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Laser module is a device or system
which generates refined beam size, line length or
pattern beam
designed for an industrial and military customer.
Dot, line, cross line beam generators are main products
of Lanics. |
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Monochromatism
:
consisting of a single wavelength or color, and emitted
in a narrow beam. This contrasts with common light sources,
such as the incandescent light bulb or LED which emit
incoherent photons in almost all directions, usually over
a wide spectrum of wavelengths. |
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Coherence
and Interference:
the property of wave-like states that enables them to
exhibit interference. It is also the parameter that quantifies
the quality of the interference (also known as the degree
of coherence). It was originally introduced in connection
with Young’s double-slit experiment in optics but is now
used in any field that involves waves, such as acoustics,
electrical engineering, neuroscience, and quantum physics.
In interference, at least two wave-like entities are combined
and depending on the relative phase between them, they
can add constructively or subtract destructively. The
degree of coherence is equal to the interference visibility,
a measure of how perfectly the waves can cancel due to
destructive interference. Because of coherence, the beam
has good directivity.
High
Energy Density and Brightness :
Due to the coherence and monochcomatism, the laser module
has high energy density and brightness. |
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Collimator
lens collects a diversied beam to collimate and line generator
spread collimated beam to
make a sharp line beam.
Collimator lens to make a dot beam are as listed below.
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| Type |
Lens |
Remark |
| Collimator(for Dot) |
spherical, non-spherical |
Collimation or focusing beam |
| Line Generator |
Deflection lens |
45 degree (short range) |
| Cylinder,Cylindrical
lens |
10,15,30,45,60,90,120 degree |
| Cross Line Generator |
Deflectioon lens |
45degree (short range) |
| Diffraction lens |
5degree (short range) |
| Cylinder,Cylindrical
lens |
10,15,30,45,60,90,120degree |
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Cylinder, cylindrical lens locates after the collimator. |
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LD is an abbreviation
of Laser Diode, and called semiconductor diode.
After conjunction of P-type and N-type semiconductor,
positive bias at P-type and negative bias at
N-type make high energy gap which derives the combination
of holes and electrons to radiate the light.
The light amplified by resonator is a Laser.
LD is a simple PN junction PN semiconductor and the light
is amplified by the polished surface of
light source.LD is very sensitive with current and circuit
must be designed to drive proper
current.
Two types of circuit are currently in common. APC is an
abbreviation of Automatic Power Control.
LD generates laser when the proper current is supplied
to the device in the specified temperature.
If the unstable current causes increase of junction temperature,
the output power decreases, and
hight emperature even break the LD junction. To prevent
and compensate this phenomena circuit
monitors the output power of LD and regulates the current.
ACC is an abbreviation of Automatic Current Control, APC
circuit supplies only specified current
without output power monitoring. ACC is usually applied
to the pulse laser drive. |
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| Picture1 is structure of TO-18 and
TO-5, picture2 shows laser generation of picture1 |
| Type |
Size |
| TO-18 |
5.6파이 |
| TO-5 |
Pie 9 |
| TO-3 |
eclipse |
| HHL |
rectangular |
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Picture1 shows the window glass
under cap and LD chip located on the substrate. To radiates
the
heat, heat sink mounted under submount. Lasing on the
chip is described in the picture2, biased
current generates laser on both side of active layer.
Diffraction casuesd by narrow active layer derives the
beam shape of eclipse with different colunm
length and row length. Laser beam is monitored by internal
photo diode to provide monitoring signal. |
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In LD spec sheet, LD is distinguished
to P and N type. When the case of LD must be connected
to
ground, it is a p-type, vise versa.
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For a thin double convex
lens, all parallel rays will be focused to a point referred
to as the principal
focal point. The distance from the lens to that point
is the principal focal length f of the lens. For a
double concave lens where the rays are diverged, the principal
focal length is the distance at which
the back-projected rays would come together and it is
given a negative sign
If LD is located at the BFL of lens, parallel lay can
be transmitted. However, because of spherical
aberration, different beam divergence angle, and astigmatism
collimation is not easy.
Focus theorem is as picture below |
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With assumption of
parallel beam incident from collimator to cylinder lens,
the beam transmits as
following trace.
Because cylinder lens is spherical at only one side, incident
beam has curvature about only one
axis, which decide length of line beam.
About another axis beam transmit directly, which decide
beam width, line beam can be generated.
Following picture shows the lens shape.
If the incident beam is controlled to focus at the
first surface of the cylinder lens, beam size can
be varied.
Which is how to control the beam width and length
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