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(11) EP 1 443 355 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int Cl.: of the grant of the patent: G02B 26/00 (2006.01) G02B 26/08 (2006.01) 22.07.2009 Bulletin 2009/30 F21S 10/00 (2006.01) H05B 37/02 (2006.01) F21V 1/00 (2006.01) (21) Application number: 04075721.3

(22) Date of filing: 07.02.1997

(54) Method of projecting an intensity modulated image and device Verfahren zur Projektion eines intensitätsmodulierten Bildes und Bühnenbeleuchtungsvorrichtung Procédé pour projeter une image modulée en intensité et dispositif d’éclairage de théâtre

(84) Designated Contracting States: (74) Representative: Charig, Raymond Julian et al DE DK FR GB IT Potter Clarkson LLP Park View House (30) Priority: 07.02.1996 US 598077 58 The Ropewalk Nottingham (43) Date of publication of application: NG1 5DD (GB) 04.08.2004 Bulletin 2004/32 (56) References cited: (62) Document number(s) of the earlier application(s) in EP-A- 0 385 706 EP-A- 0 399 496 accordance with Art. 76 EPC: EP-A- 0 511 829 EP-A- 0 662 773 97904053.2 / 0 879 437 WO-A-93/18620 GB-A- 2 267 788 US-A- 4 486 785 US-A- 4 947 302 (73) Proprietor: & , Ltd. US-A- 4 949 020 US-A- 5 023 709 Birmingham B10 0RA (GB) US-A- 5 386 250 US-A- 5 406 176

(72) Inventor: Hewlett, William Derby DE74 2LD (GB)

Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 443 355 B1

Printed by Jouve, 75001 PARIS (FR) 1 EP 1 443 355 B1 2

Description quired, therefore, has made this an impractical task. Re- search continues on how to accomplish this task more FIELD OF THE INVENTION practically. [0007] As described herein, this problem may be ob- [0001] The present invention relates to a programma- 5 viated by providing a digital light beam shape altering ble light beam shaping device. More specifically, the pro- device, e.g. a gobo, which operates completely differently grammable light beam shaping device can alter the than any previous device. Specifically, this device em- shape of light beams passing therethrough, and provide bodies the inventor’s understanding that many of the heat an edge greying effect to those shaped light beams. problems in such a system are obviated if the light beam 10 shape altering device would selectively deflect, instead BACKGROUND OF THE INVENTION of , the undesired light. [0008] The preferred mode uses a digitally-controlled [0002] It is known in the art to shape a light beam. This micromirror semiconductor device. However, any selec- has typically been done using an element known as a tively-controllable multiple-reflecting element could be gobo. A gobo element is usually embodied as either a 15 used for this purpose. These special are used to or an etched mask. The gobo shapes the light create the desired image using an array of small-sized beam like a stencil in the projected light. mirrors which are movably positioned. The micromirrors [0003] Gobos are simple on/off devices: they allow part are arranged in an array that will define the eventual im- of the light beam to pass, and block other parts to prevent age. The resolution of the image is limited by the size of those other parts from passing. Hence mechanical gobos 20 the micromirrors: here 17 um on a side. are very simple devices. Modern -etched gobos go [0009] The mirrors are movable between a first posi- a step further by providing a gray scale effect. tion in which the light is directed onto the field of a pro- [0004] Typically multiple different gobo shapes are ob- jection system, or a second position in which the tained by placing the gobos are placed into a cassette or light is deflected away from the projection lens system. the like which is rotated to select between the different 25 The light deflected away from the lens will appear as a gobos. The gobos themselves can also be rotated within dark point in the resulting image on the illuminated object. the cassette, using the techniques, for example, de- The heat problem is minimized since the micromirrors scribed in U.S. Patent Nos. 5,113,332 and 4,891,738. reflect the unwanted light rather than absorbing it. The GB 2 267 788 describes a dimmer circuit for theatrical, absorbed heat is caused by the quantum imperfections TV or film studio lighting in which the lamp power is varied 30 of the mirror and any gaps between the mirrors. by varying the duty cycle. [0010] A digital micromirror integrated circuit is cur- [0005] All of these techniques, have the drawback that rently manufactured by Texas Instruments Inc., Dallas, only a limited number of gobo shapes can be provided. Texas, and is described in "an overview of Texas Instru- These gobo shapes must be defined in advance. There ment digital micromirror device (DMD) and its application is no capability to provide any kind of gray scale in the 35 to projection displays". This application note describes system. The resolution of the system is also limited by using a digital micromirror device in a television system. the resolution of the machining. This system allows no Red, green and blue as well as intensity grey scales are way to switch gradually between different gobo shapes. obtained in this system by modulating the micromirror In addition, moving between one gobo and another is device at very high rates of speed. The inventor recog- limited by the maximum possible mechanical motion 40 nized that this would operate perfectly for the above-men- speed of the gobo-moving element. tioned purpose. [0006] Various patents and literature have suggested [0011] Also described herein is a device which has using a liquid crystal as a gobo. For example, U.S. Patent small-sized movable, digitally controllable mirrors which No. 5,282,121 describes such a liquid crystal device. Our have positions that can be changed relative to one an- own pending patent application also so suggests. How- 45 other, to use as a light beam shape altering device in this ever, no practical liquid crystal element of this type has system. ever been developed. The extremely high temperatures [0012] Also described herein is the use of such a sys- caused by blocking some of this high intensity beam pro- tem for previously unheard-of applications. These appli- duce enormous amounts of heat. The projection gate cations include active simulation of hard or soft beam sometimes must block beams with intensities in excess 50 edges on the gobo. It is yet another application to allow of 10,000 lumens and sometimes as high as 2000 watts. gobo cross-fading using time control, special effects and The above-discussed patent applications discuss vari- morphing. ous techniques of heat handling. However, because the [0013] Also described herein is a stroboscopic effect light energy is passed through a liquid crystal array, some with variable speed and intensity in a stage lighting sys- of the energy must inevitably be stored by the liquid crys- 55 tem. This includes simulation of a flower strobe. tal. Liquid crystal is not inherently capable of storing such [0014] Also described herein is a multiple colored gobo heat, and the phases of the liquid crystal, in practice, may system which can have split and rotating colors. be destabilized by such heat. The amount of cooling re- [0015] Also described herein is carrying out gobo ro-

