US20010007510A1 - Method and apparatus for reducing the formation of spots in laser projection - Google Patents

Method and apparatus for reducing the formation of spots in laser projection Download PDF

Info

Publication number
US20010007510A1
US20010007510A1 US09/773,399 US77339901A US2001007510A1 US 20010007510 A1 US20010007510 A1 US 20010007510A1 US 77339901 A US77339901 A US 77339901A US 2001007510 A1 US2001007510 A1 US 2001007510A1
Authority
US
United States
Prior art keywords
projection
laser light
microparticles
projection screen
suspension material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
US09/773,399
Other versions
US6426836B2 (en
Inventor
Andreas Dorsel
Frank Diedrich
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE19623179A external-priority patent/DE19623179C2/en
Priority claimed from US08/873,209 external-priority patent/US6092900A/en
Application filed by Individual filed Critical Individual
Priority to US09/773,399 priority Critical patent/US6426836B2/en
Publication of US20010007510A1 publication Critical patent/US20010007510A1/en
Application granted granted Critical
Publication of US6426836B2 publication Critical patent/US6426836B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00Details of colour television systems
    • H04N9/12Picture reproducers
    • H04N9/31Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3129Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] scanning a light beam on the display screen
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/48Laser speckle optics
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS 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
    • G03B21/00Projectors or projection-type viewers; Accessories therefor
    • G03B21/10Projectors with built-in or built-on screen
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS 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
    • G03B21/00Projectors or projection-type viewers; Accessories therefor
    • G03B21/14Details
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS 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
    • G03B21/00Projectors or projection-type viewers; Accessories therefor
    • G03B21/54Accessories
    • G03B21/56Projection screens
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS 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
    • G03B21/00Projectors or projection-type viewers; Accessories therefor
    • G03B21/54Accessories
    • G03B21/56Projection screens
    • G03B21/60Projection screens characterised by the nature of the surface
    • G03B21/608Fluid screens
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00Details of television systems
    • H04N5/74Projection arrangements for image reproduction, e.g. using eidophor

