Laser projector

A laser projector includes a light-mixing module and a light-splitting module. The light-mixing module provides a laser beam which includes first polarized light and second polarized light. The light-splitting module includes a dichroic mirror, a half-wave plate, a phosphor wheel module, and a light-guiding rod. The dichroic mirror allows the first polarized light to pass and reflects the second polarized light. The half-wave plate receives the first polarized light which passes the dichroic mirror and converts the first polarized light into third polarized light. The phosphor wheel module receives the second polarized light reflected by the dichroic mirror, and provides a stimulated light which passes the dichroic mirror. The light-guiding rod receives the stimulated light and the third polarized light, thereby providing an illumination beam.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Chinese application No. 201710026333.5 dated 2017 Jan. 13.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a laser projector, and more particularly, to a laser projector with reduced optical components, simple phosphor wheel design, and improved heat dissipation.

2. Description of the Prior Art

Laser projecting technology is advantageous in providing high-quality, large-screen and high-resolution images using self-focusing and wavelength-selective laser sources of high spectral brightness.FIG. 1is a diagram illustrating a prior art laser projector100. The laser projector100includes a light-mixing module10, a light-guiding module20, and a light-splitting module30. The light-mixing module10includes a plurality of laser sources for providing laser beams. The light-guiding module20includes a convex lens22and a concave lens24as condensers for adjusting the size of the laser beams. The light-splitting module30includes a dichroic mirror32, a plurality of reflectors34, a phosphor wheel36, and a light-guiding rod38.

FIG. 2is a diagram illustrating the phosphor wheel36of the prior art laser projector100. The phosphor wheel36includes a red block R, a green block G, a blue block B, and a yellow block Y. The red block R, the green block G and the yellow block Y are coated with red phosphor compound, green phosphor compound and yellow phosphor compound, respectively. The blue block B is a pervious region on the phosphor wheel36. The phosphor wheel36, driven by a motor, is configured to spin during operation so as to project laser beams on different blocks of the phosphor wheel36at different time, thereby providing light in various colors.

In the prior art laser projector100, the dichroic mirror32is designed to reflect blue laser beams and pass light in other colors. In other words, when the laser beams are incident on the light-splitting module30, the dichroic mirror32is configured to reflect blue laser beams to the phosphor wheel36. When the blue laser beams impact the red block R, the green block G and the yellow block Y, red light, green light and yellow light (represented by an arrow S1inFIG. 2) may be respectively stimulated and reflected back to the dichroic mirror32. Under such circumstance, the dichroic mirror32is configured to allow the red light, the green light and the yellow light to pass and arrive at the light-guiding rod38. On the other hand, the blue laser beams incident on the blue block B may pass the pervious region of the phosphor wheel36and be sequentially reflected by three reflectors34before being re-directed to the dichroic mirror32. Under such circumstance, the dichroic mirror32is configured to reflect the blue laser beams (represented by an arrow S2inFIG. 2) and directed the blue laser beams to the light-guiding rod38. The light-guiding rod38is configured to homogenize and project light of various colors onto an image modulation device (not shown) so that the laser projector100may produce corresponding images.

The prior art laser projector100uses laser phosphor display technology in which light generated by an array of blue laser diodes are projected onto a spinning multi-color phosphor wheel36to illuminate light in various colors. Since the prior art laser projector100adopts a blue light relay structure, the light-splitting module30needs to includes many reflectors34. Also, multiple color blocks and a pervious region needs to be arranged on the phosphor wheel36, which complicates the manufacturing process and increase the noise level of the laser projector100during operation.

SUMMARY OF THE INVENTION

The present invention provides a laser projector which includes a light-mixing module, a light-splitting module, and a color wheel. The light-mixing module is configured to provide a first laser beam which includes a first polarized light and a second polarized light, wherein a polarization of the first polarized light is different from a polarization of the second polarized light. The light-splitting module is configured to receive the first laser beam and includes a dichroic mirror, a half-wave plate, a phosphor wheel module, and a light-guiding rod. The dichroic mirror is configured to pass the first polarized light and reflect the second polarized light. The half-wave plate is configured to receive the first polarized light after the first polarized light passes through the dichroic mirror and convert the first polarized light into third polarized light, wherein a polarization of the third polarized light is the same as the polarization of the second polarized light. The phosphor wheel module is configured to receive the second polarized light after the second polarized light is reflected by the dichroic mirror and provide a first stimulated light which passes through the first dichroic mirror. The light-guiding rod is configured to receive the first stimulated light and the third polarized light, thereby providing an illumination beam. The color wheel is configured to filter the illumination beam and provide light in a plurality of color beams.

DETAILED DESCRIPTION

FIG. 3is a diagram illustrating a laser projector200according to an embodiment of the present invention. The laser projector200includes a first light-mixing module50, a second light-mixing module60, a first light-guiding module70, a second light-guiding module80, a light-splitting module90, and a color wheel95.

The first light-mixing module50is configured to provide a first laser beam, and the second light-mixing module60is configured to provide a second laser beam. The first laser beam provided by the first light-mixing module50includes P-polarized blue light L1and S-polarized blue light L2. The second laser beam provided by the second light-mixing module60includes P-polarized blue light L4and S-polarized blue light L5.

