Wednesday, March 02, 2016

Sony Introduces SNR1s Performance Index

Sony introduces SNR1s [lx] as an index used to quantitatively evaluate picture quality at low illumination. SNR1s [lx] is a proprietary index advocated by Sony, and is limited to CMOS image sensors for security camera applications. A smaller value indicates better picture quality at low illumination. SNR1s [lx] is an acronym consisting of "SNR" (Signal-to-Noise Ratio), "1" (represents that the signal level when noise = 1 is 1), and "s" (for Security).


SNR1s measurement:


Two 3200 [K] light sources illuminate an 18% gray chart from different directions, and dimming is performed to 100 [lx]. A camera is placed so that the distance from the gray chart to the imaging surface of the image sensor is 1 m, the sensitivity [e-] and dark noise [e-] are measured, and SNR1s [lx] is calculated using the relational equation (1). The luminance when equation (1) equals 1 is SNR1s [lx].


SNR1s Values of Sony CMOS Sensors for Security Applications:

8 comments:

  1. Does this mean that a Sony CMOS sensor with an SNR1S of 0.13 lx at 10 Lux illumination will have a similar image quality to a sensor with an SNR1S of 1.3 lx at 100 Lux illumination, all other factors being equal?

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    Replies
    1. As I understood it: You can not compare the two values. It is amout of the light when the noise and signal level is 1:1.

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  2. Interesting basis to compare these sensors for astronomy applications.
    But only the visible part of spectrum is used (Ir-cut filter in front of sensor).
    What would be 'cool' is to have 2 indexes : one for visible wavelength
    and one for Infrared. Both are very usefull.

    Best Regards.

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  3. A simple NEI measurement for green light would be a very objective way to compare the sensors in my opinion.

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  4. With a 3200K light source, the results will be sensitive to the detailed spec of the "IR cut filter". A 700 nm shortpass filter would be quite different from a scotopic response filter, for example.

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  5. There are 3 factors that would change from setup to setup:
    1. 18% grey patch should be calibrated as paper printed patch reflectance changes with time and amount of light exposure over lifetime.
    2. Camera lens transmittance, there are lens with 0.8 transmittance and there are ones close to 0.95.
    3. IR-cut filter characteristics, ex. transmittance vs. wavelength. As gentlemen above rightfully mentioned.

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  6. ... and since heavy mention is made to "security" application, it would not even be uncommon to use IR-cut filter with a hole around 850nm ...

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  7. "dimming is performed to 100 [lx]"
    Does this mean the illumination is fixed to 100 lx. Then, how is the SNR1s measured. Just calculation?
    Can anyone please give some light.

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