Definitions

  • This invention relates to a system for improving the image brightness and image sharpness in laser television projection systems.
  • Laser projection uses a raster procedure to produce images.
  • three primary colors red, green, and blue are emitted from one laser or from two or more different lasers.
  • the three colors are modulated separately, brought together again, and scanned over a surface.
  • the image is then formed by points, as in the standard television picture tube.
  • the color of an image point is defined by the relative power of its primary color components. Normally the beam is deflected horizontally by a polygonal mirror and vertically by a galvanometric scanner.
  • the laser beam causes image irregularities (spots) or so-called speckles in the laser image projection due to the spatial coherence of the laser light.
  • the effect can be observed by shining a diverged laser beam onto a wall.
  • the eye of a viewer sees a disk with a stochastic light-dark distribution, instead of a uniformly illuminated field.
  • the spots are perceived when light is reflected off a projection surface and to the eye.
  • the projection surface has areas which are uneven compared with the size of the light source wavelength.
  • the light waves reflected off these uneven surface areas of the projection surface reach the eye with different phase positions creating interference that is perceived in the eye. From a given standpoint of the observer, this interference produces a spatial two-dimensional light-dark pattern.
  • a laser projection system is described in European Patent No. EP0589179A1 where laser radiation consisting of three primary colors is passed through a diffusion element in a common optical path.
  • the diffusion element rotates in the range from 30 to 40 rpm to prevent the formation of spots due to interference phenomena and creates a clearer, truer-color image.
  • a projection light image display system with reduced spot formation is also described in European Patent No. EP0385706.
  • a coherent light source is used to produce a light beam.
  • a light modulator directs the light from the source onto the display screen reproducing an image.
  • the screen is coupled with a transducer that creates acoustic surface waves in the screen where the image is reproduced.
  • the acoustic waves possess an amplitude which is greater than the wavelength of the light beam.
  • the surface waves are supposed to prevent the formation of spots when viewing uniform image contents taking advantage of the fact that the eye is not quick enough to perceive the moving interference pattern created by the surface waves.
  • a system is also described in U.S. Pat. No. 5,313,479, in which a rotating diffusion element is arranged in the optical path of the laser.
  • the diffusion element moves the interference pattern so quickly that it cannot be perceived by the human eye.
  • a projection surface reduces the formation of spots during laser projection while increasing the sharpness and brightness of the laser projection after being scattered by the screen.
  • the projection surface includes scattering microparticles that are in constant motion relative to each other and a source of laser radiation of the laser projection.
  • the microparticles reduce the formation of spots that normally occurs when viewing the contents of images which are uniformly illuminated by means of laser projection and which are reflected off a projection surface.
  • the projection surface is made in such a way that although the image irregularities (spots) or speckles still occur, they are variable in time so that the two-dimensional light-dark pattern, when seen over the reaction time of the eye, is averaged out. Thus, the viewer perceives a uniform brightness.
  • the microparticles are formed in a suspension fluid. Due to Brownian molecular motion in the fluid, the microparticles continue to move. The fluid may be warmed to further increase motion of the microparticles.
  • a piezoelectric force is used to further increase motion by causing turbulence in the microparticles. It is also advantageous to constantly mix the particles to prevent settling. Both embodiments are relatively simple and are resistant to interference.
  • the projection surface has mobile scattering centers. These scattering centers are implemented by suspending the microparticles in the fluid. The motion of the microparticles creates a large number of different light/dark patterns during illumination by the laser spot. The eye perceives the patterns as a uniform image for uniform image contents.
  • the back wall of the screen is made reflective.
  • the incident laser beam passes through a front window and through the suspension fluid that backscatters the light to remove stationary speckle.
  • the light is also reflected back after hitting the back mirror. The viewer sees both the backscattered light from the incident beam as well as the forward scattered light from the reflected beam.
  • the reflected light gives rise to further scatter and thus adds to image brightness.
  • a cellular structure is located in the suspension fluid.
  • the cellular structure laterally confines light increasing the sharpness of the laser light seen by the viewer.
  • the cells can be different shapes such as, honeycomb shaped or square shaped. Different absorbing, scattering or reflective surfaces can be used on the sides of the cellular structure in contact with the suspension medium according to the desired brightness and sharpness of the laser projection.
  • FIG. 1 a shows a schematic top view of a laser projection arrangement with a fluid projection surface according to the invention.
  • FIG. 1 b shows a schematic longitudinal sectional view of the laser projection arrangement shown in FIG. 1 a.
  • FIG. 2 is a schematic longitudinal sectional view of a mirror added to the laser projection arrangement shown in FIG. 1 a.
  • FIG. 3 is a schematic longitudinal sectional view of a cellular structure added to the laser projection arrangement shown in FIG. 2.
  • FIG. 4 is a schematic front view of the cellular structure shown in FIG. 3.
  • the laser projection system includes a projection device 1 that has three coherent sources of radiation beam 3 for the primary colors red, blue, and green in the form of lasers, as is described in U.S. Pat. No. 5,313,479 to Florence.
  • the laser radiation beam 3 exits the projection device 1 through an exit opening 2 and strikes a projection surface 5 .
  • the laser radiation beam 3 is deflected in the azimuth range of angle ⁇ by means of a polygonal mirror guided around a vertical axis (not shown), and in height in the range of angle ⁇ by galvanometric scanners (not shown).
  • the azimuth angle ⁇ is typically within the range of 30-90 degrees and the height angle ⁇ is typically in the range of 25-50 degrees.
  • Means of varying the azimuth angle and height angle using polygonal mirrors and galvanometric scanners, respectively, are known to those skilled in the art and are, therefore, not described in detail.
