Page 38 - Fundamentals of Light Microscopy and Electronic Imaging

PROPERTIES OF LIGHT PERCEIVED BY THE EYE 21

Monochromatic Polychromatic

Linearly polarized Nonpolarized

Coherent Noncoherent

Collimated Divergent

Figure 2-5
Eight waveforms depicting variations in the quality of light.

fraction), or even scattered by small particles and structures having dimensions similar
to the wavelength of light itself (also known as diffraction). The diffraction of light by
small structural elements in a specimen is the principal process governing image forma-
tion in the light microscope.

PROPERTIES OF LIGHT PERCEIVED BY THE EYE

The eye-brain system perceives differences in light intensity and wavelength (color),
but does not see differences in the phase of light or its state of polarization. Thus, laser
light, which is both coherent and polarized, cannot be distinguished from random light
having the same wavelength (color). We will restrict our discussion here to the percep-
tion of light intensity, since the perception of color is treated separately in the follow-
ing section.