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Description  |
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This invention relates to video image size scaling. In one aspect, this
invention relates to method and apparatus for generating a grid on a video
display, wherein such grid is scaled so as to provide a measurement of the
size of an object displayed on the video display.
Television cameras and other devices which can create an image of an object
are often utilized to inspect structure or objects which are not easily
accessible to actual visual inspection by a person who desires to make
such an inspection. This is particularly true in underwater inspections
and surveys such as the inspection of underwater structures or pipelines,
sea bed site surveys prior to laying pipelines, surveys for drilling
sites, and surveys for platform construction sites. Also, such image
creating equipment is commonly used for inspections in hostile
environments such as the reactor areas of nuclear power plants.
When using a television camera to view structure or objects which are not
easily accessible, it is often difficult and time consuming to obtain
accurate and reliable size information concerning the structure or
objects. The distance of the camera from the object will generally not be
known and also the angle at which the camera is viewing the object may not
be known. In underwater situations, divers often must physically measure
objects of interest which are located by the television camera. This is
especially true in offshore platform inspections where it is critical to
obtain accurate and reliable information concerning the size of a defect
in the platform structure. However, such defects may be located below the
maximum diving depth for a diver and in any event there is considerable
expense and a potential for personnel hazards when a diver must be
utilized to measure an object of interest such as a defect in a platform
structure.
One technique which has been utilized to overcome the necessity of using a
diver to actually measure an object of interest or to obtain a measurement
in a hostile environment is the use of a television camera equipped with a
measuring frame. The measuring frame is placed in contact with the object
of interest and thus provides a reference which can be utilized to
determine the size of the object of interest. However, it is often
difficult to place measuring frames in contact with the object of interest
and further, measuring frames attached to a television camera make the
television camera more difficult to handle and such measuring frames are
easily entangled with cables and other structure and are thus subject to
damage.
It is thus an object of this invention to provide a video image size
scaling system which avoids the problem of having to use divers to
actually measure objects of interest which can be seen by using a
television camera or having to use measuring frames. It is another object
of this invention to provide method and apparatus for generating a grid on
a video display, wherein such grid is scaled so as to provide a
measurement of the size of an object displayed on the video display which
will allow an operator viewing such video display to directly determine
the size of the displayed object.
As used herein, the term "grid" refers to any arrangement of lines or
points which may be displayed on a video display. The term "grid"
includes, without limitation, squares, rectangles and other geometric
structures on a video display; tic-tac-toe or other arrangements of lines
on a video display; points separated by some distances on a video display
and lines having a certain length on a video display.
In accordance with the present invention, a calibrated grid for a video
display means is generated in response to a measurement of the distance
between a device, such as a television camera, being utilized to create an
image of an object and the object itself. Both the object and the grid may
be displayed on a video display means in such a manner that the object is
overlaid with the calibrated grid. The length of the lines in the
calibrated grid or the distance between points in the calibrated grid, as
actually displayed, will be representative of a particular distance and
thus an observer viewing the video display can determine the actual size
of the object by using the calibrated grid to actually measure the object.
Other objects and advantages of the invention will be apparent from the
foregoing brief description of the invention and from the claims as well
as from the drawings in which:
FIG. 1 is a diagrammatic illustration of the video image size scaling
system of the present invention;
FIG. 2 is a schematic diagram of the video interface illustrated in FIG. 1;
FIG. 3 is a schematic diagram of the sonar interface illustrated in FIG. 1;
FIG. 4 is a diagrammatic illustration of the scaling theory of the present
invention;
FIG. 5 is a flow chart for the grid data base generation;
FIG. 6 is a representation of the actual grid generated by the grid data
base; and
FIG. 7 is a flow chart for the BASIC program which controls the generation
of the grid.
The present invention is described in terms of an embodiment in which a
television camera is utilized to view an object of interest under water.
The distance measuring is based on sonar technology. The image of the
object and the calibrated grid are immediately displayed on a CRT monitor.
However, the invention is applicable to environments other than underwater
and distance measuring based on technologies other than sonar may be used.
