Abstract:
Diffusing light illuminating a light target or subject of a film or video production including placing a diffusion panel between a light source and a light target, energizing said light source so as to direct light therefrom through the diffusion panel, and electrically adjusting the transparency of the diffusion panel by changing an electric potential applied to electrodes of the diffusion panel. The electrically adjustable diffusion panel eliminates the need for manually changing diffusion papers or other filters and provides a continuous range of selectable levels of transparency/diffusion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. application Ser. No. 13/084,562 filed on Apr. 12, 2011, entitled ELECTRICALLY ADJUSTABLE OPTICAL DIFFUSION FOR LUMINAIRES. 
    
    
     BACKGROUND OF THE INVENTION 
     This disclosure relates to light diffusion techniques used in the film and video production industry and, more particularly, to diffusion of light sources used in film or video production using materials having electrically adjustable light diffusion characteristics. 
     Lighting techniques used in the production of film and video have long been carefully and diligently studied by the artists, technologists, and other professionals practicing in the film and video industry. Careful attention is paid to the creation of lighting conditions so as to achieve particular desired effects. Volumes have been written about the characteristics of light most preferred in a given situation, how various environmental or set conditions impact lighting quality, the considerations that should be given depending upon the subject of the film or video, and so on. Volumes more may be written of the particular equipment preferences that those responsible for lighting on a film or video crew use to accommodate various circumstances. In a conventional motion picture production, the gaffer or lead person on the electrical crew, for example, may work closely with the crew best boy, grips, and other electricians to design and build the lighting setup for a particular production, using experience and industry trade practices to determine the appropriate gels and diffusion materials to put on lights or windows to achieve the desired effects, or to determine whether or not to use various materials and equipment to re-create particular natural effects within a better controlled stage or to adapt such materials and equipment to allow for on-location filming. Much of the expertise of such professionals is likely maintained as closely held tricks of the trade and other proprietary information. 
     What may be generally true is that innovative approaches to film and video production have been widely sought after and favorably received by the film and video industry in the U.S., particularly where such innovations provide improvements in costs so as to lower overall production costs; improvements in the features and functionality available to the users of newly developed equipment; improvements in quality of equipment or reliability of the equipment or the processes of using various equipment; and improvements in the speed with which film and video production may be successfully completed. 
     Some of the more labor intensive aspects of film and video production involve engineering lighting effects that deliver desired results, accommodate physical space requirements of the set, and provide means for adapting to changes in set conditions such as weather, natural light position, camera angles, and subject position throughout a scene, and other factors requiring, ideally, instant changes in lighting provided for the shoot. The lighting equipment used should be reconfigurable to accommodate a range of different physical space requirements and adaptable to changing set conditions with a minimum of labor. 
     What is needed, therefore, are light diffusion techniques and equipment for the diffusion of light sources used in film or video production that address various shortcomings of existing techniques and equipment. The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL DRAWINGS 
       For a more complete understanding of the present invention, the drawings herein illustrate examples of the invention. The drawings, however, do not limit the scope of the invention. Similar references in the drawings indicate similar elements. 
         FIG. 1  illustrates a film or video set using a remotely adjustable diffusion panel, according to one embodiment. 
         FIG. 2A  illustrates no/low diffusion through an adjustable diffusion panel, according to one embodiment. 
         FIG. 2B  illustrates medium diffusion through an adjustable diffusion panel, according to one embodiment. 
         FIG. 2C  illustrates high/full diffusion through an adjustable diffusion panel, according to one embodiment. 
         FIG. 3  illustrates lighting with multiple adjustable diffusion panels, according to various embodiments. 
         FIG. 4  illustrates components of an exemplary adjustable diffusion panel. 
         FIG. 5A  illustrates exemplary material for an adjustable diffusion panel in one state of transmittance, according to one embodiment. 
         FIG. 5B  illustrates exemplary material for an adjustable diffusion panel in another state of transmittance, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, those skilled in the art will understand that the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternate embodiments. In other instances, well known methods, procedures, components, and systems have not been described in detail. 
