Power Lens for an Automated Luminaire

This invention relates generally to stage and theater lighting fixtures and more particularly to a color wash luminaire which provides variable intensity, variable color, variable positioning and variable beam angles in a single compact fixture.

Wash lights, as they are generally known, are used to provide uniform illumination and coloration to a theatrical set. Numerous lighting fixtures have been provided in the past wherein the output of the light source and reflector are selectively colored by the positioning of one or more colored media in front of the light beam. Some of these applications have included a strip of media moved across a light beam, a scrolling variable density gel media device, and gradient density color wheels. None of these variable density filters address or consider the power density of the light beam. They do not compensate for the non-linear distribution of light intensity across a light beam which results from the use of a more efficient elliptical reflector. As a result, when used with such a reflector, a linear distribution color wheel will provide a non-linear coloration of the light beam, which is darker at the edges and perceptibly lighter toward the center of the beam. A ratio of power from center of beam to beam edge is often on the order of 50%. Variable density filters which do not address the power density of the beam produce results which are non-uniform and leave an apparent white spot in the center of the beam while darkening the edge first. This accentuates the power gradient shift and makes the resultant coloration more objectionable. A further complication of this approach is that fully saturated colors cannot be used due to excessive transmission losses at fractional percentages or an exaggeration of the power density losses.

Prior art lights of the type contemplated by this invention most often utilize two moving lenses or a moving light source with a single lens and require substantial space and complex mechanical slide systems. These limitations make it difficult to provide a fixture of a compact size.

Heat dissipation is always a critical consideration in lighting fixtures. Many fixtures utilize a hot mirror reflector which is, at best, fifty percent efficient in controlling the infrared heat energy. Fan cooling is therefore typically required for an additional heat transfer capability in conventional stage and studio lighting which again detracts from a compact fixture. Also typical of such fixtures is the lack of a module based design so that, for example, the addition or removal of control and sensor functions requires redesign of the system hardware.

The foregoing illustrates limitations of the known prior art. Thus it is apparent that it would be advantageous to provide alternatives directed to overcoming one or more of the limitations as set forth above. Accordingly, suitable alternatives are provided including features and benefits more fully disclosed hereinafter.

In one aspect of the present invention, this is accomplished by providing a power lens for use in an automated color mixing wash luminaire comprising a disc formed of transparent material. The disc includes a plurality of lens elements in a honeycomb pattern. Each element has a convex surface.

The foregoing and other aspects will become apparent from the following description of the invention when considered in conjunction with the accompanying drawing figures. It is to be expressly understood, however, that the figures are not intended as a definition of the invention, but are for the purpose of illustration only.

FIG. 1 is a frontal view, with partial cutaway portions, illustrating an embodiment of the luminaire of this invention;

FIG. 2 is a perspective view, with partial cutaway portions, illustrating an embodiment of the luminaire of this invention;

FIG. 3 is a cross-sectional view, illustrating an embodiment of the housing of this invention;

FIG. 4 is a perspective view, with partial cutaway portions, illustrating an embodiment of the housing of this invention;

FIG. 5 is another perspective view, with partial cutaway portions, illustrating an embodiment of the housing of this invention;

FIG. 6 is a plan view illustrating an embodiment of the color filter of this invention;

FIG. 7 is a perspective view illustrating an embodiment of the power lens of this invention;

FIG. 8 is a diagrammatic view illustrating an embodiment of the power board of this invention; and

FIG. 9 is a diagrammatic view illustrating an embodiment of the logic board of this invention.

The present invention employs a custom designed halogen light source with a compacted filament cross-section of only 10.times.10 mm while still providing a high wattage level of 750 Watts. To achieve this, a custom lamp has been designed to operate at a relatively low fixed voltage of 110 VAC, thereby minimizing arcing within the filament winding and allowing the more compacted filament area. Compacting of the light source in this way allows for the use of a very efficient elliptical reflector. This compacting of source cross-section when utilized in conjunction with the custom computer optimized elliptical reflector allows this luminaire to obtain very high light output comparable to that of a 1000 Watt light source, but with substantial savings in power requirements and heating. Further, it provides a concentrated small beam cross-section which is ideally suited to use with the color mixing system provided.