In the laser projector200of the present invention, the first light-mixing module50and the second light-mixing module60each includes two laser modules and one or multiple reflectors. In an embodiment, the laser module51of the first light-mixing module50includes P-polarized blue laser diodes DP amounting A1and S-polarized blue laser diodes DS amounting B1for emitting P-polarized blue light L1and S-polarized blue light L2which propagates along a first path (the X-axis inFIG. 3); the laser module52of the first light-mixing module50includes S-polarized blue laser diodes DS amounting C1for emitting S-polarized blue light L2which propagates along a second path (the Y-axis inFIG. 3), wherein the first path is perpendicular to the second axis; the laser module61of the second light-mixing module60includes P-polarized blue laser diodes amounting A2and S-polarized blue laser diodes amounting B2for emitting P-polarized blue light L4and S-polarized blue light L5which propagates along the first path; the laser module62of the second light-mixing module60includes S-polarized blue laser diodes amounting C2for emitting S-polarized blue light L5which propagates along the second path. According to various applications, A1, B1, C1, A2, B2and C2may be zero or any positive integer. For illustrative purpose,FIG. 3depicts an embodiment when A1=B1=A2=B2=2 and C1=C2=4. In another embodiment, the laser module51of the first light-mixing module50may only include one or multiple P-polarized blue laser diodes (namely, B1=0) and the laser module61of the second light-mixing module60may only include one or multiple P-polarized blue laser diodes (namely, B2=0). However, the amount and polarization type of the blue laser diodes in the first light-mixing module50and the second light-mixing module60do not limit the scope of the present invention.

In the first light-mixing module50, the surface of each reflector55is disposed at a predetermined angle (such as 45 degrees) with respect to the first path, in an in-line arrangement with respect to the one or multiple blue laser diodes in the laser module52, and in a staggered arrangement with respect to the one or multiple blue laser diodes in the laser module51. Therefore, the S-polarized blue light L2originally propagating along the second path may be reflected by the reflectors55to propagate along the first path, while the P-polarized blue light L1may continue to propagate along the first path. Similarly, in the second light-mixing module60, the surface of each reflector65is disposed at a predetermined angle (such as 45 degrees) with respect to the first path, in an in-line arrangement with respect to the one or multiple blue laser diodes in the laser module62, and in a staggered arrangement with respect to the one or multiple blue laser diodes in the laser module61. Therefore, the S-polarized blue light L5originally propagating along the second path may be reflected by the reflectors65to propagate along the first path, while the P-polarized blue light L4may continue to propagate along the first path.

The first light-guiding module70includes a convex lens72, a concave lens74, and a diffuser76, wherein the convex lens72and the concave lens74are condensers for adjusting the size of the first laser beam, and the diffuser76can convert the first laser beam into an uniform planar beam. The second light-guiding module80includes a convex lens82, a concave lens84, and a diffuser86, wherein the convex lens82and the concave lens84are condensers for adjusting the size of the second laser beam, and the diffuser86can convert the second laser beam into an uniform planar beam. However, the structures of the first light-guiding module70and the second light-guiding module80do not limit the scope of the present invention.

The light-splitting module90includes a first dichroic mirror91, a second dichroic mirror92, a half-wave plate93, a reflecting mirror94, a phosphor wheel module96, and a light-guiding rod98. The first dichroic mirror91and the second dichroic mirror92are configured to reflect S-polarized blue light in the incident laser beam and pass P-polarized blue light and other color light in the incident laser beam. Different from the conventional phosphor wheel36, the phosphor wheel module96includes a reflection disc (not shown) coated with phosphor compound and excludes the pervious region.

FIG. 4aandFIG. 4bare diagrams illustrating the spectrum of the dichroic mirror in the present invention. The horizontal axis represents wavelength (nm) and LS represents the blue laser spectrum. InFIG. 4a, the vertical axis represents spectral transmittance (%) and P-Pol represents P-polarized light. InFIG. 4b, the vertical axis represents spectral reflectance (%) and S-Pol represents S-polarized light. As depicted inFIG. 4a, the spectral transmittance of the P-polarized light P-POL is larger than 95% (after integral conversion) within the blue light wavelength range. As depicted inFIG. 4b, the spectral reflectance of the S-polarized light S-POL is larger than 95% (after integral conversion) within the blue light wavelength range. More specifically, when the first laser beam provided by the first light-mixing module50is incident on the light-splitting module90, the first dichroic mirror91is configured to allow the P-polarized blue light L1to pass and arrive at the half-wave plate93, but configured to reflect the S-polarized blue light L2to the phosphor wheel module96. After receiving the S-polarized blue light L2reflected by the first dichroic mirror91, the phosphor wheel module96is configured to provide a first stimulated light Y1(such as yellow light). On the other hand, the half-wave plate93is configured to receive the P-polarized blue light L1after it passes through the first dichroic mirror91and convert the P-polarized blue light L1into S-polarized blue light L3. Therefore, the first stimulated light Y1may pass through the first dichroic mirror91and arrive at the light-guiding rod98, and the S-polarized blue light L3may be redirected to the light-guiding rod98by the second dichroic mirror92and the reflecting mirror94.

