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| 07 May 2008 04:52:04 |
| kyori |
| About CMOS Sensors SNR estimation |
Hi, I wonder how to calculate the Signal-to-Noise Ratio with the datasheet of a CMOS sensor? I calculate the total excited photons (Signal_N) from the irradiance, conversion gain and quantum efficiency. But, I am confused with the noise estimation. The datasheet gives, Parameter Specification Remarks FPN <3% RMS <10% p/p PRNU 2% RMS Half saturation Conversion gain 16uV/electron Output amplitude 1V Unity gain. Saturation charge 62.500e- Temporal noise 45e- S/N ratio 1330=60000:45=62dB Parasitic light sensitivity <0.5% Here, I just estimate the noise like bellow, Shot noise, sqrt(Signal_N) Temporal noise, 45 Thus, Noise_N = sqrt(Signal_N + 45^2), and the SNR is given by, SNR = 20log10(Signal_N / Noise_N) Is it correct? And furthermore, what confused me most is the meaning of FPN in the datasheet, and what does "<3%RMS" mean here? Shoud I consider the FPN in the noise estimation? And, how? Any help would be appreciated! Best regards, Chen |
| 07 May 2008 05:00:09 |
| Helpful person |
| Re: About CMOS Sensors SNR estimation |
On May 7, 7:52=A0am, kyori <ggky...@gmail.com > wrote: > Hi, > > I wonder how to calculate the Signal-to-Noise Ratio with the datasheet > of a CMOS sensor? > > I calculate the total excited photons (Signal_N) from the irradiance, > conversion gain and quantum efficiency. > > But, I am confused with the noise estimation. > > The datasheet gives, > > Parameter =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 Specification =A0 =A0 = =A0 =A0Remarks > FPN =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0<3% RMS =A0= =A0 =A0 =A0 =A0 <10% p/p > PRNU =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A02% RMS =A0 =A0= =A0 =A0 =A0 =A0 Half saturation > Conversion gain =A0 =A0 =A0 =A0 =A0 =A0 =A016uV/electron > Output amplitude =A0 =A0 =A0 =A0 =A0 =A0 1V =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0Unity gain. > Saturation charge =A0 =A0 =A0 =A0 =A0 =A0 62.500e- > Temporal noise =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 45e- > S/N ratio =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A01330=3D60000:= 45=3D62dB > Parasitic light sensitivity =A0 =A0<0.5% > > Here, I just estimate the noise like bellow, > Shot noise, sqrt(Signal_N) > Temporal noise, 45 > > Thus, Noise_N =3D sqrt(Signal_N + 45^2), > and the SNR is given by, > > SNR =3D 20log10(Signal_N / Noise_N) > > Is it correct? > > And furthermore, what confused me most is the meaning of FPN in the > datasheet, and what does "<3%RMS" mean here? > > Shoud I consider the FPN in the noise estimation? And, how? > > Any help would be appreciated! > > Best regards, > > Chen I suggest you obtain the CMOS detector and measure it yourself. Trying to get accurate values from a data sheet is not too reliable. The true value is dependent on your application. |
| 07 May 2008 08:32:29 |
| Phil Hobbs |
| Re: About CMOS Sensors SNR estimation |
Helpful person wrote: > On May 7, 7:52 am, kyori <ggky...@gmail.com> wrote: >> Hi, >> >> I wonder how to calculate the Signal-to-Noise Ratio with the datasheet >> of a CMOS sensor? >> >> I calculate the total excited photons (Signal_N) from the irradiance, >> conversion gain and quantum efficiency. >> >> But, I am confused with the noise estimation. >> >> The datasheet gives, >> >> Parameter Specification Remarks >> FPN <3% RMS <10% p/p >> PRNU 2% RMS Half saturation >> Conversion gain 16uV/electron >> Output amplitude 1V Unity gain. >> Saturation charge 62.500e- >> Temporal noise 45e- >> S/N ratio 1330=60000:45=62dB >> Parasitic light sensitivity <0.5% >> >> Here, I just estimate the noise like bellow, >> Shot noise, sqrt(Signal_N) >> Temporal noise, 45 >> >> Thus, Noise_N = sqrt(Signal_N + 45^2), >> and the SNR is given by, >> >> SNR = 