( s of the field-of-view. 51 52 ...)A new wide field-of-view confocal imaging system and its applications in drug discovery and pathology

In an F*Theta lens, the image height is H = F * Θ, where F is its focal length, and Θ is the scan angle, i.e., the angle formed by the incoming beam with the Z-axis of the scan lens. An F*Theta lens focuses the collimated beam entering with an angle Θ with respect to the optical axis at a distance F * Θ from the optical axis. The scanner moves at a uniform angular velocity. For the pixel positions to be uniformly spaced across a flat slide, it is necessary that the image height be proportional to the scan angle.^{51, 53} The F * Θ property makes it possible to scan the focused spot with constant linear velocity; and a constant data acquisition rate results in equally spaced measurements on the specimen. An F*Theta lens makes the image data acquisition process easier, because the pixel rate can be synchronized with the angular velocity of the scanning mirror. In an ordinary microscope objective, the pixel position is F * tanΘ. If the scan angle is small enough, as it usually is in a confocal microscope with a small field-of-view, then F * tanΘ ≈ F * Θ, so it approximates an F*Theta lens.

2.2. Excitation/Illumination Optics

The optical schematic of the wide field-of-view confocal instrument is shown in Fig. 1. Three solid state lasers, a red laser with a wavelength of 635 nm, a green laser of 535 nm, and a blue laser of 488 nm with an output power of approximately 25 mW each are used as the light sources. The lasers are used as excitation sources for fluorescence imaging, and illumination sources in reflectance and brightfield imaging. Each of the laser beams passes through a spatial filter composed of two positive lenses and a pinhole to filter out high spatial frequency components from the laser source. The spatial filters also operate as beam
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