Abstract:
Spot illumination apparatus and methods are described. According to one implementation a spot luminaire includes a light source for emitting a beam of light and a projection lens configured to project the beam of light towards a distant target. A first field stop, through which the beam of light passes, is positioned between the light source and the projection lens. A filter apparatus is positioned proximate the first field stop and is adapted for selectively moving at least one variable density filter across the beam of light. A relay lens group is positioned between the first field stop and the projection lens. The relay lens group is configured to prevent the at least one variable density filter from being imaged by the projection lens. Methods for providing stage lighting are also described.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates generally to spot luminaries having associated color-changing mechanisms and more particularly to spot luminaires which include movable variable density filters configured to selectively control the color and intensity of a projected beam of light.  
       BACKGROUND  
       [0002]     Spot luminaries, such as stage lighting instruments, nightclub lighting instruments and the like having motorized subsystems operated by remote-control means are commonly referred to as “moving lights” or “automated luminaires.” Among these are two general varieties: spot luminaires and wash luminaires. Spot luminaires are similar to the “profile spot” or ellipsoidal reflector spotlight commonly used in theaters, and provide a hard-edged beam of light. This kind of spotlight has a gate aperture at which various devices can be placed to define the shape or profile of the light beam and has a projection optical system including one or more objective lens elements. A spot luminaire projects an image of the brightly-illuminated gate aperture, including whatever light-shaping, pattern-generating, or image-forming devices might be placed there. Wash luminaires are similar to the “Fresnel Spot” luminaire, which provides a soft-edged, ill-defined beam that can be varied in size by moving the lamp and reflector towards or away from the lens. This kind of wash light has no gate aperture and projects no image, but projects only a soft-edged pool of light shaped by whatever lens or lenses are mounted over the exit aperture of the luminaire.  
         [0003]     The development of a spot luminaire having a fully cross-fadeable color mixing system and that is capable of projecting a smooth and uniformly colored beam of light has long been a goal of many lighting manufactures. Although many efforts have been made to develop such luminaires, each of these efforts has failed to achieve the desired goals. A more detailed description of such efforts can be found in U.S. Pat. No. 6,578,987 to Hough et al. which is hereby expressly incorporated by reference.  
         [0004]     Typical prior art spot luminaires, and some particular problems associated with them are now discussed with reference to  FIGS. 1-6 . When referencing the attached figures, like numerals are used to describe like structures when appropriate.  
         [0005]     Turning first to  FIG. 1 , a typical prior art spot luminaire projection optical system is generally indicated by the numeral  10 . The optical system  10  includes a lamp  15  and a concave reflector  17 . Together the lamp  15  and concave reflector  17  comprise a light source  20 . The optical system  10  also includes a field stop/projection gate  25 , a light pattern generator  26 , and a projection lens  30 . The light then exits the projection lens  30  and travels over a distance  32  to a distant projection surface  35 . For simplicity, the distant projection surface  35  can be considered to be at least six meters (twenty feet) from the projection lens  30 . It should be noted that the outer “zigzag” boundary lines between the reflector and lens of this figure represent “edge rays,” which show the outer boundaries of the path of the light from the light source  20  as it travels through the optical system from left to right. This convention applies to all figures incorporated herein. Of course, a single ray of light travels in a straight line unless being reflected or refracting through a lens.  
         [0006]     As shown in  FIG. 1 , the light source  20  can be thought of as illuminating an object  38  (here shown as an up-right arrow) located at the projection gate  25 . The object  38  can simply be an aperture formed in the field stop/projection gate  25 , or the object  38  can be a light pattern generator  26  which is located at the projection gate  25 . An image of the projection gate  25  (or the light pattern generator  26  contained therein) is projected onto the distant projection surface  35 . The image of the object  38  is shown by an inverted arrow  40  located on the distant projection surface  35 .  
         [0007]     The basic optical system which is shown in  FIG. 1  will project a polychromatic (white) beam of light. While a white beam of light is useful in many cases, the development of a smooth and uniformly colored beam of light has long been a goal of many lighting manufactures. One of the easiest ways to impart color to a beam of light is through the use of simple absorptive color filters as described below.  
         [0008]     Turning now to  FIG. 2 , the use of absorptive color filters, or “gels”, to impart color to a beam of light is described. Here a typical prior art spot luminaire projection optical system is indicated by the numeral  50 . The basic structure of the spot luminaire projection optical system  50  is the same as the optical system  10  described above with reference to  FIG. 1 . However, in addition to the previously described structures, the optical system  50  also includes an absorptive color filter media or gel  55  which is shown to the right of the projection lens  30 . Since the gel  55  is larger then the projection lens  30 , the light exiting the spot luminaire  50  passes through the gel  55 . The result is a uniformly colored image  40  of the projection gate  25  and the light pattern generator  26  contained therein.  
