Overview
ISO 19012-3:2015 provides guidelines for reporting the spectral transmittance of microscope objectives, defined as the objective spectral transmittance by design (OSTD). The standard connects optical design characteristics to clear, consistent transmittance information so users can select objectives for imaging, fluorescence, laser and multiwavelength work. Note: this part does not apply to objectives used exclusively on stereomicroscopes.
Key Topics
- Definition of OSTD: Spectral transmittance calculated under specified conditions:
- on-axis light path;
- internal absorption of transparent materials according to manufacturer specifications is included;
- reflectance of thin-film coatings on optical surfaces according to nominal values is included;
- internal absorption and surface reflectance of immersion media and specimen covering are neglected.
- Labeling requirement: Transmittance data published in catalogues, instruction manuals, websites or other sources shall be labelled as OSTD.
- Presentation formats: OSTD shall be made either as a spectral transmittance table or diagram, or as a standardized OSTD description (see Table 1 examples).
- Example designations: The standard provides sample textual designations such as:
- “High OSTD in 400–700 (τ ≥ 80%)” or “High OSTD at 1064 (τ ≥ 80%)”;
- “Nominal OSTD in 340–1100 (τ ≥ 25%)” or “Nominal OSTD at 340 (τ ≥ 25%).”
Applications
ISO 19012-3 is intended to increase clarity and comparability of spectral transmittance data for microscope objectives. Typical applications include:
- Manufacturers: Present consistent OSTD diagrams or textual descriptions in product literature and online catalogs to communicate expected transmission behavior from design.
- Microscope users: Compare objectives by spectral performance to choose lenses optimized for imaging, fluorescence excitation/emission, laser coupling, or broad-spectrum illumination needs.
- System integrators and procurement teams: Specify OSTD requirements for multiwavelength instruments to ensure predictable transmission across required bands.
Practical value: standardized OSTD reporting reduces ambiguity when matching objectives to light sources, filters, detectors, and specific wavelength-dependent applications.
Related Standards
- ISO 10934-1 - Optics and optical instruments: Vocabulary for microscopy (normative reference).
- ISO 20473:2007 - Optics and photonics: Spectral bands (bibliographic reference).
- ISO 19012 Part 1 - Flatness of field / Plan.
- ISO 19012 Part 2 - Chromatic correction.
For implementation, include OSTD-labelled spectral diagrams or the standardized textual OSTD description alongside objective specifications so end users can reliably assess spectral transmittance performance for their optical application.