Image Sensor

There are two main kinds of imagine sensor---- CCD (Charge Coupled Device), CMOS (Complementary Metal- Oxide Semiconductor) for mobile camera manufactures taking.

CCD: CCD image sensor currently offers the best available image quality. but the downside is that, compared to CMOS sensor, they tend to consume more power, dissipate more heat and are frequently larger.

CMOS: CMOS sensors are much smaller, consume less power and are beginning to challenge CCD image quality. Because CMOS sensors are fabricated using the CMOS manufacturing process they are much less expensive than CCD image sensor.

Several structures of CMOS

  • FIS: from top to bottom are lens layer, filter layer, circuit layer and sensor layer respectively, but this structure is easy to lose the light.
  • BSI: IS structure is that the photosensitive element layer is put on the circuit layer. this structure can make the light more directly into the sensor layer, reducing the loss of light and enhancing picture quality. 
  • Stack: stack structure is that all of circuit layers are removed to the bottom of the sensor layer, so it reduces the camera’s size and the light loss maximumly. The disadvantages of stack are high manufacturing technique and high costs.