JPH0477292B2 - - 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 In a conventional endoscope, a light guide and an image guide made of an optical fiber bundle extend inside a flexible outer tube that is inserted into a subject, and the light is emitted from an external illumination source. Light is guided through the light guide to the tip of the endoscope, illuminated on the subject through the illumination lens system, and the image of the subject is guided to the outside via the objective lens system and image guide, and directly observed through the eyepiece system. Alternatively, the image is captured by an imaging device and displayed 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 that incorporates such a solid-state imaging device, but the dynamic range of the solid-state imaging device varies greatly depending on the temperature, so 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 composed of a CCD. Dark current I _D increases with temperature rise, while saturation current I _S remains constant even with temperature changes. Therefore, the dynamic range decreases with increasing temperature. 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 tip of the endoscope easily becomes 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. It is not possible to maintain the temperature at a constant low temperature.
For this reason, it is necessary to take some kind of cooling means, but the diameter of the endoscope is very small, and there is a problem in that it is difficult to obtain sufficient space to incorporate a means for cooling the solid-state imaging device. For example, in an endoscope for observing inside a body cavity, in addition to the above-mentioned light guide, forceps for collecting a sample and a wire for operating the forceps are inserted, as well as a wire for cleaning the leading lens of the objective lens system. The space available for cooling is extremely limited, as a water supply tube and a ventilation tube that blows away cleaning water adhering to the leading lens and inflates the body cavity are also inserted.

Cooling a solid-state imaging device built into the tip of an endoscope has been proposed in the past, for example, in
45081, No. 55-26998, No. 58-46934, etc., but all of the conventional methods have difficulty in sufficiently cooling the solid-state imaging device.
It is not of sufficient practical use. For example, JP-A-53
Publication No. 45081 indicates that the thermoelectric element for electronic cooling is placed in close contact with or close to the solid-state imaging device, but the heat is emitted from the heat dissipation side of the thermoelectric element for electronic cooling and accumulates inside the tip of the endoscope. Since no measures have been taken to deal with the generated heat, solid-state imaging devices have poor cooling efficiency and have the disadvantage that sufficiently good characteristics cannot be maintained. Furthermore, Japanese Patent Application Laid-Open No. 58-46934 discloses an endoscope in which a light guide for illumination is arranged in a water pipe or an air pipe to cool the light guide. It is not possible to cool down to the tip, and the radiant heat of the illumination light at the tip cannot be removed sufficiently effectively, and the influence of heat on the solid-state imaging device cannot be sufficiently prevented.

Objective The objective of the present invention is to eliminate the above-mentioned conventional drawbacks,
The solid-state imaging device built into the tip can be cooled sufficiently effectively, and the dark current can therefore be maintained at a low, almost constant value during use, ensuring a wide dynamic range and allowing high-quality images to be obtained. The aim is to provide an endoscope that can

Overview The endoscope incorporating the solid-state imaging device of the present invention has an object image provided at the tip of the outer tube, which is illuminated by light emitted from the tip of the flexible outer tube inserted into the inside of the subject. a light guide configured to form an image on a solid-state imaging device disposed inside the outer cylinder by a lens system, a first electronic cooling thermionic component element being arranged near the solid-state imaging device, and extending inside the outer cylinder; A second thermoelectric element for electronic cooling is disposed near the emission end of the flexible thermoelectric element, and the heat radiated from the heat radiation side of the first and second thermoelectric elements for electronic cooling is extended inside the outer cylinder. The heat pipe is characterized in that it is configured to be emitted to the outside through a heat pipe having a heat pipe.

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

FIG. 2 is a front end view showing the configuration of an endoscope devised in the process of completing the endoscope of the present invention, and FIG. 3 is a sectional view taken along the line - in FIG. 2. The endoscope in this example is a direct-view type for observing inside body cavities, and has a flexible outer tube 1 inserted into the subject.
A tip main body 2 made of stainless steel, for example, is fitted onto the tip of the tip. Several channels 2a to 2e are formed in this tip body 2. A light guide 3 made of an optical fiber bundle is inserted into the pair of light guide channels 2a, and a concave lens 4 is fitted at the tip. The light guide 3 is covered with a cover tube 5 and extends inside the outer tube 1,
Guided to the operating section and coupled to the illumination light source. An objective lens system 6 is fitted at the tip inside the objective observation channel 2b, and a solid-state imaging device 7 is fitted inside.
The conductive wire bundle 8 connected to the solid-state imaging device 7 extends inside the outer cylinder through the flexible tube 13, is guided to the operating section, and is connected to the signal processing circuit. An air supply tube 9 is connected to the air supply channel 2c, and an air supply nozzle 10 is attached to the tip thereof, so that air can be supplied to the leading lens of the objective lens system 6. A water supply tube is connected to the water supply channel 2d, and a water supply nozzle 11 is provided at the tip so that water can be supplied to the first lens of the objective lens system 6 to wash away dirt and the like. Further, the air supply nozzle 10 blows off the cleaning water adhering to the leading lens, and also blows air into the inside of the subject to inflate it, if necessary. The forceps channel 2e allows insertion of forceps for collecting a specimen and a wire for operating the forceps from the outside. A thread groove is formed on the outer circumferential surface of the tip body 2, and the tip hood 12 is screwed into the thread groove.
As clearly shown in FIG. 3, a thermoelectric element for electronic cooling, for example, a Peltier element 20
is arranged to forcibly cool the solid-state imaging device 7, and one end of a heat pipe 21 is arranged on the heat radiation side of the Peltier element 20, and this heat pipe is made flexible and extends inside the outer cylinder 1. Then, the other end is guided to the operating section and cooled by a suitable cooling device.
With this configuration, the heat of the solid-state imaging device 7 is absorbed by the Peltier element 20, and the heat radiated from the heat radiation side of the Peltier element is absorbed by the heat pipe 2.
1, the heat propagates inside the outer cylinder 1, and is radiated at the operating section. Therefore, the operating temperature of the solid-state imaging device 7 can be maintained at a predetermined low temperature during use, and the dark current can be suppressed to a low value, so that a wide dynamic range can be stably obtained. As a result, by appropriately processing the output image signal of the solid-state imaging device 7 and then supplying it to the monitor, a high-quality image of the subject can be displayed on the monitor. Furthermore, if the heat emitted from the Peltier element 20 is dissipated to the outside by the heat pipe 21, the cooling effect of the Peltier element will be significantly improved, and even if the temperature at the tip becomes considerably high, the temperature of the solid-state imaging device 7 will be maintained. can be kept low.

