Couple-charged device (CCD) cameras are a type of image capture device that utilize an image sensor to register visible light as an electronic signal.

These types of cameras do not use photochemical film to capture stills or video. Instead, the electronic signal is recorded to either an internal memory or a remotely connected device. Of the three types of digital cameras (the others being CMOS and CID), CCD cameras are the most developed and commonly used.

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CCD Camera Operation

After the camera's record function is initiated, the camera's lens focuses light through the camera aperture, light filters, and onto the electronic image sensor. The image sensor is arranged in a grid pattern, with each individual square called a pixel. The image sensor cannot determine the color of light recorded, only the intensity.

Couple-charged device camera Images source: Ken Rockwell; RMA Electronics Inc.Couple-charged device camera Images source: Ken Rockwell; RMA Electronics Inc.Color is typically identified by the use of a color filter which will only allow one color of light from the visible spectrum into each pixel. The color filter is usually arranged in a Bayer filter pattern, which is used to average the colors of a 2 x 2 pixel square. Since the filter produces some inaccuracy, any discoloring is called interpolation.

A separate method of color identification employs separate image sensors with each dedicated to capturing part of the color image, such as one color, and the results are combined to generate the full color image. They typically employ color separation devices such as beam splitters rather than having integral filters on the sensors.

In CCD cameras, the level of photons recorded is converted to a proportional electrical signal. The ratio that is generated for photons-to-electrons is called quantum efficiency. These signals are carried away from the individual pixels to a charge amplifier, which turns the charge into a voltage. The camera has now created an authentic chronicle of the light it captured. For video cameras, this process is repeated many times per second (frame rate), and the voltages are digitized and stored in a memory. When the images are replayed, the camera has recorded a high number of sequential stills, creating the appearance of an object in motion.

CCD Advantages

Notably, CCD cameras are more mature in development, meaning they are less expensive and more accessible. These types of cameras have a high dynamic range and high uniformity. CCDs are also particularly sensitive imaging devices. Antiblooming features are well developed in CCD image sensors.

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