Field of Invention The present invention relates to the field of light projectors, and more particularly, to the field of light projectors which utilize a parabolic reflector to create a directed beam of light from a light source.

Background of the Invention Lighting projectors are known in the art, which utilize a parabolic reflector to create a directed beam of light from a light source.

In general, prior art light projectors utilize a light source, such as a xenon arc or a tungsten filament, which radiates light against a parabolic reflector. The light source is generally partially surrounded by a cylindrical cover to damper light that is not directed at the parabolic reflector. Light radiated by the light source is reflected off the parabolic reflector to generate a beam of light. The light source is movable relative to the reflector in order to vary the diameter of the beam generated by the projector. In this regard, the diameter of the generated beam increases as the light source is moved away from the reflector.

When the light source is at a first distance from the parabolic reflector commonly referred to as the focal distance, the beam of light produced is a substantially collimated beam (e. g. substantially parallel rays of reflected light). As the light source is moved further away from the parabolic reflector, the rays of light converge, cross over, and then diverge to create a beam of light with a larger diameter, but with a hole or dark spot in the middle, i. e. a doughnut shaped beam.

Summary of the Invention In accordance with a first embodiment of the present invention, a light projector is provided which includes a light source, a first parabolic reflector and a second parabolic reflector. The centers of the first and second reflectors are aligned on the same axis as the light source. The first reflector has a circumference that is smaller than the circumference of the second reflector. The first reflector and the light source are movable along the axis relative to the second reflector.

In operation, the first reflector and light source are movable between a first position and a second position. In the first position, the light source is at the focal distance for both the first reflector and the second reflector so that a substantially collimated beam of light is produced by the light projector. In the second position, the light source is at distance greater than the focal distance with respect to second reflector, but remains at the focal distance with respect to the first reflector. In this position, the rays of light reflected off the second reflector are convergent, thereby creating a beam of light that has a diameter greater than the beam generated in the first position, but which has a hole (i. e., dark spot) in its center. However, as the light source is still at the focal distance with respect to the first reflector, the rays of light reflected off of the first reflector remain substantially collimated. In this manner, the beam of light generated by the first reflector fills the hole or dark spot in the beam generated by second reflector, and a substantially contiguous beam of light is projected.

In accordance with a second embodiment of the present invention, a light projector including a light source and a parabolic reflector includes a redirecting reflector disposed in front of the light source and opposite the parabolic reflector. The redirecting reflector reflects light emitted from the light source back through the light source and then onto the parabolic reflector where it is reflected along with the rays of light which were directly incident on the parabolic reflector from the light source. In this manner, the light projector provides a more efficient beam of light as compared with prior art projectors that simply place a cylinder or shield in front of the light source to dampen light emitted by the front side of the light source. This

allows the light projector in accordance with the second embodiment of the invention to project a stronger beam of light than prior art projectors using the same type of light source.

In accordance with a third embodiment of the present invention, a light projector includes the first and second reflectors of the first embodiment and the redirecting reflector of the second embodiment.

A method for projecting light from a light projector is also provided which comprises the steps of 1) obtaining a light projector, the light projector having a light source, a first parabolic reflector, and a second parabolic reflector, the first and second parabolic reflectors each having a center point which lies on a common axis with the light source, the first parabolic reflector having a circumference which is smaller than a circumference of the second parabolic reflector; and 2) selectively altering a distance between the light source and at least one of the first parabolic reflector and the second parabolic reflector to obtain a substantially contiguous beam of light, wherein the altered distance between the light source and at least one of the first and second parabolic reflectors is not equal to a focal distance of the respective first and second parabolic reflectors.

Brief Description of the Drawings Figure 1 shows a side cross-section through a light projector in accordance with an embodiment of the invention including a first parabolic reflector-light source assembly, a second parabolic reflector, a housing, a drive mechanism, and a front support mechanism.

Figure 2 shows a front perspective exploded view of the second parabolic reflector, housing, and front support mechanism of Figure 1.

