Note: Descriptions are shown in the official language in which they were submitted.
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STAGE LIGHTING METHODS AND APPARATUS
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
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found in U.S. Patent 6,578,987 to Hough et al.
[00043
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
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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
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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'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'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
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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
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me 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;
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[0028] FIG. 11 is a pictorial representation of a motor driven color and
dimming
mechanism according to the present invention; and
[00293 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
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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 190a of the patterned color and
dimming filters 95 and first field stop 125, forming said image 190a 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 190a 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 190a. 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
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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 190b 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 190b 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 190b 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 190b 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
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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 190c 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
190d 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.
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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
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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.
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[0048]
Although specific embodiments of the present invention are disclosed,
the scope of the claims appended hereto are not to be limited by the specific
embodiment set forth in the examples but should be given the broadest
interpretation consistent with the description as a whole.
