MIL-PRF-A3314408_Draft_Vendors_Copy.docx

MIL-PRF-A3314408

Metric

MIL-PRF-A3314408

PERFORMANCE SPECIFICATION

IMAGE INTENSIFIER I²

This specification is approved for use by Program Executive Office - Soldier (PEO-SOLDIER), Department of the Army, and is available for use by all Departments and Agencies of the Department of Defense.

Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of use in improving this document should be addressed to: Product Manager Sensors and Lasers, ATTN: SFAE-SDR-SSL, 10125 Gratiot Road, Bldg 318, Fort Belvoir, VA 22060-5862

AMSC N/A FSC 5855

1. DISTRIBUTION STATEMENT C. DISTRIBUTION AUTHORIZED TO U.S. GOVERNMENT AGENCIES AND THEIR CONTRACTORS FOR OFFICIAL USE OR FOR ADMINISTRATIVE AND OPERATIONAL USE, AS DETERMINED 19 FEBRUARY 2008. OTHER REQUESTS FOR THIS DOCUMENT SHALL BE REFERRED TO PM SENSORS AND LASERS, ATTN: SFAE-SDR-SSL, 10125 Gratiot Road, Bldg 318, Fort Belvoir, VA 22060-5862.SCOPE

1.1. Scope. This specification covers the Image Intensifier Assembly

2. APPLICABLE DOCUMENTS

2.1. General. The documents listed in this section are specified in sections 2 through 4 of this specification. While every effort has been made to ensure the completeness of this list, document users are cautioned that they must meet all specified requirements documents cited in sections 2 through 4 of this specification, whether or not they are listed.

2.2. Government documents.

2.2.1. Specifications, standards, and handbooks. The following specifications, standards, and handbooks form a part of this document to the extent specified herein. Unless otherwise specified, the issues of these documents are those listed in the issue of the Department of Defense Index of Specifications and Standards (DoDISS) and supplement thereto, cited in the solicitation.

_ AT THE END OF A REFERENCE DENOTES THE CURRENT REVISION

DEPARTMENT OF DEFENSE STANDARDS

NON-GOVERNMENT PUBLICATIONS

ANSI/NCSL Z540.3-2006 Requirement For The Calibration Of Measuring And Test Equipment

(Copies of these documents are available online at https://quicksearch.dla.mil/qsSearch.aspx or from the Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094.)

2.2.2. Other Government documents, drawings and publications. The following other Government documents, drawings and publications form a part of this document to the extent specified herein. Unless otherwise specified, the issues are those cited in the solicitation. All military and government specifications/ standards excluding this specification cited in the following documents are for reference only and do not form a part of the requirements therein

DRAWINGS

A3314408 Image Intensifier I2 Tube Assembly, Aviator’s Night Vision Imaging System, AN/AVS-6(V)3 (Copies of drawings and technical manuals required by contractors in connection with specific procurement functions should be obtained from the procuring activity or as directed by the contracting officer.)

2.3. Order of precedence. In the event of a conflict between the text of this document and the references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained.

3. REQUIREMENTS

3.1. Description. The Image Intensifier Assembly herein referred to as the I² Tube, shall employ a photocathode sealed to a glass faceplate forming the input window to the I² Tube. The I² Tube shall contain an integral phosphor screen placed upon an optical inverter. The I² Tube shall include an integral power supply and be encapsulated within a hard-surface insulating envelope.

3.2. Qualification. Unless otherwise specified by the contract or purchase order, image intensifier assemblies furnished under this specification shall be qualified products. (see 3.5.20).

3.2.1. Initial Production Test (IPT) when specified in the contract or purchase order, the supplier shall furnish and test assemblies in accordance with the requirements of 4.2.

3.2.2. Material or Component change. After successful completion of IPT, any change in a supplier of the components listed in 3.3.2.1 and 3.3.3 Shall require re-qualification to the extent required by the Government. A change of any component or material used in the manufacture of the I² Tube which could impact performance must be verified by re-qualification to the extent required by the Government.

