Dot Pitch

Dot pitch (sometimes called line pitch, stripe pitch, phosphor pitch, or pixel pitch) is a specification for a computer display, computer printer, image scanner, or other pixel-based device that describes the distance, for example, between dots (sub-pixels) of the same color on the inside of a display screen. In the case of a color display dot pitch is a measure of the size of a triad plus the distance between the triads.

Dot pitch may be measured in linear units, usually millimeters(mm), or as a rate, for example dots per inch, with a larger number meaning higher resolution. Closer spacing generally produces a sharper image (as there are more pixels in a given area). However, other factors may affect image quality, including:

• measurement method not documented, complicated by general ignorance of the existence of multiple methods
• pixel spacing varying across screen area (e.g., increasing in corners compared to center)
• differing pixel geometries
• differing screen resolutions when attempting to judge picture quality
• tightness of electron beam focus and aim (in CRTs)
• differing aspect ratios

Traditionally, dot pitch in displays has been measured on the diagonal, as this gives the most accurate representation of image quality. Starting about the mid-1990s, however, some companies introduced a horizontal dot pitch as a marketing ploy. By measuring only the horizontal component of the dot pitch and ignoring the vertical component, even a cheap, low-quality monitor could be awarded a small-seeming dot pitch.

The exact difference between horizontal and diagonal dot pitch varies with the design of the monitor (see pixel geometry and widescreen), but a typical entry-level 0.28 mm (diagonal) monitor has a horizontal pitch of 0.24 or 0.25 mm, a good quality 0.26 mm (diagonal) unit has a horizontal pitch of 0.22 mm.

The above dot pitch measurement does not apply to aperture grille displays. Such monitors use continuous vertical phosphors band on the screen, so the vertical distance between scan lines is limited only by video input signal's vertical resolution and the thickness of electron beam, so there is no vertical 'dot pitch' on such devices. Aperture grille only has horizontal 'dot pitch', or otherwise known as 'stripe pitch'.