An optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens sequentially disposed from an object side toward an image side on an optical axis, and a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses. The first to fourth lenses are disposed to be spaced apart from each other by a preset distance along the optical axis, and 1.3<TTL/BFL<3.5, where TTL is a distance from an object-side surface of the first lens to an imaging plane of an image sensor, and BFL is a distance from an image-side surface of the fourth lens to the imaging plane of the image sensor.

An optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens sequentially disposed from an object side toward an image side on an optical axis, and a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses. The first to fourth lenses are disposed to be spaced apart from each other by a preset distance along the optical axis, and 1.3<TTL/BFL<3.5, where TTL is a distance from an object-side surface of the first lens to an imaging plane of an image sensor, and BFL is a distance from an image-side surface of the fourth lens to the imaging plane of the image sensor.

A lens assembly includes a first lens, a second lens, a third lens, and a fourth lens, wherein the first lens, the second lens, the third lens, and the fourth lens are arranged in order from an object side to an image side along an optical axis. The first lens is with positive refractive power and includes a convex surface facing the object side. The second lens is with negative refractive power and includes a concave surface facing the image side. The third lens is with refractive power and includes a convex surface facing the image side. The fourth lens is with refractive power. The lens assembly satisfies: FOV?56?, wherein FOV is a field of view of the lens assembly.

A lens assembly includes a first lens, a second lens, a third lens, and a fourth lens, wherein the first lens, the second lens, the third lens, and the fourth lens are arranged in order from an object side to an image side along an optical axis. The first lens is with positive refractive power and includes a convex surface facing the object side. The second lens is with negative refractive power and includes a concave surface facing the image side. The third lens is with refractive power and includes a convex surface facing the image side. The fourth lens is with refractive power. The lens assembly satisfies: FOV?56?, wherein FOV is a field of view of the lens assembly.

An optical lens includes a first lens (L1), a second lens (L2), a third lens (L3), and a fourth lens (L4), which are successively coaxially arranged along the transmission direction of incident light, wherein the first lens (L1) and the fourth lens (L4) are negative meniscus lenses, the second lens (L2) is a positive meniscus lens, and the third lens (L3) is a positive plano-convex lens. The optical lens can be applied to an optical system of a laser processing device, when a utilized processing wavelength is different from a monitoring wavelength, the imaging chromatic aberration in a monitoring system may be eliminated, particularly when a wavelength of the far infrared region is utilized as a wavelength for laser processing. When using the red light wavelength as the monitoring wavelength, the monitoring system can achieve a better imaging effect, thus ensuring the quality of laser processing.

An optical system includes, in order from an object side to an image side, a diffractive optical element having positive refractive power, and a diffractive surface with a controlled wavelength dispersion characteristic, and a lens having negative refractive power. A predetermined inequality is satisfied.

An optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens sequentially disposed from an object side toward an image side on an optical axis, and a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses. The first to fourth lenses are disposed to be spaced apart from each other by a preset distance along the optical axis, and 1.3<TTL/BFL<3.5, where TTL is a distance from an object-side surface of the first lens to an imaging plane of an image sensor, and BFL is a distance from an image-side surface of the fourth lens to the imaging plane of the image sensor.

An optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens sequentially disposed from an object side toward an image side on an optical axis, and a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses. The first to fourth lenses are disposed to be spaced apart from each other by a preset distance along the optical axis, and 1.3<TTL/BFL<3.5, where TTL is a distance from an object-side surface of the first lens to an imaging plane of an image sensor, and BFL is a distance from an image-side surface of the fourth lens to the imaging plane of the image sensor.

An optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens sequentially disposed from an object side toward an image side on an optical axis, and a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses. The first to fourth lenses are disposed to be spaced apart from each other by preset distances along the optical axis, and 1.3<TTL/BFL<3.5, where TTL is a distance from an object-side surface of the first lens to an imaging plane of an image sensor, and BFL is a distance from an image-side surface of the fourth lens to the imaging plane of the image sensor.

An optical imaging system includes a first lens, a second lens, a third lens, and a fourth lens sequentially disposed from an object side toward an image side on an optical axis, and a reflecting member disposed closer to the object side, as compared to the first lens, and having a reflecting surface configured to change a path of light to be incident to the first to fourth lenses. The first to fourth lenses are disposed to be spaced apart from each other by preset distances along the optical axis, and 1.3<TTL/BFL<3.5, where TTL is a distance from an object-side surface of the first lens to an imaging plane of an image sensor, and BFL is a distance from an image-side surface of the fourth lens to the imaging plane of the image sensor.