Page 352 - Fundamentals of Light Microscopy and Electronic Imaging

GLOSSARY 335

wave could be viewed end-on, the movement of the E vector would appear to trace
the form of a circle. 131
CLSM. See Confocal laser scanning microscope (CLSM).
CMYK. A popular format for color printing, whereby colors are reproduced using four
different inks: cyan, magenta, yellow, and black. 313
Coherent light. A beam of light defined by waves vibrating in the same phase, although
not necessarily in the same plane of vibration. To maintain the same phase over long
distances, coherent waves must be monochromatic (have the same wavelength).
Laser light is monochromatic, linearly polarized, and highly coherent. 20, 82
Collector lens. A focusable lens of the illuminator capable of collecting light over a
wide area and directing it toward the specimen. In Koehler illumination, the collec-
tor lens is used to focus a magnified real image of the filament or arc of the bulb in
the front aperture of the condenser. 7
Collimated beam. A beam in which rays proceed in the same direction and follow tra-
jectories that are parallel to one another. Collimated light need not be monochro-
matic, polarized, or coherent. 20
Colored-glass filter. A slab of glass containing colloids or metals that absorb certain
wavelengths while freely transmitting others. In microscopy, colored-glass filters are
commonly employed in fluorescence filter sets and as effective blockers of UV and
IR light. 39
Coma. An off-axis aberration of lenses, whereby rays from an off-axis point passing
through the edge of the lens are focused closer to the optic axis than are rays that pass
through the center of the lens, causing a point object to look like a comet with the tail
extending toward the periphery of the field. Coma is the most prominent off-axis
aberration. For lenses having the same focal length, coma is greater for lenses with
wider apertures. 52
Compensator. In polarization microscopy, a birefringent slab that is positioned
between the polarizer and analyzer and can be tilted or rotated. This action varies
the optical path difference between the O and E rays emergent from a birefringent
object and is performed to make quantitative measurements of relative O and E wave
retardations, or for qualitative purposes in changing image contrast and brightness.
136, 140
Composite view or projection view. In confocal microscopy, an image created by
adding together multiple optical sections acquired along the z-axis. The images of
three-dimensional objects, although blurry in conventional wide-field fluorescence
mode, are often remarkably clear in confocal composite view. 213
Compound light microscope. An optical instrument that forms a magnified image of
an object through a two-step series of magnifications: The objective forms a magni-
fied real image of the object, and the eyepiece forms a magnified virtual image of the
real image made by the objective. This basic design forms the basis of all modern
light microscopes. 1
Condenser annulus. In phase contrast and dark-field microscopy, a transparent annu-
lus in an opaque black disk located in the front aperture of the condenser that serves
as the source for illuminating the specimen. 103
Condenser lens. A lens assembly located near the specimen and specimen stage that
collects light from the illuminator and focuses it on the specimen. Proper optical per-
formance requires that the condenser be highly corrected to minimize chromatic and
spherical aberration. 2, 56
Cone cell photoreceptors. Retinal cells responsible for color vision and visual acuity.
See also Fovea. 24