Figure 3 shows a front perspective exploded view of the first parabolic reflector-light source assembly of the light projector of Figure 1.

Figure 4 shows a side cross-section through the light projector of Figure 1 with the first parabolic reflector-light source assembly in a first position.

Figure 5 shows a side cross-section through light projector of Figure 1 with the first parabolic reflector-light source assembly in a second position.

Figure 6 shows the drive mechanism of Figure 1 in greater detail.

Figure 7 shows a rear perspective view of the drive mechanism of Figure 6.

Figure 8 shows a light projector in accordance with another embodiment of the present invention.

Figure 9 shows a light projector in accordance with yet another embodiment of the present invention.

Figure 10 shows a light projector in accordance with still another embodiment of the present invention.

Figure 11 shows an embodiment of the present invention, using a single ended light source and redirecting reflector.

Detailed Description of the Preferred Embodiments Referring to Figures 1 and 2, a light projector 1 includes a truncated parabolic reflector 20 which is secured to a front housing panel 10 having a circular cut out 11.

As used herein the term truncated parabolic reflector refers to a parabolic reflector having a circular cut out 21 in its center. The centers of the cutout 11 and reflector 20 are aligned on a common axis 22.

A support assembly 30 having a center component 40 aligned with axis 22 is secured to the housing panel 10, and extends across the face of the reflector 20.

Referring to Figures 1 and 3, a first parabolic reflector-light source assembly 1000

includes a light source 130 and a parabolic reflector 110. The light source may be of any known type commonly used in the art including for example, an HMI light source, a xenon light source, a tungsten light source, or a sulfur fusion lamp.

Preferably, the light source is either an HMI or xenon light source. In the embodiment illustrated in Figures 1-7, the reflector 110 has the same parabolic shape as the reflector 20, and the circumference of the parabolic reflector 110 is substantially equal to the circumference of the circular cut out 21 in the reflector 20.

The assembly 1000 is secured at one end to the center component 40 and at the other end to a rear housing panel 50 which is located behind the truncated reflector 20.

Although omitted from the drawings for ease of illustration, the light projector 1 also includes corresponding top, bottom and side housing panels extending between the front housing panel 10 and rear housing panel 50.

The entire assembly 1000 is movable along axis 22 so that the reflector 110 and the light source 130 move toward or away from the truncated reflector 20. In this regard, the assembly 1000 which is movable into a first position (indicated in Figure 1 as A) at which the outer circumference of the reflector 110 is substantially flush with the circular cut out 21 of the truncated reflector 20. In this position, the light source 130 is at the focal distance for both the reflector 110 and the reflector 20 so that a substantially collimated beam of light is produced. Figure 4 shows the light projector 1 with assembly 1000 in the first position, along with a graphical illustration of the manner in which a collimated beam of light is generated. As shown in Figure 4, when the light source 130 is at the focal distance of both the reflector 110 and the reflector 20, the rays of light emitted by the light source 130 are reflected as a substantially parallel (or collimated) beam of light 2000, with the rays reflected off a reflector 20 identified as rays 2001, and the rays reflected off of reflector 110 identified as rays 2002. As one of ordinary skill in the art will appreciate, in the first position, a beam of light with a minimum diameter is produced because the beams are substantially collimated.

Figure 5 shows the assembly 1000 moved into a second position (indicated in Figure 1 as B) at which the reflector 110 and light source 130 have moved forward with

