JPH0511286B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an endoscope for observing the inside of a body cavity or a mechanical structure, and particularly to an endoscope having a built-in solid-state imaging device at its tip.

(Prior art) A conventional endoscope has a light guide and an image guide made of an optical fiber bundle extending inside a flexible outer tube that is inserted into a subject, and emits light from an external illumination source. The light is guided through the light guide to the tip of the endoscope, and is irradiated onto the subject through the illumination lens system.The image of the subject is guided to the outside via the objective lens system and image guide, and then directly through the eyepiece system. They either observe it or take an image with an imaging device and display it on a monitor. The resolution of conventional endoscopes using such image guides is determined by the diameter of the fibers that make up the image guide, but it is extremely difficult to make the fiber diameter even thinner than it currently is, and the resolution has almost reached its limit. has reached. Furthermore, since the image guide is easily damaged, there is also a problem in terms of durability.

In order to solve these problems, a small imaging device is built into the tip of the endoscope, which captures an image of the subject, converts it into an image signal, and guides this image signal to the outside via a conductor. It has been proposed to display a subject image on a monitor. Imaging devices include CCD, BBD, MOS-FET ARRAY, PIN
-Semiconductor solid-state imaging devices such as PHOTODIODE ARRAY and SIT ARRAY have been developed, and these solid-state imaging devices have the characteristics of being small, high resolution, and long lifespan.
Suitable for being built into an endoscope.

The applicant has already proposed an endoscope with a built-in solid-state imaging device, but since the dynamic range of the solid-state imaging device varies greatly depending on the temperature, it may be difficult to obtain good images depending on the usage conditions. I've confirmed that I can't get it.

Figure 1 shows the temperature characteristics of a typical solid-state imaging device consisting of a CCD. Dark current I _D increases as temperature rises, while saturation current I _S remains constant even with temperature changes. Therefore, the dynamic range decreases as the temperature increases. Therefore, in order to obtain high-quality images, it is necessary to maintain the operating temperature of the solid-state imaging device at a low constant value. However, the endoscope tip tends to become hot due to the radiant heat of the illumination light propagated through the light guide, the heat radiated from the subject, and the heat radiated from the solid-state imaging device itself, and the operating temperature of the solid-state imaging device cannot be maintained at a constant low temperature.

Therefore, as an endoscope with a built-in solid-state imaging device, there is an endoscope in which the solid-state imaging device or the tip of the flexible outer tube in which it is placed is cooled using an electronic cooling thermoelectric element or a cooling medium. Various proposals have been made in the past.

However, when the tip of the endoscope barrel is cooled in this way, the objective lens system becomes cloudy due to the temperature difference with the outside, and the image of the subject may not be effectively formed on the solid-state imaging device. .

(Objective of the Invention) An object of the present invention is to solve the above-mentioned problems, effectively prevent clouding of the objective lens system with a simple configuration, and always effectively form an image of a subject on a solid-state imaging device. The present invention aims to provide an endoscope incorporating such a solid-state imaging device.

(Summary of the Invention) The present invention is arranged inside the tip of a flexible outer cylinder,
In an endoscope in which an image of a subject is formed through an objective lens system on a solid-state imaging device cooled by a cooling means, a vacuum layer is formed on the subject side of the objective lens system. By providing heat insulation, fogging of the objective lens system is prevented.

(Example) Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a front view of the distal end showing the configuration of an example of the endoscope of the present invention, and FIG. 3 is a sectional view taken along the - line in FIG. 2. The endoscope of this example is a direct-view type for observing the inside of a body cavity, and a tip main body 2 made of, for example, stainless steel is fitted onto the tip of a flexible outer tube 1 that is inserted into a subject. This tip body 2 is formed with several channels 2a to 2e.
A light guide 3 made of an optical fiber bundle is inserted into the pair of light guide channels 2a,
A concave lens 4 is fitted to the tip. light guide 3
is covered by a cover tube 5, extends inside the outer cylinder 1, is guided to the operating section, and is connected to an illumination light source.

The objective observation channel 2b includes an objective lens system 6.
At the same time, a solid-state imaging device 7 is fitted, and a pair of glasses 8a and 8b are fitted to the tip of the objective lens system 6 so as to be spaced apart and facing each other in the optical axis direction, and a vacuum layer 9 is formed between these glasses. form. The conductive wire bundle 10 connected to the solid-state imaging device 7 is guided to the operating section through a flexible tube extending inside the outer cylinder, and connected to a signal processing circuit.

An air supply tube is connected to the air supply channel 2c, and an air supply nozzle 11 is attached to the tip thereof, so that air can be supplied toward the glass 8a of the objective observation channel 2b.

