The present invention discloses an improved optical device having at least a first and second optical components. The optical device further includes a first extending tube securely attached to the first and second optical components as a first building block wherein the first and second optical components are aligned and position adjusted in the position-holding-and-fixing means and securely attached thereto by a room-temperature UV curable epoxy UV cured at room temperature. The optical device then further assembled using a step-by-step building block assembling process with more building blocks assembled by optical components similar to the first building block described above. In other preferred embodiment, the first and second optical components held in the extending tube having a pre-aligned dihedral angle between the first and second optical components.