Technical Cameras

Signal-to-Noise Ratios (SNRs) for Resonon Hyperspectral Cameras

By Dr. Rand Swanson, CEO - December 12, 2023

The Signal-to-Noise Ratio (SNR) is a commonly used metric when one is evaluating the performance of a hyperspectral camera.

Our previous post covered the different variables at play, some common approximations made, and the different means available to change the SNR of hyperspectral data.

This post covers the modeled SNRs for each of Resonon’s Hyperspectral Cameras. In the plots that follow, the SNRs are determined for each spectral channel of the camera, resulting in an SNR plot that is a function of wavelength.

In these data, the hyperspectral cameras are modeled as sampling the signal from a solar-illuminated, perfectly diffuse (i.e. Lambertian) object with 100% reflectivity, resulting in the spectral radiance profile shown in Figure 1. The integration time used in the modeling (the inverse of which represents the maximum frame rate) and any default spectral binning are provided for each camera. The integration time for each camera is chosen such that the strongest channel is at approximately 90% of the pixel full-well depth.

Figure 1: Spectral radiance as a function of wavelength from a solar-illuminated Lambertian surface with 100% reflectivity.

Pika UV

Figure 2: SNR for the Pika UV with an integration time of 21.7 milliseconds and default spectral binning of 4.

The falloff of SNR for the Pika UV observed at short wavelengths is largely due to the weak solar illumination at these wavelengths.

Pika L

Figure 3: SNR for the Pika L with an integration time of 18.5 milliseconds and default spectral binning of 2.

The SNR profile of the Pika L is similar to the solar spectrum. A weak detector response at longer wavelengths contributes to small SNRs at these wavelengths.

Pika L-F

Figure 4: SNR for the Pika L-F with an integration time of 11.6 milliseconds and default spectral binning of 2.

The SNR profile of the Pika L-F is very similar to that of the Pika L.

Pika XC2

Figure 5: SNR for the Pika XC2 with an integration time of 19.25 milliseconds and default spectral binning of 2.

Like the Pika L, above, the SNR profile of the Pika XC2 is similar to the solar spectrum. This camera also has a weak detector response at longer wavelengths.

Pika IR and Pika IR-L

The Pika IR and the Pika IR-L use the same detector. While they do not use the same exact gratings, the SNR vs. wavelength for the two cameras is almost identical. As such, they are both represented by the following plot.

Figure 6: SNR for the Pika IR and the Pika IR-L with an integration time of 5.32 milliseconds and no binning.

The strong spectral features in the Pika IR and Pika IR-L SNR plot are due to the shape of the solar spectrum in this wavelength range.

Pika IR+ and Pika IR-L+

The Pika IR+ and the Pika IR-L+ use the same detector. Like the Pika IR and Pika IR-L, these two cameras do not use the same exact gratings, but the SNR vs. wavelength for the two cameras is effectively the same. As such, they are both represented by the following plot.

Figure 7: SNR for the Pika IR+ [LINK] and Pika IR-L+ [LINK] with an integration time of 19.3 milliseconds and no binning.

Like the Pika IR and Pika IR-L above, the strong spectral features in this SNR plot are due to the shape of the solar spectrum in this wavelength range.

SUMMARY

As has been shown, the peak SNR value of a hyperspectral camera does not tell the whole story. The spectral response of your application, the spectral radiance of your illumination source, and the specific hyperspectral camera and framerate you are using all determine the SNR of your collected data.

We hope that by providing you the SNR plots for each of our hyperspectral cameras, we are enabling you to make a more informed purchasing decision.

To learn more about modeling SNR in hyperspectral cameras, please see this post.

To explore all of the specifications of each of our hyperspectral imagers, please visit our cameras page.

Finally, if you have any questions about what you’ve read or if you’d like us to scan some of your samples for you to see the actual data output, please contact our Sales Team.