Long Working Distance Objectives
 Objectives for UV, Visible, or NIR Light
 5X, 7.5X, 10X, 20X, 50X, or 100X Magnification
 Ideal for Machine Vision Applications
 InfinityCorrected Design
MY5X802
5X Objective
436 nm  656 nm
MY100X806
100X Objective
436 nm  656 nm
MY50X825
50X Objective
480 nm  1800 nm
LMUL10XUVB
10X Objective
240 nm  360 nm
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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 FTheta Scan Lenses InfinityCorrected Tube Lenses 
Zemax Files 

Click on the red Document icon next to the item numbers below to access the Zemax file download. Our entire Zemax Catalog is also available. 
Click for Details
This diagram illustrates the labels, working distance, and parfocal distance. The format of the engraved specifications will vary between objectives and manufacturers. (See the Objective Tutorial tab for more information about microscope objective types.)
Features
 Long Working Distance Ideal for Machine Vision Applications
 InfinityCorrected Options for UV, Visible, or NIR Wavelengths
 Designed for a Tube Lens Focal Length of 200 mm
 M26 x 0.706 Threading
Thorlabs offers long working distance M Plan objectives for ultraviolet (UV), visible, or nearinfrared (NIR) wavelength ranges. These objectives are designed for use with a tube lens focal length of 200 mm and are ideal for machine vision applications or applications that require a significant distance between the objective lens and the object. See the Specs tab for details on each of the objectives available here.
Each objective housing is engraved with key specifications including the magnification, the numerical aperture, and an infinity symbol noting that it is infinity corrected; see the image to the right. The housings have external M26 x 0.706 threads; to convert M26 x 0.706 threads to M32 x 0.75 threads, we offer the M32M26S thread adapter.
All of the objectives found on this page have a parfocal length of 95 mm (see the Specs tab for complete specifications). To use them alongside other manufacturer standards, such as Nikon objectives with a 60 mm parfocal length, we offer parfocal length extenders. For instance, the PLE351 Extender can be used to increase the parfocal length of a Nikon objective from 60 mm to 95 mm.
These objectives are designed to be used without a cover glass and do not feature a correction collar. Imaging through a cover glass may cause spherical aberrations in an image, depending on the numerical aperture of the objective. See the Objective Tutorial tab for more on how a cover glass may impact performance. For biological applications where imaging through cover glasses is required, consider our super apochromatic objectives.
Item #  Wavelength Range 
M^{a}  WD  EFL  NA  EP^{b}  Spot Size^{c} 
Typical Transmission  OFN  PFL^{d}  Design Tube Lens Focal Length^{e}  AR Coating Reflectance 
Pulsed Damage Threshold 
Objective Threading 

Thorlabs Long Working Distance, Achromatic, MicroSpot^{®} UV Focusing Objectives  
LMUL10XUVB  240  360 nm  10X  20.0 mm  20 mm  0.25  10.0 mm  1.4 µm  Raw Data 
24  95.0 mm  200 mm  per Surface (240  360 nm)^{f} 
5.0 J/cm^{2} (355 nm, 10 ns,20 Hz, Ø0.342 mm)  M26 x 0.706; 5 mm Depth 
LMUL20XUVB  20X  15.3 mm  10 mm  0.36  7.2 mm  1 µm  Raw Data 

LMUL50XUVB  50X  12.0 mm  4 mm  0.42  3.4 mm  0.7 µm  Raw Data 

Mitutoyo Long Working Distance Apochromatic Objectives  
MY5X802 
436  656 nm  5X  34.0 mm  40 mm  0.14  11.2 mm  2.5 µm  24  95.0 mm  200 mm  Proprietary  Proprietary  M26 x 0.706; 5 mm Depth 

