BOREHOLE CAMERA MONITORING SYSTEM

SYSTEME DE SURVEILLANCE DE SONDAGE PAR CAMERA

English Abstract

The borehole camera monitoring system comprises a
camera head assembly adapted to be lowered into a borehole by
means of a cable and a control unit located above ground for
generating a control signal for the operation of the camera.
The camera head assembly comprises a fixed portion and a
rotary portion containing the camera and associated equipment
for examining the wall of the borehole. The fixed portion of
the camera head assembly comprises a micro-controller for
controlling the operation of the camera, a position encoder
for detecting the angular rotation of the camera with respect
to the fixed portion of the camera head assembly and a
communication interface including means for multiplexing the
video signal generated by the camera with an information
signal generated by the micro-controller for transmission
over the cable and means for extracting the control signal
generated by the computer and transmitted over the cable.
The control unit comprises, in addition to the above
mentioned computer, a video monitor and a communication
interface including means for extracting from the signal
transmitted over the cable the video signal for the video
monitor and the information signal for the computer and means
for multiplexing the control signal of the computer for
transmission over the cable. A depth counter is connected to
the computer for detecting the depth of the camera head
assembly from the upper edge of the borehole.

French Abstract

Système de surveillance des trous de sondage par caméra comprenant une tête de caméra adaptée pour pouvoir être descendue dans un trou de sondage à l'aide d'un câble et d'une unité de commande située à la surface servant à produire un signal de commande pour le fonctionnement de la caméra. La tête de la caméra comprend une partie fixe et une partie rotative contenant la caméra et l'équipement connexe destiné à l'examen de la paroi du trou de sondage. La partie fixe de la tête de caméra comprend un microcontrôleur qui sert à régir le fonctionnement de la caméra, un encodeur de position permettant de détecter la rotation angulaire de la caméra par rapport à la partie fixe de la tête de caméra et une interface de communication possédant un dispositif de multiplexage du signal vidéo produit par la caméra avec un signal d'information produit par le microcontrôleur pour la transmission par câble et un moyen d'extraction du signal de commande produit par l'ordinateur et transmis par câble. L'unité de commande comprend, en plus de l'ordinateur susmentionné, un écran et une interface de communication capable d'extraire du signal transmis par câble le signal vidéo nécessaire à l'écran et le signal d'information nécessaire à l'ordinateur, ainsi qu'un dispositif de multiplexage du signal de commande de l'ordinateur pour la transmission par câble. Un indicateur de profondeur est connecté à l'ordinateur et sert à mesurer la profondeur à laquelle se trouve la tête de la caméra par rapport à l'orifice du trou de sondage.

Claims

CLAIMS
1. A borehole camera monitoring system comprising:
a) a camera head assembly adapted to be lowered
into a borehole by means of a cable and including a fixed
portion and a rotary portion containing a video camera, said
fixed portion containing a micro-controller for controlling
the operation of the camera, a position encoder for
measuring the angular rotation of the camera with respect to
the fixed portion of camera head assembly and a communication
interface including means for multiplexing the video signal
from the camera with an information signal generated by the
micro-controller for transmission over the cable and means
for extracting a control signal transmitted over the cable
for controlling the operation of the camera;
b) a control unit located above ground and
including a video monitor, a computer for generating said
control signal, and a communication interface including
means for extracting from the signal transmitted over the
cable the video signal for the video monitor and the
information signal for the computer and means for
multiplexing the control signal generated by the computer for
transmission over the cable; and
c) a depth counter connected to the computer for
detecting the depth of the camera from the upper edge of the
borehole.
2. A borehole camera monitoring system as defined



in claim 1, wherein said means for multiplexing said video
signal with said first communication signal includes a
modulator for generating a carrier signal for supporting the
information signal generated by said micro-controller and a
mixer for mixing said carrier signal with said video signal.
3. A borehole camera monitoring system as defined
in claim 1, wherein said means for multiplexing said control
signal comprises a modulator for generating a carrier
frequency for supporting the control signal generated by said
computer and a means for multiplexing said carrier signal
with the multiplexed signal already transmitted over the
cable.
4. A borehole camera monitoring system as defined
in claim 1, further comprising a programmable video image
processor connected to said computer for converting said
video signal into a signal which may be stored into the
memory of the computer or on a floppy disk.
5. A borehole camera monitoring system as defined
in claim 1, further comprising means for transmitting power
to said camera over said cable.
6. A borehole camera monitoring system as defined
in claim 1, wherein said camera head assembly further
comprises an orientation device for compensating for the
torsion of the cable supporting the camera head assembly.

