U.S. patent application number 15/127783 was filed with the patent office on 2017-04-27 for laser projection system.
This patent application is currently assigned to LIGHTWAVE INTERNATIONAL, INC.. The applicant listed for this patent is LIGHTWAVE INTERNATIONAL, INC.. Invention is credited to George Dodworth.
Application Number | 20170114992 15/127783 |
Document ID | / |
Family ID | 54145419 |
Filed Date | 2017-04-27 |
United States Patent
Application |
20170114992 |
Kind Code |
A1 |
Dodworth; George |
April 27, 2017 |
Laser Projection System
Abstract
A laser projection system having built-in safety systems is
disclosed. Further disclosed is a method of operating a laser
projection system such that safe operation is a factor only of
meeting a threshold distance between the laser unit and an audience
member. To accomplish safe operation at the threshold distance, the
laser projection system is pre-calibrated to operate below maximum
permitted exposure levels at the threshold distance. In this manner
of operation, laser lighting can be accomplished by non-laser
professionals without the complexity, external sensors, and need
for calibration at the venue.
Inventors: |
Dodworth; George; (Eighty
Four, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LIGHTWAVE INTERNATIONAL, INC. |
Eighty Four |
PA |
US |
|
|
Assignee: |
LIGHTWAVE INTERNATIONAL,
INC.
Eighty Four
PA
|
Family ID: |
54145419 |
Appl. No.: |
15/127783 |
Filed: |
March 21, 2015 |
PCT Filed: |
March 21, 2015 |
PCT NO: |
PCT/US15/21904 |
371 Date: |
September 20, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61968823 |
Mar 21, 2014 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F21V 21/15 20130101;
G01J 1/26 20130101; F21V 25/00 20130101; H01S 3/0071 20130101; F21V
23/0457 20130101; G01J 2001/0285 20130101; G02B 27/20 20130101;
H01S 3/0014 20130101; G01J 1/4257 20130101; G01J 1/24 20130101 |
International
Class: |
F21V 23/04 20060101
F21V023/04; H01S 3/00 20060101 H01S003/00; F21V 21/15 20060101
F21V021/15; F21V 25/00 20060101 F21V025/00; G01J 1/42 20060101
G01J001/42; G02B 27/20 20060101 G02B027/20 |
Claims
1. A system for projecting a laser onto an audience, comprising: a
laser source; a monitoring system, wherein the monitoring system
observes a plurality of output parameters of the laser source;
wherein the monitoring system generates an output signal; a
calibration interface, wherein the plurality of output parameters
of the laser source are calibrated such that a laser beam emitted
from the laser source does not to exceed a threshold exposure level
at a given distance; a safety system that receives the output
signal, wherein the safety system attenuates the laser beam in the
event the laser beam exceeds the threshold exposure level.
2. The system of claim 1, further comprising: an anti-tampering
device operably connected to the calibration interface, wherein the
anti-tampering device prevents modification of the plurality of
output parameters of the laser source by unauthorized users.
3. The system of claim 1, further comprising: a motorized yoke,
wherein the yoke changes an axis of projection of the laser.
4. The system of claim 3, further comprising: a yoke position
sensor that generates a yoke output signal, wherein the yoke output
signal is transferred to the safety system.
5. A method of operating a laser projection system for an audience,
comprising: providing a laser projection system, the laser
projection system comprising: a laser head that projects laser
beam; a motorized yoke having a mount, wherein the laser head is
secured in the mount; a monitoring system, wherein the mounting
system determines the exposure level of the laser beam; a safety
cutout device that blocks transmission of the laser beam emanating
from the laser head when the monitoring system detects an excessive
exposure level; a calibration interface, wherein the power output,
beam divergence, and scan rate of the laser beam is adjusted;
calibrating the laser projection system to prevent exposure levels
exceeding a maximum threshold at a pre-determined distance;
installing the laser projection system at a distance no less than
the pre-determined distance from an audience.
6. The method of claim 5, further comprising: operating the laser
projection system pursuant to a governmental variance.
7. The method of claim 5, further comprising: adjusting a parameter
of the laser beam when the maximum threshold is no longer
maintained.
8. A laser projection system, comprising: a laser source configured
to project a laser beam.
9. The system of claim 8, further comprising: a monitoring system,
wherein the monitoring system observes a plurality of output
parameters of the laser source; wherein the monitoring system
generates an output signal; a calibration interface to adjust the
plurality of output parameters of the laser source; and a safety
system that receives the output signal, wherein the safety system
attenuates the laser beam in the event the laser beam exceeds a
threshold exposure level.
10. The system of claim 9, further comprising: a motorized yoke,
wherein the yoke changes an axis of projection of the laser source;
and a yoke position sensor that generates a yoke signal, wherein
the yoke signal is transferred to the safety system.
