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drawings for optical elements and systems. Stand a r d i s a t i o n of t h i s n a t u r e e a s e s the p r o b l e m of s p e cifying tolerances. T h e a f t e r n o o n s e s s i o n w a s d e v o t e d e n t i r e l y to p a p e r s g i v e n b y S i r a staff, a n d s o m e of the w o r k had p r e v i o u s l y b e e n d e s c r i b e d a t o t h e r m e e t i n g s a n d in the o p t i c s j o u r n a l s . The c o n t i n u e d r e f i n e m e n t of the t e c h n i q u e s d e v e l o p e d at S i r a was, h o w e v e r , o b v i o u s f r o m a l l the p a p e r s . The p u p i l s c a n n e r d e s c r i b e d b y T . L . W i l l i a m s h a s p r o v e d to b e a v e r s a t i l e i n s t r u m e n t f o r d i s p l a y i n g the w a v e f r o n t a b e r r a t i o n , t r a n s v e r s e r a y a b e r r a t i o n o r s p o t d i a g r a m s . The s p e e d and s i m p l i c i t y of the d i s p l a y w e r e p a r t i c u l a r l y a t t r a c t i v e f e a t u r e s of the instrument. D e t a i l s of new w o r k on ionic g l a s s p o l i s h i n g w e r e g i v e n b y R. K. B u r d e t t . T h i s w o r k h a d shown t h a t a high q u a l i t y s u r f a c e could b e o b t a i n e d with quite s i m p l e a p p a r a t u s b u t that the p r i m e n e e d w a s to i m p r o v e the r a t e of r e m o v a l of m a t e r i a l . T h e p r e d o m i n a t i n g p r o b l e m of c e n t r i n g a n d e d g i n g w a s r e t u r n e d to b y B. J . B i d d l e s when he d e s c r i b e d the S i r a c e n t r i n g a n d e d g i n g m a c h i n e . In i t s p r e s e n t f o r m the m a c h i n e h a s b e e n shown to g i v e m u c h h i g h e r a c c u r a c y t h a n e x i s t i n g m e t h o d s but m o r e d e v e l o p m e n t w o r k i s n e c e s s a r y to i n c o r p o r a t e the new p r i n c i p l e s i n v o l v e d into a c o m m e r c i a l m a c h i n e . T h e i n s t r u m e n t a p p e a r e d to b e w e l l s u i t e d to w o r k in c o n j u n c t i o n with the m o d u l a r m e t h o d of l e n s c o n s t r u c t i o n d e s c r i b e d by F. L. Oswald. A t t e n d a n c e at t h e s y m p o s i u m on a p p l i c a t i o n s of o p t i cal transfer functions showed that an increasing n u m b e r of l e n s u s e r s w e r e a w a r e of the u s e f u l n e s s of t h i s m e t h o d of d e s c r i b i n g l e n s p e r f o r m a n c e . The p a p e r s t h e m s e l v e s w e r e of a m o r e p r a c t i c a l n a t u r e than h a s b e e n u s u a l at c o n f e r e n c e s of t h i s kind.
