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CMOS and CCD Camera
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 than CCD sensor.
CMOS sensor's sensitivity are normally in the range of 6 to 15 lux. CMOS sensor have 10 times more fix pattern noise than 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 than 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 than 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 than 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 than 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 than PAL TV standard on 25 frame/sec. and it is the physical limit for a CCD device.