An optical aperture multiplier includes a first optical waveguide (10) having a rectangular cross-section and including partially reflecting surfaces (40) at an oblique angle to a direction of elongation of the waveguide. A second optical waveguide (20), also including partially reflecting surfaces (45) at an oblique angle, is optically coupled with the first optical waveguide (10). An image coupled into the first optical waveguide with an initial direction of propagation at an oblique coupling angle advances by four-fold internal reflection along the first optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be coupled into the second optical waveguide, and then propagates through two-fold reflection within the second optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be directed outwards from one of the parallel faces as a visible image.

An optical aperture multiplier includes a first optical waveguide (10) having a rectangular cross-section and including partially reflecting surfaces (40) at an oblique angle to a direction of elongation of the waveguide. A second optical waveguide (20), also including partially reflecting surfaces (45) at an oblique angle, is optically coupled with the first optical waveguide (10). An image coupled into the first optical waveguide with an initial direction of propagation at an oblique coupling angle advances by four-fold internal reflection along the first optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be coupled into the second optical waveguide, and then propagates through two-fold reflection within the second optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be directed outwards from one of the parallel faces as a visible image.

A projection lens has a lens barrel holding a lens. In a case where an image forming panel is disposed to be shifted with respect to an optical axis of the projection lens, in a second part on a side to which the image forming panel is shifted with respect to the optical axis of the projection lens, there is a great increase in temperature, and in a first part on the opposite side, there is a small increase in temperature. A lens barrel heating optical section has a first mirror, condensing lenses, and a second mirror. The lens barrel heating optical section emits the redundant light, which is reflected by the color wheel, toward the first part of the lens barrel. By heating the first part through redundant light, temperature distribution in the circumferential direction becomes uniform, and deterioration in performance of the projected image is suppressed.

A projection lens has a lens barrel holding a lens. In a case where an image forming panel is disposed to be shifted with respect to an optical axis of the projection lens, in a second part on a side to which the image forming panel is shifted with respect to the optical axis of the projection lens, there is a great increase in temperature, and in a first part on the opposite side, there is a small increase in temperature. A lens barrel heating optical section has a first mirror, condensing lenses, and a second mirror. The lens barrel heating optical section emits the redundant light, which is reflected by the color wheel, toward the first part of the lens barrel. By heating the first part through redundant light, temperature distribution in the circumferential direction becomes uniform, and deterioration in performance of the projected image is suppressed.

In a case where an image forming panel is disposed to be shifted with respect to an optical axis of a projection lens having a lens barrel holding the lens, in the lens barrel, the increase in temperature in a first part on a side to which the image forming panel is shifted is larger than that in a second part on an opposite side. A temperature adjustment section includes a cooling duct, a heating duct, a connecting duct, and blowers 27 and. Air, which is suctioned from an inlet of the cooling duct, is passed through the first part, a light source, and the second part, sequentially by the blowers. The air cools down the first part, and heats the second part. Thereby, the temperature distribution in the circumferential direction of the lens barrel becomes uniform, and deterioration of the projected image is suppressed.

In a case where an image forming panel is disposed to be shifted with respect to an optical axis of a projection lens having a lens barrel holding the lens, in the lens barrel, the increase in temperature in a first part on a side to which the image forming panel is shifted is larger than that in a second part on an opposite side. A temperature adjustment section includes a cooling duct, a heating duct, a connecting duct, and blowers 27 and. Air, which is suctioned from an inlet of the cooling duct, is passed through the first part, a light source, and the second part, sequentially by the blowers. The air cools down the first part, and heats the second part. Thereby, the temperature distribution in the circumferential direction of the lens barrel becomes uniform, and deterioration of the projected image is suppressed.

A projection lens has lens holding frames that hold lenses. In a case where an image forming panel is disposed to be shifted with respect to an optical axis of the projection lens, an increase in temperature of a first part on a side to which the image forming panel is shifted with respect to the optical axis L, is greater than that of a second part on the opposite side. A hollow structure, which makes the first part 36f and the second part 36g communicate with each other, has a porous layer and is filled with a heat storage medium. By circulating the heat storage medium through the inside of the hollow structure, the first part is cooled, and the second part is heated. Therefore, temperature distribution in the circumferential direction of the lens barrel becomes uniform, and deterioration in performance of the projected image is suppressed.

A projection lens includes: first to fifth lenses; a light shielding ring; an aperture stop; and a lens barrel. The light shielding ring is rotated in a circumferential direction of the lens barrel by a rotation mechanism. In a case where an image forming panel is shifted with respect to an optical axis of the projection lens, a part, through which the light passes, is biased in the projection lens, whereby temperature distribution occurs in the lens barrel in the direction perpendicular to the optical axis. The thermal deformation of the high temperature side of the lens barrel due to the temperature distribution is greater than that on the low temperature side. The respective lenses may be tilted due to thermal deformation. By rotating the light shielding ring through the rotation mechanism, the temperature increases uniformly in the circumferential direction of the light shielding ring.

A projection lens includes: first to fifth lenses; a light shielding ring; an aperture stop; and a lens barrel. The light shielding ring is rotated in a circumferential direction of the lens barrel by a rotation mechanism. In a case where an image forming panel is shifted with respect to an optical axis of the projection lens, a part, through which the light passes, is biased in the projection lens, whereby temperature distribution occurs in the lens barrel in the direction perpendicular to the optical axis. The thermal deformation of the high temperature side of the lens barrel due to the temperature distribution is greater than that on the low temperature side. The respective lenses may be tilted due to thermal deformation. By rotating the light shielding ring through the rotation mechanism, the temperature increases uniformly in the circumferential direction of the light shielding ring.

A projection method of an electronic device, includes detecting the presence of an object within a preset distance range from a projection unit of the electronic device, generating a projection adjusting instruction if an object is detected within the preset distance range from the projection unit, and adjusting a projection display of the projection unit in response to the projection adjusting instruction.