Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/54—Accessories
  • G03B21/56—Projection screens
  • G03B21/60—Projection screens characterised by the nature of the surface
  • G03B21/62—Translucent screens
  • G03B21/625—Lenticular translucent screens
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/10—Projectors with built-in or built-on screen
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/14—Details
  • G03B21/20—Lamp housings
  • G03B21/2006—Lamp housings characterised by the light source
  • G03B21/2033—LED or laser light sources
  • G03B21/204—LED or laser light sources using secondary light emission, e.g. luminescence or fluorescence
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N9/00—Details of colour television systems
  • H04N9/12—Picture reproducers
  • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
  • H04N9/3129—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] scanning a light beam on the display screen

Definitions

• the present invention generally relates to projecting a two-dimensional image in color on a rear projection screen while maintaining low power consumption, high resolution, miniature compact size, quiet operation and minimal vibration.
• VGA video-graphics-array
• Another object of this invention is to minimize power consumption, cost and complexity in such projection systems by not utilizing green lasers and their associated circuitry.
• Still another object of this invention is to increase the resolution of the color image projected by such systems. - -
• Yet another object of this invention is to eliminate the use of green lasers in such systems.
• An additional object of this invention is to provide a novel screen on which full color images are visible.
• An additional object is to provide a miniature, compact, lightweight, and portable color image projection system useful in many instruments of different form factors.
• an image projection system for projecting a two-dimensional, color image.
• the arrangement includes a proj ection screen; a plurality of red, blue and violet lasers for respectively emitting red, blue and violet laser beams; an optical assembly for forming a composite beam of the red, blue and violet beams; a scanner for sweeping the composite beam as a pattern of scan lines across the screen, each scan line having a number of pixels; and a controller for causing selected pixels to be illuminated, and rendered visible, by the composite beam to produce the color image.
• a phosphor in the projection screen is provided for converting the violet beam to a green laser beam to produce the image in red, blue and green colors.
• the scanner includes a pair of oscillatable scan mirrors for sweeping the composite beam along generally mutually orthogonal directions at different scan rates and at different scan angles. At least one of the scan rates exceeds audible frequencies, for example, over 18 kHz, to reduce noise. At least one of the scan mirrors is driven by an inertial drive to minimize power consumption.
• the image resolution preferably exceeds one-fourth of VGA quality, but typically equals or exceeds VGA quality.
• the lasers, scanner, controller and optical assembly preferably occupy a volume of less than seventy cubic centimeters.
• the projection screen includes a collimating lens, for example, a Fresnel lens, for collimating the red, blue and violet beams into parallel light rays; a lenticular lens array having a plurality of lenses for focusing the parallel light rays at a focusing plane; and a mask having a plurality of apertures at the focusing plane, each of the apertures being filled with the phosphor which is operative for transmitting incident red and blue beams therethrough, but for converting the incident violet beam into a green beam, thereby enabling a red, blue and green (RBG) image to be displayed on the screen.
• a plurality of lenslets is provided, one for each aperture of the mask.
• FIG. 1 is a diagrammatic view of a system for projecting an image on a rear projection screen in accordance with this invention
• FIG. 2 is an enlarged, overhead, perspective view of an image projection arrangement in accordance with this invention for installation in the system of FIG. 1 ;
• FIG. 3 is a top plan view of the arrangement of FIG. 2;
• FIG. 4 is a perspective front view of an inertial drive for use in the arrangement of FIG. 2;
• FIG. 5 is a perspective rear view of the inertial drive of FIG. 4;
• FIG. 6 is a perspective view of a practical implementation of the arrangement of FIG. 2;
• FIG. 7 is an electrical schematic block diagram depicting operation of the arrangement of FIG. 2;
• FIG. 8 is a sectional view of the proj ection screen on which the image is proj ected;
• FIG. 9 is a perspective view of the screen of FIG. 8;
• FIG. 10 is a broken-away sectional view of a detail of the projection screen of FIG. 8 in accordance with one embodiment of this invention.
