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									CEE 6100 / CSS 6600 Remote Sensing Fundamentals                                                 1
Topic 3: Frame Cameras


Some definitions:
    • Frame Camera
        – A camera which exposes the entire image frame simultaneously

    • FOV – Field of View
        – The total solid angle (or ground area) viewed by an imaging system or
          a radiometer.
        – Commonly specified as a plane angle or length on the ground.
          (Assumes that the area is square.)
    • IFOV – Instantaneous Field of View
        – The smallest solid angle (or ground area ) uniquely detected by an
          imaging system when all motion is stopped.
        – Commonly specified as a plane angle or length, as above.

                                      The Camera as radiometer

                                            FOV @ aperture = 2H tan (θFOV)

                                             s = IFOV = As / H2 sec3 = angle subtended by a
                                                             source element at a distance R
                                            a = Aa / H2 sec3  = angle subtended by a camera
                  θFOV                 s                      aperture at a distance R sec

                                                    Radiance at the aperture
                                                                    P       P
                                                           La           
                                                                  A s  a A a s
     source element              As
CEE 6100 / CSS 6600 Remote Sensing Fundamentals                                           2
Topic 3: Frame Cameras


Radiance at the aperture from the viewing direction, La(), is related to the
radiance leaving the surface element, Ls(), by:
                               La() = Ls()  + L*()
      where:        is the atmospheric attenuation factor
                   L* is the path radiance
The radiance at the focal plane is further reduced by transmission through the
camera optics (including filters), i.e.,
                            Ld () = [ Ls ()  + Ls () ] τo
      where: τo = optical transmission factor
Finally, irradiance at a point on the focal plane illuminated by radiance, L s(), is
given by:
                       Ed = Ld ()  s = (Ls ()  + L*()) os

Irradiance (w/m2) is the fundamental radiometric quantity of interest when
            working with most detectors. Irradiance is the power per unit area on
            the detecting surface.
Exposure is defined as the product of the irradiance, E f, at the focal plane with
            exposure interval, Δt. Exposure = Ef Δt [W m-2 sec]
Photographic exposure is usually defined in photometric rather than radiometric
           units. [lux sec]
Photometric units: measurements weighted by the theoretical response of the
           human visual system.

       Radiometric          unit                Photometric             unit
       Radiant Flux       watts (W)            Luminous flux        lumens (lm)
      Radiant Intensity    W sr -1           Luminous intensity candela (cd = lm sr -1)
          Radiance        W m-2 sr -1            Luminance            cd m-2
         Irradiance         W m-2               Illuminance        lux = lm m-2
CEE 6100 / CSS 6600 Remote Sensing Fundamentals                                                                     3
Topic 3: Frame Cameras

               Photographic materials                                      Solid State Detectors

                                                     film,
                                            base    glass, or
                                                     paper


• emulsion: most commonly a silver halide in
   a gelatin base
                                                                 • Each photodiode collects light independently
• base: paper, film, or glass
                                                                 • The active area is smaller than the
• anti-halation coating: an absorbing layer to                      photodiode area
    suppress "halos" -- the spreading of a
    photographic image beyond its proper
    boundaries. Halation is caused primarily           

     Characteristic (D log E) curve                                            Response function
     (darkening on the negative)




                                   gross       range

               log E
• Each film has a unique D log E curve
• The shape of the curve varies with                             Solid state analogs:
       conditions of development                                 characteristic curve  response function
• A film's sensitivity is determined from the                    Dmin  dark current
       film's characteristic curve.                              Dmax  saturation
• "Gross fog" = film base density + net fog
       (dark current for film)                                   The gain of a photodiode under reverse bias is
                                                                 extremely linear over a very wide dynamic
CEE 6100 / CSS 6600 Remote Sensing Fundamentals                                               4
Topic 3: Frame Cameras

     Film gamma,  : The slope of the straight line portion of the characteristic curve. (A
                                    measure of contrast.)
                     γ = tan  θ  =             high gamma
                                       ΔlogE        a small change in
                                                    E produces a large
                                                    change in D.
     Density (D)

                                                 low gamma
                                                    a small change in

                                                    E produces a small
                                                    change in D.

                                                 Increasing the time of development will
                                                 increase the film gamma

                          log E (Exposure)

  Solid state analog: gamma  gain

speed: The faster the film, the less the exposure required to produce a grain density.
   • film A is faster than film B
   • Speed is determined by measuring the exposure at some measurable amount of density
      above gross fog, e.g., ASA ratings are based on a "speed point" (log E values)
      corresponding to 0.1 density above gross fog.
CEE 6100 / CSS 6600 Remote Sensing Fundamentals                                                           5
Topic 3: Frame Cameras

Solid state detectors

CCD image array ( Kodak KAF-6303E ).
                      HU                      UH
                                                             CMOS image array ( Samsung

Active area: 27.65 x 18.48 mm                                S5K4AW ).UH

Active pixels: 3072 x 2048 (6 Mpixel)                        Active area: ???
Pixel size: 9x9 m                                           Active pixels: 1280 x 960 (1.2 Mpixel)
                                                             Pixel size: 2.8 x 2.8 m

                                                           Feature             CCD             CMOS
                                                      Signal out of pixel Electron packet      Voltage
                                                       Signal out of chip Voltage (analog)   Bits (digital)
                                                         Signal out of
                                                                           Bits (digital)    Bits (digital)
                                                         System Noise           Low           Moderate
                                                      System Complexity        High              Low
                                                      Sensor Complexity         Low              High
                                                        Dynamic Range          High           Moderate
                                                          Uniformity           High        Low to Moderate
                                                            Speed         Moderate to High      Higher

                   Currently most imaging systems use CCD technology
CEE 6100 / CSS 6600 Remote Sensing Fundamentals                                      6
Topic 3: Frame Cameras

Detector & Filter response characteristics


Vignetting: Darkening of an image away from the optic axis of the
imaging system.

Cos4θ falloff (also "natural" vignetting) is inherent to each lens
design and becomes more troublesome for wide angle lenses.
Optical Vignetting: Optical vignetting is related to aperture size.
The effect is most pronounced when the lens is used wide open and
will disappear when the lens is stopped down by a few stops.

CEE 6100 / CSS 6600 Remote Sensing Fundamentals       7
Topic 3: Frame Cameras

        Leica RC-10A Aerial Camera
System includes the following:

    •    Lens Cone - 153mm
    •    Drive Unit
    •    PAV 20 mount
    •    2 ea. PKA4 film cassettes
    •    Navigation Telescope
    •    Manuals
    •    Toolbox
    •    Cables and Filters
    •    Shipping containers


RMK TOP - Aerial Survey Camera System
focal length 153 mm (6 "),
angular field 93° (diagonal),
aperture f/4 to f/22 continuously,
distortion <= 3µm

focal length 305 mm (12")
angular field 56° (diagonal),
aperture f/5.6 to f/22 continuously,
distortion <= 3µm

(gyro-stabilization suspension mount)
             •    Stabilization range:
                     •    ± 5° in omega,
                     •    ± 5° in phi,
                     •    ± 6.5° in kappa
             •    max. angular speed: 10°/s
             •    max. angular acceleration: 20°/s²
CEE 6100 / CSS 6600 Remote Sensing Fundamentals                    8
Topic 3: Frame Cameras

  •   Ground pixel size: 5 cm @ 300 m
  •   Forward Motion Compensation (FMC)
  •   12-bit per pixel radiometric resolution

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