CN114647091A - Laser scanning light source and display device - Google Patents
Laser scanning light source and display device Download PDFInfo
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- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
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- G02B26/101—Scanning systems with both horizontal and vertical deflecting means, e.g. raster or XY scanners
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Abstract
The embodiment of the invention provides a laser scanning light source and display equipment, wherein the laser scanning light source comprises: a light emitting element that emits a linearly polarized visible light beam; a waveguide into which the visible light beam is incident; and the polarization rotator is integrated in the waveguide and used for realizing the mutual conversion between the TE mode light and the TM mode light in the visible light beam. The embodiment of the invention provides a laser scanning light source and display equipment, which are used for inhibiting laser speckles and improving the display effect.
Description
Technical Field
The invention relates to a display technology, in particular to a laser scanning light source and a display device.
Background
Typical laser beam scanning display systems are described in patents such as US20080225366a1, US20120257262a1 and the like. The technology utilizes the characteristic of good laser directivity, and dynamically changes the direction of a laser beam through a scanning device (a galvanometer, a scanning mirror and the like) to scan the laser beam on a screen to form a picture. The technology does not need complex optical elements, the structure can be greatly simplified, and the light utilization efficiency is greatly increased. For the dark field in the picture, because the brightness of the light source is actively controlled, the problem of light leakage does not exist, and therefore, the laser display adopting the scanning mode has high contrast. On the other hand, since a large amount of dark part images exist in a common image, the laser outputs low power most of the time, which causes the laser beam to have low power consumption when scanning and displaying a video stream in practical use. Due to these advantages, the laser beam scanning display technology is considered to have a wide application prospect in the field of micro display. In a laser beam scanning display system, due to the strong coherence of laser, random point-like interference spots appear when a picture is displayed, so that the display effect is deteriorated, and the laser beam scanning display system becomes a technical problem to be solved urgently.
At present, no mature technology for suppressing speckle based on optics exists in a laser beam scanning display system, and fig. 1 is a schematic diagram of a laser display system based on DLP in the prior art, and referring to fig. 1, the laser display system based on DLP comprises a scattering sheet 11 and a display chip 12. The rotating scattering sheet 11 introduces time-varying disturbance to the laser, so that the effect of inhibiting display picture speckles is obtained. The mode as shown in fig. 1 needs the aid of a moving device, which affects the stability and reliability of the system and limits the application range of the system.
Disclosure of Invention
The embodiment of the invention provides a laser scanning light source and display equipment, which are used for inhibiting laser speckles and improving the display effect.
In a first aspect, an embodiment of the present invention provides a laser scanning light source, including:
a light emitting element that emits a linearly polarized visible light beam;
a waveguide into which the visible light beam is incident;
the waveguide includes a polarization rotator for enabling interconversion between TE mode light and TM mode light.
Optionally, the plurality of light emitting elements comprises a first light emitting element, a second light emitting element and a third light emitting element;
the first light emitting element emits light of a first wavelength, the second light emitting element emits light of a second wavelength, and the third light emitting element emits light of a third wavelength, any two of the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength having different colors.
Optionally, the plurality of waveguides includes a first waveguide, a second waveguide and a third waveguide arranged in sequence;
the first wavelength light is incident into the first waveguide, the second wavelength light is incident into the second waveguide, and the third wavelength light is incident into the third waveguide;
the plurality of polarization rotators includes a first polarization rotator located in the first waveguide, a second polarization rotator located in the second waveguide, and a third polarization rotator located in the third waveguide.
Optionally, the plurality of waveguides includes a first waveguide, a second waveguide and a third waveguide arranged in sequence;
the first wavelength light is incident into the first waveguide, the second wavelength light is incident into the second waveguide, and the third wavelength light is incident into the third waveguide;
the first waveguide and the second waveguide form a first coupling region for coupling the first wavelength light into the second waveguide;
the second waveguide and the third waveguide form a second coupling region for coupling the third wavelength light into the second waveguide;
the polarization rotator is located in the second waveguide on a side of the first coupling region and the second coupling region away from the second light emitting element.
