Auxiliary light apparatus for borescope

An auxiliary light apparatus for a color video borescope has an auxiliary box that is connected by an umbilical to a receptacle on the video processor unit for the borescope. The insertion tube of the borescope has an interface module which normally connects to a receptacle in the video processor, but also fits a receptacle in the auxiliary box. Sequential primary color illumination is generated in the auxiliary box and supplied through the interface module and a fiber optic bundle in the insertion tube to the distal end of the tube to illuminate a remote target area. The auxiliary sequential light generator is optically synchronized from the main light generator within the video processor.

BACKGROUND OF THE INVENTION 
This invention relates to endoscopes or borescopes of the type in which a 
miniature video camera is mounted at the distal end of a flexible 
elongated insertion tube, and in which illumination is carried on a fiber 
optic bundle to the distal end of the insertion tube to illuminate a 
remote target area. 
The invention is more particularly concerned with apparatus to extend the 
range of the borescope or endoscope, that is, devices which increase the 
separation from the target area to the associated video processor unit. 
Currently, video borescopes are limited in length to about fifty feet 
(sixteen meters). This distance represents the maximum effective distance 
that the fiber optic bundle in the insertion tube can carry illumination 
for illuminating the target area. As a result, it is sometimes necessary 
to place the video processor in a precarious or highly inconvenient 
location just to permit the borescope to reach a desired remote target 
area, which may be deep within a turbine, boiler, or other complex piece 
of equipment. 
Where a color endoscope or borescope is employed, sequential primary color 
light is supplied over the fiber optic bundle to illuminate the target 
area sequentially with red, blue, and green light. This can be generated 
using a white light source and separated into primary colors with a color 
filter wheel, whose rotation speed and phase are synchronized with the 
field rate of the video signal produced by the video camera. A sequential 
color light wheel device of this type is disclosed in Longacre U.S. Pat. 
No. 4,523,224. This device is conventionally contained within the video 
processor unit of the endoscope or borescope system. 
An interface module at the proximal end of the borescope insertion tube, or 
at the proximal end of an umbilical or extension coupled to the insertion 
tube, removably couples to the video processor unit. This interface module 
includes electrical connectors to connect the video camera to circuitry in 
the video processor. The interface module also includes an optical 
interface that couples the proximal end of the fiber optic bundle to the 
sequential color light source within the video processor unit. An 
interface module of this type is disclosed in Danna et al. U.S. Pat. No. 
4,539,586. 
An auxiliary light device for a color borescope is described in U.S. Pat. 
No. 4,853,774, issued Aug. 1, 1989, and having a common assignee. This 
device is disposed between the probe interface module and the receptacle 
of the video processor. Sequential primary light is generated in the 
device and this is synchronized by special electrical conductors that 
connect to the video processor. A special modification to the processor is 
required for this. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is an object of this invention to provide apparatus that extends the 
range of a borescope or endoscope without degradation of illumination, and 
without affecting the video signal produced by the video camera or imager 
in the device. 
It is another object of the invention to provide apparatus which can be 
inserted between the endoscope or borescope's interface module and the 
socket or receptacle therefor in the video processor. 
It is yet another object of the invention to extend the borescope or 
endoscope range without modification to the existing video processor. 
According to an aspect of the invention, auxiliary illumination apparatus 
for a borescope to extend its range or working distance comprises a 
housing, a receptacle in the housing to receive the borescope interface 
module, a multiple contact connector mounted on the housing, and an 
electrical wiring harness within the housing with connectors to connect 
the pins or contacts of the interface module with corresponding pins of 
the multiple contact connector. An illumination source is situated within 
the housing with an optical interface disposed at the receptacle for 
supplying suitable illumination through the fiber optic bundle to the 
target area at the distal end of the borescope insertion tube. Preferably, 
this illumination source includes a color filter wheel and suitable 
control electronics within the housing. A flexible liquid light conduit, 
or the like, brings the light from the external source to the color wheel. 
The illumination fed to the fiber optic bundle is a sequence of primary 
colors which are synchronized with the fields of the video signal. 