         [0009]     Referring now to  FIG. 3 , the use of dichroic filters to impart color to a beam of light is described. Here a typical prior art spot luminaire projection optical system is indicated by the numeral  60 . The basic structure of the spot luminaire projection optical system  60  is the same as the optical system  10  described above with reference to  FIG. 1 . However, in addition to the previously described structures, the optical system  60  also includes a dichroic filter  65 . The dichroic filter  65  is typically positioned near the projection gate  25 , and can therefore be much smaller than corresponding gel filters of the same color. Due to their small size, it is possible for a number of dichroic filters  65  to be positioned on a wheel hub and rotated into the beam of light, allowing for rapid color changes. All of the light exiting the spot luminaire  60  passes through the dichroic filter  65 , resulting in a uniformly colored image  40  of the projection gate  25  and any light pattern generator  26  contained therein.  
         [0010]     Turning now to  FIG. 4 , a variable density patterned dichroic color filter wheel  70  is described. Variable density patterned dichroic color filter wheels  70  such as this have been employed in some prior art spot luminaire projection optical systems. When a color filter wheel  70  is used, it will typically be positioned between the concave reflector  17  and the projection gate  25  (as shown in  FIG. 5 ). As shown best in  FIG. 4 , the density of the pattern etched onto the color filter wheel  70  varies radially around the wheel  70 .  FIG. 4  shows the beam of light  75  passing through the color filter wheel  70  as a circle. When the variable density patterned dichroic color filter wheel  70  is rotated, the saturation level of the beam&#39;s color will increase or decrease, depending on the position of the wheel  70  in relation to the beam  75 .  
         [0011]     As best shown by  FIG. 4 , the patterned dichroic color filter wheel  70  is patterned with a number of fingers  77 . The thickness of each finger  77  varies radially around the wheel  70 . The saturation of the color in the projected beam  75  depends on the wheel&#39;s location in relation to the beam  75 . For example, when the wheel  70  is positioned so that the beam of light  75  passes through the clear portion of the wheel  70  (as shown in  FIG. 4 ) the projected beam will be white.  
         [0012]     Turning now to  FIG. 5 , a prior art spot luminaire projection optical system  80  which incorporates a single patterned dichroic color filter wheel  70  is shown. The basic structure of the spot luminaire projection optical system  80  is similar to the optical system described above with reference to  FIG. 1 . However, in addition to the previously described structures, the optical system  80  also includes a single patterned dichroic color filter wheel  70 . The patterned dichroic filter wheel  70  is positioned near the projection gate  25  to ensure that the wheel  70  is as small as possible. Since the pattern  77  is located adjacent to the light pattern generator  26  and the projection gate  25 , the pattern  77  etched onto the color filter wheel  70  is visible in the projected beam of light, and will be imaged on the distant projection surface  35 . The visibility and imaging of the pattern  77  is undesirable as the projected beam of light will not be smooth and uniformly colored.  
         [0013]     In an attempt to ameliorate this problem, a diffusing optical element  85  ( FIG. 6 ) can be placed in the beam path. The diffusing optical element  85  can be positioned between the patterned color filter media  70  and the projection gate  25 . The diffusing optical element  85  serves to blur the image of the pattern  77  etched onto the color filter wheel  70 . The effect is similar to viewing a scene through a frosted glass window; the detail (in this case the pattern  77  etched onto the color filter  70 ) is not discernable.  
         [0014]      FIG. 6  shows a prior art spot luminaire projection optical system  90 . The basic structure of the spot luminaire projection optical system  90  is similar to that of optical system  10  which was described above with reference to  FIG. 1 . However, in addition to the previously described structures, the optical system  90  also includes a patterned color and dimming apparatus  95  (consisting of cyan, yellow, and magenta color wheels and a patterned dimmer wheel) and a diffusing optical element  85 . Although the beam of light will be uniformly colored, the diffusing optical element  85  will scatter light out of the projection lens system  30 . This results in a loss of energy in the projected beam, which is undesirable. The light rays being scattered outside of the projection lens  30  are indicated by the numeral  97 .  
         [0015]     The present invention was principally motivated by a desire to address the above-identified issues. However, the invention is in no way so limited, and is only to be limited by the accompanying claims as literally worded and appropriately interpreted in accordance with the Doctrine of Equivalents.  