Also, other image creating devices such as acoustic devices may be
utilized in place of a television camera. Also, the image and calibrated
grid may be provided to a video tape recorder to be displayed at a later
time.
A digital computer is used to generate the calibrated grid. The digital
computer presently used is an Apple II+ but other suitable computing
systems could be utilized if desired.
The invention is also described in terms of particular electrical circuitry
which is utilized to interface the various components of the video image
size scaling system illustrated in FIG. 1. It is noted that a number of
different types of interfacing systems could be utilized to accomplish the
purpose of the present invention.
Referring now to the drawings and in particular to FIG. 1, the digital
computer 11 provides master timing and synchronization for the video image
size scaling system. Horizontal synchronization pulses and vertical
synchronization pulses are provided from the computer 11 through the video
interface 12 to the television camera 14. The internal sync generator of
the television camera 14 is disabled. When horizontal sync pulses and
vertical sync pulses are provided from the computer 11 to the television
camera 14 and the internal sync generator of the television camera 14 is
disabled, the television camera 14 will provide a composite video output
signal (referred to in the drawing as camera video) that is synchronized
to the video signals generated by computer 11. Thus, the grid video
provided from the computer 11 can be combined in the video interface with
the camera video provided from the television camera 14 to establish a
mixed video signal which is provided from the video interface 12 to the
CRT monitor 15 for display. The object 17, which is in the television
camera's 14 field of view, will be displayed on the CRT monitor 15. The
grid pattern generated by the computer 11 will overlay the display of the
object 17.
A sonar device 18 is utilized to determine the distance between the focal
plane of the television camera 14 and the object 17. Data and strobe
signals from the sonar instrument 18 are provided through the sonar
interface 19 to the computer 11. The sonar interface 19 is controlled by
address lines from the computer 11 and the strobe signals from the sonar
instrument 18. The data supplied from the sonar instrument 18, which is
representative of the distance between the focal plane of the television
camera 14 and the object 17, is utilized by computer 11 to size or scale
the grid which is displayed on the CRT monitor 15 as will be more fully
described hereinafter.
The television camera 14 presently used is a Panasonic WV 1300 television
camera which has been modified by grounding pins 3 and 11 of IC 502 to
disable the camera's internal sync generator. The sonar instrument 18
presently used is a Polaroid Ultrasonic Ranging Unit. Other television
cameras and sonar instruments could be utilized if desired. The CRT
monitor can be any black and white CRT monitor meeting Electronic
Industries Association (EIA) Std. RS-170.
The sonar instrument 18 and the television camera 14 may be mounted in any
desired manner so long as the sonar instrument 18 is located so as to be
able to provide an accurate indication of the distance between the lens of
the television camera 14 and an object of interest in the field of view of
the television camera 14. Typically, the television camera 14 and sonar 18
will be mounted close together and will be mounted in such a way that
rotation of the television camera 14 and sonar 18 as a unit is possible.
The field of view of the sonar 18 and television camera 14 should overlap
and the effective beamwidth of the sonar 18 should be less than the field
of view of the television camera 14 to insure that the object to camera
distance provided by the sonar 18 is for an object in the field of view of
the television camera 18. It is noted that distance compensation must be
provided if the sonar 18 is not located adjacent the television camera 14
and it may be difficult to meet the preferred field of view and beamwidth
criteria without such adjacent location.
Television cameras for viewing objects under water are typically mounted on
underwater vehicles or on extension arms which can be operated from the
surface. It is contemplated that the sonar unit 18 will be mounted in the
same manner as underwater television cameras are typically mounted using
techniques which are well known in the art of underwater inspections and
surveys.
A circuit which may be utilized to implement the electronic functions of
the video interface 12 is illustrated in FIG. 2 and a circuit which may be
utilized to implement the electronic functions of the sonar interface 19
is illustrated in FIG. 3. Many of the integrated circuit (I.C.) chips
illustrated as well as components such as resistors, capacitors and diodes
may be obtained from a number of manufacturers such as RCA, Motorola,
Fairchild and National. The function of each of the I.C. chips and
components is fully described by literature supplied by the manufacturers
and the manner in which the circuit operates would be obvious to one
skilled in the art of electronics. Thus, only a very general description
of the manner in which the circuits illustrated in FIGS. 2 and 3 function
is provided hereinafter.
