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Physiology Objectives, Water Dipping or Immersion


  • Especially Suited for Multiphoton Imaging
  • Numerical Aperture Options: 0.30 to 1.15
  • Working Distance Options: 0.59 to 3.5 mm
  • Designed for UV to NIR Wavelengths

Dendridic Spine Image Collected with the N60X-NIR Objective at a Laser Wavelength of 1040 nmb

N16XLWD-PF

0.8 NA, 3.0 mm WD

N25X-APO-MP

1.1 NA, 2.0 mm WD

Deep Tissue Imaging of Mouse Embryo Sectiona

N20X-PFH

1.0 NA, 2.0 mm WD

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Objective Lens Selection Guide
Objectives
Microscopy Objectives, Dry
Microscopy Objectives, Oil Immersion
Physiology Objectives, Water Dipping or Immersion
Long Working Distance Objectives
Reflective Microscopy Objectives
UV Microscopy Objectives
532 nm and 1064 nm Objectives
Scan Lenses and Tube Lenses
Scan Lenses
Infinity-Corrected Tube Lens
Mounted Condenser

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.

Thorlabs offers a selection of physiology objectives especially suited for Multiphoton Microscopy, including objectives designed for water dipping or water immersion (coverslip) setups. The high numerical apertures (NA) of these objectives help capture signal photons that are scattered through deep tissue. The long working distances (WD) and steep housing angles at the end of the objective provide access to the sample for the micromanipulators used in electrophysiology. Each objective is also designed to provide high transmission over a wide wavelength range for transmitting stimulation and emission signals. The Nikon Plan Apochromat and Plan Fluorite objectives are designed for a tube lens with focal
length 200 mm, such as the ITL200 Tube Lens, whereas the Plan Fluorite Olympus objective is designed for a tube lens with focal length 180 mm.

Thorlabs also offers the PLE153 Parfocal Length Extender for increasing the parfocal length of objectives with M25 x 0.75 threading from 60 mm to 75 mm.

  • The deep tissue image featured above is courtesy of Dr. Rieko Ajima, National Cancer Institute, Frederick, MD.
  • The dendritic spine image featured above is courtesy of Dr. Tobias Rose, Max Planck Institute for Neurobiology, Martinsreid, Germany.

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Examples of Water Dipping and Water Immersion Designs
(See Objective Tutorial Tab for More Information About Microscope Objective Types)

Objective Identification


Note: These microscope objectives serve only as examples. The format of the engraved specifications will vary between objectives and manufacturers.

Magnification Color Codes
Immersion Media Color Codes

Types of Objectives

Thorlabs offers several types of objectives from Nikon and Olympus. This guide describes the features and benefits of each type of objective.

Water-Immersion (Coverslip) or Water-Dipping Objectives
This designation refers to the medium that should be present between the front of the objective and the specimen. Water-immersion (coverslip) objectives are designed to work best with a drop of water and a coverslip between the objective and the specimen, while water-dipping objectives are designed to interface directly with the specimen.

Plan Fluorite Objectives
"Plan" designates that these objectives produce a flat image across the field of view. Plan fluorite objectives, also referred to as plan semi-apochromats, plan fluorescence objectives, or plan fluors, are corrected for chromatic aberrations at two to four wavelengths and spherical aberrations at three to four wavelengths. Plan fluorite objectives work well for color photomicrography.

Plan Apochromat Objectives
"Apochromat" refers to the correction for chromatic aberration featured in the lens design. These objectives feature sophisticated designs and are corrected for chromatic corrections at four to five wavelengths and spherical aberrations at three to four wavelengths.

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.

Widefield Viewing Optical Path
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.
Magnification & FOV Calculator
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

The rows highlighted in green denote manufacturers that do not use f = 200 mm tube lenses.

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:

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:

Equation 2

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.


Image Area on Camera

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.

Equation 5 (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:

Equation 6

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.

Image with 1X Camera Tube
Click to Enlarge

Acquired with 1X Camera Tube (Item # WFA4100)
Image with 1X Camera Tube
Click to Enlarge

Acquired with 0.75X Camera Tube (Item # WFA4101)
Image with 1X Camera Tube
Click to Enlarge

Acquired with 0.5X Camera Tube (Item # WFA4102)

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Nikon Apochromat Physiology Objectives

