Note: Descriptions are shown in the official language in which they were submitted.
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'this invention relates to the provision of lamps
equipped and ready to respond to a flow of 3D control
information (3D-ready intelligent lamps).
Robotic lamps are used primarily in the entertainment
industry such as night clubs, theatres and concert venues.
They also have additional application in areas such as
promot:ion/advertising, architectural lighting, and so-called
"immersive reality" among others. These robotic or
"intel_ligent" lamps can be remotely controlled by an
industry communications standard called "DMX-512". This is
a high speed serial data protocol which allows remote
computer control of many different features of the lamp
fixtures) such as the pan and tilt angle at which the light
beam i.s projected, beam intensity, colour selection, beam
width (iris), focus, and light pattern ("gobo" selection)
among others.
Increasingly these lamps are used in conjunction with
computer software running on external PC computers and/or
lighting desks to enhance their capabilities. Some of this
external software simulates the three dimensional (3D)
environment in which the lamps function, allowing
programming of lighting effects to occur "off-line" (i.e.
without the need for a theatre and lighting system). This
is possible since the software provides a 3D virtual
environment visualizing how the lamps will look when they
are used in real life. Other software/hardware systems such
as 3D tracking systems which follow the movements of a
performer and allow lamps to automatically track and respond
to performers' movements in various ways are described and
claimed in U.S. Patent No. 5,214,615 issued May 25, 1993, to
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Bauer and 5,412,619 issued May 2, 1995, to Bauer and in PCT
application No. PCT/CA97/00724.
As interest in using intelligent lamps to respond to 3D
cues and movements grows there is an increasing need for the
lamp itself to be "3D-ready". A 3D-ready lamp is specially
equipped and is able to respond in an optimal fashion to
streams of 3D control information.
An intelligent lamp can respond to 3D information in a
variety of ways. For many of the responses, it is necessary
to know the 3D position of the lamp and orientation.
Coordinates for the X, Y and Z axes of three dimensional
space plus pitch, yaw, and roll angles for the orientation
in space give a six degree of freedom ("6DOF") description
of the status of the lamp. This information establishes a
coordinate system which completely describes the lamp and is
necessary to calculate the way in which the lamp responds to
incoming 3D information. For example, for a lamp to follow
an object moving in three dimensions, one must know the 3D
coordinates of the object and the 6DOF coordinates of the
lamp in order to correctly calculate the pan/tilt angles
necessary to point the lamp at the moving object.
Clearly then, establishing 6DOF coordinates of the lamp
is something that a 3D ready light should be able to do with
ease. Currently with normal intelligent lighting fixtures,
it is possible to calculate the position of the lamp and
orientation by pointing the lamp at four reference points
located in a common plane (usually the stage floor) and
measuring the pan/tilt angles required to point the lamp at
each of the four points. This give enough information that
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one skilled in the art can calculate the lamp's position and
orientation. A problem with this process is that it is
quite time consuming to point each lamp to each of the four
points. Often there are many lamps for which this must be
done and it can take an inordinate amount of time. A better
solution would be to point the lamp at only one reference
point (say the centre of the stage) and have that be enough
to establish the lamp's 6DOF coordinates relative to that
point. To do this, the following capabilities of lamp are
1() necessary:
a) a method of sensing two of the lamp's three
orientation angles (pitch and roll); and
b) a method of measuring the distance from the lamp
to the reference point.
15 Requirement a) can be accomplished in a number of ways
but perhaps the easiest is to have a two-axis gravity sensor
which can measure the pitch and roll angles of the lamp's
orientation relative to the earth's gravity field. A
variety of sensors are available which do this and which are
20 easily interfaced to an inexpensive microcontroller chip.
Some are two axis accelerometers which consist of two DC
frequency response accelerometers mounted orthogonally to
each other. Others are capacitively based and sense the
orientation/position of liquid in a tube much like a
2.'~ traditional carpentry level.
