Light modulating device

Patent metadata

Field	Value
Publication number	US-9772484-B2
Application number	US-201314647403-A
Country	US
Kind code	B2
Filing date	Nov 5, 2013
Priority date	Nov 29, 2012
Publication date	Sep 26, 2017
Grant date	Sep 26, 2017

Abstract

A light modulating device 103 includes: a selective diffraction device ( 10, 10 ′) which generates diffracted light beams of a plurality of orders by diffracting illumination light into one of a plurality of directions, the illumination light being linearly polarized light having a polarization plane oriented in a first polarization direction, and which causes a phase difference between the diffracted light beams of the plurality of orders; and a polarization plane rotating device 14 which rotates the polarization plane of the diffracted light beam of each order so as to be oriented in a direction perpendicular to a direction radiating from an optical axis.

First claim

The invention claimed is:

1. A light modulating device comprising:
a selective diffraction device which generates diffracted light beams of a plurality of orders by diffracting illumination light into one of a plurality of directions, the illumination light being linearly polarized light having a polarization plane oriented in a first polarization direction, and which causes a phase difference between the diffracted light beams of the plurality of orders;
a polarization plane rotating device which rotates the polarization plane of the diffracted light beams of the plurality orders so as to be oriented in a direction perpendicular to a direction radiating from an optical axis; and
a controller,
wherein the selective diffraction device includes:
a diffractive device which diffracts the illumination light into the plurality of directions;
a shutter device through which the diffracted light beams of the plurality of orders diffracted in the one of the plurality of directions are allowed to pass; and
a phase modulating device which includes at least one first liquid crystal device for causing a phase difference between the diffracted light beams of the plurality of orders passed through the shutter device, each of the at least one first liquid crystal device including a first liquid crystal layer on which the diffracted light beams of the plurality of orders passed through the shutter device are incident,
wherein the shutter device includes:
a second liquid crystal device which includes a second liquid crystal layer; and
an analyzer which is disposed nearer the phase modulating device than the second liquid crystal device is, and which allows linearly polarized light having a polarization plane oriented in a second polarization direction among the diffracted light beams passing through the second liquid crystal device to pass through, while blocking linearly polarized light having a polarization plane oriented in a direction other than the second polarization direction among the diffracted light beams passing through the second liquid crystal device, and wherein:
the second liquid crystal layer contains liquid crystal molecules aligned in a direction that bisects an angle that the first polarization direction makes with the second polarization direction, and
the shutter device allows the diffracted light beams of the plurality of orders diffracted in the one of the plurality of directions to pass through by applying a predetermined voltage in response to the wavelength of the illumination light across a sub-region of the second liquid crystal layer through which the diffracted light beams pass, to rotate the polarization plane of the diffracted light beams passing through the sub-region so as to be oriented in parallel to the second polarization direction, and
wherein the controller changes the sub-region of the second liquid crystal layer to which the predetermined voltage is applied when the one of the plurality of directions is changed.

2. The light modulating device according to claim 1 , wherein the first liquid crystal layer contains liquid crystal molecules aligned in parallel with the polarization direction of the diffracted light beams of the plurality of orders passed through the shutter device, and wherein
a phase difference proportional to a difference between a first voltage applied to a first sub-region of the first liquid crystal layer through which a diffracted light beam of a first order among the diffracted light beams of the plurality of orders passes and a second voltage applied to a second sub-region of the first liquid crystal layer through which a diffracted light beam of a second order among the diffracted light beams of the plurality of orders passes is caused between the diffracted light beam of the first order and the diffracted light beam of the second order.

3. The light modulating device according to claim 1 , wherein the phase modulating device includes two liquid crystal devices, each as the first liquid crystal device, which are arranged along the optical axis, and wherein
the first liquid crystal layer in each of the two first liquid crystal devices is chosen to have a thickness such that a maximum value of an optical path length difference that occurs between the diffracted light beam of the first order and the diffracted light beam of the second order while passing through the first liquid crystal layer is less than the wavelength of the illumination light.

4. The light modulating device according to claim 1 , wherein the polarization plane rotating device includes a third liquid crystal device which includes a third liquid crystal layer which contains liquid crystal molecules aligned in a direction that bisects an angle that the polarization plane of the diffracted light beams of the plurality of orders emitted from the selective diffraction device makes with the direction perpendicular to the radiating direction, and wherein
when a predetermined voltage proportional to the wavelength of the illumination light is applied across the third liquid crystal layer in the third liquid crystal device, the polarization plane of the diffracted light beams of the plurality of orders passing through the third liquid crystal layer is rotated so as to be oriented in the direction perpendicular to the radiating direction.

5. The light modulating device according to claim 1 , wherein the polarization plane rotating device includes an azimuth polarization converting device by which linearly polarized light having a polarization plane parallel to the polarization plane of the diffracted light beams of the plurality of orders emitted from the selective diffraction device is converted into azimuthally polarized light.

6. A light modulating device comprising:
a selective diffraction device which generates diffracted light beams of a plurality of orders by diffracting illumination light into one of a plurality of directions, the illumination light being linearly polarized light having a polarization plane oriented in a first polarization direction, and which causes a phase difference between the diffracted light beams of the plurality of orders; and
a polarization plane rotating device which rotates the polarization plane of the diffracted light beams of the plurality orders so as to be oriented in a direction perpendicular to a direction radiating from an optical axis; and
a controller,
wherein the selective diffraction device includes:
a first liquid crystal device which displays a diffraction grating for diffracting the illumination light into a selected one of the plurality of directions and for causing a phase difference between the diffracted light beams of the plurality of orders, the first liquid crystal device including a first liquid crystal layer on which the illumination light is incident; and
a shutter device which the diffracted light beams of the plurality of orders diffracted in the selected one of the plurality of directions are allowed to pass, wherein the shutter device includes:
a second liquid crystal device which includes a second liquid crystal layer; and
an analyzer which is disposed nearer the phase modulating device than the second liquid crystal device is, and which allows linearly polarized light having a polarization plane oriented in a second polarization direction among the diffracted light beams passing through the second liquid crystal device to pass through, while blocking linearly polarized light having a polarization plane oriented in a direction other than the second polarization direction among the diffracted light beams passing through the second liquid crystal device, and wherein:
the second liquid crystal layer contains liquid crystal molecules aligned in a direction that bisects an angle that the first polarization direction make

Assignees

• Citizen Watch Co Ltd

Inventors

• Matsumoto Kenji
• Hashimoto Nobuyuki
• Kurihara Makoto
• Yokoyama Masafumi
• Tanabe Ayano

Classifications

• G02B27/4205

  having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant · CPC title

• G02B21/082 Primary

  for incident illumination only · CPC title

• G02B27/425

  in illumination systems (mask illumination systems in photolithographic systems G03F7/70158) · CPC title

• G02B5/1871

  Transmissive phase gratings · CPC title

• G02F1/1335

  Structural association of cells with optical devices, e.g. polarisers or reflectors · CPC title