     Various operations will be described as multiple discrete steps performed in turn in a manner that is helpful for understanding the present invention. However, the order of description should not be construed as to imply that these operations are necessarily performed in the order they are presented, nor even order dependent. 
     As an overview, a film or video set  100  using a remotely adjustable (or remotely controllable active) diffusion panel  106 , according to one embodiment, is shown in  FIG. 1 . When illuminating a subject  112  with a light source  104  for the purpose of photography, videography, motion picture capture, or theater, it is often desirable for the light source  104  to deliver light that is “soft” in nature/character. A light source that delivers such light is often referred to as a “soft source” and is an illumination that appears to emanate from a large area, thereby casting shadows that have gradual transitions from light to dark, or “soft shadows”. In contrast, a “hard source” is an illumination that appears to emanate from a point source such as a single bulb or filament, thereby casting “hard shadows” that have a distinct and deliberate transition from light to dark. 
     Most of the illumination sources used are point source type lights such as filament-based incandescent bulbs. Such lights cast harsh or distinct shadows. Various methods of light diffusion may be used to help soften the light source as its light appears to the subject. One method to soften the light is to place a relatively large piece of semi-transparent material between the hard light source and the subject to diffuse the hard light. The diffusion material is illuminated on one side by the hard light source and appears to glow relatively uniformly on the opposite side which faces the subject. The subject then appears to be illuminated by a soft light source effectively as large as the illuminated surface of the diffusion material. 
     Choosing among different diffusion materials most commonly involves choosing material that has particular transparency characteristics. A material with high transparency will make a hard source only slightly softer (if at all) while a more opaque material will be the most effective at softening a hard source. Each subject or lighting situation may require a unique level of diffusion to give “just the right look”, and no single diffusion material having a particular transparency may provide the “right” amount of diffusion for every situation. 
     Consequently, throughout a typical filming shoot the diffusion material (and thus the transparency of the material) is often changed multiple times before the desired level of diffusion appropriate to the subject is achieved. The process of selecting the correct diffusion requires having a wide selection of different grades of diffusion materials on hand, and the physical action of removing and replacing the diffusion material near the light source, which often is placed in locations (i.e. overhead structure  102 ) requiring a ladder or other type of scaffold or lift for sufficient access for placement of the diffusion material. 
     As shown in  FIG. 1 , a active diffusion panel  106  having diffusion material that has an electrically adjustable level of transparency may be used to soften the otherwise hard light  108  from a point source light  104 . The light transmitted  110  to the subject  112  can be selectably changed in terms of its softness using a remote control  118  to vary the degree of transparency of the (active) material used in the diffusion panel  106 . The remote control  118  is preferably connected to the panel  106  by wires  116 , but in other embodiments the control  118  may wirelessly communicate with the (active) panel  106 . Using an active panel  106  that is adapted to provide a range of transparency from clear (or transparent) to substantially opaque eliminates the need for the user  120  or other lighting crew members to physically change the diffusion material to achieve different levels of diffusion and lighting at the subject. The active material in the panel  106  may be adjusted by the user (camera operator or other crew member)  120  at will during the film shoot to compensate for changing levels of natural light, changes in desired overall illumination, or simply to satisfy the visual goals of the photographer. 
       FIGS. 2A-2C  illustrate different levels of diffusion that are preferably provided using an electrically adjustable diffusion panel  106 . Conventional diffusion paper ranges from ¼ stop diffusion paper to full or 1 and ¼ stop paper. Light diffusion or ¾ stop paper is more transparent and only slightly softens the shadows/shadow edges. Medium diffusion or ¾ stop paper softens the shadow edges more, causing shadow edges to fade. And heavy diffusion, such as “Lee Filters #216” (brand named) full stop paper causes shadow edges to fade and blend in so the shadows are nearly completely eliminated. 
