Patent Application
20100118283
The present invention relates to light source units for use in a laser device requiring a laser beam transferred through an optical fiber, for example, a projector or a rear projection television in which images are projected onto a screen using the laser beam as a light source, or in a liquid-crystal television using it as a backlight.
In a conventional light source unit, a collimation lens is used for forming a laser beam emitted from a semiconductor laser into a parallel-ray light beam, which is afterward focused by a plano-convex lens to obtain a light beam having a band-like cross-section. And then, the collimation lens and the plano-convex lens are held by separate lens barrels, and the two lens barrels are further held by their outer supporting part (for example, refer to Japanese Patent Application Publication No. H05-93881, Paragraphs 0024, 0032, FIG. 2). In addition, in another example, a laser beam emitted from a laser-diode (LD) chip having predetermined divergence angles is changed into a parallel-ray light beam by a collimation lens (convex lens), and is subsequently focused onto the front end of an optical fiber by a light-focusing or condenser lens (convex lens). And then, the collimation lens and the condenser lens are individually positioned and held in different lens holders (for example, refer to Japanese Patent Application Publication No. 2000-121888, Paragraphs 0018, 0019, FIG. 1). Moreover, in another example, after having collimated emission light from laser elements by collimation lenses each into a parallel-ray laser beam, focusing onto the front end of an optical fiber is performed using two pieces of light-focusing or condenser lenses (a cylindrical lens and an anamorphic lens). Note that, the two condenser lenses are together held in a condenser lens holder (for example, refer to Japanese Patent Application Publication No. 2007-67271, Paragraphs 0023, 0024, 0038, FIG. 2).
In such light source units disclosed in Japanese Patent Application Publication No. H05-93881 and in Japanese Patent Application Publication No. 2000-121888, a cylindrical lens is not used, so that it is difficult to form a laser beam whose longitudinal and lateral divergence angles are different with each other, into a parallel-ray laser beam, and even when a laser beam is focused by using a light-focusing or condenser lens, after it has passed through a collimation lens, focusing onto an incident end-face of an optical fiber cannot be achieved. In a light source unit in Japanese Patent Application Publication No. 2007-67271, collimation lenses are used to form laser beams into a parallel-ray laser beam, so that it is difficult to form the laser beams having different divergence angles in longitudinal direction and lateral direction, into a parallel-ray laser beam. In addition, as to the light source unit in Japanese Patent Application Publication No. 2007-67271, a cylindrical lens is used; however, it is used for a condensing optical system, and a special anamorphic lens is also used to focus laser beams onto the front end of an optical fiber.
Moreover, in the light source unit in Japanese Patent Application Publication No. H05-93881, the collimation lens and the plano-convex lens are held by separate lens barrels, and these lens barrels are individually mounted on the supporting part, so that it is difficult to accurately make the optical axes of these two pieces of lenses coincide with each other. In addition, in the light source unit in Japanese Patent Application Publication No. 2000-121888, a lens barrel that holds the collimation lens and a lens barrel that holds a condenser lens are directly coupled; however, the two lens barrels are not positioned with each other, so that it is difficult to accurately make the optical axes coincide with each other. Moreover, in the light source unit in Japanese Patent Application Publication No. 2007-67271, the condenser lens holder is coupled with a laser unit that holds collimation lenses by way of an interconnecting member, so that there is such a problem that positioning of the condenser lenses and the collimation lenses is difficult.
The present invention has been directed at solving those problems described above, and an object of the invention is to focus, without using extra components such as a special lens like an anamorphic lens or a supporting stage other than lens barrels, a laser beam emitted from a laser element, having different divergence angles in longitudinal direction and lateral direction, so as not to allow longitudinally and laterally deviating from an incident end-face of an optical fiber.
