| 摘要 |
In one form, a hollow retroreflector is here made of three plates joined together at right angles to each other with only one edge of each plate bonded to a reflecting face of another plate, thereby making non-critical the relationships between the edges of any one of the plates. In another form, one of the three plates has two edges that intersect at a slight obtuse angle that is non-critical, the length of one edge abutting the reflecting face of another plate while the other edge contacts the remaining plate only at a location remote from the common corner of the retroreflector, again involving non-critical edge relationships as to each of the plates of the retroreflector. For stability of the optically flat faces, the plates are made relatively thick and accordingly have relatively wide edges that abut others of the plates. The abutment edges are joined to related reflecting faces by bonding material restricted to a zone that is narrow relative to the width of the abutment edge. The plates have individual corners remote from the common corner of the retroreflector, and a common glass plate is bonded to those individual corners so as to resist deforming stresses that may be imposed on the plates.
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