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United States Patent |
3,935,383 |
Newitt |
January 27, 1976 |
Storage of a representation of an image
Abstract
A television camera which scans an image provides a camera video signal
having an amplitude representative of light received from an element of
the image being scanned. Prior to a scan a sync pulse is generated which
increments a raster counter. Accordingly, the roster counter provides a
signal representation of a cumulative number of scans of the image. During
the scanning, clock pulses increment a horizontal deflection counter which
provides a signal representation of a horizontal deflection number
corresponding to the horizontal coordinate of the line of sight. When the
cumulative number of scans equals the horizontal deflection number, a
comparator provides a gating signal which causes a sample and hold circuit
to store a sampled video signal having an amplitude equal to the amplitude
of the camera video signal. The sampled video signal is provided to the
input of an analog to digital converter for conversion to digital signals
which may be stored in a digital computer. A succession of sampled video
signals is representative of the image when the cumulative number of scans
exceeds a maximum horizontal deflection number.
Inventors:
Newitt; John H. (123 Puritan Lane, Sudbury, MA 01776)|
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Appl. No.: |
490035 |
Filed: |
July 19, 1974 |
Current U.S. Class: |
348/108 |
Intern'l Class: |
H04N 005/38 |
Field of Search: |
178/DIG. 28,7.2,6.8 340/173 LT,173 CR
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References Cited [Referenced By]
U.S. Patent Documents
| 3621130 | Nov., 1971 | Paine | 178/7. |
| 3715489 | Feb., 1973 | Brown et al. | 178/6. |
| 3718757 | Feb., 1973 | Gulitz et al. | 178/6. |
| 3740466 | Jun., 1973 | Marshall et al. | 178/6. |
Primary Examiner: Griffin Robert L.
Assistant Examiner: Saffian; Mitchell
Claims
Having thus described a typical embodiment of my invention, that which I
claim as new and desire to secure by Letters Patent of the United States
is:
1. In apparatus for providing groups of digital signals respectively
representative of elements of an image on an image bearing medium being
scanned by a video generator which generates a video signal having an
amplitude representative of an element being scanned, said scanning being
in response to deflection signals provided to said generator by a
deflection circuit which stores digital signals representative of a
coordinate of the location of said element being scanned, the improvement
comprising:
a raster counter connected to said deflection circuit for providing count
signals representative of a number of times said generator scans said
image;
comparison means connected to said deflection circuit and to said raster
counter for providing a gating signal when said count signals have a known
relationship to said coordinate;
storage means connected to said comparison means and said generator for
storing the video signal representative of said element being scanned when
said gating signal is provided; and
an analog to digital converter having an input connected to said storage
means, said converter providing a group of said digital signals in
response to the video signal representative of said element being scanned.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to data processing and more particularly to storing
signals representative of an image.
2. Description of the Prior Art
Recently there has been a plethora of scientific activity directed to
processing an input image to provide, for example, a processed image which
is comprised of desired features of the input image. A signal
representation of the input image may be stored in a digital computer
which provides a signal representation of the processed image. The input
image is usually provided on an image bearing medium, such as a film.
When a television camera scans an image, an array of closely spaced
parellel lines, known as a raster, may be regarded as being successively
traced on the film by a line of sight therefrom to the camera. The camera
provides a video signal having an amplitude representative of an element
of the input image on the film at an intersection thereof with the line of
sight. The video signal is provided to an analog to digital converter
which is connected to the computer.
In response to the video signal, the converter provides a group of digital
signals collectively representative of the amplitude of the video signal.
Accordingly, the video signal is converted to digital signals whereby a
signal representation of the element is provided to the computer for
storage therein.
A digital signal may have one of two values, referred to as ONE and ZERO,
respectively. ONE is typically represented by approximately five volts
whereas ZERO is typically represented by approximately zero volts. It
should be appreciated that the digital computer can only store digital
signals (not video signals).
It should be understood that the video signal is one of a multiplicity of
video signals provided by the camera during the tracing of the raster. The
multiplicity of video signals are respectively representative of
substantially all elements comprising the input image. Each one of the
multiplicity of video signals is converted to a group of digital signals
by the converter whereby the computer stores groups of digital signals
representative of the input image.
Typically, the multiplicity of video signals is provided to a television
monitor display. In response to the multiplicity of video signals the
monitor display provides a visual representation of the input image.
