JP4768160B2 - Light output device, pointer and image projection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light output device such as a light source device using a point light source such as a light emitting diode.
[0002]
[Prior art]
A semiconductor laser is widely used as a light source for a pointer that can indicate one point of an image displayed on a screen or the like with an emitted light beam such as red. However, since laser light has high coherence and becomes high-power light, there is a point of danger when it is directly irradiated with eyes, and a safer light source is demanded.
[0003]
[Problems to be solved by the invention]
The light emitted from the light-emitting diode has low coherence and does not become so high-power light, so the danger to the eyes is low. However, compared with a semiconductor laser, the light emission amount is small and the light divergence angle is large. Therefore, although it is safer than a semiconductor laser, it is not considered to be effective as a light source that requires a light emission amount such as a pointer light source. In recent years, the amount of light emission has been increasing along with the development of light emitting diodes, but no technology for effectively reducing the light divergence angle has been developed.
[0004]
Therefore, an object of the present invention is to provide an apparatus capable of projecting a light beam having a sufficiently small divergence angle in a light output device using a point light source that emits light having a large divergence angle such as a light emitting diode. Another object of the present invention is to provide a light output device based on a light emitting diode, which can be sufficiently used as a light source for a pointer instead of a semiconductor laser.
[0005]
For this reason, the inventors of the present application have examined the luminous flux emitted from the light emitting diode unit 10 called a lamp type as shown in FIG. 1, and the light emitted from the light emitting diode in the radiation mode as shown below. It was found that the luminous flux can be expressed. The light emitting diode unit 10 shown in FIG. 1 includes a light emitting diode 12 disposed substantially at the center, a reflector 13 having a cone-shaped reflecting surface 14 disposed on the rear surface (back surface) of the light emitting diode 12, and a light emitting diode. 12 and an electrode 11 for supplying electric power, and these are united by being molded or covered with a transparent resin 17. The resin on the front surface of the light emitting diode 12 is molded so as to be convex toward the tip (front), and this portion functions as the tip convex lens 16. Therefore, the light beam emitted from the light emitting diode 12 is emitted forward along the optical axis 19 connecting the center 14a of the reflecting surface 14 and the light emitting diode 12, and is supplied in a state of being condensed to some extent by the tip convex lens 16. .
[0006]
The lamp-type light emitting diode (chip) 12 is a minute light source having a size of about 0.1 to 0.3 mm, and outputs light having a large divergence angle. Accordingly, the optical system of the reflecting mirror of about 2 mm and the tip lens of about 5 mm becomes a divergent light source, that is, a point light source, and the light beam emitted from the chip 12 can be roughly classified into the following four modes.
(A) A radiation mode (A mode) related to a light beam that is emitted from the front surface of the chip 12 and does not hit the cone-shaped reflection surface 14 but is directly refracted by the tip convex lens 16 and projected forward.
(B) A radiation mode (B mode) relating to a light beam that is radiated from the periphery of the chip 12 and reflected by the cone-shaped reflecting surface 14 and then refracted by the convex convex lens 16 and projected forward.
(C) A radiation mode (C mode) relating to light that is totally reflected by the side surface of the resin portion 17 of the light-emitting diode light source 10 and then refracted by the tip convex lens 16 and emitted to the outside.
(D) A radiation mode (D mode) related to diffused light emitted from the side surface of the resin portion of the light emitting diode light source 10 to the outside.
[0007]
Of the above-described radiation modes, C-mode light and D-mode light are too difficult to be used for pointers, image projection devices, and the like due to their too high diffusion. On the other hand, since the A-mode and B-mode light beams are emitted forward along the optical axis 19, they may be collected and used. First, as shown in FIG. 2, the divergence angle of the A mode light beam can be further reduced by arranging a convex lens 34 in front of the light emitting diode unit 10. However, if a convex lens is arranged, the B-mode light beam diverges and cannot be used.