Requirement b) can be met with a ranging system that
can sense the distance between the lamp and the reference
point. There are also a variety of technologies capable of
this. For example, laser ranging systems which use light
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beams that are either pulsed or continuously present. When
pulsed, the pulse is emitted from a laser transmitter and
the time delay between its emission and the sensing of its
reflection by receiver circuitry is measured. This can
yield accuracies anywhere from one or two metres to
centimetres depending on the accuracy of the timing and the
number of measurements averaged. When used continuously, a
phase measurement is performed comparing the phase of the
transmitted wave with the phase of the reflected wave. This
method allows greater accuracy but usually fewer
measurements per second are possible. Another technology is
the use of ultrasonic waves. The time delay between the
emission and reception of ultrasonic pulses can be measured
and this varies linearly with distance.
An additional desirable, but not absolutely necessary,
characteristic of a 3D-ready lamp is the ability to be
superior at responding to streams of 3D positional data. A
problem that normal intelligent lamps have is that their
control systems are open-loop which is to say that there is
no feedback regarding the state of the lamp vis-a-vis the
state that it was commanded to assume. Particularly with
pan and tilt motor control, this can be problematic since
open-loop control greatly restricts the speed and precision
at which these motors can operate.
Closed-loop control of pan and tilt is much more
desirable for 3D positioning tasks such as follow-spot
operation since it allows far greater speed, precision, and
smoothness of movement. To this end, another desirable (but
not strictly necessary) requirement for a 3D ready lamp is
that its pan/tilt motors be equipped with shaft encoders
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which yield digital outputs of the actual pan/tilt angles at
which the light beam is being pointed. This information
should have a precision of at least 12 bits per revolution
and should be in a form where either the internal lamp
'.i microcontroller or an external controller (or both) can
access this data.
Thus it would be desirable to provide a "3D-ready
intelligent lamp" equipped with a microcontroller which
integrates a pitch/roll angle measurement, pan/tilt encoder
angle measurements, and a ranging measurement. This
information would be utilized to control lighting parameters
in real-time. In its "calibration mode" this lamp would be
capable of detecting its 6DOF position/orientation on being
pointed at one reference point. In its normal "operational
mode" it is capable of extremely fast and precise pan/tilt
positioning using the pan/tilt encoder using closed-loop
feedback. Additionally, it is capable of continuously
measuring the distance between the lamp and the surface onto
which the light is shining and modulating any of its
lighting parameters in response to that information. This
3D-ready functionality can be implemented either as a
standalone package that can be retrofitted to existing lamps
or it can be built in as an integral part of a new design of
lighting fixture.
As an example of the utility of such a lamp, consider
the problem of focussing/irising the lamp depending on where
it is pointing. This is a normal problem for intelligent
lamps: as the light beam is moved via its pan/tilt controls
of the lamp, the width, focus, and intensity of the beam
change depending on how far away the lamp is from the wall
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floor or other surface onto which the beam is being
projected. Unless an adjustment is made, the width of the
beam will be twice as wide when the projection surface is at
twice the distance from the lamp. To make the beam width be
the same, the lamp's iris or focal zoom control must be
adjusted. Clearly, if there were some way of measuring the
distance from the lamp to the projection surface, it would
be possible to modulate the lamp's controls to maintain a
constant width. In a similar manner, knowledge of the
1C> distance between the lamp and the projection surface would
allow the light beam to be kept properly focussed
continuously despite variations in this distance caused by
changing pan/tilt angles of the lamp (or, for that matter,
moving projection surfaces such as mobile scenery) in real-
1_'> time during a show.
Other possibilities include (but are not limited to)
the following:
~ being able to tell the lamp to point to a specific 3D
location with focus and beam width (controlled by iris
20 and zoom) setting determined automatically based on
parameters indicating the desired shape/pattern of the
light beam rather than just sending pan/tilt
coordinates.
~ being able to have exceptionally fast, smooth, and
25 accurate pan/tilt positioning for pointing the lamp
during follow-spot operation.
~ being able to tell the lamp to automatically change the
focus and iris setting in real time (i.e. as the lamp
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is moved about) bases on the 3D position where the lamp
is pointing so that the light is always in focus and
maintains a constant beam width.
