US-12625365-B2 - Optical device

US12625365B2US 12625365 B2US12625365 B2US 12625365B2US-12625365-B2

Abstract

An optical device comprises: an image forming lens; an objective lens; an imaging device; a beam splitter; a coaxial epi-illumination optical system; and an optical damper having a damper surface. The beam splitter, the image forming lens, and the imaging device are arranged along an optical axis of the objective lens. An optical axis of the coaxial epi-illumination optical system is perpendicular to the optical axis of the objective lens. The beam splitter and the optical damper are arranged along the optical axis of the coaxial epi-illumination optical system. A normal direction of the damper surface is perpendicular to the optical axis of the objective lens and inclines with respect to the optical axis of the coaxial epi-illumination optical system without being perpendicular to the optical axis of the coaxial epi-illumination optical system.

Inventors

Keiji Murata

Assignees

MITUTOYO CORPORATION

Dates

Publication Date: 20260512
Application Date: 20231026
Priority Date: 20221028

Claims (12)

1 . An optical device comprising: an image forming lens disposed in an optical path between an objective lens and an imaging device, the image forming lens forming an image of light incident via the objective lens on an imaging surface of the imaging device; a beam splitter disposed along an optical axis of the objective lens; a coaxial epi-illumination optical system configured to be able to illuminate an imaging target via the beam splitter, the coaxial epi-illumination optical system being arranged in an optical path different from the optical path in which the image forming lens is arranged; and an optical damper having a damper surface, wherein the beam splitter, the image forming lens, and the imaging device are arranged along the optical axis of the objective lens, an optical axis of the coaxial epi-illumination optical system is perpendicular to the optical axis of the objective lens, the beam splitter and the optical damper are arranged along the optical axis of the coaxial epi-illumination optical system, and a normal direction of the damper surface is perpendicular to the optical axis of the objective lens and inclines with respect to the optical axis of the coaxial epi-illumination optical system without being perpendicular to the optical axis of the coaxial epi-illumination optical system.
2 . The optical device according to claim 1 , comprising a housing that houses the image forming lens, wherein the housing is configured to be able to be attached to and detached from the objective lens.
3 . The optical device according to claim 1 , wherein the beam splitter comprises a film base material made of a resin film or a thin-type glass.
4 . The optical device according to claim 3 , wherein 2 ⁢ t ⁢ tan ⁡ ( sin - 1 ⁢ 1 2 ⁢ n ) < Np where n is a refractive index of the film base material, t is a thickness of the film base material, p is a pixel pitch of the imaging device, and N×N is a unit pixel count for interpolation processing of a pixel value of the imaging device.
5 . The optical device according to claim 3 , wherein the beam splitter comprises a coating film disposed on at least one surface of the film base material.
6 . The optical device according to claim 5 , wherein the coating film is disposed on each of both surfaces of the film base material, and a coating film disposed on one surface of the film base material and a coating film disposed on the other surface of the film base material have a same sign of stress resulting from coating.
7 . An optical device comprising: an image forming lens disposed in an optical path between an objective lens and an imaging device, the image forming lens forming an image of light incident via the objective lens on an imaging surface of the imaging device; a beam splitter disposed along an optical axis of the objective lens; a coaxial epi-illumination optical system configured to be able to illuminate an imaging target via the beam splitter, the coaxial epi-illumination optical system being arranged in an optical path different from the optical path in which the image forming lens is arranged; and an optical damper having a damper surface, wherein the beam splitter and the coaxial epi-illumination optical system are arranged along the optical axis of the objective lens, an optical axis of the image forming lens is perpendicular to the optical axis of the objective lens, the imaging device, the beam splitter, and the optical damper are arranged along the optical axis of the image forming lens, and a normal direction of the damper surface is perpendicular to the optical axis of the objective lens and inclines with respect to the optical axis of the image forming lens without being perpendicular to the optical axis of the image forming lens.
8 . The optical device according to claim 7 , comprising: a housing that houses the image forming lens, wherein the housing is configured to be able to be attached to and detached from the objective lens.
9 . The optical device according to claim 7 , wherein the beam splitter comprises a film base material made of a resin film or a thin-type glass.
10 . The optical device according to claim 9 , wherein 2 ⁢ t ⁢ tan ⁡ ( sin - 1 ⁢ 1 2 ⁢ n ) < Np where n is a refractive index of the film base material, t is a thickness of the film base material, p is a pixel pitch of the imaging device, and N×N is a unit pixel count for interpolation processing of a pixel value of the imaging device.
