WO1989003097A1

WO1989003097A1 - Plotting apparatus

Info

Publication number: WO1989003097A1
Application number: PCT/FI1988/000157
Authority: WO
Inventors: Usko Jokinen
Original assignee: Digipoint Oy
Priority date: 1987-10-02
Filing date: 1988-09-30
Publication date: 1989-04-06
Also published as: FI874322A0; FI874322A

Abstract

The invention concerns a plotting apparatus incorporating one or several light pens (2), actuator elements, and a control unit, which takes care of a control of pen actuator element movements. The light pen (2) is connected to a light source (4) by a light cable or optic fiber (3), which operates as a collimator for light rays and determines the width of the plotted line, whose width can be maintained constant during the plotting operation by controlling the intensity of the light source (4) proportional to the pen speed control signals. Thus, e.g., conductor pattern layouts required for printed circuit board production can now be plotted onto a photosensitive film or directly onto a PCB laminate provided with photosensitive coating.

Description

Plotting apparatus

The present invention relates to a plotting apparatus which incorporates one or several light pens with light sources, pen actuator elements and a control unit, which provides for the control of movements of actuator elements; additionally, between the light source and the light pen tip is adapted a light cable or optic fiber which operates as a guide for light rays and whose diameter defines the width of the plotted line.

Known in prior art are such plotting apparatus, in which a "light pen" provided with a light source and specially con¬ structed "light-spot optic" is arranged movable over a photo¬ sensitive film. These kinds of plotting apparatuses are much more expensive that plotting apparatuses equipped with ink pens that are conventionally used in, e.g., computer-aided drafting. However, ink pen plotters are plagued with the disadvantage of producing an inconsistent plotting quality; instead, the line density varies. Furthermore the pens may become clogged, and their maintenance causes additional effort. Known from the DE patent application 35 09 747 is a plotting apparatus of the aforementioned type where the pens of the ink pen plotter are replaced with light pens. This disclosed apparatus has an inherent drawback of requiring an essentially lower pen speed of the light pen, compared with the full pen speed of conventional ink pen plotters, when significant changes in line width are to be avoided. Additionally, the construction of the light pen in this prior art apparatus is complicated and expensive.

The present invention aims to achieve an improved plotting apparatus, whose light pen does not require a specially manufactured optic system for directing the light beam, but instead allows the use of essentially equivalent equipment technology as that used in conjunction with ink pen plotters, avoiding, however, the aforementioned problems associated with ink pens.

The particular aim of the invention is to achieve an improved plotting apparatus which allows the movement of the light pen at high speeds and speed differentials without causing essential changes in line width.

This aim according to-the invention is achieved by arranging the light source to be controllable proportionally to the control of the pen speed. By virtue of this arrangement, the incident light energy per unit area can be held during the drafting operation essentially at a preset constant value, irrespective of the variations in pen speed.

The light beam cone exits from the end of the light cable or optic fiber essentially collimated with the fiber or cable axis. No scattered light exits at the immediate vicinity of the end, which results in a sharply defined plotted trace. Thus, no dedicated "spot optic system" is required. An embodiment of the invention allows the connection of the light pen from the pen to a separate light source by a light cable or optic fiber, which is sufficiently long and flexible to allow pen movements over the plotting area. An other embodiment uses an implementation, in which the light source is located integral with the pen. The invention is especially applicable for converting an ink pen plotter into a plotting apparatus in accordance with the invention. With the use of several pens and fibers of different diameters (in the same manner as ink pens with different tip widths) desired line widths can be achieved. In addition, the line width can be controlled by regulating the light source intensity. When the desired basic level of intensity is set, the line width can be held constant during the drawing operation at pen speed variations by controlling the light source intensity with a relationship to the pen speed control. In the following the invention is described in reference to the attached drawing, which illustrates in diagrammatic form a plotting apparatus in accordance with the invention.

Omitted from the drawing are the pen actuator elements as well as their control unit, neither is shown the plotting base supporting a film 1, since these components may be iden¬ tical to those of commercially available ink pen plotters. In fact, the pens of a conventional ink pen plotter can be replaced by light pens permitting the pen actuator elements and their control unit to be retained essentially as such.

In the embodiment illustrated in the drawing, a light pen 2 is connected from the pen body to a separate light source 4 by a light cable or optic fiber 3, which is sufficiently long and flexible to allow the movements of the pen over a plotting area 1. The optic fiber of light cable terminates at the immediate tip of the pen 2, which is capable of being brought to contact a photosensitive film 1 or other photosensitive surface. The optic fiber or light cable 3 colli ates a light beam so that no essential scattered light is present at the immediate vicinity of the pen tip. Consequently, the cable or fiber diameter determines the width of the plotted line.

