CCTV Lens
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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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