I'm about to start, in my "spare time" on a laser gun type game (PIC
based of course) using visible red laser pointers. This is intended
to be similar or better in capability to commercial in-building based
operations run here - presumably they exist in profusion in the USA
and elsewhere. My daughter can't wait! I intend to send data on the
gun beams (so you know who has hit you) with storage of results for
after game analysis. At a later stage I might possibly attempt some
form of more general back direction communications.
.
Has anyone else here done anything like this?
Would anyone else possibly be interested in doing some of the work?
(This offer/invitation made "without prejudice" to what I decide to
do).
I don't anticipate the speed of development to be high (6 months?)
but it should happen.
.
To some extent I intend to define the requirement as the project
progresses - this is a game after all (both the product and the
development), as I don't really have a good idea of what it takes to
make the game a success.
(eg Consider some or all of: multiple wearer-targets, pulse or swept
beam shooting, programmable "laser reservoir" charge and discharge
rates, individual and team playing, data download via laser beam,
parameter upload via targets, voice on beam ["I have you now"], and
much more???)
.
I intend to do initial playing in PICBASIC (quick & simple, dirty,
works) but will probably end up in assembler and/or C as complexity
increases. (eg PICBASIC is not well suited to multi-taking of any
sort which may well become a requirement.).
.
Starting point:
- Get simple unmodulated transfer working.
- Establish critical data transfer parameters
Initial playing with very simple circuitry shows pointer type lasers
(3 milliwatt?) have enough beam intensity for typical playing
distances. Beams MAY need to be spread to decrease accuracy
requirements. Commercial games are played in dim conditions -
daylight may be a challenge and would make visual targeting hard (but
real sights could be used in daylight). Data at 300 baud intended for
starters - may be too slow due to time-held-on-target limitations.
Carrier modulation (30 kHz ish) may assist valid beam discrimination
in high ambient light).
Well, I'm not sure whether or not they are exactly safe with lasers, but I
can say that such products have been successfully made using high power IR
leds. When I was about 6 years old ( I am only 18 now), my parents got me a
"photon tag" (or some such name) game which consisted of two "pistols" (IR
led transmitters) and two wearable targets (hexagonal boxes with a piezo
alarm and IR phototrans). I seem to remember these working well up to about
30-50 feet away. They were alot of fun!
>Hi Russell,
>
>I am someone who believes that laser pointers are not safe, particularly
>in the hands of children.
>
>Lasers should never be pointed at people, unless for medical reasons or
>you are preparing to kill them for real.
>
>Other than that, I think it's a great idea :-)
>
>Cheers,
>Bob
>
Russell McMahon wrote:
>
> I'm about to start, in my "spare time" on a laser gun type game (PIC
> based of course) using visible red laser pointers.
The *big* problem here is beam spread, or lack of it. The only real
way to simulate a genuine wapon "hit" would be to have the *whole* of
the player wearing a laser-sensitive costume (fibre optics?).
Otherwise, you have a problem where a player can be hit almost anywhere
*but* the target, and that's a large area, and no hit is registered.
The tendency is for this to be emulated by using a wide beam. The
problem here is that this analogue is now badly range-sensitive; it is
too easy to hit a distant target, impossible to hit at close range
unless aiming at the (limited) target area. A beam with progressive
intensity reduction further off-centre is required. Conclusion: forget
about lasers - the (cheaper at least) commercial games never even
considered them. (What you may *actually* do is to use a visible laser
for aim and theatrical effect, but the *actual* weapon is a loosely-
focussed IR diode.)
Good point - safety is a real issue.
These pointers are rated at the "maximum legal limit" (in out part of
the world) for such devices - I think 3 milliwatt optical output. One
problem with legal limits is that they are generally based in
ignorance or vested interest and tend to get tighter over the years
as knowledge grows {{"you mean that little thing can REALLY cause
cataracts???"}}. Certainly you can look into the beam at close
proximity for short periods of time without *apparent* damage of any
sort but this is not something I would encourage. Looking at a 100
watt lightbulb up close is less blinding but much more obviously
damaging. The small diameter well collimated beams make the
concentration by the eye lense an issue. I may yet be decollimating
the beams somewhat to improve aimability.
.
