Tomographic imaging system with scanning apertures

A tomographic imaging system works with a conventional real image formed by, e.g., a lens. Scanning is over an image formation area of the image plane. A plurality of differently-oriented scanning apertures are disposed over the surface of a spinning element (disk or rotor drum). A detector is located behind the image plane for creating a signal proportional to light passing through the scanning apertures, which sweep over the image. The apertures are swept through the image plane in a first direction by the spinning of the disk or drum; they are simultaneously swept in a second direction, also lying in the image plane, that is perpendicular to the first direction, by appropriate mechanical mechanism. The simultaneous sweeps allow signal processing means to reconstruct from the detector signal a scanned image by using conventional tomographic algorithms. The device may include a variable-diameter aperture and means for moving the aperture over the image formation area; this acts as a "zoom".

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is in the field of electronic imaging devices, 
specifically devices where the imaging effect is generated by mechanical 
scanning. 
2. Description of the Related Art 
Imaging devices of the kind with which the invention is concerned are 
applicable to detectors sensitive to any part of the spectrum, such as 
light, X-rays, sound and others. 
In the following description and claims the term "detectors" is used for an 
electronic device which converts waves into electrical signals; 
"mozaic detector" is used to describe a two dimensional detector built from 
a plurality of smaller detector arranged in rows and columns; 
"reconstructive tomography" is used to describe the mathematical process 
that combines data from multiple scanning apertures to generate images of 
a scanned area; and 
"zooming" is used to describe the effect where a small part of an image is 
magnified and displayed with the resolution originally used for the whole 
image. 
Prior art imaging devices are based upon two major technologies. 
One well known technique is using a mozaic detector as a sensitive element 
that converts light images into electronic signals and presents images to 
the user in a video format, as in a modern television. 
The second technology is employed whenever mozaic detectors are technically 
impossible because of system complexity. This second technology employs 
single detectors, sensitive to a part of the spectrum range, in 
conjunction with a scanning mirror element that scans the image on the 
detector surface the detector generates electronic signals according to 
the part of the image lying on the detector surface at a specific moment. 
Special electronic circuitory is then used to transform the stream of 
signal into a video format. 
On the other hand, non-imaging devices known as beam profilers are in use 
for measuring laser beams. Those devices use a precision blade that moves 
across a beam blocking light from reaching a photodetector element mounted 
behind the knife. For additional information, multiple knife edges each 
oriented in an different angle on a rotating drum move across a beam in a 
different direction as the drum rotates. Consequently during a rotation a 
set of data profiles is generated each representing the intensity profile 
in that direction. 
This technique provides a way to generate a topographic and three 
dimensional low resolution intensity distribution of the incoming beam 
using reconstructive tomography. 
Such a measuring device is disclosed in Melles Griot (company headquarters 
in California U.S.A.) catalog chapter 4. The catalog title is "Lasers and 
Instrumentation Guide." Other non imaging devices for beam profilers are 
disclosed in some Japanese patent applications, such as applications 
1983-222404 and 60-7327. A technical review of that issue is presented in 
an article by John M. Fleisher and C. Breck Hitz under the title of 
"Gaussian Beam Profiling: How and Why" published in Lasers & Optronics in 
May 87. 
The above-described devices are not applicable for imaging purposes because 
of their low resolution and small number of possible scans. Moreover, 
prior art technologies have great difficulties in zooming into an area of 
interest. This zooming effect is usually performed by optical special 
lenses or optical magnification. 
It is the object of the present invention to provide an imaging system 
based on reconstructive tomography capable of detecting and creating an 
image and sensitive broad spectrum of different wavelengths implementing a 
non-optical, novel zooming mechanism superior to prior art devices. 
SUMMARY OF THE INVENTION 
In accordance with the preset invention there is provided an imaging device 
where the image is produced by reconstructive tomography. In a preferred 
embodiment, the invention includes an imaging creating element, such as a 
lens, and an image formation area. 
The imaging device of the present invention generates the image by 
mechanically scanning a set of apertures through the image formation area. 
The set of apertures, usually rectangular, are oriented at different 
angles in respect with each other. The scanning action is performed in 
front of a detector in two direction and in a plane parallel to the 
detector. 
The tomographic imaging device preferably has: 
a detecting means sensitive to incoming signals; 
an image formation area where an image is created and which lies in front 
of the detecting means; 
a set of differently oriented scanning apertures that scan the image 
formation area; 
scanning means that scan the set of apertures in two directions; 
processing means that receive signals from the detector and reconstruct the 
image by means of reconstructive tomography or other mathematical 
processes. 
According to a first embodiment, the system includes a rotating drum 
equipped with a plurality of slit apertures. The drum rotates in front of 
a detector which measures the amount of radiation that passes through the 
slit. The rotating drum has a large diameter compared to the image 
formation area, consequently its rotation in front of the detector 
generates a substantially linear motion parallel to the detector surface 
and scanning through the image formation area. 
Each slit generates a different pattern as it passes through the detector. 
In addition, for achieving the required resolution the system is equipped 
with a second motor that further rotates the rotating drum in a 
perpendicular direction to the first rotation. The additional motor 
provided the rotary motion to the rotating drum detector assembly by being 
directly keyed to said assembly or by a mechanical reduction. 
Consequently the first preferred embodiment is a tomographic imaging device 
where the scanning of said set of apertures is performed by: 
a rotating drum, in the perimeter of which a set of differently oriented 
apertures are mounted; 
motor means keyed to said rotating drum; 
detector means deployed after the drum; 
image formation area scanned by the drum & apertures assembly; 
second motor means perpendicularly keyed to the first motor drum assembly 
to provide a second rotational motion perpendicular to first rotational 
motion. 