20log10(Signal_N / Noise_N) >> >> Is it correct? >> >> And furthermore, what confused me most is the meaning of FPN in the >> datasheet, and what does "<3%RMS" mean here? >> >> Shoud I consider the FPN in the noise estimation? And, how? >> >> Any help would be appreciated! >> >> Best regards, >> >> Chen > > I suggest you obtain the CMOS detector and measure it yourself. > Trying to get accurate values from a data sheet is not too reliable. > The true value is dependent on your application. FPN is 'fixed-pattern noise'. CMOS sensors have an amplifier per pixel, whereas CCDs have an amplifier per output. Each amplifier has its own gain and offset variation, so a uniformly-illuminated sensor produces a nonuniform output. (With narrowband illumination, especially laser light, there are nasty etalon fringes that form in the microlenses on top of the sensor chip as well.) For applications where this is a problem, you need to apply gain and offset corrections pixel-by-pixel. This isn't especially difficult on the software side--it's mainly getting the test illumination really uniform that causes the worries. Image sensor data sheets are famous for being useless--if you're designing cell phone cameras, the manufacturer will talk to you, but it's harder otherwise. Cheers, Phil Hobbs |
| 07 May 2008 05:36:04 |
| kyori |
| Re: About CMOS Sensors SNR estimation |
On 5=D4=C27=C8=D5, =CF=C2=CE=E78=CA=B100=B7=D6, Helpful person <rrl...@yahoo= .com > wrote: > On May 7, 7:52 am, kyori <ggky...@gmail.com> wrote: > > > > > > > Hi, > > > I wonder how to calculate the Signal-to-Noise Ratio with the datasheet > > of a CMOS sensor? > > > I calculate the total excited photons (Signal_N) from the irradiance, > > conversion gain and quantum efficiency. > > > But, I am confused with the noise estimation. > > > The datasheet gives, > > > Parameter Specification Remarks > > FPN <3% RMS <10% p/p > > PRNU 2% RMS Half saturation > > Conversion gain 16uV/electron > > Output amplitude 1V Unity gain. > > Saturation charge 62.500e- > > Temporal noise 45e- > > S/N ratio 1330=3D60000:45=3D62dB > > Parasitic light sensitivity <0.5% > > > Here, I just estimate the noise like bellow, > > Shot noise, sqrt(Signal_N) > > Temporal noise, 45 > > > Thus, Noise_N =3D sqrt(Signal_N + 45^2), > > and the SNR is given by, > > > SNR =3D 20log10(Signal_N / Noise_N) > > > Is it correct? > > > And furthermore, what confused me most is the meaning of FPN in the > > datasheet, and what does "<3%RMS" mean here? > > > Shoud I consider the FPN in the noise estimation? And, how? > > > Any help would be appreciated! > > > Best regards, > > > Chen > > I suggest you obtain the CMOS detector and measure it yourself. > Trying to get accurate values from a data sheet is not too reliable. > The true value is dependent on your application.- =D2=FE=B2=D8=B1=BB=D2=FD= =D3=C3=CE=C4=D7=D6 - > > - =CF=D4=CA=BE=D2=FD=D3=C3=B5=C4=CE=C4=D7=D6 - Hi, Thanks, But I have no such CMOS sensor available by hand.. |
| 07 May 2008 06:13:46 |
| kyori |
| Re: About CMOS Sensors SNR estimation |
On 5=D4=C27=C8=D5, =CF=C2=CE=E78=CA=B132=B7=D6, Phil Hobbs <pcdhSpamMeSensel= ...@pergamos.net > wrote: > Helpful person wrote: > > On May 7, 7:52 am, kyori <ggky...@gmail.com> wrote: > >> Hi, > > >> I wonder how to calculate the Signal-to-Noise Ratio with the datasheet > >> of a CMOS sensor? > > >> I calculate the total excited photons (Signal_N) from the irradiance, > >> conversion gain and quantum efficiency. > > >> But, I am confused with the noise estimation. > > >> The datasheet gives, > > >> Parameter Specification Remarks > >> FPN <3% RMS <10% p/p > >> PRNU 2% RMS Half saturation > >> Conversion gain 16uV/electron > >> Output amplitude 1V Unity gain. > >> Saturation charge 62.500e- > >> Temporal noise 45e- > >> S/N ratio 1330=3D60000:45=3D62dB > >> Parasitic light sensitivity <0.5% > > >> Here, I just estimate the noise like bellow, > >> Shot noise, sqrt(Signal_N) > >> Temporal noise, 45 > > >> Thus, Noise_N =3D sqrt(Signal_N + 45^2), > >> and the SNR is given by, > > >> SNR =3D 20log10(Signal_N / Noise_N) > > >> Is it correct? > > >> And furthermore, what confused me most is the meaning of FPN in the > >> datasheet, and what does "<3%RMS" mean here? > > >> Shoud I consider the FPN in the noise estimation? And, how? > > >> Any help would be appreciated! > > >> Best regards, > > >> Chen > > > I suggest you obtain the CMOS detector and measure it yourself. > > Trying to get accurate values from a data sheet is not too reliable. > > The true value is dependent on your application. > > FPN is 'fixed-pattern noise'. CMOS sensors have an amplifier per pixel, > whereas CCDs have an amplifier per output. Each amplifier has its own > gain and offset variation, so a uniformly-illuminated sensor produces a > nonuniform output. (With narrowband illumination, especially laser > light, there are nasty etalon fringes that form in the microlenses on > top of the sensor chip as well.) > > For applications where this is a problem, you need to apply gain and > offset corrections pixel-by-pixel. This isn't especially difficult on > the software side--it's mainly getting the test illumination really > uniform that causes the worries. > > Image sensor data sheets are famous for being useless--if you're > designing cell phone cameras, the manufacturer will talk to you, but > it's harder otherwise. > > Cheers, > > Phil Hobbs- =D2=FE=B2=D8=B1=BB=D2=FD=D3=C3=CE=C4=D7=D6 - > > - =CF=D4=CA=BE=D2=FD=D3=C3=B5=C4=CE=C4=D7=D6 - On 5=D4=C27=C8=D5, =CF=C2=CE=E78=CA=B132=B7=D6, Phil Hobbs <pcdhSpamMeSensel= ...@pergamos.net > wrote: > Helpful person wrote: > > On May 7, 7:52 am, kyori <ggky...@gmail.com> wrote: > >> Hi, > > >> I wonder how to calculate the Signal-to-Noise Ratio with the datasheet > >> of a CMOS sensor? > > >> I calculate the total excited photons (Signal_N) from the irradiance, > >> conversion gain and quantum efficiency. > > >> But, I am confused with the noise estimation. > > >> The datasheet gives, > > >> Parameter Specification Remarks > >> FPN <3% RMS <10% p/p > >> PRNU 2% RMS Half saturation > >> Conversion gain 16uV/electron > >> Output amplitude 1V Unity gain. > >> Saturation charge 62.500e- > >> Temporal noise 45e- > >> S/N ratio 1330=3D60000:45=3D62dB > >> Parasitic light sensitivity <0.5% > > >> Here, I just estimate the noise like bellow, > >> Shot noise, sqrt(Signal_N) > >> Temporal noise, 45 > > >> Thus, Noise_N =3D sqrt(Signal_N + 45^2), > >> and the SNR is given by, > > >> SNR =3D 20log10(Signal_N / Noise_N) > > >> Is it correct? > > >> And furthermore, what confused me most is the meaning of FPN in the > >> datasheet, and what does "<3%RMS" mean here? > > >> Shoud I consider the FPN in the noise estimation? And, how? > > >> Any help would be appreciated! > > >> Best regards, > > >> Chen > > > I suggest you obtain the CMOS detector and measure it yourself. > > Trying to get accurate values from a data sheet is not too reliable. > > The true value is dependent on your application. > > FPN is 'fixed-pattern noise'. CMOS sensors have an amplifier per pixel, > whereas CCDs have an amplifier per output. Each amplifier has its own > gain and offset variation, so a uniformly-illuminated sensor produces a > nonuniform output. (With narrowband illumination, especially laser > light, there are nasty etalon fringes that form in the microlenses on > top of the sensor chip as well.) > > For applications where this is a problem, you need to apply gain and > offset corrections pixel-by-pixel. This isn't especially difficult on > the software side--it's mainly getting the test illumination really > uniform that causes the worries. > > Image sensor data sheets are famous for being useless--if you're > designing cell phone cameras, the manufacturer will talk to you, but > it's harder otherwise. > > Cheers, > > Phil Hobbs- =D2=FE=B2=D8=B1=BB=D2=FD=D3=C3=CE=C4=D7=D6 - > > - =CF=D4=CA=BE=D2=FD=D3=C3=B5=C4=CE=C4=D7=D6 - Hi Hobbs, Thanks for your reply. Do you have any idea the average FPN would be how many e-? The sensor here is Cypress LUPA-1300, It is a high speed CMOS sensor, and I may use it in low illuminace conditions. I donnt know if I get any signal while the photons excited is below certain value. Best regards, Chen |
