Laser light source and projection device having first and second refractive parallelizing elements

A light source apparatus comprises: a plurality of light sources that emit light having a wide spread angle at a fast axis and a narrow spread angle at a slow axis, a first refractive optical element that converts light emitted from the plurality of light sources at the fast axis to parallel light, and a second refractive optical element that converts the light emitted from the plurality of light sources at the slow axis to parallel light. The plurality of light sources are arranged along the fast axis.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2011-279814, filed on Dec. 21, 2011; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light source apparatus and a projection display apparatus provided with a plurality of light sources that emit light having a wide spread angle at a fast axis and a narrow spread angle at a slow axis.

2. Description of the Related Art

Conventionally, there has been known a light source (for example, LD: Laser Diode) that emits light having two axes (a fast axis and a slow axis). The light emitted from the light source has a wide spread angle at the fast axis and a narrow spread angle at the slow axis.

Further, it has been proposed to increase, by arranging the light sources in an array form, the amount of light emitted from a light source apparatus provided with a plurality of light sources. For example, in a light source apparatus, a plurality of light sources are arranged along a slow axis (for example, Japanese Unexamined Patent Application Publication No. 2006-337923).

However, in the aforementioned technology, etendue is not considered. Specifically, etendues at the slow axis is larger than etendue at the fast axis. As described above, when imbalance of the etendues at the two axes occurs, it becomes necessary to design an optical system provided at a rear stage of the light source in accordance with the size in an axial direction in which the etendue is larger. Therefore, an optical system with a small F number is required, resulting in an increase in the size of a lens or cost.

SUMMARY OF THE INVENTION

A light source apparatus according to a first feature comprises: a plurality of light sources (light sources210) that emit light having a wide spread angle at a fast axis and a narrow spread angle at a slow axis, a first refractive optical element (first refractive optical element220) that converts light emitted from the plurality of light sources at the fast axis to parallel light, and a second refractive optical element (second refractive optical element230) that converts the light emitted from the plurality of light sources at the slow axis to parallel light. The plurality of light sources are arranged along the fast axis.

In the first feature, the number of light sources arranged along the fast axis is larger than the number of light sources arranged along the slow axis.

In the first feature, the light source apparatus further comprises: a mirror group (mirrors240) that reflects the light, which is emitted from the plurality of light sources, toward a predetermined direction. The mirror group is arranged such that an interval of light fluxes emitted from the plurality of light sources at the fast axis is narrowed.

In the first feature, the mirror group is arranged such that each mirror is shifted in an optical axial direction of the light emitted from the plurality of light sources.

In the first feature, the light source apparatus further comprises: a plurality of light source units (light source unit200P and light source unit200Q). Each of the plurality of light source units comprises: the plurality of light sources; the first refractive optical element; the second refractive optical element; and the mirror group. The plurality of light source units are arranged to face each other.

A projection display apparatus according to a second feature comprises: the light source apparatus according to the first feature; an imager that modulates light emitted from the light source apparatus; and a projection unit that projects light emitted from the imager on a projection surface.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a projection display apparatus according to embodiments of the present invention will be described with reference to the drawings. It is noted that in the following description of the drawings, identical or similar numerals are assigned to identical or similar parts.

It will be appreciated that the drawings are schematically shown and the ratio and the like of each dimension are different from the real ones. Accordingly, specific dimensions should be determined in consideration of the explanation below. Moreover, among the drawings, the respective dimensional relations or ratios may differ.

[Overview of First Embodiment]

A light source apparatus according to the embodiment comprises: a plurality of light sources that emit light having a wide spread angle at a fast axis and a narrow spread angle at a slow axis, a first refractive optical element that converts light emitted from the plurality of light sources at the fast axis to parallel light, and a second refractive optical element that converts the light emitted from the plurality of light sources at the slow axis to parallel light. The plurality of light sources are arranged along the fast axis.

In the embodiment, the plurality of light sources are arranged along at least the fast axis, paying attention with etendues at the fast axis and the slow axis. This addresses the imbalance of etendues at the fast axis and the slow axis. Consequently, this eliminates a need of using a lens with a small F number, resulting in improvement of use efficiency of light beams emitted from the plurality of light sources.

First Embodiment

Hereinafter, a light source according to a first embodiment is explained.FIG. 1is a diagram illustrating a light source210according to a first embodiment.