2 3 EP 1 443 355 B1 4 tation in software, and allowing absolute position and ve- Figure 9A shows a block diagram of a projection locity control of the gobo rotation using a time slicing tech- system of the present invention; nique. [0016] Also described herein is allowing concentric- Figure 9B shows a color wheel ; and shaped images and unsupported images. 5 [0017] Also described herein is a control system for Figure 10 shows a block diagram of the shadowless the micromirror devices which allows such operation. follow spot embodiment. [0018] Yet another system is a shadowless follow spot, which forms an illuminating beam which is roughly of the DESCRIPTION OF THE PREFERRED EMBODIMENT same shape as the performer, and more preferably pre- 10 cisely the same as the performer. The beam shape of [0022] The preferred embodiment herein begins with the beam spot also tracks the performer’s current outline. a brief description of controllable mirror devices, and the The spot light follows the performer as it the per- way in which the currently-manufactured devices oper- former. This action could be performed manually by an ate. operator or via an automated tracking system, such as 15 [0023] Work on semiconductor-based devices which Wybron’s autopilot. tune the characteristics of light passing therethrough has [0019] Since the beam does not overlap the perform- been ongoing since the 1970’s. There are two kinds of er’s body outline, it does not cast a shadow of the per- known digital micromirror devices. A first type was orig- former. inally called the formal membrane display. This first type [0020] The present invention provides a method for 20 used a silicon membrane that was covered with a met- projecting an intensity modulated image of a scence onto alized polymer membrane. The metalized polymer mem- a stage according to claim 1. The present invention also brane operated as a mirror. provides a stage lighting device according to claim 3. [0024] A capacitor or other element was located below the metalized element. When the capacitor was ener- BRIEF DESCRIPTION OF THE DRAWINGS 25 gized, it attracted the polymer membrane and changed the direction of the resulting reflection. [0021] These and other objects will be readily under- [0025] More modem elements, however, use an elec- stood with reference to the accompanying drawings, in trostatically deflected mirror which changes in position in which: a different way. The mirror developed and available from 30 Texas Instruments, Inc. uses an aluminum mirror which Figure 1 shows a single mirror element of the is sputter-deposited directly onto a wafer. preferred mode, in its first position; [0026] The individual mirrors are shown in Fig. 1. Each individual mirror includes a square mirror plate 100 Figure 2 shows the mirror element in its second po- formed of reflective aluminum cantilevered on hollow alu- sition; 35 minum post 102 on flexible aluminum beams. Each of these mirrors 100 have two stop positions: a landing elec- Figure 3 shows the mirror assembly and its associ- trode, which allows them to arrive into a first position ated optics; shown in Fig. 2, and another electrode against which the mirror rests when in its non-deflected position. These mir- Figure 4 shows more detail about the reflection car- 40 rors are digital devices in the sense that there two "al- ried out by the DMD; lowable" positions are either in a first position which re- flects light to the lens and hence to the illuminated object, Figure 5 shows a block diagram of the control elec- and a second position where the light is reflected to a tronics; scattered position. Light scattering (i.e. selective light re- 45 flection) of this type could also be done with other means, Figure 6 shows a flowchart of a typical operation ; i.e. selectively polarizable polymers, electronically-con- trolled holograms, light valves, or any other means. Figure 7 shows a flowchart of operation of edge ef- [0027] The operation of the dark field projection optics fects operations; which is used according to the preferred micromirror de- 50 vice is shown in Fig. 4. The two bi-stable positions of the Figure 8A shows a flowchart of a first technique of preferred devices are preferably plus or minus 10% from following a performer on stage; the horizontal. [0028] An incoming illumination bundle 303 is incident Figure 8B shows a flowchart of a correlation scheme; at an arc of less than 20° on the digital micromirror device 55 220. The illumination bounces off the mirrors in one of Figure 8C shows a flowchart of another correlation two directions 230 or 232 depending on the mirror posi- scheme; tion. In the first direction 230, the position we call "on", the information is transmitted in the 0° direction towards

