Digital BW, The Print

Hi Austin,

Interlacing and interpolating are not the same. Interlacing is "shifted multi-pass" applied both in acquiring and creating an image. This allows to achieve resolution that is higher than the physical spacing between sensors (in scanning) or mussels (in ink-jet printers).

In many scanning applications the sensor is a line-CCD device - an array of several hundreds (or thousands) of sensors placed at a pre-defined distance between each other. The optical system (magnification) determines the distance between corresponding pixels on the scanned media - which is the "optical" resolution. This can be increased by multi-passing with an initial shift in CCD position so the next pass covers areas that felt "between-the-sensors" in previous pass.

Multi-passing without shift is also known technique for scanning intended to improve signal-to-noise ratio (not to improve resolution) - it is seldom used in modern scanners.

Interpolating is generally referred to a software process in which "artificial" pixels are added to existing data. This is common in scanning - my desktop scanner has an optical resolution of 600dpi, an "mechanical" resolution of 1200dpi (via interlacing or multipass) and an "electronical" resolution of 9600dpi. The 9600dpi is achieved by inserting calculated pixels in-between the "real" pixels obtained from the scanner.

Ze'ev Kantor
zeevk@...
  ----- Original Message ----- 
  From: Austin Franklin 
  To: DigitalBlackandWhiteThePrint@yahoogroups.com 
  Sent: Monday, December 17, 2001 12:59 AM
  Subject: RE: [Digital BW] Inks, Epson vs. Cone etc. was:(more newbie q's)


  > Hello,
  >
  > Interlacing in printing and scanning is a common technique to
  > achieve variable resolution - it is used in many high-end
  > products. What is important how many Dots Per Inch are on the
  > paper at the end of the print.
  >
  > Correct me if I am wrong.
  >
  > Ze'ev Kantor

  Hi Ze'ev,

  It is certainly used in video display graphics...but I don't know about its
  use at all in scanning.  What would be the point in scanning, which is an
  input?  Might you mean interpolating?

  Regards,

  Austin


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