Functions
Image Signal Processing (ISP) System Control
The system control function is used to register the 3A algorithm, register the sensor driver, initialize the ISP firmware, run the ISP firmware, exit the ISP firmware, and configure the ISP attributes. The ISP firmware consists of the ISP control unit, basic algorithm unit, AE/AWB/AF algorithm libraries (3A algorithm libraries), and sensor library.
Auto Exposure (AE)
The AE module obtains the current image exposure based on the automatic photometric system, and automatically sets the iris, sensor shutter, and gain to ensure optimal image quality.
The AE algorithm is classified into the following types:
- The iris first policy adjusts the iris to the proper position first and then allocates the exposure time and gains. It applies only to the P-iris lens and balances the noise and depth of field.
- The shutter first policy allocates the exposure time first and then the sensor gain and ISP gain, which minimizes the noises in the taken images.
- The gain first algorithm allocates the sensor gain and ISP gain first and then the exposure time, which applies to the scenario of taking images of moving objects. You can also customize the exposure allocation policies of the AE algorithm. The following figure shows the workflow of the AE module.
Automatic White Balance (AWB)
The spectral components of visible lights vary according to the color temperature. The white objects have a red cast at a low color temperature or have a blue cast at a high color temperature. Human eyes can identify the actual object color based on brain reflections. The AWB algorithm is used to reduce the impacts on the actual object color exerted by external illuminants. This ensures that the captured color information is converted into the information without color cast under an ideal illuminant.