A solid-state light source 4 (LED) is attached to the output of an amplifier 5. The amplifier 5 further receives a control signal proportional to the plotting speed of the pen 2 from a summing logic 6, whose input signals are taken from the movements of the pen 2 in perpendicular directions x and y. In practice, this information is directly obtained from the drive pulses controlling the actuator motors of the pen 2. In computer-aided drafting these pulses are obtained from a programmable data processor unit. In addition, the movement controls of the pen include an up/down command, whose corresponding control signal (ON/OFF) is routed to one of the amplifier 5 inputs via an interface unit 7. This unit ^• controls the amplifier 5 so that the light emitting diode 4 emits light only when the pen 2 is in lowered position. This function is respectively associated with the case, in which the ink pen plotter is converted into a light pen plotter in accordance with the invention. If the device is constructed and designed from the start for the light pen construction in accordance with the invention, there is no need to lift or lower the pen 2; instead, turning on and off the light source 4 is sufficient. The light source 4 can also be located integral with-conjunction with the pen 2, if the construction takes.care of providing a sufficiently long light cable or optic fiber between the light source and the pen tip to provide for the colli ation of the light beam. In this embodiment, the cable 3 is an electrical cable for supplying power to the light source.

A potentiometer 8 sets the basic intensity of the light source 4, with some effect on the plotted line width. In practice, the light intensity is preferably selected as high as possible to avoid exposing dots of greater width than the plotted line width at the instantaneous seizure points of the pen. The actual line width selection is catered to by a series of plotter-compatible pens, which use different sizes of light cables or optic fibers for line width control. The casing of each light pen in the pen series can be designed, at least over the pen clamping region reserved for the hold by the actuator elements, to comply to their form with the design of ink pens originally used in the plotter, allowing the use of a similar equipment technology as that used in ink pen plotters. The thickness of the light cable core or optic fiber at the tip area of the pen can be adjusted during light pen manufacture by heating and stretching the fiber to obtain a thinner diameter. This approach offers a higher efficiency of light transmission in the nonconstricted part of the fiber so that the thinned tip results in a relatively higher light intensity.

A particular application of the invention is found in the plotting of conductor pattern layouts for the production of printed circuit boards. In this case, plotting is performed in a dark room ..environment by a plotting apparatus in which the light pen 2 has a light cable or optic fiber 3, which transmits and collimates a light beam onto a photosensitive film or directly onto a PCB laminate provided with photo¬ sensitive coating. This method achieves both work reduction and quality improvement in comparison with the conventional technology, in which the conductor pattern layouts are first plotted with ink pens-onto a transparent film, which is then reproduced by photographic methods onto a film.

Claims

WHAT IS CLAIMED IS:

1. Plotting apparatus comprising of one or several light pens (2) with light sources (4), pen actuator elements and a control unit, with help of which the movements of the pen actuator elements are adapted controllable; additionally, arranged between the light source (4) and the tip of the light pen (2) is a light cable or optic fiber (3), which operates as a collimator for light rays and whose diameter determines the plotted line width, c h a r a c t e r i z e d in that the intensity of the light source is adapted control¬ lable in proportion to the control of the pen speed.

2. A plotting apparatus in accordance with the claim 1, c h a r a c t e r i z e d in that the plotting apparatus is equipped- ith several light pens, and each light pen has a light cable or optic fiber (3) with a different diameter, having one end of the cable or fiber adjoining with the light source (4) and the other end terminating at the tip of the pen (2), which is capable of making contact with a photo¬ sensitive film or surface during the plotting operation.

3. A plotting apparatus in accordance with the claim 1 or 2, in which the first set of pen actuator elements is arranged to move the pen in the first direction (X-direction) and the other set of pen actuator elements to move the pen in the second direction (Y-direction) , perpendicular to the first direction, and a programmable data processor unit is arranged to control the pen actuator elements, c h a r a c t e r¬ i z e d in that the aforementioned data processor unit is adapted to deliver pen speed data in both motional directions (X- and Y-directions) to a summing logic (6), which controls an amplifier (5), whose output is connected to a solid-state light source (4) .

4. A plotting apparatus in accordance with claim 3, c h a r a c t e r i z e d in that the pen lifting/lowering control circuit is connected to a second input of the amplifier (5) such as to allow the electrical on/off control of the light source (4) in relationship with the lift/lower control signal of the pen.