A light source unit according to the present invention comprises a laser element for emitting a laser beam having different divergence angles in longitudinal direction and lateral direction; at least one cylindrical lens placed with its generatrix perpendicular to an optical axis of the laser beam for forming the laser beam into a parallel-ray laser beam; a first lens barrel for holding the at least one cylindrical lens; a condenser lens placed downstream of the at least one cylindrical lens for focusing the parallel-ray laser beam; and a second lens barrel for holding the condenser lens; wherein the first lens barrel and the second lens barrel are positioned and coupled with each other so that an optical axis of the at least one cylindrical lens coincides with an optical axis of the condenser lens.
According to the present invention, a laser beam emitted from a laser element having different divergence angles in longitudinal direction and lateral direction is refracted by at least one cylindrical lens so as to form the beam into a longitudinally and laterally parallel-ray laser beam, and therefore, the laser beam can be focused into a smaller spot diameter when focusing is performed by a condenser lens after having the beam passed through the cylindrical lens. In addition, the at least one cylindrical lens and the condenser lens are held by separate lens barrels, so that it becomes possible to adopt the shape of the lens barrels that are individually made suitable for the cylindrical lens and the condenser lens.
Moreover, a lens barrel that holds the cylindrical lens and a lens barrel that holds a condenser lens are regularly positioned and coupled with each other, so that such effects can be obtained in which optical axes of the cylindrical lens and the condenser lens that are held by two respective lens barrels can be accurately coincided with each other, and performance may not be degraded due to displacement between the optical axes.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
Hereunder, a light source unit according to Embodiment 1 of the present invention will be described in detail with reference to the accompanying drawings.
As shown in
As shown in
In the second lens barrel 2, two pieces of round or circular lenses 13 and 14 are held. The second lens barrel 2 is regularly positioned and mounted with respect to the first lens barrel 1 so that optical axes of the circular lenses 13 and 14 coincide with those of the cylindrical lenses 10, 11 and 12. Note that, in Embodiment 1, an example is described in which three pieces of the cylindrical lenses are held in the first lens barrel 1, and two pieces of the circular lenses are held in the second lens barrel 2; however, the number of each of the lenses may be changed depending on the constraining conditions such as required performance, and costs or size. In addition, in Embodiment 1, the cylindrical lenses 10 and 11 are placed in the lens holder 15, which is held by the first lens barrel 1; however, in a case in which one cylindrical lens is used, which may be directly held by a lens barrel, i.e. without intervening the lens holder, like the state of the cylindrical lens 12.
The optical fiber 3 is inserted into the connector 4 so that the front end of the fiber on the side of the second lens barrel 2 coincides with the front end of the connector 4, and is fixed to the connector 4 by adhesive or the like. In addition, on the front end, i.e., on the exit side of the second lens barrel 2, the optical fiber holder 5 is mounted. Into the optical fiber holder 5, the front end of the connector 4 is inserted, which is fixed by the cap nut 4a. At this time, the front end of the connector 4 is stopped by touching at the bottom in a hole of the optical fiber holder 5, so that positioning of the front end of the optical fiber 3 is achieved in the axial direction thereof (in depth) with respect to the optical fiber holder 5. Note that, the optical fiber 3 shown in
Next, the operations of the light source unit will be explained. A laser beam 9 is emitted from the laser element 7. The laser element 7 emits the laser beam 9 whose light-rays spread in lateral directions to a large extent as shown in
The laser beam 9 that propagates through a hollow within the first lens barrel 1 is made incident to the cylindrical lens 12. The cylindrical lens 12 is placed to have its generating line or generatrix perpendicular to the generatrices of the cylindrical lenses 10 and 11, so that light-rays of the laser beam 9 that spread in lateral directions do not turn as shown in
Subsequently, the longitudinally and laterally parallel laser beam 9 incident to the circular lens 14 is refracted in longitudinal direction and lateral direction by the circular lens 14 and the circular lens 13, and is focused onto an entrance of the optical fiber 3. The laser beam 9 being incident to the optical fiber 3 is propagated within the optical fiber 3 so as to be transferred. As described above, the laser beam 9 emitted from the laser element 7, having different divergence angles in longitudinal direction and lateral direction, is formed into a longitudinally and laterally parallel-ray beam by a plurality of such cylindrical lenses 10 and 11, and 12 that are placed to have their respective generatrices perpendicular to one another, so that the laser beam can be easily focused onto the front end of the optical fiber 3 by subsequently focusing the parallel-ray beam using the circular lenses 13 and 14.