A water supply tube is connected to the water supply channel 2d, and a water supply nozzle 12 is provided at the tip so that water can be supplied to the glass 8a at the head of the objective observation channel 2b to wash away dirt and the like.

The air nozzle 11 attached to the tip of the air channel 2c blows off the cleaning water attached to the leading glass 8a of the objective observation channel 2b, and
Air can be supplied to the inside of the subject to inflate it as necessary.

The forceps channel 2e allows insertion of forceps for collecting a specimen and a wire for operating the forceps.

A thread groove is formed on the outer circumferential surface of the tip body 2, and the tip hood 13 is screwed into the thread groove.

In this example, as clearly shown in Figure 3,
A shield member 14 is provided on the tip main body 2 so as to divide the back side of the solid-state imaging device 7 into two in the radial direction of the outer cylinder 1, and two spaces 15a, 15b are formed on the back side, and these spaces 15a, 15b are Connecting passages 17a, 1 are connected to the tip body 2 so as to communicate with the space 16 formed between the front side of the solid-state imaging device 7 and the objective lens system 6 in a substantially symmetrical manner.
Form 7b. One end of an air supply tube 18 is connected to the space 15a, and the other end of this air supply tube 18 is used to supply cooling air through the outer cylinder 1 and the inside of the operating section 19, as shown in FIG. Connected to air pump 20. Further, one end of an exhaust tube 21 is connected to the space 15b, and the other end of the exhaust tube 21 is connected to the operating section 19, as shown in FIG.
The air piston 23 is connected to an air supply tube 22 provided in the air tube 22 for blowing away deposits on the surface of the leading glass 8a of the objective observation channel 2b as described above, and for inflating the inside of the subject as necessary. The connection is made through the inside of the outer cylinder 1. The flexible tube through which the conductive wire bundle 10 of the solid-state imaging device 7 is passed is extended into the outer cylinder through an opening 14a formed in the shield member 14.

In this way, the cooling air from the air pump 20 is normally transferred to the air supply tube 18 and the space 15.
a, connecting passage 17a, space 16, connecting passage 17
b. The solid-state imaging device 7 is cooled by circulating it through the space 15b and the exhaust tube 21, that is, in direct contact with the back and front surfaces of the solid-state imaging device 7 within the outer cylinder 1, and discharging it to the outside from the air piston 23. and air piston 2 if necessary.
By closing the opening 23a of 3, the air discharged from the exhaust tube 21 is removed from the exhaust tube 2.
2 to clean the leading glass 8a of the objective observation channel 2b and to inflate the inside of the body cavity.

According to this embodiment, even if the solid-state imaging device 7 is cooled as described above, the objective lens system 6 and the outside are connected to each other by a pair of glasses 8a and 8b disposed in front of the objective lens system 6. Since the formed vacuum layer 9 effectively insulates the objective lens system 6, fogging does not occur on the objective lens system 6, and the pair of glasses 8a and 8b also does not fog. Therefore, the image of the subject can always be effectively formed on the solid-state imaging device 7. Furthermore, since the solid-state imaging device 7 is cooled by applying cooling air directly to it, it can be cooled sufficiently effectively and an increase in operating temperature can be effectively prevented. Therefore, the dark current can be effectively suppressed to a predetermined low value, and a wide dynamic range can be stably obtained. By supplying this information, a high-quality image of the subject can be displayed on the monitor. Furthermore, cooling of the solid-state imaging device 7, cleaning of the leading glass 8a of the objective observation channel 2b, and expansion of the inside of the body cavity are carried out by a single air pump 20 and air piston 2.
This can be done with a simple structure using 3.

FIG. 5 is a sectional view of the distal end showing the configuration of another example of the endoscope of the present invention. In this example, a piece of glass 24 is installed at the tip of the objective observation channel 2b (see FIG. 2) into which the objective lens system 6 and solid-state imaging device 7 are fitted.
are fitted to form a vacuum layer 9 between this glass 24 and the leading lens 6a of the objective lens system 6, and the cooling air is also circulated through the output end surface of the light guide 3. The only difference is that this embodiment differs from the embodiment described above. For this reason, a shield member 25 is provided on the back side of the solid-state imaging device 7 to form a space 26 facing almost the entire back surface.
6 and the space 16 on the front side of the solid-state imaging device 7 are communicated by forming a connecting passage 27 in the tip body 2, and a space 28 is formed between the output end surface of the light guide 3 and the concave lens 4, and this space 28 and space 16
A connecting passage 29 is formed in the distal end main body 2 to allow the two to communicate with each other.