11. The system of claim 9, wherein the laser beam has a subtense
between about 1.5 milliradians and 100 milliradians.
12. The system of claim 10, wherein the laser beam has a subtense
between about 1.5 milliradians and 100 milliradians.
13. The system of claim 8, wherein the laser beam has a subtense
greater than about 100 milliradians.
14. The system of claim 8, further comprising: a motorized yoke,
wherein the yoke changes an axis of projection of the laser source,
wherein the laser beam has a subtense greater than about 100
milliradians.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119 of U.S. Provisional Application Ser. No. 61/968,823,
filed Mar. 21, 2014, which is incorporated by reference herein in
its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] The field of the invention relates generally to laser
projection systems. More specifically, the invention relates to
laser projection systems that are used in various venues to conduct
a light show, wherein the laser light is projected into the
audience to enhance the experience of the show.
[0004] Current regulations in the United States and other countries
require an expert to own and operate a laser projection system.
Regulations are required because most projection systems are
capable of causing injury if not calibrated, set-up, and operated
properly. As such, projection systems are operated by laser safety
officers who are recognized by the U.S. Food and Drug
Administration (FDA).
[0005] Currently, the operator must hold a special variance from
the FDA to project any laser light into an audience member's eyes
to ensure maximum permitted exposure levels are not exceeded. The
current method of audience scanning (technique for safely shining
lasers into the audience) further requires extensive training by
the laser safety officer and an abundance of specialized hardware
to operate. In practice, the laser safety officer installs the
laser projection system at the venue, conducts tests of the
equipment, and measures the light output at various locations where
audience members are expected to be during the show. The process is
time consuming and exposes other workers to potentially dangerous
laser light. It would therefore be advantageous to develop a laser
projection system and a method of operation that reduced the need
for extensive on-site set-up and testing while still ensuring the
safety of audience members.
BRIEF SUMMARY OF THE INVENTION
[0006] The present invention offers lasers "to the masses" in a
simple, self-contained, easy to deploy, easy to control, and safe
package. Most importantly, the laser projection system and method
of the present invention satisfy all safety regulations. The laser
projection system, in the preferred embodiment, comprises a laser
unit mounted in a motorized yoke, an optics device, and a
calibration interface. The calibration interface allows the laser
safety officer to adjust the laser power output, minimum scanning
velocity, maximum scanning dwell duration, and other parameters of
the laser which could affect safety.
[0007] To operate the laser projection system, the operator
supplies a power source and connects the unit to a standard
lighting controller, such as a Digital Multiplex (DMX) controller.
DMX is a standard for digital communication networks that are
commonly used to control stage lighting and effects. In alternative
embodiments, other controller interfaces are provided, such as an
ethernet-based interface such as ArtNet, by example. The commands
supplied by a lighting designer or other operator trigger a
built-in server in the laser projection system to provide
pre-programmed lighting effects.
[0008] The laser projection system can be safely operated through a
combination of a built-in safety system that monitors the output of
the laser and pre-calibration of the laser. During pre-calibration,
a laser safety officer sets the parameters of the laser based on a
pre-determined distance. For example, a laser operator can choose
30 feet as the threshold distance, then proceed to calibrate the
laser to ensure any lighting effect at a distance of 30 feet or
greater from the laser source is safe for the audience. The
calibration can occur at a location separate from the venue where
it is intended to be installed.
[0009] Because the laser projection system has been pre-calibrated
for a set distance, a user simply has to ensure that the laser
projection system is installed at the minimum distance or greater
from the audience. No further on-site testing is required. To
prevent the laser parameters from being changed, the laser
projection system is provided with anti-tampering devices that
prevent anyone other than the laser safety officer from accessing
the optics or laser calibration interface.
[0010] In alternative embodiments, the laser source is calibrated
to function more as an extended source rather than a point source,
an inherent quality of lasers. Extended source lighting does not
present the ocular risks that point source lasers do. As a result,
a laser projection system operating as an extended source can be
mounted and operated like a traditional lighting fixture,
regardless of distance.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] FIG. 1 shows the laser projection system according to one
embodiment of the present invention, wherein the system is
installed at a distance from the audience.
[0012] FIG. 2 shows an alternate installation of the laser
projection system.
[0013] FIG. 3 shows yet another alternate installation of the laser
projection system.
[0014] FIG. 4 is a schematic showing the minimum safety distance in
multiple directions surrounding a laser projection system.
[0015] FIG. 5 shows a block diagram of the laser projection system
according to one embodiment of the present invention.
[0016] FIG. 6 is a logic diagram of the safety features of the
laser projection system.
[0017] FIG. 7 shows a block diagram of an alternate embodiment of
the laser projection system.
[0018] FIG. 8 is a chart depicting the exposure level to a high
power laser for a given distance.
[0019] FIG. 9 is a chart depicting the exposure level to a laser
similar to one of the present invention for a given distance.
