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FRAUNHOFER INSTITUTE FOR PHOTONIC MICROSYSTEMS IPMS
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1 Ultra compact projection
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LASER PROJECTION MODULE
module.
2 Concept of projection head
with two 1D scanners.
3 LinScan MEMS scanning mirror.
Introduction
to the human eye appears. The scanner
mirrors typically have a diameter of about
Pico-projectors are considered the ultimate
one millimeter and are manufactured
Fraunhofer Institute for
feature of future mobile telephones: Projec-
from micro-crystalline silicon wafers with
Photonic Microsystems IPMS
tors so small that they can be integrated
established processes in cost-effective lots
into the mobile device. At present a projec-
in the Microsystems technology clean room
Maria-Reiche-Str. 2
tion the size of a television screen seems
at Fraunhofer IPMS.
01109 Dresden
possible from a short distance, and HD
resolution is also in demand.
Contact
System architecture
Dr. Michael Scholles
Fraunhofer IPMS has already been active for
Phone +49 351 8823-201
a few years in making customer solutions
The laser projection system consists of
[email protected]
for pico-projectors available. The Institute
the laser sources plus optics, the micro
has been focusing on the principle of
scanning mirror and system electronics
laser beam steering for image generation.
(see block diagram in fig. 3). The laser
Just like a CRT in which an electron ray
beam is collimated and directed onto the
is deflected so that it stimulated one
scanning mirror. Three different mirror
image point after the other to light up,
types are possible which have an influence
one brightness-controlled laser beam (or
on the way the image generated in detail.
three in red, green and blue for full-color
First type are bi-resonant mirrors with
Quality Management
display) is directed so quickly over the
sinusoidal oscillations of the mirror around
We are certified
projection surface by a single miniaturized
two perpendicular axes, a Lissajous figure
Voluntary participation in regular
monitoring according to ISO 9001:2008
scanner mirror that an image cohesive
is projected onto a screen. By carefully
www.ipms.fraunhofer.de
ISO 9001:2008
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laserprojektionsmodul-e
SPI-Flash
DVI-D
Analog
Video
DVI to
RGB
Video Processing
Gdigital
FPGA Implementation
Bdigital
AV to
RGB
RGB
Digital
DAC
DAC
Red Laser
DAC
Green Laser
Blue Laser
QDR-SRAM
Power Unit
12 V
Power
Supply
4
Rdigital
USB
Position Detection
USB 2.0
Mirror
4M x 18
200 V
3.3 V
Position Detection
1.2 V, 1.8 V,
2.5 V, 3.3 V,
5 V
5V
Scandrive-Chip
choosing the frequency ratio for the two
at Fraunhofer IPMS make advanced system
Path to higher resolutions is set by the
axes it can be ensured that the laser beam
parameters (SVGA, i. e. 800 x 600 pixels
new quasi-static scanner concept from
hits every virtual pixel of the image grid
and 60 fps) possible. The control circuit also
Fraunhofer IPMS called LinScan. The basic
overlay of the Lissajous pattern within the
provides SVGA resolution. Support of grey
technology doesn’t have to be changed, so
time available for a given frame rate. By
scales with 8 bit resolution per pixel and
that our customers continue to profit from
synchronous modulation of the laser source
elementary color as well as the correction
the seasoned manufacturing process. It is
and driving of the mirror, arbitrary images
of inhomogeneous illumination caused by
sufficient to tilt the actuator combs toward
can be projected.
the varying beam speed in different parts
each other permanently with a final micro-
of the projection area are integrated in the
assembly step, along with a small modifica-
control unit.
tion of the mechanical design. The Institute
The demonstrators allow a direct connection with any standard analog or digital
was able to show that a combination of
video source, no special software to control
The electronics accepts video data in digital
resonant actuator on the quick horizontal
the projector is required. Necessary adjust-
form via DVI-D as well as analog signals.
axis and LinScan on the slower vertical axis
ments can be made directly.
For backward compatibility with previous
is possible for a two-dimensional scanner
systems also sending data via USB 2.0 from
like those necessary for pico-projectors. The
a PC running a special control application
laser beam can now make targeted jumps
is possible.
from line to line according to an externally
Technical Parameters
configured frequency. Pico-projectors with
The bi-resonant micro mirrors used in full
Figure 1 shows a module for monochrome
a SVGA resolution (800 × 600) and higher
featured laser projection demonstrators
red image projection that comprises the
will be easily practicable.
achieve oscillation amplitudes of about
laser, the micro optics and the micro
10° (fast axis) and 12° (slow axis) at driving
scanning mirror. It has a volume of only
voltage of 70 V and at normal pressure
17 mm x 7 mm x 5 mm. Full color capable
with open-loop control. In order to cope
systems still have larger dimensions.
with long-term environmental changes, a
„„ Image projection
closed-loop operation with position detection is required. Analog signal processing
Applications
Alternative Approaches
is handled by the special Scandrive chip
„„ Rear projection
„„ Laser labeling
that also features generation of voltage
The second type of micro mirrors for laser
pulses for driving the mirror. The oscillation
projection also uses the Lissajous pattern
frequencies of the available micro mirrors
approach. However, instead of using a
of about 1.2 kHz (slow axis) and 28 kHz
single two-dimensional MEMS scanning
(fast axis) allow a resolution of up to 640 x
mirror, the projection head comprises two
480 pixels (VGA resolution) and refresh
1D mirrors. Figure 2 shows a drawing of
rates of up to 50 Hz. Recent developments
the projection head.
„„ Various exposure purposes
4 Block diagram of system
electronics for laser projection
module.