All About Line Interval
Line interval is the center-to-center distance between adjacent scan lines in a filled engraving. Smaller line intervals place more scan lines within each millimeter and create a denser fill, while larger intervals place fewer lines and create a sparser fill.
Density and resolution
Line interval and lines per inch describe the same scan-line density from different perspectives. Line interval measures the distance between adjacent scan lines, while lines per inch counts how many scan lines fit within one inch. They are inversely related: a smaller line interval produces a higher lines-per-inch value, while a larger interval produces a lower value. When line interval is expressed in millimeters, lines per inch equals 25.4 divided by the interval. Different laser systems and software may present either measurement. Both values describe the commanded scan-path density; neither guarantees that the focused laser spot or material can physically resolve that level of detail.
Physical overlap
When the line interval is smaller than the effective width of a single engraved track, adjacent scan lines overlap on the material. Moderate overlap may improve coverage. Excessive overlap can accumulate heat, deepen material removal, blur detail, and increase processing time. A line interval larger than the effective track width can leave visible gaps.
Examples
Reduce the line interval to close faint gaps in a solid fill after confirming that heat remains controlled. Increase it to create a deliberate hatch texture or produce a faster draft. Compare line interval with a measured spot-size or track-width test when seeking efficient, even coverage. Sweep line interval during fauxlographic calibration because microscopic groove spacing can determine how the finished engraving diffracts light.
Direction matters
Line interval measures the spacing perpendicular to the scan direction. Scan angle changes how the laser's neighboring paths meet edges, surface grain, and marks from previous passes. Crosshatching adds one or more additional sets of scan lines, which increases both processing time and total laser exposure.
Testing
Test line interval using the intended lens, focus distance, scanning speed, power, and material. A smooth screen preview does not prove that the physical engraved tracks will overlap correctly on the workpiece.