Patent Application
20210149110
The present invention relates to an optical waveguide-type optical multiplexer, an optical waveguide-type multiplexing light source optical device and an image projection device, and relates to, for example, a configuration for attenuating the intensity of a light beam emitted from a light source to a desired value without installing an additional optical attenuator element.
Various forms of light beam multiplexing light sources have been known as conventional devices for multiplexing a plurality of light beams such as laser beams so as to radiate one beam. From among these, light beam multiplexing light source devices where semiconductor lasers and optical waveguide-type optical multiplexers are combined are characterized in that the device can be made compact and the power can be lowered, and thus are applied to a laser beam scanning-type color image projection device (see Patent Literature 1 through 3).
Conventional light beam multiplexing light sources where semiconductor lasers and optical waveguide-type optical multiplexers are combined include a light beam multiplexing light source for multiplexing laser beams of three primary colors as illustrated in Patent Literature 3, for example.
A blue semiconductor laser chip 41, a green semiconductor laser chip 42 and a red semiconductor laser chip 43 are installed at the entrance ends of the optical waveguides 23 through 25 for light input that correspond to the respective colors. Here, light beams propagate through the core layer in the optical waveguides 23 through 25 for light input so as to be multiplexed in the optical waveguide-type optical multiplexer 30, and after that, the multiplexed light is emitted from the emission end of the optical waveguide 28 on the light emission side, which is an extended portion of the optical waveguide 24 for light input.
In this image formation device, a control unit 90 has a sub-control unit 91, an operation unit 92, an external interface (I/F) 93, an R laser driver 94, a G laser driver 95, a B laser driver 96 and a two-dimensional scanning driver 97. The sub-control unit 91 is formed of a microcomputer that includes a CPU, a ROM and a RAM, for example. The sub-control unit 91 generates an R signal, a G signal, a B signal, a horizontal signal and a vertical signal that become elements for synthesizing an image on the basis of the image data supplied from an external device such as a PC via an external I/F 93. The sub-control unit 91 transmits an R signal to an R laser drive 94, a G signal to a G laser driver 95 and a B signal to a B laser driver 96, respectively. In addition, the sub-control unit 91 transmits a horizontal signal and a vertical signal to a two-dimensional scanning driver 97 so as to control a current to be applied to an electromagnetic coil 86, and thus controls the operation of a movable mirror unit 84.
The R laser driver 94 drives the red semiconductor laser chip 43 so that red laser light with a light quantity that corresponds to the R signal from the sub-control unit 91 is generated. The G laser driver 95 drives a green semiconductor laser chip 42 so that green laser light with a light quantity that corresponds to the G signal from the sub-control unit 91 is generated. The B laser driver 96 drives the blue semiconductor laser chip 41 so that blue laser light with a light quantity that corresponds to the B signal from the sub-control unit 91 is generated. It becomes possible to synthesize laser light having a desired color by adjusting the intensity ratio of the laser light of the respective colors.
The respective laser beams generated by the blue semiconductor laser chip 41, the green semiconductor laser chip 42 and the red semiconductor laser chip 43 are multiplexed in the optical multiplexing unit 30 in the optical waveguide-type optical multiplexer, and after that the multiplexed light is used for the two-dimensional scanning by means of the movable mirror unit 84. An image formed on a retina 100 is scanned with the multiplexed laser light, which is reflected from a concave reflecting mirror 98 so as to pass through a pupil 99.
As for a conventional light beam multiplexing light source device where semiconductor lasers and an optical waveguide-type multiplexer are combined, a light beam multiplexing light source device for multiplexing laser beams of three primary colors is formed of optical waveguides made of a core and a clad where semiconductor lasers for generating red, blue and green light beams, for example, are installed at the entrance ends of the optical waveguides that correspond to the respective colors. Here, the light beams propagate through the cores of the optical waveguides, and a multiplexed light beam is emitted from the emission end of the optical multiplexer.
Efforts have been made to develop the conventional light beam multiplexing light source devices of this type in order to maximize the efficiency in the transmission from the semiconductor laser output to the light source device output. It is possible to make the efficiency in the transmission 90% or greater by improving the efficiency in the coupling between the semiconductor lasers and the optical waveguides of the multiplexer and the efficiency in the optical multiplexing. In this case, conventional semiconductor lasers can be operated with the rated output so as to make the multiplexer output several mW.
In a retina scanning-type display to which a multiplexing light source device is mainly applied, the optical power for the final entrance into a pupil of a viewer is approximately 10 μW. In the case where the semiconductor lasers are driven with a small current in order to make the optical power for the entrance into a pupil smaller, such a problem arises that the optical dynamic range shrinks due to a spontaneous light component emission.
As another method for lowering the optical power, there is a technique for inserting an optical attenuator element such as a light absorber/reflector or an optical axis shift coupling unit into the optical path. In this case, an additional element for causing a light attenuation is necessary, and moreover, there is a concern that the reliability may be lowered due to the change in the characteristics of the additional optical element or the displacement in the alignment.
An object of the present invention is to provide an optical waveguide-type optical multiplexer having an optical waveguide for light input, an optical waveguide on the light emission side and an optical multiplexing unit where the intensity of a light beam emitted from a light source can be attenuated to a desired value without installing an additional optical attenuator element.