  • the projection surface 5 is provided within a housing 7 .
  • a transmitting boundary surface 6 resides on a side facing the projection device radiation source.
  • the transmitting boundary surface 6 and housing 7 are shown schematically and contain a suspension fluid 8 with light scattering particles 9 .
  • the scattering particles 9 scatter the laser beam 3 entering through the boundary surface 6 .
  • the motion of the particles 9 prevents the formation of an interference pattern.
  • the path length changes due to the motion of particles 9 are greater than the wavelength of the reflected light. Thus, the eye of a viewer does not perceive changes in brightness of the scattered laser beam 3 .
  • the largest average diameter of the particles 9 is on the order of 100 ⁇ m or less down to the order of nanometers. Due to Brownian motion, the suspension fluid 8 constantly moves at room temperature sufficiently to prevent interference patterns. An alternative embodiment, heats suspension fluid 8 with additional heating resistors 11 to increase the Brownian motion and to further reduce spot formation in the eye of the viewer when viewing the projection surface 5 .
  • the motion of the particles 9 in the suspension fluid 8 is also increased by using piezo oscillators 12 acting on one or several membrane that each comprise scattering particles in a suspension material.
  • the piezo oscillators 12 force even mixing of the scattering particles in the suspension fluid.
  • the deflection path of the particles 9 caused by the effect of the piezoelectric force is also above the wavelength of the reflected laser light 3 .
  • FIGS. 1 a and 1 b show the projection surface 5 in a top sectional view and a longitudinal sectional view, respectively.
  • the longitudinal sectional view in FIG. 1 b shows a projection surface suitable for motion picture/television or video purposes.
  • the projection housing of the laser projection device 1 should ideally be located not too far above the height of the viewer so the scattered light is headed toward the eyes of the viewer.
  • the radiation from laser light 3 passes through the transmitting boundary surface 6 and is reflected by the projection surface 5 made up of light scattering particles 9 .
  • the layer of suspension fluid 8 can be different thicknesses. However, a thickness between 0.1 centimeters and 2.0 centimeters provides sufficient scattering and also reduced weight.
  • One embodiment of the invention uses milk as the projection surface 5 .
  • the milk contains coagulated protein and fat particles 9 suspended in water 8 .
  • the milk is illuminated by the laser radiation 3 .
  • a spot observed on the surface of the milk produces more uniform brightness compared with the same laser spot when shone onto solid cardboard.
  • the medium causing the required back-scatter could be a suspension of glass spheres of very small particles such as aluminum oxide particles or silicon oxide particles suspended in, e.g., water or oil.
  • the suspension material 8 can alternatively be a gas or any alternative material that can evenly suspend scattering particles.
  • Mechanical and electronic devices, other than the piezoelectric transducer 12 can be used to keep the scattering particles 9 evenly mixed in the suspension material 8 .
  • the scatter length over which all but a fraction of the incoming laser beam 3 is scattered should not be large compared to the depth of the cell in order to have good power efficiency. This is controlled by particle concentration in the suspension material 8 or by choosing the cell depth accordingly.
  • the function of the liquid 8 is to move the particles sufficiently by diffusion over the retinal integration time. Also, it is advantageous to make the scatter length comparable to or smaller than the desired lateral resolution so that photon diffusion, as opposed to particle diffusion, does not cause image blur.
  • the angular distribution of scattered light is optimized by controlling the shape and size (distribution) of the scattering particles 9 .
  • the refractive index/indices of the different media making up the emulsion/suspension material can also be varied to optimize the angular distribution of the scattered light.
  • a screen housing 7 includes a front glass window 16 and a mirrored surface 14 located on a back substrate 15 .
  • the incident laser beam 3 passes through the front window 16 and into the suspension material 8 .
  • the suspension material 8 backscatters the laser beam light reducing stationary speckle.
  • the laser beam 3 is also reflected by the mirror 14 , giving rise to further scatter that increases the brightness of the laser light image.
  • the reflective mirror 14 on the back side of the housing 7 allows a person viewing the projection surface 5 to see both the backscattered light 19 from the incident laser beam 3 as well as forward scattered light 18 from the laser beam 3 reflected off the mirror 14 .
  • the amount of reflectivity of the back mirror 14 can be varied according to the desired brightness of the laser light image visually observed on the front boundary surface 6 . For example, a less reflective material will reduce brightness and a more reflective material will increase brightness.
  • FIG. 3 Another embodiment of the invention is shown in FIG. 3.
  • a cellular structure 20 is located in the suspension material 8 between the front glass 16 and the rear mirror 14 .
  • the multi-cell structure 20 is bonded between the glass 16 and the mirror 14 with an adhesive.
  • the multi-cell structure 20 is located in a housing 7 similar to that shown in FIGS. 1A and 1B that does not include a back mirror 14 .
  • FIG. 4 is an enlarged schematic diagram of a square cellular structure 20 .
  • the individual cells 24 are formed by the cellular structure 20 and each retain some of the scattering particles 9 .
  • the cellular structure 20 confines lateral scattering of the incident laser light 19 to individual cells 24 improving sharpness of the viewed laser light image.
  • the diameter of each individual cell 24 is preferably the same or smaller than the diameter of the individual pixels displayed on the projection surface 5 . This prevents the laser light 3 from different pixels from bleeding into each other without having to align the cellular structure 20 with the display locations of the individual pixels.
  • the cellular structure 20 has either absorbing, scattering or reflective sides 22 that contact with the suspension material 8 .
  • the sides 22 are black for light absorption or an aluminum or silver color for higher reflectivity.
  • the cellular structure 20 can be made out of a variety of materials such as plastic, metal, synthetic resin or a fibrous sheet.
  • the cellular structure 20 can be different shapes, such as the square shape shown in FIG. 4, a honeycomb shape, a circular shape or any shape preferable in a particular application.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Optics & Photonics (AREA)
  • Overhead Projectors And Projection Screens (AREA)