Description

7~,




~ H~LE ~F~ NONITORING ~Y~- ~
This invention relates to a borehole camera
monitoring system.
It is known to use a camera for examining the walls
of a borehole to detect rock fractures. One such apparatus
is disclosed in U.S. Patent No. 4,855,820 granted August 8,
1989. The apparatus comprises a video camera which is
lowered into a borehole by means of a cable and a video
monitor in conjunction with a video cassette recorder
located above ground fo~ visualizing and recording the wall
of the borehole. However, with such an apparatus, too much
time is being spent reviewing video tapes to detect and
orient the rock fractures. Furthermore, the ~ystem is heavy
to handle due mainly to the weight of the cable
interconnecting the camera to the video monitor above ground
because the cable contains a large number of electrical
conductors.
It is the object of the invention to provide a
borehole camera monitoring system which is portable and use
a light coaxial cable for interconnecting the camera to the
video monitor above ground.



2 h ~ f ~-
lt is also an object of the present to provide a
system wherein logging of the borehole is done using a
computer which allows live detection and orientation of the
rock fractures and graphic representation of such fractures
on a stereonet pole plot.
It is a further object of the present invention to
provide a system wherein a frame grabber is used to store
still pictures on a floppy disc to allow easy presentation
and storage of data.
The borehole camera monitoring system, in accordance
with the present invention, comprises generally a camera head
assembly adapted to be lowered into a borehole by means of a
cable and a control unit located above ground for generating
a control signal for the operation of the camera. The camera
head assembly comprises a fixed portion and a rotary portion
containing the camera and associated equipment for examining
the wall of the borehole. The fixed portion of the camera
head assembly comprises a micro-controller for controlling
the operation of the camera, a position encoder for detecting
the angular rotation of the camera with respect to the fixed
portion of the camera head assembly and a communication
interface including means for multiplexing the video signal
generated by the camera with an information signal generated
by the micro-controller for transmission over the cable and
means for extracting the control signal generated by the
computer and transmitted over the cable. The control unit
comprises, in addition to the above mentioned computer, a



3 ~ '3
video monitor and a communication interface including means
for extracting from the signal transmitted over the cable the
video signal for the video monitor and the information signal
for the computer and means for multiplexing the control
signal of the computer for transmission over the cable. A
depth counter is connected to the computer for detecting the
depth of the camera head assembly from the upper edge of the
borehole.
The means for multiplexing the video signal with the
10 information signal generated by the micro-controller includes
a modulator for generating a carrier signal for supporting
the information signal generated by the micro-controller and
a mixer for mixing the carrier signal with the video signal.
The means for multiplexing the control signal
15 comprises a modulator for generating a carrier signal for
supporting the control signal generated by the computer and a
mixer for multiplexing the carrier signal with the
multiplexed signal already transmitted over the cable.
The control unit further comprises a programmable
2~ video image processor connected to the computer for
converting the video signal into a signal which may be
stored into the memory of the computer or on a floppy disk.
The control unit further comprises means for
transmitting power to the camera over the cable.
An orientation device, such as a gyroscope, may be
used for compensating for any torsion of the cable supporting
the camera head assembly.

L, ~




The invention will now be disclosed, by way of
example, with reference to the accompanying drawings in
which:
Figure 1 is a block diagram of the borehole
monitoring system in accordance with the present invention:
Figure 2 is a block diagram of the communication
interface of the camera head assembly;
Figure 3 is a block diagram of the communication
interface of the control unit;
Figure 4 shows an example of the frequency spectrum
of the composite signal sent over the cable;
Figure 5 is a view showing how the orientation of
the fracture is determined; and
Figure 6 is a view showing a stereonet illustrating
fractures in the wall of the borehole.
Referring to Figure l of the drawings, the
monitoring system comprises a camera head assembly lO
adapted to be lowered into a borehole by means of a regular
coaxial cable 12 which is reinforced with a Kevlar cord. The
camera head assembly is made of a top portion lOa which is
rigidly fixed to the cable and a bottom portion lOb which is
rotatably mounted to the top portion. The top portion of the

camera head assembly contains a communication interface 14, a
micro-controller 16, an orientation device 18 and a position
encoder 19 to be more fully disclosed later. The bottom
portion contains the camera and associated control, lighting
and viewing equipment 20. Located above ground is a control



