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Products Home / Optical Systems / Objective Lenses, Scan Lenses, and Tube Lenses / Imaging/Focusing Microscope Objectives, Oil ImmersionImaging/Focusing Microscope Objectives, Oil Immersion
- Infinity-Corrected Microscope Objectives for UV, Visible, and NIR
- Designed for Oil Immersion Medium Applications
- Magnifications Ranging from 40X to 100X
RMS100X-O
100X Plan Achromat
RMS100X-PFOD
100X Plan Fluorite
N100X-PFO
100X Plan Fluorite
MOIL-30
Immersion Oil
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| Objective Lens Selection Guide |
|---|
| Objectives |
| Super Apochromatic Microscope Objectives Microscopy Objectives, Dry Microscopy Objectives, Oil Immersion Physiology Objectives, Water Dipping or Immersion Phase Contrast Objectives Long Working Distance Objectives Reflective Microscopy Objectives UV Focusing Objectives VIS and NIR Focusing Objectives |
| Scan Lenses and Tube Lenses |
| Scan Lenses F-Theta Scan Lenses Infinity-Corrected Tube Lenses |
Did You Know?
Multiple optical elements, including the microscope objective, tube lens, and eyepieces, together define the magnification of a system. See the Magnification & FOV tab to learn more.
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Example of an Oil Immersion Objective Design
(See Objective Tutorial Tab for More Information About Microscope Objective Types)
Thorlabs offers oil immersion objective designs from Olympus and Nikon. The majority of the objectives are plan fluorite objectives, while one (RMS100X-O) is a plan achromat design. For details about the differences between these types of objectives, please see the Objective Tutorial tab above.
These microscope objectives should be used in applications like traditional and multiphoton microscopy and confocal imaging and are suitable for a variety of imaging modalities, including epi-illumination, oblique illumination, brightfield, and DIC applications. These infinity-corrected objectives have optical elements with an ultra-wide broadband AR coating, designed for use with either 180 mm or 200 mm focal length tube lenses.
The Olympus objectives on this page have RMS (0.800"-36) threading, and the Nikon objective has M25 x 0.75 threading. To use these objectives with a different thread standard, please see our microscope objective thread adapters. When choosing a microscope objective, it is important to keep in mind that objectives are often designed to integrate with a particular manufacturer's microscopes and are not necessarily interchangeable due to tube length differences and variations in thread pitch or diameter. Please note that the performance of each objective may vary from the engraved specifications when integrated with components and systems from different manufacturers. See the Magnification and FOV tab for more information.
All objectives featured on this page are compatible with our microscope nosepiece modules for DIY Cerna® systems, which accept RMS, M25 x 0.75, or M32 x 0.75 objective threading.
| Oil-Imersion Objectives | ||||||
|---|---|---|---|---|---|---|
| Item # | RMS40X-PFO | RMS60X-PFOD | RMS100X-PFOa | RMS100X-PFOD | RMS100X-O | N100X-PFOa |
| Manufacturer | Olympus | Nikon | ||||
| Manufacturer Part # | 1-U2B530 | 1-U2B532 | 1-U2B5352 | 1-U2B5362 | 1-U2B235 | MRH01902 |
| Magnification | 40X | 60X | 100X | 100X | 100X | 100X |
| Numerical Aperture (NA) | 1.3 | 1.25 - 0.65 | 1.3 | 1.3 - 0.55 | 1.25 | 1.3 |
| Effective Focal Length (EFL) | 4.5 mm | 3 mm | 1.8 mm | 1.8 mm | 1.8 mm | 2.0 mm |
| Entrance Pupil Diameterb | 11.7 mm | 7.5 - 3.9 mm | 4.7 mm | 4.7 - 2.0 mm | 4.5 mm | 5.2 mm |
| Field Number | 26.5 | 26.5 | 26.5 | 26.5 | 22 | N/A |
| Working Distance (WD)c | 0.2 mm | 0.12 mm | 0.2 mm | 0.2 mm | 0.15 mm | 0.16 mm |
| Parfocal Lengthc | 45.06 mm | 60 mm | ||||
| Compatible Tube Lens Focal Length | 180 mm | 200 mm | ||||
| Coverslip Correction | 0.17 mm | - | 0.17 mm | |||
| Diameterc | 28 mm | 28 mm | 26 mm | 28 mm | 24 mm | 30 mm |
| Lengthc | 49.4 mm | 49.5 mm | 49.2 mm | 49.3 mm | 49.2 mm | 64.8 mm |
| Design Wavelength | Visible and NIR | Visible | Visible | |||
| Threading | RMS | M25 x 0.75 | ||||
| Thread Depth | 4.7 mm | 4.7 mm | 4.5 mm | 4.5 mm | 4.5 mm | 5.1 mm |
Dimensional Drawing
Objective Identification
Note: These microscope objectives serve only as examples. The format of the engraved specifications will vary between objectives and manufacturers.
