CCTV Lens
If there is one sector in which the rapid pace of change in the
security sector is reflected, it is lens technology. Let’s take a look at the
marketplace, current trends and likely developments of CCTV lens techonology.
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By David Craig
More and more integrators and
end-users are looking for long range varifocal lenses as an economic alternative
to zoom lenses. And the concern with
costs means that more and more companies and public bodies are turning to
varifocals for surveillance of large areas.
Some of the products are already in place to meet this change in demand
while others are being developed. It was
not so long ago that a varifocal lens with a focal length of 5-50mm was
acceptable, now integrators are looking for 20-100mm and 20-120mm.
ZOOMS VS. SPEED DOMES
Another growth area is the
motorized zoom lens market which has seen demand increase with heightened
concern over border security after terrorist outrages.
Particular attention is being paid
to infrastructure projects and Rainbow’s own 10-100mm motorized zoom units are
being used by Tyco Integrated Systems on motorways throughout the
Netherlands. Tyco have also used Rainbow
lenses at the port of Dover, one of the points of entry in Europe.
Despite the burgeoning of speed
domes, certain users continue to see the advantages of long-range zoom lenses
although speed domes will remain popular.
This is because of their all-in-one nature and suitability for many
indoor and outdoor locations such as shopping malls and town centres.
But a perennial disadvantage of the
lenses used in speed domes is they are not fast and do not give good results in
low-light conditions when compared with a traditional zoom lens. And yet their ease of installation and
generally acceptable performance have grabbed significant market share
particularly in any environment which is well lit.
Despite the success of speed domes,
there remains a need to service applications requiring high quality images even
in low light. And on such projects the
optimum solution is often traditional zoom lenses or high quality varifocals
that offer equivalent functionality.
There is growing interest in
varifocals but also a spate of high-level enquires about motorized zoom lenses,
a product group for which the number of quality manufacturers is now
limited. This market trend is attributed
to increasingly rigorous surveillance of the infrastructure where performance is
of the highest priority and users expect this to come at a premium.
Environments where there is a need
for quality performance even in low light and sometimes across vast areas
include airport perimeters together with air, naval and military bases. Mobile surveillance vehicles -- often used to
protect politicians and heads of state -- are another niche sector where the
application of zoom lenses is essential.
Integrators are now frequently
asked to work on applications where security staff at ports need quality
long-range images of vessels early in their approach to the harbour. Timely images mean that any likely security
threat can be better evaluated.
Naturally such images have general logistical value and harbour masters
can use them to decide if known vessels are experiencing difficulty in extreme
weather.
CONVERGING TECHNOLOGIES
Many technologies are converging to
improve airport and harbour security and it is increasingly common for
integrators to be asked to incorporate thermal imaging technology into their
solutions. The sophistication of these
systems is such that thermal imaging can now tell whether an individual on the
deck of an approaching vessel is carrying a gun or a fishing rod.
THE VARIFOCAL MARKET
The varifocal market is moving
towards longer-range models. It remains
a price-sensitive sector particular across common focal ranges. To stay ahead, reputable companies with
trusted products and active R&D departments need to offer standard items but
also present high quality products for niche areas, perhaps concentrating on an
unusual focal length or the suitability of lenses for demanding
environments. And yet it would be a
naive manufacturer who did not expect to compete on price as well.
Playing the price game is
inescapable but high-end units are less price sensitive and manufacturer,
integrator and end-user can work together constructively.
It is projects such as the use of
Rainbow’s lenses on the Dutch motorway network which underline general
trends. Here, Tyco Integrated Systems
chose the 10-100mm motorized zoom model and employed it as part of pan&tilt
assemblies on purpose-built CCTV poles, gantries and bridges at junctions in
areas including Amsterdam, Utrecht, Rotterdam and The Hague. It is this kind of usage which renders zoom
lenses a viable product for manufacture despite the popularity of speed domes.
CHOICE OF LENS: THE CRITERIA
When selecting a lens, customers
should look at the immediate starting points which include field of view,
desired area of coverage and the amount and nature of ambient light. Normally a large telephoto lens will produce
a dark picture at night or in low lighting so there can be some delicate
trade-offs making for awkward decisions.
A zoom with a large focal length
may not perform well at night but at a site where observation is performed
during the day and movement after nightfall is an exception then such a zoom may
be acceptable. If daytime surveillance
is of prime importance a client might opt for a lens that is compact but still
has a large focal length. This fits into
standard housings and can be a boon to integrators since it will operate in
locations where it would not be feasible to deploy a large zoom. For low-light applications customers have the
option of using Rainbow’s 10-250mm lens.
The lens is larger and more expensive than the 15-300 but this is the
trade-off for good performance when light is poor.
IR SHIFT AND ITS IMPLICATIONS
The issue of night-time performance
is important to integrators as they make more use of IR illumination. But such illumination brings with it the
complication of IR shift, the difference in focal points for a lens under white
and IR lighting.
Rainbow is an acknowledged leader
in the manufacture of day-night lenses which correct this shift, making both
visible and IR rays focus on the same point and so eliminating the need for
adjustment.
It is Rainbow’s experience that
operators and end users are never slow to tell integrators and manufacturers
that the more they zoom in on an object the more IR shift becomes noticeable.
Locations requiring continuous day
and night observation of objects that are 50 feet or more away are particularly
fraught since the greater the zoom factor the more depth of focus goes
down. At night when the iris is
generally sitting wide open you are already at your worst depth of focus.
This is why IR shift becomes more
pronounced and why Rainbow impresses on customers that it is critical to invest
in high quality day-night lenses for applications using IR illumination. If the application requires observation 24
hours a day and relies on IR rather than street lighting or floodlights, then a
day-night lens becomes a must.
In the past clients were often
asked to specify whether day or night-time images were more important and were
then expected to settle for an unfocused image for part of the day. Few will
accept this now.
Of course focus shift is not so
important in a motorised zoom that is manned all the time since the operator can
simply refocus. But with the popularity
of remote observation and automated intelligent scene analysis such usage is
becoming rare. Similarly, an application
that uses pre-sets will normally need a day-night lens since images during IR
illumination employing a pre-set chosen in daylight are bound to be blurred.
COST SAVINGS
Judicious use of day-night lenses
should produce cost savings for customers.
Applications with a color camera set up for daytime viewing and a
separate black and white unit with the lens focused under IR to compensate for
the shift, are cumbersome in the extreme and can be wasteful in their use of
space. And of course there is the
expense and logistical consequences of switching circuitry.
The advantages of IR lenses extend
to integrators who can make more effective use of the client’s budget. Additionally, they no longer have to find a
reason for explaining why lenses go out of focus when IR lighting kicks in. While clients may initially balk at the extra
cost of a day-night lens, the economies associated with being able to use a
single camera soon win the day. The user
knows he is going to get a focused picture 24/7 and nobody has to climb up poles
to make adjustments.
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