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The Antikythera Mechanism is a unique Greek geared device, constructed around the end of the second century bc. It is known1, 2, 3, 4, 5, 6, 7, 8, 9 that it calculated and displayed celestial information, particularly cycles such as the phases of the moon and a luni-solar calendar. Calendars were important to ancient societies10 for timing agricultural activity and fixing religious festivals. Eclipses and planetary motions were often interpreted as omens, while the calm regularity of the astronomical cycles must have been philosophically attractive in an uncertain and violent world. Named after its place of discovery in 1901 in a Roman shipwreck, the Antikythera Mechanism is technically more complex than any known device for at least a millennium afterwards. Its specific functions have remained controversial11, 12, 13, 14 because its gears and the inscriptions upon its faces are only fragmentary. Here we report surface imaging and high-resolution X-ray tomography of the surviving fragments, enabling us to reconstruct the gear function and double the number of deciphered inscriptions. The mechanism predicted lunar and solar eclipses on the basis of Babylonian arithmetic-progression cycles. The inscriptions support suggestions of mechanical display of planetary positions9, 14, 15, now lost. In the second century bc, Hipparchos developed a theory to explain the irregularities of the Moon's motion across the sky caused by its elliptic orbit. We find a mechanical realization of this theory in the gearing of the mechanism, revealing an unexpected degree of technical sophistication for the period.

Direct measurement of pulse broadening in the second harmonic of a mode-locked Nd: glass laser has been made using a high-speed streak camera. Recorded pulsewidths varied from 3.8 psec to greater than 15 psec.

Although phototherapy with blue fluorescent light effectively lowered the serum bilirubin concentration in congenitally jaundiced Gunn rats, no effect on red blood cell surivival as determined by chromium-51 labeling of homologous red blood cells and carboxyhemoglobin concentration was observed. Furthermore, attempts to demonstrate metabolic stress to the red blood cells failed to show increased glucose consumption. No oxidant damage to red cells as reflected by methemoglobin production and Heinz body formation was observed. Thus the anticipated hemolysis secondary to oxidant damage to red blood cells from phototherapy was not found.

High speed Image Converter Cameras have become an accepted means of analysis in the fields of fundimental research and military R and D. Industry, however, has been slow to consider the advantages, primarily due to the lack of awareness of what high speed photography is and what it is capable of doing. As industrial processes inevitably become faster, so more sophisticated instrumentation is required for their analysis. The examples below illustrate how image converter cameras have been used to solvs industrial problems.

Image converter cameras as multi channel recordersB. A. Speyer, R. HadlandHadland Photonics Limited, Newhouse Laboratories, Newhouse Road,Bovingdon, Hemel Hempstead, Herts HP3 OEL, U.K.AbstractHigh speed image converter cameras used in the streak mode of operation are beingincreasingly used as multi channel recorders to record large numbers of independentlypositionable data channels. Monofilament fibre optic light guides are used as opticalswitches for each data channel providing flexibility in the spatial positioning of eachdata measuring point and excellent synchronicity between channels. This paper describessome examples of the applications to which this technique may be put.Detonics researchDavid Bridge et al from The Royal Armaments Research and Development Establishment(R.A.R.D.E.) in the U.K. have been using the technique of multi channel fibre optic recor-ding to develop a shaped charge initiator consisting of a centrally detonated explosiveincorporating an inert wave shaper. For optimum performance of the shaped charge theinitiator must produce a detonation shock front that has a high degree of axial symmetrywith minimum time jitter of the arrival of the shock front at a plane perpendicular to theaxis of the shaped charge. In order to monitor the arrival time of the shock front at theouter surface of the initiator the polished ends of 16 monofilament plastic fibre opticprobes were placed in a circle in close proximity to the surface of the explosive charge.The ends of the fibres were held in accurate register by mounting them in a machinedaluminium plate which was spaced off from the explosive surface by approximately 70 microns.This provided an air gap between the explosive and the end of the fibre which is brieflyionised on the arrival of the detonation shock front producing a flash of light which istransmitted along the fibre optic. Figure 1 shows the circular aluminium register platewith the fibre optics attached formed into a straight line. Figure 2 shows detail of theregister plate relative to the explosive charge.Figure 1

A high—frequency oscillator has been used to drive the deflector plates of an image converter tube capable of recording pulses of light of duration in the order of units of picoseconds. The oscillator is synchronised to the repetition frequency of these pulses, and by appropriate adjustment the pulses may be superimposed at the centre of the tube screen, and recorded photographically. A variation of the method, “Stroboscan”, is to set the frequency of oscillation slightly removed from the recurrence frequency of the pulses, a technique which enables a train of pulses to be displayed and recorded. Another variation gives a circular scan, useful for recording of intensity against time, with continuous access. The apparatus has been designed specifically for use as an accessory to an Imacon 600 ultra—high—speed image converter camera.

A picosecond streak camera which operates at a repetition rate of 140 MHz in synchronism with a CW mode-locked laser is described. Experi-mental results are presented which indicate that the SYNCHROSCAN system at present has a temporal resolution ≈ 1Opsec and the possibility of improving this resolution;Opsec is discussed. SYNCHROSCAN has been built into a commercially available camera (IIIACON 675) and a temporal resolution ⪅2Opsec demonstrated in this form.© (1979) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.