JP2000010024A - Rigid mirror optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rigid mirror optical system which is good in peripheral image quality with an elongated insertion part by arranging a visual field stop for observation of an image of a specific range with respect to an effective image range of the max. outside diameter of an image transmission optical system between the image transmission optical system and an eyepiece optical system integrally with the eyepiece optical system. SOLUTION: This optical system consists, successively from an object side, an objective optical system O, the image transmission optical system RL, the visual field stop FS and the eyepiece optical system E. The visual field stop FS is used for observation of the image of the range smaller than the effective surface image range of 70% of the max. outside diameter of the image transmission optical system RL. The visual field stop ES and the eyepiece optical system E are integrally arranged. When the diameter of the effective image range is defined as B and the diameter of the image range to be used as A, the conditions 0.4<A/B<0.6 are desirably satisfied. If A/B is too small having 0.4 of the lower limit, brightness for practicable use is hindered. If A/B increases excessively beyond 0.6 of the upper limit, the sufficiently satisfactory correction of curvature of the field is not longer possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rigid endoscope having a narrow insertion portion and a relatively narrow viewing angle, which is mainly used in the field of urology.

[0002]

2. Description of the Related Art A rigid mirror optical system has a plurality of relay lenses as image transmission means, and corrects a negative curvature of field generated by a relay lens by an objective optical system.

A rigid endoscope used in the field of urology has a long insertion portion as thin as about 4 mm in diameter and about 300 mm in length. Such a thin and long rigid endoscope is usually transmitted about five times by a relay lens.

FIG. 7 shows a conventional example of such a rigid endoscope. A urinary rigid endoscope used for a prostate treatment or the like has a perspective angle θ because it is necessary to magnify and observe electrodes around a visual field during surgery.
However, a perspective of 10 ° to 20 ° is used.

Further, in order to prevent blurring of the visual field at the distal sheath, the viewing angle 2ω of the rigid endoscope is a relatively narrow angle of about 50 ° to 60 °.

A conventional example of a perspective optical system of a fiberscope is disclosed in Japanese Patent Application Laid-Open No. 51-218 shown in FIG.
There is one disclosed in Japanese Patent Publication No. 35-35. This optical system realizes perspective by decentering the image fiber IF with respect to the image plane of the objective lens.

[0007]

In the medical field where a rigid endoscope is used, the penetration of the less invasive means has required a further reduction in the diameter of the insertion portion of the endoscope.

In a rigid endoscope, the reduction in the diameter of the insertion section increases the number of relays of the relay optical system, for example, from 5 to 7 times. The first reason is to reduce the length of a relay at one time and to avoid destruction of a rod glass or the like used in a relay optical system due to bending stress of an insertion portion. The second reason is to increase the NA so that a practically necessary level of brightness can be obtained.

Image observation with a rigid endoscope is often performed on a monitor mainly using a television camera.
The pixel size of a CCD of a television camera tends to be reduced due to a tendency toward high resolution and compactness.

The decrease in brightness due to the reduction in the diameter of the insertion section of the rigid endoscope can be improved by improving the brightness (sensitivity) of the television camera by improving the circuit processing technology and improving the light source technology. On the other hand, a reduction in the size of a CCD pixel causes a reduction in the depth of focus. For this reason, the detection sensitivity of the television camera to the peripheral image quality due to the one-sided blur or the like becomes high, and it is necessary to sufficiently correct it at the time of designing.

However, when the viewing angle is narrow, the field curvature increases as the number of relays by the relay optical system increases, and it is difficult to correct this with the weak field curvature of the objective optical system.

In order to correct this curvature of field without increasing the ray height on the object side, it is necessary to increase the power of the concave lens. The ability is limited.

In the conventional example (JP-A-51-21835), the eccentricity is made on the image plane of the objective optical system. It is difficult to implement the work of adjusting and fixing at the time of assembling with high accuracy due to restrictions such as.

The present invention is to provide a rigid mirror optical system which has a narrow viewing angle, a narrow insertion portion having a diameter of about 4 mm or less and a length of about 300 mm or more, and excellent peripheral image quality.

The present invention also provides a weak perspective hard mirror optical system having a good image quality (a hard mirror optical system having a relatively small perspective angle).

[0016]

The rigid mirror optical system according to the present invention comprises, in order from the object side, an objective optical system, an image transmission optical system,
The field stop and the eyepiece optical system are used for observing an image in a range where the field stop is smaller than an effective surface image area of 70% of the maximum outer diameter of the image transmission optical system. And are arranged integrally.

In the rigid mirror optical system of the present invention, an image range larger than the image range to be used is designed in advance to have a wide-angle design, the field curvature is sufficiently corrected, and an image range with a narrow angle required for this is cut out. We are trying to expand it.

