Projector having diffusing unit and polarization conversion element

• US 9,004,692 B2
• Filed: 08/30/2012
• Issued: 04/14/2015
• Est. Priority Date: 09/07/2011
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Akiyama, Koichi
• Primary Examiner(s): Reilly-Diakun, Jori S
• Application Number:
  US13/599,574
• Publication Number:
  US 20130057832A1
• Time in Patent Office: 957 Days
• Field of Search: 353/20, 353 30- 31, 353 33- 34, 353/82, 353/98, 353 37- 3, 353/988, 359/483.01, 359/485.01, 35948506-48507, 359/489.01, 35948907-48908, 359/558, 359/566, 359/574
• US Class Current: 353/20
• CPC Class Codes: G02B 27/0944 Diffractive optical elements, e.g. gratings, holograms gratings per se G02B5/18; holograms used as optical elements per se G02B5/32
• CPC Class Codes: G03B 21/2073 Polarisers in the lamp house peculiar to electronic spatial light modulators H04N9/3197
• CPC Class Codes: G03B 21/208 Homogenising, shaping of the illumination light
• CPC Class Codes: H04N 9/3152 for shaping the light beam beam shaping per se G02B27/09
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

A projector includes an illumination device having a light source device emitting light, and a polarization conversion element adapted to emit light from the light source device as polarized light, a light modulation device adapted to modulate the light from the illumination device in accordance with image information, and a projection optical system adapted to project the light from the light modulation device, and the illumination device further includes a light diffusing unit disposed in at least one of upstream and downstream of the polarization conversion element.

Claims

1. A projector comprising:

an illumination device including;

a light source device emitting light,

a polarization conversion element adapted to emit light from the light source device as polarized light and having a plurality of polarization conversion sections arranged in an arrangement direction, each of the polarization conversion sections having a polarization separation section and a reflecting section, and

a light diffusing unit disposed in at least one of upstream and downstream of the polarization conversion element and having a plurality of light diffusing sections;

a light modulation device adapted to modulate light from the illumination device in accordance with image information; and

a projection optical system adapted to project light from the light modulation device,

wherein a width of each of the light diffusing sections in the arrangement direction is smaller than a width of each of the polarization separation sections in the arrangement direction.

2. The projector according to claim 1, wherein

the light diffusing unit diffuses light along the arrangement direction.

3. The projector according to claim 2, wherein

each of the light diffusing sections extends in a direction, which is perpendicular to an optical axis of the illumination device and is perpendicular to the arrangement direction, and is disposed on at least one of a surface of the light diffusing unit facing to the light source device and a surface of the light diffusing unit facing to the light modulation device, and

one of the plurality of light diffusing sections has a roughly semicircular cross-sectional shape viewed in a cross-section perpendicular to the direction in which the one of the light diffusing sections extends.

4. The projector according to claim 2, wherein

each of the light diffusing sections extends in a direction, which is perpendicular to an optical axis of the illumination device and is perpendicular to the arrangement direction, and is disposed on at least one of a surface of the light diffusing unit facing to the light source device and a surface of the light diffusing unit facing to the light modulation device, and

one of the plurality of light diffusing sections has a triangular cross-sectional shape viewed in a cross-section perpendicular to the direction in which the one of the light diffusing sections extends.

5. The projector according to claim 2, wherein

each of the light diffusing sections extends in a direction, which is perpendicular to an optical axis of the illumination device and is perpendicular to the arrangement direction, and is disposed on at least one of a surface of the light diffusing unit facing to the light source device and a surface of the light diffusing unit facing to the light modulation device, and

one of the plurality of light diffusing sections has a rectangular cross-sectional shape viewed in a cross-section perpendicular to the direction in which the one of the light diffusing sections extends.

6. The projector according to claim 3, wherein

the plurality of light diffusing sections are arranged at regular intervals along the arrangement direction.

7. The projector according to claim 3, wherein

the plurality of light diffusing sections are arranged at random intervals along the arrangement direction.

8. The projector according to claim 2, wherein

a number of the plurality of light diffusing sections is equal to or larger than twice of a number of the polarization conversion sections.

9. The projector according to claim 2, wherein

the polarization conversion element has two polarization conversion sections.

10. The projector according to claim 1, further comprising:

a reflecting unit adapted to reflect light, which proceeds toward outside of an irradiation area of the light modulation device, to inside of the irradiation area, and disposed between the polarization conversion element and the light modulation device.

11. The projector according to claim 10, wherein

the reflecting unit has a prismatic cylindrical shape having an inner surface formed as a reflecting surface, and is disposed so that one opening section faces to a light exit surface of the polarization conversion element and an other opening section faces to the irradiation area of the light modulation device.

12. The projector according to claim 11, wherein

an aperture area of the one opening section of the reflecting unit is larger than an aperture area of the other opening section.

13. The projector according to claim 10, wherein

at least a part of the reflecting surface of the reflecting unit has a scattering property.

14. The projector according to claim 1, wherein

each of the polarization separation sections is adapted to transmit a first linearly polarized component and reflect a second linearly polarized component among the polarization components included in the incident light having entered the polarization conversion element,

each of the reflecting sections is adapted to reflect the second linearly polarized component, which has been reflected by the polarization separation section, in a direction parallel to a transmission direction of the first linearly polarized component, and

the polarization conversion element includes

a wave plate adapted to convert one of the first linearly polarized component and the second linearly polarized component into the other of the first linearly polarized component and the second linearly polarized component, and

a reflectance of the second linearly polarized component in the polarization separation section is higher than a transmittance of the first linearly polarized component in the polarization separation section.

15. The projector according to claim 14, wherein

a difference between the reflectance of the second linearly polarized component in the polarization separation section and the transmittance of the first linearly polarized component in the polarization separation section is higher than 0% and lower than 15%.