Next, configurations of each of the lens units will be explained. In the lens unit 100 shown in
The cylindrical lens 12 is directly fitted in the first lens barrel 1, and is fixed being spring-biased toward the lens-barrel side by a plate spring 18. The plate spring 18 is fastened onto the first lens barrel 1 by four pieces of screws 19a through 19d shown in
The cylindrical lens 10 is placed in the lens holder 15 from the opposite side to the cylindrical lens 11, and is made contact with the protrusions 15a and 15b from the incident side of the laser beam 9, so that positioning in optical axis directions is achieved. And then, the cylindrical lens 10 is held, as shown in
As described above, the cylindrical lenses 10 and 11, and 12 are held in proximities to the respective entrance and exit sides of the first lens barrel 1, so that the first lens barrel 1 can be made as a single component in a tubular shape, and it is not only possible to reduce the number of components, but also easy to secure positional accuracy among a plurality of lenses. Moreover, the stiffness of the lens barrel can be enhanced, so that it becomes possible to reduce the thickness of material and also to lower costs.
An assembling method of the lens unit 200 will be explained using
As described above, the cylindrical lenses 10 through 12, and the circular lenses 13 and 14 are held by the separate lens barrels, so that it becomes possible to adopt the shape of the lens barrels that are individually made suitable for the cylindrical lenses 10 through 12, and the circular lenses 13 and 14. As for a lens barrel that holds the circular lenses, a lens barrel whose cross-section is circular can be used, and thus cylindrical machining is possible to apply using a lathe during additional machining such as on the inner surface, so that machining accuracy can be made high, a machining time can be also shortened, and costs can be reduced as well. In addition, when a lens barrel in a circular cross-section is used, it is easy to secure optical axes of the lenses, and at the time of assembling, each of the components can be assembled by a drop-in technique, so that assembling is easy, the assembly time can be shortened, and assembly costs can be reduced.
In addition, because the lens barrel that holds the cylindrical lenses can have a shape of rectangular cross-section and be made to adopt the shape suitable for an external shape of the cylindrical lenses, material thickness can be made uniform, and the material can be efficiently used. When cylindrical lenses and circular lenses are used in combination, a lens barrel takes a complex shape, and thus it is hard to form the lens barrel and also to additionally machine it; therefore, it is difficult to secure machining accuracy, resulting in rising costs.
In addition, the laser beam 9 emitted from the laser element 7 having different divergence angles in longitudinal direction and lateral direction is refracted by the cylindrical lenses 10 and 11, and 12 so as to from the beam into a longitudinally and laterally parallel-ray laser beam, so that it is possible to focus the laser beam 9 that has passed through the cylindrical lenses 10 and 11, and 12 by using the circular lenses 13 and 14. Thus, focusing a smaller spot diameter can be achieved when the laser beam 9 is focused by the circular lenses 13 and 14.
Moreover, the laser beam 9 emitted from the laser element 7 having different divergence angles in longitudinal direction and lateral direction is formed into a parallel-ray laser beam by the cylindrical lenses 10 and 11, and 12, and therefore, displacement occurred between the two lens barrels in direction parallel to their optical axes may provides a little influence. Namely even if the second lens barrel is shifted from the first lens barrel in the direction to depart therefrom, the laser beam 9 is a parallel-ray laser beam, so that it is possible to focus the laser beam 9 onto the incident end-face of the optical fiber 3 by means of the circular lenses 13 and 14.
Next, a positioning method of the first lens barrel 1 and the second lens barrel 2 will be explained. In
In each cases of
In addition, the first lens barrel 1 and the second lens barrel 2 are regularly positioned and directly coupled with each other, so that it is possible to accurately make optical axes of the cylindrical lenses 10 through 12 held by the first lens barrel 1, and those of the circular lenses 13 and 14 held by the second lens barrel 2 coincide with each other. Therefore, performance may not be degraded due to displacement between the optical axes. Moreover, as in Embodiment 1, when the lenses are held at positions near to respective lens-barrel end-faces, and positioning is thus difficult using the outer circumference and the inner circumference of the lens barrels, the positioning method according to Embodiment 1 is effective.