~ being able to send to the lamp either 3D coordinates
(X,Y,Z) of where to point, or normal pan/tilt
coordinates with an added range parameter.
~ being able to feed back real time information such as
the current distance to where the lamp is pointing or
the 3D coordinates of where it is pointing plus
calibration information such as its 6DOF coordinates to
a master controller such as a lighting console.
~ being able to tell the lamp to move in specific
geometric patterns. since the lamp would have
knowledge of the geometric distortions involved based
on its 6DOF coordinates and the desired centre of the
patterns, it could correct for these distortions and
generate (for example) true circular movements. This
functionality could also be implemented on a lighting
console that had been sent the lamp's 6DOF coordinates.
~ being capable of generating a 3D map of a particular
theatre stage. The light would be scanned over the
entire stage area, transmitting the 3D coordinates of
where the lamp was pointing with a precision
appropriate to the situation. This 3D map could then
2.'~ be stored by a lighting console and used to coordinate
or match up a previously generated 3D model of the
stage (which can currently be generated using a variety
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of lighting design software packages) with the actual
one.
Accordingly the invention provides a lighting system
equipped to respond to a flow of three dimensional control
information comprising at least one variably responsive
intelligent lamp controlled by a computer communication
means to provide input data for the lamp characterized in
that the system includes feed back means from the lamp to
the computer to provide data to the computer in real-time as
to the six degrees of freedom of the lamp, the actual
pan/tilt coordinates of the lamp and to provide ranging
means between the lamp and a surface on which it is
projected. For example, the communication means may be a
serial data protocol such as a DMX source connected in a
loop to provide feedback.
DMX-512 is not normally a bidirectional protocol;
normally one may send data from one source to many
destinations but one cannot send from the many destinations
to the one source. To provide the possibility for 3D lights
to provide feedback about their 6DOF coordinates or about
the distance between the lamp and the surface onto which it
was shining, it is necessary to reallocate some of the
lamp's channels (for use in calibration mode) and add
additional DMX channels for distance data, pan data and tilt
data respectively. Normally, lamps are set to receive data
from a contiguous range of DMX channels, the lowest numbered
of which is called the ~~base channel". Thus a lamp might be
set to receive data covering DMX channels 98 to 111 i.e. a
base channel of 98. It is also normal practice that all
3C' other lamps would be set to avoid this range of channels
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(unless it was somehow advantageous to send the same data to
several lamps at the same time) so this range is normally
reserved for one lamp. A sub-range of these lighting
channels may be reserved for the transmission of data
specific to the lamp. Thus if, for example, if channels 98
to 101 inclusive are reserved, the lamp will receive data on
DMX channels 1 to 512 inclusive but it will not retransmit
data that was incoming on channels 98 - 101 but rather will
replace that data with its own internally generated values.
In this way, by connecting the DMX serial connection in a
loop one can transmit data from a controller such as a
lighting console and receive back the data generated by each
lamp. This may be possible using a normal serial data UART
chip or it may necessitate a special DMX control FPGA chip
1'i programmed to replace the specific channels of data but such
things are well within the scope of one versed in the art.
A preferred embodiment will now be described by way of
example with reference to the drawings in which:
Figures lA and 1B depict the problem of maintaining
constant beam width on a moving projection surface;
Figure 2 is a block diagram of one embodiment of the
invention; and
Figure 3 is a block diagram of the internal functioning
of the 3D light controller of Figure 2.
One problem is easily understood from Figures lA and
1B. Figure lA shows a focussed light source 10 projected on
a projection surface 11 which is located a distance R from
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the light source. The image on the projection surface 11
covers an area of diameter D. Figure 1B, on the other hand,
shows the projection surface 11 having moved to a distance
2R from the light source 10. The diameter of the image has
correspondingly grown to 2D although it would be desirable
for it to remain at the original size.