Two i l l u s t r a t e d t h a t the o.t.f, c o u l d b e u s e d in e v a l u a t i n g the q u i t e d i f f e r e n t r e q u i r e m e n t s of t e l e v i s i o n a n d a i r p h o t o g r a p h y . The t e l e v i s i o n s y s t e m w a s shown to b e i d e a l l y s u i t e d to the o.t.f, c o n c e p t . The w o r k , d e s c r i b e d b y W . N. S p r o s o n ( B . B . C . ) on c o r r e l a t i n g s u b j e c t i v e i m a g e q u a l i t y a s s e s s m e n t with the o.t.f, of a s y s t e m h a s l e d to u s e f u l s p e c i f i c a t i o n s for television lenses. K. J . R o s e n b r u c h ( P h y s i k a l i s c h - T e c h n i s c h e B u n d e s a n s t a l t ) s a i d t h a t in G e r m a n y a g r e a t d e a l of w o r k on s u b j e c t i v e q u a l i t y had a l r e a d y b e e n done and that it s h o u l d b e p o s s i b l e to w r i t e o.t.f, s p e c i f i c a t i o n s f o r a w i d e r r a n g e of l e n s a p p l i c a t i o n s . L a t e r p a p e r s on t h e m a t h e m a t i c a l d e s c r i p t i o n of the p e r f o r m a n c e of the e y e a n d of p h o t o g r a p h i c f i l m m a d e it c l e a r t h a t t h e s e a r e a s w e r e r e c e i v i n g a t t e n t i o n and that the l e n s s p e c i f i c a t i o n p r o b l e m c o u l d not b e i s o lated from them. R. E . L i t t l e (Rank P r e c i s i o n I n d u s t r i e s ) in a p a p e r r e a d b y A. A s h t o n , d e s c r i b e d a n o t h e r a p p r o a c h to the problem. Various common shapes, such as edges and l i n e s , w e r e s y n t h e s i s e d f r o m o.t.f, c u r v e s b y a p p r o x i m a t i n g the c u r v e s to t h o s e of a d i f f r a c t i o n l i m i t e d l e n s of s m a l l e r a p e r t u r e . T h i s s i m p l e a p p r o a c h w a s w e l c o m e d but it w a s a c k n o w l e d g e d t h a t a v a r i e t y of m e t h o d s of a p p r o x i m a t i n g the o.t.f, c u r v e s of l e n s e s ought to b e i n v e s t i g a t e d . A m o r e g e n e r a l d i s c u s s i o n on the w a y in w h i c h a lens specification should be presented arose from a p a p e r b y C. D. R e i d (A .W .R .E . ) . M r . R e i d ' s m a i n p o i n t w a s t h a t in the not t o o - d i s t a n t f u t u r e one m i g h t find m a s s - p r o d u c e d l e n s e s s p e c i f i e d b y a s i n g l e n u m b e r p u r p o r t i n g to r e p r e s e n t the o.t.f, of the l e n s . T h i s w a s thought to b e d i s a s t r o u s a s no s i n g l e n u m b e r c o u l d f a i r l y b e s a i d to d e s c r i b e the p e r f o r m a n c e of a lens. A. Ashton
LASER FOR SCIENCE AND INDUSTRY E x h i b i t i o n , US T r a d e C e n t e r , F r a n k f u r t , 2 - 6 D e c e m b e r 1968
THE F I R S T of i t s k i n d in E u r o p e , t h i s e x h i b i t i o n p r e s e n t e d p r o d u c t s of the A m e r i c a n l a s e ~ i n d u s t r y . M a n y of the s m a l l e r m a n u f a c t u r e r s , who had not b e e n r e p r e s e n t e d in E u r o p e b e f o r e , t o o k the o p p o r t u n i t y of e x h i b i t i n g . The e x h i b i t i o n p r e s e n t e d a unique o p p o r t u n i t y f o r E u r o p e a n s to i n s p e c t a n d c o m p a r e c u r r e n t l y a v a i l a b l e e q u i p m e n t f o r the USA. A t h r e e - d a y s y m p o s i u m on the l a t e s t d e v e l o p m e n t s