Magnification 25X 25X 40X 40X 60X
Item # N25X-APO-MP N25X-APO-MP1300 N40XLWD-NIR N40X-NIR N60X-NIR
Manufacturer Part # MRD77220 MRD77225 MRD77410 MRD07420 MRD07620
Numerical Aperture (NA) 1.10 1.15 0.80 1.0
Working Distance (WD) 2.0 mm 0.59 - 0.61 mm 3.5 mm 2.8 mm
Parfocal Length 75 mm 60 mm
Compatible Tube Lens Focal Length 200 mm
Coverslip Correctionb 0 - 0.17 mm 0.15 - 0.19 mm N/A N/A
Immersion Water Dipping or
Water Immersion (Coverslip)
Water Immersion (Coverslip) Water Dipping
Wavelength Range 380 - 1050 nm 420 - 1400 nm 360 - 1100 nm 380 - 1100 nm
Threading M32 x 0.75 M25 x 0.75
Temperature Rangea -18 - 60 °C (0 - 140 °F)
Objective Case
(Available for Purchase Separately)
Lid OC2M32 OC2M25
Canister OC24
  • These objectives are not recommended for use in extreme temperatures. All specifications are measured at 23 °C (73 °F).
  • A coverslip correction given as a range of thicknesses indicates that the objective has a correction ring (see Objective Tutorial for details).
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
N25X-APO-MP Support Documentation
N25X-APO-MPCustomer Inspired! 25X Nikon CFI APO LWD Objective, 1.10 NA, 2.0 mm WD, 380 - 1050 nm
$27,122.29
Lead Time
N25X-APO-MP1300 Support Documentation
N25X-APO-MP1300Customer Inspired! 25X Nikon CFI APO LWD Objective, 1.10 NA, 2.0 mm WD, 420 - 1400 nm
$29,495.00
Lead Time
N40XLWD-NIR Support Documentation
N40XLWD-NIR40X Nikon CFI APO LWD NIR Objective, 1.15 NA, 0.59 - 0.61 mm WD
$15,603.57
Today
N40X-NIR Support Documentation
N40X-NIR40X Nikon CFI APO NIR Objective, 0.80 NA, 3.5 mm WD
$2,814.45
Today
N60X-NIR Support Documentation
N60X-NIR60X Nikon CFI APO NIR Objective, 1.0 NA, 2.8 mm WD
$4,485.57
Today

Nikon Plan Fluorite Physiology Objectives

Magnification 10X 16X 20X 40X 60X
Item # N10XW-PF N16XLWD-PF N20XW-PF N40XW-PF N60XW-PF
Manufacturer Part # MRH07120 MRP07220 MRF07220 MRF07420 MRF07620
Numerical Aperture (NA) 0.30 0.80 0.50 0.80 1.00
Working Distance (WD) 3.5 mm 3.0 mm 2.0 mm 2.0 mm 2.0 mm
Parfocal Length 60 mm 75 mm 60 mm
Compatible Tube Lens Focal Length 200 mm
Coverslip Correction N/A
Immersion Water Dipping
Wavelength Range 360 - 1500 nm 380 - 1100 nm 360 - 1050 nm
Threading M25 x 0.75 M32 x 0.75 M25 x 0.75
Temperature Rangea 18 - 60 °C (0 - 140 °F)
Objective Case
(Available for Purchase Separately)
Lid OC2M25 OC2M32 OC2M25
Canister
OC24
  • These objectives are not recommended for use in extreme temperatures. All specifications are measured at 23 °C (73 °F).
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
N10XW-PF Support Documentation
N10XW-PFCustomer Inspired! 10X Nikon CFI Plan Fluorite Objective, 0.30 NA, 3.5 mm WD
$1,452.29
Today
N16XLWD-PF Support Documentation
N16XLWD-PF16X Nikon CFI LWD Plan Fluorite Objective, 0.80 NA, 3.0 mm WD
$6,718.64
Today
N20XW-PF Support Documentation
N20XW-PFCustomer Inspired! 20X Nikon CFI Plan Fluorite Objective, 0.50 NA, 2.0 mm WD
$2,593.72
Today
N40XW-PF Support Documentation
N40XW-PFCustomer Inspired! 40X Nikon CFI Plan Fluorite Objective, 0.80 NA, 2.0 mm WD
$2,712.71
Today
N60XW-PF Support Documentation
N60XW-PFCustomer Inspired! 60X Nikon CFI Plan Fluorite Objective, 1.00 NA, 2.0 mm WD
$3,855.36
Today

Olympus Plan Fluorite Physiology Objective

Magnification 20X
Item # N20X-PFH
Manufacturer Part # 1-U2B965
Numerical Aperture (NA) 1.00
Working Distance (WD) 2.00 mm
Parfocal Length 75 mm
Compatible Tube Lens Focal Length 180 mm
Coverslip Correction N/A
Immersion Water Dipping
Wavelength Range 400 - 900 nm
Threading M25 x 0.75
Objective Case
(Available for Purchase Separately)
Lid OC2M25
Canister
OC24
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
N20X-PFH Support Documentation
N20X-PFH20X Olympus XLUMPLFLN Objective, 1.00 NA, 2.0 mm WD
$7,939.15
Today
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