The present invention utilizes a unique color mix system. Color mixing is obtained through the use of a fixed color wheel which provides 5 primary colors plus white, used in combination with a new subtractive color mix system. The color mix system uses three gradient color wheels whose color distribution has a linear gradient characteristic in the circumferential direction of rotation while the radial distribution of color is Ctaussian. This patterning results in compensation for the non-linear Ctaussian distribution of intensity through the light beam as results in a device of this type where an elliptical reflector is used with the light source. This Ctaussian distribution results in much more uniform coloration of the light beam unlike a conventional gradient wheel which has fixed distribution in the radial direction and linear distribution in the circumferential direction of the color wheel.

The use of Ctaussian distribution of color on the color wheel compensates for non-linearity of the light source in an inverse fashion, thereby providing for a coloration of the beam which is essentially linear across the light beam. The color mixing system of the present invention provides for 167,000,000 color possibilities (6 colors on main color wheel.times.256 gradient colors/wheel cubed for 3 wheels=167 million color permutations). An additional wheel may be provided for the purposes of incorporating mechanical dimming of the light source where the resultant color temperature shift that occurs with electronic dimming of the lamp is not desired.

In this invention, three dichroic color filters, magenta, cyan and yellow, are utilized where the gradient colored portions of these filters are patterned to be coincident with the inverse of the power gradient of the source. That is, the color filter gradient is greatest toward the center of the arc where it crosses the maximum power point of the source, dropping proportionally to the outer edge of the gradient wheel and light beam. Saturation of the color pattern increases proportionally as the filter is rotated further, culminating in 100% saturation at 300 degrees of the angular travel. The "gradient" of the filter can be achieved through multiple small "fingers" of color whose width is varied proportional to the angular travel or, alternatively, where a printed pattern is increased in density as the angular travel is increased. In all cases, the coloration of the filter is concentrated toward the center of the filter arc coincident with the wheels travel over the point of maximum power gradient of the light source. The construction of the gradient wheel also includes a beam cut-out located in a position where the beam will pass through when only white light is desired. This eliminates the loss due to passing through the glass substrate when maximum white light out put is desired.

This invention also includes a variable beam angle achieved through the use of a variable power rotating lens. This lens contains very small lens elements of different powers located at six adjacent portions of the lens wheel. The intervening spaces between these six portions are comprised of a transitional power lens made up of approximately equal numbers of the first and second adjacent lens powers. In this way, six distinct lens powers are available as well as six intermediate power sections. Rotation of the lens wheel by a motor allows for a very rapid change in lens power and correspondingly, a change in the beam angle of the fixture. The particular lenses used in the present invention allow for a variation in beam angle from about 10 degrees to about 60 degrees; this transition occurring in as little as 1 second for any lens power. Further, the multiple small lenses produce a homogenizing of the beam, further integrating the colors obtained from the color mix system. The rotating lens used herein allows the fixture to remain very compact while still providing a wide range of lens power and beam angle.

This invention further includes a unique approach to the mechanical considerations of a lighting system which comprises an optimized reflector/heat sink assembly and IR filter assembly to direct and control heat generated by its incandescent light source. The assembly incorporates a spun aluminum reflector mounted in the heat sink assembly. The resultant concentrated light beam is directed to a pair of angularly mounted dichroic filters which redirect the IR portion of the light beam into integral internal heat sinks. The internal sinks capture the IR energy from the light source and conduct it to the outer portion of the integral sink assembly. The external fins of the heat sink assembly are oriented vertically to the plane of movement of the fixture, providing optimized convection and dissipation of the heat from the internal source. This arrangement provides approximately 85% reduction of heat between the rear chamber and the optical section. The heat sink assembly also provides the mechanical basis for the remainder of the mechanical system, providing a high integrity structure from which the remaining secondary assemblies are mounted. In addition, a heat blocking wall is provided in the front portion of the heat sink/reflector assembly which further isolates the lamp heat from the remaining electronic and optical components located in the front portion of the fixture. The front optical section is shrouded by a high impact plastic bezel which allows for easy access to the mechanical and optical systems for service and/or maintenance.

