JP2003131144A - Light distribution lens of endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light distribution lens of an endoscope which consists of a single lens, facilitates processing and obviates the drastic degradation in the light intensity of a peripheral part in spite of an increase in a light distribution angle. SOLUTION: This light distribution lens of the endoscope which is a light distribution lens consisting of the single lens situated at the distal end of an internal insertion portion of an endoscope to irradiate an observation object with the light of a light source, in which the single lens consists of a first recessed part formed on the surface opposite to the light source and a second recessed part formed on the surface on the observation object side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light distribution lens provided at the tip of an internal insertion portion of an endoscope.

[0002]

2. Description of the Related Art Illumination of a distal end of an insertion portion of an endoscope is generally performed by illuminating light from an external light source with a bundle of illumination optical fibers disposed inside the insertion portion of the insertion portion. It is performed by irradiating the object to be observed with a light distribution lens provided at the tip of the insertion portion. Conventionally, as a light distribution lens, a plano-concave single lens having a concave light-beam exit end side of an optical fiber bundle for illumination is generally used, but a plano-concave light distribution lens has a sufficient center of illumination range. Although a high light intensity can be obtained, the light amount is significantly reduced in the peripheral portion. In recent years, the viewing angle of an endoscope has been widened from 120 ° to 140 °, and accordingly, the illumination of the distal end of the insertion portion is required to have a wide illumination range and a light intensity that does not decrease even in the periphery. A light distribution lens consisting of a single lens cannot meet this demand.

Further, in order to prevent the light intensity of the peripheral portion from being significantly reduced even when the light distribution angle is increased, Japanese Patent Laid-Open No. 7-
The light distribution lens is composed of a plurality of lenses as in the invention of 311349, or an aspherical lens is provided in the light distribution lens as in the inventions of JP-A-5-53063 and JP-A-5-119272. May be used.

However, in the case of the constitution of a plurality of lenses, it becomes difficult to miniaturize the tip of the insertion portion of the endoscope and the manufacturing cost also rises.

Further, when an aspherical lens is used as the light distribution lens, the shape of the aspherical lens is an aspherical surface whose curvature increases with distance from the optical axis of the light source in order to satisfy the requirement of increasing the light intensity of the peripheral portion. Since the lens is designed, the lens thickness is large in the case of a positive lens, and the edge thickness is large in the case of a negative lens. For this reason, the tip of the insertion portion of the endoscope becomes large, and the number of light rays scattered on the edge surface increases, resulting in poor efficiency.

Further, a Fresnel lens is generally used to reduce the lens thickness while using an aspherical lens, but a minute lens such as a light distribution lens of an endoscope is processed as a Fresnel lens. Is not easy.

[0007]

An object of the present invention is to provide a light distribution lens for an endoscope, which is composed of a single lens, is easy to process, and does not significantly reduce the light intensity in the peripheral portion even if the light distribution angle becomes large. The purpose is to do.

[0008]

SUMMARY OF THE INVENTION The light distribution lens of an endoscope of the present invention is a light distribution lens which is located at the tip of the insertion portion of the endoscope and which is a single lens for irradiating the light of the light source toward the observation target. There
It is characterized by having a first concave portion formed on the surface facing the light source and a second concave portion formed on the surface on the observation target side.

The light source may be a light flux emitting end face of the illumination optical fiber bundle.

The light source may be a light emitting element.

Further, the second concave portion has the following conditional expression (1).
It is preferable to satisfy (2). (1) tan {90-sin ⁻¹ (1 / n)} <h / d ₃ <11.5 (2) 0.35 <h / h ₀ where h: observation of the second concave portion from the optical axis of the light source Height to target end, h ₀ : Height from light source optical axis of light source, d ₃ : Depth of second recess.

The second concave portion may be formed of a part of a concave spherical surface, and in this case, it is preferable that the concave spherical surface satisfies the following conditional expression (3). (3) 0.35h ₀ <h <0.95r _{3 where} , h: height from the light source optical axis to the end of the second concave portion on the observation target side, h ₀ : height from the light source optical axis of the light source, r ₃ : radius of curvature of concave spherical surface.

The second concave portion may be formed of a concave conical surface, and the apex of the concave conical surface may be a curved surface. In this case, the concave conical surface is
It is preferable that the following conditional expression (4) is satisfied. (4) 90-sin ⁻¹ (1 / n) <α where α is the angle [unit: deg] formed by the optical axis of the light source and the generatrix of the concave conical surface, and n is the refractive index of the light distributing lens.

