Spectral Imaging: Methods, Design, and Applications - Biomedical Optical Imaging Technologies: Design and Applications - page 122

Fig. 4.3 Principle design of infinity-corrected optics for a spectral imaging system. Lens L1
transmits a collimated beam while lens L2 focuses the image on the image plane. If the spectral
dispersion element is mounted in the collimated beam, and if it does not deflect the beams in a
wavelength-dependent manner, it will form an adequate image. The optical axis and principal rays
from two spots on the object are shown
Fig. 4.4 Methods that compromise spectral or spatial resolution in favor of speed to acquire
complete information simultaneously. a A device for splitting up to four colors on the same CCD.
The spectral range of each band can be selected with adequate filters. b A three-layered array
sensors, each measuring different basic colors. A similar technology also uses a combination of
three CCD cameras and a set of dichroic filters that split each basic color to a different array
sensor. c A typical CCD or CMOS chip of array sensors. Each unit of the array sensor is defined
from four smaller pixels; two are measuring the green and the other two the blue and red . Here, the
spatial information is compromised (50% of the green and 75% of the blue and red )
molecules becomes smaller, thereby leading to energy transfer from the CFP to the
YFP. Therefore, when measuring the intensity of these two fluorescent molecules at
each pixel, one can find the areas in the cell that are rich with Ca 2C . An important
advantage of this method is the ability to select the exact spectral range for each of
the images that are being measured. The measurement is rather fast, limited only by
the frame rate of the CCD and the required exposure time that provides good-enough
signal-to-noise ratio.
Other methods for measuring such a color image can be implied through a
simultaneous measurement with three CCD or CMOS. Figure 4.4 bshowsan
example of such a method using three layers of sensors array, each one measuring
a different wavelength. Such a sensor was developed some time ago [ 11 ]andis
available commercially (Foveon Inc., Santa Clara, CA). Another similar technique