Photographing system for endoscope

A photographing system for an endoscope comprises an endoscope including a light guide and an image guide, a camera unit including a shutter button for producing an instruction signal for starting a photographing cycle and a mirror shutter for opening a light path of an image supplied from an image guide; and a light source unit including a photographing light source for producing photographing light, an observation light source for producing observation light and a reflective mirror for switching light supplied to the light guide from the observation light to the photographing light. The camera unit further includes a switch for producing a light path switching signal for operating the reflective mirror simultaneously with the depression of the shutter button and a switch closed by the mirror shutter released a predetermined period of time after the depression of the shutter button and producing a signal for energizing the photographing light source. Thus, in the light source unit the photographing light source is turned on after the reflective mirror is switched.

BACKGROUND OF THE INVENTION 
This invention relates to a photographing system for an endoscope and, more 
particularly, to a photographing system for an endoscope, in which 
observation light from an observation light source is used for observing a 
region of interest and photographing light from a photographing light 
source is used for photographing the region of interest. 
In the usual photographing system for an endoscope, an observation light 
from an observation light source, for instance a halogen lamp, and a 
photographing light from a photographing light source, for instance an 
electric flash tube, can be introduced into a light guide of the 
endoscope. In an optical path, an optical path switching mirror is 
provided for directing the observation light to the light guide at the 
time of the observation and directing the photographing light to the light 
guide at the time of the photographing. 
The problems in such an endoscopic photographing system are that the color 
reproduction of the photograph image is likely to be deteriorated, or the 
photograph image is likely to become blurred. The region for this is as 
follows. Usually, the optical path switching mirror is shifted 
simultaneously with or after the releasing of the shutter of the camera 
unit. However, at the time of the shifting of the mirror, a mechanical 
delay is involved, so that not only the photographing light but also the 
observation light is supplied after the releasing of the shutter. The dual 
exposure of the film to both photographing light and observation light 
blurs the resultant photograph image and also deteriorates the color 
reproduction thereof. 
The object of the invention is to provide a photographing system for an 
endoscope, which prevents the exposure of a film in the camera unit to the 
observation light and permits exposure only to the photographing light at 
the time of the photographing, thus permitting a photograph of high 
clarity and good color reproduction to be obtained. 
SUMMARY OF THE INVENTION 
According to the invention, there is provided a photographing system for an 
endoscope comprising: 
an endoscope including a light guide for transmitting light to a region of 
interest for photographing or observation and an image guide for 
transmitting an image of said region of interest; 
a light source unit including a light source for producing photographing 
light which is supplied to said light guide through a first optical path, 
a light source for producing observation light which is supplied to said 
light guide through a second optical path, an optical path switching means 
for switching the second optical path to the first optical path, a means 
for energizing said photographing light source, and a means for operating 
light path switching means; and 
a camera unit including a shutter means for opening an optical path from 
said image guide to a film, a shutter drive means for driving said 
shutter, a shutter release button for producing an instruction signal for 
starting a photographing cycle, a means for producing an optical path 
switching signal for energizing said operation means in synchronism to the 
instruction signal, a means for producing a shutter release signal for 
starting said shutter drive means predetermined time period after the 
receiving the instruction signal, and a means for producing a 
photographing light emission signal for starting said energizing means in 
synchronism to the release of said shutter means.

