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Blackcrow
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 Posted - 2004/09/07 : 00:29:09
Can someone here do a www.howstuffworks.com on rave lasers for me please.
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silver
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 Posted - 2004/09/07 : 05:23:08
Well I tell you how a laser works because I have build two but that how stuff works is a for dummy's guide and that would take me too long...
If you have any questions I can answer them.
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Shade0
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Posted - 2004/09/07 : 08:53:01
yeah, thats quite a specific question you got there crow.. Youd probabally be better checking google for some plans or something.
Chris.SHADE
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Blackcrow
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Posted - 2004/09/07 : 13:26:37
Specificialy a Rave laser's i'm after guys i already know how a standard laser works.
And i've already tryed looking for a rave laser on google and i found nothing.
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bulby_g
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Posted - 2004/09/07 : 13:49:52
Don't they work in a similar way as a normal laser and just reflect the beam using a system of moving mirrors with patterns controlled by a computer. The flat beams etc are created by the beam moving so fast that it creates the illusion of a fixed tunel, flat beam or whatever.
This is pretty much just a guess though, no doubt silver or someone will correct me.
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Edited by - bulby_g on 2004/09/07 14:06:47 |
Blackcrow
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Posted - 2004/09/07 : 16:40:48
I have heard that rave lasers have no moving parts, or at least thats how some are designed.
I think they may work by pieces of glass
that are only transparant when an electrical curent is applyed,
thats only a gues tho.
With a few "beam splitters"
I dont know personaly
Also would'nt the motor of a moving mirror burn out.
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Edited by - Blackcrow on 2004/09/07 16:41:54 |
bulby_g
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Posted - 2004/09/07 : 16:53:45
I have a couple of really cheap s**t lasers that have moving mirrors in them I dont know what controls them though and i'm not about to pull them apart to find out. I dont know if this is true of the huge lasers used in big events though as mine are just £500 crappy things.
If the mirrors had motors they would burn out yes but this happens in other things and it doesn't stop them using them. I was speaking to Silver about lasers before and he said they were high maintenance so maybe they do have them and they do need replacing. Your theory seems very feasible though.
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Edited by - bulby_g on 2004/09/07 16:58:10 |
silver
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Posted - 2004/09/08 : 06:43:40
The most important part of laser projection system are the galvos, more commonly called scanners. Graphics, animations, abstracts and dynamic beam effects are generated by X-Y scanning of the laser beam using galvanometer scanners.
High speed galvanometers with various mirror sizes
The galvanometer (often abbreviated to galvo) is a current-sensitive device that operates in a similar manner to an analogue meter. In an analogue meter, a small coil of wire is wound around a lightweight aluminium bobbin that is suspended in the gap of a permanent magnetic field by means of pivots. The coil has a thin needle attached which extends over an indicating face that is the part of the meter you see.
When electrical energy is applied to the coil, it develops a magnetic field that will act against the field in the gap causing the coil to move the indicating needle proportionally to the current applied. Some meters are designed to be at rest at one end of the scale (such as analogue VU meters), while others are at rest in the centre of the scale (an analogue FM tuning indicator for example).
The first type of meter is a unipolar device as it reacts only to an increase in the current applied; while the second type of meter is a bipolar device as it reacts not only to the current applied, but also the polarity of the current. When the signal is negative, the indicating needle moves in one direction away from its central position: when the signal is positive, it moves in the opposite direction away from its central position.
Unfortunately meter movements are too small, to slow, and to delicate to allow us to attach a mirror and control laser beam deflection. We must use a more rugged type of device, a scanning type galvanometer. Galvos can be thought of as very high speed, current sensitive, limited rotation electrical motors. The amount of rotation (within the rotational limits of the galvo) is determined by the amount of current applied; with the direction of the limited rotation controlled by the polarity of the current applied. Galvos (scanners) are a current-sensitive bipolar device that are at rest in the centre of their limited rotation.
Usage Note: The words galvo or galvanometer refers to the basic galvanometer itself, without an attached mirror. Scanner refers to a galvanometer that has a mirror attached to it such that it can deflect a laser beam by applying appropriate control signals.
The type of galvos used in laser scanning systems typically use a moving magnet or soft iron rotor. Since the shaft has to reciprocate (move back and forth) many thousands of times per second, it would be very difficult to build a rugged device that used a moving coil due to the flexing of the wires that would be needed to supply the current to the coil. Laser scanners are build "inside out" from the typical meter movement described above; the coils are wound on the outside pole pieces (armature), and a magnetic or soft iron rotor, mounted in small precision bearings and suspended in the gaps of the pole pieces, moves the shaft with the mirror. The shaft has a spring or torsion bar to return the rotor to the central at-rest position when no current is applied.
