Image display device

Patent metadata

Field	Value
Publication number	US-9817233-B2
Application number	US-201515508436-A
Country	US
Kind code	B2
Filing date	Aug 25, 2015
Priority date	Sep 3, 2014
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

The image display device ( 100 ) provides images perceivable from the area of the eye box (E), and includes a light source unit ( 110 ), a screen ( 140 ), a scanning unit ( 130 ) and an optical system ( 155 ). The screen ( 140 ) has a single micro lens array ( 1 ) on which multiple micro lenses ( 3 ) are arranged. The scanning unit ( 130 ) includes a mirror ( 130 a ) to reflect beams emitted from the light source unit ( 110 ), and swings the mirror ( 130 a ) around a pivot center ( 130 c ) to scan the beams thereover, thereby generating images. The optical system ( 155 ) brings the images formed on the screen ( 140 ) to the eye box (E). An angle (θ out ) formed between a zero-order diffracted beam and a first-order diffracted beam, which are among a luminous flux of beams diffracted by the screen ( 140 ) and pass through the center of the eye box (E), is smaller than a minimum visual angle (V min ).

First claim

The invention claimed is:

1. An image display device to allow an image to be visible from within an area of an eye box, the device comprising:
a light source to emit a beam;
a screen including a micro lens array formed by arranging multiple micro lenses, and
a scanner that includes a first mirror to reflect the beam emitted from the light source and that scans the beam to generate the image on the screen by swinging the first mirror,

wherein, in an optical path to direct the image on the screen to the eye box, an angle formed between a zero-order diffracted beam passing through the eye box center and a first-order diffracted beam passing through the eye box center, which are among a luminous flux of beams diffracted by the screen, is smaller than a minimum visual angle.

2. The image display device according to claim 1 , wherein the micro lens array is formed by repeatedly arranging a basic pattern lens group that is an area in which apexes of the micro lenses are randomly arranged.

3. The image display device according to claim 2 , further comprising a second mirror to direct the image on the screen to the eye box,
wherein,
under the following definitions:
a wavelength of the beam emitted from the light source being X;
an angle formed between a beam that enters the screen and corresponds to the zero-order diffracted beam to pass through the eye box center, and a beam that enters the screen and corresponds to the first-order diffracted beam to pass through the eye box center being θ 0 ;
a diffracted angle of the first-order diffracted beam from the micro lens array being θ in ;
a distance between the second mirror and the eye box being D 2 ;
a focal distance of the second mirror being f; and
a human eyesight being a,

within a range of

θ

i
⁢

⁢
n

<

f
-

D
2

f

·

1
a

·

1
60

·

2
⁢
π

360

⁡

[
rad
]

,

a repetition period L of the basic pattern lens groups that is an interval between micro lenses arranged at corresponding positions in adjoining basic pattern lens groups satisfies an expression of

L
>



λ

sin
⁢

⁢

θ

i
⁢

⁢
n

+

sin
⁢

⁢

θ
0



⁡

[
mm
]

.

4. The image display device according to claim 3 , wherein the repetition period of the basic pattern lens groups is larger than 0.36 mm.

5. The image display device according to claim 3 , wherein
the basic pattern lens groups are based on a primitive lattice which is a square lattice, and the apexes are randomly positioned;
the primitive lattice includes lattice cells comprising lattice cell points at their centers;
each of dividing lines between the adjoining basic pattern lens groups includes a straight line; and
apexes of multiple micro lenses adjoining to each other across the straight line in common are positioned line-symmetrically with respect to the shared straight line and are displaced to positions along straight lines passing through the lattice cell points parallelly to the shared straight line.

6. The image display device according to claim 5 , wherein
in the basic pattern lens groups, on the basis of a hexagonal primitive lattice, the apexes are randomly arranged with their displacement directions and amounts from respective lattice cell points being varied;
the primitive lattice includes the lattice cell points at centers of respective lattice cells;
a first reference line and a second reference line opposed to the first reference line are set over the hexagonal lattice;
the displacement directions and amounts are the same in first unit pattern areas that are positioned at corresponding positions on the first reference line and the second reference line;
the displacement directions and amounts are the same in second unit pattern areas that are positioned in a first side of a perpendicular direction to the first reference line, and in the first side of a perpendicular direction to the second reference line;
the displacement directions and amounts are the same in third unit pattern areas that are positioned in a second side of the perpendicular direction to the first reference line, and in the second side of the perpendicular direction to the second reference line; and
a dividing line between the adjoining basic pattern lens groups is set either to a boundary between each of the first unit pattern areas and each of the second unit pattern areas, or to a boundary between each of the first unit pattern areas and each of the third unit pattern areas.

7. The image display device according to claim 5 , wherein the screen includes multiple basic pattern lens groups that have different degrees in apex-positioning-randomness, or multiple basic pattern lens groups that have different diffusion angles in the micro lenses.

8. The image display device according to claim 3 , wherein
in the basic pattern lens groups, on the basis of a hexagonal primitive lattice, the apexes are randomly arranged with their displacement directions and amounts from respective lattice cell points being varied;
the primitive lattice includes the

Assignees

• Mitsubishi Electric Corp

Inventors

• Nakagawa Nozomi
• Nakahara Hironori
• Kishigami Tomo
• Takeshita Nobuo

Classifications

• G02B2027/0145

  creating an intermediate image · CPC title

• G02B27/0101 Primary

  characterised by optical features (G02B27/0172 takes precedence) · CPC title

• G02B2027/0154

  with movable elements · CPC title

• G02B2027/0114

  comprising dichroic elements · CPC title

• G02B3/0056

  arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses (G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085) · CPC title