International hydrographic organization specifications for chart content and display aspects of ecdis
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S-52 Appendix 2 - IHO
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| B.2 Initial Calibration This process will provide the conversion between CIE x, y, L coordinates and RGB signals to be applied to the monitor. B Equipment required Make sure your ECDIS hardware has an image generator capable of giving "blacker than black, i.e. complete control of colour, and that the software can control that function. The monitor maybe calibrated independently of the image generator. In this case, the generator is expected to output a signal that is linear and repeatable from unit to unit. If the accuracy of the image generator output is unknown, then it should be calibrated as an integrated unit with the monitor. 61 S, Edition 6.0 March 2010 The equipment required for the process is listed below - Monitor to be calibrated. It is important to note that the monitor to be calibrated must be capable of a white screen (D) of at least 85 cd/m², or the calibration process will fail. - Image generator to be used with the monitor. - Photometer. The photometer must have a luminance accuracy of better than +/- 5% and a sensitivity of 1.0 x 10 -4 candelas per square metre. The photometer is one that must be intended for use in measurement of the selected monitor, and should have colourimeter capability. The required performance can be achieved by a Graseby model 370 "Optometer" with a model 221 radiometric head used in conjunction with a Minolta CS Colorimeter for measuring phosphor coordinates and calibrating the Graseby radiometric head for each phosphor. The Minolta CS 100 must be calibrated to "Illuminant A. - Software to generate the required colours for use during the calibration. This will be a program that allows the user to adjust the colour DAC values from 0 to 255 in each of Red, Green and Blue. - Software to calculate the transformation between RGB and CIE x, y, L values. This software is part of the Presentation Library) B Calibration setup Important - The calibration procedure is very sensitive to stray light, and inaccurate results will occur if special care is not taken. All measurements should betaken in the dark, and all stray light and sources of reflections must be removed from the measurement area. The measurements are best taken with light absorbers in place around the monitor and measurement apparatus. This can be created by making a matte black cardboard tunnel around the monitor and colourimeter. Care must betaken by the operator that his clothing does not reflect light back into the measurement area. The instrument that is measuring the screen of the monitor must point at the same location on the screen for all measurements, otherwise errors will result. B Monitor setup for calibration The monitor must beset up properly before calibration. The following are required for accurate calibration B Burn-in To age the monitor sufficiently, a burn-in of 48 hours is required with a 50% luminance white picture covering the entire screen. B Colour temperature tracking The monitor should not show any change in colour on white signals, when they go from dark gray to bright white. This can be best checked out by displaying a gray scale of about 8 steps from dark gray to white. If the colour of the gray changes or shows adrift to pink, blue, or green, as the level changes, then the monitor is improperly adjusted and should not be calibrated. This step is a qualitative 62 S, Edition 6.0 March 2010 assessment, and requires some judgement from the tester. B Setting the Controls The controls are used to adjust the black level of the monitor. This is the point where the monitor screen is seen as black, and this setting will create the blackest black that can be displayed. After the control is set, it must be locked in place. Any further Download 0.98 Mb. Share with your friends:
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