Abstract:
A dimmer wheel which is formed to absorb large amounts of light and to disperse the light that is absorbed. The dimmer wheel has a bottom surface that is irregular, and a reflective material in that bottom surface to scatter the light. A light absorbing material also receives some of the light.

Description:
BACKGROUND 
     Stage lighting systems typically use an array of structures arranged along an optical axis to effect the characteristics of the light along that optical axis. 
     Our copending application Ser. No. 11/687,579 describes the use and functions of a relay lens in such a stage lighting device. 
     SUMMARY 
     The present application describes a special dimmer for use in a stage lighting device and describes formation of that dimmer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an optical train of an embodiment;
           FIG. 2  shows a rotatable dimmer wheel;     FIG. 3  shows a cross section of etched glass;     FIG. 4  shows a laser operation from the front; and     FIG. 5  shows a laser operation from the rear.       

     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an embodiment as used in an optical system of the type described in our copending application Ser. No. 11/687,579, the entire disclosure of which is herewith incorporated by reference. A lighting device  100  produces light along an optical path shown as  105 . A number of light altering elements are within the optical path. A first gobo  110  can shape the light or otherwise create effects within the light beam. The gobo can be etched metal or dichroic, for example. In the embodiment, for example, the gobo may be a dichroic or half-tone gobo of a specified pattern. 
     A relay lens assembly  120  is formed of a first relay lens part  121  and a second relay lens part  122 . A stop  123  is defined between the first and second relay lens parts. Optical items that are placed into the stop  123  are integrated by the action of the relay lens. A second gobo  130  is located optically downstream of the relay lens. When the first gobo  110  and second gobo  130  are placed precisely in the same focus position, certain effects may be obtained. 
     A zoom lens assembly  140  receives the light that has been altered in this way, and projects it towards a target, for example a stage shown as  150 . 
     Different items placed in the stop effect the light that passes through the system. A dimmer, for example  160 , may be placed into the stop  123 . The dimmer may be partially or completely inserted into the stop  123 . The amount of dimming effect may depend, for example, on the amount by which the dimmer is inserted into the stop  123 . 
     However, the inventor noticed that if the dimmer is metal or absorptive, it absorbs the energy in the optical stop, and this energy may significantly heat the material of the dimmer. This may cause the dimmer to get hot enough to cause problems with the dimmer. For example, when the dimmer gets too hot, it may crack some of the glass, or cause other heat related effects. 
     A dark mirror, if used, for example, could burn up from the heat. 
     The inventor realized that a dimmer than is reflective and neither specular nor diffuse could be used for such a system. An embodiment of such a dimmer is shown in  FIG. 2 . 
       FIG. 2  illustrates a dimmer wheel which is rotatable around a central axis  200  by a dimmer motor  205 . The location of the dimmer motor sets the amount of the dimming effect. For example, the dimmer wheel  199  includes fingers  210  which are narrower at one location and gradually broaden towards another rotational location. The fingers are narrowest at the area  211 , and are broadest at the area  212 . Therefore, rotating the dimmer in a counterclockwise direction causes more of the area of the fingers to be placed in the light beam, and hence more of a dimming effect. The wheel may also have a completely opaque portion  215 , and a completely clear portion  220 , so that the dimming effect can be maximum when the portion  215  is in the stop, and can be minimized when the portion  220  as in the stop. 
     In an embodiment, the wheel is formed from etched glass. Each of the fingers such as  210 ,  213  are formed of etched glass with an irregular surface. The irregular surface is filled with a material (e.g., the aluminum/dark mirror sandwich as described herein) that disperses the incoming light rather than absorbing or fully reflecting it. 
       FIG. 3  illustrates a cross-section of the etched glass. Vias  300  are formed within the glass, and filled with an aluminum/dark mirror sandwich. Aluminum  305  is formed below the top surface of the glass  299  in the etched via. Dark mirror material  310  is formed above the surface of the glass. A weak etchant is used to flake the surface in a way that causes an irregular bottom portion instead of flat portions, can be used for this purpose. 
     The inventors noticed another problem illustrated with reference to  FIG. 4 .  FIG. 4  shows a cross-section of a typical light absorbing part including glass  400 , aluminum  405 , and dark mirror material  410 . Removing portions of this light absorbing part this might typically be done with a laser such as a UV laser shown as  415 . 
     A problem, however, is that it may be difficult to remove a thin layer of the aluminum. This can chip the glass  400 , and/or leave a hole in the glass substrate. In the embodiment, therefore, a laser is used from the backside of the device, that is, the uncoated side of the substrate. 
     In an embodiment the laser  450  shown in  FIG. 5  from the backside of the substrate, to remove a thin layer. 
     In an embodiment, a thin layer of reflective silicon  500  is used under the dark mirror material  505  in place of the aluminum. This thin layer of this embodiment is transparent to infrared, and therefore does not heat up as much as other materials. 
     Although only a few embodiments have been disclosed in detail above, other embodiments are possible and the inventors intend these to be encompassed within this specification. The specification describes specific examples to accomplish a more general goal that may be accomplished in another way. This disclosure is intended to be exemplary, and the claims are intended to cover any modification or alternative which might be predictable to a person having ordinary skill in the art. For example, other commands and command forms can be used. 
     Also, the inventors intend that only those claims which use the words “means for” are intended to be interpreted under 35 USC 112, sixth paragraph. Moreover, no limitations from the specification are intended to be read into any claims, unless those limitations are expressly included in the claims. The computers described herein may be any kind of computer, either general purpose, or some specific purpose computer such as a workstation. The computer may be a Pentium class computer, running Windows XP or Linux, or may be a Macintosh computer. The computer may also be a handheld computer, such as a PDA, cellphone, or laptop. 
     The programs may be written in C, or Java, Brew or any other programming language. The programs may be resident on a storage medium, e.g., magnetic or optical, e.g. the computer hard drive, a removable disk or media such as a memory stick or SD media, or other removable medium. The programs may also be run over a network, for example, with a server or other machine sending signals to the local machine, which allows the local machine to carry out the operations described herein.