This week I was given another task about the CCD optical sensors. CCD is called Charge-coupled device where it is capable of transforming light pattern from an image into an electric charge pattern just like an electronic image. It can collect, store and transport electrical charge from one element to another. Each pixels are represented by p-doped MOS capacitors. It is widely used in professional, medical, and scientific applications as it can provide high-quality image data. The active pixel sensors (CMOS) are used in applications with less quality demands, such as consumer and professional digital cameras.

CCD image sensors can either be color sensor or monochrome sensor.  In a color image sensor, RGB color filter array provides color responsivity and separation.  A monochrome image sensor senses only black and white.  Different array types include linear array, frame transfer area array, full frame area array, and interline transfer area array.

I have to find sensors that meet the requirements of having 2K resolution with frame rate of 30 fps. 2K resolution means the horizontal resolution with order of 2000 pixels. The Digital Cinema Initiatives (DCI) defines 2K to have 2048 horizontal pixels  and 1080 vertical pixels (2048 x 1080). In some cases, the 1998 x 1080 is called flat presentation. 2K is different from Full HD, where Full HD (1080p) means 1080 vertical pixels and the horizontal pixels is less than that in 2K. The DCI does not recognise 1080p as 2K resolution. 2K resolution can be said to be 2 Megapixels (MP)

For frame rate, it means the number of frame composed in a second. A camera may run at higher frame rate by reducing resolution either by binnnig pixels together or restricting area of interest. This can reduce the amount of data per frame, thus allowing mroe frames to be transferred for a fixed transfer rate. Frame rate can be estimated to be inverse of exposure time.

After searching for the datasheets of this sensor, I noticed that most of the sensors have more than 2048 horizontal pixels, like 2140 pixels and 1560 pixels. I don’t think I have found sensors with exactly 2048 horizontal pixels yet. I’m not sure why is it so. Then there are some sensors with only 1688 (H) x 1248 (V) resolution, which makes up about 2.1 MP. All of these sensors above have at least 30 fps. Through this task, I have gained a clearer understanding of megapixels in terms of their horizontal and vertical pixels. Higher megapixels will of course produce sharper images with more details.


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