Browse Prior Art Database

Laser Variable Focus/ Flash On Fly Optical Head

IP.com Disclosure Number: IPCOM000048487D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

Moore, GW: AUTHOR

Abstract

There is shown and described an improved flash-on-fly technique for generating conductive lines using a variably focused laser light source.

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Laser Variable Focus/ Flash On Fly Optical Head

There is shown and described an improved flash-on-fly technique for generating conductive lines using a variably focused laser light source.

Laser light by nature is highly collimated, coherent, and very monochromatic. These qualities qualify lasers as highly suitable sources for applications dealing with the creation of artwork for circuit panel manufacturing. The near perfect light source allows the optics to obtain results more representative of theoretical projections than incandescent or high voltage arc sources.

Fig. 1 schematically illustrates the optical system of the variable focus head, which has the beams passing through an electro-optical Q-switch 6 which acts as the flash-on-fly shutter. The use of the Q-switch 6 enables closer control of exposure time, while operating in the flash mode, than a mechanical shutter. The beam 2 is expanded in beam expander 10 and passed through a circular variable density filter 14 which is controlled by the photodiode 22 which monitors a portion of the beam which is allowed to be transmitted through beam splitter mirror 18. This arrangement permits accurate table speed to light intensity correlation.

To flash lands, the variable density filter 14 rotates to a position allowing maximum transmission and the mechanical shutter 34 opens. The Q-switch 6 acts as a shutter to the system by flashing short bursts of high intensity light on the emulsion 42. The table (not shown) appears motionless relative to the flash of light creating a strobe effect. Since the wavelength of the laser is selected close to the maximum absorption wavelength of the emulsion to be used, a more efficient use of the light results as compared to the broad band of light generated by conventional sources.

Although the energy level will vary with emulsion used, the energy striking the emulsion during a flash is slightly over the threshold of the emulsion. Additional filters, or use of the variable density filter 14, may be needed to attenuate the energy down to the level required. Ignoring the slight divergence of beam 2, the average irradiance or power density E (watts cm...