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Super Apochromatic Microscope Objectives


  • Infinity-Corrected Microscope Objectives for Visible Wavelength Range
  • Designed for Use with Air between Objective and Sample
  • Super Apochromatic Axial Color Correction

TL4X-SAP

4X Super Apochromat Objective

Image of a Dicot Flower Bud Taken with the Thorlabs 4X Super Apochromatic Objective

TL2X-SAP

2X Super Apochromat Objective

Related Items


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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
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.

Webpage Features
info icon Zemax blackbox files for the objectives on this page can be accessed by clicking this icon below.
Objective Storage
Case Lid: OC2M25
Container: OC22

Features

  • Diffraction-Limited Axial Color Performance over 400 - 750 nm
  • High Transmission Down to 350 nm
  • No Vignetting over Entire Field
  • Higher NA than Other Dry Objectives with the Same Magnification
  • Long Working Distance
  • Ideal for Widefield Imaging, Fluorescence, and Illumination Applications
  • Designed for a Tube Lens Focal Length of 200 mm

Thorlabs' super apochromatic microscope objectives are designed to provide diffraction-limited axial color performance over a wide field of view with no vignetting over the entire field. The high numerical aperture (NA) of these objectives makes them ideal for widefield imaging and light-starved environments. The super apochromatic objective design provides axial color correction throughout the visible range, and a broadband AR coating improves transmission over the 350 - 700 nm range. See the Specs tab for complete specifications.

These microscope objectives are ideal for applications such as traditional microscopy and fluorescence imaging. Additionally, they are suitable for use in confocal imaging and in a variety of imaging modalities, including epi-illumination, oblique illumination, and brightfield imaging. The images below were taken using the TL4X-SAP microscope objective, and a comparison with a 0.13 NA objective is also provided. As shown in the comparison, the high NA of the TL4X-SAP objective yields a clearer image than the other 4X objective.

Each objective housing is engraved with the item #, magnification, NA, wavelength range, and working distance. The housings have external M25 x 0.75 threading and are designed for a tube lens of focal length 200 mm. To use the objectives with a different thread standard, please see our M25 x 0.75 thread adapters.

The TL2X-SAP and TL4X-SAP objectives have parfocal lengths of 95.0 mm and 60.0 mm, respectively (see the Specs tab for complete specifications). To use these objectives alongside each other, we offer the PLE351 Parfocal Length Extender to increase the parfocal length of the TL4X-SAP objective from 60.0 mm to 95.0 mm.


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Mouse Retina Imaged Using the Thorlabs TL4X-SAP

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These images of a mouse kidney tissue sample show a comparison between the Thorlabs TL4X-SAP objective (left) and an objective with 4X magnification and 0.13 NA from a major manufacturer (right). The two images were taken using a 1.4 MP scientific camera under the same illumination conditions.

Click Here to Download High-Resolution, 16-Bit TIFF Files (ImageJ Recommended for Viewing)

Item # TL2X-SAP TL4X-SAP
Magnification 2X 4X
Numerical Aperture 0.10 0.20
AR Coating Wavelength Range 350 - 700 nma
Axial Color Diffraction Limited over 400 - 750 nma
Field of View Ø11 mm Ø5.5 mm
Field Numberb 22
Working Distancec 56.3 mm 17.0 mm
Effective Focal Length 100 mm 50 mm
Parfocal Lengthc 95.0 mmd 60.0 mmd
Diameterc 30.5 mm
Lengthc 43.5 mm 46.4 mm
Housing Threads M25 x 0.75
Design Tube Lens Focal Lengthe 200 mm
  • For details on this spec, please see the Graphs tab.
  • The field number definition can vary between manufacturers. The field number for these objectives represents performance over the full operating wavelength range with no vignetting over the entire field of view.
  • These dimensions are defined in the drawing to the right.
  • Note that these objectives have different parfocal lengths. When switching between the objectives in a single setup, adjusting the microscope will be necessary. Alternatively, the parfocal length of the TL4X-SAP objective can be increased to 95.0 mm using our PLE351 Parfocal Length Extender.
  • For information on compatibility between tube lenses and objectives, see the Magnification & FOV tab.

Dimensional Drawing

2X Objective Performance Graphs

Click here for raw data for all plots.


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Transmission of the TL2X-SAP Objective. The blue shaded region denotes the wavelength range of the AR coating.

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Axial color describes the shift in the image plane across the operating wavelength range of the 2X super apochromatic microscope objective. The pink shaded region denotes diffraction-limited performance.

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The Strehl Ratio is a quantitative measurement of optical image formation quality. The Strehl Ratio for the TL2X-SAP over its field of view is shown in the graph above.

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This graph shows the Strehl Ratio of the TL2X-SAP over the objective's full operating wavelength range.

4X Objective Performance Graphs

Click here for raw data for all plots.


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Transmission of the TL4X-SAP Objective. The blue shaded region denotes the wavelength range of the AR coating.

Click to Enlarge

Axial color describes the shift in the image plane across the operating wavelength range of the 4X super apochromatic microscope objective. The pink shaded region denotes diffraction-limited performance.

Click to Enlarge

The Strehl Ratio is a quantitative measurement of optical image formation quality. The Strehl Ratio for the TL4X-SAP over its field of view is shown in the graph above.

Click to Enlarge

This graph shows the Strehl Ratio of the TL4X-SAP over the objective's full operating wavelength range.

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.


Click to Enlarge

This graph shows the effect of a cover slip on image quality at 632.8 nm.

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.

The graph to the right shows the magnitude of spherical aberration versus the thickness of the coverslip used, for 632.8 nm light. For the typical coverslip thickness of 0.17 mm, the spherical aberration caused by the coverslip does not exceed the diffraction-limited aberration for objectives with NA up to 0.40.

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
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Acquired with 1X Camera Tube (Item # WFA4100)
Image with 1X Camera Tube
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Acquired with 0.75X Camera Tube (Item # WFA4101)
Image with 1X Camera Tube
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Acquired with 0.5X Camera Tube (Item # WFA4102)

Posted Comments:
a.andreski  (posted 2017-11-28 15:40:24.44)
Do these objectives have a flat field of view (are they plan)? If I use the TL2X-SAP with a TTL100A tubelens, what is the maximum object field of view that is possible without abberations? Thanks.
tfrisch  (posted 2017-12-15 04:35:36.0)
Hello, thank you for contacting Thorlabs. The Field of View will be flat, yes. TL2X-SAP will be diffraction limited over its full Field of View. I will reach out to you directly with details on the Strehl ratio.
ludoangot  (posted 2016-11-07 15:31:29.6)
Which tube lens do you recommend to match the extended transmission of these microscope lenses in the deep blue / UV (your recent TTL200 is for 400 to 700nm)?
tfrisch  (posted 2016-11-10 10:24:31.0)
Hello, thank you for contacting Thorlabs. I would typically recommend TTL200 which performs well over the range of TL2X-SAP and TL4X-SAP. You can see some performance graphs here: https://www.thorlabs.us/newgrouppage9.cfm?objectgroup_id=5834&tabname=Graphs
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TL2X-SAP Support Documentation
TL2X-SAP2X Super Apochromatic Microscope Objective, 0.1 NA, 56.3 mm WD
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TL4X-SAP Support Documentation
TL4X-SAP4X Super Apochromatic Microscope Objective, 0.2 NA, 17.2 mm WD
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