In commercial television, it is a standard practice to trace in one
sixtieth of a second a raster comprised of raster lines which are each
traced in 53 microseconds. It is usually desirable to provide a display
representative of at least 450 elements along a raster line. To
successively provide groups of digital signals respectively representative
of the 450 elements along a standard raster line, the converter operates
rapidly. The rapid operation causes the converter to be complex, expensive
and unreliable.
When the raster is traced at a rate slower than one sixtieth of a second,
the converter operates at a correspondingly slower rate. However, the
visual representation (on the monitor display) may appear to flicker.
SUMMARY OF THE INVENTION
An object of the present invention is to represent an image with digital
signals which may be stored in a computer.
Another object of the present invention is to represent an image with
digital signals which may be stored in a computer and concurrently provide
a visual representation of the image which does not appear to flicker.
Another object of the present invention is to provide digital signals
representative of elements of an image scanned by a television camera in
accordance with standard television practice, the logic signals being of a
type which may be stored in a computer.
According to the present invention, when a video generator scans an image,
input video signals are provided which are representative of respective
elements of said image along a line thereof; in response to said input
video signals, a network provides for a desired duration a sampled video
signal representative of a selected element; when a known number of
rasters are traced, sampled video signals are provided which are
representative of said image.
The invention may be utilized to provide a sampled video signal during a
time greater than the time for the tracing of a raster line in accordance
with standard television practice, where the sampled video signal is
representative of an element of an image. Sampled video signals
respectively representative of elements of the image are thereby provided
at a rate suitable for conversion to groups of digital signals which may
be stored in a computer.
Other objects, features and advantages of the present invention will become
more apparent in the light of the following detailed description of a
preferred embodiment thereof as illustrated in the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic block diagram of a preferred embodiment of the
present invention;
FIG. 2 is a timing diagram of waveforms, all on a common time base, of
signals associated with a horizontal deflection of a line of sight in the
embodiment of FIG. 1; and
FIG. 3 is a timing diagram of waveforms, all on a common time base, of
signals associated with a vertical deflection of the line of sight in the
embodiment of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, a television camera 20 has an optical input 22
which receives light along a line of sight 24 from an element of an image
on a film 26. When the camera 20 scans the image the line of sight 24 may
be regarded as being deflected to trace rasters on the film 26 whereby the
camera 20 provides a video signal representative of an element on a raster
line being scanned.
For illustrative purposes, and in order to enable the teaching of the
principles of the invention without unduly complicating the details
thereof, in an exemplary embodiment disclosed herein, a raster is
comprised of sixteen raster lines. As explained hereinafter, an image is
represented by ten elements thereof along each raster line.
In accordance with the invention, groups of digital signals respectively
representative of one element along each raster line are successively
provided to a computer during a first scan of the image. Groups of digital
signals respectively representative of another element along each line are
successively provided during a second scan of the image. In a similar
manner, digital signals representative of eight other elements on each
raster line are provided to the computer during successive scans of the
image.
The camera 20 scans the image in response to horizontal and vertical
deflection voltages provided to a horizontal input 28 and to a vertical
input 30, respectively, of the camera 20. The input 28 is connected to the
output of a horizontal deflection aplifier 32 through a signal line 32a.
The input 30 is connected to the output of a vertical deflection amplifier
34 through a signal line 34a. The amplifiers 32, 34 have inputs connected
to a sync pulse generator 36 through signal lines 38, 40, respectively.
The generator 36 provides sync pulses which cause the amplifiers 32, 34 to
provide the deflection voltages referred to hereinbefore. The sync pulses
and the deflection voltages are described hereinafter.
The generator 36 includes a clock pulse source 42 which alternately
provides ONEs and ZEROs at a clock rate. ONE provided by the clock 42 is
referred to as a clock pulse. The clock 42 is connected to a horizontal
deflection counter 44 at an input thereof whereby clock pulses are
provided to the counter 44. Clock pulse sources are well known in the art.
The counter 44 stores logic signals representative of a horizontal
deflection number (referred to as a stored horizontal deflection number)
which is within a range, 0-10. When the stored horizontal deflection
number is within a range, 0-9, the number, one, is added thereto in
response to a clock pulse. However, the stored horizontal deflection
number, ten, is changed to the stored horizontal deflection number, zero,
in response to a clock pulse.
