JP3065030B2 - Light source optical system for endoscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source optical system for an endoscope, and more particularly, to an endoscope provided with a light guide for receiving a focused illumination light beam at an incident end face and transmitting it to an exit end face. The present invention relates to an improvement in a filter for preventing an incident end face other than a light guide from being burned or damaged by light other than visible light emitted from an illumination light source in a light source optical system.

[0002]

2. Description of the Related Art A conventional light source optical system for an endoscope includes an illumination light source that emits white light, an infrared cutoff filter that interrupts infrared light among white light emitted from the illumination light source, and an illumination light source that emits light from the illumination light source. A condensing lens for condensing the collected light on the end face of the light guide, a diaphragm mechanism for adjusting the brightness, and a light for receiving the light condensed by the condensing lens at the incident end side and transmitting the light to the emission end side It is composed of a guide and the like.

In general, a xenon lamp or a halogen lamp is often used as an illumination light source of this type of endoscope light source optical system, and these light source lamps are usually integrated with a reflecting mirror. The bright spot of the light source lamp is arranged at the focal position of the reflecting mirror, and the reflected light is substantially a parallel light beam. Light emitted from the illumination light source includes light having a wavelength component other than visible light. In particular, a xenon lamp has a high ratio of emitting light in the infrared region of 750 nm or more. Since the light emitted from the illumination light source is collected by the condenser lens on the incident end face of the light guide,
At the incident end face of the light guide, light energy is so aggregated that the incident end face is burned by heat.

For this reason, in order to prevent burning of the light guide entrance end face, a filter for blocking infrared rays is arranged on the optical path from the illumination light source to the light guide entrance end face. Even when only the light belonging to the visible region among the light emitted from the illumination light source is collected by the condenser lens on the incident end face of the light guide, the energy amount at the condensing part, that is, the incident end face of the light guide is considerable. As a result, the temperature of the incident end face of the light guide rises. For this reason, in order to reliably prevent the incident end face of the light guide from burning, it is necessary to at least completely block light belonging to the infrared region.

[0005] The infrared cutoff filter is provided with a coating composed of a multilayer interference film on a transparent substrate, the coated surface of which reflects infrared light and transmits other light. There is an infrared absorption type filter made of a material that absorbs. An infrared absorption filter generally has a spectral transmittance characteristic as shown in FIG. 1, and is excellent in that it can block most of the light belonging to the infrared region. However, when the infrared absorption filter is used alone, the filter substrate may not be able to withstand the thermal expansion caused by the absorbed heat and may be destroyed. Therefore, as described in Japanese Utility Model Laid-Open No. 3-51411, a reflection filter is arranged between the illumination light source and the absorption filter, and light emitted from the illumination light source first enters the infrared reflection filter. A part of the infrared region light is reflected, and then the remaining infrared region light is absorbed by an infrared absorption filter to block the infrared light in a divided manner.
According to the embodiment described in the publication, the spectral transmittance characteristics of the infrared reflection type filter and the infrared absorption type filter are as shown by curves A and B in FIG.

However, even in a light source device employing the above-described infrared cutoff filter configuration, if illumination is performed for a relatively long period of time, the incident end face of the light guide is burned out, and the light guide from the emission end side of the light guide is damaged. The amount of emitted illumination decreases extremely. If the light source device is used for a long time, the absorption filter is deformed or broken by heat. Taking the case where a xenon lamp is used as the illumination light source as an example, the causes of the burning of the light guide incident end face and the damage of the infrared absorption filter will be described as follows.

FIG. 3 shows a spectral energy emissivity characteristic curve of a general xenon lamp. According to this, the xenon lamp has a very high ratio of emitting light belonging to the infrared region between 750 nm and 1100 nm. On the other hand, according to the spectral transmittance characteristic curve of the infrared cutoff filter of the conventional light source device shown in FIG. 2, the infrared reflection type filter disposed next to the illumination light source transmits most of light having a wavelength of 750 nm to 800 nm. , Light having a wavelength of 800 nm to 1100 nm is transmitted with a transmittance of at least 10% or more, and the transmission amount increases as the wavelength shifts to the longer wavelength side. Further, the infrared absorption type filter disposed after the infrared reflection type filter completely absorbs light belonging to the wavelength range of 900 nm or more, but cannot completely absorb light belonging to the wavelength range between 700 nm and 900 nm. The part is transparent. as a result,
Of the light having a wavelength between 750 nm and 1100 nm emitted from the illumination light source, the light of 750 nm to 900 nm cannot be completely removed by the infrared cutoff filter and is condensed on the light guide incident end face, causing the light guide incident end face to burn. Become.

