Illumination – Light source and modifier – Adjustable or repositionable light source or light source...
Reexamination Certificate
1998-11-17
2001-07-10
Quach, Y. (Department: 2875)
Illumination
Light source and modifier
Adjustable or repositionable light source or light source...
C362S259000
Reexamination Certificate
active
06257739
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates generally to the field of optical imaging, and more particularly to optical scanning for high resolution, full width page scan, xerographic printing applications.
Xerographic exposure systems are important for printing. In xerographic printing, lasers or LEDS may be used to expose tiny dots on a photoreceptor surface. The photoreceptor has the property of holding an electrical charge in the absence of light. Illumination of a spot on the photoreceptor by a laser or LED causes the loss of charge at the exposed spot. In a typical xerographic system, charge left on the photoreceptor attracts toner that is then transferred to paper which has a greater charge than the photoreceptor.
Desirable features for xerographic exposure printing systems include full page-width printing, high resolution addressability, elimination of moving mechanical parts, and low power consumption. These features are important for achieving performance comparable to offset lithography and occupy a parameter space that lies beyond the speed and width capabilities of polygon raster output scanning (ROS) print engines. Polygon ROS printers typically consist of a laser light source, a polygon scanning beam deflector, an optical system of lenses and mirrors, a xerographic marking engine and the electronics to control the printer operation.
Solid state semiconductor light emitters are important devices in such diverse applications such as optoelectronic communication systems and high-speed printing systems. It is well-known in the proven art of silicon to provide suspension and actuation schemes, for example, comb drives using bending springs or parallel plate actuation using torsion springs. For optical beam steering applications, these silicon steering elements are typically combined with a light source in a separate package, or even with a light source ‘glued’ or bonded onto the silicon steering chip.
U.S. Pat. Nos. 5,536,988, 5,640,133, 5,025,346, “Fabrication of Submicron High-Aspect-Ratio GaAs Actuators” Zhang et al., Journal of Microelectromechanical Systems Vol. 2, No.2, p. 66-73, June 1993, “Laterally Driven Polysilicon Resonant Microstructuren” Tang et al., IEEE Micro Electro Mechanical Systems pp. 53-59, February 1989 (reprint), “Electrostatic-comb Drive of Lateral Polysilicon Resonators” Tang et al., Transducers '89, Proceedings of the 5th International Conference on Solid-State Sensors and Acutators and Eurosensors III, Vol. 2, pp. 328-331, June 1990 (reprint) and “Comb-drive actuators for large displacements”, Legtenberg et al., Journal of Micromechanics and Microengineering, Vol. 6, pp.320-329, 1996 show the state of the art of micro-electromechanical systems (MEMS) actuators and methods of fabricating these devices. U.S. Pat. Nos. 5,747,366 and 5,719,891 show the state of the art of semiconductor light emitting assemblies.
U.S. patent application Ser. No. 08/761,681, entitled “Raster Output Scanner with Pivotal Mirror for Process Direction Light Spot Position Control” filed on Dec. 6, 1996 and assigned to the same assignee as the present invention teaches a MEMS torsional control device.
U.S. patent application Ser. No. 08/940,867, entitled “Highly compact Vertical Cavity Surface Emitting Lasers” filed on Sep. 30, 1997 and assigned to the same assignee as the present invention teaches the formation of highly compact and well-defined VCSELs.
All of the above references are hereby incorporated by reference.
SUMMARY OF INVENTION
In accordance with this invention, a solid state scanning imager is used to replace the polygon ROS used in optical display and printing applications. A VCSEL shuttle having a large movable stage carrying hundreds of scanning vertical cavity surface emitting lasers (VCSELs) is suspended by mechanical beams. Pairs of comb-drive structures are used to electrostatically actuate the movable stage. One set of comb-drive fingers (fixed fingers) is attached to the stationary mechanical beams while another set of comb-drive fingers (movable fingers) is attached to the movable stage. Alternating application of a bias voltage to selected fixed fingers causes the movable stage to travel back and forth in a scanning motion. The comb-drive structures need to possess enough flexibility to allow the movable stage to move sufficiently to allow scanning over half of the pitch of the VCSEL array.
The VCSEL shuttle is typically fabricated using III-V micromachining technology. This allows in situ manufacturing of III-V based light emitters which have highly desirable optical properties. For example, VCSELs can be made in the movable stage material as opposed to being attached separately. Undoped III-V material is used for the substrate for better enabling the electrical isolation of different parts of the VCSEL shuttle.
REFERENCES:
patent: 5025346 (1991-06-01), Tang et al.
patent: 5536988 (1996-07-01), Zhang et al.
patent: 5628917 (1997-05-01), MacDonald et al.
patent: 5640133 (1997-06-01), MacDonald et al.
patent: 5719891 (1998-02-01), Jewell
patent: 5747366 (1998-05-01), Brillouet et al.
patent: 5764671 (1998-06-01), Lebby et al.
Judy, M. W. “Micromechanisms Using Sidewall Beams.” PhD Dissertation Faculty of Electrical Engineering and Computer Sciences, University of California, Berkley, CA. 1994, pp. 1-215.
Legtenberg, R. et al. “Comb-drive actuators for large displacements.”J. Micromech. Microeng.vol. 6, 1996, Printed in the UK, pp. 320-329.
Tang, W.C.; Nguyen, T.H.; Judy, M.W.; Howe, R.W. “Electrostatic-comb Drive of Lateral Polysilicon Resonators”,Transducers '89: Proceedings of the 5thInternational Conference on Solid-State Sensors and Actuators and Eurosensors III, vol. 2, Jun., 1990, pp. 194-197.
Tang, W.C.; Nguyen, T.H.; Howe, R.T. “Laterally Driven Polysilicon Resonant Microstructures”,Proceedings IEEE Micro Electro Mechanical Systems, Feb., 1989, pp. 187-193.
Zhang, Z.L.; MacDonald, N.C. “Fabrication of Submicron High-Aspect-Ratio GaAs Actuators”,Journal of Microelectromechanical Systems, vol. 2, No. 3, Jun., 1993, pp. 66-73.
U.S. application No. 08/761,681, entitled “Raster Output Scanner with Pivotal Mirror for Process Direction Light Spot Position Control” filed on Dec. 6, 1996.
U.S. application No. 08/940,867, entitled “Highly Compact Vertical Cavity Surface Emitting Lasers” filed Sep. 30, 1997.
Sun Decai
Tran Alex T.
Krause-Pozstorfe J.
Quach Y.
Robb Linda M.
Xerox Corporation
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