Homemade Scanning Laser Color Projector/TV

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SUMMARY

This discussion details a homemade scanning laser color projector that utilizes two mirrors to deflect a laser beam for image projection on a rectangular screen. The project boasts a total cost of under $10 in mass production, low power consumption of approximately 4W, and the ability to project images on any screen without the need for lenses. The fast axis mirror operates at a maximum speed of 25 KHz, allowing for 50,000 lines scanned per second, while the system is designed to work with conventional video signals at a resonant frequency of 15,625 Hz.

PREREQUISITES
  • Understanding of laser modulation techniques
  • Familiarity with mirror scanning mechanisms
  • Knowledge of video signal processing
  • Basic principles of optics and color mixing
NEXT STEPS
  • Research laser modulation methods for color projection
  • Explore designs for resonant and non-resonant scanning systems
  • Investigate the use of piezoelectric actuators in mirror control
  • Learn about the integration of multiple color lasers for image synthesis
USEFUL FOR

This discussion is beneficial for hobbyists, engineers, and developers interested in low-cost laser projection technology, as well as those exploring innovative methods for image scanning and display systems.

kuntman
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In this project, by means of two mirrors (which can be tilted about two perpendicular axis) we deflect the laser beam so as to scan a rectangular screen and modulate the laser source to obtain a colored image on the screen. We don’t make use of sophisticated devices such as MEMS micromirror and acousto-optical-modulators.

Advantages of our technique are:
- Total cost will not exceed 10 USD in mass production. (Mechanical part costs only few dollars)
- Low power consumption (Approx. 4 W.)
- Pictures can be performed on any screen
- No lenses are needed for focusing
- Scanning had can be made as small as a cigarette box.

Max. speed of the fast axis mirror is 25 KHz. That corresponds to 50000 back and fro lines per second.
In order to make use of the conventional video signal, the resonant frequency of the present scanner is tuned to 15625Hz.
Therefore number scanned lines in each frame is 625. Refresh rate is 25 frames (50 fields) per second.
Vibrations of both axis are resonant, therefore sinusoidal.
Slow axis is driven by piezo.
Fast axis is elecromagnetically driven.
Laser modulation is analog.







http://www.photonlexicon.com/forums/album.php?albumid=104

And related videos on Youtube posted by sltvm2007 and sltvm2008
 
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The fast scan mirror is tricky
You have to scan a line quickly ( ie in 1/30*625 s) but then get back the start in one flyback time - can't remember what that is for pal but it's only about 1/50 of the line time
So you can't use a tuned resonant scanner, if you use a spinning mirror you need a huge f-theta lens

You will also need 3 colour lasers and some optics to superimpose them.
Red is easy, green is getting easier but solid state Ti-Sapphire (blue) replacements are still expensive, especially if you want watts of power which you will need to get a bright spot.
 
mgb_phys said:
The fast scan mirror is tricky
You have to scan a line quickly ( ie in 1/30*625 s) but then get back the start in one flyback time - can't remember what that is for pal but it's only about 1/50 of the line time


There is no trick
Scanning scheme is as follows:
First line of the first feld is scanned from left to the right.
Second line of the first field is scanned from left to the right with the video content inverted in time.
Same technique is applied to the successive fields which are scanned up and down and up...
 
Thats a good idea
 
kuntman said:
There is no trick
Scanning scheme is as follows:
First line of the first feld is scanned from left to the right.
Second line of the first field is scanned from left to the right with the video content inverted in time.
Same technique is applied to the successive fields which are scanned up and down and up...


I believe there is a fundamental problem with resonant scanning. How do you intend to get your scan lines parallel? You need linear, single-direction scanning to get that.
 
berkeman said:
I believe there is a fundamental problem with resonant scanning. How do you intend to get your scan lines parallel? You need linear, single-direction scanning to get that.

When the beam scans sinusoidally this does not mean that successive lines will not be parallel.
However the content of the video will be somehow distorted.

You may view the picture of scanned lines from the last link.
 
You can linearise the f-theta out in software to some extent.
This is patented (at least for scanners that measure a surface) - I had to design a multi resonant scanner system once to cancel out the effect without changing the timing.

For the vertical (field) axis you don't need to use a resonant scanner - an normal coil driven one is fast enough and the field flyback time is long enough,
 
I tried to make a linear slow (vertical) axis which uses coils etc. It is easy to actuate the mirror to move linearly, but it is almost impossible to stop it and get back to the starting point during the flyback time because of the considerable moment of inertia.
 
Thanks for sharing. It's really a low cost
 

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