Camera - 02 image sensor

sensor brief introduction

1. image sensor : A sensor that converts an optical image of a two-dimensional light intensity distribution into a one-dimensional sequential electrical signal
2. Divide according to the original CCD（ Electrically coupled device ）,CMOS（ Metal oxide semiconductor devices ）
3. sensor Six hardware indicators
   （1） Target size : CCD/CMOS The bigger the size , The larger the sensitive area , The better the image .
   
   （2） Pixels , Each photosensitive unit corresponds to one pixel , More pixels , More details of objects can be sensed , The clearer the image
   （3） Sensitivity ,CCD/CMOS And the intensity of the incident light induced by the relevant electronic circuit
      [1] The higher the sensitivity , The more sensitive to light , The higher the shutter speed
      [2] Company ：V/LUX-SEC,V（ v ） Voltage unit ,LUX-SEC A unit of light intensity , The bigger the value is. , The better the night vision effect .
   （4） Electronic shutter , Control the photosensitive time of the image sensor , photosensitive ↑, Signal charge accumulation time ↑, Amplitude of output signal current ↑.
      [1] The faster the electronic shutter , The lower the sensitivity , Suitable for shooting in strong light .
      [2] The global shutter is designed according to the pixel , Rolling shutter
   （5） Frame rate , The number of pictures recorded or played per unit time .
   （6） Signal-to-noise ratio , The ratio of signal voltage to noise voltage , Company db
      [1] Signal-to-noise ratio ↑, quality ↑, Typical values 45-55db,50db There is a little noise , Good quality .
4. Color filter array (CFA/CFM), A mosaic overlay over the pixel sensor
   （1） Generally, it can only sense the intensity of light , Can not distinguish the wavelength of light ( color ), Therefore, color filtering is needed to obtain the color information of pixels .
   （2） The most common Bayer Filter, also called RGGB Filter, The human eye is more sensitive to green , therefore 50% Green ratio .
5. Spectral effect , It refers to the responsiveness of the chip to different light wavelengths .
6. Transmission interface
   （1）MIPI: Mobile industry processor interface , Serial data , Fast , anti-interference , Main stream .
   （2）LVDS： Low voltage differential signal technology interface .
   （3）DVP： Parallel port transmission , Slower , The transmission bandwidth is low .
   （4）Parallel： Parallel data , contain 12 Bit data signal , Line field synchronization signal and clock signal .
   （5）HISPI: High speed pixel interface , Serial data .
   （6）SLVS-EC: For high frame rate and high resolution image acquisition .
7. Dynamic range ： The ability of the sensor to distinguish strong light and weak light at the same time
   （1） Dynamic range ↑, Detect the scene information within the light intensity range ↑, Richer image details .
8. CRA： The maximum angle of light that can be focused on a pixel
9. Quantum efficiency ： A measure of photoelectric conversion efficiency , The ratio of incident photons to photons collected by pixels .
10. Full well capacity ： The limit of the number of electrons a pixel can collect and hold , Directly determine the maximum signal-to-noise ratio of the sensor .
11. Dark noise （ Time domain dark noise ）： Limit detection capability for weak signals .
12. Mainstream CMOS manufacturer