Contents
Test Image Data

Sample image data - nine differently positioned balls


Sample image data - nine differently positioned balls




Test data was acquired using the "Philips VGA Digital Camera" by capturing pictures of a real tennis ball in motion on a white background. Each position of the ball satisfies the criteria set down on the motion of the ball (see "Assumptions & Design Restrictions" in the "Design & Specification" scetion), except the last. This was included as to provide a "stray" ball that did not follow along a path as with the other images of the ball.

Each image is 350 by 285 pixels in physical size (45.6Kbytes memory) and can be fully processed by the edge detection algorithm in less than half a second.


Camera Resolution

The camera was positioned at a perpendicular distance of 216cm (85") from a flat wall and the physical view dimensions were measured.



Camera Resolution
(x x y pixels)
Distance d
(cm)
Physical View Width
(cm)
Physical View Height
(cm)
Image Size
(bytes)
128 x 96 216.0 106.7 76.2 18432
160 x 120 216.0 165.1 114.3 28800
176 x 178 216.0 147.3 116.8 38016
260 x 144 216.0 121.9 86.4 63360
320 x 240 216.0 165.1 116.8 115200
352 x 288 216.0 149.9 119.4 152064
640 x 480 216.0 165.1 119.4 460800


These measurements were then used to calculate the corresponding angles of projection of the different camera resolutions.




Camera Resolution
(x x y pixels)
Horizontal Angle
()
Vertical Angle
()
128 x 96 13.9 6.7
160 x 120 20.9 10.0
176 x 178 18.8 10.2
260 x 144 15.8 7.6
320 x 240 20.9 10.2
352 x 288 19.1 10.4
640 x 480 20.9 10.4


An estimate of 66.0cm was placed on the distance at which the camera would be placed on the final constructed camera rig for the third year part of the project. Using this as correct, calculations were done using basic trigonometry to work out the visible area for each camera resolution.


Camera Resolution
(x x y pixels)
Height
(cm)
View Width
(cm)
View Height
(cm)
View Area
(cm2)
128 x 96 66.0 35.5 23.4 830.7
160 x 120 66.0 50.5 35.1 1772.6
176 x 178 66.0 45.0 35.6 1602.0
260 x 144 66.0 37.3 26.4 984.7
320 x 240 66.0 50.5 35.6 1797.8
352 x 288 66.0 45.7 36.3 1658.9
640 x 480 66.0 50.5 36.3 1832.2


Finally, a resolution of 160120 was chosen to accommodate both the physical view are of the camera and the size of the image in memory at this resolution. At the height of 66.0cm, this covers approximately one fifth of the total proposed area that the camera will need to cover. This is adequate because the camera will be moving around on the motors on which it is mounted.


Camera Mounting Rig

The third year part of the project included the design and construction of a rig suitable for the mounting of the Philips VGA Digital Camera. Pictures of this rig can be seen below.






This camera rig can be controlled via the serial port of a desktop PC. The camera position can be altered by movement of the stepper motors mounted on the rig.


Philips Vesta Pro WebCam

The camera chosen for the image capture parts of the project is the Philips VGA Vesta Pro Digital Camera.

This camera is capable of capturing both colour and black and white images at various resolutions.


Philips Vesta Pro Webcam

Philips Vesta Pro Webcam       Philips Vesta Pro Webcam

Philips Vesta Pro WebCam