Long Working Distance Objectives

Overview
Specs
Objective Tutorial
Magnification & FOV
Feedback

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

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.

Features

Long Working Distance Ideal for Machine Vision Applications
Infinity-Corrected 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 near-infrared (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. 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
LMUL-10X-UVB	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	<1.5% per Surface (240 - 360 nm)^f	5.0 J/cm² (355 nm, 10 ns,20 Hz, Ø0.342 mm)	M26 x 0.706; 5 mm Depth
LMUL-20X-UVB		20X	15.3 mm	10 mm	0.36	7.2 mm	1 µm	Raw Data
LMUL-50X-UVB		50X	12.0 mm	4 mm	0.42	3.4 mm	0.7 µm	Raw Data
Mitutoyo Long Working Distance Apochromatic Objectives
MY5X-802	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
MY7X-807		7.5X	35.0 mm	27 mm	0.21	11.2 mm	1.7 µm	Proprietary
MY10X-803		10X	34.0 mm	20 mm	0.28	11.2 mm	1.3 µm
MY20X-804		20X	20.0 mm	10 mm	0.42	8.4 mm	0.8 µm
MY50X-805		50X	13.0 mm	4 mm	0.55	4.4 mm	0.6 µm
MY100X-806		100X	6.0 mm	2 mm	0.70	2.8 mm	0.5 µm
Mitutoyo Long Working Distance Apochromatic NIR Objectives
MY5X-822	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
MY10X-823		10X	30.5 mm	20 mm	0.26	10.4 mm	1.3 µm
MY20X-824		20X	20.0 mm	10 mm	0.40	8.0 mm	0.9 µm
MY50X-826		50X	17.0 mm	4 mm	0.42	3.4 mm	0.8 µm

When Used with a 200 mm Focal Length Tube Lens
Entrance pupil diameter (EP) is defined at the back aperture of the objective and calculated as EP=2*NA*EFL.
Spot size is calculated assuming the entrance pupil is filled and the input beam profile is Gaussian.
This dimension is shown in the diagram to the right.
For information on compatibility between tube lenses and objectives, see the Magnification & FOV tab.
Using these objectives outside of their AR coating range is not recommended because of surface reflections that can create ghost images and significantly reduce the overall transmission through the optic.

M = Magnification
WD = Working Distance
EFL = Effective Focal Length
NA = Numerical Aperture

EP = Entrance Pupil Diameter
OFN = Optical Field Number
PFL = Parfocal Length

Diagram Showing General Objective Dimensions

Objective Identification

Click to Enlarge
Note: The diagrams above serve only as an example. The format of the engraved specifications will vary between objectives and manufacturers.

Thorlabs offers long working distance plan apochromat objectives. This guide describes the features and benefits of these objectives.

Air Objectives
This designation refers to the medium that should be present between the front of the objective and the object being examined. Air objectives are designed to work best with an air gap between the objective and the specimen.

Plan Achromat and Plan Apochromat Objectives
"Plan" designates that these objectives produce a flat image across the field of view. "Achromat" and "Apochromat" refer to the correction for chromatic aberration featured in the lens design. Achromatic objectives have chromatic aberration correction for two wavelengths, while apochromat objectives have chromatic aberration correction for three wavelengths. In white light, the plan achromats give satisfactory images for photomicrography, but the results are not as good as objectives that feature better correction, such as plan apochromats objectives below.

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

Magnification Color Codes

Immersion Media Color Codes

NA = n_i × sinθ_a

Click to Enlarge
This graph shows the effect of a cover glass on image quality at 632.8 nm for a #1.5 cover glass (0.17 mm thickness) with a refractive index of 1.51.

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
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 focal plane. For instances in which the parfocal length needs to be increased, parfocal length extenders are available.

Working Distance
The distance from bottom surface of the objective to the top surface of the sample (for objectives designed to be used without a cover glass) or to the top surface of the cover glass (for objectives designed for use with a cover glass) when the sample is in focus.