Power supplies and other conventional circuitry required by the various
I.C. chips have not been illustrated in FIGS. 2 and 3 for the sake of
simplicity. Also, additional circuitry required for conventional operation
of the various I.C. chips has not been illustrated. Also, in general, only
the pins on the I.C. chips actually utilized are illustrated. Again, such
power supplies and additional circuitry are specified by the manufacturers
and are well known to those skilled in the art of electronics.
Referring now to FIG. 2, all video signals are transmitted on coaxial
cable. Also, the vertical sync pulse to the television camera 14 and the
horizontal sync pulse to the television camera 14 are conducted on coaxial
cable. The camera video signal is applied across resistor 21 which
provides an impedance match to the coaxial cable. The potentiometer 22 is
utilized as an attenuator and may be considered a contrast control.
Capacitors 23-25 and resistor 27 provide RC coupling of the camera video
signal into the base of transistor 29. The nonlinear base-emitter
characteristics of transistor 29 will cancel the nonlinear base emitter
characteristics of transistor 31. Transistor 31 is nominally a
common-emitter amplifier with emitter degeneration such that the voltage
gain is approximately the ratio of resistor 32 to resistor 33 (in this
preferred embodiment the voltage gain is 10). The emitter of transistor 31
is reversed biased by the voltage divider action of potentiometer 36 and
diode 37. Transistor 31 does not conduct until its base becomes
approximately 0.6 volts more positive than its emitter. At this point,
diode 37 becomes reverse biased and transistor 31 functions as a linear
amplifier with a gain of 10. Because the base emitter "turn-on"
characteristic of transistor 31 is cancelled by the equal but opposite
base emitter characteristic of transistor 29, the "turn-on" voltage can be
set very near to zero volts at the input.
Transistor 41 together with resistors 43 and 44 form a unity gain level
shifting stage.
The entire circuit made up of transistors 29, 31 and 41 and the associated
components may be thought of as an amplifier with the potentiometer 36
functioning as a brightness control. The potentiometer 36 is adjusted
based on the output signal from the camera to provide the best picture on
the video display. Resistor 45 is used as a damping resistor.
Transistor 46 and resistor 47 compose an emitter follower which provides a
bias voltage for transistor 48. Essentially, the approximately 0.7 V rise
from the base to emitter of transistor 46 compensates for the
approximately 0.7 V drop from the base to emitter of transistor 48, which
preserves linearity and maintains the relative brightness of the image on
the video display.
The video signal from computer 11 is provided through resistor 52, which is
used for damping, to the base of the transistor 54. The resistor 55 and
transistor 54 compose an emitter follower which provides a bias voltage
for transistor 49 in the same manner that transistor 46 provides a bias
voltage for transistor 48.
Transistors 48 and 49 are operated as two emitter followers having a common
emitter resistor 51. Essentially, the video signal from the computer is
applied to the base of transistor 49 while the video signal from the
camera is applied to the base of transistor 48. The one of transistors 48
and 49 having the most positive base voltage will reverse bias the emitter
of the other transistor. The circuit output taken at resistor 51 will thus
be equal to the most positive base voltage. This output is provided by
coaxial cable to the CRT monitor.
In operation, the circuit made up of transistors 46, 48, 49 and 54 provides
for very fast, smooth switching between the computer video and the camera
video. The composite video is thus a multiplexed combination of the
computer video and the camera video. The switching is done so rapidly that
it has no effect on the observer.
The circuit illustrated in FIG. 2 for combining two video signals has
several advantages. First, the circuit has an excellent frequency response
which prevents overshoot or ringing which would cause smearing or shadows
on the CRT display. Second, because there is no actual addition of the
video signals, both video signals may be adjusted for maximum dynamic
range without saturating the CRT.
