- Email: [email protected]
Air pollution monitor
RECENT DEVELOPMENTS
Photo-matrix for moire fringe work WORK on photovoltalc cells for space use has led to development of a photocell m a t r i x for m o i r e fringe machine control. Thin film cadmium sulphide/copper sulphide heterojunction cells, investigated at IRD as an alternative to silicon ' s o l a r ' cells, a r e fabricated in m a t r i c e s of 100 and 1000 photovoltaic lines per inch. The a r r a y s are used in a displacement m e a s u r i n g grating s y s t e m designed to operate on a reflection basis. In Fig. la a simple m o i r e fringe s y s t e m is shown with a fixed scale grating and a movable index grating. The separate detector can be eliminated and the s y s t e m simplified by making each line on the index grating into a photodetector (Fig. lb). If the second grating is made reflective the d e t e c t o r s can form the f i r s t grating, Fig. lc. The fixed elements in the s y s t e m are now on one side of the broken line and the moving p a r t s on the other, simplifying machine mounting. The d e t e c t o r s a r e made by vacuum deposition of ptype CdS to 5-10~m thick on a glass substrate with c h r o m e / g o l d deposited to f o r m one set of contacts (Fig. ld). Effects of ambient light on the s y s t e m can be eliminated by connecting cells in quadrature, using four times the number of cells. This also r e s u l t s in availability of sine and cosine outputs and i n c r e a s e s sensitivity. The devices were d e s c r i b e d by R. S. Pinder, L. Clark, K. Moore & R. S. Mytton at the Solid-State Devices Conference, Exeter, 8-12 September.
PROF H O P K I N S ICO P R E S I D E N T PROFESSOR H. H. Hopkins of the University of Reading has been elected P r e s i d e n t of the I n t e r national C o m m i s s i o n for Optics, in s u c c e s s i o n to P r o f e s s o r G. Toraldo di F r a n c i a . P r o f e s s o r Hopkins is well-known for his contributions to optics including the invention (independently with Van Heel) of fibre optics, the design of zoom lenses and m o r e recently novel types of medical endoscope. F o r his work on diffraction and coherence theory and optical t r a n s f e r functions, he was elected the 21st Thomas Young O r a t o r in 1961 by the P h y s i c a l Society and received an h o n o r a r y doctorate of the University of Besan~on in the same y e a r . P r o f e s s o r Hopkins moved to Reading f r o m I m p e r i a l College in 1967. He was appointed to a new Chair in Applied Optics established at Reading by a generous grant f r o m Rank P r e c i s i o n Industries (then Taylor Hobson Division of Rank). The new department already
284
optics Technology
November 1969
a
~coa~eng
Indexgrating intoindexgroting
.~deff
~ C
use region
iI~speculor reflector potymerised orthoresist.. Cu2S _
_
_
_
p-t pe
~ ~ . - - - - - C d s 5-10llm g loss ~"'-opoque ~'g light chrome/gold
Fig. la-c. Evolution of reflection grating system for machine displacement measurement using heterojunction photomatrix. (d) Construction of graling.
has a successful o n e - y e a r M. Sc. c o u r s e in Applied and Modern Optics, and this may be followed p a r t time over a period of two y e a r s . R e s e a r c h in the new group includes advanced computer techniques for optical design, theoretical studies in diffraction and coherence, p r e c i s i o n i n t e r f e r o m e t r y , t h i n - f i l m s and coherent optical techniques for optical data processing.
AIR POLLUTION MONITOR ATMOSPHERIC POLLUTION is being monitored using a pulsed ruby l a s e r s y s t e m to locate the source of pollution. The r e c e i v e r s y s t e m consists of 3Ocm receiving m i r r o r and photomultiplier tube with provisions for monitoring input and output powers and including water cooling for the l a s e r . An adjustable r a n g e - g a t e can be set to the d e s i r e d a c c u r a c y up to
the maximum range of 12km. L a s e r output is 3040MW peak with up to 1 p u l s e / s e c . The s y s t e m can scan automatically horizontally and v e r t i c a l l y giving range and date print out. The t r a n s m i t t e r / r e c e i v e r head is shown in the photograph. Water vapour and l a r g e p a r t i c l e s such as fly ash and soot can be detected at p r e s e n t and it is hoped to adapt the s y s t e m to m e a s u r e p a r t i c l e size, density and nature (in p a r t i c u l a r to detect sulphurous fumes). To ensure pollution complies with by-laws, the West G e r m a n Ministry of Labour and the Institut ftir E m m i s i o n Schutz have installed a s y s t e m in Duisberg, near Essen. Main c u s t o m e r s are expected to be large industrial establishments wishing to monitor their own pollution output. Cost of the system, including operative t r a i n ing is around £30, 000. L a s e r Associates, PO Box 10, Iver, Bucks. Tel. Slough 27725
Two new additions to the Laser la'i range Laser Associates Limited announce two new equipments uti!ising modular engineering concepts which will ensure compatibility with the systems of the '70s.
