This is a Unitron biological microscope objective. It is a simple achromat and probably dates from the early 1970s or 1960’s. The adjustment length is the earlier standard of 37mm (distance from thread shoulder to sample plane when focused). This lens should not be employed on the same turret as more recent 45mm adjustment length lenses!

Magnification � 10
Numerical aperture � 0.25
Achromat
Not flat field
Tube length � 160mm
Standard RMS attachment thread

The lens is in excellent optical condition and very good cosmetic condition.

Photo set 2032
***MPN
***OEM Unitron
***SKU*** 32225

This is a most interesting microscope objective. It is intended for use in reflected light applications for the quantitative study of surface finish or very small-scale step height profiles. The objective is a complete multi-beam interferometer. The objective threads into the microscope nosepiece like a normal lens. The front of the objective is threaded and carries a small interchangeable reflective beam-splitter. Once the sample is focused, the beam-splitter may be lowered until it touches the sample. Contact with the sample produces interference fringes that relay information about the surface topography of the sample.

The beam-splitter mirror included with the objective is marked ‘FLAT’, and appears to have a reflection coating of approximately 60%. In practice, it is best to come close to matching the reflectivity of the sample to that of the beam-splitter. For highly reflective samples, such as mirrors and silicon wafers, the nominal beam-splitter value would be closer to 90%.

The surface of the reference mirror appears to be free of scratches, however the reflective beam-splitter surface has several voids. Fringes will still be seen in these areas, but they will be far fainter. It would be best to have the mirror re-coated. Because of the contact nature of this type of interference, and the fact that the reference mirror is rotating is it is brought to bear on the sample, exceptional care should be exercised when employing this type of objective. Ideally, the mirror should be ‘pre-focused’ � easily done using the voids in the surface, then the fine focus of the microscope used to bring the sample to the proper position. Samples should never be scanned when the interferometer plate is touching the sample!

The reference mirror cannot be tilted independently of the optic axis, so it would helpful if the sample were supported on some sort of cup-bearing stage with very fine tilt adjustments. This would enable one to adjust the spacing and the direction of the fringes. Also required for fringe coherence and measurements would be a precision line filter or a spectral lamp source of known wavelength. We have several different monochromatic filters available. Please inquire!

Photo set 2031
***MPN
***OEM Unitron
***SKU*** 32224

Leitz 569 237 NPL 50x / 0.85 * Metallurgical

This objective is a member of the Leitz metallurgical ‘NPL’ series. It has the additional infinity / ‘0’ engraving, which means the lens MUST be used with an infinity corrected optical system (as found on most Leitz vertical illuminators for industrial and metallurgical applications). The ‘0’ means it is vitally important to adhere to the uncovered sample stricture common to most metallurgical samples. The single knurl instead of a double-knurl indicates it was among the most recent of the plain NPL objective series.

Magnification � 50x
Numerical Aperture � 0.85
Achromatic color correction
Flat field for normal 18mm oculars
Standard RMS thread
Infinity corrected
MUST be used without cover slip
Adjustment length � 45mm
Working distance � 0.24mm
Spring-loaded optics

The objective is in superb condition both optically and cosmetically.

Photo set 1961.

***MPN 569 237
***OEM Leitz
***SKU*** 30165