Mirror Wedge Blocks
The 180-degree fold of the receiver beam path beyond the T/R switch is accompanied by a level change of the beam--from the 61-mm level of the laser beam to a 4.5-inch level of the receiver tube. This allows the receiver to have a "snout" that pokes beyond the laser output and enhances the shielding aspect of the receiver—not to mention providing more room for the APD at the end of the receiver tube.
The nominal displacement between the outbound laser beam and the receiver is five inches in the plane of the laser table, but the T/R switch imparts a roughly 0.33-inch refractive jog (assumes a 1-inch T/R thikcness) to the receiver beam, so that the x-separation is about 5.33 inches. The z separation is just the 4.5-inches minus 61-mm already mentioned. So the two-mirror arrangement that accomplishes the 180° turn is rotated about the y-axis by about 21.6°. The mirror mounts involved are the New Focus models 9855 and 88??. Using the New Focus pedestal mounting scheme, we need two wedges of aluminum that bolt to the optical bench and provide a surface for each pedestal at the correct angle. These wedges must also have tapped holes to accommodate the holding fork at some reasonable position.