As illustrated inFIG. 1, the light source210has an emitter211. The emitter211emits light having a spread angle at the fast axis, which is wider than a spread angle at the slow axis. In other words, the emitter211emits light having a spread angle at the slow axis, which is narrower than a spread angle at the fast axis. The emitter211has a width at the fast axis, which is narrower than a width at the slow axis. In other words, the emitter211has a width at the slow axis, which is wider than a width at the fast axis.

Etendue is generally expressed by π·Asin2θ, and is held in a conjugate relation. That is, etendue on an object plane is equal to etendue on an image plane. In the formula, A denotes an area of an emitter, and θ denotes a spread angle of light emitted from the emitter.

Furthermore, in order to consider the fast axis separately from the slow axis, when one-dimensional etendue is introduced, the one-dimensional etendue is expressed by √π·ysinθ. Such one-dimensional etendue is also held in a conjugate relation. In the formula, y denotes a width of the emitter.

Hereinafter, in order to simplify explanation, sine is allowed to approximate to u, so that it is possible to derive the following relation (Equation 1) for the width y of the emitter and a spread angle u of light emitted from the emitter. The product of y and u is called a Lagrangian invariant, and is approximately held in a conjugate relation.
[Equation 1]
yl×ul=yp×up(Equation 1)

In Equation 1 above, the yl denotes the width of the emitter, the ul denotes the spread angle of the light emitted from the emitter, the yp denotes the width of an imager, and the up denotes a converging angle of light incident onto the imager.

For this relation, when considering the fast axis separately from the slow axis, Equation 1 may be expressed as follows.

For the fast axis, the following relation (Equation 2) is established as illustrated inFIG. 2.
[Equation 2]
ylf×θlf=ypf×θpf(Equation 2)

In Equation 2 above, the ylf denotes the width of the emitter at the fast axis, the θlf denotes the spread angle of the light emitted from the emitter at the fast axis, the ypf denotes the width of the imager at the fast axis, and the θpf denotes the converging angle of the light incident onto the imager at the fast axis.

For the slow axis, the following relation (Equation 3) is established as illustrated inFIG. 3.
[Equation 3]
yls×θls=yps×θps(Equation 3)

In Equation 3 above, the yls denotes the width of the emitter at the slow axis, the θls denotes the spread angle of the light emitted from the emitter at the slow axis, the yps denotes the width of the imager at the slow axis, and the θps denotes the converging angle of the light incident onto the imager at the slow axis.

Furthermore, when a general semiconductor laser is used as the light source210, the etendue at the fast axis is significantly smaller than the etendue at the slow axis. That is, the following relation (Equation 4) is satisfied.
[Equation 4]
ylf×θlf<<yls×θls(Equation 4)

The ypf and the yps approximately are the same in order in size, and thus, when the light emitted from the light source210enters, with irradiation, onto the imager, the converging angle θpf of the light incident onto the imager at the fast axis is, as is obvious from (Equation 2) to (Equation 4), significantly smaller than the converging angle θps of the light incident onto the imager at the slow axis. As described above, when the imbalance of the etendues at the fast axis and the slow axis occurs, in order to allow all of light beams emitted from the imager to be received in a projection lens, it is necessary to use a projection lens with a F number corresponding to the wide spread angle θls. When the projection lens with the F number corresponding to the θls is used, the size of the projection lens becomes excessive with respect to the narrow spread angle θlf.

In order to solve such a problem, in the first embodiment, a plurality of light sources210are arranged along the fast axis. Specifically, the plurality of light sources210are arranged such that a relation of N×ylf×θlf nearly equal to yls×θls (N denotes the number of the light sources210arranged along the fast axis) is satisfied.

Alternatively, the number of the light sources210arranged along the fast axis is larger than the number of the light sources210arranged along the slow axis. Specifically, the plurality of light sources210are arranged such that a relation of N×ylf×θlf nearly equal to M×yls×θls (N denotes the number of the light sources210arranged along the fast axis and M denotes the number of the light sources210arranged along the slow axis) is satisfied.

Consequently, the imbalance of the etendues at the fast axis and the slow axis is eliminated. That is, an increase in the size of the lens or cost is suppressed.

Hereinafter, a light source apparatus according to the first embodiment is explained.FIG. 4is a diagram illustrating a light source unit200according to the first embodiment. In the first embodiment, a description will be provided for a case in which the light source apparatus includes one light source unit200.

As illustrated inFIG. 4, the light source unit200includes a plurality of light sources210, a plurality of first refractive optical elements220, a plurality of second refractive optical elements230, and a plurality of mirrors240.