Similarly, when the second laser beam provided by the second light-mixing module60is incident on the light-splitting module90, the second dichroic mirror92is configured to allow the P-polarized blue light L4to pass and arrive at the half-wave plate93, but configured to reflect the S-polarized blue light L5to the phosphor wheel module96. After receiving the S-polarized blue light L5reflected by the second dichroic mirror92, the phosphor wheel module96is configured to provide a second stimulated light Y1(such as yellow light). On the other hand, the half-wave plate93is configured to receive the P-polarized blue light L4after it passes through the second dichroic mirror92and convert the P-polarized blue light L4into S-polarized blue light L6. Therefore, the second stimulated light Y2may pass through the second dichroic mirror92and reflected to the light-guiding rod98by the reflecting mirror94, and the S-polarized blue light L6may be reflected by the first dichroic mirror91to arrive at the light-guiding rod98.

FIG. 5is a diagram illustrating an enlarged view of the light-guiding rod98according to an embodiment of the present invention. The light-guiding rod98includes a first incident surface2, a relay surface4, and a second incident surface6. The first incident surface2corresponds to the phosphor wheel module90for receiving the first stimulated light Y1and the S-polarized blue light L6. The relay surface4is disposed at an angle of 45 degrees with respect to the first incident surface2. The second incident surface corresponds to the relay surface4for receiving the second stimulated light Y2and the S-polarized blue light L3. The relay surface4may reflect the incident second stimulated light Y2and the S-polarized blue light L3to the same direction where the first stimulated light Y1and the S-polarized blue light L6propagate. After receiving the first stimulated light Y1, the second stimulated light Y2, the S-polarized blue light L3, or the S-polarized blue light L6, the light-guiding rod98is configured to provide a lighting beam LB to the color wheel95. After filtering the lighting beam LB, the color wheel95is configured to provide light in a plurality of color beams for the laser projector200. Various images may be projected using color beams by an image modulation device (not shown) and a lens (not shown) of the laser projector200.

FIG. 6is a diagram illustrating the phosphor wheel module96according to an embodiment of the present invention. In this embodiment, the phosphor wheel module96includes a phosphor wheel PW which includes a center8, a first part R1and a second part R2. The phosphor wheel module96, driven by a motor (not shown), is configured to spin during operation. The phosphor wheel PW is coated with phosphor compound associated with a specific color light, such as one which produces yellow light when stimulated by incident light. The S-polarized blue light L2provided by the first light-mixing module50is incident on the first part R1of the phosphor wheel PW with a circular stimulation path represented by P1. The S-polarized blue light L5provided by the second light-mixing module60is incident on the second part R2of the phosphor wheel PW with a circular stimulation path represented by P2. As can be seen inFIG. 5, a first distance d1between the circular stimulation path P1and the center is different from a second distance d2between the circular stimulation path P2and the center8, thereby improving thermal quenching and heat dissipation of the phosphor wheel module96.

In another embodiment, the S-polarized blue light L2provided by the first light-mixing module50may be incident on a first location of the phosphor wheel PW and the S-polarized blue light L5provided by the second light-mixing module60may be incident on a second location of the phosphor wheel PW, wherein the distance between the first location and the center8is equal to the distance between the second location and the center8. For example, both the S-polarized blue light L2provided by the first light-mixing module50and the S-polarized blue light L5provided by the second light-mixing module60may be incident on the first part R1or second part R2of the phosphor wheel PW.

FIG. 7is a diagram illustrating the phosphor wheel module96according to another embodiment of the present invention. In this embodiment, the phosphor wheel module96includes a first phosphor wheel PW1and a second phosphor wheel PW2. The first phosphor wheel PW1and the second phosphor wheel PW2, driven by the same motor or by respective motors, are configured to spin during operation. The phosphor wheel PW1and the second phosphor wheel PW2are coated with phosphor compound associated with a specific color light, such as one which produces yellow light when stimulated by incident light. The S-polarized blue light L2provided by the first light-mixing module50is incident on the first phosphor wheel PW1with a circular stimulation path represented by P1. The S-polarized blue light L5provided by the second light-mixing module60is incident on the second phosphor wheel PW2with a circular stimulation path represented by P2. As can be seen inFIG. 6, the phosphor wheel module96includes two phosphor wheels, thereby improving thermal quenching and heat dissipation of the phosphor wheel module96.

In the present invention, the laser projector200uses laser phosphor display technology in which light generated by an array of blue laser diodes are projected onto a spinning single-color phosphor wheel module. Since the present laser projector200provides two blue light transmission paths using two dichroic mirrors and a half-wave plate, the number of the reflectors can be reduced and thermal quenching can be avoided. Also, the monochromatic block arranged on the phosphor wheel simplifies the manufacturing process. Therefore, the present invention can provide a laser projector with reduced optical components, simple phosphor wheel design, reduced noise level, and improved heat dissipation.