Further, a cover glass made of a plane parallel plate can be arranged on the surface of the light distributing lens having the second recess.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 to 10 as an example of an electronic endoscope.

The electronic endoscope 1 has an in-body inserting section 2 to be inserted into a body cavity and an operating section 4 connected to the in-body inserting section 2 via a connecting section 3. The body insertion part 2 has a rigid part 5, a bending part 6 and a flexible tube part 7 in this order from the distal end side, and the flexible tube part 7 is connected to the operation part 4 via the connecting part 3.

An objective lens holding hole, a light distribution lens holding hole, an air / water feeding channel outlet, a treatment instrument insertion channel outlet and the like (all not shown) are formed in the rigid portion 5 at the tip of the body insertion portion 2. An objective lens for image formation and a light distribution lens L1 for illumination are fitted and held in the objective lens holding hole and the light distribution lens holding hole, respectively.

Two bending operation knobs 8 provided on the operation section 4,
When each of 9 is rotated, the bending portion 6 bends in the left-right direction and the up-down direction.

At the end of the universal tube 10 extending from the operation section 4, a connector section 11 connected to a processor (not shown) is provided. Connector part 1
1, a signal transmission cable (not shown) disposed inside the electronic endoscope 1 and the universal tube 10, an end portion of an optical fiber bundle 12 for illuminating optical fibers, an air supply tube and a water supply tube (both are shown). (Not shown) is provided, and by connecting the connector part 11 to the processor, these elements are connected to the image processing device, light source, air supply source, and water supply source (all not shown) on the processor side. Connected.

In the rigid portion 5, a CCD (not shown) is provided behind the objective lens, and the image of the observation object entered from the objective lens into the light receiving surface of the CCD is photoelectrically converted.
From CCD to connector part 11 of universal tube 10
It is sent to the processor as an electronic image through the above-mentioned signal transmission cable provided up to. The processor can display an electronic image on a monitor (not shown) or record it on an image recording medium. The operation unit is provided with a plurality of remote operation button switches 13 for performing remote operations related to image processing.

The operation unit 4 is provided with an air / water supply button 14, and when the air / water supply button 14 is pressed, air supplied from the processor-side air supply source and the water supply source to the air supply tube and the water supply tube, The liquid is jetted from the air / water supply channel outlet of the rigid portion 5.

The connecting portion 3 is provided with a treatment instrument insertion port projection 15 for inserting a treatment instrument such as forceps or a high frequency cautery treatment instrument, and is inserted from the treatment instrument insertion port projection 15 into the electronic endoscope 1. The treated instrument (not shown) protrudes from the outlet of the instrument insertion channel provided in the rigid portion 5 to the observation target side.

As shown in FIGS. 2 and 5, inside the rigid portion 5, the luminous flux exit end surface 12a of the illumination optical fiber bundle 12 is located behind the light distribution lenses L1 and L2 and is provided in the processor. The light from the light source enters from the light flux incident end surface of the illumination optical fiber bundle 12, and the light flux exit end surface 1
It is emitted from 2a. The light flux emission end face 12a is a light source having a substantially circular cross section (front face). The light source may be a light emitting element such as an LED, in addition to the light flux emission end face 12a of the illumination optical fiber bundle 12.

First concave portions L1a, L2a, L3a are formed on the surfaces of the light distributing lenses L1, L2, L3 of the first to fifth embodiments which will be described below, which face the light beam exit end surface 12a. The observation target side surfaces of the light distribution lenses L1, L2, L3 are planes orthogonal to the light source optical axis O, and second concave portions L1b, L2b, L3b are formed on this surface.