• FIG. 11 is a view analogous to FIG. 10, but of another embodiment of the projection screen.
• Reference numeral 10 in FIG. 1 generally identifies a housing in which a lightweight, compact, image projection arrangement 20, as shown in FIG. 2, is mounted and operative for projecting a composite beam onto a stationary rear mirror 12 for reflection therefrom onto a rear projection screen comprising a collimating lens 14, a lenticular lens array 16, and an apertured mask 18, whose structure and function are described below in connection with FIGS. 8-12.
• An observer in front of the screen sees a two-dimensional, red, blue and green color image thereon, as described below.
• the arrangement 20 includes a solid-state, preferably a semiconductor laser 22 which, when energized, emits a bright red laser beam 58 at about 630- 675 nanometers.
• Lens 24 is a biaspheric convex lens having a positive focal length and is operative for collecting virtually all the energy in the red beam and for producing a diffraction- limited beam.
• Lens 26 is a concave lens having a negative focal length. Lenses 24, 26 are held by non-illustrated respective lens holders apart on a support (not illustrated in FIG.2 for clarity). The lenses 24, 26 focus the red beam onto the screen.
• Another solid-state, semiconductor laser 28 is mounted on the support and, when energized, emits a diffraction-limited blue laser beam 56 at about 435-490 nanometers.
• Another biaspheric convex lens 30 and a concave lens 32 are employed to focus the blue beam on the screen in a manner analogous to lenses 24, 26.
• Still another solid-state, semiconductor laser 34 is mounted on the support and, when energized, emits a diffraction-limited violet laser beam 40 having a wavelength preferably on the order of 400-415 nanometers. For some applications, shorter wavelengths on the order of 350-370 nanometers may be preferable.
• Still another biaspheric convex lens 44 and a concave lens 46 are employed to focus the violet beam 40 on the screen in a manner analogous to lenses 24, 26.
• the violet laser instead of a green laser, is eventually used to generate a green beam, as described below, to create a full color, red, blue and green (RBG) image for viewing.
• the arrangement includes a pair of dichroic filters 52, 54 arranged to make the violet, blue and red beams substantially co-linear before reaching a scanning assembly 60.
• Filter 52 allows the violet beam 40 to pass therethrough, but the blue beam 56 from the blue laser 28 is reflected by the interference effect.
• Filter 54 allows the violet and blue beams 40, 56 to pass therethrough, but the red beam 58 from the red laser 22 is reflected by the interference effect.
• the substantially co-linear beams 40, 56, 58 are directed as a composite beam to, and reflected off, a stationary bounce mirror 62.
• the scanning assembly 60 includes a first scan mirror 64 oscillatable by an inertial drive 66 (shown in isolation in FIGS. 4-5) at a first scan rate to sweep the composite beam reflected off the bounce mirror 62 over a horizontal scan angle, and a second scan mirror 68 oscillatable by an electromagnetic drive 70 at a second scan rate to sweep the composite beam reflected off the first scan mirror 64 over a vertical scan angle.
• the scan mirrors 64, 68 can be replaced by a single two-axis mirror.
• the inertial drive 66 is a high-speed, low electrical power-consuming component. Details of the inertial drive can be found in U.S. Patent Application Serial No. 10/387,878, filed March 13, 2003, assigned to the same assignee as the instant application, and incorporated herein by reference thereto.
• the use of the inertial drive reduces power consumption of the scanning assembly 60 to less than one watt and, in the case of projecting a color image, as described below, to less than ten watts.
• the drive 66 includes a movable frame 74 for supporting the scan mirror 64 by means of a hinge that includes a pair of co-linear hinge portions 76, 78 extending along a hinge axis and connected between opposite regions of the scan mirror 64 and opposite regions of the frame.
• the frame 74 need not surround the scan mirror 64, as shown.
• the frame, hinge portions and scan mirror are fabricated of a one-piece, generally planar, silicon substrate which is approximately 15 O ⁇ thick.
