.. auto-generated by script ../../../../utils/nxdl2rst.py from the NXDL source NXoptical_system_em.nxdl.xml

.. index::
    ! NXoptical_system_em (base class)
    ! optical_system_em (base class)
    see: optical_system_em (base class); NXoptical_system_em

.. _NXoptical_system_em:

===================
NXoptical_system_em
===================

**Status**:

  base class, extends :ref:`NXobject`

**Description**:

  A container for qualifying an electron optical system.

**Symbols**:

  No symbol table

**Groups cited**:
  none

**Structure**:

  .. _/NXoptical_system_em/camera_length-field:

  .. index:: camera_length (field)

  **camera_length**: (optional) :ref:`NX_NUMBER <NX_NUMBER>` {units=\ :ref:`NX_LENGTH <NX_LENGTH>`}

    Citing the JEOL TEM glossary this is *an effective distance from a specimen
    to a plane where an observed diffraction pattern is formed*.

  .. _/NXoptical_system_em/magnification-field:

  .. index:: magnification (field)

  **magnification**: (optional) :ref:`NX_NUMBER <NX_NUMBER>` {units=\ :ref:`NX_DIMENSIONLESS <NX_DIMENSIONLESS>`}

    The factor of enlargement of the apparent size, not physical size, of an object.

  .. _/NXoptical_system_em/defocus-field:

  .. index:: defocus (field)

  **defocus**: (optional) :ref:`NX_NUMBER <NX_NUMBER>` {units=\ :ref:`NX_LENGTH <NX_LENGTH>`}

    The defocus aberration constant oftentimes taken as the C_1_0 which
    is described in more details in NXaberration.

  .. _/NXoptical_system_em/semi_convergence_angle-field:

  .. index:: semi_convergence_angle (field)

  **semi_convergence_angle**: (optional) :ref:`NX_NUMBER <NX_NUMBER>` {units=\ :ref:`NX_ANGLE <NX_ANGLE>`}

    Citing the JEOL TEM glosssary this is the value *when a cone shaped,
    convergent electron beam illuminates a specimen, the semi-angle of the cone
    is termed convergence angle.*

  .. _/NXoptical_system_em/field_of_view-field:

  .. index:: field_of_view (field)

  **field_of_view**: (optional) :ref:`NX_NUMBER <NX_NUMBER>` {units=\ :ref:`NX_LENGTH <NX_LENGTH>`}

    The extent of the observable parts of the specimen given the current
    magnification and other settings of the instrument.

  .. _/NXoptical_system_em/working_distance-field:

  .. index:: working_distance (field)

  **working_distance**: (optional) :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_LENGTH <NX_LENGTH>`}

    Citing `Globalsino <https://www.globalsino.com/EM/page4586.html>`_ this is
    *a distance between the specimen and the lower pole piece in SEM system*.

  .. _/NXoptical_system_em/beam_current-field:

  .. index:: beam_current (field)

  **beam_current**: (optional) :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_CURRENT <NX_CURRENT>`}

    Beam current as measured relevant for the illumination of the specimen.
    Users should specify further details like how the beam current was measured
    using the beam_current_description field.

  .. _/NXoptical_system_em/beam_current_description-field:

  .. index:: beam_current_description (field)

  **beam_current_description**: (optional) :ref:`NX_CHAR <NX_CHAR>`

    Specify further details how the beam current was measured or estimated.


Hypertext Anchors
-----------------

List of hypertext anchors for all groups, fields,
attributes, and links defined in this class.


* :ref:`/NXoptical_system_em/beam_current-field </NXoptical_system_em/beam_current-field>`
* :ref:`/NXoptical_system_em/beam_current_description-field </NXoptical_system_em/beam_current_description-field>`
* :ref:`/NXoptical_system_em/camera_length-field </NXoptical_system_em/camera_length-field>`
* :ref:`/NXoptical_system_em/defocus-field </NXoptical_system_em/defocus-field>`
* :ref:`/NXoptical_system_em/field_of_view-field </NXoptical_system_em/field_of_view-field>`
* :ref:`/NXoptical_system_em/magnification-field </NXoptical_system_em/magnification-field>`
* :ref:`/NXoptical_system_em/semi_convergence_angle-field </NXoptical_system_em/semi_convergence_angle-field>`
* :ref:`/NXoptical_system_em/working_distance-field </NXoptical_system_em/working_distance-field>`

**NXDL Source**:
  https://github.com/nexusformat/definitions/blob/main/base_classes/NXoptical_system_em.nxdl.xml