Abstract

A projection surface includes scattering microparticles that are in constant motion in relation to each other and to a source of laser radiation in a laser projection system. The microparticles reduce the formation of spots that normally occur when viewing the contents of images which are uniformly illuminated by means of laser projection and which are reflected off a projection surface. The microparticles are reflective in a suspension fluid and move due to Brownian molecular motion. A mirror is placed on the back wall of the screen so that the viewer sees both the backscattered light from the incident beam as well as the forward scattered light from the reflected beam. A cellular structure is located in the suspension fluid to laterally confine the scattered light increasing the sharpness of the laser light seen by the viewer.

Description

  • This application is a continuation of Ser. No. 08/933,185, filed Sep. 18, 1997, which is a continuation of Ser. No. 08/873,209, filed Jun. 11, 1997. [0001]
  • BACKGROUND OF THE INVENTION
  • This invention relates to a system for improving the image brightness and image sharpness in laser television projection systems. [0002]
  • Laser projection uses a raster procedure to produce images. In the raster procedure, three primary colors red, green, and blue are emitted from one laser or from two or more different lasers. The three colors are modulated separately, brought together again, and scanned over a surface. The image is then formed by points, as in the standard television picture tube. The color of an image point is defined by the relative power of its primary color components. Normally the beam is deflected horizontally by a polygonal mirror and vertically by a galvanometric scanner. [0003]
  • The laser beam causes image irregularities (spots) or so-called speckles in the laser image projection due to the spatial coherence of the laser light. The effect can be observed by shining a diverged laser beam onto a wall. The eye of a viewer sees a disk with a stochastic light-dark distribution, instead of a uniformly illuminated field. [0004]
  • The spots are perceived when light is reflected off a projection surface and to the eye. The projection surface has areas which are uneven compared with the size of the light source wavelength. The light waves reflected off these uneven surface areas of the projection surface reach the eye with different phase positions creating interference that is perceived in the eye. From a given standpoint of the observer, this interference produces a spatial two-dimensional light-dark pattern. [0005]
  • A laser projection system is described in European Patent No. EP0589179A1 where laser radiation consisting of three primary colors is passed through a diffusion element in a common optical path. The diffusion element rotates in the range from 30 to 40 rpm to prevent the formation of spots due to interference phenomena and creates a clearer, truer-color image. [0006]
  • A projection light image display system with reduced spot formation is also described in European Patent No. EP0385706. A coherent light source is used to produce a light beam. A light modulator directs the light from the source onto the display screen reproducing an image. The screen is coupled with a transducer that creates acoustic surface waves in the screen where the image is reproduced. The acoustic waves possess an amplitude which is greater than the wavelength of the light beam. The surface waves are supposed to prevent the formation of spots when viewing uniform image contents taking advantage of the fact that the eye is not quick enough to perceive the moving interference pattern created by the surface waves. [0007]
  • A system is also described in U.S. Pat. No. 5,313,479, in which a rotating diffusion element is arranged in the optical path of the laser. The diffusion element moves the interference pattern so quickly that it cannot be perceived by the human eye. [0008]
  • The systems described above require mechanical transducers and, therefore, are relatively expensive. The diffusion elements mentioned above also induce lateral diffusion of photons in the screen which reduce image sharpness and brightness. If the reflectivity of a laser projection screen is low, more powerful lasers are needed which are more costly, require more power and cooling and have a shorter operating life. [0009]
  • Thus, a need exists for reducing interference in light image display systems while at the same time maintaining high image sharpness and brightness. [0010]
  • SUMMARY OF THE INVENTION
  • A projection surface reduces the formation of spots during laser projection while increasing the sharpness and brightness of the laser projection after being scattered by the screen. The projection surface includes scattering microparticles that are in constant motion relative to each other and a source of laser radiation of the laser projection. The microparticles reduce the formation of spots that normally occurs when viewing the contents of images which are uniformly illuminated by means of laser projection and which are reflected off a projection surface. [0011]
  • The projection surface is made in such a way that although the image irregularities (spots) or speckles still occur, they are variable in time so that the two-dimensional light-dark pattern, when seen over the reaction time of the eye, is averaged out. Thus, the viewer perceives a uniform brightness. [0012]
  • In one embodiment of the invention, the microparticles are formed in a suspension fluid. Due to Brownian molecular motion in the fluid, the microparticles continue to move. The fluid may be warmed to further increase motion of the microparticles. In another embodiment of the invention, a piezoelectric force is used to further increase motion by causing turbulence in the microparticles. It is also advantageous to constantly mix the particles to prevent settling. Both embodiments are relatively simple and are resistant to interference. [0013]
  • In place of a solid projection wall, the projection surface has mobile scattering centers. These scattering centers are implemented by suspending the microparticles in the fluid. The motion of the microparticles creates a large number of different light/dark patterns during illumination by the laser spot. The eye perceives the patterns as a uniform image for uniform image contents. [0014]
  • In another embodiment of the invention, the back wall of the screen is made reflective. The incident laser beam passes through a front window and through the suspension fluid that backscatters the light to remove stationary speckle. The light is also reflected back after hitting the back mirror. The viewer sees both the backscattered light from the incident beam as well as the forward scattered light from the reflected beam. The reflected light gives rise to further scatter and thus adds to image brightness. [0015]
  • In another embodiment of the invention, a cellular structure is located in the suspension fluid. The cellular structure laterally confines light increasing the sharpness of the laser light seen by the viewer. The cells can be different shapes such as, honeycomb shaped or square shaped. Different absorbing, scattering or reflective surfaces can be used on the sides of the cellular structure in contact with the suspension medium according to the desired brightness and sharpness of the laser projection. [0016]
  • The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention which proceeds with reference to the accompanying drawings. [0017]
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • FIG. 1[0018] a shows a schematic top view of a laser projection arrangement with a fluid projection surface according to the invention.
  • FIG. 1[0019] b shows a schematic longitudinal sectional view of the laser projection arrangement shown in FIG. 1a.
  • FIG. 2 is a schematic longitudinal sectional view of a mirror added to the laser projection arrangement shown in FIG. 1[0020] a.
  • FIG. 3 is a schematic longitudinal sectional view of a cellular structure added to the laser projection arrangement shown in FIG. 2. [0021]
  • FIG. 4 is a schematic front view of the cellular structure shown in FIG. 3. [0022]
  • DETAILED DESCRIPTION