3 5 EP 1 443 355 B1 6 lens which focuses the information to the desired loca- light of the properly-shaped onto the stage. The tion. In the second direction of the mirror, the position we rest of the light is reflected away. call "off", the information is deflected away from the de- [0035] The micromirror can be switched between its sired location to the direction. positions in approximately 10 Ps. A normal time for frame [0029] The human eye cannot perceive actions faster 5 refresh rate, which takes into account human persistence than about 1/30 second. Importantly, the mirror transit of vision, is 1/60th of a second or 60 hertz. time from tilted left to tilted right is on the order of 10 Ps. [0036] Various effects can be carried out by modulat- This allows the to be changed in operation many ing the intensity of each mirror pixel within that time frame. orders of magnitude faster than the human eye’s persist- [0037] The monolithic integration which is being ence of vision. 10 formed by Texas Instruments includes associated row [0030] Light source 310 is preferably a high intensity and column decoders thereon. Accordingly, the system light source such as a xenon or metal halide bulb of be- need not include those as part of its control system. tween 600 and 1000 watts. The bulb is preferably sur- [0038] Detailed operation of DMD 320 is shown in Fig. rounded by a of the parabolic or ellipsoidal type 3. The source beam is input to the position 322 which which directs the output from bulb 300 along a first optical 15 transmits the information either towards the stage along incidence path 305. path 325 or away from the stage along path 335. [0031] The preferred embodiment provides a color [0039] The various effects which are usable include cross-fading system 315, such as described in my patent automatic intensity dimming, use of a "shadowless follow no. 5,426,476. Alternately, however, any other color spot", hard or soft beam edges, shutter cut simulation, changing system could be used. This cross-fading sys- 20 gobo cross fading, gobo special effects, stroboscopic ef- tem adjusts the color of the light. The light intensity may fects, color gobos, rotating gobos including absolute po- also be controlled using any kind of associated dimmer; sition and velocity control, and other such effects and either electronic, mechanical or electromechanical combinations thereof. According to the present invention means. More preferably, the DMD 320 could be used to an edge graying effect is produced. All of these effects control beam intensity as described herein. 25 can be controlled by software running on the processor [0032] The light beam projected along path 305 is in- device. Importantly, the characteristics of the projected cident to the digital light altering device embodied as beam (gobo shape, color etc) can be controlled by soft- DMD 320, at point 322. The DMD allows operations be- ware. This enables any software effect which could be tween two different states. When the mirror in the DMD done to any image of any image format to be done to the is pointed to the right, the right beam is reflected along 30 light beam. The software that is used is preferably image path 325 to projection/ combination 330, 332. processing software such as Adobe photoshop ™ Kai’s The zoom lens combination 330, 332 is used to project power tools ™ or the like which are used to manipulate the image from the DMD 320 onto the object of illumina- images. Any kind of image manipulation can be mapped tion, preferably a stage. The size and sharpness quality to the screen. Each incremental changes to the image of the image can therefore be adjusted by repositioning 35 can be mapped to the screen as it occurs. of the lens. When the mirror is tilted to the right, the light [0040] Another important feature of the gobo is its abil- beam is projected along the light path 335, away from ity to project unconnected shapes that cannot be formed projection lens 330/332. The pixels which have light by a stencil. An example is two concentric circles. A con- beams projected away from the lens appear as dark centric circle gobo needs physical connection between points in the resulting image. The dark spots are not dis- 40 the circles. Other unconnected shapes which are capable played on the stage. of rendering as an image can also be displayed. [0033] This DMD system reflects information from all [0041] The effects carried out by the software are pixels. Hence, minimal energy is absorbed in the DMD grouped into three different categories: an edge effects itself or any of the other optics. The device still may get processing; an image shape processing; and a duty cycle hot, however, not nearly as hot as the liquid crystal gobos. 45 processing. Cooling 325 may still be necessary. the DMDs can be [0042] The overall control system is shown in block cooled using any of the techniques described in (Born- diagram form in Fig. 5. Microprocessor 500 operates horst LCD), or by a heat sink and convection, or by blow- based on a program which executes, inter alia, the flow- ing cold air from a refrigeration unit across the device. chart of Fig. 6. The light shape altering operates accord- More preferably, a hot or cool mirror can be used in the 50 ing to a stencil outline. This stencil outline can be any path of the light beam to reflect infrared out of the light image or image portion. An image from image source beam to minimize the transmitted heat. Figure 3 shows 550 is input to a format converter 552 which converts the hot mirror 340 reflecting infra red 332 to heat sink 334. image from its native form into that is com- A cold mirror would be used with a folded optical path. patable with storage on a computer. The preferred digital [0034] This basic system allows selecting a particular 55 image formats include a bitmap format or compressed aperture shape with which to which pass the light. That bitmap form such as the GIF, JPEG, PCX format (1 bit shape is then defined in terms of pixels, and these pixels per pixel) file, a "BMP" file (8 bits/pixel B/W or 24 bits/ are mapped to DMD 320. The DMD selectively reflects pixel color) or a geometric description (vectorized image).

