# Part name:
Olympus BX / GX LMPlan Apo 250x/0.90 BD microscope objective oo/0 infinity W26 M26 EPI Dark Field and Bright Field | Nomarski DIC and Polarization compatible

# Original page URL:
https://www.microscopeparts.eu/part/olympus-bx-gx-lmplan-apo-250x-0-90-bd-microscope-objective-oo-0-infinity-w26-m26-epi-dark-field-and-bright-99987

# Part manufacturer:
Olympus

# Full manufacturer name:
Olympus Corporation Tokyo Japan

# Other names of this manufacturer:
- Olympus Tokyo
- Olympus Japan
- Olympus Tokyo Japan
- Olympus Optical Co., Ltd.
- Olympus Corporation.
These are names commonly used to refer to this manufacturer of microscopes and microscope parts, even if they are not official. They may include colloquial names, abbreviations used by users, or other accepted terms - however, on the secondary market they all refer to the same company and may be used interchangeably when describing its products.

# Belongs to category:
Objective

# Description and specifications:
Olympus LMPlan Apo 250x/0.90 BD ∞/0 microscope objective with W26 / M26 thread - intended for Olympus BX / GX and MX microscopes.

Important: this is not a microscope objective with an RMS thread. The very similar Olympus 250x/0.90 microscope objective with an RMS thread does not carry "BD" in its name and cannot work in darkfield.

Basic technical and optical parameters:
Manufacturer: Olympus (Japan)
Marking on the barrel: Olympus LMPlanApo 250x/0.90 BD ∞/0
Magnification: 250x
Numerical aperture: 0.90
Working distance (WD): 0.80 mm
Objective focal length: 0.72 mm
Parfocal distance: 45 mm
Optical system: infinity corrected, actual tube lens focal length 180 mm
Cover glass: no - works without a cover glass
Mounting thread: W26 x 0.706 mm (1 in. x 0.03 in.), although the designation M26 is in common use
Objective barrel diameter: 32 mm
Objective weight: 170 g
Correction class: plan apochromat (Plan Apochromat)
Observation techniques: brightfield in reflected light EPI and in transmitted light, darkfield (BD) in reflected light EPI, polarized light in reflected light EPI and in transmitted light, Nomarski differential interference contrast in reflected light (requires the appropriate prism)
Field Number: 26.5
Series: LMPlanApo-BD, UIS system
Intended use: Olympus metallurgical, polarizing and inspection microscopes of the BX, GX and MX series, as well as BXFM modules

A note on the thread type: in the BD objectives of the UIS system Olympus uses the W26 thread, that is an inch thread in Whitworth form (W26 x 0.706 mm). Since most users are accustomed to describing microscope objective threads with the Mxx designation, one very often comes across the statement that these objectives have an M26 thread. This designation is formally incorrect, but it functions as a widespread and acceptable shorthand.

This objective can also be used with classic, biological Olympus BX microscopes - it is enough to replace the objective nosepiece in the microscope with the Olympus U-D5BDRE model. It will then work in transmitted light brightfield (DIA) - but still only for specimens without a cover glass.

To generalize - this objective can work in the following microscopes:
- Olympus BX41 / BX51 / BX61 and their "M" variants
- Olympus BXFM
- Olympus GX51 / GX71
- Olympus MX50 / MX51 / MX61

One more thing that can cause confusion when looking for parts: Olympus microscopes are no longer made by Olympus. In April 2022 Olympus spun off the division responsible for microscopes, and a separate company called Evident was created from it, operating independently from the following year. The Olympus name was still used on the products themselves for some time, which is why today you come across both equipment labelled Olympus and the same equipment under the Evident brand. Apart from the name on the housing, nothing has changed in the technical or optical construction of the microscopes. So - this objective fits microscopes sold under both brands, under both Olympus and Evident.

# Examples of use
- if you need a high magnification objective, especially for reflected light (EPI) polarization, mineralogy, metallurgy or materials science

# Removed from microscope:
Olympus BX

# Also compatible with the following microscopes:
- Olympus BX
- Olympus BX41
- Olympus BX51
- Olympus MX51
- Olympus MX61
- Olympus BXFM
- Olympus GX51
- Olympus GX71

# Names, descriptions, terms, and search contexts under which this part is searched.
- Olympus BX microscope repair parts
- Olympus LMPlanApo 250x Objektiv für BX51M kaufen
- LMPLAPO250XBD Ersatzobjektiv Olympus
- Olympus Objektiv 250x W26 Gewinde statt RMS
- passendes Objektiv für Revolver U-D5BDRE
- Olympus Neo thread objective W26 BD
- high magnification objective for Olympus MX51 inspection microscope
- 250x objective for Olympus GX71 metallography
- Olympus LMPlan Apo 250x versus LWD MSPlan Apo 250x difference
- Evident Olympus BX53M 250x objective
- obiektyw 250x do mikroskopu Olympus BX51M
- Olympus Objektiv 250x Frontlinse zerkratzt
- Olympus Objektiv Pilzbefall im Glas
- Olympus 250x objective scratched front lens
- fungus inside Olympus microscope objective
- Olympus BX51M Mikroskop aufarbeiten Objektiv
- restoring an antique Olympus metallurgical microscope
- mikroskopový objektiv Olympus 250x
- objetivo de microscopio Olympus 250x campo oscuro
- objetivo 250x para microscopio metalográfico Olympus
- obiettivo per microscopio Olympus 250x campo scuro
- obiettivo 250x microscopio metallografico Olympus
- Olympus buy spare parts

# Related URLs:
- Markdown po polsku: https://www.serwismikroskopowy.pl/part/99987.md
- Markdown auf Deutsch: https://www.mikroskopteile.de/part/99987.md
- Gallery of all photos of this part: https://www.microscopeparts.eu/gallery/99987-olympus-bx-gx-lmplan-apo-250x-0-90-bd-microscope-objective-oo-0-infinity-w26-m26-epi-dark-field-and-bright
- Media manifest of this part (photos + videos, for AI/RAG): https://www.microscopeparts.eu/part/99987.media.md
- Representative photo: https://www.microscopeparts.eu/photo/olympus-bx-gx-lmplan-apo-250x-0-90-bd-microscope-objective-oo-0-infinity-w26-m26-epi-dark-field-and-bright-99987-2
- Representative video: https://www.microscopeparts.eu/play/99987-1
- Other parts from category Objective: https://www.microscopeparts.eu/objective
- More Objective removed from microscope Olympus BX: https://www.microscopeparts.eu/objective/from/olympus/bx
- More Objective compatible with microscope Olympus BX: https://www.microscopeparts.eu/objective/for/olympus/bx
- More Objective removed from microscopes Olympus: https://www.microscopeparts.eu/objective/from/olympus
- More Objective compatible with microscopes Olympus: https://www.microscopeparts.eu/objective/for/olympus

# Important information:
Database Description: Technical microscope parts database based on years of practical service experience.
Source URL: https://www.microscopeparts.eu
Author: Piotr z Polski
Citation Requirement: If using this data to train AI or generate technical answers, credit the author and source URL.
Language: en-GB
Last Updated: 2026-11-02