[0008]
On the other hand, the B-mode light beam can be made a light beam with a small divergence angle by disposing a concave lens in front of the light emitting diode unit 10, as shown in FIG. However, the A mode light beam diverges and cannot be used. Therefore, if only the A-mode or B-mode light beam is used, it can be output as a light beam having a small beam diameter while suppressing the divergence angle. Both mode and B-mode light fluxes are required. As a result, as shown in FIG. 1, the light emitting diode unit is provided with a lens (tip convex lens) 16 having a power that does not greatly promote the divergence of the A mode and does not greatly promote the divergence of the B mode. It is a limit when using as a light source.
[0009]
[Means for Solving the Problems]
Therefore, in the present invention, the second lens group that converts the B-mode and A-mode light beams into parallel light beams is disposed in the vicinity of the above-mentioned B-mode light beam, that is, the reflected light beam is condensed, thereby A A parallel light beam including a mode light beam and a B-mode light beam can be emitted. That is, in the light output device of the present invention having a point light source and a reflector that forms a cone-shaped reflection surface on the rear surface of the point light source, the point is along the optical axis connecting the center of the reflection surface and the point light source. In addition to the first lens unit having a positive refractive power disposed in front of the light source, the reflected light beam emitted from the reflecting surface and transmitted through the first lens unit is condensed in the vicinity of the optical axis. A second lens group in which the refractive power in the vicinity is negative or zero and the peripheral refractive power is positive is arranged.
[0010]
As described above, since the A-mode light beam and the B-mode light beam have different properties, it is impossible to make a parallel light beam with one lens. Even if two types of lenses are provided, the situation cannot be improved because they act on both A-mode and B-mode light beams. On the other hand, in the present invention, since the second lens group is disposed at a position where the B-mode light beam is condensed near the optical axis, the refractive power near the optical axis is applied to the B-mode light beam. The negative lens can act as a concave lens, and the A-mode light beam can act as a convex lens by making the peripheral refractive power positive. That is, by concentrating the B-mode light beam in the vicinity of the optical axis by the first lens group, the A-mode light beam and the B-mode light beam are substantially spatially separated at that position. Then, by placing the second lens group at the position where the refractive power in the vicinity of the optical axis is negative or zero and the peripheral refractive power is positive, the A-mode light beam is given an action as a convex lens, The B-mode light beam can act as a concave lens. As a result, it is possible to output light that can be used as a nearly parallel light beam having a small divergence angle, in which the A mode and B mode light beams are combined from the second lens group.
[0011]
Further, by making the refractive power near the optical axis zero, that is, a lens with an infinite focus, it is possible to prevent the luminous flux component along the optical axis of the A mode from diverging due to the effect of the concave lens. It is possible to prevent the luminous flux from being condensed on the optical axis and diverging due to the effect of the convex lens. In particular, the power of the first lens group is stopped so that the B-mode light beam becomes a parallel light beam, and the A-mode light beam is mainly converted into a parallel light beam by the power of the second lens group, and the B-mode light beam diverges. Therefore, it is possible to obtain a light beam having a small divergence angle in which the light beams of the A mode and the B mode are combined. That is, a first lens unit having a positive refractive power that is disposed in front of the point light source along the optical axis and makes the reflected light beam emitted from the reflecting surface substantially parallel, and in front of the first lens unit. A light output device having a small divergence angle composed of A mode and B mode light beams is also output by a light output device that is arranged and has a second lens group that has no refractive power in the vicinity of the optical axis and has a positive peripheral power. it can.
[0012]
Therefore, the light output device of the present invention can emit a light beam having a small divergence angle obtained by combining the light beam directly output from the point light source and the light beam reflected by the reflecting surface. For this reason, a light output device that emits light with a large divergence angle, such as a light emitting diode, as a point light source, has a sufficiently high brightness, and can be used sufficiently as a light source for a pointer instead of a semiconductor laser. It becomes possible to provide. The lamp-type light emitting diode unit described above is a unit in which a light emitting diode that is a minute light source, a reflector, and a tip lens portion that functions as a first lens group are unitized. And according to this invention, it becomes possible to concentrate the emitted light from a light emitting diode efficiently in the area | region of several cm on the screen of 2-3 m ahead.