       SUMMARY OF THE INVENTION  
       [0016]     According to one implementation a spot luminaire includes a light source for emitting a beam of light and a projection lens configured to project the beam of light towards a distant target. A first field stop, through which the beam of light passes, is positioned between the light source and the projection lens. A filter apparatus is positioned proximate the first field stop and is adapted for selectively moving at least one variable density filter across the beam of light. A relay lens group is positioned between the first field stop and the projection lens. The relay lens group is configured to prevent the variable density filter from being imaged by the projection lens. In another implementation, the filter apparatus is adapted for selectively rotating a plurality of variable density filters across the beam of light, and the relay lens group positions an image of the filter apparatus so that the image of the filter apparatus is not imaged by the projection lens. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:  
         [0018]      FIG. 1  is a schematic diagram of a prior art projection optical system;  
         [0019]      FIG. 2  is schematic diagram of a prior art projection optical system including an absorptive color filter;  
         [0020]      FIG. 3  is schematic diagram of a prior art projection optical system containing an unpatterned dichroic color filter;  
         [0021]      FIG. 4  is a pictorial representation of a patterned dichroic color wheel;  
         [0022]      FIG. 5  is schematic diagram of a prior art projection optical system including a patterned dichroic color filter;  
         [0023]      FIG. 6  is schematic diagram of a prior art projection optical system including a patterned color filter and dimming apparatus and a diffusing optical element;  
         [0024]      FIG. 7  is schematic diagram of a projection optical system including a patterned color and dimming apparatus and a relay lens system;  
         [0025]      FIG. 8  is schematic diagram of a projection optical system including a patterned color and dimming apparatus and a relay lens system including a negative lens at the first field stop according to the present invention;  
         [0026]      FIG. 9  is schematic diagram of a projection optical system including a patterned color and dimming apparatus and a relay lens system including a negative lens at the second field stop according to the present invention;  
         [0027]      FIG. 10  is schematic diagram of a projection optical system including a patterned color and dimming apparatus and a relay lens system including a negative lens positioned within the relay lens according to the present invention;  
         [0028]      FIG. 11  is a pictorial representation of a motor driven color and dimming mechanism according to the present invention; and  
         [0029]      FIG. 12  is a pictorial representation of a relay lens color and dimming apparatus according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0030]     The readers of this document should understand that the embodiments described herein may rely on terminology used in any section of this document and other terms not readily apparent from the drawings and language common therefore. This document is premised upon using one or more terms with one embodiment that may also apply to other embodiments for similar structures, functions, features and aspects of the invention. Wording used in the claims is also descriptive of the invention and the text of the claims is incorporated by reference into the description entirely in the form of the claims as originally filed. Terminology used with one, some or all embodiments may be used for describing and defining the technology and exclusive rights associated herewith.  
         [0031]     The present invention utilizes a patterned color and dimming apparatus, deployed near a small aperture, to uniformly color a projected beam of light. It should be noted, that because the size of the color and dimmer wheels depend on the size of the aperture, it is advantageous that the aperture be as small as possible.  
         [0032]     To avoid losing energy from the projected beam due to the scattering of light by a diffusing optical element, as was the case with the prior art depicted in  FIG. 6  and described above, it is desirable to relocate the real image of the patterned color and dimming wheels to a volume of space that is not imaged by the projection lens. As described below, the addition of a weak negative lens to a relay lens group can serve to relocate the image of the color and dimming system to a volume of space that is not imaged by the projection lens. By “weak” is meant that the absolute value of the negative power of the lens is less than the combined power of the downstream positive lens group. This results in a highly efficient projection system with a uniformly colored projected beam.  
         [0033]     Referring now to  FIG. 7 , this figure shows a spot luminaire projection optical system generally indicated by the numeral  110 . The optical system  110  includes a lamp  115  and a concave reflector  117 . Together, the lamp  115  and the concave reflector  117  form the light source  120 . The optical system  110  also includes a first field stop  125 . A patterned color and dimming apparatus  95  is located in a volume contiguous to the first field stop  125 . A positive relay lens group  130  is shown to include a first positive lens  140  and a second positive lens  150 . The optical system  110  also includes a second field stop  160  which is coincident with the projection gate, a light pattern generator  166 , and a projection lens  170 . A distance  175  separates the projection lens  170  from a distant projection surface  180 . The positive relay lens group  130  relays an image  190   a  of the patterned color and dimming filters  95  and first field stop  125 , forming said image  190   a  at a volume contiguous to the second field stop  160 . The second field stop  160  is located some distance downstream of the positive relay lens group  130 . The second field stop  160  is the same size, and in the same location, as the projection gate. Since the second field stop/projection gate  160  are coincident, the real images  190   a  of the patterned color and dimming wheels  95  act as objects for the projection lens  170 . Therefore, the projected beam not only contains an image of the projection gate  160  and the pattern generator  166 , but also contains an image of the patterned color and dimmer wheels  190   a . It would, however, be preferable to not have the image of the patterned color and dimming filters  95  formed at the projection surface  180 .  
