ChemiMOS: 16-bit Image Modes

ChemiMOS has a market-leading dynamic range with a native full well capacity of over 50k e- and a read noise of less than 1.3 e-. However, these can not be addressed at the same time. Atik Cameras have a number of options to allow both the lowest level of detection and the highest maximum pixel well to be captured in one image output.

Our combined shot modes allow the best of both worlds to capture two images and quantifiably combine them to produce a single resultant image with an improved dynamic range.

Combined Shot Mode – Gain

2.5x Dynamic Range Improvement

Two exposures are captured, one at the gain state with the highest full well and one
with the gain giving the lowest read noise. These are then combined in an intelligent
manner to give a linearly responding image with a greatly improved dynamic range.
This mode will double the time taken to acquire an image but gives an optimum trade
off between the length of acquisition and the resultant image.

Combined Shot Mode – Exposure

4x Dynamic Range Improvement

Two exposures are captured with the exposure time set being used to capture the
shorter exposure and then a second exposure of four times the length captured and
combined to increase dynamic range in the darker areas of the scene. This lowers
the effective lowest level of detection by 4x whilst not saturating the brightest objects
in the scene at the cost of taking 5x the exposure time to capture the final image.

Combined Shot Mode – Gain & Exposure

 

10x Dynamic Range Improvement

By combining both gain and exposure we can maximise the use of the 14 bit ADC
of ChemiMOS to capture in image with 4x the exposure in the lowest intensities, at
the lowest read noise whilst still not saturating the brightest points. This will have the
same acquisition length as Combined Shot – Exposure (5x the exposure time) but has
an even further improved dynamic range due to the lowering of the read noise in the
lowest light levels.

Stretch Mode

 

ChemiMOS captures data using a 14 bit ADC and converted into a 16 bit dataset.
Using this mode images are consistently displayed in a 16 bit dataset without
requiring the need to rescale between 14 bits and 16 bit.

Binning Mode

With a CMOS camera, binning is often only possible after reading out. This means that
adding the pixels together multiplies the full well capacity by the number of pixels but
only increasing the read noise by the root of the sum of the squares (a much smaller
proportion).

For a 2×2 bin, the read noise will go up by a factor of two but the full well capacity will
go up by a factor of four. Therefore the increase in dynamic range is beneficial to several applications where a larger pixel is usable. ChemiMOS can bin these pixels
into a 16-bit image meaning that the increased dynamic range can be accessed.