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COMMERCIAL POST:

Dear Sivaram,

Imaging with EMCCD cameras offers the best sensitivity in low-light imaging. When background signals contaminating the image are not the limiting factor, the noise generated by the camera starts having a significant impact on the image quality. 

The three main specifications when comparing EMCCDs for spinning disk are speed, dark current (or thermal noise) and clock-induced charges (CIC, also called spurious background). All high grade EMCCD camera manufacturers use the same e2v sensors, so have roughly the same quantum efficiency (that can will vary slightly depending on the coating). The main differences between cameras are with the quality of the vacuum, the thermoelectric cooling (TEC) and the electronics. The vacuum and TEC will influence the dark current. Only cameras with high quality vacuum and TEC will reach a stabilized temperature of -85 +/- 0.01°C with air cooling at 20MHz. Dark current roughly doubles with every 7°C. The EM gain is extremely sensitive to temperature variations, so a stabilized cooling is key for quality images. Better electronics will minimize CIC, which is the dominant source of noise in low-light imaging with EMCCDs.

You can find more details on EMCCDs in low light imaging here:

http://labrigger.com/blog/2013/01/16/emccd-specs/
http://www.photonics.com/Article.aspx?AID=56742

As for the comparison with sCMOS, you will find that EMCCD cameras, with their larger pixels, higher quantum efficiency and negligible readout noise, are more sensitive than sCMOS in low-light imaging. The main advantage of using sCMOS cameras is the pixel readout speed. Most EMCCD cameras now read at approx. 20MHz pixel readout rate, which gives ~60 fps with a 512 x 512 camera. A sCMOS camera can reach 100 fps with a 2048 x 2048 sensor. However, the faster you image with a camera, the lower the exposure time, which means that you need more sensitivity to get quality images. That is why a lot of sCMOS users do not use the max. speed of their sCMOS camera while using binning, which decrease the spatial resolution of your sensor.

Feel free to contact me with any question you might have on the matter. I would be happy to discuss this in more details.

Regards,

Yoann Gosselin, B.Eng., M.A.Sc.
Ingénieur en applications
Applications Engineer
Nüvü Caméras Inc.
+1.514.733.8666, ext. 1019
nuvucameras.com

Venez nous rencontrer prochainement :: Meet us at an upcoming event:
Photonics West 2015, San Francisco, CA (USA) 2015.02 07-12

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