Q:What is CMOS camera. What is it different from CCD camera.
A: CMOS sensor is a kind of sensor that is normally 10 times less
sensitivity then CCD sensor.
As human eye can see object under 1 lux illumination ( full moon night ). CCD
sensor normally will see better or as good as human eye in the range of 0.1 ~3
lux and are 3 to 10 times more sensitive then CMOS sensor.
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More:
CMOS sensor's sensitivity are normally in the range of 6 to 15 lux. CMOS
sensor have 10 times more fix pattern noise then CCD sensor. Fixed pattern
noise is the kind of noise that stay on screen as if there is a patterned. As
CMOS sensor will become useless under 10 lux. All camera for serious
application are using CCD sensor. CMOS sensor are normally using on toy
or very low end home security.
There 2 exception. CMOS sensor can be made very big and have same sensitivity
as CCD sensor. CMOS sensor are very fast , it is 10 ~100 times faster then CCD
sensor, so it is very good for special application such as high ens DSC camera
( Cannon D-30 ) or fast frame camera.
CMOS sensor can have all the logic and control circuit be build on the same
silicon wafer dice so as to make the camera simple and easy to handle. Hence
CMOS camera can be very small in size.
CMOS camera though consume same or more power then CCD sensor but CMOS sensor
use less peripheral circuit such as CDS, TG and DSP circuit, so the
total power consumption is 1/2 to 1/4 less then a CCD camera on same size.
There is only one exception that Mintron C series camera is using only 12V/65
mA power which is almost same as CMOS camera but having much better image quality.
C series camera using 0.35um 3.3v DSP hence consume very
small power (
54C0,54C1,54C2,54C1,54C5,54C6) . All other CCD camera making by other company
are consuming 12V/150~300mA, hence is 2 to 4 times more then CMOS camera that
is on 5~12v and 35~70 mA
Ironically,
although CCD stand for "Charge Couple Device" and CMOS stand
for "Complementary Metal Oxide Silicon" but actually neither
CCD nor CMOS have anything to do with image sensing. The actuarial sensor is a
device called "Photo Diode" Both CCD sensor and CMOS sensor (
as so called ), are actually using same kind of sensor called Photo diode.
Photo diode is a P N junction diode that will convert photon of the light that
is bombing the junction into proportional amount of electron. The amount of
electron are them calculated and read as voltage of signal. The more the light
that entering the photo diode the more the electron generated and the higher
the voltage out put from the sensor.
CCD stand for "Charge Couple Device" , CCD actually is only
the technology to store the electron charge and the method to move these
charge out of photo sensor in and organized way.
CMOS stand for "Complementary Metal Oxide Silicon" . CMOS actually
is only a technology to make transistor on silicon wafer, and have no further
meaning. Sensor being called CMOS sensor was a convenient way to discriminate
it from CCD sensor and have nothing to do with the real ways that the sensor
handling image.
CMOS sensor convert electron generated by photo
diode into voltage signal immediately without complicate process. hence it is
much faster. This good point makes CMOS sensor very useful for fast frame
camera, the frame speed can be as high as 400 ~2000 frame/sec. This point
makes it very good for high speed moving object survey. however due to lack of
good fast speed DSP there are little high speed camera on the market and are normally
very expensive $3000 ~ 300,000 per unit. Mintron makes 75 frame CCD
camera which is 3 times faster then PAL TV standard on 25 frame/sec. and it is
the physical limit for a CCD device.