[0020] FIG. 10 is an alternate chart depicting the exposure level
to a laser similar to one of the present invention for a given
distance.
[0021] FIG. 11 is a sample warning sticker that can be affixed to
the laser projection system.
[0022] FIG. 12 is a sample calibration sticker that can be affixed
to the laser projection system.
[0023] FIG. 13 is a schematic of a laser projection system
according to one embodiment of the present invention.
[0024] FIG. 14 is a flowchart of the method of operating the laser
projection system.
[0025] FIG. 15 is an alternate view of an overhead installation of
multiple units.
[0026] FIG. 16 shows a single unit having a motorized yoke in an
overhead installation.
[0027] FIG. 17 shows a single unit without a motorized yoke in an
overhead installation.
DETAILED DESCRIPTION OF THE INVENTION
[0028] Disclosed herein is a laser projection system 100 comprising
a laser source 101 configured to safely shine laser light onto an
audience. The laser projection system 100 further comprises, in
some embodiments, a monitoring system 102, a calibration interface
103, a vector scanning engine (galvanometers), diverging optics
108, and a safety system 104. The calibration interface 103 allows
a laser safety officer, or other user, to set safe operating
limits. As a failsafe during operation, the safety system 104 can
limit maximum source power, maximum dwell time, and minimum beam
velocity to prevent any unnecessary risk of exposure to an audience
member in the event an operator attempts to project content that is
unsafe for the audience or the system experiences a malfunction.
The safety system 104 is further able to monitor the integrity of
the system voltages, scanner error, and shutter state. The
Professional Audience Safety System offered by Pangolin Laser
Systems is an example of a safety system 104 that can be used in
the laser projection system 100 of the present invention. FIG. 13
is a schematic representing the laser projection system having a
motorized yoke 106, according to one embodiment.
[0029] In one embodiment, the method of operating the laser
projection system 100 comprises installing the projection system
100 at a fixed distance relative to a crowd. As shown in FIG. 1,
multiple laser projection systems 100 are installed on a stage at a
distance of 30 feet from the nearest audience member. Prior to
installation, a certified laser safety officer calibrated each unit
to provide safe operation beyond 22 feet. A buffer distance of 8
feet is provided in the installation example shown in FIG. 1 to
allow safe operation in the event an audience member breaches the
security barrier. Alternatively, if site-specific regulations
require on-site calibration, the units can be calibrated after
installation.
[0030] FIG. 2 shows an alternative installation of the plurality of
laser projection systems 100. In this example, the units are
mounted on a truss above a stage. With the units mounted overhead,
it is more difficult for an audience member to encroach into the
safety distance. As such, an additional buffer is not provided.
FIG. 3 is an alternative view of the installation shown in FIG. 2,
showing that the distance from the front of the laser projection
system 100 to the nearest audience member is greater than the
installation height, due to the setback distance from the front of
the stage. FIG. 15 shows a similar installation of the laser
projection systems 100 mounted to a truss above an audience. In all
of FIGS. 15-17, the distance between the laser source 101 and the
audience is visible for various embodiments of the system 100. For
example, FIG. 15 shows multiple systems 100 having a motorized yoke
106, FIG. 16 shows a single system 100 having a yoke 106, and FIG.
17 shows a single system 100 without a yoke 106.
[0031] FIG. 4 represents the safety zone around a laser projection
system 100 according to one embodiment in which a laser source is
mounted on a motorized yoke 106. Because the yoke 106 is capable of
moving the laser source 101 in all directions, the safety distance
must be observed in three axes. Current systems are not installed
on motorized yokes 106 because it is difficult for the laser safety
officer to account for the number of variables in calibrating the
machine. However, according to the method of the present invention,
the laser safety officer calibrates each unit for a set,
pre-determined distance, such that the laser is safe regardless of
the position of rotation within the yoke 106. As shown in this
example, power levels of the laser are not based on the region into
which the laser is projecting. In prior art systems, laser output
is often increased when projected above the audience, but
attenuated when directed onto the audience.
[0032] With the system 100 calibrated for safety at any distance
beyond a threshold distance, the opportunities for use of laser
units in lighting effects is greatly increased. Instead of a laser
safety officer installing, testing, and calibrating each unit, a
stage hand can install the unit as he would with a typical light
source. The only factor the stage hand must be cognizant of is the
distance to the audience in the location of installation. The
complete integrated system is self-contained, plug-and-play, and
ready to operate. Because of the built-in safety, the laser
projection system can use lighting industry standard controls (such
as DMX or ArtNet) or International Laser Display Association (ILDA)
standards as an option.
