Frequently Asked Questions
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Q: What are some definitions regarding LCD panels and dot defects?

A: Dot defects are imperfections in an LCD panel. Following are some definitions regarding LCD panels, dot defects, and how to determine if there is a defect.

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.

Pixel - Formed by a group of three horizontal sub-pixels or "dots"; one each red, green, and blue.

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.

Dot defect - A defect that affects a single sub-pixel.

Bright dot defect - A sub-pixel (red, green, or blue) that is bright (stuck "on") or visible and can always be seen on an all-black background.

Dark dot defect - A sub-pixel (red, green, or blue) that is dark (stuck "off") and can always be seen on an all-white background.

Linked dot defect - A defect that affects two adjacent sub-pixels. Vertically-linked dot defects are always the same color. Horizontally-linked dot defects are always of different colors.

Visual inspection conditions - All displays must be inspected under the following conditions.

  • Viewing distance - 35 to 50 centimeters (13 to 20 inches)
  • Ambient illumination - 300 to 700 Lux (nominal 500 Lux)
  • Ambient temperature - 25° ±5° Celsius (77° ±9° Farenheit)
  • Viewing angle - Normal to the front surface (Off angle viewing is not allowed.)
Note: 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.

Dot defect criteria - The number of defects allowed is determined by the size and dot density of the panel.

Foreign material in the display - During the manufacture of liquid crystal displays (LCD), 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.

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

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