Shutter for image projection system

Information

  • Patent Grant
  • 6726335
  • Patent Number
    6,726,335
  • Date Filed
    Friday, February 21, 2003
    21 years ago
  • Date Issued
    Tuesday, April 27, 2004
    20 years ago
Abstract
An image projection system comprises an image projector, such as a film or television projector and a projection screen. The projection screen is fabricated of a substantially transparent material, such as glass or plastic. The screen of transparent material has one or more areas or portions formed therein which areas or portions may be made to be translucent upon the application of a stimulus. Once in a translucent condition, the projected image can be received and viewed on the translucent portion. A mirror can be positioned behind the projection screen so that a person can view the reflection of themselves in the mirror when the screen is transparent, and an image can be projected when the projection screen is made to be substantially translucent.
Description




TECHNICAL FIELD




The present invention is generally related to the field of image projection systems.




BACKGROUND INFORMATION




In U.S. patent applications Ser. Nos. 09/519,537 and 09/876,400, an invention was disclosed whereby a substantially transparent medium could be used as a projection screen for capturing an image from an image projector. When the medium was not capturing an image from an image projector, its substantially transparent characteristic permitted persons to see through the medium. However, the system also provided an ability for the medium to capture an image from an image projector for viewing by persons. In one embodiment, the medium was made to have a characteristic that caused it to be nearly opaque, or substantially translucent (permitting the passage of light, but not sufficient as to be able to view objects clearly), so that persons could see clearly the image projected.




The present invention takes the advantages of this system to further uses.











BRIEF DESCRIPTION OF THE DRAWINGS




For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:





FIG. 1

illustrates a prospective view of a projection screen in accordance with the present invention;





FIG. 2

illustrates a side view of the projection screen shown in

FIG. 1

;





FIG. 3

is a side view of an image projection system;





FIG. 4

illustrates an alternative embodiment of the present invention;





FIG. 5

illustrates an embodiment of the present invention;





FIG. 6

illustrates a flow diagram of an embodiment of the present invention;





FIGS. 7A-7E

illustrate alternative embodiments of the present invention; and





FIG. 8

illustrates a circuit diagram of a video controlled shutter.











DETAILED DESCRIPTION




In the following description, numerous specific details are set forth such as specific materials to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. In other instances, well-known circuits have been shown in block diagram form in order not to obscure the present invention in unnecessary detail. For the most part, details concerning timing considerations and the like have been omitted in as much as such details are not necessary to obtain a complete understanding of the present invention and are within the skills of persons of ordinary skill in the relevant art.




While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward.




Referring now to

FIG. 3

, there is illustrated therein a cross-sectional side view of the image projection system


300


as disclosed in U.S. patent application Ser. No. 09/876,400. The system


300


comprises a projector


301


of any type commonly used, examples of which include an LCD projector, a television projector currently used on conventional projection television systems, a film projector, a slide projector or a computer for providing computer generated images, to name but a few. The system


300


further includes a projection screen


101


. However, the projection screen herein is a glass or other transparent (or semi-transparent) material, having one or more switchable portions. More particularly, the screen


101


may comprise a sheet of glass having a portion


102


or portions that can be switched between the glass' typical transparent characteristic, to a translucent appearance or condition. Projector


301


may project an image onto portion


102


, which will be viewable by viewers on both sides of screen


101


when portion


102


is translucent, on the right side when it is opaque. Alternatively, when portion


102


is translucent or opaque, another projector


302


can be used to project an image onto the other side of screen


101


so that such an image is viewable by viewers on the left side of screen


101


.




The invention is also applicable for projection on reflective surfaces such as mirrors.




As is readily apparent, light, as from a projected image, projected onto a sheet of glass or other transparent material leaves no readily viewable impression. This is due of course to the fact that the projected light passes substantially unimpeded through the glass. Accordingly, heretofore retail establishments, for example, having large areas of display glass windows were forced to post paper sign advertising, for example, an on-going sale. This type of advertising is neither dynamic, nor particularly effective. Conversely, an advertising scheme taking advantage of the projection system described herein has many advantages. In particular, by projecting an image onto the translucent area of the glass substrate, the projected image is visible by viewers on both sides of the glass. Moreover, while only a portion of the glass or other substrate may by switchable between the transparent and the translucent condition, the whole of the substrate may in fact be switchable. This allows a condition in which, for example, a glass pane becomes an entire wall of e.g., advertising area.




Referring now to

FIGS. 1 and 2

, the transparent screen


101


may be a glass panel such as a display window, or some other type of transparent medium. Examples of such transparent media include various types of plastics, cast or fabricated as plastic sheets. The switchable portion


102


switches between the transparent (or semi-transparent) state, which is unsuitable for the receipt of a projected image, to a translucent or opaque state which will readily receive a projected image.




