Patent ID: 11966012
Assignee: CORETRONIC CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 5:
6. A projection lens configured to project an image beam provided by a light valve onto a screen, wherein the projection lens comprises a first lens, a second lens, a third lens, and a fourth lens in order from a screen side to a display side along an optical axis, wherein each of the first lens to the fourth lens has a screen side surface facing the screen side and allowing the image beam to pass, and a display side surface facing the display side and allowing the image beam to pass, wherein:
the first lens has a negative refractive power, the second lens has a positive refractive power, the third lens has a negative refractive power, and the fourth lens has a positive refractive power; and
the projection lens satisfies:

2<TTL/f<5,

wherein TTL is a distance from the screen side surface of the first lens to the display side surface of the fourth lens on the optical axis, and f is an effective focal length of the projection lens,
wherein the projection lens further comprises a diaphragm and a reflective element, the diaphragm is configured between the second lens and the third lens on the optical axis,
the reflective element is configured between the diaphragm and the third lens on the optical axis, wherein the optical axis comprises a first optical axis and a second optical axis that does not coincide with the first optical axis, and the first optical axis and the second optical axis intersect at an intersection point on a reflective surface of the reflective element.