3.3. Construction. The I² Tube shall be constructed in accordance with the applicable drawing (see 2.2.2) and all the requirements of this specification and other associated drawings which affect interface and/or interchangeability (see 3.3.8).

3.3.1. Weight. The weight of the I² Tube shall not exceed 85 grams.

3.3.2. Parts and materials. Parts and materials shall be as specified and as defined by the applicable drawing (see 2.2.2). The contractor shall select parts and materials which shall be capable of meeting all of the operational and environmental requirements specified herein. Any change of a part or material after qualification requires notification of the procuring activity and submittal of proposed re-qualification. Recovered materials shall be used to the maximum extent possible.

3.3.2.1. Phosphor screen. The phosphor screen shall be type P-45 (White Phosphor), P-43 (Green Phosphor), or equivalent.

3.3.3. Components. The following requirements shall be met by each component delivered without damage (see 3.5.8) nor degradation of performance (see 3.5.27) to the I² Tube.

3.3.3.1. Power supply. The integral power supply shall meet all of the operational characteristics when powered by a 2.0 to 3.0 volts direct current (Vdc) power source.

3.3.3.2. Optical inverter. The optical inverter shall exhibit the following characteristics:

3.3.3.2.1. Shear distortion. Shear distortion (see 3.5.3.1) shall not exceed 25 micrometers over the display area.

3.3.3.2.2. Gross distortion. Gross distortion (see 3.5.3.2) shall cause no point on the image of a straight line, through any axis, to be displaced more than ± 30 microns relative to the best-fit straight line (see 3.5.3.3). Displacement measurements shall be rounded to the nearest whole micron. The maximum slope of the straight line image shall be less than 15 microns per millimeter across the line image and less than 25 microns per any two millimeters from the best-fit straight line. Distortion shall be measured along four (4) axes which are 45 degrees apart. Distortion measurements shall be initiated from an identifiable reference point located on the fiber optic inverter. The line image cannot have more than two slope reversals. Slope reversals less than ± 5 microns shall not be considered as a change in slope.

3.3.3.2.3. Image inversion. The fiber optic inverter shall rotate a straight line image 180 ± 1 degree relative to the end points of the best-fit straight line (see 3.5.3.3). Image inversion measurements shall be rounded off to the nearest tenth of a degree.

3.3.3.2.4. Chicken wire. When the optical inverter is uniformly illuminated and viewed under 10-power magnification perpendicular to the plane surface, the optical inverter shall meet the chicken wire (see 3.5.4) limits specified in Table I.

Table I Optical Inverter allowable chicken wire

(mm) Maximum length (mm)

Chicken wire (zone 1)

Disregard lengths which are ≤ 0.0762 mm

Chicken wire (zone 2)

Disregard lengths which are ≤ 0.0762 mm

Chicken wire (zone 3)

Disregard lengths which are ≤ 0.381 mm

Zone 1 – 0.7493 cm diameter circle center of optic Zone 2 – 0.7493 to 1.4732 cm annulus concentric with Zone 1 Zone 3 – 1.4732 to1.8034 cm annulus concentric with Zone 2

3.3.3.2.5. Optical inverter surface finish. The output surface of the fiber optic inverter shall have a minimum of a 60/40 (scratches/digs) finish over the full useful area of tube (see 3.5.17).

3.3.3.3. Ion barrier film . If an ion barrier film is used, there shall be no more than 5 type-B holes (see 3.5.28) over the total useful area of the output screen. There shall be no holes present having an area greater than a circle with a diameter of 125 micrometers.

3.3.3.4. Input faceplate. The input faceplate shall be of optical quality Grade A with a minimum of a 60/40 (scratches/digs) finish and flat within 100 fringes using the sodium D light.

3.3.3.5. Photocathode. The photocathode Shall be a material with visible through near-infrared response including a spectral range of at least 500 nm – 900 nm with sensitivity required in section 3.4.1.

3.3.4. Photocathode electrical contact inspection. The photocathode electrical contact shall not be visible between the photocathode and blackened glass of the input faceplate.

