Street Lighting

New Light Source

Osram-G.E.C. announces major advances in the development of an entirely new light source, the high-pressure sodium lamp.

The new lamp, based on advanced construction techniques, is likely to become the first of a new generation of light sources which will have higher luminous efficiencies and, in some cases, better colour rendering properties that present day light sources.

The new 400W lamp has nearly double the light output of a comparable 400W highpressure mercury vapour lamp, and its colour quality makes it ideal for street lighting and the lighting of large industrial interiors.

The company's research into the lamp is now at such an advanced stage that fifteen of the lamps in cut-off lanterns, are installed. Outside its headquarters in East Lane, Wembley, and are operating under test.

History thus repeats itself, for it was in East Lane in 1933 that Osram operated the first-ever working installation of highpressure mercury vapour lamps.

Osram's announcement follows hard on i statement issued recently by the General Electric Company of America-no connection with the British G. E. C.—that it, too, had developed a 400W high-pressure sodium lamp.

The "secret" of the new lamp is the use of a recently developed translucent ceramic naterial in the construction of the arc tube. This highly resistant material withstands the attack of high-pressure sodium vapour which will destroy glass or quartz in a very short time. This material enables a high light output of over 90 lumens per watt to be achieved.

Said an Osram spokesman: "Research into a high-pressure sodium lamp has been going on for some years. Now we have reached the stage when we can put it on public trial. The lamp will not be commercially available before 1967."

spectacles for certain sight defects? Can optical correction cope with the night seeing problems of older drivers?

These questions were asked by Mr. W. Robinson, of the Electricity Council, and of the President Association of Public Lighting Engineers, when he addressed a meeting organised by the Association of Optical practitioners on 9th June. The symposium, on "Seeing and Road Safety", was held at the English Speaking Union, London, and attended by representatives of medical bodies, safety and motoring organisations and police.

Mr. Robinson said that the standard of

sight needed for night driving was a matter which should receive much more attention. Sight defects which were relatively unimportant in daylight, could be almost crippling under night-time lighting conditions.

faced with a task resources and his limit," said Mr.

state of street

"The driver at night is which stretches his visual endurance almost to the Robinson. "In the present and vehicle lighting he can be sure to have to overcome not only the hazard of seeing distance which barely exceeds his stopping distance, but also very poor contrast conditions, periods of intense visual disability through dazzle from approaching vehicles, and severe distraction from lights of all kinds extraneous to the street lights. The driver is likely to be at less than his best even at the start of his journey, his condition towards the end of it can, in the worst cases, be dangerously impaired. It is not difficult, therefore, to understand why the night-time accident situation is deteriorating more rapidly than the day-time

situation."

Dealing with the problem of headlight dazzle, Mr. Robinson said that the effect of meeting even dipped headlamps was considerable on otherwise unlighted roads. On lighted roads the effect was less serious but advocates of dipped headlights in well lighted streets should bear in mind the (Continued on page 51)

Since the invention of electric light, scientists have been troubled by the thought that light bulbs turn most of the electricity to heat and only a relatively small portion to light.

For many years, U. S. researchers have been seeking ways to curb this waste of electric energy. Though there has been Some progress, the basic problem still persists.

Now, leading firms in the U. S. lighting industry are taking another step toward that goal.

The General Electric Company began production early in 1966 of a lamp (the term lighting engineers use in place of "bulb") which company officials describe as the most efficient lighting source made by man. It transmits more light per unit of electricity consumed than any other kind of lamp now in existence.

Its illumination per watt of electricity consumed is a third greater than fluorescent lamps, double that of mercury vapour lamps,

and six times the light from ordinary household incandescent lamps.

The advantages of the new lamp are made ceramic named possible by a Lucalox. Developed in 1956, it is pure aluminium oxide pressed into a dense crystalline material from a fine powder. The new lamp has an elongated "cucumber-shaped" glass bulb encasing the cigarette-shaped arcing chamber made of Lucalox.

So far, only 400-watt bulbs have been manufactured for lighting streets, highways, landscapes, building exteriors, parking lots, lobbies and factory installations. Eventually, the firm will produce bulbs of higher and lower wattage, including some suitable for home and office use where needs generally range for from 15 to 200-watt bulbs.

The Lucalox lamps employ a highintensity current passing through sodium vapour within the ceramic arcing tube. However, they avoid the common disadvantage of sodium-vapour lamps which normally emit a yellowish-orange light. Instead, the new lamps produce what the scientists describe as a "pleasing 'golden-white."

This is accomplished by heating the sodium vapour to such a high temperature that it almost reverses its normal range in the light spectrum.

Experiments prior to the invention of Lucalox showed that 400 watts of electricity melted pencil-thick glass and quartz tubes which had been in use instead of the new ceramic.

The new lamps average only about 6,000 hours of lighting compared to an average life expectancy of 13,000 hours for fluorescent, more than 16,000 hours for mercury vapour, and 750 to 1,200 hours for incandes

cent.

Additional research is expected to lengthen the life of Lucalox bulbs. Researchers have pointed out that fluorescent bulbs also had short life spans when they were first introduced in 1938, and that Lucalox bulbs represent the first major change in the lighting industry since then.