Changing spectra

When analyzing spectral data in Breeze, you can choose between different spectral modes: Absorbance, Reflectance, or Radiance. The preferred mode often depends on the user's experience or the specific analysis being conducted.

To switch between these modes, navigate to the Analysis Tree and select the Measurement node.

In the pane to the right, find the option labeled Convert to where you can choose among the following modes: Radiance, Reflectance, Absorbance or None.

Breeze can work with hyperspectral data in different formats, and convert between them in visualizations and in the analysis tree. There are four modes: None (raw values), Reflectance, Absorbance or Radiance.

None - Raw values

The Raw intensity values from the camera sensor is used without any dark- or white reference adjustments.

The range of the signal varies between different cameras depending on the underlying data type: A RGB camera might have values from 0-255 (byte) while a hyperspectral camera has 0-65535 (short int).

Breeze always use float to store data, and to perform calculations.

Reflectance

Reflectance represents the relative reflectance of the target and is calculated using the raw values of the captured signal, a dark reference image, and a white reference image.

where

• is the raw intensity values from the camera sensor

• is the dark reference image associated with the image. This is used to remove background noise and correct for sensor offsets in the spectral or spatial dimensions.

• is the white reference image associated with the image. This is used to take illumination and sensor sensitivity into account.

The Dark and White references for a measurement is stored together with the raw data in Breeze. Learn more about Dark and White References .

Absorbance

Absorbance represents the pseudo-absorbance of the image and is calculated from on the reflectance. This is useful for analyzing absorption characteristics of a material.

Radiance

Radiance measures the light energy emitted or reflected by a target, taking into account both intensity and direction across different wavelengths. Radiance provides detailed spectral information useful for understanding the material properties and composition of the observed target.

It is calculated by adjusting the captured light intensity for factors such as integration time and sensor gain to quantify the energy received by the sensor. Radiance is expressed in units of power per unit area per unit solid angle (W/m²/sr).

where

• is the raw intensity values from the camera sensor

• is the dark reference image associated with the image. This is used to remove background noise and correct for sensor offsets in the spectral or spatial dimensions.

• : A gain factor that amplifies the signal, compensating for low light conditions.

• Integration Time : The amount of time the sensor is exposed to light, affecting the intensity of the signal.