In this case, when the diameter of the effective image area is B and the diameter of the image area to be used is A, it is desirable to satisfy the following condition (1). (1) 0.4 <A / B <0.6

If the ratio A / B, which is the ratio of the image area used as the observation image to the effective image area, exceeds the lower limit of 0.4 of the condition (1), and becomes too small, practically the brightness is hindered. Also, when the value exceeds the upper limit of 0.6 of the condition (1), A / B
Is too large, it is not possible to sufficiently satisfactorily correct the field curvature.

The image range that can be used in a rigid endoscope depends on the outer diameter of the image transmission system. When a relay optical system is used as the image transmission system, both the pupil diameter and the size of the image are affected. Therefore, if the image size is the same, the brightness is proportional to the fourth power of the outer diameter. For this reason, it is common practice to increase the effective image range with respect to the outer diameter of the relay optical system. This range slightly varies depending on the thickness of the spacer and the power arrangement (aperture efficiency) of the image transmission system. It is in the range of 70% to 80% of the outer diameter of the relay optical system. Therefore, in the present invention, 70% of the outer diameter of the relay optical system is set as the effective image range.

Further, as described above, the rigid mirror optical system of the present invention comprises, in order from the object side, an objective optical system, an image transmission optical system,
It consists of a field stop and an eyepiece optical system, and the field stop and the eyepiece optical system are integrally decentered in the direction perpendicular to the optical axis for perspective use, and the eyepiece optical system is decentered in the same direction as the perspective direction. It is characterized in that it is adjusted and fixed in a state where it is made to be in contact.

As described above, when an image range to be used is decentered in order to make a weakly oblique rigid endoscope, that is, a rigid endoscope having a relatively small oblique angle as described above, the amount of eccentricity with respect to the oblique angle is set as follows. It is desirable to set it within the range satisfying 2). (2) 0.25 <2 × C / B <0.7 where C is the amount of eccentricity of the center of the used observation image with respect to the effective screen range.

If the ratio C / B is too small below the lower limit of 0.25 in the condition (2), a sufficient oblique angle cannot be obtained. On the other hand, if the value of C / B is too large beyond the upper limit of 0.7, the peripheral image quality deteriorates and the peripheral light quantity decreases due to scorching.

Next, a description will be given of a case where the rigid optical system of the present invention obtains a perspective by using wedges for the objective optical system.

The rigid mirror optical system according to the present invention is a weak perspective rigid mirror optical system of 5 ° to 20 ° using a deflection wedge at the tip of the objective optical system, that is, the object side closest to the object, for oblique use.

That is, the present invention is a weakly squinting rigid mirror optical system in which the angle θ with respect to the optical axis of the objective optical system in the oblique direction shown in FIG. 7 is within the range of the following condition (A). (A) 5 ° <θ <20 °

It is desirable that the deflection wedge used in such a weak perspective hard mirror optical system satisfies the following conditions (3) and (4). (3) n _d > 1.65 (4) ν _d > 60 where n _d is the refractive index of the deflection wedge with respect to the d-line, and ν _d is the Abbe number of the deflection wedge.

When the value of n _d is smaller than the lower limit of 1.65 of the condition (3), the image plane tilt increases, and the image forming performance in the periphery of the image deteriorates. On the other hand, when the value of ν _d is smaller than the lower limit of 60 of the condition (4), the occurrence of chromatic aberration becomes large, which is not preferable.

The surface of the deflected wedge that contacts the surface is A
l ₂ O ₃ single crystal, Al ₂ O ₃ sintered body, be constituted of a material including any of M _g O single crystal, also does not deteriorate even in an environment of high temperature and humidity, is a sterilizing method of the rigid endoscope Sterilization in an autoclave can prevent degradation.

Conventionally, a sapphire cover glass has been arranged to protect the front surface of the wedge from humidity. For this reason, there was a disadvantage that the light beam height was increased and the outer diameter of the tip of the optical system was increased.However, by using a moisture-resistant wedge as in the above-described optical system, the cover glass was omitted, and the wedge was made the most object. Since it can be arranged on the side, the required image range can be obtained without increasing the diameter of the tip.

In the rigid mirror optical system of the present invention, when the oblique angle wedge is used for a weak perspective of 10 ° to 20 °, that is, when the oblique angle θ satisfies the following condition (A-1). ,
Instead of the conditions (3) and (4), the following condition (3-1)
It is desirable to satisfy (4-1). (A-1) 10 ° < θ <20 ° (3-1) n d> 1.7 (4-1) ν d> 65

In order to correct the field curvature generated in the objective optical system, basically, the power of the concave lens should be increased. As a means for increasing the power of the concave lens, it is conceivable to reduce the radius of curvature of the lens surface. However, since the diameter of the objective optical system of the rigid endoscope is extremely small, it is difficult to process the lens if the radius of curvature of the lens surface is extremely small, and the radius of curvature that can be processed is about 0.45 mm. In order to better correct the curvature of field using a concave lens having such a workable radius of curvature, it is necessary to increase the refractive index of the concave lens, and it is desirable to satisfy the following condition (5). (5) n _d (N)> 1.8 where n _d (N) is the refractive index for the d-line of the concave lens.

