Preliminary Design Review

1. Preliminary Design Review The Lone Rangers Brad Alcorn Tim Caldwell Mitch Duggan Kai Gelatt Josh Peifer Capstone – Spring 2007

2. 3D Object Scanner • Goal: To be able to capture any small physical object as a three dimensional, digital model.

3. 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

4. Triangulation How do we know the distance to one point?

5. Block Diagram

6. Mechanical Equipment • Turntable • Stepper Motor • Rotary Encoder • Neat stand for turntable • Even more neat stand for camera (tripod)

7. 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

8. Line Laser • Projected vertically onto the object to be scanned • Set at a known angle from the camera for triangulation calculations

9. 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

10. 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

11. 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

12. 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

13. 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.

14. 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

15. 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

16. Wireframes 3-Dimensional Connect the Dots

17. Cubic Splines Guessing Between Points Si(x) = m1ix + m2i Si(x) = m1ix3 + m2ix2 + m3ix + m4i

18. Division of Labor • Brad- FPGA • Josh- FPGA, Software • Mitch- Optics • Kai- Optics, Machining • Tim- Software, Encoder • All- Stepper Motor

19. Schedule

20. Risks • Data is inaccurate. • Not enough funding available for legit parts. • Calibration of camera data is not plausible. • CCD interface is too time consuming.

21. Contingency Plans • Use a Webcam instead of CCD • Use wireframe only instead of smooth imaging. • Simply plot points in MATLAB.

22. 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.