The plurality of light sources210are arranged along at least the fast axis. The plurality of light sources210may also be arranged along the slow axis. However, the number of the light sources210arranged along the fast axis is larger than the number of the light sources210arranged along the slow axis.

The plurality of first refractive optical elements220convert light beams emitted from the plurality of light sources210to parallel light at the fast axis. The plurality of first refractive optical elements220may be provided separately from one another, or may also be provided integrally with one another.

The plurality of second refractive optical elements230convert the light beams emitted from the plurality of light sources210to parallel light at the slow axis. The plurality of second refractive optical elements230may be provided separately from one another, or may also be provided integrally with one another.

The plurality of mirrors240configure a mirror group that reflects the light beams, which are emitted from the plurality of light sources210, toward a predetermined direction. The plurality of mirrors240are arranged such that an interval of light fluxes emitted from the plurality of light sources210at the fast axis is narrowed. In other words, a width A (a width at the fast axis) of the light flux reflected by the plurality of mirrors240is narrower than a width B (a width at the fast axis) of the light flux emitted from the plurality of light sources210. Specifically, the plurality of mirrors240are arranged so that each mirror24is shifted in an optical axial direction of the light emitted from the plurality of light sources210.

In this way, the interval of the light flux emitted from the plurality of light sources210at the fast axis is narrowed, so that an increase in etendue at the fast axis is suppressed.

In the first embodiment, the plurality of light sources210are arranged along at least the fast axis, paying attention with the etendues at the fast axis and the slow axis. This addresses the imbalance of etendues at the fast axis and the slow axis. Consequently, this eliminates a need of using a lens with a large diameter, resulting in improvement of use efficiency of light beams emitted from the plurality of light sources210.

In the first embodiment, the plurality of mirrors240are arranged such that an interval of light fluxes emitted from the plurality of light sources210at the fast axis is narrowed. In this way, an increase in the etendue at the fast axis is suppressed. That is, the arrangement of the plurality of mirrors240contributes to the solution of the imbalance of the etendue at the fast axis and the slow axis.

Hereafter, a first modification of the first embodiment is explained. Mainly the differences from the first embodiment are described, below.

In the first modification, the light source unit200includes four light sources210along the fast axis as illustrated inFIG. 5. Meanwhile, each light source210is a bar-shaped semiconductor laser including eight emitters211along the slow axis as illustrated inFIG. 6. Furthermore, one light source210includes a plurality of emitters211along the slow axis.

In the first modification, the aforementioned first refractive optical elements220and second refractive optical elements230have a configuration (a lens array) in which lenses are provided integrally with one another at the slow axis to convert light emitted from each emitter211to parallel light. Furthermore, the first refractive optical elements220are provided at the side of the plurality of light sources210with respect to the second refractive optical elements230.

In the first modification, a width A (a width at the fast axis) of the light flux reflected by the plurality of mirrors240is approximately equal to a width C (a width at the slow axis) of the light flux emitted, from the plurality of light sources210. That is, the light emitted from the plurality of light sources210is adjusted such that the etendue at the fast axis coincides with the etendue at the slow axis.

A description will be given below of a second modification of the first embodiment. Mainly the differences from the first embodiment are described, below.

In the second modification, the light source unit200includes four light sources210along the fast axis as illustrated inFIG. 7. Meanwhile, each light source210includes eight emitters211along the slow axis as illustrated inFIG. 8.

Furthermore, one light source210includes a plurality of emitters211along the slow axis. In other words, the plurality of emitters211are provided on one heat sink.

In the second modification, the aforementioned first refractive optical elements220and second refractive optical elements230have a configuration (a lens array) in which lenses are provided integrally with one another at the slow axis to convert light emitted from each emitter211to parallel light. Furthermore, the second refractive optical elements230are provided at the side of the plurality of light sources210with respect to the first refractive optical elements220.

In the second modification, a width A (a width at the fast axis) of the light flux reflected by the plurality of mirrors240is approximately equal to a width C (a width at the slow axis) of the light flux emitted from the plurality of light sources210. That is, the light emitted from the plurality of light sources210is adjusted such that the etendue at the fast axis coincides with the etendue at the slow axis.

A description will be given below of a third modification of the first embodiment. Mainly the differences from the first embodiment are described, below.

In the third modification, a light source apparatus includes a plurality of light source units200(a light source unit200P and a light source unit200Q) as illustrated inFIG. 9.

The light source unit200P includes a plurality of light sources210P, a plurality of first refractive optical elements220P, a plurality of second refractive optical elements230P, and a plurality of mirrors240P. The light source unit200Q includes a plurality of light sources210Q, a plurality of first refractive optical elements220Q, a plurality of second refractive optical elements230Q, and a plurality of mirrors240Q.

