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BACKGROUND OF THE INVENTION
This invention relates to a photographing apparatus for an endoscope, which
is used for automatic exposure signal circuits, and in which the coupling
between a camera and the endoscope and/or coupling between the endoscope
and a light source unit are free from mechanical electric switches or
contacts.
In the usual photographing apparatus for an endoscope, a camera and a light
source for the endoscope are electrically coupled together. This coupling
is made for the purposes of synchronizing flashlight for photographing and
shutter release action and obtaining automatic exposure control. Usually,
the coupling is accomplished through a plurality of mechanical electric
switches or contacts provided in a connector section on the side of an
eyepiece section of the endoscope. These switches or contacts are all
exposed on the outer surface of the connector section, so that contact
failure is likely to result from such causes as their contamination,
oxidation and corrosion. This drawback can be avoided by adopting a
water-proof construction for the switches. However, water-proof electric
switches are complicated in construction and cannot fundamentally solve
the problem.
There are teachings concerning the solution of the above problem, for
instance one disclosed in Japanese Patent Disclosure No. 38322/78. In this
disclosure, a light emission device is provided in the camera, and a light
reception device is provided in the light source section. Light emitted
from the light emission device is transmitted through a signal light guide
within the endoscope to the light reception device. The disclosed
apparatus makes use of light emitted from the light emission device as a
synchronizing signal for the flashlight. Thus, no mechanical electric
switches for the synchronization purposes are needed. However, this
apparatus cannot be adopted where the automatic exposure control is made
on the light source side.
SUMMARY OF THE INVENTION
The invention is contemplated in the light of the above circumstances, and
its object is to provide a photographing apparatus for an endoscope, which
enables the coupling of the camera and endoscope light source unit for the
automatic exposure control without need of any mechanical electric switch.
According to the invention, the above object is achieved by a photographing
apparatus for an endoscope, which comprises an endoscope body including an
observational optical system and a light guide, a light source for
providing light to the light guide, a photographing means mounted on a
light path, through which an optical image obtained by light given to the
light guide and led out through the observational optical system proceeds,
a photoelectric converting means disposed on the light path of the optical
image and serving to produce a brightness signal corresponding to the
brightness of the optical image, a transmitting means connected to the
photoelectric converting means and serving to produce a transmission
signal corresponding to the brightness signal, a receiving means serving
to produce a feedback signal corresponding to the brightness signal by
receiving the transmission signal and a control means to control the light
source according to the feedback signal for controlling the quantity of
light provided from the light source to the light guide.
The photographing apparatus of the above construction has the following
advantages:
In the first place, no electric switches or contacts exposed on the outer
surface of the endoscope are needed, so that not only the water-proof
construction of the endoscope is simplified but also freedom from the
problem of contact failure due to contamination, oxidation or corrosion of
electric switches or contacts can be obtained.
In the second place, since it is possible to select a frequency band used
for transmission and/or reception, a plurality of photographing apparatus
can be concurrently used without the possibility of malfunction due to
radio interference. In addition, wrong use of the individual photographing
apparatus can be avoided by providing each apparatus with an
identification indication.
In the third place, there is no need of providing any electric wire for
signal transmission or signal transmission light guide in the light guide
protective tube connecting the endoscope and light source unit or like
curved portions. Thus, no signal transmission wire breakage trouble
results. In addition, since no signal transmission light guide is needed,
satisfactory flexibility of the light guide protective tube can be ensured
.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of an embodiment of the photographing
apparatus for an endoscope according to the invention;
FIGS. 2A and 2B are perspective views showing examples of camera and light
source unit provided with an identification indication;
FIGS. 3A and 3B to 5A and 5B are perspective views showing modifications of
the examples of FIGS. 2A and 2B;
FIG. 6 is a block diagram showing an example of a transmitter 36 shown in
FIG. 1;
FIG. 7 is a block diagram showing an example of a receiver 42 shown in FIG.