A mounting method of the optical fiber holder 5 and a position adjustment method of the optical fiber 3 will be explained referring to
The screws 34a through 34c having been tentatively secured are loosened, so that the optical fiber holder 5 is allowed movable in the plane of the surface. The optical fiber holder 5 can be moved by the amount of looseness and play of holes 5a through 5c drilled in the planar bottom portion, and the screws 34a through 34c. As shown in
The optical fiber holder 5 is movably held in the plane of the surface, i.e., on the exit surface 2a of the second lens barrel 2 by the amount of looseness and play of the holes 5a through 5c and the screws 34a through 34c, so that a complex adjustment mechanism is not required, and the number of components can be reduced. Therefore, a position adjustment mechanism for the optical fiber 3 is realized with lower costs and higher reliability. In addition, the position adjustment of the optical fiber 3 is performed by sliding, with respect to the exit surface 2a, the optical fiber holder 5 on which the optical fiber 3 is mounted by way of the connector 4, and therefore, the position adjustment of the optical fiber 3 is proceeded without deviating the incident end-face of the optical fiber 3 in optical axis directions, and highly precise positioning is made possible.
Shown in
In the board holder 38, a window 38a is provide so as to accommodate the light sensor 36, and the board 37 is fixed to a lateral side of the first lens barrel 1 by two pieces of screws 39b and 39c, with the mounting face of the board for the light sensor 36 facing down. In addition, the board holder 38 has a bathtub-shaped structure so that the light sensor 36 is not brought close contact with the lateral side of the first lens barrel 1, and is held to provide an interspace to the first lens barrel 1. Meanwhile, a light detection hole 40 is provided on the lateral side of the first lens barrel 1, so that, part of the laser beam 9 is introduced into the board holder 38 through the hole.
The hole 40 provided in the first lens barrel 1 is placed off the light path of the laser beam 9, that is, at the position where the laser beam 9 does not directly enter into the hole 40, so that scattered light that is reflected diffusely in the first lens barrel 1 is introduced into the hole. If intensity of the laser beam 9 incident to the light sensor 36 is too high, the light sensor 36 becomes functionally saturated, so that the intensity of the beam cannot be detected. For this reason, in addition to make the hole 40 in an appropriate size, the light sensor 36 is placed off, and slightly shifted, the axis line of the hole 40, whereby part of the laser beam 9 to be detected is reflected and attenuated in the board holder 38. In order to further attenuate the part of the laser beam 9, the inner surface of the board holder 38 may be roughened or colored in black.
According to the configuration in which the hole 40 provided in the first lens barrel 1 to introduce part of the laser beam 9 is placed at the position where the laser beam 9 does not directly enter, the light sensor 36 is placed at a position apart slightly from the axis line of the hole 40; and then, a shape of the board holder 38 is designed so that the part of the laser beam 9 is internally reflected and attenuated, and the inner surface of the board holder 38 may be roughened or colored in black, therefore light intensity detection can be stably carried out even when the intensity of the laser beam 9 is strong. In addition, because intensity of the laser beam 9 is detected by the light sensor 36, and changes in the intensity of the laser beam are monitored, it is possible to determine an unexpected malfunction of the laser element 7 or its operating life. Moreover, when the detected intensity is compared with that of the output of the exit side of the optical fiber 3, it is also possible to detect a disconnection in the optical fiber 3, reduction of transmissivity therein, or the like.
As shown in
The condensing optical system 510 is constituted of light source units 511 having a plurality of colors (three colors in
In the condensing optical system 510, laser beams emitted from the light source units 511 are guided into the illumination optical system 540 by way of the optical fibers 3 corresponding to the light source units 511.
