PROJECTOR AND OPTICAL UNIT

• US 20120099031A1
• Filed: 09/22/2011
• Published: 04/26/2012
• Est. Priority Date: 10/26/2010
• Status: Abandoned Application

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kinoe, Yusuke, Goto, Takafumi
• Application Number:
  US13/240,811
• Publication Number:
  US 20120099031A1
• Time in Patent Office: Days
• US Class Current: 349/8
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 2201/121 common or background
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3158 for controlling the spectrum

Abstract

A projector includes a plurality of reflective liquid crystal panels (for example, a red liquid crystal panel, a green liquid crystal panel, and a blue liquid crystal panel). The film thickness of an ITO film that forms a common electrode of the blue liquid crystal panel is smaller than the film thickness of an ITO film that forms a common electrode of any one of the red liquid crystal panel and the green liquid crystal panel. The film thicknesses of the ITO films that form the common electrodes of the red liquid crystal panel and the green liquid crystal panel are the same.

Claims

1. A projector comprising:

a light source unit;

three or more liquid crystal panels each including a first substrate, a second substrate, and a liquid crystal layer between the first substrate and the second substrate, the first substrate including reflective pixel electrodes formed on a side thereof, the second substrate being light-transmissive and including a common electrode formed on a side thereof facing the side of the first substrate, the common electrode being light-transmissive, each of the three or more liquid crystal panels being supplied with a light beam emitted from the light source unit, the light beams being in different wavelength ranges; and

a projection optical system that projects light generated by combining the light beams modulated by the three or more liquid crystal panels,

wherein the common electrode of a short-wavelength liquid crystal panel, the short-wavelength liquid crystal panel being one of the three or more liquid crystal panels that modulates a light beam in a shortest wavelength range among the three or more liquid crystal panels, has a film thickness that is smaller than a film thickness of the common electrode of any one of the other liquid crystal panels, and

wherein the film thicknesses of the common electrodes of the other liquid crystal panels are the same.

2. The projector according to claim 1,

wherein the short-wavelength liquid crystal panel has spectral reflection characteristics such that a difference between a maximum reflectance and a minimum reflectance in the shortest wavelength range, which is a wavelength range of the light beam that the short-wavelength liquid crystal panel modulates, is smaller than a difference between a maximum reflectance and a minimum reflectance in a range of wavelength that is longer than wavelength of the shortest wavelength range, the spectral reflection characteristics representing a relationship between the wavelength of a light beam supplied to the liquid crystal panel and a reflectance of the liquid crystal panel.

3. The projector according to claim 1,

wherein the film thickness of the common electrode of the short-wavelength liquid crystal panel is in a range of 0.70 to 0.90 times the film thickness of the common electrodes of the other liquid crystal panels.

4. The projector according to claim 3,

wherein an optical film thickness of the short-wavelength liquid crystal panel at a center wavelength of the shortest wavelength range, which is the wavelength range of the light beam that the short-wavelength liquid crystal panel modulates, is about half the center wavelength, the optical film thickness being a product of a refractive index of the common electrode and the film thickness of the common electrode of the short-wavelength liquid crystal panel.

5. The projector according to claim 4,

wherein the optical film thickness of one of the other liquid crystal panels, the one of the other liquid crystal panels modulating a light beam having a shorter wavelength among the other liquid crystal panels, at a center wavelength of the wavelength range of the light beam that the one of the other liquid crystal panels modulates is about half the center wavelength, the optical film thickness being the product of the refractive index of the common electrode and the film thickness of the common electrode of the one of the other liquid crystal panels.

6. The projector according to claim 4,

wherein the common electrode of the short-wavelength liquid crystal panel has spectral transmission characteristics such that a peak transmittance is located in the wavelength range of the light beam that the short-wavelength liquid crystal panel modulates, the spectral transmission characteristics representing a relationship between the wavelength of a light beam supplied to the common electrode and the transmittance of the common electrode.

7. The projector according to claim 1,

wherein the common electrodes of the three or more liquid crystal panels are ITO films.

8. The projector according to claim 1,

wherein the liquid crystal panels are a red liquid crystal panel to which a red light beam is supplied, a green liquid crystal panel to which a green light beam is supplied, and a blue liquid crystal panel to which a blue light beam is supplied,

wherein the blue liquid crystal panel is the short-wavelength liquid crystal panel including the common electrode that has a film thickness smaller than those of the common electrodes of the red liquid crystal panel and the green liquid crystal panel, and

wherein the red liquid crystal panel and the green liquid crystal panel are the other liquid crystal panels including the common electrodes having the same film thickness.

9. An optical unit comprising,

a plurality of liquid crystal panels each including a first substrate, a second substrate, and a liquid crystal layer between the first substrate and second substrate, the first substrate including reflective pixel electrodes formed on a side thereof, the second substrate being light-transmissive and including a common electrode formed on a side thereof facing the side of the first substrate, the common electrode being light-transmissive, each of the plurality of liquid crystal panels being supplied with a light beam, the light beams being in different wavelength ranges;

and

a light-combining optical system that emits light generated by combining light beams emitted from the plurality of liquid crystal panel,

wherein the common electrode of a short-wavelength liquid crystal panel, the short-wavelength liquid crystal panels being one of the plurality of liquid crystal panels that modulates a light beam in a shortest wavelength range among the plurality of liquid crystal panels, has a film thickness that is smaller than a film thickness of the common electrode of other liquid crystal panel of the plurality of liquid crystal panels.