Patent ID: 8305689

Claim:
An optical module having a light incident end for introducing a laser beam and a light emitting end for emitting a laser beam to an object, the optical module comprising: a collimator collimating a laser beam introduced through the light incident end, and outputting the collimated light with a predetermined beam diameter as a forward propagating beam; an optical isolator of polarization-independent type including a plurality of birefringent elements, and having a first end upon which the collimated light outputted from the collimator is incident, and a second end from which the collimated light is outputted, the optical isolator outputting a backward propagating beam, normal incident upon the second end, from the first end by an emission angle θ; and an oblique-beam blocking section having a first optical component and a second optical component through which light emitted from the second end of the optical isolator passes, each of the first and second optical component being provided with a window of a diameter D and arranged so that centers of the window thereof coincides with an optical axis of the forward propagating beam outputted from the second end of the optical isolator, the oblique-beam blocking section blocking light incident at a predetermined angle θ relative to the optical axis of the forward propagating beam out of the backward propagating beam propagating from the light emitting end toward the light incident end, by separating the first optical component from the second optical component by a predetermined distance, wherein the diameter D is defined by a diameter of a projected pattern when opening edges of the respective first and second optical components, the opening edge defining the window, is projected onto a plane perpendicular to the optical axis of the forward propagating beam, and wherein, when an emission angle of a backward propagating beam at the first end of the optical isolator is denoted by θ, the backward propagating beam being normal incident upon the second end of the optical isolator, a distance X between the first optical component and the second optical component satisfies the following relation: X> 2 D /tan θ.