According to one aspect of the invention, an optical waveguide-type optical multiplexer is provided with: a plurality of optical waveguides for light input into which light having different wavelengths enters from a plurality of light sources; an optical multiplexer unit for distributing/multiplexing light that has propagated through the optical waveguides for light input; and a plurality of optical waveguides on the light emission side for emitting light that has been distributed/multiplexed in the optical multiplexer unit, wherein one of the optical waveguides on the light emission side excluding an optical waveguide on the light emission side in which the greatest output light power can be gained for each wavelength from among the optical waveguides on the light emission side in the case where the plurality of light sources is driven is used as an optical waveguide for light emission, and the optical waveguides on the light emission side excluding the optical waveguides for light emission are not linear up to the emission end.
According to another aspect of the invention, an optical waveguide-type optical multiplexer is provided with: a plurality of optical waveguides for light input into which light having different wavelengths enters from three or more light sources; an optical multiplexer unit for distributing/multiplexing light that has propagated through the optical waveguides for light input; and a plurality of optical waveguides on the light emission side for emitting light that has been distributed/multiplexed in the optical multiplexer unit, wherein an optical waveguide on the light emission side where the maximum output light power can be gained for at least one wavelength from among the optical waveguides on the light emission side excluding an optical waveguide on the light emission side where the greatest multiplexed output light power can be gained in the case where the three or more light sources are driven with the same output is used as an optical waveguide for light emission, and the optical waveguides on the light emission side excluding the optical waveguide for light emission are not linear up to the emission end.
According to still another aspect of the invention, an optical waveguide-type multiplexing light source optical device is provided with: a plurality of light sources; a plurality of optical waveguides for light input into which light enters from the plurality of light sources; an optical multiplexer unit for distributing/multiplexing light that has propagated through the optical waveguides for light input; and a plurality of optical waveguides on the light emission side for emitting light that has been distributed/multiplexed in the optical multiplexer unit, wherein one of the optical waveguides on the light emission side excluding an optical waveguide on the light emission side in which the greatest output light power can be gained for each wavelength from among the optical waveguides on the light emission side in the case where the plurality of light sources is driven is used as an optical waveguide for light emission, and the optical waveguide-type multiplexing light source optical device further comprises an optical element that can be optically coupled with a signal light from the optical waveguide for light emission.
According to yet another aspect of the invention, an optical waveguide-type multiplexing light source optical device is provided with: three or more light sources for emitting light with different wavelengths; a plurality of optical waveguides for light input into which light having different wavelengths enters from the three or more light sources; an optical multiplexer unit for distributing/multiplexing light that has propagated through the optical waveguides for light input; and a plurality of optical waveguides on the light emission side for emitting light that has been distributed/multiplexed in the optical multiplexer unit, wherein an optical waveguide on the light emission side where the maximum output light power can be gained for at least one wavelength from among the optical waveguides on the light emission side excluding an optical waveguide on the light emission side where the greatest multiplexed output light power can be gained in the case where the three or more light sources are driven with the same output is used as an optical waveguide for light emission, and the optical waveguide-type multiplexing light source optical device further comprises an optical element that can be optically coupled with a signal light from the optical waveguide for light emission.
According to still yet another aspect of the invention, an image projection devise is provided with: the optical waveguide-type multiplexing light source optical device that includes the above-described optical element for scanning with light; and an image formation unit for projecting onto a projection surface an image scanned with light that has been multiplexed by the optical element for scanning with light in the optical waveguide-type multiplexing light source optical device.
In accordance with one aspect of an optical waveguide-type optical multiplexer having an optical waveguide for light input, an optical waveguide on the light emission side and an optical multiplexing unit, it becomes possible for the intensity of a light beam emitted from a light source to be attenuated to a desired value without installing an additional optical attenuator element. A compact retina scanning-type display with high reliability can be gained by using such an optical waveguide-type optical multiplexer.
Here, an example of the optical waveguide-type optical multiplexer according to an embodiment of the present invention is described in reference to
Here, the attenuation coefficient for adjusting the output light power is set depending on the lengths of the directional coupler that forms the respective optical coupling parts 61, 62 and 7 and the gaps between the optical waveguides that form the directional coupler. In the optical waveguide (8) on the light emission side that becomes the optical waveguide for light emission, at least the optical waveguide in linear form in the region other than the proximity to the emission end agrees with the propagation axis line of the optical multiplexer unit 5 by +/−10° or less. Here, the propagation axis line means an axis line that agrees with the direction in which light progresses as a whole through the inside of the optical waveguide that forms the multiplexer unit 5 and that approximately agrees with the center axis of the optical multiplexer unit 5. In addition, the size of the output power for each wavelength is proportional to the ratio of the quantity of light that has entered into the optical waveguides 2 through 4 for light input to the quantity of light (light power) emitted from the optical waveguides 8 through 10 on the light emission side.
In addition, a modification thereof has a plurality of optical waveguides 2 through 4 for allowing light having different wavelengths to enter from three or more light sources 111 through 113, the optical multiplexer unit 5 for distributing/multiplexing light that has propagated through the optical waveguides 2 through 4 for light input, and a plurality of optical waveguides 8 through 10 on the light emission side for emitting light that has been distributed/multiplexed in the optical multiplexer unit 5. In the case where the light sources 111 through 113 are driven with the same output, the optical waveguide on the light emission side other than the optical waveguide on the light emission side where the greatest multiplexed output light power can be gained from among the optical waveguides 8 through 10 on the light emission side and where the greatest output light power can be gained for at least one wavelength is used as an optical waveguide for light emission. The optical waveguide for light emission is not linear up to the emission end and is preferably an optical waveguide in linear form in at least a region other than the proximity to the emission end. The optical waveguides on the light emission side other than the optical waveguide for light emission is preferably inclined relative to the propagation axis line of the optical multiplexer unit 5. Here, the lengths of the directional couplers that form the respective optical coupling parts 61, 62 and 7 and the gap between the optical waveguides that form the directional coupler are set so as to be different from those in the embodiment.