DETAILED DESCRIPTION 
Referring now to FIG. 1, there is shown an embodiment of the endoscopic 
system according to the invention. A photographing system for an endoscope 
comprises an endoscope 6, which includes a light guide 2 and an image 
guide 4, a camera unit 8 coupled to the endoscope 6, and a light source 
unit 10 for supplying light to the light guide 2. The light source unit 10 
includes an observation light source, for instance a halogen lamp 12, for 
illuminating the region of interest at the time of making a diagnosis, and 
a photographing light source, for instance an electronic flash tube 14, 
for illuminating the region of interest at the time of photographing that 
region. A reflective mirror 16 is so arranged to reflect the observation 
light to the end face of the light guide 2 and to prevent the 
photographing light from being transmitted to the end face of the light 
guide 2. The mirror 16 is mounted on a solenoid 20 driven by a solenoid 
energizing circuit 18 such that it can be shifted by the solenoid to 
direct the photographing light to the end face of the light guide 2. The 
endoscope 6 is provided with a synchronizing cord 22 which electrically 
connects the camera unit 8 and light source unit 10. The synchronizing 
cord 22 is provided at its one end with connector pins 24, which are 
connected to connector pins 26 provided on the camera side when the 
endoscope 6 is mounted on the camera. One of the connector pins 26 on the 
side of the camera unit 8 are connected through a resistor 28 to a first 
switch 30 and is also connected to a second switch 32, the resistor 28 and 
switches 30 and 32 being provided within the camera unit. The second 
switch 32 practically has a function of a synchronizing switch for turning 
on the electronic flash tube 14 to be described hereinafter. While the 
first switch 30 is closed when a camera shutter release button 34 is 
depressed, the second switch 32 is adapted to be closed with a jerk-up 
motion of a mirror shutter 17 which is also provided within the camera 
unit. The camera unit further includes a third switch 38 which is also 
closed by the shutter release button 34 simultaneously with the first 
switch 30. The third switch 38 is connected through a delay circuit 40 to 
a shutter drive circuit 42, which drives the mirror shutter 17. The camera 
unit 8 further includes a film 44 disposed behind the mirror shutter 17, 
and the endoscope 6 is provided with a photographing lens 48 which faces 
the film 44 for projecting the image of the region of interest transmitted 
through an objective lens 46 and an image guide 4 on the film 44. 
The synchronizing cord 22 is provided at the other end with connector pins 
52, which are connected to light source side connector pins 50 when the 
endoscope is coupled to the light source unit 10. One of the light source 
side connector pins 50 is connected through a resistor 54 to a positive 
terminal of a DC power source 56 within the light source unit 10. One of 
the connector pins 50 is connected to the negative input terminal of each 
of first and second comparators 58 and 60, which have their respective 
positive input terminals connected through respective DC power sources 62 
and 64 to the other connector pin 50, to which the negative terminal of 
the DC power source 56 is connected. The voltages V.sub.s1 and V.sub.s2 of 
the respective power sources 62 and 64 are set as follows: 
EQU V.sub.s1 .gtoreq.V.sub.1 .multidot.R.sub.1 /(R.sub.2 +R.sub.2) 
and 
EQU 0&gt;V.sub.s2 &gt;V.sub.1 .multidot.R.sub.1 /(R.sub.1 +R.sub.2) 
where V.sub.1 is the voltage of the power source 56, R.sub.1 is the 
resistance of the resistor 28 in the camera unit 8, and R.sub.2 is the 
resistance of the resistor 54 in the light source unit 10. 
The circuit elements 54, 56, 58, 60, 62 and 64 constitute a circuit for 
detecting the on-off states of the first and second switches 30 and 32. 
The output terminal of the first comparator 58 is connected to the 
solenoid energizing circuit 18 for operating the solenoid 20, which is 
thus energized according to the output of the comparator 58. The output 
terminal of the second comparator 60 is connected to a trigger circuit 66 
for triggering the electronic flash tube 14, which is thus energized 
according to the output of the second comparator 60. The discharging 
circuit for the flash tube 14 has a well-known construction having a main 
capacitor 68 and an electric power source 70 as shown in FIG. 1. 
Between the flash tube 14 and the end face of the light guide 2 a condenser 
lens 71 for focusing photographing light from the flash tube 14 onto the 
end face is provided. 
With the above construction of the photographing system for an endoscope 
according to the invention, at the time of the diagnosis the region of 
interest (not shown) is observed by observation light from the observation 
light source 12. At this time, the observation light is reflected by the 
mirror 16 and introduced into the light guide 2. The observation light 
transmitted through the light guide 2 is reflected from the region of 
interest and is led through an objective lens 46 to the image guide 6, so 
that the image of the region of interest can be observed through the 
photographing lens 48, mirror 17 and a prism (not shown). 