A horizontal sync pulse output 45 of the counter 44 provides ONE when the
stored horizontal deflection number is ten, ZERO being provided when the
stored horizontal deflection number is in the range, 0 - 9. The provision
of ONE by the output 45 is referred to as a horizontal sync pulse. It
should be understood that horizontal sync pulses are provided at a
constant horizontal sync rate because the clock pulses are provided at the
clock rate.
The output 45 is connected to the amplifier 32 through the line 38 whereby
the horizontal sync pulses are provided to the amplifier 32.
Referring now to FIG. 2, illustration (a) is a representation of clock
pulses 100 - 110 which cause the counter 44 to the store signal
representations of the horizontal deflection numbers, 0 - 10,
respectively. Illustration (b) includes a representation of a horizontal
sync pulse 46 which occurs in response to the clock pulse 110.
FIG. 2, illustration (c) is a representation of the horizontal deflection
voltage having a trace portion 48 which is initiated in response to a
trailing edge 50 of the pulse 46 (illustration (b) ). In this embodiment,
the trailing edge 50 occurs when the stored horizontal deflection number
changes from ten to zero.
The portion 48 is terminated in response to a leading edge 52 of a
horizontal sync pulse which occurs after the pulse 46. In this embodiment,
the leading edge 52 occurs when the stored horizontal deflection number
changes from nine to ten.
The portion 48 is a linearly increasing voltage which causes the line of
sight 24 (FIG. 1) to be deflected from the left side to the right side of
the film 26 at a constant horizontal deflection rate. Because the clock
pulses are provided at the clock rate, and the horizontal deflection of
the line of sight 24 is at the horizontal deflection rate, the stored
horizontal deflection number corresponds to the horizontal coordinate of a
location of an element intersected by the line of sight 24. Therefore, the
horizontal deflection numbers collectively represent horizontal
coordinates of locations of elements which are successively intersected by
the line of sight 24.
When the stored horizontal deflection number is ten, a retrace portion 54
of the horizontal deflection voltage causes a rapid deflection of the line
of sight 24 from right to left across the film 26 whereby the line of
sight 24 is conditioned to start a trace of a raster line.
The output 45 is additionally connected to a counter 56 at an input thereof
through the line 38 whereby the horizontal sync pulses are provided to the
counter 56.
The counter 56 stores a logic signal representation of a vertical
deflection number (referred to as a stored vertical deflection number)
which is within a range, 0-16. When the stored vertical deflection number
is within a range, 0-15, the number, one, is added thereto in response to
a horizontal sync pulse. However, the stored vertical deflection number,
sixteen, is changed to the stored vertical deflection number, zero, in
response to a horizontal sync pulse.
A vertical sync pulse output 57 of the counter 56 provides ONE when the
stored vertical deflection number is sixteen, ZERO being provided when the
stored vertical deflection number is in the range, 0-15. The provision of
ONE by the output 57 is referred to as a vertical sync pulse. It should be
understood that vertical sync pulses are provided at a constant rate
because the horizontal sync pulses are provided at the constant horizontal
sync rate.
The output 57 is connected to the amplifier 34 through the line 40 whereby
the vertical sync pulses are provided to the amplifier 34. As explained
hereinafter, a vertical sync pulse is provided prior to the tracing of a
raster.
Referring now to FIG. 3, illustration (a) is a representation of horizontal
sync pulses 200 - 216 which cause the counter 56 to store the signal
representations of the vertical deflection numbers, 0 - 16, respectively.
Illustration (b) includes a representation of a vertical sync pulse 58
which occurs in response to the horizontal sync pulse 216.
FIG. 3, illustration (c) is a representation of the vertical deflection
voltage where a trace portion 60 is initiated in response to a trailing
edge 62 of the pulse 58 (FIG. 3, illustration (b) ). The trailing edge 62
is concurrent with the counters 44, 56 providing signal representations of
horizontal and vertical deflection numbers which change from ten to zero
and sixteen to zero, respectively.
The portion 60 is terminated in response to a leading edge 64 of a vertical
sync pulse which occurs after the pulse 58.
The portion 60 is a linearly increasing voltage which causes the line of
sight 24 (FIG. 1) to be deflected from the top to the bottom of the film
26 at a constant vertical deflection rate during the tracing of a raster.