Types of Objectives
Thorlabs offers several types of objectives from Nikon, Olympus, and Mitutoyo. This guide describes the features and benefits of each type of objective.
Dry or Oil-Immersion Objectives
This designation refers to the medium that should be present between the front of the objective and the cover glass of the microscope slide. Dry objectives are designed to work best with an air gap between the objective and the specimen, while oil-immersion objectives require the use of a drop of immersion oil (such as MOIL-30) between and in contact with the front lens of the objective and the cover glass. Oil immersion is required in order to achieve numerical apertures greater than 1.0. Note that if an oil immersion objective is used without the oil present, the image quality will be very low. Our dry objectives are presented here.
Plan Achromat and Plan Apochromat Objectives
"Plan" designates that these objectives produce a flat image across the field of view. "Achromat" refers to the correction for chromatic aberration featured in the lens design. These objectives have chromatic aberration correction for two wavelengths and spherical aberration correction at one wavelength. Plan achromats produce their best images for green light. The apochromat objectives on this page have chromatic aberration correction for three wavelengths and spherical aberration correction at two wavelengths. In white light, the plan achromats give satisfactory images for color photomicrography, but the results are not as good as objectives that feature better correction, such as plan apochromats or the plan fluorite objectives below.
Plan Fluorite Objectives
Plan fluorite objectives, also referred to as plan semi-apochromats, plan fluorescence objectives, or plan fluors, also produce a flat image across the field of view. Plan fluorite objectives are corrected for chromatic aberrations at two to four wavelengths and spherical aberrations at three to four wavelengths. In addition to being corrected for more wavelengths, plan fluorite objectives generally offer reduced aberrations between the design wavelengths relative to plan achromats. These objectives also work well for color photomicrography.
| Magnification Color Codes |
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| Immersion Media Color Codes |
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Glossary of Terms
Magnification
The magnification of an objective is the lens tube focal length (L) divided by the objective's focal length (F):
M = L / F .
The total magnification of the system is the magnification of the objective multiplied by the magnification of the eyepiece or camera tube. The specified magnification on the microscope objective housing is accurate as long as the objective is used with a compatible tube lens focal length.
Numerical Aperture (NA)
Numerical aperture, a measure of the acceptance angle of an objective, is a dimensionless quantity. It is commonly expressed as
NA = ni × sinθa
where θa is the maximum 1/2 acceptance angle of the objective, and ni is the index of refraction of the immersion medium. This medium is typically air, but may also be water, oil, or other substances.
Parfocal Length
Also referred to as the parfocal distance, this is the length from the top of the objective (at the base of the mounting thread) to the bottom of the cover glass (or top of the specimen in the case of objectives that are intended to be used without a cover glass). For instances in which the parfocal length needs to be increased, parfocal length extenders are available.
Working Distance
This is the distance between the front element of the objective and the specimen, depending on the design of the objective. The cover glass thickness specification engraved on the objective designates whether a cover glass should be used.
Field Number
The field number corresponds to the size of the field of view (in millimeters) multiplied by the objective's magnification.
FN = Field of View Diameter × Magnification
Coverslip Correction and Correction Collar (Ring)
A typical coverslip (cover glass) is designed to be 0.17 mm thick, but due to variance in the manufacturing process the actual thickness may be different. The correction collar present on select objectives is used to compensate for coverslips of different thickness by adjusting the relative position of internal optical elements. Note that many objectives do not have a variable coverslip correction (for example, an objective could be designed for use with only a standard 0.17 mm thick coverglass), in which case the objectives have no correction collar.
