|
 |
|
CHAMP consists of an assembly of nine custom lenses, with the rear lense attached to the camera CCD. Focus is obtained by modifying the spacing between the lenses. The lenses themselves are mounted in low-outgassing RTV-566 silicone rubber (in titanium cells) and individually aligned with a laser fixture. No elements are cemented, resulting in variable back focal distance, focal length, and f/#. The CCD is on focus screws and uses linear guide bearings and a precision drive screw. This actuates the imager over a focus range of 105mm. Two home positions exist on this range: one at infinity and one at maximum magnification. The front mechanical system utilizes a transparent cover mechanism to shield the front instrument lense when not in use. A white-light LED illumination system is positioned around the lense for use in close-up situations where light is not readily available. Additionally, potentiometers (on springs) are mounted to the system. These compress on contact with the rock, resulting in 8-bit potentiometer data for use by the rover. Three pins measure orientation to aid optimal rover arm alignment (for better depth of field), and the potentiometers simplify the focus search by measuring object distance for short ranges. Through the use of a 4-position filter wheel, CHAMP is able to take wide-band and RGB images (a seperate filter is used to obtain red, green, and blue image data, and then combined to form an RGB image). The filter wheel is actuated by a step motor, and uses hard stops at home and end positions for position indication (with the wide-band filter at the home position). Please view the tables below for information about the CHAMP prototype performance. For more detailed information about CHAMP specifications, please contact program manager John Boynton. |
 |
PROTOTYPE PERFORMANCE (13.4 micrometer pixels) |
|||||||||
| Object Distance (mm) |
7.4
|
8.4
|
10.3
|
13.2
|
26.5
|
43
|
71
|
153
|
Infinity
|
|
| Magnification |
4.7
|
3.88
|
3.1
|
2.32
|
1.08
|
0.65
|
3.38
|
0.18
|
-----
|
|
| Two-Pixel Resolution (micrometers) |
5.7
|
6.9
|
8.6
|
11.6
|
24.8
|
41
|
71
|
149
|
0.96
millirad
|
|
| Focal Length (mm) |
5.1
|
6
|
7.1
|
8.7
|
13.6
|
16.9
|
19.8
|
23
|
26.7
|
|
| FOV (mm diagonal) |
1.85
|
2.23
|
2.79
|
3.72
|
8.07
|
13.5
|
22.6
|
49.4
|
-----
|
|
| Diagonal Angular FOV (degrees) |
14.3
|
15.2
|
15.5
|
16.1
|
17.5
|
17.9
|
18.3
|
18.5
|
18.7
|
|
|
PERFORMANCE
COMPARISON
|
|||||
|
Sojourner
Rover (Pathfinder)
|
Microscopic
Imager ('03 Athena Rovers)
|
Robotic
Arm Camera ('98 Polar Lander)
|
CHAMP
|
||
| Maximum Magnification |
~0.015
|
~0.4
|
1
|
>4
(this prototype); 5 achievable
|
|
| Best Spatial Resolution (2-pixel criteria) |
~1.6
mm
|
60
mm
|
46
mm (24 mm
achievable with smaller pixels)
|
6
to 7 mm (this prototype); 3 to 4 mm
achievable
|
|
| Best Identification (6-pixel criteria) |
~4.8
mm
|
180
mm
|
~138
mm
|
18
mm (this prototype); 9 to 12 mm
achievable
|
|
| Focus Range (object distance) |
250
mm to infinity (fixed focus)
|
60-120
mm (fixed focus)
|
Close-up
to infinity
|
7
mm to infinity
|
|
|
|
| Images of CHAMP integration with the K9 rover at NASA Ames Research Center can be viewed in the images section, along with examples of CHAMP imaging capabilities. | |
