CCD DSP lux 36 mm f12 70 deg 13 Definitions radiometric vs photometric Photometry is just like radiometry except that everything is weighted by the spectral response of the eye Luminance ID: 303235
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Slide1
Camera/VideoSlide2
CCD DSP
lux
3.6 mm f/1.2
70 deg.
1/3”Slide3
Definitions
radiometric vs. photometric
Photometry is just like radiometry except that everything is weighted by the spectral response of the eye
Luminance (
cd
/m2)-Describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle.
Luminous flux (lm)- The measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.
Lux (lx = lm/m2)-is the SI unit of
illuminance, and measuring luminous flux per unit area.QUANTITY RADIOMETRIC PHOTOMETRIC
QUANTITY
RADIOMETRICPHOTOMETRIC
powerwatt (W)lumen (lm)
power per unit area
W/m
2
lm/m
2
= lux (lx)
power per unit solid angle
W/sr
lm/sr = candela (cd)
power per area per solid angle
W/m
2
-sr
lm/m
2
-sr =
cd
/m
2
= nitSlide4
Illuminance
of surfaces illuminated by:
(Power/Area, Intensity)
0.0001 lux -Total starlight0.002 lux
-Moonless clear night sky0.01 lux - Quarter moon0.27 lux
-Full moon on a clear night1 lux - Full moon overhead at tropical latitudesSlide5
Focal length-f
The focal point of a lens is defined as that point at which rays from infinity (parallel rays) impinging on the lens are focused. The focal length is the distance of the focal point from the center of the lens.Slide6
F number
In optics, the f-number is given by
f
/D where f is the focal length, and D is the diameter of the entrance pupil
Ex. f =100 mm and D = 25 mm 100/25 = f/4 Ex. f= 200 mm and D = 50 mm
200/50 = f/4 The 200 mm lens's f/4 opening is larger than that of the 100 mm lens but both will produce the same
illuminance in the focal plane when imaging an object of a given luminance.Slide7
FOV (Field of View)
FOV underwater
Angle of coverage (FOV)
α = 2*tan
-1(d /2f)Note small f
large α
α
=80
° Field of View
α=8° Field of ViewSlide8
Snell’s Law
Diagonal coverage of lenses on the 35mm format
The refractive index of (sea) water was taken to be 1.339 for underwater (UW)
Focal
Length (mm)
Coverage
in Air (degrees)Coverage UW (Flat Port) degrees
1997.4268.27
2094.4966.51
2484.0660.00
2875.3854.34
3071.5951.80
α' = 2
sin
-1
[
Sin(
α/2) /
n
w
]
T
he port itself has no effect on the angle of coverage (although it does alter the effective position of the lens entrance pupil as seen from outside the housing
).
DerivationSlide9
CCD-Charged Coupled Device
Type
Aspect
Ratio
Diameter (mm)Diagonal(mm)Width (mm)
Height (mm)1/3.6”4:3
7.0565.004.00
3.001/3.2”4:3
7.9385.684.536
3.4161/3”4:3
8.4676.004.6
3.6
The type designation harks back to a set of standard sizes given to TV camera tubes in the 50's. These sizes were typically 1/2", 2/3" etc.Slide10
Depth of Field
Image distance vs. object distance
If the object becomes closer to the lens, the image moves further away from the lens and becomes larger.
If
one moves a real film plane back and forth a bit, a
range
of object distances remains in acceptable focus, this is the depth of field
One can
change the depth of field by changing the focal length or
aperture size of the lens. The width of the non-converged beam for the near-tree image becomes much less, and can be made too small to notice. Then both trees will be in acceptable focus.
Focus the camera on the far tree. Near tree out of focusSlide11
CCD-Charged Coupled Device
CCD Overview
Animation
DSP-digital signal processing
The signal processor within the camera receives the information from the charged coupled device, or CCD, and combines it into video framesSlide12
Some Calculations
Outland UWC-325/p
Focal length
f=3.6 mm f/1.2 Using
f/1.2=f/D and solving for DD= 3.6/1.2= 3 mmFOV α =
2tan-1(d / 2f)=2tan
-1(6/(2*3.6)) = 79.61oNotice that a
small f gives a larger FOVUnderwater FOV using nw
=1.339α' = 2sin-1[ sin(
α/2) / nw ]=2sin-1
[sin(80/2)/1.339]= 57.3 oSlide13
High-definition video
or
HD video
is any video system of higher resolution than standard-definition (SD) video, and most commonly involves display resolutions of 1,280×720 pixels (720p) or 1,920×1,080 pixels (1080i/1080p).
640 x 480 Pixels with 4:3 Aspect Ratio
1920 x 1080 Pixels with 16:9 Aspect RatioSlide14
Camera
Outland Technology
Seaview
Remote Ocean System
InsiteGoProGoPro 3D
Camera PottingOceanPro HD
Deepsea Power and LightLights-camera-actionSlide15
Glossary
f = F number
f
= focal lengthD = diameter of apatureα
= Field of View in air (FOV)α’ = Field of View in waterd = diagonal of imaging device