4 7 EP 1 443 355 B1 8

Moving images could also be sent in any animation for- special effects. Each of these processing elements can mat such as MPEG or the like. It should be understood select the speed of the processing to effectively time- that any image representation format could be used to slice the image. The morphing preferably synchronizes represent the image, and that any of these representa- keyframes of the morph with desired time slices. tions can be used to create information that can modify 5 [0049] Step 602 defines the operation. As described reflecting positions of the array of reflecting devices. The above, this operation can include rotation, position shift, present specification uses the term "digital representa- and the like. Step 604 defines the time or velocity of op- tion" to generically refer to any of these formats that can eration. This time can be ending time for all or part of the be used to represent an image, and are manipulable by movement, or velocity of the movement. Note that all of computers. 10 the effects carried out in step 602 require moving some [0043] Image 554 is input into a working memory 556. part of the image from one position to another. BMP format represents each "pixel" picture element of [0050] Step 606 determine the interval of slicing, de- the image by a number of bits. A typical gray scale bit pending on the velocity. It is desireable to slice an ap- map image has 8 bits representing each pixel. A colored propriate amount such that the user does not see jerky image of this type has 8 bits representing each of red, 15 motion. Ideally, in fact, we could slice movement of the green, and blue representations. This color representa- image one pixel at a time, but this is probably unneces- tion is called a 24-bit representation, since 24-bits are sary for most applications. One hundred pixel slicing is necessary for each pixel. The description herein will be probably sufficient for all applications. The pixel slices given with reference to gray scale images although it are selected at step 606. should be understood that this system can also be used 20 Step 608 calculates using the time or velocity entered at with color images by forming more detailed maps of the step 604 to determine the necessary time for operation information. Bit maps are easiest to process, but ex- based on the amount of position shift for rotation over tremely wasteful of storage space. 100 pixel slices. This is done as follows. Position shift, [0044] Each memory area, representing each pixel, rotate, and sprite animation are all simple movements. therefore, has 8 bits therein. The memory 556 is 576 x 25 In both, the points of the image which define the gobo 768 area, corresponding to the number of mirror ele- shape move over time. It is important, therefore, to decide ments in the preferred use. how much movement there is and how much time that [0045] This image is defined as image No. x, and can movement will take. A rate of change of points or velocity be stored in nonvolatile memory 520 (e.g., RAM or is then calculated. Of course velocity need not be calcu- hard disk) for later recall therefrom. The images are 30 lated if it has already been entered at step 604. stored electronically, and hence these images can also [0051] Having velocity of movement and pixels per be electronically processed in real time using image second, the time between slices is calculated using 100 processing software. Since the preferred mode of the pixels per slice divided by the velocity in pixels per sec- present invention manipulates the image information in ond. The direction of movement is defined by this oper- bitmap form, this image processing can be carried out in 35 ation. a very quick succession. [0052] Therefore, the image is recalculated at step 610 [0046] The image to be projected is sent, by processor for each time interval. This new image becomes the new 500, over channel 560, to VRAM 570. Line driver 562 gobo stencil at the new location. That is to say, the outline and line receiver 564 buffer the signal at both ends. The of the image is preferably used as the gobo-light within channel can be a local bus inside the lamp unit, or can 40 the image is passed, and light outside the image is be a transmission line, such as a serial bus. The image blocked. In the color embodiment described herein, more information can be sent in any of the forms described sophisticated operations can be carried out on the image. above. For example, this is not limited to stencil images, and [0047] Standard and commonly available image could include for example concentric circles or letter text processing software is available to carry out many func- 45 with font selection. tions described herein. These include for example, mor- [0053] At any particular time, the image in the VRAM phing, rotating, scaling, edge blurring, and other opera- 570 is used as the gobo stencil. This is carried out as tions that are described herein. Commercial image follows. Each element in the image is a gray scale of 8- processing can use "Kai’s Power Tools", "CorelDraw!", bits. Each 1/60th of a second is time-sliced into 256 dif- or "Morph Studio" for example. These functions are 50 ferent periods. Quite conveniently, the 8-bit pixel image shown with reference to the flowchart of Fig. 6. corresponds to 28 = 256. [0048] Step 600 represents the system determining [0054] A pixel value of 1 indicates that light at the po- the kind of operation which has been requested: between sition of the pixel will be shown on the stage. A pixel value edge processing, image processing, and duty cycle of zero indicates that light at the position of the pixel will processing. The image processing operations will be de- 55 not be shown on the stage. Any gray scale value means fined first. Briefly stated, the image processing operations that only part of the intensity pixel will be shown (for only include rotation of the image, image morphing from im- part of the time of the 1/60th of a second time slice). age 1 to image 2, dynamic control of image shape and Hence, each element in the memory is applied to one