The horizontal synchronization pulses from the computer 11 are buffered by
two inverters 61 and 62 which are connected in parallel. In like manner,
the vertical synchronization pulses from the computer 11 are buffered by
two inverters 64 and 65 which are connected in parallel. The inverter 67
is connected in series with the parallel combination of inverters 61 and
62 and is utilized to avoid polarity inversion of the horizontal sync
pulses.
The diode 37 in FIG. 2 is a 1N914. All NPN transistors are 2N3904. All PNP
transistors are 2N3905.
Referring now to FIG. 3, the range data in the Polaroid Ultrasonic Ranging
Unit 18 is generated in a three-decade binary-coded decimal (BCD) counter
with multiplexed outputs. This data is supplied from the ranging unit in
parallel to three octal D flip-flops 81-83 which have tri-state outputs.
The tri-state outputs permit the octal D flip-flops 81-83 to be
multiplexed directly onto the data bus of the Apple II+ Computer.
The three-decade BCD counter, located in the Polaroid Ultrasonic Ranging
Unit 18, sequentially places the BCD code for each decade on the BCD
output lines and activates a corresponding strobe signal. The timing of
the strobes and data from the three-decade BCD counter is such that data
is not stable on either edge of the strobes. Therefore, each strobe
triggers a monostable multivibrator 86-88 respectively. The trailing edge
of the monostable multivibrator output pulse clocks the BCD data into the
corresponding octal D flip-flops 81-83. The strobe for the most
significant digit sets a "new data ready" flip-flop 91 as well as loading
the BCD data into octal D flip-flop 83.
The Apple II+ Computer provides an address to the sonar interface board 19
through the decoder 93. Four specific hexadecimal addresses (COA0, COA1,
COA2 and COA3) appear on the output pins of the decoder 93 during the
"phase zero" clock period of the Apple II+ Computer. The decoded address
COA0 causes the data stored in the least significant digit flip-flop 81 to
be placed on the data lines for the Apple II+ Computer. The addresses COA1
and COA2 place the more significant digits on the data lines in a similar
manner. The new "data ready" flip-flop 91 is reset by address C0A3.
Referring now to FIG. 4, the image on a television screen is a
two-dimensional projection of the three-dimensional space viewed by the
television camera. If an observing viewpoint (referred to hereinafter as
the "Eye") is positioned at the proper distance from the television screen
(as determined by the field of view of the camera lens), then the image on
the television screen will reproduce the perspective of the original scene
as recorded by the camera. It is as though the original scene lies beyond
the screen, with all of the full sized objects located at the appropriate
distances from the Eye.
The sonar distance information is utilized to determine the proper size of
the grid to draw onto the CRT screen. The grid must be drawn such that its
projection into space behind the screen would make a grid of the proper
dimensions at a distance from the Eye equal to the original objects
distance from the camera as is illustrated in FIG. 4. It is noted that the
size of the CRT screen will affect image size and therefore apparent
distance, but the CRT screen size affects the grid display and the camera
image identically so that there is no distortion of scale.
A commercially available 3-D animation program from Sublogic Company
(Sublogic A2-3D1 Animation Program) is used as a base for the generation
of a grid pattern in the Apple II+ computer. The grid pattern is defined
in a special graphics language set forth in Appendix I which is then
interpreted by the animation program.
The Sublogic A2-3D1 Animation Program works by converting an artificial 3-D
world (as defined in the graphics language by the user) into a 2-D
projection in the computer's memory. To do this, the animation program
must be given a data base consisting of an arrangement of points and lines
in an artificial volume of space, the location and orientation of the Eye,
and the Eye-to-screen distance.
The grid pattern is defined as a pattern of lines and points lying on the
XY plane. The Eye is located on the Z axis facing the origin. The Z
position of the Eye is determined by the camera-to-object distance as
measured by the sonar instrument.
The grid data base listing in the 3-D animation language of Appendix I is
set forth in Appendix II. A flow chart for the grid data base generation
is illustrated in FIG. 5. The grid generated by the grid data base listing
is illustrated in FIG. 6. It is noted that the Apple II+ Computer can
display either of two memory areas as high resolution graphics on the CRT
screen. These memory areas are referred to as memory 1 and memory 2 in the
flow chart illustrated in FIG. 5 and also in the flow chart illustrated in
FIG. 7. The grid data base program is designed to display the contents of
the first memory while the second memory is being erased and redrawn.
