A method of calculating beam landing errors in an electronic display device having color phosphor elements and electron guns to generate electron beams to impinge on corresponding phosphor elements requires a magnetic field to be generated to deflect an electron beam relative to the corresponding phosphor element on which the electron beam is impinge. The intensity if light emitted by the phosphor elements in the measurement area is measured as the electron beam impinges thereon. The polarity of the magnetic field is reversed and the above step is repeated. Thereafter, the magnitude of the magnetic field is changed and the above two steps are repeated thereby to measure at least two different light intensities resulting from electron beams influenced by each polarity magnetic filed. The at least two different light intensities resulting from electron beams influenced by each polarity magnetic field are then approximated with straight lines and an intersection point of the straight lines is determined. A corresponding magnetic field to the intersection point is also determined. A magnetic filed is then generated corresponding to the intersection point and the intensity of light emitted by the phosphor element as the electron beam impinges thereon is measured. A beam landing error is then calculated using a characteristic of the phosphor element and at least some of the measured light intensities and corresponding generated magnetic fields.
Purity/beam landing error measurement method for electronic display devices