US Patent 10520717 Binocular capable of measuring distance and prism module thereof

A prism module includes a first prism including a first surface, a second surface and a third surface, a roof prism including a roof surface and a fourth surface, a second prism including a fifth surface, a sixth surface and a seventh surface, and a third prism including a light access surface, a first reflecting surface and a second reflecting surface. A light source is disposed above the second prism and adjacent to the first and the roof prisms. A light beam emitted by the light source enters and is reflected by the third prism, enters the second prism through the seventh surface, passes through the sixth surface, enters the first prism through the third surface, and is reflected by the second surface to leave the prism module. The light beam leaving the prism module is parallel to a baseline passing through the first, the second and the fourth surfaces.