For photographing the region of interest, the shutter release button 34 is 
depressed as shown in FIG. 2A, whereupon the first and third switches 30 
and 38 are simultaneously closed as shown in FIGS. 2B and 2C. With the 
closure of the third switch 38 the delay circuit 40 is energized. When a 
predetermined delay time set in the delay circuit 40 is elapsed, the 
shutter drive circuit 42 is rendered operative as shown in FIG. 2D, 
whereupon the mirror shutter 17 starts to move. The mirror shutter 17 is 
completely removed from the optical path between the photographing lens 48 
and film 44 not as soon as the shutter drive circuit 42 is rendered 
operative, but after the lapse of a short mechanical delay time T.sub.L1, 
as shown in FIG. 2E. When the mirror shutter 17 is completely removed from 
the optical path, the second switch 32 is closed as shown in FIG. 2F, and 
the exposure of the film 44 is enabled. 
With the closure of the first switch 30 the voltage on the negative input 
terminals of the comparators 58 and 60 is reduced from the level of the 
voltage V.sub.1 of the power source 56 to V.sub.1 .multidot.R.sub.1 
/(R.sub.1 +R.sub.2). As a result, only the first comparator 58 is rendered 
operative as shown in FIG. 2G, thus rendering the solenoid energizing 
circuit 18 operative as shown in FIG. 2H to energize the solenoid 20. 
Thus, the mirror 16 is completely removed from the optical path between 
the electronic flash tube 14 and light guide 2 after a mechanical delay 
time T.sub.L2 as shown in FIG. 2I. Consequently, light from the 
observation light source 12 is no longer introduced into the light guide 
2, and light from the sole photographing light source 14 can be introduced 
into the light guide 2. 
When the second switch 32 is closed after the mechanical delay time 
T.sub.L1 from the instant of start of the releasing of the mirror shutter 
as shown in FIG. 2E after the lapse of the delay time as shown in FIG. 2D, 
the voltage on the negative input terminals of the comparators 58 and 60 
is reduced from the value V.sub.1 .multidot.R.sub.1 /(R.sub.1 +R.sub.2) 
substantially to the level of the negative side potential on the power 
source, whereupon the comparator 60 is rendered operative to produce an 
output supplied to the trigger circuit 66. As a result, the trigger 
circuit 66 is rendered operative as shown in FIG. 2J, causing the 
electronic flash tube 14 to emit light as shown in FIG. 2K. This light is 
introduced as photographing light to the light guide 2 for illuminating 
the region of interest, and reflected light therefrom is led through the 
objective lens 46, image guide 4 and photographing lens 48 to the film 
surface 44. 
While the observation light is introduced into the light guide 2 as shown 
in FIG. 2L until the completion of switching of the mirror 16 as shown in 
FIG. 2I, the mirror shutter 17 is released as shown in FIG. 2E after the 
switching the mirror 16. Thus, the image of the region of interest 
obtained by the sole photographing light is transmitted to the film 
surface 44 as shown in FIG. 2M. It is thus possible to solve the prior-art 
problem of the dual exposure of the film to the observation light and 
photographing light. 
FIG. 3 shows a different embodiment of the photographing system for an 
endoscope using a rigid endoscope 72. In this embodiment, synchronizing 
cord 22 is not provided within the endoscope, but it is provided within a 
cord 78 having exclusive connectors 74 and 76. The reason for using such 
an exclusive cord 78 is that it is difficult to provide the cord 22 within 
the rigid endoscope 72 from the standpoint of sterilization. In the 
embodiment of FIG. 3 the corresponding parts to those shown in FIG. 1 are 
designated by like reference numerals, and their description is omitted 
here. As is described in the embodiment of FIG. 3, various modifications 
of the wiring of the photographing system are possible. Further, it is 
possible to appropriately modify the circuit construction of the 
photographing system according to the invention. 
As has been described in the foregoing, according to the invention it is 
possible to provide a photographing system for an endoscope, which not 
only eliminates blur due to dual exposure but also permits to obtain 
photographic images of good color reproduction since the mirror shutter is 
released for photographing the region of interest after the switching of 
the observation light source to the photographing light source.