Referring now to the drawings, FIGS. 1 and 2 illustrate the wash luminaire of the present invention, generally designated 10. Luminaire 10 comprises a housing 12 connected to a yoke 14 which may be suspended from a supporting truss (not shown) by means of a clamp (also not shown) attached to yoke 14 at connector 16.

Yoke 14 comprises a suitable metal frame 18 including a metal bracket 20 to reinforce yoke 14. Connector 16 is beating mounted and connected by means of a shaft 22 to a gear 24 positioned adjacent bracket 20. Gear 24 includes a notch (not shown) which operates with an adjacent position sensor (not shown) for pan position control. A motor 26, supported by frame 18, drives belt 28 to rotate gear 24 for the purpose of providing a 360 degree rotation about the centroidal axis P of shaft 22. This provides the pan capability to luminaire 10. A suitable idler arrangement 30 is provided to engage belt 28.

Another motor 31, also supported by frame 18, drives belt 32 to rotate gear 34 for the purpose of providing at least a 270 degree rotation about the centroidal axis T of a shaft 36. Similar to gear 24, gear 34 includes a notch 34a which operates with an adjacent position sensor 34b for tilt position control. This provides the tilt capability to luminaire 10. Another suitable idler arrangement 38 is provided to engage belt 32. A travel stop 37 is connected to the tilt mechanism to limit movement of luminaire 10 to a desired tilt angle.

A manual off-on switch or breaker 52 is also mounted externally on yoke 14. A cooling fan 48 mounted in a housing 50 is operable to draw cooling air into yoke 14 through a plurality of vents 54, across the internal components of yoke 14, and outwardly through a similar plurality of vents 56. A cover 59, formed of a rigid synthetic material, which includes vents 54 and 56, encloses yoke 14 and the above described components.

In FIGS. 3, 4, and 5, housing 12 is illustrated and generally comprises an aluminum casting 57 and a bezel 58, formed of a suitable rigid synthetic material. Casting 57 includes a base 60, at a first end, from which a first plurality of contoured external cooling fins 62 extend. A stepped annular relief 66 is provided within casting 57 and includes an annular portion 64 and a truncated elliptical portion 69. Annular portion 64 also includes cooling vents 65. A second plurality of internal cooling fins 63 are disposed about an inner annular periphery of annular portion 64. First and second fins 62, 63, respectively, are aligned.

An aluminum end cap 68 is mounted on a second end of casting 57. A lamp base 70 and lamp 72 are mounted on end cap 68. Lamp 72 extends into open annular relief 66. An elliptical reflector 74 is also mounted in elliptical portion 69 so as to suitably surround lamp 72. Lamp 72 is powered by AC power in a conventional manner.

An aluminum heat blocking wall, or hot plate 76, is mounted on the first end of casting 57, and is spaced from a motor mounting plate 78 by spacer elements 80. A plurality of motors 82 are mounted on motor mounting plate 78 and rotating shafts 84, extending from motors 82, are operable to be belt driven to rotate a plurality of staggered color filters 86, a power lens 88, a mechanical dimming wheel 89, and a frost wheel 87. Tabs, such as tab 86a, on color filter 86, are provided on these shaft mounted, rotating lenses, filters, etc., to operate with a plurality of respective adjacent position sensors 257 mounted on a pair of motor/driver sensor boards 94 mounted between plates 76, 78 for the purpose of sensing the positions of each of the shaft mounted rotating devices including color wheels 86, etc.

Light beam L, FIG. 3, is condensed to a diameter of about 1.25 inches in diameter where it exits casting 57 at hot plate 76. The beam then passes through the series of wheels; color filters, lens, etc. In the embodiment of FIG. 3, bezel 58 houses a series of 6 wheels. Dimming wheel 89, dichroic coated color filter (yellow) 86y, dichroic coated color filter (cyan) 86c, dichroic coated color filter (magenta) 86m , power lens 88 and frost wheel 87. Three of these wheels are mounted on shaft 84 and another three are mounted on a corresponding shaft 84. The 2 sets of 3 wheels are interleaved, i.e. partially overlapped, in known fashion, to optimize the number of surfaces exposed to beam L. The positions of the three wheels on one shaft 84 are sensed by their respective sensors 257 on one of the boards 94, and the positions of the other three wheels on the other shaft 84 are similarly sensed by their respective sensors 257.

