QUARTER WAVE PLATE, OPTICAL PICKUP DEVICE, AND REFLECTIVE LIQUID CRYSTAL DISPLAY DEVICE

• US 20100103084A1
• Filed: 10/22/2009
• Published: 04/29/2010
• Est. Priority Date: 10/27/2008
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Epson Toyocom Corporation (Seiko Group)
• Inventors: OTO, Masayuki
• Granted Patent: US 8,477,272 B2
• Time in Patent Office: Days
• US Class Current: 345/88
• CPC Class Codes: G02B 1/02 made of crystals, e.g. rock-salt, semi-conductors G02B1/08 takes precedence
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G03B 13/18 Focusing aids
• CPC Class Codes: G09G 3/001 using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background slide projectors per se G03B23/00 = 42 HP
• CPC Class Codes: G11B 7/1365 Separate or integrated refractive elements, e.g. wave plates
• CPC Class Codes: G11B 7/1369 Active plates, e.g. liquid crystal panels or electrostrictive elements
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

A quarter wave plate that is a crystal plate made of an inorganic material having birefringence and optical rotatory power and has an optical axis, includes an incident surface positioned on one surface of the crystal plate; and an emitting surface positioned on another surface, which is opposed to the incident surface, of the crystal plate. In the quarter wave plate, linearly-polarized light incident from the incident surface is converted into circularly-polarized light so as to be emitted from the emitting surface, and circularly-polarized light incident from the incident surface is converted into linearly-polarized light so as to be emitted from the emitting surface. Further, in the wave plate, an angle φ formed by a normal line on the incident surface and the optical axis is set in a range of 0°<φ<90°, and an optical axis azimuth angle θ formed by an optical axis projection line, which is formed by projecting the optical axis on the incident surface, and a polarization plane of the linearly-polarized light is set in one of a range of 0°<θ<90° under θ≠45° and a range of 90°<θ<180° under θ≠135°.

Claims

1. A quarter wave plate that is a crystal plate made of an inorganic material having birefringence and optical rotatory power and has an optical axis, comprising:

an incident surface positioned on one surface of the crystal plate; and

an emitting surface positioned on another surface, opposed to the incident surface, of the crystal plate, wherein

linearly-polarized light incident from the incident surface is converted into circularly-polarized light so as to be emitted from the emitting surface,

circularly-polarized light incident from the incident surface is converted into linearly-polarized light so as to be emitted from the emitting surface,

an angle φ

formed by a normal line on the incident surface and the optical axis is set in a range of 0°

<

φ

<

90°

, and

an optical axis azimuth angle θ

formed by an optical axis projection line, the optical axis projection line being formed by projecting the optical axis on the incident surface, and a polarization plane of the linearly-polarized light is set in one of a range of 0°

<

θ

<

90°

under θ

≠

45° and

a range of 90°

<

θ

<

180°

under θ

≠

135°

.

2. The quarter wave plate according to claim 1, wherein the crystal plate is made of quartz crystal;

when the quartz crystal is right-handed quartz crystal, the optical axis azimuth angle θ

is set as 0°

<

θ

<

45° and

phase difference Γ

due to the birefringence of the quartz crystal is set as Γ

>

90°

; and

when the quartz crystal is left-handed quartz crystal, the optical axis azimuth angle θ

is set as 45°

<

θ

<

90° and

the phase difference Γ

due to the birefringence of the quartz crystal is set as Γ

<

90°

.

3. The quarter wave plate according to claim 1, wherein the crystal plate is made of quartz crystal;

when the quartz crystal is right-handed quartz crystal, the optical axis azimuth angle θ

is set as 90°

<

θ

<

135° and

phase difference Γ

due to the birefringence of the quartz crystal is set as Γ

>

90°

; and

when the quartz crystal is left-handed quartz crystal, the optical axis azimuth angle θ

is set as 135°

<

θ

<

180° and

the phase difference Γ

due to the birefringence of the quartz crystal is set as Γ

<

90°

.

4. The quarter wave plate according to claim 2, wherein when the optical axis azimuth angle θ

is set as θ

=45°

−

a and the phase difference Γ

is set as Γ

=90°

+b in a case where the quartz crystal is right-handed quartz crystal under the angle φ

set in a range of 5°

≦

φ

≦

30°

, and when the optical axis azimuth angle θ

is set as θ

=45°

+a and the phase difference Γ

is set as Γ

=90°

−

b in a case where the quartz crystal is left-handed quartz crystal under the angle φ

set in a range of 5°

≦

φ

≦

30°

, 1°

≦

a≦

30° and

0°

≦

b≦

12°

are satisfied.

5. The quarter wave plate according to claim 3, wherein when the optical axis azimuth angle θ

is set as θ

=135°

−

a and the phase difference Γ

is set as Γ

=90°

+b in a case where the quartz crystal is right-handed quartz crystal under the angle φ

set in a range of 5°

≦

φ

≦

30°

, and when the optical axis azimuth angle θ

is set as θ

=135°

+a and the phase difference Γ

is set as Γ

=90°

−

b in a case where the quartz crystal is left-handed quartz crystal under the angle φ

set in a range of 5°

≦

φ

≦

30°

, 1°

≦

a≦

30° and

0°

≦

b≦

12°

are satisfied.

6. The quarter wave plate according to claim 4, wherein the a and the b respectively satisfy Formula 1 and Formula 2:

7. An optical pickup device, comprising:

a light source;

an objective lens focusing light emitted from the light source on a recording medium;

a detector detecting light reflected by the recording medium; and

the quarter wave plate, according to claim 1, disposed on an optical path between the light source and the objective lens.

8. A reflective liquid crystal display device, comprising:

a light source;

a color separation optical system separating light emitted from the light source into a plurality of light having different colors from each other;

a plurality of polarization conversion elements allowing the respective light of different colors received from the color separation optical system to pass therethrough;

a plurality of polarization beam splitters allowing the respective light having passed through the polarization conversion elements to pass therethrough;

a plurality of reflective liquid crystal display elements on which the light respectively having passed through the polarization beam splitters are made incident;

a color mixing optical system mixing the light respectively reflected by the reflective liquid crystal display elements;

a projection lens projecting light, the light being obtained by the mixture of the color mixing optical system, so as to form an image; and

a plurality of quarter wave plates, according to claim 1, disposed on respective optical paths between the reflective liquid crystal display elements and the polarization beam splitters.