  • Referring to FIGS. 1[0023] a and 1 b, the laser projection system according to the invention includes a projection device 1 that has three coherent sources of radiation beam 3 for the primary colors red, blue, and green in the form of lasers, as is described in U.S. Pat. No. 5,313,479 to Florence. The laser radiation beam 3 exits the projection device 1 through an exit opening 2 and strikes a projection surface 5. The laser radiation beam 3 is deflected in the azimuth range of angle α by means of a polygonal mirror guided around a vertical axis (not shown), and in height in the range of angle β by galvanometric scanners (not shown).
  • The azimuth angle α is typically within the range of 30-90 degrees and the height angle β is typically in the range of 25-50 degrees. Means of varying the azimuth angle and height angle using polygonal mirrors and galvanometric scanners, respectively, are known to those skilled in the art and are, therefore, not described in detail. [0024]
  • The [0025] projection surface 5 is provided within a housing 7. A transmitting boundary surface 6 resides on a side facing the projection device radiation source. The transmitting boundary surface 6 and housing 7 are shown schematically and contain a suspension fluid 8 with light scattering particles 9. The scattering particles 9 scatter the laser beam 3 entering through the boundary surface 6. The motion of the particles 9 prevents the formation of an interference pattern. The path length changes due to the motion of particles 9 are greater than the wavelength of the reflected light. Thus, the eye of a viewer does not perceive changes in brightness of the scattered laser beam 3.
  • The largest average diameter of the [0026] particles 9 is on the order of 100 μm or less down to the order of nanometers. Due to Brownian motion, the suspension fluid 8 constantly moves at room temperature sufficiently to prevent interference patterns. An alternative embodiment, heats suspension fluid 8 with additional heating resistors 11 to increase the Brownian motion and to further reduce spot formation in the eye of the viewer when viewing the projection surface 5.
  • The motion of the [0027] particles 9 in the suspension fluid 8 is also increased by using piezo oscillators 12 acting on one or several membrane that each comprise scattering particles in a suspension material. The piezo oscillators 12 force even mixing of the scattering particles in the suspension fluid. The deflection path of the particles 9 caused by the effect of the piezoelectric force is also above the wavelength of the reflected laser light 3.
  • FIGS. 1[0028] a and 1 b show the projection surface 5 in a top sectional view and a longitudinal sectional view, respectively. The longitudinal sectional view in FIG. 1b shows a projection surface suitable for motion picture/television or video purposes. The projection housing of the laser projection device 1 should ideally be located not too far above the height of the viewer so the scattered light is headed toward the eyes of the viewer. The radiation from laser light 3 passes through the transmitting boundary surface 6 and is reflected by the projection surface 5 made up of light scattering particles 9. The layer of suspension fluid 8 can be different thicknesses. However, a thickness between 0.1 centimeters and 2.0 centimeters provides sufficient scattering and also reduced weight.
  • One embodiment of the invention uses milk as the [0029] projection surface 5. The milk contains coagulated protein and fat particles 9 suspended in water 8. The milk is illuminated by the laser radiation 3. A spot observed on the surface of the milk produces more uniform brightness compared with the same laser spot when shone onto solid cardboard.
  • The medium causing the required back-scatter could be a suspension of glass spheres of very small particles such as aluminum oxide particles or silicon oxide particles suspended in, e.g., water or oil. The [0030] suspension material 8 can alternatively be a gas or any alternative material that can evenly suspend scattering particles. Mechanical and electronic devices, other than the piezoelectric transducer 12, can be used to keep the scattering particles 9 evenly mixed in the suspension material 8.
  • The scatter length over which all but a fraction of the [0031] incoming laser beam 3 is scattered should not be large compared to the depth of the cell in order to have good power efficiency. This is controlled by particle concentration in the suspension material 8 or by choosing the cell depth accordingly. The function of the liquid 8 is to move the particles sufficiently by diffusion over the retinal integration time. Also, it is advantageous to make the scatter length comparable to or smaller than the desired lateral resolution so that photon diffusion, as opposed to particle diffusion, does not cause image blur. The angular distribution of scattered light is optimized by controlling the shape and size (distribution) of the scattering particles 9. The refractive index/indices of the different media making up the emulsion/suspension material can also be varied to optimize the angular distribution of the scattered light.
  • Another embodiment of the invention is shown in FIG. 2. A [0032] screen housing 7 includes a front glass window 16 and a mirrored surface 14 located on a back substrate 15. The incident laser beam 3 passes through the front window 16 and into the suspension material 8. The suspension material 8 backscatters the laser beam light reducing stationary speckle. The laser beam 3 is also reflected by the mirror 14, giving rise to further scatter that increases the brightness of the laser light image. Thus, when illuminated and viewed from a front side, the reflective mirror 14 on the back side of the housing 7 allows a person viewing the projection surface 5 to see both the backscattered light 19 from the incident laser beam 3 as well as forward scattered light 18 from the laser beam 3 reflected off the mirror 14.
  • The amount of reflectivity of the back mirror [0033] 14 can be varied according to the desired brightness of the laser light image visually observed on the front boundary surface 6. For example, a less reflective material will reduce brightness and a more reflective material will increase brightness.
  • Another embodiment of the invention is shown in FIG. 3. A [0034] cellular structure 20 is located in the suspension material 8 between the front glass 16 and the rear mirror 14. The multi-cell structure 20 is bonded between the glass 16 and the mirror 14 with an adhesive. Alternatively, the multi-cell structure 20 is located in a housing 7 similar to that shown in FIGS. 1A and 1B that does not include a back mirror 14.
  • FIG. 4 is an enlarged schematic diagram of a square [0035] cellular structure 20. The individual cells 24 are formed by the cellular structure 20 and each retain some of the scattering particles 9. The cellular structure 20 confines lateral scattering of the incident laser light 19 to individual cells 24 improving sharpness of the viewed laser light image. The diameter of each individual cell 24 is preferably the same or smaller than the diameter of the individual pixels displayed on the projection surface 5. This prevents the laser light 3 from different pixels from bleeding into each other without having to align the cellular structure 20 with the display locations of the individual pixels.
  • The [0036] cellular structure 20 has either absorbing, scattering or reflective sides 22 that contact with the suspension material 8. For example, the sides 22 are black for light absorption or an aluminum or silver color for higher reflectivity. The cellular structure 20 can be made out of a variety of materials such as plastic, metal, synthetic resin or a fibrous sheet. The cellular structure 20 can be different shapes, such as the square shape shown in FIG. 4, a honeycomb shape, a circular shape or any shape preferable in a particular application.
  • Cellular structures similar to [0037] cellular structure 20 are used in the drawing toy “Magna Doodle” produced by Tyco Industries, Mt. Laurel, N.J. 08054, and is described is U.S. Pat. No. 4,143,472.
  • Having described and illustrated the principles of the invention in a preferred embodiment thereof, it should be apparent that the invention can be modified in arrangement and detail without departing from such principles. I claim all modifications and variation coming within the spirit and scope of the following claims. [0038]

