cs781 - Colour for Computer Graphics - Winter 2012

Course Notes

Lecture 9 - Other Additive Devices

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  1. Assignment 1
  2. Magnifying glasses

A Generic Additive Device

These assumptions must be checked and the size of deviation quantified.

Tristimulus Values of Generic Additive Devices

Primary Values of Generic Additive Devices

  1. A_R           X
    A_G = [M^-1]  Y
    A_B           Z
  2. R = R0 * (A_R/e_R)^(1/g)
    G = G0 * (A_G/e_G)^(1/g)
    B = B0 * (A_B/e_B)^(1/g)

Spatial and Temporal Non-uniformity

Not much at high spatial and temporal frequencies

Lots at low spatial and temporal frequencies.



Other Additive Devices

Colour LCD

These are widely used because they occupy little volume, use little energy, and weigh little compared to CRTs. Their colour performance is comparable to CRTs, but the structure of the images they produce can be intrusive




Capacitor filled with liquid crystal

Colour filters

Colour OLED

Solid state photodetectors and LEDs are very closely related

Plasma Display Panel (PDP)

Fuorescent Lights

Contrast with incandescent lights

They consist of

  1. A gas tube coated on the inside with a phosphor.
  2. It is filled mostly with inert gases, to which a small amount of mercury vapour is added.
  3. Electrodes at each end of the tube

They make light by


A PDP is an array of electrodes and phosphors which, in the off state maintain a gas just below it breakdown level.

Fluorescent light is turned off and on by applying varying voltages to the electrodes.

Thus, a PDP is in effect an array of tiny fluorescent lamps..

Field Effect Display (FED)

Just as the PDP is an array of tiny fluorescent lamps, an FED is an array of tiny CRTs.

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