MY7X807  7.5X  35.0 mm  27 mm  0.21  11.2 mm  1.7 µm  Proprietary  
MY10X803  10X  34.0 mm  20 mm  0.28  11.2 mm  1.3 µm  
MY20X804  20X  20.0 mm  10 mm  0.42  8.4 mm  0.8 µm  
MY50X805  50X  13.0 mm  4 mm  0.55  4.4 mm  0.6 µm  
MY100X806  100X  6.0 mm  2 mm  0.70  2.8 mm  0.5 µm  
Mitutoyo Long Working Distance Apochromatic NIR Objectives  
MY5X822  480  1800 nm  5X  37.5 mm  40 mm  0.14  11.2 mm  2.5 µm  24  95.0 mm  200 mm  Proprietary  Proprietary  M26 x 0.706; 5 mm Depth 

MY10X823  10X  30.5 mm  20 mm  0.26  10.4 mm  1.3 µm  
MY20X824  20X  20.0 mm  10 mm  0.40  8.0 mm  0.9 µm  
MY50X826  50X  17.0 mm  4 mm  0.42  3.4 mm  0.8 µm 
Chromatic Aberration Correction per ISO Standard 190122  

Objective Class  Common Abbreviations  Axial Focal Shift Tolerances^{a} 
Achromat  ACH, ACHRO, ACHROMAT  δ_{C'}  δ_{F'} ≤ 2 x δ_{ob} 
Semiapochromat (or Fluorite) 
SEMIAPO, FL, FLU  δ_{C'}  δ_{F'} ≤ 2 x δ_{ob} δ_{F'}  δ_{e} ≤ 2.5 x δ_{ob} δ_{C'}  δ_{e} ≤ 2.5 x δ_{ob} 
Apochromat  APO  δ_{C'}  δ_{F'} ≤ 2 x δ_{ob} δ_{F'}  δ_{e} ≤ δ_{ob} δ_{C'}  δ_{e} ≤ δ_{ob} 
Super Apochromat  SAPO  See Footnote b 
Parts of a Microscope Objective
Click on each label for more details.
This microscope objective serves only as an example. The features noted above with an asterisk may not be present on all objectives; they may be added, relocated, or removed from objectives based on the part's needs and intended application space.
Objective Tutorial
This tutorial describes features and markings of objectives and what they tell users about an objective's performance.
Objective Class and Aberration Correction
Objectives are commonly divided by their class. An objective's class creates a shorthand for users to know how the objective is corrected for imaging aberrations. There are two types of aberration corrections that are specified by objective class: field curvature and chromatic aberration.
Field curvature (or Petzval curvature) describes the case where an objective's plane of focus is a curved spherical surface. This aberration makes widefield imaging or laser scanning difficult, as the corners of an image will fall out of focus when focusing on the center. If an objective's class begins with "Plan", it will be corrected to have a flat plane of focus.
Images can also exhibit chromatic aberrations, where colors originating from one point are not focused to a single point. To strike a balance between an objective's performance and the complexity of its design, some objectives are corrected for these aberrations at a finite number of target wavelengths.
The four common objective classes are shown in the table to the right; only three are defined under the International Organization for Standards ISO 190122: Microscopes  Designation of Microscope Objectives  Chromatic Correction.
Immersion Methods
Click on each image for more details.
Objectives can be divided by what medium they are designed to image through. Dry objectives are used in air; whereas dipping and immersion objectives are designed to operate with a fluid between the objective and the front element of the sample.
Glossary of Terms  

