Fast CCD clearing

[Paddy Oates]

Tim and Tim and others,
	
	We have used a fast clear option on our Teks foe a few years. We have 
also now implemented a FLASH clear on the EEV42 device as they come with a dump 
drain along the serial register. 

	We gained a factor of about 80 on the Teks going from Std clear (1 row 
at a time with a register scan, done twice) to Quick clear which implements a 50 
rows bin into the S.register, with the register clock highs, and at the end does 
a 50x1 row shift into the SR with a SReg scan(twice). I think the latter is 
important to ensure the register is clear and no charge flows back into the 
image area.
	
	The flash clear on the EEV gets down to 0.4s to clear the whole array 
twice using the dump drain BUT we still scan the SR at the end. If we dont I saw 
charge flow back to the image area. Peter Poole told me a time delay after the 
last row was dumped into the SR would also have achieved the same effect - 
allowing the charge to fully drain down the plug-hole....


Hope this helps 


Paddy

--
Contact - work :: Tele     +44 (0)1223 374836
                  Fax      +44 (0)1223 374700
                  E-Mail   apo at ast.cam.ac.uk
                           apo at apoates.demon.co.uk
 
                  WWW Page http://www.ast.cam.ac.uk/~apo/
                  CCD Page http://www.ast.cam.ac.uk/~apo/docs/ccds.html

		  Personal Web Pages
			   http://www.apoates.demon.co.uk
--------------------------------------------------------------






--
Contact - work :: Tele     +44 (0)1223 374836
                  Fax      +44 (0)1223 374700
                  E-Mail   apo at ast.cam.ac.uk
                           apo at apoates.demon.co.uk
 
                  WWW Page http://www.ast.cam.ac.uk/~apo/
                  CCD Page http://www.ast.cam.ac.uk/~apo/docs/ccds.html

		  Personal Web Pages
			   http://www.apoates.demon.co.uk
--------------------------------------------------------------