in l a s e r t e c h n o l o g y a n d i t s a p p l i c a t i o n s w a s h e l d b u t it w a s u n f o r t u n a t e f o r m o s t t h a t the p a p e r s w e r e r e a d in G e r m a n . The e x h i b i t i o n e m p h a s i s e d the i m p o r t a n c e of l o w p o w e r c.w. l a s e r s to the A m e r i c a n l a s e r i n d u s t r y . Many w e r e on d i s p l a y , a n d a l a r g e p r o p o r t i o n w e r e shown w i t h a c c e s s o r i e s to f o r m e d u c a t i o n a l , a l i g n ment, i n t e r f e r o m e t r i c o r h o l o g r a p h i c s y s t e m s . The two m e d i u m p o w e r CO 2 l a s e r s d e m o n s t r a t e d a t t r a c t e d the g r e a t e s t a t t e n t i o n i n d i c a t i n g s i g n i f i c a n t
102
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i n t e r e s t in E u r o p e in t h e i r h e a t i n g a p p l i c a t i o n s . The m o s t p o w e r f u l of the two w a s the O T I M o d e l 260. The M o d e l 260, (£6, 700 fob B e l g i u m ) w a s shown c u t t i n g thin m e t a l s h e e t s a n d is c l a i m e d to p r o d u c e 250W m u l t i m o d e . The s h o r t o v e r a l l l e n g t h of 1 . 9 m i s a c h i e v e d b y f o l d i n g the tube f o u r t i m e s . C o h e r e n t R a d i a t i o n L a b o r a t o r i e s M o d e l 40 l a s e r i s a l s o a w e l l e n g i n e e r e d l a s e r , ( c o s t i n g £ 4, 485 e x c l u s i v e of duty) a n d p r o d u c e s up to 100W m u l t i m o d e . A v a i l a b l e a c c e s sories include a pulsed power supply and a rotary Q - s w i t c h . R e s a l a b Inc., H o l o b e a m a n d S y l v a n i a S y s t e m s d e m o n s t r a t e d s m a l l e r s e a l e d CO 2 l a s e r s w i t h p o w e r s in the r a n g e 3-10W. The m a j o r e x h i b i t o r of H e - N e l a s e r s w a s S p e c t r a P h y s i c s , w h o s e l a s e r s i n c l u d e d the new l o w - p r i c e M o d e l 132, c o s t i n g £ 135 f o r l m W . H e - N e l a s e r s in the r a n g e 0 . 3 m W and 5roW w e r e a l s o e x h i b i t e d b y
Perkin-Elmer, Electro-Optical Associates, ElectroNuclear L a b o r a t o r i e s , U n i v e r s i t y L a b o r a t o r i e s and Jodon E n g i n e e r i n g A s s o c i a t e s . The m o s t powerful, OIP Model 181E, is c l a i m e d to p r o d u c e 150mW m u l t i mode ( a p p r o x i m a t e l y £ 4400 fob Belgium). G r e a t i n t e r e s t w a s shown in the ion l a s e r s which w e r e d e m o n s t r a t e d by CRL, S p e c t r a - P h y s i c s and RCA. CRL Model 52, with d.c. excitation, is o f f e r e d with e i t h e r a r g o n (2w total) or k r y p t o n (300mW total) as the l a s e r m e d i u m . P o l a r i z a t i o n is c l a i m e d to be l i n e a r to 1 p a r t in 100. Selection of a single w a v e length r e q u i r e s use of the Model 431 P r i s m . (Model 52 c o s t s £ 4, 700 and the p r i s m £ 450, both p r i c e s e x c l u s i v e of duty). S p e c t r a - P h y s i c s Model 140 l a s e r , a l s o quoted a s 2W total, is r . f . induction e x c i t e d and i n c o r p o r a t e s an i n t r a c a v i t y p r i s m f o r w a v e - l e n g t h s e l e c t i o n . P o l o r i z a t i o n is c l a i m e d to be l i n e a r to b e t t e r than 1 p a r t in 1000. (Model 140 c o s t s £ 8, 950 e x c l u s i v e of duty and f r e i g h t c h a r g e s . ) RCA have a