Dimming wheel 89 is used to attenuate the light and is a dichroic coated glass substrate identical in patterning (discussed later) to the color filters 86 except that the coloration is done with an aluminum or silver coating so that it transmits a percentage of light and reflects a percentage. Dimming wheel 89 can be interchanged with a conventional color wheel if desired. Frost wheel 87 provides variable frost (softens the light) due to five trapezoidal sections of acid etched glass. Each section is etched to a different degree to provide variable frost. A sixth and final section of the frost wheel is an open position. A conventional color wheel may also replace frost wheel 87 if desired.

Color filters 86y, 86c and 86m, FIG. 6 comprise a disc-shaped boro-silicate glass substrate 301 having a planar surface 302 which includes a photolithographically etched film 303 deposited thereon. Film 303 forms a Ctaussian pattern arcuate band 304 extending around a substantial portion of planar surface 302. Band 304 has an inner edge 305 and an outer edge 306 and the density of film 303 is greater in an area designated g+ along a radius r between inner edge 305 and outer edge 306 and less in an area designated g- along radius r at inner edge 305 and less in a corresponding area g- along radius r at outer edge 306. A portion of substrate 301 is cut away to form a notch 307 which interrupts arcuate band 304. A portion p of planar surface 302 adjacent notch 307 is coated with a solid film 303a having no pattern as the etched film 303 in band 304.

Color filters 86y, 86c and 86m are used in combination with lamp 72 to produce desired color effects. Beam L, produced by lamp 72, has a typical power gradient, which is not uniform across the beam. A ratio of power from the center of the beam to beam edge is often on the order of 50%. Known variable density filters which do not address the power gradient of the beam, produce results which are non-uniform and leave an apparent white spot in the center of the beam while darkening the beam edge which makes the coloration objectionable.

Advantageously, the Ctaussian patterning of the color filters of this invention is coincident with the inverse of the power gradient of the beam L. That is, the color filter gradient is greatest toward the center of the band 304 where it crosses the maximum power point of the beam L. In this manner, the maximum power of the beam L is coincident with the maximum filtering effect of filters 86y, 86c and 86m.

Saturation of the Ctaussian color pattern increases proportionally as the filter is rotated in a direction represented by directional arrow D, FIG. 6, culminating in 100% saturation at about 300 degrees of angular travel where portion p of planar surface 302 is coated with solid film 303a.

A bracket 90 is mounted on hot plate 76 to position a heat filter 92 to reflect IR radiation R back to the cooling fins 63, 62 to be dissipated from housing 12. Heat filter 92 comprises the bracket 90, FIGS. 3 and 4, which is generally of an A-frame construction and includes a first filter 98a mounted at about a ninety degree angle relative to a second filter 98b. Filter 92 is used to reflect damaging infrared radiation R away from the previously mentioned heat sensitive optical components mounted on shafts 84. Thus, these filters are at an angle to light beam L passing therethrough. The result is a reflection of IR radiation outwardly toward the fins, as is best shown in FIG. 3. First and second filters 98a, 98b, respectively are preferably formed of a suitable 1.75 mm thick substrate of boro-silicate glass material and has a thin film dichroic coating on both sides. The coating on one side facing lamp 72, will provide infrared reflectance of from about 730 nm to about 1,050 nm. The coating in the opposite side will provide reflectance of from about 1,050 nm to about 1,700 nm.

