Technique for optimizing grayscale character displays

Claim 1

A method for calibrating luminance linearisation values for a grayscale display device (40), comprising the steps of: displaying a first field on a first area of said display device, said first field having a sharp transition line (46), separating a first white field portion (42) and a first black field portion (44); displaying a second field on a second area of said display device adjacent said first area, said second field having a second white field portion (48) and a second black field portion (50) separated by an intermediate graystrip (52), said gray strip being substantially parallel with said sharp transition line; positioning a viewer at a distance from said display device; varying the grayscale setting of the gray strip; selecting the grayscale setting which minimises line discontinuities between said sharp transition and a transition line between said second white field portion and said second black field portion apparent to said viewer; and setting a luminance linearisation value for said display device in accordance with the grayscale setting selected by said selecting step.

Claim 2

A method for calibrating luminance linearisation values for a grayscale display device (40), comprising the steps of: displaying a first field on a first area of said display device, said first field having a sharp transition line (46), separating a first white field portion (42) and a first black field portion (44); displaying a second field on a second area of said display device adjacent said first area, said second field having a second white field portion (48) and a second black field portion (50) separated by an intermediate graystrip (52), said gray strip being substantially parallel with said sharp transition line; positioning a viewer at a distance from said display device; varying the grayscale setting of the gray strip; selecting the grayscale setting which minimises line discontinuities between said sharp transition and a transition line between said second white field portion and said second black field portion apparent to said viewer; and setting a luminance linearisation value for said display device in accordance with the grayscale setting selected by said selecting step.

Claim 5

The method of any preceding claim, wherein said gray strip (52) is centred on said display device.

Claim 6

The method of any preceding claim, wherein said white portion (42) of said first field abuts said white portion (48) of said second field along one edge, and wherein said black portion (44) of said first field abuts said black portion (50) of said second field along one edge.

Claim 7

The method of any preceding claim, wherein said displaying, positioning, varying, and selecting steps are repeated for a plurality of viewers, and said setting step sets a luminance linearisation value in accordance with an average of the selected grayscale settings.

Claim 8

The method of any of claims 2 to 6, wherein said visual angle is predetermined by a method comprising the steps of: setting said viewer at an arbitrary distance from said display device (40), varying the grayscale setting of the gray strip (52), selecting the range of grayscale settings which provide no apparent line discontinuities between said sharp transition (46) and a transition line between said second white field portion and said second black field portion, and repeating these steps for a plurality of distances from said display device; and the method further comprises the steps of determining the distance at which the range of grayscale settings which provide no apparent line discontinuities between said sharp transition and a transition line between said second white field portion and said second black field portion is minimised, and calculating the visual angle in accordance with the distance determined in said determining step and the height of said gray strip.

Claim 9

The method of any preceding claim, wherein the steps are repeated for a plurality of sub-pixel edge placements.