Optionally, the plurality of waveguides includes a first waveguide, a second waveguide and a third waveguide arranged in sequence;
the first wavelength light is incident into the first waveguide, the second wavelength light is incident into the second waveguide, and the third wavelength light is incident into the third waveguide;
the first waveguide and the second waveguide forming a first coupling region and a third coupling region, both for coupling the first wavelength light into the second waveguide;
the second waveguide and the third waveguide form a second coupling region for coupling the third wavelength light into the second waveguide;
the polarization rotator is located in the second waveguide on a side of the first, second, and third coupling regions away from the second light emitting element.
Optionally, the plurality of light emitting elements further comprises a fourth light emitting element and a fifth light emitting element; the fourth light emitting element emits light of the second wavelength and the fifth light emitting element emits light of the third wavelength;
the plurality of waveguides further includes a fourth waveguide and a fifth waveguide; the light with the second wavelength is incident into the fourth waveguide, and the light with the third wavelength is incident into the fifth waveguide;
the plurality of polarization rotators further comprises a fourth polarization rotator located in the fourth waveguide and a fifth polarization rotator located in the fifth waveguide.
Optionally, the light converted by the polarization rotator includes TE mode light and TM mode light, and light energy of the TE mode light is ITELight energy of TM mode light is ITMAnd satisfies the following conditions:
optionally, a waveguide substrate, the waveguide substrate being glass;
the waveguide is formed by means of ion implantation on the waveguide substrate;
the polarization rotator comprises a body part and an additional part, wherein the body part and the waveguide have the same width and height, the additional part and the body part are integrally formed, and the width of the additional part is gradually increased along the direction away from the light-emitting element;
wherein the height refers to a distance in a direction perpendicular to the waveguide substrate, and the width refers to a distance in a direction parallel to the waveguide substrate and perpendicular to the waveguide extending direction.
Optionally, the optical waveguide further comprises a waveguide substrate and a covering layer, wherein the waveguide is positioned between the waveguide substrate and the covering layer, and the waveguide substrate and the covering layer both comprise SiO2The waveguide comprises Si3N 4;
the polarization rotator includes a body part having the same width and height as the waveguide, and a removal part which is a groove formed on the body part;
wherein the height refers to a distance in a direction perpendicular to the waveguide substrate, and the width refers to a distance in a direction parallel to the waveguide substrate and perpendicular to the waveguide extending direction.
In a second aspect, an embodiment of the present invention provides a display apparatus, which includes the laser scanning light source of the first aspect, and a scanning device that two-dimensionally scans a visible light beam emitted from the laser scanning light source to form an image.
In the embodiment of the invention, the light-emitting element emits visible light beams, the visible light beams are laser, the visible light beams are coupled into the waveguide, because the visible light beam is linearly polarized light and is transmitted in a single polarization mode (namely TE mode light or TM mode light) after entering the waveguide, one or more sections of polarization rotators are added in a passage of the waveguide to convert part of light into a mode orthogonal to the polarization state of incident light (for example, when the incident light is TE mode light, part of the TE mode light is converted into TM mode light, and when the incident light is TM mode light, part of the TM mode light is converted into TE mode light), so that the emergent light beam simultaneously comprises the TE mode light and the TM mode light, and the state number of the emergent light beam is increased by utilizing different transmission characteristics of the TE mode light and the TM mode light, thereby reducing the speckle contrast of a display picture, inhibiting laser speckle and improving the display effect.
Drawings
FIG. 1 is a schematic diagram of a laser beam scanning display system in the prior art;
fig. 2 is a top view of a laser scanning light source according to an embodiment of the present invention;
FIG. 3 is a top view of another laser scanning light source according to an embodiment of the present invention;
FIG. 4 is a top view of another laser scanning light source according to an embodiment of the present invention;
FIG. 5 is a top view of another laser scanning light source according to an embodiment of the present invention;
FIG. 6 is a schematic cross-sectional view along AA' in FIG. 2;
fig. 7 is a schematic structural diagram of a polarization rotator according to an embodiment of the present invention;
FIG. 8 is a schematic cross-sectional view taken along line BB' in FIG. 3;
FIG. 9 is a schematic diagram of another polarization rotator according to an embodiment of the present invention;
FIG. 10 is a schematic cross-sectional view taken along line CC' of FIG. 4;
fig. 11 is a schematic structural diagram of a display device according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
When laser is irradiated on the surface of rough objects such as wall or paper, many granular patterns with relative uniformity but no specific distribution rule are generated, and the random fluctuation of the light intensity is an interference phenomenon formed by the irradiation of coherent light on the rough surface, which is called speckle.
