Rudolf's laser comm site



Laserlink pictures

     Pictures of my laser communication project. The purpose of it is to establish a good connection between my PC and a LAN. The distance is 300m clear line of sight. I started to build the link 1999  and I hope it will soon be ready.

A map of my neighbourhood
Here you can see my situation - I can't place a cable for our LAN anywhere :(
Thatswhy I had to make wireless comm. I found the design for a laserlink on the
net (schematic and other stuff at
  GKD design's homepage)

The balcony of my flat
The place where the laser is mounted on the wall is marked red.

 Laser mount
This photo is unsharp :( I need some practice in photography.This is the laser mount
in the balcony. It's a 50 cm long and 5cm wide iron plate mounted with 2 screws on the
wall. There are two levers for adjusting the laser on x and y axes. The laser is actually
a laser diode ripped from a pointer (635nm @ 3mW).

 View from my balcony
The other laserlink will be placed in the place marked with a red circle. Thats the house
where my friend lives.

 Friends house
A closer view of the below mentioned house.

 My house
This picture is taken from the roof. My balcony is marked red. The unsharp thing on the
foreground is the top of an airhole. The laser transceiver will be placed on it.

 Sight from roof on the right side of my house

 Sight from roof
Here you can see many airhole tops (first I thood that were chimneys:)

 Sight from roof on the left side
In that houses live five more people of our LAN

 Pipe construction for ambient light gathering (assambled)
The construction consists of four parts: two pipe pieces, a collimating lens and a 
adjustable focusing unit.

 Diagram of the construction

 Back view of the pipe (photo)

 Front view

 Side view of pipe (unassambled)

 Optics
On this picture you can see my binoculars (necessary for work on great distances),
big magnifying glass, some large lens (glaucous) and the two smaller lenses 10cm 
in diameter. The later are in each receivers ambient light gathering pipe.

 Equipment and components
In the foreground you can see some laser modules ripped from pointers, BPW-42
photodiodes, a SONY optical block from a CD-ROM and some other stuff. On the 
photo is also my ANTEX soldering iron, digital VOM and all kinds of components.

 The component side of my laser link circuits

 Solder side
It's hard to get a close sharp photo with my camera :)

 My o-scope
An old (but good) army o-scope

 Laser beam at night
This photo is taken from the roof of my friends house. The beam (marked with a 
red circle) is comming from my balcony.

 Laser beam taken from a different angle
That night was rainy.

 Another picture of the beam
Rain and snow improved the beam visibility.

 Other photo of the beam
The beam looked cooler in real !

 The last beam photo that is taken from the roof
This photo was made with a ISO400/27 film, all the other beam photos were made 
with a ISO200 film.

 Beam on a screen
Here my friend holds a white A3 page in front of the beam. I hadn't time to adjust the  
lasers focus. The narrowest beam that I got once was about 15cm in diameter without
additional optics.

 Beam in my room comming from the roof
It looked big and bright.

 Beam on the window of my room
The same beam as above.

 Another photo of the beam on window

 The thrid and last pic
On all three photos are reclections from streetlights.

 Junk box
There is all my electronic riff-raff.

 Cheap lasershow equipment :)
It's made on a old flopy drive frame. There are two motors with mirrors mounted on
the shaft of each motor. You can see there two potentiometers for changing the motors
speed.

 Side view of the laser show thing
It is easy to make, try it ! I'm just afraid you cannot impress your friends with it :[ unless 
you use a 20W Argon Ion laser or something similar instead of a pointer :))

 Some laser light
I think this photo is from a pointer, can't remember :]

 And finaly ME


Beam calculation program

    This program could be of use for those who make laser comm experiments. It calculates the beam diameter on a target, if you enter your laser wavelenght, beam initial diameter (collimator) and the distance to target. The program uses Maxwell's equations (see below).

draving.gif (2448 bytes)

diam.gif (1220 bytes)

angle.gif (401 bytes)

This program runs in a dos prompt window. In the archive you'll find the progs source and executable.
laser-calc.exe
If you want a graphical version of this program download the Flash version of my beam calculation program
laser-flash.exe


Laser beam demodulator

    This circuit uses amplitude modulation and converts a reflected (and modulated by the vibrating surface) beam into a audio signal. The incomming amplitude modulated light signal is detected by a phototransistor and amplified by a 741 OP amp IC. The audio signal is amplified by a 386 audio amp IC and then passed to headphones or a speaker.

demod-dia.gif (7195 bytes)

    The circuit diagram of the beam demodulator
    PCB layout
    PCB if you want to make a PCB, then resample this image to 50 x 23 mm
Here are also two photos of my homemade demodulator pcb: component side and solder side.


Links to other laser pages

N1BUG's laser DX page
Introduction to laser communication with many links and other cool stuff.

Optical communications handbook
Really great informations resource for laser experimenters

UPN Laser Transceiver
115kbit/sec laserlink design


Personal stuff

Great thanks to Jim Moss for placing my page on the web !!!

You can send me a short message to my pager, I'll receive it in ~2min.
Remember to leave your e-mail and the message lenght is limited to 150 characters !
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All questions, suggestions, and corrections are welcome !
E-mail: Rudolfs Osins rudis@inka.cs.llu.lv

This page was last updated on 10.04.2000