Reflection density

In some situations measurement of the reflected, rather than the transmitted, radiation may be made to assess the amount of radiation that has been absorbed by the sample. There are two main ways by which radiation might be reflected. Specular reflection is similar to the reflection by a mirror and, for quantitative work, the angles of the incident and the reflected radiation are important. Diffuse reflection is from within the layers of the material and the reflected light is disbursed over a range of 180°. This type of reflection is measured in the thin films used in dry chemistry systems. The term reflectance density is often used, which is defined in a manner comparable to absorbance the logarithm of the ratio of incident to reflected light. 

Z)r = reflection density (similar to the optical density in conventional photometry),... 

P = proportional to the reciprocal absorption. Dr = reflection density of the blank. 

Fig. 5. Reflection density D as a function of the glucose concentration in the multilayer film. Dr represents the density of reflection before and Dt after application of the Williams-Clapper function.

R = measured reflection) is the ratio of the reflected light /r of the sample to the incident light /q. The reflection density... 

Since the reflection density Dr does not have a linear relation to the transmission density Dj, Beer-Lambert s law does not exactly represent the conditions of reflection. 

For this reason Williams and Clapper developed a mathematical equation on the basis of a simple physical model, describing the relation between the reflection density Dr and the transmission density Dj. Practice, however, has shown that for a more exact description empirical reflection curves must be measured. From these empirical curves the transformed reflection density g(Dn) can be obtained. This transformation is effected from a multitude of comparisons with patient samples (the concentration of which should be distributed over the entire range of measurement) by means of wet chemistry methods. 

Dl = primary reflection density (1st wavelength), t = time (minutes),... 

Characterization. Optical reflection densities on the final image were measured with a Macbeth model 914 filter densitometer. Photographic sensitivities were estimated from the threshold intensity values in relative units corresponding to the shoulder and toe regions on the D-log 1 curves. 

In isotropic systems and at isotropic perturbations such as temperature and pressure changes, the term 55 only reflects density (volume) changes. 

X-Rite 3 1 OTR) and evaluated as the degree of remaining dye. The reflective density is measured at 3 points. 

Electrical conductivity, thermal conductivity, color/absorbance Refractive index, reflectance Density/speciflc gravity Damping, creep and relaxation, dielectric constant Coefficient of expansion... 

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