RGB lasers for laser projection displays - Crystech

0.1
0.2
Efficiency "Blue"
0.3
0.4
0.5
0.6
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
Efficiency "Red"
Fig. 11 IR laser power for specified RGB output in dependence of efficiencies of SFM processes
for OPO efficiency of 45 %
7. MODULATION UNIT
The modulation of RGB light is realized by acusto-optical modulators (AOM) instead of previously used electro-optical
modulators (EOM). A very high contrast ratio of better than 1:1,000 (EOM: < 1:500), a small modulation voltage of
about
1 V (EOM: 200 V), small dimensions of about 10 cm 3 only (EOM: 50 cm 3 ) and easier alignment are the advantages of
AOM over EOM. The AOM has a carrier frequency of 180 MHz and a diffraction efficiency of 75 %. The red, green
and blue beams are modulated with a maximum frequency of 32 MHz. Fig. 12 shows the modulation unit which
includes the AOMs, the white light balancing, an active angle and position stabilization system of the three beams
and the fiber coupling optics.
Fig. 12 Modulation unit with dimensions of 300 x 500 mm²
40
20
0
120
100
80
60
180
160
140
Power/W
160-180
140-160
120-140
100-120
80-100
60-80
40-60
20-40
0-20