Then, the contents of the second memory is displayed while the first
memory is redrawn. This provides a steady display.
A program written in BASIC controls the loading and execution of the
animation program and the grid data base. This program is set forth in
Appendix III. A flow chart for the program is illustrated in FIG. 7. Line
500 in the BASIC program controls a jump instruction in the grid data base
which effectively selects either memory 1 or memory 2. Line 510 causes the
Sublogic Animation Program to interpret the grid data base instruction
which will cause the contents of one memory to be displayed while the
other memory is erased and redrawn. The position of the Eye and the jump
destination are defined by the BASIC program before this program is
interpreted. Line 29494 defines field of view and aspect ratio for the
camera. It is noted that the field of view and aspect ratio for the camera
must be tailored to the optics of the specific camera and lens. It would
be possible to accommodate a zoom (variable focal length) lens with the
present invention if a signal indicating lens focal length was interfaced
to the computer.
The invention has been illustrated and described in terms of a preferred
embodiment as illustrated in FIGS. 1-7. It is noted that the circuitry
illustrated in FIGS. 2 and 3 is the preferred circuitry for interfacing
the elements of the video image size scaling system. Many different
circuit configurations could be utilized to accomplish this function and
such different circuit configurations are within the scope of the present
invention, as claimed.
Also, the software utilized to generate the grid required for the video
image size scaling has been described in terms of a preferred software
listing and flow chart. As in the case of the electrical circuitry, many
different software packages could be utilized to accomplish the generation
of the grid and such different software packages and listings are within
the scope of the present invention, as claimed.
APPENDIX I
__________________________________________________________________________
A2-3D1 3D ANIMATION PROGRAM LANGUAGE
COMMAND
COMMAND
COMMAND
NAME (decimal)
(hex) ARGUMENTS FUNCTION
__________________________________________________________________________
PNT 00 00 X lsb, X msb, Y lsb, Y msb, Z lsb, Z
Define 3D Point
SPNT 01 01 X lsb, X msb, Y lsb, Y msb, Z lsb, Z
Define 3D Start Point
CPNT 02 02 X lsb, X msb, Y lsb, Y msb, Z lsb, Z
Define 3D Continue Point
RAY 03 03 X lsb, X msb, Y lsb, Y msb, Z lsb, Z
Define 3D Ray
CLPSW 04 04 n where n = 0 clipper on, n = 1 clipper
Clipper Control Switch
EYE 05 05 X lsb, X msb, Y lsb, Y msb, Z lsb, Z msb, P, B,
Viewer's X, Y, Z, P, B, H
LIN2D 06 06 X1, Y1, X2, Y2 Draw 2D Line from Point 1
to 2
DISP 07 07 n where n = 50 set graphics n = 51 set
Display Screen Select
n = 52 clear mixed n = 53 set mixed
n = 54 page 1 set n = 55 page 2 set
n = 56 clear HI-RES n = 57 set HI-RES