1;
FIG. 8 is a block diagram showing a light source control device 44 shown in
FIG. 1;
FIG. 8A shows an auxiliary circuit to be used with the circuit of FIG. 8;
FIGS. 9A to 9F form a timing chart for illustrating the operation of the
circuit shown in FIG. 8; and
FIG. 10 is a block diagram showing a modification of the device 44 shown in
FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the invention will now be described with reference to the
accompanying drawings. In the drawings like parts are designated by like
reference symbols for the sake of avoiding repeated explanation.
FIG. 1 is a schematic representation of an embodiment of the invention. An
endoscope body 10 has a fiber image guide 12 for transferring an optical
image and a fiber light guide 14. Light from a lamp 20 is coupled through
a condenser lens 18 and a diaphragm 16 to a light receiving end 14.sub.1
of the fiber light guide 14. A reflector 19 is disposed on the back of the
lamp 20 to increase the illumination efficiency. The diaphragm 16 and lamp
20 constitute a light source section 21. Light coupled to the light
receiving end 14.sub.1 of the fiber light guide 14 is led therethrough and
emitted from a light guide end 14.sub.2 of a distal end 10.sub.1. The
distal end 10.sub.1 is connected through a bendable section 10.sub.2 and a
flexible tube (insertion tube) 10.sub.3 to the endoscope body 10. The
distal end 10.sub.1 has a conventional observational optical system
12.sub.1 provided within it. An optical image of a foreground subject
caught by the optical system is led through the fiber image guide 12 to a
lens system 22. The optical image having been transmitted through the lens
system 22 is transmitted through a semi-transparent prism 24 and led to a
movable mirror 26. When photographing is not made, the optical image
incident on the movable mirror 26 is led through a lens system 27, a
penta-prism 28 and a lens system 30 to the outside of the camera 32, which
is mounted on the endoscope 10. When taking a picture, the movable mirror
26 is moved to a position of broken lines in FIG. 1. As a result, the
optical image having been transmitted through the semi-transparent prism
24 is led to a film 33.
The afore-mentioned optical image is spectroscopically split by the
semi-transparent prism 24, and part of it is led therefrom to the left in
FIG. 1. The prism 24 is provided at its left hand end with a photoelectric
converter or photo-diode 34. As the photoelectric converter may be used a
cadmium sulfide (CdS) cell or a solar battery as well. The photo-diode 34
produces a brightness signal at a level corresponding to the brightness of
the optical image transmitted through the prism 24. This brightness signal
is coupled to a transmitter 36 of AM or FM type. The transmitter 36
produces a transmission signal corresponding to the afore-said brightness
signal. The transmission signal is transmitted to the outside via an
antenna 38. A power supply 37 is connected to the transmitter 36. The
transmission signal radiated from the antenna 38 is intercepted by an
antenna 40, and thence it is coupled to a receiver 42. Where the
transmitter 36 is of FM type, the receiver is also of FM type. The
receiver 42 demodulates a feedback signal corresponding to the
transmission signal. The tuning frequency of the receiver 42 can be varied
by a frequency selection switch 43, which serves to switch the resonance
frequency of an LC tuning circuit in the receiver 42. Where the receiver
42 is provided with a so-called frequency synthesizer tuner, the dividing
ratio of a programmable frequency divider within the synthesizer is varied
by the switch 43.
The demodulated feedback signal is coupled from the receiver 42 to a light
source control device 44. This control device 44 provides a control signal
to the light source section 21 and may have a conventional construction.
The quantity of light given from the light source section 21 to the light
receiving end 14.sub.1 of the fiber light guide 14 can be controlled by
controlling the power supplied to the lamp 20, the on-off frequency of the
lamp 20 or the aperture of the diaphragm 16 according to the
afore-mentioned control signal. The light source section 21, control
device 44 and receiver 42 constitute a light source unit 46. The light
source unit 46 is installed on the endoscope 10 via a light guide
protective tube 11. In the construction of FIG. 1, an automatic control
system having a closed loop including the foreground subject (not shown)
such as the colon membrane present ahead of the distal end 10.sub.1. When
the foreground subject is dark, the optical image led to the photo-diode
34 is also dark. In this case, the level of the brightness signal produced
from the photo-diode 34 is low, so that modulation is obtained in the
transmitter 36 to little extent. In consequence, the level of the
demodulated feedback signal in the receiver 42 is low. When the level of
the feedback signal is low, the light source control device 44 acts to
increase the current supplied to the lamp 20 or on-off frequency of the
lamp 20 or the aperture of the diaphragm 16. As a result, the quantity of
light given to the fiber light guide 14 is increased to make the
foreground subject brighter.
