Logo of the Human Brain Project

Logarithmic Response CMOS Image Sensor

Within the scope of this project several image sensors based on CMOS photoreceptors have been developed. Their dynamical range covers 6 decades and logarithmic compression to a reasonable range of voltage is applied. Due to the high variations from one pixel to the next it is necessary to perform an offset correction of each pixel value. This correction has been integrated into the chip using analog calibration.

The developed image sensor (Divichi) has both an analog video output as well as a 10 bit digital output (on-chip ADC). The different parameters can be programmed using a serial interface and important adjustments can also be done directly by means of 3 buttons mounted on the camera. The following list summarizes the most important propererties of the camera:

  • Resolution: 384x288 Pixel
  • Dynamical range of 6 decades with logarithmic characteristic curve
  • On-Chip Fixed Pattern Noise Correction
  • Max. readout frequency of pixels: 8 MHz
  • Possibility to readout random image parts
  • Digital zoom in 32 steps
  • Averaging of up to 8x8 neighboring pixels
  • On-Chip 10 bit ADC
  • Low voltage differential bidirectional serial interface (120 Mbit/s)
  • Parallel bidirectional interface
  • Automatic exposure control
  • On-screen Display
  • EEPROM-port for saving parameters
up