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We produce
OEM quantities of narrow and wide band interference filters,
long and short pass filters, neutral density filters and other
specialty filters. New techniques and processes have been
developed to allow us to offer you beneficial pricing
structures and performance standards that are unmatched in the
optics industry. Sizes may range from a tenth of an inch
square to eight inches in diameter. Standard sizes listed in
this section of our site are ½", 1" and 2"
diameter.
Transmittance
(T)
Also called
"Transmission", this symbol represents the
conductance of radiant energy through the filter medium. It
denotes the percentage of energy transmitted through the
filter medium and is used to describe the filter’s
efficiency within the pass band.
Out-of-Band
Rejection
This is the
degree of transmittance in the out-of-pass band area of the
filters. Usually referred to as "blocking density"
or simply "blocking".
Optical
Density (OD)
This is the
unit of measure used to describe the " blocking
density" of the filter. It can be expressed as 10 to the
power of transmittance. For example, an OD = 4, can be
expressed as 10-4 transmittance, which means that
transmittance peaks in the out-of-pass band do not exceed
0.01%. Formula: OD = log10 (1/T)
Bandwidth (FWHM)
Also called
full-width-half-maximum. This is the width (in nm) of the pass
band between the half-power points of transmittance.
Center
Wavelength (CWL)
This is the
center wavelength of the bandwidth and can be referred to as
the average of the half-power wavelengths.
Dependency
of CWL on Incident Angle
CWL shifts
toward the short wavelength when the incidence angle of the
radiant energy is tilted away from normal incidence. The
following formula may be used to estimate such a shift:
CWL = CWL0
{1-(1/Ne)2sin2 q }0.5
| Where: |
| CWL0
: wavelength at normal incidence |
| CWL
: wavelength at incidence angle |
| Ne
: effective index of the filter |
| q :
incidence angle |
Temperature
Effects
Our filters
are specially formulated to withstand severe temperatures from
-60°C to 70°C with a recommended temperature gradient with
respect to time of 5°C/min. However, an increase in
temperature can still shift the CWL as well as broaden the
FWHM, or vice versa. Contact us for specific temperature
coefficients.
Humidity
Effects
While
humidity does not affect spectral characteristics of filters,
the mechanical strength and lifetime may be deteriorated when
exposed to moisture. We recommend mounting filters in our
black anodized aluminum housings for harsh operating
conditions.
Reliability
Testing Specifications
Surface
Quality: 80/50
Rejection Range: X-ray to Far IR unless otherwise specified
Clear Aperture: > 80% of outside diameter
Size tolerance: +0/-0.5 mm
Thickness: < 6.4 mm
Abrasion: MIL-C-48497, para. 3.4.3.1
Adhesion: MIL-C-48497, para. 3.4.1.1
Cleanability: MIL-C-48497, para. 3.4.2.2
Humidity: MIL-STD-810E, Method 507.3, Procedure III
Band Shape
The shape
of the pass band is a function of the number of cavities
employed (see part number listings). The more cavities used
results in a more rectangular shape, while less cavities
results in a more triangular-like shape of the transmittance
curve.
Warranty
MK
Photonics Inc. warrants all filters to be free from defects in
material or workmanship
for a period of one year after delivery.
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