Preliminary Design Review

The Lone Rangers

Brad AlcornTim CaldwellMitch Duggan

Kai GelattJosh 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 spaceThe system will consist of a laser, a CCD camera, a turntable, and an FPGA to control everythingData will be gathered by the system, and sent to a PC where the 3D model will be constructed

TriangulationHow do we know the

distance to one point?

Block Diagram

Mechanical Equipment

TurntableStepper MotorRotary EncoderNeat stand for turntableEven more neat stand for camera (tripod)

MaterialsInitially, we will construct the turntable and stand from wood or PlexiglasIf 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 Low light intensity on CCD Resolution not adequate for

our needs

Lens objective 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 signalsRead encoder from main axle to know angle of the objectTell camera/CCD when to take picturesReceive RGB data from camera/CCDSend data to computer for processingControl laser on/off and possibly movement

FPGA Choices

Xilinx or AlteraBuy 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 USBImage processing – take RGB data and turn into b/w bitmapUse 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

Wireframes3-Dimensional Connect the Dots

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Cubic Splines Guessing Between Points

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1Linear Spline

Si(x) = m1ix + m2i Si(x) = m1ix3 + m2ix2 + m3ix + m4i

Division of Labor

Brad- FPGAJosh- FPGA, SoftwareMitch- OpticsKai- Optics, Machining Tim- Software, EncoderAll- Stepper Motor

Schedule5/3

1/29 PDR

2/2 CDR

3/2 Milestone 1

3/23 Milestone 2

4/20 Expo

3/22

1/29 Select camera system and laser

2/19 Aquire camera and laser

2/5 Machine mounts for camera and laser

2/26 Calibrate optics, (if needed)

3/23

2/19 CCD PCB schematic

3/5 CCD PCB Layout

5/3

1/29 Be able to program FPGA (simple stuff)

2/12 Interface FPGA with motor and encoder

2/19 Interface FPGA with camera

3/5 Configure data processing

3/26 Software Interface

5/3

1/29 Setup Matlab code for displaying objects (data points)

1/29 User Interface

31 3 6 9 12 15 18 21 24 27 30 2 5 8 11 14 17 20 23 26 1 4 7 10 13 16 19 22 25 28 31 3 6 9 12 15 18 21 24 27 30 3 6 9 12 15 18 21 24 27 30 2 5 8 11 14 17 20 23 26 29 2January February March April May June July

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 CCDUse 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.