       FIG. 2A  illustrates the active panel  106  in a fully transparent mode  214 . In such a mode  214  the panel  106  allows the light  108  projected from light source  104  to appear to the subject  112  without any scattering. The shadows  220  from such setting of the adjustable panel  106  have sharp edges, and the light transmitted  202  is unsoftened. Viewed from the subject  112 , the light source  104  behind the panel  106  may be represented as shown in view  208 , indicating that the light source  104  remains an unsoftened point source of light. In the view  208 , the panel material is fully transparent, without color. As the diffusion setting  214  is adjusted to provide some diffusion, the view  208  starts to take on, in preferred embodiments, a whitish or cloudy appearance. 
       FIG. 2B  illustrates a medium diffusion setting  216 , where the transmitted light  204  is diffused (or scattered) to a medium setting  216  whereby the incident light  108  is scattered somewhat as it passes through the panel  106 . With such setting  216 , the shadow  222  is softened so as to lose its distinct edges, and viewing the panel  106  from the view point of the subject  112  may be represented as shown in view  210 , indicating that the light source behind the panel  106  has become softened and made less distinct. With the medium setting  216  the panel  106  material in view  210  takes on a whitish appearance, and the detail of the light source  104  is lost due to the scattering of light allowed through the diffusion material. 
       FIG. 2C  illustrates a heavy diffusion setting  218 , where the transmitted light  206  is now diffused (or scattered) to a heavy setting  218  whereby the incident light  108  is heavily scattered as it passes through the panel  106 . With such setting  218 , the shadow  224  is softened so as to be nearly eliminated, and viewing the panel  106  from the view point of the subject  112  may be represented as shown in view  212 , indicating that the light source behind the panel  106  has become nearly undefined. With the heavy setting  218  the panel  106  material in view  212  takes on a more uniformly whitish appearance, and even the outline of the light source  104  is lost due to the scattering of light allowed through the diffusion material. Adjusting the diffusion of panel  106  to an even heavier (i.e. more diffused) setting preferably causes the panel  106  to become opaque, presenting a view to the subject  112  of a solidly (uniformly) whitish panel. At such a setting, the opaque panel fully blocks the subject  112  from view of the light source  104 . 
     In preferred embodiments, the diffusion provided by panel  106  may be adjusted using a remote control  118  from completely transparent (no diffusion/scattering of the incident light from the light source  104 ) to fully opaque (complete scattering of the incident light from the light source  104 ), with the adjustment of diffusion being continuous so that the user  120  may select from any amount of transparency using the control  118 , from full transparency to no transparency and any selection of transparency therebetween. In other embodiments, the diffusion provided may be adjusted between nearly transparent to nearly opaque, with any selection of transparency therebetween. In still other embodiments, the diffusion may be adjusted so as to correspond with diffusion papers or filters or scrims available in the film and video industry. For example, the diffusion setting  214  may correspond with ¼ stop diffusion papers commonly available, setting  216  may correspond with ¾ stop papers available, and setting  218  may correspond with full stop papers available. In one embodiment, the control  118  may include detents at various commonly used settings or settable/resettable/programmable presets for the convenience of the user  120  to return to desired diffusion settings. 
     Although any type of light source may be used, the light source  104  is preferably a cool light source such as LED or fluorescent lighting. Commonly used incandescent or other hot type lighting may be used with sufficient shielding incorporated into panel  106 , with sufficient spacing between the light source  104  and the panel  106 , and/or with use sufficient cooling means (such as fans, heat sinks, favorable ambient/cooling temperatures, etc.). Preferably, LED lighting such as lighting provided by Zylight LLC (www.zylight.com) is used for the light source  104 . Suitable lighting is also described in the application for U.S. letters patent, application Ser. No. 11/423,443 filed on Jun. 11, 2006, which is hereby incorporated by reference herein in its entirety, and which describes wirelessly controllable and wirelessly networked LED lighting modules. 
     Referring to  FIG. 3 , multiple remotely controllable diffusion panels  104  may be used together. For example, a typical film or video production set may include the lighting set up  300  shown in  FIG. 3 , including a key (or primary) light source  104 , a fill light  302 , a back light  304 , and a background light  306 . In preferred embodiments, each of the active diffusion panels  106  may be remotely electrically controlled so as to provide desired levels of diffusion. The panels  314  and  308  may be set, for example, to medium-to-heavy diffusion settings for transmitting diffused light  322  and  318 , respectively. The panels  310  and  312 , similarly, may be set, for example, to lower diffusion/greater transparency settings for transmitting diffused light  320  and  316 , respectively. 