5 9 EP 1 443 355 B1 10 pixel of the DMD, e.g. one or many micromirrors, to dis- ow is undesirable. play that one pixel on the stage. [0063] It is an object of this embodiment to illuminate [0055] When edge processing is selected at step 600, an area of the stage confined to the performer, without control passes to the flowchart of Fig. 7. The edge graying illuminating any location outside of the performer’s area. can be selected as either a gradual edge graying or a 5 This is accomplished by advantageous processing struc- more abrupt edge graying. This includes one area of total ture which forms a "shadowless follow spot". This is done light, one area of only partial light, and one area of no using the basic block diagram of Fig. 10. light. The intensity of the gray scaled outline is continu- [0064] The preferred hardware is shown in Fig. 10. ously graded from full image transmission to no image Processor 1020 carries out the operations explained with transmission. The intensity variation is effected by ad- 10 reference to the following flowcharts which define differ- justing the duty cycle of the on and off times. ent ways of following the performer. In all of these em- [0056] Step 700 obtains the image and defines its out- bodiments, the shape of the performer on the stage is lines. This is carried out by determining the boundary determined. This can be done by (1) determining the per- point between light transmitting portions (1’s) and light former’s shape by some means, e.g. manual, and follow- blocking portions (0’s). The outline is stretched in all di- 15 ing that shape; (2) correlating over the image looking for rections at step 702 to form a larger but concentric image a human body shape; (3) infra red detection of the per- -- a stretched image. former’s location followed by expanding that location to [0057] The area between the original image and the the shape of the performer; (4) image subtraction; (5) stretched image is filled with desired gray scale informa- detection of special indices on the performer, e.g. an ul- tion. Step 704 carries this out for all points which are 20 trasonic beacon, or, any other technique even manual between the outline and the stretch image. following of the image by, for example, an operator fol- [0058] This new image is sent to memory 570 at step lowing the performer’s location on a screen using a 706. As described above, the image in the memory is mouse. always used to project the image-shaped information. [0065] Fig. 8A shows a flowchart of (1) above. At step This uses standard display technology whereby the dis- 25 8001, the performer is located within the image. The cam- play system is continually updated using data stored in era taking the image is preferably located at the lamp the memory. illuminating the scene in order to avoid parallax. The im- [0059] The duty cycle processing in the flowchart of age can be manually investigated at each lamp or down- Figure 6 is used to form strobe effects and/or to adjust loaded to some central processor for this purpose. intensity. In both cases, the image is stored in memory 30 [0066] Once identified, the borders of the performer and removed from memory at periodic intervals. This op- are found at 8005. Those borders are identified, for ex- eration prevents any light from being projected toward ample, by abrupt color changes near the identified point. the stage at those intervals, and is hence referred to as At step 8010, those changes are used to define a "stencil" masking. When the image is masked, all values in the outline that is slightly smaller than the performer at 8010. memory become zero, and hence this projects all black 35 That stencil outline is ued as a gobo for the light at 8015. toward the source. This is done for a time which is shorter [0067] The performer continues to move, and at 8020 than persistence of vision, so the information cannot be the processor follows the changing border shape. The perceived by the human eye. Persistence of vision aver- changing border shape produces a new outline which is ages the total light impinging on the scene. The eye fed to 8010 at which time a new gobo stencil is defined. hence sees the duty cycle processing as a different in- 40 [0068] Alternative (2) described above is a correlation tensity. technique. A flowchart of this operation is shown in Fig. [0060] The stroboscopic effect turns on and off the in- 8B. At step 8101, the obtains an image of the tensity, ranging from about 1 Hz to 24 Hz. This produces performer, and the performer is identified within that im- a strobe effect. age. That image issued as a kernel for further later cor- [0061] These and other image processing operations 45 relation. The entire scene is obtained at step 8105. The can be carried out: (1) in each projection lamp based on whole scene is correlated against the kernel at 8110. This a pre-stored or downloaded command; (2) in a main uses known image processing techniques. processing console; or (3) in both. [0069] The above can be improved by (3), wherein in- [0062] Another aspect which will now be described is fra red detection gives the approximate area for the per- based on the inventor’s recognition of a problem that has 50 former. existed in the art of stage lighting. Specifically, when a [0070] As explained in previous embodiments, the performer is on the stage, a spotlight illuminates the per- DMD is capable of updating its position very often: for former’s area. However, the inventor of the present in- example, 106 times a second. This is much faster than vention recognized a problem in doing this. Specifically, any real world image can move. Thirty times a second since we want to see the performer, we must illuminate 55 would certainly be sufficient to image the performer’s the performer’s area. However, when we illuminate out- movements. Accordingly, the preferred embodiment al- side the performer’s area, it casts a shadow on the stage lows setting the number of frame updates per second. A behind the performer. In many circumstances, this shad- frame update time of 30 per second is sufficient for most

