Short answer
DLP typically uses anywhere from 0.16 to 0.75" although popular imagers include the 0.24" 1080P and 0.47" 4K imager. LCOS is generally slightly larger due to slightly lower reflectivity, typically from 0.36" to 0.8". 1LCD is much larger due to its transmissivity - typically starting at 2" and can be as large at 6". A 6" imager requires extremely large optics and is usually very large in design.
What the imager measurement means
Projector imager size is normally stated as the diagonal measurement of the active imaging area. It is not the size of the projected picture. A small chip can still produce a very large image because the projection lens magnifies that image onto the screen.
Typical DLP imager sizes
DLP imagers can be extremely compact because the Digital Micromirror Device is reflective and its microscopic mirrors switch light toward or away from the lens. Devices across the approximate 0.16" to 0.75" range appear in products ranging from pico projectors to professional systems. The 0.24" 1080P and 0.47" 4K imagers are especially common reference points in consumer projection.
A smaller DMD can support a compact optical engine and lower manufacturing cost, but it also concentrates heat and light into a smaller area. The complete design must balance illumination density, lens quality, thermal control, pixel pitch and the desired brightness.
Typical LCoS imager sizes
LCoS panels are also reflective, but the liquid-crystal layer and silicon backplane use a different optical structure from DLP. LCOS is generally slightly larger due to slightly lower reflectivity, with common designs typically ranging from about 0.36" to 0.8". The larger surface can support fine pixel structures and high native contrast, but it also contributes to the larger optics and chassis associated with many premium LCoS projectors.
Typical 1LCD imager sizes
A 1LCD projector shines light through a full-color transmissive panel rather than reflecting light from a DMD or LCoS backplane. Because of that transmissive architecture, 1LCD imagers are much larger—typically starting around 2" and extending to approximately 6" in some designs.
As the panel grows, the projection lens must cover a larger image circle. A 6" imager therefore requires extremely large optics, a longer and wider optical path, more physical spacing and a correspondingly large projector design.
Does a larger imager guarantee better picture quality?
No. Imager size influences optical design, heat density, pixel pitch and chassis dimensions, but it does not determine picture quality by itself. Resolution, contrast, fill factor, color system, lens sharpness, panel alignment, cooling and image processing must be considered together. Imager size is best understood as an engineering characteristic rather than a standalone quality score.