In this case, it is desirable for the light attenuation from the input power for the optical waveguides 2 through 4 for light input to the output power from the optical waveguide (8) for light emission to be set to a value in a range from 5 dB to 40 dB. That is to say, depending on the rated output PId (=1 mW to 10 mW) of the semiconductor laser, the loss of coupling αcp with an optical waveguide and the loss of transmittance αsys through the display optical system, the value required for the light attenuation αmpx (=10 log (PId/Pdp)−αcp−αsys) from the entrance power of light that has entered into the optical waveguides 2 through 4 for light input to the multiplexed light output power outputted from the optical waveguide (8) for light emission is in a range from 5 dB to 40 dB, more preferably from 10 dB to 30 dB. Here, Pdp is a so-called display light power and approximately 1 μW to 10 μW. In addition, the loss (αcp+αsys) becomes 15 dB or less. When the attenuation is lower than 5 dB, the display light power becomes a value that exceeds a required range Pdp even in the case where PId is the minimum of 1 mW and the loss (αcp+αsys) is the maximum of 15 dB. Meanwhile, when the attenuation is greater than 40 dB, the required quantity of light cannot be gained.
The optical waveguide on the light emission side that becomes the optical waveguide for light emission (8 in the case in
Here, the optical waveguides 9 and 10 on the light emission side other than the optical waveguide (8) for light emission are optical waveguides for discarding light or an optical waveguide for monitoring. The number of optical waveguides 2 through 4 for light input is arbitrary (three in the case in
Here, the optical multiplexer unit 5 is typically an optical multiplexing unit for multiplexing at least three primary colors, red light, blue light and green light. Here, the arrangement of the light sources 111 through 113 and the order in which light couples are arbitrary.
Alternatively, the direction in which light is guided through a plurality of optical waveguides 2 through 4 for light input may be inclined at an angle of 85° to 95° in proximity to the input end relative to the optical waveguide (8) in linear form. The arrangement in this manner can make the size of the optical waveguide-type optical multiplexer smaller in the direction of the length, and at the same time can reduce the effects of stray light from the light sources.
In this case, the plurality of light sources 111 through 113 may be arranged along one side of the substrate 1 so that the direction in which light is guided in proximity to the input ends of the plurality of optical waveguides 2 through 4 for light input forms an angle of 85° to 95° with the optical axis of the optical waveguide (8) in linear form. Alternatively, at least one (111) from among the plurality of light sources 111 through 113 may be arranged along a first side of the substrate, and the remaining light sources (112 and 113) may be arranged along a second side that face the first side so that the direction in which light is guided in proximity to the input ends of the plurality of optical waveguides 2 through 4 for light input forms an angle of 85° to 95° with the optical axis of the optical waveguide (8) in linear form.
In the case where an optical waveguide-type multiplexing light source optical device is formed, a plurality of light sources is provided to a waveguide-type optical coupler or a modification thereof that are depicted in the embodiment, and at the same time, an optical element may be optically coupled with a signal light from the optical waveguide (8) for light emission that becomes an optical waveguide for light emission.
In this case, typical examples of the optical element include a condenser lens, an optical fiber, an optical element for scanning with light and any combinations of these. Here, the light sources 111 through 113 are typically semiconductor lasers and may be light emitting diodes (LEDs) or light sources via optical fibers or optical fibers with a lensed end. In the case where optical fibers or optical fibers with a lensed end are used, a liquid laser or a solid laser may be used as the light source thereof. In addition, in the case of a light source other than an optical fiber with a lensed end, condenser lenses may be provided between the light sources 111 through 113 and the optical waveguides 2 through 4 for light input.
The emission ends of the optical waveguides (9 and 10) on the light emission side other than the optical waveguide for light emission may be arranged along a first side of the substrate 1, and the emission end of the optical waveguide (8) that becomes the optical waveguide for light emission may be arranged along a second side that crosses the first side.
In order to form an image projection device, as illustrated in
Here, the substrate 1 may be any from among an Si substrate, a glass substrate, a sapphire substrate, a metal substrate, a plastic substrate and the like. As for the material for the lower clad layer, the core layer and the upper clad layer, an SiO2 glass-based material can be used, and in addition, a transparent plastic such as an acrylic resin and other transparent materials may be used. In the case of wavelengths other than RGB, a semiconductor material such as an Si or a GaN-based material may be used for the clad layer and the core layer.
As for the structure of each optical waveguide, each core in the core layer may be covered with a common upper clad layer, each core in the core layer may by covered with an individual upper clad in the upper clad layer, or each core in the core layer may be covered with an individual lower clad in the lower clad layer and an individual upper clad in the upper clad layer.
The structure of the optical multiplexer unit 5 is arbitrary, and an example of the optical multiplexer end is described in reference to
In
Here, the optical waveguide-type optical multiplexer in Example 1 of the present invention is described in reference to
As illustrated in
As illustrated in
As for the size of the optical waveguide-type optical multiplexer, the length is 3 mm and the width is 3.1 mm. The length of the optical coupling part 31 is 240 μm, the length of the optical coupling part 32 is 240 μm, and the length of the optical coupling part 33 is 200 μm. The wavelength of light emitted from the blue semiconductor laser chip 41 is 450 nm, the wavelength of light emitted from the green semiconductor laser chip 42 is 520 nm, and the wavelength of light emitted from the red semiconductor laser chip 43 is 638 nm.