3.3.5. Phosphor. The phosphor shall be type P-45 (White Phosphor), P-43 (Green Phosphor), or equivalent.

3.3.6. Identification and marking. Each I² Tube shall be marked in accordance with drawing A3314408 with the exception that the part number and national stock number are to be obtained from the procuring activity. The markings shall include a coded acceptance date (CAD). The first two numbers of the code shall be the last two digits of the year. The last two digits numbers of the code shall be two digits indicating the calendar week of the year (01 through 52). Reading from left to right or top to bottom, the code number shall indicate the year and week of acceptance in that order.

3.3.7. Workmanship. The image intensifier I² Tube shall be free from burrs, chips, dirt, grease, or any embedded or surface foreign material. Optical surfaces of the image intensifier shall be free from imperfections that adversely affect the prescribed performance.

3.3.8. Interchangeability. The image intensifier I² Tube shall be interchangeable (see 3.5.29) between qualified systems from any supplier.

3.4. Test requirements. Performance requirements shall be verified using test methods approved by the procuring activity. Unless otherwise specified herein, performance requirements shall be complied with under the following conditions without damage (see 3.5.8) nor degradation of performance (see 3.5.27):

a. The radiation source used for evaluation of photocathode sensitivity, Equivalent Background Input (EBI), luminance gain, signal-to-noise, output brightness uniformity, and reliability shall be a tungsten filament lamp operated at a color temperature of 2856 ± 50 Kelvin (K).

b. The radiation source used for evaluation of burn-in/Environmental Stress Screening (ESS), temperature extremes, halo, bright source protection, fixed pattern noise, image alignment, resolution, Modulation Transfer Function (MTF), useful cathode diameter, screen quality, veiling glare and Electromagnetic Interference (EMI) shall be a tungsten filament lamp operated at a color temperature of 2700K to 2900K.

c. The actual values of input illuminance or irradiance employed in performance tests shall be within ± 10% of that specified. These actual values shall be used in all computations used to determine compliance with the performance requirements.

d. Measuring devices used for monitoring or evaluating performance shall be compliant with ANSI/NCSL 540.3-2006_.

e. Tests unless otherwise specified shall be performed at room temperature (see 3.5.6).

f. Neutral density filters used in test equipment shall have transmission characteristics within 10 percent of the nominal filter transmission from 0.35 to 1.0 micrometer.

g. Input voltage on the I² Tube shall be 3.0 ± 0.05 Vdc.

h. Environmental test chambers shall maintain the temperature within ± 2°C of the specified test temperature.

3.4.1. Photocathode sensitivity/Photoresponse (PR). Over a 16mm diameter circle with uniform incident radiation as indicated, the radiant sensitivity (see 3.5.23) shall meet the minimum requirements given in Table II. Sensitivity will be measured with a voltage ± 50 Vdc of the operating voltage actually applied to the photocathode in the final tube I² Tube.

Table II Photocathode sensitivity requirements

White light

0.001 lm ± 0.0005 lm

830 nm ±1 nm 1x10-8 - 5x10-6 Watt

880 nm ±1 nm 1x10-8 - 5x10-6 Watt

3.4.2. Equivalent background input (EBI). The equivalent background input at room temperature shall not exceed 2.0 x 10-7 lux (lx) (2.0 x 10-11 phot (lumens/square centimeter)) when tested at room temperature.

3.4.3. Luminance gain. The I² Tube shall exhibit at room temperature luminance gain and high light level saturation characteristics per Table III and Figure 1 (see 3.5.6 and 3.5.25).

Table III Saturation requirements for luminance gain Nominal light input lx (fc) Minimum allowable Gain cd/m²/lx (fL/fc) Minimum allowable output cd/m² (fL) Maximum allowable gain cd/m²/lx (fL/fc) Maximum allowable output cd/m² (fL) Maximum allowable input current (mA)

2.15 x 10-5 (2 x 10-6) 25,500 (80,000)

(160,000)

2.15 x 10-3 (2 x 10-4) 4,000 (12,500)

(25,000)

3.4.4. Halo. The halo (see 3.5.7) produced by projecting light through an aperture and a f/1.2 objective lens onto the input of the I² Tube, such that a 0.350 ± 0.02mm diameter spot is produced on the photocathode, shall be no greater than 0.750mm in diameter. The illuminance in the spot shall be not less than 5.4 x 10-3 lx (5 x 10-4 footcandle (fc)). The illuminance incident on the photocathode in the region outside the 0.350mm spot shall not exceed 5.4 x 10-6 lx (5 x 10-7 fc). The variation between the largest halo and the smallest halo anywhere in the useful area shall be no greater 0.15mm.