The illumination optical system 540 includes a light intensity uniformizing device 541 that uniformly distributes the intensity of laser beams emitted from the condensing optical system 510 (optical fibers 3), a relay-lens group 542, a diffusion device 544, and a mirror group 543 constituted of a first mirror 543a and a second mirror 543b. The illumination optical system 540 thus guides by means of the relay-lens group 542 and the mirror group 543 a light beam emitted from the light intensity uniformizing device 541 onto the reflection-type light modulation device 520.
The light intensity uniformizing device 541 has a function to uniformize the light intensity of the laser beams (for example, a function to reduce inconsistencies of illuminance) emitted from the condensing optical system 510. The light intensity uniformizing device 541 is disposed in the illumination optical system 540 so that an incident face (incident end-face) that is an entrance of incident light is set facing toward the optical fibers 3, and an emission face (emission end-face) that is a light emission exit is set facing toward the relay-lens group 542.
The light intensity uniformizing device 541 is made of a transparent material, for example, glass, resin or the like. The light intensity uniformizing device 541 includes a polygonally columned rod (columned member having its cross-sectional shape polygonal) whose sidewall has an internal surface of total reflection, or a polygonal pipe (tubular member) having inwardly arranged light reflection surfaces tubularly combined with its cross-sectional shape polygonal.
When the light intensity uniformizing device 541 is a polygonally columned rod, light is emitted from an emission end (emission exit) after having light reflected a number of times by utilizing a total reflection action on an interface between a transparent material and air.
When the light intensity uniformizing device 541 is a polygonal pipe, light is emitted from the emission exit after having light reflected a number of times by utilizing a reflection action by the surface mirror inwardly facing.
When an appropriate length is secured for the light intensity uniformizing device 541 in the traveling direction of the light beam, the light internally reflected a number of times is superimposed and emitted in proximity to the emission face of the light intensity uniformizing device 541; therefore, a substantially uniform intensity distribution can be obtained in the proximity to the emission face of the light intensity uniformizing device 541. Light emitted from the emission face having the substantially uniform intensity distribution is guided by the relay-lens group 542 and the mirror group 543 onto the reflection-type light modulation device 520, so that the illumination surface 520a of the reflection-type light modulation device 520 is illuminated.
In addition, in the illumination optical system 540, the diffusion device (diffusing portion) 544 is provided downstream of the relay-lens group 542. The diffusion device 544 is a device that reduces speckle by diffusing the light propagated by way of the relay-lens group 542 and then by sending it to the mirror group 543. The diffusion device 544 is a holographic diffusion device or the like that can specify light diffusion angles using a hologram pattern provided on the substrate, and that mitigates coherency attributed to the light source units 511.
In addition, by rotating, moving or vibrating the diffusion device 544, or doing the like, the coherency attributed to the light source units 511 can be effectively mitigated.
The reflection-type light modulation device 520 is, for example, a light modulation device of a reflection-type such as a digital micromirror device (DMD). The reflection-type light modulation device 520 is configured in such a manner that a large number of movable micromirrors corresponding to pixels each (for example, hundreds of thousands of pieces) are arranged in a planar surface, and a slope angle (tilt) of each of the micromirrors is changed depending on pixel information.
The projection optical system 530 enlarges and projects onto a transmission-type screen 550 images on the illumination surface (image producing area) 520a of the reflection-type light modulation device 520. According to this arrangement, the images are displayed on the transmission-type screen 550.
Note that, shown in
Note that in
While the present invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be realized without departing from the scope of the invention.
“1” designates a first lens barrel; “2,” second lens barrel; “2a,” exit surface; “3,” optical fiber; “5,” optical fiber holder; “7,” laser element; “9,” laser beam; “10,” “11,” “12,” cylindrical lens; “13,” “14,” circular lens; “25,”
26,” positioning boss; “27,” positioning hole; “28,” oblong hole; “30,” “31,” positioning boss; “32,” positioning hole; “33,” oblong hole; “36,” light sensor; “37,” board; “38,” board holder; “40,” hole; “100,” lens unit; “200,” lens unit; “300,” laser module; and “400,” light sensor unit.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-240610 | Sep 2008 | JP | national |