     Referring to  FIG. 4 , the components  400  of an exemplary adjustable diffusion panel  106  preferably include active material  408  that provides a range of electrically selectable degrees of transparency, frame fastening material  402  for affixing the active material  408  to a rigid or semi-rigid frame  404 , and a controller  414  having circuitry adapted to control an electrical potential applied to the material  408  causing the material to change its transparency in response to the electrical potential selected by the user of the controller  414  and thereby applied to the active material  408 . In one embodiment the controller includes a 9 volt battery, a potentiometer or other potential changing selection knob  416 , wires  412  for delivering an electrical potential (i.e. voltage) to the material  408  via a connection  410 . Preferably the material  408  and frame fastening material  402  (which may be a magnetic backed material, Velcro type material, or other material preferably easily removable from rigid or semi-rigid frame  404 ) are rollable  406  so as to facilitate easy mobility from shoot to shoot. Other structures may be used in place of the frame  404 , and other shapes of the frame  404  may be used. 
     Preferable sizes include a 2 foot by 2 foot diffusion panel  106 , a 3 foot by 3 foot version, and a 4 foot by 4 foot version. Other sizes may be fabricated. Generally, any size and any shape (square, rectangular, irregular, circular, etc.) may be used. Preferably the surface area of the material  408  is large relative to the light source  104  for most applications. An electrically adjustable active diffusion panel  106  may also be used, however, with panel lights (such as the IS3 by Zylight LLC) in soft box or other applications. 
     The active material  408  may comprise any material whose transparency may be electrically adjusted from transparent (or nearly transparent) to opaque (or nearly opaque). In preferred embodiments, the material  408  comprises a polymer dispersed liquid crystal (PDLC) film between layers of flexible, transparent plastic that include a thin layer of conductive, transparent material. The conductive material form transparent electrodes with liquid crystal droplets trapped therebetween, and the liquid crystal droplets align together in varying degrees in response to a voltage applied across the electrodes. With greater voltage, more of the liquid crystals align thus increasing the material&#39;s effective transparency. 
       FIG. 5A  illustrates a cross-section  500  of material  408 , according to one embodiment, where the material  408  is in an “off” state, and  FIG. 5B  illustrates a cross-section  502  of material  408  where the material  408  is in an “on” state. 
     As shown in  FIG. 5A , with no applied voltage  512 , transparent electrodes  520  and  522  do not cause any alignment of the liquid crystal droplets  526 ,  528 , and  524 . Therefore, because each of the liquid crystals transmits light in one direction  530  and blocks light in a perpendicular direction  532 , the cross-section  500  causes incident light  508  to scatter  510  rather than allow transmittance of the light  508  through the PDLC matrix. 
     As shown in  FIG. 5B , the cross-section  502  allows incident light  506  to pass through the PDLC matrix as transmitted light  504  due to the alignment of the liquid crystals  534 ,  536 , and  540  in response to a voltage  514  applied to the transparent electrodes  518  and  516 . The degree of transparency depends upon the voltage applied and degree to which the liquid crystal droplets align together. As shown, the liquid crystals  534 ,  536 , and  540  are all aligned so as to allow incident light to pass through. As the voltage is varied, the alignments are changed causing the material to scatter incident light and take on a milky white or cloudy appearance. For example, reducing the voltage applied to electrodes  518  and  516  preferably causes the liquid crystal  540  to spin out of alignment such that the direction  538  is no longer aligned with the incident light  506  and the direction  542  begins to block the incident light  506 . 
     Although the material  408  in preferred embodiments is constructed as shown and operates as described in  FIGS. 5A and 5B , other arrangements, materials, and configurations may be used that provide the desired electrically adjustable transparency adapted for a diffusion panel  106  as shown and described herein. 
     The terms and expressions which have been employed in the forgoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalence of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.