3.4.5. Bright source protection. With operating potential applied, the I² Tube shall not be damaged (see 3.5.8) when subjected to an input illumination of not less than 50 millilumens concentrated on the photocathode within an area no greater than one square millimeter for a time interval not less than 60 seconds. There shall be no discernible damage (see 3.5.8) after a non-operating period of not more than 24 hours.

3.4.6. Signal-to-noise ratio. The signal-to-noise (S/N) ratio (see 3.5.26) shall be a minimum of 33.0.

3.4.7. Fixed pattern noise.

3.4.7.1. Multi-to-multi pattern variation. With the operating potential applied to the I² Tube and the entire photocathode uniformly illuminated at a level of 1.08 to 2.15 x 10-3 lx (1 to 2 x 10-4 fc), multi-to-multi brightness deviations from the mean value shall not exceed ± 5 percent. The mean value shall be established from the suspect multi and the 6 adjacent multies.

3.4.7.2. Multi-boundary pattern noise. With the operating potential applied to the I² Tube and the entire photocathode uniformly illuminated at a level of 1.08 to 2.15 x 10-3 lx (1 to 2 x 10-4 fc), the average value of the brightness deviations of the multi-boundary intensities shall not deviate from the mean value of the adjacent multi intensities by more than ± 8 percent. The mean value shall be established from the three adjacent multies containing the above multi-boundaries.

3.4.8. Output brightness uniformity. When the photocathode is uniformly illuminated with between 5.4 x 10-5 and 1.08 x 10-4 lx (5 x 10-6 to 1 x 10-5 fc), the output brightness uniformity shall be such that the ratio of the maximum to minimum brightness over the useful screen area (see 3.5.17 shall not exceed 3:1.

3.4.9. Image alignment. With the operating potential applied and the photocathode illuminated to provide best contrast, a test reticle projected on the photocathode of the I² Tube concentric with the optical axis shall produce an image on the screen of the I² Tube such that the center of the reticle's image shall fall within a circle 0.152 mm in diameter concentric with the optical axis of the I² Tube.

3.4.10. Resolution.

3.4.10.1. Center resolution. The limiting resolution (see 3.5.15) of the I² Tube at the optical axis (see 3.5.15), referenced to the photocathode, shall not be less than 72 line pairs per millimeter (lp/mm).

3.4.10.2. Peripheral resolution. The limiting resolution (see 3.5.15) of the I² Tube at points along a 14mm diameter circle concentric with the optical axis (see 3.5.14), referenced to the photocathode, shall not be less than 64 lp/mm.

3.4.10.3. Bright light level center resolution. With the entire photocathode of the I² Tube illuminated with not less than 215 lx (20 fc), the minimum center resolution shall be 36 lp/mm.

3.4.11. Modulation transfer function. With an input illuminance of not greater than 8.6 x 10-3 lx (8 x l0-4 fc), the minimum I² Tube MTF (see 3.5.11) shall be as follows:

a. 83 percent at 2.5 lp/mm

b. 75 percent MTF at 7.5 lp/mm

c. 58 percent MTF at 15.0 lp/mm

d. 40 percent MTF at 25.0 lp/mm

3.4.12. Useful cathode diameter.The useful cathode diameter shall be not less than 17.5 mm concentric with the optical axis of the I² Tube

3.4.13. Screen quality.

3.4.13.1. Bright spots. With no light input to the I² Tube, observe and locate bright spots or discernible field emissions (see 3.5.12) on the screen when viewed with a 10-power magnifier. With 2.15 x 10-5 lx (2 x 10-6 fc) incident on the photocathode, there shall be no bright spots or discernible field emissions (see 3.5.12) brighter or larger than the background scintillations (see 3.5.13) on the screen when viewed with a 10-power magnifier. With the radiation level on the photocathode adjusted to obtain the best contrast, there shall be no bright spots visible on the screen when viewed with a 10-power magnifier.

