Page 369 - Fundamentals of Light Microscopy and Electronic Imaging

352 GLOSSARY

with a mouse over the image. The ability to define an ROI is useful during image pro-
cessing, and when saving a part of an image as a new image. 269
Relative error. The reciprocal of the signal-to-noise ratio and therefore the ratio of the
noise to the signal. 302
Relative retardation. In polarization optics, the relative shift in phase between two
waves expressed in fractions of a wavelength. 127, 139
Relay lens. An intermediate magnifying lens in an imaging system placed between the
objective and the real intermediate image. In video, so-called TV lenses increase the
magnification of the image projected on the camera 2- to 8-fold. 246
Resolving power. See Spatial resolution.
Retardation plate or retarder. In polarization optics, a birefringent plate positioned
between the polarizer and analyzer that introduces a relative retardation between the
O and E rays in addition to that produced by a birefringent object to change image
contrast or render path differences in color. When used in a device to measure the
amount of relative retardation in the object, the plate is called a compensator. See
also Compensator. 136, 139
RGB. Red, green, and blue. A mode of color image display that is based on the red-
green-blue tricolor stimulus system for the visual perception of color. Commonly
used in television, computer monitors, and other image display devices. 313
Rod cell photoreceptors. Retinal cells located outside the fovea and in the periphery of
the retina responsible for vision in dim light. Rod cell vision, or scotopic or night
vision, is absent of color. 23
ROI. See Region of interest.
RS-170 broadcast format. The format used for signal generation and display in com-
mercial television broadcasting, based on the 2:1 interlace of two raster fields pro-
ducing an image frame of 485 display lines at a rate of 30 frames/s. 236
RS-330 broadcast format. A variant of the RS-170 format frequently used for closed-
circuit television, differing in how raster lines are encoded, synchronized, and dis-
played on the monitor. The format is based on the 2:1 interlace of two raster fields
producing an image frame of 485 display lines at a rate of 30 frames/s. 236
Scotopic vision. Night vision based on rod cell photoreceptors. See Rod cell photo-
receptors. 23
Serial register. In CCD cameras, a single row of pixels that receives charge packets
from all of the adjacent columns of pixels in the parallel register. The serial register
transmits the charge packets pixel by pixel to the on-chip preamplifier and analogue-
to-digital converter until the register is emptied. 262
Shade-off. In phase contrast microscopy, the gradient in light intensity that is
observed from the edge to the center of extended phase objects of uniform thick-
ness and refractive index. In central regions of uniform objects where diffraction is
minimal, the corresponding amplitude in the image can approach that of the back-
ground. 109
Shading correction. In video microscopy, the electronic controls of an in-line digital
image processor that are used to remove light gradients across the image field, such
as those arising from uneven illumination. 241
Shear axis. In DIC microscopy, the axis of displacement of the O and E rays caused by
the DIC prisms. In a DIC image, the axis is identified as the line connecting the
bright and dark shaded edges of refractile objects. 159
Short-pass filter. A colored-glass or interference filter that transmits (passes) short
wavelengths and blocks long ones. 37