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

Correction Collar (Ring) and Cover Glass Thickness
A typical #1.5 cover glass (coverslip) is designed to be 0.17 mm thick, but due to variance in the manufacturing process the actual thickness may be different. These differences in thickness can introduce spherical aberrations, the severity of which is impacted by the objective numerical aperture. The graph to the right shows the relationship between the thickness of a cover glass and the spherical aberrations introduced to an uncorrected system. Note that for relatively low NA systems (approximately less than 0.20), this effect is negligible. The correction collar present on select objectives is used to compensate for cover glasses of different thickness by adjusting the relative position of internal optical elements. Note that many objectives do not have a collar for variable cover glass correction (for example, an objective could be designed for use with only a standard 0.17 mm thick coverglass).

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

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:

(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' 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.

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

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

Click to Enlarge
Acquired with 0.5X Camera Tube (Item # WFA4102)

Posted Comments:

Verena Buehler (posted 2020-08-14 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 2020-08-17 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 2020-06-22 17:43:38.59)

Is it possible to get objective AR coated for high transmission at a specific wavelength?

YLohia (posted 2020-06-23 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 2020-04-07 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 2020-04-13 09:54:47.0)

Thank you for your feedback. The focal shift can be up to 15 µm for wavelengths in the 1100-1600 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 2019-10-17 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 MY50x-825. How is that achieved? I just do not feel comfortable about using optics that I do not fully understand. Thanks!

YLohia (posted 2019-10-17 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 2019-02-03 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 2019-02-06 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 2018-03-26 20:46:08.447)

Can you please tell what is the location of the back focal plane of the MY100X-806 relative to the end of the lens?

nbayconich (posted 2018-03-31 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 2017-10-04 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 2017-10-12 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.

Thorlabs Achromatic, MicroSpot^® UV Focusing Objectives

Thorlabs Achromatic, MicroSpot<sup>®</sup> UV Focusing Objectives<br>

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Click to Enlarge
Click Here for Raw Data

AR Coated for 240 - 360 nm
Ideal for Laser Focusing and UV Imaging Applications
Diffraction-Limited 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. Diffraction-limited 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 micro-imaging 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 laser-focusing applications in the UV as well as visible and near-IR 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
LMUL-10X-UVB	240 - 360 nm	10X	20.0 mm	20 mm	0.25	10.0 mm	1.4 µm	Raw Data	24	95.0 mm	<1.5% per Surface (240 - 360 nm)	5.0 J/cm² (355 nm, 10 ns, 20 Hz, Ø0.342 mm)	M26 x 0.706; 5 mm Depth
LMUL-20X-UVB		20X	15.3 mm	10 mm	0.36	7.2 mm	1.0 µm	Raw Data
LMUL-50X-UVB		50X	12.0 mm	4 mm	0.42	3.4 mm	0.7 µm	Raw Data

When Used with a 200 mm Focal Length Tube Lens
Entrance pupil diameter (EP) is defined at the back aperture of the objective and calculated as EP=2*NA*EFL.
Spot size is calculated at the center wavelength, assuming the entrance pupil is filled and the input beam profile is Gaussian.
Using these objectives outside of their AR coating range is not recommended because of surface reflections that can create ghost images and significantly reduce the overall transmission through the optic.

M = Magnification
WD = Working Distance
EFL = Effective Focal Length
PFL = Parfocal Length

NA = Numerical Aperture
EP = Entrance Pupil Diameter
OFN = Optical Field Number

Mitutoyo Apochromatic Objectives

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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.

