Projection-type display apparatus

• US 7,281,805 B2
• Filed: 07/06/2004
• Issued: 10/16/2007
• Est. Priority Date: 07/22/2003
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Hasegawa, Masahide
• Primary Examiner(s): Sever; Andrew T
• Application Number:
  US10/886,116
• Publication Number:
  US 20050018148A1
• Time in Patent Office: 1,197 Days
• Field of Search: 353/74, 353/77, 353/78, 353/79, 353/80, 353/81, 353/98, 353/119, 359/443, 359/449, 359/453, 359/454, 359/456, 359/457, 359/459, 359/460, 348787-789, 348/794
• US Class Current: 353/77
• CPC Class Codes: G02B 27/0018 with means for preventing ghost images anti-reflection coatings G02B1/11
• CPC Class Codes: G02B 27/18 for optical projection, e.g. combination of mirror and condenser and objective photographic, cine and overhead projectors G03B21/00; photographic projection printing G03B27/32; photolithographic projectors G03F7/20; projection television H04N5/74; colour projection television H04N9/31
• CPC Class Codes: G03B 21/10 Projectors with built-in or built-on screen
• CPC Class Codes: H04N 5/72 Modifying the appearance of television pictures by optical filters or diffusing screens
• CPC Class Codes: H04N 5/7408 Direct viewing projectors, e.g. an image displayed on a video CRT or LCD display being projected on a screen
• CPC Class Codes: H04N 5/7416 involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
• CPC Class Codes: H04N 9/3141 Constructional details thereof details not peculiar to the presence of an electronic spatial light modulator G03B21/14

Abstract

A thin-shaped projection-type display apparatus capable of displaying a high-quality image without causing any ghost image is provided. The projection-type display apparatus includes a screen having a prism, and a projection optical system for guiding image light to the screen. The projection optical system includes a plurality of optical elements. An optical element disposed nearest to the screen on an optical path of the image light among the plurality of optical elements is a mirror. An angle made by the normal to a surface of the mirror approximately at the center of the mirror and the normal to a surface of the screen is between 75 degrees and 87.5 degrees inclusive.

Claims

1. A projection-type display apparatus, comprising:

a projection optical system for guiding image light to the screen, the projection optical system including a plurality of optical elements;

a screen having a plurality of arc-curved prisms;

a cross sectional share of the plurality of prisms being triangle;

wherein an optical element disposed nearest to the screen on an optical path of the image light among the plurality of optical elements is a substantially flat mirror,

wherein θ

t is between 50 degrees and 58 degrees when an apex angle of the triangle facing the flat mirror is θ

t, and

wherein an angle by a surface of the substantially flat mirror and a surface of the screen is between 75 degrees and 87.5 degrees inclusive.

2. The projection-type display apparatus according to claim 1, wherein the mirror is a flat mirror, wherein a plane of the mirror is oriented more perpendicular than parallel to a plane of the screen.

3. A projection-type display apparatus according to claim 1, wherein the apex angle θ

t is constant with respect to all the prisms in the screen.

4. A projection-type display apparatus according to claim 1, wherein the plurality of prisms include a first prism disposed on the first arc and a second prism disposed on a second arc which is concentric with the first arc and different from the first arc, and wherein the cross sectional shape of the first prism is different from that of the second prism.

5. A projection-type display apparatus, comprising:

a screen having a plurality of arc-curved prisms;

a cross sectional share of the plurality of prisms being triangle;

a projection optical system for guiding image light to the screen, the projection optical system including a plurality of optical elements;

wherein an optical element disposed nearest to the screen on an optical path of the image light among the plurality of optical elements is the mirror,

wherein an apex angle θ

t is facing the mirror, wherein θ

t is between 50 degrees and 58 degrees,

wherein an angle α

made by an optical path of the image light falling on the screen after passing through the center of a pupil of the projection optical system and a normal to a surface of the screen is between 60 degrees and 85 degrees inclusive, and

wherein an angle made by a normal to a surface of the mirror approximately at the center of the mirror and the normal to the surface of the screen is between (45+(a minimum value of the angle α

)/2) degrees and (45+(a maximum value of the angle α

)/2) degrees inclusive.

6. A projection-type display apparatus according to claim 5, wherein the angle α

made by an optical path of the image light falling on the screen after passing through the center of a pupil of the projection optical system and a normal to a surface of the screen is 65 degrees or more.

7. A projection-type display apparatus according to claim 5, wherein the angle α

made by an optical path of the image light falling on the screen after passing through the center of a pupil of the projection optical system and a normal to a surface of the screen is 80 degrees or less.

8. A projection-type display apparatus according to claim 5, wherein the apex angle θ

t is constant with respect to all the prisms in the screen.

9. A projection-type display apparatus according to claim 5, wherein the plurality of prisms include a first prism disposed on the first arc and a second prism disposed on a second arc which is concentric with the first arc and different from the first arc, and wherein the cross sectional shape of the first prism is different from that of the second prism.