Laser-Scan

Laser-Scan was a British technology company based in Cambridge, England, which produced world-leading graphics hardware and then advanced software for computer graphics, digital mapping, charting, and geographic information handling.

Read the LSL History for a summary of company history, then the LSL Hardware page for a summary of hardware products, and then see below for more detail on the company's principal graphic display and plotting devices.

LSL Logo 2

Laser-Scan Laser Deflection System

The Laser_Scan display/plotter products all used a patented two-tier laser deflection system. This used a pair of main mirrors about the size of the palm of a hand, one deflecting in X and one in Y. If we drew using just these big mirrors then the beam would be slow to start and stop moving and would overshoot on sharp corners. So, a second set of very small minimirrors are used to compensate. These are galvanometer mirrors on torsion fibres, and have very low mass so can respond quickly, but can only deflect over a small angle.

The main mirrors have a second measuring laser bounced off the back of them, measuring their position to a microradian of angle. We know at all times where they should be pointing (that's where we told them to go), and the difference between the ideal and actual positions is negated, turned into a voltage and used to swing the minimirrors to compensate. The result of the writing laser beam passing through all four mirrors is that it can be positioned accurately and quickly.

HRD-1 High Resolution Display/Plotter

In the HRD-1, the deflection system described in the previous section is used to draw on A6 (149 x 105mm) sized films - either a diazo film for permanent hardcopy producing a clear trace on a dark background, or a photochromic film for display with dark lines on a light orange background. The brochure Laser-Scan Presents The HRD-1 Laser Display/Plotter gives a description and pictures.

The HRD-1 is not called high resolution for nothing - it has an addressability of 140,000 by 100,000 addressible points, and a line resolution in excess of 7000 x 5000.

The writing laser in an HRD-1 was a blue Argon ion laser, consuming 30A on three-phase in order to produce a bit less than one watt of turquoise light focussed into a spot about 10 microns across. The measuring laser was a red Helium-Neon laser of much lower power.

More informnation is in the following brochures:

LASERPLOT Very High Speed A3 Plotter

In the LASERPLOT, the deflection system described above is used to draw on silver-halide film, about A3 (297 x 420mm) in size.

See LASERPLOT - Very High Speed LaserPlotter for a description of the LASERPLOT A3 film plotter.

MLP-1 Microfilm Plotter

See The MLP-1 Laser Plotter for a description ofthe MLP-1 microfilm plotter (to be continued).


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