         [0034]     Referring now to  FIG. 8 , a spot luminaire projection optical system according to the present invention is generally indicated by the numeral  200 . The optical system  200  includes a lamp  115  and a concave reflector  117 . Together, the lamp  115  and the concave reflector  117  form the light source  120 . The optical system  200  also includes a first field stop  125 . A patterned color and dimming apparatus  95  is located in a volume contiguous to the first field stop  125 . A positive relay lens group  130  is shown to include a first positive lens  140  and a second positive lens  150 . The optical system  200  also includes a negative relay lens group  210 . Together the positive relay lens group  130  and the negative relay lens group  210  comprise the relay lens group or overall relay lens group  220 . The optical system  200  also includes a second field stop  160  which is coincident with the projection gate and a light pattern generator  166 . The optical system  200  further includes a projection lens  170  which functions to project a beam of light across distance  175  to a distant projection surface  180 .  
         [0035]     As shown in  FIG. 8 , the addition of a weak negative lens  210  (negative relay lens group) serves to relocate the image  190   b  of the color and dimming system to a volume of space that is not imaged by the projection lens  170 . It is therefore possible, through design, to force the image  190   b  of the patterned filter media  95  and the first field stop  125  to lie within or beyond the projection lens train, in a volume that is not imaged by the projection lens  170 . In one embodiment, this will be accomplished by disposing image  190   b  away from the second field stop. In another embodiment, the image of the color and dimming system is disposed downstream of the second field stop. In another embodiment, the image is disposed downstream of the upstream surface of the projection lens. In another embodiment, the image of the color and dimming system projected by the relay lens group  210  is disposed downstream of the downstream surface of the projection lens  170 , but not proximate the projection surface.  
         [0036]     A properly designed relay lens system  220  allows the patterned filter media  95  to be placed near the first field stop  125  which is the smallest area in the beam of light, while ensuring that the images  190   b  of the patterned filter media  95  and first field stop  125  occupy a volume that is not re-imaged by the projection lens  170 . The result is superior color mixing of the projected beam while minimizing the size of the patterned color filter material. It is believed that this type of relay lens color and dimming apparatus will provide uniform color mixing and high optical throughput.  
         [0037]     Referring now to  FIG. 9 , another spot luminaire projection optical system  300  according to the present invention is described. Here the basic structure of the spot luminaire projection optical system  300  is similar to the optical system  200  described above with reference to  FIG. 8 . However, in this example, the negative relay lens group  310  is positioned near the second field stop  160 . Together the positive relay lens group  130  and the negative relay lens group  310  comprise the relay lens group or overall relay lens group  320 . The addition of a weak negative lens  310  serves to relocate the image  190   c  of the color and dimming system  95  to a volume of space that is away from the second field stop and not imaged by the projection lens  170 .  
         [0038]     Referring now to  FIG. 10 , yet another spot luminaire projection optical system  400  according to the present invention is shown. Here the basic structure of the spot luminaire projection optical system  400  is similar to the optical system  200  described above with reference to  FIG. 8 . However, in this example, the negative relay lens group  410  is positioned within the positive relay lens group  130  (between the first positive lens  140  and the second positive lens  150 ). Together the positive relay lens group  130  and the negative relay lens group  410  comprise the relay lens group  420 . The addition of a weak negative lens  410  serves to relocate the image  190   d  of the color and dimming system  95  to a volume of space that is not imaged by the projection lens  170 .  
         [0039]     Referring now primarily to  FIGS. 11 and 12 , the filter apparatus  95  and other aspects of the invention are further described. As discussed previously, the filter apparatus  95  can be positioned proximate the first field stop  125 . This placement of the filter apparatus  95  is shown in  FIGS. 8-10  and  12 . In these figures, one may also appreciate that the filter apparatus  95  can include a plurality of variable density filters.  