Laser speckle is judged by the index of speckle contrast. The speckle contrast C is defined as the standard deviation σ of the speckle image intensity valuesIAnd the average value
Ratio ofNamely:
c is between 0 and 1, and the higher the value of the speckle contrast C, the more apparent the speckle and the stronger the graininess. Typically, the threshold value for speckle contrast that can be perceived by the human eye is 0.04.
In the field of laser imaging, the smaller the speckle contrast, the better. The use of a stack of several independent speckles can reduce the overall speckle contrast to some extent. For intensity of InThe total intensity speckle contrast after the superposition of the N independent coherent light beams is
When the average intensity of each individual speckle is equal there are:
it can be seen that the greater the number of independent speckle patterns, the lower the speckle contrast.
Fig. 2 is a top view of a laser scanning light source according to an embodiment of the present invention, and referring to fig. 2, the laser scanning light source includes a light emitting element 20 and a waveguide 30. The light emitting element 20 emits a linearly polarized visible light beam. The visible light beam emitted by the light emitting element 20 is incident into the waveguide 30, and the waveguide 30 serves as a propagation channel of the visible light beam for transmitting the visible light beam, and has at least the following advantages:
(1) light waves propagate in the waveguide 30 and are easily controlled and retain their energy. (2) The firm location that integrates and bring. Integrated optics expects several devices to be fabricated on the same substrate and thus there are no assembly problems with discrete optical devices, which allows for a stable combination and therefore a strong adaptability to environmental factors such as vibration and temperature. . . (3) Integrated optical devices are typically integrated on millimeter-scale substrates and have the characteristics of small size and light weight.
With continued reference to fig. 2, the laser scanning light source further includes a polarization rotator 40, the polarization rotator 40 being integrated in the waveguide 30 for achieving interconversion between TE mode light and TM mode light in the visible light beam. The polarization rotator 40 is formed by modifying the shape of a portion of the waveguide 30 on the basis of the waveguide 30. Wherein, the electric field direction of the TE mode light is always perpendicular to the propagation direction of the light in the waveguide 30 during the propagation process, and the magnetic field direction of the TM mode light is always perpendicular to the propagation direction of the light in the waveguide 30 during the propagation process. The TE mode light and the TM mode light have different propagation velocities in the waveguide 30. The polarization rotator 40 may convert a portion of the incident TE mode light into TM mode light, or may convert a portion of the incident TM mode light into TE mode light.
In the embodiment of the present invention, the light emitting element 20 emits a visible light beam, the visible light beam is a laser, the visible light beam is coupled into the waveguide 30, and since the visible light beam is linearly polarized light, the visible light beam propagates in a single polarization mode (i.e. TE mode light or TM mode light) after entering the waveguide 30, one or more sections of polarization rotators 40 are added in a path of the waveguide 30 to convert a part of light into a mode orthogonal to the polarization state of the incident light (for example, if the incident light is TE mode light, a part of the TE mode light is converted into TM mode light, and if the incident light is TM mode light, a part of the TM mode light is converted into TE mode light), so that the emitted light beam simultaneously includes TE mode light and TM mode light, and the state number of the emitted light beam is increased by using different transmission characteristics of the TE mode light and the TM mode light, thereby reducing the speckle contrast of the display screen and suppressing laser speckle, the display effect is improved.
In one embodiment, the laser scanning light source includes a light emitting element 20 and a waveguide 30, and a visible light beam emitted from the light emitting element 20 is projected into the waveguide 30.
In another embodiment, the laser scanning light source comprises a plurality of light emitting elements 20 and a plurality of waveguides 30, the number of light emitting elements 20 being the same as the number of waveguides 30. The visible light beams emitted from the light emitting elements 20 are projected into the waveguides 30 corresponding to one of them. The plurality of light emitting elements 20 have the same emission color.
In another embodiment, the laser scanning light source comprises a plurality of light emitting elements 20 and a plurality of waveguides 30, the number of light emitting elements 20 being the same as the number of waveguides 30. The visible light beams emitted from the light emitting elements 20 are projected into the waveguides 30 corresponding to one of them. Since the plurality of light-emitting elements 20 have a plurality of different emission colors, color display can be realized. Hereinafter, a laser scanning light source for realizing color display will be further described.