3.4.13.2. Dark spots. The dark spots which exceed a contrast (see 3.5.19) of 30 percent of their surrounding areas shall not exceed the sizes and quantities specified in Table IV. If the spot is non-circular, the diameter of the circular spot of an equal area shall be used. When the distance between one or more spots and a given spot is less than the maximum dimension of the given spot, all the above spots shall be considered as one circular spot whose area is equal to that of the smallest rectangle or circle (whichever has least area) which encompasses the above spots and the separation between them. Graininess caused by grainy or "peppery" phosphor screen, channel-to-channel gain variations, or photocathode irregularities shall not be discernible over the useful diameter to the degree that it detracts from normal operation, when viewed with at least a 10- power magnifier with the photocathode uniformly illuminated.

Table IV I² Tube dark spots

NOTES:

* The 5.59 and 14.732 mm circles on the image screen shall be concentric with the optical axis of the I² Tube.

3.4.14. Stray light: The stray light generated by the I² tube when a bright spot is projected outside the useful cathode diameter (UCD) shall not exceed the limits of Table V. The projected spot shall be generated by f/1.2 optics and be no more than 20 μm in diameter with illuminance of 3200±100 lx. The average tube background luminance of the I² tube shall be less than 5x10-3 cd/m².

Table V Off-axis veiling glare Spot location (mm outside UCD) Maximum Luminance of Veiling Glare cd/m² (fL)

3.4.15. Environmental characteristics. The I² Tube shall meet the performance requirements specified herein when subjected to the following environmental conditions. MIL-STD-810_ shall be used in developing environmental test methods. Environmental test methods must be approved by the Government.

3.4.15.1. Vibration. The I² Tube, with no operating voltage applied, shall not be damaged (see 3.5.8) nor suffer degradation of performance (see 3.5.27) after being or when subjected to resonance search (see 3.5.18), resonance dwell, and cycling with vibrations of the frequency and amplitude represented in Figure 2 applied both parallel to and perpendicular to the optical axis of the I² Tube for not less than one (1) hour in each axis.

3.4.15.2. Shock. With no radiation incident on the photo-cathode, the operating I² Tube shall not be damaged (see 3.5.8) nor suffer degradation of performance (see 3.5.27) when subjected to 6 shock impacts parallel to the optical axis and 6 shock impacts perpendicular to the optical axis with no more than 2 flashes in each axis. Impacts shall be half-sine wave with a minimum peak amplitude of 75g (see 3.5.5) and a duration of 6 ±2 ms measured at the 10 percent amplitude points.

3.4.15.3. Temperature extremes. The I² Tube shall meet the requirements specified in 3.4.16.3.1 and shall not be damaged (see 3.5.8) nor suffer degradation of performance (see 3.5.27) by continuous operation from +52°C to –40°C or after storage from +85°C to -54°C. The I² Tube shall not be damaged nor suffer degradation of performance by sudden temperature changes from +85°C to +23°C; +23°C to -40°C; and -54°C to +23°C each transition occurring within five (5) minutes. Room temperature pre-test and room temperature post-test values shall be taken. Temperature profile showing operating times and indicating when to perform operational checks (see3.5.30) is given in Figure 3 and profile steps are given in Table VII.

3.4.15.3.1. Operating requirements for +52°C and -40°C.

a. Input current – not greater than 57 mA at +52°C and 46 mA at -40°C.

b. Gain at 2.15 x 10-5 lx (2 x 10-6 fc) – between 16,000 cd/m²/lx (50,000 fL/fc) and 70,000 cd/m²/lx (220,000 fL/fc) at both temperatures.

c. Gain at 2.15 x 10-3 lx (2 x 10-4 fc) – not less than 3,200 cd/m²/lx (10,000 fL/fc) and not greater than 9,500 cd/m²/lx (30,000 fL/fc) at both temperatures.

d. Operational stability at > 3.43 cd/m² (1 fL) tube output:

(1) The output brightness shall not fluctuate more than ± 10 percent from a steady-state condition and shall not drift more than ± 15 percent from a steady-state condition for a period of 2 minutes after an initial operating time of 2 seconds. All fluctuations shall be random after the initial 2 seconds. There shall be no flickering, flashing, or blinking visible to the naked eye.