[0033] Referring to FIG. 5, a block diagram representing one
embodiment of the present invention is depicted and shows several
state-of-the-art components. At the heart of the system is a laser
source 101, such as a solid state laser, which projects through a
shutter and light sensor onto a scanner. The scanner contains a
front surface mirror that is able to reflect the laser light in
different directions. At adequately fast speeds, the scanner is
able to utilize human persistence of vision to create effects, such
as drawing shapes or letters onto a projection surface, or three
dimensional volumes of light in the air such as sheets, tunnels, or
beams. The laser light exits the system through an optics system
108. The optics system 108 can be an integral part of making the
laser system 100 safe, to the extent that lenses have the ability
to alter the divergence of a laser beam. More divergent beams are
inherently safer, but decrease intensity by reducing irradiance in
relation to distance from the laser, which is the power density of
the light in Watts per meter squared. The divergence of a beam is
used in connection with other beam parameters, such as power and
dwell time to determine the maximum permitted exposure level that
may be directly viewed by entry into the occulus of an audience
member.
[0034] Other components of the laser projection system 100 interact
with the safety system 104 to ensure proper operation. As shown on
FIG. 5, sensors, or monitoring system 102, that measure light
output, scanner position and velocity, yoke position, shutter
operation, and wheel effects, to name a few, are input into the
safety system 104. If the safety system 104 detects a state of
operation that would expose an audience member to a level of laser
light exposure that exceeds a maximum permitted level, the safety
system attenuates the beam through operation of the shutter,
reducing power, reduction of dwell time, or temporarily terminating
operation. In the system 100 shown in FIG. 5, a shutter driver
controls operation of the shutter.
[0035] Control of the laser projection system 100 can be
accomplished by an industrial standard lighting controller
connected to a media server with Ethernet and external media
inputs. In alternative embodiments, the laser source 101 is mounted
in a motorized yoke 106, which can be controlled by a separate
interface connected to the lighting controller. A global smart lens
or other attachments are optional to respond to physical changes of
the environment.
[0036] FIG. 6 is a flow diagram showing the inputs that factor into
meeting applicable governmental safety standards. The inputs
include user safety inputs, system managed safety inputs, and
physical properties of the system and environment. For the system
of the present invention according to one embodiment, the only user
safety input is the distance from the laser unit to the closest
audience member. For embodiments employing an extended source
laser, there are no user safety inputs. System managed inputs
relate to the calibration of the laser projection system and
include items such as lenses, optics, effects wheels, and laser
beam diffusion, profile coherence, and polarization. Physical
properties relate to items such as exposure expected for a fully
dilated human pupil, intrinsic divergence, and system power. Safety
standards are set to define a maximum permitted exposure and are a
factor of maximum irradiance (expressed as power per area), maximum
exposure pulse width (time), maximum exposure dwell time (time),
exposure repetition rate (unit per time), and approved calculations
and ratings.
[0037] In the preferred method of operating the laser projection
system, each of the safety inputs are encoded, or pre-calibrated,
through a calibration interface 103 into the system 100 such that
only the user safety input (i.e. distance) has to be met in order
to achieve safe operation as defined by applicable governing
standards. That is, the operation of the laser projection system
will be safe if the system is installed at a pre-determined
distance from the audience. FIG. 14 is a flowchart depicting the
basic steps of this process. To further protect the integrity of
the pre-calibration and to prevent any tampering or modification of
the values by the operator, the pre-calibration settings can be
stored in a non-volatile memory or set using fixed components
values in the controlling circuits such that only the manufacturer
or laser safety officer are able change the pre-calibration values.
If the settings are stored digitally in a memory of the unit, the
unit can adjust to a smart accessory, such as a lens, that is
recognized by the unit. For example, the laser projection system
may recognize the addition of a lens having a certain power and use
a calibration table created by a laser safety officer for that
particular lens.
[0038] FIG. 7 shows a component block diagram of an alternative
embodiment of the laser projection system 100. This system 100 has
similar components to the system shown in FIG. 5, but with the
inclusion of controls to change user settings for manual
calibration of the system by the laser manufacturer or laser safety
officer and a motorized lens which can dynamically change beam size
or divergence. In addition, external computer inputs are provided
which allow updated programming content to be sent to the media
server. In this configuration, the external computer can behave as
an external server according to the user input or the industrial
standard lighting controller's protocol.
[0039] In alternative embodiments, the laser projection system can
comprise the following features: [0040] Standard pan/tilt/rotate
lighting yoke as is typically used in standard lighting fixtures;
[0041] Safety systems that incorporate data from yoke sensors to
increase laser beam brightness based on yoke velocity; [0042] Yoke
controls from industry standard DMX, ArtNet, or Ethernet control
protocols; [0043] Imbedded laser media server, containing
preprogrammed cues; [0044] Laser control based on industry standard
DMX, ArtNet, Ethernet, Contact Closure, RS232, RS485, or other
commercially available control protocols; [0045] Bypass control
where the laser source is controlled from an external input such as
an ILDA connector; and [0046] Optics system 108 to obtain audience
safety at a given distance.
