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Indispensable Tool for Materials Analysis
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Confocal Laser Scanning Microscopy (CLSM) is a optical 3-dimensional (3D) surface profiler
with a high-resolution. With a high numerical aperture objective lens (up to 0.95) and a shorter
wavelength laser provide a high-resolution imaging along both the optical and transverse
direction. A confocal pinhole also improves the imaging quality by rejecting the noise outside
the focal point. Real time imaging is achieved by a fast scanning module and a signal
processing algorithm. It takes less than 1 second to get the 3D surface profile of the sample.
CLSM is a non-destructive high-resolution optical 3D surface profiler for the micro-structure.
It is an ideal solution to measure and inspect the semiconductor wafers, FPD products,
MEMS devices, glass surfaces, and material surfaces.
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The height measuring ability comes from the
confocal setup of a source, a sample, and a
detector. When the sample is located in the
focal plane of the objective lens, the light
reflected at the surface of the sample is
focused at the confocal aperture thus the photo
detector collects the signal from the sample.
However the sample is placed in the out-of-
focus position, the light signal is rejected by
the confocl aperture. Thus only the in-focus
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signal is collected by the photo detector. It
gives the optical sectioning ability to the
CLSM.
To get the 3D surface profile of the sample,
optical sections are collected through the z-
axis. Due to the confocal aperture, the light
intensity is maximum when the sample is
placed in the focal plane. |
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Maximum intensity is detected at the focal
plane. The intensity decreases when the
sample is away from the focal plane. To find
the maximum intensity precisely, multi-points
near the maximum position are used for the
curve fitting. This provides high repeatability on
measuring the height. The height is calculated
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by the curve fitting at every pixel. This height map shows the surface profile of the sample.
A CLSM has many applications in the industrial fields since it is fast, nondestructive, and
reliable 3D surface profiler. It can measure 3D shape, step height and volume of the micro
structures. The LCD panels, semiconductor wafers, MEMS devices, material surfaces, and
even transparent glass surfaces can be measured and inspected. Moreover, a CLSM is
widely used for the biological researches. With a fluorescent die it can get a clear image of
biological specimens from its own nature. 3D structure and dynamics of the cells also can be
measured. Since a CLSM can observe the tissues under the skin it is applied to skin cancer
detection. Recently, confocal endoscope system has been introduced for the sub-micron
gastrointestinal examinations.
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