| 07 May 2008 06:26:12 |
| Helpful person |
| Re: About CMOS Sensors SNR estimation |
On May 7, 8:32=A0am, Phil Hobbs > > FPN is 'fixed-pattern noise'. =A0CMOS sensors have an amplifier per pixel,= > whereas CCDs have an amplifier per output. =A0Each amplifier has its own > gain and offset variation, so a uniformly-illuminated sensor produces a > nonuniform output. =A0(With narrowband illumination, especially laser > light, there are nasty etalon fringes that form in the microlenses on > top of the sensor chip as well.) > > For applications where this is =A0a problem, you need to apply gain and > offset corrections pixel-by-pixel. =A0This isn't especially difficult on > the software side--it's mainly getting the test illumination really > uniform that causes the worries. > > Image sensor data sheets are famous for being useless--if you're > designing cell phone cameras, the manufacturer will talk to you, but > it's harder otherwise. > > Cheers, > > Phil Hobbs- Hide quoted text - > > - Show quoted text - Some manufactureers will actually supply a map of the "noise" pixel by pixel. However, as this is a function of illumination (different gains in different pixels as you pointed out) it is difficult to use. In addition schott (quantum) noise can become significant. It's a fairly involved calculation / experiment to determine the CMOS (or CCD) true performance. I'm still in the learning stage myself. |
| 07 May 2008 10:22:39 |
| Bob Knowlden |
| Re: About CMOS Sensors SNR estimation |
I wonder how our friends at Schott would feel about having their name applied to shot noise. ;-) Return address scrambled. Replace nkbob with bobkn. Top posting - a way of life. "Helpful person" <rrllff@yahoo.com > wrote in message news:447c889b-57e3-46a5-a2ff-fdf35c942007@c65g2000hsa.googlegroups.com... (snip) In addition schott (quantum) noise can become significant. (snip) |
| 07 May 2008 08:05:00 |
| Helpful person |
| Re: About CMOS Sensors SNR estimation |
On May 7, 10:22=A0am, "Bob Knowlden" <nk...@comcast.net > wrote: > I wonder how our friends at Schott would feel about having their name > applied to shot noise. ;-) > > Return address scrambled. Replace nkbob with bobkn. > > Top posting - a way of life. > > "Helpful person" <rrl...@yahoo.com> wrote in message > > news:447c889b-57e3-46a5-a2ff-fdf35c942007@c65g2000hsa.googlegroups.com... > > (snip) > > In addition schott (quantum) noise can become significant. > > (snip) Slip of the brain! However, trying to get information out of Schott regarding the future supply of optical glasses is not possible. In a few short years (for me) they have gone from the supplier of choice to the supplier that I avoid like the plague. |
| 09 May 2008 03:19:33 |
| Phil Hobbs |
| Re: About CMOS Sensors SNR estimation |
kyori wrote: > > Do you have any idea the average FPN would be how many e-? > > The sensor here is Cypress LUPA-1300, > > It is a high speed CMOS sensor, and I may use it in low illuminace > conditions. > > I donnt know if I get any signal while the photons excited is below > certain value. > > Best regards, > > Chen Fixed pattern noise is multiplicative, so it's a more or less fixed fraction of the signal. FPN of 1% on a 1000-electron signal is 10 electrons, but with 60,000 electrons it's 600. Cheers, Phil Hobbs |