Light guide plate and virtual image display device equipped with the same

Patent metadata

Field	Value
Publication number	US-9291822-B2
Application number	US-201113272548-A
Country	US
Kind code	B2
Filing date	Oct 13, 2011
Priority date	Oct 21, 2010
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

The sizes of the respective reflecting units vary in the image take-out section along the Z direction in association with the state of the total reflection angle in the light guide section. Thus, it becomes possible to keep the sufficient effective light beam width of the image light input thereto in all of the reflecting units. Therefore, the deterioration in the image light caused by the reflection in the reflecting units can be avoided, and as a result, the degradation of the resolution of the image due to the virtual image light thus emitted can be prevented.

First claim

What is claimed is:

1. A light guide plate comprising:
a light entrance section adapted to take in an image light inside, and project the image light into a plurality of light rays travelling in different directions;
a light guide section having a first total reflection surface and a second total reflection surface extending so as to be opposed to each other, and adapted to guide the image light taken in from the light entrance section by total reflection on the first total reflection surface and the second total reflection surface;
an image take-out section comprising:
a plurality of reflecting units arranged in a predetermined arranging direction, and adapted to make it possible to take out the image light, which enters via the light guide section, to an outside by a bend of a light path in the plurality of reflecting units,
a first reflecting unit adapted to perform the bend of the light path on the image light having a relatively large total reflection angle, and
a second reflecting unit adapted to perform the bend of the light path on the image light having a relatively small total reflection angle,

a reflecting surface of the first reflecting unit being larger than a reflecting surface of the second reflecting unit,
the first total reflection surface and the second total reflection surface extending from the light source guide section through the image take-out section, and the plurality of reflecting units of the image take-out section having a constant thickness H measured from the first total reflection surface, which forms an upper boundary portion of the plurality of reflecting units, to a line L connecting apexes K forming a lower boundary portion of the plurality of reflecting units, and
the plurality of reflecting units of the image take-out section having a varying thickness measured from the first total reflection surface to apexes P forming an upper boundary portion of the plurality of reflecting units, the plurality of reflecting units including a plurality of minute mirrors, each of the plurality of minute mirrors extending between a respective one of the plurality of apexes K and a respective one of the plurality of apexes P; and
a light emission section adapted to emit the image light, which passes through the image take-out section, to the outside,
shapes of reflecting surfaces of the plurality of reflecting units varying along the predetermined arranging direction in the image take-out section in accordance with a value of a total reflection angle of the image light, which is bent by the plurality of reflecting units, in the light guide section so as to prevent degradation of resolution of the image light,
a first light ray of the plurality of light rays being reflected by a closest reflection surface to the light entrance section, the first light ray having a maximum reflection angle with respect to the first total reflection surface and the second total reflection surface, and the closest reflection surface being the reflecting surface of the plurality of reflecting units that is closest to the light entrance section in the predetermined arranging direction, and
a second light ray of the plurality of light rays being reflected by a furthest reflection surface to the light entrance section, the second light ray having a minimum reflection angle with respect to the first total reflection surface and the second total reflection surface, and the furthest reflection surface being the reflecting surface of the plurality of reflecting units that is furthest from the light entrance section in the predetermined arranging direction.

2. A virtual image display device comprising:
the light guide plate according to claim 1 ; and
an image forming device adapted to form the image light to be guided by the light guide plate.

3. The light guide plate according to claim 1 , wherein
a distance from a light emission surface of the light emission section to a tip of each of the reflecting units of the image take-out section with respect to an emission direction of the image light bent is constant.

4. A virtual image display device comprising:
the light guide plate according to claim 3 ; and
an image forming device adapted to form the image light to be guided by the light guide plate.

5. The light guide plate according to claim 1 , wherein
sizes of the reflecting units vary so as to keep an effective light beam width of the image light entering each of the reflecting units in a value larger than a predetermined value.

6. A virtual image display device comprising:
the light guide plate according to claim 5 ; and
an image forming device adapted to form the image light to be guided by the light guide plate.

7. The light guide plate according to claim 1 , wherein
assuming that incident angles of light beams of the image light each entering two of the plurality of reflecting units of the image take-out section at respective angles different from each other are respectively α 1 , α 2 , and pitches of the two reflecting units, which the light beams of the image light enter, are respectively d 1 , d 2 ,
d 1 ≦d 2 is true if α 1 <α 2 is true.

8. A virtual image display device comprising:
the light guide plate according to claim 7 ; and
an image forming device adapted to form the image light to be guided by the light guide plate.

9. The light guide plate according to claim 1 , wherein
pitches of the plurality of reflecting units vary in a range of 0.5 mm through 1.3 mm.

10. A virtual image display device comprising:
the light guide plate according to claim 9 ; and
an image forming device adapted to form the image light to be guided by the light guide plate.

11. The light guide plate according to claim 1 , wherein
each reflecting unit constituting the plurality of reflecting units is mainly composed of a first reflecting surface and a second reflecting surface forming a predetermined angle with the first reflecting surface, and reflects the image light, which is guided by the light guide section, by the first reflecting surface, and further reflects the image light, which is reflected by the first reflecting surface, by the second reflecting surface to thereby perform the bend of the light path.

12. A virtual image display device comprising:
the light guide plate according to claim 11 ; and
an image forming device adapted to form the image light to be guided by the light guide plate.

13. The light guide plate according to claim 11 , wherein
a size of the reflecting unit located on an anti-light entrance section side distant from the light entrance section out of the plurality of reflecting units is larger than a size of the reflecting unit located on the light entrance section side.

14. A virtual image display device comprising:
the light guide plate according to claim 13 ; and
an image forming device adapted to form the image light to be guided by the light guide plate.

15. The light guide plate according to claim 11 , wherein
a pitch of the reflecting units located on an anti-light entrance section side distant from the light entrance section out of the plurality of reflecting units is larger than a pitch of the reflecting units located on the light entrance section side.

16. A virtual image display device comprising:
the light guide plate according to claim 15 ; and
an image forming device adapted to form the image light to be guided by the light guide plate.

17. A virtual image display device comprising:
the light guide plate according to claim 1 ; and
an image forming device adapted to form the image light to be gu

Assignees

• Totani Takahiro
• Takagi Masayuki
• Miyao Toshiaki
• Komatsu Akira
• Takeda Takashi
• Seiko Epson Corp

Inventors

• Totani Takahiro
• Takagi Masayuki
• Miyao Toshiaki
• Komatsu Akira
• Takeda Takashi

Classifications

• G02B6/0018

  Redirecting means on the surface of the light guide · CPC title

• G02B6/0038

  Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide · CPC title

• G02B27/0172 Primary

  characterised by optical features · CPC title

• G02B2027/0147

  comprising a device modifying the resolution of the displayed image · CPC title