STV-USB-VGA-R01 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'STV-USB-VGA-R01' PDF : 41 Pages View PDF
Customer Datasheet, Rev 3.1, 29 November 2000
STV0672-chipsetf-3-1.fm
4.4 VV6500 Optical Characterisation Data
Optical Parameter
Min
Typical
Max
Dark Current
-
TBA
-
Average Sensitivity
-
TBA
-
Fixed Pattern Noise (FPN)
-
TBA
-
Vertical Fixed Pattern Noise (VFPN)
-
TBA
-
Random Noise
-
TBA
-
Sensor SNR
-
TBA
-
Shading (Gross)
-
TBA
-
Table 12 : VV6500 Optical Characterisation Data
Units
mV/sec
V/lux.sec
mV
mV
mV
dB
mV
4.4.1 Noise Parameters and Dark Current
Various noise parameters are measured on the 410 and 500 series sensors as follows:
• Fixed Pattern Noise (FPN)
• Vertical Fixed Pattern Noise (VFPN)
• Random Noise
• Fine Shading
• Gross Shading
The parameters will be described in more detail below along with the data produced by the characterisation programme.
4.4.2 Blooming
Blooming is a phenomenon that does not affect CMOS sensors in the same way as CCD imagers are afflicted. With a CCD
blooming can cause an entire column/columns to flood and saturate.
CMOS imagers are however affected by a different type of saturation. If an intense light source, (e.g. Maglite torch), is shone at
very close proximity to the image sensor the pixel sampling mechanism will break down and rather than displaying a saturated
white light a black image will occur.
The 410 pixel architecture uses Correlated Double Sampling (CDS) to help reduce noise in the system. The pixel is read normally
first, yielding the true integrated signal information, then the pixel is reset and very quickly read for a second time. This normally
yields black information - as the pixel has had no exposure time - that can be subtracted from the signal from the first read. This
subtraction will remove much of the noise from the pixel leaving only the useful signal information.
In an example where a pixel has saturated in both the first and the second reads due to an intense light source. When the noise
cancellation subtraction operation is then performed the result is close to zero signal from the pixel therefore resulting in the
displayed black image.
We do not perform any test measurements for this phenomenon.
4.4.3 Dark Current
This is defined as the rate at which the average pixel voltage increases over time with the device not illuminated. The dark current
will be measured at a gain setting of 4 and a clock divisor of 16 at a fixed temperature and will be expressed in mV.
4.4.4 Fixed Pattern Noise
The FPN of an image sensor is the average pixel non-temporal noise divided by the average pixel voltage. The illumination
29 November 2000
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