCOPE: This SAE Aerospace Recommended Practice (ARP) reviews the basics of NVIS compatibility and discusses the specific illuminated pushbutton switch and indicator requirements for sunlight readability, color, luminance, and NVIS radian
7、ce when used in NVIS compatible cockpits. The recommendations and special considerations set forth in this document are made to give the design engineer a better understanding of MIL-L-85762A NVIS compatibility requirements and to provide information on the visual characteristics of NVIS compatible
8、pushbutton switch and indicator displays. 1.1 Purpose: The purpose of this document is to recommend the design requirements and considerations which the design engineer should observe when selecting and using NVIS compatible illuminated pushbutton switches and indicators. NVIS compatible lighting is
9、 defined as any lighting whose spectral radiance has been selectively filtered to meet the NVIS radiance and chromaticity requirements of MIL-L-85762A when dimmed to the specified luminance value. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or netw
10、orking permitted without license from IHS-,-,-SAE ARP4822 - 2 - 2. REFERENCES: 2.1 Applicable Documents: The following publications form a part of this specification to the extent specified herein. 2.1.1 U.S. Government Publications: Available from the Document Automation and Production Service (DAP
11、S), Building 4/D, 700 Robbins Avenue, Philadelphia, PA 19111-5094, Tel: 215-697-6257, http:/assist.daps.dla.mil/quicksearch/. MIL-L-85762A Lighting, Aircraft, Interior, Night Vision Imaging System (NVIS) Compatible MIL-PRF-22885G Switches, Push Button, Illuminated, General Specification for MIL-S-38
12、039B Systems, Illuminated, Warning, Caution, and Advisory, General Specification for 3. NVIS COMPATIBILITY BASICS: 3.1 Night Vision Imaging System (NVIS): NVIS are devices that provide aircrew members with the ability to see at night by greatly amplifying outside scenes illuminated by the night sky.
13、 3.1.1 Image Intensifiers: NVIS use third generation (GEN III) image intensifier tubes having a gallium-arsenide photocathode and microchannel plate to produce the amplification necessary to operate in starlight. 3.1.2 Mechanics of NVIS Operation: The night sky irradiates objects with photons which
14、are reflected as photon images. These photon images are focused by the objective lens onto the photocathode which emits electrons in direct proportion to the number of photons striking its surface. These electrons are greatly multiplied by the microchannel plate and are directed onto a phosphor scre
15、en where the amplified image is viewed through the ocular lens (see Figure 1). 3.2 Classification: NVIS compatible lighting requirements are stated based on the type and class NVIS being used. 3.2.1 NVIS Types: 3.2.1.1 Type I: These are direct view image NVIS which display the intensified image on a
16、 phosphor screen in the users direct line of sight. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4822 - 3 - FIGURE 1 3.2.1.2 Type II: These are projected image NVIS which project the intens
17、ified image on a see-through medium in the users line of sight. 3.2.2 NVIS Classes: 3.2.2.1 Class A: Any NVIS utilizing a 625 nm minus blue objective lens filter conforming to the specifications in Figure 2 are Class A. The relative spectral response of the Class A NVIS is shown in Figure 3 and the
18、tabulated values are listed in Table 6 of MIL-L-85762A. 3.2.2.2 Class B: Any NVIS utilizing a 665 nm minus blue objective lens filter conforming to the specifications in Figure 4 are Class B. The relative spectral response curve of the Class B NVIS is shown in Figure 5 and the tabulated values are l
19、isted in Table 7 of MIL-L-85762A. 3.3 NVIS Compatible Lighting: NVIS compatible lighting is lighting which can be seen with the unaided eye without causing interference or degradation of the NVIS intensification capabilities. 3.3.1 NVIS Radiance: NVIS radiance is the amount of energy emitted by a li
20、ght source that is visible through NVIS and represents the amount of interference produced by the light source. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4822 - 4 - FIGURE 2 - (Class A)
21、625 nm Minus Blue Filter Specification Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4822 - 5 - FIGURE 3 Copyright SAE International Provided by IHS under license with SAENot for ResaleNo re
22、production or networking permitted without license from IHS-,-,-SAE ARP4822 - 6 - FIGURE 4 - (Class B) 665 nm Minus Blue Filter Specification Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP48
23、22 - 7 - FIGURE 5 3.3.2 Definition of NVIS Radiance: NVIS radiance (NR) is the integral of the curve generated by multiplying the spectral radiance of a light source by the relative spectral response of the Class A or Class B NVIS. d )SN( )G(max )G( = NR930450(Eq. 1) where: NR = NVIS radiance G() ma
24、x = 1 mA/W (for the correct units) G() = Relative NVIS response N() = Spectral radiance of lighting component (W/cm2*sr*nm) d = 5 nm increments S = Scaling factor LR/LMwhere: LR= Luminance required LM= Luminance measured Copyright SAE International Provided by IHS under license with SAENot for Resal
25、eNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4822 - 8 - 3.3.3 Definition of Compatible Lighting: A lighting component produces compatible lighting if its NVIS radiance does not exceed a specified maximum when set to produce a specified luminance. For primary cockpit l
26、ighting the maximum allowable NVIS radiance is 1.7 x 10-10when the lighting is set to produce 0.1 fL. 4. RECOMMENDATIONS: Illuminated pushbutton switches and indicators are used in crew stations as visual signals to provide crew members with vital status information. Functionally, they serve as caut
27、ion and advisory lights, master caution lights, and warning lights. When these crew stations are required to be compatible with NVIS, the pushbutton switch and indicator displays must meet the lighting requirements of MIL-L-85762A. These compatibility requirements must be strictly observed so as not