The switchable portion


102


may be provided by equipping the transparent screen


101


with an electrical, chemical or photosensitive material which is transparent in the absence of a stimulus, but switches to a translucent or opaque state upon receipt of a particular stimulus. Examples of electrochromic, photochromic, and electrophoretic materials which may be advantageously employed in this function are well known to those of ordinary skill in the art. For example, a polymer dispersed liquid crystal material as is commonly available may be sandwiched between sheets of glass or plastic in one or more portions of a transparent sheet. As oriented in the standard configuration, the molecules of liquid crystal material will allow for the passage of light there through, i.e., the portion is transparent. However, upon application of a relatively small electrical stimulus, the molecules of liquid crystal material may be made to change their orientation, thus taking on a translucent or nearly opaque appearance and making such area of the transparent sheet suitable for the receipt of a projected image. Such switchable materials are disclosed within J. W. Doane et al.,


Displays from a New Type of Liquid Crystal Microdroplet Dispersion


, IEEE, 1985 International Display Research Conference, pp. 153-154 (1985); J. W. Doane et al.,


Wide-Angle-View PDLC Displays


, SID 90 DIGEST, pp. 224-226 (1990); Z. Yaniv et al.,


Active Matrix Polviner Dispersed Liquid Crystal Display


, JAPAN DISPLAY, pp. 572-575 (1989), which are all incorporated by reference herein.




Alternatively, the medium


101


may be coated with a special resin called a photopolymer which is capable of refracting light in the manner of a prism. The screen is configured to polarize the incident light falling on different areas of the screen (angle of incidence at screen center may be 35°) so that it emerges from the front evenly to produce a bright and clear image with a high degree of uniformity. Thus, when the projector is off, light entering the medium in a substantially perpendicular manner will be allowed to pass through so that a person can see directly through the medium. However, if an image is projected at a specified angle to the medium, such an image is projected onto the medium for viewing. Such a projection system is available commercially from Hitachi.




While

FIGS. 1

,


2


and


3


illustrate but a single switchable portion


102


on the transparent sheet


101


, it is to be understood that the invention is not so limited. For example, and as is illustrated in

FIG. 4

, a plurality of image projectors


404


,


405


may be used to provide a plurality of projected images onto a plurality of switchable portions


402


,


403


of a transparent sheet


401


or plural sheets. Such an embodiment would have great utility in, for example, retail settings.




In yet another embodiment, two or more portions may be arranged in an overlapping relationship. This overlapping relationship may be either a situation in which two portions directly overlay one another, or partially do so. If two overlay one another completely, such a configuration may be employed to allow images to be projected in differing light conditions. For example, the first portion may be a darker translucent portion for better image quality in a first set of light conditions, while the second portion may be a lighter translucent portion adapted for a second set of light conditions. Each of the portions would of course be independently controllable.




Referring to

FIG. 5

, there is illustrated a projection system in accordance with the present invention whereby an image projector


501


is projecting an image onto portion


102


of medium


101


. A microcontroller or personal computer (PC)


503


may control what images are projected by projector


501


, and may control a shutter


502


so that projector


501


can remain continuously on, without having to be turned on and off, and merely provide for the projection of the image out of the projector


501


in accordance with the algorithm as described below with respect to FIG.


6


. Simultaneously, when the shutter


502


is opened, the medium


101


can be made to have its portion


102


be translucent for receipt of the projected image. Furthermore, if a shutter is not used, there may be a residual leaking of light projected from the projector onto the screen, thus causing a noticeable light spot. Use of the shutter maintains a “true” black image on the screen when there is no video.




The shutter


502


can be controlled to open only when the video source is actually projecting an image. Such a video source could be a videotape, DVD, or any other source that provides a video signal. In addition, the switching of the medium from translucent to transparent and vice versa can also be made dependent upon the presence of a video signal sending video images.




Referring to

FIG. 8

, there is illustrated an embodiment of a circuit that can accomplish the foregoing. Such a circuit could be implemented anywhere within the systems described herein. Video is received at Jack J


1


and looped through via jack J


2


. Capacitor C


1


AC couples the video signal to the amplifier A


1


while resistor R


2


provides a DC reference. Resistors R


3


and R


4


are used to provide a fixed DC offset to the amplifier A


1


that in turns saturates the AC signal to the power supply rails. Transistor Q


1


converts the digitized AC signal while the combination of resistors R


6


and R


7


and capacitor C


3


provide further delay to insure a more digitized AC signal. The basic function of this portion of this circuit is to provide an asserted digital signal (e.g., a high or 1 signal) when any form of an AC signal has been received at jack J


1


, and a negated digital signal (e.g., a low or 0 signal) when there is no AC signal (e.g., no video signal).




The combination of inverter


11


, diode D


1


, resistor R


8


and capacitor C


4


provides a first past delay while inverter


11


, diode D


2


, resistor R


10


, resistor R


11


, and capacitor C


6


provide an adjustable delay for when there is a brief blank space (i.e., no video signal) imbedded within the video stream received at jack J


1


. This reduces false triggering of the shutter and window control signals as discussed below. Inverter


13


provides further buffering to inverters


14


and


15


. Switch S


2


is used to place the window control and shutter control signals in either a manual mode (i.e., window off and shutter open) or an automatic mode. An automatic mode turns the window control signal on or off and closes or opens the shutter control signal depending on whether or not a video signal has been detected. For example, when a video signal is detected at jack J


1


, the shutter control signal will transition to an open shutter state, and the window control signal will switch to a translucent state. Transistor Q


2


is used as a high current driver for the control signals, while diode D


4


is a status LED indicating when the shutter control signal is active.