• the silicon is etched to form omega- shaped slots having upper parallel slot sections, lower parallel slot sections, and U-shaped central slot sections.
• the scan mirror 64 preferably has an oval shape and is free to move in the slot sections.
• the dimensions along the axes of the oval-shaped scan mirror measure 749 ⁇ x 1600 ⁇ .
• Each hinge portion measure 27 ⁇ in width and 1130 ⁇ in length.
• the frame has a rectangular shape measuring 31 OO ⁇ in width and 4600 ⁇ in length.
• the inertial drive is mounted on a generally planar, printed circuit board 80 and is operative for directly moving the frame and, by inertia, for indirectly oscillating the scan mirror 64 about the hinge axis.
• One embodiment of the inertial drive includes a pair of piezoelectric transducers 82, 84 extending perpendicularly of the board 80 and into contact with spaced apart portions of the frame 74 at either side of hinge portion 76.
• An adhesive may be used to insure a permanent contact between one end of each transducer and each frame portion.
• the opposite end of each transducer projects out of the rear of the board 80 and is electrically connected by wires 86, 88 to a periodic alternating voltage source (not shown).
• the periodic signal applies aperiodic drive voltage to each transducer and causes the respective transducer to alte ⁇ iatingly extend and contract in length.
• transducer 82 extends
• transducer 84 contracts, and vice versa, thereby simultaneously pushing and pulling the spaced apart frame portions and causing the frame to twist about the hinge axis.
• the drive voltage has a frequency corresponding to the resonant frequency of the scan mirror.
• the scan mirror is moved from its initial rest position until it also oscillates about the hinge axis at the resonant frequency.
• the frame and the scan mirror are about 150 ⁇ thick, and the scan mirror has a high Q factor. A movement on the order of I ⁇ by each transducer can cause oscillation of the scan mirror at scan rates in excess of 20 kHz.
• Transducers 90, 92 extends perpendicularly of the board 80 and into permanent contact with spaced apart portions of the frame 74 at either side of hinge portion 78.
• Transducers 90, 92 serve as feedback devices to monitor the oscillating movement of the frame and to generate and conduct electrical feedback signals along wires 94, 96 to a feedback control circuit (not shown).
• the electromagnetic drive 70 includes a permanent magnet jointly mounted on and behind the second scan mirror 68, and an electromagnetic coil 72 operative for generating a periodic magnetic field in response to receiving a periodic drive signal.
• the coil 72 is adjacent the magnet so that the periodic field magnetically interacts with the permanent field of the magnet and causes the magnet and, in turn, the second scan mirror 68 to oscillate.
• the inertial drive 66 oscillates the scan mirror 64 at a high speed at a scan rate preferably greater than 5 kHz and, more particularly, on the order of 18 IcHz or more. This high scan rate is at an inaudible frequency, thereby minimizing noise and vibration.
• the electromagnetic drive 70 oscillates the scan mirror 68 at a slower scan rate on the order of 40 Hz which is fast enough to allow the image to persist on a human eye retina without excessive flicker.
• the faster mirror 64 sweeps a horizontal scan line
• the slower mirror 68 sweeps the horizontal scan line vertically, thereby creating a raster pattern which is a grid or sequence of roughly parallel scan lines from which the image is constructed.
• Each scan line has a number of pixels.
• the image resolution is preferably XGA quality of 1024 x 768 pixels. Over a limited working range, a high-definition television standard of 72Op, 1270 x 720 pixels can be displayed. In some applications, a one-half VGA quality of 320 x 480 pixels, or one-fourth VGA quality of 320 x 240 pixels, is sufficient. At minimum, a resolution of 160 x 160 pixels is desired.
• mirror 64 can be reversed so that mirror 68 is the faster, and miiTor 64 is the slower.
• Mirror 64 can also be designed to sweep the vertical scan line, in which event, mirror 68 would sweep the horizontal scan line.
• the inertial drive can be used to drive the mirror 68. Indeed, either mirror can be driven by an electromechanical, electrical, -mechanical, electrostatic, magnetic, or electromagnetic drive.
