Editing Photoplotter

A '''photoplotter''' is a specialized electro-opto-mechanical machine that exposes a latent image on a medium, usually high-contrast monochromatic ([[black-and-white]]) [[photographic film]], using a light source being controlled by a [[computer]].<ref name="Clark2012">{{cite book|author=Raymond H. Clark|title=Handbook of Printed Circuit Manufacturing|url=https://books.google.com/books?id=hCAyBwAAQBAJ&pg=PA17|date=6 December 2012|publisher=Springer Science & Business Media|isbn=978-94-011-7012-3|pages=17–}}</ref> Once the film has been exposed, it must be [[photographic processing|processed]] before it is ready for use. Photoplotters are used primarily for industrial production of [[printed circuit board|printed circuit boards (PCBs)]] and [[integrated circuit]] (IC) packaging.

In the PCB industry, photoplotting is the first step of making [[photolithography]] masks for printed circuit boards.  These masks are called ''photoplots'' and are limited in resolution by the technology in use; in 1998, photoplots with resolvable details of 2.5 [[micrometre|μm]] or more were possible.<ref>{{cite book|title=Electronic Products|url=https://books.google.com/books?id=v8YpAQAAMAAJ|year=1989|publisher=United Technical Publications}}</ref> Integrated circuits are made in a similar fashion utilizing ''[[photomask]]s'' with sub-micrometer feature sizes; photomasks are traditionally made by photoreducing photoplotter output.<ref>{{cite book|title=Electronic Packaging and Production|url=https://books.google.com/books?id=lMMpAQAAMAAJ|year=1987|publisher=Cahners Pub.}}</ref> 

Other application of photoplotters include chemical milling and specialized graphic arts.<ref name="Sharpe1994">{{cite book|author=Carill Sharpe|title=Kempe's Engineers Year-book|url=https://books.google.com/books?id=y3NRAAAAMAAJ|year=1994|publisher=Morgan Bros.}}</ref>

==History==
The first photoplotter was introduced by [[Gerber Scientific|Gerber Scientific, Inc.]] in the 1960s.<ref name="Gerber2015">{{cite book|author=David J. Gerber|title=The Inventor's Dilemma: The Remarkable Life of H. Joseph Gerber|url=https://books.google.com/books?id=8YKqCgAAQBAJ&pg=PA167|year=2015|publisher=Yale University Press|isbn=978-0-300-12350-0|pages=167–}}</ref><ref name="Schroeder1998">{{cite book|author=Chris Schroeder|title=Printed Circuit Board Design Using AutoCAD|url=https://books.google.com/books?id=t0fPJOGYaasC&pg=PA17|year=1998|publisher=Newnes|isbn=978-0-7506-9834-4}}</ref>{{rp|17-}} The company's file standard, the [[Gerber format]] for PCB files, eventually became an industry standard for describing the printed circuit board images such as the copper layers, solder mask and legend.<ref name="Sanz1988">{{cite book|author=Jorge L.C. Sanz|title=Advances in Machine Vision|url=https://books.google.com/books?id=K3Wz6l2tFU0C&pg=PA196|date=1 December 1988|publisher=Springer Science & Business Media|isbn=978-0-387-96822-3|pages=196–}}</ref><ref name="Khandpur2005">{{cite book|author=R. S. Khandpur|title=Printed Circuit Boards: Design, Fabrication, Assembly and Testing|url=https://books.google.com/books?id=VY8iBAAAQBAJ&pg=PA244|year=2005|publisher=Tata McGraw-Hill Education|isbn=978-0-07-058814-1}}</ref>{{rp|244-}}

Early machines used a [[xenon flash lamp]], and projected an image mounted in a rotating ''aperture wheel'' onto the photosensitive surface of the film or glass plate.<ref name="Mitzner2009">{{cite book|author=Kraig Mitzner|title=Complete PCB Design Using OrCAD Capture and PCB Editor|url=https://books.google.com/books?id=z7RCh8bK6_8C&pg=PA54|date=28 May 2009|publisher=Newnes|isbn=978-0-08-094354-1}}</ref>{{rp|54}} The imaging head assembly traversed over the surface of the media without touching it to produce ''draws'' and ''flashes''. Draws are vectors or arcs created by continuous illumination as the imaging head moves over the photosensitive surface. A flash creates a single simple graphic in a location by shining light through an aperture of the appropriate shape at a fixed location.<ref name="Khandpur2005"/>{{rp|234}}

Modern photoplotters are generally [[raster graphics|raster-scan]] devices that use a [[laser]] beam focused to one or more spots, modulated at multi-[[megahertz]] rates to form the image.<ref name="Schroeder1998"/>{{rp|283-}}

The most recent development related to photoplotting is laser direct imaging (LDI) which utilizes a high-power laser or xenon lamp to directly expose photoresist on a coated substrate instead of exposing photographic film. This eliminates the handling of photographic film.<ref name="Mitzner2009"/>{{rp|6-}}

The input of photoplotters is a vector graphics file, typically in [[Gerber format]].<ref name="Schroeder1998"/>{{rp|235-}}

Manufacturers of photoplotters include Gerber Scientific, [[Orbotech]] and [[Ucamco]].

==References==
{{reflist}}

==External links==
* Ronald B. Webster, [http://patentimages.storage.googleapis.com/pdfs/US3695154.pdf Variable Aperture Photoexposure Device], 15 September 1970, 3 October 1972. Gerber variable shutter patent.

[[Category:Electronics manufacturing]]
[[Category:Plotters]]