The circuitry encompassing switch S


1


, AC male plug J


3


, fuse F


1


, the transformer, bridge, capacitors C


7


and C


8


, resistor R


17


and diode D


5


function as a basic AC to DC converter used to supply overall power to the remainder of the circuitry in FIG.


8


.




The circuit in

FIG. 8

applies to a single video signal. For video sources with multiple video signals, such as RGB or S-video, the portion of this circuit comprising jacks J


1


and J


2


, resistors R


6


and R


7


and capacitor C


1


can be duplicated for the required number of multiple video sources and electrically OR'd to the remainder of the circuit.





FIG. 6

illustrates a flow diagram of this process. In step


601


, microcontroller


503


will send an image to projector


501


. In step


602


, the image is projected by projector


501


. In step


603


, substantially simultaneously with the opening of the shutter in step


604


the portion


102


is transformed (optionally, in response to the window control signal from circuit


800


) to a translucent state for receipt of the projected image. In step


604


, shutter


502


is opened by circuit


800


using the shutter control signal. The sequence of steps


602


,


603


and


604


can be interchangeable. For example, the process could first switch the screen to a translucent state, then open the shutter, and then project the image. At a later time, in step


606


the shutter


502


will be closed in response to circuit


800


stopping projection


606


of the image (step


605


). Substantially simultaneously with step


606


portion


102


of screen


101


will be switched to a transparent state (optionally, in response to circuit


800


). In a manner similarly as described above, steps


605


,


606


and


607


are interchangeable.




Referring to

FIG. 7A

, there is illustrated an alternative embodiment of the present invention where screen


101


is placed in front of a mirror


701


shown in sideview. As a result, when screen


101


is in a transparent state, viewer


702


will see a reflection of the viewer. When screen


101


is placed in a translucent state and shutter


502


is opened to allow projection of an image from projector


501


, viewer


702


will see the projected image onto screen


101


.




As an example, referring to

FIG. 7B

there is shown a front view of the system in

FIG. 7A

where a viewer


702


sees himself/herself through the transparent screen


101


within the mirror


701


.

FIG. 7C

illustrates the system when an image is projected onto screen


101


so that viewer


702


now sees the projected image.





FIGS. 7D and 7E

illustrate an alternative embodiment of the present invention where screen


101


is positioned in front of mirror


701


so that when the screen


101


is in a transparent state, with no image being projected, the viewer


702


sees himself/herself in mirror


701


.

FIG. 7E

illustrates the projection of a clothing article, such as a dress


705


, projected onto screen


101


so that viewer


702


, who sees himself/herself partially in mirror


701


, can view himself/herself in a virtual image with the dress.




Alternatively, a film implementing the properties of screen


101


could be attached directly onto the glass surface of the mirror.




Furthermore, screen


101


could be positioned so that it is incognito and thus does not present an image to be reflected in mirror


701


. Then, when an image is projected onto screen


101


(maybe in reverse), it will be reflected by mirror


701


, and viewed by persons.




Note, all of the projectors described herein could operate with a shutter implemented as described with respect to FIG.


8


. Also, any projector with a shutter can operate in this manner, without the need for screen


101


.




Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.



Claims
  • 1. An image projection system comprising:a screen controllable between a first state of being substantially transparent and a second state of being substantially translucent; a projector; a mirror, wherein the screen is positioned near the mirror; circuitry for placing the screen in the first state; circuitry for placing the screen in the second state; and circuitry for projecting an image from the projector onto the screen when it is in the second state so that a person views the image reflected from the screen.
  • 2. A method for projecting an image comprising the steps of:positioning a screen a distance away from a projector, the projector incorporating a shutter for permitting or preventing passage of an image projected from the projector towards the screen; automatically opening the shutter upon receipt of a video image by the projector thereby permitting passage of the image from the projector to the screen; and automatically closing the shutter when the video image is not received by the projector.
  • 3. The method as recited in claim 2, wherein the screen further comprises a material that reflects the image when it is projected at an angle relative to the screen.
  • 4. The method as claim 2, wherein the screen further comprises a material that is substantially transparent when the screen is configured to allow the object to be viewed through the screen, and wherein the material is substantially opaque when the image is projected upon it.
  • 5. An image projector comprising:a shutter; and circuitry for automatically opening the shutter upon receipt of a video image by the projector, and automatically closing the shutter when the video image is not received by the projector.
CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of U.S. patent application Ser. No. 09/876,400 entitled “Image Projection System” filed Jun. 7, 2001.

US Referenced Citations (3)
Number Name Date Kind
5426531 Tsukagoshi Jun 1995 A
6572232 Yaniv Jun 2003 B2
6577355 Yaniv Jun 2003 B1
Continuations (1)
Number Date Country
Parent 10/198183 Jul 2002 US
Child 10/372005 US
Continuation in Parts (2)
Number Date Country
Parent 09/876400 Jun 2001 US
Child 10/198183 US
Parent 09/519537 Mar 2000 US
Child 09/876400 US