Furthermore, the light source210P and the light source210Q have the same configuration as that of the light source210. The first refractive optical element220P and the first refractive optical element220Q have the same configuration as that of the first refractive optical element220. The second refractive optical element230P and the second refractive optical element230Q have the same configuration as that of the second refractive optical element230. The mirror240P and the mirror240Q have the same configuration as that of the mirror240.

In the third modification, the light source unit200P and the light source unit200Q are arranged to face each other as illustrated inFIG. 9. The light source unit200P and the light source unit200Q are arranged at shifted positions at the slow axis as illustrated inFIG. 10.

In the third modification, it is noted that an amount for narrowing a width of the light flux emitted from the plurality of light sources210at the fast axis is determined according to a width (an entire width) of the light flux emitted from the light source apparatus (the light source unit200P and the light source unit200Q) at the fast axis and the slow axis. That is, a shift amount of the plurality of mirrors240(the mirrors240P and the mirrors240Q) is determined according to the width (the entire width) of the light flux emitted from the light source apparatus (the light source unit200P and the light source unit200Q) at the fast axis and the slow axis.

A description will be given below of a fourth modification of the first embodiment. Mainly the differences from the first embodiment are described, below.

In the fourth modification, a projection display apparatus using the aforementioned light source apparatus is explained.FIG. 11is a diagram illustrating a projection display apparatus100according to the fourth modification. In addition, in the first embodiment, a description will be provided for the case of using red component light R, green component light G, and blue component light B as reference video light.

As illustrated inFIG. 11, firstly, the projection display apparatus100includes a plurality of light source units200(a light source unit200R, a light source unit200G, and a light source unit200B), a dichroic mirror10, a dichroic mirror20, a rod integrator30, a DMD40, and a projection unit50.

The light source unit200R emits the red component light R. Similarly, the light source unit200G emits the green component light G, and the light source unit200B emits the blue component light B.

The dichroic mirror10transmits the red component light R and reflects the green component light G. The dichroic mirror20transmits the red component light R and the green component light G and reflects the blue component light B.

The rod integrator30is a solid rod including a transparent member such as glass. The rod integrator30uniformizes the light emitted from the light source unit200. In addition, the rod integrator30may be a hollow rod in which an inner wall thereof includes a mirror surface.

The DMD40modulates the light emitted from the light source unit200. Specifically, the DMD40includes a plurality of micromirrors, wherein the plurality of micromirrors are movable. Each micromirror is basically equivalent to one pixel. The DMD40switches whether to reflect light toward the projection unit50by changing an angle of each micromirror.

In the first embodiment, as the DMD40, a DMD40R, a DMD40G, and a DMD40B are provided. The DMD40R modulates the red component light R on the basis of a red video signal R. The DMD40G modulates the green component light G on the basis of a green video signal G. The DMD40B modulates the blue component light B on the basis of a blue video signal B.

The projection unit50projects a video light modulated by the DMD40on the projection surface.

Secondly, the projection display apparatus100has desired lens group and mirror group. As the lens group, lenses114to116are provided, and as the mirror group, a mirror125is provided.

The lens114is a light condenser lens that condenses the light beams emitted from each of the light source units200on a light incident surface of the rod integrator30. The lens115and the lens116are relay lenses that approximately focus the light emitted from the rod integrator30onto each DMD40as an image. The mirror125is a reflection mirror that reflects each color component light.

Thirdly, the projection display apparatus100has a desired prism group. As the prism group, a prism210, a prism220, a prism230, a prism240, and a prism250are provided.

The prism210is formed of a light transmitting member and has a surface211and a surface212. Since an air gap is provided between the prism210(the surface211) and the prism250(a surface251) and an angle (an incident angle), at which light incident onto the prism210is incident onto the surface211, is larger than a total reflection angle, the light incident onto the prism210is reflected by the surface211. Meanwhile, since an air gap is provided between the prism210(the surface212) and the prism220(a surface221), but an angle (an incident angle), at which the light reflected by the surface211is incident onto the surface212, is smaller than the total reflection angle, the light reflected by the surface211passes through the surface212.