By the afore-mentioned automatic control action the brightness of the
optical image led out from the fiber image guide 12 can be automatically
controlled to a desired level.
The photographing apparatus shown in FIG. 1 is used in the following way.
When taking a picture after mounting the camera 32 on the endoscope body
10, the eyepiece (not shown) of the endoscope is removed from the optical
path. The movable mirror 26 is set at its position of solid lines in FIG.
1 until a spot to be photographed is found out. When the photographing
spot is determined, a shutter release switch 48 is depressed. As a result,
the transmitter 36 is rendered operative, and a synchronizing signal is
transmitted therefrom. With the operation of the shutter release switch 48
the movable mirror 26 is moved to its position of broken lines in the
Figure. When the synchronizing signal is captured by the receiver 42, the
lamp 20 is caused to flash. The flashlight is reflected by the
afore-mentioned photographing spot ahead of the distal end 10.sub.1, and
the optical image of the spot is led through the semi-transparent prism 24
to the film 33. The brightness of the optical image at this time is
detected by the photo-diode 34 and transmitted through the transmitter 36
and receiver 42 to the light source control device 44. When an adequate
quantity of exposure light is obtained, the illumination by the lamp 20 is
interrupted. During the "off" period of the lamp the movable mirror 26 is
returned to the position of solid lines in the Figure, and then the
illumination by the lamp 20 is resumed. In this way, one photographing
cycle or sequence is ended. The adequate exposure light quantity is
suitably determined in dependence upon the sensitivity of the film 33 used
and other conditions.
The above description was concerned with the case of controlling the
exposure on the side of the light source unit 46. However, it is also
possible to adopt a system, in which the exposure control is made on the
side of the camera 32 (i.e., a camera 32 of EE type is used) with only the
synchronizing signal transmitted to the light source unit.
FIGS. 2A and 2B to 5A and 5B are perspective views showing examples of the
camera 32 and light source unit 46 separated from the endoscope body 10.
The camera 32 and the light source unit 46 are each given an
identification indication 50, for instance using a numeral such as "3".
Such an indication is given from the following ground. In frequent cases
of endoscopic examination, several endoscopic sets are concurrently
operated in the same place. In such a case, that is, when a plurality of
the endoscopic photographing apparatus as shown in FIG. 1 are concurrently
used, different frequencies are set for the individual photographing
apparatus. This is done so because the use of a single frequency would
lead to malfunction due to radio interference. Such malfunction can be
avoided by providing exclusive frequency bands to the individual
photographing apparatus such that do not overlap one another. However,
when concurrently using a plurality of cameras 32 and associated light
source units 46 for which different frequencies are set, it is likely that
the user cannot tell which camera is paired with which light source unit.
This inconvenience can be overcome by providing the afore-mentioned
identification indication 50.
In the case of FIGS. 2A and 2B, the camera 32 is given an identification
figure "3", and the frequency selection dial 43 of the light source unit
46 is set to a mark "3". In the case of FIGS. 3A and 3B, different colors
are utilized for the identification indication. For instance, when the
camera 32 has an identification color of, for instance, "read", the
frequency selection dial 43 of the associated light source unit 46 is set
to a red color mark. As the identification color may, for instance, be
used black, blue, red, white and yellow. In the case of FIGS. 4A and 4B, a
frequency selection dial 43 is provided on the side of the camera 32, and
in the case of FIGS. 5A and 5B the frequency selection dial 43 is provided
on both the camera 32 and light source unit 46.
FIG. 6 shows a specific construction of the transmitter 36 shown in FIG. 1.