[0047] During the pre-calibration process, the system can be
calibrated, tested, and audited by a laser safety officer with full
laser safety officer training, knowledge, and experience to
calculate and determine all maximum permitted exposure (MPE)
factors in accordance with applicable standards, such as ANSI
Z136.1 and/or IEC 60825-1.
[0048] The trained and experienced officer shall determine and
confirm through testing that the MPE level is not exceeded with the
desired laser effect both in normal operation of the laser, and in
various failure modes such as improper input from the operator or
failure of a scanner. If a scanner fails, the maximum dwell time
may be exceeded, for example. To account for these possible
failures, an operator should present the scan protected laser with
worst-case control inputs such as static beams, low scan rate
beams, and high dwell time beams. Thus, in the pre-calibration
process, the officer ensures that the calibration of the scan fail
system will provide safe, sub-MPE output, in all cases of normal
operation or even during equipment failures and in all audience
areas.
[0049] The pre-calibration process is performed in the context of a
pre-determined threshold value. For example, one individual laser
projection system 100 may be calibrated for a distance of 30 feet.
At this distance, which represents the minimum audience separation
from the laser, the officer optimizes the various calibration
calculations by selecting the appropriate laser power from those
available in inventory, and adjusting the laser divergence. The
final adjustment is achieved, if necessary, by adjustment of the
minimum velocity and/or the maximum dwell time via the audience
scanning protection system. Any combination of these variables may
be used to safely calibrate the laser projection system 100.
[0050] While the laser projection system 100 can be calibrated at a
location separate from the venue, it is possible for the laser
projection system to be calibrated on-site, like traditional
systems. On-site calibration may be required by regulators in the
jurisdiction in which the system is installed, for example. In
these situations, a laser safety officer would calibrate the
machine to be safe at for the distance between the audience and the
point of installation.
[0051] A sample calculation performed by the officer, for on-site
or off-site calibration, is as follows, by way of example, for a 30
foot separation distance: [0052] Total source laser power: 600 mW
[0053] Wavelength: 400-700 nm (Tab. A.1 IEC60825-1, Ed. 3, 2007-03
applies) Table applies to exposure times from 5.times.10.sup.-6 S
to 10 Seconds [0054] Nearest Audience Location: >10 Meters
[0055] Beam Diameter at source: 3 mm minimum (*prior to lens)
[0056] Beam divergence: 10 mRad minimum [0057] Beam diameter at
closest audience location: 10 cm minimum [0058] Angular velocity
for scan protection device: 10 radians/second minimum [0059] Beam
Mode: Tophat or other non-ideal, non-gaussian profile (worst-case
calculation) [0060] Linear velocity of beam at closest location: 10
Rad/s.times.10 m=100 m/s=10,000 cm/s Since the beam is larger than
the eye aperture (100 mm >7 mm) the duration of ocular exposure
is the diameter of the beam divided by the linear speed. For a more
conservative approach, the officer can include additional
worst-case transit time for a nonideal tophat profile equal to 1/2
of the eye's diameter. This is a more conservative calculation than
a traditional full width at half maximum (FWHM) exposure. [0061]
Where eye diameter=7 mm=0.7 cm Beam size=10 cm Linear Speed=10,000
cm/second (0.35 cm+10 cm)/10,000 cm/second=1035 uS Exposure to eye
[0062] For retinal thermal limits, visible wavelengths 400-700 nm:
MPE=18 t.sup.0.75 J/m.sup.2 t=0.001035 Seconds Single pulse
energy=18.times.0.001035.sup.(0.75) J/M.sup.2=0.1039 J/m.sup.2
[0063] Converting to more familiar units: MPE=0.0139
J/m.sup.2/10,000 cm.sup.2/m.sup.2=10.386.times.10.sup.-6 J/cm.sup.2
[0064] Simplified worst-case exposure analysis (normal operation)
[0065] 600 mW.times.0.001039 seconds=621 uJ. [0066] Area of 10 cm
diameter spot=78.54 cm.sup.2 621 uJ/78.54 cm.sup.2=7.9068
uJ/cm.sup.2 (Top hat profile) So, MPE.sub.single pulse=10.386
uJ/cm.sup.2: and actual exposure=7.79068 uJ/cm.sup.2
[0067] This exposure is 76% of the MPE for a single pulse and is
acceptable. Using the data calculated above, the worst case
scenario of a scanner failure can be further analyzed. Note that
this is also a conservative calculation for the dwell limit
calibration which is set on the scan protection device. (minimum
dwell time plus failure reaction time calculated here)
Prior data: 600 mW emitted power 10 cm beam diameter=78.54 cm.sup.2
MPE.sub.single pulse=10.386 uJ/cm.sup.2: and actual
exposure=7.79068 uJ/cm.sup.2 (76% of permitted MPE)
Analysis:
[0068] Irradiance of beam at closest audience location: 600 mW
power/78.54 CM.sup.2=7.639 mW/cm.sup.2 Area of 7 mm aperture=0.385
cm.sup.2, so power to aperture=7.639 mW/cm.sup.2.times.0.385
cm.sup.2=2.94 mW
[0069] The scan protection system, or safety system 104, is
specified and tested to terminate output within 10 uS. When maximum
dwell time is 1 ms, or 1000 uS, the total time to terminate output
is 1010 uS. This is a conservative analysis demonstrating a static
beam exposure. In reality one scanning axis could remain moving,
and even a failed scanner may take 100-200 uS or more to come to a
stop. In alternative embodiment of the laser projection system 100,
the movement of the entire yoke assembly 106 provides additional
safety.
