The Audio Control of Laser Displays


Not long after my wife Nora and I returned from our 1970 adventures in Japan and India, laser–related and otherwise, we relocated at The University of Iowa, where I was hired to direct the audio and recording operations in a recently completed performing arts facility for the School of Music—and where my work with lasers was looked upon with favor by William Hibbard (1939–1989), a composer and the director of the then flourishing Center for New Performing Arts (CNPA). After the funding for a new laser system was secured under the auspices of the CNPA, Jeffries and I began to work in 1971, 2,000 miles apart, on VIDEO/LASER III.



Figs. 2 and 3. VIDEO/LASER III

During the interim since the 1968–69 design period for VIDEO/LASER I and II, General Scanning Inc., Watertown, Massachusetts, had patented and introduced a series of optical scanners with vastly improved characteristics over previous designs. (The mirror galvanometers in VIDEO/LASER I and II, made by Honeywell and Bell & Howell, were intended for strip–chart recording instruments, which used light sources, and moving photographic paper; Jeffries and I had to adapt them for x–y laser scanning.) The General Scanning units offered a controllable bandwidth up to 10 times greater than that of the other galvanometers, they also could be mounted in the proper geometrical relationship for unimpeded x–y scanning applications. Like its predecessor, VIDEO/LASER III was designed to have independent x–y scanning in each of four principal colors (red, yellow, green and blue), so we ordered eight scanners from general Scanning, carefully specified for our new system. The design parameters for these scanners were optimized for bandwidth, frequency response, and scanning angle. We also ordered four beam “choppers” to provide z–axis modulation and to control the relative brightness levels in the four colors. Jeffries undertook the mechanical construction of the system in his Berkeley sculpture studio, with assistance in Iowa City from the University’s Physics Machine Shop. I supervised the electronic design and assembly in the new facilities o f the School of Music, which included a suitable area for a laser studio, which I named “Laser Hall.” VIDEO/LASER III was given its premiere on November 29, 1972 in Hancher Auditorium on the Iowa campus, in my piece Electro–Acustica for orchestral instruments, electronic sound (“live” and on tape), soloists, and laser system. William Hibbard conducted, and Carson Jeffries assisted me in the laser performance. Between 1972 and 1980, the system was seen in numerous performances within the U.S., and on tours to Mexico (1976), Germany (1977 and 1979), and more recently, Italy and Austria (1980), where David Tudor and I gave performances at the Venice Biennale, at the Roman Forum, and at Ars Electronica associated with the International Bruckner Festival, Linz. Touring with VIDEO/LASER III requires advance planning for shipping, customs clearance, local laser safety regulations, and performance logistics. The standards for 3–phase AC power vary in voltage and configuration in different localities (wye vs. delta; neutral and grounding conventions) as do those for hose fittings for the water supply. Our air freight shipment to Italy and Austria weighed 630 kg (1,385 lb).


Fig. 4. Carson Jeffries and VIDEO/LASER III

Before the 1980 European tour, VIDEO/LASER III was converted to six–beam operation with funding from a grant by The University of Iowa Foundation. The mechanical reconstruction was performed by Jerry Swails, machinist, University of Iowa Medical instruments, and the electronic drive amplifiers for the scanners and choppers were redesigned and optimized by Stephen Julstrom, engineer for the Recording Studios and VIDEO/LASER Projects in the School of Music. There are now 12 optical scanners in the system, one each for horizontal (x) and vertical (y) for the six beams: red, yellow, green, blue, either blue–green or deep blue (approaching violet), and “white”—derived from the total output beam of the mixed–gas laser (see wavelength chart above). There are now also six choppers, including an example of a new design proposed by Stephen Julstrom, with improved mechanical characteristics, and custom–fabricated for us by General Scanning Inc.