The photo-diode or photosensor 34 produces a brightness signal E10 which
is coupled to an amplifier 36.sub.1 for amplification. The amplifier
36.sub.1 amplifies the signal E10 with a predetermined degree and produces
a resultant modulation signal E12 which is coupled to a modulation circuit
36.sub.2. To the circuit 36.sub.2 is supplied a carrier wave signal E14 at
a fixed frequency f1 from a carrier oscillator 36.sub.3. When the release
switch 48 is depressed, an operation command signal E16 is provided from
the switch 48 to the circuit 36.sub.2, whereupon the circuit 36.sub.2
produces a modulated carrier signal E18 produced by modulation of the
carrier with the signal E12. The signal E18 is amplified by a
radio-frequency amplifier 36.sub.4 to produce a transmission signal E20
which is supplied to the antenna 38. The components 36.sub.1 to 36.sub.4
are furnished with power from the power supply 37.
FIG. 7 shows a specific construction of the receiver 42. The transmission
signal E20 intercepted by the antenna 40 is coupled to a tuner circuit
42.sub.1. The frequency selection switch 43 is set such that the tuning
frequency f2 of the circuit 42.sub.1 is made equal to the carrier wave
frequency or fixed frequency f1 of the camera 32 side. When the frequency
selection switch 43 is set such that f1=f2, the circuit 42.sub.1 produces
a first signal E24 corresponding to the signal E20. The signal E24 is
coupled to a detector or demodulator circuit 42.sub.2. Where the
modulation circuit 36.sub.2 shown in FIG. 6 is an AM modulator, the
circuit 42.sub.2 is an AM detector, whereas when the circuit 36.sub.2 is
an FM modulator the circuit 42.sub.2 is an FM demodulator.
The signal E24 is detected or demodulated by the circuit 42.sub.2 to
produce a second signal E26 corresponding to the modulation signal
component (E12) of the signal E20. The signal E26 is amplified by an
amplifier 42.sub.3 to produce a feedback signal E30 corresponding to the
signal E20. The signal E30 corresponds to the brightness signal E10
transmitted from the transmitter 36 to the receiver 42. In other words,
the level of the signal E30 is changed with changes in the level of the
signal E10.
FIG. 8 shows a specific construction of the light source control device 44
shown in FIG. 1. FIGS. 9A to 9E represent a timing chart illustrating the
operation of the device 44. The feedback signal E30 as shown in FIG. 9B is
subjected to wave shaping and level inversion by an inverter 44.sub.1,
whereby a signal E32 as shown in FIG. 9C is obtained. The signal E32 is
coupled to a clock input terminal of a D type flip-flop (D-FF) 44.sub.2.
Before an instant t14 a signal E40 of logic level "1" as shown in FIG. 9A
is inputted at a D input terminal of the D-FF 44.sub.2. When the release
switch 48 shown in FIG. 6 is turned on at an instant t10, the signal E30
is inverted to high level, while the signal E32 is inverted to low level.
The D-FF 44.sub.2 is not clocked with the falling edge of the signal E32.
Consequently, the output from the Q output terminal of the D-FF 44.sub.2
remains at logic level "0".
Until an instant t12 after the switch 48 has been turned on, the mirror 26
in the camera 32 is moved to the position of broken lines in FIG. 1. At
the instant t12, the signal E30 is inverted again to low level, while the
signal E32 is inverted again to high level. The signal E30 is used for its
period of high level between the instants t10 and t12 as synchronizing
signal E30.sub.1. The pulse width of the signal E30.sub.1 is determined
by, for instance, a monostable multivibrator which is triggered with the
rising edge of the signal E30, that is, the pulse width (between the
instants t10 and t12) of the signal E30 can be determined according to the
time constant of this multivibrator. The D-FF 44.sub.2 is clocked at the
instant t12 with the rising edge of the signal E32. As a result, the
signal E34 produced from the Q output terminal of the D-FF 44.sub.2 is
inverted to logic level "1" as shown in FIG. 9D.
