Conversion method, optical device, and optical microscope

A conversion method comprising

• converting a repetition frequency of pulsed light emitted from a light source by a converter, and
• allowing the repetition frequency converted by the converter to be variable,
• wherein the conversion of the repetition frequency by the converter includes
• a first stage for changing a polarization direction of the pulsed light to a first direction via a half-wave plate,
• a second stage for splitting the pulsed light polarized in the first direction into a first polarized light and a second polarized light orthogonal to the first polarized light,
• a third stage for imparting a predetermined optical-path-length difference between the first polarized light and the second polarized light, and
• a fourth stage for generating the pulsed light the repetition frequency of which is changed by combining the first polarized light and the second polarized light after the impartation of the predetermined optical-path-length difference,
• wherein the converter converts the repetition frequency by a factor of 2n (where n is an integer greater than or equal to one) by executing n iterations a series of processes including the first stage, the second stage, the third stage, and the fourth stage, and
• wherein, among the n iterations, the second stage of an odd-numbered iteration and the fourth stage of an even-numbered iteration are performed by a first polarizing beam splitter, and the fourth stage of the odd-numbered iteration and the second stage of the even-numbered iteration are performed by a second polarizing beam splitter different from the first polarizing beam splitter.

A conversion method comprising

• converting a repetition frequency of pulsed light emitted from a light source by a converter, and
• allowing the repetition frequency converted by the converter to be variable,
• wherein the conversion of the repetition frequency by the converter includes
• a first stage for changing a polarization direction of the pulsed light to a first direction via a half-wave plate,
• a second stage for splitting the pulsed light polarized in the first direction into a first polarized light and a second polarized light orthogonal to the first polarized light,
• a third stage for imparting a predetermined optical-path-length difference between the first polarized light and the second polarized light, and
• a fourth stage for generating the pulsed light the repetition frequency of which is changed by combining the first polarized light and the second polarized light after the impartation of the predetermined optical-path-length difference,
• wherein the converter converts the repetition frequency by a factor of 2n (where n is an integer greater than or equal to one) by executing n iterations a series of processes including the first stage, the second stage, the third stage, and the fourth stage,
• wherein the second stage and the fourth stage are performed by a single polarizing beam splitter,
• wherein the first polarized light is P-polarized light, and the second polarized light is S-polarized light,
• wherein a first quarter-wave plate is installed in an optical path of the P-polarized light, and a second quarter-wave plate is installed in an optical path of the S-polarized light,
• wherein, in the third stage, the P-polarized light passes through the first quarter-wave plate twice, and the S-polarized light passes through the second quarter-wave plate twice, and
• wherein, a position at which the P-polarized light passes through the first quarter-wave plate in the third stage in each iteration of the n iterations differs from that in other iteration, and a position at which the S-polarized light passes through the second quarter-wave plate in the third stage in each iteration of the n iterations differs from that in other iteration.

An optical device comprising

• a converter that converts a repetition frequency of a pulsed light by a factor of 2n (where n is an integer greater than or equal to one), and
• a switcher capable of changing the repetition frequency converted by the converter,
• wherein the converter includes n units of optical units,
• wherein the optical unit includes
• a first polarizing beam splitter that splits the pulsed light polarized in the first direction into a first polarized light and a second polarized light orthogonal to the first polarized light,
• an optical-path-length-difference imparter that imparts a predetermined optical-path-length difference between the first polarized light and the second polarized light, and
• a second polarizing beam splitter that forms the pulsed light the repetition frequency of which is changed by combining the first polarized light and the second polarized light after impartation of the predetermined optical-path-length difference, and
• wherein the switcher changes the polarization direction of the pulsed light incident on the first polarizing beam splitter to either the first direction or a second direction different from the first direction, and
• wherein a single polarizing beam splitter is used as, among the n units of the optical units, the first polarizing beam splitter that is odd-numbered and the second polarizing beam splitter that is even-numbered.

An optical device comprising

• a converter that converts a repetition frequency of a pulsed light by a factor of 2n (where n is an integer greater than or equal to one), and
• a switcher capable of changing the repetition frequency converted by the converter,
• wherein the converter includes n units of optical units,
• wherein the optical unit includes
• a first polarizing beam splitter that splits the pulsed light polarized in the first direction into a first polarized light and a second polarized light orthogonal to the first polarized light,
• an optical-path-length-difference imparter that imparts a predetermined optical-path-length difference between the first polarized light and the second polarized light, and
• a second polarizing beam splitter that forms the pulsed light the repetition frequency of which is changed by combining the first polarized light and the second polarized light after impartation of the predetermined optical-path-length difference, and
• wherein the switcher changes the polarization direction of the pulsed light incident on the first polarizing beam splitter to either the first direction or a second direction different from the first direction,
• wherein a single polarizing beam splitter is used as the first polarizing beam splitter and the second polarizing beam splitter,
• wherein a first quarter-wave plate is installed in an optical path of the P-polarized light, and a second quarter-wave plate is installed in an optical path of the S-polarized light,
• wherein, in a process of imparting the predetermined optical-path-length difference, the P-polarized light passes through the first quarter-wave plate twice, and the S-polarized light passes through the second quarter-wave plate twice, and
• wherein, a position at which the P-polarized light passes through the first quarter-wave plate in each of the n units of the optical units differs from that in other of the n units of the optical units, and a position at which the S-polarized light passes through the second quarter-wave plate in each of the n units of the optical units differs from that in other of the n units of the optical units.