The blue semiconductor laser chip 41, the green semiconductor laser chip 42 and the red semiconductor laser chip 43 are mounted in such a manner that the emission areas thereof are respectively matched with the entrance areas of the optical waveguides 23 through 25 for light input in the lateral direction and in the height direction with a gap vis-a-vis the input ends of the optical waveguides 23 through 25 for light input being 10 μm. The emission ends of the optical waveguides 27 through 29 on the light emission side may be a simple plane such as a plane of cleavage, and the shape of the beams may be controlled by using a spot size converter or the like.
Here, the lengths of the directional couplers that form the optical coupling parts 31 through 33 and the gaps between the optical waveguides are controlled so that the ratio of the quantity of light emitted from the optical waveguides on the light emission side to the quantity of light that has entered into the respective optical waveguides 23 through 25 for light input becomes the following value. In the case where light with a wavelength of 638 nm enters into the optical waveguide 25 for light input, as for the ratio of the quantity of light emitted from each optical waveguide 27 through 29 on the light emission side (light power) to the quantity of light that has entered, the quantity ratio of light emitted from the optical waveguide 27 on the light emission side that becomes the optical waveguide for light emission is 4.5% (the light attenuation is 13.5 dB), the quantity ratio of light emitted from the optical waveguide 28 on the light emission side is 74%, and the quantity ratio of light emitted from the optical waveguide 29 on the light emission side is 19%.
As for the ratio of the quantity of light emitted from each optical waveguide 27 through 29 on the light emission side (light power) to the quantity of light that has entered in the case where light having a wavelength of 520 nm has entered into the optical waveguide 24 for light input, the quantity ratio of light emitted from the optical waveguide 27 on the light emission side that becomes the optical waveguide for light emission is 4% (the light attenuation is 14 dB), the quantity ratio of light emitted from the optical waveguide 28 on the light emission side is 95%, and the ratio of the quantity of light emitted from the optical waveguide 29 on the light emission side is 1%.
As for the ratio of the quantity of light emitted from each optical waveguide 27 through 29 on the light emission side (light power) to the quantity of light that has entered in the case where light having a wavelength of 450 nm has entered into the optical waveguide 23 for light input, the quantity ratio of light emitted from the optical waveguide 27 on the light emission side that becomes the optical waveguide for light emission is 21.5% (the light attenuation is 6.7 dB), the quantity ratio of light emitted from the optical waveguide 28 on the light emission side is 72.5%, and the quantity ratio of light emitted from the optical waveguide 29 on the light emission side is 4%.
The optical waveguide 27 on the light emission side from which a light attenuation of 11.4 dB on average was gained as described above was used as an optical waveguide for light emission. The optical waveguide 28 on the light emission side from which the maximum emission power is outputted and the optical waveguide 29 on the light emission side having a small emission power were used as an optical waveguide for discarding light. In Example 1 of the present invention, an optical waveguide-type optical coupler having both a light multiplexing function and a light attenuation function can be gained, and therefore, it becomes possible to attenuate the intensity of a light beam emitted from a light source to a desired value without installing an additional optical attenuator element. In addition, there is almost no light leakage from the middle of an optical waveguide and no stray light is caused in the middle on an optical multiplexer, and thus, high-quality output light was gained without being affected by stray light.
Next, the optical waveguide-type optical multiplexer in Example 2 of the present invention is described. Only the size of the optical multiplexing unit is different, and the basic configuration is the same as in Example 1, and therefore, the optical waveguide-type optical coupler is described in reference to
As a result of the above-described setting of the size, as for the ratio of the quantity of light emitted from each optical waveguide 27 through 29 on the light emission side (light power) to the quantity of light that has entered in the case where light having a wavelength of 638 nm has entered into the optical waveguide 25 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes the optical waveguide for light emission is 1% (the light attenuation is 20 dB), the ratio of the quantity of light emitted from the optical waveguide 28 on the light emission side is 23.5%, and the ratio of the quantity of light emitted from the optical waveguide 29 on the light emission side is 73%.
As for the ratio of the quantity of light emitted from each optical waveguide 27 through 29 on the light emission side (light power) to the quantity of light that has entered in the case where light having a wavelength of 520 nm has entered into the optical waveguide 24 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes the optical waveguide for light emission is 4% (the light attenuation is 14 dB), the ratio of the quantity of light emitted from the optical waveguide 28 on the light emission side is 95%, and the ratio of the quantity of light emitted from the optical waveguide 29 on the light emission side is 1%.
As for the ratio of the quantity of light emitted from each optical waveguide 27 through 29 on the light emission side (light power) to the quantity of light that has entered in the case where light having a wavelength of 450 nm has entered into the optical waveguide 23 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes the optical waveguide for light emission is 23.5% (the light attenuation is 6.3 dB), the ratio of the quantity of light emitted from the optical waveguide 28 on the light emission side is 74.5%, and the ratio of the quantity of light emitted from the optical waveguide 29 on the light emission side is 1%.
As described above, the maximum light quantity is gained for light having a wavelength 520 nm and light having a wavelength of 450 nm from the optical waveguide 28 on the light emission side at the center, and the maximum light quantity is gained for light having a wavelength of 638 nm from the optical waveguide 29 on the light emission side, which is not the optical waveguide at the center, and thus, a light attenuation of 13.4 dB on average was gained from the optical waveguide 27 on the light emission side that is the optical waveguide for light emission. In Example 2 of the present invention as well, an optical waveguide-type optical multiplexer having both a light multiplexing function and a light attenuation function can be gained, and therefore, it becomes possible to attenuate the intensity of a light beam emitted from a light source to a desired value without installing an additional optical attenuator element. In addition, there is almost no light leakage from the middle of the optical waveguide and no stray light is caused in the middle of the multiplexer, and thus, high-quality output light was gained without being affected by stray light.
