by Chris Peterson » Sun Jun 10, 2012 4:13 pm
owlice wrote:From what I have read, this "transparency" may be a result of detector persistence; because the AIA detectors were continually awash in light from the sun, the detectors retained the previous image (similar, I think, to the old "ghosting" one might have seen on an old television immediately after it was turned off, or burn-in on an old computer monitor) of the surface of the sun as Venus eclipsed the disk. Detectors are refreshed when looking at blank sky or dark areas. It may be that some detectors are more sensitive or prone to this persistence, which may account for this showing up more in some tracks than in others.
What you are talking about is called residual bulk image, and it occurs in CCD detectors because some electrons (which are produced when photons are captured) are trapped in the bulk structure of the silicon, below the actual pixel layer. It can be a challenge to deal with in some cases. It's certainly an issue with almost all the cameras used professionally, both on the ground and in space. It is certainly a likely candidate for this ghosting.
If anyone has another explanation for this, please share; thanks!
I've seen some comments from the camera operators that this effect might be caused by some sort of readout crosstalk between the different camera channels. The image is apparently placed simultaneously on four different detector quadrants, through different filters.
[quote="owlice"]From what I have read, this "transparency" may be a result of detector persistence; because the AIA detectors were continually awash in light from the sun, the detectors retained the previous image (similar, I think, to the old "ghosting" one might have seen on an old television immediately after it was turned off, or burn-in on an old computer monitor) of the surface of the sun as Venus eclipsed the disk. Detectors are refreshed when looking at blank sky or dark areas. It may be that some detectors are more sensitive or prone to this persistence, which may account for this showing up more in some tracks than in others.[/quote]
What you are talking about is called residual bulk image, and it occurs in CCD detectors because some electrons (which are produced when photons are captured) are trapped in the bulk structure of the silicon, below the actual pixel layer. It can be a challenge to deal with in some cases. It's certainly an issue with almost all the cameras used professionally, both on the ground and in space. It is certainly a likely candidate for this ghosting.
[quote]If anyone has another explanation for this, please share; thanks![/quote]
I've seen some comments from the camera operators that this effect might be caused by some sort of readout crosstalk between the different camera channels. The image is apparently placed simultaneously on four different detector quadrants, through different filters.