Laser beam intensity adjustment method and laser beam intensity adjustment apparatus
An apparatus for emitting an incident laser beam that is a linearly polarized laser beam at a predetermined intensity, includes: an intensity changing optical element (polarization beam splitter) disposed on the optical path of the incident laser beam, for changing the intensity of an outgoing laser beam by allowing a transmission of a component of the incident laser beam polarized in a predetermined variable transmission direction and to rotate around the optical axis of the incident laser beam within a range of at least 90° with respect to a predetermined reference angle; and a polarization direction changing optical element (concave lens) disposed upstream the optical path of the incident laser beam with respect to the intensity changing optical element, and for changing the polarization direction of the incident laser beam and to emit the incident laser beam, the change direction being variable.
1 . A laser beam intensity adjustment method for emitting an incident laser beam that is a linearly polarized laser beam at a predetermined intensity, the laser beam intensity adjustment method comprising steps of:
disposing an intensity changing optical element on an optical path of the incident laser beam, the intensity changing optical element being configured to change an intensity of an outgoing laser beam by allowing a transmission of a component of the incident laser beam polarized in a predetermined transmission direction and to rotate around an optical axis of the incident laser beam within a range of at least 90° with respect to a predetermined reference angle, the transmission direction being variable;
disposing a polarization direction changing optical element upstream the optical path of the incident laser beam with respect to the intensity changing optical element, the polarization direction changing optical element being configured to change a polarization direction of the incident laser beam and to emit the incident laser beam; and
rotating the polarization direction changing optical element such that the polarization direction of the incident laser beam emitted from the polarization direction changing optical element coincides with the transmission direction when a rotation angle of the intensity changing optical element is at the predetermined reference angle,
wherein the predetermined reference angle is an angle at which the polarization direction of the incident laser beam coincides with the transmission direction of the intensity changing optical element when the incident laser beam enters the intensity changing optical element without passing through the polarization direction changing optical element.
2 . The laser beam intensity adjustment method according to claim 1 , wherein the polarization direction changing optical element is a concave lens.
3 . The laser beam intensity adjustment method according to claim 1 , wherein the intensity changing optical element is a polarization beam splitter.
4 . A laser beam intensity adjustment apparatus for emitting an incident laser beam that is a linearly polarized laser beam at a predetermined intensity, the laser beam intensity adjustment apparatus comprising:
an intensity changing optical element disposed on an optical path of the incident laser beam, configured to change an intensity of an outgoing laser beam by allowing a transmission of a component of the incident laser beam polarized in a predetermined transmission direction, and configured to rotate around an optical axis of the incident laser beam within a range of at least 90° with respect to a predetermined reference angle, the transmission direction being variable;
a polarization direction changing optical element disposed upstream the optical path of the incident laser beam with respect to the intensity changing optical element, and configured to change a polarization direction of the incident laser beam and to emit the incident laser beam; and
a polarization direction changing optical element rotation mechanism configured to rotate the polarization direction changing optical element such that the polarization direction of the incident laser beam emitted from the polarization direction changing optical element coincides with the transmission direction when a rotation angle of the intensity changing optical element is at the predetermined reference angle;
wherein the predetermined reference angle is an angle at which the polarization direction of the incident laser beam coincides with the transmission direction of the intensity changing optical element when the incident laser beam enters the intensity changing optical element without passing through the polarization direction changing optical element.
5 . The laser beam intensity adjustment apparatus according to claim 4 , wherein the polarization direction changing optical element is a concave lens.
6 . The laser beam intensity adjustment apparatus according to claim 4 , wherein the intensity changing optical element is a polarization beam splitter.
7 . A mass spectrometer, comprising:
the laser beam intensity adjustment apparatus according to claim 4 ; and
a sample holding unit disposed on an optical path of the laser beam transmitted through the intensity changing optical element, and configured to hold a sample to be analyzed.