Image Resolution Enhancement Technology (IRET) is a halftone
technology for obtaining superior image quality on a laser printer by
utilizing laser modulations. A hybrid scheme is used to combine a
clustered dot pattern for stability and a stochastic screen (super
smooth dither) for minimum halftone texture.
The top picture shows an eye rendered on a HP Color LaserJet
without REt. The bottom picture shows it rendered on a HP Color
LaserJet with Image REt 1200.
Q. Lin, "High resolution color laser printing", HPL
Technical Report, No. HPL-94-78, August, 1994.