,?
{ - 1 0 w a t t C W gAG Laser Systems, 254 Series,
~
~
including intra-cavity Q-switching and frequency-doubling u m t s . ~/~, Application areas include macro" machining, holography, and communications. 10 to 20 PPS Laser Systems, 252 Series, using calcium t u n g s t a t e or YAG
producing up to 1 joule per pulse, or 0.1 joule per pulse when Q-switched. High-efficiency, frequencydoubling units are available. ~'~-'~--~,. Application areas include micro" ~ ) drilling, range /j measurement, :. " / and photochemistry.
Nd-GLASS LASER OF 140 PUI.,SE/SEC 140 p u l s e s / s e c have been achieved with a Q-switched N d - g l a s s l a s e r using a r e c t a n g u l a r N d - g l a s s rod. The r e c t a n g u l a r rod (see illustration) minimizes b i r e f r i n gence and i m p r o v e s the optical distortion caused by t h e r m a l effects. In a r e c t a n g u l a r g l a s s rod the effective thickness for cooling is that of the r o d ' s s m a l l e s t dimension. T h e r m a l gradients in the rod a r e one dimensional r a t h e r than radial, so t h e r m a l l y induced lens power
b
l
Systems for the '70s ? -- talk to
Laser Associates P.O. Box 10, Iver, Buckinghamshire Telephone: Slough 27725
Optics Technology
N o v e m b e r 1969
285
Photo-matrix for moire fringe work WORK on photovoltalc cells for space use has led to development of a photocell m a t r i x for m o i r e fringe machine control. Thin film cadmium sulphide/copper sulphide heterojunction cells, investigated at IRD as an alternative to silicon ' s o l a r ' cells, a r e fabricated in m a t r i c e s of 100 and 1000 photovoltaic lines per inch. The a r r a y s are used in a displacement m e a s u r i n g grating s y s t e m designed to operate on a reflection basis. In Fig. la a simple m o i r e fringe s y s t e m is shown with a fixed scale grating and a movable index grating. The separate detector can be eliminated and the s y s t e m simplified by making each line on the index grating into a photodetector (Fig. lb). If the second grating is made reflective the d e t e c t o r s can form the f i r s t grating, Fig. lc. The fixed elements in the s y s t e m are now on one side of the broken line and the moving p a r t s on the other, simplifying machine mounting. The d e t e c t o r s a r e made by vacuum deposition of ptype CdS to 5-10~m thick on a glass substrate with c h r o m e / g o l d deposited to f o r m one set of contacts (Fig. ld). Effects of ambient light on the s y s t e m can be eliminated by connecting cells in quadrature, using four times the number of cells. This also r e s u l t s in availability of sine and cosine outputs and i n c r e a s e s sensitivity. The devices were d e s c r i b e d by R. S. Pinder, L. Clark, K. Moore & R. S. Mytton at the Solid-State Devices Conference, Exeter, 8-12 September.
