This is description of this part:
Achromatic Nikon Ph3 DL 40x / 0.55 LWD microscope objective for brightfield and phase contrast, with 0 - 2.0 mm correction collar, for 160 mm tube length - for inverted and upright biological microscopes, made in Japan.
Basic objective parameters:
Manufacturer: Nikon, Japan
Model: Ph3 40 DL 0.55 LWD 160/0-2
Magnification: 40x
Numerical aperture (N.A.): 0.55
Optical correction: achromat
Phase contrast: Ph3 DL - Ph3 indicates the size of the phase ring (requires a matching Ph3 annulus in the condenser), DL (Dark Low) means dark, i.e. positive phase contrast - the object appears darker than the background
Working distance (WD): ~2.1 - 2.5 mm - LWD (Long Working Distance)
Correction collar: compensates for cover glass or vessel bottom thickness in the range 0 - 2.0 mm
Cover glass: the objective can be used without a cover glass, with a standard cover glass approx. 0.17 mm thick, and also with specimens observed through the bottom of a Petri dish up to 2.0 mm thick
Immersion: no (dry objective)
Tube length: 160 mm
Parfocal length: 45 mm
Thread: RMS
Optics: CF (Nikon CF-160) - requires no compensating eyepiece and allows photography by direct projection
This objective is suitable for:
- inverted microscopes - observation through the bottom of a Petri dish or cell culture flask
- upright biological microscopes - observation of specimens with or without a cover glass
Phase contrast work requires a compatible phase contrast condenser or a slider with a phase contrast annulus.
Commonly used, inexpensive cover glasses are 0.17 mm thick mainly in theory. Even the standard for class #1.5 allows a range of 0.16 - 0.19 mm, and in cheap Chinese cover glasses you will find in practice pieces from approx. 0.13 to 0.25 mm, often not matching the thickness stated on the box. Only #1.5H (high precision) cover glasses have a guaranteed thickness of 0.170 mm with a tolerance of +/- 0.005 mm. Variation in cover glass thickness clearly degrades image contrast and resolution (spherical aberration). The correction collar fitted to the objective offered here lets you adjust the optics to the combined thickness of the cover glass and the medium layer beneath it. This compensates for most of the variation found in practice.
In addition, the correction collar of this objective can be set to "0" for work without a cover glass, or to large values (up to 2.0 mm) to adapt the optics to observation through a microscope slide (0.8 - 1.2 mm), a glass Petri dish (usually 1.5 - 2.0 mm - thicker dishes are outside the collar range) or a plastic Petri dish (usually approx. 1 mm, in the range 0.8 - 1.2 mm).
This objective fits practically any microscope from any manufacturer, provided it has an RMS thread and uses objectives for 160 mm tube length with a parfocal length of 33, 37 or 45 mm. Some example microscopes are listed in the "compatibility" section, but the list is not complete.
What is this part needed for?
- if your microscope is missing a 40x objective - for brightfield or phase contrast
- if you observe cell cultures, algae, protozoa or fungi in Petri dishes on an inverted microscope
- if a standard 40x objective cannot focus through the thick bottom of a Petri dish or culture flask, or touches the vessel
- if you want to observe living, unstained specimens in phase contrast
- if you need an objective with correction for cover glass or vessel bottom thickness
- if you work with specimens without a cover glass
- if you want to photograph specimens by direct projection
- if you already have such an objective, but it is damaged or of very poor quality