Next, the optical waveguide-type optical multiplexer in Example 3 of the present invention is described in reference to
As illustrated in
Next, the optical waveguide-type optical multiplexer in Example 4 of the present invention is described in reference to
As illustrated in
Next, the optical waveguide-type optical multiplexer in Example 5 of the present invention is described in reference to
The blue semiconductor laser chip 41 and the green semiconductor laser chip 42 are mounted so as to respectively match the entrance areas of the optical waveguides 23 and 24 for light input in the lateral direction and in the height direction with a gap vis-a-vis the entrance ends of the optical waveguides 23 and 24 for light input being 10 μm. Meanwhile, the red semiconductor laser chip 43 is mounted so as to match the emission area in the lateral direction with the gap vis-a-vis the entrance end of the optical waveguide 25 for light input being 10 μm; however, the red semiconductor laser chip 43 is slightly shifted from the entrance end of the optical waveguide 25 for light input in the height direction. The emission ends of the optical waveguides 27 through 29 on the light emission side may be a simple plane such as a plane of cleavage; however, the shape of the beams may be controlled by using a spot size converter or the like.
Here, the lengths of the directional couplers that form the optical coupling parts 31 through 33 and the gaps between the optical waveguides are controlled so that the ratio of the quantity of light emitted from the optical waveguides 27 through 29 on the light emission side to the quantity of light that has entered into the respective optical waveguides 23 through 25 for light input becomes the following value. In the case where light with a wavelength of 638 nm enters into the optical waveguide 25 for light input, as for the ratio of the quantity of light emitted from each optical waveguide 27 through 29 on the light emission side (light power) to the quantity of light that has entered, the quantity ratio of light emitted from the optical waveguide 27 on the light emission side that becomes the optical waveguide for light emission is 2%, the quantity ratio of light emitted from the optical waveguide 28 on the light emission side is 42.5%, and the quantity ratio of light emitted from the optical waveguide 29 on the light emission side is 52%.
As for the ratio of the quantity of light emitted from each optical waveguide 27 through 29 on the light emission side (light power) to the quantity of light that has entered in the case where light having a wavelength of 520 nm has entered into the optical waveguide 24 for light input, the quantity ratio of light emitted from the optical waveguide 27 on the light emission side that becomes the optical waveguide for light emission is 3%, the quantity ratio of light emitted from the optical waveguide 28 on the light emission side is 94%, and the ratio of the quantity of light emitted from the optical waveguide 29 on the light emission side is 0.5%.
As for the ratio of the quantity of light emitted from each optical waveguide 27 through 29 on the light emission side (light power) to the quantity of light that has entered in the case where light having a wavelength of 450 nm has entered into the optical waveguide 23 for light input, the quantity ratio of light emitted from the optical waveguide 27 on the light emission side that becomes the optical waveguide for light emission is 22.5%, the quantity ratio of light emitted from the optical waveguide 28 on the light emission side is 74%, and the quantity ratio of light emitted from the optical waveguide 29 on the light emission side is 1%.
The characteristics of the optical waveguide-type optical multiplexer were gained as described above; however, in the case where the blue semiconductor laser chip 41, the green semiconductor laser chip 42 and the red semiconductor laser chip 43 are operated with the same output, the following results were gained concerning the output light power from the respective optical waveguides 27, 28 and 29 on the light emission side due to a shift in the height direction between the emission area of the red semiconductor laser chip 43 and the entrance end of the optical waveguide 25 for light input. That is to say, for light having a wavelength of 638 nm from the red semiconductor laser chip 43, the quantity of light emitted from the optical waveguide 27 on the light emission side (light power) was 0.02 mW, the quantity of light emitted from the optical waveguide 28 on the light emission side (light power) was 0.4 mW, and the quantity of light emitted from the optical waveguide 29 on the light emission side (light power) was 0.5 mW. For light having a wavelength of 520 nm from the blue semiconductor laser chip 42, the quantity of light emitted from the optical waveguide 27 on the light emission side (light power) was 0.3 mW, the quantity of light emitted from the optical waveguide 28 on the light emission side (light power) was 9.4 mW, and the quantity of light emitted from the optical waveguide 29 on the light emission side (light power) was 0.05 mW. For light having a wavelength of 450 nm from the blue semiconductor laser chip 41, the quantity of light emitted from the optical waveguide 27 on the light emission side (light power) was 2.25 mW, the quantity of light emitted from the optical waveguide 28 on the light emission side (light power) was 7.4 mW, and the quantity of light emitted from the optical waveguide 29 on the light emission side (light power) was 0.1 mW.
As a result, the multiplexed output light quantity emitted from the optical waveguide 27 on the light emission side (light power) was 2.57 mW, the multiplexed output light quantity emitted from the optical waveguide 28 on the light emission side (light power) was 17.2 mW, and the multiplexed output light quantity emitted from the optical waveguide 29 on the light emission side (light power) was 0.65 mW. Therefore, in the case where the three light sources, the blue semiconductor laser chip 41, the green semiconductor laser chip 42 and the red semiconductor laser chip 43, are driven with the same output, the optical waveguide 29 on the light emission side that can gain the maximum output light power at least for the wavelength of 638 nm from among the optical waveguides on the light emission side excluding the optical waveguide 28 on the light emission side that can gain the greatest multiplexed output light power was used as the optical waveguide for light emission.