28、 to compromise the safety of crew members performing tasks while using NVIS. 4.1 Sunlight Readability: Illuminated pushbutton switches and indicators requiring readability in sunlight must meet the daylight legibility and readability requirements of MIL-L-85762A. Two separate requirements are define
29、d depending on whether or not the display is to be readable in direct reflected specular sunlight. 4.1.1 Specular Sunlight Readability Requirements: Illuminated switches and indicators requiring readability in direct reflected specular sunlight must have a lighted contrast CLnot less than 0.4 and an
30、 unlighted contrast CULwith an absolute value less than or equal to 0.1 under 10 000 fc of illumination as defined in MIL-L-85762A and MIL-PRF-22885G when set at full rated voltages. 4.1.1.1 Test Arrangement: The test arrangement must be as shown in Figure 6 where the 10 000 fc source is set to an a
31、ngle of 15 off the normal to the display and is the angle of incidence. The photometer is set at the angle of reflectance of 15. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4822 - 9 - FIGU
32、RE 6 4.1.1.2 Contrast Requirements: The contrast requirements for CLand CULare: 1.00.0BBBCcontrastBackground/OffThe4.0BBBCcontrastBackground/OnThe113UL112L=(Eq. 2) where: B1= Average background luminance B2= Average character luminance, lighted B3= Average character luminance, unlighted The average
33、character and background luminance measurements should include three readings per character in accordance with the sunlight readability test procedure defined in MIL-S-22885. 4.1.2 Daylight Readability Excluding Specular Sunlight: Illuminated pushbutton switches and indicators not requiring readabil
34、ity in direct reflected specular sunlight must have a contrast, CL, of not less than 1.0 in a 10 000 fc diffuse white light environment as defined in MIL-S-38039. 4.1.2.1 Test Arrangement: The test arrangement is not defined in MIL-S-38039 but a suggested test arrangement is shown in Figure 7. Copyr
35、ight SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4822 - 10 - FIGURE 7 4.1.2.2 Contrast Requirement: The contrast requirements for CLis: 0.1BBBCContrast112L= (Eq. 3) where: B1= Average brightness of
36、the unlighted portion B2= Average brightness of the lighted portion The average character and background luminance measurements should include three readings per character in accordance with the sunlight readability test procedure defined in MIL-S-22885. Copyright SAE International Provided by IHS u
37、nder license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4822 - 11 - 4.1.3 Special Considerations: 4.1.3.1 Specular Reflections: The sunlight readability test requiring readability in direct reflected specular sunlight is the most severe test for
38、 sunlight readability. It represents the worst case situation where the display is exposed to direct sunshine and positioned such that the pilot sees a specular reflection of the sun. In this case it is recommended that the display have hidden legends and a low reflective, diffuse front surface to a
39、void ghosting (appearing illuminated when unenergized) and to eliminate surface specular reflections. 4.1.3.2 Contrast Values: The specular sunlight contrast value of CL 0.4 has been reduced from 0.6 minimum to allow for the additional filtering necessary to achieve NVIS compatibility. A contrast of
40、 0.4 is marginally acceptable and it is desirable for displays to have higher contrast values for improved sunlight readability. 4.1.3.3 Minimum Display Luminance: It is recommended that a display have a minimum average luminance of 250 fL at full rated voltage to meet the requirements for sunlight
41、readability. Displays with an average luminance less than 250 fL may be difficult to recognize in high illuminance conditions. 4.2 Caution and Advisory Displays Using NVIS Green A or Green B: Illuminated pushbutton switches and indicators that are used as caution and advisory signals in an NVIS comp
42、atible crew station must meet the requirements of MIL-L-85762A. 4.2.1 Chromaticity and Luminance Requirements: 4.2.1.1 NVIS Green A: The color of caution and advisory displays are required to be NVIS Green A when they are set to produce 0.1 fL. The NVIS Green A color is the area within a circle whos
43、e radius is 0.037 and is located at uo = 0.088 and vo= 0.543 on the CIE 1976 UCS Diagram (see Figure 8). This is the same color requirement as that required for primary instrument and panel lighting. 4.2.1.2 NVIS Green B: MIL-L-85762A recognizes that in some cases NVIS Green A displays may not produ
44、ce sufficient brightness to be sunlight readable. As an alternative the specification allows displays to be NVIS Green B where increased display emphasis by highly saturated colors is necessary or adequate display sunlight readability cannot be achieved with NVIS Green A. The NVIS Green B color is t
45、he area bounded by the spectral locus and a circle whose radius is 0.057 and is located at uo= 0.131 and vo= 0.623 shown in Figure 8. The display must produce this color when set to 0.1 fL. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking
46、permitted without license from IHS-,-,-SAE ARP4822 - 12 - FIGURE 8 Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4822 - 13 - 4.2.1.3 NVIS Radiance Requirements: The NVIS radiance of caution
47、and advisory displays must be less than 1.7 x 10-10when set to produce 0.1 fL. The NVIS radiance is calculated using the Class A response curve. This is the same radiance requirement as that required for primary instrument and panel lighting. The NVIS radiance is measured at 15 fL then scaled down t
48、o 0.1 fL since MIL-L-85762A requires the measurement to be made at full rated voltage or 15 fL, whichever is less. 4.2.2 Special Considerations: 4.2.2.1 Visual Appearance of NVIS Green A: The NVIS Green A region includes various shades of blue-green, green, and yellowish-green. In some applications this nonuniformity of color can be a problem. In these instances the color requirement is tightened to allow only colors in the upper half of the NVIS Green A region. 4.2.2.2 Dimming Effect on NVIS Green A: When