When viewing an image with a camera, the system magnification is the product of the objective and camera tube magnifications. When viewing an image with trinoculars, the system magnification is the product of the objective and eyepiece magnifications.
| Manufacturer | Tube Lens Focal Length |
|---|---|
| Leica | f = 200 mm |
| Mitutoyo | f = 200 mm |
| Nikon | f = 200 mm |
| Olympus | f = 180 mm |
| Thorlabs | f = 200 mm |
| Zeiss | f = 165 mm |
Magnification and Sample Area Calculations
Magnification
The magnification of a system is the multiplicative product of the magnification of each optical element in the system. Optical elements that produce magnification include objectives, camera tubes, and trinocular eyepieces, as shown in the drawing to the right. It is important to note that the magnification quoted in these products' specifications is usually only valid when all optical elements are made by the same manufacturer. If this is not the case, then the magnification of the system can still be calculated, but an effective objective magnification should be calculated first, as described below.
To adapt the examples shown here to your own microscope, please use our Magnification and FOV Calculator, which is available for download by clicking on the red button above. Note the calculator is an Excel spreadsheet that uses macros. In order to use the calculator, macros must be enabled. To enable macros, click the "Enable Content" button in the yellow message bar upon opening the file.
Example 1: Camera Magnification
When imaging a sample with a camera, the image is magnified by the objective and the camera tube. If using a 20X Nikon objective and a 0.75X Nikon camera tube, then the image at the camera has 20X × 0.75X = 15X magnification.
Example 2: Trinocular Magnification
When imaging a sample through trinoculars, the image is magnified by the objective and the eyepieces in the trinoculars. If using a 20X Nikon objective and Nikon trinoculars with 10X eyepieces, then the image at the eyepieces has 20X × 10X = 200X magnification. Note that the image at the eyepieces does not pass through the camera tube, as shown by the drawing to the right.
Using an Objective with a Microscope from a Different Manufacturer
Magnification is not a fundamental value: it is a derived value, calculated by assuming a specific tube lens focal length. Each microscope manufacturer has adopted a different focal length for their tube lens, as shown by the table to the right. Hence, when combining optical elements from different manufacturers, it is necessary to calculate an effective magnification for the objective, which is then used to calculate the magnification of the system.
The effective magnification of an objective is given by Equation 1:
 |
(Eq. 1) |
Here, the Design Magnification is the magnification printed on the objective, fTube Lens in Microscope is the focal length of the tube lens in the microscope you are using, and fDesign Tube Lens of Objective is the tube lens focal length that the objective manufacturer used to calculate the Design Magnification. These focal lengths are given by the table to the right.
Note that Leica, Mitutoyo, Nikon, and Thorlabs use the same tube lens focal length; if combining elements from any of these manufacturers, no conversion is needed. Once the effective objective magnification is calculated, the magnification of the system can be calculated as before.
Example 3: Trinocular Magnification (Different Manufacturers)
When imaging a sample through trinoculars, the image is magnified by the objective and the eyepieces in the trinoculars. This example will use a 20X Olympus objective and Nikon trinoculars with 10X eyepieces.
Following Equation 1 and the table to the right, we calculate the effective magnification of an Olympus objective in a Nikon microscope:
 |
The effective magnification of the Olympus objective is 22.2X and the trinoculars have 10X eyepieces, so the image at the eyepieces has 22.2X × 10X = 222X magnification.
Sample Area When Imaged on a Camera
When imaging a sample with a camera, the dimensions of the sample area are determined by the dimensions of the camera sensor and the system magnification, as shown by Equation 2.
 |
(Eq. 2) |
The camera sensor dimensions can be obtained from the manufacturer, while the system magnification is the multiplicative product of the objective magnification and the camera tube magnification (see Example 1). If needed, the objective magnification can be adjusted as shown in Example 3.
As the magnification increases, the resolution improves, but the field of view also decreases. The dependence of the field of view on magnification is shown in the schematic to the right.
Example 4: Sample Area
The dimensions of the camera sensor in Thorlabs' 1501M-USB Scientific Camera are 8.98 mm × 6.71 mm. If this camera is used with the Nikon objective and trinoculars from Example 1, which have a system magnification of 15X, then the image area is:
 |
Sample Area Examples
The images of a mouse kidney below were all acquired using the same objective and the same camera. However, the camera tubes used were different. Read from left to right, they demonstrate that decreasing the camera tube magnification enlarges the field of view at the expense of the size of the details in the image.
