OptdAvrg, OptdI, OptdSD

Menu:   Measure > Parameters

Script:   SelectParam ("OptdAvrg", "OptdI","OptdSD")

Select these parameters to compute the optical density of the objects. The optical density determines the relative amount of matter in a material by measuring the amount of light that passes through it. At a given point of the image the optical density is defined by the inverse logarithm formula that assumes an exponential decay of light inside the material:

,

where is the gray value of the current pixel and is the average background intensity which is equivalent to the intensity of the incident light.

The average background intensity is established during the Background correction procedure that should be performed prior to the optical density measurements. If no background correction was done, the maximum intensity value for the current image type is used in calculations. If the image is of the floating point type, the non-corrected background is assigned the value of 1.

The gray values of pixels can optionally be scaled by using the Intensity calibration in order to compensate for the non-linearity of the imaging tract.

OptdAvrg returns the average optical density within the object.

, where N is number of pixels within the object

OptdI returns the integral optical density within the object:



The integral optical density is frequently used as a measure of the amount of the matter contained within the object.


OptdSD returns the standard deviation of the transmission within the object:



In the Field Measurements the parameters are calculated for the whole phase rather than for separate objects.

Note – because optical density measures the amount of light passing through a material, these measurements are meaningful only in the analysis of images that have been captured with the light source radiating from behind th