What is a CCD Sensor?

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The CCD (charge coupled device) was first invented at the Bell laboratories in the 1960s. CCDs are thin wafers which consist of a number of buried electrodes that facilitate the movement of electrons from the device to a desired point.

Image Sensing Using CCDs

CCDs were initially used as computer memory circuits and later entered into the field of image sensing due to their superior light detection abilities.

Image sensing using CCDs is carried out in one of the three ways:

• Point scanning
• Line scanning
• Area scanning

How does a CCD Work?

The CCD image sensing process takes place in three steps:

1. The exposure to light converts light into an electrical charge at discrete sites, also known as pixels.
2. The electrical charge is transferred through the movement of charge packets within the silicon substrates.
3. The accumulated electrical charge is finally converted into a voltage.

Constructing a CCD

Charge coupled devices consist of an array of capacitive wells which form the photoactive region. This photoactive region is made of silicon, which has been doped with a positive substrate such as boron. Certain areas of the silicon are also n-doped with phosphorus.

There are three types of architecture of CCDs:

• Full frame
• Frame transfer
• Interline

The difference in these architectures is brought about by the type of photo detectors they use; full frame and frame transfer use photo capacitors while interline uses photodiodes.

Applications of CCD Sensors

Some of the application areas of CCD sensors include:

• Signal processing
• Digital imaging
• Astronomy
• Professional photography
• Raman spectroscopy
• Fluorescence microscopy
• Super resolution microscopy