In order to reduce the diameter of the distal end of the insertion portion of the rigid endoscope, a cover glass (a wedge having a surface inclined to the optical axis of the objective optical system on the concave lens side) is disposed closest to the object side. And the outer diameter of the concave lens disposed on the image side of the cover glass preferably satisfies the following condition (6). (6) 0.6 <D / E <0.75 where D is the outer diameter of the concave lens, and E is the outer diameter of the cover glass.

In this condition (6), when the value of D / E is smaller than the lower limit of 0.6, the outer diameter of the concave lens is sufficient to allow all the rays to pass through the concave lens. And the surrounding light flux is removed. Also, the upper limit of 0.75
Is exceeded, the distance between the cover glass and the concave lens is increased, and the peripheral light beam is cut off by the cover glass.

In order to keep the height of the light beam incident on the cover glass low and to obtain a required viewing angle, it is desirable to satisfy the following condition (7). (7) 0.5 <E _np /f<1.5 However, E _np is the entrance pupil position of the objective optical system, f is the focal length of the objective optical system.

In condition (7), if the lower limit of 0.5 is exceeded, the radius of curvature of the concave lens becomes small, making processing difficult.
When the value exceeds the upper limit of 1.5, the light beam becomes high and the diameter of the objective optical system cannot be reduced.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the rigid mirror objective optical system of the present invention will be described based on the following examples.

