68
2 Holographic Microscopy of Phase and Diffuse Objects …
structure and optical characteristics of nerve fibers study experiments [1–3, 5, 8, 9,
15]. These studies were carried out with the use of the specially developed and
mounted holographic microscope, the optical scheme of which is shown in Fig. 2.3b.
Such schemes provide in holographic microinterferometry more fringes per unit
object length than the schemes with lensless object holographing. Really, if two final
width fringes are produced by inclining a hologram under an angle α, then in the
scheme with preliminary increase within the reconstructed image area, period of
reference fringes T is determined by formula T =
λ
2
/ sin
α
2
, and in the scheme of
“lensless” registration with further increase T =
λ
2N
/ sin
α
2
, where N is the increase
of a microobjective.
2.1.2 Shortly About Coherent Noises in the Images
of Diffusive Microobjects—Speckles and the Ways
of Their Elimination
Small space resolution (10 μm), reached in [143, 144] during the microobject holographing, is connected with the fact that high space frequencies in its spectrum and
corresponding to small parts demand high efficiency of numerical aperture of the
recording system and its high resolving power. High coherent radiation scattered on
heterogeneous glasses, diaphragms edges, specks of dust and on the object leads to
the formation of speckles chaotic interference structure which deteriorates image
quality [145, 146]. To a large degree, the losses depend on the light scattering of
coherent radiation by a microobject. First of all, it covers diffusely scattered microobjects where we can observe radiation dispersion from their surfaces as well as by the
depth. Moreover, it is the result of the nonlinearity of the record and its own noises of
the recording media. And yet, in spite of the difficulties, emerged during the study of
microobjects, space resolution can be increased. For example, in [147], it is realized
using the scheme in colliding beams. Just one this methodological approach decreases
image speckle-pattern due to the reconstruction by white incoherent light source, on
the one hand, and on the other hand—due to the microobject recording in immediate
proximity from the photographic medium that corresponds to the hologram aperture
magnification.
Partial speckles suppression can be carried out by multiple exposure on the one
photoplate of the same object image, but with different speckle-pattern [148, 149]
at including into the light beam, which reconstructs a hologram, randomly moving
phase heterogeneity or during the hologram recording in the light of several wavelengths [150, 151]. The last one is of utmost interest, because at the same time,
it is possible to decide an issue about color rendering in the microobject image.
The authors [152] also showed the possibility of speckle-pattern decreasing in the
microobject reconstructed image by the way of hologram recording of the focused
image because such holograms make it possible to reconstruct their sources with
2 Holographic Microscopy of Phase and Diffuse Objects …
structure and optical characteristics of nerve fibers study experiments [1–3, 5, 8, 9,
15]. These studies were carried out with the use of the specially developed and
mounted holographic microscope, the optical scheme of which is shown in Fig. 2.3b.
Such schemes provide in holographic microinterferometry more fringes per unit
object length than the schemes with lensless object holographing. Really, if two final
width fringes are produced by inclining a hologram under an angle α, then in the
scheme with preliminary increase within the reconstructed image area, period of
reference fringes T is determined by formula T =
λ
2
/ sin
α
2
, and in the scheme of
“lensless” registration with further increase T =
λ
2N
/ sin
α
2
, where N is the increase
of a microobjective.
2.1.2 Shortly About Coherent Noises in the Images
of Diffusive Microobjects—Speckles and the Ways
of Their Elimination
Small space resolution (10 μm), reached in [143, 144] during the microobject holographing, is connected with the fact that high space frequencies in its spectrum and
corresponding to small parts demand high efficiency of numerical aperture of the
recording system and its high resolving power. High coherent radiation scattered on
heterogeneous glasses, diaphragms edges, specks of dust and on the object leads to
the formation of speckles chaotic interference structure which deteriorates image
quality [145, 146]. To a large degree, the losses depend on the light scattering of
coherent radiation by a microobject. First of all, it covers diffusely scattered microobjects where we can observe radiation dispersion from their surfaces as well as by the
depth. Moreover, it is the result of the nonlinearity of the record and its own noises of
the recording media. And yet, in spite of the difficulties, emerged during the study of
microobjects, space resolution can be increased. For example, in [147], it is realized
using the scheme in colliding beams. Just one this methodological approach decreases
image speckle-pattern due to the reconstruction by white incoherent light source, on
the one hand, and on the other hand—due to the microobject recording in immediate
proximity from the photographic medium that corresponds to the hologram aperture
magnification.
Partial speckles suppression can be carried out by multiple exposure on the one
photoplate of the same object image, but with different speckle-pattern [148, 149]
at including into the light beam, which reconstructs a hologram, randomly moving
phase heterogeneity or during the hologram recording in the light of several wavelengths [150, 151]. The last one is of utmost interest, because at the same time,
it is possible to decide an issue about color rendering in the microobject image.
The authors [152] also showed the possibility of speckle-pattern decreasing in the
microobject reconstructed image by the way of hologram recording of the focused
image because such holograms make it possible to reconstruct their sources with