Claims (20)

1. A projection surface for reducing interference patterns perceived in a laser light image transmitted from a laser radiation source in a laser projection system, comprising:
a suspension material that includes multiple light scattering microparticles constantly in motion relative to each other and to the laser radiation source of the laser projection system, the suspension material while scattering the laser light image varying the interference patterns in time thereby preventing perception of the interference patterns; and
a mirror located adjacent to the suspension material reflecting back the laser light passing through the suspension material thereby increasing laser light image brightness.
2. A projection surface according to
claim 1
including a cellular structure located in the suspension material.
3. A projection surface according to
claim 2
wherein the cellular structure comprises a plurality of honeycomb cells or square cells.
4. A projection surface according to
claim 2
wherein the cells in the cellular structure each have a width less than a diameter for individual pixels of the laser light image transmitted onto the projection surface such that the laser light from different pixels is prevented from bleeding into each other without having to align the cellular structure.
5. A projection surface according to
claim 2
wherein the cellular structure is made of a metal, plastic, synthetic resin or fibrous sheet.
6. A projection surface according to
claim 2
wherein the cellular structure includes sides that primarily reflect light.
7. A projection surface according to
claim 2
wherein the cellular structure includes sides comprising mirrors.
8. A projection surface according to
claim 2
wherein the cellular structure includes sides that primarily absorb light.
9. A projection surface according to
claim 1
wherein the suspension material comprises a fluid and a constant motion of the microparticles is produced by Brownian motion.
10. A projection surface according to
claim 2
wherein the suspension material comprises a coagulated protein.
11. A projection system, comprising:
a projection device transmitting images with a light source;
a projection screen including scattering microparticles suspended in a suspension material and moving in relation to the light source, the microparticles deflecting light from the transmitted images thereby reducing perceived phase interference; and
a cellular structure located in the suspension material for confining lateral deflection of the light thereby increasing the sharpness of the transmitted images on the projection screen.
12. A projection system according to
claim 11
wherein the projection screen includes a mirror located in back of the suspension material that reflects back the light passing through the suspension material.
13. A projection system according to
claim 11
wherein the suspension material comprises a coagulated protein.
14. A projection system according to
claim 11
wherein width of the cells in the cellular structure is smaller than a diameter of individual pixels of the images transmitted onto the projection screen such that the laser light from different pixels is prevented from bleeding into each other without having to align the cellular structure.
15. A method for projecting images with a laser light source onto a projection screen, comprising:
suspending light scattering microparticles in a projection screen suspension material;
moving the microparticles in relation to each other and the laser light source;
deflecting the laser light off of the scattering microparticles in the projection screen for reducing perceived phase interference in the laser light;
reflecting back the deflected laser light from a back side of the projection screen to increase the brightness of the deflected laser light; and
laterally confining the deflected laser light confining the microparticles in multiple cells in the projection screen.
16. A method for projecting images with a laser light source onto a projection screen, comprising:
suspending light scattering microparticles in a projection screen suspension material;
moving the microparticles in relation to each other and the laser light source;
deflecting the laser light off of the scattering microparticles in the projection screen for reducing perceived phase interference in the laser light; and
reflecting back the deflected laser light from a back side of the projection screen to increase the brightness of the deflected laser light or laterally confining the deflected laser light confining the microparticles in multiple cells in the projection screen.
17. A method according to
claim 15
including increasing the movement of the microparticles by heating the projection screen.
18. A method according to
claim 15
including increasing the movement of the microparticles by applying a piezoelectric force or other mixing mechanism to the projection screen.
19. A method according to
claim 16
including increasing the movement of the microparticles by heating the projection screen.
20. A method according to
claim 16
including increasing the movement of the microparticles by applying a piezoelectric force or other mixing mechanism to the projection screen.
US09/773,399 1996-06-11 2001-01-31 Method and apparatus for reducing the formation of spots in laser projection Expired - Fee Related US6426836B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US09/773,399 US6426836B2 (en) 1996-06-11 2001-01-31 Method and apparatus for reducing the formation of spots in laser projection

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
DE19623179A DE19623179C2 (en) 1996-06-11 1996-06-11 Method and device for reducing spot formation in laser projection
DE19623179.5 1996-06-11
DE19623179 1996-06-11
US08/873,209 US6092900A (en) 1997-06-11 1997-06-11 Method and apparatus for reducing the formation of spots in laser projection
US93318597A 1997-09-18 1997-09-18
US09/773,399 US6426836B2 (en) 1996-06-11 2001-01-31 Method and apparatus for reducing the formation of spots in laser projection

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US93318597A Continuation 1996-06-11 1997-09-18

Publications (2)

Publication Number Publication Date
US20010007510A1 true US20010007510A1 (en) 2001-07-12
US6426836B2 US6426836B2 (en) 2002-07-30

Family

ID=27216329

Family Applications (1)

Application Number Title Priority Date Filing Date
US09/773,399 Expired - Fee Related US6426836B2 (en) 1996-06-11 2001-01-31 Method and apparatus for reducing the formation of spots in laser projection

Country Status (1)