c o m p l e t e r a n g e of c.w. ion l a s e r s , using a r g o n , k r y p t o n and neon, with output p o w e r s ranging f r o m 10mW to 2W. Most of p u l s e d s o l i d state l a s e r s on d i s p l a y w e r e f i r s t g e n e r a t i o n vintage. Raytheon f e a t u r e d a diamond d r i l l i n g l a s e r c o n s t r u c t e d in c o - o p e r a t i o n with L a s e r Technique S.A. This m a c h i n e ' s c a p a b i l i t y was i l l u s t r a t e d by some ruby s a m p l e s through which 0 . 5 m m holes of good quality had been d r i l l e d . P e r k i n - E l m e r and E l e c t r o Optical A s s o c i a t e s e m p h a s i s e d the a p p l i c a t i o n of low power c.w. l a s e r s to m e t r o l o g y , and in p a r t i c u l a r f o r the r e m o t e - m e a s u r e ment of s m a l l d i s p l a c e m e n t s . The P e r k i n - E l m e r L a s e r I n t e r f e r o m e t e r , (costing £ 5, 021 including the f r i n g e counter) is c l a i m e d to r e s o l v e 1/4 fringe over
d i s t a n c e s up to 30m while the EOA l a s e r tooling s y s t e m (~2,100 fob USA) r e s o l v e s 25pm p e r 30m up to a m a x i m u m of 300m. E l e c t r o - O p t i c a l A s s o c i a t e s a l s o e x h i b i t e d t h e i r T r a n s i t l a s e r and L a s e r l e v e l , d e s i g n e d for s u r v e y i n g , and c l a i m e d to p r o d u c e a c o l l i m a t e d 1 . 8 c m b e a m up to 300m (£ 1,100 fob USA). The exhibition was c e r t a i n l y s u c c e s s f u l f o r it s e r v e d well the dual p u r p o s e of i n t r o d u c i n g a s i g n i f i c a n t p r o p o r t i o n of the A m e r i c a n L a s e r i n d u s t r y to the E u r o p e a n m a r k e t and p e r m i t t i n g many E u r o p e a n s to conveniently a s s e s s c u r r e n t l y a v a i l a b l e A m e r i c a n l a s e r s and a s s o c i a t e d equipment. Many e x h i b i t o r s e x p r e s s e d s u p r i s e at the l a r g e attendance, both f r o m G e r m a n y and e l s e w h e r e in Europe, and the depth of i n t e r e s t shown. C o n v e r s e l y , m o s t v i s i t o r s w e r e i m p r e s s e d by the high t e c h n i c a l s t a n d a r d s and quality of finish of the p r o d u c t s , although p r i c e s a p p e a r e d e x p e n s i v e by E u r o p e a n s t a n d a r d s . The s a f e t y a s p e c t was p a r t i c u l a r l y n e g l e c t e d by the CO 2 e x h i b i t o r s , on whose s t a n d s l i t t l e or no p r o t e c tive m e a s u r e s w e r e taken. O r g a n i s e r s of future e x hibitions would be a d v i s e d to i n s i s t on the n e c e s s a r y p r e c u a t i o n s where a p p r o p r i a t e . The a b s e n c e of machining l a s e r s c a p a b l e of u s e in i n d u s t r i a l e n v i r o n m e n t s was noted although t h e s e have a p p e a r e d r e c e n t l y in the a d v e r t i s i n g l i t e r a t u r e . It is hoped that the exhibition will, in the light of its s u c c e s s , b e c o m e an annual affair, p e r h a p s a p p e a r i n g in a d i f f e r e n t E u r o p e a n country each y e a r . It might a l s o s t i m u l a t e the E u r o p e a n l a s e r i n d u s t r y , though s m a l l by A m e r i c a n s t a n d a r d s , to p r e s e n t t h e i r w a r e s in a s i m i l a r m a n n e r . D. L. Hodgett
Oplics Technology
February 1969
103