Alternatively, referring to fig. 2, the plurality of light emitting elements 20 includes a first light emitting element 21, a second light emitting element 22, and a third light emitting element 23. The first light emitting element 21 emits light of a first wavelength, the second light emitting element 22 emits light of a second wavelength, and the third light emitting element 23 emits light of a third wavelength. Any two of the first wavelength light, the second wavelength light and the third wavelength light have different colors, and any two of the first wavelength light, the second wavelength light and the third wavelength light have different light-emitting wavelengths.
Alternatively, referring to fig. 2, the plurality of waveguides 30 includes a first waveguide 31, a second waveguide 32, and a third waveguide 33 arranged in this order. The light of the first wavelength is incident into the first waveguide 31, the light of the second wavelength is incident into the second waveguide 32, and the light of the third wavelength is incident into the third waveguide 33. The plurality of polarization rotators 40 includes a first polarization rotator 41, a second polarization rotator 42, and a third polarization rotator 43. A first polarization rotator 41 is located in the first waveguide 31, a second polarization rotator 42 is located in the second waveguide 32, and a third polarization rotator 43 is located in the third waveguide 33. In the embodiment of the present invention, the first polarization rotator 41 is correspondingly disposed for the first waveguide 31, and is used for interconversion between TE mode light and TM mode light in the first wavelength light. A second polarization rotator 42 is correspondingly provided for the second waveguide 32 for interconversion between TE mode light and TM mode light at the second wavelength light. A third polarization rotator 43 is correspondingly provided for the third waveguide 33 for interconversion between TE mode light and TM mode light in the third wavelength light.
Fig. 3 is a top view of another laser scanning light source according to an embodiment of the present invention, and referring to fig. 3, the plurality of waveguides 30 includes a first waveguide 31, a second waveguide 32, and a third waveguide 33 arranged in sequence. The light of the first wavelength is incident into the first waveguide 31, the light of the second wavelength is incident into the second waveguide 32, and the light of the third wavelength is incident into the third waveguide 33. The first waveguide 31 and the second waveguide 32 form a first coupling region 51, the first coupling region 51 being for coupling the first wavelength light into the second waveguide 32. The second waveguide 32 and the third waveguide 33 form a second coupling region 52, the second coupling region 52 being for coupling the third wavelength light into the second waveguide 32. The polarization rotator 40 is located in the second waveguide 32 on a side of the first coupling region 51 and the second coupling region 52 remote from the second light emitting element 22. In the embodiment of the present invention, the first wavelength light is coupled into the second waveguide 32 at the first coupling region 51, and the third wavelength light is coupled into the second waveguide 32 at the second coupling region 52, so that the first wavelength light, the second wavelength light, and the third wavelength light all propagate in the second waveguide 32, and therefore, the polarization rotator 40 is only disposed in the second waveguide 32, and the polarization rotator 40 is used for mutual conversion between TE mode light and TM mode light in the first wavelength light, the second wavelength light, and the third wavelength light.
Fig. 4 is a top view of another laser scanning light source provided in an embodiment of the present invention, and referring to fig. 4, the first waveguide 31 and the second waveguide 32 form a first coupling region 51 and a third coupling region 53, and both the first coupling region 51 and the third coupling region 53 are used for coupling the light of the first wavelength into the second waveguide 32. The second waveguide 32 and the third waveguide 33 form a second coupling region 52, the second coupling region 52 being for coupling the third wavelength light into the second waveguide 32. The polarization rotator 40 is located in the second waveguide 32 on a side of the first coupling region 51, the second coupling region 52 and the third coupling region 53 remote from the second light emitting element 22. In the embodiment of the present invention, the polarization rotator 40 is disposed only in the second waveguide 32, and the polarization rotator 40 is used for interconversion between TE mode light and TM mode light among the first wavelength light, the second wavelength light and the third wavelength light.
In an embodiment, the first coupling region 51, the second coupling region 52 and the third coupling region 53 may comprise a wave combiner for coupling the visible light beams propagating in the at least two waveguides 30.