respect to the truncated reflector 20. In this position, the light source 130 is now at a distance greater than the focal distance with respect to reflector 20. Therefore, the rays of light 2001 reflected off of reflector 20 are convergent, thereby creating a beam of light with a diameter greater than the beam 2000 generated by in the first position shown in Figure 4. However, as the rays are convergent, the beam generated by reflector 20 has a hole or dark spot in its center. In other words, the beam generated by reflector 20 is doughnut shaped. However, the light source 130 in Figure 5 is still at the focal distance with respect to reflector 110 so that the rays of light 2002 reflected off of reflector 110 remain substantially collimated. In this manner, the beam 2002 generated by reflector 110 fills the hole or dark spot in the doughnut shaped beam 2001 generated by reflector 20. In this regard, the diameter of the reflector 110 and the diameter of the reflector 20 are selected so that the beam generated by the reflector 110 has a sufficient diameter to substantially fill the hole or dark spot in the doughnut shaped beam generated by the reflector 20, when the beam of light generated by the light projector 1 is viewed by the naked eye. In this manner, a substantially contiguous beam of light is produced. In the context of the present invention, a beam of light is considered"substantially contiguous"if, when viewed by the naked eye, no holes or dark spots are visible in the projected beam.

For example, in accordance with a preferred embodiment of the present invention, for a reflector 20 which, in the second position, generates a doughnut shaped beam with a hole or dark spot having a diameter X, a reflector 110 is selected which generates a collimated beam in the first and second positions having a diameter which is at least about X, and preferably slightly larger than X.. It should be appreciated that the diameter X is a function of both the projection distance of the beam 2001 and the relative convergence of rays reflecting off reflector 20 at the second position. Therefore, for a collimated beam 2002 generated from reflector 110 with a diameter X, the lamp can also be viewed as having a range of possible second positions at which the hole or dark spot in the beam 2001 is about X, and preferably less.

Referring to Figures 1 and 2, the assembly 1000 further includes a redirecting

reflector 140 disposed in front of the light source 130, opposite the reflectors 110 and 20. As illustrated in Figures 1 and 4, the redirecting reflector 140 is a spherical reflector (i. e., a reflector in the shape of a portion of a sphere) which reflects light emitted from the light source toward the reflector 140 back through the light source and onto the reflectors 1 I land 20, where it is reflected outward as part of the beam of light 2000. In this manner, the light projector 1 in accordance with the preferred embodiment of the present invention provides a more efficient beam of light as compared with prior art projectors which simply place a cylinder or shield in front of the light source to damper the unfocused light emitted by the front side of the light source. This allows the light projector 1 to project a stronger beam of light as compared to a prior art light projector using the same type of light source.

Preferably, the position, shape, and size of the redirecting reflector is selected so that substantially all the rays of light emitted from the light source that would fall outside of the reflectors 20 and 110 will be reflected by the redirecting reflector 140 back onto one of the reflectors 20 and 110 as illustrated in Figure 4 by dashed line 191, which illustrates that a ray of light 190 which strikes the outermost point of redirecting reflector 140 would have fallen outside of the outermost point on the reflector 20.

The assembly 1000 also includes a heat sink 150 located between the redirecting reflector 140 and the center portion 40 of the support assembly 30. The heat sink 150 has a plurality of apertures to cool the light source 130 by allowing air to travel from the light source 130 through the redirecting reflector 140 and through the apertures of the heat sink 150.

Movement of the assembly 1000 between the first and second positions is controlled by the belt and pulley assembly shown in Figures 6 and 7. A drive pulley 56, which is coupled to a motor (not shown), drives pulleys 52,53,54,55, and 51 (via belt 57), which in turn, moves mounting members 70 having threaded rods 72 in a direction parallel to the axis 22. As illustrated in Figure 3, mounting members 70 are coupled to support components 90 and 80; reflector 110 is coupled to components 80,90 via

seals or retaining rings 120,100 and support rods 95; and light source 130 is secured to components 80,90. While the drive mechanism shown in Figures 6 and 7 is preferred, it should be understood that any conventional drive mechanism may be alternatively employed which causes the assembling 1000 to move along the axis 22.

It should be understood that in accordance with the present invention, the redirecting reflector 140 may be used in a light projector that does not include a first parabolic reflector 110 and a second parabolic reflector 20. Similarly, in accordance with the present invention, a light projector including the first and second parabolic reflectors need not also employ the redirecting reflector. In addition, it should be noted that the first reflector 110 and the second reflector 20 need not be of the same parabolic shape. In this regard, two reflectors are considered to have the same parabolic shape if they are defined by the same parabolic equation.