It is preferable that the concave portion formed on the surface on the side of the observation object satisfies the following conditional expression. (1) tan {90-sin ⁻¹ (1 / n)} <h / d ₃ <11.5 (2) 0.35 <h / h ₀ where h: observation of the second concave portion from the optical axis of the light source Height to target side end portion, h ₀ : height from the light source optical axis of the light source, d ₃ : depth of the second concave portion,

Conditional expression (1) is defined by the second recesses L1b and L2.
Conditional expression (1) that defines the shapes of b and L3b
Below the lower limit of the second recesses L1b, L2b, L3b
Since the depth is larger than the diameter of the second recess L2,
The amount of light rays totally reflected on the surfaces of 2b and L3b increases and the light amount decreases, and when the upper limit value of the conditional expression (1) is exceeded, the second recesses L1b, L2b, L3b become shallow and the effect of expanding the light amount is small. turn into. The conditional expression (2) is the second
The size of the recesses L1b, L2b, L3b is defined. If this conditional expression is not satisfied, the size of the second recesses L1b, L2b, L3b is smaller than that of the light source. The effect of spreading is reduced.

The shape satisfying the conditional expression (1) includes, for example, a part of a spherical surface, a part of an aspherical surface, a cone and the like.

As shown in FIG. 2, when the second recess L1b is composed of a part of the spherical surface, the second recess L1b is
It is preferable to satisfy the following conditional expression (3). (3) 0.35h ₀ <h <0.95r _{3 where} , h: height from the light source optical axis to the end of the second concave portion on the observation target side, h ₀ : height from the light source optical axis of the light source, r ₃ is the radius of curvature of the concave spherical surface.

When h is less than the lower limit value of the conditional expression (3), the effect of improving the light distribution characteristic becomes small because the second recess L1b is too small as compared with the size of the light source. Further, when h exceeds the upper limit value of the conditional expression (3), the dent amount of the second recess L1b becomes deeper than h, so that the second recess L1
The light rays totally reflected at the peripheral portion of b increase, the light amount decreases, and the cleaning property of the second recess L1b significantly decreases.

As shown in FIG. 5, the second recess L2b is
It may have a conical shape. When the second recess L2b has a conical shape, a light beam substantially parallel to the light source optical axis O (a light beam with a small exit angle from the light source) can be strongly refracted to the outside.

When the second recess L2b has a conical shape, it is desirable to satisfy the conditional expression (4). (4) 90-sin ⁻¹ (1 / n) <α where α: angle formed by the optical axis of the light source and the generatrix of the concave conical surface [unit: de
g], n: refractive index of the light distribution lens.

When α is less than the lower limit value of the conditional expression (4), the second concave portion L2b has a more pointed shape, and a ray parallel to the optical axis O of the light source and reaching the surface on the side of the observation object is a conical surface. The amount of light reflected and emitted decreases. Further, since the depth of the second recess L2b is deeper than the radius, the workability is deteriorated and the cleanability is greatly reduced.

Next, concrete numerical examples of the light distribution lenses L1, L2, L3 and the optical fiber bundle 12 for illuminating optical fibers will be described. 2 to 4 show Embodiments 1 and 2, FIGS. 5 to 8 show Embodiments 3 and 4, and FIGS. 9 and 10 show Embodiment 5. In these embodiments, the first and second recesses are arranged so as to be rotationally symmetrical with respect to the optical axis of the light source. A comparative example in which the light distribution lens L is a plano-concave lens will be finally described with reference to FIGS. 11 and 12.

[Example 1] In the following table, r1 is the first recess L
1a has a radius of curvature [mm], r2 has a radius of curvature [mm] of the surface of the light distribution lens L1 on the side to be observed, r3 has a radius of curvature [mm] of the second recess L1b, and d1, d2, and d3 denote light distribution lenses. The thickness [mm] of each part of L1, n is the refractive index of the light distribution lens L1 with respect to the d line, ν is the Abbe number, and h ₀ is the radius [mm] of the optical fiber bundle 12 for illumination of the optical fiber. Also, FIG.
And "intensity ratio" on the vertical axis of the graph in Fig. 4 is the light distribution angle (horizontal axis)
Shows the ratio of the light intensity at each light distribution angle when the light intensity when 0 is 0 [deg] is 1.0.

[0035]

Table 1 r1 = 0.900 r2 = ∞ r3 = 0.300 d1 = 0.45 d2 = 0.20 d3 = 0.20 n = 1.51633 ν = 64.1 h ₀ = 0.75

FIG. 3 is a graph showing the light distribution characteristics of the light distribution lens L1 of the first embodiment. As you can see from this graph,
Compared with the comparative example, even if the light distribution angle becomes large, the light intensity of the peripheral portion does not significantly decrease, so that the entire illumination range can be illuminated relatively uniformly and brightly.