         [0040]     In its basic form, the filter apparatus  95  can be adapted for selectively moving at least one variable density filter across the beam of light. However, as shown in  FIGS. 11 and 12 , the filter apparatus  95  can also be adapted for selectively moving or rotating a plurality of variable density filters  500  across the beam of light. These variable density filters  500  can be color filters and/or dimming filters. Therefore, movement can allow the operator to control the color and intensity (luminance) of the beam of light.  
         [0041]     Referring now to  FIG. 11 , one implementation of the filter apparatus  95  is shown. In this example, the filter apparatus  95  is shown to include a series or stack of patterned wheels  500 . Here the stack of patterned wheels  500  includes three color filter patterned wheels  510 ,  520  and  530 . These correspond respectively to a cyan color wheel  510 , a yellow color wheel  520 , and a magenta color wheel  530 . The remaining wheel is a dimming wheel  540 . The filter apparatus  95  also includes a plurality of actuators or motors  600  which can be used for driving, moving, or causing rotation of the patterned wheels  500  in the beam of light.  
         [0042]     Each of the wheels  500  includes a central hub. However, only the central hub  560  of the dimming wheel  540  is shown in the view provided by  FIG. 11 . The hub  560  of the dimming wheel  540  serves as a point of attachment for a drive belt  580 . The drive belt  580  is also connected to one of the actuators  600 . Here the drive belt  580  is connected to an actuator or motor  680  The hubs (not shown) of the remaining wheels ( 510 ,  520  and  530 ) are similarly coupled to drive belts  586 ,  584  and  582 . These drive belts are in turn coupled to actuators or motors  686 ,  684  and  682 . For example, when actuator  680  is activated, it will cause belt  580  to move, thereby causing rotation of the dimming wheel  540 . The motors or actuators  600  can be mounted to a plate containing the first field stop  125 . As each color filter  500  is rotated into the beam, it colors a portion of the rays passing through the first field stop  125 . As the dimmer wheel  540  is rotated into the beam, it attenuates a portion of the rays passing through the first field stop  125  of the relay lens.  
         [0043]     Thus, the patterned wheels  500  in the stack can be either color filters or dimming filters. One should appreciate that it is therefore possible to place a dimming filter, such as patterned wheel  540  at the first field stop location  125  ( FIG. 12 ). The dimming filter works on the same principle as the color filters, except that it blocks the light rather than coloring it. Like the color filters, the dimmer can be located near the first field stop  125 . Therefore, any pattern etched onto the dimmer  540  will not visible in the projected beam, and the dimmer  540  will merely control the amount of light present in the projected beam. It should be noted that, although patterned wheels  500  are depicted, the patterned media need not be in a wheel configuration. For example, the patterned media can be disposed on a sliding plate which can be used to slidably move to place the desired portion of the media into the light beam, rather than by rotating it, as with the wheel  500 .  
         [0044]     As described, the various color mixing systems or filter apparatus  95  can be positioned near the first field stop  125 , which is located between the concave reflector  117  and the projection lens  170 . The relay lens group (e.g., groups  220 ,  320  and  420 ) is designed so that a real image of the field stop  125  and color filter means  95  occupies a volume that is not re-imaged by the projection lens  170 . These color filters can be composed of patterned color filter material deposited on substrates having any shape. As the filters  95  are moved into the path of the light beam, their edges are not visible and the projected image is evenly colored.  
         [0045]     Regardless of the specific configuration of the filters and the dimmer, the projected image will have a fully blended homogeneous color. The actual shade and intensity of the image is dependent on the area of the field stop  125  covered by the unpatterned filter material. The principles of color filtering at a field stop are thus independent of any specific actuator means or specific filter shape.  
         [0046]     Referring now to  FIG. 12  which shows a relay lens color and dimming apparatus  95  according to the present invention. Patterned cyan, yellow, magenta, and dimmer wheels  510 ,  520 ,  530  and  540  are shown positioned before a first field stop plate  125 . A weak negative lens  210  can be positioned in, and held by, the field stop plate aperture  125 . A pair of lenses  140  and  150  comprises the positive lens relay group  130 . A second field stop plate  160  is the same size, and in the same location, as the projection gate.  
         [0047]     The color mixing system is well-suited for placement in the path of a high-intensity beam of light for illuminating a light pattern generator, gobo, or an image generator system. The color mixing system can also be used independently in any spot luminaire having a projection lens with a well defined projection gate.  
         [0048]     Although specific embodiments of the present invention are disclosed, these are not to be construed as limiting the scope of the present invention. Many variants of the invention will become apparent to those skilled in the art in light of this specification. The scope of the invention is only limited by the claims appended hereto.