340 megapixel camera

[arcticpenguin]

http://news.bbc.co.uk/1/hi/sci/tech/2936235.stm

Here's a report on a 340 megapixel digital camera. It's attached to a 3 meter telescope.

The light detectors - CCD (charged coupled devices) - have to be kept cold to optimise their sensitivity. They have also to be kept in a vacuum to minimise outside influences that might affect the quality of the images. Forty CCDs are combined to produce MegaPrime.

Lower temps mean lower noise for CCDs, but I don't understand the vacuum bit. Does anyone know anything about that?

It has an unusually large field of view of one square degree, the size of four full Moons.

Cool.

 

[roger]

I'm no expert, but this link (http://www.spectro-ai.com/pages/e/p060033.htm) alludes to using vacuum to avoid wavelength absorption.

cool 'scope!

 

[arcticpenguin]

But it's a ground-based telescope! You can't evacuate the entire optical column above the scope. And if you do evacuate a space in front of the CCD chip, inside the telescope, you have to have a sealed chamber, so the light has to come in through a window, and that probably kills any advantage you had from the vacuum.

I still don't get it.

 

[Crossbow]

Just to toss in my two cents.

It sounds like what they are trying to do with the vaccuum system is to prevent dust, dirt, and other gunk from building up on the CCDs.

AP is right when he says that the window would degrade the signal, however I expect that that is less of a problem than is dirty CCDs. Unlike film, which is changed after every exposure, the CCDs will remain in place and cleaning them may be a non-trival exercise, therefore it may be worth the bit of signal loss to preserve the integrity of the CCDs.

I hope this helps!

 

[garys_2k]

Perhaps the vacuum chamber is to prevent condensation from forming on the CCDs' surfaces. They could heat the window the light has to penetrate to prevent it there, but still keep the CCDs themselves very cold.

 

[peptoabysmal]

Sorry if this is a little off topic.

There is a great new camera available called the Sigma D9, which uses the new Foveon chip. It can be had for under $2000

The Foveon chip is more like film. It allows light to penetrate the silicon chips with filters sandwiched in between to separate red, green and blue. You get a sharper image with a much lower pixel requirement for an equivalent sharpness to a high pixel CCD.

http://www.foveon.com

And, no I don't own any stock in the company

 

[arcticpenguin]

Sorry if this is a little off topic.

There is a great new camera available called the Sigma D9, which uses the new Foveon chip. It can be had for under $2000

The Foveon chip is more like film. It allows light to penetrate the silicon chips with filters sandwiched in between to separate red, green and blue. You get a sharper image with a much lower pixel requirement for an equivalent sharpness to a high pixel CCD.

http://www.foveon.com

And, no I don't own any stock in the company

That's good, because your description is inaccurate.

The Foveon chip does not have filters. it relies on the quantum mechanical phenomenon that longer wavelengths of light penetrate further into the surface of the CMOS sensor.

 

[peptoabysmal]

That's good, because your description is inaccurate.

The Foveon chip does not have filters. it relies on the quantum mechanical phenomenon that longer wavelengths of light penetrate further into the surface of the CMOS sensor.

Sorry, my bad.