I will be doing some more reading up on the various aspects involved
before these get into the hands of "children" (see below).
.
In a typical laser tag game the amount of accidental eye contact made
by the beams is minimal - I have played a few such games recently and
don't recall being struck in the eye directly by a beam on any
occasions. Pointers in the hands of children (either sex up to 15
years old and males <=d110 years old) are liable to be shone in eyes
intentionally. In a laser tag game this is extremely unlikely (but
this doesn't make it any safer per se).
.
Pointing lasers at people to "kill them for real" is not where I'm at
:-).
I worked at the Australian version of the indoor game called "Lazerzone"
for six months, they used a laser for effect, it was activated with the
trigger, but only for 250msec. this was long enough to make it visible but
not to do any damage.
In my time working there, I played many games (to test the guns I had
just fixed :>) and didn't once get a laser in the eye.
These guns had an 8051 variant as the heart, used IR to communicate at
around 37KHz and had sensors on the gun and on the shoulders. this meant
that the laser could be tightly focused and the IR a wider beam.
They passed lots of info in the shot, and each gun recorded who hit them,
then at the end of the game you walked through an "energiser" which was an
IR rs232 link back to a 386. it then printed out the game results.
I fiddled aroundwith making a system of my own last uni holidays, but came
stuck with the IR recieving. I could directly plug two guns in and had
them shooting each other etc... but when I tried it with IR, there was so
much interference from the clock, which was divided down to 38KHz for
modulation and even lower to drive the 3 7segment displays that I couldn't
decypher the signal through the noise. I think that the baud rate I
was using was too high as well. When Uni started back I ran out of time...
(doing more than a full load and getting married in Dec)
I would love know how you go with your system. If anyone else has any
ideas on how to clean up the IR I would appreciate your comments. I don't
have any money to buy expensive parts, so any solution must be cheap.
Andrew
|
| "For God so loved the world that
----+---- he gave his only son, that who
| so ever believes in him will not
| perish but have eternal life"
| John 3:16
|
|
the so called laser gun and target game does NOT use a laser, but uses a IR
LED and sensor. My son was playing with the neighborhood kids the other
nighta and I was able to shoot him with the TV remote. BANG BANG.
I hate to mention the possibly obvious, but did you consider using an IR
filter over your transceiver? That's what many of the targets use to keep
the noise out and only let in the right wavelength.
Ken
>I would love know how you go with your system. If anyone else has any
>ideas on how to clean up the IR I would appreciate your comments. I don't
>have any money to buy expensive parts, so any solution must be cheap.
It's safe as long as the beam is not parallel all the way,
the eye is acting like a lense thus when receiving a "perfect"
parallel beam in a 90 degree angle, it focusses.
Laser pointer are indeed dangerous and can cause eye damage, little
and unnoticable if it has a fast contact with the eye, but still...
When a beam is spreaded, even at a minimal value, it's less likely
to cause damage because it won't focus on one single point, although
you must be careful, if you stare at a 10W bulb light for example,
it won't damage your eye, but if you stare at a 500W source, well
good luck :). Same logic applies for laser light.
Anyways if you are making such a toy, you should really check
that issue, I've played with lasers a lot, and you don't want
your daughter to have "black" spots (well more than natural blind
spots). So be sure to defocus the beam (easy test is to point
the laser on a wall at 2M distance and the spot should be bigger
than it's source (straightfoward). You lose a bit of range,
but not your eyes, Good tradeoff :).
>
> Hi Russell,
>
> I am someone who believes that laser pointers are not safe, particularly
> in the hands of children.
>
> Lasers should never be pointed at people, unless for medical reasons or
> you are preparing to kill them for real.
>
> Other than that, I think it's a great idea :-)
>
> Cheers,
> Bob
> Has anyone else here done anything like this?
> Would anyone else possibly be interested in doing some of the work?
> (This offer/invitation made "without prejudice" to what I decide to
> do).
I am VERY interested, this kind of thing was the original reason I started
with PICs (2 years ago,
done much in the meantime, but little progress on the laser game...)
FYI, there are roughly two kinds of laser games:
- indoor / arena, often with a radio link from each player's harness to a
central computer
- outdoor with simple equipment (can be bought in larger toy shops)
BOTH kinds use IR light (like your TV remote control) to transfer data.