• the slower mirror is preferably moved at a constant velocity during the time that the image is displayed. During return of the mirror, the mirror moves at the significantly higher velocity of its resonant frequency, and the lasers are powered down in order to reduce power consumption.
• FIG.6 is a practical implementation of the arrangement 20 in the same perspective as that of FIG. 2.
• the aforementioned components are mounted on a support or chassis 100 and define an optical path 102.
• Holders 106, 108, 110, 112 respectively hold folding mirror 48, filters 52, 54 and bounce mirror 62 in mutual alignment.
• Each holder has a plurality of positioning slots for receiving positioning posts stationarily mounted on the support. Thus, the mirrors and filters are correctly positioned. As shown, there are three posts, thereby permitting two angular adjustments and one lateral adjustment.
• Each holder can be glued in its final position.
• the image is constructed by selective illumination of the pixels in one or more of the scan lines.
• a controller 114 causes selected pixels in the raster pattern to be illuminated, and rendered visible, by the three laser beams.
• red, blue and violet power controllers 116, 118, 120 respectively conduct electrical currents to the red, blue and violet lasers 22, 28, 34 to energize the latter to emit respective light beams at each selected pixel, and do not conduct electrical currents to the red, blue and violet lasers to deenergize the latter to non-illuminate the other non-selected pixels.
• the resulting pattern of illuminated and non-illuminated pixels comprise the image, which can be any display of human- or machine-readable information or graphic.
• the composite beam is swept by the inertial drive from an end point along the horizontal direction at the horizontal scan rate to an opposite end point to form a scan line.
• the composite laser beam is swept by the electromagnetic drive 70 along the vertical direction at the vertical scan rate to another end point to form a second scan line.
• the formation of successive scan lines proceeds in the same manner.
• the image is created in the raster pattern by energizing or pulsing the lasers on and off at selected times under control of the microprocessor 114 or control circuit by operation of the power controllers 116, 118, 120.
• the lasers produce visible light and are turned on only when a pixel in the desired image is desired to be seen.
• the color of each pixel is determined by one or more of the colors of the beams.
• the green color is derived from the violet beam, as described below. Any color in the visible light spectrum can be formed by the selective superimposition of one or more of the laser beams, as described below.
• the raster pattern is a grid made of multiple pixels on each line, and of multiple lines.
• the image is a bit-map of selected pixels. Every letter or number, any graphical design or logo, and even machine-readable bar code symbols, can be formed as a bit-mapped image.
• an incoming video signal having vertical and horizontal synchronization data, as well as pixel and clock data, is sent to red, blue and violet buffers 122, 124, 126 under control of the microprocessor 114.
• the storage of one full VGA frame requires many kilobytes, and it would be desirable to have enough memory in the buffers for two full frames to enable one frame to be written, while another frame is being processed and projected.
• the buffered data is sent to a formatter 128 under control of a speed profiler 130 and to red, blue and violet look up tables (LUTs) 132, 134, 136 to correct inherent internal distortions caused by scanning, as well as geometrical distortions caused by the angle of the display of the projected image.
• LUTs red, blue and violet look up tables
• red, blue and violet digital signals are converted to red, blue and violet analog signals by digital to analog converters (DACs) 138, 140, 142.
• DACs digital to analog converters
• the red, blue and violet analog signals are fed to red, blue and violet laser drivers (LDs) 144, 146, 148 which are also connected to the red, blue and violet power controllers 116, 118, 120.
• LDs red, blue and violet laser drivers
• Feedback controls are also shown in FIG. 7, including red, blue and violet photodiode amplifiers 152, 154, 156 connected to red, blue and violet analog-to-digital (AfO) converters 158, 160, 162 and, in turn, to the microprocessor 114.
• Red, blue and violet photodiode amplifiers 152, 154, 156 connected to red, blue and violet analog-to-digital (AfO) converters 158, 160, 162 and, in turn, to the microprocessor 114.