[Example 2]

Table 2 r1 = 0.900 r2 = ∞ r3 = 0.600 d1 = 0.45 d2 = 0.20 d3 = 0.20 n = 1.51633 ν = 64.1 h ₀ = 0.75

FIG. 4 is a graph showing the light distribution characteristics of the light distribution lens L1 of the second embodiment. As you can see from this graph,
Even if the light distribution angle becomes large, the reduction of the light intensity in the peripheral portion can be further suppressed as compared with the first embodiment, so that the entire illumination range can be illuminated more uniformly and brightly.

Next, concrete numerical examples of the light distribution lens L2 and the optical fiber bundle 12 for illuminating optical fibers will be described. In the following table, r1 is the radius of curvature of the first recess L2a
[mm], r2 is the radius of curvature [mm] of the surface of the light distribution lens L2 on the observation target side, d1, d2, and d3 are the thicknesses [mm] of each part of the light distribution lens L2, and α is the light source optical axis O and The angle [deg] formed by the peripheral surface of the concave portion L2b of No. 2, n is the refractive index of the light distribution lens L2 with respect to the d line, ν is the Abbe number, and h ₀ is the radius [mm] of the optical fiber bundle 12 for illumination of the optical fiber. ing.

[Example 3]

Table 3 r1 = 0.900 r2 = ∞ d1 = 0.45 d2 = 0.25 d3 = 0.15 n = 1.51633 ν = 64.1 α = 80 h ₀ = 0.75

FIG. 6 is a graph showing the light distribution characteristics of the light distribution lens of the third embodiment. As can be seen from this graph, compared to the comparative example, even if the light distribution angle is large, the decrease in the light intensity in the peripheral portion is small, so that the entire illumination range can be illuminated relatively uniformly and brightly.

[Example 4]

Table 4 r1 = 0.900 r2 = ∞ d1 = 0.45 d2 = 0.15 d3 = 0.25 n = 1.51633 ν = 64.1 α = 60 h ₀ = 0.75

FIG. 7 is a graph showing the light distribution characteristics of the light distributing lens of the fourth embodiment. As can be seen from this graph, even if the light distribution angle becomes large, the reduction of the light intensity in the peripheral portion can be further suppressed as compared with the third embodiment, so that the entire illumination range can be illuminated more uniformly and brightly.

FIG. 8 shows a modification of the third and fourth embodiments. In this modification, a transparent cover glass G made of a plane parallel plate is arranged on the surface of the light distribution lens L2 on the observation target side.

By providing such a cover glass G, body fluid, dust, etc. do not accumulate in the second recess L2b, so that the rigid portion 5 of the electronic endoscope 1 can be easily washed. The light distribution characteristics of this embodiment are almost the same as those of the third and fourth embodiments.

Next, a fifth embodiment of the present invention will be described with reference to FIGS. 9 and 10. The same members as those in the other embodiments are denoted by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 9, a conical second recess L3b having a curved vertex is formed on the surface of the light distributing lens L3 of this embodiment on the side of the observation object.

Next, concrete numerical examples of the light distribution lens L3b and the optical fiber bundle 12 for illuminating optical fibers will be described. In the following table, r1 is the radius of curvature of the first recess L3a
[mm], r2 is the radius of curvature [mm] of the surface of the light distribution lens L3 on the observation target side, d1, d2, d3 are the thicknesses [mm] of the respective parts of the light distribution lens L3, and α is the light source optical axis O and the The angle [deg] formed by the peripheral surface of the concave portion L3b of No. 2, n is the refractive index of the light distributing lens L3 with respect to the d line, ν is the Abbe number, and h ₀ is the radius [mm] of the optical fiber bundle 12 for illumination of the optical fiber. ing.

[Example 5]

Table 5 r1 = 0.820 r2 = ∞ d1 = 0.36 d2 = 0.20 d3 = 0.16 n = 1.51633 ν = 64.1 α = 70 h ₀ = 0.65

Comparative Example FIG. 11 shows, as a comparative example, a plano-concave lens L having a concave surface on the surface facing the light beam exit end surface 12a. Table 6 shows the data of the plano-concave light distribution lens L,
The light distribution characteristics are shown in FIG.

