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Laser Scanner |
Topics:
Solid State Laser
Principle of Scanning
Galvo Scanner
Closed Loop Scanner
Imaging
Laser Light Show |
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Fast and precise scribing or writing of
information has been a topic since the computer invaded the
market. More and more so called laser printers are replacing the
existing printer technology. Another field of application in
industry is the scribing on objects of mass production. In this
case powerful lasers are used to scribe permanent information
into metal, plastic, paper, etc. Last but not least laser
scanners will be used for the next generations of colour TV,
large displays, and are even used for entertainment in festivals
like the Olympic games and in modern discotheques. To generate
arbitrary patterns the laser beam must be deflected in two
orthogonal directions as it is known from TV or oscilloscopes.
Generally one has to distinguish two main fields of application,
one is the fast material processing and the second is the
entertainment. For the material processing, it is necessary in
almost all cases to focus the laser beam onto the surface to be
processed. With simple lens systems this cannot be achieved
since the location of the foci lies in the plane of a sphere. A
special optical system has been designed to image the focus
always in a plane and is termed as f-θ lens system. For
entertainment like laser light shows, etc. a focusing of the
beam is not required. However, for both applications the same
beam deflectors, so-called Galvo scanners are used. This name
stems from the historical Galvanometer, a moving coil instrument
where a mirror was attached to the torsion band of the coil.
Such instruments were used to demonstrate slow varying electric
currents. The Galvo scanner uses the same principle, however,
they are designed for rapid movement of the attached mirror.
Instead of using a torsion band, electromagnetic forces are
applied. Commercial Galvo scanners are supplied with closed loop
circuits to make sure that the desired position will be reached
with high precision. Within this course, an open frame laser
scanner system with two scanning mirrors, one for the X the
other one for the Y direction including the necessary control
electronics and personal computer are used to become well
experienced in this exciting field of laser application.
Principle of operation
The beam of the laser
(LS) is directed to the first galvo (GX) which mirror is set to
45°. The beam leaves the mirror perpendicular to the incoming
beam and hits the second galvo (GY). The mirror is set in such a
way that the beam leaves the galvo (GY) with an angle of 90° to
the incoming beam. When the galvo GX starts to oscillate, the
output beam is fanned out in a horizontal plane. If the galvo (GY)
would oscillate a beam fan in the vertical plane is generated.
Depending on the input signal of each scanner arbitrary patterns
can be generated. Since the galvo is kept in position by
electromagnetic forces it requires a substantial amount of
electrical power which must be provided by sufficiently designed
power supplies. Professional galvos as also used in this project
are equipped with angular encoders which are part of a closed
loop control system in order to reach the desired movement.
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Required Equipment
| Cat. No. |
Qty. |
Description |
Illustration |
02.0300
02.0500 |
1
1 |
Profile rail OCM 650, 300 mm
profile rail OCM 650, 500 mm
The main components of the experimental systems are the
optical rails OCM 650. They are manufactured
distortion-free and are of thermally stabilized
aluminium. The surface is electro-polished and black
anodized. Because of the precise manufacturing, the
smoothness deviation is less than 25 µm/m and the
deviation of the symmetry axis of the rail is less than
10 µm/m, thus maintaining the optical axis during
displacement of the carrier.
The rail has a dovetail like profile. Gear racks can be
inserted and fixed into the slots.
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05.0234 |
1 |
DIMO Diode
laser module 532 nm (green) incl. adjustment holder and
carrier
As laser source a solid state laser with an output power
of 1 mW at a wavelength of 532 nm is used. The laser is
mounted in an adjustment holder with four degrees of
freedom to align the beam with respect to the optical
axes of a system. The power supply of the laser is
provided with a blanking input.
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07.0224 |
1 |
LSI-01
Power amplifier for galvo scanner
The scanners are connected to the power amplifier with a
flat line terminated on both sides with 9 pin sub D
connectors. To monitor the individual scanner signals,
two BNC connectors are provided at the front panel in
the section “OUTPUTS”. For blanking the laser beam, an
additional output is provided which will be connected to
the power supply of the laser. For this purpose the
cable which is terminated on one side with a mini BNC
connector is used. Finally, the power amplifier is
connected with the supplied 25 pin connection cable to
the scanner controller board which is built into the PC.
This is either supplied as an option or by the user. The
mains switch and connection is located at the rear panel
of the power amplifier.
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09.0282 |
1 |
XY Galvo scanner mounted on optical rails
Two closed loop galvo scanners are mounted into a double
cube which is supplied with a T - piece carrier to be
placed onto the optical rail system OCM650. Each galvo
has an angle range of 15° that means 30° optical
deflection range. In a distance of 1 m, a scan area of
536 mm x 536 mm can be covered. For the generation of
the electronically driver signals, the power amplifier
LSI-01 (07.0224) is needed.
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09.0284 |
1 |
F-theta lens system incl. holder
A f-theta lens forms a special arrangement of multiple
lenses in order to image the focus of an incident laser
beam always in a flat instead of a curved field. Its
application is found in laser material processing in
conjunction with scanning mirrors. In this case, the
beam enters the systems under different angles, however,
requiring that the focus of the laser beam always lies
on a flat surface.
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10.0280
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1 |
EXP 28 manual |
No illustration |
19.1130 |
1 |
PCI Scanner control
board and laser light show software
For the creation of patterns to be displayed by the
laser beam this hardware and software is needed. The
created patterns are submitted to the scanners in real
time. By means of this software, laser light shows as
well as structures for material processing can be
generated and performed by the scanner. A library with
existing show effects is part of the software. The
generated patterns will be transferred as electrical X
and Y signals via the PCI scanner control board to the
power amplifier LSI-01 (07.0224).
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No illustration |
Required Options
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19.1000 |
1 |
IBM compatible PC, incl. VGA monitor and keyboard
For some experiments a PC is a must whereas others can
operate without one. However, some nice features may be
not accessible. Due to the steadily changing models and
operating systems a picture is not given. Please ask for
current models.
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No
illustration |
Options
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09.0289 |
1 |
Set of spare parts
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No
illustration |
19.0140 |
1 |
Dual trace oscilloscope 100 MHz
Features:
Frequency Range: 150 kHz ~ 100MHz
Fully Digital Phase Locked Loop Technique Design
High Frequency Stability: ±10ppm
High Input Protection Level: +30dBm, ±25VDC
Reference Level Range: -30dBm ~ +20dBm
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