Optical: systems and elements – Diffusing of incident light
Reexamination Certificate
2002-02-01
2003-06-17
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Diffusing of incident light
C359S277000, C359S236000
Reexamination Certificate
active
06580560
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of laser light display projectors and, more particularly, to laser projectors used to project graphic images, patterns and arrays of beams, for entertainment display purposes, and capable of producing multiple projection line widths.
BACKGROUND OF THE INVENTION
Laser projectors used in the field of entertainment display applications typically consist of a laser, a light modulator and a deflector. In some cases, laser projectors may also include a fiber optic cable to allow the laser to be located remotely from the other projector elements and in some cases, laser projectors may also incorporate fixed lenses or other devices to focus and shape the projected laser beam. But in almost every case, laser projectors project a fixed beam diameter that in turn produces a fixed spot size on the target medium. For example, the beam diameter on a projection screen might be 1 centimeter, and no matter what image is being projected, the beam diameter remains at 1 centimeter.
Several approaches have been devised to rapidly change the spot size and shape of a projected laser beam. These approaches are described in U.S. Pat. No. 5,274,492 by Mahmoud Razzaghi and in U.S. Pat. No. 5,621,561 by Robert V. Belfatto et al.
In U.S. Pat. No. 5,274,492, Razzaghi describes one embodiment that uses a piezoelectric bimorph to deform a mirror, and another embodiment that uses secondary sub-scanner. While these approaches seem valid on the surface, there are major obstacles that hinder their implementation.
The use of piezoelectric bimorphs leads to hysteresis in the optical system. If the beam diameter is made large and then small again, there is a residual error caused by the bimorph, which tends to make the beam diameter larger than the input signal would prescribe. Likewise, if the beam is then made large again, the residual error tends to make the beam diameter smaller than the input signal has commanded. To date, only one system, the prototype system, has been manufactured using this method.
In U.S. Pat. No. 5,274,492, Razzaghi describes a second embodiment which includes the use of a subscanner to change the size and shape of the projected laser beam. The use of subscanners can dramatically increase the system cost. What's more, the subscanners have to be extremely fast—capable of scanning in the megahertz range—to prevent the sub-scanned image from actually causing distortion in the main image. Finally, the optical system must be designed very carefully to avoid an effect called optical vignetting. To date, not a single system has been manufactured using this method.
In U.S. Pat. No. 5,621,561, Belfatto et al describes several embodiments that include the use of multiple reflectors, lenses, cubes and other optical elements. In general, all of these embodiments greatly increase system cost and complexity, and due to the relatively large number of optical elements employed, a great deal of time is needed to adjust and align all of these components for proper operation.
There is one thing in common between the one of the approaches taken by Razzaghi and all of the approaches taken by Belfatto et al, and that is the use of optical magnification to change the size and shape of the laser beam. In the case of Razzaghi, optical magnification is produced by changing the shape of a reflective surface. In the case of Belfatto et al, optical magnification is produced by changing the apparent path length between two lenses. Extremely careful alignment is needed in any system which uses optical magnification to change the spot size or shape, to avoid displacing or “scanning” the beam as a result of the magnification. In other words, if the beam does not travel precisely through the center of the optical system, some displacement of the beam will be observed as the system operates.
SUMMARY OF THE INVENTION
With the foregoing in mind, the present invention advantageously provides a laser light beam projector for creating visually perceptible images and capable of changing the shape and size of a light beam so as to alter the image produced. The projector diffuses the laser light beam rapidly, precisely, does so with a minimum of components, and is therefore easily aligned.
The invention discloses a laser light display projector for projecting a beam of laser light so as to produce a light pattern forming a visually perceptible light image. The projector comprises a laser light source generating a substantially parallel light beam; a diffuser positioned so that the light beam passes therethrough prior to forming the visually perceptible display, the diffuser having a diffusion pattern effective for diffusing the light beam by a predetermined amount; a rotary actuator bearing the diffuser to thereby impart a rotating motion to the diffuser so that the diffusion pattern rotatably intersects the light beam; and a controller operatively connected to at least the rotary actuator to control rotational positioning of the diffuser in the light beam. The diffuser may be positioned so that the light beam is incident thereon at a non-perpendicular angle and passes therethrough prior to forming the visually perceptible display, the diffuser having a diffusion pattern effective for diffusing the light beam by a predetermined amount. Additionally, the projector may include at least one reflector positioned adjacent the diffuser to reflect the light beam following a first pass through the diffuser, so as to redirect the light beam toward the diffuser for a second pass therethrough.
A method aspect of the invention includes creating a visual display by diffusing a laser light beam forming a visually perceptible image for a laser light display. The method of the invention comprises energizing a laser light source; generating from the laser light source a laser light beam having substantially parallel light rays; and diffusing the laser light beam prior to forming the visually perceptible image for display by controllably rotating a diffuser intersecting the laser light beam so that the beam passes therethrough, the diffuser having a diffusion pattern effective for diffusing the laser light beam by a predetermined amount responsive to rotation of the diffuser.
REFERENCES:
patent: 3807849 (1974-04-01), Lobb
patent: 5125740 (1992-06-01), Sato et al.
patent: 5695895 (1997-12-01), Johnson et al.
patent: 5851740 (1998-12-01), Sawyer
patent: 6061133 (2000-05-01), Freischlad
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