US-12625421-B2 - Projector having a modulated light reduction relay lens system and a control unit correcting white balance based on F-number

US12625421B2US 12625421 B2US12625421 B2US 12625421B2US-12625421-B2

Abstract

A projector includes a relay system reducing a luminous flux width of a first color light modulated by a first light modulation element, a light combining prism outputting a combined light formed by combining the first color light having the luminous flux width reduced by the relay system and another color light modulated by a second light modulation element, a projection system projecting the combined light as a projection image, a detection unit detecting an F-number of the projection system, and a control unit correcting a white balance of the projection image by controlling an amount of a light output from at least one of the first light modulation element and the second light modulation element based on the F-number detected by the detection unit. A pixel pitch of the first light modulation element is larger than a pixel pitch of the second light modulation element.

Inventors

Junichi Wakabayashi
Hidefumi Sakata
Eiji Morikuni

Assignees

SEIKO EPSON CORPORATION

Dates

Publication Date: 20260512
Application Date: 20240226
Priority Date: 20230227

Claims (8)

1 . A projector comprising: a light source unit outputting an output light containing a first color light and another color light having a longer wavelength range than the first color light; a first light modulation element irradiated with the first color light and modulating the first color light; a second light modulation element irradiated with the other color light and modulating the other color light; a relay system, with the first light modulation element placed on an enlargement-side imaging surface, reducing a luminous flux width of the first color light modulated by the first light modulation element on a reduction-side imaging surface; a light combining prism outputting a combined light formed by combining the first color light having the luminous flux width reduced by the relay system and the other color light modulated by the second light modulation element; a projection system projecting the combined light output from the light combining prism as a projection image; a detection unit detecting an F-number of the projection system; and a control unit correcting a white balance of the projection image by controlling an amount of a light output from at least one of the first light modulation element and the second light modulation element based on the F-number detected by the detection unit, wherein an effective area of the first light modulation element is larger than an effective area of the second light modulation element, and a pixel pitch of the first light modulation element is larger than a pixel pitch of the second light modulation element.
2 . The projector according to claim 1 , wherein the light source unit includes a light emitting element outputting the first color light in a first polarization state, a wave plate converting a part of the first color light output from the light emitting element into a second polarization state, a polarization separation element respectively separating the first color light in the first polarization state and the first color light in the second polarization state, a phosphor element converting the first color light in the first polarization state separated by the polarization separation element into the other color light and reflecting the other color light, a diffusion element reflecting the first color light in the second polarization state separated by the polarization separation element, and a combining element combining the first color light reflected by the diffusion element and the other color light reflected by the phosphor element to form the output light, and the control unit controls amounts of lights output from the first light modulation element and the second light modulation element by controlling an angle of the wave plate.
3 . The projector according to claim 1 , wherein the control unit controls the amount of the light output from at least one of the first light modulation element and the second light modulation element by controlling a gradation of the at least one of the first light modulation element and the second light modulation element.
4 . The projector according to claim 1 , wherein the light source unit includes a first light source outputting the first color light and a second light source outputting the other color light, and the control unit controls the amount of the light output from at least one of the first light modulation element and the second light modulation element by controlling an amount of a light of at least one of the first light source and the second light source.
5 . The projector according to claim 1 , wherein the first color light has a first wavelength range containing a blue light.
6 . The projector according to claim 5 , wherein the other color light includes a second color light having a longer wavelength range than the first color light and a third color light having a longer wavelength range than the first color light and the second color light, the second light modulation element includes a third light modulation element irradiated with the second color light and modulating the second color light and a fourth light modulation element irradiated with the third color light and modulating the third color light, the effective area of the first light modulation element is larger than effective areas of the third light modulation element and the fourth light modulation element, and the pixel pitch of the first light modulation element is larger than pixel pitches of the third light modulation element and the fourth light modulation element.
7 . The projector according to claim 6 , wherein the second color light has a second wavelength range containing a green light, and the third color light has a third wavelength range containing a red light.
8 . The projector according to claim 1 , wherein the projection system is a zoom lens, and the detection unit detects the F-number based on a projection distance of the projection system.

Description

The present application is based on, and claims priority from JP Application Serial Number 2023-028142, filed Feb. 27, 2023, the disclosure of which is hereby incorporated by reference herein in its entirety. BACKGROUND 1. Technical Field The present disclosure relates to a projector. 2. Related Art JP-A-2005-345767 discloses a projector in which an effective area of one light modulation element of a plurality of light modulation elements is larger than effective areas of the other light modulation elements. The projector of JP-A-2005-345767 includes a first modulation element modulating a blue light, a second modulation element modulating a green light, a third modulation element modulating a red light, a prism combining the respective modulated color lights, a prism combining the respective modulated color lights, a correction lens placed between the second modulation element and the prism, and a projection lens projecting the combined light output from the prism as a projection image on a projection surface. A light modulation area size of the second light modulation element is larger than light modulation area sizes of the first light modulation element and the third light modulation element. The correction lens reduces the luminous flux width output from the second modulation element to be the same as the luminous flux widths of the lights output from the first light modulation element and the third light modulation element. The prism outputs a combined light formed by combining the green light output from the second modulation element, the blue light output from the first modulation element, and the red light output from the third modulation element. In the projector of JP-A-2005-345767, when the numbers of pixels of the first light modulation element, the second light modulation element, and the third light modulation element are the same, the light modulation area size of the second light modulation element is larger than the light modulation area sizes of the first light modulation element and the third light modulation element, and the pixel pitch of the second light modulation element is larger than the pixel pitches of the first light modulation element and the third light modulation element. As a result, the intensity distributions of the lights output from the first light modulation element and the third light modulation element are the same, however, the intensity distribution of the light output from the second light modulation element is different from the intensity distributions of the lights output from the first light modulation element and the third light modulation element because the degrees of influences by diffraction are different due to differences in pixel pitch. Thereby, when the combined light combined by the prism is projected as the projection image by the projection lens, there is a problem that a white balance of the projection image is not in a desired condition. SUMMARY In order to solve the above described problem, a projector according to an aspect of the present disclosure includes a light source unit outputting an output light containing a first color light and another color light having a longer wavelength range than the first color light, a first light modulation element irradiated with the first color light and modulating the first color light, a second light modulation element irradiated with the other color light and modulating the other color light, a relay system, with the first light modulation element placed on an enlargement-side imaging surface, reducing a luminous flux width of the first color light modulated by the first light modulation element on a reduction-side imaging surface, a light combining prism outputting a combined light formed by combining the first color light having the luminous flux width reduced by the relay system and the other color light modulated by the second light modulation element, a projection system projecting the combined light output from the light combining prism as a projection image, a detection unit detecting an F-number of the projection system, and a control unit correcting a white balance of the projection image by controlling an amount of a light output from at least one of the first light modulation element and the second light modulation element based on the F-number detected by the detection unit, wherein an effective area of the first light modulation element is larger than an effective area of the second light modulation element, and a pixel pitch of the first light modulation element is larger than a pixel pitch of the second light modulation element. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a main part of a projector of Embodiment 1. FIG. 2 is a schematic diagram of a light source unit of Embodiment 1. FIG. 3 shows an example of light intensity distributions of a first color light, a second color light, and a third color light entering a light combining prism. FIG. 4 is a schematic diag