|Estimated Requirement||Requirement + contingency|
|Board size||42mm x 28mm x 10mm||x|
|Lens dimensions||24mm long, 15mm diameter||x|
Contact (append @le.ac.uk to all email addresses)
Fraser Kettle (fk52)
Anshika Mittra (am346)
Stuart Turner (smrt1)
Henry Simms (hs171)
The camera subsystem uses a pre-fabricated CMOS OV7640 camera and lens, supplied by Omnivision technologies. This piece of hardware is not mission critical, which along with the cost and complexity advantages of such a design lightens the decision to use non-flight tested hardware.
The OV7640 is a full-featured webcamera, capable of full motion 640x480 video at 30 frames per second. The camera's onboard computer is far faster by default than our more conservative FM430 MCU can handle - even taking a single image will mean slowing the camera output down by a factor of sixty-four.
System block diagram
Figure 1: Figure showing basic sections of the camera subsystem
There are four main components to the camera: the board itself, the shield, the buffers and the power switch. The camera board is supplied whole by Omnivision, but the other parts must be made in-house.
The C.M.O.S. sensor will require shielding, although as indicated by SPENVIS, only a thin sheet should be required. For more detail, see Table 1 on the Radiation Environment page. A sheet of aluminium 1mm thick should be more than sufficient to provide adequate protection to the camera.
The camera is not rated for spaceflight, and a failure in its digital logic systems could damage the MCU.
Depending on the waveband that the detector is sensitive to, an infrared (I.R.) cutoff filter may be required. This will reduce reddening of the image, as I.R. photons will be registered as red photons. An image of the effects of an I.R. cutoff filter are shown in Figure 2 below, taken from Edmund Optics. Edmund Optics and Jessops have a broad range of I.R. cutoff filters available, which can be used so long as they are not made from plastic.
Figure 2: Graph of transmittence through an infrared cutoff filter as a a function of wavelength