Lumonics Inc.

Canadian Patents & Dev. Limited

Terrence J McKee

Clive Willis

Douglas J James

Kenneth J Andrews

The known technique of marking (including machining) a workpiece by light energy, e.g. a pulsed laser beam, in order to create a pattern of marks on the workpiece is improved by converting a primary beam into a plurality of individual beamlets that are arranged in an array corresponding to the desired pattern and are each focused independently of the other beamlets. This independent focusing enables the size and energy density (and hence the marking effect) of each beamlet when it strikes the workpiece to be dependent on the relative location of the workpiece and the respective beamlet, while being independent of the size of the overall pattern. This feature enables variation of the ratio between the pitch between individual marks (which determines the size of the overall pattern) and the size of each mark, and hence selection of the optimum value of this ratio for a given situation. As a result, a pattern of a chosen size can be made using a primary beam of lower power than has previously been possible, or alternatively, the same beam power can be used to make a larger mark. In another aspect the invention provides for utilization of the previously wasted energy of those beamlets not used to form the patterned array, by redirecting these beamlets either to reinforce one or more of those beamlets that do form the array or to form a second pattern of marks on the workpiece.

Marking of a workpiece by light energy

Variable attenuation of a light beam is achieved by mounting a rotatable multilayer dielectric attenuator in the beam. A first portion of the beam is transmitted through the attenuator and a second portion is reflected. Rotation of the attenuator about an axis transverse to the beam varies the ratio between these portions. The main application of this attenutator is to control an output characteristic, e.g. output power, of a laser, and may include a feedback loop to maintain this characteristic constant.

Light beam attenuation

A gas laser includes a pair of subsidiary electrodes to form a sharpening gap. These subsidiary electrodes are located within the envelope of the laser so as to be exposed to the same gas or mixture of gases that flow between the main electrodes and support the main lasing action. The efficiency of the laser and the lifetime of the electrodes of the sharpening gap are thereby improved, together with other advantages.

Laser

A rare-gas hydrogen-halide laser is improved by including or adding a predetermined quantity of a hydrogen donor additive to its gas mixture. The closed-off operation lifetime of lasers such as XeCl, KrCl, or XeBr are tripled by adding up to 0.05% hydrogen to the laser gas mixture.

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Nepean, Canada

Terrence J McKee