[0038] Example 1 a perspective angle = 11.7 ° (air), the angle of view = 53 °, field stop diameter _{= 1.28mm, f = 1 r 1} = ∞ d 1 = 0.3067 n 1 = 1.76820 ν 1 = 71.70 r 2 = ∞ d ₂ = 0.2800 r ₃ = ∞ d ₃ = 0.1500 n ₂ = 1.84666 ν ₂ = 23.78 r ₄ = 0.410 d ₄ = 0.2500 r ₅ = ∞ d ₅ = 6.13 n ₃ = 1.83481 ν ₃ = 42.72 r ₆ = -2.6650 _{d 6 = 0.4000 r 7 = 1.9610} d 7 = 0.7000 n 4 = 1.72916 ν 4 = 54.68 r 8 = -3.3640 d 8 = 0.8300 n 5 = 1.78472 ν 5 = 25.68 r 9 = 3.3640 d 9 = 1.1400 r 10 = -0.7580 d ₁₀ = 0.6800 n ₆ = 1.84666 v ₆ = 23.78 r ₁₁ = 6.3130 d ₁₁ = 0.9800 n ₇ = 1.83481 v ₇ = 42.72 r ₁₂ = -1.5220 d ₁₂ = 5.4408 r ₁₃ = 5.7020 d ₁₃ = 14.8500 n ₈ = 1.58913 v _{8 = 61.18 r 14 = ∞ d} 14 = 1.5220 r 15 = 5.3552 d 15 = 0.8300 n 9 = 1.61272 ν 9 = 58.75 r 16 = -3.3640 d 16 = 2.3500 n 10 = 1.78800 ν 10 = 47.38 r 17 = 3.3640 d 17 = 0.8300 n ₁₁ = 1.61272 ν _{1 1 = 58.75 r 18 = -5.3552 d} 18 = 1.5220 r 19 = ∞ d 19 = 14.8500 n 12 = 1.58913 ν 12 = 61.18 r 20 = -7.2040 d 20 = 6.9190 r 21 = 7.2040 d 21 = 14.8500 n 13 = 1.58913 ν _{13 = 61.18 r 22 = ∞ d} 22 = 1.5220 r 23 = 5.3552 d 23 = 0.8300 n 14 = 1.61272 ν 14 = 58.75 r 24 = -3.3640 d 24 = 2.35 n 15 = 1.78800 ν 15 = 47.38 r 25 = 3.3640 d 25 = 0.8300 n ₁₆ = 1.61272 v ₁₆ = 58.75 r ₂₆ = -5.3552 d ₂₆ = 1.5220 r ₂₇ = ∞ d ₂₇ = 14.8500 n ₁₇ = 1.58913 v ₁₇ = 61.18 r ₂₈ = -7.2040 d ₂₈ = 6.9190 r ₂₉ = 7.2040 d ₂₉ = 14.8500 n ₁₈ = 1.58913 ν ₁₈ = 61.18 r ₃₀ = ∞ d ₃₀ = 1.5220 r ₃₁ = 5.3552 d ₃₁ = 0.8300 n ₁₉ = 1.61272 ν ₁₉ = 58.75 r ₃₂ = -3.3640 d ₃₂ = 2.35 n ₂₀ = 1.78800 ν ₂₀ = 47.38 r ₃₃ = 3.3640 d ₃₃ = 0.8300 n ₂₁ = 1.61272 ν ₂₁ = 58.75 r ₃₄ = -5.3552 d ₃₄ = 1.5220 r ₃₅ = ∞ d ₃₅ = 14.8500 n ₂₂ = 1.58913 ν ₂₂ = 61.18 r ₃₆ = -7.2040 d _{36 = 6.9190 r 37 = 7.2040 d} 37 = 14.8500 n 23 = 1.58913 ν 23 = 61.18 r 38 = ∞ d 38 = 1.5220 r 39 = 5.3552 d 39 = 0.8300 n 24 = 1.61272 ν 24 = 58.75 r 40 = -3.3640 d 40 = 2.35 n ₂₅ = 1.78800 v ₂₅ = 47.38 r ₄₁ = 3.3640 d ₄₁ = 0.8300 n ₂₆ = 1.61272 v ₂₆ = 58.75 r ₄₂ = -5.3552 d ₄₂ = 1.5220 r ₄₃ = ∞ d ₄₃ = 14.8500 n ₂₇ = 1.58913 v ₂₇ = _{61.18 r 44 = -7.2040 d 44 =} 6.9190 r 45 = 7.2040 d 45 = 14.8500 n 28 = 1.58913 ν 28 = 61.18 r 46 = ∞ d 46 = 1.5220 r 47 = 5.3552 d 47 = 0.8300 n 29 = 1.61272 ν 29 = 58.75 _{r 48 = -3.3640 d 48 = 2.35} n 30 = 1.78800 ν 30 = 47.38 r 49 = 3.3640 d 49 = 0.8300 n 31 = 1.61272 ν 31 = 58.75 r 50 = -5.3552 d 50 = 1.5220 r 51 = ∞ d 51 = 14.8500 _{n 32 = 1.58913 ν 32 = 61.18} r 52 = -7.2040 d 52 = 6.9190 r 53 = 7.2040 d 53 = 14.8500 n 33 = 1.58913 ν 33 = 61.18 r 54 = ∞ d 54 = 1.5220 r 55 = 5.3552 _{55 = 0.8300 n 34 = 1.61272 ν} 34 = 58.75 r 56 = -3.3640 d 56 = 2.35 n 35 = 1.78800 ν 35 = 47.38 r 57 = 3.3640 d 57 = 0.8300 n 36 = 1.61272 ν 36 = 58.75 r 58 = -5.3552 d _{58 = 1.5220 r 59 = ∞ d} 59 = 14.8500 n 37 = 1.58913 ν 37 = 61.18 r 60 = -7.2040 d 60 = 6.9190 r 61 = 7.2040 d 61 = 14.8500 n 38 = 1.58913 ν 38 = 61.18 r 62 = ∞ d 62 = 1.5220 r ₆₃ = 5.3552 d ₆₃ = 0.8300 n ₃₉ = 1.61272 v ₃₉ = 58.75 r ₆₄ = -3.3640 d ₆₄ = 2.35 n ₄₀ = 1.78 800 v ₄₀ = 47.38 r ₆₅ = 3.3640 d ₆₅ = 0.8300 n ₄₁ = 1.61272 v ₄₁ = 58.75 r ₆₆ = -5.3552 d ₆₆ = 1.5220 r ₆₇ = ∞ d ₆₇ = 14.8500 n ₄₂ = 1.58913 ν ₄₂ = 61.18 r ₆₈ = ∞ d ₆₈ = 4.8329 r ₆₉ = ∞ (image) d ₆₉ = 0.0077 r ₇₀ = ∞ ( field _{stop) d 70 = 6.8190 r 71 =} 9.3300 d 71 = 0.3200 n 43 = 1.84666 ν 43 = 23.78 r 72 = 3.6370 d 72 = 1.44 n 44 = 1.58267 ν 44 = 46.39 r 73 = -5.1350 d 73 = 10.84 1 r ₇₄ = ∞ (pupil) A / B = 0.47, 2 × C / B = 0.32, D / E = 0.67 E np = 0.95, E np /f=0.95