[0070] Static beam exposure as a worst case:
2.94 mW.times.0.00101 Seconds=2.94 uJ MPE for 1010 uS=18 t.sup.0.75
J/m.sup.2=18.times.0.00101.sup.0.75=0.102 J/m.sup.2=10.2
uJ/cm.sup.2 MPE energy through a 7 mm aperture: 10
uJ/cm.sup.2.times.0.385 cm.sup.2=3.85 uJ. In this case, the
exposure of 2.94 uJ is less than the MPE of 3.85 uJ. This exposure
is MPE via 7 mm aperture=3.85 uJ, while exposure via 7 mm
measurement aperture=2.94 uJ The exposure for a minimum dwell time
calibration and/or a scanner failure is demonstrated to be 76.4% of
the maximum permitted MPE.
[0071] After applying the adjustments to the system 100, the laser
safety officer, or other technician, verifies the calibration by
taking necessary measurements (static beam irradiance, minimum
velocity, and maximum dwell, for example) at the point of minimum
audience separation using a power meter and pulse measuring
equipment. In this manner, an officer can pre-calibrate audience
scanning failsafe systems prior to shipment.
[0072] A pre-calibration process has several advantages over the
current method of calibrating and testing the laser on sight. For
example, calibration of an audience scanning failsafe system
requires a base measurement of an unprotected static beam. This
means a full power beam from an unprotected system must be
presented in the live show setup environment for testing and
calibration of the system 100, requiring the stage and/or venue to
be cleared of all non-essential personnel. Pre-calibration
eliminates the need for this high powered beam to be introduced
into the live show environment. The use of naked, high power beams,
which are required for baseline irradiance measurements, are best
reserved for a controlled facility as opposed to live venues.
[0073] After pre-calibration is completed, a sticker or other form
of notification can be affixed to the laser projection system to
provide instructions for the installer. A sample warning sticker is
depicted in FIG. 11. In addition, a calibration verification
sticker can also be affixed to the laser projection system; a
sample calibration sticker is shown in FIG. 12. To prevent
tampering, the stickers or labels are provided with security
features, such as holographic overlays and foil backing, which
causes the sticker to be destroyed if removal is attempted. As a
result, the stickers and labels act as a type of anti-tampering
device 105.
[0074] The calibration sticker provides notice that the laser
projection system 100 is safe for a given distance. However, in one
embodiment, the systems 100 can also be audited on an annual basis
to ensure the emissions meet MPE requirements and any deviations
shall be recorded in a maintenance log for that device. In the
situation where devices 100 are sold or rented to other operators,
the devices can be returned to the manufacturer or receive a visit
from certified laser safety officer for annual calibration. Failure
to maintain calibration would preclude the device from further use
in commerce until such calibration is performed.
[0075] To prevent unauthorized access to the laser projection
system after it has been calibrated, tamper-proof hardware 105 is
provided. For example, the calibration interface 103 can be secured
behind a locked assess panel. Alternatively, the calibration may be
stored into a non-volatile memory, or by using fixed component
values in the controlling circuits such that only the manufacturer
or laser safety officer may change the calibration values. The
tamper-proof hardware 105 should be provided for any component of
the system capable of making adjustments and would include the
lenses and optical elements 108 as well.
[0076] Alternatively, the laser projection system 100 can be
matched to physical modifiers, such as lenses. For example, the
laser safety officer can create discrete safety pairs. That is, for
a calibrated system MPE might be reached at 30' with a power 2
lens. A different calibration would allow for MPE delivery at 25'
with a power 3 lens. It extends that the calibration for each
scenario for a given system follow the lens power. Accordingly, the
calibration for each distance may be incorporated into the lens via
an active electronic component and sensor integrated into the
projector 100. In this manner, the calibration at a given distance
may not be defeated by any user, offering an additional layer of
safety and redundancy. Such a system may also automatically display
the safe separation distance on a highly visible display so that
the laser safety officer, operator, staff, and inspectors have no
doubt as to the proper required separation.
