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Super Apochromatic Microscope Objectives
TL4XSAP 4X Super Apochromat Objective Image of a Dicot Flower Bud Taken with the Thorlabs 4X Super Apochromatic Objective TL2XSAP 2X Super Apochromat Objective Related Items Please Wait
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.
Features
Thorlabs' super apochromatic microscope objectives are designed to provide diffractionlimited 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 lightstarved 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 epiillumination, oblique illumination, and brightfield imaging. The images below were taken using the TL4XSAP microscope objective, and a comparison with a 0.13 NA objective is also provided. As shown in the comparison, the high NA of the TL4XSAP 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 The TL2XSAP and TL4XSAP 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 TL4XSAP objective from 60.0 mm to 95.0 mm. Click to Enlarge Mouse Retina Imaged Using the Thorlabs TL4XSAP Click to Enlarge These images of a mouse kidney tissue sample show a comparison between the Thorlabs TL4XSAP 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 HighResolution, 16Bit TIFF Files (ImageJ Recommended for Viewing)
Dimensional Drawing2X Objective Performance GraphsClick here for raw data for all plots. Click to Enlarge Transmission of the TL2XSAP 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 2X super apochromatic microscope objective. The pink shaded region denotes diffractionlimited performance. Click to Enlarge The Strehl Ratio is a quantitative measurement of optical image formation quality. The Strehl Ratio for the TL2XSAP over its field of view is shown in the graph above. Click to Enlarge This graph shows the Strehl Ratio of the TL2XSAP over the objective's full operating wavelength range. 4X Objective Performance GraphsClick here for raw data for all plots. Click to Enlarge Transmission of the TL4XSAP 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 diffractionlimited performance. Click to Enlarge The Strehl Ratio is a quantitative measurement of optical image formation quality. The Strehl Ratio for the TL4XSAP over its field of view is shown in the graph above. Click to Enlarge This graph shows the Strehl Ratio of the TL4XSAP over the objective's full operating wavelength range. Glossary of TermsMagnification 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) NA = n_{i} × sinθ_{a}where θ_{a} is the maximum 1/2 acceptance angle of the objective, and n_{i} 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 Working Distance Click to Enlarge This graph shows the effect of a cover slip on image quality at 632.8 nm. Field Number FN = Field of View Diameter × MagnificationCoverslip Correction and Correction Collar (Ring) 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 diffractionlimited aberration for objectives with NA up to 0.40. 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 and Sample Area CalculationsMagnificationThe 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 Example 2: Trinocular Magnification Using an Objective with a Microscope from a Different ManufacturerMagnification 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:
Here, the Design Magnification is the magnification printed on the objective, f_{Tube Lens in Microscope} is the focal length of the tube lens in the microscope you are using, and f_{Design 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) 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 CameraWhen 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.
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 Sample Area ExamplesThe 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.
 