Further, the infrared absorption type filter almost absorbs infrared rays having a wavelength of 700 nm or more which cannot be completely removed by the infrared reflection type filter, and generates heat by itself. In general, it is known that a heating element emits infrared rays by itself, but an infrared absorption filter absorbs infrared rays from an illumination light source and generates heat, thereby generating a new infrared radiation source (hereinafter, referred to as a “radiation source”).
The infrared light emitted from this secondary light source is partially collected on the light guide entrance end face,
This may cause burning of the light guide entrance end face.

The greater the amount of infrared light absorbed by the infrared absorbing filter, the greater the amount of heat generated and the amount of infrared light emitted from the secondary light source. Therefore, in order to prevent the incident end face of the light guide from burning, it is necessary to control the amount of infrared light absorbed by the infrared absorption type filter by an infrared reflection type filter arranged closer to the light source than the infrared absorption type filter. As shown in FIG. 2, in the conventional infrared reflection type filter, infrared rays of 750 nm to 1100 nm emitted from a xenon lamp at a high rate are not sufficiently blocked. For this reason, the infrared absorption filter mainly absorbs infrared rays in the above wavelength range and generates heat, becomes a secondary light source, and emits an infrared ray in an amount sufficient to cause burning of the light guide entrance end face. In this case, the surface temperature of the infrared absorption type filter is 400 to 45 degrees Celsius.
Since the temperature is as high as 0 degrees, distortion due to thermal expansion occurs in the infrared absorption type filter, which leads to deformation and destruction after long-term use.

[0010]

As described above, according to the configuration of the conventional infrared cutoff filter, the light having a wavelength of 750 nm or more cannot be sufficiently blocked out of the light emitted from the illumination light source. Inadequately removing the infrared reflection filter of 750 nm to 1100 nm of the infrared reflection filter disposed closest to the light guide, there is a problem that the incident end face of the light guide is burned or the infrared absorption filter is damaged. Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and particularly, by removing infrared rays having a wavelength of 750 nm or more, light emitted from an illumination light source may burn the incident end face of a light guide, An object of the present invention is to provide a light source optical system for an endoscope having a transmission wavelength selection filter that does not damage the filter.

[0012]

In order to achieve the above object, a light source optical system for an endoscope according to the present invention comprises an endoscope in which light emitted from an illumination light source is condensed on an incident end face of a light guide by a condenser lens. In the mirror light source optical system, at least two or more transmission wavelength selection filters are disposed between the illumination light source and the incident end surface of the light guide, and the at least two or more transmission wavelength selection filters are arranged on the illumination light source side. In this order, an infrared reflective filter whose transmitted energy of infrared light of 750 nm or more is represented by the following formula and a rotating color filter are arranged in this order. Here, R (λ) is the spectral energy emissivity of light of wavelength λ emitted from the illumination light source, and T (λ) is the spectral transmission for the wavelength λ of the transmission wavelength selection filter disposed closest to the illumination light source. Rate, P, is the power consumption of the lamp used for the illumination light source, and the integral in the above equation is 750
performed for wavelengths λ greater than or equal to

[0013]

According to the light source optical system for an endoscope according to the present invention, at least two or more transmission wavelength selection filters are arranged between the illumination light source and the incident end face of the light guide, and a wavelength of 750 nm or more is provided. By removing the light of
Burnout of the incident end face of the light guide can be completely prevented. That is, light belonging to the infrared region of 750 nm or more is blocked by the transmission wavelength selection filter and is not condensed on the incident end face of the light guide, so that the incident end face of the light guide is not exposed to high heat and does not burn out. In addition, if the transmission wavelength selection filter has a property of blocking light in the ultraviolet region of 400 nm or less, even if the adhesive for bonding the fiber bundle of the light guide is of a type that absorbs ultraviolet light, the light guide does not enter the light guide. The end face does not burn.

Furthermore, since the filter disposed closest to the illumination light source has a characteristic of almost blocking out light (infrared rays) having a wavelength of at least 750 nm to 1100 nm, the transmission wavelength selection filter is sequentially arranged from the illumination light source side. A first filter having a property of transmitting light belonging to a necessary wavelength range and reflecting light belonging to an unnecessary wavelength range, and a light transmitting a light belonging to a required wavelength range and belonging to an unnecessary wavelength range If the second filter has the property of absorbing light, the second filter absorbs infrared light in the above wavelength range and generates heat, and the second filter itself becomes a new infrared radiation source, and is incident on the light guide. Does not burn the end face. Also, the second filter generates heat and becomes hot,
Deformation or damage due to thermal expansion is prevented.

