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Long Working Distance Objectives

  • Plan Apochromat Objectives
  • 5X, 10X, 20X, or 100X Magnification
  • Infinity-Corrected Design for Visible Light
  • Ideal for Machine Vision Applications



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Protective Accessories
Case Lid: OC2M26
Canister: OC24


  • Long Working Distance Ideal for Machine Vision Applications
  • Plan Apochromat Design
    • Chromatic Correction at Three Wavelengths
    • Spherical Correction at Two Wavelengths
  • Infinity-Corrected for Visible Wavelengths
  • Designed for a Tube Lens Focal Length of 200 mm
  • M26 x 0.706 Threading

Thorlabs offers Mitutoyo Plan Apochromat Objectives with 5X, 10X, 20X, or 100X magnification. These plan apochromat objectives feature chromatic correction at three wavelengths and spherical correction at two wavelengths to provide a flat field of view. The long working distance provides a wide space between the lens surface and the object. See the Objective Tutorial tab for more information about this objective type. Designed for a tube lens focal length of 200 mm, these objectives are ideal for machine vision applications or any application that requires a significant distance between the objective lens and the object. See the Specs tab for details on each of the objectives available here.

The objective housings are engraved with the magnification and the numerical aperture. The housings have external M26 x 0.706 threads. The objectives can be integrated into an SM1 lens tube system with the use of an SM1A27 adapter. These objectives do not feature adjustment to correct for cover glass thickness and should be used without a cover slip.

These Mitutoyo objectives have a parfocal length of 95 mm (see the Specs tab for complete specifications). To use these objectives 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 an Nikon objective from 60 mm to 95 mm.

Magnification 5X 10X 20X 100X
Item # MY5X-802 MY10X-803 MY20X-804 MY100X-806
Manufacturer Part # 378-802-6 378-803-3 378-804-3 378-806-3
Numerical Aperture (NA) 0.14 0.28 0.42 0.70
Field Number (FN) 24 24 24 24
Working Distance (WD) 34.0 mm 34.0 mm 20.0 mm 6.0 mm
Lengtha 66.0 mm 66.0 mm 80.0 mm 94.0 mm
Compatible Tube Lens Focal Length 200 mm
Parfocal Lengtha 95 mm
Diametera 34.0 mm
Threading M26 x 0.706b
  • These dimensions are defined in the drawing to the right.
  • An SM1A27 adapter allows an M26 x 0.706 objective to be used with our SM1 lens tubes.

Dimensional Drawing

Olympus Objective Dimensional Drawing

Objective Identification

Click to Enlarge

Note: This microscope objective serves only as an example. The format of the engraved specifications will vary between objectives and manufacturers.

Magnification Color Codes
Immersion Media Color Codes

Thorlabs offers plan apochromat objectives from Mitutoyo. 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 Apochromat Objectives
"Plan" designates that these objectives produce a flat image across the field of view. "Apochromat" refers to the correction for chromatic aberration featured in the lens design. These apochromat objectives have chromatic correction for three wavelengths and spherical correction at two wavelengths. In white light, plan apochromats give better images for color photomicrography than achromat objectives.

These objectives do not feature adjustment to correct for cover glass thickness and should be used without a cover slip.

Glossary of Terms

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

Posted Comments:
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.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
MY5X-802 Support Documentation
MY5X-802Customer Inspired! 5X Mitutoyo Plan Apochromat Objective, 0.14 NA, 34 mm WD
MY10X-803 Support Documentation
MY10X-803Customer Inspired! 10X Mitutoyo Plan Apochromat Objective, 0.28 NA, 34 mm WD
MY20X-804 Support Documentation
MY20X-804Customer Inspired! 20X Mitutoyo Plan Apochromat Objective, 0.42 NA, 20 mm WD
MY100X-806 Support Documentation
MY100X-806Customer Inspired! 100X Mitutoyo Plan Apochromat Objective, 0.70 NA, 6 mm WD
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