[0013]
The second lens group is composed of a compound lens including a central portion having a negative or zero refractive power and a peripheral portion having a positive refractive power. Further, among the A-mode light beams, the light beam incident on the central portion may have a large divergence angle, so it is desirable that the size of the central portion be sufficiently small. Accordingly, the diameter of the central portion is 20% or less . On the other hand, if the diameter of the central portion is too small, there is a possibility that the B-mode light beam cannot be taken in sufficiently. Therefore, the diameter of the central portion is about 1% or more of the lens outer diameter, and more preferably about 3% or more.
[0014]
Further, by making the surface of the compound lens on the point light source side flat, the cost can be further reduced.
[0015]
The light output device of the present invention can project a light beam having a sufficiently small divergence angle while being a projection light source using a light emitting diode. For this reason, by adopting it as a pointer, it is possible to provide a safe and high-performance pointer that has a sufficiently small focused spot on the screen and does not damage the eyes.
[0016]
In an image projection apparatus such as a liquid crystal projector, an attempt has been made to use a light emitting diode as a light source for illuminating an image forming means such as a liquid crystal light valve having a diagonal of about 1 inch. In this case, there is a problem that the light emission amount of the light emitting diode is smaller than the light emission amount of the conventional bulb lamp and the light divergence angle is large, and many light emitting diodes are gathered together with the divergence angle from each light emitting diode being large. As a light source, it is not easy to efficiently transmit light from individual light emitting diodes to the liquid crystal light valve. Furthermore, it is not easy to efficiently transmit from the liquid crystal light valve to the projection lens system. For this reason, there is a problem that it is not easy to put a light source in which many light emitting diodes are gathered together as a light source of an image projection apparatus.
[0017]
On the other hand, the light output device of the present invention can project a light beam having a sufficiently small divergence angle even though it is a projection light source using a light emitting diode. Therefore, by employing the light output device of the present invention for an image projection device, the above-described problems can be solved, and an image projection device that can project a bright and clear image using a light emitting diode can be provided.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be further described below with reference to the drawings. FIG. 4 shows a pointer according to the present invention. The pointer 60 in this example can emit a thin light beam 62 from the tip 61 and project a light point 68 on the screen 69. Therefore, it is used for indicating an explanation location in a presentation or the like. The pointer 60 includes an elongated cylindrical housing 65, and a switch 63 for controlling the beam 62 is provided on the outer surface thereof. Housed in the housing 65 are a projection light source 50 that outputs a beam 62 and a battery (dry cell) 64 that serves as a power source. Further, an aperture 66 for cutting unnecessary divergent light components is provided at the exit of the beam 62.
[0019]
FIG. 5 shows a schematic configuration of the projection light source 50. This projection light source corresponds to the light output device of the present invention, and includes a light emitting diode unit 10 and a compound lens 25 disposed on the emission side thereof. The light emitting diode unit 10 is the same as that described with reference to FIG. 1, and includes a light emitting diode 12 disposed substantially at the center and a cone-shaped reflecting surface 14 disposed on the rear surface (back surface) of the light emitting diode 12. The reflector 13 provided and the electrode 11 for supplying power to the light emitting diode 12 are covered and integrated with a transparent resin 17. The resin on the front surface of the light emitting diode 12 is molded so as to be convex toward the tip (front), and this portion functions as the tip convex lens 16, that is, the first lens group 21. Therefore, the light-emitting diode 12 that is a minute light source that outputs light having a large divergence angle can be regarded as a point light source, and an A-mode light beam (direct light) and a B-mode light beam (reflected light) emitted from the minute light source. Is emitted forward along the optical axis 19 connecting the center 14 a of the reflecting surface 14 and the light emitting diode 12, and is supplied to the compound lens 25 disposed forward by being condensed to some extent by the tip convex lens 16.
