Frequently Asked Questions
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Q: What is the dot defect standard for the portable computer's Active Matrix screen?

A: Active Matrix Pixel Structure

LCD Resolution - Denoted by the number of pixels in a row by number of pixels in a column for LCD panels. For example, 800 × 600 indicates a panel with 800 pixels across and 600 pixels down.

Pixels - Formed by groups of three sub-pixels: a red "dot", a green "dot", and a blue "dot".

Note: Sub-pixels are rectangular in shape even though they are referred to as "dots". Pixels are aligned in a panel so that like-colored dots line up vertically.

Definitions

Dot Defect - A defect that affects a single "dot" or sub-pixel.

Two Adjacent Dots - Two adjacent dots in the horizontal direction are considered one dot.

Bright Dot Defect - Sub-pixel (red, green, or blue) is bright or visible and can always be seen on an all black background.

Dark Dot Defect - Sub-pixel (red, green, or blue) is dark and can always bee seen on an all white background.

Linked Dot Defect - Defect that affects two adjacent sub-pixels. Vertically-linked dot defects are always the same color. Horizontally-linked dots are always of different color dots.

Visual Inspection Conditions

All displays MUST be inspected under the following conditions. Ambient lighting falling outside of these parameters, the use of "Magnification", temperature extremes, and extreme viewing angles are not allowed in determining the accept or reject of any display.

  • Viewing distance: 35 to 50 centimeters (cm) or 13 to 20 inches
  • Ambient illumination: 300 to 700 Lux (nominal 500 Lux)
  • Ambient temperature: 25° ±5° Celsius (77° ±9° Fahrenheit)
  • Viewing angle: Normal to the front surface; off angle viewing is not allowed

Dot Defect Criteria

The number of defects allowed is determined by the size and dot density of the panel.

Defect Type Accept Count (Number)
  12.1SVGA 13.3 XGA 14.X XGA 15 XGA 15.7 SXGA 17.1 SXGA
Bright dots (random) 5 5 5 5 5 3
Bright dots (two adjacent) 1 1 1 1 1 1
Dark dots (random) 5 5 5 5 5 3
Dark dots (adjacent) 2 2 2 2 2 1
Dark dots (three or more adjacent) 0 0 0 0 0 0
Total bright and dark dots 10 10 10 10 10 6
Minimum Distance Between Defects
Bright to bright dots 15 mm 15 mm 15 mm 15 mm 15 mm 15 mm
Dark to dark dots 5 mm 5 mm 5 mm 5 mm 5 mm 5 mm

Foreign Material in the Display

During the manufacture of LCDs, extreme care is taken to minimize the amount of foreign material present in the display envelope. However, under the most stringent clean room procedures, foreign material can get lodged inside the display envelope.

The following sets limits as to the maximum acceptable levels for this contamination.

Defect Type

Accept Size

Accept Count (MAX)
Bright / dark spots (foreign material 0.1 mm <D £ 0.7 mm 4
Bright or dark line or filament (foreign material)   0.01 <W £ 0.07 mm 0.3, L£ 1.0 mm 3
Polarizer / linear scratch 0.01 <W £ 0.1 mm 0.3 <L£ 5.0 mm 3
Polarizer dent / bubble Average D £ 0.5 6
Maximum allowable defect count   7

Light Leakage

There shall be no visible light leakage around the edges of the display active area. Light leakage appears as a washed out area along the edge of the display and is usually caused by misalignment of the backlight components.

Image Retention

The latent image after turning off the display, or changing the display pattern, shall not last longer than 10 seconds. This is sometimes referred to as Image Sticking.