An umbilical connects this auxiliary apparatus to the video processor unit, 
and permits the auxiliary apparatus to be remoted from it a sufficient 
distance. The umbilical includes a sheath that carries a number of 
conductors, and a distal end connector which contacts these conductors 
with respective pins or contacts of the multiple contact connector. At the 
proximal end of the umbilical is an auxiliary interface module that mates 
with the receptacle in the video processor unit. This connects the 
appropriate conductors to send power, synchronizing signals and auxiliary 
signals to the video camera in the borescope, and to receive the video 
signals from it. To bring the appropriate power and synchronizing signals 
to the color filter wheel circuitry, a sensor (i.e., a red-sensitive 
photodetector) receives the output of the main color filter wheel of the 
video processor. The output of this detector is carried on a conductor in 
the umbilical and the color filter wheel of the auxiliary illumination 
apparatus locks in phase with the lamp and main color filter wheel in the 
video processor. The video and electrical signals are passed straight 
through the umbilical and apparatus, but the sequential primary color 
light is generated in the auxiliary apparatus. A slave circuit that 
employs a phase-lock loop can be employed for this purpose. 
The above and many other objects, features, and advantages of this 
invention will become more fully understood from the ensuing description 
of a preferred embodiment which should be read in connection with the 
accompanying Drawing.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
With reference to the Drawing, FIG. 1 shows a video borescope assembly 
which comprises a borescope 10 having an elongated, flexible insertion 
tube 12 approximately fifty feet (sixteen meters) in length. A viewing 
head 14 is incorporated into the distal end of the tube 12. This viewing 
head contains optical lenses and a miniature camera. The camera can be a 
CCD device or other solid state imager capable of providing a full-color 
image of a remote target area, e.g. the inside of a boiler tube of a heat 
exchanger, or a stator vane of a turbine. An example of a suitable solid 
state imager is disclosed in U.S. Pat. No. 4,491,865. 
At the proximal end of the insertion tube 12 is a steering and control unit 
16 which couples the insertion tube 12 to a flexible tubular umbilical or 
extension 18. At the proximal end of the umbilical 18 is a borescope 
interface module 20 of the plug-in type, substantially as disclosed in 
U.S. Pat. No. 4,539,586. The module 20 fits a mating receptacle 22 in an 
auxiliary light box 24. This light box is coupled in turn to an auxiliary 
illumination source 26 by means of a suitable flexible light guide 28. In 
this case the light guide 28 is a liquid light guide. An auxiliary 
umbilical 30, which is a flexible sheath containing a plurality of 
conductors, extends from a rear side 32 of the auxiliary light box 24 and 
has an auxiliary interface module 34 that fits a receptacle on a video 
processor unit 36. 
The auxiliary interface module 34 is structurally and functionally similar 
to the borescope interface module 20, and serves to connect corresponding 
conductors in the borescope insertion tube 12 to the video processor unit 
36. This feed-through provides video signals to a video monitor or screen 
38 to produce an image of the remote target area. 
As shown in FIG. 1, an auxiliary video monitor can be remoted to the 
location of the auxiliary light box, if desired. 
The borescope insertion tube 12 has a wire bundle within it to carry video 
signals, synchronizing signals, power and auxiliary signals between the 
video processor unit 36 and the imager of the viewing head 14. Also, there 
is a fiber optic bundle extending through the insertion tube 12 and 
umbilical 18 to carry illumination from a main sequential primary color 
generator in the video processor unit 36 to the distal tip of the 
borescope insertion tube 12 to illuminate the target area. Because of 
intrinsic characteristics of this fiber optic bundle, the insertion tube 
is limited to a maximum length of fifty feet. Beyond that distance, 
transmission losses in the bundle prevent sufficient illumination to 
obtain a clear color video signal. 
The interfacing of the fiber optic bundle to the color illumination 
generator is carried out by the interface module 20, such as the one as 
explained in U.S. Pat. No. 4,539,586. 
Inspection of equipment with this type of borescope becomes difficult for 
confined areas, such as a boiler manifold, where there is insufficient 
space for the video processor unit. In such case, the auxiliary light unit 
26 can be employed to remote the video processor unit by several meters. 
As shown in FIG. 2, the auxiliary light box 24 is formed of a housing or 
case 46 with a multiple-pin connector 48 mounted on its rear wall 32. This 
connects with a mating multiple contact connector 50 on the distal end of 
the auxiliary umbilical 30. 