The indoor type ADDITIONALLy uses a visible laser beam to enhance the game
effect.
Some kind of mist is used to make the beam visible.
There is MUCH info on the web about outdoor equipment (especially using a
16c841)
For a start, look for "Dave Bodger".
> It's safe as long as the beam is not parallel all the way,
> the eye is acting like a lense thus when receiving a "perfect"
> parallel beam in a 90 degree angle, it focusses.
Don't be so sure. FYI I wear glasses, and when I do NOT wear them I am
susceptible for eye damage from semiconductor IR lasers that are NOT
focussed. Incidentally the divergence of these coincides with my
short-sightedness...
Actually NO laser beam above a set power level is safe in ANY conditions
for looking into by most people, even un-focussed.
>Now, the safety issue... Well, that's easy. Don't use the visible
>portion
>of the beam spectrum. Most HeNe lasers operate at 628nm wavelength -
>red.
>However, you can get laser diodes and small gas lasers which operate
>at
>+700nm, extending well into the IR. Use one of these, and an IR
>filter as
>the last stage in your optics to filter out the harmful radiation.
>You
>could look at one of these all day and it wouldn't hurt you.
NO! A thousand times NO! Don't believe this self-proclaimed "expert."
A moderately powerful 700-900 nm laser can cause permanent eye damage in
a hurry. In fact, the legal limit on the "safe" exposure of the public
to these laser wavelengths is lower than that for visible lasers.
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>
> On Tue, 22 Sep 1998 10:47:35 -0500 Kenneth Adamson <.....kenKILLspam.....vrlemmings.com>
> writes:
> > I believe
> >myself to
> >be an expert in the field of lasers.
>
> [...]
>
> >Now, the safety issue... Well, that's easy. Don't use the visible
> >portion
> >of the beam spectrum. Most HeNe lasers operate at 628nm wavelength -
> >red.
> >However, you can get laser diodes and small gas lasers which operate
> >at
> >+700nm, extending well into the IR. Use one of these, and an IR
> >filter as
> >the last stage in your optics to filter out the harmful radiation.
> >You
> >could look at one of these all day and it wouldn't hurt you.
>
> NO! A thousand times NO! Don't believe this self-proclaimed "expert."
> A moderately powerful 700-900 nm laser can cause permanent eye damage in
> a hurry. In fact, the legal limit on the "safe" exposure of the public
> to these laser wavelengths is lower than that for visible lasers.
>
I'd just like to add to Mike's reply immediatly above,
Kenneth's assumption that an I.R. filter would "filter out the harmful
radiation" is wrong. Ever heard of an infrared heat lamp Kenneth ?
If the radiated form of light (whatever the frequency), stops without
reflection then the light energy is converted to heat energy. Making
assumptions otherwise is asking for the full laser output to be utilised
in COOKING your retina.
Graham Daniel.
>NO! A thousand times NO! Don't believe this self-proclaimed "expert."
>A moderately powerful 700-900 nm laser can cause permanent eye damage in
>a hurry. In fact, the legal limit on the "safe" exposure of the public
>to these laser wavelengths is lower than that for visible lasers.
Yes! A thousand times YES! I have reasons to say what I say - but I
perhaps didn't elaborate enough on how to do this, that is, create a "safe"
laser out of an unsafe one.
Requirements:
Infrared laser diode - 800nm and up
Beam expander - to calculate the correct expansion power, use the formula
below:
Bi = B + oL(.3048)
where:
Bi = Beam Diamter (mm) at L
L = Distance from module
B = Original Beam Diamter x Expansion Power
o = Decrease in Beam divergence (Beam Divergence (mrad) / Expander Power)
IR Filter - more below on selection.
Spatial filter (this is a special device, I'll explain below)
Calculate the filter objective focal length using the formula below:
B = (1.27 x W x f) / D
where:
B = Beam Diamter
W = Wavelength
f = focal length
D = Input Beam Diamter
Pinhole Dia = 1.5 x B
Set your equations equal to each other, and solve accordingly.
Laser diodes, contrary to popular belief do *not* have a pure emission
spectrum. They output a range of wavelengths, with a peak at the
documented wavelength, and harmonic multiples above and below that number.
