What Factors Can Affect the Performance of the Imaging Colorimeter?

In terms of hardware, the actual performance of the imaging colorimeter is highly dependent on the specific types of CCD and color filters used. Most colorimeters are constructed using one of the following three different types of CCDs: full-frame type, interlaced transmission type, and interlaced transmission type with integrated color filters. The full-frame CCD is an unobstructed rectangular photodetector array. When the light hits the CCD, the electronic charge will accumulate in each pixel. By moving each row of pixels to the read register in sequence, the read is performed until the entire column is cleared. During the readout cycle, an external shutter must be used to prevent light from reaching the CCD to avoid image blurring.

There are multiple CCD characteristics that have a major impact on the performance of the imaging colorimeter. One of them is the dynamic range, which is defined as the maximum charge capacity of each pixel (called the "maximum well capacity") divided by the RMS dark noise (the amount of charge read from the device without inputting a light source). The maximum well capacity increases as the pixel size increases. A full-frame CCD usually has larger pixels, and the maximum well capacity ranges from 200,000 to 700,000 charges. This enables the sensor to provide a dynamic range of 14 bits (16,384:1) or even 16 bits (65,536:1). In contrast, the typical maximum well capacity range of an interlaced transmission CCD is usually 100,000 to 20,000 charges, so the dynamic range is limited to 12 bits (4096:1) or less.