[0077] Pre-calibration creates an inherently safer system. With
traditional techniques, a laser safety officer may feel compelled
to eliminate certain steps of the calibration process, assuming
there will be no problems. For example, a technician under pressure
from a fast-paced production that expects impossible installation
schedules might cut corners, thinking "I have done this a dozen
times, and it always measures perfectly." While this situation
might be rare, it still presents a risk should there be a
malfunction or if the system is used outside of safe specifications
for the show conditions such as being too close to the audience,
having excessive power levels, or using too low of a divergence of
the beam.
[0078] FIGS. 8-10 show the relative safety of the laser projection
system of the present invention, as compared to high-powered
systems, such as Class III/IV lasers. In FIG. 8, it is shown how
the transition from a safe show to a disastrous exposure of
.about.90,000% MPE is only protected with approximately 3 ft of
separation for a 6 ft tall audience member for a typical Class IV
terminated show. FIGS. 9-10 show the exposure level for a laser of
the system of the present invention, where exposure levels increase
gradually as distance decreases.
[0079] A mild penetration of the minimum separation distance
increases the exposure, but at a much slower rate. For example, if
an audience member crosses a security barrier, the effect of making
the transition to unsafe space is visible and known to both the
operator and the audience member. Given the gradual risk to
exposure, security personnel and the lighting operator would have
more warning time before the person reached significantly hazardous
space than a penetration of a class IV zone, which could be
instantaneous. Moreover, protected systems at a typical height when
rigged in a truss may be impossible to reach for violation of the
safety buffer. If the operator can insure that the safety distance
is maintained, than all other areas of audience performance, and
airspace, are automatically clear. The operator's area of
concentration is significantly reduced, improving the inherent
safety of the system.
[0080] Additional safety procedures can be incorporated into the
laser projection system to prevent excessive exposure despite
proper calibration by a laser safety officer. An external shutter
is triggered if the scanner power supply voltage and scanning
safety system voltage are not in range, a scanner failure is
detected, or the emergency stop is activated. Moreover, the laser
source can be blanked (i.e. pulled to ground) to dynamically
intervene if the scanner velocity or dwell time drop below a
pre-calibrated threshold or the projected image is too small,
indicating an insufficient velocity.
[0081] In addition, the laser scanner may be mounted into a moving
yoke assembly 106 with position and velocity measurements sampled
from the moving yoke. Such a yoke 106 may employ up to three axes
of rotation, but typically employs two axes of rotation. Position
and velocity are measured on each axis and processed by the safety
monitoring system. The resultant velocity vector is compared
against the calibrated minimum velocity (10 Radians per second, for
example) and dwell time (1.0 mS for example). Processing of the
additional velocity vectors is identical in procedure to the
methods employed by the traditional two axis system. Additional
axes, especially those offered by high inertia moving axes,
increase safety due to the increased decay time until zero stasis
is reached. Such high inertia movements have decay times ranging
from milliseconds to seconds and are magnitudes of order slower to
reach zero velocity than electromechanical scanners. Increase of
time to reach zero velocity increase the intrinsic safety of the
system since the system has a much longer time to react when an
unsafe condition or default are detected.
[0082] Moreover, the laser scanner may be mounted on a linear
trolley system with up to three additional dimensions of freedom,
but typically with only one or two dimensions. Position and
velocity measurements are sampled to determine linear velocity.
Such inputs are provided to the safety monitoring system. The
resultant velocity vector is compared against the calibrated
minimum velocity (10 Radians per second, by example) and dwell time
(1.0 mS by example). Processing of the additional velocity vectors
is identical in procedure to the methods employed by the
traditional two axis system.
[0083] As a result, the complete integrated system could contain up
the three axis of rotation, and three dimensions of linear
translation. Therefore a system could contain up to 8 velocity
inputs including the laser scanners. However, additional frames of
reference could be incorporated such as a truss with global
movement, or installation into a moving vehicle. A protected
audience scanning system, by example, is easily demonstrated to
decrease exposure when installed in a moving trolley system or
vehicle which may be found in a movie set environment. Precision
measurement of these additional movements allows for safer
exposures, and additional redundancies. Such freedom of movement
cannot be incorporated in traditional projection systems, which
must be safely calibrated for a static, non-moving
installation.
[0084] While the safety of the laser projection system 100 has thus
far been described in terms of a pre-determined distance of
separation between the laser source and the audience, safety can be
achieved by purposefully degrading the inherent qualities of the
laser beam. As the divergence of a laser is increased, through the
use of optics and the geometric design of the optical system, the
laser beams makes a transition to becoming less laser-like.
