Reading from a charge coupled device (ccd) © D Hoult 2010

Each pixel in a ccd consists of a photoelectric cell and a capacitor (to store the charge emitted)

Each pixel in a ccd consists of a photoelectric cell and a capacitor (to store the charge emitted) The voltage across the capacitor is proportional to the charge stored

Each pixel in a ccd consists of a photoelectric cell and a capacitor (to store the charge emitted) The voltage across the capacitor is proportional to the charge stored and hence to the intensity of the illumination of the pixel

The pixels in this diagram have been magnified...

The pixels in this diagram have been magnified... quite a lot !

This ccd has not yet been exposed to light

After exposure, the capacitors in the illuminated pixels now store a small charge

The data are read 1 pixel at a time

First, all the voltages are “shifted” towards a special row of pixels at one end of the chip

First, all the voltages are “shifted” towards a special row of pixels at one end of the chip

First, all the voltages are “shifted” towards a special row of pixels at one end of the chip

Now the data voltages are “shifted”, one at a time, towards a pixel at the end of that special row

After each shift, the voltage in the special pixel is read and stored in memory

After each shift, the voltage in the special pixel is read and stored in memory, in this case, zero

voltage = V

voltage = 0

voltage = 0

voltage = V

voltage = 0

voltage = V

voltage = 0

voltage = 0

voltage = V

voltage = V

voltage = V

voltage = V

voltage = V

voltage = 0