6 11 EP 1 443 355 B1 12 applications. This minimizes the load on the processor, en by a rotating source 910, synchronized with the op- and enables less expensive image processing equip- eration of spinning of the color disk 902. The video is ment to be used. driven to produce a red frame, then a green frame, then [0071] Figure 8C shows the image subtracting tech- a blue frame, one after another, for example. The red nique. 5 filtered video is transferred at the same moment when [0072] First, we must obtain a zeroing image. There- the red sector 950 is in the light path. So as long as the fore, the first step at step 800, is to obtain an image of different colors are switched faster than the eye’s per- the stage without the performer(s) thereon. This zero im- sistence of vision, the eye will average them together to age represents what the stage will look like when the see a full color scene. performers are not there. 10 [0078] Although only a few embodiments have been [0073] Between processing iterations, the processor described in detail above, those having ordinary skill in can carry out other housekeeping tasks or can simply the art will certainly understand that many modifications remain idle. are possible in the preferred embodiment without depart- [0074] Step 802 represents the beginning of a frame ing from the teachings thereof. update. An image is acquired from the video camera 550 15 [0079] For example, any direction deflecting device at step 804. The image is still preferably arranged in units could be used in place of the DMD. A custom micro mirror of pixels, with each pixel including a value of intensity device would be transparent, and have thin mirrors that and perhaps red, green, and blue for that pixel. "stowed" at 90°. to the light beam to allow the beam to [0075] At step 806 subtracts the current image from pass, and turned off by moving to a reflecting position to the zeroed image. The performer image that remains is 20 scatter select pixels of the light beam. The color changing the image of the performer(s) and other new elements devices could be any device including dichroics. on the stage only. The computer determines at this time which part of that image we want to use to obtain the shadowless follow spot. This is done at step 808 by cor- Claims relating the image that remains against a reference, to 25 determine the proper part of the image to be converted 1. A method of projecting an intensity modulated image into a shadowless follow spot. The image of the performer of a scene onto a stage (582), comprising: is separated from other things in the image. Preferably it is known for example what the performer will wear, or determining a factor of modulation; some image of a unique characteristic of the performer 30 translating the factor into a duty cycle, each por- has been made. That unique characteristic is correlated tion of the duty cycle being a time shorter than against the performer image to determine the performer a persistence of vision of the human eye; only at the output of step 808. This image is digitized at defining (602) a first shape of light to be project- step 810: that is all parts of this image which are not ed; performer are set to zeros so that light at those positions 35 adjusting some portion of the first shape of light is reflected. In this way, a gobo-like image is obtained at to form a second shape of light different from step 810, that gobo-like image being a changing cutout the first shape so as to project said portion at a image of the performer. An optional step 812 further proc- duty cycle ratio less than one, said duty cycle esses this image to remove artifacts, and preferably to having a frequency greater than a persistence shrink the image slightly so that it does not come too 40 of vision of the human eye; and close to the edge of the performer’s outline. This image alternately projecting the first shape of light and is then transferred to the VRAM at step 814, at which the second shape of light onto the stage at al- time it is re-entered into the DMD 1012 to form a gobo- ternate times defined by said duty cycle to create like mask for the lamp. This allows the light to be appro- said intensity modulated image of the scene, priately shaped to agree with the outline of the performer 45 and so that persistence of vision averages the 1004. total light impinging on the stage, characterised [0076] Another embodiment uses the above described in that said portion is an edge portion of the techniques and basic system to provide color to the lamp shape which is displayed at the duty cycle ratio, gobo. This is done using techniques that were postulated while other portions of the first shape are dis- in the early days of color tv, and which now find a renewed 50 played substantially continuously thereby pro- use. This system allows colored gobos, and more gen- ducing an edge graying effect. erally, allows any video image to be displayed. [0077] Figure 9A shows the lamp 310 in a series with 2. The method of claim 1 wherein said duty cycle is a rotating multicolored disk 902. Fig. 9B shows the three greater than 60 Hz. sectors of the disk. Red sector 950, a blue sector 952, 55 and a green sector 954. The light along the optical path 3. A stage lighting device for projecting an intensity 904 is colored by passing through one of these three modulated image of a scene onto a stage (582), com- quadrants, and then through DMD 320. DMD 320 is driv- prising:

