Patent Publication Number: US-11393372-B2

Title: Video lighting apparatus with full spectrum white color

Description:
BACKGROUND OF THE INVENTION 
     Motion picture visual effects have relied heavily on blue screen and green screen compositing techniques. The use of high resolution video walls or displays to replace green screens is becoming more common. The video image relies on the principle of Red, Green and Blue LEDs (RGB) to render the image. Increasingly cinematographers are trying to use the RGB light emanating from the display screen as an illuminant for the foreground images they are photographing. The RGB spectrum is deficient in broad spectrum white light which is critical for properly rendered skin tones as well as other subject colors. 
     Conventional lighting apparatus are controlled from lighting dimmer boards that send a digital multiplex (DMX) signal for a light to behave in a predetermined manner. Lighting apparatus can consist of several independently controlled elements or pixels. A lighting board can be tailored to synchronize with a video signal but can only generate as many pixel controls as the lighting instrument is designed with. They are large in area and are not designed to reproduce a video image. 
     This invention sets out to create an Illumination apparatus operating on the principles of an RGB video display such as shown in  FIG. 1 . It consists of a plurality of individual pixels per panel, controlled through a video signal as in a video display wall. 
     SUMMARY OF THE INVENTION 
     This invention sets out to remedy the color imbalance which exists in the prior art from the blending of RGB LEDs as well as their shadow enhancement capabilities. This invention utilizes a light source that operates from a video signal and uses the RGB data to illuminate foreground subject or subjects appearing in front of the video wall. This illumination apparatus operates on a video signal through pixels formed using RGB LEDs plus additional LEDs which are not RGB LEDs as shown in  FIG. 2 . The additional LEDs take the white light information of the video RGB which is processed into a fuller and broader white light spectrum. Examples of a display which could be used as a lighting panel which include pixels with additional LEDs include commercially available megapixel video walls. The video display and illumination apparatus can operate from the same video signal in synchronization. This ensures color changing or shadow changing effects on foreground subjects synchronized to the background display in real time. Broad light spectrum is necessary for better color rendering of real world colors in skin tones, objects and the environment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a typical prior art lighting panel with only RGB LED pixels with one pixel magnified to show one pixel with 3 LEDs. 
         FIG. 2  shows the invented lighting panel with RGB LED pixels and an additional LED with one pixel magnified to show one pixel with 4 LEDs. 
         FIG. 3  is a block diagram showing the operation of a 3DLut. 
         FIG. 4  show LEDs forming a lighting panel fitted with lenses. 
         FIG. 5  shows four lighting panels mechanically interlocked each other. 
         FIG. 6  shows a variable frame rate camera and the lighting panel operating at a frequency which allows synchronization with frame rates of the variable camera and lighting panel. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invented solution is to use a greater than three LED system (for example; Red, Green, Blue, Cool White and Warm White) for a video wall used as a light source for subjects captured on camera. This allows for higher quality white light compared to white light created by narrow FWHM (full width at half maximum) RGB LEDs. The pixelated nature of the video wall allows the light emanating from the video wall to be used to create specific effects and light movement that cannot be done with existing lighting systems. 
     To do this, the RGB video signal needs to be mapped to the greater than three LED system as shown in  FIG. 3 . A three input, greater than three output 3DLut (3D look up table) is needed to drive the LEDs appropriately. The output of the 3DLut is determined by the desired criteria. This could be to have the highest color quality and maintain input luminance within the frame, create maximum luminance based on the capability of LEDs or any other criteria. 
