ISPRS Commission III, Vol.34, Part 3A „Photogrammetric Computer Vision‘, Graz, 2002
THE RESOLUTION ENHANCEMENT BY
SOFTWARE METHOD OF RANDOM SHIFT
Tomas Ponik, Jaroslav Placek
FMFI UK, Bratislava
Abstract
The goal of the paper is to describe one
method of software resolution enhancement of records
obtained by CCD cameras or other devices able to
view and digitalize the image. The paper is divided
into two parts. The first one explains the theoretical
principle of the random shift method. The second part
is dedicated to application HimRes which tests these
method and creates resulti images with enhanced
resolution.
Keywords: CCD camera, linear properties of the
CCD camera, light-sensitive element, raster, center of
gravity
Used terms: pixel, object, record, random shift,
detection object, resulting image, actual pixel,
covering, overlap (definitions are explained bellow).
Introduction
The CCD camera is nowadays a well-known
devide used in many areas of science, development
and industry. It is cheap and easy to use. Analog CCD
cameras produce analog signal (PAL or NTSC) as the
output which has the resolution of 768x576 pixels.
This can be enough for simple image analysis but in
many cases user wants to see further, to see details and
other features in the image which is impossible with
the use of analog cameras. The digital CCD camera
with resolution up to 1280x1024 exists already but it's
price is 40 times higher than ordinary analog one.
There is a way to enhance the resolution of
camera image by snapping more pictures of the same
scene and computing the new image using suitable
features of these image series.
The explanation of used terms:
CCD camera — The device for viewing of the image.
CCD-elements — The elements of the CCD camera
sensitive to light intensity which are created by MOS
condensors or PN transitions.
Light-sensitive element (shortly element) — CCD-
element, which represents pixel in raster image.
Pixel — Two-dimensional image element, which has a
color. The definition of color is bellow.
Scene — The part of the real world viewed by te CCD
camera or other device able to record the image.
Object — The part of the scene.
Record - Scene viewed by the CCD camera and
digitalized to 2D space. Every record is with respect to
other obtained records shifted, resp. rotated in the
image plane.
Random shift — Informations of record positions in
choosed coordinate system are not contained in the
input data. The record capture is performed by random
shift of the CCD camera, resp. of the viewed object.
Detection object — The circle or other geometric solid
invariant to the operation of rotation which is used by
determination the relative position of the record with
respect to other records.
Image with compressed sampling (shortly resulting
image) — Raster image with higher pixel density as on
the records.
Actual pixel in resulting image (shortly actual pixel) —
Actually processed pixel in resulting image.
The pixel color — Integer value representing the
illuminance recorded by the image element. During
creation of resulting image the domain for these
values is the set of real numbers between 0 and 255.
The cover of actual pixel by the record pixels parts —
Parts of the record pixels cover actual pixel if and only
if the actual pixel surface is created by the unification
of these parts (Figure 1).
Overlap of actual pixel by the record pixels — Record
pixels overlap the actual pixel if and only if their parts
cover actual pixel (Figure 1).
pixel
Figure 1 Cover and overlap of actual pixel
The coordinate system of image plane (shortly
Choosed coordinate system) —The two-dimensional
cartesian coordinate system is used in this paper. It is
oriented according to the first captured record (Figure
2). The coordinate axis are parallel to record rows and
columns. The center of the coordinate system is placed
in the intersection of first row and first column of
record.
For easier explanation only grayscale images
are considered with black color evaluated as 255 and
white color as 0. In the next explanation the resolution
enhancement of factor two is considered.
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