International hydrographic organization specifications for chart content and display aspects of ecdis
Download 0.98 Mb. View original pdf
|
S-52 Appendix 2 - IHO
| B.5 Calibration Verification This section discusses the instrumental verification of the calibration of the colours in the earlier PL edition 3.2 bright sun (DAY_BRIGHT) colour table. The procedure applies equally to the edition 3.3 "DAY" table. Basically, it is carried out by measuring blocks of known colour and comparing their coordinates to the standard colours. All of the distinct colours of the bright sun colour table should be verified instrumentally, however certain colour pairs are exempt from the comparison as explained in B 5.5. The procedure for verifying the remaining colour tables visually is described in B 5.6. Note The procedure of calibrating/verifying all three colour tables of an LCD instrumentally by the current method used for CRTs on the Day table alone, together with remote control of the calibration settings, should also be used for LCDs. There are no inexpensive instruments available that will directly measure and readout x, y, and L coordinates over the entire range of specified colours. (It is the low luminance colours that area problem) With a mathematical routine, colour coordinate data can be derived from the Graseby 370 radiometer that is used for the basic monitor calibration. This has the advantage of being accurate over a very wide range of luminances. B Theory of measurement Mathematical relationships exist between red, green, and blue luminance components of a colour as seen on a monitor and its x, y, and L coordinates. (This relationship is developed in B. This requires that the chromaticity of the principal colour producing elements is known, and that the luminance of the red, green, and blue components of each measured colour are known. Using this information, and the mathematical relationship, it is possible to derive the colour coordinates of any onscreen colour. The actual measurements are made by measuring individually the red, green and blue colour luminance components of each colour to be measured. These are then computed to give the colour coordinates. Note that each colour sample must be displayed three times - once each with only its red, green, and blue components. B Equipment required This testing requires that the proper signals be generated and that the colour coordinates be measured. The following equipment is required 65 S, Edition 6.0 March 2010 - Monitor to be verified, connected to image generation system. - Software in image system to create all the colours of each colour table. This must allow the red green and blue components to be displayed separately for each colour. These colours should be displayed in a rectangle of about 5 cm square, in the centre of the screen. - Luminance meter such as the Graseby 370 to measure the luminance of the red, green, and blue components of the test colours. - Colorimeter, such as Minolta CS 100 to measure the colour coordinates of the phosphor on the test CRT. This should be calibrated to "Illuminant A. - Software utility to perform the calculations to verify the calibration integrity. - Calibration factors for each phosphor to convert Graseby readings from amperes to candelas per metre squared (cd/m²). (See section BB Download 0.98 Mb. Share with your friends:
|