A receptacle 54 for the light conduit 28 is also located on the rear wall 
32 of the auxiliary box 24. 
The light guide or conduit 28 has a male fitting 56 at its proximal end to 
connect to a suitable fitting at the auxiliary lamp unit 26. An adapter 
can be employed to mate this fitting to other light sources. At the distal 
end of the light guide 28 is a male coupling or probe 58 which is inserted 
into the receptacle 54 on the auxiliary box 24, protruding to a position 
adjacent the receptacle 22. A retaining nut 60 with inside threads retains 
the probe 58 in the receptacle 54. A dust cap 62 is provided for the 
multiple pin connector 48 and a dust cover 63 is provided for the 
receptacle 22. 
As shown in FIG. 3, the auxiliary interface module 34 is basically similar 
to the module of U.S. Pat. No. 4,539,586, with a screw rod 35 that extends 
longitudinally through the module and engaging a threaded bore within the 
receptacle of the processor 36. There are also numerous electrical 
connections made between conductors of the umbilical 30 and the processor 
36. Unlike the module 20 of the borescope assembly, and unlike the 
interface module disclosed in U.S. Pat. No. 4,539,586, a red light sensor 
40 is included in the module 34 in place of the usual light transmitting 
fiber optic bundle. This sensor 40 can be a barcode reader wand. This 
sensor provides a pulse signal over a conductor to the auxiliary light box 
24 through the umbilical 30. 
As further shown in FIG. 4, the housing 46 of the auxiliary box 24 has a 
sleeve 64 within it connected to the receptacle 54 to guide the light 
guide probe 58 to a suitable position with respect to a color generator 
66, which can be of the same general construction as disclosed in U.S. 
Pat. No. 4,523,224. This generator includes a rotary color filter wheel 68 
which presents a succession of red, blue, and green filters between the 
end of the probe 58 and the receptacle 22. A synchronous motor or stepper 
motor 70 drives the color filter wheel 68 in synchronism with the color 
wheel of the processor 36, employing the color pulse signal from the 
sensor 40. Synchronizing signals are generated in the video processor 
units including a lamp-enable signal LEN generated at the field rate and a 
sweep signal .phi.p that corresponds to twice the line or horizontal sweep 
rate. The box 24 can be used for either NTSC or systems, as preferred, 
depending on how the signals .phi.p and LEN are handled. 
As shown in FIG. 4, the auxiliary color generator includes a motor driver 
circuit printed circuit board 72. A timing pin 74 on the shaft of the 
motor 70 passes a magnetic or optical sensor 76 which produces a pulse 
when the motor shaft reaches a predetermined angular position. The color 
generator also includes suitable interface optics 78, and a 
color/monochrome selector which can constructed as described in U.S. Pat. 
No. 4,862,253, having a common assignee herewith. 
As shown in more detail in FIG. 5 the timing pin 74 is mounted on a shaft 
82 of the motor 70 to rotate with the color wheel 68. The rotary position 
sensor 76 here includes a first optical sensor 84 and a second optical 
sensor 86 angularly spaced by a predetermined angle. These sensors provide 
position or index pulses I.sub.1 and I.sub.2 that are phase separated from 
one another by the same predetermined angle. 
On the motor driver circuit board 72 a wheel control unit 88 sends motor 
drive control signals .phi..sub.1, .phi..sub.2, .phi..sub.3 and 
.phi..sub.4 in response to the position pulses I.sub.1, I.sub.2 from the 
sensors 84 and 86, in response to timing pulses s that corresponds to the 
horizontal synch pulses, and in response to a blue-red field index signal 
BRLFI. This signal BRLFI is generated in response to color pulses from the 
sensor 40 and in response to the lamp enable signal LEN, which is sent to 
the video camera at the field rate from the processor unit. 
Within the enclosure 46 of the auxiliary box 24 is a wiring harness, not 
specifically shown, but which has a plurality of conductors which connect 
the receptacle 22 directly to the multiple pin connector 48, for 
connection via the connector 50, auxiliary umbilical 30 and auxiliary 
interface module 34, to the video processor unit 36. Some of those 
conductors in the wiring harness connect between the video processor 36 
and the video camera, and these can be used to power and synchronize the 
motor 70 of the color signal generator. In particular, these conductors 
carry power at +5 volts, +12 volts, and -12 volts, and also carry the 
signal LEN provided at the video field rate and the signal .phi.p provided 
at twice the line rate. 
