sCMOS Cameras For Low Light Microscope Applications

sCMOS Is A Break Through Technology

Tucsen 3.0Mp sCMOS Camera

For the last couple decades we have relied on CCD technology to provide us with scientific grade digital cameras capable of low light, high resolution, image capture.  But the problem with CCD technology has always been the trade off between dynamic range and speed.  In order to keep the pixel readout noise low, the pixel charge had to be sampled slowly.  So as the pixel array size of CCD cameras increased, the frame rates had to drop to maintain a usable dynamic range.  Even a relatively small 1 megapixel CCD could not be readout at frame rates greater than 10-15 per second, without suffering a loss of dynamic range.  At which point, there isn't much reason to suffer the expense of a 12-bit or 16-bit ADC design.

But the introduction of  Scientific CMOS (sCMOS)  technology has been a game changer.  For decades conventional CMOS imagers wer viewed as CCDs poor ugly brother.  Incapable of matching the image quality of CCD, it was relegated to usage in cheaper devices.  The one thing CMOS had going for it was that the design favored standard semiconductor fabrication techniques so they could be cranked out cheaply along side other semiconductor devices.  CCD technology, on the other hand, required a completely different production setup which made them far more expensive to fabricate.

But sCMOS designs have advanced performance features that renders it suitable for applications requiring superior fidelity and quantitative scientific imaging.  sCMOS cameras stand apart in their ability to deliver on several key performance parameters simultaneously, thereby overcoming the 'trade-offs' inherent in CCD technology, and eliminating performance drawbacks traditionally associated with conventional CMOS imagers.

Consider these performance specifications for one of the initial sCMOS designs;

Sensor format: 5.5 megapixels (2560(h) x 2160(v))
Read noise: < 2 e- rms @ 30 frames/s; < 3 e- rms @ 100 frames/s
Maximum frame rate: 100 frames/s
Pixel size: 6.5 μm
Dynamic range: > 16,000:1 (@ 30 frames/s)
QE_max: 60% (with excellent red/NIR response)
Read out modes: Rolling and Global shutter (user selectable) 

What this means for low light microscopy is that high quality, low light, low noise, images can be captured in real time with cameras that cost a fraction of CCD sensor based cameras.

The images below are excerpted from the white paper 'sCMOS Scientific Imaging Technology', produced by the sCMOS consortium of Andor Technology, PCO Imaging, and Fairchild Imaging, the group that developed the new technology.

Using an array of blue LEDs and controlling the brightness, they measured the noise floor and dynamic range of  sCMOS and CCD imagers for comparison.  Intensity profiles were plotted through the LED images at varying intensity levels.

With a readout noise of just 1.5 electrons, compared to 5 electrons for CCD, the sCMOS imager provides clearly superior images with lower noise floors.

(Image Copyright, sCMOS)

In this next image, a microscope resolution target was back illuminated at minimal intensities and captured by both sCMOS and CCD imagers.  Again, you can clearly see the superior image quality and higher contrast produced by the sCMOS imager compared to CCD.

(Image Copyright, sCMOS)

 
In this final image, low light fluorescence microscopy images are compared under conditions typical of those employed in dynamic live cell imaging.  In this test neutral density optical filters were used on a wide field fluorescence microscope to reduce fluorescence intensities relative to the noise floor of the imagers.  A 5.5 megapixel sCMOS imager captured images at 70 frames/sec and along side it 1.3  megapixel CCD imager running at it's maximum frame rate of just 11 frames/sec.  Even at the much higher frame rates, notice the superiod signal-to-noise and contrast delivered by the sCMOS imager compared to the smaller, and slower, CCD imager.

(Image Copyright, sCMOS)

With the introduction of sCMOS cameras, It is no longer necessary to spend thousands of dollars for digital video cameras capable of low noise, high speed, and high resolution imaging.  Certainly additional gains can be had by super cooling the sCMOS imagers, just as with CCD imagers.  However, for many applications this is simply not necessary.

Tucsen Imaging has recently introduced their first line of sCMOS based USB2.0 cameras.  They are available in 12-bit monochrome, or 36-bit color, and in 1.3 Megapixel or 3.0 Megapixel models with prices starting at just $600, and includes a full software suite of tools for Mac, Windows, or Linux.

For more information on this technology visit http://www.scmos.com/. Or to purchase Tucsen sCMOS cameras visit http://www.industrialcamerasales.com.