PROF H O P K I N S ICO P R E S I D E N T PROFESSOR H. H. Hopkins of the University of Reading has been elected P r e s i d e n t of the I n t e r national C o m m i s s i o n for Optics, in s u c c e s s i o n to P r o f e s s o r G. Toraldo di F r a n c i a . P r o f e s s o r Hopkins is well-known for his contributions to optics including the invention (independently with Van Heel) of fibre optics, the design of zoom lenses and m o r e recently novel types of medical endoscope. F o r his work on diffraction and coherence theory and optical t r a n s f e r functions, he was elected the 21st Thomas Young O r a t o r in 1961 by the P h y s i c a l Society and received an h o n o r a r y doctorate of the University of Besan~on in the same y e a r . P r o f e s s o r Hopkins moved to Reading f r o m I m p e r i a l College in 1967. He was appointed to a new Chair in Applied Optics established at Reading by a generous grant f r o m Rank P r e c i s i o n Industries (then Taylor Hobson Division of Rank). The new department already
284
optics Technology
November 1969
a
~coa~eng
Indexgrating intoindexgroting
.~deff
~ C
use region
iI~speculor reflector potymerised orthoresist.. Cu2S _
_
_
_
p-t pe
~ ~ . - - - - - C d s 5-10llm g loss ~"'-opoque ~'g light chrome/gold
Fig. la-c. Evolution of reflection grating system for machine displacement measurement using heterojunction photomatrix. (d) Construction of graling.
has a successful o n e - y e a r M. Sc. c o u r s e in Applied and Modern Optics, and this may be followed p a r t time over a period of two y e a r s . R e s e a r c h in the new group includes advanced computer techniques for optical design, theoretical studies in diffraction and coherence, p r e c i s i o n i n t e r f e r o m e t r y , t h i n - f i l m s and coherent optical techniques for optical data processing.
AIR POLLUTION MONITOR ATMOSPHERIC POLLUTION is being monitored using a pulsed ruby l a s e r s y s t e m to locate the source of pollution. The r e c e i v e r s y s t e m consists of 3Ocm receiving m i r r o r and photomultiplier tube with provisions for monitoring input and output powers and including water cooling for the l a s e r . An adjustable r a n g e - g a t e can be set to the d e s i r e d a c c u r a c y up to
the maximum range of 12km. L a s e r output is 3040MW peak with up to 1 p u l s e / s e c . The s y s t e m can scan automatically horizontally and v e r t i c a l l y giving range and date print out. The t r a n s m i t t e r / r e c e i v e r head is shown in the photograph. Water vapour and l a r g e p a r t i c l e s such as fly ash and soot can be detected at p r e s e n t and it is hoped to adapt the s y s t e m to m e a s u r e p a r t i c l e size, density and nature (in p a r t i c u l a r to detect sulphurous fumes). To ensure pollution complies with by-laws, the West G e r m a n Ministry of Labour and the Institut ftir E m m i s i o n Schutz have installed a s y s t e m in Duisberg, near Essen. Main c u s t o m e r s are expected to be large industrial establishments wishing to monitor their own pollution output. Cost of the system, including operative t r a i n ing is around £30, 000. L a s e r Associates, PO Box 10, Iver, Bucks. Tel. Slough 27725
Two new additions to the Laser la'i range Laser Associates Limited announce two new equipments uti!ising modular engineering concepts which will ensure compatibility with the systems of the '70s.
,?
{ - 1 0 w a t t C W gAG Laser Systems, 254 Series,
~
~
including intra-cavity Q-switching and frequency-doubling u m t s . ~/~, Application areas include macro" machining, holography, and communications. 10 to 20 PPS Laser Systems, 252 Series, using calcium t u n g s t a t e or YAG
producing up to 1 joule per pulse, or 0.1 joule per pulse when Q-switched. High-efficiency, frequencydoubling units are available. ~'~-'~--~,. Application areas include micro" ~ ) drilling, range /j measurement, :. " / and photochemistry.
Nd-GLASS LASER OF 140 PUI.,SE/SEC 140 p u l s e s / s e c have been achieved with a Q-switched N d - g l a s s l a s e r using a r e c t a n g u l a r N d - g l a s s rod. The r e c t a n g u l a r rod (see illustration) minimizes b i r e f r i n gence and i m p r o v e s the optical distortion caused by t h e r m a l effects. In a r e c t a n g u l a r g l a s s rod the effective thickness for cooling is that of the r o d ' s s m a l l e s t dimension. T h e r m a l gradients in the rod a r e one dimensional r a t h e r than radial, so t h e r m a l l y induced lens power
b
l
Systems for the '70s ? -- talk to
Laser Associates P.O. Box 10, Iver, Buckinghamshire Telephone: Slough 27725
Optics Technology
N o v e m b e r 1969
285