Method to reduce RF noise generation and required peak laser output in raster scan portable projectors
View Patent ↗A method and apparatus that projects a two-dimensional image is disclosed. The method may include emitting a laser beam, sweeping the laser beam with a first scan mirror along a first scan direction to form a scan line on the projection surface, and sweeping the scan line with a second scan mirror along a second scan direction generally orthogonal to the first scan direction to form a raster pattern of scan lines on the projection surface. The scanner for the first scan mirror is driven with a stimulus waveform, wherein the stimulus waveform has a fundamental frequency that is substantially equal to the resonance frequency of the scanner but also contains harmonics to achieve a nearly constant velocity of the laser beam spot during its scan across the projection surface. The stimulus thereby reduces peak laser output power and corresponding noise generation while maintaining image brightness and image quality.
1. A method for projecting a two-dimensional image, the method comprising:
emitting at least one laser beam;
sweeping the laser beam with a first scan mirror along a first scan direction to form a scan line on the projection surface, and sweeping the scan line with a second scan mirror along a second scan direction generally orthogonal to the first scan direction to form a raster pattern of scan lines on the projection surface;
driving the scanning means of the first scan mirror with a stimulus waveform, wherein the stimulus waveform has a fundamental frequency that is substantially equal to the resonance frequency of the first scanning means and contains harmonics of that resonance frequency to produce a substantially constant velocity of the swept laser beam on the projection surface along the first scanning direction; and
causing selected pixels to be illuminated, and rendered visible, by the laser beam to produce the image;
wherein the stimulus waveform is a combination of a first waveform and a second waveform and the second waveform is a pulse waveform.
2. The method of claim 1 , the method further comprising:
emitting respective laser beams of different wavelengths, and co-linearly arranging all of the laser beams into a composite beam directed at the first scan mirror.
3. The method of claim 1 , wherein the first waveform is a triangular waveform.
4. An apparatus for projecting a two-dimensional image, the apparatus comprising:
a laser for emitting a laser beam;
a first scan mirror for sweeping the laser beam along a first scan direction to form a scan line on the projection surface, and a second scan mirror for sweeping the scan line along a second scan direction generally orthogonal to the first scan direction to form a raster pattern of scan lines on the projection surface;
a driving circuit for driving a transducer attached to the first scan mirror with a stimulus waveform including harmonics, wherein the stimulus waveform has a fundamental frequency that is substantially equal to the resonance frequency of the transducer, and
a controller for causing selected pixels to be illuminated, and rendered visible, by the laser beam to produce the image;
wherein the stimulus waveform is a combination of a first waveform and a second waveform and the second waveform is a pulse waveform.
5. The apparatus of claim 4 , the apparatus further comprising:
additional lasers for emitting respective laser beams of different wavelengths, and co-linearly arranging all of the laser beams into a composite beam directed at the first scan mirror.
6. The apparatus of claim 4 , wherein the first waveform is a triangular waveform.
7. An electronic device for projecting a two-dimensional image, the apparatus comprising:
a laser for emitting a laser beam;
a first scan mirror for sweeping the laser beam along a first scan direction to form a scan line on the projection surface, and a second scan mirror for sweeping the scan line along a second scan direction generally orthogonal to the first scan direction to form a raster pattern of scan lines on the projection surface;
a driving circuit for driving a transducer attached to the first scan mirror with a stimulus waveform including harmonics, wherein the stimulus waveform has a fundamental frequency that is substantially equal to the resonance frequency of the transducer, and
a controller for causing selected pixels to be illuminated, and rendered visible, by the laser beam to produce the image;
wherein the stimulus waveform is a combination of a first waveform and a second waveform and the second waveform is a pulse waveform.
8. The apparatus of claim 7 , the apparatus further comprising:
additional lasers for emitting respective laser beams of different wavelengths, and co-linearly arranging all of the laser beams into a composite beam directed at the first scan mirror.
9. The apparatus of claim 7 , wherein the first waveform is a triangular waveform.