The closer to the documented wavelength you get, the more powerful the
emission line.
A spatial filter will create a gaussian emission spectrum, centered on the
desired wavelength (a rating of the spatial filter). You then pass the
filtered beam through a pinhole to "trim" the edges a bit and focus the
beam slightly.
Selecting the correct IR filter is then extrememly important, because you
have to use one which will pass a frequency emitted by the laser as a
harmonic "overtone". I leave this to you to figure out, but let's say that
it involves either knowing, or calculating the input voltage phase
frequency, and knowing something about how and why the diode substrate does
what it does (n and p junction interaction, etc.).
Now, for practical reasons - like cost - this is probably not feasible in a
toy :)
That, however, does not diminish the correctness of what I've postulated.
My suggestion - use a plain-ole red LED for effect, and a modulated IR
emitter to "kill" :)
This is not a "flame" message, but just a friendly correction
and warning.
The post below seems to imply that if the beam is invisible
then it is safe.
The fact that you cannot *see* the laser beam does not mean
that the radiated energy is not being absorbed by the eye.
Two examples from opposite ends of the spectrum:
(1) You can't see x-rays, but they will surely harm your eye and other
body parts.
(2) You can't see infra red or the even lower frequency microwaves,
but they can surely affect your eyes.
Working with infra-red laser diodes is every bit as dangerous as working
with visible laser diodes. The fact that you cannot actually *see* the
beam makes working with these devices even **more** dangerous than working
with visible laser diodes, as you are not even aware that the damage
is being done.
> > I believe
> >myself to
> >be an expert in the field of lasers.
>
> [...]
>
> >Now, the safety issue... Well, that's easy. Don't use the visible
> >portion
> >of the beam spectrum. Most HeNe lasers operate at 628nm wavelength -
> >red.
> >However, you can get laser diodes and small gas lasers which operate
> >at
> >+700nm, extending well into the IR. Use one of these, and an IR
> >filter as
> >the last stage in your optics to filter out the harmful radiation.
> >You
> >could look at one of these all day and it wouldn't hurt you.
>
Peter L. Peres wrote:
>
> On Tue, 22 Sep 1998, Eric Slight wrote:
>
> > It's safe as long as the beam is not parallel all the way,
> > the eye is acting like a lense thus when receiving a "perfect"
> > parallel beam in a 90 degree angle, it focusses.
>
> Don't be so sure. FYI I wear glasses, and when I do NOT wear them I am
> susceptible for eye damage from semiconductor IR lasers that are NOT
> focussed. Incidentally the divergence of these coincides with my
> short-sightedness...
>
Like I Said before, high-powered source are like normal high-intensity
lights
it CAN damage eye. Don't tell me you'll get eye damage from a 5mw Diode
that
sends diffuse or unfocussed beam, please. :) it will *DO* damage if for
example
it sends collimated "emissions" and your eye intercepts it, but if it's
out of
focus, yes, it might be laser, but it'll "act" like a normal spotlight
exept you don't want to look at it just for no reason.
The point is: for a laser tag-type game, the security issue is 1. don't
look
straight in the gun when activating it, and defocus the beam. And since
you can't predict every action and scenario that would probably make you
look into the gun when the other fires, I would suggest an additionnal
such as glass with a special filter or gelatine coated to filter some
of the laser light. Example, glass with a greenish coating would do
the trick. It doesn't have to be overkill (like buying laser-specific
protection glasses), because again, if the spread angle is big enough
it won't damage the eye at low power (~3mW @ 5-10 inch diameter @ 30M)
the glasses could be simple greenish things like I've mentionned,
since it's low power and it'll absorb let's say 50% of the energy, the
remaining will be either diffused or rebounced so leaving a minimal
energy trace to the eyes).
I've worked with lasers for 4 years in a holographic lab, never wore
glasses
(you need to see the laser when you are doing holography anyways so
glasses
would be kinda useless) with different sources and power. Of course if
I would
have received a "pure" beam in the eye straight from the laser source,
or a
reflection on a mirror of the "pure" beam, issh.. I would have a lot of
problems. but looking at diffused laser light and long-term exposure
didn't
affect me. (HeNe ranging from 10mW to 70mW).