~ ?
unit including a computer 22 and associated keyboard 24 and
screen 26. The computer may be a Little Board AT286 having a
16 MHz-CPU and a 4Mb random access memory. The computer
controls communication between a regular video monitor 25 and
the camera head assembly 10 through a communication interface
27 which will be disclosed more fully in Figure 3 of the
drawings. A programable video image processor 28,
conventionally known as a frame grabber, is used to transform
the video images taken by the camera into a digital form and
store them in the computer memory and/or on floppy discs to
allow easy presentation on other computers. A suitable image
processor may be a Matrox PlP-512B. A depth counter 30 such
as a wheel in contact with the cable may be used for
providing a digital signal to the computer to measure the
length of cable paid off and thus the position of the camera
from the upper edge of the borehole.
Referring to Figure 2 of the drawings, a video
signal in the frequency band of, for example, 0-5 MHz
originating from the camera 20 is fed to a mixer 32 through a
suitable buffer amplifier 34. The video signal is
multiplexed with a carrier signal of a frequency outside the
video band, for example, 7 MHz generated by a modulator 36
under the con~rol of the micro-controller 16. The signal
transmitted over the cable also includes a control signal
originating from the computer and transmitted through the
communication interface 27 of the control unit. As it will
be seen later in the description of Figure 3 of the drawings


6 j ~ r -~



such signal is modulated by a carrier signal of a frequency
different from the above frequencies, say 8 MHz. The signal
transmitted over the cable is thus a composite signal
con~in;ng the video signal and two communication signals.
The frequency spectrum of an example of the composite signal
is shown in Figure 4 of the drawings. The 8 MHz component of
the composite signal is extracted from the composite signal
by means of demodulator 40 to produce the control signals
which are fed to micro-controller 16 for distribution to the
various motors operating the iris, focus and rotation of the
camera as well as the viewing equipment. As it will be seen
in the description of Figure 3 of the drawings, electrical
power for operating the various components of the camera head
assembly is also transmitted through a separate conductor
forming part of the cable or multiplexed with the composite
signal. Such signal is extracted by a suitable power
extractor 42 and fed to the various electronic boards of the
equipment.
Referring to Figure 3 of the drawings, the composite
signal received over the cable is fed to a mixer 44 forming
part of the communication interface 27. The 7 MHz
communication signal is extracted from the composite signal
by a demodulator 46 and sent to the computer whereas the
video signal is sent to the video monitor through a buffer
amplifier 48. The video signal is also sent to a
programmable video image processor for transformation into a
digital form for storing in the memory of the computer and/or



7 ~ ~ ~, ,~, g _ ~
in floppy discs. A modulator 50 generates a communication
signal having a carrier frequency of 8 MHz, as mentioned
previously, for transmitting the control signals of the
computer to the micro-controller of the camera over the
cable. A power inserter 52 is used to transmit power to the
camera and associated equipment over the cable. The power
may be sent through a separate conductor or multiplexed with
the composite signal over the cable.
The computer is programmed for using some of the
function keys Fl-F9 of the regular keyboard to control the
operation of the various motors of the camera head assembly
to adjust the iris, focus and rotation of the camera as well
as the selection of the front or side lights and control of
the lighting intensity. The computer is also programmed so
that upon request of the operator, the distance of the
fractures from the edge of the borehole and the orientation
of such fractures may be determined. To orient a fracture
passing through a borehole, it is sufficient to locate on the
monitor the two extreme positions A and B on the major axis
of the fracture on the wall as shown in Figure 5 of the
drawings. Upon a suitable command from one of the function
keys, the operator can request the computer to memorize such
positions and the angle of rotation of the camera with
respect to the fixed portion of the camera head assembly as
determined by position encoder 19. Such angle of rotation is
compensated for any torsion of the cable supporting the
camera head assembly by means of the orientation device 18.


8 ~ 3 i i~
From these data, the computer will calculate the coordinates
of the fracture with respect to the axis of the korehole.
Knowing the coordinates of the borehole previously entered
into its memory, the computer will calculate the real
coordinates of the fracture and show them on the screen in
the form of a stereonet as shown in Figure 6 of the drawings.
The ou~uL files of the computer are compatible with the
program DIPS developed by the University of Toronto.
Although the invention has been disclosed, by way of
example, with reference to a preferred embodiment
illustrated in the drawings, it is to be understood that it
is not limited to such embodiment and that other alternatives
are also envisaged within the scope of the following claims.

Representative Drawing