New CMOS ASI183MM camera

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New CMOS ASI183MM camera

Postby Christian Buil » Sat Apr 07, 2018 11:00 pm

Test of the high performance ASI183MM (use the backside CMOS Sony IMX183) - up to 80% quantum efficiency and low noise - a possible alternative to the famous ATIK460EX CCD camera. And fringing default not present.

http://www.astrosurf.com/buil/asi183mm/



Test de la toute nouvelle caméra ASI183MM, avec un capteur CMOS aminci (70% de rendement quantique à 400 nm et bruit de 1,5 électron).
Très bonne nouvelle : absence de franges lorsqu'on l'utilise en spectrographie haute résolution (avec Lhires III par exemple).
Il y a de quoi hésiter avec une Atik460EX (format très proche et performances)... :

http://www.astrosurf.com/buil/asi183mm/

Christian Buil
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Re: New CMOS ASI183MM camera

Postby Ken Harrison » Sun Apr 08, 2018 6:32 am

Christian,
That's very interesting!
I just purchased a ASI 183MM for solar imaging due to the pixel size ( to suit my shorter refractors and to give full disk imaging) I never thought of applying it to spectroscopy......
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before....
"Imaging Sunlight - Using a digital Spectroheliograph" - Springer
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Re: New CMOS ASI183MM camera

Postby etienne bertrand » Sun Apr 08, 2018 7:16 pm

Merci pour cette étude.
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Re: New CMOS ASI183MM camera

Postby Michel Verlinden » Mon Apr 09, 2018 5:13 pm

Bonjour et Merci Christian des informations précieuses que tu véhicules à travers ce test.
Les darks doivent-ils rigoureusement de même durée que les images spectrales en raison du bruit d'électroluminescence affectant le capteur ?
Cordialement,
Michel Verlinden
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Re: New CMOS ASI183MM camera

Postby Christian Buil » Tue Apr 10, 2018 1:48 pm

Yes Ken, I suspect (laboratory tests) fine results is the ASI183MM is used in the field of spectrography. In Toulouse (France) 4-month of cloudy night (!!!!!! :-((( ) - no test on the sky for the moment...

Michel V. à vrai dire il n'est pas utile de faire un dark pour chaque image avec le même TI. Le glow étant proportionnel au temps d'intégration, on a le même régime que pour le signal d'obscurité. La stratégie : on fait une carte du signal d'obscurité avec un temps long (genre 10 minutes), puis si on fait un spectre d'un objet avec un temps plus court, on multiplie la carte de référence dark (+ glow) avec le ratio des temps d'intégration (par exemple 0,5 si la pose est de 5 minutes).

A noter, que je viens de faire une mise à jour de la page avec des données justes obtenues avec un LISA, plus fines qu'avec l'Aply600 employé jusqu'alors. Ca ne change pas significativement les résultats, ca confirme en fait.

Christian
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Re: New CMOS ASI183MM camera

Postby Robin Leadbeater » Tue Apr 10, 2018 5:32 pm

Hello Christian,

What are the statistics of the amp glow ? Does it reduce the SNR in the spectrum in the same way as the sky background ?

Thanks
Robin
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Re: New CMOS ASI183MM camera

Postby Christian Buil » Tue Apr 10, 2018 10:47 pm

Hi Robin, the amp glow generate a photon noise in the same way as the sky background, i.e. same statistic.

Christian
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Re: New CMOS ASI183MM camera

Postby Ken Harrison » Tue Apr 10, 2018 10:49 pm

Christian, et al,
Following discussions on other forums Re AR coating of the chip cover plate on the ASI 183MM, I contacted SONY directely and received this reply:


With regards to your inquiry about “Does the Sony 183 chip have an AR coated cover plate?"

I’ve checked with our Japan engineers and they indicated that IMX183 has an AR coated cover panel.

Hopefully that removes any ambiguity.
Last edited by Ken Harrison on Thu Apr 12, 2018 1:02 am, edited 1 time in total.
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before....
"Imaging Sunlight - Using a digital Spectroheliograph" - Springer
http://www.astronomicalspectroscopy.com
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Re: New CMOS ASI183MM camera

Postby Peter Somogyi » Wed Apr 11, 2018 6:54 am

Christian,

This looks to be the first serious CMOS chip to consider as an upgrade of our common CCDs.
Could you please test:
- the amp glow reproduceablitity, e.g. linear with time, pattern won't change in longterm (e.g. rotating camera in other physical directions), light leakage (parasite light), internal reflections
- dark is linear with time (unlike many DSLRs - yet astrophotographers take equal dark time, without bias); do we need different dark for different gain?
- bias reproduceability: is readout noise changing with light? (for CCDs it won't; but who knows with a CMOS ?)
- any problem with the smaller pixel size? why RMS increasing with binning?
- linearity test - per gain setting (this is my main concern)

Thanks,
Peter
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Re: New CMOS ASI183MM camera

Postby Christian Buil » Thu Apr 12, 2018 12:52 am

Peter, the most important point concern the RMS noise and the Signal to Noise Ratio (SNR)...

From bin 1x1 to bin 2x2 acquisition mode, the ASI183MM noise is multiplied by 2 because we quadratically add the signal of 4 adjacents pixels, so RMS = SQR (4) = 2 (i.e. digital binning)

With the CCD, the noise would be the same in bin 1x1 and bin 2x2 (analog binning, the big advantage).

At the same time, the signal is multiplied by 4 in both situations.

The gain in SNR passing from bin 1x1 to bin 2x2 is therefore:

For CMOS: 2X
For CCD: 4X

CMOS is less efficient than CCD, but there is always a benefit of doing bin 2x2 with CMOS compared to bin 1x1 if the sampling condition is compatible (4.8 microns pixel size for the ASI183MM).

Now we compare ATIK460EX and ASI183MM for nearly the same pixel size...

For 1x1 binning mode the pixel size for the ATIK460EX camera is 4.54 microns and the noise is 5.5 electrons.

For 2x2 binning mode the pixel size of the ASI183MM camera is 4.80 microns (close to the ATIK camera) and the noise is 3.0 electrons.

In this situation and for very faint flux imagery (readout noise regime), the ASI183MM camera offers a gain in SNR compared to the ATIK460EX camera of : (4.54 / 4.80)^2 x 5.5 / 3.0 = 1.64.

The ASI183MM camera continues to be superior to the ATIK460EX camera for the Signal to Noise Ratio criteria and a similar sampling (nearly 4.6 microns pixel size). And we can also add a higher quantum efficiency in the blue for the ASI camera... 1.4 time better at 400 nm (so the effective SNR gain is 1.64 x 1.4 = 2.3 for the ASI183MM at this wavelength). Of course, we must confirm that on the sky, but on the paper, it is a clear situation.

The situation is inverted is we consider now a 9 microns sampling pixel size (bin 2x2 for the ATIK camera, bin 4x4 for the ASI camera) : (9.08 / 9.60)^2 x 5.50 / 5.92 = 0.83.

I recommend to limit the binning modes for the ASI CMOS camera to bin 1x1 or bin 2x2.

Regarding the amp-glow and the dark signal, the values are really proportional to the integration time. No differences between CMOS and CCD.

Christian
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