CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of China application serial no. 202010279727.3, filed on Apr. 10, 2020. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The disclosure relates to a projection device, and in particular to a focusing mechanism and a projection device.

Description of Related Art

Most projection devices are placed on the desktop, hung on the ceiling, or hung on the wall. In order to improve the sharpness of the projection image thereof, the projection device is equipped with a focusing mechanism for the user to adjust the focal length according to actual operation conditions. After adjusting the focal length, if the projection device is shaken by an external force, the focusing mechanism is likely to loosen and shift, causing the originally set focal length to change, such that the projection image becomes out of focus.

The information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the Background section does not mean that one or more problems to be resolved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.

SUMMARY

The disclosure provides a focusing mechanism and a projection device, which help in preventing an out-of-focus situation from happening.

Other objectives and advantages of the invention may be further understood from the technical features disclosed in the disclosure.

In order to achieve one, part, or all of the above objectives or other objectives, the disclosure provides a focusing mechanism, including a positioning seat, a focus ring, a lens, and a knob. The lens has an optical axis. The positioning seat has a first surface, a second surface opposite to the first surface, and a sliding groove penetrating the first surface and the second surface. The focus ring is slidably and rotatably disposed on the second surface of the positioning sea and the lens is fixed to the focus ring. The focus ring has a positioning hole, wherein the focus ring is located between the positioning seat and the lens, and the positioning hole is aligned to the sliding groove in a direction perpendicular to the optical axis. The knob passes through the sliding groove and is inserted into the positioning hole. The knob is pressed against the first surface of the positioning seat.

In order to achieve one, part, or all of the above objectives or other objectives, the disclosure provides a projection device, including a light source, a light valve, and a projection lens. The light source is configured to provide an illumination beam. The light valve is disposed on a transmission path of the illumination beam and is configured to convert the illumination beam into an image beam. The projection lens is disposed on a transmission path of the image beam and the projection lens includes an optical module and a focusing mechanism. The focusing mechanism is disposed on one side of the optical module and the optical module is located between the light valve and the focusing mechanism. The focusing mechanism includes a positioning seat, a focus ring, a lens, and a knob. The lens has an optical axis, wherein the lens is located on the transmission path of the image beam and is configured to project the image beam. The positioning seat has a first surface, a second surface opposite to the first surface, and a sliding groove penetrating the first surface and the second surface. The focus ring is slidably and rotatably disposed on the second surface of the positioning seat and the lens is fixed to the focus ring. The focus ring has a positioning hole, wherein the focus ring is located between the positioning seat and the lens, and the positioning hole is aligned to the sliding groove in a direction perpendicular to the optical axis. The knob passes through the sliding groove and is inserted into the positioning hole. The knob is pressed against the first surface of the positioning seat.

Based on the above, the embodiments of the disclosure have at least one of the following advantages or effects. In the focusing mechanism and the projection device of the disclosure, the user may drive the focus ring and the lens fixed to the focus ring through the knob, so as to adjust the focal length or the sharpness of the projection image. After adjusting the focal length or the sharpness of the projection image, the user may lock the focus ring to the positioning seat through the knob to prevent the focus ring and the lens fixed to the focus ring from being shaken by an external force, thereby preventing an out-of-focus situation from happening.

Other objectives, features and advantages of the disclosure will be further understood from the further technological features disclosed by the embodiments of the disclosure wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention.

