Image sensor

An image sensor or imager is a special tool that helps us capture pictures and images. It works by detecting light and other types of energy that come from objects around us. When light waves pass through or bounce off things, the sensor changes these waves into tiny electrical signals. These signals carry the information needed to create an image, whether it’s a photograph, a video, or even a picture from a medical device.

Image sensors are used in many everyday devices, like digital cameras, camera phones, and optical mouse devices. They are also important in tools that help doctors see inside the body, in night-vision goggles, and in equipment that uses radar or sonar to detect objects far away. As technology improves, more and more devices are using digital image sensors instead of older methods.

There are two main types of image sensors used today: the charge-coupled device (CCD) and the active-pixel sensor (CMOS sensor). Both of these sensors use special materials and tiny electronic parts to turn light into signals we can record and see. Whether you’re taking a picture with a camera or using a phone to snap a photo, an image sensor is at work behind the scenes, helping us capture and share the world around us.

Comparison between CCD and CMOS sensors

The two main types of digital image sensors are the charge-coupled device (CCD) and the active-pixel sensor (CMOS sensor). Both are made using special technology that allows them to capture light and turn it into electrical signals.

Cameras in small devices usually use CMOS sensors because they cost less and use less power. CCD sensors are often used in high-quality video cameras. Each type of sensor works by catching light and changing it into tiny electric charges that can be read and turned into an image. CMOS sensors have an amplifier for each pixel, which helps them work faster and use less power than CCD sensors.

Performance

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When we look at how well an image sensor works, we can check things like how well it can see in dark places and how many different levels of light it can show. Bigger sensors often do a better job because they can catch more light during the time the camera is taking a picture. This helps the sensor make clearer and more detailed images.

Exposure-time control

The time an image sensor is exposed to light is controlled in two main ways: using a mechanical shutter, like in older film cameras, or an electronic shutter. Electronic shuttering can happen all at once for the whole image, called "global," or it can happen row by row, called "rolling." Rolling shutter moves across the image, usually from top to bottom, and is more common because it doesn’t need extra circuits to store information.

Color separation

There are several ways to create color images with sensors. One common method uses a special pattern of colors placed over a single sensor, called a color filter array. This pattern, known as the Bayer pattern, helps the sensor detect red, green, and blue light by using more green pixels than red or blue. The sensor then uses nearby pixels to figure out the missing color information.

Other methods include the Foveon X3 sensor, which uses layers to sense different colors at each point, and the 3CCD system, which uses three separate sensors and special glass to split the colors apart. These methods can create very sharp and clear color images, especially in low-light conditions, and are often used in television broadcasting, video editing, and special visual effects like chroma key.

Specialty sensors

Special sensors are used in many interesting applications. They can help create multi-spectral images, assist in medical procedures like video laryngoscopes, and are used in gamma cameras and flat-panel detectors for x-rays. There are also special arrays for thermography and astronomy.

In 2014, Sony created a curved sensor to improve photos. This curved design helps reduce problems that happen with flat sensors, allowing for smaller, shorter lenses that let in more light and give better results at the edges of the photo.

History

See also: Digital imaging

Early cameras used special tubes to capture images, starting in the 1930s. These were later replaced by newer, solid-state sensors in the 1990s. These modern sensors are built using a technology called MOS, invented in 1959. This led to the creation of two main types of sensors: CCD and CMOS.

In June 2022, Samsung announced a new sensor with 200 million pixels, making images clearer than ever before. The CCD type was invented in 1969 and was used in early digital video cameras. The CMOS type became more popular by the 2010s because it worked better for most new devices. These sensors are now used in many devices, from cameras to computer mice.