[0039] Example 2 a perspective angle = 16.6 ° (air), the angle of view = 55 °, field stop diameter _{= 1.56mm, f = 1.278 r 1} = ∞ d 1 = 0.5600 n 1 = 1.76820 ν 1 = 71.70 r 2 = ∞ d ₂ = 0.3200 r ₃ = ∞ d ₃ = 0.1500 n ₂ = 1.88300 ν ₂ = 40.78 r ₄ = 0.4910 d ₄ = 0.2500 r ₅ = ∞ d ₅ = 5.0700 n ₃ = 1.83481 ν ₃ = 42.72 r ₆ = -2.6340 _{d 6 = 0.7000 r 7 = 2.3850} d 7 = 1.3300 n 4 = 1.77250 ν 4 = 49.60 r 8 = -1.2180 d 8 = 0.6200 n 5 = 1.78472 ν 5 = 25.68 r 9 = 4.8010 d 9 = 1.5000 r 10 = -0.6750 d ₁₀ = 0.4000 n ₆ = 1.83481 v ₆ = 42.72 r ₁₁ = ∞ d ₁₁ = 0.9700 n ₇ = 1.78590 v ₇ = 44.19 r ₁₂ = -1.2980 d ₁₂ = 5.1430 r ₁₃ = 5.7020 d ₁₃ = 14.8500 n ₈ = 1.58913 v _{8 = 61.18 r 14 = ∞ d} 14 = 1.5220 r 15 = 5.3552 d 15 = 0.8300 n 9 = 1.61272 ν 9 = 58.75 r 16 = -3.3640 d 16 = 2.3500 n 10 = 1.78800 ν 10 = 47.38 r 17 = 3.3640 d 17 = 0.8300 n ₁₁ = 1.61272 _{11 = 58.75 r 18 = -5.3552 d} 18 = 1.5220 r 19 = ∞ d 19 = 14.8500 n 12 = 1.58913 ν 12 = 61.18 r 20 = -7.2040 d 20 = 6.9190 r 21 = 7.2040 d 21 = 14.8500 n 13 = 1.58913 ν _{13 = 61.18 r 22 = ∞ d} 22 = 1.5220 r 23 = 5.3552 d 23 = 0.8300 n 14 = 1.61272 ν 14 = 58.75 r 24 = -3.3640 d 24 = 2.3500 n 15 = 1.78800 ν 15 = 47.38 r 25 = 3.3640 d 25 = 0.8300 n ₁₆ = 1.61272 v ₁₆ = 58.75 r ₂₆ = -5.3552 d ₂₆ = 1.5220 r ₂₇ = ∞ d ₂₇ = 14.8500 n ₁₇ = 1.58913 v ₁₇ = 61.18 r ₂₈ = -7.2040 d ₂₈ = 6.9190 r ₂₉ = 7.2040 d ₂₉ = 14.8500 n ₁₈ = 1.58913 ν ₁₈ = 61.18 r ₃₀ = ∞ d ₃₀ = 1.5220 r ₃₁ = 5.3552 d ₃₁ = 0.8300 n ₁₉ = 1.61272 ν ₁₉ = 58.75 r ₃₂ = -3.3640 d ₃₂ = 2.3500 n ₂₀ = 1.78800 ν ₂₀ = 47.38 r ₃₃ = 3.3640 d ₃₃ = 0.8300 n ₂₁ = 1.61272 ν ₂₁ = 58.75 r ₃₄ = −5.3552 d ₃₄ = 1.5220 r ₃₅ = ∞ d ₃₅ = 14.8500 n ₂₂ = 1.58913 ν ₂₂ = 61.18 r ₃₆ = −7.2 _{040 d 36 = 6.9190 r 37 =} 7.2040 d 37 = 14.8500 n 23 = 1.58913 ν 23 = 61.18 r 38 = ∞ d 38 = 1.5220 r 39 = 5.3552 d 39 = 0.8300 n 24 = 1.61272 ν 24 = 58.75 r 40 = -3.3640 d ₄₀ = 2.3500 n ₂₅ = 1.78800 ν ₂₅ = 47.38 r ₄₁ = 3.3640 d ₄₁ = 0.8300 n ₂₆ = 1.61272 ν ₂₆ = 58.75 r ₄₂ = -5.3552 d ₄₂ = 1.5220 r ₄₃ = ∞ d ₄₃ = 14.8500 n ₂₇ = 1.58913 ν _{27 = 61.18 r 44 = -7.2040 d} 44 = 6.9190 r 45 = 7.2040 d 45 = 14.8500 n 28 = 1.58913 ν 28 = 61.18 r 46 = ∞ d 46 = 1.5220 r 47 = 5.3552 d 47 = 0.8300 n 29 = 1.61272 ν 29 _{= 58.75 r 48 = -3.3640 d 48} = 2.3500 n 30 = 1.78800 ν 30 = 47.38 r 49 = 3.3640 d 49 = 0.8300 n 31 = 1.61272 ν 31 = 58.75 r 50 = -5.3552 d 50 = 1.5220 r 51 = ∞ d 51 _{= 14.8500 n 32 = 1.58913 ν 32} = 61.18 r 52 = -7.2040 d 52 = 6.9190 r 53 = 7.2040 d 53 = 14.8500 n 33 = 1.58913 ν 33 = 61.18 r 54 = ∞ d 54 = 1.5220 r 55 _{5.3552 d 55 = 0.8300 n 34 =} 1.61272 ν 34 = 58.75 r 56 = -3.3640 d 56 = 2.3500 n 35 = 1.78800 ν 35 = 47.38 r 57 = 3.3640 d 57 = 0.8300 n 36 = 1.61272 ν 36 = 58.75 r 58 = - 5.3552 d ₅₈ = 1.5220 r ₅₉ = ∞ d ₅₉ = 14.8500 n ₃₇ = 1.58913 ν ₃₇ = 61.18 r ₆₀ = −7.2040 d ₆₀ = 6.9190 r ₆₁ = 7.2040 d ₆₁ = 14.8500 n ₃₈ = 1.58913 ν ₃₈ = 61.18 r ₆₂ = ∞ _{d 62 = 1.5220 r 63 = 5.3552} d 63 = 0.8300 n 39 = 1.61272 ν 39 = 58.75 r 64 = -3.3640 d 64 = 2.3500 n 40 = 1.78800 ν 40 = 47.38 r 65 = 3.3640 d 65 = 0.8300 n 41 = 1.61272 ν ₄₁ = 58.75 r ₆₆ = -5.3552 d ₆₆ = 1.5220 r ₆₇ = ∞ d ₆₇ = 14.8500 n ₄₂ = 1.58913 ν ₄₂ = 61.18 r ₆₈ = -19.0010 d ₆₈ = 4.226 r ₆₉ = ∞ (image) d ₆₉ = 0.021 r ₇₀ = ∞ (field stop) d ₇₀ = 8.223 r ₇₁ = 14.544 d ₇₁ = 0.6000 n ₄₃ = 1.80518 v ₄₃ = 25.43 r ₇₂ = 4.3300 d ₇₂ = 1.7000 n ₄₄ = 1.62374 v ₄₄ = 47.10 r ₇₃ = -6.5 _{830 d 73 = 12.6400 r 74 =} ∞ ( pupil) D / E = 0.63, E np = 1.03, E np /f=0.806 However r _1, r _2, ··· the radius of curvature of each lens surface, d
_.. , D ₂ ,...
₁ , n ₂ ,... Are the refractive indices of each lens for the d-line, ν
₁ , ν ₂ ,... Are Abbe numbers of the respective lenses.