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determining means to determine a factor of mod- sten Form im Wesentlichen kontinuierlich ange- ulation; zeigt werden, wodurch ein Kantengraueffekt er- translating means to translate the factor into a zeugt wird. duty cycle, each portion of the duty cycle being a time shorter than a persistence of vision of the 5 2. Verfahren nach Anspruch 1, bei dem der Lastzyklus human eye; größer als 60 Hz ist. a controller, adapted to define a first shape of light to be projected onto the stage (582) and to 3. Bühnenbeleuchtungsvorrichtung zur Projizierung ei- adjust some portion of the first shape of light to nes intensitätsmodulierten Bildes einer Szene auf form a second shape of light different from the 10 eine Bühne (582) mit: first shape so as to project said portion at a duty cycle ratio less than one, said duty cycle having Bestimmungsmitteln zum Bestimmen eines a frequency greater than a persistence of vision Faktor der Modulation; of the human eye; and Übersetzungsmittel zum Übersetzen des Fak- projecting means (310, 320) to alternately 15 tors in einen Lastzyklus, wobei jeder Abschnitt project the first shape of light and the second des Lastzyklus kürzer als die Augenträgheit des shape of light onto the stage at alternate times menschlichen Auges ist; defined by said duty cycle to create said intensity einer Steuerung, die ausgestaltet ist, um eine modulated image of the scene, and so that per- erste Form des Lichtes festzulegen, die auf die sistence of vision averages the total light imping- 20 Bühne (582) zu projizieren ist, und um einen Ab- ing on the stage, characterised in that said por- schnitt der ersten Form des Lichtes anzupas- tion is an edge portion of the shape which is sen, um eine zweite Form des Lichtes zu bilden, displayed at the duty cycle ratio, while other por- die von der ersten Form unterschiedlich ist, um tions of the first shape are displayed substan- so den Abschnitt mit einem Lastzyklusverhältnis tially continuously thereby producing an edge 25 kleiner als 1 zu projizieren, wobei der Lastzyklus graying effect. eine Frequenz hat, die größer als die Augen- trägheit des menschlichen Auges ist; und Projektionsmitteln (310, 320) zum abwechseln- Patentansprüche den projizieren der ersten Form des Lichts und 30 der zweiten Form des Lichts auf die Bühne mit 1. Verfahren zur Projizierung eines intensitätsmodu- abwechselnden Zeiten, die durch den Lastzy- lierten Bildes einer Szene auf eine Bühne (582) mit: klus festgelegt sind, um so das intensitätsmo- dulierte Bild der Szene zu erzeugen, und sodass Bestimmen eines Faktors der Modulation; die Augenträgheit das gesamte Licht, das auf Übersetzen des Faktors in einen Lastzyklus, 35 die Bühne einfällt, mittelt, dadurch gekenn- wobei jeder Teil des Lastzyklus in der Zeit kürzer zeichnet, dass als die Augenträgheit des menschlichen Auges der Abschnitt ein Randabschnitt der Form ist, ist; der während des Lastzyklusverhältnisses ange- Festlegen (602) einer ersten Form des zu pro- zeigt wird, während andere Abschnitte der er- jizierenden Lichtes; 40 sten Form im Wesentlichen kontinuierlich ange- Anpassen eines Teils der ersten Form des Lich- zeigt werden, wodurch ein Kantengraueffekt er- tes zur Ausbildung einer zweiten Form des Lich- zeugt wird. tes, die sich von der ersten Form unterscheidet, um so den Teil mit einem Lastzyklusverhältnis, das kleiner als 1 ist, zu projizieren, wobei der 45 Revendications Lastzyklus eine Frequenz größer als Augenträg- heit des menschlichen Auges hat; und 1. Procédé de projection d’une image à modulation abwechselndes Projizieren der ersten Form des d’intensité d’une scène sur une plate-forme (582), Lichtes und der zweiten Form des Lichtes auf comprenant les étapes consistant à : die Bühne zu abwechselnden Zeiten, die durch 50 den Lastzyklus festgelegt sind, um so das inten- déterminer un facteur de modulation ; sitätsmodulierte Bild der Szene zu erzeugen, traduire le facteur en un cycle de service, cha- und sodass die Augenträgheit das Gesamtlicht, que partie du cycle de service étant d’une durée das auf die Bühne fällt, mittelt, dadurch ge- plus courte qu’une persistance de vision de l’oeil kennzeichnet, dass 55 humain ; der Abschnitt ein Randabschnitt der Form ist, définir (602) une première forme de lumière des- der während des Lastzyklusverhältnisses ange- tinée à être projetée ; zeigt wird, während andere Abschnitte der er- ajuster une certaine partie de la première forme