Further, if the transmission wavelength selection filter is constituted only by a filter having a characteristic of transmitting light belonging to a necessary wavelength range and reflecting light belonging to an unnecessary wavelength range,
Since the filter does not absorb infrared rays and generate heat, the filter itself becomes a new infrared radiation source, which can prevent the incident end face of the light guide from burning and causing thermal expansion and damage. .

As the illumination light source of the endoscope light source device, various types of lamps are used in addition to the xenon lamp and the halogen lamp. Each of the spectral energy emissivity distributions of the light emitted from these lamps is unique. Has characteristics. Further, even if the lamps of the same type have different power consumptions, the amount of radiant energy of light emitted from the lamps is different. Therefore, in the light source optical system for an endoscope according to the present invention in which at least two or more transmission wavelength selection filters are disposed, the amount of infrared energy transmitted through the filter disposed closest to the illumination light source among the transmission wavelength selection filters is small. It is desirable that the following formula be satisfied. (1) Here, R (λ) is the spectral energy emissivity of light of wavelength λ emitted from the illumination light source, and T (λ) is the selection of the transmission wavelength arranged closest to the illumination light source. S is the spectral transmittance of the filter with respect to the wavelength λ, and P is the power consumption value of the lamp used as the illumination light source.
m for wavelengths λ or more.

In the equation (1), the denominator of the fraction in the parenthesis on the left side corresponds to the energy amount of infrared light having a wavelength of 750 nm or more emitted from the illumination light source, and the numerator is the transmission wavelength arranged closest to the illumination light source. 7 through the selection filter
It corresponds to the energy amount of infrared rays having a wavelength of 50 nm or more. Therefore, the fraction in parentheses on the left side of the equation (1) represents the ratio of the energy amount of infrared light transmitted through the transmission wavelength selection filter disposed closest to the illumination light source to the energy amount of infrared light emitted from the illumination light source. I have. Further, if the power consumption value of the lamp used for the illumination light source is different, the energy amount of infrared rays emitted from the illumination light source is also different.
For example, the energy amount of infrared rays emitted from an illumination light source using a lamp having a power consumption of 300 W is equal to the power consumption 1
It is larger than the energy amount of infrared rays emitted from an illumination light source using a 50 W lamp. Therefore, the value of the right side of the expression (1) in which the energy ratio represented by the fraction in the parentheses of the expression (1) is allowable varies depending on the power consumption value of the lamp used for the illumination light source. This is adjusted by multiplying the fraction within by the power consumption value.

If the energy amount of the infrared light transmitted through the transmission wavelength selection filter arranged closest to the illumination light source does not satisfy the expression (1), the infrared energy amount reaching another filter arranged behind the same filter Is excessively large, and the filter is damaged, or the filter becomes a new infrared radiation source, causing problems such as burning of the incident end face of the light guide.

Hereinafter, embodiments of the present invention will be described.

FIG. 4 is a sectional view of a light source optical system for an endoscope according to a first embodiment of the present invention. The transmission wavelength selection filter 1 according to the present embodiment includes, in order from the illumination light source side, a reflective filter 2 having a property of reflecting a light of an unnecessary wavelength by depositing a multilayer interference film on a transparent glass substrate, and an infrared ray. It consists of two filters, an absorption filter 3 made of an absorbing material. FIG. 5 (a) and (b)
FIG. 3 shows respective spectral transmittance characteristic curves of the reflection type filter 2 and the absorption type filter 3. Of the light emitted from the illumination light source, light having a wavelength of 400 nm or less (ultraviolet light) and light having a wavelength of 750 nm to 1100 nm (infrared light) are removed by the reflection filter 2. Next, light (infrared rays) having a wavelength of 1100 nm or more is removed by the absorption filter 3. As described above, since the reflection type filter 2 and the absorption type filter 3 share and remove the ultraviolet light and the infrared light, only the light in the visible region is collected on the incident end face 4 of the light guide. 750 nm to 11 due to the reflective filter 2 located closest to the illumination light source
Since light (infrared rays) having a wavelength of 00 nm has been removed, the absorption type filter 3 disposed behind the filter absorbs infrared rays in the above wavelength range and generates heat, thereby becoming a new infrared radiation source, and the incident end face of the light guide. 4 does not cause burnout or breaks due to expansion. Note that a condenser lens 5 is disposed between the transmission wavelength selection filter 1 and the incident end face 4 of the light guide.

