An LCD pixel is one of the tiny units that make up the picture on a liquid crystal display, or LCD, such as a computer monitor or a flat-screen television. The word pixel is short for "picture element". On a 27-inch full-HD computer monitor, each pixel is about 0.3 millimeters, or 300 micrometers, wide. A micrometer is a millionth of a meter.

Size

A pixel has no standard size. It depends on how big the screen is and how many pixels it holds. Screens are measured diagonally, from one corner to the opposite corner. A full-HD screen is 1,920 pixels across and 1,080 pixels down, about 2 million pixels in all.

Monitor makers give a pixel's size as its pixel pitch. Dell lists 0.3114 millimeters for a 27-inch full-HD monitor, and 0.2745 millimeters for a full-HD model with a 23.8-inch screen. A 27-inch screen is about 60 centimeters (23.5 inches) wide, and dividing that width by 1,920 pixels gives the same 0.31 millimeters. The explorer's 300 micrometers matches a full-HD monitor of about this size.

Packing more pixels into the same screen makes each one smaller. A 27-inch 4K monitor is 3,840 pixels across, twice as many, so its pixels are 0.1554 millimeters wide, half the width.

Size comparisons

• About 82 pixels of a 27-inch full-HD monitor fit side by side in one inch (2.54 centimeters). Dell lists this as the screen's pixels per inch.
• About 40 red blood cells, each about 7–8 micrometers across, would fit across one pixel.
• A grain of table salt about 0.5 millimeters wide covers about 1.6 pixels.
• When a pixel's three colored cells sit side by side, as in the explorer's picture, each is about 0.1 millimeters wide. That is about the width of a human hair.

How a pixel makes color

An LCD does not make its own light. A light at the back of the screen shines forward through every pixel. Each pixel is divided into three cells with red, green and blue filters, and each cell is controlled on its own.

Each cell holds a thin layer of liquid crystal, a liquid whose molecules can line up in the same direction. The light reaching it is polarized, meaning its waves vibrate in one direction. The liquid crystal turns that direction by 90 degrees, so the light passes through a polarizing filter at the front.

A voltage across the liquid crystal switches off the turning, and the filter blocks the light. Varying the voltage makes the cell brighter or dimmer. The colors a viewer sees come from mixing the three colors in different strengths. Red and green together look yellow, and all three together look white.

Sources

• Dell 27 Monitor - E2724HS. Dell.
• Dell Pro 24 Plus Monitor - P2425H. Dell.
• Dell 27 Plus 4K Monitor - S2725QS. Dell.
• Polarization. In University Physics Volume 3. OpenStax, 2016.
• Color and Color Vision. In College Physics 2e. OpenStax, 2022.
• Erythrocytes. In Anatomy and Physiology 2e. OpenStax, 2022.
• Just How Small Is "Nano"?. National Nanotechnology Initiative.