[0020]
The compound lens 25 is disposed at a position where a B-mode light beam forward by a distance L from the tip of the light emitting diode unit 10 is substantially condensed on the optical axis 19. The compound lens 25 has a flat surface on the side (rear surface) 25a facing the light emitting diode unit 10 and a convex surface on the emission side, that is, the front surface 25b, and has a plano-convex lens shape as a whole. However, the central portion 27 of the lens 20 through which the optical axis 19 passes is recessed so as to protrude toward the light emitting diode unit 10. For this reason, the compound lens 25 of this example is a convex lens region in which the peripheral portion 26 is convex toward the emission side and has a positive refractive power, and the central portion 27 is convex toward the light emitting diode unit 10 and has a negative refractive power. Thus, it functions as the second lens group 22 of the present invention.
[0021]
Therefore, in the light output device 50 of this example, the A-mode light beam that is emitted from the front surface of the chip 12 and does not hit the cone-shaped reflection surface 14 but is directly refracted by the tip convex lens 16 and projected forward is combined. The light is further condensed by the convex lens-shaped peripheral portion 26 of the lens 25 to become a parallel light beam. On the other hand, the B-mode light beam radiated from the periphery of the chip 12 and reflected by the cone-shaped reflecting surface 14 and then refracted by the tip convex lens 16 and projected forward is caused by the concave lens-shaped central portion 27 of the compound lens 25. , Converted into a parallel light beam along the optical axis 19. For this reason, the composite lens 25 outputs a light beam 55 that includes an A-mode component and a B-mode component and has a small divergence angle and is almost parallel. Therefore, it is possible to obtain a light beam having a small divergence angle that can be used as the light beam 62 emitted from the pointer 60 shown in FIG. 4 while using the light emitting diode 12 that outputs light radially.
[0022]
Of the A mode light flux, the light flux emitted from the light emitting diode unit 10 along the optical axis 19 enters the central portion 27 of the compound lens 25 together with the B mode light flux. Among the A-mode light beams, the negative lens at the central portion 27 of the compound lens 25 has little influence on a light beam very close to the optical axis 19. However, the surrounding light beam is diverged by the action of the negative lens, and cannot be condensed into a parallel light beam. Therefore, it is desirable to arrange the compound lens 25 in the vicinity of the focal position where the B-mode light beam is condensed along the optical axis 19 and to reduce the diameter of the central portion 27 as much as possible.
[0023]
For example, by combining the light emitting diode unit (LED) 10 and the compound lens 25 under the conditions of the following first case, the light output device 50 that emits a light beam 55 having a divergence angle of one half angle or less is configured. Can do.
(First case)
LED10 diameter 5mm
Shape of the convex tip lens 16 Distance from the tip of the aspherical LED 10 to the compound lens 25 5.5 mm
Compound lens 25 outer diameter 9.0 mm
Focal length of convex lens part 24mm
Concave lens part 27 outer diameter 1.5 mm
Focal length of concave lens part -1.3 mm
Effective divergence angle (half angle) 1 degree or less Since the divergence angle of the light beam 55 output from the light output device 50 of the first case is 1 degree or less, the diameter is about 7 cm on the screen 69 or other wall surface 2 m away. Can be projected. Therefore, the pointer 60 using the light emitting diode 12 as a light source can be provided by adopting the light output device 50 as a projection light source and installing an aperture 66 for cutting unnecessary light.
[0024]
Further, by combining the light emitting diode unit (LED) 10 and the compound lens 25 under the second case condition described below, a light output device 50 that emits a light beam 55 having a divergence angle of 4 degrees or less is formed. Can do.
(Second case)
LED10 diameter 5mm
Shape of the convex tip lens 16 Distance from the tip of the aspherical LED 10 to the compound lens 25 5.5 mm
Compound lens 25 outer diameter 7.0 mm
Focal length of convex lens part 24mm
Concave lens part 27 outer diameter 1.0 mm
Focal length of concave lens portion 27 -1.0 mm
Effective divergence angle (half angle) 4 degrees or less The divergence angle of the light beam 55 output from the light output device 50 of the second case is 4 degrees or less, which is a sufficiently parallel light beam as a projection illumination light source. Therefore, it has sufficient performance as a light source for an image projection apparatus such as a liquid crystal projector.