(2) Rise time shall not be greater than 7 seconds and overshoot (see 3.5.16) shall not be greater than 40 percent of steady-state output brightness.

e. Gain and EBI. The variation between the room temperature pre-test gain and the room temperature post-test gain shall not be greater than ± 20 percent. Post-test EBI shall be as specified in 3.4.2.

3.4.15.4. Humidity. The unprotected image intensifier I² Tube shall not be damaged (see 3.5.8) nor suffer degradation of performance (see 3.5.27) after being subjected to not less than 10 cycles of the humidity and temperature profile shown in Figure 4. The gain and input current shall not vary more than ± 20 percent, EBI shall not exceed 2.0x10-7 lx, and all parameters must remain within specified limits. All performance tests must be completed within 8 hours after completion of the final humidity cycle.

3.4.16. Electromagnetic interference (EMI). The I² Tube, when properly incorporated within a qualified system, shall comply with all EMI system requirements. (MIL-STD-461_)

3.4.17. Reliability. The I² Tube shall have a minimum mean time to failure of not less than 12,500 hours (2,500 hours accelerated). The reliability test sample size and number of failures allowed shall be as specified in the Government approved Quality Validation Plan. Following and during reliability testing, the I² Tube shall not exhibit damage (see 3.5.8) or degradation of performance (see 3.5.27) and shall comply with the requirements specified in Table VI.

Table VI Reliability acceptance levels

3.4.18. Storage life. The I² Tube shall not be damaged (see 3.5.8) nor suffer degradation of performance (see 3.5.27) after exposure to 12 continuous temperature cycles of +85°C to - 54°C followed by either a storage period of not less than 60 days at room temperature (see 3.5.6) or reliability testing (see 3.4.18). During cycling, the I² Tube shall remain at each temperature extreme until the I² Tube is thermally stabilized (2 hours minimum), and the chamber temperature rate of change shall be not less than 3°C per minute during transitions. As a minimum, conformance to the luminance gain, input current, signal-to-noise ratio, output brightness uniformity, screen quality, and useful cathode diameter requirements shall be verified upon completion of the 60 day storage period or reliability test.

3.4.19. Room temperature turn-on/operational stability.

a. When the tube I² Tube is turned on after a non-operational period of not less than 10 minutes, it shall reach 90% or more of its steady-state output brightness within 1.0 second, for each of the following input illuminances: 2.15 x 10-5 lx (2 x 10-6 fc), 2.15 x 10-3 lx(2 x 10-4 fc), and 10.8 lx (1.0 fc). Overshoot shall be no more than 40% of its steady- state output brightness. The tube I² Tube’s output brightness shall not drift more than ± 15% from the steady-state condition for a period of two (2) minutes after turn-on.

b. Upon switching to an input illuminance between 1.08 x 10-5 lx (1 x 10-6 fc) and 1.08 x 10-4 lx (1 x 10-5 fc) immediately after exposure to an input illuminance not less than 2.15 lx (0.2 fc) for not less than 3 seconds, the tube I² Tube shall reach 90% or more of its steady-state output brightness within 1.0 second. Overshoot shall be no more than 40% of its steady-state output brightness. The tube I² Tube’s output brightness shall not drift more than + 15% from the steady- state condition for a period of two (2) minutes after the switch to the lower input illuminance.

3.5. Technical interpretations. The following technical interpretations shall be, when referenced in sections 3 or 4, mandatory for this specification.

3.5.1. Photocathode. The glass input window with a photo sensitive substrate bonded to it is referred to as the photocathode.

