Purpose and Goal:

To build the most capabable LiDAR possible for 50-150 US$.

As I have found the existing solutions absolutely apalling. 400 dollars to buy and dissasemble a Neato vacuum just to get a primative lidar, or spend from 1200 to 6500 US$ for a slow phase differentiating Hykouo lidar, or perhaps 20,000 US$ on a real true time-of-flight lidar.
The need for and lack of a useful lidar for hobby and professional use has now become an intolerable obstacle, if no one else can or will resolve this matter, then i guess ill have too. The problem of robot control and manuevering within human occupied or natural enviroments can only be solved through the use of LiDAR and SLAM. Therefore, without good data (from a LiDAR) it doesnt matter how good your SLAM implementation is. Thus the unavoidable need for cheap, plentiful, and capable LiDAR for robotic fleets of all types (civil and martial).

Solution:
The use of structured light, as demonstranted by the XV-11 lidar in the Neato robotic vacuum. Im hoping for assistance from SparkFun and Parrallax companies and similar minded groups and individuals. I intend for the end device to be open source as much as possible ...

Connection:
im thinking of using SPI for the conection method. So the connection will work as follows :
(Lidar with internal STM32 MCU w/SPI) --> SPI --> (End-User Embedded MCU w/SPI)
Im thinking this will be easier and faster than a crap RS-232 serial TTL 115kbps connection like inb the XV-11.

Previous Threads and Research:

Previous Threads:
<- SLAM for Dummies Like Me!!!
<- Does anyone know how these LiDARs work?
<- CSU Chico Tilt Rotor Flying Machine, (Programming and CPU, 3 of 3).

Links and Research:

Initial Idea:

Specs for Final Device:

Range: 1 foot min, 45 feet max.
Resolution: about 1 inch
Wavelength: NIR or IR, (700nm -1000nm) [Visible (red) for initial calibration only.]
Viewable arc: 360 degrees (i hope)
Enviromental: above freezing, below 150 degree F (*Earth use only), eye safe (i hope) significant unwanted light between 700nm and 1000nm may be a problem.
Size: 4 inch cube
Power: 5v at 300-500mA

Components:

Filter: IR filter passes 700nm and longer, will suppress all visible and UV light.
Main Lens: 12mm diameter, 33mm FL, uncoated, glass.
Main Mirror: TBD, probably a tiny normal mirror cut on a tile saw.
Motor: Probably a DVD/CD motor, about 1200-3000rpm.
Laser: IR 780nm or IR 808nm, laser line, 60 degrees cut down to 20 deg by blinders. 5 and 20mW. (The line will be vertical.)
MCU:Probably STM32 F1.
Detecting Element: Panavision DLIS-2k or DLIS-4k linear pixel senor (monochromatic) [the DLIS-4k is no longer made.]

Cost:

Lasers: 11 and 14 US$
Lens: 4 to 9 US$
filter: 2 US$ (once cut to size)
Mirror: 1 US$ (estimated)
Detector: Unkown
Motor: 2-5 US$ (estimated)
MCU, and PCB: 10 US$ or less
Screws, Case, Wire and Plastic: Aproxiamtley 10 US$\

(I'm trying to keep the build cost to about 50 US$)

Data Sheets and Application Notes:

]app0002_rev_d_appnote.pdf[/file] Panavision DLIS sensor family App Note.

]pds0038revg_datasheet.pdf[/file]Panavision DLIS family Data Sheet. (DLIS-2k)

Technical Points:

A Specific Note On The Filter And Detector:
The filter that i found will pass 700nm and longer, but will block all visible and UV light. The panavision DLIS family is sensitive to a suprisingling limited amount of the IR spectrum. It has been optimised for the detection of viisble light, red specifically, for bar code and fingerprint type machine vision applications. it is insensitive to longer than 1000nm light. Therfore all light that will reach the DLIS senor will be longer than 700nm and shorter than 1000nm, a narrow 300nm passband! i am hoping this will lead to a high signal and low noise condition at the sensor plane.

And for the Lasing Physics:
Within the narrow 300nm passband there will be two possible laser light beams. either a 780nm, 5mw, NIR laser diode module, or a 808nm, 20mW, IR. Both will be line generating lasers. This line will be vertical to the sensor plane, which is horizontal. This arrangement ensures alignment and a narrow but definante fall pattern on the sensor, even with age, vibration and temperature creep.


Supporting graphs for sensor and filter:


Filter, frequency/transmitivity graph.



Frequency sensitivity of Sensor, Panavision DLIS family.


Frome the above graphs we see, the filter will pass 85% of the IR at near 800nm, the DLIS sensor is sensitive to 80% at 780nm and 75% at 808nm compared to red being 100% .

Sat Nov 24 2012, 06:41PM - 1:55AM
First Structured Light Experiments ! (Proof of concept / Technology demonstrator)

(Version 1, Type 1, Mod 10, Gen A) [Success!]



The Setup-up... (A poor college students optical test bench, a plywood table painted white.)



Seen in the above pic, a 12" (y-axis near) target and a 16" (y-axis, Far) Target. Which cuased a visible change of 1.4 inches in the x-axis. The camera was static for the above to pictures, however the Auto Focus did jitter a bit. Still a valid test.



Animated .gif file! Click Me!




Electro-Optical and physical configuration of the would-be sensor.



Far target, a Sharpie paint marker.



Near target, a tube of silver solder.

Lesson learned:
As expected, the width of the laser line as it falls on the DLIS sensor will deteremin the possible vs. actual resolution, as each pixel is
only 4 micrometers wide... (if the laser lights up several pixels, that reduces resolution.)

EDIT: its 1:40am and im drunk, so i might be \wrong, but CAD is indicating i can get the laser width down to 12um at the sensor plane, so that means 3 or 4 pixels will be lit buy my 2mm wide line laser beam... thus about 1 inch of resolution should be possible.