Country Link
US (1) US6426836B2 (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006024998A2 (en) * 2004-08-30 2006-03-09 Koninklijke Philips Electronics N.V. A laser projection system
US20060126022A1 (en) * 2004-12-14 2006-06-15 Govorkov Sergei V Laser illuminated projection displays
WO2006065537A2 (en) * 2004-12-14 2006-06-22 Coherent, Inc. Laser illuminated projection displays
US20080123704A1 (en) * 2006-11-24 2008-05-29 Raylase Ag System and method for regulating the power of a laser beam
WO2009065438A1 (en) * 2007-11-20 2009-05-28 Osram Gesellschaft mit beschränkter Haftung Laser projection device and method for laser projection
US20110199686A1 (en) * 2008-10-23 2011-08-18 Nippon Kayaku Kabushiki Kaisha Light Diffusion Cell For Laser Light, Light Source Device And Image Display Device Using Same
WO2011135008A1 (en) 2010-04-28 2011-11-03 Delphi Technologies, Inc. Speckle reducer and projection unit comprising a speckle reducer
JP2018180164A (en) * 2017-04-07 2018-11-15 大日本印刷株式会社 Screen and display device

Families Citing this family (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6997558B2 (en) * 2002-12-11 2006-02-14 New York University Volumetric display with dust as the participating medium
US7156522B2 (en) * 2003-07-16 2007-01-02 Plut William J Projection-type display devices with reduced weight and size
US7928994B2 (en) * 2003-07-16 2011-04-19 Transpacific Image, Llc Graphics items that extend outside a background perimeter
US7281807B2 (en) 2003-07-16 2007-10-16 Honeywood Technologies, Llc Positionable projection display devices
US7274382B2 (en) * 2003-07-16 2007-09-25 Plut William J Customizable background sizes and controls for changing background size
US20060291049A1 (en) * 2005-06-24 2006-12-28 Hewlett-Packard Development Company L.P. Screen
US7614750B2 (en) * 2005-08-24 2009-11-10 Hewlett-Packard Development Company, L.P. Light interaction states
US20070206280A1 (en) * 2006-03-06 2007-09-06 Hewlett-Packard Development Company Lp Light source and screen
JP4193864B2 (en) * 2006-04-27 2008-12-10 セイコーエプソン株式会社 Projector, screen, projector system, and scintillation removal apparatus
JP4172502B2 (en) * 2006-06-14 2008-10-29 セイコーエプソン株式会社 Screen, rear projector and image display device
US7724431B2 (en) * 2006-09-29 2010-05-25 Hewlett-Packard Development Company, L.P. Active layer
US20080219303A1 (en) * 2007-03-02 2008-09-11 Lucent Technologies Inc. Color mixing light source and color control data system
US9778477B2 (en) * 2007-03-02 2017-10-03 Alcatel-Lucent Usa Inc. Holographic MEMS operated optical projectors
US7440158B2 (en) * 2007-03-02 2008-10-21 Lucent Technologies Inc. Direct optical image projectors
US7502160B2 (en) * 2007-03-02 2009-03-10 Alcatel-Lucent Usa Inc. Speckle reduction in laser-projector images
US7782521B2 (en) * 2007-05-31 2010-08-24 Texas Instruments Incorporated System and method for displaying images
US7750286B2 (en) * 2007-06-19 2010-07-06 Alcatel-Lucent Usa Inc. Compact image projector having a mirror for reflecting a beam received from a polarization beam splitter back to the polarization beam splitter
US8247999B2 (en) * 2008-01-22 2012-08-21 Alcatel Lucent Time division multiplexing a DC-to-DC voltage converter
US8129669B2 (en) * 2008-01-22 2012-03-06 Alcatel Lucent System and method generating multi-color light for image display having a controller for temporally interleaving the first and second time intervals of directed first and second light beams
US8109638B2 (en) 2008-01-22 2012-02-07 Alcatel Lucent Diffuser configuration for an image projector
US20090184976A1 (en) * 2008-01-22 2009-07-23 Alcatel-Lucent System and Method for Color-Compensating a Video Signal Having Reduced Computational Requirements
US8226241B2 (en) * 2009-05-15 2012-07-24 Alcatel Lucent Image projector employing a speckle-reducing laser source
US20110234985A1 (en) * 2010-03-26 2011-09-29 Alcatel-Lucent Usa Inc. Despeckling laser-image-projection system
KR101178363B1 (en) * 2010-10-26 2012-08-29 최해용 window projection screen

Family Cites Families (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2287556A (en) * 1938-02-25 1942-06-23 Polaroid Corp Translucent screen
US3650608A (en) * 1969-12-23 1972-03-21 Texas Instruments Inc Method and apparatus for displaying coherent light images
US4143943A (en) * 1977-02-17 1979-03-13 Xerox Corporation Rear projection screen system
US4140369A (en) * 1977-04-11 1979-02-20 Massachusetts Institute Of Technology Efficient light diffuser
JPS5947676B2 (en) * 1977-04-11 1984-11-20 株式会社パイロット magnetic panel
US4184762A (en) * 1978-06-16 1980-01-22 Oscar Guzman Variable definition projection systems
DD154401A1 (en) * 1980-12-23 1982-03-17 Ludwig Drechsel PROJECTION SCREEN FOR OPTICAL PURPOSES
NL8503526A (en) * 1985-12-20 1987-07-16 Philips Nv TRANSPARENT PROJECTION SCREEN.
US5270752A (en) * 1991-03-15 1993-12-14 Ushio U-Tech Inc. Method and apparatus for a fog screen and image-forming method using the same
KR970002673B1 (en) * 1991-06-03 1997-03-07 다이닛뽕 인사쓰 가부시기가이샤 Reflection type projection screen, production process thereof,and production apparatus thereof
FR2684198B1 (en) * 1991-11-22 1994-09-23 Thomson Csf SCREEN FOR IMAGE PROJECTION.
US5192197A (en) * 1991-11-27 1993-03-09 Rockwell International Corporation Piezoelectric pump
KR960015507B1 (en) * 1991-12-24 1996-11-14 가부시끼가이샤 히다찌세이사꾸쇼 An image display apparatus of back projector type and a screen of back projector type
US6092900A (en) * 1997-06-11 2000-07-25 Hewlett-Packard Company Method and apparatus for reducing the formation of spots in laser projection