Each drum rotation provides a set of different patterns according to the 
number of mounted slits on the drum, when the second motor rotates the 
assembly of the drum detector another set of different pattern is 
generated. 
The overall number of different patterns generated by the system is the 
number of slits mounted on the drum multiplied by the number of different 
positions generated by the second motor. 
The signals generated by the detector are digitized and processed by a 
processor means that mathematically combines the information to 
reconstruct the scanned image by reconstructive tomography. 
According to a further embodiment, a controlling aperture is disposed at 
the image formation area. This controlling aperture down-controls the size 
of the image formation area causing the scanning apertures to scan an area 
which is substantially smaller than the size of the original image 
formation area. Since the number of scans remains unchanged the 
reconstructed image will have the size of the controlling aperture with 
the same effective number of scans. Consequently, a smaller area with the 
same resolution will be displayed, thus creating the required zooming 
effect. 
By varying the size of the controlling aperture a varying zooming effect is 
achieved. Consequently, the zooming tomographic device of the above 
embodiment includes: 
the combination of the embodiment already disclosed with a controlling 
aperture mounted at the image formation plane; 
means for scaling up and down the size of the controlling aperture in the 
image formation plane. 
Another preferred embodiment further includes different means for scanning 
the set of apertures in two directions: 
rotating disk on the front surface of which the set of differently oriented 
apertures are mounted; 
motor means keyed to the rotation disk; 
second motor means parallel keyed to the first motor disk assembly to 
provide a second rotation substantially parallel to first rotation and 
concentric with the image formation area; 
detecting means parallel to the image formation area.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 a prior art imaging device is disclosed, where the detecting 
element is a mozaic detector. 
The object 101 is imaged by a lens element 102 onto a mozaic detector 103 
which transforms the image into electronic signals. 
In FIG. 2 a different prior art imaging device is disclosed in a schematic 
way, where the image is created by scanning the object on a single 
detector by mirror means. 
The object 201 is first imaged by lens means, 202, then reflected by a 
scanning mirror 204 to be imaged on a single detector 203. 
The detector is substantially smaller than the required image and the 
scanning action of mirror 204 is to scan across the detector surface the 
required image and the scanning action of mirror 204 is to scan across the 
detector surface the required image. 
Referring to FIG. No. 3 there is shown a tomographic imaging device 
according to the present invention where the image is formatted at plane 
301 by some optical means L. The image plane is scanned by a set of 
rectangular apertures, denoted 302, each oriented at a different angle 
with respect to each other at the perimeter of a rotating drum 303 which 
rotates by motor means 309 around axis 304. 
The scanning apertures allow only a part of the electromagnetic radiation 
at the image plane to penetrate through the apertures and reach a detector 
305. 
The rotating drum detector assembly is further keyed to a second motor 
(306) rotating the system around an axis (denoted 307) which is 
substantially perpendicular to axis 304 and substantially concentric to, 
perpendicular to and centered on, the image plane. The said second motor 
oscillates the drum assembly through a limited angle to generate an 
additional set of scanning directions allowing multiple scans to be taken. 
The overall scanning direction of the system are given by the formula 
N=m.times.n, where N is the total number of scanning directions, m is the 
number of apertures on the rotating drum, and n is the number of different 
positions of the second motor 306. 
Signal processor and display means 310 receives the signals from the 
detector 305. 
FIG. 4 is a graphic illustration of the image formation area showing that 
by scanning the image formation area with differently oriented rectangular 
apertures denoted as 401 passing through the image formation plane (402) a 
set of different signals (403) will be generated. Each signal is a 
function of aperture orientation, the scanned image, and the scanning 
speed. Feeding the signals 403 to a processor means (not shown) and using 
reconstructive tomography the said original image 402 is reconstructed. 
Referring to FIG. 5, there is shown a tomographic imaging device where the 
image is formatted at plane 501 by some optical lens (not shown.) The 
image plane is scanned by a set of apertures 502 each oriented at a 
different angle with each other. 
The scanning apertures are mounted on the surface of a disk 503, the plane 
of which rotates within the image formation plane. The disk rotation is 
achieved by an additional motor means 504 keyed to the disk. 
The rotating motor disk assembly is further keyed to an additional motor 
505 which is substantially parallel to the first motor and rotates the 
disk assembly around an axis 506, which is substantial concentric to 
perpendicular to and centered on, the image formation area. 
According to a further embodiment, the motor is keyed to rotating elements 
through mechanical reduction means, such as gear box 509. 
FIG. 6 there is shown a tomographic imaging device where the image 
formation plane is equipped with a variable controlling aperture 601 that 
down-controls the image formation area. By moving the controlling to 
different areas on said image formation plane along directions denoted 
602, 603 the controlling aperture is disposed anywhere in the image 
formation are allowing zooming of any part of image formation area. 
The foregoing description of the specific embodiments will so fully reveal 
the general nature of the invention that others can, by applying current 
knowledge, readily modify and/or adapt for various applications such 
specific embodiments without undue experimentation and without departing 
from the generic concept, and, therefore, such adaptations and 
modifications should and are intended to be comprehended within the 
meaning and range of equivalents of the disclosed embodiments. The means 
and materials for carrying out various disclosed functions may take a 
variety of alternative forms without departing from the invention. It is 
to be understood that the phraseology or terminology employed herein is 
for the purpose of description and not of limitation.