'lensless photography', records a sub- ject through the interference of two laser beams on a photographic plate. One beam is aimed directly at the plate, and the other reaches the plate after being transmitted through, or re- flected by, the subject being 'photo- graphed'.
The original subject exists only as a group of numbers or coordinate points in three dimensions, for example, in the computer's memory. The holo- gram is made in two steps. First the computer is programmed to construct a series of two-dimensional pictures, or projections, each showing the 3-D data from a precisely defined unique angle. A microfilm plotter, connected to the computer, produces a microfilm frame for each picture.
In the second step a holographic transparency is made. The frames of the microfilm are used as subjects to make very small holograms (1 to 3mm across), which are positioned sequen- tially on a holographic medium.
Thus, a composite hologram is made up of a series of small holo- grams, each of which is formed with a two-dimensional image. But the com- posite image appears three-dimen- sional, and shows a 360-degree view of the object. With this type of hologram, the viewer can see the object rotating through a full cycle by simply moving his head from side to side in front of the hologram.
METRIC CONVERSION
Two metric-conversion calculators, known as the Models M.2 and M.3, allow conversions within the range 0 in. to 100 ft. (30-48 m.) and 0 to 10 in. (229 mm.) respectively. The cir- cular white Perspex instruments have
Mear metric convertor
spiral scales engraved on both sides and readings are taken through trans- parent cursors.
The M.2 is a pocket-size instru- ment, 5% in. in diameter by in, thick (146 by 6.4 mm.), designed for all normal applications where dimensions are measured in feet, inches and frac tions of an inch. The scaling is varied to suit practical requirements, being more open at the lower end so that small dimensions are easily read to
1/64 in. (0.4 mm.), while larger dimen- sions near 100 ft. are read to in. (6.4 mm.). The double-sided scale is ar ranged with 0 to 10 ft. (3.048 mm.) on one side and 10 to 100 ft. on the other.
A larger instrument, in. (279 mm.) in diameter by in. thick, the Model M.3 is for those who need ac- curate conversions from measurements in inches and decimals of an inch to millimetres, and vice versa. Its basic scaling is from 0 to 10 in. with calibra- tions at each 0.001 in. (0.025 mm.), so that interpolation to practically one ten thousandth is possible by means of the cursor.
Dimensions from 10 to 100 in. (2.54 m.) are handled by moving the decimal point, and ten times the above accuracy is obtainable for dimensions below 1 in. (25 mm.), again by moving the decimal point.
Makers are M.H. Mear & Co., 56 Nettleton Road, Dalton, Huddersfield, UK.
EXTERIOR COATING
Unicote, a new type of exterior surface coating developed by Union Carbide, may be applied to any type
Unicote surface textures
―
has good resistance to dampness and fire. The intermediate layer of foamed vinyl gives extra thermal and sound in- sulation, and the top surface comprises
Bermuda flooring
a layer of embossed vinyl, covered with an extra thick coating of hard- wearing clear p.v.c.
There are six patterns and 14 colourways. Bermuda (illustrated) makes use of two types of straw mat- ting square in a natural colour.
Roll lengths may be up to 75ft. The material is 6ft, wide and 2mm thick. Nairn Floors, Kircaldy, Fife, Scotland, are the makers.
SLIDING/SWINGING DOOR
The Stanley Auto-Slide door has a breakaway mechanism that allows the sliding door panels to be swung manu- ally for emergency exit. The door panels can be swung from any sliding position, which is made possible by side panels that also swing open.
In addition, swinging open both the sliding panels and the side panels clears the entire width of the doorway
up to 12ft. The door has a 4in. thick frame and is easily adaptable to new or remodelled shop front construction.
A new type of door carrier sup- wood, metal, ports the entire weight of the door, eliminating the need for floor tracks or bottom door pivots. The carrier is a
of exterior surface plaster or asbestos cement.
The coating is applied with a high pressure spray gun and is about 12 times thicker than a coat of paint. There are nine basic colours.
Unicote is weatherproof, having a latex base which covers structural de- fects, holes and cracks. It is said to re- quire no maintenance or re-application for about ten years.
Marketing in Hong Kong is hand- led by Pacific Supply Co.
FLOOR COVERING
A foamed-vinyl flooring, known as Cushionflor Supreme, is being market- ted for light contract applications such as in hairdressing salons. It has a tex- tured surface and very good sound and thermal insulation properties.
The flooring combines several lay ers of materials bonded together into one composite sheet of flooring. The backing, made of plastic bound asbes- tos fibre. is dimensionally stable and
Stanley Auto-Slide door
patented, one-piece trussed trolley with built-in steel ball bearings that maintain positive door alignment.
The makers are The Stanley Works, 195 Lake Street, New Britain, Conn., USA.
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Far East BUILDER, April 1970