[0051]

[Table 6] r1 = 0.900 r2 = ∞ d1 = 0.45 d2 = 0.40 n = 1.51633 ν = 64.1 h ₀ = 0.75

As can be seen from the graph of FIG. 12, the conventional plano-concave light distribution lens has a bright center in the illumination range,
When the light distribution angle becomes large, the light intensity in the peripheral portion largely decreases (because the surroundings become dark), so that uneven illumination occurs.

The cover glass G may be arranged on the surface of the light distribution lens L3 of the fifth embodiment on the side of the observation target.

[0054]

According to the present invention, there is provided a light distribution lens of an endoscope, which is a light distribution lens composed of a single lens and in which the light intensity of the peripheral portion does not largely decrease even if the light distribution angle increases. can get.

[Brief description of drawings]

FIG. 1 is an overall view of an embodiment of the present invention.

FIG. 2 is an enlarged side view of the inside of the distal end portion of the electronic endoscope of Examples 1 and 2.

FIG. 3 is a graph showing the light distribution characteristics of the light distribution lens of Example 1.

FIG. 4 is a graph showing the light distribution characteristics of the light distribution lens of Example 2.

FIG. 5 is an enlarged side view of the inside of the distal end portion of the electronic endoscope of Examples 3 and 4.

FIG. 6 is a graph showing the light distribution characteristics of the light distribution lens of Example 3.

FIG. 7 is a graph showing the light distribution characteristics of the light distribution lens of Example 4.

FIG. 8 is an enlarged side view of the inside of the distal end portion of the electronic endoscope of a modified example of Examples 3 and 4.

FIG. 9 is an enlarged side view of the inside of the distal end portion of the electronic endoscope of Example 5.

FIG. 10 is a graph showing the light distribution characteristics of the light distribution lens of Example 5.

FIG. 11 is an enlarged side view of the inside of the distal end portion of the endoscope of the comparative example.

FIG. 12 is a graph showing a light distribution characteristic of a light distribution lens of a comparative example.

[Explanation of symbols]

1 Electronic endoscope 2 Internal insertion section 12 Optical fiber bundle for illumination 12a Emitting end face (light source) L1 light distribution lens L1a first recess L1b second recess L2 light distribution lens L2a first recess L2b second recess G cover glass L3 light distribution lens L3a first recess L3b second recess O light source optical axis

Claims (10)

[Claims] 1. The endoscope is located at the tip of the insertion portion of the endoscope,
A light distributing lens comprising a single lens for irradiating light from a light source toward an observation target, wherein a first recess formed on a surface facing the light source and a second recess formed on a surface on the observation target side. And a light distribution lens for an endoscope. 2. The light distribution lens for an endoscope according to claim 1, wherein the light source is a light flux emitting end surface of a bundle of optical fibers for illumination. 3. The endoscope light distributing lens according to claim 1, wherein the light source is a light emitting element. 4. The endoscope light distributing lens according to claim 1, wherein the second concave portion satisfies the following conditional expressions (1) and (2). Light lens. (1) tan {90-sin ⁻¹ (1 / n)} <h / d ₃ <11.5 (2) 0.35 <h / h ₀ where h: observation of the second concave portion from the optical axis of the light source Height to target end, h ₀ : Height from light source optical axis of light source, d ₃ : Depth of second recess. 5. The light distribution lens for an endoscope according to claim 1, wherein the second concave portion is a part of a concave spherical surface. 6. The light distributing lens for an endoscope according to claim 5, wherein the concave spherical surface satisfies the following conditional expression (3). (3) 0.35h ₀ <h <0.95r _{3 where} , h: height from the light source optical axis to the end of the second concave portion on the observation target side, h ₀ : height from the light source optical axis of the light source, r ₃ : radius of curvature of concave spherical surface. 7. The light distributing lens for an endoscope according to claim 1, wherein the second concave portion is a concave conical surface. 8. The light distribution lens for an endoscope according to claim 7, wherein the apex of the concave conical surface is a curved surface. 9. The light distribution lens for an endoscope according to claim 7 or 8, wherein the concave conical surface satisfies the following conditional expression (4). (4) 90-sin ⁻¹ (1 / n) <α where α is the angle [unit: deg] formed by the optical axis of the light source and the generatrix of the concave conical surface, and n is the refractive index of the light distributing lens. 10. The light distribution lens for an endoscope according to claim 1, wherein the second light distribution lens is a second lens.
A light distribution lens for an endoscope in which a cover glass made of a plane parallel plate is arranged on a surface having a concave portion.