The lateral extension of the dCV (ddCV) (estimated from the typical size of the speckle in the objective pupil (dspeckle) by ddCV ≈1.22 λfobj/dspeckle [ 27, 28], where fobj is the focal length of the objective) increases monotonically and seems to saturate at large depths (Fig. 5(c), FOV 1000 µm and Fig. 5(d), FOV 530 µm).
Because the focal length of an objective decreases as the N.A. and magnifying power increase, the working distance, or distance from the front of the objective to the top of the slide, is shorter for higher-power objectives.
The magnification, sometimes referred to as magnifying power, is determined by dividing the focal length of the objective by the focal length of the eyepiece.
The focal length of the objective is inversely proportional to the magnification and, in the majority of modern microscopes, equals the tube length (usually 160 mm [6.3 inches]) divided by the magnification.
The angular resolution of a telescope is equal to the angle subtended by the least resolvable image separation at the focal length of the objective, the light-gathering lens.
In the beam-pointing modulation, δ z) is expressed by where δ0 is the maximum displacement of the focal spot and fOB is the focal length of the objective lens.
The effective focal length of the objective lens is 1.8 mm, which corresponds to an F/# of 6, the full FOV is 70°, and the image diameter is 2.2 mm.
As shown in previous theoretical work, larger or smaller ranges, and correspondingly higher or lower resolutions, may be obtained by changing the focal length of the objective lens [ 13].
The theoretical lateral resolution (4λf/πD) given by the beam diameter D = 10 mm, focal length of the objective f = 40 mm and wavelength λ = 1.275 µm is 6.5 µm.
D e = f o b j f r e l a y × D r e l a y (2 where f obj is the effective focal length of the objective lens, when the FOV is 70þ, f obj = 1.3/tan 35þ) = 1.85mm; f relay is the effective focal length of the relay lenses, and f relay = 1.3/tan(θ t) = 16.09 mm as shown in Fig. 2 ; D relay is the pupil diameter of the relay lenses, and its maximum value is 2.6 for a 4mm endoscope.
In the equation, fo refers to the focal length of the objective lens and fe to the focal length of the eyepiece lens.