Cross section of a typical galvo
The two permanent magnets crate a strong flux in the gaps of the central pole pieces of the armature. The rotor moves - moving the shaft with attached mirror - in response to variations in this magnetic flux caused by current applied to the drive coils.
Photo of the Cambridge Technology CT6800 scanners in an orthogonal mount which is attached to a heatsink. A line has been drawn in to show the path the laser beam takes through the X-Y scanners.
The laser beam first encounters the X (horizontal) scanner. This deflects the beam at right angles to it's line of travel and upwards onto the Y mirror. If the X scanner were fed a sine wave, the movement of the mirror would draw a line on the Y (vertical) mirror placed above the X mirror. The Y mirror takes the line drawn by the X mirror and moves it vertically. If the Y scanner were fed with the same sine wave as the X scanner, the projected image would be a line at a 45 degree angle. If the two sine waves were out of phase, a circle would be drawn.
Using an X-Y scanning system fed from analogue oscillator circuits, the position of the beam can be controlled so as to allow for the projection of complex abstracts. By digitizing and storing images in a computer, complex graphics and animations can be projected.
Blanking
In addition to the scanners, a separate device is used for blanking -- rapid on/off control of the laser beam. In an un-blanked system, all letters in a word (or all parts of an image) drawn by the laser are joined together like cursive script. In a blanked system, the letters are individual (not connected) like printing. In actual fact the letters are still joined by a line however the laser is turned off as it jumps between segments by the blanking device so that the join line is not visible.
The word "laser": without blanking at the top - note the join lines between and within the letters. The bottom image is blanked to eliminate the join lines.
The most common form of blanking for many years, was to send the beam through a third scanner which deflected it to a pair of small mirrors set at right angles to one another (a corner reflector). The corner reflector sent the beam back to the scanner and from there it was deflected into the X-Y scan pair. This arrangement formed an optical switch as any movement of the scanner caused misalignment of the beam through the corner reflector, turning the beam off. This method is still used in some high power laser projectors as there is a limitation to the amount of power a PCAOM cell can handle, and the corner reflector blanking system has little optical loss.
Most newer laser projectors, especially full colour systems, use the PCAOM for blanking as well as colour control. Since the PCAOM can control the brightness of all the laser lines at MHz speeds, it is trivial for it to extinguish the beam for the short periods of time required to blank unwanted sections of the image. Even newer YAG lasers have blanking built into the laser head itself, this can either be digital or analogue blanking (analogue gives you fading effects - while digital is laser on or laser off).
Those are the only moving parts in the laser system... they cost about 2000 dollars... the mirrors move at 64,000 times a second!
The mirrors are also special highly reflective mirrors - they also cost alot of money.
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bulby_g
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Posted - 2004/09/08 : 14:22:37
There you have it then, don't know how the ones I have work cuz they cost less than that for the whole unit but they are rubbish, there not very bright you need smoke/fog to make them even worth using and they only display a few set patterns.
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silver
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Posted - 2004/09/09 : 05:13:40
^^ yeah they are crappy.... I can get you lasers upto 40 watts, you can see them in the daylight without problems...
For clubs yeah 1 watt is sweet, don't really need smoke and you can see them with the club lights on as well.
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bulby_g
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Posted - 2004/09/09 : 11:54:30
^^^^Thats why we need a decent one :o)^^^^
they make a good effect in a tiny little venue but there still absolutely rubbish. You can see the beam without smoke but not to a decent clear level and they are ok with other lights on as well but..... there still rubbish, I dont think it helps that there red either.
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Edited by - bulby_g on 2004/09/09 12:09:01 |
silver
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Posted - 2004/09/09 : 12:10:59
Red lasers and generally poor quaility brightness wise... white, blue and green are better and brighten up somewhat more under UV lights.
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bulby_g
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Posted - 2004/09/09 : 12:56:38
Yeah its a shame beacause it is a nice colour but a bit of smoke/fog does bring it out quite nicely.
Thinking about it all the big party's in the UK i've been to have only ever used green lasers, bit of variety would be nice i'd love to see some blue.
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Edited by - bulby_g on 2004/09/09 13:07:14 |
silver
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Posted - 2004/09/09 : 13:23:27
A white laser via crystal can produce all the colors of the rainbow :)
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bulby_g
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Posted - 2004/09/09 : 13:39:40
Could it produce muliple colours at the same time?
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Edited by - bulby_g on 2004/09/09 13:40:34 |
silver
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Posted - 2004/09/09 : 14:35:51
Yep... the laser beam splitter can mix it all together to produce 16 million colors... and with blanking the mirrors can move so fast it looks like the laser is producing several beams of different laser colors...
If a laser has multiple heads about 6-7 mirrors on it then that laser is generally a cheap laser... The better lasers only have 1 point to project the laser and move so fast that to the normal eye it's all okay.
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