1stVision Inc. – Machine Vision Articles

Specifications

Round 1  – Saturation Capacity and Dynamic Range
Saturation capacity (aka well depth) is the amount of charge in electrons a pixel can hold, whereas dynamic range relates to the signal to noise of the temporal dark noise.  Comparing saturation capacity and dynamic range, the IMX250 knocks out the ICX625 in one punch.

 Although the pixel sizes are the same, the new CMOS pixel wells have a saturation capacity of ~ 10.3K electrons compared to 5.9K for the ICX625.  This contributes to increased dynamic range allowing images to not saturate quickly, allowing more dark and bright areas to be viewed.  

In general, the more electrons in the pixel well along with low noise provides better signal to noise ratios.  As shown in the graphic, we ideally want a lot of signal electrons vs the noise electrons.



Round 2 – Temporal Dark noise

Temporal dark noise also known as read noise is measured in electrons, in which a lower temporal dark noise provides better images.  This noise is produced within the sensor electronics and show up in the pixel well as unwanted noisy electrons.  The new IMX250 has incredibly low dark noise with only 2.3 electronics compared to the older IMX625 CCD having approximately 9 electrons.  The IMX250 clearly wins this round providing better fidelity!

Round 3 – Sensitivity & Quantum Efficiency

Sensitivity can be measured looking at the number of photons required to have a signal equal to the noise level.  A lower number of electronics are better indicating higher sensitivity.  Quantum efficiency measures the percentage of photons converted to electronics at a given wavelength.  In comparing the sensitivity thresholds, it takes ~ 4 electrons to gain a signal versus 22 comparing the IMX250 vs ICX625 making it much more sensitive.  Reviewing the quantum efficiency at 525nm, further supports this with a higher percentage of photons being converted on the new CMOS sensor with 76% vs 57%.  Its a knockout in round 3!

.. And the winner is… the Sony IMX250 CMOS sensor!  This comparison shows excellent gains in technology with this 5MP sensor!   If you are using the ICX625 sensor, the IMX250 is a drop in replacement allowing you to keep the optics, gain better performance and drop the price of your camera substantially!

Several camera manufacturers have the new Sony Pregius IMX250 5MP sensor in their lineup and more on the horizon.  Links to the current cameras as follows listed by interface. 

As a note, the IMX250 is the faster sensor vs its counterpart, the IMX264.  Both of these sensors have essentially the same performance, but speed and price are lower with the IMX264.  In many cases, you will see both sensors within a camera product line, but the IMX264 sensor will be at a lower price.

Cameras in the current lineup are as follows:  

USB3

IDS  UI-3080CP   – IMX250
IDS UI-3280CP – IMX264


GigE Vision

Teledyne Dalsa Nano 2450 – IMX250
Teledyne Dalsa Nano 2420 – IMX264

JAI GO-5100 – IMX250
JAI GO-5101 – IMX264

This is the second of our sensor battles!  See our comparison and learn how the Sony IMX174 (and its counterpart the IMX249) compare against a CMOSIS 2MP sensor!