Two i l l u s t r a t e d t h a t the o.t.f, c o u l d b e u s e d in e v a l u a t i n g the q u i t e d i f f e r e n t r e q u i r e m e n t s of t e l e v i s i o n a n d a i r p h o t o g r a p h y . The t e l e v i s i o n s y s t e m w a s shown to b e i d e a l l y s u i t e d to the o.t.f, c o n c e p t . The w o r k , d e s c r i b e d b y W . N. S p r o s o n ( B . B . C . ) on c o r r e l a t i n g s u b j e c t i v e i m a g e q u a l i t y a s s e s s m e n t with the o.t.f, of a s y s t e m h a s l e d to u s e f u l s p e c i f i c a t i o n s for television lenses. K. J . R o s e n b r u c h ( P h y s i k a l i s c h - T e c h n i s c h e B u n d e s a n s t a l t ) s a i d t h a t in G e r m a n y a g r e a t d e a l of w o r k on s u b j e c t i v e q u a l i t y had a l r e a d y b e e n done and that it s h o u l d b e p o s s i b l e to w r i t e o.t.f, s p e c i f i c a t i o n s f o r a w i d e r r a n g e of l e n s a p p l i c a t i o n s . L a t e r p a p e r s on t h e m a t h e m a t i c a l d e s c r i p t i o n of the p e r f o r m a n c e of the e y e a n d of p h o t o g r a p h i c f i l m m a d e it c l e a r t h a t t h e s e a r e a s w e r e r e c e i v i n g a t t e n t i o n and that the l e n s s p e c i f i c a t i o n p r o b l e m c o u l d not b e i s o lated from them. R. E . L i t t l e (Rank P r e c i s i o n I n d u s t r i e s ) in a p a p e r r e a d b y A. A s h t o n , d e s c r i b e d a n o t h e r a p p r o a c h to the problem. Various common shapes, such as edges and l i n e s , w e r e s y n t h e s i s e d f r o m o.t.f, c u r v e s b y a p p r o x i m a t i n g the c u r v e s to t h o s e of a d i f f r a c t i o n l i m i t e d l e n s of s m a l l e r a p e r t u r e . T h i s s i m p l e a p p r o a c h w a s w e l c o m e d but it w a s a c k n o w l e d g e d t h a t a v a r i e t y of m e t h o d s of a p p r o x i m a t i n g the o.t.f, c u r v e s of l e n s e s ought to b e i n v e s t i g a t e d . A m o r e g e n e r a l d i s c u s s i o n on the w a y in w h i c h a lens specification should be presented arose from a p a p e r b y C. D. R e i d (A .W .R .E . ) . M r . R e i d ' s m a i n p o i n t w a s t h a t in the not t o o - d i s t a n t f u t u r e one m i g h t find m a s s - p r o d u c e d l e n s e s s p e c i f i e d b y a s i n g l e n u m b e r p u r p o r t i n g to r e p r e s e n t the o.t.f, of the l e n s . T h i s w a s thought to b e d i s a s t r o u s a s no s i n g l e n u m b e r c o u l d f a i r l y b e s a i d to d e s c r i b e the p e r f o r m a n c e of a lens. A. Ashton
LASER FOR SCIENCE AND INDUSTRY E x h i b i t i o n , US T r a d e C e n t e r , F r a n k f u r t , 2 - 6 D e c e m b e r 1968
THE F I R S T of i t s k i n d in E u r o p e , t h i s e x h i b i t i o n p r e s e n t e d p r o d u c t s of the A m e r i c a n l a s e ~ i n d u s t r y . M a n y of the s m a l l e r m a n u f a c t u r e r s , who had not b e e n r e p r e s e n t e d in E u r o p e b e f o r e , t o o k the o p p o r t u n i t y of e x h i b i t i n g . The e x h i b i t i o n p r e s e n t e d a unique o p p o r t u n i t y f o r E u r o p e a n s to i n s p e c t a n d c o m p a r e c u r r e n t l y a v a i l a b l e e q u i p m e n t f o r the USA. A t h r e e - d a y s y m p o s i u m on the l a t e s t d e v e l o p m e n t s in l a s e r