Further, 400 n
Since ultraviolet rays of m or less are also removed, the incident end face of the light guide does not burn out even if the adhesive for bonding the fiber bundle of the light guide is of a type that absorbs ultraviolet rays. In the present embodiment, the reflection type filter 2 removes ultraviolet rays of 400 nm or less, but the absorption type filter 3 may be provided with a multilayer interference film having a property of reflecting ultraviolet rays of 400 nm or less. .

In this embodiment, a xenon lamp having a power consumption of 300 W is used as an illumination light source. In this case, the value on the left side of Expression (1), which defines the amount of energy of infrared light having a wavelength of 750 nm or more transmitted through the reflection filter 2, is 24.2, which satisfies Expression (1).

FIG. 6 is a sectional view of a light source optical system for an endoscope according to a second embodiment of the present invention. The transmission wavelength selection filter 11 in the present embodiment is configured by combining two reflection filters having a characteristic of reflecting light of an unnecessary wavelength by depositing a multilayer interference film on a transparent glass substrate.
Among the two reflection filters, the first reflection filter 12 arranged closest to the illumination light source has the structure shown in FIG.
7 is used for the other reflection type filter 13 having the spectral transmittance characteristic shown in FIG.
The reflection type filter having the spectral transmittance characteristics shown in FIG. The light emitted from the illumination light source is irradiated with light having a wavelength of 400 nm or less (ultraviolet light) and light having wavelengths of 750 nm and 1100 nm (infrared light) by the first reflection type filter 12.
Is removed. Next, light (infrared rays) having a wavelength of 1100 nm or more is removed by the second reflection type filter 13, so that only light in the visible region is collected on the incident end face 4 of the light guide. Note that a condenser lens 5 is disposed between the transmission wavelength selection filter 11 and the incident end face 4 of the light guide.

As described above, the first reflection type filter 12
By using a reflective filter for the second filter placed behind the filter, the filter absorbs infrared rays and does not generate heat, so the filter itself becomes a new infrared radiation source and the entrance end face of the light guide Can be completely removed. In this embodiment, a xenon lamp having a power consumption of 300 W is used as the illumination light source, and the infrared rays emitted from the illumination light source are removed by the first reflection filter 12 and the second reflection filter 13 respectively. Thus, the first reflection type filter 12 satisfies the expression (1) which defines the amount of transmitted energy of infrared rays of 750 nm or more. When the first reflection type filter 12 does not satisfy the expression (1), the energy amount of infrared rays transmitted through the first reflection type filter 12 increases, and the load of infrared rays applied to the second reflection type filter 13 increases. . For this reason, the second reflection type filter 13 must improve the function of removing infrared rays. For that purpose, it is necessary to further increase the number of multilayer interference films deposited on a transparent glass substrate.
As a result, the interference film becomes too multi-layered, the film strength is extremely deteriorated, and the film is easily affected by heat. Therefore, there is a problem that the multilayer interference film is broken by the load of infrared rays. Therefore, even when the transmission wavelength selection filter is constituted only by the reflection type filter as in the present embodiment, the first reflection type filter 12 arranged closest to the illumination light source can satisfy the expression (1). desirable.

In this embodiment, the ultraviolet rays having a wavelength of 400 nm or less are removed on the first reflection filter 12 side, but may be removed on the second reflection filter 13 side.

FIG. 8 is a sectional view of a light source optical system for an endoscope according to a third embodiment of the present invention. The transmission wavelength selection filter 21 according to the present embodiment includes, in order from the illumination light source side, a reflective filter 22 having a property of reflecting a light of an unnecessary wavelength by depositing a multilayer interference film on a transparent glass substrate, and a transparent filter. A color separation filter that has the property of transmitting only light belonging to the wavelength range of each color for three colors of red, blue, and green and reflecting light of other wavelengths by depositing a multilayer interference film on a glass substrate. And a rotating color filter 23 arranged on the circumference of the same disk. Reflective filter 22
Uses a filter having the spectral transmittance characteristic shown in FIG. 5A as in the first and second embodiments, so that the light emitted from the illumination light source Of light (ultraviolet light) and light (infrared light) having a wavelength of 750 nm to 1100 nm. Next, the image is time-divided into three colors of red, blue and green by a rotating color filter 23 composed of a color separation filter having a spectral transmittance characteristic shown in FIG.
Since light (infrared rays) of the above wavelengths has hardly been removed, these three colors of light are time-divided and condensed on the incident end face 4 of the light guide, and infrared rays of a wavelength of 1100 nm or more are constantly collected. Will be lighted. Note that a condenser lens 5 is disposed between the transmission wavelength selection filter 21 and the incident end face 4 of the light guide.

