Charge-Coupled Device

                            Charge-Coupled Device(CCD) (1969)

 

Boyle and Smith Pioneer a form of Memory

Fundamentally, a charge coupled device (CCD) is an integrated circuit etched onto a silicon surface forming light sensitive elements called pixels. Photons incident on this surface generate charge that can be read by electronics and turned into a digital copy of the light patterns falling on the device. CCDs come in a wide variety of sizes and types and are used in many applications from cell phone cameras to high-end scientific applications. Shown above are various CCDs, the largest is mounted on a 6" wafer and is used in some of Spectral Instrument’s products.

The function of a CCD can be visualized as an array of buckets (pixels) collecting rainwater (photons). Each bucket in the array is exposed for the same amount of time to the rain. The buckets fill up with a varying amount of water, and the CCD is then read one bucket at a time. This process is initiated by pouring water into the adjacent empty column. The buckets in this column transfer their ‘water’ down to a final pixel where the electronics of the camera read-out this pixel (the computer measuring the bucket) and turn it into a number that can be understood and stored by a computer.

Of course, this is an oversimplification – in fact, this ‘model’ (shown above) is actually wrong in some ways, all the pixels in a CCD are actually shifted simultaneously, not one column at a time. We’ll start the explanation process by explaining how a simple pixel works.