Fig. 5 is a top view of another laser scanning light source according to an embodiment of the present invention, and referring to fig. 5, the plurality of light emitting elements 20 further includes a fourth light emitting element 24 and a fifth light emitting element 25. The fourth light emitting element 24 emits light of the second wavelength and the fifth light emitting element 25 emits light of the third wavelength. The plurality of waveguides 30 further includes a fourth waveguide 34 and a fifth waveguide 35. The light of the second wavelength emitted by the fourth light emitting element 24 is incident into the fourth waveguide 34, and the light of the third wavelength emitted by the fifth light emitting element 25 is incident into the fifth waveguide 35. The plurality of polarization rotators 40 further comprises a fourth polarization rotator 44 and a fifth polarization rotator 45, the fourth polarization rotator 44 being located in the fourth waveguide 34 and the fifth polarization rotator 45 being located in the fifth waveguide 35. In the embodiment of the present invention, the first polarization rotator 41 is correspondingly disposed for the first waveguide 31, and is used for interconversion between TE mode light and TM mode light in the first wavelength light. A second polarization rotator 42 is correspondingly provided for the second waveguide 32 for interconversion between TE mode light and TM mode light at the second wavelength light. A third polarization rotator 43 is correspondingly provided for the third waveguide 33 for interconversion between TE mode light and TM mode light at the third wavelength light. A fourth polarization rotator 44 is correspondingly provided for the fourth waveguide 34 for interconversion between TE mode light and TM mode light at the second wavelength. A fifth polarization rotator 45 is correspondingly provided for the fifth waveguide 35 for interconversion between TE mode light and TM mode light in the third wavelength light. The laser scanning light source in the embodiment of the present invention can provide a greater illumination luminance because five light emitting elements 20 are provided.
Optionally, the first wavelength light is blue light, the second wavelength light is green light, and the third wavelength light is red light.
Optionally, the light converted by the polarization rotator 40 includes TE mode light and TM mode light, and the light energy of the TE mode light is ITELight energy of TM mode light is ITMAnd satisfies the following conditions:
in the embodiment of the present invention, the light converted by the polarization rotator 40 includes TE mode light and TM mode light, that is, the emergent light of the laser scanning light source includes TE mode light and TM mode light, and the light energy of the two light satisfies the above formula, so that the display speckle contrast can be effectively reduced, the laser speckle is suppressed, and the display effect is improved.
Fig. 6 is a schematic cross-sectional structure along AA' in fig. 2, fig. 7 is a schematic structural view of a polarization rotator according to an embodiment of the present invention, and referring to fig. 2, fig. 6 and fig. 7, the laser scanning light source further includes a waveguide substrate 61, and the waveguide substrate 61 is glass. The waveguide 30 is formed by ion implantation on the waveguide substrate 61. The polarization rotator 40 includes a body portion 401 and an additional portion 402, the body portion 401 has the same width and height as the waveguide 30, the additional portion 402 is integrally formed with the body portion 401, and the width of the additional portion 402 gradually increases in a direction away from the light emitting element 20 (i.e., in the Z direction), and a side surface of the additional portion 402 is an inclined surface. Here, the height refers to a distance in a direction perpendicular to the waveguide base material 61, that is, a distance in the X direction. The width refers to a distance in a direction parallel to the waveguide substrate 61 and perpendicular to the extending direction of the waveguide 30, i.e., a distance in the Y direction. In the embodiment of the present invention, the difference between the propagation constants of the TE mode light and the TM mode light in the waveguide 30 is small, and a disturbance-type polarization rotator can be used to effectively reduce the display speckle contrast.
Illustratively, the first light emitting element 21 is a GaN-based semiconductor laser, and the first wavelength light is blue light having a wavelength of 450 nm. The second light emitting element 22 is an InAlGaN-based semiconductor laser, and the second wavelength light is green light having a wavelength of 520 nm. The third light emitting element 23 is an AlGaInP-based semiconductor laser, and the third wavelength light is red light having a wavelength of 638 nm. The first wavelength light, the second wavelength light and the third wavelength light are all incident on the end face of the waveguide in a transverse linear polarization state. Coupled into the waveguide and propagating primarily in the TE0 mode.
The waveguide substrate 61 was glass and had a refractive index of 1.520. The waveguide 30 produced using ion implantation has a central refractive index of 1.527, with the refractive index profile being the highest gaussian profile at the center. The waveguide 30 has a width of 4um and a height of 2um, the waveguide 30 can support TE0 mode and TM0 mode, and the propagation constant of TE0 mode is 550nm
Propagation constant of TM0 mode
The propagation constant difference between TE and TM in these modes is small, and a perturbation-type polarization rotator can be used.