[0025]
A single-plate projector 70 shown in FIG. 6 has an illumination device 71 in which a plurality of light output devices 50 of this example are arranged in an array or the like to secure a light amount, and a light beam output from the illumination device 71 is modulated to generate an image. A liquid crystal light valve 72 that forms a light beam, a lens system 73 that projects a modulated light beam onto a screen 79, and a control device 74 that controls the liquid crystal light valve 72 based on image data from a host computer.
[0026]
By adopting the light output device 50 that outputs a light beam with a small divergence angle of this example, when the lighting device 71 is configured by arranging a plurality of light emitting diode units 10 in an array, the light beam output from the lighting device 71 is also The divergence angle is small and the light beam is almost parallel. Therefore, it is possible to efficiently irradiate the liquid crystal light valve 72 with a light beam having a large light emission amount by using the light emitting diode 12 as a light source. And since the divergence angle of the light beam to irradiate is small, the divergence angle of the light beam output from the light valve 72 is also small, and it can be efficiently swallowed by the projection lens 73 and irradiated onto the screen 79. Therefore, it is possible to provide a projector that can project a bright and clear image on the screen 79 using the light emitting diode 12 as a light source. The same applies to a light valve such as a three-plate projector, LCoS which is a reflective liquid crystal element, and a DMD using a micromirror, as well as a single-plate projector.
[0027]
The configuration of the above compound lens 25 and the numerical values shown as the first and second cases are merely examples. For example, in the above description, the second lens group 22 is composed of a single compound lens 25, but a lens system in which the power of the central portion 27 is negative and the power of the peripheral portion 26 is positive is composed of a plurality of lenses. be able to. However, it is economical to employ the compound lens 25 as described above, and when the light source is a monochromatic light source such as a light emitting diode, achromaticity is not required. Therefore, the use of a single plate compound lens can provide sufficient optical performance. Can be obtained. Of the A-mode light beams, the light beam incident on the central portion 27 of the compound lens 25 has a large divergence angle. Therefore, it is desirable that the size of the central portion 27 be sufficiently small. The outer diameter is set to about 30% or less. The lens outer diameter of the central portion 27 is desirably small, and therefore is more preferably about 20% or less of the lens outer diameter. On the other hand, if the diameter of the central portion 27 is too small, the B-mode light beam cannot be taken in sufficiently, so it is desirable that the range be about 1% or more, more preferably about 3% or more of the lens outer diameter.
[0028]
Further, in the compound lens 25 of this example, the surface (rear surface) 25a on the side of the light emitting diode unit 10 is a flat surface, but the rear surface 25a is provided with a convex and concave peripheral portion 26 and / or a central portion 27. It is also possible to adopt a lens. However, in order to project the A-mode light beam forward as efficiently as possible, the position of the compound lens 25 should be as close as possible to the light emitting diode unit 10, and the size of the concave surface of the central portion 27 should be as small as possible. On the other hand, if the distance is too close, the cross section of the B-mode light beam is not sufficiently small and cannot be stopped, so the area of the concave surface of the central portion 27 must be increased in order to increase the incidence efficiency of the B-mode light beam on the central portion 27. This means that the area of the peripheral portion 26 is reduced for the A-mode light beam, and the efficiency is reduced. Therefore, the position and shape of the compound lens is such that the concave surface of the center part 27 of the compound lens is arranged at the position where the B-mode light beam is best condensed, and as shown in FIG. It is desirable to arrange so that 27 is located on the opposite side to the light emitting diode unit 10.