When the stored vertical deflection number is sixteen, a retrace portion 66
of the vertical deflection voltage causes a rapid deflection of the line
of sight 24 from the bottom to the top of the film 26 whereby the line of
sight 24 is conditioned to start a trace of a raster. Accordingly, prior
to the tracing of a raster, a vertical sync pulse is provided by the
counter 56.
The output of the counter 56 is connected to a raster counter 68 (FIG. 1)
through a signal line 40. The counter 68 provides a signal representation
of a stored raster count equal to the number of vertical sync pulses
provided by the counter 56. From the explanation given hereinbefore, the
raster count equals the number of times the camera 20 scans the image.
Outputs of the counter 68 are respectively connected to a comparator 70 at
a first group of inputs thereof through a plurality of signal lines 72
whereby the signal representation of the stored raster count is provided
to the comparator 70. The comparator 70 has a second group of inputs
respectively connected to the counter 44 through a plurality of signal
lines 74 whereby the signal representation of the stored horizontal
deflection number is provided to the comparator 70.
The comparator 70 is a type which provides ONE at an output thereof in
response to respectively similar patterns of logic signals being provided
to the first and second groups of inputs. Therefore, the comparator 70
provides ONE when the stored horizontal deflection number equals the
stored raster count.
During the tracing of a first exemplary raster when the stored raster count
equals the number, zero, the comparator 70 provides ONE in response to the
line of sight 24 intersecting an element having a horizontal coordinate
corresponding to the horizontal deflection number, zero. Since each of the
sixteen raster lines has one element having a horizontal coordinate
corresponding to the horizontal deflection number, zero, the comparator 70
provides sixteen ONEs, a ONE being provided during the intersecting of one
element on each raster line.
After the tracing of the first exemplary raster, a vertical sync pulse
causes the raster number to equal the number, one and a second exemplary
raster is traced. During the tracing of the second exemplary raster, the
comparator 70 provides ONE in response to the line of sight 24
intersecting an element having a horizontal coordinate corresponding to
the horizontal deflection number, one. Since each of the sixteen raster
lines has one element having a horizontal coordinate corresponding to the
horizontal deflection number, one, the comparator 70 provides sixteen
ONE's, a ONE being provided during the intersecting of one element of each
raster line.
In a similar manner, the comparator provides ONE during the tracing of
elements having other horizontal coordinates. It should be understood that
the comparator 70 provides successive ONE's with a time interval
therebetween slightly greater than the time for the tracing of a raster
line (referred to as a line time).
The output of the comparator 70 is connected to a sample and hold circuit
76 at a gate input thereof through a signal line 78. Additionally
connected to the sample and hold 76 at a video input thereof is the output
of the camera 20 through a signal line 80 whereby the video signal is
provided to the sample and hold 76.
In response to the comparator 70 providing ONE to the gate input, the
sample and hold 76 stores a sampled video signal having an amplitude
substantially equal to the amplitude of the camera video signal. Because
the comparator 70 provides ONEs with an interval therebetween equal to the
line time, the sampled video signal remains unchanged for a duration equal
to the line time. Sample and hold networks are well known to those skilled
in the art.
In accordance with the explanation given hereinbefore, in response to the
image being scanned ten times by the camera 20, the sample and hold 76
successively stores sampled video signals respectively representative of
ten elements on each raster line.
The sample and hold 76 is connected to an analog to digital converter 82 at
an input thereof whereby the sampled video signals are applied to the
input of the converter 82. The converter 82 provides a group of converter
digital signals representative of the amplitude of an applied input
signal. The converter digital signals are provided after a conversion time
following the application of the input signal.
According to the present invention, because a sampled video signal remains
unchanged for a duration equal to the line time, the converter 82 may have
a conversion time equal in duration to the line time.
The converter 82 is connected to a computer 84 whereby the converter
digital signals are provided to the computer 84.
The computer 84 successively stores the converter digital signals thereby
storing a signal representation of the image on the film 26.
The video signal, the horizontal sync pulses, and the vertical sync pulses
may be provided to a television monitor display 86 through the lines 80,
32a, 34a, respectively. The display 86 is utilized to provide a visual
representation of the image on the film 26.
Although the invention has been shown and described with respect to a
preferred embodiment thereof, it should be understood by those skilled in
the art that changes and omissions in the form thereof may be made therein
without departing from the spirit and the scope of the invention.
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