In Example 5 of the present invention, an optical waveguide-type optical multiplexer having both a light multiplexing function and a light attenuation function can be gained, and therefore, it becomes possible to attenuate the intensity of a light beam emitted from a light source to a desired value without installing an additional optical attenuator element. In addition, there is almost no light leakage from the middle of the optical waveguides and no stray light is caused in the middle of the optical multiplexer, and thus, high-quality output light is gained without being affected by stray light.
Next, the optical waveguide-type optical multiplexer in Example 6 of the present invention is described in reference to
In Example 6 of the present invention, the respective semiconductor laser chips are arranged along the long sides of an Si substrate, and therefore, in the case where a light source module is formed thereof, the length of the light source module can be made short. In addition, such a configuration can allow an optical multiplexing light source device having an extremely simple structure with both a light multiplexing function and a light attenuation function to be realized with only being slightly affected by stray light.
Next, the optical waveguide-type optical multiplexer in Example 7 of the present invention is described in reference to
In Example 7 of the present invention, the respective semiconductor laser chips are arranged along one long side of the Si substrate, and therefore, in the case where a light source module is formed, the length of the light source module can be made short, and at the same time, the width can be made short. Such a configuration can be extremely simple, and makes it possible to realize an optical multiplexing light source device having both a light multiplexing function and a light attenuation function without being affected by stray light.
Next, the optical waveguide-type optical multiplexer in Example 8 of the present invention is described in reference to
As illustrated in
Next, the optical waveguide-type optical multiplexer in Example 9 of the present invention is described in reference to
As illustrated in
Next, the optical waveguide-type optical multiplexer in Example 10 of the present invention is described in reference to
As illustrated in
Next, the optical waveguide-type optical multiplexer in Example 11 of the present invention is described in reference to
In Example 11 of the present invention, the optical coupling ratio between the optical waveguides 23 through 25 for light input and the optical waveguide 51 for light input is adjusted so that the attenuation of the output from each semiconductor laser chip can be arbitrarily set, which makes designing easy.
Next, the optical waveguide-type optical multiplexer in Example 12 of the present invention is described in reference to
In Example 12 of the present invention, a bent optical waveguide 38 is provided in proximity to the emission end of the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission, and therefore, stray light that has leaked out from the optical coupling parts 31 through 33 in the optical multiplexing unit 30 can surely be prevented from overlapping with the multiplexed light.
Next, the optical waveguide-type optical multiplexer in Example 13 of the present invention is described in reference to
As illustrated in
As illustrated in
As for the ratio of the quantity of light (light power) emitted from each optical waveguide 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 638 nm has entered into the optical waveguide 25 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission is 1.5% (the light attenuation is 18.2 dB), the ratio of quantity of light emitted from the optical waveguide 28 on the light emission side is 41%, and the ratio of quantity of light emitted from the optical waveguide 29 on the light emission side is 8%.
As for the ratio of the quantity of light (light power) emitted from each optical waveguide 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 520 nm has entered into the optical waveguide 24 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission is 4% (the light attenuation is 14 dB), the ratio of quantity of light emitted from the optical waveguide 28 on the light emission side is 95%, and the ratio of quantity of light emitted from the optical waveguide 29 on the light emission side is 1%.
As for the ratio of the quantity of light (light power) emitted from each optical waveguide 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 450 nm has entered into the optical waveguide 23 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission is 21.5% (the light attenuation is 6.7 dB), the ratio of quantity of light emitted from the optical waveguide 28 on the light emission side is 72.5%, and the ratio of quantity of light emitted from the optical waveguide 29 on the light emission side is 4%.
As for the ratio of the quantity of light (light power) emitted from each optical waveguide 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 570 nm has entered into the optical waveguide 48 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission is 12.5% (the light attenuation is 9 dB), the ratio of quantity of light emitted from the optical waveguide 28 on the light emission side is 7.5%, and the ratio of quantity of light emitted from the optical waveguide 29 on the light emission side is 22.5%.
From among these, the optical waveguide 25 for light input through which red light with a wavelength of 638 nm propagates and the optical waveguide 48 for light input through which yellow light with a wavelength of 570 nm propagates are connected through the Y-branched type multiplexer so as to multiplex the red and yellow light, and therefore, a loss of 3 dB is caused in the Y-branched type multiplexer. As a result, the quantity of light emitted from the optical waveguide 29 on the light emission side that becomes an optical waveguide for emitting light relative to the quantity of light that has entered into the respective optical waveguides 23 through 25 and 48 for light input becomes 16 dB for light with a wavelength of 638 nm and 20 dB for yellow light with a wavelength of 570 nm. As described above, the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission has a light attenuation of 16.1 dB on average relative to the light that has entered into the optical waveguides for light input.
Next, the light source module in Example 14 of the present invention is described in reference to
Next, the optical waveguide-type multiplexing light source optical device in Example 15 of the present invention is described in reference to
In this case, the MEMS mirror 74 for two-dimensional scanning with light is an electromagnetic drive type MEMS mirror where the reflecting surface is formed of metal glass. This metal glass is also used as the optical scanning rotation axis for rotating the mirror. The MEMS 74 for two-dimensional scanning with light is fabricated by forming an Fe—Pt thin film (thickness of 142 nm) and a metal glass film (thickness of 10 μm) in this order on top of an Si substrate having a (100) surface as the main surface and a thickness of 100 μm. The size of the mirror that becomes the reflecting unit is 500 μm×300 μm. The size of the entirety of the MEMS mirror 74 for two-dimensional scanning with light is 2.7 mm×2.5 mm, and the optical scanning rotation axis in the mirror portion agrees with the <010> direction of the Si substrate having a (100) surface as the main surface. An electromagnetic coil made of a solenoid coil as illustrated in
An image was projected on a screen with the reflected beams in order to evaluate the deflection angle of the light beam. As a result, the beam deflection angles of 30 degrees in the longitudinal direction and 5 degrees in the lateral direction were gained, and thus, it was possible to project an image.