With the inversion of the signal E34 to logic level "1" at the instant t12,
an NPN type drive transistor 44.sub.3 is biased through a resistor R10,
whereupon the transistor 44.sub.3 is turned-on. As a result, the lamp 20
which is connected to the collector circuit of the transistor 44.sub.3 is
energized to emit light. The logic "1" of the signal E34 is coupled after
level inversion through an inverter 44.sub.4 to the gate of a MOS
transistor 44.sub.5. When the gate potential on the transistor 44.sub.5 is
reduced after the instant t12, the transistor 44.sub.5 is cut off. An
integrating capacitor C12 of an integrator 44.sub.6 is connected between
the drain and source of the transistor 44.sub.5. When the transistor
44.sub.5 is cut off, the integrator 44.sub.6 starts integration of the
signal E30 which is supplied to an integrating resistor R12. The
integration input to the integrator 44.sub.6 corresponds to the brightness
of the optical image sensed by the photo-sensor 34 shown in FIG. 1
according to the glowing of the lamp 20 after the instant t12. In other
words, after the instant t12 the signal E30 constitutes a brightness
signal E30.sub.2 having a level L1 corresponding to the brightness of the
optical image as shown in FIG. 9B. This signal E30.sub.2 is integrated by
the integrator 44.sub.6 to produce an integration output signal E36 as
shown in FIG. 9E.
The signal E34, which is level inverted at the instant t12, is coupled
through a delay circuit 44.sub.7 consisting of a resistor R14 and a
capacitor C14 to an inverter 44.sub.8. When the level of the input to the
inverter 44.sub.8 exceeds a threshold level thereof, the inverter 44.sub.8
inverts the input level and produces the signal E40. In other words, the
delay circuit 44.sub.7 delays the input signal after the instant t12, so
that at an instant t14 the D input of the D-FF 44.sub.2 is inverted to
logic level "0" as shown in FIG. 9A.
The integration output signal E36 from the integrator 44.sub.6 is coupled
to a comparator 44.sub.9, which compares the signal E36 with a
predetermined comparison voltage V.sub.ref. Before an instant t16,
E36<V.sub.ref, so that the comparison output signal E38 from the
comparator 44.sub.9 is at logic level "0". When E36.gtoreq.V.sub.ref at
the instant t16 is obtained as shown in FIG. 9E, the signal E38 is
inverted to logic level "1" as shown in FIG. 9F. The signal E38 is coupled
to a clear input terminal of the D-FF 44.sub.2. As a result, the D-FF
44.sub.2 is cleared at the instant t16, whereupon the signal E34 is
inverted to logic level "0".
With the inversion of the signal E34 to logic level "0" at the instant t16,
the transistor 44.sub.3 is cut off to turn off the lamp 20. As a result,
light having previously been incident on the photo-sensor 34 in FIG. 1 or
6 disappears, so that the signal E10 is reduced substantially to zero
level, reducing the modulation degree of the transmission signal E20 to
zero. Then, the feedback signal E30 produced from the receiver 42 is
reduced to zero level. When the signal E30 is reduced to zero level, the
signal E32 is inverted to high level. The D-FF 44.sub.2 is clocked with
the rising edge of the signal E32. However, since the D input has been at
logic level "0" after the instant t14, the signal E34 is held at logic
level "0" after the instant t16.
With the inversion of the signal E34 to logic level "0" at the instant t16,
the transistor 44.sub.5 is turned-on to reset the integrator 44.sub.6. As
a result, the signal E36 returns to zero level in a very short period of
time as shown in FIG. 9E. When the condition E36<V.sub.ref is satisfied
again as a result of the resetting of the integrator 44.sub.6, the signal
E38 is inverted again to logic level "0" immediately after the instant t16
as shown in FIG. 9F. The level inversion of the signal E34 at the instant
t16 is transmitted through the delay circuit 44.sub.7 to the inverter
44.sub.8. When the level of the input to the inverter 44.sub.8 becomes
lower than the threshold level at an instant t18, the signal E40 is
inverted to logic level "1" as shown in FIG. 9A. After the instant t18 the
same state as that before the instant t10 is maintained until the next
synchronizing signal E30.sub.1 of the signal E30 appears. After the
instant t18 the release switch 48 shown in FIG. 6 is turned off, and as a
result the mirror 26 shown in FIG. 1 is returned to its initial position.