t e c h n o l o g y a n d i t s a p p l i c a t i o n s w a s h e l d b u t it w a s u n f o r t u n a t e f o r m o s t t h a t the p a p e r s w e r e r e a d in G e r m a n . The e x h i b i t i o n e m p h a s i s e d the i m p o r t a n c e of l o w p o w e r c.w. l a s e r s to the A m e r i c a n l a s e r i n d u s t r y . Many w e r e on d i s p l a y , a n d a l a r g e p r o p o r t i o n w e r e shown w i t h a c c e s s o r i e s to f o r m e d u c a t i o n a l , a l i g n ment, i n t e r f e r o m e t r i c o r h o l o g r a p h i c s y s t e m s . The two m e d i u m p o w e r CO 2 l a s e r s d e m o n s t r a t e d a t t r a c t e d the g r e a t e s t a t t e n t i o n i n d i c a t i n g s i g n i f i c a n t
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optics Technology
February 1969
i n t e r e s t in E u r o p e in t h e i r h e a t i n g a p p l i c a t i o n s . The m o s t p o w e r f u l of the two w a s the O T I M o d e l 260. The M o d e l 260, (£6, 700 fob B e l g i u m ) w a s shown c u t t i n g thin m e t a l s h e e t s a n d is c l a i m e d to p r o d u c e 250W m u l t i m o d e . The s h o r t o v e r a l l l e n g t h of 1 . 9 m i s a c h i e v e d b y f o l d i n g the tube f o u r t i m e s . C o h e r e n t R a d i a t i o n L a b o r a t o r i e s M o d e l 40 l a s e r i s a l s o a w e l l e n g i n e e r e d l a s e r , ( c o s t i n g £ 4, 485 e x c l u s i v e of duty) a n d p r o d u c e s up to 100W m u l t i m o d e . A v a i l a b l e a c c e s sories include a pulsed power supply and a rotary Q - s w i t c h . R e s a l a b Inc., H o l o b e a m a n d S y l v a n i a S y s t e m s d e m o n s t r a t e d s m a l l e r s e a l e d CO 2 l a s e r s w i t h p o w e r s in the r a n g e 3-10W. The m a j o r e x h i b i t o r of H e - N e l a s e r s w a s S p e c t r a P h y s i c s , w h o s e l a s e r s i n c l u d e d the new l o w - p r i c e M o d e l 132, c o s t i n g £ 135 f o r l m W . H e - N e l a s e r s in the r a n g e 0 . 3 m W and 5roW w e r e a l s o e x h i b i t e d b y
Perkin-Elmer, Electro-Optical Associates, ElectroNuclear L a b o r a t o r i e s , U n i v e r s i t y L a b o r a t o r i e s and Jodon E n g i n e e r i n g A s s o c i a t e s . The m o s t powerful, OIP Model 181E, is c l a i m e d to p r o d u c e 150mW m u l t i mode ( a p p r o x i m a t e l y £ 4400 fob Belgium). G r e a t i n t e r e s t w a s shown in the ion l a s e r s which w e r e d e m o n s t r a t e d by CRL, S p e c t r a - P h y s i c s and RCA. CRL Model 52, with d.c. excitation, is o f f e r e d with e i t h e r a r g o n (2w total) or k r y p t o n (300mW total) as the l a s e r m e d i u m . P o l a r i z a t i o n is c l a i m e d to be l i n e a r to 1 p a r t in 100. Selection of a single w a v e length r e q u i r e s use of the Model 431 P r i s m . (Model 52 c o s t s £ 4, 700 and the p r i s m £ 450, both p r i c e s e x c l u s i v e of duty). S p e c t r a - P h y s i c s Model 140 l a s e r , a l s o quoted a s 2W total, is r . f . induction e x c i t e d and i n c o r p o r a t e s an i n t r a c a v i t y p r i s m f o r w a v e - l e n g t h s e l e c t i o n . P o l o r i z a t i o n is c l a i m e d to be l i n e a r to b e t t e r than 1 p a r t in 1000. (Model 140 c o s t s £ 8, 950 e x c l u s i v e of duty and f r e i g h t c h a r g e s . ) RCA have a c o m p l e t e r a n g e of c.w. ion l a s e r s , using a r g o n , k r y p t o n and neon, with output p o w e r s ranging f r o m 10mW to 2W. Most of p u l s e d s o l i d state l a s e r s on d i s p l a y w e r e f i r s t g e n e r a t i o n vintage. Raytheon f e a t u r e d a diamond d r i l l i n g l a s e r c o n s t r u c t e d in c o - o p e r a t i o n with L a s e r Technique S.A. This m a c h i n e ' s c a p a b i l i t y was i l l u s t r a t e d by some ruby s a m p l e s through which 0 . 5 m m holes of good quality had been d r i l l e d . P e r k i n - E l m e r and E l e c t r o Optical A s s o c i a t e s e m p h a s i s e d the a p p l i c a t i o n of low power c.w. l a s e r s to m e t r o l o g y , and in p a r t i c u l a r f o r the r e m o t e - m e a s u r e ment of s m a l l d i s p l a c e m e n t s . The P e r k i n - E l m e r L a s e r I n t e r f e r o m e t e r , (costing £ 5, 021 including the f r i n g e counter) is c l a i m e d to r e s o l v e 1/4 fringe over
d i s t a n c e s up to 30m while the EOA l a s e r tooling s y s t e m (~2,100 fob USA) r e s o l v e s 25pm p e r 30m up to a m a x i m u m of 300m. E l e c t r o - O p t i c a l A s s o c i a t e s a l s o e x h i b i t e d t h e i r T r a n s i t l a s e r and L a s e r l e v e l , d e s i g n e d for s u r v e y i n g , and c l a i m e d to p r o d u c e a c o l l i m a t e d 1 . 8 c m b e a m up to 300m (£ 1,100 fob USA). The exhibition was c e r t a i n l y s u c c e s s f u l f o r it s e r v e d well the dual p u r p o s e of i n t r o d u c i n g a s i g n i f i c a n t p r o p o r t i o n of the A m e r i c a n L a s e r i n d u s t r y to the E u r o p e a n m a r k e t and p e r m i t t i n g many E u r o p e a n s to conveniently a s s e s s c u r r e n t l y a v a i l a b l e A m e r i c a n l a s e r s and a s s o c i a t e d equipment. Many e x h i b i t o r s e x p r e s s e d s u p r i s e at the l a r g e attendance, both f r o m G e r m a n y and e l s e w h e r e in Europe, and the depth of i n t e r e s t shown. C o n v e r s e l y , m o s t v i s i t o r s w e r e i m p r e s s e d by the high t e c h n i c a l s t a n d a r d s and quality of finish of the p r o d u c t s , although p r i c e s a p p e a r e d e x p e n s i v e by E u r o p e a n s t a n d a r d s . The s a f e t y a s p e c t was p a r t i c u l a r l y n e g l e c t e d by the CO 2 e x h i b i t o r s , on whose s t a n d s l i t t l e or no p r o t e c tive m e a s u r e s w e r e taken. O r g a n i s e r s of future e x hibitions would be a d v i s e d to i n s i s t on the n e c e s s a r y p r e c u a t i o n s where a p p r o p r i a t e . The a b s e n c e of machining l a s e r s c a p a b l e of u s e in i n d u s t r i a l e n v i r o n m e n t s was noted although t h e s e have a p p e a r e d r e c e n t l y in the a d v e r t i s i n g l i t e r a t u r e . It is hoped that the exhibition will, in the light of its s u c c e s s , b e c o m e an annual affair, p e r h a p s a p p e a r i n g in a d i f f e r e n t E u r o p e a n country each y e a r . It might a l s o s t i m u l a t e the E u r o p e a n l a s e r i n d u s t r y , though s m a l l by A m e r i c a n s t a n d a r d s , to p r e s e n t t h e i r w a r e s in a s i m i l a r m a n n e r . D. L. Hodgett
Oplics Technology
February 1969
103