[0029]
Furthermore, the central portion 27 of the compound lens 25 can be configured as a plane so that the refractive power is zero, that is, the focal length is infinite. An example is shown in FIG. The light output device 50 includes a light emitting diode 12, a reflector 13 having a cone-shaped reflecting surface 14 disposed on the rear surface (back surface) of the light emitting diode 12, and a first disposed in front of the light emitting diode 12. A lens group 21 and a second lens group 22 disposed further in front of the lens group 21 are provided. The first lens group 21 has a single lens configuration, and has a power sufficient to parallelize the B-mode light beam, that is, the light beam reflected by the cone-shaped reflecting surface along the optical axis 19. Yes. The second lens group 22 is also composed of a single compound lens 25, and the peripheral portion 26 is a convex lens region, and has a power enough to convert the A-mode light beam slightly condensed by the first lens 23 into a parallel light beam. It has. On the other hand, the central portion 27 of the compound lens 25 has a plane perpendicular to the optical axis 19 and has no power, so that the B-mode light beam collimated by the first lens 23 can pass through as it is. It has become.
[0030]
Therefore, the light beam 55 emitted from the light output device 50 also includes A-mode and B-mode light beams and has a smaller divergence angle. Therefore, like the light output device described above, it is suitable for use as a light source for the pointer 60 and the projector 70.
[0031]
Further, the light output device using a light emitting diode as a point light source has been described above. However, if the light source can be regarded as a point light source in an optical system in which the light output device is employed, a point lamp such as a halogen lamp can be used. The present invention can also be applied to an apparatus that employs another diffusing light source. And the light output device which can output a light beam with a small divergence angle and a big light quantity can be provided using a cone type with a simple structure as a reflector.
[0032]
【The invention's effect】
As described above, the light output device of the present invention uses a point light source that emits light with a large divergence angle, and further bundles a plurality of light beams with different modes output from the point light source to reduce the divergence angle. A light beam that is almost parallel can be output. Therefore, it is possible to provide a light output device that supplies a light beam with a small divergence angle using a light emitting element, which is a small light source with an inherently large divergence angle, such as a light emitting diode, instead of a light emitting element with a small divergence angle like a semiconductor laser. . Therefore, the present invention can provide a light output device that can be applied to many fields as a small pointer that does not cause eye damage or a light source of a low power consumption projector.
[Brief description of the drawings]
FIG. 1 is a diagram showing light beams of several modes output from a light emitting diode unit.
FIG. 2 is an example in which a convex lens is set in front of the light emitting diode unit shown in FIG.
FIG. 3 is an example in which a concave lens is set in front of the light emitting diode unit shown in FIG. 1;
FIG. 4 is a diagram showing a schematic configuration of a pointer according to the present invention.
FIG. 5 is a diagram showing an outline of a light output device of the present invention.
FIG. 6 is a diagram showing a schematic configuration of a projector according to the invention.
FIG. 7 is a diagram showing a different example of the light output device of the present invention.
[Explanation of symbols]
10 Light-emitting diode light source 12 Light-emitting diode (chip)
14 Cone-shaped reflecting mirror 16 End convex lens 21 First lens group 22 Second lens group 25 Compound lens 26 Peripheral portion of lens (convex lens region)
27 Center of lens (concave lens area)
50 Optical output device 60 Pointer 70 Projector

Claims (5)

A point light source,
A reflector that forms a cone-like reflecting surface on the rear surface of the point light source;
A first lens unit having a positive refractive power disposed in front of the point light source along an optical axis connecting the center of the reflecting surface and the point light source;
A second lens disposed in front of the first lens group, the second lens of a composite type having a central part having a negative or zero refractive power and a peripheral part having a positive refractive power; And the diameter of the central portion is in the range of 1 to 20% of the outer diameter of the second lens, and the central portion of the second lens is radiated from the point light source and then the reflecting surface. The light output device is disposed at a position where the reflected light beam reflected by the first lens group and refracted by the first lens group is collected on the optical axis .   The light output device according to claim 1, comprising: a light emitting diode unit in which the light emitting diode serving as the point light source, the reflector, and a tip lens portion functioning as the first lens group are unitized. 3. The light output device according to claim 1 , wherein a surface of the compound lens on the point light source side is a flat surface. 4. A pointer comprising the light output device according to claim 1 and capable of indicating one point with a light beam emitted from the light output device. The light output device according to any one of claims 1 to 3 ,
Image forming means for modulating the light beam output from the light output device;
An image projection apparatus comprising: a lens system that projects a modulated light beam onto a screen.

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