Figure 2 shows a normal intelligent light 12 connected
normally by a unidirectional DMX path 14 to a lighting
control console or other DMX source such as a 3D tracking
light control system 16 through a 3D light controller module
18. For simplicity only one 3D light controller module is
shown but there is no reason why more than one of these
modules should not form part of the DMX chain. While the 3D
light controller module 18 is shown separately from the
1.'~ ~~normal lamp" 12 it could be built as an integral part of
the lamp itself thus forming a sub-system of the lamp. In
this case DMX might well not be used to communicate with the
normal portion of the lamp 12 since connections could be
made by more direct means within the light circuitry itself.
Figure 2 also shows the DMX signal path 20 for the
light controller module 18 whose input is connected to the
lighting console 16 and whose output is connected to a
series of other DMX controllable lamps 22. DMX data leaves
the lighting control console 16 and is sent via DMX to the
2'.i 3D light controller module 18. The incoming DMX data is
echoed to the DMX output of the module 18 with channels
reserved for the transmission of internal data germane to
the 3D light controller module 18 and the normal intelligent
lamp 12 to which it is attached.
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The data sent from the DMX output of the 3D light
controller module 18 continues along the DMX chain until it
leaves the DMX output of the last lamp 22 in the DMX chain
and is returned to the DMX input of the lighting control
console. DMX data entering at this input contains reserved
channel information from all 3D light controller modules 18
connected in the DMX chain which can then be received,
examined, and acted upon by software of the lighting
controller 18.
Figure 3 is a block diagram of the internal working of
the 3D light controller module 18. The base DMX address of
the module 18 is set via the base address dip switches 24
and is read at power-up of microcontroller/DSP 30 or when
the switches are changed during operation. Incoming DMX
data is sent both to the DMX I/0 controller 26 and to the
module's light DMX out connector 28 where it is sent to the
normal lamp's DMX input.
The DMX I/0 controller 26 functions as a device which
echoes incoming DMX data to the DMX output with minimum
latency. The only DMX data not echoed is incoming data sent
on the reserved channels for this module. These data are
discarded and replaced by data generated by the module 18
itself. What is actually sent on these channels will vary
with functional mode and with the type of operated desired
2_'> but it will generally be information germane to either the
6DOF coordinates of the lamp its real-time pan/tilt encoder
coordinates from the pan/tilt encoders 40, or to the results
of calculations involving these coordinates done by the
microcontroller/DSP 30.
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The microcontroller/DSP 30 can be either a relatively
inexpensive microcontroller such as the 89C52, a more
complex DSP chip such as the TMS320C50, or a PC '486 chip or
chip set depending on the complexity of calculation it is
desired to perform. In some situations it may be desirable
to have all complex calculations performed externally by the
lighting control console 16 and/or 3D tracking light control
system (see Figure 2). In other situations, it may be
desirable to have the 3D light controller module 18 perform
1() a variety of complex calculations itself. In any event, the
microcontroller/DSP 30 monitors the incoming DMX stream for
commands. At the same time, it monitors a laser ranging
sub-system 32 via a parallel or serial port connection. The
laser ranging sub-system 32 provides information about the
15 distance between the lamp and the surface onto which the
light is shining. When the laser ranging sub-system 32 is
active (something that is controlled by the
microcontroller/DSP) this information is updated up to 10
times per second. The microcontroller/DSP is also connected
20 to an analog to digital ("A/D") converter 34 and a two
position SPDT Electronic Switch 36. This switch is
connected to a two axis orientation sensor which
continuously measures the pitch and roll angles of the 3D
light controller module (which is mounted on the normal lamp
2'.~ 12 so that its orientation is the same as that of the normal
lamp). By this arrangement, the microcontroller/DSP can
measure these angles during calibration. The
microcontroller/DSP 30 is also provided with some RAM and/or
ROM memory 38 for storing data plus configuration
30 information such as light patterns etc. and it accesses/uses
the RAM/ROM as needed.
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As an addition, the microcontroller/DSP 30 may also
monitor the outputs of pan/tilt encoders 40 which provide
real-time information about where the lamp is pointing.
This information by be used to provide closed-loop control
of the lamp's positioning with all of the advantages this
entails.
