Preliminary Design Review
The Lone Rangers
Brad Alcorn
Tim Caldwell
Mitch Duggan
Kai Gelatt
Josh Peifer
Capstone – Spring 2007
3D Object Scanner
Goal: To be able
to capture any
small physical
object as a three
dimensional,
digital model.
How do you do that?
We will use a process called
Triangulation to map points in 3D space
The system will consist of a laser, a
CCD camera, a turntable, and an FPGA
to control everything
Data will be gathered by the system,
and sent to a PC where the 3D model
will be constructed
Triangulation
How do we know the
distance to one point?
Block Diagram
Mechanical Equipment
Turntable
Stepper Motor
Rotary Encoder
Neat stand for
turntable
Even more neat
stand for
camera (tripod)
Materials
Initially, we will construct the turntable and
stand from wood or Plexiglas
If possible, time and money permitting, we
would construct a final design of machined
aluminum
Line Laser
Projected vertically onto the object to be
scanned
Set at a known angle
from the camera for
triangulation
calculations
CCD
Texas Instruments TC346RGB







658(H) x 496 (V) Active Pixels in Image Sensing
Area
10um square pixels
Low dark current
R, G, B primary mosaic filters
on chip
30 frames/s readout speed
Serial connection to A/D
converter
12.5 MHz clock signal
Analog Front End
A/D converter between CCD and FPGA
Compatible with CCD and FPGA
interfaces
Fast enough conversion rate to keep up
with data from CCD
CCD Objective
Pinhole objective

Pros






low cost
decent resolution
more rugged than a lens
Cons

Lens objective
Low light intensity on CCD
Resolution not adequate for
our needs
Pros



Higher light intensity
on CCD
Higher resolution
Cons


Higher cost
More
delicate/vulnerable
to damage
FPGA Tasks
User interface that gets input from computer
(keystrokes)
Send stepper motor control signals
Read encoder from main axle to know angle of the
object
Tell camera/CCD when to take pictures
Receive RGB data from camera/CCD
Send data to computer for processing
Control laser on/off and possibly movement
FPGA Choices
Xilinx or Altera
Buy FPGA and design a PCB for it
 Could be costly and difficult
 Less I/O options
 Efficient and small
Buy dev. Board
 Simplest method b/c board
already designed
 Many prebuilt I/O options
ex. Rs232, USB, GPIO pins etc.
Possible Alterations to
FPGA Design
If camera is hard to control, connect to
computer directly via USB
Image processing – take RGB data and
turn into b/w bitmap
Use VGA output for a more self
sustaining user interface
3D Plotting
Problem: Using points in R3 to generate
visually nice 3D pictures represented in 2D.
Solution: Use Matlab. Matlab has nice 3D
plotting ability with zoom and rotate. May
need to create algorithms for better pictures.
Eg:


Wireframes
Cubic Splines
Wireframes
3-Dimensional Connect the Dots
1
1
0.5
0.5
0
0
-0.5
-0.5
-1
1
-1
1
0.5
1
0.5
0
0
-0.5
-0.5
-1
-1
0.5
1
0.5
0
0
-0.5
-0.5
-1
-1
Cubic Splines
Guessing Between Points
Linear Spline
Cubic Spline
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
-0.2
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1
0
1
2
3
4
5
Si(x) = m1ix + m2i
6
7
8
9
10
-1
0
1
2
3
4
5
6
7
8
Si(x) = m1ix3 + m2ix2 + m3ix + m4i
9
10
Division of Labor
Brad- FPGA
Josh- FPGA, Software
Mitch- Optics
Kai- Optics, Machining
Tim- Software, Encoder
All- Stepper Motor
Schedule
Risks
Data is inaccurate.
Not enough funding available for legit
parts.
Calibration of camera data is not
plausible.
CCD interface is too time consuming.
Contingency Plans
Use a Webcam instead of CCD
Use wireframe only instead of smooth
imaging.
Simply plot points in MATLAB.
Extensions
Add color to 3D model, scan object for color
as well as shape.
Interface with 3D printer in the ITLL to
duplicate the scanned object.
Filter out noise due to vibrations or
surrounding light sources from camera data
to increase accuracy of scanner.
Add another camera to increase the accuracy
of the scanner.