However, the energy of the visible light on the incident end face 4 of the light guide is substantially 1/3 due to the time division of the visible light into three colors. The temperature rise due to light is considerably suppressed as compared with the case where light of three colors is incident at once. Therefore,
Even if a small amount of infrared light enters and contributes to a rise in the temperature of the incident end face 4 of the light guide, it does not lead to burning of the incident end face 4 of the light guide.

In addition, the reflection type filter 22 satisfies the expression (1), and most of the infrared rays emitted from the illumination light source are removed by the reflection type filter 22. Therefore, even if the remaining infrared rays having a wavelength of 1100 nm or more transmitted through the reflection type filter 22 are condensed on the incident end face 4 of the light guide after passing through the rotary color filter 23, the incident end face 4 of the light guide does not burn out. .

As in the present embodiment, the transmission wavelength selection filter is constituted by a combination of a reflection type filter and a rotating color filter. By defining the energy amount of the infrared light transmitted through the filter by the expression (1), it is possible to realize a light source optical system in which the incident end face of the light guide is not burned. In this embodiment, a xenon lamp having a power consumption of 300 W was used as an illumination light source.

[0030]

As described above, the present invention relates to a light source optical system for an endoscope in which light emitted from an illumination light source is condensed on an incident end face of a light guide by a condenser lens. At least two or more transmission wavelength selection filters are arranged between the light-receiving surface and the filter to remove light having a wavelength of 750 nm or more. By defining the amount of infrared energy to be emitted, it is possible to prevent the incident end face of the light guide from burning and the filter from being damaged.

[Brief description of the drawings]

FIG. 1 shows a spectral transmittance characteristic curve of a general infrared absorption type filter.

FIG. 2 shows a spectral transmittance characteristic of an infrared reflection type filter, and a curve B shows a spectral transmittance characteristic of an infrared absorption type filter.

FIG. 3 shows a spectral energy emissivity characteristic curve of a general xenon lamp.

FIG. 4 is a sectional view of a light source optical system for an endoscope according to a first embodiment of the present invention.

FIG. 5 shows a spectral transmittance characteristic curve (a) of the reflection type filter and a spectral transmittance characteristic curve (b) of the absorption type filter of the first embodiment.

FIG. 6 is a sectional view of a light source optical system for an endoscope according to a second embodiment of the present invention.

FIG. 7 shows a spectral transmittance characteristic curve of the second reflection type filter of the second embodiment.

FIG. 8 is a sectional view of a light source optical system for an endoscope according to a third embodiment of the present invention.

FIG. 9 shows a spectral transmittance characteristic curve of each color separation filter constituting the rotating color filter of the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission wavelength selection filter 2 Reflection filter 3 Absorption type filter 4 Incident end face 5 Condensing lens 11 Transmission wavelength selection filter 12 First reflection type filter 13 Second reflection type filter 21 Transmission wavelength selection filter 22 Reflection type filter 23 Rotation Color filter

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Tomioka 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd. (56) References JP-A-5-232387 (JP, A) Hei 3-51411 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 23/26 A61B 1/06 F21V 8/00 G02B 5/26

Claims (1)

(57) [Claims] 1. An endoscope light source optical system for condensing light emitted from an illumination light source on an incident end face of a light guide by a condenser lens, wherein at least two light sources are provided between the illumination light source and the incident end face of the light guide. The above-described transmission wavelength selection filter is disposed, and the at least two transmission wavelength selection filters are, in order from the illumination light source side, an infrared reflection type filter in which the amount of transmitted energy of infrared light of 750 nm or more is represented by the following equation. A light source optical system for an endoscope, wherein a light source and a rotating color filter are arranged. Here, R (λ) is the spectral energy emissivity of light of wavelength λ emitted from the illumination light source, and T (λ) is the spectral transmission for the wavelength λ of the transmission wavelength selection filter disposed closest to the illumination light source. Rate, P, is the power consumption of the lamp used for the illumination light source, and the integral in the above equation is 750
This is performed for a wavelength λ of nm or more.