Embodiments 1 and 2 have the structures as shown in FIGS. 1 and 2, respectively. In these embodiments, in order from the object side, the first
In the embodiment, a parallel flat plate is used. In the second embodiment, a deflection prism P is used.
(R ₁ -r ₂ ), objective optical system O (r ₃ -r ₁₂ ), image transmission optical system RL (r ₁₃ -r ₆₈ ), field stop FS
(R ₇₀ ) and an eyepiece optical system E (r _{71 to} r ₇₃ ). Again
₆₇ is an image position I, and r ₇₃ is an exit pupil position EP. The unit of the length such as the focal length is mm.

[0041] Also, the image transmission optics is first relay lens system having the same configuration RL1 (r ₁₃ ~r _20), a second relay lens system RL2 (r ₂₁ ~r _28), the third relay lens system RL3 (r
₂₉ ~r _36), the fourth relay lens system RL4 (r ₃₇ ~
r _44), the fifth relay lens system RL5 (r ₄₅ ~r _52), the sixth relay lens system RL6 (r ₅₃ ~r _60), consisting of the seventh relay lens system RL7 (r ₆₁ ~r _68).

In the first embodiment, a parallel flat plate (cover glass) is disposed at the tip of the objective optical system, and the parallel flat plate is orthogonal to the optical axis of the observation optical system. This prevents the angle of inclination in the viewing direction from being reduced during observation in water.

In the first embodiment, the diameter of the insertion portion is as small as 3 mm, so that the number of relays by the image transmission optical system is increased.

The diameter of the plane-parallel plate of Example 1 is 1.8 m.
m, the diameter of the objective optical system is 1.2 mm.

In the first embodiment, if the relay distance (the distance from the intermediate image to the next intermediate image) of the relay lens system constituting the image transmission optical system is the same as that of the hard mirror optical system having a thick insertion portion, Since the outer diameter of the lens is small due to the reduction in diameter, the numerical aperture of the relay lens system is reduced. As described above, when the numerical aperture is reduced, the brightness of the image is reduced, which is not preferable.