[0085] In typical systems, the builder endeavors to perfect the
properties of the laser, not purposefully degrade them. Those
properties include the size of the apparent source and the
divergence, polarization, and coherence of the beam. An ideal laser
has an apparent source that is a single point, or point source. As
a point source, an ideal laser has near zero divergence. This
property, however, is limited by the physical properties of the
source such as the beam profile, the m 2, and the diffraction limit
for the source's wavelength. A typical entertainment laser might
have a divergence of 0.5-2 mRad, which is quite small and
non-diverging. With such a small divergence, the aesthetic
qualities of the light are maintained over long distances. Typical
lasers are further defined by a coherence of the light source, as
well as perfectly controlled polarization.
[0086] From the viewpoint of safety, an ideal laser is the most
dangerous to direct ocular viewing. Such an ideal source focuses
almost perfectly on the retina of the observer due to the lenses of
the eye, creating a power density on the retina that is many times
the density of the incident beam to the occulus. Such an exposure
may cause immediate and permanent damage to the retina.
[0087] An alternative embodiment of the present invention increases
safety by intentionally disturbing the ideal qualities of the laser
light source. This approach is counterintuitive to the conventional
design of lasers, but the result is that the laser can be made to
be safe for direct viewing. To accomplish this task, the angular
subtense of the laser source 100 is increased, which has the effect
of transitioning the laser from a point source to an extended
source.
[0088] An extended source does not resolve or focus to a
diffraction limited dot on the retina as is seen with a traditional
laser's point source structure. Instead, a laser that is
constructed to perform as an extended source simply images on the
retina. That is, the occulus is presented with a more familiar type
of light such is found in the natural world, and this light source
projects a pattern onto the retina much like viewing a distant
object. This is a broad departure from the behavior of a
traditional laser which has a destructive focusing ability and
destroys the retinal tissues.
[0089] The calculation of the angular subtense is normally
performed as a safety measurement to determine safe areas of
viewing for traditional lasers. For example, a doctor performing
surgery may see some laser light from the side of his instrument
despite the working beam being directed towards the patient and
away from the doctor. In this example, it is not intended for the
doctor to view a direct beam. While the exposure to the doctor is
much lower than the exposure to the patient, the doctor's exposure
is unwanted collateral exposure and is not intended.
[0090] In a similar manner, a laser source for direct viewing can
be made safe by having it function as an extended source, or one
where the maximum angular subtense exceeds 100 milliradians. In
other words, the divergence of the laser beam is increased to
degrade its point source qualities.
[0091] In the context of laser light shows, direct exposure to
laser beams allows audience members to experience beautiful and
compelling lighting effects. These effects may be presented with
traditional laser beams by carefully controlling the properties of
the beam to insure that MPE levels are not exceeded. This is
achieved, for example, by limiting total power and limiting the
time of exposure. These restrictions are required due to the
focusing effects of a traditional laser on the retina. The retina
requires adequate time for cooling via conduction of heat to
surrounding tissue and the cooling effects of active blood flow in
the retina.
[0092] In an alternative embodiment of the present invention, the
laser beam emanating from the system 100 can have an angular
subtense greater than 100 mRad. With a subtense greater than 100
mRad, the dangerous focusing effects are eliminated and the light
may be treated as a traditional light source, or extended source. A
laser in this regime of operation presents a large effective image
to the retina that is well within the retina's ability to cool
without an exposure time limitation or the risk of injury, removing
the exposure limitations that are imposed on conventional point
source lasers used for entertainment purposes. Thus, the laser
projection system 100 of the invention does not require a
limitation on exposure time or power level. More importantly, laser
projection system does not require any specialized training or
certification for operation from the relevant regulators, such as
the FDA in the United States, the TUV in Germany, or Health 86
Safety in the UK.
[0093] When a laser has an angular subtense that is less than 100
mRad, it is no longer considered an extended source. However, the
transition from a point source laser to an extended source laser is
not an abrupt change. It is possible to allow a laser with an
audience scanning safety system 104 to increase delivered power
while maintaining safe MPE levels by calculating the relationship
between increased angular subtense and allowable power
increase.
[0094] The allowable increase in laser exposure is calculated by
multiplying a coefficient `c` times the standard MPE calculation:
MPE=18 ct.sup.0.75 J/m.sup.2. For angular subtense less than 1.5
mRad, the coefficient is equal to 1 and thus there is no change to
the MPE level. For angular subtense greater than 1.5 mRad or less
than 100 mRad, the coefficient is simply the ratio of measured
angular subtense divided by 1.5 mRad. For example, the MPE of a
projector with an angular subtense of 15 mRad is increased by a
factor of ten (15 mRad/1.5 mRad=10). A laser projection system 100
between 1.5 mRad and 100 mRad would be regulated by worldwide
authorities having jurisdiction, but the brightness can be
increased, which improves the level of enjoyment experienced by the
audience.
[0095] While the disclosure has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope of the
embodiments presented. Thus, it is intended that the present
disclosure cover the modifications and variations of this
disclosure provided they come within the scope of the appended
claims and their equivalents.
* * * * *