ERAS 08 08 n where n = 00 erase page 1 n = 01 erase page
Erase Screen
n = 02 fill page 1 n = 03 fill page 2
DRAW 09 09 n where n = 00 draw page 1 n = 01 draw page
Write Screen Select
PNT2D 10 0A X, Y Plot 2D Point
JMP 11 0B A lsb, A msb where A is the jump address
Interpretive Jump
LMODE 12 0C n where n = 00 normal line n = 01 exclusive or
Set Line Drawing Mode
ARRAY 13 0D A lsb, A msb where A is output array start
Turn On Output Array
Generation
SCRSZ 14 0E Screen width, Screen height, X center, Y
Screen Size Selection
FIELD 15 0F axr lsb, axr msb, ayr lsb, ayr msb, azr lsb, azr
Field of View Selection
INIT 16 10 none Easy Initialize
NOP 17 11 none No Operation
__________________________________________________________________________
APPENDIX II
__________________________________________________________________________
GRID DATA BASE LISTING
>RUN
ENTER STARTING MEMORY LOCATION (DECIMAL)
?29440
29440 JMP
29465 29506 SPNT
-120,
-120,
0
29443 NOP 29513 CPNT
-120,
120,
0
29444 NOP 29520 CPNT
120,
120,
0
29445 NOP 29527 CPNT
120,
-120,
0
29446 NOP 29534 CPNT
-120,
-120,
0
29447 NOP 29541 SPNT
10, 0, 0
29448 NOP 29548 CPNT
20, 0, 0
29449 INIT 29555 SPNT
30, 0, 0
29450 DISP
CLEAR MIXED 29562 CPNT
40, 0, 0
29452 DISP
SET PAGE 2 29569 SPNT
50, 0, 0
29454 ERAS
ERASE PAGE 1 29576 CPNT
60, 0, 0
29456 DRAW
PAGE 1 29583 SPNT
70, 0, 0
29458 NOP 29590 CPNT
80, 0, 0
29459 NOP 29597 SPNT
90, 0, 0
29460 NOP 29604 CPNT
100,
0, 0
29461 NOP 29611 SPNT
110,
0, 0
29462 JMP
29480 29618 CPNT
120,
0, 0
29465 NOP 29625 SPNT
0, 10, 0
29466 NOP 29632 CPNT
0, 20, 0
29467 NOP 29639 SPNT
0, 30, 0
L L
29468 DISP
SET PAGE 1 29646 CPNT
0, 40, 0
29470 ERAS
ERASE PAGE 2 29653 SPNT
0, 50, 0
29472 DRAW
PAGE 2 29660 CPNT
0, 60, 0
29474 NOP 29667 SPNT
0, 70, 0
29475 NOP 29674 CPNT
0, 80, 0
29476 NOP 29681 SPNT
0, 90, 0
29477 NOP 29688 CPNT
0, 100,
0
29478 NOP 29695 SPNT
0, 110,
0
29479 NOP 29702 CPNT
0, 120,
0
29480 NOP 29709 SPNT
0, -10,
0
29481 NOP 29716 CPNT
0, -20,
0
29482 NOP 29723 SPNT
0, -30,
0
29483 NOP 29730 CPNT
0, -40,
0
29484 EYE 29737 SPNT
0, -50,
0
0 0, -102
29744 CPNT
0, -60,
0
P = 0
B = 0
H = 0
29751 SPNT
0, -70,
0
29494 FIELD
25000,
32767,
5200
29758 CPNT
0, -80,
0
29501 NOP 29765 SPNT
0, -90,
0
29502 NOP 29772 CPNT
0, -100,
0
29503 NOP 29779 SPNT
0, 110,
0
29504 NOP L
29505 NOP
29786 CPNT
0, -120,
0 29996 SPNT
0, -180,
0
29793 SPNT
-10, 0, 0 30003 CPNT
0, -240,
0
29800 CPNT
-20, 0, 0 30010 SPNT
0, -300,
0
29807 SPNT
-30, 0, 0 30017 CPNT
0, -360,
0
29814 CPNT
-40, 0, 0 30024 SPNT
-360,
-360,
0
29821 SPNT
-50, 0, 0 30031 CPNT
-360,
360,
0
29828 CPNT
-60, 0, 0 30038 CPNT
360,
360,
0
29835 SPNT
-70, 0, 0 30045 CPNT
360,
-360,
0
29842 CPNT
-80, 0, 0 30052 CPNT
-360,
-360,
0
29849 SPNT
-90, 0, 0 30059 PNT
120,
240,
0
29856 CPNT
-100,
0, 0 L
29863 SPNT
-110,
0, 0
29870 CPNT
-120,
0, 0 30066 PNT
-120,
240,
0
29877 PNT
60, 60, 0 30073 PNT
120,
-240,
0
29884 PNT
-60, 60, 0 30080 PNT
-120,
-240,
0
29891 PNT
-60, -60,
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