Spectrophotometers For Coaters
Optical Monitoring Systems
Thin Film Calculation Software
LINZA 150 LENS MEASUREMENT SPECTROPHOTOMER
APPLICATION NOTES
Measurement of Short‐Throw Mini Objectives
Using The LINZA 150 Lens Measurement Spectrophotometer
Introduction
Modern optical devices consist of lenses having
different and often extreme specifications. Lenses
are designed in a wide range of sizes and optical
characteristics which bring about a set of
characterization challenges. Measurement of the
optical characteristics of each lens is not possible in
most cases. So traditionally witness samples are
used as a reference instead. Coating engineers place
them on the calotte in the vacuum chamber
together with the coated lenses. Measurement of
the lens objectives is even a more challenging task.
This Application Note illustrates the practical
example of transmittance measurement of the
short‐throw mini objectives using the
LINZA 150
Lens Measurement Spectrophotometer.
Project Description
For one of our
customers
it
was necessary to
measure transmittance
of three objectives
with the
following characteristics:
Focal length: 12mm
Clear aperture: 9 mm
Overall length of objective: 22 mm
Number of objectives: 3 pcs
.
LINZA 150 spectrophotometers allow measuring
transmittance and reflectance on lenses. The
instrument can generate transmittance and
reflectance data for a wide range of focal lengths
(from ‐20 mm to ∞ and from +20 mm to ∞) and
clear apertures of lenses (starting from 8 mm).
However, the present case is a special one because
the extremely small focal length and clear aperture
of the objective lead to inability to guide all
transmitted illumination to the detector inside the
measurement channel of the instrument.
Solution
The experts at EssentOptics came up with an idea to
measure objectives in pairs. However, the paired
objectives
shall
be
arranged
in
the
spectrophotometer as an afocal system (Fig. 1):
Fig. 1. Afocal optical system
This solution ensures that all illumination
transmitted through paired objectives will be
collimated and will also enter the detector without
losses. Based on the available design specifications
of the objectives we determined the required
distance
between
objectives.
Next,
three
transmittance measurements of three pairs of the
objectives were taken: T(1‐2), T(2‐3) and T(1‐3). The
measurement results are shown below.
Fig.2. Spectral transmittance of three pairs of mini
objectives
The obtained measurements of the paired objectives
represent the classical system of three equations
with three unknowns. The solution of this system of
the equations does not present any problem and
allows to accurately determine the transmittance of
each separate objective (Fig.3):
Fig.3. Actual spectral transmittance of individual short‐
throw mini‐objectives.
Conclusion
We demonstrated a possibility to measure spectral
transmittance of the short‐through mini‐objectives
using
the
LINZA
150
Lens
Measurement
Spectrophotometers. The obtained measurement
results allow to precisely determine the optical
characteristics of each objective and compare the
data with the initial product specifications.
About EssentOptics
EssentOptics Ltd
is a leading
producer
of the test and
measurement instrumentation for optics and
photonics industry. Our products are widely used by
coating experts and cover the following applications:
PHOTON RT UV‐VIS‐MWIR spectrophotometer
f
or
measurement of the transmittance and
absolute specular reflectance
of the planar
optical components
at variable angles of
incidence and polarizations;
LINZA 150
UV‐VIS‐SWIR Lens Measurement
Spectrophotometer
for
transmittance
and
reflectance measurement
of the
spherical optics
and lens objectives;
IRIS and AKRA broadband optical monitoring
systems for accurate
supervision of thin film
deposition processes.
Find out more about EssentOptics:
www.essentoptics.com