After the first wavelength light, the second wavelength light and the third wavelength light pass through the polarization rotator 40, part of TE0 mode light is converted into TM0 mode light, and the length of the polarization rotator 40 is designed so that the energy ratio of the TE0 mode light to the TM0 mode light in the light mode at the outlet of the polarization rotator is 0.5-2, and therefore the display speckle contrast can be effectively reduced.
Exemplarily, referring to fig. 7, the length of the polarization rotator 40 refers to a length of the polarization rotator 40 along the extending direction of the waveguide 30 (i.e., the Z direction), and the length L of the polarization rotator 40 is greater than 2um and less than 10 um.
Fig. 8 is a schematic cross-sectional structure along BB' in fig. 3, fig. 9 is a schematic structural view of another polarization rotator according to an embodiment of the present invention, and referring to fig. 3, fig. 8 and fig. 9, the laser scanning light source further includes a waveguide substrate 61 and a cladding layer 62, and the waveguide 30 is located between the waveguide substrate 61 and the cladding layer 62. The waveguide substrate 61 and the cladding layer 62 each comprise SiO2Waveguide 30 comprises Si3N 4. The polarization rotator 40 includes a body portion 401 and a removed portion 403, the body portion 401 having the same width and height as the waveguide 30, and the removed portion 403 being a groove formed on the body portion 401. In the embodiment of the present invention, the difference between the propagation constants of the TE mode light and the TM mode light in the waveguide 30 is large, and a default polarization rotator may be used to effectively reduce the display speckle contrast.
Illustratively, the first light emitting element 21 is a GaN-based semiconductor laser, and the first wavelength light is blue light having a wavelength of 450 nm. The second light emitting element 22 is an InAlGaN-based semiconductor laser, and the second wavelength light is green light having a wavelength of 520 nm. The third light emitting element 23 is an AlGaInP-based semiconductor laser, and the third wavelength light is red light having a wavelength of 638 nm. The first wavelength light, the second wavelength light and the third wavelength light are all incident on the end face of the waveguide in a transverse linear polarization state. Coupled into the waveguide and propagating primarily in the TE0 mode.
The waveguide substrate 61 is SiO2The refractive index was 1.46. The waveguide 30 made of Si3N4 material is manufactured on the top by deposition-etching, and the refractive index of the waveguide 30 is 2.05. The waveguide 30 has a material of SiO2The cladding layer 62 ensures the reliability of the waveguide 30. The width of the waveguide 30 is 0.35um, the height of the waveguide 30 is 0.15um, and the waveguide 30 can support the TE0 mode and the TM0 mode. Propagation constant of TE0 mode at 550nm
Propagation constant of TM0 mode
Such mode propagation constant differences are large and a truncated-angle type polarization rotator can be used.
After the first wavelength light, the second wavelength light and the third wavelength light enter the waveguide 30, the first wavelength light and the third wavelength light pass through the two sections of coupling regions, so that the first wavelength light and the third wavelength light are coupled and enter the second waveguide 32. A polarization rotator 40 is added at the second waveguide 32, the first wavelength light, the second wavelength light and the third wavelength light of a TE0 mode in the waveguide 30 are partially converted into a TM0 mode, and the length of the polarization rotator 40 is designed, so that the energy ratio of a TE0 mode and a TM0 mode in the light mode at the outlet of the polarization rotator is 0.5-2, and the display speckle contrast can be effectively reduced.
Illustratively, referring to fig. 9, the area of the polarization rotator 40 has a rectangular unfilled cross-section of 0.6um x 1.2um, and the length L of the polarization rotator 40 is 4.5 um. After passing through the polarization rotator 40, the light (including the first wavelength light, the second wavelength light and the third wavelength light) in the TE0 mode with energy accounting for about 40% is converted into the TM0 mode, so that the number of independent speckles of the light source is increased, and the display speckle contrast can be effectively reduced.
Illustratively, referring to FIG. 9, the length L of the polarization rotator 40 is greater than 2um and less than 10 um.
FIG. 10 is a schematic cross-sectional view taken along line CC' in FIG. 4. referring to FIGS. 4 and 10, the laser scanning light source further comprises a waveguide substrate 61, and the waveguide substrate 61 is covered by a waveguide substrate 61SiO is included2. The waveguide 30 is formed by ion exchange on the waveguide substrate 61. The laser scanning light source provided by the embodiment of the invention can adopt a disturbance type polarization rotator or a unfilled corner type polarization rotator.