Next, the optical waveguide-type multiplexing light source optical device in Example 16 of the present invention is described in reference to
In Example 16, the light output that is originally to be discarded is used for monitoring, and therefore, fluctuations of a signal light from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission can be controlled.
Next, the optical waveguide-type multiplexing light source optical device in Example 17 of the present invention is described in reference to
Next, the optical waveguide-type multiplexing light source optical device in Example 18 of the present invention is described in reference to
Next, the optical waveguide-type multiplexing light source optical device in Example 19 of the present invention is described in reference to
Here, an optical fiber having a fiber diameter of 125 μm through which light in a visible light range propagates in a single mode is used as the optical fiber 72. A biconvex lens having a focal distance of 10 mm and a diameter of 3 mm is used as the condenser lens 71. The distance between the optical waveguide 27 on the light emission side and the center of the condenser lens 71 is 20 mm, and the distance between the center of the condenser lens 71 and the entrance end of the optical fiber 72 is 20 mm.
In this case as well, the light beam that has entered via the condenser lens 71 is emitted from the opposite side of the optical fiber 72 so as to be reflected from the MEMS mirror for two-dimensional scanning with light, and thus, an image can be projected onto a screen.
Next, the optical waveguide-type multiplexing light source optical device in Example 20 of the present invention is described in reference to
Here, a biconvex lens having a focal distance of 10 mm and a diameter of 3 mm is used as the condenser lenses 44 through 46. The distance between the emission ends of the blue semiconductor laser chip 41, the green semiconductor laser chip 42 and the red semiconductor laser chip 43 and the centers of condenser lenses 44 through 46 is 20 mm, and the distance between the centers of the condenser lenses 44 through 46 and the entrance ends of the optical waveguides 23 through 25 for light input is 20 mm.
As for the ratio of the quantity of light (light power) emitted from each optical waveguide 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 638 nm has entered into the optical waveguide 25 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission is 4.5% (the light attenuation is 13.5 dB), the ratio of quantity of light emitted from the optical waveguide 28 on the light emission side is 74%, and the ratio of quantity of light emitted from the optical waveguide 29 on the light emission side is 19%.
As for the ratio of the quantity of light (light power) emitted from each optical waveguide 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 520 nm has entered into the optical waveguide 24 for light input, the ratio of the quantity of light emitted from the optical waveguide 29 on the light emission side that becomes an optical waveguide for light emission is 4% (the light attenuation is 14 dB), the ratio of quantity of light emitted from the optical waveguide 28 on the light emission side is 95%, and the ratio of quantity of light emitted from the optical waveguide 29 on the light emission side is 1%.
As for the ratio of the quantity of light (light power) emitted from each optical waveguide 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 450 nm has entered into the optical waveguide 23 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission is 21.5% (the light attenuation is 6.7 dB), the ratio of quantity of light emitted from the optical waveguide 28 on the light emission side is 72.5%, and the ratio of quantity of light emitted from the optical waveguide 29 on the light emission side is 4%.
As described above, a light attenuation of 11.4 dB on average was gained. In addition, there was almost no light leakage from the middle of the optical waveguides and no stray light was caused in the middle of the multiplexers, and thus, high-quality output light was gained without being affected by stray light. In addition, the light beam from the emission end of the optical waveguide 29 on the light emission side that became an optical waveguide for light emission was able to be made to enter the MEMS mirror for two-dimensional scanning with light via a condenser lens in the same manner as in Example 17, and as a result of scanning with light, it was possible to project an image onto a screen.
Next, the optical waveguide-type multiplexing light source optical device in Example 21 of the present invention is described in reference to
As illustrated in
Here, an optical fiber with a lensed end having a fiber diameter of 125 μm, a beam spot diameter of 2.5 μm and a working distance of 14 μm through which light in a visible light range propagates in a single mode is used as the optical fibers 64 through 66 with a lensed end. The wavelength of light that propagates through the optical fiber 64 with a lensed end is 450 nm, the wavelength of light that propagates through the optical fiber 65 with a lensed end is 520 nm, and the wavelength of light that propagates through the optical fiber 66 with a lensed end is 638 nm.
In this case as well, almost the same characteristics as in Example 14 were gained. In addition, the light beam from the emission end of the optical waveguide 27 on the light emission side that became an optical waveguide for light emission was able to be made to enter the MEMS mirror for two-dimensional scanning with light via a condenser lens in the same manner as in Example 17, and as a result of scanning with light, it was possible to project an image onto a screen. Here, the optical fibers 64 through 66 with a lensed end were used; however, it was possible to gain similar results with regular optical fibers that are cut with an end surface, though the entrance efficiency was lower by 3 dB.
Next, the optical waveguide-type multiplexing light source optical device in Example 22 of the present invention is described in reference to
As illustrated in
Here, optical fibers having a fiber diameter of 125 μm through which light in a visible light range propagates in a single mode are used as the optical fibers 61 through 63. Biconvex lenses having a focal distance of 10 mm and a diameter of 3 mm are used as the condenser lenses 44 through 46. The distance between the emission ends of the optical fibers 61 through 63 and the centers of the condenser lenses 44 through 46 is 20 mm, and the distance between the centers of the condenser lenses 44 through 46 and the entrance ends of the optical waveguides 23 through 25 for light input is 20 mm.