In the first embodiment, the numerical aperture of the relay lens system is not reduced even if the outer diameter of the relay lens system is reduced by shortening one relay distance.
Since one relay distance is shortened, the number of relays is set to seven times as compared with the conventional number of five times.

The outer diameter of each lens constituting the image transmission optical system of the first embodiment is 1.9 mm, and a spacer for positioning and holding the lens is arranged between the lenses. The thickness of this spacer is 0.05 mm. The thickness of the spacer used in the conventional rigid endoscope is 0.1 mm. However, if the insertion portion becomes thin as in this embodiment, there is a problem of light quantity loss due to the thickness of the spacer. For example, the outer diameter is 2mm
When a spacer having a thickness of 0.1 mm is used for the above lens, the effective diameter of the lens becomes 1.8 mm.

On the other hand, as in this embodiment, the thickness is 0.05 mm.
When the spacer is used, the effective diameter of the lens becomes 1.9 mm, and a light amount loss of about 20% can be prevented. The lens surface in contact with the spacer has a chamfer of 0.05 mm.

[0049] Furthermore, this embodiment 1, the nearest to the first relay lens system in the objective optical system (r ₁₃ ~r ₂₀₎ is adapted to enlarge an optical system for enlarging an image formed by the objective optical system.
That is, the off-axis principal ray of the light beam incident on the first relay lens system is obliquely incident on the incident surface (the surface on the side of the objective optical system) of the first relay lens system so that the exit surface of the objective optical system (the objective optical system). The height of the light beam at the last surface of the system can be reduced, and as a result, the upper light beam of the off-axis light beam can be prevented from being shaken by the spacer at the exit surface.

The image transmission optical system of this embodiment is a 1 × optical system from the second relay lens system (r _{21 to} r ₂₈ ) to the sixth relay lens system (r _{53 to} r ₆₀ ). 7 relay lens system (r ₆₁ ~r ₆₈₎ is about 1.48 times the magnifying optical system.

Since the outer diameter of the relay lens system of Example 1 is small, the relayed image is also small. When such a small image is magnified and observed with the eyepiece optical system, if the eyepiece optical system is used to enlarge the image to a desired size, the focal length of the eyepiece optical system must be shortened. ) Approaches the eyepiece optical system, making it difficult for an observer wearing eyeglasses to observe, and cannot properly correct the aberration of the eyepiece optical system. By setting the seventh relay lens system to the magnification, the burden of the magnification by the eyepiece optical system is reduced, the eye point of the eyepiece optical system can be kept at an appropriate position, and the aberration correction of the eyepiece optical system becomes easy. .

In the first embodiment, a part of the effective image area is cut out as an observation area for actual observation.
Since the curvature of field is satisfactorily corrected in advance within the effective image range, an observation image having no curvature of field can be obtained no matter where the image is cut out.

The effective image range is, for example, a range in which the size of the intermediate image formed by the second relay lens system to the sixth relay lens system is 1.28 mm in diameter and 0.9 mm in diameter which is 70% of the effective image range. Are used as observation images. This is magnified about 1.48 times by the seventh relay lens system to obtain a final image having a diameter of 1.89 mm. Diameter 1.28mm
And the area of about 70% of the effective image area is the observation image area.

In the first embodiment, the eyepiece optical system frame is decentered by 0.305 mm with respect to the optical axis of the seventh relay lens system, and
The oblique angle is 1.7 °. Since the effective image area B at this time is 1.89 mm, 2 × C / B = 2 ×
0.305 / 1.89 = 0.32, thereby satisfying the condition (2).

Further, as shown in FIG. 5, the field stop FS for determining the size of the image is held integrally with the frame 3 holding the eyepiece optical system F, thereby moving the eyepiece optical system E. However, the relationship between this and the field stop FS is always kept constant, so that the field stop FS can always be seen in focus. The eyepiece optical system frame 3 includes a seventh relay lens RL7.
The system can be moved in the optical axis direction by loosening the screw 5 shown in FIG. 5 with respect to the system. Therefore, in order to adjust the focus of the eyepiece optical system E to the final image formed by the seventh relay lens system RL7, the screw 5 is loosened to loosen the eyepiece optical system frame, and the eyepiece optical system frame is moved back and forth in the optical axis direction. And adjust it.

The movement in a plane perpendicular to the optical axis is provided by screws 6 in three directions with respect to a holding member 4 for holding the eyepiece optical system frame 3. Therefore, the field stop may be adjusted and fixed in the same direction as the perspective direction so that a desired perspective angle is obtained at the center of the field stop.

In order to display and view the observation image on a television monitor, an imaging adapter is connected behind the eyepiece optical system. In this case, an afocal system is provided between the eyepiece optical system and the imaging adapter, and a connection portion is located at a pupil position. Therefore, even if the optical axis of the imaging adapter is aligned with either the optical axis of the eyepiece optical system or the optical axis of the image transmission optical system, there is no adverse effect on the imaging performance. Thus, conventional imaging adapters designed to match the optical axis of the image transmission optics can be used.