If it is desired to cause glowing of the lamp 20 before the instant t10 and
after instant t18 in FIGS. 9A to 9F, that is, when the mirror 26 shown in
FIG. 1 is in the position of solid lines, a logic circuit as shown in FIG.
8A may be used. Here, the signals E40, E32 and E34 are coupled to an AND
gate 44A, with the signal E34 being coupled to a level inversion input
terminal. The AND output E35 of the gate 44A is coupled through a resistor
R11 to the base of the transistor 44.sub.3. The output E35 is at logic
level "1" before the instant t10 and after the instant t18, that is,
during the periods when the shutter release switch 48 is not operated.
During these periods, the transistor 44.sub.3 is thus "on", and the lamp
20 emits light.
With the control device 44 shown in FIG. 8, the lamp 20 emits light during
the period of the "on" state of the transistor 44.sub.3, i.e., during the
period between the instants t12 and t16, during which the signal E34 is at
logic level "1". This period between the instants t12 and t16 corresponds
to an exposure period T1 from the start of integration by the integrator
44.sub.6 (E36=0) until the signal E36 becomes equal to V.sub.ref. This
exposure period T1 is inversely proportional to the slope .theta.1 of the
signal E36, and the slope .theta.1 is proportional to the level L1 of the
brightness signal E30.sub.2. This means that the exposure period T1 is
inversely proportional to the brightness of the optical image sensed by
the photo-sensor 34. In other words, the brighter the optical image the
shorter the exposure period is, and the darker the optical image the
longer the exposure period is.
The sequence of events that take place in case when the optical image is
darker (i.e., L1>L2) are shown between instants t20 and t28 in FIGS. 9A to
9F. In this case, the slope of the signal E36 is reduced
(.theta.1>.theta.2), and the exposure period is increased (T1<T2). This
means that the quantity of light given to the film 33 shown in FIG. 1 is
automatically controlled to a predetermined value according to the
brightness of the optical image. In this way, automatic exposure control
can be obtained.
FIG. 10 shows a modification of the control device 44 shown in FIG. 8.
Here, the feedback signal E30 is coupled to a signal switch 44.sub.10,
which is an analog gate circuit for separating the synchronizing signal
E30.sub.1 and brightness signal E30.sub.2 in the signal E30. In other
words, a portion of the signal E30 from the rising edge till the falling
edge (i.e., between the instants t10 and t12 in FIG. 9B) is supplied as
the signal E30.sub.1 to a trigger circuit 44.sub.11. In consequence, the
circuit 44.sub.11 produces a trigger pulse E32.sub.1 with the falling edge
of the signal E30.sub.1 (at the instant t12 in FIG. 9C). The pulse
E32.sub.1 is inputted to a switch circuit 44.sub.2 which is constructed
with an SCR or the like. When the pulse E32.sub.1 is inputted, the circuit
44.sub.12 is turned on to supply the signal E34 (between the instants t12
and t16 in FIG. 9D) for causing the glowing of the lamp 20.
Meanwhile, a portion of the signal E30 from the second rising edge till the
second falling edge (i.e., between the instants t12 and t16 in FIG. 9B) is
inputted as the signal E30.sub.2 to an integrator 44.sub.6. The integrator
44.sub.6 integrates the level L1 of the signal E30.sub.2, and supplies the
integration output signal E36 to a comparator 44.sub.9. The comparator
44.sub.9 is provided with a predetermined reference voltage V.sub.ref, and
couples a comparison output signal E38 to the circuit 44.sub.12 when a
condition E36.gtoreq.V.sub.ref is satisfied (at the instant t16 in FIG.
9F). When the signal E38 is inputted, the circuit 44.sub.12 is turned off,
and the light source 21 stops light emission.
Although specific constructions have been illustrated and described herein,
it is not intended that the invention be limited to the elements and
constructions disclosed. One skilled in the art will recognize that the
particular elements or sub-constructions may be used without departing
from the scope and spirit of the invention.
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