In this case as well, almost the same characteristics as in Example 14 were gained. In addition, the light beam from the emission end of the optical waveguide 27 on the light emission side that became an optical waveguide for light emission was able to be made to enter the MEMS mirror for two-dimensional scanning with light via a condenser lens in the same manner as in Example 17, and as a result of scanning with light, it was possible to project an image onto a screen.
Next, the light source module in Example 23 of the present invention is described in reference to
As for the ratio of the quantity of light (light power) emitted from the respective optical waveguides 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 240 nm enters into the optical waveguide 25 for light input, the quantity ratio of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission is 5% (the light attenuation is 13 dB), the quantity ratio of light emitted from the optical waveguide 28 on the light emission side is 75%, and the quantity ratio of light emitted from the optical waveguide 29 on the light emission side is 18%.
As for the ratio of the quantity of light (light power) emitted from each optical waveguide 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 522 nm has entered into the optical waveguide 24 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission is 4% (the light attenuation is 14 dB), the ratio of quantity of light emitted from the optical waveguide 28 on the light emission side is 95%, and the ratio of quantity of light emitted from the optical waveguide 29 on the light emission side is 1%.
As for the ratio of the quantity of light (light power) emitted from each optical waveguide 27 through 29 on the light emission side to the quantity of light that has entered in the case where light with a wavelength of 452 nm has entered into the optical waveguide 23 for light input, the ratio of the quantity of light emitted from the optical waveguide 27 on the light emission side that becomes an optical waveguide for light emission is 20% (the light attenuation is 7 dB), the ratio of quantity of light emitted from the optical waveguide 28 on the light emission side is 73%, and the ratio of quantity of light emitted from the optical waveguide 29 on the light emission side is 4%.
As described above, a light attenuation of 11.3 dB on average was gained. In addition, there was almost no light leakage from the middle of the optical waveguides, and no stray light was caused in the middle of the multiplexer, and thus, a high-quality output light was gained without being affected by stray light. In addition, the light beam from the emission end of the optical waveguide 27 on the light emission side that became an optical waveguide for light emission was able to be made to enter the MEMS mirror for two-dimensional scanning with light via a condenser lens in the same manner as in Example 17, and as a result of scanning with light, it was possible to project an image onto a screen. Though end surface emission-type light emitting diodes are used in Example 22, other types of light emitting diodes, for example, surface emission-type light emitting diodes, may be used.
Next, the optical waveguide-type multiplexing light source optical device in Example 24 of the present invention is described in reference to
Next, the image formation device in Example 25 of the present invention is described. The basic configuration is the same as that of the image formation device illustrated in
In this image formation device, in the same manner as in the prior art, a control unit 90 has a sub-control unit 91, an operation unit 92, an external interface (I/F) 93, an R laser driver 94, a G laser driver 95, a B laser driver 96 and a two-dimensional scanning driver 97. The sub-control unit 91 is formed of a microcomputer that includes a CPU, a ROM, a RAM and the like. The sub-control unit 91 generates an R signal, a G signal, a B signal, a horizontal signal and a vertical signal that become elements for synthesizing an image on the basis of the image data supplied from an external apparatus such as a PC via the external I/F 93. The sub-control unit 91 transmits the R signal to the R laser driver 94, the G signal to the G laser driver 95, and the b signal to the B laser driver 96, respectively. In addition, the sub-control unit 91 transmits the horizontal signal and the vertical signal to the two-dimensional scanning driver 97, and controls the current to be applied to the electromagnetic coil 86 so as to control the operation of the movable mirror unit 84.
The R laser driver 94 drives the red semiconductor laser chip 43 so that a red laser beam of which the optical quantity corresponds to the R signal from the sub-control unit 91 is generated. The G laser driver 95 drives the green semiconductor laser chip 42 so that a green laser beam of which the optical quantity corresponds to the G signal from the sub-control unit 91. The B laser driver 96 drives the blue semiconductor laser chip 41 so that a blue laser beam of which the light quantity corresponds to the B signal from the sub-control unit 91 is generated. It becomes possible to synthesize a laser beam having a desired color by adjusting the intensity ratio between the laser beams of the respective colors.
The respective laser beams generated in the blue semiconductor laser chip 41, the green semiconductor laser chip 42 and the red semiconductor laser chip 43 are multiplexed in the optical multiplexing unit 30 in the optical waveguide-type optical multiplexer, and after that reflected from the movable mirror unit 84 for two-dimensional scanning. An image is formed on a retina 100 as a result of scanning with the multiplexed laser beam that has been reflected from a concave reflection mirror 98 and passed through a pupil 99.
Next, the optical waveguide-type optical multiplexer in Example 26 of the present invention is described in reference to
As illustrated in
Next, the optical waveguide-type optical multiplexer in Example 27 of the present invention is described in reference to
As illustrated in
Next, the optical waveguide-type optical multiplexer in Example 28 of the present invention is described in reference to
As illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-046162 | Mar 2019 | JP | national |
This application is a continuation application of International Application Number PCT/JP2020/006480 filed on Feb. 19, 2020, now pending, herein incorporated by reference. Further, this application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2019-46162, filed on Mar. 13, 2019, entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2020/006480 | Feb 2020 | US |
| Child | 17159476 | US |
