Sensor

(CCD, CMOS) The CCD (Charged Couple Device) is for video applications developed chip which is able to record light. The CCD is a monochrome device which requires a color filter, produced by painting directly onto the surface of the CCD  to produce a colored image.

In most CCD's the filter pixels are arranged in a G-R-G-B Bayer mosaic pattern. As color technology is created on human eye perception, for luminance properties two green colors for each red and blue pixel are used. So, the number of pixels do not present real resolution of the CCD, but has to be recalculated (interpolated) by averaging into a 24 bit for each pixel. The result is real camera LPH (lines per height) resolution , which depends of interpolation program and is mostly a bit over a half of pixel number of  CCD.

Some manufacturers have used a cyan, yellow, green and magenta pattern. The recalculating  algorithm in this case is subtractive.

In CCD, the problem of exposure had to be solved. Consumer digital cameras use so-called Interline Transfer CCD, where CCD itself has a electronic shutter. That means the CCD controls the electronic signal with shifting values of each pixel into shift registers. These CCDs don't need mechanical shutter, because can be controlled with electronics around each photodiode. The effective size of the photodiode in this case is three times smaller so the light is amplified with micro lenses.

In professional cameras the Full Frame Transfer method is used.  CCD shifts data into the serial register where is processed as the "RAW" image. Full Frame CCD is simpler and don't need extra electronics for each pixel, have much better Fill Factor and don't require the micro lenses.

The measuring system of CCD does not present metric dimension of CCD surface area. 'One inch' chip has 16 mm diagonal sensor array. On example, Minolta's Dimage 7 has 2/3-type CCD which incorporates a total of 5.24 million (2,658 x 1,970) pixels. It has actual 11 mm diagonal.

 Last change 14 december 2001