JP2009142372A - Endoscope light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent breaking of a heat absorbing filter caused by thermal distortion by relieving the stress concentration caused by the sharp temperature gradient. <P>SOLUTION: The light source device has a lens barrel 10 which holds a condenser lens 6 and the glass heat absorbing filter 12 for absorbing heat generated from the light source light in a lens barrel body 15, and a gap d<SB>1</SB>in the radial direction corresponding to the difference in the linear expansion coefficient is formed between the lens barrel body 15 and the heat absorbing filter 12. The lens barrel body 15 to hold the heat absorbing filter 12 is made of a nonmetal material having a heat conductivity approximating to that of the glass heat absorbing filter 12, such as phenol resin whose heat conductivity is approximately 0.21 W/mK. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an endoscope light source device for supplying light for illuminating an object to be observed, and in particular, to eliminate the influence of heat generated in a lens barrel that holds a lens that condenses light source light onto a light guide. Concerning configuration.

  In an endoscope apparatus, an object to be observed is illuminated with light output from a light source device, and the object to be observed is mounted on a distal end portion of an endoscope (scope), for example, a CCD (Charge Coupled Device) which is a solid-state imaging device. ), An image signal from the CCD is supplied to the processor device, and predetermined signal processing is performed by the processor device, whereby an image of an object to be observed such as a digestive organ is displayed on the monitor.

  3 and 4 show a configuration of a conventional endoscope light source device. In this light source device, as shown in FIG. 3, a light source lamp 1 such as a halogen lamp and a lens barrel 2 are provided. The lens barrel 2 collects the light source light at the incident end of the light guide 3 and supplies the light source light to the distal end portion of the endoscope through the light guide 3. The lens barrel 2 includes a cylindrical barrel 5 made of aluminum (aluminum). The lens barrel 5 includes, in order from the light source side, a condenser lens 6, a glass heat absorption filter 7, an infrared ray (cut). ) The filter 8 is retained.

The heat absorption filter 7 is a glass filter that absorbs heat rays from the light source lamp 1, but based on the difference in thermal expansion coefficient from the lens barrel 5, between the heat absorption filter 7 and the lens barrel 5, radial gap (backlash) _{d 0} is provided. That is, the aluminum that is the material of the lens barrel 5 and the glass that is the material of the heat absorption filter 7 have different thermal expansion coefficients, so that a radial compressive stress is generated in the heat absorption filter 7. Since it becomes very high temperature, there is an inconvenience that itself breaks. Therefore, considering the thermal expansion coefficient of the lens body 5 and the heat absorption filter 7, the provided clearance d ₀ in the radial direction therebetween, thereby to prevent damage to the heat absorption filter 7 due to the expansion.
JP 58-14127 A JP 2001-343576 A

However, the conventional endoscope light source device has a problem that the heat absorption filter 7 is cracked even when the gap d ₀ is provided between the lens barrel 5 and the heat absorption filter 7 as described above. . That is, as shown in FIG. 4, since the clearance d ₀ is provided, the heat absorption filter 7 makes point contact at the lowest point P on the inner peripheral surface of the lens barrel 5 by its own weight. Heat dissipation from the lower point P to the aluminum barrel 5 having a high heat dissipation effect progresses, and thermal distortion occurs on the heat absorption filter 7, which causes the bottom as shown by the chain line 100. It was found that a crack starting from the point P occurred.

  Although the fracture strength (stress) of general glass is about 100 MPa, when a stress distribution in the heat absorption filter 7 made of glass is calculated and analyzed, an abrupt temperature gradient is generated at the lowest point P of the heat absorption filter 7. The maximum stress at this point P reaches about 300 MPa (Pascal), and it has been found that cracking occurs due to this concentrated stress.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an endoscope light source device that can relieve concentrated stress due to a rapid temperature gradient and prevent cracking of a heat absorption filter due to thermal strain. It is to provide.

In order to achieve the above object, the invention of claim 1 is a lens in which a lens for condensing light source light to a light guide and a glass heat absorption filter for absorbing heat generated by the light source light are held in a lens barrel. In the endoscope light source device in which a lens barrel is provided and a radial gap (backlash) corresponding to a difference in linear expansion coefficient is formed between the lens barrel of the lens barrel and the heat absorption filter. The lens barrel holding the absorption filter is made of a non-metallic material having a thermal conductivity close to that of the glass heat absorption filter.
The invention according to claim 2 is characterized in that the non-metallic material is a resin material or a ceramic material having a thermal conductivity of 20 W / mK or less.

