JP2940132B2 - Light emitting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a light emitting device used when light in a specific direction is required, such as a liquid crystal projector or an overhead projector (OHP).

[Summary of the Invention] In the light emitting device of the present invention, the reflection plate is formed as a spheroid, and a light extraction hole is provided in the major axis direction of the spheroid. It is configured to be disposed at one of the two focal positions, and the light reflected a plurality of times inside the spheroid is emitted from the light extraction hole, so that the light output from the light source is It improves the usage efficiency.

[Related Art] For example, as a light emitting device used for OHP, a reflecting plate 1 formed in a spherical shape as shown in FIG. 5 is provided, and a light source 2 such as a halogen lamp is arranged at a center position of the spherical surface. By doing so, a part of the light output from the light source 2 and directed backward is reflected forward by the reflector 1 for use.

When a parallel light beam is required as in a liquid crystal projector, for example, as shown in FIG. 6, a light emitting device having a rotating paraboloidal reflector 4 formed around the light source 3 using a metal halide lamp is used. Part of the output light 3 (shaded portion U) is reflected by the reflector 4 so that a parallel light beam can be obtained.

[Problems to be Solved by the Invention] As described above, in these light emitting devices for obtaining a light beam in a specific direction, a part of the light generated from the light source is reflected by using a reflector, and Although the light is output more efficiently in a specific direction, in any case, a part of the light generated from the light source is directly or reflected by the reflector, and goes to the specific direction However, there is a problem that the utilization rate of light generated from the light source is not good, and it is difficult to further improve the light utilization rate and save power.

[Means for Solving the Problems] The present invention has been made in view of the problems as described above, and the reflector is formed as a spheroid, and light is extracted in the direction of the major axis of the spheroid. A structure in which a hole is provided, and a light source is arranged at one of two focal positions of a spheroid, so that light reflected a plurality of times inside the spheroid can be extracted through an extraction hole. It is.

[Operation] The light source is arranged so as to coincide with the focal point on the major axis of the ellipse, and almost all directions of the light source are covered by the spheroidal reflector, and light is extracted on the major axis of the spheroid. If the holes are formed, the light components in almost all directions output from the light source are output from the light extraction holes to the outside of the light emitting device directly or by repeating reflection once or several times.

[Embodiment] FIG. 1 shows a light emitting device adapted to obtain a parallel light beam for use in a liquid crystal projector as one embodiment of the present invention. A reflecting plate 11 is formed by forming a dichroic mirror that transmits light through a spheroid.

12 is a light extraction hole formed in the direction of the elliptical major axis J _L of the reflection plate 10, 13 is a convex lens which is disposed on the outer side of the light extracting hole 12.

The light source 11 has a light emitting portion located at a point F ₁ (one focal point) on the elliptical major axis J _L , and light is emitted from the focal point F ₁ with a light distribution characteristic substantially as shown in FIG. At this time, if the reflection plate 10 is a spheroid, as is well known, the focal point F ₁
The light emitted is reflected from will be focused on the other focus F _2.

Therefore, for example, of the light output from the light source 11,
Light component L ₁ shown by a dotted line reaches the light extracting hole 12 through the focal point F ₂ after being reflected by a point. The light component L ₂ is reflected at the point b to reach the focal point F ₂ , further reflected at the point c and returned to the focal point F ₁ , and then reflected at the point d and then passes through the focal point F ₂ again to emit light. The discharge hole 12 is reached. Similarly, the light component L ₃ is reflected three times while passing through the focal points F ₁ and F ₂ and reaches the light extraction hole 12.

Such reflection of light will be applied to all three-dimensional light output by the light distribution characteristics of the light source 11 shown in FIG. 2, and the focal property will be extremely high.

That is, most of the light emitted from the light source 11 reaches the focal point F ₂ by one reflection, then passes through the final focus F ₂ after both reflected twice more, direct light from the focal point F ₂ Exit hole 12
Will be reached. Here, a convex lens 13 provided outside of the light extraction holes 12 are the focus F ₂ is the focal position. Accordingly, light components reaching the final focal point F ₂ to the light extracting hole 12 is output after being collimated by the convex lens 13.

Because this way most of the components of the light output from the light source 11 in the present embodiment that is ultimately derived from the focus F ₂ to the light extracting hole 12, as a very effective parallel rays emitted light of the light source 11 Will be available. Further, since the reflecting plate 10 is formed of the dichroic mirror that passes infrared rays as described above, the inside of the substantially closed spheroid does not become extremely hot.

Meanwhile, the chain line light component (e.g., a point was reached direct light extraction hole 12 without passing through the focal point F ₂ from the light source 11 in this embodiment
Since the light component) is indicated by L ₄ can not be collimated by the convex lens 13, it is impossible that utilizes light emitted as substantially close to 100% parallel light.

FIG. 3 shows an embodiment in which a light component reaching such a direct light extraction hole 12 can also be used as a parallel light beam.
The light source 11 is obtained by adapted to place the focal point F ₂ is the focal position of the convex lens 13.

In this embodiment, similarly to the embodiment of FIG.
That the light emitted, for example, as shown as an optical component L _5, reaches the light extraction hole 12 passes through the focal point F ₂ is reflected by the further point h passes through the focal point F ₁ is reflected to point g of like,
After being reflected once or several times by the reflector 10 while passing through the focal points F ₁ and F ₂ , the light is finally passed through the focal point F ₂ and led out of the light extraction hole 12, which can be used as a parallel ray. but those further by being arranged light source 11 to the point F ₂ is the focal position of the convex lens 13, light components reaching the direct light extraction holes 12 are outputted from the light source 11 (e.g., L ₆₎ also It can be used as a parallel ray. That is, the light utilization rate can be improved as compared with the embodiment of FIG.

