News Column

Patent Issued for Projector

June 4, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Kaneko, Tsuyoshi (Shimosuwa, JP); Takeda, Takashi (Suwa, JP), filed on August 22, 2013, was published online on May 20, 2014.

The assignee for this patent, patent number 8727541, is Seiko Epson Corporation (JP).

Reporters obtained the following quote from the background information supplied by the inventors: "The present invention relates to a projector.

"A super luminescent diode (hereinafter also referred to as an 'SLD') is a semiconductor element capable of providing an output up to several tens of mW in the light output characteristic similarly to a semiconductor laser while showing an incoherent property and a wideband spectrum shape similarly to an ordinary light emitting diode. Similarly to a semiconductor laser, the SLD uses a mechanism in which the spontaneous-emission light generated by the recombination of the injected carriers is amplified in accordance with a high gain due to the stimulated emission while proceeding toward a light emitting end surface, and then emitted from the light emitting end surface. It should be noted that unlike the semiconductor laser the SLD requires to prevent formation of the resonator due to the end surface reflection, thereby preventing the laser oscillation from occurring.

"As a measure for preventing the laser oscillation, there has been known a configuration of tilting the gain region (optical waveguide) with respect to the emission end surface as shown in, for example, JP-A-2007-165689. In the technology described in the document mentioned above, two such linear optical waveguides tilted with respect to the emission end surface are formed in order for achieving high output power.

"In the light emitting element provided with the linear gain regions (optical waveguides) tilted with respect to the emission end surface as described above, the light beams emitted from the plurality of gain regions might proceed in respective directions different from each other in some cases. However, if the SLD is used as a light source of a projector, it is preferable that the light beams emitted from the SLD proceed in the same direction. According to such an SLD, it is possible to make the light axis adjustment in the projector easier."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "An advantage of some aspects of the invention is to provide a projector, which is provided with a light emitting device for making the light beams emitted from a plurality of gain regions proceed in the same direction, and is easy in adjusting the light axis.

"According to an aspect of the invention, there is provided a projector including a light emitting device, a light modulation device adapted to modulate a light beam emitted from the light emitting device in accordance with image information, and a projection device adapted to project the image formed by the light modulation device, wherein the light emitting device includes a light emitting element, and an optical member which a light beam emitted from the light emitting element enters, the light emitting element is a super luminescent diode provided with a stacked structure having an active layer sandwiched between a first cladding layer and a second cladding layer, at least a part of the active layer constitutes a first gain region and a second gain region which become current channels of the active layer, a first surface and a second surface out of exposed surfaces of the active layer opposed to each other in the stacked structure, the first gain region is disposed linearly from the first surface to the second surface of the active layer so as to be tilted in a clockwise direction with respect to a perpendicular of the first surface in a plan view along a stacking direction of the stacked structure, the second gain region is disposed linearly from the first surface to the second surface of the active layer so as to be tilted in a counterclockwise direction with respect to a perpendicular of the first surface in the plan view along the stacking direction of the stacked structure, and the optical member refracts the light beams emitted respectively from an end surface of the first gain region on the second surface side and an end surface of the second gain region on the second surface side to thereby emit the light beams as light beams proceeding in the same direction.

"According to such a projector as described above, the light emitting device making the light beams emitted from the at least first gain region and at least one second gain region proceed in the same direction is provided, and it becomes possible to make the light axis adjustment easier.

"In the projector of the above aspect of the invention, it is also possible that the proceeding direction of the light beams emitted from the optical member is a direction of a perpendicular of the second surface.

"According to such a projector as described above, the positions of the entrance surface and the exit surface of the optical member can be determined using the second surface as a reference. Thus, it becomes possible to make the alignment between the light emitting element and the optical member easier.

"In the projector of the above aspect of the invention, it is also possible that the first gain region and the second gain region constitute a V-shaped gain region in which an end surface of the first gain region on the first surface side and an end surface of the second gain region on the first surface side overlap each other on the first surface, and a reflectance of the first surface is higher than a reflectance of the second surface in a wavelength band of light generated in the first gain region and the second gain region.

"According to such a projector as described above, some of the light generated in the first gain region is reflected by an overlapping plane (an overlapping plane between the end surface of the first gain region on the first surface side and the end surface of the second gain region on the first surface side), and can further proceed in the second gain region while obtaining the gain. Further, the same can be applied to some of the light generated in the second gain region. Therefore, since the distance for amplifying the light intensity becomes longer compared to the case in which, for example, the light is not actively reflected by the overlapping plane, the high light output can be obtained.

"In the projector of the above aspect of the invention, it is also possible that the number of the first gain region is more than one, and the number of the second gain region is more than one.

"According to such a projector, higher output of the whole light emitting device can be achieved.

"In the projector of the above aspect of the invention, it is also possible that the optical member has a translucency to a wavelength of the light beams emitted from the light emitting element.

"According to such a projector, the absorption loss of the light can be reduced.

"In the projector of the above aspect of the invention, it is also possible that at least one of a light entrance area and a light exit area of the optical member is covered by a reflection reduction member.

"According to such a projector, the reflection loss of the light can be reduced on at least either one of the entrance surface and the exit surface of the optical member.

"In the projector of the above aspect of the invention, it is also possible that the light emitting element is mounted to a support member, a thermal conductivity of the support member is higher than a thermal conductivity of the light emitting element, and the active layer is disposed on the support member side in the light emitting element.

"According to such a projector as described above, the light emitting device can have high heat radiation performance.

"In the projector of the above aspect of the invention, it is also possible that the light emitting element is mounted to a support member, the active layer is disposed on a side opposite to the support member side in the light emitting element, the stacked structure further includes a substrate, and the substrate is disposed between the active layer and the support member.

"According to such a projector as described above, since the substrate is disposed between the active layer and the support member, the active layer is disposed at the position at least by the thickness of the substrate further from the support member. Therefore, the outgoing light beam with a much preferable shape (cross-sectional shape) can be obtained."

For more information, see this patent: Kaneko, Tsuyoshi; Takeda, Takashi. Projector. U.S. Patent Number 8727541, filed August 22, 2013, and published online on May 20, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=119&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=5930&f=G&l=50&co1=AND&d=PTXT&s1=20140520.PD.&OS=ISD/20140520&RS=ISD/20140520

Keywords for this news article include: Electronics, Semiconductor, Seiko Epson Corporation.

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Source: Electronics Newsweekly


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