  According to the above configuration, instead of aluminum having a thermal conductivity of 200 W / mK, a phenol resin having a thermal conductivity close to 0.55 to 0.75 W / mK, for example, a thermal conductivity of 0.21 is used. A lens barrel is produced as a material, and a glass heat absorption filter is attached to the lens barrel. This heat absorption filter comes into contact with the lens barrel at the lowest point due to the presence of a gap, but since the difference in thermal conductivity with the lens barrel is small, the stress at the contact point (P) is as small as about 5 Mpa. . As a result, the concentrated stress at the contact point is alleviated and the filter is prevented from being damaged.

  According to the endoscope light source device of the present invention, the concentrated stress due to the rapid temperature gradient with respect to the contact point between the lens barrel and the heat absorption filter is alleviated, and the heat absorption filter can be favorably prevented from cracking due to thermal strain. There is an effect.

  1 and 2 show the configuration of an endoscope light source device (lens barrel) according to the embodiment. The light source device of this embodiment is the same as that in FIG. A light source lamp such as a xenon lamp is provided, and the light from the light source lamp is collected by the lens barrel 10 and supplied to the incident end of the light guide.

As shown in FIG. 1, the lens barrel 10 of the embodiment includes a condenser lens 11, a glass heat absorption filter 12, and an infrared (cut) filter 13 in this order from the light source lamp arrangement side. A cylindrical lens barrel 15 is attached. The lens barrel 15 is formed of a nonmetallic material having a thermal conductivity close to 0.55 to 0.75 W / mK of the glass heat absorption filter 12.
As this non-metallic material, for example,
Thermal conductivity: a phenolic resin that is about 0.21 W / mK,
Thermal conductivity: a polyimide resin of about 0.24 W / mK,
Photovale (registered trademark) [Machinable ceramics] having a thermal conductivity of about 1.7 W / mK,
Thermal conductivity: There are zirconia ceramics etc. which become about 2.7 W / mK,
Those having a thermal conductivity of 20 W / mK or less are preferred.

As shown in FIG. 2, a gap d ₁ is provided between the heat absorption filter 12 and the lens barrel 15 to prevent cracking due to radial compressive stress. That is, in the embodiment, considering the difference in thermal expansion coefficient between the glass that is the material of the heat absorption filter 12 and the phenol resin that is the material of the lens barrel 15, the radial compression to the heat absorption filter 12 is performed by the thermal expansion. gap d ₁ is provided, such as stress is not applied.

  According to such an embodiment, the heat absorption filter 12 makes point contact at the lowest point P on the inner peripheral surface of the lens barrel 15 due to its own weight, but the thermal conductivity of the lens barrel 15 is that of the heat absorption filter 12. Since the heat conductivity becomes a value close to 0.55 to 0.75 W / mK, when the heat absorption filter 12 is heated by the heat rays of the light source lamp, the heat radiation from the lowest point P to the lens barrel 15 is also abrupt. Therefore, thermal strain does not occur, and cracking starting from the lowest point P is prevented.

  In the embodiment, when the stress distribution in the heat absorption filter 12 when the lens barrel 15 is made of phenol resin (thermal conductivity: 0.21 W / mK) is obtained, the maximum stress at the lowest point P is about 5.0 MPa (pascals). ) This value is extremely smaller than 100 MPa, which is the breaking strength point of glass, resulting in relaxation of thermal strain and concentrated stress due to a rapid temperature gradient.

  In the embodiment, the entire lens barrel 15 is made of a non-metallic material. However, for example, a lens barrel holding the condenser lens 11 and a lens barrel holding the heat absorption filter 12 and the infrared filter 13 are used. The body 15 may be divided and only the lens body holding at least the heat absorption filter 12 may be formed of a nonmetallic material having a thermal conductivity close to the thermal conductivity of the glass heat absorption filter.

It is sectional drawing which shows the structure of the lens barrel of the endoscope light source device which concerns on the Example of this invention. It is sectional drawing which cut | disconnected the lens barrel of FIG. 1 in the part of the heat absorption filter. It is a partial cross section figure which shows schematic structure of the conventional endoscope light source device. It is sectional drawing which cut | disconnected the lens barrel of FIG. 3 in the part of the heat absorption filter.

Explanation of symbols

1 ... light source lamp, 3 ... light guide,
2, 10 ... lens barrel, 5, 15 ... lens barrel,
6, 11 ... Condensing lens, 7, 12 ... Heat absorption filter,
d ₀ , d ₁ ... gaps.

Claims (2)

There is provided a lens barrel for holding a lens for condensing the light source light to the light guide and a glass heat absorption filter for absorbing heat generated by the light source light, and the lens barrel and the heat of the lens barrel. In the endoscope light source device in which a radial gap corresponding to the difference in linear expansion coefficient is formed between the absorption filter,
An endoscope light source device characterized in that the lens barrel holding the heat absorption filter is made of a nonmetallic material having a thermal conductivity close to that of the glass heat absorption filter.   2. The endoscope light source device according to claim 1, wherein the non-metallic material is a resin material or a ceramic material having a thermal conductivity of 20 W / mK or less.

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