(19) & (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 stage lighting 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: Light & Sound Design, 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 blocking, 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 optics are used to shutter 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 laser-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 lens 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 stage lighting 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 colors 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 color 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 lights 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.