Infrared_Imager_Specifications.pdf

Infrared Imager Specifications for

AEDC MWIR Imager Upgrade (Job 14611)

1.0 Introduction

The Arnold Engineering Development Complex (AEDC) Signature Measurement Team routinely acquires high-resolution infrared imagery in fulfilling its mission of providing state-of-the-art signature measurements in support of DoD testing all over the world. Given that the current imaging sensors fielded by AEDC are often needed to support conflicting test events, AEDC has a requirement for additional mid-wavelength infrared (MWIR) imagers to deconflict mission support requirements. This requisition is for one MWIR Indium Antimonide (InSb) 640x512 windowing focal plane array (FPA) camera system which will form a part of a complete multi-spectral imaging system.

2.0 Scope

This document defines the specifications for one MWIR infrared imaging system to be procured on AF Project 14611. The complete imaging system will consist of a 640x512 snapshot integration InSb FPA and FPA scanning electronics providing a 14-bit digital output for recording with COTS CameraLink and/or Coaxpress (CXP) frame grabbers A summary of the imager system specifications is shown in Table 1.

3.0 Imaging System Technical Details

3.1 Optical Head

The optical head shall be designed and fabricated to meet the following specifications:

3.1.1 Spatial Response and Detector

Detector Array Size: The focal plane array of the imaging system shall have at least 640 horizontal x 512 vertical pixels. The focal plane must provide for windowing to allow for higher frame rates at lower spatial resolution. The minimum acceptable reduction in resolution is 4:1 (i.e. FPA must be capable of operating at 128x128; 64x64 would be preferable).

Pixel Size: The pixel size shall be >=20 µm square.

Detector Material and Integration Mode: The FPA detector material shall be Indium Antimonide (InSb). The detector must utilize snap-shot mode integration.

Also, the integration time must be independent of the frame rate and must be adjustable from 1 usec or less up to 10msec.

Geometric Fill Factor: Active pixel area to total pixel area ≥0.95.

Focal Ratio: The cold shield f/# shall be f/2.5. The camera head should be designed to use commercially available lenses.

Lens Mount: The camera should be designed to use commercially available “3-tab” bayonet mount lenses (e.g. those manufactured by Janos and/or DIOP).

Out-of-FOV Rejection: The optical train of the imager shall be baffled sufficiently to reduce stray radiation entering from 10 degrees or greater off the optical axis by a factor of 1,000 or more.

Field-of-View Uniformity: Measured output across the total FOV while viewing a uniform scene filling the total FOV shall not vary more than ±15% before non-uniformity correction and ±1% after non-uniformity correction at the longest operable integration time.

Bad Pixels: ≤1% bad pixels; ≥99% shall be correctable and operable pixels.

3.1.2 Spectral Response

Array Total Coverage: The imaging system's FPA spectral response shall be nominally 3.40 – 4.15 µm. Wider spectral response is not acceptable. A lower cutoff wavelength between 3.40 and 3.45 is acceptable. An upper cutoff wavelength between 4.10 and 4.15 is acceptable. This response function will be obtained using a custom cold filter (supplied by AEDC if required, preferably provided by vendor).

3.1.3 Radiometric Accuracy and Sensitivity

The radiometric measurement accuracy must allow for repeatable measurements within +/- 2% of full scale reading or 2o C up to 100 C. The Noise Equivalent Temperature Difference (NETD) must be at least 0.03oC at 300K.

3.1.4 Dynamic Range

Dynamic range is defined as the ratio of the radiance at which saturation occurs to the minimum measurable radiance in that band. Single frame dynamic range shall be at least 1000.

3.1.5 Calibration Stability

Calibration stability is defined as constant FPA output vs. time reading from the digital channel for any pixel for a fixed input target radiance. The imager must have a stability of ±5% of reading over the time and ambient temperature ranges given below:

Ambient temperature range: 0 to 50oC

Long-term stability: Two weeks minimum between total system calibrations.

Short-term stability: Forty-five minutes minimum between internal calibrations.

3.1.6 Linearity

Linearity of the system output digital reading to input radiance shall be within ±1% of reading from 0.5% to 98% full well. This specification must be tested prior to delivery of the camera system, results to be provided by vendor.

3.1.7 Frame Rate

The imager system shall be able to operate at a full (unwindowed) frame rate of at least 560 FPS. When ‘windowed’ to 256x256, the frame rate must be at least 1000 FPS. Digitized pixel data (14-bit) must be provided for every pixel in the active array window at these frame rates.

3.1.8 System I/O

The camera head must provide the following simultaneous I/O capabilities:

1) NUC-Corrected Analog NTSC Video on BNC connector

2) 14-bit Digital Data via Gigabit Ethernet and Camera Link and/or Coaxpress.

3) IRIG-B input providing individual frame time stamps in the recorded data.

4 ) Ability to cycle integration time between frames, providing up to four discrete integration times sequentially during a single recording.

3.1.9 Software

Software shall be provided for communicating with the imager head, for display of the digital real-time data, and for recording both the Gig-E and CameraLink/CXP data streams. The following operating parameters should be programmable via graphical user interface (GUI): frame rate, integration time, window size and location, global gain and offset. Digital data may be recorded in uncorrected format in real-time, although corrected data is preferred. The NUC correction tables must be available for post-processing of digital data.

The file format for the recorded data should be compatible with the Arnold AFB AMSC Standard Archive Format. Details regarding this format can be provided to prospective bidders.

3.2 System Electrical Requirements

The imaging system shall operate from the following electrical power and shall meet all performance specifications over the following power tolerances:

Voltage: 115 ± 15 Volts Frequency: 60 ± 3 Hz Maximum Current: 5 Amperes

4.0 Acceptance Testing

Acceptance testing for the imaging system will be performed by employees at AEDC.

Acceptance testing will include verification of the following:

1) NETD <= 0.03K

2) Spectral response 3.40-4.15 µm (see tolerances below)

2) Operation at highest frame rates.

3) Bad pixel count (<1%)

4) Uncorrected non-uniformity (<15%)

5) Non-Linearity ( < 1% from 0.5% - 98% full well)

Table 1: Summary of Infrared Imaging System Technical Specifications

System Feature Requirement Detector material InSb Integration mode Snap-shot

Detector resolution (pixels) 640H x 512V Pixel size (microns) >20 x 20

Lower cutoff wavelength range (3.40 desired) 3.40-3.45 Upper cutoff wavelength range (4.15desired) 4.10-4.15

Cold shield f/# f/2.5 Full frame rate capability (frames per second) ≥560 fps

Windowed frame rate capability (frames/sec at 256x256) ≥1000 fps Single frame dynamic range ≥1000

Imager head A/D resolution. (bits) 14 Radiometric measurement accuracy +/- 2% or 2° C

Bad or inoperable pixels < 1% Uncorrected non-uniformity < 15% Corrected non-uniformity < 1%

Response Linearity (0.5%-98% full-well) +/- 1%