Illustratively, the first wavelength light is blue light having a wavelength of 455 nm. The second wavelength light is green light with the wavelength of 525 nm. The third wavelength light is red light with the wavelength of 642 nm. The first wavelength light, the second wavelength light and the third wavelength light are all incident on the end face of the waveguide in a transverse linear polarization state. Coupled into the waveguide and propagating primarily in the TE0 mode.
The waveguide substrate 61 is SiO2The refractive index was 1.47. The waveguide 30 is made by ion exchange, and the refractive index of the waveguide 30 is 1.51. The width of the waveguide 30 is 1.6um, the height of the waveguide 30 is 0.8um, and the waveguide 30 can support the TE0 mode and the TM0 mode. Propagation constant of TE0 mode at 550nm
Propagation constant of TM0 mode
After the first wavelength light, the second wavelength light and the third wavelength light enter the waveguide, the first wavelength light and the third wavelength light pass through the three sections of coupling regions, so that the first wavelength light and the third wavelength light are coupled and enter the second waveguide 32. A polarization rotator 40 is added at the second waveguide 32 to partially convert the TE0 mode light (including the first wavelength light, the second wavelength light and the third wavelength light) in the waveguide 30 into a TM0 mode, and the length of the polarization rotator 40 is designed to enable the energy ratio of the TE0 mode to the TM0 mode in the light mode at the outlet of the polarization rotator to be 0.5-2, so that the display speckle contrast can be effectively reduced.
Exemplarily, referring to fig. 8 or 10, the laser scanning light source further includes a substrate 63, and the waveguide base 61 and the waveguide 30 are both formed on the substrate 63.
Fig. 11 is a schematic structural diagram of a display apparatus according to an embodiment of the present invention, and referring to fig. 11, the display apparatus includes a laser scanning light source 100 and a scanning device 200, and the scanning device 200 two-dimensionally scans a visible light beam emitted from the laser scanning light source 100 to form an image.
Alternatively, the scanning device 200 includes a MEMS galvanometer, and the direction of the visible light beam is dynamically changed by the vibration of the MEMS galvanometer to scan the visible light beam on the screen to form a picture.
Optionally, the display device further includes a collimating lens 300, and the collimating lens 300 is located on an optical path between the laser scanning light source 100 and the scanning device 200, and is configured to collimate and project the visible light beam emitted from the laser scanning light source 100 onto the scanning device 200.
It is to be noted that the foregoing description is only exemplary of the invention and that the principles of the technology may be employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A laser scanning light source, comprising:
a light emitting element that emits a linearly polarized visible light beam;
a waveguide into which the visible light beam is incident;
and the polarization rotator is integrated in the waveguide and used for realizing the mutual conversion between the TE mode light and the TM mode light in the visible light beam.
2. The laser scanning light source according to claim 1, wherein the plurality of light emitting elements include a first light emitting element, a second light emitting element, and a third light emitting element;
the first light emitting element emits light of a first wavelength, the second light emitting element emits light of a second wavelength, and the third light emitting element emits light of a third wavelength, any two of the light of the first wavelength, the light of the second wavelength, and the light of the third wavelength having different colors.
3. The laser scanning light source according to claim 2, wherein the plurality of waveguides includes a first waveguide, a second waveguide, and a third waveguide arranged in this order;
the first wavelength light is incident into the first waveguide, the second wavelength light is incident into the second waveguide, and the third wavelength light is incident into the third waveguide;
the plurality of polarization rotators includes a first polarization rotator located in the first waveguide, a second polarization rotator located in the second waveguide, and a third polarization rotator located in the third waveguide.
4. The laser scanning light source of claim 2, wherein the plurality of waveguides includes a first waveguide, a second waveguide, and a third waveguide arranged in this order;
the first wavelength light is incident into the first waveguide, the second wavelength light is incident into the second waveguide, and the third wavelength light is incident into the third waveguide;
the first waveguide and the second waveguide form a first coupling region for coupling the first wavelength light into the second waveguide;
the second waveguide and the third waveguide form a second coupling region for coupling the third wavelength light into the second waveguide;
the polarization rotator is located in the second waveguide on a side of the first coupling region and the second coupling region away from the second light emitting element.