Item #	Wavelength Range	M^a	WD	EFL	NA	EP^b	Spot Size^c	Typical Transmission	OFN	PFL	AR Coating Reflectance	Pulsed Damage Threshold	Objective Threading
MY5X-802	436 - 656 nm	5X	34.0 mm	40 mm	0.14	11.2 mm	2.5 µm		24	95 mm	Not Available	Not Available	M26 x 0.706; 5 mm Depth
MY7X-807		7.5X	35.0 mm	26.7 mm	0.21	11.2 mm	1.7 µm	Proprietary
MY10X-803		10X	34.0 mm	20 mm	0.28	11.2 mm	1.3 µm
MY20X-804		20X	20.0 mm	10 mm	0.42	8.4 mm	0.8 µm
MY50X-805		50X	13.0 mm	4 mm	0.55	4.4 mm	0.6 µm
MY100X-806		100X	6.0 mm	2 mm	0.70	2.8 mm	0.5 µm

When Used with a 200 mm Focal Length Tube Lens
Entrance pupil diameter (EP) is defined at the back aperture of the objective and calculated as EP=2*NA*EFL.
Spot size is calculated at 550 nm, assuming the entrance pupil is filled and the input beam profile is Gaussian.

M = Magnification
WD = Working Distance
EFL = Effective Focal Length
PFL = Parfocal Length

NA = Numerical Aperture
EP = Entrance Pupil Diameter
OFN = Optical Field Number

Based on your currency / country selection, your order will ship from Newton, New Jersey

+1 Qty Docs Part Number - Universal Price Available

MY5X-802 Customer Inspired! 5X Mitutoyo Plan Apochromat Objective, 436 - 656 nm, 0.14 NA, 34 mm WD

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MY7X-807 Customer Inspired! 7.5X Mitutoyo Plan Apochromat Objective, 436 - 656 nm, 0.21 NA, 35 mm WD

$1,380.20

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MY10X-803 Customer Inspired! 10X Mitutoyo Plan Apochromat Objective, 436 - 656 nm, 0.28 NA, 34 mm WD

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MY20X-804 Customer Inspired! 20X Mitutoyo Plan Apochromat Objective, 436 - 656 nm, 0.42 NA, 20 mm WD

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MY50X-805 Customer Inspired! 50X Mitutoyo Plan Apochromat Objective, 436 - 656 nm, 0.55 NA, 13 mm WD

$2,770.70

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MY100X-806 Customer Inspired! 100X Mitutoyo Plan Apochromat Objective, 436 - 656 nm, 0.70 NA, 6 mm WD

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Mitutoyo Apochromatic NIR Objectives

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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 Near-Infrared (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.

Item #	Wavelength Range	M^a	WD	EFL	NA	EP^b	Spot Size^c	OFN	PFL	AR Coating Reflectance	Pulsed Damage Threshold	Objective Threading
MY5X-822	480 - 1800 nm	5X	37.5 mm	40 mm	0.14	11.2 mm	2.5 µm	24	95 mm	Not Available	Not Available	M26 x 0.706; 5 mm Depth
MY10X-823		10X	30.5 mm	20 mm	0.26	10.4 mm	1.3 µm
MY20X-824		20X	20.0 mm	10 mm	0.40	8.0 mm	0.9 µm
MY50X-825		50X	17.0 mm	4 mm	0.42	3.4 mm	0.8 µm

When Used with a 200 mm Focal Length Tube Lens
Entrance pupil diameter (EP) is defined at the back aperture of the objective and calculated as EP=2*NA*EFL.
Spot size is calculated at 550 nm, assuming the entrance pupil is filled and the input beam profile is Gaussian.

M = Magnification
WD = Working Distance
EFL = Effective Focal Length
PFL = Parfocal Length

NA = Numerical Aperture
EP = Entrance Pupil Diameter
OFN = Optical Field Number

View All »Matching Part Numbers

Long Working Distance Objectives

Features

Objective Identification

Glossary of Terms

M = L / F .

NA = ni × sinθa

FN = Field of View Diameter × Magnification

Magnification and Sample Area Calculations

Magnification

Using an Objective with a Microscope from a Different Manufacturer

Sample Area When Imaged on a Camera

Sample Area Examples

Thorlabs Achromatic, MicroSpot® UV Focusing Objectives

Mitutoyo Apochromatic Objectives

Mitutoyo Apochromatic NIR Objectives

NA = n_i × sinθ_a

Thorlabs Achromatic, MicroSpot^® UV Focusing Objectives