In accordance with other embodiments of the present invention, the relative positions of the lamp 130 and reflectors 20,110, and 140 can be altered to produce a variety of alternative lighting effects. Three such embodiments are described below with regard to Figures 8 through 10 with similar components bearing identical reference numerals to Figures 1-7.

In the embodiment of Figure 8, the lamp 130, redirecting spherical reflector 140, and parabolic reflector 110 move together from position 1 to position 2, in the same manner as described above with regard to Figures 1-7. Thereafter, the parabolic reflector 110 remains fixed, while the lamp 130 and spherical reflector 140 continue to move along the axial path 22 to position 3. In this manner, the distance between the parabolic reflector 110 and the lamp 130 and spherical reflector 140 can be increased, causing the beam of light 2002 to converge and then diverge as shown in Figure 8. This has the effect of defocusing the ray reflected from the parabolic reflector 110, which produces a larger projected spot. It is believed that this embodiment may increase beam angle and yield an even field better than the design of Figures 1 through 7.

This embodiment allows the fixture to project a wider field angle, because the beam projected by the parabolic reflector 110 is divergent, rather than collimated as in the embodiment of Figures 1-7. This divergent center beam can then fill the larger hole or dark spot in the wider doughnut shaped beam projected by the parabolic reflector 20 as the lamp moves forward to position 3. It should also be noted that if the lamp 130 and the spherical reflector 140 continue moving along the axial path, the image from the parabolic reflector 110 will become larger than the image from the parabolic reflector 20. This phenomenon is caused by the proximity difference of the lamp to the reflecting surfaces. This could also be described as angular magnification. The closer the lamp is to the mirror, the less axial movement from optimum focus is required to defocus the apparent image.

In the embodiment of Figure 9, the parabolic reflector 110 moves independently along the axial path 22 until it has reached position 2, with the lamp 130 and spherical reflector 140 remaining stationary. This movement progressively diverges the beam reflected from the reflector 110 creating a larger beam angle and projected image. From position 2, the lamp 130, spherical reflector 140, and parabolic reflector 110 move together along the axial path to position 3. This progressively converges the beam reflected from the parabolic reflector 20. At longer throws (e. g., more than 100 feet), a projector in position 3 creates a larger doughnut shaped projected image with parabolic reflector 110. The hole or dark spot in the image is then filled in with the converging (and then diverging) beam of the reflector 20.

In the embodiment of Figure 10, the lamp 130 and spherical reflector 140 move along the axial path until they arrive at position 2, while the parabolic reflector 110 remains stationary. At position 2, rays 2001 and 2002 are both converging.

However, the rays 2001 on the parabolic reflector 20 are converging at a different angle than the rays 2002 on the reflector 110. At medium throws (e. g. 50-100 feet), the inner rays 2002 from the parabolic reflector 110 create a doughnut shaped beam and are filled in with the converging rays 2001 from the parabolic reflector 20. As the lamp 130, spherical reflector 140, and the parabolic reflector 110 move together from position 2 to position 3, the light reflecting from the parabolic reflector 20

converges even more, producing an even wider projected image. It should be noted, moreover, that the effect generated from position 3 of Figure 10 can be similarly generated in position 3 of Figure 8.

In accordance with further aspects of the embodiments of Figures 1-10, the light source 130 could be a single ended light source, such as the light source 130'shown in Figure 10. Brackets 500 can be secured to the reflector 110 (for the embodiments in which the lamp always moves with the reflector 110) or to the lamp support (for embodiments in which the lamp moves independently from the reflector 110).

In connection with the embodiments of Figures 8 through 10 it should be noted that because the arc length in the lamp is not a point source, rays are created that diverge naturally. For this reason, it is believed that HMI lamps are more suitable for these embodiments than lamps with extremely small arc gaps such as Xenon lamps.