3.5.2. Phosphor. The phosphor used in image intensifier tubes is a cathodoluminescent material that emits light in response to impacting electrons. The phosphors presently employed in image intensifier tubes are typically composed of rare-earth compounds.

3.5.3. Distortion. The two types of distortion that are important in an optical inverter are shear distortion and gross distortion.

3.5.3.1. Shear distortion. Causes the image of a straight line to have a discrete, localized lateral displacement (break). Shear distortion is due to localized misalignment errors in the I² Tube.

3.5.3.2. Gross distortion. Causes the image of a straight line to curve. Gross distortion is caused by a long-range deformation of the flow of fibers during fabrication.

3.5.3.3. Best-fit straight line. A straight line intersecting the +8 and -8 mm points of the input straight line image. The +8 and -8 mm measurements are relative to the projected pattern center point.

3.5.4. Chicken wire. Defined as a predominant pattern of dead fibers which has a width not greater than 0.00127 cm (2 single fibers) whose light transmission is so degraded that with light projected through the optic, single fibers in the area in question cannot be distinguished or identified as single fibers with the use of 50-power magnification.

3.5.5. "g". A “g” is defined as the nominal acceleration due to gravity at the earth’s surface (i.e., 9.81 m/sec2 or 32.2 ft/sec2 ).

3.5.6. Room temperature. Room temperature is defined as +23°C +10/-2°C.

3.5.7. Halo. Halo is defined as a circular area of brightness evidenced on the I² Tube output imaging screen occurring as a result of a small bright source input and concentric with the input.

3.5.8. Damage. Damage is defined as:

a. Electrical failure or malfunctioning, intermittent or continuous, including arcing, corona, flashing, flickering, emission point(s) or blinking, or a change in input current greater than ± 20 percent during or subsequent to completion of testing.

b. Cracks, breakage, deformation, burrs, corrosion, or deterioration of any part or finish, and missing or loose components.

c. Imperfections of optical components that adversely affect optical performance.

3.5.9. Multi-to-multi pattern variation. Discernible spatial gain variation between individual multi-patterns or groups of multi-patterns.

3.5.10. Multi-boundary pattern noise. Discernible spatial gain variation between peripheral and interior channels or groups of channels in a multi-pattern.

3.5.11. Modulation transfer function (MTF). Modulation transfer function is a measure of the degradation of an image as it appears at the output screen of the I² Tube as correlated to the input pattern which is normalized to 100 percent contrast at a spatial frequency equal to or less than 0.25 lp/mm.

3.5.12. Field emission. Discernible field emission is voltage-dependent extraneous emission which appears as bright spots or a pattern that may flicker or appear intermittently on the image screen in one general area. Field emission is voltage dependent and is best observed with a low level of radiation incident on the photocathode.

3.5.13. Scintillations. Bright spots which occur on the image screen randomly in space and time.

3.5.14. Optical axis. The optical axis of the I² Tube is defined as the mean centerline of that cylindrical portion of the I² Tube used to align the I² Tube in the system housing.

3.5.15. Limiting resolution. Limiting resolution is defined as the smallest resolution pattern for which the observer can distinguish three black lines and the clear areas between the black lines, for both the vertical and horizontal test patterns per United States Air Force (USAF) 1951 Resolving Power Test Target

3.5.16. Overshoot. The percent amplitude of output brightness above or below a steady-state condition at turn-on and during output brightness transitions.

3.5.17. Useful area. The useful photocathode and phosphor screen area shall comprise a circle of diameter not less than 17.5 mm centered on the I² Tube optical axis.

3.5.18. Resonant frequency. A resonant frequency is defined as any frequency where the response amplitude is greater than or equal to two times the input vibration amplitude at that frequency.

3.5.19. Contrast. Contrast is defined as

Bmax is the brightness of the light area.

Bmin is the brightness of the dark area.

3.5.20. Qualified product. A product that has successfully met all requirements of initial production testing (IPT) witnessed by the a Government representative. Should the supplier make substantial changes in the process, material (see 3.2.2), or location used to produce the qualified product or have not delivered a qualified product to the Government for 12 months or more, an IPT shall be performed to the extent necessary to verify continued compliance to specification requirements.

