D. Numerical Evaluation of Longitudinal Magnification
In order to prove the real magnification of a 3-D object,
we made a numerical evaluation of longitudinal or depth
magnification. We use a 3-D II technique that computationally
reconstructs the 3-D scene as a 3-D volumetric image
[26]–[28]. Image display planes are computed for arbitrary distances
from the lenslet array by back propagating the elemental
images through a virtual pinhole array. The computation and
reconstruction is based on ray optics.
Three volumetric reconstructions were obtained for original,
optical magnified and digital magnified elemental image arrays.
Fig. 10 shows the reconstructed image planes for the button with
a footprint on it and button with a peace mark on it. This results
show that the magnification changes the location of the plane of
the reconstruction times far from the lenslet compared with
original reconstruction, where is the magnification factor.
The calculated depth for the original objects was 8.5 mm as
show in Fig. 10(a). In Fig. 10(b) the reconstructed planes for
optical magnified objects has a depth of 17 mm, this means that
the longitudinal magnification is equal to the lateral magnification.
Digital magnification has a depth equal to 17 mm similar
to optical magnification, as is shown in Fig. 10(c).
This numerical evaluation proves the true 3-D magnification
for both optical and digital methods. It means that lateral magnification
and longitudinal magnification has the same factor.
Also we appreciate the similarity between optical and digital
magnification techniques.
E. 3-D Optical Reconstructed Integral Image
Experimental reconstruction results are shown in Fig. 11.
Fig. 11(a) is a 3-D reconstructed integral image without magnification.
Fig. 11(b) is the 3-D reconstructed integral image
magnified by the OM method. Fig. 11(c) is a digital magnified
3-D reconstructed integral image.
Magnification is proved by visual comparison between original
reconstruction and both magnified reconstructions. Visual
appearance of magnified reconstruction are clear, it means the
elemental images have almost accurate direction information.
This similarity proves the same behavior of DM compared with
optical magnification.
V. CONCLUSIONS AND REMARKS
In this paper, we proposed a simple digital magnification
method applied to 3-D integral imaging using interpolation
principles. When we use a digital magnification method in
integral imaging, adjacent elemental images are used for calculation
of new middle elemental images. The new elemental
images are generated by average and replication of information
of the neighbor elemental images.
In this simple algorithm the direction information is related
with the calculation of which defines the information in the
elemental image to be average or replicate. Consequently, when
we used a digital magnification method with direction information,
we can magnify small objects without lens movement and
quality degradation of the reconstructed 3-D integral images.
However, using a digital magnification method alone to magnify
the object increases error rate of elemental images in proportion
to the magnification factor. Therefore we can propose
the use of optical magnification in a first step following by a
digital magnification method in order to obtain higher magni-
fication factors and attain a good quality image with less complexity