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ElectroViewer 7215 Frequently Asked Questions
(and their answers)
Can I see an infrared laser beam in “mid-air”
with my ElectroViewer?
It is a misconception that an IR viewer can be used
to view infrared laser beams in “mid-air”. However,
as with the beam from a flashlight, if dust particles
are in the beam path, the beam will become partly
visible. Ordinarily, IR viewers can be used to see
the projection of the infrared beam spot on a flat
diffusing surface such as a white card.
How sensitive is my ElectroViewer?
The minimum detectable signal for a near-infrared
viewer depends upon a large number of factors,
namely: the wavelength of incident radiation (µm),
the power density (density of radiation in µW/cm2
at the faceplate), the effective aperture of the
objective lens, the distance between the spot and
the viewer, the time duration of the signal (pulsed
or continuous), the reflectivity of the diffusing
surface, the sensitivity of the human eye or device
used in viewing the output of the IR viewer.
With detailed information on all these relevant factors and the spectral response characteristic (shown
on the ElectroViewer Technical Data Sheet), the
viewing performance can be precisely calculated.
As an approximation, the following are the minimum power densities required to view an infrared
laser beam from a distance of approximately one
meter: 30µW/cm2 for a 1.06µm laser, 600µW/cm2
for a 1.3µm laser, and 10 mW/cm2 for a 1.5µm laser
diode. Other intermediate values can be estimated
by considering the spectral response characteristic.
cesium-based exhibiting an S1 spectral response
characteristic. However, the improved performance
is due to lower noise levels rather than higher
sensitivity at longer wavelengths.
How does the ElectroViewer 7215 compare
with a CCD camera?
Firstly, it is important to note that the ElectroViewer
7215 is a Viewer and not a video camera. The
image output is not rasterized and can only be
viewed optically; there is no electronic signal
output. (Video output from the 7215 can be
obtained with the use of the video relay lens
adapter, part number 7215-202). Because CCD
cameras utilize silicon-based detectors, certain
models can be used to observe near-infrared
radiation at wavelengths up to about 1.1µm.
However, because these cameras are designed for
optimum performance in the visible wavelength
range, as a result, they exhibit mediocre
performance in the near-infrared range. Image
bleeding, blooming, low sensitivity and low contrast
imaging are some of the observed characteristics.
The ElectroViewer produces significantly better
results for viewing radiation at wavelengths longer
than about 0.75µm.
How much more sensitive is the
ElectroViewer 7215P over the standard
7215?
The Premium extended ElectroViewer is a
“selected” version of the 7215 and exhibits
exceptional performance at longer wavelengths.
In both versions, the photocathode material is
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ElectroViewer 7215 Frequently Asked Questions (continued)
How can I use the ElectroViewer 7215
to align an infrared emitter and detector
separated by a distance?
on a 1/3" CCD camera, the center of the image will
be magnified and no vignetting will appear. Note
that the 7215-202 has been designed for use on
C-mount cameras — not CS-mount. For the use on
the latter, a 5mm spacer will be required.
Since the ElectroViewer 7215 cannot see laser
beams in mid-air, to align a narrow laser beam so
that it illuminates an infrared detector located at
some distance away, we recommend the following
procedure:
Why are there small black spots in the image
of my IR viewer?
Small black spots can be found for several reasons.
Because the image converter tube utilizes high
voltage signals, the front and back face plates very
often attract dust. These can easily be removed
with a cotton swab or lens cleaning cloth. In
addition, because of the manufacturing processes
involved in producing all similar electro-optical
devices, sometimes very small cosmetic blemishes
can actually occur inside the image converter tube.
These black spots do not affect the performance or
reliability of the near-infrared viewer. We select only
those image converters that have blemishes smaller
than the maximum size constraints shown in the
image below. For example, a blemish in the central
part of the image can only be as large as 0.13mm
(<2% of the screen size).
1) Start at the infrared emitter side.
2) Place a white card (such as a white business card)
in the beam path and view the diffuse reflection
of the beam on the card.
3) Follow the beam from the emitter to the detector
by moving the card along the beam path and
viewing the reflection with the ElectroViewer. If
the distance between the emitter and detector
is very far (one mile, for example), it may be
more expedient to begin at the detector and
view the emitter. Although this is a more difficult
alignment procedure, in the latter situation,
moving the emitter will brighten and darken the
beam as viewed at the detector.
Do I need to use eye safety goggles when I
use the ElectroViewer?
ZONE 2
3.4 to 6.8mm
YES. An IR Viewer is not a replacement for eyesafety equipment. It is not designed to withstand
high power laser beams. In fact, the ElectroViewer
has been designed to accommodate the use of
these goggles and still permit a clear view of the
infrared image.
BLEMISH
ZONE 1
<3.4mm
What happens when the 7215-202 CCD relay
lens is used on 2/3" cameras?
The 7215-202 was designed for use on 1/2" format
CCD cameras. If this relay lens is used on a 2/3"
camera, the video image will vignette and show
an infrared image surrounded by a dark circle. The
circle will have a diameter approximately equal to
the picture width (so only the corners of the image
will show dark). If the 7215-202 relay lens is used
7215
7215P
ZONE 1
ZONE 2
<0.13mm
<0.33mm
<0.05mm
<0.10mm
[2]
REGION
POLYTEC GmbH
Tel: +49 (72 43) 60 41 54
Polytec-Platz 1 - 7
Fax: +49 (72 43) 6 99 44
D -76337 Waldbronn
E-Mail: osm@polytec.de
GERMANY
www.polytec.de © 2007 Electrophysics Corp. All Rights Reserved. An ISO 9001:2000 Certified Company UKAS #7096 - ANAB #A060693
Edition: 09-07 EV7215 FAQ
MAXIMUM BLEMISH SIZE CONSTRAINTS
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