3.5.21. Veiling glare. Veiling glare is defined as ghost images, crescents or other geometrically shaped images appearing in the system’s FOV,when a bright point source outside the FOV, illuminates the entrance pupil of the objective lens.

3.5.22. Luminance sensitivity. The photocurrent (in microamperes), corrected for leakage and dark current, divided by the actual input (in lumens).

3.5.23. Radiant sensitivity. The photocathode current (in milliamperes), corrected for leakage and dark current, divided by the actual input radiation (in watts).

3.5.24. Equivalent background input (EBI). EBI is the residual output screen luminance in the absence of photocathode illumination divided by the luminance gain of the I² tube.

3.5.25. Luminance gain. When the photocathode of the operational tube I² Tube is illuminated with input light uniformly distributed over the full useful diameter of the faceplate, the luminance gain is defined as the screen luminance (in cd/m²) divided by the actual input illuminance (in lx) where screen luminance is measured such that the acceptance angle (of the measuring instrument) subtends a minimum 16mm diameter area centered on the phosphor screen. The screen luminance value utilized in this computation shall be corrected by the background (i.e., no input) luminance value.

3.5.26. Signal-to-noise. Signal-to-noise is a measure of the image intensifier tube’s average output brightness (signal) divided by the standard deviation of output brightness (noise) per the following equation:

Where, S = dc signal N = root mean squared noise S0 = average signal output from the S/N test set Sbkd = average background signal from S/N test set with light off N0 = noise of the signal output from the S/N test set Nbkd = noise of the background signal from S/N test set with light off K = correlation factor to obtain a S/N ratio over an equivalent bandwidth of 10 Hz independent of I² Tube’s phosphor temporal response. K = 1.15 for a P-45 white phosphor

These statistics are measured with a specified input spot of light no greater than 0.2 mm in diameter placed within a 1 mm radius from the I² Tube optical axis, and at a light level of 1.08 x 10-4 lx (1 x 10-5 fc) of 2856 ± 50K black body illuminance. The standard deviation of brightness is measured over a 10 Hertz noise equivalent bandwidth. The output signal is determined with a sample aperture no greater than 0.3 mm.

3.5.27. Degradation of performance. Degradation of performance is defined as a cumulative change in measurable characteristics which can result in failure of the I² Tube to meet specified requirements.

3.5.28. Type-B hole defect. A type-B hole is a hole in the ion barrier film which exists over a series of channels, and has an area equal to a circle with a diameter not greater than 125 micrometers. A type-B hole is manifested as a bright spot on the output screen when the photocathode of a packaged tube is illuminated with not less than 1.08 lx (1 x 10-1 fc).

3.5.29. Interchangeable. An item which possesses such functional and physical characteristics as to be equivalent in performance, reliability, and maintainability, to another item of similar or identical purposes; and is capable of being exchanged for the other item without selection for fit or performance, and without alteration of the items themselves or of adjoining items, except for adjustment.

3.5.30. Operational Checks: Apply 3.0 ± 0.05 Vdc to the I² Tube and verifying presense of luminous output.

4. VERIFICATION

4.1. Classification of inspections. The inspection requirements specified herein are classified as follows:

a. Initial production testing (IPT) / Qualification(see 4.2).

b. Conformance inspection (CI) (see 4.3).

4.2. Initial production testing (IPT) / Qualification. Unless otherwise specified in the contract or purchase order, the IPT shall be performed by the contractor. The IPT shall consist of the inspections/tests as specified in the Government approved Quality Validation Plan. Disposition of IPT samples shall be as specified in the contract or purchase order.

4.3. Conformance inspection. Unless otherwise specified in the contract or purchase order, the requirements for conformance inspection shall be as specified in the Government approved Quality Validation Plan.

Figure 1 Gain/Saturation requirement

Figure 2 Vibration profile

Figure 3 Temperature Extreme Profile

Table VII Temperature Extreme Profile Steps

Duration (min)

Figure 4 Humidity Profile image1.png image2.png image3.png image4.png