The apparatus of this embodiment provides straight passthrough of 
electrical signals between the borescope imager and the video processor 
unit 36. However, the color sequential illumination is generated in the 
auxiliary box 24 at a distance from the unit 36. This permits the monitor 
38 and video processor unit 36 to be remoted at a desired location away 
from the target area without exceeding the critical limit mentioned 
earlier. 
No modification is required to the video processor unit, or its internal 
wiring. 
The color wheel synchronization circuitry can by constructed as generally 
shown in FIGS. 6 and 7. 
FIG. 6 shows a divide-by-three circuit 90 to generate a blue-red field 
index signal BRLFI synchronized with the red color pulses from the scanner 
or sensor 40. Here, the red color pulses are fed through an amplifier 92 
and inverter 94 to a one-shot multivibrator 96 that shapes the pulse 
train, e.g., serving as a blue-to-red transition detector. The output of 
this one-shot is fed to clear terminals of a pair of JK flip flops 98 and 
100 that are connected to serve as a divide-by-three counter. These flip 
flops 98, 100 are clocked by the light enable signal LEN that is furnished 
on the conductors passing through the auxiliary light box wiring harness. 
The output of the circuit 90 is the signal BRLFI provided us at pulses 
one-third the field rate and timed to coincide with the transition from 
the blue to the red filter on the main color wheel in the processor unit 
36. 
As shown in FIG. 7 the wheel control circuit 88 has a frequency divider 102 
that receives the signal .phi.P and feeds a divided-down pulse train to a 
phase-locked loop circuit 104. This circuit 104 generates an output 
frequency that is fed to another frequency divider 106 whose divisor can 
be controlled e.g. between "104" and "105" for NTSC or between "124" and 
"125" for , by a control signal from an index circuit 108. The index 
signal BRLFI is fed to a clock input of the circuit 108 while the index 
pulse I.sub.1 from the optical sensor 84 is applied to a D terminal 
thereof, so that the output signal from the Q terminal of this circuit 104 
depends on the relative timing of the index signals BRLFI and I.sub.1. A 
velocity detector circuit 110 is a logic circuit which is input with the 
position index pulses I.sub.1 and I.sub.2 and produces an error signal 
that is fed to a VCO input terminal of the phase locked loop circuit. The 
output of the divider 106 is fed to a motor drive circuit 112 which 
further divides the frequency by 8 and provides four phase drive signal 
.phi..sub.1, .phi..sub.2, .phi..sub.3, and .phi..sub.4, to the motor and 
also provides a field-rate clock signal to the velocity defector circuit 
110. Details of this circuit can be seen in U.S. Pat. No. 4,523,224. The 
exact circuitry used can be varied to obtain the same results. 
When there is a wide discrepancy in phase or motor velocity between the 
main and auxiliary color light generators, the velocity detector 110 will 
adjust the error signal fed to the phase-locked loop circuit 104. However 
for minor phase adjustment, the index circuit 108 will adjust the divisor 
of the frequency divider 106 to correct the phase of the motor drive 
signals .phi..sub.1 to .phi..sub.4. 
Although in this embodiment the sensor 40 is sensitive to red light, in 
other embodiments a green - or blue-sensitive device could be employed, 
either within the interface module 34, as illustrated, or within the 
auxiliary box and coupled by fiber optics to the main color generator in 
the processor 36. 
It should be appreciated that this device permits extension from existing, 
unmodified video processors, so that the same auxiliary box 24 could be 
employed with a variety of borescope or endoscope systems. 
Also, while this invention has been employed with a borescope in this 
example, the same or similar system could be employed with a medical or 
veterinary endoscope, if desired. 
Here, this invention has been described with reference to one particular 
embodiment, but it should be recognized the invention is not limited to 
that embodiment. Rather, many modifications and variations would present 
themselves to those of skill in the art without departing from the scope 
and spirit of this invention, as defined in the appended claims.