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de lumière pour former une seconde forme de lumière différente de la première forme afin de projeter ladite partie à un rapport de cycle de service inférieur à un, ledit cycle de service pos- sédant une fréquence plus importante qu’une 5 persistance de vision de l’oeil humain ; et projeter en alternance la première forme de lu- mière et la seconde forme de lumière sur la pla- te-forme à des temps alternés définis par ledit cycle de service pour créer ladite image à mo- 10 dulation d’intensité de la scène, et de sorte que la persistance de vision atteigne une moyenne de la lumière totale incidente sur la plate-forme, caractérisé en ce que ladite partie est une par- tie de bord de la forme qui est affichée au rapport 15 de cycle de service, alors que d’autres parties de la première forme sont affichées de façon sensiblement continue, produisant ainsi un effet grisé de bord. 20 2. Procédé selon la revendication 1, dans lequel ledit cycle de service est supérieur à 60 Hz.

3. Dispositif d’éclairage de plate-forme pour projeter une image à modulation d’intensité d’une scène sur 25 une plate-forme (582), comprenant :

des moyens de détermination destinés à déter- miner un facteur de modulation ; des moyens de traduction destinés à traduire le 30 facteur en un cycle de service, chaque partie du cycle de service étant d’une durée plus courte qu’une persistance de vision de l’oeil humain ; un dispositif de commande, adapté pour définir une première forme de lumière destinée à être 35 projetée sur la plate-forme (582) et pour ajuster une certaine partie de la première forme de lu- mière pour former une seconde forme de lumiè- re différente de la première forme afin de proje- ter ladite partie à un rapport de cycle de service 40 inférieur à un, ledit cycle de service possédant une fréquence plus importante qu’une persis- tance de vision de l’oeil humain ; et des moyens de projection (310, 320) pour pro- jeter en alternance la première forme de lumière 45 et la seconde forme de lumière sur la plate-for- me à des temps alternés définis par ledit cycle de service pour créer ladite image à modulation d’intensité de la scène, et de sorte que la per- sistance de vision atteigne une moyenne de la 50 lumière totale incidente sur la plate-forme, ca- ractérisé en ce que ladite partie est une partie de bord de la forme qui est affichée au rapport de cycle de service, alors que d’autres parties de la première forme sont affichées de façon 55 sensiblement continue, produisant ainsi un effet grisé de bord.

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• US 5113332 A [0004] • US 5282121 A [0006] • US 4891738 A [0004] • US 5426476 A [0031] • GB 2267788 A [0004]

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