Let's not make this an OT thread, lasers are dangerous, yes, they can
cause damage, YES, there's a tradeoff between Security and performance,
YES.
but there are ways to secure the thing like many people mentionned here,
and
besides, laser tags wouldn't be sold todays, and those laser quest games
would be banned big time if they were THAT unsecure. So ripping that
design
and adding glasses *IS* secure if well calculated.
> Actually NO laser beam above a set power level is safe in ANY conditions
> for looking into by most people, even un-focussed.
>
Again, a 70mW source even unfocused would probably do big damage if all
or
most of the energy would go into your eye, but I don't think that kind
of power is needed for a laser gun toy, 2-5mw diode in the 635nm should
be enough. So *again* if the design is secure, the last issue is to
tell
the kids "don't look in the hole when triggering", hmmm then again you
probably wouldn't want to tell them that because they'd probably do this
first :) but seriously, receiving a 3mw unfocussed beam (like 5-10
inches
diameter at 30M divergence) for
a fraction of a second (at the speed of electronics nowadays you don't
need
this to be 1s), is not more harmful than a flash. Well I'd be blind big
time today if it was because I've put my eyes in more risk than that.
Again...add the glasses for extra security and you are all set.
part 0 2596 bytes A real .38 was modified with an IR diode (not laser)
and lens. The hammer fall triggered a pulse of IR
light courtesy of a minature micophone. A TV
camera, with its IR cut filter removed, was mounted
on the projector and looked at the screen. The gun's
IR spot was much brighter than any other light level
on the screen and easy to pick up and freeze the
Horizontal and Vertical coordinates for later playback.
During playback, the spot was represented by a full
screen crosshair, and the action was frozen while
the instructor critiqued the performance..
I had trouble finding a good diode to project an nice
clean spot until one day, just by accident, I brought
in one of those point and shoot autofocus cameras,
the kind that go for about $130, and saw the beautiful
spot it made on the wall, observing with a TV camera.
This was only from its own built-in lens. It was a metal
can TO-46 with a spherical lens crimped on top. It should
be about right divergence for the laser tag game you mention.
I decided to remove the lens from the component and
use a longer lens to make the spot very compact in the .38,
but I needed more precision and the gun barrel gave me the room
I needed for a 3" focus lens, resulting in a spot only
an inch in diameter at 12 feet.
The diode from these cameras is very special. The
active element looks like a black dot, and
the emission is off the front surface only. On the
other hand with virtually all low cost IR diodes, the
structure is a tiny chip at the bottom of a polished
spherical depression, acting as a mirror. The light
come out the sides of the chip, is reflected forward
by the sides of the pit, and is further focused by
the molded plastic lens. The uniformitiy and focus
are poor, and unsuitable for long distance projection.
Fine for controlling the TV channel, however.
If you can get your hands on the IR diode from an
autofocus camera, you have the great beginnings
for a laser tag gun. We had to get all ours from
camera shops out of dead cameras, since no
camera manufacturer would reveal his source.
By the way, I would be interested in your project.
I'm about to start, in my "spare time" on a laser gun type game (PIC
based of course) using visible red laser pointers.[snip]
.
Has anyone else here done anything like this?
Would anyone else possibly be interested in doing some of the work?
>This is not a "flame" message, but just a friendly correction
>and warning.
>
>The post below seems to imply that if the beam is invisible
>then it is safe.
>
>The fact that you cannot *see* the laser beam does not mean
>that the radiated energy is not being absorbed by the eye.
>
>Two examples from opposite ends of the spectrum:
>(1) You can't see x-rays, but they will surely harm your eye and other
>body parts.
>(2) You can't see infra red or the even lower frequency microwaves,
>but they can surely affect your eyes.
>
>Working with infra-red laser diodes is every bit as dangerous as working
>with visible laser diodes. The fact that you cannot actually *see* the
>beam makes working with these devices even **more** dangerous than working
>with visible laser diodes, as you are not even aware that the damage
>is being done.
>
>Hope this helps.
>Fr. Tom McGahee
>
cornell.edu Phone(USA): (607) 253-0315 ICQ #: 3329174
