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Hi David, Prabhakar, Julio,
I work at Andor and can explain what's going on here. The Andor/PCO version of the Sensor is a 5.5MP sensor, and the Hamamatsu sensor is 4MP (they don't limit the number of useable pixels or use a mask). In addition to the number of pixels, these sensors differ in only one way...
The Andor version has a 5 transistor pixel design (5T design), this permits both Rolling shutter* readout mode (a fast, but transient mode of readout) and Global Shutter* readout (AKA snapshot or interline mode).
The 4MP sensor has one less transistor on each pixel (4T design), the result is two fold, 1.) there is a positive effect, an increase in QE (due to lack of the transistor circuit on the sensor pixel). And 2.) there is a negative impact, this sensor variant is limited to rolling shutter readout (transient readout only), so this variant does not permit global shutter /Snapshot mode.
The 'Gen II' label used to describe the 4MP/4T variant is just a label, the pixel design is identical, with the exception of the missing transistor.
In addition to appreciating the various modes of sCMOS readout the QE must always be considered in context of noise. As David comments CMOS sensors suffer from hot pixels, (more than CCDs), and there is a different distribution of noise across CMOS pixels compared with CCD. As you cool the sensor many of the hot pixels are "fixed" so less need to be corrected, the colder it is, the more pixels are corrected. If you have any further questions please feel free to ask me directly or through the listserv.
Andrew
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*Brief explanation of Global and Rolling shutter:
Global Shutter: the photoelectrons in each pixel are simultaneously moved into readout circuitry, where they are measured. This is a traditional shapshot acquisition and is very analogous to an Interline sensor readout.
Rolling shutter: the readout takes place as a wave traversing the sensor and travelling form a line across the centre of the sensor towards the outsides. The result is that the time of acquisition is different at different portions of the sensor. This can be avoided by switching off the light source during readout, but this has an obvious impact on data acquisition rates.
-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On Behalf Of David Baddeley
Sent: 27 June 2012 02:10
To: [log in to unmask]
Subject: Re: CMOS Camera
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Was just about to say the same thing - as far as I know they use a different chip (PCO and Andor both use the same chip, but Hamamatsu wasn't part of that consortium and decided to go it alone). The Gen I vs Gen II is probably mostly marketing hype ... In addition to QE I'd also pay attention to hot pixels and pixel to pixel gain/noise variations, as these tend to be the limiting features of sCMOS technology at the moment (you might get a mean read noise of ~ 1 e-, but a handful of pixels have much larger read noises). The manufacturers tend to offer soft/firmware solutions to mask these noisy pixels (often replacing the value by interpolation from neighbouring pixels), but whether this is desirable or not will depend on the application (it's one of the major concerns when evaluating sCMOS for PALM/STORM applications).
cheers,
David
________________________________
From: Julio Vazquez <[log in to unmask]>
To: [log in to unmask]
Sent: Wednesday, 27 June 2012 12:11 PM
Subject: Re: CMOS Camera
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Hi Prabhakar,
Do you know for a fact they use the same chip? The Andor sCMOS camera's spec sheet reports 5.5 MP (2,560 x 2,160 pixels) while Hamamatsu reports 2,048 x 2,048 effective pixels for the Flash 4. Could still be the same chip but why would Hamamatsu waste 1.5 MP? Also, the QE curve of the Andor resembles the QE curves of what Hamamatsu calls "Generation I" sCMOS, while the Flash 4 uses a "Gen II" chip with higher QE.... I'd suggest asking the respective reps. Maybe Andor is just a bit behind and will release an sCMOS with 70% QE in the next few months, or they chose a different chip for some other reason...
--
Julio Vazquez
Fred Hutchinson Cancer Research Center
Seattle, WA 98109-1024
http://www.fhcrc.org/
On Jun 26, 2012, at 2:17 PM, B. Prabhakar Pandian wrote:
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> To join, leave or search the confocal microscopy listserv, go to:
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>
> Hello All,
> We are planning on purchasing a CMOS camera from either
>Andor (Neo) or Hamamatsu (ORCA Flash 4). We are going to be demo them before deciding. However, looking at the specs, ORCA claims 70% QE vs 55% for Neo. Since both of them have the same chip, is this information accurate.
> Any help in resolving this question is appreciated.
>
> Thanks,
>
> -Prabhakar
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