Back Focal Length and Infinity Correction  The back focal length defines the location of the intermediate image plane. Most modern objectives will have this plane at infinity, known as infinity correction, and will signify this with an infinity symbol (∞). Infinitycorrected objectives are designed to be used with a tube lens between the objective and eyepiece. Along with increasing intercompatibility between microscope systems, having this infinitycorrected space between the objective and tube lens allows for additional modules (like beamsplitters, filters, or parfocal length extenders) to be placed in the beam path. Note that older objectives and some specialty objectives may have been designed with finite back focal lengths. In their inception, finite back focal length objectives were meant to interface directly with the objective's eyepiece. 
Entrance Aperture  This measurement corresponds to the appropriate beam diameter one should use to allow the objective to function properly. Entrance Aperture = 2 × NA × Effective Focal Length 
Field Number and Field of View  The field number corresponds to the diameter of the field of view in object space (in millimeters) multiplied by the objective's magnification. Field Number = Field of View Diameter × Magnification 
Magnification  The magnification (M) of an objective is the lens tube focal length (L) divided by the objective's effective focal length (F). Effective focal length is sometimes abbreviated EFL: M = L / EFL . 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. Objectives will have a colored ring around their body to signify their magnification. This is fairly consistent across manufacturers; see the Parts of a Microscope section for more details. 
Numerical Aperture (NA)  Numerical aperture, a measure of the acceptance angle of an objective, is a dimensionless quantity. It is commonly expressed as: 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. 
Working Distance 
The working distance, often abbreviated WD, is the distance between the front element of the objective and the top of the specimen (in the case of objectives that are intended to be used without a cover glass) or top of the cover glass, depending on the design of the objective. The cover glass thickness specification engraved on the objective designates whether a cover glass should be used. 
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, 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)
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' 1501MUSB 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:  
Verena Buehler
(posted 20200814 11:39:42.21) Hello Thorlabs Team,
I was wondering why you do not offer a black box file for this popular Objective?
It would be helpful to simulate in Zemax how or if a individual setup works with it.
Please contact me for any helpful information.
Kind regards,
Verena Buehler nbayconich
(posted 20200817 10:10:52.0) Thank you for your feedback. Our vendor Mitutoyo unfortunately does not provide us with zemax models for these objectives. I will reach out to you directly to discuss your application. Shankar MENON
(posted 20200622 17:43:38.59) Is it possible to get objective AR coated for high transmission at a specific wavelength? YLohia
(posted 20200623 09:22:58.0) Hello, thank you for contacting Thorlabs. Custom optics can be requested by emailing techsupport@thorlabs.com. We will reach out to you directly to discuss the possibility of offering this. user
(posted 20200407 10:43:42.103) Concerning Mitutoyo NIR objectives, do you have any info how much the focal length changes (e.g. at 1550 [nm]) respective to the visible range? It would typically be helpful to know if it is more or less than the Rayleigh range. llamb
(posted 20200413 09:54:47.0) Thank you for your feedback. The focal shift can be up to 15 µm for wavelengths in the 11001600 nm range. More detailed information could be provided after discussing your application further. I see that your contact information was not provided, so feel free to reach out to techsupport@thorlabs.com if you would like further information. Clara Rittmann
(posted 20191017 10:12:14.72) Hi, I do not understand why the effective focal length can be significantly smaller than the working distance at the long distance working objectives such as the MY50x825. How is that achieved? I just do not feel comfortable about using optics that I do not fully understand.
Thanks! YLohia
(posted 20191017 11:30:33.0) Hello Clara, the EFL is defined as the distance between the principal plane and the focus spot, in order provide users a number to perform calculations for field of view, focused spot size, etc. The principle plane does not necessarily have to be within the length of the objective itself and, in this case, is specifically designed to be outside of it in order to achieve a long working distance. user
(posted 20190203 23:59:26.797) Have you considered, as e.g. order on demand item, also to supply the rest of the Mitutoyo Plan App line e.g. the HR Plan Apo series. nbayconich
(posted 20190206 03:29:34.0) Thank you for contacting Thorlabs. At the moment we do not have plans to release additional Mitutoyo objectives but we can provide special orders upon request. Please contact techsupport@thorlabs.com regarding any special order requests. np
(posted 20180326 20:46:08.447) Can you please tell what is the location of the back focal plane of the MY100X806 relative to the end of the lens? nbayconich
(posted 20180331 03:51:36.0) Thank you for contacting Thorlabs. Information such as the back focal plane location is typically proprietary for most objective lens manufacturers and can only provide certain specifications to particular end users. I will reach out to you directly to discuss your application and provide more information if possible. maciej.koperski
(posted 20171004 11:50:15.6) Dear Sir/Madam
Could you please provide information, in which spectral range can this objective be used? Could you perhaps show transmission spectra?
With best regards,
Maciej Koperski nbayconich
(posted 20171012 10:36:40.0) Thank you for contacting Thorlabs. Mitutoyo's objective transmission spectrum is proprietary information. The recommended performance range for these objectives is between 450nm  650nm. I will reach out to you directly. 
 AR Coated for 240  360 nm
 Ideal for Laser Focusing and UV Imaging Applications
 DiffractionLimited Performance
 10X, 20X, or 50X Magnification
Thorlabs MicroSpot objectives provide long working distances while keeping axial focal shift low. Their optical design is chromatically optimized in the UV wavelength range. Diffractionlimited performance is guaranteed over the entire clear aperture. These objectives are ideal for laser cutting, surgical laser focusing, and spectrometry applications. They can also be used for scanning and microimaging applications like brightfield imaging under narrowband, UV laser illumination. Each objective is shipped in an objective case comprised of an OC2M26 lid and an OC24 canister.
Each objective is engraved with its class, magnification, numerical aperture, wavelength range, a zero (noting that it is to be used to image a sample without a cover glass) and optical field number. For an explanation of the defining properties of these objectives, please see the Objective Tutorial tab.
Thorlabs can provide these objectives with custom AR coatings on request by contacting Tech Support; options include broadband NUV (325 nm  500 nm), dual band (266 and 532 nm), and laser line (248 nm, 266 nm, 355 nm, or 532 nm). We also offer additional MicroSpot objectives for laserfocusing applications in the UV as well as visible and nearIR wavelengths.
Item #  Wavelength Range 
M^{a}  WD  EFL  NA  EP^{b}  Spot Size^{c} 
Typical Transmission  OFN  PFL  AR Coating Reflectance^{d} 
Pulsed Damage Threshold 
Objective Threading 