| Posted Comments: | |
Philip Binner
(posted 2020-10-30 13:27:24.633) 1.25-0.65 NA
I am confused by the notation of this ^. Does this mean the numerical aperture can take on any value between 0.65 and 1.25? YLohia
(posted 2020-10-30 02:08:32.0) Thank you for contacting Thorlabs. The -PFOD objectives have built-in irises that allow for the effective NA to be changed between the specified values (for example, between 0.65 and 1.25). |
Zoom
- Oil Immersion Objectives for NIR and Visible Light
- Infinity-Corrected Plan Fluorite or Plan Achromat Designs
- Iris Diaphragm for Darkfield Microscopy on RMS60X-PFOD and RMS100X-PFOD
- RMS (0.800"-36) Threading
- Designed for a Tube Lens Focal Length of 180 mm
- 45.06 mm Parfocal Length
These objectives provide 40X, 60X, or 100X magnification, flat images across the entire visible spectrum, high numerical aperture values, and excellent resolution. The RMS40X-PFO, RMS50X-PFOD, RMS100X-PFO, and RMS100X-POFD are plan fluorite designs, while the RMS100X-O is a plan achromat design. The differences between these designs can be found in the Objective Tutorial tab.
All of these objectives are suitable for brightfield microscopy, and all but the RMS100X-O are suitable for DIC microscopy. Additionally, the RMS60X-PFOD and RMS100X-PFOD objectives feature a built-in iris diaphragm, which is designed to be partially closed during darkfield microscopy in order to preserve the darkness of the background. This is absolutely necessary for high numerical aperture (above NA = 1.2) oil immersion objectives when using an oil immersion darkfield condenser. For ordinary brightfield observations, the iris diaphragm should be left fully open. The iris diaphragm adjustment is pictured above and to the right.
These objectives use standard RMS threading. To use these objectives with a different thread standard, please see our RMS Thread Adapters.
Objective manufacturers recommend using immersion oils from the same manufacturer for best performance; Thorlabs offers a variety of immersion oils below. A protective cap is also available for these objectives; see below for details.
Zoom- Oil Immersion Objectives for the Visible Spectrum
- Infinity-Corrected, Plan Fluorite Design
- Ideal for High-NA Imaging
- M25 x 0.75 Threading
- Designed for a Tube Lens Focal Length of 200 mm
- 60 mm Parfocal Length
This objective provides 100X magnification, features high transmission, particularly at UV wavelengths, and produces flat images across the field of view, making this objective well suited for use in laser scanning microscopy. It is designed for DIC microscopy, but can also be utilized for brightfield microscopy, fluorescence, and polarized light microscopy. The high NA of this objective also makes it suitable for Optical Tweezer applications. These objectives use M25 x 0.75 threading, which can be converted to other thread standards using Thorlabs' selection of M25 x 0.75 adapters.
This objective is designed for use from -18 °C to 60 °C (0 °F to 140 °F) and is not recommended for use at extreme temperatures. Objective manufacturers recommend using immersion oils from the same manufacturer for best performance; Thorlabs offers a variety of immersion oils below.
Zoom- Oils for Use with Oil Immersion Objectives
- Very Low Autofluorescence Oils are Optimized for Fluorescence Microscopy
- Non-Drying and Polychlorinated Biphenyl (PCB) Free
These Microscope Immersion Oils are designed for use with Oil Immersion Microscope Objectives. Placing an oil medium between the front surface of the objective and the cover glass allows the objective to achieve a high numerical aperture, maximizing light collection by the objective. To minimize refraction of light from the sample, the refractive indices of immersion oils are very close to those of cover glass.
Immersion oils are available with low or very low autofluorescence. Autofluorescence is the natural fluorescence emission of the oil when exposed to light. Each immersion oil has a different level of background emission, which either increases or decreases the contrast of the image; oils with very low autofluorescence are optimized for use in sensitive or UV fluorescence microscopy applications.
To clean immersion objectives after use with immersion oils, use a soft optical cleaning tissue such as our MC-5 premium lens tissues.
| Item # | MOIL-30 | MOIL-20LN | OILCL30 | MOIL-10LF | ||
|---|---|---|---|---|---|---|
| Refractive Indexa | 1.518 at 546.1 nm | |||||
| Abbe Numbera (at 546.1 nm) | 40.8 | 42.1 | 41 | 45.8 | ||
| Type | Olympus Type F | Leica Type N | Cargille Type LDF | Leica Type F | ||
| Viscositya,b | 450 mm2/s | 825 mm2/s | 500 mm2/s | 435 mm2/s | ||
| Autofluorescence | Low | Low | Very Low | Very Low | ||
| Volume | 30 mL / 28 g | 20 mL | 30 mL | 10 mL | ||
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