If the eyepiece optical system is composed of a small number of lenses consisting of only doublets, curvature of field occurs in the eyepiece optical system. In this case, the eyepiece optical system may be arranged so as to focus on the center of the field of view, and shift the field stop position toward the eyepiece optical system by the curvature of the field of view of the eyepiece optical system with respect to the center of the field of view.

The optical system according to the second embodiment of the present invention has a configuration as shown in FIG. 2 and includes, in order from the object side, a wedge, an objective optical system, a relay optical system, and an eyepiece optical system. The relay optical system is a seven-time relay of a first relay lens system to a seventh relay lens system. Also in Example 2, the diameter of the wedge is 1.9 mm, the diameter of the objective optical system is 1.2 mm, and the diameter of the image transmission optical system is 1.9 mm.

In the second embodiment, a wedge as shown in FIG. 6 is arranged closest to the object side (the object side of the objective optical system) to make the endoscope optical system of a weak perspective. In the case where the wedge is arranged in the optical system to provide a weak perspective, it is necessary to suppress the chromatic aberration and the tilt of the image plane caused by the wedge. Also, in order to be able to perform sterilization by an autoclave, the outer surface of the wedge needs to be sufficiently resistant to a high-temperature and humid environment.

In order to satisfy these requirements, in the second embodiment, the wedge glass material has a high refractive index and a low dispersion (n
_d = 1.76 and ν _d = 71.7) are used. The vertex angle of the wedge is 21 °.

By providing a protective film on the surface of the wedge that can sufficiently withstand high temperature and high humidity, it is possible to use a glass material having no resistance to high temperature and high humidity. As such a protective film, for example, Balzer I
If RALIN56 (trade name) is used, an antireflection effect can be obtained together.

In the hard mirror optical system of the present invention described above, in addition to the optical systems described in the claims, the optical systems described in the following items can also achieve the object of the invention.

(1) The optical system according to claim 1 or 2, wherein an angle of view used for observation satisfies the following condition (1). (1) 0.4 <A / B <0.6

(2) In the optical system according to claim 1 or 2 or (1), the objective optical system satisfies the following conditions (3), (5), and (6). A rigid mirror optical system. (5) n _d (N)> 1.8 (6) 0.6 <D / E <0.75 (7) 0.5 <E _np /F<1.5

(3) The optical system according to claim 2, wherein the amount of eccentricity satisfies the following condition (2). (2) 0.25 <2 × C / B <0.7

(4) An object optical system, an image transmission optical system, a field stop, and an eyepiece optical system are arranged in this order from the object side, and an Al ₂ O ₃ single crystal and an Al ₂ O ₂
Made of a material containing any one of a single crystal of the baked crystalline body or M _g O, rigid endoscope optical system, characterized in that a wedge that satisfies the following condition. (A) 5 ° <θ <20 ° (3) n _d > 1.65 (4) ν _d > 60

(5) In the optical system described in the above item (4), the following conditions (3-1) and (4-
A rigid mirror optical system that satisfies 1). (A-1) 10 ° < θ <20 ° (3-1) n d> 1.7 (4-1) ν d> 65

[0069]

The rigid mirror optical system of the present invention has a narrow viewing angle, an outer diameter of about 4 mm or less, and an elongated insertion section having a length of about 300 mm or more. It is an optical system that is obtained and has good image quality and a weak perspective.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 3 is an aberration curve diagram according to the first embodiment of the present invention.

FIG. 4 is an aberration curve diagram according to the second embodiment of the present invention.

FIG. 5 is a sectional view of a lens barrel incorporating the optical system of the present invention.

FIG. 6 is a view showing a wedge according to a second embodiment of the present invention;

FIG. 7 is a diagram showing a configuration of a conventional rigid endoscope.

FIG. 8 is a diagram showing a configuration of a conventional oblique rigid mirror optical system.

Claims (2)

[Claims] 1. An image system comprising an objective optical system, an image transmission optical system, and an eyepiece optical system in order from the object side, and observing an image in a range smaller than an effective image range of 70% of a maximum outer diameter of the image transmission optical system. A hard disk optical system, wherein a field stop for performing the operation is disposed integrally with the eyepiece optical system between the image transmission optical system and the eyepiece optical system. 2. An optical system in which the field stop and the eyepiece optical system are integrally decentered in a direction perpendicular to an optical axis to perform observation in a perspective direction. 2. The apparatus according to claim 1, wherein the field stop and the eyepiece optical system are adjusted and fixed in an eccentric state.
2. The rigid mirror optical system according to 1.