11 . The optical device according to claim 9 , wherein the beam splitter comprises a coating film disposed on at least one surface of the film base material.
12 . The optical device according to claim 11 , wherein the coating film is disposed on each of both surfaces of the film base material, and a coating film disposed on one surface of the film base material and a coating film disposed on the other surface of the film base material have a same sign of stress resulting from coating.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based upon and claims the benefit of Japanese Patent Application No. 2022-172809, filed on Oct. 28, 2022, the entire contents of which are incorporated herein by reference. BACKGROUND Field Embodiments described herein relate generally to an optical device used for a microscope, a vision measuring device, a vision measuring probe, and the like. Description of the Related Art There has been known an objective lens that includes: an image forming lens disposed in an optical path between an objective lens and an imaging device; a beam splitter disposed along an optical axis of the objective lens; and a coaxial epi-illumination optical system configured to be able to illuminate an imaging target via the beam splitter and arranged in an optical path different from the optical path in which the image forming lens is arranged. In such an optical device, a part of unnecessary light transmitted through the beam splitter from the coaxial epi-illumination optical system is applied to the imaging device via the image forming lens, causing a flare. Therefore, in Japanese Patent Application Publication No. 2013-140032, suppression of a flare is attempted by irradiating flocked fabric with unnecessary light transmitted through a beam splitter to absorb the unnecessary light. However, the flocked fabric causes contamination. In addition, since a reflectance of the flocked fabric is not zero, a flare occurs when an attempt is made to ensure brightness of coaxial epi-illumination. Accordingly, the effects thereof are not sufficient. Further, in Japanese Utility Model Application Publication No. 7-014412, suppression of a flare is attempted by reflecting unnecessary light transmitted through a beam splitter in a direction approximately parallel to or perpendicular to the beam splitter (described as a half mirror in the document). However, in Japanese Utility Model Application Publication No. 7-014412, the reflected light enters an inside of a surface including an optical axis of an image forming system and becomes new flare light. For example, the light reflected in a direction approximately parallel to the beam splitter enters the image forming lens and is easily reflected as a flare. The light reflected in a direction perpendicular to the beam splitter enters the objective lens, thereby causing illumination unevenness, and the light that hits members, such as a frame and a spacer, is reflected and scattered and thereby reflected as a flare. In particular, when a decrease in the size of an entire optical device is attempted, lenses having a large refractive power are densely arranged. Accordingly, an event in which the above-described flare light contrarily becomes noticeable upon receiving light condensing action possibly happens. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an optical device according to a first embodiment of the present invention; FIG. 2 is a schematic diagram of the optical device; FIG. 3 is a side view of a beam splitter of the optical device; FIG. 4 is a side view of an enlarged part of the beam splitter of the optical device; FIG. 5 is a schematic diagram viewed from an imaging device side of the optical device; FIG. 6 is a schematic diagram of an optical device according to a second embodiment of the present invention; FIG. 7 is a schematic diagram of an optical device according to a third embodiment of the present invention; FIG. 8 is a schematic diagram of an optical device according to a fourth embodiment of the present invention; FIG. 9 is a schematic diagram of an optical device according to a fifth embodiment of the present invention; FIG. 10 is a schematic diagram of an optical device according to a sixth embodiment of the present invention; and FIG. 11 is a schematic diagram of an optical damper according to the sixth embodiment of the present invention. DETAILED DESCRIPTION An optical device according to one embodiment of the present invention comprises: an image forming lens disposed in an optical path between an objective lens and an imaging device, the image forming lens forming an image of light incident via the objective lens on an imaging surface of the imaging device; abeam splitter disposed along an optical axis of the objective lens; a coaxial epi-illumination optical system configured to be able to illuminate an imaging target via the beam splitter, the coaxial epi-illumination optical system being arranged in an optical path different from the optical path in which the image forming lens is arranged; and an optical damper having a damper surface. The beam splitter, the image forming lens, and the imaging device are arranged along the optical axis of the objective lens. An optical axis of the coaxial epi-illumination optical system is perpendicular to the optical axis of the objective lens. The beam splitter and the optical damper are arranged along the optical axis of the coaxial epi-illumination