LMUL10XUVB  240  360 nm  10X  20.0 mm  20 mm  0.25  10.0 mm  1.4 µm  Raw Data 
24  95.0 mm  (240  360 nm) 
5.0 J/cm^{2} (355 nm, 10 ns, 20 Hz, Ø0.342 mm) 
M26 x 0.706; 5 mm Depth 
LMUL20XUVB  20X  15.3 mm  10 mm  0.36  7.2 mm  1.0 µm  Raw Data 

LMUL50XUVB  50X  12.0 mm  4 mm  0.42  3.4 mm  0.7 µm  Raw Data 
 For Use from 436 nm to 656 nm
 Suitable for Brightfield Observation
 5X, 7.5X, 10X, 20X, 50X, or 100X Magnification
Thorlabs offers Mitutoyo Plan Apochromat Objectives with 5X, 7.5X, 10X, 20X, 50X, or 100X magnification. They feature a flat field of focus and chromatic correction in the visible range. The long working distance provides a wide space between the lens surface and the object making them ideal for machine vision applications. Each objective is engraved with its class, magnification, numerical aperture, a zero (noting that it is to be used to image a sample without a cover glass) and the tube lens focal length for which the specified magnification is valid. For an explanation of the defining properties of these objectives, please see the Objective Tutorial tab. If the case shipped with each of these objectives is lost or broken, Thorlabs offers an objective case (item #s OC2M26 and OC24) that can be used as a replacement.
 For Use from 480 nm to 1800 nm
 Suitable for Brightfield Observation and Laser Focusing
 5X, 10X, 20X, or 50X Magnification
Thorlabs offers Mitutoyo Plan Apochromat NearInfrared (NIR) Objectives with 5X, 10X, 20X, or 50X magnification. They feature a flat field of focus and chromatic correction in the visible range with extended transmission to 1800 nm. The long working distance provides a wide space making them ideal for machine vision applications or laser focusing. Each objective is engraved with its class, magnification, numerical aperture, a zero (noting that it is to be used to image a sample without a cover glass) and the tube lens focal length for which the specified magnification is valid. For an explanation of the defining properties of these objectives, please see the Objective Tutorial tab. If the case shipped with each of these objectives is lost or broken, Thorlabs offers an objective case (item #s OC2M26 and OC24) that can be used as a replacement.