NIST Agency Report May 2012 OUTLINE. The case for traceability NMI capabilities A view to the future the HIP Current/recent NIST activities

Transcription

1 NIST Agency Report May 2012 OUTLINE The case for traceability NMI capabilities A view to the future the HIP Current/recent NIST activities

2 The case for traceability

3 Earth Radiation Budget: Solar irradiance 1361 W/m 2 π R 2 E sun R Reflected Solar 2 ρ π R E sun IR Thermal Emission π R σ ε T 3

4 4

5 Traceability Foundation for Accurate Measurements Property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties (VIM, 6.10) and defensible! Based on the SI International System of Units 5

6 Earth Radiation Budget: affected by Atmospheric constituents Earth s albedo Keeling curve (atmospheric CO 2 ): Carbon dioxide (ppm) 6

7 What do good measurements get us? Faster time to characterization of climate change, forcings, causes, etc. Test for human influence Test climate models 7

8 NMI capabilities

9 NIST Optical Measurements are Traceable to the Electrical Watt through the Primary Optical Watt Radiometer (POWR) POWR provides optical power to 0.01% (k = 2) Liquid Nitrogen Liquid He at 2K Jeanne Houston Joe Rice 9

10 with the aid of SIRCUS Spectral Irradiance and Radiance Responsivity Calibrations using Uniform Sources (SIRCUS) Tunable Laser Intensity Stabilizer Reference Detector Detector Under Test Spectrum Analyser Wavemeter Chopper or Shutter Exit Port Computer Integrating Sphere Lens Speckleremoval System Monitor Detector (output to stabilizer) λ=uv to LWIR Keith Lykke Steve Brown George Eppeldauer 10

11 Example of a short traceability chain: Detector based temperature realization in SIRCUS Laser Cryogenic Electrical Substitution Radiometer Precision Aperture Precision Aperture Si trap Detector Integrating Sphere d Radiation Thermometer L ( λ, T ) = n 2 c 1L 5 c 2 λ exp n λ T 1 Realization, dissemination of temperature scales above Ag freezing point 11

12 and to the Meter through Aperture Area Measurements Performed by the Absolute Aperture Area Measurement Machine CCD camera Aperture area to better than 0.01% High resolution microscope XY Stage Guide bar Granite table Fiber optic light source Optics table Aperture holder Differential plane interferometer Wavelength compensator Koehler illuminator Ratio Aperture Area [Lab/NIST] RMIB WRC ERBE Aperture Designation Toni Litorja Joel Fowler 12

13 A view to the future the HIP (Hyperspectral Image Projector)

14 Hyperspectral Imaging Projector (HIP) Consider the complexity of real world scenes: Scene viewed by a typical optical sensor instrument Scene viewed by an Imaging instrument In practice

15 Supercontinuum Fiber Laser Hyperspectral Image Projector (HIP) Prototype L1 L2 L3 Beam Stop 1 Prism1 L4 M1 Prism2 Relative Intensity Band M Spectral Image Projection Screen Beam Stop 2 λ 2 λ 1 DMD1 Projection Optics L Wavelength (nm) Spectral Engine Homogenizer Spatial Engine Illumination Optics L6 DMD2 Fold Mirror Unit Under Test (UUT) (or Reference Instrument) Band M Spatial Image Can substitute with other foreoptics to present to UUT

16 Example image as projected by the prototype HIP onto a white screen and taken using a digital camera

17 Current/Recent NIST activities Support of NPP/Soumi Support of JPSS/VIIRS, etc. Support of GOES R/(ABI,EXIS,SUVI) Cal/val of MOBY SEAWIFS, MODIS Support of Aeronet, ACE, CLARREO, GLORY/TIM, OCO 2, new TIM, NISTAR on DSCOVR LANDSAT, LDCM LDCM/Sentinel 2 cross validation Stellar, solar irradiance [TOA & ground (WRR)] Lunar radiance & irradiance calibrations

18 Digital tissue phantom Light source IMAGER (camera) recorded image Image Projector IMAGER (camera) NIST Hyperspectral Image Projector (HIP) Facility actual scene HIP projected Pig Skin flap Original spectra HIP projected 18

19 Digital Micromirror Device (DMD) An array of MEMS micromirror elements Commercially available: 1024 x 768 elements Aluminum mirrors 13.7 micron pitch For visible to 2500 nm applications: commercially available hardware For longer wavelength infrared developments we are using DMDs where the glass window is replaced by a ZnSe window. Control algorithms are being written using everyday control software for everyday hardware interfaces and operating systems.

20 Digital Light Processing (DLP) Projectors Reference:

21 Intensity How the DMD is used to create an arbitrarily programmable spectrum UV Visible Near IR 768 mirrors 1024 mirrors Wavelength mirror array