• AfO analog-to-digital
• the scan mirrors 64, 68 are driven by drivers 168, 170 which are fed analog drive signals from DACs 172, 174 which are, in turn, connected to the microprocessor.
• Feedback amplifiers 176, 178 detect the position of the scan mirrors 64, 68, and are connected to feedback A/Ds 180, 182 and, in turn, to the microprocessor.
• a power management circuit 184 is operative to minimize power while allowing fast on-times, preferably by keeping the current of the red, blue and violet lasers just below the lasing threshold.
• a laser safety shut down circuit 186 is operative to shut the lasers off if either of the scan mirrors 64, 68 is detected as being out of position.
• the rear projection screen is modified.
• the composite (red, blue and violet) beam emanating from the projection arrangement 20 and, in turn, reflected off the rear mirror 12 in FIG. 1 is projected onto the collimating lens 14, which is preferably a Fresnel lens, as shown in more detail in FIGS. 8-9.
• the collimated light rays exiting the collimating lens is directed onto the lenticular lens array 16, also shown in more detail in FIGS. 8-9.
• the lenticular lens array 16 has a two-dimensional array of lenses 36, each operative for focusing the incoming collimated light rays in the plane of the apertured mask 18 and, more particularly, in apertures 38 thereof, as more clearly shown in the enlarged view of FIG. 10.
• Each lens 36 is about 50-100 microns in size and is preferably smaller than the basic pixel size of the screen.
• each aperture 38 is filled with a phosphor 50 which, when excited by the incoming focused light, transmits/scatters the red and blue components of the incoming light, but creates green light from the violet component. In other words, the phosphor 50 responds only to the violet light to generate green light, but scatters the red and blue laser wavelengths essentially unchanged.
• TMs is advantageous since a small amount of green laser light is mixed with the blue laser light to simulate an effectively longer wavelength (460-480 nanometers) blue light, normally obtained in standard LCD and CRT displays.
• phosphors There are several phosphors that have this characteristic, especially phosphors being marketed by Nichia Corporation of Japan as Model Numbers NP- 2211. NP-2221 and NP 108-83.
• the lenses 36 can be highly selective in the amount of light that is transmitted/scattered along a certain direction, thereby insuring that most of the light is directed to a location where an observer is expected to be. For example, since the observer usually sits at the same height as the screen, there is no need for any radiation emitted from the screen to be greater than 10° along the vertical direction. Along the horizontal direction, the radiation need not be emitted over angles greater than 30°-40°. This enhances the gain or the amount of light that the observer sees.
• a separate phosphor plate 42 is positioned adjacent the mask 18.
• Miniature lenses 150 on the order of 10-20 microns are positioned within the apertures of the mask to increase the gain.
• the apertures 38 need not have a rectangular cross-section as shown in FIG. 9, but can have any cross-section, such as circular, oval, or square.
• the screen is, as described, a rear projection screen, especially useful as a television or monitor display.
• the screen can also be a front projection screen where the violet light is converted to green light, and wherein the red and blue laser beams are scattered back towards the observer.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Optics & Photonics (AREA)
• Signal Processing (AREA)
• Mechanical Optical Scanning Systems (AREA)
• Overhead Projectors And Projection Screens (AREA)
• Transforming Electric Information Into Light Information (AREA)
• Video Image Reproduction Devices For Color Tv Systems (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

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ID=36741021

Family Applications (1)

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Cited By (3)

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• 2005
  • 2005-01-26 US US11/043,302 patent/US7357512B2/en not_active Expired - Fee Related
• 2006
  • 2006-01-25 JP JP2007552398A patent/JP4671443B2/ja not_active Expired - Fee Related
  • 2006-01-25 DE DE112006000275T patent/DE112006000275T5/de not_active Withdrawn
  • 2006-01-25 CN CN200680003281XA patent/CN101263420B/zh not_active Expired - Fee Related
  • 2006-01-25 WO PCT/US2006/002650 patent/WO2006081297A2/en not_active Ceased

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