The prism220is formed of a light transmitting member and has a surface221and a surface222. Since an air gap is provided between the prism210(the surface212) and the prism220(the surface221) and an angle (an incident angle), at which blue component light B initially reflected by the surface222and blue component light B emitted from the DMD40B are incident onto the surface211, is larger than the total reflection angle, the blue component light B initially reflected by the surface222and the blue component light B emitted from the DMD40B are reflected by the surface221. Meanwhile, since an angle (an incident angle), at which the blue component light B reflected by the surface221and then reflected by the surface222at the second time is incident onto the surface211, is smaller than the total reflection angle, the blue component light B reflected by the surface221and then reflected by the surface222at the second time passes through the surface221.

The surface222is a dichroic mirror surface that transmits the red component light R and the green component light G, and reflects the blue component light B. Accordingly, among the light beams reflected by the surface211, the red component light R and the green component light G pass through the surface222, and the blue component light B is reflected by the surface222. The blue component light B reflected by the surface221is reflected by the surface222.

The prism230is formed of a light transmitting member and has a surface231and a surface232. Since an air gap is provided between the prism220(the surface222) and the prism230(the surface231) and an angle (an incident angle), at which red component light R reflected by the surface232by passing through the surface231and red component light R emitted from the DMD40R are incident onto the surface231again, is larger than the total reflection angle, the red component light R reflected by the surface232by passing through the surface231and the red component light R emitted from the DMD40R are reflected by the surface231. Meanwhile, since an angle (an incident angle), at which the red component light R reflected by the surface232after being emitted from the DMD40R and reflected by the surface231is incident onto the surface231again, is smaller than the total reflection angle, the red component light R reflected by the surface232after being emitted from the DMD40R and reflected by the surface231passes through the surface231.

The surface232is a dichroic mirror surface that transmits the green component light G, and reflects the red component light R. Accordingly, among the light beams having passed through the surface231, the green component light G passes through the surface232, and the red component light R is reflected by the surface232. The red component light R reflected by the surface231is reflected by the surface232. The green component light emitted from the DMD40G passes through the surface232.

The prism240is formed of a light transmitting member and has a surface241. The surface241is configured to transmit the green component light G. In addition, the green component light G incident onto the DMD40G and the green component light G emitted from the DMD40G pass through the surface241.

The prism250is formed of a light transmitting member and has a surface251.

In other words, the blue component light B is reflected by the surface211(1), is reflected by the surface222(2), is reflected by the surface221(3), is reflected by the DMD40B (4), is reflected by the surface221(5), is reflected by the surface222(6), and passes through the surface221and the surface251(7). In this way, the blue component light B is modulated by the DMD40B and is guided to the projection unit50.

The red component light B is reflected by the surface211(1), is reflected by the surface232after passing through the surface212, the surface221, the surface222, and the surface231(2), is reflected by the surface231(3), is reflected by the DMD40R (4), is reflected by the surface231(5), is reflected by the surface232(6), and passes through the surface231, the surface232, the surface221, the surface212, the surface211, and the surface251(7). In this way, the red component light R is modulated by the DMD40R and is guided to the projection unit50.

The green component light G is reflected by the surface211(1), is reflected by the DMD40G after passing through the surface212, the surface221, the surface222, the surface231, the surface232, and the surface241(2), and passes through the surface241, the surface232, the surface231, the surface222, the surface221, the surface212, the surface211, and the surface251(3). In this way, the green component light G is modulated by the DMD40G and is guided to the projection unit50.

Other Embodiments

The present invention is explained through the above embodiment, but it must not be understood that this invention is limited by the statements and the drawings constituting a part of this disclosure. From this disclosure, various alternative embodiments, examples, and operational technologies will become apparent to those skilled in the art.

In the embodiment, three DMDs are exemplified as the imager. However, the embodiment is not limited thereto. For example, the imager may be one DMD. Alternatively, the imager may be one liquid crystal panel or three liquid crystal panels (a red liquid crystal panel, a green liquid crystal panel, and a blue liquid crystal panel). The liquid crystal panel may be a transmissive liquid crystal panel or a reflective liquid crystal panel.

In the embodiment, the plurality of mirrors240configure an adjustment unit that adjusts light beams emitted from the plurality of light sources210such that that the etendue at the fast axis coincides with the etendue at the slow axis. However, the embodiment is not limited thereto. Specifically, the plurality of light sources210provided in the light source apparatus may be arranged such that the widths (entire widths) of the light fluxes emitted from the light source apparatus at the fast axis and the slow axis coincide with each other. In such a case, the plurality of mirrors240may not be always shifted. That is, the adjustment unit, which is configured to adjust the light beams emitted from the plurality of light sources210such that the etendue at the fast axis coincides with the etendue at the slow axis, is configured by the arrangement of the plurality of mirrors240.