Pairing a Michelson Objective Lens With a Transmission Flat

Quick answer

Match the objective to the mount before you touch the flat: confirm the 2.75X, 0.08NA Michelson objective's M25 thread and 60mm parfocal length suit your turret, then bring in the 33mm Dynaflect transmission flat and align it only after the objective is seated and clean.

Step-by-step pairing routine

1. Confirm thread and parfocal fit before mounting: Check that the turret or mount accepts M25 threads and that the 60mm parfocal length matches the other objectives in the nosepiece. Test thread engagement by hand, never by force. Common mistake: cross-threading the objective because the mount was assumed to be M25 without checking. If the objective does not start by hand, stop and verify the mount specification.
2. Inspect and clean the objective first: Look at the front and rear surfaces under a light before installation. Remove loose dust with a gentle air bulb; do not wipe a dry surface. Common mistake: cleaning the flat while the objective still carries dust that will settle onto it. Clean from the objective outward, not the other way around.
3. Seat the objective and check focus travel: Thread the objective fully home, then confirm the stage still reaches focus across its normal range. If focus runs out of travel, the parfocal height is wrong for this mount. Common mistake: compensating with the flat's tilt instead of fixing the objective seating. Focus travel should remain comfortable after the objective is seated.
4. Place the transmission flat and check orientation: Mount the 33mm Dynaflect flat in its holder and confirm the coated surface faces the beam path as your setup requires. Bring it in gently and check that the holder is not pinching the rim. Common mistake: overtightening the retaining ring, which can stress the optic. The flat should be held, not clamped.
5. Align the flat at low coherence or reduced intensity: Start with the flat slightly tilted and bring it in until fringes appear, then fine-tune tilt and position. Common mistake: chasing fringes with large mount movements when a small adjustment is enough. If fringes will not settle, recheck the objective seating before moving the flat again.
6. Record the working position and store both parts clean: Note the flat's mount position and the objective's turret slot so the next session starts from a known point. Return both to their cases with covers in place. Common mistake: leaving the flat exposed on the bench between sessions. A logged position saves the next alignment session.

Product facts

• 2.75X, 0.08NA Michelson objective Lens: 2.75X magnification, 0.08NA, M25 threads, and a 60mm parfocal length. The thread and parfocal figures decide whether the objective drops into your turret without refocusing every other position.

  

• 33mm Dynaflect Transmission Flat: 33mm Dynaflect transmission flat specified at 1/20 wave, PV, with a Dynaflect coating. The 1/20 wave surface figure is the reference quality you are protecting, so handling and alignment deserve more care than the price suggests.