# US 12,213,647 B2 · Objective optical system, image pickup apparatus, and endoscope

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- Number: US 12,213,647 B2
- Document ID: US12213647B2
- Status: Granted
- Kind: B2
- Application number: 17/884,351
- Filed: 2022-08-09
- Published: 2022-12-08
- Granted: 2025-02-04
- Earliest claimed: 2020-02-19
- Assignees: Olympus Corporation
- Applicants: Olympus Corporation
- Inventors: Tsutomu Igarashi
- Web page: https://patentgrep.com/patent/US12213647B2

## CPC

- A61B 1/00188: {with focusing or zooming features}
- G02B 13/00: Optical objectives specially designed for the purposes specified below (with variable magnification {in general} G02B15/00)
- G02B 23/243: {Objectives for endoscopes}
- A61B 8/12: in body cavities or body tracts, e.g. by using catheters
- A61B 8/4416: {related to combined acquisition of different diagnostic modalities, e.g. combination of ultrasound and X-ray acquisitions}
- A61B 8/445: {Details of catheter construction}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

There is provided an objective optical system that is easy to produce, capable of forming optical images that can be observed without difficulties while small in size. The objective optical system includes, in order from the object side, a flat plate OP1, an aperture stop S, and a substantially hemispherical planoconvex lens L1 having an outer diameter substantially equal to the outer diameter of the flat plate. The flat plate and the planoconvex lens L1 are cemented together with the aperture stop between. The objective optical system satisfies the following conditional expressions (1), (2), and (3): 0.3<IH/Dp<0.45 (1) 1.7<1+Dp×ωr/(2×IH)<2.1 (2) 0.9<NL/(1+Dp×ωr/(2×IH))<1.1 (3).

## Claims

### Claim 1

An objective optical system comprising, in order from the object side:
a flat plate;
an aperture stop; and
a substantially hemispherical planoconvex lens having an outer diameter substantially equal to the outer diameter of the flat plate,
wherein the flat plate and the planoconvex lens are cemented together with the aperture stop between, and the objective optical system satisfies the following conditional expressions (1), (2), and (3):
0.3<IH/Dp<0.45 (1)
1.7<1+Dp×ωr/(2×IH)<2.1 (2)
0.9<NL/(1+Dp×ωr/(2×IH))<1.1 (3)
where ωr=2×π×|ω|/360°, IH is the largest image height, Dp is the outer diameter of the flat plate, ω is the half angle of view, and NL is the refractive index of the planoconvex lens.

### Claim 2 (depends on 1)

An objective optical system according to claim 1, wherein the objective optical system satisfies the following conditional expressions (4) and (5):
1.7<Np (4)
0.3<Tp/Dp<0.7 (5)
where Np is the refractive index of the flat plate, Tp is the thickness of the flat plate on the optical axis, and Dp is the outer diameter of the flat plate.

### Claim 3 (depends on 1)

An objective optical system according to claim 1, wherein the objective optical system satisfies the following conditional expression (6):
75°≤θ≤105° (6),
where θ is the magnitude of the angle formed by the optical axis and the straight line connecting a point on the outer circumference of the object side surface of the planoconvex lens and the center of curvature of the image side surface.

### Claim 4 (depends on 1)

An objective optical system according to claim 1, wherein the aperture stop has a light transmitting portion and a light blocking portion formed by a light blocking film.

### Claim 5 (depends on 1)

An objective optical system according to claim 1, wherein the aperture stop is provided on the image side surface of the flat plate or the object side surface of the planoconvex lens.

### Claim 6 (depends on 1)

An objective optical system according to claim 1, wherein the F-number of the objective optical system is equal to or larger than 3.5.

### Claim 7

An image pickup apparatus comprising an objection optical system, the objective optical system comprising, in order from the object side:
a flat plate;
an aperture stop; and
a substantially hemispherical planoconvex lens having an outer diameter substantially equal to the outer diameter of the flat plate,
wherein the flat plate and the planoconvex lens are cemented together with the aperture stop between, and the objective optical system satisfies the following conditional expressions (1), (2), and (3):
0.3<IH/Dp<0.45 (1)
1.7<1+Dp×ωr/(2×IH)<2.1 (2)
0.9<NL/(1+Dp×ωr/(2×IH))<1.1 (3)
where ωr=2×π×|ω|/360°, IH is the largest image height, Dp is the outer diameter of the flat plate, ω is the half angle of view, and NL is the refractive index of the planoconvex lens.

### Claim 8 (depends on 7)

An image pickup apparatus according to claim 7, wherein the objective optical system satisfies the following conditional expressions (4) and (5):
1.7<Np (4)
0.3<Tp/Dp<0.7 (5)
where Np is the refractive index of the flat plate, Tp is the thickness of the flat plate on the optical axis, and Dp is the outer diameter of the flat plate.

### Claim 9 (depends on 7)

An image pickup apparatus according to claim 7, wherein the objective optical system satisfies the following conditional expression (6):
75°≤θ≤105° (6),
where θ is the magnitude of the angle formed by the optical axis and the straight line connecting a point on the outer circumference of the object side surface of the planoconvex lens and the center of curvature of the image side surface.

### Claim 10 (depends on 7)

An image pickup apparatus according to claim 7, wherein the aperture stop has a light transmitting portion and a light blocking portion formed by a light blocking film.

### Claim 11 (depends on 7)

An image pickup apparatus according to claim 7, wherein the aperture stop is provided on the image side surface of the flat plate or the object side surface of the planoconvex lens.

### Claim 12 (depends on 7)

An objective optical system according to claim 7, wherein the F-number of the objective optical system is equal to or larger than 3.5.

### Claim 13

An endoscope comprising an objection optical system, the objective optical system comprising, in order from the object side:
a flat plate;
an aperture stop; and
a substantially hemispherical planoconvex lens having an outer diameter substantially equal to the outer diameter of the flat plate,
wherein the flat plate and the planoconvex lens are cemented together with the aperture stop between, and the objective optical system satisfies the following conditional expressions (1), (2), and (3):
0.3<IH/Dp<0.45 (1)
1.7<1+Dp×ωr/(2×IH)<2.1 (2)
0.9<NL/(1+Dp×ωr/(2×IH))<1.1 (3)
where ωr=2×π×|ω|/360°, IH is the largest image height, Dp is the outer diameter of the flat plate, ω is the half angle of view, and NL is the refractive index of the planoconvex lens.

### Claim 14 (depends on 13)

An endoscope according to claim 13, wherein the objective optical system satisfies the following conditional expressions (4) and (5):
1.7<Np (4)
0.3<Tp/Dp<0.7 (5)
where Np is the refractive index of the flat plate, Tp is the thickness of the flat plate on the optical axis, and Dp is the outer diameter of the flat plate.

### Claim 15 (depends on 13)

An endoscope according to claim 13, wherein the objective optical system satisfies the following conditional expression (6):
75°≤θ≤105° (6),
where θ is the magnitude of the angle formed by the optical axis and the straight line connecting a point on the outer circumference of the object side surface of the planoconvex lens and the center of curvature of the image side surface.

### Claim 16 (depends on 13)

An endoscope according to claim 13, wherein the aperture stop has a light transmitting portion and a light blocking portion formed by a light blocking film.

### Claim 17 (depends on 13)

An endoscope according to claim 13, wherein the aperture stop is provided on the image side surface of the flat plate or the object side surface of the planoconvex lens.

### Claim 18 (depends on 13)

An endoscope according to claim 13, wherein the F-number of the objective optical system is equal to or larger than 3.5.