A photoplotter is an electro-mechanical-optical machine that exposes a latent image on a media, usually high-contrast monochromatic (black-and-white

Black-and-white

Black-and-white, often abbreviated B/W or B&W, is a term referring to a number of monochrome forms in visual arts.Black-and-white as a description is also something of a misnomer, for in addition to black and white, most of these media included varying shades of gray...

) photographic film

Photographic film

Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...

, using a light source under computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 control. Once the exposing step is complete, the media is processed in a film processor using a developer

Photographic developer

In the processing of photographic films, plates or papers, the photographic developer is a chemical that makes the latent image on the film or print visible. It does this by reducing the silver halides that have been exposed to light to elemental silver in the gelatine matrix...

 solution, along with fixing

Photographic fixer

Photographic fixer is a chemical or a mix of chemicals used in the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed silver halide remaining on the photographic film or photographic paper, leaving behind the reduced metallic silver...

, washing, and drying.

Nearly any conceivable image can be formed. Photoplotters are used primarily for the production of PCB's (printed circuit boards) and IC packaging. Other application areas include chemical milling and specialized graphic arts. Photoplotting is the first step of making photolithography

Photolithography

Photolithography is a process used in microfabrication to selectively remove parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical "photoresist", or simply "resist," on the substrate...

 masks for printed circuit board

Printed circuit board

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

s. In the PCB industry, these masks are called photoplots and are generally limited to features of 20 µm

Micrometre

A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

 or more. Integrated circuit

Integrated circuit

An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

s are made in a similar fashion utilizing photomask

Photomask

A photomask is an opaque plate with holes or transparencies that allow light to shine through in a defined pattern. They are commonly used in photolithography.-Overview:...

s with sub-micrometer feature sizes; photomasks are traditionally made by photoreducing photoplotter output.

The first photoplotter was introduced by the Gerber

Gerber Scientific

Gerber Scientific Inc. , located in Tolland, Connecticut, is the parent of companies which provide end-to-end customer solutions to the world's sign making and specialty graphics, ophthalmic lens processing, and apparel and flexible materials industries. They also supply purpose-built software to...

 Scientific Inc. (now Ucamco, see http://www.ucamco.com) in the 1960s

1960s

The 1960s was the decade that started on January 1, 1960, and ended on December 31, 1969. It was the seventh decade of the 20th century.The 1960s term also refers to an era more often called The Sixties, denoting the complex of inter-related cultural and political trends across the globe...

. 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. 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 flashe create single simple graphic in a location by shining light through an aperture of the appropriate shape at a fixed location.

Modern photoplotters are generally raster-scan

Raster graphics

In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...

 devices that use a laser

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 beam focused to one or more spots, and modulated at multi-megahertz rates, to form the image. Initially, green

Green

Green is a color, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 520–570 nanometres. In the subtractive color system, it is not a primary color, but is created out of a mixture of yellow and blue, or yellow and cyan; it is considered...

 argon

Argon

Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...

-ion lasers and blue

Blue

Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal...

 helium-cadmium

Cadmium

Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...

 lasers were frequently used. Current models utilize a red

Red

Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...

 helium

Helium

Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

-neon

Neon

Neon is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or...

 laser, red laser diodes or even red LEDs (light-emitting diode

Light-emitting diode

A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...

s).

Photoplotters are closely related to imagesetter

Imagesetter

An imagesetter is an ultra-high resolution large-format computer output device. It exposes rolls or sheets of either photographic film or bromide paper to a laser light source. Once the film or paper is developed, a very high quality black and white image is revealed...

s. Photoplotters differ from their imagesetting counterparts in the type of controller used to produce the image, and in the resolution and absolute accuracy of the image, with photoplotters meeting much more stringent specifications than imagesetters.

The most recent development related to photoplotting is LDI (Laser Direct Imaging) 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. LDI machines currently sell for prices in the one-half million U.S. dollar range.

The input of photoplotters is a vector graphics file, typically in Gerber Format. Some photoplotters also accept bitmap formats such as TIFF.