Features

Problems

Prototype 1

·         8 big key chain laser pointer laser diodes

·         Single row

·         Hold by single acrylic plate (laser cut)

·         Skyliner™ electronics

·         8-faced mirror, continuously rotating

·         System not closed loop: synchronizing motor speed with laser pulses not possible

·         Mirror way too bulky for mobile use

·         Alignment of laser diodes virtually impossible, since the laser diode capsules are imprecise

Prototype 2

·         8 big laser diodes

·         Two parallel rows, interlaced

·         Hold by two parallel acrylic plates (laser cut)

·         8 secondary mirrors for laser beam alignment, mounted on U wires

·         Left-right sweeping mirror, driven by commercial RC servo, controlled by PWM signal created by PIC

·         Custom electronics (including small PIC controller 16F84)

·         Very high brightness and visibility of projection, even on black backgrounds

·         Relies on persistence of vision principle, so only very low refresh rate (3Hz)

·         Relatively noisy

·         Still too big for mobile use

Features

Problems

Prototype 3

·         8 big laser diodes

·         Two parallel rows, interlaced

·         Hold by two parallel acrylic plates

·         8 secondary mirrors for laser beam alignment

·         Custom electronics (16F84 PIC)

·         Add-on mirror assembly (3D printed)

·         Continuously rotating, two-faced mirror (single stainless steel strip, no continuous axle), held with 3D printed parts on each end

·         Driven by 6mm motor

·         Closed-loop system with IR LED and photodiode

·         Mirror not turning lightly enough: the stainless steel strip by itself was not rigid enough, because there was no continuous axle

·         Laser diodes not bright enough for the low duty cycle of 360-degrees continuously rotating mirror: with a projection angle of 60 degrees, only about 8% of the time the lasers are actually on

Prototype 4 (CAD model only)

·         8 smaller laser diodes (Lumex or Honeywell)

·         Mirror made of two strips of stainless steel and centered axle (all the way through)

·         Continuously rotating mirror

·         Belt driven via pulleys and by 6mm motor

·         Compact size (no secondary mirrors, motor is parallel to laser array)

·         Diodes mounted via their contact wires, for easy alignment

·         Gear box difficult to align: if belt tension too high, then friction too high; if tension too low, the belt jumps out of the pulleys easily

·         My laser diodes not bright enough for such low duty cycle of rotating mirror

Features

Problems

Prototype 5 (just holder)

·         8 Lumex laser diodes

·         Single row, very compact, very rugged

·         Diodes and lenses mounted directly on 3D printed holder

·         Holder not precise enough, due to limitations of 3D printing head

·         Alignment calibration not possible, and very much necessary!

Prototype 6 (just mirror)

·         Continuously rotating, very light going mirror assembly; virtually NO vibration!

·         Mirror made of single axle (centered) and 2 strips of stainless steel, very rigid

·         Direct driven by 6mm pager motor

·         My laser diodes not bright enough for such low duty cycle of rotating mirror

Features

Problems

Prototype 7 (just mirror)

·         Left-right sweeping mirror

·         Mounted on simple scotch tape hinge

·         Driven via one-arm crank (ABS) on a 6mm motor

·         Closed-loop system with IR LED and photodiode

·         Modest vibrations

·         With ABS crank arm very jittery projection trajectory of the laser beams

Prototype 8 (just mirror)

·         Left-right sweeping mirror

·         Mounted on simple scotch tape hinge

·         Driven via one-arm crank (ABS) on a 11mm diameter motor

·         Very high refresh rate possible!

·         Noisy

·         Strong vibrations

·         Relatively big

Features

Problems

Prototype 9

·         8 Lumex laser diodes

·         Single, compact row

·         Separately 3D printed holder for lenses and diodes

·         Diodes mounted with U shaped double wires

·         Sweeping mirror (single strip stainless steel), mounted on single axle at one edge of strip

·         Driven via one-arm crank (aluminum) and 6mm pager motor

·         Closed-loop system with IR LED and photodiode

·         Refresh rate 25Hz

·         Bigger PIC (16F877) with enough memory to display all characters

·         Serial connection

·         Can be connected to Palm Pilot™ or Java enabled cellphone

·         Fragile, since all laser mountings (double wires), as well as the motor crank, are mechanically exposed

Prototype 10 (CAD model only)

·         Like prototype 9, but with complete housing, protecting the laser mountings and the motor crank