Q:  Why are 3CCD cameras necessary?

CCTV cameras normally use B/W CCD with mosaic color filter to create pseudo color rendering. Unfortunately, it still has some defects.

1. Color filter reduces 1/3 of light, so the sensitivity will drop to 30% of the original.

2. The mosaic structure needs a low pass filter to split light to four pixels to create color images. Therefore, luminance resolution will automatically reduce to half of the original image information.

A 3 CCD camera needs 3 pieces of B/W CCD that are precisely aligned together. The CCD has a prism to beam split and a dichroic filter to divide color portions and purify  spectrum of each color channel.