5. The laser scanning light source of claim 2, wherein the plurality of waveguides includes a first waveguide, a second waveguide, and a third waveguide arranged in this order;
the first wavelength light is incident into the first waveguide, the second wavelength light is incident into the second waveguide, and the third wavelength light is incident into the third waveguide;
the first waveguide and the second waveguide forming a first coupling region and a third coupling region, both for coupling the first wavelength light into the second waveguide;
the second waveguide and the third waveguide form a second coupling region for coupling the third wavelength light into the second waveguide;
the polarization rotator is located in the second waveguide on a side of the first, second, and third coupling regions away from the second light emitting element.
6. The laser scanning light source of claim 3, wherein the plurality of light emitting elements further includes a fourth light emitting element and a fifth light emitting element; the fourth light emitting element emits light of the second wavelength and the fifth light emitting element emits light of the third wavelength;
the plurality of waveguides further includes a fourth waveguide and a fifth waveguide; the light with the second wavelength is incident into the fourth waveguide, and the light with the third wavelength is incident into the fifth waveguide;
the plurality of polarization rotators further comprises a fourth polarization rotator located in the fourth waveguide and a fifth polarization rotator located in the fifth waveguide.
7. The laser scanning light source of claim 1, wherein the light converted by the polarization rotator comprises TE mode light and TM mode light, and the light energy of the TE mode light is ITELight energy of TM mode light is ITMAnd satisfies the following conditions:
8. the laser scanning light source of claim 1, further comprising a waveguide substrate, the waveguide substrate being glass;
the waveguide is formed by means of ion implantation on the waveguide substrate;
the polarization rotator comprises a body part and an additional part, wherein the body part and the waveguide have the same width and height, the additional part and the body part are integrally formed, and the width of the additional part is gradually increased along the direction away from the light-emitting element;
wherein the height refers to a distance in a direction perpendicular to the waveguide substrate, and the width refers to a distance in a direction parallel to the waveguide substrate and perpendicular to the waveguide extending direction.
9. The laser scanning light source of claim 1, further comprising a waveguide substrate and a cladding layer, the waveguide being located between the waveguide substrate and the cladding layer, the waveguide substrate and the cladding layer each comprising SiO2The waveguide comprises Si3N 4;
the polarization rotator includes a body part having the same width and height as the waveguide, and a removal part which is a groove formed on the body part;
wherein the height refers to a distance in a direction perpendicular to the waveguide substrate, and the width refers to a distance in a direction parallel to the waveguide substrate and perpendicular to the waveguide extending direction.
10. A display device comprising the laser scanning light source according to any one of claims 1 to 9 and a scanning device that two-dimensionally scans a visible light beam emitted from the laser scanning light source to form an image.
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| JPH04113327A (en) * | 1990-09-03 | 1992-04-14 | Nikon Corp | Laser beam source |
| US20080158638A1 (en) * | 2005-02-25 | 2008-07-03 | Matsushita Electric Industrial Co., Ltd. | Wavelength Conversion Optical Device, Laser Light Source, and Image Display Optical Device |
| CN103336330A (en) * | 2013-07-05 | 2013-10-02 | 中国科学院半导体研究所 | Polarization rotator based on asymmetric vertical slot waveguide |
| JP2014191248A (en) * | 2013-03-28 | 2014-10-06 | Seiko Epson Corp | Illumination apparatus and projector |
| CN104777626A (en) * | 2015-04-27 | 2015-07-15 | 中国科学院光电研究院 | Device and method for inhibiting laser speckles and laser display projection system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04113327A (en) * | 1990-09-03 | 1992-04-14 | Nikon Corp | Laser beam source |
| US20080158638A1 (en) * | 2005-02-25 | 2008-07-03 | Matsushita Electric Industrial Co., Ltd. | Wavelength Conversion Optical Device, Laser Light Source, and Image Display Optical Device |
| JP2014191248A (en) * | 2013-03-28 | 2014-10-06 | Seiko Epson Corp | Illumination apparatus and projector |
| CN103336330A (en) * | 2013-07-05 | 2013-10-02 | 中国科学院半导体研究所 | Polarization rotator based on asymmetric vertical slot waveguide |
| CN104777626A (en) * | 2015-04-27 | 2015-07-15 | 中国科学院光电研究院 | Device and method for inhibiting laser speckles and laser display projection system |
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