TinyProjector Lab Notebook

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Original Proposal


Basic Idea

The basic idea is to build a small portable character projector, based on inexpensive laser diodes, that is able to project a single line of text onto nearby walls, tables, and other surfaces. This would be useful for projecting text from portable and wearable devices, e.g., cellphones, PocketPCs, etc., that are connected via serial port (wireless) or Bluetooth.


Figure 1: First design sketches for TinyProjector, developed in October 2000 for a MIT Media Lab class. It was conceived as the output module of an interface to an intelligent single-point remote control for all home appliances. The underlying metaphor is a "magic lamp" that is home of a genie. The projection would appear out of the top of an old oil lamp when the user rubs the lamp, symbolizing the friendly ghost that can control all home appliances.



One of the major user interface design challenges for mobile communication devices is that the devices should be as small as possible, but still have a display as big as possible. There has been a lot of work done in the field of small displays, and whether or not big-screen user interface metaphors like the desktop can be adapted to the limited display real estate.


One solution for the dilemma would be look-through devices like Invisio’s eCase (http://www.inviso.com/ecase.html). However, they are only one-person displays: only a single person can see the content.


It looks like another, radically simple solution to this problem, might have been mostly overlooked: One does not have to accept small displays on even smaller devices if projection capabilities are added to the mobile communication device itself. The basic idea of the TinyProjector is to create a as small as possible character projector which can be either integrated in a mobile device, or linked dynamically with wireless RF connections like Bluetooth or serial low range transceivers.



I suggest two steps for the realization:


Step 1: Testing the idea by replacing the 8 LEDs of a Skyliner™ toy with 8 laser diodes of small key chain laser pointers.


The Skyliner™ (http://www.theskyliner.com) is a little gadget, approximately the same shape as, and a bit larger than a New Year's noisemaker. It runs on two AAA batteries. There is a row of 8 red LEDs on the end. Three buttons located near the handle allows the user to change to any of 10 pre-set messages, or create up to three new ones. One holds the thing over the head and whirls it about by its handle, and messages, spelled out in red LEDs, appear “magically” in mid-air.




Figure 2: Skyliner™ toy


By replacing the LEDs with laser diodes, and adding a turning mirror in front of the laser beams, the device should project the messages (pre-set or programmed), onto nearby walls or tabletops.


Figure 3: Key chain laser pointer (left), laser diodes (right)


The laser pointers would be powered via a transistor and a separate 3V power source. A rotating mirror would project the laser beams (theoretically) 360 degrees onto the walls (Figure 4).




Figure 4: Array of eight laser pointer diodes, arranged in one row, and a rotating mirror with two surfaces.


To make the projector more compact, an additional set of secondary mirrors would allow bringing the laser beams closer to each other (Figure 5).




Figure 5: Array of eight diodes, arranged in two rows, with secondary mirror.


Step 2: Replace the Skyliner™ electronics with a PIC chip that drives the laser pointers directly.


The PIC chip would receive the text to project as serial data, perhaps wirelessly from serial low range transceivers (Abacom, Linx) or Bluetooth chipset. The PIC needs at least one leg (input) per laser diode (8), and possibly other inputs for adjusting the scan frequency as well as synchronization of refresh rate with mirror rotation. Hopefully PICs like the 16F84 that can power the laser diodes directly (can provide enough current and voltage), making transistors obsolete.


Figure 6: Abacom/Linx low range RF transmitter/receivers (left, middle), PIC chip 16F84

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Send me some comments! Stefan Marti Last updated February 23, 2003.

Copyright © 1997-2004 by Stefan Marti and MIT Media Lab. All rights reserved