Page 25 - Studio International - March 1967

Mark Tobey
Electric Dimensions 1960
Tempera
9 5/8 x 6 3/4 in.
Coll.: Galerie Beyeler, Basel

field which contains a certain amount of order; this is, is as orderly and well-behaved as laser light, the tops of
however, not very easy to see or describe. If an even grid the waves can be pictured as forming a set of concentric
of parallel straight lines is laid over this, the moire circles (in normal light there is a mixture of wavelengths
pattern changes as the grid is rotated, revealing various and the waves are out of phase so that we should get a
aspects of the rather disorderly arrangement of the back- misty blur rather than precise separated circles). As
ground. It is this effect which is utilized by the hologram figure 1 demonstrates, if we have two lamps placed
technique. This was first invented about twenty years ago some distance apart, the waves will intersect and give
by Gabo in England but has only recently become prac- rise to a moire pattern which, in this case, is known as a
ticable in a developed form following the invention of set of interference fringes. Even if we have an intersection
Lasers. between one source of light which is quite orderly and
Lasers are a variety of lamp which produces light all of another which is rather disorderly, we shall still get some
one wavelength and with all the waves very precisely in pattern formed in their interaction as figure 2 shows. In
phase, that is to say with their peaks and troughs coin- the system of recording an image which we are consider-
ciding. The method uses the principle rather similar to ing (which is known as 'wave front analysis') an object is
that of moire patterns. If the light emerging from a lamp illuminated with light from a laser and, of course, reflects