Abstract: The present disclosure provides an eyesight protection device, an eyesight protection system and an detection method for the eyesight protection device, which belongs to the technical field of communication, and can solve some problems in the prior art. The present disclosure provides an eyesight protection device, which includes: a millimeter-wave radar detection circuit, a control circuit and an alarm circuit. The millimeter-wave radar detection circuit is configured to detect a distance between a user and a reading material read by the user. The control circuit is configured to generate a first control signal at least when it is determined that the distance detected by the millimeter-wave radar detection circuit is smaller than a first predetermined value. The alarm circuit is configured to send out an alarm signal in response to the first control signal.

Abstract: A coaxial assembly includes a first member, a second member, and at least two position members. The first member has an assembly hole with a sidewall. The second member having a lateral wall. The at least two position members are evenly arranged along a circumference of the lateral wall of the second member. The second member and assembly hole are configured such that when the second member is within the assembly hole, the at least two position members tightly abut the sidewall of the assembly hole, thereby causing the second member to be coaxial with the first member. An assembly method is also provided.

Abstract: An coaxial assembly includes a first member, a second member, and at least two position members. The first member has an assembly hole with a sidewall. The second member having an lateral wall. The at least two position members are evenly arranged along a circumference of the lateral wall of the second member. The second member and assembly hole are configured such that when the second member is within the assembly hole, the at least two position members tightly abut the sidewall of the assembly hole, thereby causing the second assembly member to be coaxial with the first assembly member. An assembly method is also provided.