In the embodiment of FIGS. 1 and 3 described above, the light output from the light source 11 is a light component reaching the mounting portion of the metal halide lamp serving as the light source 11 (and in the case of FIG. All of the light components other than the light component that reaches the light source can be used as parallel rays by the convex lens 13, so that almost 100% of the output light from the light source 11 can be used, and significant power saving can be achieved. (As can be seen from the light distribution characteristics in FIG. 2, the light component emitted in the direction of the mounting portion of the metal halide lamp is considerably small.) The cross-sectional area of the light flux of the parallel light depends on the size of the light extraction hole 12. by such change or, or to set an appropriate lens diameter while separable convex lens 13 from the light extracting hole 12, can be the easily changed design (where the focal position of the convex lens is always set to the focal point F ₂ There must be). For example,
If the larger-diameter convex lens is configured away from the light extraction hole 12, a thicker parallel light beam can be obtained.

Therefore, the light emitting device of the above embodiment can be used regardless of the size of the liquid crystal screen portion of the liquid crystal projector, and can also supply highly accurate parallel rays particularly to a small liquid crystal.

Incidentally, for example when the point light source is required as an OHP or the like, may be utilized focus F ₂ as a point light source portion.

Figure 4 is a further embodiment of the present invention, the longitudinal direction of the metal halide lamp as a light source 11, but arranged in a state along the long axis J _L of the reflection plate 10 of the spheroid.

Advantage compared to those configured to attach a metal halide lamp and perpendicular longitudinal axis J _L, design and mounting operation of the mounting portion becomes easily as in the embodiment of Figure 1 and Figure 3 in this embodiment There is.

However, in this embodiment, the light component emitted in other than the portion indicated by the shaded portion U from the light source 11 is, for example, as shown as an optical component L _7, 2 times the reflecting plate 10 while passing through the focal point F ₂ reflected through the focal point F _1, since the result is released from the mounting hole 14 of the metal halide lamp to light radiation outside the device, it becomes that light utilization rate decreased slightly. However, the output light in this portion is very small as understood from the second light distribution characteristic, and does not pose a serious problem in practical use.

In addition, in order to further improve the light utilization rate in consideration of such conditions, the ratio of the major axis J _L : the minor axis J _S of the spheroid is increased to make the reflector 10 more flat spheroid. The divergence angle (= tan ^-1 (diameter of light extraction hole 12 / focal length F _d )) from light extraction hole 12 is preferably 30 ° or less. In addition,
Here, the angle of 30 ° is the case of the present embodiment using a metal halide lamp based on the light distribution characteristics of FIG. 2 in which the light component is output most in the direction of approximately 30 ° to 150 °,
Different light distribution characteristics have different set values.

If the above conditions are satisfied, the light component emitted from the mounting hole 14 is minimized, and the light utilization rate can be maximized in this embodiment.

[Effects of the Invention] As described above, the light emitting device of the present invention includes a reflecting plate,
By forming the spheroid with a light extraction hole in the direction of the major axis of the ellipse and arranging the light source at one focal point, most of the light emitted from the light source can be changed one or more times inside the spheroid. The light is reflected twice and condensed at the focal position, and the light can be used as light output in a specific direction, and the light utilization factor is significantly improved, so that a brighter light beam can be obtained or a predetermined brightness. Is obtained with low power.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment of a light emitting device according to the present invention, FIG. 2 is an explanatory view of light distribution characteristics of a metal halide lamp used in the present embodiment, and FIG. 3 is another embodiment of the present invention. FIG. 4 is an explanatory view of still another embodiment of the present invention. FIG. 5 is an explanatory view of a conventional light emitting device for OHP. FIG. 6 is a conventional light emitting device for a liquid crystal projector. FIG. 10 is a reflection plate, 11 is a light source, 12 is a light extraction hole, 13 is a convex lens,
14 indicates a mounting hole, and F ₁ and F ₂ indicate focal points.

Claims (6)

(57) [Claims] 1. A light emitting device comprising a light source and a reflector disposed around the light source, wherein the reflector is formed as a spheroid having a light extraction hole in a major axis direction of the ellipse. At the same time, the light source is disposed at one of the two focal points of the spheroid, and among the emission light emitted to the outside from the light extraction hole, light reflected a plurality of times inside the spheroid is A light emitting device characterized in that it is configured to be included. 2. The light source according to claim 1, wherein said light source comprises a metal halide lamp.
A light emitting device according to claim 1. 3. The light emitting device according to claim 1, wherein said light extraction hole is formed in a wall surface of said spheroid. 4. The light extraction hole according to claim 1, wherein the light extraction hole is disposed near a focal point on a side different from the one focal point on which the light source is disposed at two focal points of the spheroid. The light emitting device according to 1). 5. A focusing lens according to claim 1, wherein a focusing lens having a focal point on a side closer to the light extraction hole is disposed at the two focal points of the spheroid. The light emitting device as described in the above. 6. The light emitting device according to claim 1, wherein a longitudinal direction of said light source and a direction of a straight line connecting two focal points of said spheroid coincide with each other.