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7775670B2 (en) 2004-08-30 2010-08-17 Koninklijke Philips Electronics N.V. Laser projection system
WO2006024998A3 (en) * 2004-08-30 2006-10-26 Koninkl Philips Electronics Nv A laser projection system
WO2006024998A2 (en) * 2004-08-30 2006-03-09 Koninklijke Philips Electronics N.V. A laser projection system
US20080278692A1 (en) * 2004-08-30 2008-11-13 Koninklijke Philips Electronics, N.V. Method Liquefaction of Starchcontaining Material
US20060126022A1 (en) * 2004-12-14 2006-06-15 Govorkov Sergei V Laser illuminated projection displays
WO2006065537A2 (en) * 2004-12-14 2006-06-22 Coherent, Inc. Laser illuminated projection displays
WO2006065524A2 (en) * 2004-12-14 2006-06-22 Coherent, Inc. Laser illuminated projection displays
WO2006065537A3 (en) * 2004-12-14 2006-09-08 Coherent Inc Laser illuminated projection displays
WO2006065524A3 (en) * 2004-12-14 2006-09-14 Coherent Inc Laser illuminated projection displays
US7244028B2 (en) 2004-12-14 2007-07-17 Coherent, Inc. Laser illuminated projection displays
US20080123704A1 (en) * 2006-11-24 2008-05-29 Raylase Ag System and method for regulating the power of a laser beam
WO2009065438A1 (en) * 2007-11-20 2009-05-28 Osram Gesellschaft mit beschränkter Haftung Laser projection device and method for laser projection
US20110199686A1 (en) * 2008-10-23 2011-08-18 Nippon Kayaku Kabushiki Kaisha Light Diffusion Cell For Laser Light, Light Source Device And Image Display Device Using Same
US8730580B2 (en) 2008-10-23 2014-05-20 Nippon Kayaku Kabushiki Kaisha Light diffusion cell for laser light, light source device and image display device using same
WO2011135008A1 (en) 2010-04-28 2011-11-03 Delphi Technologies, Inc. Speckle reducer and projection unit comprising a speckle reducer
FR2959574A1 (en) * 2010-04-28 2011-11-04 Delphi Tech Inc SPECKLE REDUCER AND PROJECTION UNIT COMPRISING A SPECKLE REDUCER
CN102844697A (en) * 2010-04-28 2012-12-26 德尔菲技术公司 Speckle reducer and projection unit comprising speckle reducer
US8833945B2 (en) 2010-04-28 2014-09-16 Delphi Technologies, Inc. Speckle reducer and projection unit including a speckle reducer
JP2018180164A (en) * 2017-04-07 2018-11-15 大日本印刷株式会社 Screen and display device

Also Published As

Publication number Publication date
US6426836B2 (en) 2002-07-30

Similar Documents

Publication Publication Date Title
US6426836B2 (en) Method and apparatus for reducing the formation of spots in laser projection
US6092900A (en) Method and apparatus for reducing the formation of spots in laser projection
CN113866998B (en) System for imaging in the air
JP5237635B2 (en) Laser image display device and laser image display screen
EP0589179B1 (en) Speckle-free display system using coherent light
CN102652272B (en) Optical element, screen and display device
CN101203802B (en) 2-dimensional image display device, illumination light source, and exposure illumination device
CN1216500C (en) Method and apparatus for displaying three-dimensional images
KR100477462B1 (en) Flat-panel display
US20060209374A1 (en) Projection device
US6502942B2 (en) Rear projection display apparatus and translucent screen for use therein
CN104423036A (en) Optical scanning unit, and apparatus including the optical scanning unit
CN107148589A (en) Head-up display
JP2002535699A (en) Fresnel lens for projection screen
JPH05501619A (en) TV with an aperture to modulate the intensity of the light beam
US6597417B1 (en) Optical panel having black material between apexes of serrations on the inlet face
CN102053383B (en) Speckle eliminating device based on Mie scatter and perturbation drive
GB2302963A (en) Rear projection screen with light absorbing bodies totally reflecting light from a Fresnel lens
GB1580639A (en) Optical system for producing a two dimensional display
JP2942214B2 (en) Holographic screen with convex protrusions having light diffusion and / or light scattering function
EP0367246B1 (en) Head-up display apparatus
JPH10115805A (en) Method and device for reducing formation of spot in laser projection
JP2000221309A (en) Light diffuser and liquid crystal display device using the same
JP4158817B2 (en) Screen, rear projector and image display device
KR101817417B1 (en) Laser Projection Device

Legal Events

Date Code Title Description
FPAY Fee payment

Year of fee payment: 4

FPAY Fee payment

Year of fee payment: 8

REMI Maintenance fee reminder mailed
LAPS Lapse for failure to pay maintenance fees
STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362

FP Lapsed due to failure to pay maintenance fee

Effective date: 20140730