As a result of further examination of the endoscope mentioned above,
It was confirmed that heat is generated by the diffusion of light near the output end of the light guide 3, and this heat is transmitted to the solid-state imaging device 7 via the tip component, thereby increasing the temperature of the solid-state imaging device. Therefore, if an attempt is made to improve the quality of a subject image by using a powerful light source, there is a drawback that the temperature of the solid-state imaging device undesirably increases.

FIG. 4 is a sectional view showing an embodiment of the endoscope of the present invention, and the same parts as in the previous example are denoted by the same reference numerals, and the explanation thereof will be omitted. In this example, the second Peltier element 22 is arranged near the output end of the light guide 3, and the heat radiation side of the first Peltier element 20 and the second Peltier element 22 are arranged on the rear side of the solid-state imaging device 7. side by a first heat pipe 23, and one end of a second heat pipe 24 is arranged on the heat radiation side of the second Peltier element 22.
The heat pipe 24 is extended inside the outer cylinder 1 and guided to the operating section. With this configuration, the heat of the solid-state imaging device 7 is absorbed by the first Peltier element 20 and then transferred to the first and second heat pipes 23 and 2.
4 and is emitted to the outside through light guide 3.
The heat near the output end of is absorbed by the second Peltier element 22 and is emitted to the outside via the second heat pipe 24. Therefore, the temperature at the end of the endoscope can be kept lower, and as a result, the operating temperature of the solid-state imaging device 7 can be kept even lower. Furthermore, if the heat near the light guide output end is forcibly removed as in this example, even more powerful illumination light can be used, and an even higher quality image of the object can be obtained.

The present invention is not limited to the embodiments described above, but can be modified in many ways. For example, in the above-mentioned embodiment, a direct view type is used, but it is of course possible to use a side view type. Furthermore, although the Peltier element is placed in close contact with the back surface of the solid-state imaging device, it can also be placed somewhat apart from the back surface.

Effects of the Invention As described above, according to the present invention, the first Peltier element is arranged near the solid-state imaging device, and the second Peltier element is arranged near the output end of the light guide, and the heat dissipation of these Peltier elements is improved. Since the heat radiated from the side is radiated to the outside through a heat pipe extending inside the outer cylinder, it is possible to reduce the heat transferred to the solid-state imaging device, and also remove the heat from the solid-state imaging device. can,
Therefore, the solid-state imaging device can be cooled extremely efficiently. As a result, the temperature of the solid-state imaging device is kept at an almost constant low temperature during use, making it possible to stably obtain a wide dynamic range and use a powerful light source.
A high-quality subject image can be displayed.

[Brief explanation of drawings]

Fig. 1 is a graph showing the temperature characteristics of a solid-state imaging device, Fig. 2 is a plan view showing the configuration of the tip of an endoscope devised in the process of completing the endoscope according to the present invention, and Fig. 3 is a graph showing the temperature characteristics of the solid-state imaging device. FIG. 4 is a sectional view showing the structure of an embodiment of the endoscope of the present invention. DESCRIPTION OF SYMBOLS 1... Flexible outer tube, 2... Tip main body, 3... Light guide, 6... Objective lens system, 7... Solid-state imaging device, 20, 22... Peltier element, 21, 2
3,24...Heat pipe.

Claims (1)

[Claims] 1 An image of the subject illuminated by light emitted from the tip of a flexible outer tube inserted into the subject is formed on a solid-state imaging device placed inside the outer tube using an objective lens system provided at the tip of the outer tube. A first thermoelectric component element for electronic cooling is arranged near the solid-state imaging device, and a second thermoelectric element for electronic cooling is arranged near an output end of a light guide extending inside the outer cylinder. The heat emitted from the heat radiation sides of the first and second electronic cooling thermoelectric elements is radiated to the outside through a flexible heat pipe extending inside the outer cylinder. An endoscope with a built-in solid-state imaging device.