     The 3DLut is in the video pipeline right before the LED driver electronics. The 3DLut could be applied to the gamma encoded signal or a 1DLut could be used to modify the video signal and the 3DLut could be applied to the modified video. As to the specifics of a 3DLut (or 1DLut), such look up tables are well known mechanisms to map one color space to another to, for example, calculate preview colors for a monitor or digital projector of how an image will be reproduced on another display device, typically the final digitally projected image or a release print of a movie. More specifically, persons skilled in the art would readily know how to create a 3DLut which maps a set of three RGB values to another set of three RGB values, typically to adjust the output which is displayed on a particular display so that the colors appear closer to the actual RGB values than would otherwise be the case. According to the invention, instead of a 3 to 3 mapping, a 3 to 3+n mapping is used where n is the additional number of LEDs used to produce a full white spectrum with a higher quality white than would otherwise be the case. As one example, assume 3×8 bit color space with R=255, G=255 and B=255 which should be displayed as pure white. But due to the characteristics of the RGB LEDs of the display, the white as displayed is not of the highest quality. A person skilled in the art knowing the characteristics of the RGB, and non RGB LEDs of the display would know that the display produces a high quality pure white by transforming the 255 255 255 RGB values to 255 254 250 255 255 where the first three values are the values provided to the RGB pixels respectively and the last two values are respectively mapped to the two additional LEDs. A 3DLut is created in this manner. Of course, the specific mappings would depend on the characteristics of the LEDs in use and the desired lighting output. In an embodiment, instead of or in addition to a 3DLut, controls could be used to adjust the output values until the desired lighting effect is obtained. Separate control of the additional LEDs allows for the color quality to be adjusted to desired settings. The specifics of such a control mechanism which simply adjusts a value provided to each of the LEDs making up a pixel are well known to video lighting practitioners and is usually implemented via software in commercially available video wall processors. The 3DLut and control mechanism can be embedded in the panel or as a separate element which connects to the panel such as a commercially available receiver card. 
     Another objective of this invention is to be able to simulate moving image patterns from a scene in synchronization with the video image from the source. For example, walking or driving under a tree canopy results in patterns of sunlight penetrating the leaves. Simply using a synchronized display wall above an actor would project the green of the leaves as well as any sunlight in a blended fashion that would appear as a soft light wash over the foreground scene. The scene in its blended form would appear greener than daylight. There would not be any visible distinct pattern of sunlight through leaves. Direct beams of light need to be generated at a narrow beam angle. To lessen the influence of other colors, the light should be able to independently control and desaturate the RGB pixels while independently controlling the additional LEDs to simulate the sunlight. 
     The invention is directed to an LED display panel using more than three LEDs for each pixel. The LEDs would consist of Red, Green, Blue and at least one additional source LED. Each LED pixel in one embodiment is fitted with narrow beam lenses as shown in  FIG. 4 . Another iteration of the panel would have unlensed LEDs. Lens LEDs allow a narrow beam angle for directional throw. The lighting panel is able to operate as a stand-alone panel or interlinked with additional panels to form a larger panel, or in greater numbers as a wall of panels as shown in  FIG. 5 . 
     The panel or panels operate at sufficient frequency to allow for the video to be genlocked or synchronized to a camera at various frame rates per second. Traditionally, cameras can be set to frame rates of, but not limited to 24 fps, 48 fps, 96 fps and 120 fps. The panel allows for separate control of the RGB portion of the video data stream from the one or more additional LEDs. The separate control over the RGB pixels would allow the colors to be desaturated while maintaining the visual pattern of the streaming video image. 
       FIG. 6  shows an example of a use of the invented LED lighting panel  61  used to illuminate a foreground subject (not shown). Video processor  63  such as Megapixel VR®&#39;s HELIOS LED Processing Platform receives a video feed in the form of video signals from media server  65  as is well known in the art. Such video signals would be, for example, serial digital data. A variable frame rate camera  67  such as a commercially available high end cinema camera typically used for motion pictures provides video signals representing the foreground subject. Sync device  68  is a commercially available master sync device which generates sync signals to processor  63 , server  65  and camera  67  to ensure that each video frame provided by server  65  and camera  67  are synchronized when the video signals generated by processor  63  are provided to LED lighting panel  61  and modular LED display  69  which displays the foreground subject and background provided by media server  65 . 
     The foregoing descriptions of specific embodiments and devices is used to illustrate the invention and how it may be implemented, but such embodiments and devices are not intended to limit the scope of the invention as defined by the following claims.