In this way, the air supply tube 18 is connected to the space 2.
The exhaust tubes 21 are connected to the spaces 28 and 6, and the cooling air from the air pump 20 shown in FIG.
6. Circulate through the connecting passage 27, the space 16, the connecting passage 29, the space 28, and the exhaust tube 21, that is, in the outer cylinder 1 while being in direct contact with the back and front surfaces of the solid-state imaging device 7 and the output end surface of the light guide 3. The air discharged from the exhaust tube 21 is then discharged to the outside from the air piston 23 shown in FIG. The air is introduced into the air supply tube 22 and used for cleaning the glass 24 at the tip of the objective observation channel 2b and for expanding the inside of the body cavity.

According to this embodiment, since the vacuum layer 9 is defined by a single glass 24 and the leading lens 6a of the objective lens system 6, the objective lens can be constructed with a simpler structure than in the embodiments described above. Clouding of system 6 can be effectively prevented. In addition, since not only the solid-state imaging device 7 but also the output end face of the light guide 3 can be directly cooled, the temperature at the end of the endoscope can be reliably maintained at a predetermined low temperature, and therefore the solid-state imaging device 7 can be cooled directly. A rise in the operating temperature of the imaging device 7 can be more reliably prevented.

Note that the present invention is not limited to the above-mentioned example, and can be modified or changed in many ways. For example, in the example described above, a vacuum layer was defined by placing a glass in front of the objective lens system, but instead of using such a glass, the objective lens system could be separated and opposed to the object lens system on the subject side. A vacuum layer may be provided between the lenses, for example, between the leading lens and the next lens facing away from each other. Also,
In the example described above, the back and front surfaces of the solid-state imaging device 7 are configured as part of the cooling air flow path, but only one of them may be configured as part of the flow path, or the back or front surface is configured as a part of the flow path. Only a portion of the channel may be configured as part of the flow path. Furthermore, when the back surface of the solid-state imaging device 7 is configured as a part of the flow path, the cooling effect can be further improved by providing cooling fins in the direction of the flow of cooling air. Furthermore, in the example described above, the air is discharged from the air piston 23 using the exhaust tube 21, but instead of using the exhaust tube 21, it is possible to pass the air that has finished its cooling action through the gap in the outer cylinder 1. The air may be discharged from the air piston 23.
Furthermore, in the example described above, one air pump 20 was used in common to supply air to the cooling system path and the air supply system path for cleaning and inflation within the body cavity. They may also be configured independently of each other. Furthermore, although the solid-state imaging device 7 is cooled using air in the above example, it may be cooled using a gas or liquid other than air, or an electronic cooling device may be provided near the solid-state imaging device 7. A thermoelectric element may be provided for cooling. Also,
The present invention is not limited to the above-mentioned direct-viewing endoscope, but can also be effectively applied to side-viewing endoscopes. Furthermore, in the above example, the light from the light source passes through the light guide and is emitted from the tip of the outer cylinder.
It is also possible to provide a light source such as a lamp or a light emitting diode at the tip of the outer cylinder to illuminate the subject without using a light guide. in this case,
It is also possible to use light-emitting diodes of three colors, red, blue, and green, and make them emit light in sequence. In this case, a color filter provided on the light-receiving surface of the solid-state imaging device is not necessary.

(Effects of the Invention) As described above, according to the present invention, a vacuum layer is formed on the subject side of the objective lens system, and the objective lens system is Clouding of the system can be effectively prevented, so that the image of the subject can always be effectively formed on the solid-state imaging device.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the temperature characteristics of a solid-state imaging device, Fig. 2 is a diagram showing the tip configuration of an embodiment of the endoscope of the present invention, and Fig. 3 is a cross section taken along the - line in Fig. 2. 4 are diagrams showing the overall structure of the endoscope shown in FIG. 2, and FIG. 5 is a sectional view showing the structure of another embodiment of the endoscope of the present invention. DESCRIPTION OF SYMBOLS 1...Flexible outer tube, 2...Tip body, 3...Light guide, 6...Objective lens system, 6a...Top lens, 7...Solid-state imaging device, 8a, 8b, 24
... Glass, 9 ... Vacuum layer, 18 ... Air supply tube, 20 ... Air pump, 21 ... Exhaust tube.

Claims (1)

[Scope of Claims] 1. An objective lens system provided at the tip of a flexible outer cylinder inserted into the object allows an image of the object to be placed inside the outer cylinder tip, and a solid body is cooled by a cooling means. An endoscope configured to form an image on an imaging device, comprising a built-in solid-state imaging device, characterized in that a vacuum layer is formed on the subject side of the objective lens system to prevent fogging of the lens. Endoscope. 2. An endoscope incorporating a solid-state imaging device according to claim 1, characterized in that at least one piece of glass defining the vacuum layer is provided in front of the objective lens system.