Vector photo-plotters

 

Vector plotters are very old equipment not in use anymore due to high number of drawbacks for plotting the manufacturing file. This information is provided primarily as a historical background for understanding laser photo-plotter terminology.

 

Drawbacks:

    Limited number of apertures;

    Non-punctual light points;

    Large plotting time due to vector plotting;

    Possibility of over exposure of the film.

 

Aperture Wheels

 

Traditionally, the photo-plotter counterpart to a pen plotter’s pen rack has been the aperture wheel. The aperture wheel is a disk with 24 or 70 apertures arrayed radial along its circumference. When the photo-plotter selects an aperture, the aperture wheel is rotated to place the desired aperture between the light source and the film. Apertures are themselves pieces of film and can be made to any shape required, although in practice this is a time consuming process and there is a physical limitation on size.

 

Flash and Draw Apertures

 

To achieve constant exposure on a vector photo-plotter, apertures used for flashing pads are filtered differently than those used for drawing traces. Therefore, Flash and Draw apertures cannot be used interchangeably without risk of localized over-exposure and under-exposure.