Power lens 88, FIG. 7, is rotatably mounted adjacent one side of motor mounting plate 78. Lens 88 is mounted on a shaft which is rotatably driven by one of the motors 82 suitably attached on another side of motor mounting plate 78. Power lens 88 comprises a disc shape and is formed of cast transparent material, such as a commercially available glass suitable for use as a lens material in a fixture of this type. A plurality of lens elements 188, FIG. 7, form the lens 88 in a honeycomb pattern. A first side 288 of lens 88 is smooth and a second opposite side 388 is comprised of protruding convex surfaces of each of the lens elements 188. In all, there are six adjacent groups of the lens elements, i.e., six different radii are used to form the convex surfaces. These radii are consecutively 10 mm, 17 mm, 24 mm, 31 mm, 38 mm and 45 min. These six groups are arrayed, for example, so that in a certain first portion of lens 88, several of the lens elements 188a having a first radius are clustered in abutting relationship. In this manner, when light beam L passes through an area A of lens 88, the area A of the light beam is of such a size that several of the lens elements 188a are within that light beam area A, see FIG. 7. In a second portion of lens 88 adjacent the first portion, several of the lens elements 188b having a second radius, different from the first radius, are similarly clustered in abutting relationship. However, where lens elements 188b abut elements 188a, the elements of the two portions are interspersed so as to provide a transitional portion of lens 88 made up of approximately equal numbers of elements 188a, 188b. In this manner, when light beam L passes through any transitional light beam area A' of lens 88, the area A' of the light beam is of such a size that no more than two different lens elements 188a, 188b are within that light beam area A', see FIG. 7.

Also included in yoke 14 is a power supply board 146, best shown in FIG. 8, mounted behind a portion designated 46 of metal frame 18. Power supply board 146 is the motor and logic power supply for movement of luminaire 10. Power supplied to board 146 may be 100 to 240 VAC (50/60 Hz). A voltage selection rectification 148, changes AC to DC voltage and operates to double the voltage if less than 150 VAC. Output is stored in capacitors 150, 151 and then a half bridge 152 switches the DC back to AC voltage at 40 kHz. The 40 kHz goes into a transformer 154 which steps the voltage down and isolates the live voltage from the low voltage output circuit. The AC voltage is rectified back to DC voltage and filtered via an inductor-capacitor arrangement at 156. A voltage mode, pulse width modulator controller 158 is responsible for the feedback of the output voltage and controls the half bridge 152 to produce a constant output voltage. Also, a voltage sensor for doubler circuit control is provided at 160.

A logic board 246, best shown in FIG. 9, is mounted in yoke 14 behind a portion designated 40, of metal frame 18. The logic board is operably connected to a controller and controls the above-mentioned pan and tilt, and also controls color wheels, etc., and other operable components of the luminaire 10. Power from power board 146 is fed to logic board 26 at from about 9 VDC to about 40 VDC through a voltage regulator circuit 248. The power is then communicated to a commercially available embedded microprocessor 250. The power is also communicated to a memory block 252 which comprises 3 different types of memory including Static RAM, Flash ROM and EEPROM. The memory 252 is utilized by the microprocessor 250 to perform read/white operations on the code and data stored in the 250 memory which signals pan and tilt commands to luminaire 10. A serial transceiver 254 provides RS 485 compatible signals to industry standard USITT DMX512 controllers and exchanges (receives and transmits) information with microprocessor 250. A slave serial module 256 receives information from microprocessor 250 and serializes data received and sends it out over 5 wires to slave modules including motor driver/sensor boards 94 which include infrared photo interrupter sensors 257, FIG. 3, which respond to tabs and/or notches on component parts of luminaire 10 such as notch 34a formed in gear 34, FIG. 2 or tab 86a on color filter 86, FIG. 3, which tells the microprocessor 250 the initial (zero or homing) position of motors 26, 82, respectively. The serial module 256 retrieves the position information from sensors 257 and sends it to the microprocessor 250 which determines whether to continue to move the filter or gear or to look for the tab/notch.

A stationary lens 96, is mounted in bezel 58, best shown in FIG. 1. Lens 96 is a common light diffusing lens similar to a lens used in an automotive headlight. Such lenses are commercially available. The above described combination of power lens 88 and stationary lens 96 provide a beam angle which is preferably from about 10 degrees to about 60 degrees. This can be varied by rotation of power lens 88 and enhanced by interchanging a selected diffusing lens 96.

While this invention has been illustrated and described in accordance with a preferred embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.